Abstract:
A visible light communication system identifies the location of a mobile device using light intensities corrected by mobile device orientation. This location can be used to generate a dynamic cluster of visible light transmitters about the mobile device providing improved “handoff” between transmitters and reduced shadowing.

Description:
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     This invention was made with government support under CNS1318292, CNS1343363, CNS1350039, and CNS1404613 awarded by the National Science Foundation. The government has certain rights in the invention. 
    
    
     CROSS REFERENCE TO RELATED APPLICATION 
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     BACKGROUND OF THE INVENTION 
     The present invention relates to systems for accurately locating mobile devices, and in particular to a system providing location-aware visible light communication. 
     Increased use of light emitting diodes (LEDs) to provide for the primary environmental lighting in buildings and the like (termed herein “ambient lighting”) has raised the possibility of using these lights for data communication. Such data communication systems take advantage of the ability of the LEDs to switch on and off at a high rate of speed imperceptible to human eyes but suitable for communicating data. The IEEE 802.1 5.7 standard has established a basis for visible light communication protocols allowing communication of up to 96 megabits per second. 
     While such visible light communication is practical for point-to-point communication with a stationary device, ideally, such a system could supplant standard wireless radio communication used for mobile devices such as cell phones and the like. Extending visible light communication to such devices, however, raises a number of problems including sharing bandwidth when multiple users are present and shadowing of the mobile device (for example, by the user&#39;s body). 
     SUMMARY OF THE INVENTION 
     The present invention provides a system that can determine the location of a mobile device using the light communication signals by analyzing the intensity of the signals from various light fixtures (of known position) adjusted by a measured orientation of the mobile device. This location information may be used to generate dynamic clusters of light fixtures that follow the user with motion of the mobile device, allowing a reduced number of light fixtures to be dedicated to a particular user while reducing shadowing and interruptions during handoff between light fixtures. 
     The present invention generally provides a system that moves beyond localization using radio waves, which are far less predictable in their falloff with distance, by correcting for the confounding problem of inherent sensitivity of light signal measurement to mobile device orientation. 
     Specifically, the invention provides a location-aware communication system for mobile devices including a plurality of light transmission units spatially dispersed in an area through which a mobile device may move, the light transmission units outputting a light signal into the area including an identifier for each given light transmission unit; a mobile device and a location server communicating with the mobile device. The mobile device includes a light sensor for receiving light from a set of the light transmission units and processing that light to extract the identifier of the light transmission units of the set and an intensity of the light signal and an orientation sensing system sensing an orientation of the mobile device. The mobile device and location server execute stored programs held in non-transitory medium to: (i) for each given light transmission unit of the set, determine an intensity of the light signal received at the mobile device by the light sensor, (ii) identify at least one possible location of the mobile device with respect to the given light transmission unit of the set based on a relationship between intensity of the light signal and location of the mobile device corrected for orientation of the mobile device; and (iii) use the at least one possible location of the mobile device to determine a single location of the mobile device with respect to the light transmission units of the set. 
     It is thus a feature of at least one embodiment of the invention to provide a system that allows mobile devices to identify their location without the need for auxiliary location hardware such as radio beacons or the like. 
     The orientation sensor system may sense roll and/or pitch. 
     It is thus a feature of at least one embodiment of the invention to make use of common orientation sensors in mobile devices to correct for changes in light sensor sensitivity as the light sensor moves from an optimal vertical orientation. 
     In addition, the orientation sensor system may sense yaw of the device with respect to a predefined azimuth heading. 
     It is thus a feature of at least one embodiment of the invention to determine a “compass bearing” direction in which the light sensor is oriented such as preferentially may receive light from certain directions. 
     The correction of the intensity of the light signal at the mobile device may use predetermined relationships between light dispersion from the given light transmission unit as a function of angle and light sensitivity of the mobile device light sensor unit as a function of angle, and a determination of a degree of alignment between the light transmission unit and the light sensor unit based on the orientation of the mobile device. 
     It is thus a feature of at least one embodiment of the invention to correct for the primary variability in receive light signal intensity using the known angular gain curves of the light transmitter and light receiver thereby allowing light intensity to be used for localization. 
     The system may collect possible locations of the mobile device with respect to multiple given light transmission units to determine a single location of the mobile device with respect to the light transmission units of the set. In one example, the system may find an intersection of possible locations determined among different given light transmission units to determine the single location among an intersection of the possible locations. 
     It is thus a feature of at least one embodiment of the invention to permit a trilateralization type location using multiple light transmitters for improved accuracy and reduced noise influence. 
     The mobile device may further include at least one movement sensor that may calculate movement since a last determined single location. In this case, the determined single location may be determined by locations deduced by light intensity and the movement since the last determined signal location. 
     It is thus a feature of at least one embodiment of the invention to augment light intensity-based location sensing with dead reckoning to minimize the number of light sources necessary for localization or to refine that localization. 
     The light sensor may be a single photosensing element providing an identification of the possible location with respect to the given light transmission unit by receiving a light intensity signal from only a single light sensor. 
     It is thus a feature of at least one embodiment of the invention to allow localization without the need to provide an imaging system such as a camera or to use camera functionality if it is available. 
     The location server may communicate with the light transmission units over a network to control the light transmission units, and the single location of the mobile device is used to dynamically define the set of light transmission units to move with the mobile device as the mobile device moves. 
     It is thus a feature of at least one embodiment of the invention to improve the efficiency of allocating light transmitters to mobile devices by following or anticipating movement of the mobile device with a small set of transmitters. 
     The light transmission units of the set may be selected to surround the mobile device to reduce shadowing on the mobile device by a mobile device user. 
     It is thus a feature of at least one embodiment of the invention to provide a mobile experience using visible light communication that better approximates shadow-free performance provided by wireless radio signals. 
     The network may be a powerline communication network communicating data together with power over power lines communicating with the light transmission units. 
     It is thus a feature of at least one embodiment of the invention to provide for the benefits of dynamic clustering of light transmitters without requiring extensive infrastructure changes through the use of existing power wiring. 
     The location server may communicate data to be transmitted synchronously from each of the light transmission units of the set of light transmission units. 
     It is thus a feature of at least one embodiment of the invention to provide improved signal strength and resistance to shadowing by synchronous transmission through a cluster of light transmitters. 
     The light signal maybe visible light and the light transmission units may operate to provide ambient light to the area. 
     It is thus a feature of at least one embodiment of the invention to provide a system that is compatible with the needs for environmental lighting and the distribution of light emitters as is necessary for environmental lighting. 
     The mobile device and the location device may both further include a wireless transceiver for communicating therebetween and wherein data needed to determine the location of the mobile device is communicated from the mobile device to the location server using the wireless transceivers. 
     It is thus a feature of at least one embodiment of the invention to provide a system that does not rely on light transmissions from the wireless device requiring capabilities not typically present in portable wireless devices such as cell phones. 
     These particular objects and advantages may apply to only some embodiments falling within the claims and thus do not define the scope of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a mobile device within an area having multiple light transmission units providing ambient lighting and communicating with a location server and cooperating with the mobile device to locate the mobile device within the area and to provide data to the mobile device; 
         FIG. 2  is a simplified block diagram of each light transmission unit showing the angular dispersion pattern of the light produced by the light transmission unit; 
         FIG. 3  is a figure similar to that of  FIG. 2  showing a block diagram of the mobile device and the angular sensitivity pattern of a light sensor on the mobile device; 
         FIG. 4  is a simplified top plan view of the light transmission units of  FIG. 3  showing a clustering provided by one embodiment of the invention to select light transmitting units around the location of the mobile device to reduce shadowing and to provide more uniform transitions as the mobile device moves and showing an optional clustering pattern to anticipate that movement; 
         FIGS. 5 a  and 5 b    are simplified top plan views of the expected intensity detection patterns of a given light transmitting unit with respect to two different orientations of the mobile unit, the latter depicted in elevation; 
         FIG. 6  is a top plan view showing possible locations of the mobile device with respect to two light transmitting units and depicting the determination of a single mobile device location using a combination of possible positions calculated with respect to two light transmitting units and a projected trajectory determined by dead reckoning; 
         FIG. 7  is a flowchart showing the operation of the light transmitting units under control of a system typically including the location server and at least one mobile device; and 
         FIG. 8  is a detailed flowchart of the calculation of location. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to  FIG. 1 , the present invention may provide for a locator system  10  operating within a volume  12 , for example, the interior of a structure such as a store, office building, hospital, airline terminal or the like, having a floor area  14  over which users  16  may move together with the users&#39; wireless devices  18 . 
     Volume  12  may be illuminated, for example, by ceiling mounted luminaires  20 , in one example, each projecting a downward cone  22  of visible light to illuminate the floor area  14  as is generally understood in the art. The volumes of the cones  22  will typically overlap for the purpose of providing uniform lighting; however, overlap is not critical to the present invention. The term cone is used generally in this application, it being understood that the shape of the illuminated region for a given luminaire is highly variable and that the boundaries of projected light are generally gradated and indistinct. 
     Each of the luminaires  20  may communicate data with a location server  24  over a network  23 . In one embodiment, the network  23  makes use of power line communication in which communication signals are impressed upon standard power wiring simultaneously used to provide power to the luminaires  20 . This powerline communication largely eliminates the need for a separate wiring in the installation of the present invention. Commercial powerline communication transmitter and receiver, following the IEEE 1901 (HomePlug) standard, are already available on the market. 
     The location server  24  may include a computer processor  26  communicating with a memory  28  holding a stored program and stored data  30  for implementing the invention that will be described below. In one embodiment, the location server  24  may also connect with one or more wireless access points  32  which may communicate via radio waves  34  data between the location server  24  and the mobile devices  18 , for example, using the IEEE 802.11 (Wi-Fi) standard. In a principal embodiment, this data is largely one way, passing from the mobile devices  18  to the location server  24  to conserve radio wave bandwidth. The location server  24  may also generally communicate with the Internet  25  and with various terminals  27  providing data to individuals attached thereto as is generally understood in the art. 
     Referring now to  FIG. 2 , each of the luminaires  20  may connect to powerline  35  which also provides the network  23  using powerline communication as discussed above. The powerline  35  may connect to an internal power regulator  36  for converting high-voltage AC power into power levels suitable for operation of the luminaire  20  and its components and to a communication modulator/demodulator  38  which extracts high-frequency Ethernet protocol information from the same conductors used as the network  23 . In this case, a similar modulator/demodulator  38  connects the network  23  to the location server  24 . 
     The modulator/demodulator  38  in each luminaire  20  may provide unidirectional or bidirectional communication between the location server  24  and a processor  40  in the luminaire  20 . This latter processor  40  may communicate with a memory  42  holding a program  45  for execution, program instructions, data, and one or more illumination models  44  that will be described below. The program instructions may be used with the stored program and data  30  in the location server  24  and to implement the present invention as will be discussed. 
     The processor  40  may also communicate with a luminaire power control module  46  providing electrical power (for example, controlled in-current and power) to a bank of light emitting diodes (LED)  48 , for example, positioned within a reflector/light shield  50  projecting the downward cone  22 . The power control module  46  may provide the desired operating characteristics of the LEDs  48  in producing the desired high average power output commensurate with providing illumination to the area  14  and may also provide for a high-frequency modulation of the LEDs  48  above the flicker rate perceptible to the human eye. As will be understood in the art, the intensity of the light from the LEDs  48  as a function of the angle of the light within the cone  22  (from a center line  53  of the illumination, normally vertically directed) will provide an intensity profile  52  that may be pre-characterized at the factory and stored in a illumination model  44 . This intensity profile  52  is dependent on the arrangement and characteristics of the LEDs  48  and the surrounding reflector/light shield  50 . The LEDs  48  may be white LEDs employing phosphors or without phosphors but using different colored red, green and blue LEDs for higher modulation speeds. 
     Referring now to  FIG. 3 , the mobile device  18  may be, for example, a standard smart phone, tablet or the like and provides a housing  60  that may be conveniently carried with the user  16  having an exposed display touch surface  62  or the like for providing input and output communication with the user  16 . A processor  63  within the mobile device  18  may communicate with an internal memory  64  holding a stored program  67  whose operation in conjunction with other programs discussed below implement the present invention. 
     Generally, as is understood in the art, the processor  63  may also communicate with a Wi-Fi transceiver  68  allowing communication of data by radio waves  34  with the wireless access points  32  discussed above with  FIG. 1 . Importantly, the processor  63  also communicates with an orientation sensor systems  70  including but not limited to a three-axis accelerometer, magnetometers and a three-axis gyroscope that serve to provide an indication of the orientation of the housing  60  with respect to gravity and the Earth&#39;s magnetic field, as well as providing motion signals (linear and angular accelerations) that allow for inertial-based guidance or dead reckoning to identify the location and orientation of the mobile device  18  for short periods of time through the multiple integration of accelerations into positional changes. 
     The mobile device  18  may also include a light sensor  72  which may, for example, be a single photodiode or phototransistor or a pixel on a CCD camera device. Notably, the present invention does not require any characterization of the angle of the received light with respect to other light sensors, for example, as would be obtainable through the spatial mapping of a CCD camera with multiple pixels. 
     The light sensor  72  will nevertheless have an angular sensitivity characteristic  74  indicating its sensitivity at various angles with respect to an axis  75  normal to the detecting surface of the sensor  72 . Generally the sensor  72  is fixed relative to the housing  60  and thus the orientation of axis  75  may be deduced using the orientation sensor system  70  discussed above. The sensitivity characteristic  74  may be stored as a model  66  in the memory  64 . Desirably, the angular sensitivity characteristic  74  will be substantially uniform over a given angular range of as much as 180 degrees; however, most light sensors  72  provide significant sensitivity variation in as little as 60 degrees. For this reason, a fisheye lens  73  or the like may be placed over the light sensor  72  to decrease angular sensitivity in conjunction with other techniques described herein for managing this angular sensitivity variation. 
     Referring now to  FIG. 1  and  FIG. 7 , the location server  24  and the luminaires  20  will cooperate to control the luminaires  20 , as indicated by process block  80 , to transmit, one at a time from each luminaire  20 , a beacon signal providing a luminaire identification code uniquely indicating the identity of a given luminaire  20 . This identification code may be transmitted, for example, with the illumination model  44  of the luminaire&#39;s distribution pattern  52  or this latter information may be provided only to the location server  24 . During this transmission, the light from the other luminaires  20  is held constant or may be momentarily switched off to provide greater signal-to-noise in the transmitted beacon signal. 
     In between each transmission or periodically with respect to each transmission of process block  80 , multiple luminaires  20  of a cluster (whose identity will be described below) may operate synchronously as indicated by process block  82  to transmit data to one or more mobile devices  18 . This data, for example, may be streamed audio or video data or any type of data normally desired by the user  16  of the mobile device  18  and will be obtained from the location server  24  over the network  23 , for example, as downloaded from the Internet  25 . 
     At process block  84  the location server  24 , optionally in conjunction with the mobile device  18  and the luminaires  20 , may calculate a location of a given mobile device  18  from data uploaded from the mobile device  18 , for example, over the radio link. This process will be described in much greater detail below. 
     After the location of the mobile device  18  is determined, at process block  86  the cluster of luminaires  20  used for the transmission of data at process block  82  may be reformulated by the location server  24  based on the location data derived at process block  84 . After this reformulation, the process of process blocks  80 ,  82 ,  84 , and  86  may be repeated. It will be appreciated to the extent these devices (the location server  24 , luminaires  20  and the mobile device  18 ) intercommunicate that these tasks of process blocks  80 ,  82 ,  84  and  86  may be freely distributed among these devices except as constrained by the need for specialized hardware which will be evident from context. 
     Referring now to  FIG. 4 , as noted above with respect to process block  80  and  86 , the luminaires  20  are formed into “clusters”  90  for the purpose of communicating with a given mobile device  18 . Generally, location data derived at process block  84  will be used to construct a cluster  90  defining a set of luminaires  20  including one luminaire  20 ′ closest to the user  16  and other “scout” luminaires  20  on different sides of the user  16  with respect to the luminaire  20 ′. The scout luminaires  20  ideally provide overlapping light at the location of the user  16  such as prevents shadows  91  of the user  16  from falling on the mobile device  18  for all luminaires  20  in the cluster  90 . As the mobile device  18  moves in the area  14 , the luminaires  20  within the cluster  90  are changed so that the center of mass of the cluster (being the weighted distance between the mobile device  18  and each luminaire  20  weighted according to its light output) follows the user  16 . This approach will generally surround the user  16  with luminaires  20 . As will be discussed below, tracking the location of the mobile device  18  allows a trajectory of the device  18  to be determined such as may permit a predicted trajectory  93  of the device  18  to be determined. The center of mass of the cluster  90  may be shifted from the device  18  to a point along the predicted trajectory  93  in order to anticipate movement of the mobile device  18  and to accommodate assumptions about the mobile device  18  being in front of the user  16  as the user  16  moves. The amount of shifting may, for example, be proportional to the speed of movement of the user  16  and may anticipate movement in the orientation of the mobile device  18  as well. The size of the cluster  90  may be increased, for example, by adding frontward cluster areas  90 ′ to the cluster  90  addressing the greater probability of user  16  movement into these forward areas over time and may be skewed along the predicted trajectory  93  depending on the anticipated or current orientation of the mobile device  18 . 
     The number of luminaires  20  in the cluster  90  may be dynamically changed depending on bandwidth demands by a given mobile device but will generally be far fewer than all of the luminaires  20  and may be practically limited to the region just around the user  16 . 
     Determining the set of luminaires  20  in the cluster  90  may be done by using a pre-prepared map linking luminaire identifiers (and hence luminaires  20 ) to particular locations in the volume  12  that can be matched to the location of the mobile device. This map may be held, for example, as data in the location server  24  and may be generated either empirically by moving a photosensor with a constant orientation through the area  14  or by mathematical modeling using the known illumination models  44  and measured positions of the luminaires  20 . Initially, when the mobile device  18  arrives in the area  14 , for example, as detected by radio waves  34  (for example, a Wi-Fi beacon signal) from the mobile device  18 , the cluster  90  may be arbitrarily large to accommodate the fact that the location of the mobile device  18  is not yet been determined. Once the location is determined, the size of the cluster may be reduced. Alternatively, predetermined clusters  90  may be located at entrances to the area  14  with the expectation that they will capture new users  16 . 
     Referring now to  FIG. 8 , the process of identifying the location of the user  16  and the mobile device  18  may begin as indicated by process block  94  by collecting intensity information at the mobile device  18  indicating the light intensity detected by the mobile device  18  from particular luminaires  20 . This intensity information is collected through the light sensor  72  (shown in  FIG. 3 ) and will generally not include any identification of the orientation of the received light but will simply be a list of light intensities and identifications of associated luminaries  20 . 
     At process block  96  the orientation of the mobile device  18  is determined, for example, using the sensor system  70  as described above. This orientation generally determines how vertical axis  75  is (altitude) and, to the extent that the axis  75  is not vertical, in what direction it is tipping (azimuth). Altitude can be determined from a three-axis accelerometer providing an indication of the dominant acceleration of gravity along an x-axis (roll) and y-axis (pitch) of the housing of the portable device  18 . In the case of a smart phone or the like where the light sensor  72  is on a front face of the phone that also provides the touch sensing display, the x-axis will generally be oriented along the long dimension (height) of the housing parallel to the display and y-axis will also be parallel to the display but perpendicular to the x-axis. The azimuth (yaw) will generally be measured about a z-axis perpendicular to the x-axis and y-axis and parallel to the axis  75  using the magnetometer, when possible, augmented by rotational motion sensing by the internal gyroscopes extrapolating from previously determined yaw orientations. 
     Once the orientation of the mobile device  18  is established, an estimate of the location of the mobile device  18  may be determined by a variety of methods. One embodiment of the present invention contemplates that location will be deduced by the intensity of the light from different luminaires  20  of known position. The raw intensity received by the light sensor  72 , however, will normally not yield an accurate location because of the confounding effect of the orientation of the mobile device  18  on those intensities. That is, the intensity of light from a given luminaire  20  will vary significantly depending on the orientation of the mobile device  18  as either facing toward or away from that luminaire  20 . Accordingly, at process block  98 , information conveyed by the intensities and known locations of the associated luminaires  20  is corrected by the information of orientation available from process block  96 . 
     Referring momentarily to  FIGS. 5 a  and 5 b   , a given luminaire  20  may have a well-described illumination pattern described by the illumination model  44  associated with the luminaire  20  and as represented in  FIG. 5  by the intensity iso-curves  100 , each following a path of constant intensity of received light. For a conical light pattern, the iso-curves  100  will generally be concentric circles about the location of the luminaire  20 . The actual light detected by the mobile device  18  will depend on its orientation, however, so that when the mobile device  18  is oriented so that axis  75  is substantially vertical, a given intensity reading associated with the luminaire  20  will place the mobile device  18  on one of the iso-curves  100  based on the received intensity weighted by the sensitivity characteristic  74  of the mobile device  18 . This iso-curve  100  describes a locus of possible location points. 
     As shown in  FIG. 5 b   , however, if the mobile device  18  is tipped such that axis  75  has an altitude of, say, 45 degrees (toward the left as shown in  FIG. 5 b   ), the effective iso-curves  100  as detected by the mobile device  18  will shift rightward with respect to the location of the luminaire  20  as a result of the preferential sensitivity of the mobile device  18  in the left direction. The exact amount of shifting will depend on the curve  74  which will also tend to distort the iso-curves  100 . 
     Based on this observation, knowledge of the orientation of the mobile device  18  derived at process block  96  may correct the received intensity information, for example, by adjusting the expected modeled iso-curves  100  associated with each luminaire  20 . This modification may, for example, consider hypothetical placement of the mobile device  18  over the area of the iso-curves  100  modifying the value of the iso-curves  100  by the degree of alignment of axis  75  of the mobile device  18  and a straight line path between the luminaire  20  and the mobile device  18 . The more these two axes deviate, the more the intensity of the iso-curves  100  is decreased. These modified iso-curves may then be used to determine a locus of possible locations of the mobile device  18  with respect to each luminaire  20 . 
     It will be appreciated that an additional intensity effect will also occur if the elevation of the mobile device  18  is changed; however, these elevational effects will generally be small given the range of heights of most users  16  and may be corrected over the course of time by monitoring maximum intensity as the user  16  moves through the volume  12  which will give an idea of the user&#39;s height. 
     Referring now to  FIGS. 6 and 8 , various loci of possible locations for different luminaires  20  are then reconciled at process block  106  by one of several means. If two or more luminaire  20  provide adequate signal strength to each to develop a locus  108  of possible positions, their intersections may be used to narrow the locus to two points (in the case of two luminaires  20  or a single-point in the case of three or more luminaires  20 ). Looking at the case of one or two luminaires  20 , where intersection of loci  108  do not define a single location point but rather multiple points  114 , an estimated single location point may be obtained at process block  96 , for example, from previously identified locations  110  (using the techniques described herein) by selecting the closest point  114  from the intersection of loci  108  to that point. Preferably, however, a dead reckoning of new position estimation  112  of the mobile device  18  will be calculated from a last identified location of the mobile device  18 , and the movement since that time determined from elapsed time and acceleration of the mobile device will be measured by the sensor system  70 . The intersection of this new position estimation  112 , which may be, for example, a portion of a trajectory, with the multiple points  114  may then provide for a single identified location  116 . 
     Other location estimates may be used to resolve a single identified location  116  in the event that the intensity of light from three or more luminaires  20  cannot be determined. For example, a location estimate based on a GPS signal, wireless triangulation, or local near field beacons may be used. Mismatch between various location measures that may not perfectly intersect can be averaged to provide a single identified location  116 . Present experiments by the inventors indicate that resolution of less than 0.5 meters can readily be obtained. 
     Referring again to  FIG. 8 , as indicated by process block  120 , this single location value  116  may be output, for example, to other programs, that may use the location of the mobile device  18  to provide location-based content to the user  16 , for example, information about the user&#39;s location, points of interest, promotions in a particular part of a store or retail environment. The location value  116  may also be provided to the server  24  to be transmitted to others, for example, in hospitals or airports where this location information may be provided to individuals who need to find critical personnel quickly. 
     In addition, this location information may be used at process block  86  to reform the cluster  90  as discussed above. 
     Certain terminology is used herein for purposes of reference only, and thus is not intended to be limiting. For example, terms such as “upper”, “lower”, “above”, and “below” refer to directions in the drawings to which reference is made. Terms such as “front”, “back”, “rear”, “bottom” and “side”, describe the orientation of portions of the component within a consistent but arbitrary frame of reference which is made clear by reference to the text and the associated drawings describing the component under discussion. Such terminology may include the words specifically mentioned above, derivatives thereof, and words of similar import. Similarly, the terms “first”, “second” and other such numerical terms referring to structures do not imply a sequence or order unless clearly indicated by the context. 
     When introducing elements or features of the present disclosure and the exemplary embodiments, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of such elements or features. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements or features other than those specifically noted. It is further to be understood that the method steps, processes, and operations described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated, unless specifically identified as an order of performance. It is also to be understood that additional or alternative steps may be employed. 
     References to “a microprocessor” and “a processor” or “the microprocessor” and “the processor,” can be understood to include one or more microprocessors that can communicate in a stand-alone and/or a distributed environment(s), and can thus be configured to communicate via wired or wireless communications with other processors, where such one or more processor can be configured to operate on one or more processor-controlled devices that can be similar or different devices. Furthermore, references to memory, unless otherwise specified, can include one or more processor-readable and accessible memory elements and/or components that can be internal to the processor-controlled device, external to the processor-controlled device, and can be accessed via a wired or wireless network. 
     It is specifically intended that the present invention not be limited to the embodiments and illustrations contained herein and the claims should be understood to include modified forms of those embodiments including portions of the embodiments and combinations of elements of different embodiments as come within the scope of the following claims. All of the publications described herein, including patents and non-patent publications are hereby incorporated herein by reference in their entireties.