Patent Publication Number: US-8975827-B2

Title: Lighting fixture for distributed control

Description:
This application claims the benefit of U.S. provisional patent application No. 61/738,749 filed Dec. 18, 2012, and is a continuation-in-part of U.S. patent application Ser. Nos. 13/589,899 filed Aug. 20, 2012 and 13/589,928 filed Aug. 20, 2012, the disclosures of which are incorporated herein by reference in their entireties. 
     CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is related to concurrently filed U.S. patent application Nos. 13/782,022, entitled LIGHTING FIXTURE FOR AUTOMATED GROUPING, 13/782,053 entitled EFFICIENT ROUTING TABLES FOR LIGHTING NETWORKS, 13/782,068 entitled HANDHELD DEVICE FOR COMMUNICATING WITH LIGHTING FIXTURES, 13/782,078 entitled AUTO COMMISSIONING LIGHTING FIXTURE, now U.S. Pat. No. 8,829,821, 13/782,096 entitled MASTER/SLAVE ARRANGEMENT FOR LIGHTING FIXTURE MODULES, and 13/782,131 entitled COMMISSIONING FOR A LIGHTING NETWORK, the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     FIELD OF THE DISCLOSURE 
     The present disclosure relates to lighting fixtures, and in particular to lighting fixtures that are employed in a lighting network. 
     BACKGROUND 
     In recent years, a movement has gained traction to replace incandescent light bulbs with lighting fixtures that employ more efficient lighting technologies as well as to replace relatively efficient fluorescent lighting fixtures with lighting technologies that produce a more pleasing, natural light. One such technology that shows tremendous promise employs light emitting diodes (LEDs). Compared with incandescent bulbs, LED-based light fixtures are much more efficient at converting electrical energy into light, are longer lasting, and are also capable of producing light that is very natural. Compared with fluorescent lighting, LED-based fixtures are also very efficient, but are capable of producing light that is much more natural and more capable of accurately rendering colors. As a result, lighting fixtures that employ LED technologies are expected to replace incandescent and fluorescent bulbs in residential, commercial, and industrial applications. 
     Unlike incandescent bulbs that operate by subjecting a filament to a desired current, LED-based lighting fixtures require electronics to drive one or more LEDs. The electronics generally include a power supply and a special control circuitry to provide uniquely configured signals that are required to drive the one or more LEDs in a desired fashion. The presence of the control circuitry adds a potentially significant level of intelligence to the lighting fixtures that can be leveraged to employ various types of lighting control. 
     Lighting control systems for traditional or LED-based lighting fixtures generally employ a central controller to control a group of lighting fixtures. The central controller is configured to send commands or signals to each of the lighting fixtures in the group, and the lighting fixtures will respond to the commands or signals to turn on or off, dim to a desired level, and the like. As such, the lighting control decisions are made by the central controller based on inputs received by the central controller, and the lighting fixtures are simply controlled in response to these lighting control decisions. 
     SUMMARY 
     The present disclosure relates to a lighting network where control of the lighting fixtures in the network may be distributed among the lighting fixtures. The lighting fixtures may be broken into groups that are associated with different lighting zones. At least some of the lighting fixtures will have or be associated with one or more sensors, such as occupancy sensors, ambient light sensors, and the like. Within the overall lighting network or the various lighting zones, the lighting fixtures may share sensor data from their sensors. Each lighting fixture may process sensor data provided by its own sensor, a remote standalone sensor, or lighting fixture, and process the sensor data according to the lighting fixture&#39;s own internal logic to control operation of the lighting fixture. The lighting fixtures may also receive control input from other lighting fixtures, control nodes, light switches, commissioning tools, gateways, and remote devices via the Internet or other like network. The control input may be processed along with the sensor data according to the internal logic to further enhance control of the lighting fixture. 
     Accordingly, control of the lighting network of the present disclosure may be decentralized so that each lighting fixture essentially operates independently of the lighting network; however, the internal logic in each of the lighting fixtures is configured so that the lighting fixtures may act in concert as a group. While acting in concert, each lighting fixture may operate in a different manner, such as providing different light output levels, depending on the goals for the particular lighting application. The lighting fixtures may also respond to any user inputs that are presented. 
     In one embodiment, each lighting fixture includes a solid-state light source and circuitry to control operation. In particular, the circuitry is adapted to receive remote sensor data from at least one other lighting fixture and drive the solid-state light source based on the remote sensor data. The lighting fixture may include a local sensor, such as an ambient lighting sensor, occupancy sensor, or the like. With the local sensor, the circuitry is further adapted to determine local sensor data from the local sensor and drive the solid-state light source based on both the remote sensor data and the local sensor data. The local sensor data may also be sent to other lighting fixtures, which may use the local sensor data to help control those lighting fixtures. In addition to controlling the lighting fixtures, sensor activity can show use patterns in fine detail. Some examples would be occupancy sensor patterns within a room showing what areas are used in a room over an extended time period, or the ambient light sensors showing how efficiently daylight is being captured and distributed from the windows to the room. 
     As such, these lighting fixtures may share their sensor data with other lighting fixtures in a lighting network and control their light output based on the local and remote sensor data in view of their own internal logic. The internal logic is configured such that each of the lighting fixtures operates independently from one another while providing light or functionality in a concerted fashion. 
     For example, a switch may be used to turn on all of the lighting fixtures in a particular zone. However, the amount of light provided by the various lighting fixtures may vary from one lighting fixture to the next based on the amount of ambient light present in the different areas of the lighting zone. The lighting fixtures closer to windows may provide less light or light of a different color or color temperature than those lighting fixtures that are near an interior wall. 
     Those skilled in the art will appreciate the scope of the disclosure and realize additional aspects thereof after reading the following detailed description in association with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings incorporated in and forming a part of this specification illustrate several aspects of the disclosure, and together with the description serve to explain the principles of the disclosure. 
         FIG. 1  is a perspective view of a troffer-based lighting fixture according to one embodiment of the disclosure. 
         FIG. 2  is a cross section of the lighting fixture of  FIG. 1 . 
         FIG. 3  is a cross section of the lighting fixture of  FIG. 1  illustrating how light emanates from the LEDs of the lighting fixture and is reflected out through lenses of the lighting fixture. 
         FIG. 4  illustrates a driver module and a communications module integrated within an electronics housing of the lighting fixture of  FIG. 1 . 
         FIG. 5  illustrates a driver module provided in an electronics housing of the lighting fixture of  FIG. 1  and a communications module in an associated housing coupled to the exterior of the electronics housing according to one embodiment of the disclosure. 
         FIG. 6  illustrates a lighting system for an exemplary floor plan. 
         FIG. 7  is a table illustrating lightcast data for the lighting system illustrated in  FIG. 6 . 
         FIGS. 8A-8E  illustrate exemplary zones for the floor plan illustrated in  FIG. 6 , when the lightcast process is provided with the doors from each room into the hallway open. 
         FIG. 9  is a communication flow diagram illustrating a grouping process according to one embodiment of the present disclosure. 
         FIG. 10  is a communication flow diagram illustrating the sharing of sensor data among the lighting fixtures of the lighting system. 
         FIG. 11  is a communication flow diagram illustrating the sharing of sensor data and the creation of instructions within the lighting system. 
         FIG. 12  is a communication flow diagram illustrating both the relay of instructions and the ability to modify instructions within the lighting system. 
         FIG. 13A  illustrates a lighting system with three distinct zones, wherein each zone may have a different output level based on the presence of ambient light. 
         FIG. 13B  illustrates a lighting system wherein there is a gradient in the light output based on the presence of ambient light. 
         FIG. 14  is a block diagram of a lighting system according to one embodiment of the disclosure. 
         FIG. 15  is a cross section of an exemplary LED according to a first embodiment of the disclosure. 
         FIG. 16  is a cross section of an exemplary LED according to a second embodiment of the disclosure. 
         FIG. 17  is a schematic of a driver module and an LED array according to one embodiment of the disclosure. 
         FIG. 18  is a block diagram of a communications module according to one embodiment of the disclosure. 
         FIG. 19  is a block diagram of a lighting fixture according to a first embodiment of the disclosure. 
         FIG. 20  is a block diagram of a lighting fixture according to a second embodiment of the disclosure. 
         FIG. 21  is a block diagram of a lighting system wherein the functionality of the driver module and the communications module is integrated. 
         FIG. 22  is a block diagram of a standalone sensor module according one embodiment of the disclosure. 
         FIG. 23  is a block diagram of a commissioning tool according to one embodiment of the disclosure. 
         FIG. 24  is a block diagram of a switch module according to one embodiment of the disclosure. 
         FIG. 25  is a block diagram of a smart fixture according to one embodiment of the disclosure. 
         FIG. 26  is a block diagram of an indoor RF communication module 
         FIG. 27  outdoor RF communication module according to one embodiment of the disclosure. 
         FIG. 28  is a block diagram of a lighting fixture comprising a smart fixture and an indoor RF communication module according to one embodiment of the disclosure. 
         FIG. 29  is a block diagram of a lighting fixture comprising a smart fixture, an indoor RF communication module, and a fixture sensor module according to one embodiment of the disclosure. 
         FIG. 30  is a block diagram of a wireless sensor according to one embodiment of the disclosure. 
         FIG. 31  is a block diagram of a wireless relay module that is capable of driving a legacy fixture according to one embodiment of the disclosure. 
         FIG. 32  is a block diagram of a wireless switch according to one embodiment of the disclosure. 
         FIG. 33  is a communication flow diagram illustrating an iterative process for selecting a coordinator according to one embodiment of the disclosure. 
         FIG. 34  is a communication flow diagram illustrating an iterative process for selecting a coordinator according to another embodiment of the disclosure. 
         FIGS. 35A-35C  are communication flow diagrams illustrating an iterative process for selecting a coordinator according to another embodiment of the disclosure. 
         FIG. 36  is a block diagram of an exemplary lighting fixture according to one embodiment of the disclosure. 
         FIG. 37  illustrates a routing diagram for a first lighting system configuration. 
         FIG. 38  illustrates a routing diagram for a second lighting system configuration. 
         FIG. 39  illustrates a routing diagram for a third lighting system configuration. 
         FIG. 40  is an alternative lighting fixture configuration according to a second embodiment of the disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The embodiments set forth below represent the necessary information to enable those skilled in the art to practice the disclosure and illustrate the best mode of practicing the disclosure. Upon reading the following description in light of the accompanying drawings, those skilled in the art will understand the concepts of the disclosure and will recognize applications of these concepts not particularly addressed herein. It should be understood that these concepts and applications fall within the scope of the disclosure and the accompanying claims. 
     It will be understood that relative terms such as “front,” “forward,” “rear,” “below,” “above,” “upper,” “lower,” “horizontal,” or “vertical” may be used herein to describe a relationship of one element, layer or region to another element, layer or region as illustrated in the figures. It will be understood that these terms are intended to encompass different orientations of the device in addition to the orientation depicted in the figures. 
     The present disclosure relates to a lighting network where control of the lighting fixtures in the network may be distributed among the lighting fixtures. The lighting fixtures may be broken into groups that are associated with different lighting zones. At least some of the lighting fixtures will have or be associated with one or more sensors, such as occupancy sensors, ambient light sensors, and the like. Within the overall lighting network or the various lighting zones, the lighting fixtures may share sensor data from the sensors. Each lighting fixture may process sensor data provided by its own sensor, a remote standalone sensor, or lighting fixture, and process the sensor data according to the lighting fixture&#39;s own internal logic to control operation of the lighting fixture. The lighting fixtures may also receive control input from other lighting fixtures, control nodes, light switches, and commissioning tools. The control input may be processed along with the sensor data according to the internal logic to further enhance control of the lighting fixture. 
     Accordingly, control of the lighting network of the present disclosure may be decentralized so that each lighting fixture essentially operates independently of the lighting network; however, the internal logic in each of the lighting fixtures is configured so that the lighting fixtures may act in concert as a group. While acting in concert, each lighting fixture may operate in a different manner depending on the goals for the particular lighting application. The lighting fixtures may also respond to any user inputs that are presented. 
     For example, a switch may be used to turn on all of the lighting fixtures in a particular zone. However, the amount of light provided by the various lighting fixtures may vary from one lighting fixture to the next based on the amount of ambient light present or the relative occupancy in the different areas of the lighting zone. The lighting fixtures closer to windows may provide less light or light of a different color or color temperature than those lighting fixtures that are near an interior wall. Further, lighting fixtures closer to people or those proximate to larger groups of people may provide more light or light of a different color or color temperature relative to the other lighting fixtures. For example, in a long hallway, the presence of an occupant could not only turn on the hallway group of lighting fixtures, but could also dictate dimming levels for the various fixtures so that the whole hallway is lit with a low light level while the area (or areas) immediately around the occupant (or occupants) has a higher light level. The areas with more occupants could have higher light output than those with fewer or more occupants. The speed of travel could also dictate relative light output levels. 
     Traditional lighting control systems rely on a central controller to make all decisions and control the various lighting fixtures from afar. The distributed control approach of the present disclosure is not so limited. While a central controller may be employed, the commands from the central controller may be treated as a suggestion or just another input to be considered by each lighting fixture&#39;s internal logic. Particularly unique to the present disclosure is the ability to share sensor data between lighting fixtures. Being able to share sensor data allows otherwise independently functioning lighting fixtures to act as a group in a coordinated fashion. 
     For example, each lighting fixture in a lighting zone may take its own ambient light reading, but rather than acting only on its own ambient light reading, the ambient light reading is shared with the other lighting fixtures in the group. When all of the light fixtures in the lighting zone have shared their ambient light readings, each lighting fixture can independently determine an average or a minimum light output based on the ambient light readings from the entire group. As such, the lighting fixtures in the group will adjust their output consistently with one another while operating independently from one another. 
     Prior to delving into the details of the present disclosure, an overview of an exemplary lighting fixture in which the distributed lighting control system may be employed is described. While the concepts of the present disclosure may be employed in any type of lighting system, the immediately following description describes these concepts in a troffer-type lighting fixture, such as the lighting fixture  10  illustrated in  FIGS. 1-3 . While the disclosed lighting fixture  10  employs an indirect lighting configuration wherein light is initially emitted upward from a light source and then reflected downward, direct lighting configurations may also take advantage of the concepts of the present disclosure. In addition to troffer-type lighting fixtures, the concepts of the present disclosure may also be employed in recessed lighting configurations, wall mount lighting configurations, outdoor lighting configurations, and the like. Reference is made to co-pending and co-assigned U.S. patent application Ser. Nos. 13/589,899 filed Aug. 20, 2013, 13/649,531 filed Oct. 11, 2012, and 13/606,713 filed Sep. 7, 2012, the contents of which are incorporated herein by reference in their entireties. Further, the functionality and control techniques described below may be used to control different types of lighting fixtures, as well as different groups of the same or different types of lighting fixtures at the same time. 
     In general, troffer-type lighting fixtures, such as the lighting fixture  10 , are designed to mount in a ceiling. In most applications, the troffer-type lighting fixtures are mounted into a drop ceiling (not shown) of a commercial, educational, or governmental facility. As illustrated in  FIGS. 1-3 , the lighting fixture  10  includes a square or rectangular outer frame  12 . In the central portion of the lighting fixture  10  are two rectangular lenses  14 , which are generally transparent, translucent, or opaque. Reflectors  16  extend from the outer frame  12  to the outer edges of the lenses  14 . The lenses  14  effectively extend between the innermost portions of the reflectors  16  to an elongated heat sink  18 , which functions to join the two inside edges of the lenses  14 . 
     Turning now to  FIGS. 2 and 3  in particular, the back side of the heatsink  18  provides a mounting structure for an LED array  20 , which includes one or more rows of individual LEDs mounted on an appropriate substrate. The LEDs are oriented to primarily emit light upwards toward a concave cover  22 . The volume bounded by the cover  22 , the lenses  14 , and the back of the heatsink  18  provides a mixing chamber  24 . As such, light will emanate upwards from the LEDs of the LED array  20  toward the cover  22  and will be reflected downward through the respective lenses  14 , as illustrated in  FIG. 3 . Notably, not all light rays emitted from the LEDs will reflect directly off of the bottom of the cover  22  and back through a particular lens  14  with a single reflection. Many of the light rays will bounce around within the mixing chamber  24  and effectively mix with other light rays, such that a desirably uniform light is emitted through the respective lenses  14 . 
     Those skilled in the art will recognize that the type of lenses  14 , the type of LEDs, the shape of the cover  22 , and any coating on the bottom side of the cover  22 , among many other variables, will affect the quantity and quality of light emitted by the lighting fixture  10 . As will be discussed in greater detail below, the LED array  20  may include LEDs of different colors, wherein the light emitted from the various LEDs mixes together to form a white light having a desired color temperature and quality based on the design parameters for the particular embodiment. 
     As is apparent from  FIGS. 2 and 3 , the elongated fins of the heatsink  18  may be visible from the bottom of the lighting fixture  10 . Placing the LEDs of the LED array  20  in thermal contact along the upper side of the heatsink  18  allows any heat generated by the LEDs to be effectively transferred to the elongated fins on the bottom side of the heatsink  18  for dissipation within the room in which the lighting fixture  10  is mounted. Again, the particular configuration of the lighting fixture  10  illustrated in  FIGS. 1-3  is merely one of the virtually limitless configurations for lighting fixtures  10  in which the concepts of the present disclosure are applicable. 
     With continued reference to  FIGS. 2 and 3 , an electronics housing  26  is shown mounted at one end of the lighting fixture  10 , and is used to house all or a portion of the electronics used to power and control the LED array  20 . These electronics are coupled to the LED array  20  through appropriate cabling  28 . With reference to  FIG. 4 , the electronics provided in the electronics housing  26  may be divided into a driver module  30  and a communications module  32 . 
     At a high level, the driver module  30  is coupled to the LED array  20  through the cabling  28  and directly drives the LEDs of the LED array  20  based on control information provided by the communications module  32 . The driver module  30  provides the intelligence for the lighting fixture  10  and is capable of driving the LEDs of the LED array  20  in a desired fashion. The driver module  30  may be provided on a single, integrated module or divided into two or more sub-modules depending the desires of the designer. 
     The communications module  32  acts as an intelligent communication interface that facilitates communications between the driver module  30  and other lighting fixtures  10 , a remote control system (not shown), or a portable handheld commissioning tool, which may also be configured to communicate with a remote control system in a wired or wireless fashion. The commissioning tool is referred to herein as a commissioning tool  36 , which may be used for a variety of functions, including the commissioning of a lighting network. As noted above, these communications may include the sharing of sensor data, instructions, and any other data between the various lighting fixtures  10  in the lighting network. In essence, the communications module  32  functions to coordinate the sharing of intelligence and data among the lighting fixtures  10 . 
     In the embodiment of  FIG. 4 , the communications module  32  may be implemented on a separate printed circuit board (PCB) than the driver module  30 . The respective PCBs of the driver module  30  and the communications module  32  may be configured to allow the connector of the communications module  32  to plug into the connector of the driver module  30 , wherein the communications module  32  is mechanically mounted, or affixed, to the driver module  30  once the connector of the communications module  32  is plugged into the mating connector of the driver module  30 . 
     In other embodiments, a cable may be used to connect the respective connectors of the driver module  30  and the communications module  32 , other attachment mechanisms may be used to physically couple the communications module  32  to the driver module  30 , or the driver module  30  and the communications module  32  may be separately affixed to the inside of the electronics housing  26 . In such embodiments, the interior of the electronics housing  26  is sized appropriately to accommodate both the driver module  30  and the communications module  32 . In many instances, the electronics housing  26  provides a plenum rated enclosure for both the driver module  30  and the communications module  32 . 
     With the embodiment of  FIG. 4 , adding or replacing the communications module  32  requires gaining access to the interior of the electronics housing  26 . If this is undesirable, the driver module  30  may be provided alone in the electronics housing  26 . The communications module  32  may be mounted outside of the electronics housing  26  in an exposed fashion or within a supplemental housing  34 , which may be directly or indirectly coupled to the outside of the electronics housing  26 , as shown in  FIG. 5 . The supplemental housing  34  may be bolted to the electronics housing  26 . The supplemental housing  34  may alternatively be connected to the electronics housing snap-fit or hook-and-snap mechanisms. The supplemental housing  34 , alone or when coupled to the exterior surface of the electronics housing  26 , may provide a plenum rated enclosure. 
     In embodiments where the electronics housing  26  and the supplemental housing  34  will be mounted within a plenum rated enclosure, the supplemental housing  34  may not need to be plenum rated. Further, the communications module  32  may be directly mounted to the exterior of the electronics housing  26  without any need for a supplemental housing  34 , depending on the nature of the electronics provided in the communications module  32 , how and where the lighting fixture  10  will be mounted, and the like. The latter embodiment wherein the communications module  32  is mounted outside of the electronics housing  26  may prove beneficial when the communications module  32  facilitates wireless communications with the other lighting fixtures  10 , the remote control system, or other network or auxiliary device. In essence, the driver module  30  may be provided in the plenum rated electronics housing  26 , which may not be conducive to wireless communications. The communications module  32  may be mounted outside of the electronics housing  26  by itself or within the supplemental housing  34  that is more conducive to wireless communications. A cable may be provided between the driver module  30  and the communications module  32  according to a defined communication interface. 
     The embodiments that employ mounting the communications module  32  outside of the electronics housing  26  may be somewhat less cost effective, but provide significant flexibility in allowing the communications module  32  or other auxiliary devices to be added to the lighting fixture  10 , serviced, or replaced. The supplemental housing  34  for the communications module  32  may be made of a plenum rated plastic or metal, and may be configured to readily mount to the electronics housing  26  through snaps, screws, bolts, or the like, as well as receive the communications module  32 . The communications module  32  may be mounted to the inside of the supplemental housing  34  through snap-fits, screws, twistlocks, and the like. The cabling and connectors used for connecting the communications module  32  to the driver module  30  may take any available form, such as with standard category 5 (cat 5) cable having RJ45 connectors, edge card connectors, blind mate connector pairs, terminal blocks and individual wires, and the like. Having an externally mounted communications module  32  relative to the electronics housing  26  that includes the driver module  30  allows for easy field installation of different types of communications modules  32  for a given driver module  30 . 
     In one embodiment, the capabilities of the lighting fixtures  10  allow them to be readily grouped into different lighting zones. With reference to  FIG. 6 , assume that there are 18 ceiling mounted lighting fixtures  10 , which are uniquely referenced as lighting fixtures A through R and placed in different rooms RM 1  through RM 4  and hallway HW 1  of floor plan FP 1 . 
     In particular, lighting fixture A resides in room RM 1 ; lighting fixtures B-E reside in room RM 2 ; lighting fixtures I, J, L, M, Q, and R reside in room RM 3 ; lighting fixtures N and O reside in room RM 4 , and lighting fixtures F, G, H, K, and P reside in hallway HW 1 . Assuming that the doors from the hallway HW 1  into each of the respective rooms RM 1 -RM 4  are closed, lighting fixtures A-R may be grouped into five unique lighting zones using a lightcast procedure. During a lightcast procedure, one light fixture A-R will adjust or modulate its light output while the other lighting fixtures A-R attempt to monitor or detect the adjusted or modulated light output of the first lighting fixture A-R. 
     Assume that the modulated or adjusted lightcast signal is a visible or near visible, such as infrared, light signal, which can be detected by the ambient light sensors that are provided in or associated with the various lighting fixtures A-R. Initially, assume lighting fixture A emits the visible or near visible lightcast signal, while the rest of the lighting fixtures B-R monitor their ambient light sensors to detect the relative strength of the lightcast signal being received by the integrated or associated ambient light sensors. Again assuming that the door between room RM 1  and the hallway HW 1  is closed, none of the other lighting fixtures A-R will detect the lightcast signal provided by lighting fixture A, and thus lighting fixture A will be grouped alone. Next, lighting fixture B will provide a lightcast signal, and lighting fixtures A and C-R will begin monitoring for the lightcast signal being provided by lighting fixture B. In this instance, lighting fixture C will detect the lightcast signal relatively strongly, lighting fixture D will detect the lightcast signal more weakly, and lighting fixture E will detect a faint lightcast signal, if the lightcast signal is detected at all. 
     A relative magnitude may be assigned to the lightcast signal monitored by each of the lighting fixtures C-E. These magnitudes may be used to populate a table, such as that illustrated in  FIG. 7 , or a portion thereof that is pertinent for to a specific lighting fixture A-R. In this example, the lightcast signal emitted by lighting fixture B is assigned a relative strength of 0.7 for a range of 0 to 1.0 by lighting fixture C, 0.3 by lighting fixture D, and 0.1 by lighting fixture E. Since the door between room RM 2  and the hallway HW 1  is closed, none of the other lighting fixtures A or F-R will be able to detect the lightcast signal from lighting fixture B. 
     Next, lighting fixture C will begin providing the lightcast signal and the other lighting fixtures A, B, and D-R will begin monitoring for the lightcast signal provided by lighting fixture C. Lighting fixtures B, D, and E in room RM 2  will detect the lightcast signal and assign a relative magnitude for the lightcast signal. The magnitudes are provided in  FIG. 7 . Again, lighting fixtures A and F-R will not detect the lightcast signal due to their relative locations. This process is systematically repeated for each of the remaining lighting fixtures D-R such that the table of  FIG. 7  is fully populated. By analyzing the signal strength magnitudes of the various lighting fixtures A-R, one can readily divide the various groups of lighting fixtures A-R into associated lighting zones. Visually, one can readily determine that lighting fixture A should be in a zone by itself, lighting fixtures B-E should be in a second zone, lighting fixture I, J, L, M, Q, and R should be in a third zone, lighting fixtures N and O should be in a fourth zone, and lighting fixtures F, G, H, K, and P should be in a fifth zone. Each of these zones directly corresponds to the placement of the various lighting fixtures A-R in rooms RM 1 -RM 4  and the hallway HW 1 . In additional to simply grouping the lighting fixtures A-R of the different rooms into corresponding zones, one can readily determine the relative proximity and placement of the various lighting fixtures A-R with respect to each other based on the relative magnitudes of the lightcast signals. 
     As described further below, the various lighting fixtures A-R may also monitor RF signals strengths from the one another. The RF signal strength between the various lighting fixtures A-R can be used to determine the distance between and relative location of lighting fixtures A-R. Further, the relative distance between and location of groups with respect to one another may be determined. As such, a relative distance and location can be determined for every fixture in the RF network and any groups thereof using the lightcast signal, RF signal strength, or a combination thereof. The results can be used to generate a scaled map of the lighting fixtures A-R and other elements in the lighting network. The map may include the commissioning tool  36  as well. In addition to using RF signal strength, microphones and speakers could be used in association with or instead of lightcasting techniques for grouping, communications, and the like. Each lighting fixture A-R could have or be associated with a microphone, or like acoustic (sonic or ultrasonic) sensor, and an audio amplifier and speaker (sonic or ultrasonic). 
     The microphones would allow the lighting fixture to pick up voice commands, like “brighter,” “dimmer,” “on,” or “off,” (or other acoustic data, perhaps footsteps for occupancy) and process the acoustic information. The information may cause the lighting fixture to control the light source in a desired fashion, issue commands to other lighting fixtures A-R (or other nodes), or share the acoustic information with other lighting fixtures A-R (or other nodes). A network of distributed microphones provided by the lighting fixtures A-R or in association therewith could determine not only things like where sounds are coming from (is the user in the same room?), but which direction and how fast the source of the sounds is moving (if the user is hurrying toward the exit, or even yelling “fire,” maybe there&#39;s an emergency and the space should be more well-lit for safety reasons). 
     There is also the capability to provide a network of noise suppressing or noise canceling lighting fixtures all working together to keep office spaces quiet. The speakers may be driven with white or pink noise, which is configured to reduce the impact of ambient noise. For true noise canceling, the ambient noise monitored by the microphones at one or a group of the lighting fixtures A-R could be inverted (or played out of phase with respect to the ambient noise) and played back with the corresponding speakers at a volume that will provide a noise canceling effect for nearby occupants. 
     Notably, each lighting fixture A-R may generate its own table, as shown in  FIG. 7 , or a portion thereof. For example, each lighting fixture A-R may simply maintain an array that stores the relative magnitudes of the lightcast signals from the other lighting fixtures A-R. In this instance, each of the lighting fixtures A-R will respond to commands and share data with only those lighting fixtures A-R from which a lightcast signal was detected at all or detected above a certain magnitude. In these instances, each lighting fixture A-R can effectively associate itself with a zone. Alternatively, all of the lightcast signal data may be delivered to a master lighting fixture  10 , which is capable of collecting all of the data for the table of  FIG. 7 , analyzing the data, assigning each of the lighting fixtures A-R to various zones, and communicating the zoning information to the lighting fixtures A-R. Further, the processing provided by the master lighting fixture  10  could also be outsourced to a remote control entity, such as the commissioning tool  36 , or a central control system. 
     In the prior example, all of the doors in the hallway HW 1  were closed. As such, grouping the various lighting fixtures A-R into the five different zones was relatively clear cut, wherein all of the lighting fixtures in a room RM 1 -RM 4  or the hallway HW 1  were grouped into different zones. As such, none of the lighting fixtures A-R were assigned to more than one zone. 
     However, it may be desirable to have certain lighting fixtures A-R assigned to more than one zone. As an example, if the door into room RM 1  is normally open, it may be desirable to have lighting fixtures F and G, which are in the hallway HW 1 , associated in some fashion with the zone for room RM 1 , which includes lighting fixture A. Continuing with this concept, when lighting fixture A is providing the lightcast signal, lighting fixtures F and G of the hallway HW 1  may detect the lightcast signal. Similarly, when lighting fixtures F and G are providing a lightcast signal, they may pick up each others&#39; lightcast signal, and lighting fixture A may also pick up the lightcast signals of lighting fixtures F and G. As such, respective lighting fixtures A, F, and G, or another control entity, will analyze the lightcast signal information and associate lighting fixtures A, F, and G with zone Z 1  as illustrated in  FIG. 8A . If all of the doors in the hallway HW 1  remain open, the lightcast process may continue such that lighting fixtures B, C, D, and E of room RM 2  are grouped with lighting fixtures G, H, and K of hallway HW 1  in zone Z 2  as illustrated in  FIG. 8B . Similarly, the lighting fixtures I, J, L, M, Q, and R of room RM 3  may also be associated with lighting fixtures G, H, and K of hallway HW 1  in zone Z 3 , as shown in  FIG. 8C . Lighting fixtures N and O of room RM 4  may be associated with lighting fixtures F and G of hallway HW 1  for zone Z 4 , as illustrated in  FIG. 8D . 
     With reference to the hallway HW 1 , when the doors are all open, the lighting fixtures H, G, K, and P may be associated with various lighting fixtures A, B, C, I, L, N, and O of the various rooms RM 1 -RM 4 . If this is not desired, a user may modify the grouping of the various lighting fixtures A-R such that just the lighting fixtures F, G, H, K, and P are associated with zone Z 4 , which represents the lighting for just the hallway HW 1 , as illustrated in  FIG. 8E . Accordingly, the automatic grouping of the lighting fixtures  10  can be readily modified through direct interaction with each of the lighting fixtures  10  or from a remote control entity, such as the commissioning tool  36 . Further details with respect to how the lighting fixtures  10  communicate with each other, share data, and operate in a concerted fashion are provided further below. 
     With reference to  FIG. 9 , a partial communication flow is provided to illustrate an exemplary lightcast process and the functionality of each lighting fixture  10  involved in the process. The operation of lighting fixtures B-D, which are assumed to be in the same room, is highlighted. Initially, lighting fixture B decides to enter the lightcast mode based on an instruction from lighting fixture A or some other control entity (step  100 ). Deciding to enter the lightcast mode may be triggered internally, from an external input over a wired or wireless network, or optically in response to receiving a lightcast signal with a certain signature. For example, lighting fixture B may enter a lightcast mode based on the time of day, periodically, based on sensor readings, or in response to a manual (user) request. Alternatively, the lightcast signal may always be monitored for, and may take the form of a specific off/on signature or modulation of the light, which gets automatically detected and measured by the monitoring light fixture  10 . 
     Upon entering the lightcast mode, lighting fixture B will send an instruction out to the other lighting fixtures  10  directly or via a broadcast signal to look for a lightcast signal from lighting fixture B. Notably, these instructions may be sent directly from one lighting fixture  10  to another or may be relayed from one lighting fixture  10  to another throughout the lighting fixture network. As illustrated, the instructions to look for the lightcast signal provided by lighting fixture B is received by lighting fixture C (step  102 ) and relayed to lighting fixture D (step  104 ). However, instructions may be sent directly to lighting fixture D from lighting fixture B without being relayed. 
     At this point, both lighting fixtures C and D will begin monitoring for the lightcast signal to be provided by lighting fixture B (steps  106  and  108 ). Accordingly, lighting fixture B will begin adjusting or modulating its light source in some fashion to provide the lightcast signal (step  110 ). Notably, the lightcast signal is an optical signal that will not be relayed from one lighting fixture  10  to another. Instead, lighting fixtures C and D will detect and process the lightcast signal to generate the grouping data (steps  112  and  114 ). The grouping data may range from simply determining whether or not the lightcast signal is detected or detected above a given threshold to assigning a relative magnitude to the lightcast signal, as discussed in association with the table of  FIG. 7 . After a certain amount of time, lighting fixture B will stop providing the lightcast signal (step  116 ) and provide instructions for lighting fixture C to enter the lightcast mode (step  118 ). Alternatively, a remote controlling entity, such as the commissioning tool  36 , may provide instructions to lighting fixture C to enter the lightcast mode. At this point, lighting fixture C will decide to enter lightcast mode (step  120 ) and the process will repeat for lighting fixture C. This sequence of events will continue for each of the lighting fixtures  10  in the lighting network. 
     With regard to processing the lightcast signals, the lightcast signal measurements, which are monitored by the receiving lighting fixtures  10 , may be associated with an ID of the sending lighting fixture  10 , the receiving lighting fixture  10 , or both. The sending lighting fixture  10  may be identified based on an ID provided in the message to look for a lightcast signal (in step  110 ) or a unique modulation signal that either includes the ID of the sending lighting fixture  10  or that is associated with the lighting fixture  10 . The associations may be done by internal or remote control systems. Further, associations could be made based on time stamping or synchronizing the sending of lightcast signals by the different lighting fixtures  10  so that the sending lighting fixture  10  can be associated with the lightcast signal measurements from the various receiving fixtures  10 . 
     The receiving lighting fixtures  10  may report the lightcast signal measurements along with the associated IDs of the receiving lighting fixtures  10  and the synchronizing or identifying information that can be used to associate the lightcast signal with a particular sending lighting fixture  10 . Timestamping or other sensor information may be included in such a measurement report. These types of lightcast measurement reports can be used to develop tables of information, such as that shown in  FIG. 7 , for different times and include other sensor parameters. As such, greater granularity is provided into the control of the lighting fixtures  10  or light groupings, wherein the type of control can change at different times and/or based on different inputs from the sensors. For instance, control may change once an hour or when certain sensor readings are monitored. 
     Throughout this process or at the end of the process, each of the lighting fixtures  10  will either exchange the grouping data or provide the grouping data to a master lighting fixture  10  or a remote control entity to process the grouping data and assign the various lighting fixtures  10  to corresponding zones (step  122 ). In a primarily distributed control process, the internal logic provided in each of the lighting fixtures  10  will allow the lighting fixtures  10  to effectively assign themselves to an appropriate zone based on the grouping data. Once a lighting fixture  10  has been assigned to a zone or has identified itself as being associated with a group of lighting fixtures  10 , various information may be exchanged between the lighting fixtures  10  within a given zone. This information may range from sensor data to instructions for controlling operation. 
     Lightcast techniques may also be used to detect occupancy or lack thereof. The lighting fixtures  10  (and any other lightcast capable devices) may be configured to periodically or relatively continuously providing lightcasting, perhaps in a manner not visible or perceptible to the human eye, to compare lightcast readings relative to an empty room. Changes in the reference lightcast readings may indicate the presence of occupants, the amount of change may be indicative of the number of occupants, and the locations of the changes may be indicative of the location of the occupants. A return to the reference lightcast reading may indicate the area has been vacated, thus potentially eliminating the need to check for vacancy using traditional body heat or motion sensors. 
     Notably, acknowledgments may be provided in response to each communication signal or message as well as upon detecting a lightcast signal. These acknowledgements may be provided over the wired or wireless networks that support inter-lighting fixture communications, or may be provided optically using a type of lightcast signal having a certain modulation signature that is indicative of an acknowledgement. The acknowledgement signals or other response signals may be used to exchange status, signal strength information, requests for additional information, and the like. Within a given lighting system, different communication techniques (wired, wireless, lightcast modulation) may be used for different types of communications, data/information exchange, control, and the like. Communications may also be provided over AC power lines using conventional techniques. 
     With reference to  FIG. 10 , a partial communication flow is provided to illustrate how sensor data may be exchanged among the various lighting fixtures  10  within a zone or a lighting network in general. Assume that lighting fixtures B, C, and D have been assigned to a particular zone. During operation, lighting fixtures B, C, and D will monitor and exchange sensor data and collectively use the sensor data to determine how to adjust their respective light outputs. Initially, lighting fixture B will monitor its sensor data, which is data from an associated ambient light, occupancy, or other sensor (step  200 ). Lighting fixture B will send its sensor data to the other lighting fixtures C and D in the zone (step  202 ). Meanwhile, lighting fixture C is monitoring its sensor data (step  204 ) and providing the sensor data to lighting fixtures B and D (step  206 ). Similarly, lighting fixture D is monitoring its sensor data and (step  208 ) and providing the sensor data to lighting fixtures C and B (step  210 ). Thus, each of the lighting fixtures B, C, and D has access to its own sensor data and the sensor data of the other lighting fixtures in its zone. While this example is zone-oriented, all of the lighting fixtures  10  in the entire lighting network may be providing all sensor data to one another or certain sensor data or all or certain ones of the lighting fixtures  10  in the lighting network. Within a given zone, a group of fixtures may separate themselves into one or more separate (or sub) zones if their ambient light sensors detect more light than the rest of the lighting fixtures in the zone. This could correspond to a group of lights that are closest to the window. 
     In a relatively continuous fashion, lighting fixture B will process the sensor data from its own sensor and the sensor data from the other lighting fixtures C and D (step  212 ) and determine how to adjust its light output based on the sensor data (step  214 ). Accordingly, lighting fixture B is independently controlling its light output; however, the internal logic of lighting fixture B may take into consideration not only its own sensor data but the sensor data of the other lighting fixtures C and D when determining precisely how to adjust its light output. In an independent yet concerted fashion, lighting fixtures C and D will also process their sensor data and the sensor data from the other lighting fixtures, and adjust their light output based on the sensor data (steps  216 - 222 ). 
     Interestingly, the internal logic of the different lighting fixtures B, C, and D may be configured to function identically to one another or differently from one another. For example, lighting fixtures B, C, and D may apply the same weighting to the sensor data as the other lighting fixtures B, C, and D in the zone. Thus, given the same sensor data from its own sensor and from the other lighting fixtures B, C, and D, each lighting fixture B, C, and D will adjust its light output in exactly the same fashion. If the internal logic varies among the lighting fixtures B, C, and D, the light output of the respective lighting fixtures B, C, and D may vary given the same sensor data. Notably, the sensor data may include data from different types of sensors. For example, sensor data from both ambient light and occupancy sensors may be exchanged and processed as dictated by the internal logic of each lighting fixture B, C, and D to determine how to adjust their respective light outputs. 
     In addition to exchanging sensor data and controlling operation in view thereof, the lighting fixtures B, C, and D may also use their own sensor data as well as the sensor data received from other lighting fixtures B, C, and D to control operation of other lighting fixtures B, C, and D. With reference to  FIG. 11 , a partial communication flow is shown to illustrate this concept. Initially, assume that lighting fixture B and lighting fixture D are gathering sensor data from their respective sensors and providing that sensor data to lighting fixture C (steps  300  and  302 ). While not illustrated, lighting fixture C may be providing its sensor data to the other lighting fixtures B and D. Lighting fixture C may also be monitoring its own sensor data (step  304 ), and processing the sensor data from its own sensor as well as the sensor data from the other lighting fixtures B and D (step  306 ) to generate instructions for lighting fixtures B and C (step  308 ). Once the instructions are generated, they may be provided to the respective lighting fixtures B and D (steps  310  and  312 ). Accordingly, lighting fixture B may adjust its light output based on the instructions provided from lighting fixture C, the sensor data of lighting fixture D, or a combination thereof, depending on the internal logic of lighting fixture B (step  314 ). Lighting fixture C may adjust its light output based on its own sensor data or a combination of its own sensor data and the sensor data received from lighting fixtures B and D (step  316 ). Like lighting fixture B, lighting fixture D may adjust its light output based on instructions received from lighting fixture C, sensor data from lighting fixture D, or a combination thereof (step  318 ). 
     As a practical example, lighting fixtures B, C, and D may share ambient light information, which may dictate the intensity of the light output, the color temperature of the light output, the color of the light output, or any combination thereof. However, lighting fixture C may also be associated with an occupancy sensor. As such, the instructions provided by lighting fixture C to lighting fixtures B and D may instruct lighting fixtures B and D to turn on and provide light output at a certain level, color temperature, or color. Lighting fixtures B and D may respond directly to these instructions or may process these instructions in light of their respective internal logic to determine whether to turn on and how to control the respective light outputs. As such, the instructions provided from one lighting fixture  10  to another may be taken as an absolute command and responded to accordingly, or may be taken as a mere “suggestion” depending on the programming of the lighting fixture  10  that receives the instructions. For example, in the scenario above wherein lighting fixture C is instructing lighting fixture B to turn on, there may be sufficient sunlight measured at lighting fixture B that negates the need for lighting fixture B to turn on. Or, if lighting fixture B does decide to turn on, the color, intensity, or color temperature of the light may be adjusted by the amount and color of the sunlight being measured at lighting fixture B. Again, the distributed control described in the present disclosure allows these lighting fixtures  10  to operate independently, yet in concert if the internal logic so dictates. 
     As shown in the partial communication flow of  FIG. 12 , the instructions provided from one lighting fixture  10  to another may be relayed through an intermediate lighting fixture  10 . Further, the instructions may be modified as they are passed from one lighting fixture  10  to another, based on internal logic, sensor data, or the like. Initially, assume that lighting fixture A, a commissioning tool  36 , or some other control point, switch, or node provides instructions to lighting fixture B (step  400 ). Lighting fixture B may receive these instructions and pass the unmodified instructions on to one or more other lighting fixtures  10  such as lighting fixture C (step  402 ). Lighting fixture B may then monitor its own sensor data (step  404 ), process the sensor data (step  406 ), and generate modified instructions for the other lighting fixtures  10 , including lighting fixture C, based on its own sensor data, the sensor data of others, the instructions provided, or a combination thereof (step  408 ). The modified instructions may be sent to the other lighting fixtures  10 , such as lighting fixture C (step  410 ). Lighting fixture B can then adjust its light output based on its own sensor data, the sensor data of others, and the instructions received (step  418 ). Lighting fixture C may monitor its own sensor data (step  412 ), process its sensor data (step  414 ), and then adjust its light output based on the various sensor data, the modified instructions, the unmodified instructions, or a combination thereof (step  416 ). Through this ability to share sensor data, communicate with each other, and operate independently according to internal logic, the various lighting fixtures  10  provide tremendous flexibility to lighting configurators. 
     With reference to  FIGS. 13A and 13B , a floor plan FP 2  with lighting fixtures A-R is illustrated. In  FIG. 13A , the lighting fixtures A-R may be grouped such that the six lighting fixtures A, B, G, H, M, and N that are farthest from the windowed end of the room are at their full light outputs when on, the six lighting fixtures C, D, I, J, O, and P in the middle of the room are producing an intermediate light output when on, and the six lighting fixtures E, F, K, L, Q, and R that are closest to the windows are producing the least amount of light output when on and sunlight is detected by one of more of the lighting fixtures A-R. In this instance, the portion of the room with the most ambient sunlight will employ the least amount of artificial light. Each of the lighting fixtures A-R is associated with an overall zone for the room and different sub-zones for each of the three sets of six lighting fixtures A-R. While the lighting fixtures A-R are broken into three groups providing three distinct light output levels when ambient sunlight is detected, the lighting fixtures A-R may be configured such that every one of the lighting fixtures A-R provides light output at a different intensity (or color and color temperature) when ambient sunlight is detected. 
     For example and with reference to  FIG. 13B , each of the lighting fixtures A-R may be treated as being in the same zone, yet the light output is subject to a gradient that occurs across the entire zone. The gradient may be linear or non-linear. For example, lighting fixture M, which is farthest away from any of the windows, will provide the most light output, while lighting fixture F, which is likely to be in an area receiving the most ambient sunlight, will provide the least light output. 
     Each of the lighting fixtures between lighting fixtures M and F may provide a continuously decreasing amount of light output according to a defined linear or non-linear gradient that is shared amongst the lighting fixtures A-R. Notably, the gradient may be known by all of the lighting fixtures A-R, wherein the gradient is continuously adjusted based on the amount of ambient sunlight available. Thus, the effective slope of the gradient is greatest when lighting fixture F detects the greatest amount of ambient sunlight, wherein the light output differential between the lighting fixtures M and F is the greatest. At night, when there is no ambient sunlight and very little light, if any, being received through the windows, all of the lighting fixtures A-R may determine to provide the same amount of light output, based on those lighting fixtures A-R that are closest to the windows sharing ambient light sensor data with the other lighting fixtures A-R in the zone. Again, the lighting fixtures A-R are capable of acting independently based on their own or shared sensor data. The internal logic used to control the light output based on the various sensor data may be fixed, manually adjusted, or dynamically adjusted based on interaction among the lighting fixtures A-R. 
     With continued reference to  FIGS. 13A and 13B , assume that a doorway (not shown) is located near lighting fixture A and that at least lighting fixture A has or is associated with an occupancy sensor S O . Further assume that all, or at least numerous ones of the lighting fixtures A-R have or are associated with ambient light sensors S A  and are currently in an off state. When someone walks into the room through the doorway into the room, the occupancy sensor S O  will provide an occupied signal, which will alert lighting fixture A that the room is now occupied. In response, lighting fixture A may be programmed to instruct all of the other lighting fixtures B-R to turn on. Alternatively, lighting fixture A may share its occupancy sensor (or other sensor) information with the other lighting fixtures B-R, which will independently use their own internal logic to process the occupancy sensor information and turn themselves on. 
     Alternatively, lighting fixture A may instruct only a subgroup that is associated with a zone to turn. In the latter case, lighting fixture A may be programmed to only instruct lighting fixtures A, B, G, H, M, and N to turn on. The other zones [C, D, I, J, O, P] and [E, F, K, L, Q, R] in the room may turn on only when occupancy sensors S O  associated with those zones detect an occupant. In either case, all of the lighting fixtures A-R may monitor the amount of ambient light being received through the windows, and perhaps the doorway, and individually control the level, color, and color temperature of the light to output once turned on. The level, color, and color temperature may dynamically change as ambient light levels change. 
     Instead of being instructed to turn on by another lighting fixture, each of the lighting fixtures A-R may have or be associated with an occupancy sensor S O  and react independently to detecting an occupant. The occupancy sensor S O  may employ any available type of motion, heat, or like sensor technology that is capable of detecting movement or the presence of people. The lighting fixtures A-R could also be programmed to turn on when light from another lighting fixture A-R is detected. Thus, when lighting fixture A turns on in response to detecting an occupant, the other lighting fixtures B-R will detect the presence of light from lighting fixture A and turn on in response to detecting the light from lighting fixture A turning on. 
     In certain embodiments, only one of the lighting fixtures A-R needs to be wired or wirelessly coupled to an on/off switch or dimmer. If lighting fixture A is coupled to the switch or dimmer, lighting fixture A can instruct the other lighting fixtures to turn on (as well as dim to a certain level). Alternatively, lighting fixture A could simply turn on to a certain output level. The other lighting fixtures B-R would detect the light as a result of lighting fixture A turning on, and perhaps the relative level of dimming through an associated ambient light sensor S A , and turn on to a certain output level. If not sensed, the relative dimming level could be shared with lighting fixtures B-R by lighting fixture A. 
     The intelligence of the network is virtually limitless and affords the potential for highly intelligent lighting systems. For example, the lighting fixtures A-R may be able to determine (or be programmed with) their relative location to one another. Using the occupancy sensors S O , the collective group of lighting fixtures A-R may be configured to develop predictive algorithms based on historical occupancy data and use these predictive algorithms to determine how long to keep lights on, what lights should turn on as a person walks into a room or down a hallway, and the like. For instance, the lighting fixtures  10  along a hallway may turn on sequentially and well in advance of a person walking down the hallway. The lights may turn off sequentially and behind the person as well. The sequential turning on of the lights may be triggered by a first lighting fixture  10  detecting the person, but the remaining lighting fixtures  10  in the hallway may sequentially turn on based on the historical walking speeds, paths, and the like that are embodied in the predictive algorithms. Each of the lighting fixtures  10  may share sensor data, instructions, and the like and then operate independently in light of this shared information. 
     The above concept of “light tracking” is illustrated below with two examples. For the first example, reference is made to  FIG. 8A , which provides a light tracking example for a person walking along the hallway HW 1 . Assume that the person enters the hallway near lighting fixture F, and exits the hallway near lighting fixture P. Also assume that each of the lighting fixtures F, G, H, K, and P include occupancy sensors S O . As the person enters the hallway near lighting fixture F, lighting fixture F will sense the presence of the person via its occupancy sensor S O  and turn itself on. Lighting fixture F may be programmed to alert lighting fixture G that lighting fixture F has detected a user. Lighting fixture G may know that lighting fixture H is currently off, and since lighting fixture F is detecting the presence of a person, lighting fixture G may turn itself on in a predictive fashion. If lighting fixture G subsequently detects the presence of a person, it may alert lighting fixture H and lighting fixture F. Once lighting fixture H receives an indication that the occupancy sensor of lighting fixture G has detected a person, it may turn on. If lighting fixture H detects the presence of a person through its occupancy sensor S O , it may alert lighting fixture K, lighting fixture G, and lighting fixture F. Lighting fixture F may take this information as an indication that the person is travelling along the hallway HW 1  toward lighting fixture P, and thus turn off, as it may no longer be needed. Lighting fixture G may remain on for the time being, while lighting fixture K will turn on in a predictive fashion. This process may continue such that one, two, or more lights are on in the hallway HW 1  near the current location of the person. The time between adjacent occupancy sensor detections can also be used to approximate the speed at which the person is traveling. This can be used to predict where the person or object is going. For example, if someone is slowing down to enter a room, then the lights in the room may react accordingly. 
     Further, the ability of the lights to communicate with each other and to share their occupancy sensor information allows the group of lighting fixtures in the hallway HW 1  to light the current location of the person and predictively turn on lighting fixtures in advance of the person reaching a particular lighting fixture. Of course, all of the lighting fixtures in the hallway HW 1  could be turned on when lighting fixture F detects the presence of a person, and turn off when none of the lighting fixtures F, G, H, K, and P detect the presence of a person after a certain amount of time. As yet another tracking example, each of the lighting fixtures F, G, H, K, and P may merely turn on when they detect the presence of a person and turn off after a certain amount of time of no longer detecting the presence of a person or when none of the lighting fixtures in the group detects the presence of a person. 
     The tracking concepts are equally applicable to larger areas, such as rooms or outdoor areas. Reference is made to  FIG. 13A  or  13 B for the following example. In a simplistic example, each of the lighting fixtures A-R may include an occupancy sensor S O  and be programmed as follows. If the occupancy sensor S O  for a particular lighting fixture A-R detects the presence of a person, that lighting fixture will turn on and instruct immediately adjacent lighting fixtures to turn on if they are not already on. As such, different ones of the lighting fixtures A-R or groups thereof may turn on and track the people in the room. The lighting fixture that detected the presence of a person (as well as those fixtures that were instructed to turn on by that lighting fixture) may stay on for a set period of time after the presence of the person is no longer detected. While the prior example is a simplistic tracking of room occupants and selectively turning lighting fixtures on or off based thereon, predictive algorithms may also be employed. For example, assume a person enters the room near lighting fixture M and walks diagonally across the room to the opposing corner near lighting fixture F. When lighting fixture M detects the presence of the person, it may turn on and instruct lighting fixtures G, H, and N to turn on. The remaining lighting fixtures will remain off. If lighting fixture N subsequently detects the presence of the person, it will remain on and will instruct lighting fixtures I and O to turn on, because it knows that lighting fixture M first detected the person and now lighting fixture N is detecting the person. When lighting fixture I detects the person, it may alert lighting fixtures B, C, D, H, J, N, O, and P to turn on as well, and may alert lighting fixture M as well. Lighting fixture M may no longer detect the presence of a person and may turn off, based on the knowledge that it is no longer detecting the presence of a person, and that lighting fixtures N and I have subsequently detected the presence of the person. This process may continue across the room, as lighting fixtures J, K, E, L, and F progressively turn on as lighting fixtures M, H, N, and the like turn off after the person has left the corresponding area of the room. Thus, basic tracking and predictive control may be used in virtually any environment to selectively turn on and turn off or otherwise control lighting fixtures in a room, group, or the like. 
     Turning now to  FIG. 14 , a block diagram of a lighting fixture  10  is provided according to one embodiment. Assume for purposes of discussion that the driver module  30 , communications module  32 , and LED array  20  are ultimately connected to form the core of the lighting fixture  10 , and that the communications module  32  is configured to bidirectionally communicate with other lighting fixtures  10 , the commissioning tool  36 , or other control entity through wired or wireless techniques. In this embodiment, a standard communication interface and a first, or standard, protocol are used between the driver module  30  and the communications module  32 . This standard protocol allows different driver modules  30  to communicate with and be controlled by different communications modules  32 , assuming that both the driver module  30  and the communications module  32  are operating according to the standard protocol used by the standard communication interface. The term “standard protocol” is defined to mean any type of known or future developed, proprietary or industry-standardized protocol. 
     In the illustrated embodiment, the driver module  30  and the communications module  32  are coupled via a communication (COMM) bus  38  and a power (PWR) bus  40 . The communication bus  38  allows the communications module  32  to receive information from the driver module  30  as well as control the driver module  30 . An exemplary communication bus  38  is the well-known inter-integrated circuitry (I 2 C) bus, which is a serial bus and is typically implemented with a two-wire interface employing data and clock lines. Other available buses include: serial peripheral interface (SPI) bus, Dallas Semiconductor Corporation&#39;s 1-Wire serial bus, universal serial bus (USB), RS-232, Microchip Technology Incorporated&#39;s UNI/O®, and the like. 
     In this embodiment, the driver module  30  is configured to collect data from the ambient light sensor S A  and the occupancy sensor S O  and drive the LEDs of the LED array  20 . The data collected from the ambient light sensor S A  and the occupancy sensor S O  as well as any other operational parameters of the driver module  30  may be shared with the communications module  32 . As such, the communications module  32  may collect data about the configuration or operation of the driver module  30  and any information made available to the driver module  30  by the LED array  20 , the ambient light sensor S A , and the occupancy sensor S O . The collected data may be used by the communications module  32  to control how the driver module  30  operates, may be shared with other lighting fixtures  10  or control entities, or may be processed to generate instructions that are sent to other lighting fixtures  10 . 
     The communications module  32  may also be controlled in whole or in part by a remote control entity, such as the commissioning tool  36  or another lighting fixture  10 . In general, the communications module  32  will process sensor data and instructions provided by the other lighting fixtures  10  or remote control entities and then provide instructions over the communication bus  38  to the driver module  30 . An alternative way of looking at it is that the communications module  32  facilitates the sharing of the system&#39;s information, including occupancy sensing, ambient light sensing, dimmer switch settings, etc., and provides this information to the driver module  30 , which then uses its own internal logic to determine what action(s) to take. The driver module  30  will respond by controlling the drive current or voltages provided to the LED array  20  as appropriate. An exemplary command set for a hypothetical protocol is provided below. 
     
       
         
           
               
            
               
                   
               
               
                 Exemplary Command Set 
               
            
           
           
               
               
               
               
            
               
                 Command 
                 Source 
                 Receiver 
                 Description 
               
               
                   
               
               
                 On/Off 
                 Communications 
                 Driver Module 
                 On/Off 
               
               
                   
                 Module 
                   
                   
               
               
                 Color 
                 Communications 
                 Driver Module 
                 Color temperature  
               
               
                 Temperature 
                 Module 
                   
                 of solid state light 
               
               
                 Dimming Level 
                 Communications 
                 Driver Module 
                 Set light level 
               
               
                   
                 Module 
                   
                   
               
               
                 Fixture ID 
                 Driver Module 
                 Communications 
                 Solid State light id 
               
               
                   
                   
                 Module 
                   
               
               
                 Health 
                 Driver Module  
                 Communications  
                 Health of solid  
               
               
                   
                   
                 Module 
                 state light 
               
               
                 Power Usage 
                 Driver Module 
                 Communications  
                 Power used by  
               
               
                   
                   
                 Module 
                 solid state light 
               
               
                 Usage 
                 Driver Module 
                 Communications 
                 Hours of use 
               
               
                   
                   
                 Module 
                   
               
               
                 Lifetime 
                 Driver Module 
                 Communications  
                 Useful life  
               
               
                   
                   
                 Module 
                 (factors hours,  
               
               
                   
                   
                   
                 ambient temp 
               
               
                   
                   
                   
                 and power level) 
               
               
                 Zone ID 
                 Driver Module 
                 Communications 
                 Identifies the zone  
               
               
                   
                   
                 Module 
                 the fixture is in 
               
               
                 Temperature 
                 Driver Module 
                 Communications 
                 Solid State  
               
               
                   
                   
                 Module 
                 temperature 
               
               
                   
                   
                   
                 level (protection) 
               
               
                 Emergency 
                 Driver Module 
                 Communications 
                 Indentifies the  
               
               
                 Enabled 
                   
                 Module 
                 fixture as  
               
               
                   
                   
                   
                 an emergency  
               
               
                   
                   
                   
                 enabled fixture. 
               
               
                 Emergency 
                 Driver Module 
                 Communications 
                 Battery State 
               
               
                 Health 
                   
                 Module 
                   
               
               
                 Emergency 
                 Communications 
                 Driver Module 
                 Remote method to  
               
               
                 Test 
                 Module 
                   
                 allow testing  
               
               
                   
                   
                   
                 of emergency  
               
               
                   
                   
                   
                 solid state fixture 
               
               
                 Emergency 
                 Driver Module  
                 Communications  
                 Pass indication for 
               
               
                 Pass 
                   
                 Module 
                 emergency test 
               
               
                 Emergency 
                 Driver Module 
                 Communications 
                 Battery time left 
               
               
                 time remaining 
                   
                 Module 
                   
               
               
                 Occupancy 
                 Driver Module 
                 Communications 
                 Number of  
               
               
                 Statistics 
                   
                 Module 
                 occupancy events 
               
               
                 Daylighting 
                 Driver Module 
                 Communications  
                 Average dim level  
               
               
                 statistics 
                   
                 Module 
                 to maintain  
               
               
                   
                   
                   
                 ambient  
               
               
                   
                   
                   
                 light level 
               
               
                 Sensor Data 
                 Any Device with 
                 Any Device 
                 Ambient light  
               
               
                 Update 
                 Sensor(s) 
                   
                 level, occupancy  
               
               
                   
                   
                   
                 detection 
               
               
                   
                   
                   
                 status, etc. 
               
               
                 User 
                 Dimmer/Switch  
                 Fixtures &amp; 
                 Value of dimmer  
               
               
                 Dimmer/Switch 
                   
                 Wireless Relay 
                 switch setting 
               
               
                 Setting Update 
                   
                 Modules 
               
               
                   
               
            
           
         
       
     
     The above table has four columns: command, source, receiver, and description. The command represents the actual instruction passed either from the communications module  32  to the driver module  30  or from the driver module  30  to the communications module  32 . The source identifies the sender of the command. The receiver identifies the intended recipient of the command. The communication column provides a description of the command. For example, the “on/off” command is sent by the communications module  32  to the driver module  30  and effectively allows the communications module  32  to instruct the driver module  30  to either turn on or turn off the LED array  20 . The “color temperature” command allows the communications module  32  to instruct the driver module  30  to drive the LED array  20  in a manner to generate a desired color temperature. The “color temperature” command may actually include the desired color temperature or a reference to available color temperature. 
     The “dimming level” command is sent from the communications module  32  to the driver module  30  to set an overall light level based on a desired level of dimming. The “fixture ID” command allows the driver module  30  to identify itself to the communications module  32 . The “health” command allows the driver module  30  to send the communications module  32  information relative to its operational capability or, in other words, health. The “power usage” command allows the driver module  30  to tell the communications module  32  how much power is being used by the driver module  30  on average or at any given time, depending on the capabilities of the driver module  30 . The “usage” command allows the driver module  30  to identify the total hours of use, hours of consistent use, or the like to the communications module  32 . The “lifetime” command allows the driver module  30  to provide an estimate of the useful remaining life of the driver module  30 , the LED array  20 , or a combination thereof to the communications module  32 . Based on the capabilities of the driver module  30 , the amount of remaining life may factor in past usage, ambient temperatures, power levels, or the like. 
     The “zone ID” command allows the driver module  30  to tell the communications module  32  in which zone the driver module  30  resides. This command is useful when the other lighting fixtures  10  or the remote control entity is controlling multiple lighting fixtures and is collecting information about the zones in which the lighting fixtures  10  reside. The “temperature” command allows the driver module  30  to provide ambient temperature information for the driver module  30  or the LED array  20  to the communications module  32 . 
     The “emergency enabled” command allows the driver module  30  to tell the communications module  32  that the lighting fixture  10  is an emergency enabled fixture, which can be used for emergency lighting. The “emergency health” command allows the driver module  30  to provide information bearing on the ability of the driver module  30  or the lighting fixture  10  to function as an emergency lighting fixture. In a simple embodiment, the command may provide the state of an emergency backup battery that has been made available to drive the lighting fixture  10  in case of an emergency. The “emergency test” command allows the communications module  32  to send an instruction to the driver module  30  to run an emergency lighting test to ensure that the lighting fixture  10  can operate in an emergency lighting mode, if so required. The “emergency pass” command allows the driver module  30  to inform the communications module  32  that the emergency test was passed (or failed). The above commands primarily describe the direction of information flow. However, the protocol may allow the communications module  32  or the driver module  30  to selectively or periodically request any of this or other information specifically or in batches. 
     The use of a standard communication interface and a standard protocol for communications between the driver module  30  and the communications module  32  supports a modular approach for the driver module  30  and the communications module  32 . For example, different manufacturers may make different communications modules  32  that interface with a particular driver module  30 . The different communications modules  32  may be configured to drive the driver module  30  differently based on different lighting applications, available features, price points, and the like. As such, the communications module  32  may be configured to communicate with different types of driver modules  30 . Once a communications module  32  is coupled to a driver module  30 , the communications module  32  identifies the type of driver module  30  and will interface with the driver module  30  accordingly. Further, a driver module  30  may be able to operate over various ranges for different lighting parameters. Different communications modules  32  may be configured to control these parameters to varying degrees. The first communications module  32  may only be given access to a limited parameter set, wherein another communications module  32  may be given access to a much greater parameter set. The table below provides an exemplary parameter set for a given driver module  30 . 
     
       
         
           
               
             
               
                   
               
               
                 Parameters 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                   
                 PWM dimming Frequency 
                 200 Hz through 1000 Hz 
               
               
                   
                 Maximum Light Level 
                 50% to 100% 
               
               
                   
                 Color Temperature 
                 2700K to 6000K 
               
               
                   
                 Maximum allowable hours 
                 50,000 to 100,000 
               
               
                   
                 Minimum dimming level 
                 0 to 50% 
               
               
                   
                 Response time 
                 100 ms to 1 sec 
               
               
                   
                 Color temperature settable  
                 0 or 1 
               
               
                   
                 Dimming curve 
                 Linear, exponential. Dim to 
               
               
                   
                   
                 warmer or cooler color temperature 
               
               
                   
                 Alarm Indication 
                 0 or 1 
               
               
                   
               
            
           
         
       
     
     The parameters in the above table may represent the available control points for a given driver module  30 . A given parameter set may be assigned to the driver module  30  during manufacture or may be set by the communications module  32  during installation of the lighting fixture  10  or upon associating the communications module  32  with the driver module  30 . The parameter set includes various parameters, such as the pulse width modulation (PWM) dimming frequency, maximum light level, and color temperature. The parameter set represents the allowable ranges for each of these parameters. Each parameter may be set within the identified range in the parameter set during operation or the like by the communications module  32  or the remote control system, depending on the desires of the designer or the particular application. 
     As an example, the maximum light level for the exemplary parameter set indicates it can be set from anywhere from 50% to 100% of the capabilities of the driver module  30  and the associated LED array  20 . If the end user or owner of the lighting system that employs the lighting fixture  10  initiates the appropriate instructions, the maximum light level may be set to 80% in an appropriate parameter field. As such, the driver module  30  would not drive the LED array  20  to exceed 80%, even if the communications module  32  provided a command to the driver module  30  to increase the lighting level above 80% of its maximum capability. These parameters may be stored in the driver module  30  or in the communications module  32  in non-volatile memory. 
     In certain embodiments, the driver module  30  includes sufficient electronics to process an alternating current (AC) input signal (AC IN) and provide an appropriate rectified or direct current (DC) signal sufficient to power the communications module  32 , and perhaps the LED array  20 . As such, the communications module  32  does not require separate AC-to-DC conversion circuitry to power the electronics residing therein, and can simply receive DC power from the driver module  30  over the power bus  40 , which may be separate from the communication bus  38  or may be integrated with the communication bus  38 , as will be described below. 
     In one embodiment, one aspect of the standard communication interface is the definition of a standard power delivery system. For example, the power bus  40  may be set to a low voltage level, such as 5 volts, 12 volts, 24 volts, or the like. The driver module  30  is configured to process the AC input signal to provide the defined low voltage level and provide that voltage over the power bus  40 , thus the communications module  32  or auxiliary devices may be designed in anticipation of the desired low voltage level being provided over the power bus  40  by the driver module  30  without concern for connecting to or processing an AC signal to a DC power signal for powering the electronics of the communications module  32 . 
     A description of an exemplary embodiment of the LED array  20 , driver module  30 , and the communications module  32  follows. As noted, the LED array  20  includes a plurality of LEDs, such as the LEDs  42  illustrated in  FIGS. 15 and 16 . With reference to  FIG. 15 , a single LED chip  44  is mounted on a reflective cup  46  using solder or a conductive epoxy, such that ohmic contacts for the cathode (or anode) of the LED chip  44  are electrically coupled to the bottom of the reflective cup  46 . The reflective cup  46  is either coupled to or integrally formed with a first lead  48  of the LED  42 . One or more bond wires  50  connect ohmic contacts for the anode (or cathode) of the LED chip  44  to a second lead  52 . 
     The reflective cup  46  may be filled with an encapsulant material  54  that encapsulates the LED chip  44 . The encapsulant material  54  may be clear or contain a wavelength conversion material, such as a phosphor, which is described in greater detail below. The entire assembly is encapsulated in a clear protective resin  56 , which may be molded in the shape of a lens to control the light emitted from the LED chip  44 . 
     An alternative package for an LED  42  is illustrated in  FIG. 16  wherein the LED chip  44  is mounted on a substrate  58 . In particular, the ohmic contacts for the anode (or cathode) of the LED chip  44  are directly mounted to first contact pads  60  on the surface of the substrate  58 . The ohmic contacts for the cathode (or anode) of the LED chip  44  are connected to second contact pads  62 , which are also on the surface of the substrate  58 , using bond wires  64 . The LED chip  44  resides in a cavity of a reflector structure  65 , which is formed from a reflective material and functions to reflect light emitted from the LED chip  44  through the opening formed by the reflector structure  65 . The cavity formed by the reflector structure  65  may be filled with an encapsulant material  54  that encapsulates the LED chip  44 . The encapsulant material  54  may be clear or contain a wavelength conversion material, such as a phosphor. 
     In either of the embodiments of  FIGS. 15 and 16 , if the encapsulant material  54  is clear, the light emitted by the LED chip  44  passes through the encapsulant material  54  and the protective resin  56  without any substantial shift in color. As such, the light emitted from the LED chip  44  is effectively the light emitted from the LED  42 . If the encapsulant material  54  contains a wavelength conversion material, substantially all or a portion of the light emitted by the LED chip  44  in a first wavelength range may be absorbed by the wavelength conversion material, which will responsively emit light in a second wavelength range. The concentration and type of wavelength conversion material will dictate how much of the light emitted by the LED chip  44  is absorbed by the wavelength conversion material as well as the extent of the wavelength conversion. In embodiments where some of the light emitted by the LED chip  44  passes through the wavelength conversion material without being absorbed, the light passing through the wavelength conversion material will mix with the light emitted by the wavelength conversion material. Thus, when a wavelength conversion material is used, the light emitted from the LED  42  is shifted in color from the actual light emitted from the LED chip  44 . 
     For example, the LED array  20  may include a group of BSY or BSG LEDs  42  as well as a group of red LEDs  42 . BSY LEDs  42  include an LED chip  44  that emits bluish light, and the wavelength conversion material is a yellow phosphor that absorbs the blue light and emits yellowish light. Even if some of the bluish light passes through the phosphor, the resultant mix of light emitted from the overall BSY LED  42  is yellowish light. The yellowish light emitted from a BSY LED  42  has a color point that falls above the Black Body Locus (BBL) on the 1931 CIE chromaticity diagram wherein the BBL corresponds to the various color temperatures of white light. 
     Similarly, BSG LEDs  42  include an LED chip  44  that emits bluish light; however, the wavelength conversion material is a greenish phosphor that absorbs the blue light and emits greenish light. Even if some of the bluish light passes through the phosphor, the resultant mix of light emitted from the overall BSG LED  42  is greenish light. The greenish light emitted from a BSG LED  42  has a color point that falls above the BBL on the 1931 CIE chromaticity diagram wherein the BBL corresponds to the various color temperatures of white light. 
     The red LEDs  42  generally emit reddish light at a color point on the opposite side of the BBL as the yellowish or greenish light of the BSY or BSG LEDs  42 . As such, the reddish light from the red LEDs  42  mixes with the yellowish or greenish light emitted from the BSY or BSG LEDs  42  to generate white light that has a desired color temperature and falls within a desired proximity of the BBL. In effect, the reddish light from the red LEDs  42  pulls the yellowish or greenish light from the BSY or BSG LEDs  42  to a desired color point on or near the BBL. Notably, the red LEDs  42  may have LED chips  44  that natively emit reddish light wherein no wavelength conversion material is employed. Alternatively, the LED chips  44  may be associated with a wavelength conversion material, wherein the resultant light emitted from the wavelength conversion material and any light that is emitted from the LED chips  44  without being absorbed by the wavelength conversion material mixes to form the desired reddish light. 
     The blue LED chip  44  used to form either the BSY or BSG LEDs  42  may be formed from a gallium nitride (GaN), indium gallium nitride (InGaN), silicon carbide (SiC), zinc selenide (ZnSe), or like material system. The red LED chip  44  may be formed from an aluminum indium gallium nitride (AlInGaP), gallium phosphide (GaP), aluminum gallium arsenide (AlGaAs), or like material system. Exemplary yellow phosphors include cerium-doped yttrium aluminum garnet (YAG:Ce), yellow BOSE (Ba, O, Sr, Si, Eu) phosphors, and the like. Exemplary green phosphors include green BOSE phosphors, Lutetium aluminum garnet (LuAg), cerium doped LuAg (LuAg:Ce), Maui M535 from Lightscape Materials, Inc. of 201 Washington Road, Princeton, N.J. 08540, and the like. The above LED architectures, phosphors, and material systems are merely exemplary and are not intended to provide an exhaustive listing of architectures, phosphors, and materials systems that are applicable to the concepts disclosed herein. 
     As noted, the LED array  20  may include a mixture of red LEDs  42  and either BSY or BSG LEDs  42 . The driver module  30  for driving the LED array  20  is illustrated in  FIG. 17  according to one embodiment of the disclosure. The LED array  20  may be electrically divided into two or more strings of series connected LEDs  42 . As depicted, there are three LED strings S 1 , S 2 , and S 3 . For clarity, the reference number “ 42 ” will include a subscript indicative of the color of the LED  42  in the following text where ‘R’ corresponds to red, ‘BSY’ corresponds to blue shifted yellow, ‘BSC’ corresponds to blue shifted green, and ‘BSX’ corresponds to either BSG or BSY LEDs. LED string  51  includes a number of red LEDs  42   R , LED string S 2  includes a number of either BSY or BSG LEDs  42   BSX , and LED string S 3  includes a number of either BSY or BSG LEDs  42   BSX . The driver module  30  controls the current delivered to the respective LED strings S 1 , S 2 , and S 3 . The current used to drive the LEDs  42  is generally pulse width modulated (PWM), wherein the duty cycle of the pulsed current controls the intensity of the light emitted from the LEDs  42 . 
     The BSY or BSG LEDs  42   BSX  in the second LED string S 2  may be selected to have a slightly more bluish hue (less yellowish or greenish hue) than the BSY or BSG LEDs  42   BSX  in the third LED string S 3 . As such, the current flowing through the second and third strings S 2  and S 3  may be tuned to control the yellowish or greenish light that is effectively emitted by the BSY or BSG LEDs  42   BSX  of the second and third LED strings S 2 , S 3 . By controlling the relative intensities of the yellowish or greenish light emitted from the differently hued BSY or BSG LEDs  42   BSX  of the second and third LED strings S 2 , S 3 , the hue of the combined yellowish or greenish light from the second and third LED strings S 2 , S 3  may be controlled in a desired fashion. 
     The ratio of current provided through the red LEDs  42   R  of the first LED string S 1  relative to the currents provided through the BSY or BSG LEDs  42   BSX  of the second and third LED strings S 2  and S 3  may be adjusted to effectively control the relative intensities of the reddish light emitted from the red LEDs  42   R  and the combined yellowish or greenish light emitted from the various BSY or BSG LEDs  42   BSX . As such, the intensity and the color point of the yellowish or greenish light from BSY or BSG LEDs  42   BSX  can be set relative to the intensity of the reddish light emitted from the red LEDs  42   R . The resultant yellowish or greenish light mixes with the reddish light to generate white light that has a desired color temperature and falls within a desired proximity of the BBL. 
     Notably, the number of LED strings Sx may vary from one to many and different combinations of LED colors may be used in the different strings. Each LED string Sx may have LEDs  42  of the same color, variations of the same color, or substantially different colors, such as red, green, and blue. In one embodiment, a single LED string may be used, wherein the LEDs in the string are all substantially identical in color, vary in substantially the same color, or include different colors. In another embodiment, three LED strings Sx with red, green, and blue LEDs may be used, wherein each LED string Sx is dedicated to a single color. In yet another embodiment, at least two LED strings Sx may be used, wherein different colored BSY LEDs are used in one of the LED strings Sx and red LEDs are used in the other of the LED strings Sx. 
     The driver module  30  depicted in  FIG. 17  generally includes rectifier and power factor correction (PFC) circuitry  66 , conversion circuitry  68 , and control circuitry  70 . The rectifier and power factor correction circuitry  66  is adapted to receive an AC power signal (AC IN), rectify the AC power signal, and correct the power factor of the AC power signal. The resultant signal is provided to the conversion circuitry  68 , which converts the rectified AC power signal to a DC power signal. The DC power signal may be boosted or bucked to one or more desired DC voltages by DC-DC converter circuitry, which is provided by the conversion circuitry  68 . Internally, The DC power signal may be used to power the control circuitry  70  and any other circuitry provided in the driver module  30 . 
     The DC power signal is also provided to the power bus  40 , which is coupled to one or more power ports, which may be part of the standard communication interface. The DC power signal provided to the power bus  40  may be used to provide power to one or more external devices that are coupled to the power bus and separate form the driver module  30 . These external devices may include the communications module  32  and any number of auxiliary devices, which are discussed further below. Accordingly, these external devices may rely on the driver module  30  for power and can be efficiently and cost effectively designed accordingly. The rectifier and PFC circuitry  66  and the conversion circuitry  68  of the driver module  30  are robustly designed in anticipation of being required to supply power to not only its internal circuitry and the LED array  20 , but also to supply power to these external devices as well. Such a design greatly simplifies the power supply design, if not eliminating the need for a power supply, and reduces the cost for these external devices. 
     As illustrated, the DC power signal may be provided to another port, which will be connected by the cabling  28  to the LED array  20 . In this embodiment, the supply line of the DC power signal is ultimately coupled to the first end of each of the LED strings S 1 , S 2 , and S 3  in the LED array  20 . The control circuitry  70  is coupled to the second end of each of the LED strings S 1 , S 2 , and S 3  by the cabling  28 . Based on any number of fixed or dynamic parameters, the control circuitry  70  may individually control the pulse width modulated current that flows through the respective LED strings S 1 , S 2 , and S 3  such that the resultant white light emitted from the LED strings S 1 , S 2 , and S 3  has a desired color temperature and falls within a desired proximity of the BBL. Certain of the many variables that may impact the current provided to each of the LED strings S 1 , S 2 , and S 3  include: the magnitude of the AC power signal, the resultant white light, ambient temperature of the driver module  30  or LED array  20 . Notably, the architecture used to drive the LED array  20  in this embodiment is merely exemplary, as those skilled in the art will recognize other architectures for controlling the drive voltages and currents presented to the LED strings S 1 , S 2 , and S 3 . 
     In certain instances, a dimming device controls the AC power signal. The rectifier and PFC circuitry  66  may be configured to detect the relative amount of dimming associated with the AC power signal and provide a corresponding dimming signal to the control circuitry  70 . Based on the dimming signal, the control circuitry  70  will adjust the current provided to each of the LED strings S 1 , S 2 , and S 3  to effectively reduce the intensity of the resultant white light emitted from the LED strings S 1 , S 2 , and S 3  while maintaining the desired color temperature. Dimming instructions may alternatively be delivered from the communications module  32  to the control circuitry  70  in the form of a command via the communication bus  38 . 
     The intensity or color of the light emitted from the LEDs  42  may be affected by ambient temperature. If associated with a thermistor S T  or other temperature-sensing device, the control circuitry  70  can control the current provided to each of the LED strings S 1 , S 2 , and S 3  based on ambient temperature in an effort to compensate for adverse temperature effects. The intensity or color of the light emitted from the LEDs  42  may also change over time. If associated with an LED light sensor S L , the control circuitry  70  can measure the color of the resultant white light being generated by the LED strings S 1 , S 2 , and S 3  and adjust the current provided to each of the LED strings S 1 , S 2 , and S 3  to ensure that the resultant white light maintains a desired color temperature or other desired metric. The control circuitry  70  may also monitor the output of the occupancy and ambient light sensors S O  and S A  for occupancy and ambient light information. 
     The control circuitry  70  may include a central processing unit (CPU) and sufficient memory  72  to enable the control circuitry  70  to bidirectionally communicate with the communications module  32  or other devices over the communication bus  38  through an appropriate communication interface (I/F)  74  using a defined protocol, such as the standard protocol described above. The control circuitry  70  may receive instructions from the communications module  32  or other device and take appropriate action to implement the received instructions. The instructions may range from controlling how the LEDs  42  of the LED array  20  are driven to returning operational data, such as temperature, occupancy, light output, or ambient light information, that was collected by the control circuitry  70  to the communications module  32  or other device via the communication bus  38 . As described further below in association with  FIG. 21 , the functionality of the communications module  32  may be integrated into the driver module  30 , and vice versa. 
     With reference to  FIG. 18 , a block diagram of one embodiment of the communications module  32  is illustrated. The communications module  32  includes a CPU  76  and associated memory  78  that contains to the requisite software instructions and data to facilitate operation as described herein. The CPU  76  may be associated with a communication interface  80 , which is to be coupled to the driver module  30 , directly or indirectly via the communication bus  38 . The CPU  76  may also be associated with a wired communication port  82 , a wireless communication port  84 , or both, to facilitate wired or wireless communications with other lighting fixtures  10  and remote control entities. 
     The capabilities of the communications module  32  may vary greatly from one embodiment to another. For example, the communications module  32  may act as a simple bridge between the driver module  30  and the other lighting fixtures  10  or remote control entities. In such an embodiment, the CPU  76  will primarily pass data and instructions received from the other lighting fixtures  10  or remote control entities to the driver module  30 , and vice versa. The CPU  76  may translate the instructions as necessary based on the protocols being used to facilitate communications between the driver module  30  and the communications module  32  as well as between the communications module  32  and the remote control entities. In other embodiments, the CPU  76  plays an important role in coordinating intelligence and sharing data among the lighting fixtures  10  as well as providing significant, if not complete, control of the driver module  30 . While the communications module  32  may be able to control the driver module  30  by itself, the CPU  76  may also be configured to receive data and instructions from the other lighting fixtures  10  or remote control entities and use this information to control the driver module  30 . The communication module  32  may also provide instructions to other lighting fixtures  10  and remote control entities based on the sensor data from the associated driver module  30  as well as the sensor data and instructions received from the other lighting fixtures  10  and remote control entities. 
     Power for the CPU  76 , memory  78 , the communication interface  80 , and the wired and/or wireless communication ports  82  and  84  may be provided over the power bus  40  via the power port. As noted above, the power bus  40  may receive its power from the driver module  30 , which generates the DC power signal. As such, the communications module  32  may not need to be connected to AC power or include rectifier and conversion circuitry. The power port and the communication port may be separate or may be integrated with the standard communication interface. The power port and communication port are shown separately for clarity. The communication bus  38  may take many forms. In one embodiment, the communication bus  38  is a 2-wire serial bus, wherein the connector or cabling configuration may be configured such that the communication bus  38  and the power bus  40  are provided using four wires: data, clock, power, and ground. 
     In other embodiments, the communication bus  38  and the power bus  40  may be effectively combined to provide a communication bus  38   P  that not only supports bidirectional communications, but also provides DC power, as shown in  FIG. 19 . In a 4-wire system, two wires may be used for data and clock signals, and another two wires may be used for power and ground. The availability of the communication bus  38   P  (or communication bus  38 ) allows auxiliary modules to be coupled to the communication bus  38   P . As shown in  FIG. 19 , the driver module  30 , a communications module  32 , and an auxiliary sensor module  86  are all coupled to the communication bus  38   P  and configured to use a standard protocol to facilitate communications therebetween. The auxiliary sensor module  86  may be specially configured to sense occupancy, ambient light, light output, temperature, or the like and provide corresponding sensor data to the communications module  32  or the driver module  30 . The auxiliary sensor module  86  may be used to provide different types of supplemental control for the driver module  30  as well as the communications module based on different lighting applications or requirements. 
     While any number of functions or control techniques may be employed by an auxiliary sensor module  86 , several examples are shown in  FIG. 20 . The illustrated auxiliary sensor modules include: an occupancy module  86   O , an ambient light module  86   A , a temperature module  86   T , and an emergency module  86   E . The occupancy module  86   O  may be configured with an occupancy sensor and function to provide information bearing on whether the room in which the lighting fixture  10  is mounted is occupied. When the room is initially occupied, the communications module  32  may instruct the driver module  30  to drive the LED array  20  such that the lighting fixture  10  is effectively turned on and provide instructions for other lighting fixtures  10  in the same zone to do the same. 
     The ambient light module  86   A  may include an ambient light sensor that is capable of measuring ambient light, determining the characteristics of the ambient light, and then providing such information to the communications module  32  or the driver module  30 . As a result, either the communications module  32  will instruct the driver module  30  or the driver module  30  will independently function to drive the LED array  20  in a manner based on the amount or characteristics of the ambient light. For example, if there is a lot of ambient light, the driver module  30  may only drive the LED array  20  to a level corresponding to 20% of its maximum light output. If there is little or no ambient light, the driver module  30  may drive the LED array  20  at or near maximum capacity. In more sophisticated embodiments, the ambient light module  86   A , the driver module  30 , or the communications module  32  may analyze the quality of the ambient light and cause the driver module  30  to drive the LED array  20  in a manner based on the quality of the ambient light. For example, if there is a relatively large amount of reddish light in the ambient light, the ambient light module  86   A  may instruct the driver module  30  to drive the LED array  20  such that the less efficient, red LEDs  42   R  are driven at a lower level than normal to improve the overall efficiency of the lighting fixture  10 . The communications module  32  may share the ambient light data with the other lighting fixtures  10  or remote control entities as well as process the ambient light data from one or more lighting fixtures  10  and provide instructions to other lighting fixtures  10  based thereon. 
     The temperature module  86   T  may include a sensor capable of determining the ambient temperature of the room, the LED array  20 , or electronics associated with any of the modules. The ambient temperature data may be used to cause the driver module  30  to drive the LED array  20  in an appropriate fashion. The last illustrated auxiliary sensor module is an emergency module  86   E . The emergency module  86   E  illustrates an application type module, wherein the overall lighting fixture  10  may be converted to operate as an emergency lighting fixture when associated with the emergency module  86   E . The emergency module  86   E  may be able to communicate with the driver module  30  and determine the state of the AC input signal (AC IN), the operational state of the driver module  30 , or the like, and then control the driver module  30  in an appropriate fashion or provide information bearing on the operational state to the communications module  32 . For example, if there is a power failure in the AC input signal (AC IN), the emergency module  86   E  may instruct the driver module  30  to switch over to a battery backup supply (not shown) and drive the LED array  20  at an appropriate level for an emergency lighting condition. The emergency module  86   E  may also retrieve various metrics for the AC input signal (AC IN), the driver module  30 , or the LED array  20 , and pass this information to the communications module  32 . The communications module  32  may then pass the information or generate instructions for the other lighting fixtures  10  or a remote control entity. 
     For the various modules that are coupled to the communication bus  38   P , one embodiment assigns a unique ID to each of the modules, such that one or more of the other modules can uniquely identify them. The identifiers may also correspond to the functionality or type of module. As such, the driver module  30  may be able to identify the various auxiliary sensor modules  86  and communications module  32  that reside on the communication bus  38   P  and recognize the functionality provided by those modules. As such, the driver module  30  or communications module  32  can prioritize commands received by the various modules and manage conflicts therebetween. 
     With reference to  FIG. 21 , an embodiment is provided wherein the functionality of the above-described driver module  30  and communications module  32  are integrated. In essence, the control circuitry  70  is expanded to include the functionality of the communications module  32 . As such, the control circuitry  70  may be associated with various wired or wireless communication ports  82 ′ and  84 ′ to facilitate communications with the other lighting fixtures  10  and remote control entities, as described above. Such an embodiment is generally less expensive to manufacture, but may not provide as much flexibility as the above embodiments that employ distinct communications modules and driver modules  30 . 
     As shown in  FIG. 22 , a standalone sensor module  86 ′ may be provided in the lighting system. The standalone sensor module  86 ′ may include one or more sensors, such as an ambient light sensor S A  and an occupancy sensor S O  as shown, and be proximately located with lighting fixtures  10  that do not have these sensors. As such, the communications modules  32  of the lighting fixtures  10  that do not have these sensors may communicate with the standalone sensor modules  86 ′ to obtain ambient light, occupancy, or other available sensor data and then function as described above. As such, some or all of the lighting fixtures  10  in a zone or area of the lighting system need not have sensors or certain types of sensors. For example, some or all of the lighting fixtures  10  in a room may have ambient lighting sensors S A ; however, none of the lighting fixtures  10  may need an occupancy sensor S O , if one or more standalone sensor modules  86 ′ are available with at least an occupancy sensor S O  in the room. 
     The electronics of the standalone sensor module  86 ′ may appear similar to a communications module  32 . For example, the communications module  32  includes a CPU  76 ′ and associated memory  78 ′ that contains the requisite software instructions and data to facilitate operation as described herein. The CPU  76 ′ may also be associated with a wired communication port  82 , a wireless communication port  84 , or both, to facilitate wired or wireless communications with the other lighting fixtures  10  or remote control entities. The standalone sensor modules  86 ′ may also be configured to provide control instructions, in addition to just sensor data, to the other lighting fixtures  10  of a lighting system. Various types of control may be provided based on its own sensor data as well as sensor data collected from other lighting fixtures  10  and standalone sensor modules  86 ′. 
     With reference to  FIG. 23 , an exemplary commissioning tool  36  is illustrated. The commissioning tool  36  may include a CPU  88 , and sufficient memory  90  to facilitate the functionality described above. The CPU  88  may be associated with a keypad  94  and display  96 , which act in combination to provide a user interface. The keypad may be a traditional alpha-numeric keypad and/or a series of buttons that have specifically assigned functions. The display  96  may be a touchscreen display, wherein a separate hardware-based keypad  94  is not needed. Status indicators  98  may be used to provide the user feedback regarding the status of a function, a certain activity, and the like. The CPU  88  is associated with one or more communication interfaces, such as a wired communication interface  100  and a wireless communication interface  102 , which facilitates wired or wireless communications with any of the lighting fixtures  10 , other control entities, standalone sensor modules  86 ′, and the like. The LED driver  104  may also function as a communication interface to allow the commissioning tool  36  to communicate with the lighting fixtures  10 , sensors, and switches that are equipped with an ambient light sensor S A  or other light receiver. The ambient light used for communications may reside in the visible and/or non-visible light spectrum. For instance, the communications may be infrared. 
     All of the electronics in the commissioning tool  36  may be powered from an appropriate power source  106 , such as a battery. The commissioning tool  36  may be used to program the lighting fixtures  10 , sensors, and switches, as well as adjust any settings, load settings, receive sensor data, provide instructions, and the like. In essence, the commissioning tool  36  may act as a portable user interface for each of the lighting fixtures  10  and standalone sensors and switches as well as act as a remote control entity via which various data processing and control may be provided. Typically, the commissioning tool  36  will be used to initiate the setup of a lighting network, make adjustments to the network, and receive information from the lighting network. The commissioning tool  36  is particularly useful when the lighting network has no other interface to facilitate connection to another remote control entity. 
     Once the lighting fixtures  10  and any standalone sensors and switches are installed, the commissioning tool  36  may initially be used to assign addresses or IDs to the lighting fixtures  10  and standalone sensors and switches, if addresses or IDs are not pre-programmed into the devices. The commissioning tool  36  may also be used to assign the various lighting fixtures  10  and standalone sensors and switches into various groups, which will represent the lighting entities for a particular zone. The commissioning tool  36  may also be used to change group assignments as well as remove a lighting fixture  10  or a standalone sensor or switch from a group or lighting system in general. The commissioning tool  36  may also be able to instruct a particular lighting fixture  10  or standalone sensor or switch to provide this functionality for a particular zone or for the overall lighting system. Exemplary commissioning processes that employ the commissioning tool  36  are illustrated further below. 
     For access control, the commissioning tool  36  will be able to establish communications with a particular entity and authenticate itself. Once the commissioning tool  36  has authenticated itself with a lighting fixture  10  or a standalone sensor or switch in a particular group or in the overall lighting system, the commissioning tool  36  may be authenticated automatically with the other members of the group or lighting system. Further, various lighting fixtures  10  or standalone sensor or switch may be able to facilitate communications between other lighting fixtures  10  and standalone sensor or switch and the commissioning tool  36 . Alternatively, the commissioning tool  36  may be configured only to communicate with a lighting fixture  10  or standalone sensor or switch when in close proximity. This may be accomplished through a physical plug-in connection or through a low-power infrared or radio frequency communication link. Employing direct or short-range communication techniques allows the commissioning tool  36  to be placed in close proximity to a particular lighting fixture  10  or standalone sensor or switch and only communicate with the entity or entities within the limited communication range. 
     The internal logic or programming of the standalone sensors or switches may be downloaded from, modified by, or replaced by the commissioning tool  36 , or by any other remote control entity. As such, lighting designers and maintenance technicians are equipped to configure the overall lighting network to function in a way that best achieves their intended lighting goals. Accordingly, all or various groups of lighting fixtures  10  and standalone sensors or switches may be configured to act in synch with one another for certain applications and independently from one another in other applications. The commissioning tool  36  may take various forms, such as a handheld device with a form factor similar to a smartphone or tablet. Various ports on the communication interface  92  may be used to install external sensors, displays, keypads, and the like, as well as facilitate an interface to a personal computer or computer network. The commissioning tool  36  may also be a device with an architecture as described above and connected with a portable computing device such as a notebook PC, tablet, or smart phone. The combination could perform the commissioning tool functionality 
     As indicated above, the various lighting fixtures  10 , as well as the standalone sensors or switches, share sensor data, instructions, and other information. In many instances, such information may need to be routed through one or more intermediate lighting fixtures  10  or standalone sensor modules  86 ′ before reaching an intended destination. As such, these lighting fixtures  10  and standalone sensors or switches may function as routing nodes within the overall lighting system. The following describes unique and efficient techniques for assigning addresses, configuring routing tables, and accessing these routing tables to facilitate the exchange of information among the various entities of the lighting system. These techniques make lighting systems such as the one described above more reliable and predictable in terms of their requirements. 
     With reference to  FIG. 24 , an exemplary standalone switch module  110  is provided. The switch module  110  may include a CPU  112  and sufficient memory  114  to facilitate operation of the switch. Switch circuitry  116  is capable of determining whether the switch should be on or off, as well as a dimming position. Based on the on/off/dimming position, the switch circuitry  116  will provide corresponding information to the CPU  112 , which is capable of processing the information and determining whether or not to send a command or corresponding status information to one or more nodes in the lighting network. The switch module  110  may communicate with other nodes in the lighting network through a wired communication interface  120  or a wireless communication interface  122 . For the wired communication interface  120 , the type of connectivity may range from running signals over existing AC lines, a separate interface cabling, which would perhaps support serial bus communications, or a proprietary interface. The wireless communication interface  122  may facilitate communications wirelessly with the network and effectively be another node in the mesh network provided by the lighting network. The switch module  110  may also include an ambient light sensor S A  and an occupancy sensor S O , which can provide ambient light conditions and/or occupancy information to the CPU  112 , which may process ambient light conditions and/or occupancy information in order to control how to instruct the other nodes in the lighting network to function, or merely pass the ambient light and/or occupancy information to a controlling node in the lighting network. The switch module  110  may also include a light source  118 , such as an LED, to provide status indication or facilitate near field visible or non-visible light-based communications with the commissioning tool  36  or other device. The ambient light sensor S A  may also receive visible or non-visible light-based communications from the commissioning tool  36  or other device. Notably, the switch module  110  may include additional or less functionality relative to that illustrated in  FIG. 24 . 
     Network Devices in Exemplary Lighting System 
     The following is a description of a particular system that employs exemplary wireless communication techniques of the present disclosure. The devices in the system may include switches, sensors, and lighting fixtures  10  of varying configurations. The system&#39;s communications topology may be an RF mesh network based on the IEEE 802.15.4 standard. As such, the various nodes on the network may communicate on one or more channels in the 2.4 GHz band. The data rate in this configuration is nominally 200 kbps but actual throughput depends heavily on messaging overhead and traffic volume. 
     Once the network is formed, most communications occur within groups, where groups include devices, such as the switches, sensors, and lighting fixtures, operating in tandem. With this particular system&#39;s emphasis on grouping, RF traffic should be relatively minimal once the system is up and running. Consequently for most applications, the RF mesh network will provide a perceptually instantaneous response, such that delays are not noticeable to the user. In practice, this means that lighting fixtures  10  may typically respond within 100 msec to switch, sensor, or other control operations within their group. 
     The following describes the particular components and configurations of the switches, sensors, and lighting fixtures  10  of the illustrated system. As illustrated in  FIG. 25 , a smart fixture  130  is a component that includes a driver module  30 , which is integrally associated with an LED array  20 , ambient light sensor S A , and occupancy sensor S O . Communications with other modular components, as described below, are facilitated via an I 2 C serial bus or the like, as noted above. In this configuration, the driver module  30  is capable of providing DC power to modules or components connected thereto. 
     As illustrated in  FIGS. 26 and 27 , an indoor RF communication module iRFM  32 ′ and outdoor RF communication module  32 ″ oRFM are variants of the communication module  32 . The iRFM  32 ′ and the oRFM  32 ″ may connect to and provide wireless connectivity to the mesh network for various lighting components, such as the smart fixture  130 . The iRFM  32 ′ and the oRFM  32 ″ may receive power from and communicate with a coupled smart fixture  130  or other component via a standard connector. The iRFM  32 ′ and oRFM  32 ″ support wireless connectivity to other devices that have wireless communication capabilities.  FIG. 28  illustrates an iRFM  32 ′ directly coupled to a smart fixture  130  to create a variant of a lighting fixture  10 . DC power is provided to the iRFM  32 ′ by the smart fixture  130 . The iRFM  32 ′ and the smart fixture  130  communicate with each other via the I 2 C serial bus. 
     As illustrated in  FIG. 29 , a fixture sensor module (FSM)  132  may be connected to the iRFM  32 ′ and smart fixture  130  of  FIG. 28  to add additional sensing capabilities to the lighting fixture  10 . The FSM  132  is a type of auxiliary module  86  ( FIG. 20 ) and is configured to obtain power from the smart fixture  130  and provide pass-through connectors for plugging in the iRFM  32 ′ and the smart fixture  130 . When the ambient light sensor S A , occupancy sensor S O , or other sensor type generates an output change, the FSM  132  communicates the changes via the local I 2 C bus to both the attached smart fixture  130 , and if present, the iRFM  32 ′. If an iRFM  32 ′ is connected, it wirelessly communicates the FSM sensor updates to an associated group of lighting devices in the system. 
     As illustrated in  FIG. 30 , an indoor or outdoor wireless sensor module  134 , which is either AC or battery-powered, may also be provided. The wireless sensor  134  has a wireless communications interface and is configured to monitor ambient light conditions, room occupancy, or the like using one or more ambient light or occupancy sensors S A , S O . To maximize battery life, the wireless sensor&#39;s communication and processing circuitry may remain turned off over 99% of the time. When outputs from the sensors change, the communication and processing circuitry turns on and sends a sensor update to lighting devices in an associated group. The wireless sensor  134  is intended to be located physically apart from other lighting fixtures  10 , smart fixtures  130 , and the like. Wireless sensors  134  may be placed in locations where sensors, but not necessarily lighting elements, are needed or desired. 
     As illustrated in  FIG. 31 , a wireless relay module  136  may be used to allow wireless control of legacy (light) fixtures  138  to provide on/off control and dimming thereof. When wireless communication circuitry receives a wireless control signal, a relay may control AC power supplied to the legacy fixture  138  and/or a control signal (0-10V) may be provided to control a dimming level. The wireless relay module  136  may also include ambient light and occupancy sensors S A , S O , and report output changes wirelessly to other devices in the associated group. 
     As illustrated in  FIG. 32 , a version of the switch module  110  configured as a wireless on/off/dimming switch (WS)  140  is provided. The WS  140  resides on the wireless communications network, and as described above, may include an ambient light sensor S A , on/off control, and dimming circuitry. When ambient light sensor S A  activates, the WS  140  sends an update to the devices in its group. The RF design supports low power operation for battery power, but may be hardwired to an AC power source. 
     Exemplary Network Commissioning Procedure 
     Commissioning generally includes the steps of 1) forming the network, 2) collecting data for grouping network devices into groups, 3) running the grouping process, 4) assigning groups for each device, and 5) revising group assignments. 
     In this example, the handheld commissioning tool  36  is used to initiate and control the commissioning process. For an uninitialized system, a user asserts a ‘Start Commissioning’ process from the commissioning tool  36  to begin network formation. This may simply entail moving the commissioning tool  36  near a routing node, such as a lighting fixture  10 , and then initiating a one-button command on the commissioning tool  36 , which sends a ‘start network formation’ message. A routing node may be any device on the network, such as a lighting fixture  10 , that is capable of acting as the coordinator and is able to route information from one node to another. 
     For a routing node to become the coordinator, it may monitor a received signal strength indicator (RSSI) associated with a message or the like, and determine that the RSSI is above a defined threshold. Other routing nodes may receive the message, but the RSSI will be below the defined threshold. Sleeper nodes, such as battery-powered wireless sensors  134 , wireless switches  140 , and the like, will either be asleep or ignore the start network formation message. 
     In this embodiment, assume the proximate routing node accepts the start network formation message and asserts itself as the coordinator. The coordinator broadcasts a Join My Network (JMN) message to the other non-coordinator routing nodes and subsequently allows the non-coordinator nodes in the system to join the network. The coordinator permits joining and may assign “short” network addresses, which may be 24, 16, 8 or so bits, to those non-coordinator routing nodes that joined the network. The short addresses are “short” in that they are shorter than the corresponding MAC addresses for the devices, and will be used instead of the MAC addresses to facilitate communications throughout the network once they are assigned. In this first stage of network formation, the coordinator effectively establishes a network that includes all of the routing nodes. 
     In particular, the coordinator is tasked with sending a JMN message on multiple, if not all, available communication channels. In that JMN message, the coordinator may indicate a selected channel on which the non-coordinator routing nodes should respond. During the joining process, the coordinator will provide short addresses to those non-coordinator routing nodes that are joining the network. The coordinator will also have a default short address, or will assign itself a short address. As noted, these short addresses will be used for communications during normal network operation. The coordinator will also build its own routing tables to use when routing information from one routing node to another. 
     In a cooperative fashion, the non-coordinator routing nodes will initially listen for the JMN message. When the broadcasted JMNmessage is received, the non-coordinator routing nodes will respond on the selected channel identified by the coordinator. The routing nodes will also receive the short addresses assigned by the coordinator, store the short addresses, and build their own routing tables. The unique MAC addresses for the various routing nodes may also be exchanged during this process. The coordinator will keep track of the nodes that have responded and may inform each node of the other nodes that make up the network and the respective short addresses to effectively form the routing core of the network. 
     After allowing sufficient time for all routing nodes to join, the coordinator will initiate and control the above described lightcasting process to help group the various routing nodes into different groups. As such, the coordinator will enter itself and then sequentially request each routing node to enter a lightcast mode. An exemplary lightcast would entail providing a light output at 50% duty cycle at a pre-defined PWM frequency. As an alternative to the PWM frequency for the lightcast signal, an on-off sequencing could be used. 
     While lightcasting, a routing node is considered a ‘lightcaster’ and will transmit to routing nodes a stream of RF messages identifying itself and indicating it is the current lightcaster. The other routing nodes act as lightcast receivers (or lightcatchers) by monitoring the lightcast signal from the given lightcaster, calculating the magnitude of the lightcast signal, and storing the magnitudes of the lightcast signal for the given lightcaster. Sleeper nodes, such as battery-powered wireless sensors  134 , wireless switches  140 , and the like, may receive the lightcast signal and turn on their radio receivers to hear the RF message indicating the identity of the lightcaster. During the lightcasting process, sleeper nodes may be triggered to wake up and request to join the network. The coordinator node will assign them short addresses while approving their join requests. After lightcasting wraps up for all devices, the coordinator will send a message to the commissioning tool  36  that network formation is complete. 
     Accordingly, the coordinator will sequentially send lightcast request messages to the routing nodes, accept join requests from sleeper nodes, and assign short addresses to those joining sleeper nodes. The coordinator will also save lightcast reception data, which is gathered when the other lightcasters are lightcasting. The coordinator will also retain the lightcast reception data until requested by the commissioning tool  36  or other device. The non-coordinator lighting nodes will perform lightcasting when requested as well as gather and save lightcast reception data during lightcasting from other lightcasters. Again, the lightcast reception data is stored until requested by the commissioning tool  36  or other device. For the sleeper nodes, which are normally asleep, they will fully power on and submit Join Network’ (JN) request messages upon sensing the presence of a lightcast signal. The sleeper nodes will receive short addresses from the commissioning tool  36  as well as gather and save lightcast reception data. The lightcast reception data is saved until requested by the commissioning tool  36  or another device. In other embodiments, the lightcast reception data may be sent to a designated node, such as the coordinator, or to the commissioning tool  36 , as it is gathered. 
     Assuming that the lightcast reception data is stored until requested, the following process may be employed. To collect the lightcast reception data, the commissioning tool  36  queries each node for its lightcast reception data. Since a wireless mesh network is already formed, the commissioning tool  36  may communicate with any routing node to establish the entry point to the network. Each node responds with its lightcast data. 
     In particular, the commissioning tool  36  may send out a request for the lightcast reception data. Both the coordinator and the non-coordinator routing nodes will respond with the lightcast reception data. In certain embodiments, the sleeper nodes may share their lightcast reception data with a non-sleeper node, such as the non-coordinator routing nodes and the coordinator. If this is the case, the lightcast reception data for the sleeper nodes may be provided to the commissioning tool  36 . If the sleeper nodes did not share their lightcast reception data with a non-sleeper node, the sleeper nodes may respond with their own lightcast reception data, if they are awake or when they are ultimately awakened automatically or through a lightcast or light signal. 
     After collecting the lightcast reception data, the commissioning tool  36  proceeds with a grouping process. The commissioning tool  36  itself, or possibly an attached notebook computer, executes a grouping algorithm for determining optimal node grouping based on the lightcast reception data. Once the commissioning tool  36  (or attached PC) runs the grouping algorithm, it communicates the group assignments and a group address to each routing node in the network, wherein the group assignment data (inducing the group address) is sent to each routing node and includes all nodes within that routing node&#39;s group. 
     All sleeping nodes are grouped with at least one routing node. Sleeping nodes may receive their group assignment by either of two methods. First, each sleeping node wakes up periodically to send out its sensor data and to request system status updates from the network. In response to the sleeper node&#39;s message, the associated routing node may respond and provide the sleeper node with its group assignment via the group assignment data. The second method for assigning the group address to the sleeper nodes requires that a routing node with sleeper nodes in its group perform lightcasting to awaken the sleeper nodes. An awakened sleeper node subsequently sends out its sensor data and requests system status updates from the network. In response to the sleeper node&#39;s message, the associated routing node responds and provides the sleeper node its group assignment data. 
     Inevitably some group assignments will need to be modified. The commissioning tool  36  provides a way for checking and changing group assignments. The commissioning tool  36  may include an LED (or other visible or non-visible light) output that the user may point at an ambient light sensor S A , which is embedded in a lighting fixture  10 , wireless sensor  134 , wireless relay module  136 , wireless switch  140 , or the like that needs to be assigned to a different group. The commissioning tool  36  may use the LED to provide a lightcast signal as well as send and receive RF messages to effect a group assignment change. 
     An exemplary process for reassigning a node, such as a smart fixture  130 , from one group to another follows. Initially, a user will point the commissioning tool  36  at the smart fixture  130  to be reassigned and provide a user input that is associated with reassigning a node from one group to another. The commissioning tool  36  will initiate a corresponding lightcast signal via its LED output, as well as send an RF message to request the short address of the smart fixture  130 . The smart fixture  130  will receive the lightcast signal and listen for the RF message. The smart fixture  130  will provide an RF acknowledgement message, which includes the short address and the group address for the smart fixture  130 . 
     Next, the user will point the commissioning tool  36  at a node in the new group to which the smart fixture  130  is being moved. The user will press a button or provide an input instructing the commissioning tool  36  to move the smart fixture  130  to the new group. In response, the commissioning tool  36  will initiate a lightcast signal as well as send a corresponding RF message indicating that a node is being moved to the new group. The RF message will include the short address of the smart fixture  130 . The node in the new group that is receiving the lightcast signal will also receive the RF message from the commissioning tool  36 . 
     Upon receipt, the node in the new group will send an acknowledgement to the commissioning tool  36  as well as send a message to the smart fixture  130  using the appropriate short address to provide the address for the new group. The smart fixture  130  will update its group address and send a message to the commissioning tool  36  indicating that the move has been completed. Information associated with the other nodes in the new group may also be provided to the smart fixture  130  via the mesh network. After receiving the new group address from the node in the new group, the smart fixture  130  may also send an acknowledgement back to the commissioning tool  36  as well as send a message to one or more nodes in the old group indicating that it is changing groups. At this point, the smart fixture  130  may monitor any sensor levels and provide any available sensor data to the nodes in the new group via the mesh network. While the example reassigned a smart fixture  130  from one group to another, this technique applies to any type of node in the network. 
     If the network requires re-initialization, the user may employ the commissioning tool  36  to instruct the network nodes to revert to their pre-commissioned settings. Presumably, starting this process will require a multi-step sequence to prevent inadvertent undo commands. Once commissioning is completed, and grouping corrections are made, the system is ready to operate. In general, switches and sensors provide inputs to the system. Lighting fixtures  10  interpret these inputs within the framework of their energy-saving settings and function accordingly. 
     Operation of the different types of devices in the network is described below. A wireless relay module  136  ( FIG. 31 ) monitors input data from its group. This includes data from other switches, remote sensors, and its own internal sensors. Data from switches and remote sensors arrives via wireless network communications. Data from internal sensors is gathered and stored internally. The wireless relay module  136  independently executes internal logic that interprets the various inputs and settings, and correspondingly outputs the 0-10V dimming control and relay on/off control. The wireless relay module  136  relies on its wireless communication circuitry to perform message routing within the mesh network. Routing occurs as a background activity and has no impact on the light-control operation. 
     The wireless relay module  136  may hold a message for a sleeping sleeper node in its group. When the node next awakens and requests an update, the wireless relay module  136  sends the held message to the awakened sleeper node. Notably, the wireless relay module  136  processes its internal ambient light sensor data looking for a lightcast signal. With the network in normal operating mode, the only expected lightcast signal will be from the commissioning tool  36 . When the wireless relay module  136  receives a commissioning tool&#39;s lightcast signal, it will perform the requested wireless command. 
     In most respects, a smart fixture  130  operates similarly to the wireless relay module  136 . One major difference is that smart fixtures  130  are generally coupled with a communication module  32  to form a lighting fixture. The two modules may communicate with each other via the I 2 C bus. Either of the modules may be used to process and store the sensor data; however, communications are provided by the communications module  32 . 
     Wireless sensors  134  provide ambient light and occupancy sensor data to their groups. The wireless switches  140  provide on/off and dimming information via RF messages. The wireless sensors  134  periodically wake up, monitor the sensors, and send sensor update messages to their group. The wireless switches  140  provide RF messages to indicate on, off, and dimming state changes. This allows group members to monitor the wireless sensors  134  and wireless switches  140  within the group, process the information provided in the messages, and react accordingly. If routing nodes within the group have messages for the wireless sensors  134 , they communicate these messages during the waking interval. 
     Automatic Coordinator Selection and Grouping Initiation 
     The preceding example relied on the commissioning tool  36  to initiate network formation by selecting a routing node, such as a lighting fixture  10 , to act as the coordinator. The coordinator will then assign short addresses to the various network elements and assist the commissioning tool  36  in making group assignments through the lightcasting process. For the next embodiment, a variant is described wherein routing nodes automatically discover each other and work together to identify a coordinator, without external aid from the commissioning tool  36  or other entity. The coordinator will automatically assign short addresses for use with normal communications within the network as well as automatically initiate and control the grouping process using the previously described lightcasting. 
     Identification of the coordinator in this embodiment is an iterative process wherein the various routing nodes will essentially exchange their typically 64-bit MAC addresses and decide that the routing node with the lower (or higher) MAC address should be the coordinator, at least for the time being. The routing node with the lower MAC address (coordinator) will assign the routing node with the higher MAC address a unique short address. The coordinator and the other routing nodes will periodically send out requests, such as the JMN requests, to join their networks. If a first routing node that has been assigned as coordinator exchanges MAC addresses with a second routing node that has a lower MAC address, the first routing node will relinquish its coordinator role to the second routing node having the lower MAC address. The second routing node will promptly assign a short address to the first routing node. After a few iterations, the routing node with the lowest (or highest) MAC address in the network will be set as the coordinator and will have assigned short addresses for to each routing node in the network. Again, the coordinator assignment process could just as easily find the routing node with the highest MAC address as opposed to the one with the lowest MAC address. Also, other unique identifying criteria may be exchanged to identify the coordinator in an analogous process. Further, short addresses are optional, and are used merely to speed up the routing process during normal operation. Alternative embodiments may forego the use of short addresses and rely on the MAC or other addresses for routing, as done in traditional mesh networks. 
     Sleeper or other non-routing nodes will wake up periodically and obtain their short addresses from the coordinator directly or from the coordinator via an associated routing node. All other functions, such as overall control, exchanging switch and sensor information, setting up routing tables, routing messages through the network, lightcasting control, grouping, and the like can be handled as described above. Further, a commissioning tool  36  may still be used to tweak settings, regroup elements, and the like as described above. 
     A few exemplary communication flows are described below to illustrate various scenarios for selecting a coordinator for a network. In these flows, four different routing nodes A through D are described. In the various flows, 64-bit MAC addresses are provided for these nodes. For simplicity&#39;s sake, the MAC addresses used are: EEEE EEEE EEEE EEEE (the highest MAC address in the examples); AAAA AAAA AAAA AAAA; 8888 8888 8888 8888; and 1111 1111 1111 1111 (the lowest MAC address in the examples). For conciseness and readability, these MAC addresses are referenced below and in the associated communication flows as [E-E], [A-A], [ 8 - 8 ], and [ 1 - 1 ], respectively. 
     With reference to the communication flow of  FIG. 33 , assume routing node A has a MAC address of [A-A], and routing node B has a MAC address of [E-E]. As such, routing node B has a higher MAC address than routing node A. In this example and in the examples following this one, assume that the coordinator role should be assigned to the routing node with the lowest MAC address. Initially, routing node A is set to its default settings and is programmed to periodically broadcast a JMN (Join My Network) message to request other routing nodes to join routing node A&#39;s network, which at this point is a one-element network. As such, routing node A&#39;s initial network will only include routing node A. In essence, routing node A may default to thinking that it is a coordinator. 
     With continued reference to  FIG. 33 , assume that routing node A broadcasts a JMN message, including its MAC address (MAC-A) (step  600 ). Routing node B will be listening for JMN messages, and will respond to routing node A&#39;s JMN message by storing the MAC address (MAC-A) for routing node A (step  602 ) and then comparing routing node A&#39;s MAC address (MAC-A) with its own MAC address (MAC-B) (step  604 ). Routing node B will recognize that routing node A&#39;s MAC address [A-A] is less than routing node B&#39;s MAC address [E-E] and will set the coordinator for its associated network to routing node A&#39;s MAC address (step  606 ). At this point, routing node B assumes that routing node A, which is associated with the MAC address [A-A], is the coordinator of the network to which it belongs. 
     In response to the JMN message, routing node B will also send a JMN response with its MAC address (MAC-B) back to routing node A (step  608 ). Routing node A will compare its MAC address (MAC-A) with that of routing node B (MAC-B) (step  610 ) and will recognize that it has the lower MAC address, and thus should remain the coordinator of the network. Accordingly, routing node A will generate a short address (B A ) for routing node B&#39;s MAC address (MAC-B) (step  612 ) and will send the short address to routing node B (step  614 ). Routing node B will then save the short address (B A ), which was assigned by routing node A (step  616 ), and if not subsequently changed by another routing node that becomes the coordinator, will use the short address for communications and routing within the network. 
     In the above example, the routing node (A) with the lower MAC address originated the JMN message, and the routing node (B) with the higher MAC address joined the JMN message originator&#39;s network. In the next example, illustrated in  FIG. 34 , the routing node (B) receiving the JMN message becomes the coordinator because it has a lower MAC address. In this example and with reference to  FIG. 34 , routing node A is associated with a higher MAC address [A-A] than routing node B, which has a lower MAC address [ 8 - 8 ]. At some point, assume that routing node A broadcasts a JMN message, which includes routing node A&#39;s MAC address (MAC-A) (step  700 ). The broadcast message is received by routing node B, which proceeds to store the MAC address (MAC-A) for routing node A (step  702 ) and then compares routing node A&#39;s MAC address (MAC-A) with routing node B&#39;s MAC address (MAC-B) (step  704 ). In contrast with the example illustrated in  FIG. 33 , routing node B will recognize that it should set itself as the coordinator, since its MAC address (MAC-B) is less than routing node A&#39;s MAC address (MAC-A) (step  706 ). Since routing node B is the coordinator, it will generate a short address (A B ) associated with routing node A&#39;s MAC address (MAC-A) (step  708 ). Next, routing node B will send a JMN response message, which includes routing nodes B&#39;s MAC address (MAC-B) to routing node A (step  710 ) and immediately follow with a message providing the short address (A B ) to routing node A (step  712 ). Routing node A will then recognize that it is no longer the coordinator, and will set the coordinator to routing node B&#39;s MAC address (MAC-B) (step  714 ), which effectively recognizes routing node B as the coordinator for the network to which routing node A belongs. Routing node A will also save the short address (A B ) as the short address that routing node A will use for communications over the network (step  716 ). 
     Turning now to the communication flow illustrated in  FIGS. 35A-35C , a more complex scenario is illustrated wherein multiple routing nodes (B and C) receive an initial JMN message from routing node A. The example also shows a fourth routing node (D) that does not initially receive the JMN message of routing node A, but ultimately joins the network, recognizes the network&#39;s coordinator, and receives a short address from the coordinator. This example shows the coordinator being transitioned from routing node A to routing node B and then to routing node C. Assume that the MAC addresses for routing nodes A, B, C, and D are as follows:
         MAC-A [A-A];   MAC-B [ 8 - 8 ];   MAC-C [ 1 - 1 ]; and   MAC-D [E-E].       

     Thus, routing node C has the lowest MAC address and routing node D has the highest MAC address. 
     Initially, assume that routing node A broadcasts a JMN message with its MAC address (MAC-A) (step  800 ). Assume that routing node B and routing node C receive the JMN message, and that routing node D does not receive the JMN message. Further assume that routing node B is the faster routing node to respond to the JMN message. As such, routing node B will process the JMN message by storing routing node A&#39;s MAC address (MAC-A) (step  802 ) and comparing routing node A&#39;s MAC address (MAC-A) with its own MAC address (MAC-B) (step  804 ). As with the previous example, routing node B will set itself as the coordinator since routing node B&#39;s MAC address (MAC-B) is less than routing node A&#39;s MAC address (MAC-A) (step  806 ). Routing node B will generate a short address (A B ) for routing node A&#39;s MAC address (MAC-A) (step  808 ) and send an appropriate JMN response including routing node B&#39;s MAC address (MAC-B) to routing node A (step  810 ). Routing node B will also send the short address for routing node A (A B ) to routing node A in a separate message (step  812 ). Although separate messages are used for the JMN response and providing the short address, those skilled in the art will recognize that this information may be provided in a single message. Again, routing node A, having the higher MAC address, will set the coordinator to routing node B&#39;s MAC address (MAC-B), indicating that routing node B will become the coordinator, at least for the time being (step  814 ). Routing node A will also store the short address (A B ) assigned by routing node B (step  816 ). 
     Substantially concurrently, routing node C will also process the JMN message that was provided by routing node A (in step  800 ). In response, routing node C will store routing node A&#39;s MAC address (MAC-A) (step  818 ) and compare routing node A&#39;s MAC address (MAC-A) with routing node C&#39;s MAC address (MAC-C) (step  820 ). Routing node C will also recognize that its MAC address (MAC-C) is lower than routing node A&#39;s MAC address (MAC-A) and set itself as the coordinator (step  822 ). As the coordinator, routing node C will generate a short address (A C ) for routing node A&#39;s MAC address (step  824 ). Routing node C will then send a JMN response message including its MAC address (MAC-C) (step  826 ) and another message providing the short address (A C ) for routing node A (step  828 ) to routing node A. Routing node A will recognize that routing node C thinks it should be the coordinator, and will reset the identified coordinator to routing node C&#39;s MAC address (MAC-C), since routing node C&#39;s MAC address is less than routing node B&#39;s MAC address (step  830 ). Routing node A will also update its short address with the short address (A C ), assigned by routing node C (step  832 ). As such, routing node B has been uprooted as the coordinator from the perspective of routing node A. In certain examples, if routing node B would have had the lower MAC address, routing node A would have maintained that routing node B was the coordinator and would have ignored the messages from routing node C. This portion of the example highlights the fact that multiple routing nodes may think they are the coordinator during this iterative coordinator identification process. 
     At this time, routing node B may continue to think that it is the coordinator, and will periodically broadcast JMN messages to other routing nodes. In this instance, routing node B broadcasts a JMN message including routing node B&#39;s MAC address (MAC-B) that is received by both routing node A and routing node C (step  834 ). Routing node A will effectively ignore the JMN message sent by routing node B, because it recognizes that the currently assigned coordinator, routing node C, has a MAC address less than that of routing node B (step  836 ). However, routing node C will respond differently, because routing node C has a lower MAC address (MAC-C) than routing node B. As such, routing node C will store routing node B&#39;s MAC address (MAC-B) (step  838 ) and compare routing node B&#39;s MAC address (MAC-B) with routing node C&#39;s MAC address (MAC-C) (step  840 ). Routing node C will then recognize that it should remain the coordinator, because it has a lower MAC address (step  842 ) and then generate a short address (B C ) for routing node B&#39;s MAC address (MAC-B) (step  844 ). Routing node C will then send a JMN response including its MAC address (MAC-C) (step  846 ) and a short address message including the short address (B C ) for routing node C (step  848 ) to routing node B. In response, routing node B will reset the coordinator to routing node C using routing node C&#39;s MAC address (MAC-C) (step  850 ) and store B C  as its short address (step  852 ). 
     During this time, assume that routing node D becomes available (step  854 ), and as coordinator, routing node C begins periodically broadcasting JMN messages. As such, routing node C will send a JMN message including its MAC address (MAC-C), which is received by routing node A, routing node B, and routing node D (step  856 ). Routing nodes A and B will effectively ignore the JMN messages, because they recognize that these messages are sent by the recognized coordinator, routing node C (steps  858  and  860 ). Since routing node D is a new party within communication range of the network, routing node D will process the JMN message. Accordingly, routing node D will store routing node C&#39;s MAC address (MAC-C) (step  862 ) and compare routing node C&#39;s MAC address (MAC-C) with routing node D&#39;s MAC address (MAC-D) (step  864 ). Since routing node D will recognize that it has a higher MAC address than routing node C, routing node D will recognize that routing node C should be the coordinator and will set the coordinator to routing node C&#39;s MAC address (MAC-C) (step  866 ). As such, routing node D will not assign a short address for routing node C, since routing node C is the coordinator. Routing node D will simply respond to the JMN message by providing a JMN response message, which includes routing node D&#39;s MAC address (MAC-D) to routing node C (step  868 ). Routing node C will compare its MAC address (MAC-C) with routing node D&#39;s MAC address (MAC-D) (step  870 ). Since routing node C has the lower MAC address and should remain the coordinator, routing node C will generate a short address (D C ) for routing node D&#39;s MAC address (MAC-D) (step  872 ) and will send a message including the short address (D C ) for routing node D to routing node D (step  874 ). Routing node D will store the short address (D C ) for use with subsequent communications (step  876 ). 
     At some point during the process, if routing node C does not have a default short address that is known to the other routing nodes, it will assign itself a short address (step  878 ). Routing node C may assign itself a short address and provide the short address to the other routing nodes in any desired fashion. The benefit of having a default short address for the coordinator is that all other routing nodes, whether they have been assigned a short address or not, may use a short address to route messages through the network to the coordinator using traditional mesh network routing techniques. 
     At this point, the coordinating routing node C can join non-routing (sleeper) nodes to the network and assign them short addresses (step  880 ) as well as initiate the aforementioned grouping process (step  882 ) and carry out various control, routing, and the like using the assigned short addresses (step  884 ). Nodes that are subsequently added to the network may have lower MAC addresses than that of routing node C, and in those situations, the newly added routing node with the lower MAC address may take over as coordinator and reassign short addresses to all the routing and non-routing nodes in the network. Further, the commissioning tool  36  may interact with the automatically identified coordinator to modify grouping assignments and the like. The coordinator may also be changed or reassigned by the commissioning tool  36  as desired by the network administrator. 
     Multiple Master Lighting Fixture Configuration 
     With reference to  FIG. 36 , an exemplary lighting fixture  10  is illustrated as having a driver module  30  with an associated LED array  20 , a communication module  32 , a fixture sensor module  132 , and a gateway  142 . The driver module  30 , communication module  32 , fixture sensor module  132 , and the gateway  142  may be configured to communicate with each other over a 2 or more wire serial interface, such as the I 2 C bus, to allow each of the devices to exchange information, such as data and control information, as desired. As described above, the communication module  32  may facilitate wireless communications with other nodes in the wireless network, and essentially act as a communication interface for the lighting fixture  10  in general, and in particular for the gateway  142 , the driver module  30 , and the fixture sensor module  132 . The gateway  142  may facilitate wireless communications with entities outside of the network, such as a remote controller or to a remote network, perhaps using a different wireless communication interface. For example, the communication module  32  may facilitate wireless communications with other nodes in the lighting network using the IEEE 802.15.4 standard on one or more channels in the 2.4 GHz band, whereas the gateway  142  may facilitate communications in a different band, using a different communication standard, such as cellular or other IEEE standard, or the like. Accordingly, one of the lighting fixtures  10  may be provided with the gateway  142 , which will act as an access point or node for the entire lighting network. The gateway  142  is shown with a CPU  144 , a wireless communication interface  146 , and a serial communication interface  148 . The wireless communication interface  146  supports wireless communications with external networks or devices, whereas the serial communication interface  148  facilitates communications over the 2-wire serial interface. 
     Also shown is an exemplary (on/off/dim) switch  140 ′, which has an ambient light sensor S A , and in this embodiment, a cable that is capable of interfacing with the 2-wire serial interface of the lighting fixture  10 . As such, the switch  140 ′ may be located remotely from the lighting fixture  10 , and yet be integrated via the 2-wire serial interface. On, off, and dimming control may be provided to the communication module  32  or the driver module  30  via the 2-wire serial interface, where either of the communication module  32  or the driver module  30  will process these commands internally as well as provide the commands to other nodes, such as other lighting fixtures, that reside within the same group as the lighting fixture  10 . The fixture sensor module  132  may have both ambient light and occupancy sensors S A  and S O , wherein ambient light and occupancy measurements may be shared with either the communication module  32  or the driver module  30 , either of which may process the commands and react accordingly internally as well as share the information with other members of the group. Again, the driver module  30  may also include various sensors, such as the ambient light sensor S A  that is illustrated. 
     Overall control for the lighting fixture  10  may be provided by the communication module  32 , wherein all internal and directly attached control information is sent to the communication module  32 , which will process the information according to its internal logic and control the associated driver module  30  accordingly, as well as send control information to other nodes in its group or to the network in its entirety. Conversely, the driver module  30  may provide this functionality, wherein sensor and switch information is provided to the driver module  30  and processed by its internal logic to control the LED array  20 . The driver module  30  may also share this control information or the data and sensor information with other members of the network via the communication module  32 . A further modification of this scenario would be wherein the on/off/dim switch  140 ′ is capable of wirelessly communicating with the communication module  32  to share its sensor input, as well as send information to other devices on the network. 
     As noted, various serial interface technologies may be employed. In the following example, an I 2 C interface is employed in an uncharacteristic fashion. In this embodiment, primary control of the lighting fixture  10  is provided in the driver module  30 . If an I 2 C interface is used, the driver module  30  is configured as a slave device, whereas the other entities that are communicating over the I 2 C interface, including the communication module  32 , fixture sensor module  132 , gateway  142 , and the on/off/dim switch  140 ′, are all configured as master devices. This configuration is counterintuitive to previous implementations of an I 2 C based bus structure. With the driver module  30  acting as a slave device, the other master devices can initiate transfers, and thus send or request data to or from the driver module  30 , at any time without having to wait or alert the driver module  30  in advance of initiating the transfer. As such, the driver module  30  does not have to periodically or constantly poll the other devices that are attached to the I 2 C interface in search of switch, sensor, or communication changes. Instead, the master devices are configured to automatically initiate switch, sensor, or communication changes to the driver module  30 , wherein the driver module  30  is configured to readily receive this information and process it accordingly. The master devices may also request information from the driver module  30 , which may have the information on hand and provide it back to the requesting master device, or may retrieve the information from another network node via the communication module  32 , or another device within or associated with the lighting fixture  10 . 
     As an example, if the ambient light sensor S A  or the occupancy sensor S O  of the fixture sensor module  132  detects a change, the fixture sensor module  132  is configured to initiate a transfer of information representative of the sensor change or changes to the driver module  30 . The driver module  30  will process the information and determine whether or not the LED array  20  needs to be turned on or off or varied in light output based on its own internal logic. The driver module  30  may also generate a control command or message that includes the sensor information that is sent to other nodes in its associated group or the network in general via the communication module  32 . For a control command, the receiving device may respond as directed. For the sensor information, the receiving device may process the sensor information and determine how to control itself based thereon. Similar operation is provided by the on/off/dim switch  140 ′, wherein an on/off or dimming adjustment is detected, and the on/off/dim switch  140 ′ will initiate a transfer of the switch status or status change to the driver module  30 , which will again process the information to control the LED array  20  as needed and provide any necessary instructions to other nodes on the network via the communication module  32 . 
     Commands or shared data, such as sensor information, may also arrive at the lighting fixture  10  via the communication module  32 . As such, the communication module  32  will receive a command or the shared data from another node in the associated group or the network in general, and initiate a transfer to the driver module  30 , which will process the command or interpret the shared data based on its own internal logic and control the light array  20  in an appropriate fashion. In addition to simply providing status information, data, and commands to the driver module  30 , any of these devices may request information that the driver module  30  maintains. For example, in a lightcasting process, the communication module  32  may receive a request for the lightcast data from the commissioning tool  36 . The communication module  32  will initiate a request for the information to the driver module  30 , which will provide the information back to the communication module  32 . The communication module  32  will then route the information back to the commissioning tool  36 , directly or indirectly through other routing nodes in the network. 
     While the illustrated master-slave configuration is very beneficial, it is not necessary to practice the concepts disclosed herein. A benefit of this type of configuration is that the other devices within the lighting fixture  10  need not be aware of the others&#39; existence, if their data and status information is collected and maintained on the driver module  30 . Other nodes need only make requests of the communication module  32  or the gateway  142 , which will obtain the information from the driver module  30  and respond accordingly. Notably, the driver module  30  may maintain or collect all types of status or performance information for the lighting fixture  10  and make it available to any device within the lighting fixture  10 , on the network via the communication module  32 , or to a remote entity via the gateway  142 . Further, the master and slave devices for a given lighting fixture  10  need not be maintained within the housing of the lighting fixture  10 . 
     In certain embodiments, the functionality of the communication module  32  may be integrated into the driver module  30 , or vice versa. For instance, the integrated module would have a microcontroller with a built in or closely associated radio frequency transceiver, wherein the microcontroller would provide all of the requisite processing of the driver module  30  and the communication module  32 . The transceiver would facilitate RF communications with other elements (fixtures, sensors, switches, etc.) of the lighting network as well as the commissioning tool  36  and other remote entities. As such, the integrated module could also provide the functionality of the gateway  142 . The integrated module could also include various sensors, such as the ambient light sensor S A , the occupancy sensor S O , and the like. Any AC-DC conversion could be provided on the same PCB as the microcontroller and transceiver or may be provided by a remote module or PCB. 
     Extensive research has been performed in the last few decades on improving wireless networks in general. However, much of this research has focused on reducing power requirements or increasing throughput. For a lighting system, these priorities should be shifted to increasing response time and reducing cost. In a first embodiment, the lighting nodes, such as lighting fixtures  10  and standalone sensors and switches, may be assigned unique addresses starting from the number one. Further, the maximum number of lighting nodes in a given lighting system is bounded at a defined number, such as 256. For the following example, assume that there are six lighting nodes in the lighting network, and each node is sequentially addressed  1 - 6 . A representation of such a lighting network is provided in  FIG. 37 . 
     Routing tables are used to identify the next hop along a routing path, and perhaps a number of hops necessary to reach a destination from the current location. An exemplary routing table for lighting node  1 , constructed according to related art techniques, is provided immediately below (Table A). For this example, assume that a packet of data needs to be routed from lighting node  1  to lighting node  6 . In the below routing table, three columns of information are required: the destination address, the next hop address, and the number of hops to the destination from the current location. In operation, the lighting node will identify a destination address for the packet of data being routed, and search the destination address field in the routing table to find a match. If the destination address for the packet to be routed is number  6 , lighting node  1  will search the entries in the destination address field to find one for lighting node  6 . The corresponding next hop address ( 5 ) for destination address  6  is identified, and the packet of data is routed to the next hop address ( 5 ), wherein the process repeats at each lighting node until the packet of data reaches its intended destination. 
     
       
         
           
               
               
               
             
               
                 TABLE A 
               
               
                   
               
               
                 Destination 
                 Next Hop 
                 Number of 
               
               
                 Address 
                 Address 
                 Hops 
               
               
                   
               
             
            
               
                 5 
                 5 
                 1 
               
               
                 3 
                 2 
                 2 
               
               
                 2 
                 2 
                 1 
               
               
                 6 
                 5 
                 3 
               
               
                 4 
                 5 
                 2 
               
               
                   
               
            
           
         
       
     
     For the present disclosure, the size of the routing table can be reduced by approximately one third, and thus save on the amount of required system memory as well as the processing necessary to identify the next hop address. As shown in the table below (Table B), the column for destination address is removed. Instead, the routing table is reorganized such that the rows correspond to the destination address. In other words, the first entry in the routing table corresponds to destination address  1 , the second row of the routing table corresponds to destination address  2 , the third row in the routing table corresponds to destination address  3 , and so on and so forth. Accordingly, and again assuming that the routing table below corresponds to lighting node  1 , a routing decision is determined as follows. The destination for the packet of data is determined. Since the destination address directly corresponds to the location in the routing table, lighting node  1  need only access the sixth entry in the routing table to identify the next hop address for routing a packet of data to destination address  6 , which corresponds to lighting node  6 . Notably, the routing tables are preferably ordered corresponding to destination address. However, the destination address does not need to match the position in the routing table. Offsets and the like may be used to compensate for lighting networks or zones that employ lighting nodes that are not associated with addresses starting with one. With this embodiment, the size of the routing table is reduced and the amount of processing required to compare a destination address with various entries in a routing table is reduced. In essence, there is no need to scan through the table to find a matching destination address, because the position in the table corresponds to the destination address. 
     
       
         
           
               
               
               
             
               
                   
                 TABLE B 
               
               
                   
                   
               
               
                   
                 Next Hop  
                 Number of 
               
               
                   
                 Address 
                 Hops 
               
               
                   
                   
               
             
            
               
                   
                 1 
                 0 
               
               
                   
                 2 
                 1 
               
               
                   
                 2 
                 2 
               
               
                   
                 5 
                 2 
               
               
                   
                 5 
                 1 
               
               
                   
                 5 
                 3 
               
               
                   
                   
               
            
           
         
       
     
     With reference to  FIG. 38 , the addresses for the lighting nodes may be assigned based on the lighting zone in which the lighting nodes reside. For example, there are three lighting zones: group  1 , group  2 , and group  3 . Lighting nodes  1 - 6  are in group  1 , lighting nodes  7 - 9  and  11  are in group  2 , and lighting nodes  10 ,  12 , and  13  are in group  3 . Table C corresponds to a routing table for lighting node  9  wherein a traditional routing table architecture is employed. From analyzing the configuration for  FIG. 38 , a large number of the lighting nodes, including all the nodes within group  1 , will route through lighting node  8  when routing data from one group to another. Applicants have discovered that it is more efficient for lighting node  9  to have two separate sections, which correspond to Table D and Table E below. 
     
       
         
           
               
               
               
             
               
                 TABLE C 
               
               
                   
               
               
                 Destination 
                 Next Hop 
                 Number of 
               
               
                 Address 
                 Address 
                 Hops 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 6 
                 8 
                 4 
               
               
                 2 
                 8 
                 3 
               
               
                 12 
                 10 
                 2 
               
               
                 8 
                 8 
                 1 
               
               
                 7 
                 8 
                 2 
               
               
                 5 
                 8 
                 2 
               
               
                 10 
                 10 
                 1 
               
               
                 3 
                 8 
                 4 
               
               
                 1 
                 8 
                 3 
               
               
                 11 
                 11 
                 1 
               
               
                 13 
                 10 
                 2 
               
               
                 4 
                 8 
                 3 
               
               
                   
               
            
           
         
       
     
     
       
         
           
               
               
               
             
               
                 TABLE D 
               
               
                   
               
               
                 Destination 
                 Next Hop 
                 Number of 
               
               
                 Group 
                 Address 
                 Hops 
               
               
                   
               
             
            
               
                 3 
                 10 
                 1 
               
               
                 1 
                  8 
                 2 
               
            
           
           
               
               
            
               
                 2 
                 See Next Section 
               
               
                   
               
            
           
         
       
     
     The first section of the routing table for lighting node  9  includes three fields (or columns): destination group, next hop address, and number of hops. This is referred to as the group section. When determining the next hop address, lighting node  9  will identify the group in which the destination address resides and use the table to determine the next hop address for that group destination. Thus, if the destination address corresponds to  10 ,  12 , or  13  of group  3 , the routing table will identify the next hop address as  10 . If the destination address is  1 - 6 , which correspond to group  1 , the next hop address for group  1 , which is destination address  8 , is selected and used for routing the packet of data. Notably, if the destination address resides in the same group, the second section of the routing table is searched. The second section may take the configuration of a traditional routing table, wherein the destination address is used, such as that shown in Table E below. 
     
       
         
           
               
               
               
             
               
                 TABLE E 
               
               
                   
               
               
                 Destination 
                 Next Hop 
                 Number of 
               
               
                 Address 
                 Address 
                 Hops 
               
               
                   
               
             
            
               
                   
               
            
           
           
               
               
               
            
               
                 7 
                 8 
                 2 
               
               
                 11 
                 11 
                 1 
               
               
                 8 
                 8 
                 1 
               
               
                   
               
            
           
         
       
     
     Alternatively, the entire destination address field may be dropped from the second section of the routing table. Using the techniques described in association with  FIG. 37 , the next hop addresses in the second section of the routing table may be positioned in the routing table in a position corresponding to the destination address. Thus, when the second section of the routing table is used, the positioning of the next hop address in the routing table will correspond to the actual destination address. 
     With reference to  FIG. 39 , yet another routing table configuration is illustrated. The basic configuration of the lighting network shown in  FIG. 39  is the same as that of  FIG. 38 . The only difference is that the addresses for the respective lighting nodes have been reassigned to facilitate the creation of very condensed routing tables. An exemplary routing table for lighting node  9  is shown below (Table F). 
     
       
         
           
               
               
               
             
               
                   
                 TABLE F 
               
               
                   
                   
               
               
                   
                 Criterion 
                 Next Hop Address 
               
               
                   
                   
               
             
            
               
                   
                 Destination &lt; 9 
                  7 
               
               
                   
                 Destination = 10 
                 10 
               
               
                   
                 Destination &gt; 10 
                 11 
               
               
                   
                   
               
            
           
         
       
     
     As illustrated, the routing table only has two fields, and instead of determining the next hop address based on an actual destination address or a group in which the actual destination address resides, routing criteria is defined for selecting the next hop address. The routing criteria are based on a range in which the destination addresses fall, and in certain instances, the actual destination address. For example, and again using lighting node  9 , the next hop address for any destination address less than  9  is destination address  7 . The next hop address for any destination address greater than  10  is destination address  11 . Finally, if the destination address is  10 , the next hop is destination address  10 . This embodiment illustrates the concept of assigning addresses to the various lighting nodes within the individual zones (or groups) and the overall system as a whole, with an eye toward the routing tables. With routing tables in mind, addresses may be assigned to the various lighting nodes in a manner that greatly reduces the number of entries in the routing tables, and wherein at least certain next hop address selections are based on a range in which the destination address falls. These improvements in routing may be used in virtually any networking scheme, and are not limited solely to lighting applications. 
     While the embodiments described above were focused on a troffer-type lighting fixture  10 , the concepts disclosed herein apply to any type of lighting fixture. For example, a recessed-type lighting fixture  10 ′ as illustrated in  FIG. 40  may also incorporate all of the concepts described above. As illustrated, the lighting fixture  10 ′ includes a main housing  12 ′, a lens  14 ′, and an electronics housing  26 ′. The various modules described above may be housed within the electronics housing  26 ′ or attached thereto, outside of or within supplemental plenum rated enclosures. These configurations will vary based on the particular application. However, the concepts of a modular system that allows any of the modules to be readily replaced and new modules added are considered to be within the scope of the present disclosure and the claims that follow. 
     The present disclosure relates to a lighting network where control of the lighting fixtures in the network may be distributed among the lighting fixtures. The lighting fixtures may be broken into groups that are associated with different lighting zones. At least some of the lighting fixtures will have or be associated with one or more sensors, such as occupancy sensors, ambient light sensors, and the like. Within the overall lighting network or the various lighting zones, the lighting fixtures may share sensor data from the sensors. Each lighting fixture may process sensor data provided by its own sensor, a remote standalone sensor, or lighting fixture, and process the sensor data according to the lighting fixture&#39;s own internal logic to control operation of the lighting fixture. The lighting fixtures may also receive control input from other lighting fixtures, control nodes, light switches, and commissioning tools. The control input may be processed along with the sensor data according to the internal logic to further enhance control of the lighting fixture. 
     Accordingly, control of the lighting network of the present disclosure is decentralized so that each lighting fixture essentially operates independently of the lighting network; however, the internal logic in each of the lighting fixtures is configured so that the lighting fixtures may act in concert as a group. While acting in concert, each lighting fixture may operate in a different manner depending on the goals for the particular lighting application. The lighting fixtures may also respond to any user inputs that are presented. 
     In one embodiment, a lighting fixture having a light sensor, a solid-state light source, and associated circuitry is provided. The circuitry is adapted to determine that a given lighting fixture of a plurality lighting fixtures is entering a lightcast mode. Via the light sensor, the circuitry will monitor for a first lightcast signal provided by the given lighting fixture and effect generation of grouping data for the given lighting fixture based on receipt of the first lightcast signal. The grouping data may be used, at least in part, for grouping the lighting fixture with one or more of the plurality of lighting fixtures. For grouping the lighting fixture with one or more of the plurality of lighting fixtures, the circuitry may send the grouping data to a remote entity, which will determine how to group the plurality of lighting fixtures, and receive information identifying a group to which the lighting fixture belongs. Alternatively, the circuitry may send the grouping data to one of the plurality of lighting fixtures that will determine how to group the plurality of lighting fixtures. 
     For grouping the lighting fixture with one or more of the plurality of lighting fixtures, the circuitry may process the grouping data along with other grouping data received from one or more of the plurality lighting fixtures to determine a group of the plurality of lighting fixtures in which the lighting fixture belongs. If the first lightcast signal is detected, the grouping data may be indicative of a relative signal strength of the lightcast signal. 
     In another embodiment, the circuitry may be adapted to enter the lightcast mode and then drive the solid-state light source to provide a second lightcast signal to be monitored by the plurality of lighting fixtures. In advance of providing the lightcast signal, the circuitry may send, to the plurality of lighting fixtures, an instruction to begin monitoring for the second lightcast signal. 
     The circuitry may be further adapted to receive remote sensor data from at least one of the plurality of lighting fixtures and drive the solid-state light source based on the remote sensor data. As such, the circuitry may determine local sensor data from the light sensor or another local sensor of the lighting fixture and drive the solid-state light source based on both the remote sensor data and the local sensor data. The circuitry may also send the local sensor data to at least one of the plurality of lighting fixtures. 
     The circuitry may also identify a group of the plurality of lighting fixtures to which the lighting fixture has been assigned and drive the solid-state light source in response to an instruction intended for the group. Each lighting fixture may be assigned to just one group or may be assigned to multiple groups in the case of overlapping groups, which share at least one lighting fixture. 
     The circuitry may be split into a driver module that is adapted to drive the solid-state light source and a communications module that is adapted to communicate with the plurality of lighting fixtures and control the driver module. The driver module and the communications module communicate with one another over a communications bus. 
     In yet another embodiment, a lighting network is provided with a plurality of lighting fixtures having associated light sensors. During a monitor mode, each of the plurality of lighting fixtures is adapted to determine that a given lighting fixture of the plurality lighting fixtures is entering a lightcast mode; via the light sensor, monitor for a lightcast signal provided by the given lighting fixture; and effect generation of grouping data for the given lighting fixture based on receipt of the first lightcast signal. During a receive mode, each lighting fixture will drive an associated solid-state light source to provide the lightcast signal for monitoring by others of the plurality of lighting fixtures. Each of the plurality of lighting fixtures may be automatically assigned to at least one of a plurality of groups based on the grouping data. 
     The grouping data associated with any two of the plurality of lighting fixtures may indicate a relative magnitude of the lightcast signal, which was provided by a first of the two, and received by a second of the two. Further, each of the plurality of lighting fixtures may be adapted to exchange the grouping data that is gathered for others of the plurality of lighting fixtures and automatically assign itself to one of a plurality of groups based on the grouping data, such that each of the plurality of groups comprises those lighting fixtures that were able to detect the lightcast signal from other lighting fixtures in the particular group. Alternatively, each of the plurality of lighting fixtures may be adapted to exchange the grouping data that is gathered for others of the plurality of lighting fixtures and automatically assign itself to one of a plurality of groups based on the grouping data, such that each of the plurality of groups comprises those lighting fixtures that were able to detect, at a magnitude above a set threshold, the lightcast signal from other lighting fixtures in the particular group. 
     The grouping data gathered by each of the plurality of lighting fixtures may be sent to a remote entity, which assigns the plurality of lighting fixtures to groups based on the grouping data. The grouping data gathered by each of the plurality of lighting fixtures may also be sent to one of the plurality of lighting fixtures, which assigns the plurality of lighting fixtures to groups based on the grouping data. 
     Also, each lighting fixture may be adapted to share sensor data from its light sensor or another associated sensor with others of the plurality of lighting fixtures, and control light output based on the sensor data in light of its own internal logic. The internal logic may be configured such that each of the plurality of lighting fixtures operates independently from one another while providing light in a concerted fashion. 
     In yet another embodiment, a lighting network is provided with a group of lighting fixtures, which have sensors and solid-state light sources. Each lighting fixture of the group of lighting fixtures may be adapted to coordinate with at least one of the of the group of lighting fixtures to determine a light output level, and drive the solid-state light sources to provide the light output. At least certain of the group of lighting fixtures will concurrently provide a different light output level. Different subgroups of the group of lighting fixtures may provide different light output levels or output levels that are graduated among the group of lighting fixtures. The light output level for each lighting fixture may be determined, at least in part, on ambient light. The amount of ambient light may be detected via the light sensor of the lighting fixture. Notably, the light output level for each lighting fixture may be determined, at least in part, on an amount of ambient light detected via a light sensor of another lighting fixture of the group of lighting fixtures. 
     Each of the plurality of lighting fixtures, including the group of lighting fixtures, may be adapted to determine that a given lighting fixture of the plurality of lighting fixtures is entering a lightcast mode; via the light sensor, monitor for a lightcast signal provided by the given lighting fixture; and effect generation of grouping data for the given lighting fixture based on receipt of the first lightcast signal. Each of the plurality of lighting fixtures may drive an associated solid-state light source to provide the lightcast signal for monitoring by others of the plurality of lighting fixtures. Each of the plurality of lighting fixtures may be automatically assigned to at least one of a plurality of groups based on the grouping data. 
     The present disclosure relates to a lighting network where control of the lighting fixtures in the network may be distributed among the lighting fixtures. The lighting fixtures may be broken into groups that are associated with different lighting zones. At least some of the lighting fixtures will have or be associated with one or more sensors, such as occupancy sensors, ambient light sensors, and the like. Within the overall lighting network or the various lighting zones, the lighting fixtures may share sensor data from their sensors. Each lighting fixture may process sensor data provided by its own sensor, a remote standalone sensor, or lighting fixture, and process the sensor data according to the lighting fixture&#39;s own internal logic to control operation of the lighting fixture. The lighting fixtures may also receive control input from other lighting fixtures, control nodes, light switches, commissioning tools, gateways, and remote devices via the Internet or other like network. The control input may be processed along with the sensor data according to the internal logic to further enhance control of the lighting fixture. 
     Accordingly, control of the lighting network of the present disclosure may be decentralized so that each lighting fixture essentially operates independently of the lighting network; however, the internal logic in each of the lighting fixtures is configured so that the lighting fixtures may act in concert as a group. While acting in concert, each lighting fixture may operate in a different manner, such as providing different light output levels, depending on the goals for the particular lighting application. The lighting fixtures may also respond to any user inputs that are presented. 
     In one embodiment, each lighting fixture includes a solid-state light source and circuitry to control operation. In particular, the circuitry is adapted to receive remote sensor data from at least one other lighting fixture and drive the solid-state light source based on the remote sensor data. The lighting fixture may include a local sensor, such as an ambient lighting sensor, occupancy sensor, or the like. With the local sensor, the circuitry is further adapted to determine local sensor data from the local sensor and drive the solid-state light source based on both the remote sensor data and the local sensor data. The local sensor data may also be sent to other lighting fixtures, which may use the local sensor data to help control those lighting fixtures. In addition to controlling the lighting fixtures, sensor activity can show use patterns in fine detail. Some examples would be occupancy sensor patterns within a room showing what areas are used in a room over an extended time period, or the ambient light sensors showing how efficiently daylight is being captured and distributed from the windows to the room. 
     As such, these lighting fixtures may share their sensor data with other lighting fixtures in a lighting network and control their light output based on the local and remote sensor data in view of their own internal logic. The internal logic is configured such that each of the lighting fixtures operates independently from one another while providing light or functionality in a concerted fashion. 
     For example, a switch may be used to turn on all of the lighting fixtures in a particular zone. However, the amount of light provided by the various lighting fixtures may vary from one lighting fixture to the next based on the amount of ambient light present in the different areas of the lighting zone. The lighting fixtures closer to windows may provide less light or light of a different color or color temperature than those lighting fixtures that are near an interior wall. 
     The present disclosure relates to a lighting network where control of the lighting fixtures in the network may be distributed among the lighting fixtures. The lighting fixtures may be broken into groups that are associated with different lighting zones. At least some of the lighting fixtures will have or be associated with one or more sensors, such as occupancy sensors, ambient light sensors, and the like. Within the overall lighting network or the various lighting zones, the lighting fixtures may share sensor data from their sensors. Each lighting fixture may process sensor data provided by its own sensor, a remote standalone sensor, or lighting fixture, and process the sensor data according to the lighting fixture&#39;s own internal logic to control operation of the lighting fixture. The lighting fixtures may also receive control input from other lighting fixtures, control nodes, light switches, and commissioning tools. The control input may be processed along with the sensor data according to the internal logic to further enhance control of the lighting fixture. 
     Accordingly, control of the lighting network of the present disclosure may be decentralized so that each lighting fixture essentially operates independently of the lighting network; however, the internal logic in each of the lighting fixtures is configured so that the lighting fixtures may act in concert as a group. While acting in concert, each lighting fixture may operate in a different manner, such as providing different light output levels, depending on the goals for the particular lighting application. The lighting fixtures may also respond to any user inputs that are presented. 
     In such a lighting system, the lighting fixtures need to communicate information between them, and in many instances, route information in the form of data packets from one lighting fixture to another. As such, the lighting fixtures may generate data packets and route them to another lighting fixture, which may process the information in the data packet or route the data packet toward another lighting fixture. 
     In a first embodiment, each lighting fixture includes a light source and circuitry to control operation. For providing light output, the circuitry is adapted to drive the lighting source to provide light output. For routing data packets, the circuitry employs a routing table having a next hop address for each of a plurality of destination addresses. Each next hop address is positioned in the routing table based on a corresponding one of the plurality of destination addresses. As such, the plurality of destination addresses need not be used to access the routing table. 
     The circuitry may first determine a position in the routing table based on a destination address of the data packet. Next, the next hop address for the destination address is accessed based on the position in the routing table; and then the data packet is routed toward the next hop address. In essence, the next hop address for each of the plurality of destination addresses may be positioned in the routing table in an order corresponding to a numerical ordering of the plurality of destination addresses. To access the next hop address for the destination address, the circuitry may use the destination address as an index to identify the next hop address for the destination address from the routing table. The routing table may include a number of hops for each next hop address. The number of the plurality of nodes may correspond to a number of positions in the routing table. In one scenario, a value of each destination address directly corresponds to a position that contains a corresponding next hop address in the routing table. 
     In a second embodiment, the routing table is broken into at least a first section and a second section. The first section includes a next hop address for each of a plurality of groups of lighting fixtures to which the lighting fixture does not belong. The second section comprises a next hop address corresponding to each of a plurality of destination addresses associated with a group of lighting fixtures to which the lighting fixture belongs. 
     In one implementation, the second section comprises each of the plurality of destination addresses in association with the corresponding next hop address. The next hop address is accessed based directly on the corresponding destination address. In another implementation, each next hop address is positioned in the routing table based on a corresponding one of the plurality of destination addresses such that the plurality of destination addresses are not used to access the routing table. 
     If the data packet is intended for one of the plurality of groups of lighting fixtures to which the lighting fixture does not belong, the circuitry will access the first section and determine the next hop address based on the one of the plurality of groups of lighting fixtures to which the lighting fixture does not belong. If the data packet is intended for the group of lighting fixtures to which the lighting fixture belongs, the circuitry will access the second section to determine the next hop address for the data packet. Once the next hop address is identified, the circuitry will route the data packet toward the next hop address. 
     In a third embodiment, a lighting fixture comprising routing criteria is provided that has a next hop address for each of at least two ranges of destination addresses. When routing a data packet toward one of the at least two ranges of destination addresses, the circuitry will first determine a destination address for the data packet. Next, the circuitry will select a next hop address from the routing criteria based on one of the at least two ranges of destination addresses in which the destination address falls; and then route the data packet toward the next hop address. The routing criteria may also include a next hop address for at least one destination address. If the next hop address is directly associated with a destination address instead of a range of addresses, the circuitry will determine a destination address for the data packet, select a next hop address from the routing criteria based on the at least one destination, and route the data packet toward the next hop address. 
     The present disclosure relates to a lighting network where control of the lighting fixtures in the network may be distributed among the lighting fixtures. The lighting fixtures may be broken into groups that are associated with different lighting zones. At least some of the lighting fixtures will have or be associated with one or more sensors, such as occupancy sensors, ambient light sensors, and the like. Within the overall lighting network or the various lighting zones, the lighting fixtures may share sensor data from their sensors. Each lighting fixture may process sensor data provided by its own sensor, a remote standalone sensor, or lighting fixture, and process the sensor data according to the lighting fixture&#39;s own internal logic to control operation of the lighting fixture. The lighting fixtures may also receive control input from other lighting fixtures, control nodes, light switches, and commissioning tools. The control input may be processed along with the sensor data according to the internal logic to further enhance control of the lighting fixture. 
     Accordingly, control of the lighting network of the present disclosure may be decentralized so that each lighting fixture essentially operates independently of the lighting network; however, the internal logic in each of the lighting fixtures is configured so that the lighting fixtures may act in concert as a group. While acting in concert, each lighting fixture may operate in a different manner, such as providing different light output levels, depending on the goals for the particular lighting application. The lighting fixtures may also respond to any user inputs that are presented. 
     In one embodiment, a handheld device may be used to setup, configure, and control the various lighting fixtures through wired or wireless communications means once the lighting fixtures are installed in a lighting network. The handheld device may be used to configure the internal logic of the various lighting fixtures to operate in a desired, coordinated fashion; assign the lighting fixtures to groups associated with defined lighting zones; reassign the lighting fixtures to other groups, and the like. For grouping, the handheld device may be configured to receive grouping data from the various lighting fixtures and group the lighting fixtures based on the grouping data. Once the groups have been determined, the handheld device may inform each lighting fixture of the group or groups to which the lighting fixture has been assigned. 
     The present disclosure relates to a lighting fixture that includes a driver module and at least one other module that provides a lighting fixture function, such as a sensor function, lighting network communication function, gateway function, and the like. The driver module communicates with the other modules in a master/slave scheme over a communication bus. The driver module is configured as a slave communication device, and the other modules are configured as master communication devices. As such, the other modules may initiate communications with the driver to send information to or retrieve information from the driver module. 
     In one embodiment, a lighting fixture is provided that includes a driver module and a communications module. The driver module is adapted to drive an associated light source and to facilitate communications over a communication bus as a slave communication device. The communications module is adapted to facilitate wireless communications with other elements in a lighting network and communicate as a master communication device with the driver module over the communication bus. The lighting fixture may also include an auxiliary module adapted to provide a lighting fixture function for the lighting fixture as well as facilitate communications as a master communication device with the driver module over the communication bus. Being master communication devices, both the auxiliary device and the communications module may initiate communications with the driver module. The driver module may be adapted to receive AC power and provide DC power to the communications module and the auxiliary module. The communication bus may be a serial communication bus, such as an I 2 C bus. 
     Communications with the driver module may include requesting information from the driver module and transferring information to the driver module. The auxiliary module may be configured to have 1) an occupancy sensor wherein the lighting fixture function is detecting occupancy, 2) an ambient light sensor wherein the lighting fixture function is detecting ambient light, and 3) a communication gateway wherein the lighting fixture function is providing a wireless communication gateway to at least one of a remote device and a network outside of the lighting network. 
     In one scenario, the communications module is adapted to wirelessly receive first information from one of the other elements of the lighting network and, as the master communication device, initiate transfer of the first information to the driver module, which will control the light source based on the first information. Further, the auxiliary module may include a sensor and be adapted to determine second information bearing on an output of the sensor. As the master communication device, the auxiliary module may initiate transfer of the second information to the driver module, which will control the light source based on the second information. 
     The communications module may be adapted to wirelessly receive information from one of the other elements of the lighting network and, as the master communication device, initiate transfer of the information to the driver module, which will control the light source based on this information. 
     The driver module may be further adapted to communicate with a remote switch via the communication bus, wherein the remote switch is also configured as a master communication device, which is adapted to initiate transfer of switch information to the driver module, which will control the light source based on the switch information. 
     The present disclosure relates to lighting fixtures for use in a lighting network where the lighting fixtures and other elements are able to communicate with each other via wired or wireless communication techniques. When the lighting network is being formed or modified, the lighting fixtures may be able to communicate with each other and automatically determine a single lighting fixture to act as a coordinator during a commissioning process. In essence, the lighting fixtures can exchange their communication addresses, such as MAC addresses, wherein the lighting fixture with the lowest (or highest) normal communication address becomes the coordinator. The coordinator may also be configured to assign short addresses to use for communications once the lighting network is formed instead of the longer MAC, or like, addresses. The short addresses can reduce routing overhead, and thus make the routing of messages including control information, sensor data, and the like, more efficient. 
     In one exemplary embodiment, a lighting fixture is provided that has a first address and is intended to be employed in a lighting network with any number of elements. The lighting fixture generally includes a light source, a communication interface, and circuitry for controlling the lighting fixture. In addition to controlling the light source, the circuitry is adapted to receive from a first remote lighting fixture a first ‘join my network’ message, which includes a second address for the first remote lighting fixture. The circuitry will compare the first address with the second address. If the first address does not have a predefined relationship with the second address, the circuitry may recognize the first remote lighting fixture as the coordinator for the lighting network. If the first address has the predefined relationship with the second address, the circuitry may set its own lighting fixture as the coordinator for the lighting network. The predefined relationship may simply be whether the first address is higher or lower than the second address; however, the concepts disclosed herein are not limited to these two relationships. 
     If short addresses are to be used, the circuitry may generate a short address for the first remote lighting fixture and send the short address to the first remote lighting fixture, if the first address has the predefined relationship with the second address. In this case, the lighting fixture will, at least temporarily, consider itself the coordinator for the first remote lighting fixture. Again, the first short address is shorter than the first address. For example the first address may be a 64-bit MAC address, and the short address may be an 8, 16, or 24-bit address or the like. The circuitry will send the first short address to the first remote lighting fixture. If the first address does not have the predefined relationship with the second address, the circuitry may wait to receive a first short address for the lighting fixture to use for communications within the lighting network, wherein the first short address is shorter than the first address. 
     The lighting fixture may receive ‘join my network’ messages from different lighting fixtures during the commissioning process. The lighting fixture may initially think it is the coordinator relative to one remote lighting fixture during a first exchange and the then give up its coordinator role during a second exchange with another remote lighting fixture. For example, the circuitry may be adapted to receive from a second remote lighting fixture a second ‘join my network’ message including a third address for the second remote lighting fixture, and compare the first address with the third address. If the first address does not have the predefined relationship with the third address, the circuitry may recognize the first remote lighting fixture as the coordinator for the lighting network. If the first address has the predefined relationship with the third address, the circuitry may set its own lighting fixture as the coordinator, at least temporarily, for the lighting network. 
     When the lighting fixtures are mostly routing nodes for a mesh network, the circuitry for the lighting fixture that ultimately becomes the coordinator may assign short addresses to each of the non-routing elements, which may include sensor modules, switch modules, certain lighting fixtures, and the like in the lighting network. 
     The circuitry for the coordinator may effect delivery of instructions to the various elements, both routing and non-routing, to initiate a grouping process, wherein the elements coordinate with each other to form a plurality of groups of elements. The grouping process may employ lightcasting processing wherein as one element emits a lightcast signal, other ones of the elements monitor the lightcast signal to determine lightcast data that is used determine the plurality of groups of elements. One or more elements, such as a coordinator, may collect the lightcast data from the other ones of the elements as well as send to the other ones of the elements information that identifies a group to which each of the ones of the elements are assigned. The coordinator may actually determine the groups or use a remote entity, such as a commissioning tool or other control system, to determine the groups. Alternatively, certain of the elements may exchange all of the data and independently identify themselves with a group. 
     The present disclosure relates to lighting fixtures for use in a lighting network where the lighting fixtures and other elements are able to communicate with each other via wired or wireless communication techniques. When the lighting network is being formed or modified, a lighting fixture is selected to act as a coordinator for forming the lighting network. For example, a user may employ a commissioning tool to select a particular lighting fixture as the coordinator. The coordinator will send out one or more ‘join my network’ messages toward the other elements of the lighting network. The elements that receive the ‘join my network’ message may respond in order to make the coordinator aware of their presence and join them to a lighting network. 
     In certain embodiments, the coordinator will assign short addresses to itself and to the other elements in the lighting network. While the elements already have MAC or like addresses, once the short addresses are assigned, the elements of the routing network will use the short addresses for normal communications. The short addresses can reduce routing overhead, and thus make the routing of messages including control information, sensor data, and the like, more efficient. 
     The lighting network may be a mesh network formed from the various elements wherein some elements act as routing nodes and other elements act as non-routing nodes. For example, some or all of the lighting fixtures may be routing nodes while switches, stand-alone sensors, and the like may be non-routing nodes in select embodiments. However, there is no limitation as to whether a particular type of element can be configured as a routing or non-routing element. 
     The coordinator may effect delivery of instructions to the various elements, both routing and non-routing, to initiate a grouping process, wherein the elements coordinate with each other to form a plurality of groups of elements. The grouping process may employ lightcasting processing wherein as one element emits a lightcast signal, other ones of the elements monitor the lightcast signal to determine the plurality of groups of elements. One or more elements, such as a coordinator, may collect the lightcast data from the other ones of the elements as well as send information to the other ones of the elements that identifies a group to which each of the ones of the elements are assigned. The coordinator may actually determine the groups or it may use a remote entity, such as a commissioning tool or other control system, to determine the groups. Alternatively, certain of the elements may exchange all of the data and independently identify themselves with a group. 
     Those skilled in the art will recognize improvements and modifications to the embodiments of the present disclosure. All such improvements and modifications are considered within the scope of the concepts disclosed herein and the claims that follow.