Patent Publication Number: US-11662450-B2

Title: Occupant detection device

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of Provisional U.S. Patent Application No. 62/722,462, filed Aug. 24, 2018, and Provisional U.S. Patent Application No. 62/799,497, filed Jan. 31, 2019, the disclosures of which are incorporated herein by reference in their entireties. 
    
    
     BACKGROUND 
     To manage a user environment, such as a residence or an office building, it may be desirable to have the ability to estimate the number of people occupying the user environment at a given time. Knowing the number of the people in an environment may improve occupant-driven control measures, such as energy control, air quality control, room assignment and/or scheduling, and/or the like. Further, the user environment may include one or more regions/areas that are of particular interest for monitoring. These regions/areas of interest may include, for example, entryways, desk areas, certain aisle or shelve space in a retail store, certain sections of a concert hall, etc. Having the ability to monitor the movements of people in and out of these regions/areas and determine a count of the number of the people in the regions/areas may assist with decisions such as workspace sharing, merchandising, security management, traffic control, etc. Prior art systems, methods, and instrumentalities lack the ability to perform these and other related tasks accurately and economically, and often cause privacy concerns. 
     SUMMARY 
     As described herein, an occupant detection device (e.g., an occupant detection sensor) configured to detect occupants in a space (e.g., a room) may comprise an occupant detection circuit (e.g., a radar detection circuit) and a control circuit. The occupant detection circuit may be configured to determine the location of an occupant in the space with reference to a first coordinate system associated the detection circuit. The control circuit may store a relationship between the first coordinate system and a second coordinate system associated with a region of interest in the space. Based on the relationship, the control circuit may convert the location of the occupant in the first coordinate system into a corresponding location in the second coordinate system and determine if the occupant is inside or outside the region of interest. 
     The relationship between the first and second coordinate systems may comprise an offset vector between the respective origins of the two coordinate systems. The relationship may also comprise a rotation angle between an axis of the first coordinate system and an axis of the second coordinate system. The control circuit may determine the relationship between the first and second coordinate systems during a configuration or commissioning process. The control circuit may also acquire knowledge about the region of interest during the configuration or commissioning process. Such knowledge may include, for example, the shape, dimensions and/or corner locations of the region of interest. The control circuit may obtain the relationship between the first and second coordinate systems and/or the knowledge about the region of interest from a programming device (e.g., based on one or more inputs received from a programming device). The control circuit may also determine the relationship between the first and second coordinate systems and/or acquire the knowledge about the region of interest based on one or more location markers placed in the space or in the region of interest. Multiple regions of interest may be configured for the space, which may have different shapes (e.g., polygon, circle, irregular or complex shapes, etc.). One or more masked areas may also be configured within each region and used to exclude certain occupants from an occupant count. 
     The control circuit may also be configured to determine whether an occupant in inside a region of interest without transforming the location of the occupant between the two coordinate systems. For example, the control circuit may make the determination based on whether respective vectors extending from each corner of the region of interest are all directed into the region of interest, and to determine that an occupant is within the region of interest when the respective vectors are all directed into the region of interest. The control circuit may be configured to determine that the occupant is not within the region of interest when at least one of the vectors is not directed into the region of interest. 
     The control circuit may maintain a count of the number of occupants (e.g., an occupant count) in the region of interest based on whether the locations of the occupants are within the region of interest or not. The control circuit may adjust the occupant count in response to determining that an occupant has entered or exited the region of interest. For example, the occupant detection circuit may be configured to assign respective tracking numbers to one or more occupants upon detecting the one or more occupants in the space and the control circuit may be configured to store the tracking numbers and the locations of the one or more occupants in memory. The control circuit may use the tracking number and/or the locations of the occupants to determine whether the occupants have entered the region of interest, exited the region of interest, or become stationary in the region of interest. The control circuit may then adjust the occupant count for the region of area accordingly. The occupant count may be reported by the control circuit to an external device such as a system controller. The report may be transmitted via a communication circuit of the occupant detection device, for example, via a wireless communication link. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a simple diagram of an example load control system including one or more occupant detection devices. 
         FIGS.  2 A- 2 C  illustrate example coverage areas of occupant detection devices. 
         FIGS.  3 A- 3 C  are perspective views of example occupant detection devices. 
         FIG.  4    is a block diagram of an example occupant detection sensor as described herein. 
         FIGS.  5 - 18 ,  19 A and  19 B  illustrate example configuration procedures that may be executed to configure an occupant detection sensor. 
         FIG.  20    is a simplified flowchart of an example control procedure that may be executed by a control circuit of an occupant detection sensor, e.g., when using a circular region of interest. 
         FIG.  21    is a simplified flowchart of an example control procedure that may be executed by a control circuit of an occupant detection sensor, e.g., when using one or more rectangular and/or circular regions of interest. 
         FIG.  22    is a simplified flowchart of an example location determination procedure that may be executed by a control circuit of an occupant detection sensor. 
         FIGS.  23 A and  23 B  show a simplified flowchart of an example occupant tracking procedure that may be executed by a control circuit of an occupant detection sensor. 
         FIG.  24    is a simplified flowchart of another example control procedure that may be executed by a control circuit of an occupant detection sensor. 
         FIG.  25    is a simplified flowchart of an example location determination procedure that may be executed by a control circuit of an occupant detection sensor. 
         FIG.  26 A- 26 C  are top-down views of example rooms for illustrating the operation of the location determination procedure of  FIG.  25   . 
     
    
    
     DETAILED DESCRIPTION 
       FIG.  1    is a simple diagram of an example load control system  100  for controlling the amount of power delivered from an alternating-current (AC) power source (not shown) to one or more electrical loads. The load control system  100  may be installed in a room  102  of a building. The load control system  100  may comprise a plurality of control devices configured to communicate with each other via wireless signals, e.g., radio-frequency (RF) signals  108 . Alternatively or additionally, the load control system  100  may comprise a wired digital communication link coupled to one or more of the control devices to provide for communication between the load control devices. The control devices of the load control system  100  may comprise a number of control-source devices (e.g., input devices operable to transmit messages in response to user inputs, occupancy/vacancy conditions, changes in measured light intensity, etc.) and a number of control-target devices (e.g., load control devices operable to receive messages and control respective electrical loads in response to the received messages). A single control device of the load control system  100  may operate as both a control-source and a control-target device. 
     The control-source devices may be configured to transmit messages (e.g., digital messages) directly to the control-target devices. In addition, the load control system  100  may comprise a system controller  110  (e.g., a central processor or load controller) operable to communicate digital messages to and from the control devices (e.g., the control-source devices and/or the control-target devices). For example, the system controller  110  may be configured to receive digital messages from the control-source devices and transmit digital messages to the control-target devices in response to the digital messages received from the control-source devices. The control-source and control-target devices and the system controller  110  may be configured to transmit and receive the RF signals  108  using a proprietary RF protocol, such as the ClearConnect® protocol. The RF signals  108  may be transmitted using a different RF protocol, such as, a standard protocol, for example, one of WIFI, BLUETOOTH, THREAD, ZIGBEE, Z-WAVE, KNX-RF, ENOCEAN RADIO protocols, or a different proprietary protocol. 
     The load control system  100  may comprise one or more load control devices, e.g., a dimmer switch  120  for controlling a lighting load  122 . The dimmer switch  120  may be adapted to be wall-mounted in a standard electrical wallbox. The dimmer switch  120  may comprise a tabletop or plug-in load control device. The dimmer switch  120  may comprise a toggle actuator (e.g., a button) and an intensity adjustment actuator (e.g., a rocker switch). Actuations (e.g., successive actuations) of the toggle actuator may toggle (e.g., turn off and on) the lighting load  122 . Actuations of an upper portion or a lower portion of the intensity adjustment actuator may respectively increase or decrease the amount of power delivered to the lighting load  122  and thus increase or decrease the intensity of the receptive lighting load from a minimum intensity (e.g., approximately 1%) to a maximum intensity (e.g., approximately 100%). The dimmer switch  120  may comprise a plurality of visual indicators, e.g., light-emitting diodes (LEDs), which may be arranged in a linear array and are illuminated to provide feedback of the intensity of the lighting load  122 . Examples of wall-mounted dimmer switches are described in greater detail in U.S. Pat. No. 5,248,919, issued Sep. 28, 1993, entitled LIGHTING CONTROL DEVICE, and U.S. Pat. No. 9,676,696, issued Jun. 13, 2017, entitled WIRELESS LOAD CONTROL DEVICE, the entire disclosures of which are hereby incorporated by reference. 
     The dimmer switch  120  may be configured to wirelessly receive digital messages via the RF signals  108  (e.g., from the system controller  110 ) and to control the lighting load  122  in response to the received digital messages. Examples of dimmer switches operable to transmit and receive digital messages is described in greater detail in commonly-assigned U.S. Patent Application Publication No. 2009/0206983, published Aug. 20, 2009, entitled COMMUNICATION PROTOCOL FOR A RADIO-FREQUENCY LOAD CONTROL SYSTEM, the entire disclosure of which is hereby incorporated by reference. 
     The load control system  100  may comprise one or more remotely-located load control devices, such as a light-emitting diode (LED) driver  130  for driving an LED light source  132  (e.g., an LED light engine). The LED driver  130  may be located remotely, for example, in or adjacent to the lighting fixture of the LED light source  132 . The LED driver  130  may be configured to receive digital messages via the RF signals  108  (e.g., from the system controller  110 ) and to control the LED light source  132  in response to the received digital messages. The LED driver  130  may be configured to adjust the color temperature of the LED light source  132  in response to the received digital messages. Examples of LED drivers configured to control the color temperature of LED light sources are described in greater detail in commonly-assigned U.S. Pat. No. 9,538,603, issued Jan. 3, 2017, entitled SYSTEMS AND METHODS FOR CONTROLLING COLOR TEMPERATURE, the entire disclosure of which is hereby incorporated by reference. The load control system  100  may further comprise other types of remotely-located load control devices, such as, for example, electronic dimming ballasts for driving fluorescent lamps. 
     The load control system  100  may comprise one or more daylight control devices, e.g., motorized window treatments  150 , such as motorized cellular shades, for controlling the amount of daylight entering the room  102 . Each motorized window treatments  150  may comprise a window treatment fabric  152  hanging from a headrail  154  in front of a respective window  104 . Each motorized window treatment  150  may further comprise a motor drive unit (not shown) located inside of the headrail  154  for raising and lowering the window treatment fabric  152  for controlling the amount of daylight entering the room  102 . The motor drive units of the motorized window treatments  150  may be configured to receive digital messages via the RF signals  108  (e.g., from the system controller  110 ) and adjust the position of the respective window treatment fabric  152  in response to the received digital messages. The load control system  100  may comprise other types of daylight control devices, such as, for example, a cellular shade, a drapery, a Roman shade, a Venetian blind, a Persian blind, a pleated blind, a tensioned roller shade system, an electrochromic or smart window, and/or other suitable daylight control device. Examples of battery-powered motorized window treatments are described in greater detail in U.S. Pat. No. 8,950,461, issued Feb. 10, 2015, entitled MOTORIZED WINDOW TREATMENT, and U.S. Pat. No. 9,488,000, issued Nov. 8, 2016, entitled INTEGRATED ACCESSIBLE BATTERY COMPARTMENT FOR MOTORIZED WINDOW TREATMENT, the entire disclosures of which are hereby incorporated by reference. 
     The load control system  100  may comprise one or more temperature control devices, e.g., a thermostat  160  for controlling a room temperature in the room  102 . The thermostat  160  may be coupled to a heating, ventilation, and air conditioning (HVAC) system  162  via a control link (e.g., an analog control link or a wired digital communication link). The thermostat  160  may be configured to wirelessly communicate digital messages with a controller of the HVAC system  162 . The thermostat  160  may comprise a temperature sensor for measuring the room temperature of the room  102  and may control the HVAC system  162  to adjust the temperature in the room to a setpoint temperature. The load control system  100  may comprise one or more wireless temperature sensors (not shown) located in the room  102  for measuring the room temperatures. The HVAC system  162  may be configured to turn a compressor on and off for cooling the room  102  and to turn a heating source on and off for heating the rooms in response to the control signals received from the thermostat  160 . The HVAC system  162  may be configured to turn a fan of the HVAC system on and off in response to the control signals received from the thermostat  160 . The thermostat  160  and/or the HVAC system  162  may be configured to control one or more controllable dampers to control the air flow in the room  102 . The thermostat  160  may be configured to receive digital messages via the RF signals  108  (e.g., from the system controller  110 ) and adjust heating, ventilation, and cooling in response to the received digital messages. 
     The load control system  100  may comprise one or more other types of load control devices, such as, for example, a screw-in luminaire including a dimmer circuit and an incandescent or halogen lamp; a screw-in luminaire including a ballast and a compact fluorescent lamp; a screw-in luminaire including an LED driver and an LED light source; an electronic switch, controllable circuit breaker, or other switching device for turning an appliance on and off; a plug-in load control device, controllable electrical receptacle, or controllable power strip for controlling one or more plug-in loads; a motor control unit for controlling a motor load, such as a ceiling fan or an exhaust fan; a drive unit for controlling a motorized window treatment or a projection screen; motorized interior or exterior shutters; a thermostat for a heating and/or cooling system; a temperature control device for controlling a setpoint temperature of an HVAC system; an air conditioner; a compressor; an electric baseboard heater controller; a controllable damper; a variable air volume controller; a fresh air intake controller; a ventilation controller; a hydraulic valves for use radiators and radiant heating system; a humidity control unit; a humidifier; a dehumidifier; a water heater; a boiler controller; a pool pump; a refrigerator; a freezer; a television or computer monitor; a video camera; an audio system or amplifier; an elevator; a power supply; a generator; an electric charger, such as an electric vehicle charger; and an alternative energy controller. 
     The load control system  100  may comprise one or more input devices, e.g., a remote control device  170  and one or more occupant detection devices, such as a ceiling-mounted occupant detection sensor  180  and a wall-mounted occupant detection sensor  182 . The input devices may be fixed or movable input devices. The system controller  110  may be configured to transmit one or more digital messages to the load control devices (e.g., the dimmer switch  120 , the LED driver  130 , the motorized window treatments  150 , and/or the thermostat  160 ) in response to the digital messages received from the remote control device  170 , the ceiling-mounted occupant detection sensor  180 , and/or the wall-mounted occupant detection sensor  182 . The remote control device  170 , the ceiling-mounted occupant detection sensor  180 , and/or the wall-mounted occupant detection sensor  182  may be configured to transmit digital messages directly to the dimmer switch  120 , the LED driver  130 , the motorized window treatments  150 , and/or the thermostat  160 . While  FIG.  1    shows two occupant detection devices, the load control system  100  may only comprise a single occupant detection device (e.g., one or the other of the ceiling-mounted occupant detection sensor  180  and the wall-mounted occupant detection sensor  182 ). 
     The remote control device  170  may be configured to transmit digital messages via the RF signals  108  to the system controller  110  (e.g., directly to the system controller) in response to an actuation of one or more buttons of the remote control device. For example, the remote control device  170  may be battery-powered. The load control system  100  may comprise other types of input devices, such as, for example, temperature sensors, humidity sensors, radiometers, cloudy-day sensors, shadow sensors, pressure sensors, smoke detectors, carbon monoxide detectors, air-quality sensors, motion sensors, security sensors, proximity sensors, fixture sensors, partition sensors, keypads, multi-zone control units, slider control units, kinetic or solar-powered remote controls, key fobs, cell phones, smart phones, tablets, personal digital assistants, personal computers, laptops, timeclocks, audio-visual controls, safety devices, power monitoring devices (e.g., such as power meters, energy meters, utility submeters, utility rate meters, etc.), central control transmitters, residential, commercial, or industrial controllers, and/or any combination thereof. 
     The system controller  110  may be coupled to a network, such as a wireless or wired local area network (LAN), e.g., for access to the Internet. The system controller  110  may be wirelessly connected to the network, e.g., using Wi-Fi technology. The system controller  110  may be coupled to the network via a network communication bus (e.g., an Ethernet communication link). The system controller  110  may be configured to communicate via the network with one or more network devices, e.g., a mobile device  140 , such as, a personal computing device and/or a wearable wireless device. The mobile device  140  may be located on an occupant  142 , for example, may be attached to the occupant&#39;s body or clothing or may be held by the occupant. The mobile device  140  may be characterized by a unique identifier (e.g., a serial number or address stored in memory) that uniquely identifies the mobile device  140  and thus the occupant  142 . Examples of personal computing devices may include a smart phone (for example, an iPhone® smart phone, an Android® smart phone, or a Blackberry® smart phone), a laptop, and/or a tablet device (for example, an iPad® hand-held computing device). Examples of wearable wireless devices may include an activity tracking device (such as a FitBit® device, a Misfit® device, and/or a Sony Smartband® device), a smart watch, smart clothing (e.g., OMsignal® smartwear, etc.), and/or smart glasses (such as Google Glass® eyewear). In addition, the system controller  110  may be configured to communicate via the network with one or more other control systems (e.g., a building management system, a security system, etc.). 
     The mobile device  140  may be configured to transmit digital messages to the system controller  110 , for example, in one or more Internet Protocol packets. For example, the mobile device  140  may be configured to transmit digital messages to the system controller  110  over the LAN and/or via the internet. The mobile device  140  may be configured to transmit digital messages over the internet to an external service (e.g., If This Then That (IFTTT®) service), and then the digital messages may be received by the system controller  110 . The mobile device  140  may transmit and receive RF signals  109  via a Wi-Fi communication link, a Wi-MAX communications link, a Bluetooth communications link, a near field communication (NFC) link, a cellular communications link, a television white space (TVWS) communication link, or any combination thereof. Alternatively or additionally, the mobile device  140  may be configured to transmit RF signals according to the proprietary protocol. The load control system  100  may comprise other types of network devices coupled to the network, such as a desktop personal computer, a Wi-Fi or wireless-communication-capable television, or any other suitable Internet-Protocol-enabled device. Examples of load control systems operable to communicate with mobile and/or network devices on a network are described in greater detail in commonly-assigned U.S. Patent Application Publication No. 2013/0030589, published Jan. 31, 2013, entitled LOAD CONTROL DEVICE HAVING INTERNET CONNECTIVITY, the entire disclosure of which is hereby incorporated by reference. 
     The system controller  110  may be configured to determine the location of the mobile device  140  and/or the occupant  142 . The system controller  110  may be configured to control (e.g., automatically control) the load control devices (e.g., the dimmer switch  120 , the LED driver  130 , the motorized window treatments  150 , and/or the temperature control device  160 ) in response to determining the location of the mobile device  140  and/or the occupant  142 . One or more of the control devices of the load control system  100  may transmit beacon signals, for example, RF beacon signals transmitted using a short-range and/or low-power RF technology, such as Bluetooth technology. The load control system  100  may also comprise at least one beacon transmitting device  144  for transmitting the beacon signals. The mobile device  140  may be configured to receive a beacon signal when located near a control device that is presently transmitting the beacon signal. A beacon signal may comprise a unique identifier identifying the location of the load control device that transmitted the beacon signal. Since the beacon signal may be transmitted using a short-range and/or low-power technology, the unique identifier may indicate the approximate location of the mobile device  140 . The mobile device  140  may be configured to transmit the unique identifier to the system controller  110 , which may be configured to determine the location of the mobile device  140  using the unique identifier (e.g., using data stored in memory or retrieved via the Internet). An example of a load control system for controlling one or more electrical loads in response to the position of a mobile device and/or occupant inside of a building is described in greater detail in commonly-assigned U.S. Patent Application Publication No. 2016/0056629, published Feb. 25, 2016, entitled LOAD CONTROL SYSTEM RESPONSIVE TO LOCATION OF AN OCCUPANT AND MOBILE DEVICES, the entire disclosure of which is hereby incorporated by reference. 
     The operation of the load control system  100  may be programmed and configured using, for example, the mobile device  140  or other network device (e.g., when the mobile device is a personal computing device) during a commissioning procedure (e.g., a configuration procedure). The mobile device  140  may execute a graphical user interface (GUI) configuration software for allowing a user or installer to program how the load control system  100  will operate. For example, the configuration software may run as a PC application or a web interface. The configuration software and/or the system controller  110  (e.g., via instructions from the configuration software) may generate a load control database that defines the operation of the load control system  100 . For example, the load control database may include information regarding the operational settings of different load control devices of the load control system (e.g., the dimmer switch  120 , the LED driver  130 , the motorized window treatments  150 , and/or the thermostat  160 ). The load control database may comprise information regarding associations between the load control devices and the input devices (e.g., the remote control device  170 , the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , etc.). The load control database may comprise information regarding how the load control devices respond to inputs received from the input devices. Examples of configuration procedures for load control systems are described in greater detail in commonly-assigned U.S. Pat. No. 7,391,297, issued Jun. 24, 2008, entitled HANDHELD PROGRAMMER FOR A LIGHTING CONTROL SYSTEM; U.S. Patent Application Publication No. 2008/0092075, published Apr. 17, 2008, entitled METHOD OF BUILDING A DATABASE OF A LIGHTING CONTROL SYSTEM; and U.S. Patent Application Publication No. 2014/0265568, published Sep. 18, 2014, entitled COMMISSIONING LOAD CONTROL SYSTEMS, the entire disclosure of which is hereby incorporated by reference. 
     The occupant detection sensors  180 ,  182  may each be configured to detect locations and movements of occupants in and near (e.g., in a doorway of) room  102 . The occupant detection sensors  180 ,  182  may each be configured to determine the number of occupants in the room  102  (e.g., an occupant count). For example, each of the occupant detection sensors  180 ,  182  may comprise an occupant detection circuit (e.g., an image sensing circuit, such as a radar detection circuit) for determining the number and location of the occupants in the room  102  (e.g., as will be described in greater detail below). The occupant detection circuit may be configured to determine the locations of an occupant as coordinates in a two-dimensional or three-dimensional coordinate system, e.g., a Cartesian or polar coordinate system. For example, the occupant detection circuit may be configured to determine the locations of the occupant as X-Y-Z coordinates where the Z-axis extends from the occupant detection sensor towards the occupant (e.g., the Z-coordinate may indicate the distance from the occupant detection sensor to the occupant). 
     The ceiling-mounted occupant detection sensor  180  may be mounted to the ceiling of the room  102  (e.g., in the center of the room) and may be configured to determine a top-down view of the locations of the occupants of the room  102  in response to the occupant detection circuit.  FIG.  2 A  is an example view of the ceiling-mounted occupant sensor  180  illustrating a coverage area  200  (e.g., a range) and a plurality of occupants  202  within the coverage area. As shown in  FIG.  2 A , the coverage area  200  of the ceiling-mounted occupant detection sensor  180  may have a circular shape. The ceiling-mounted occupant detection sensor  180  may be configured to generate an occupant map, e.g., a two-dimensional (2D) radar image indicating the locations of the occupants  202  within the coverage area. The ceiling-mounted occupant detection sensor  180  may be configured to determine the locations of the occupants  202  as coordinates (e.g., X-Y coordinates) in a two-dimensional coordinate system  204  associated with (e.g., defined by) the occupant detection circuit of the ceiling-mounted occupant detection sensor  180 . For example, the ceiling-mounted occupant detection sensor  180  may ignore (e.g., discard) the Z-coordinate information determined by the occupant detection circuit. In addition, the ceiling-mounted occupant detection sensor  180  may set the Z-coordinate to a value (e.g., a constant value) and determine the X-Y coordinates of the occupants  202  at that particular value of the Z-coordinate. For example, the ceiling-mounted occupant detection sensor  180  may set the Z-coordinate to a value that corresponds to a particular height (e.g., approximately 2.5-3 feet) so as to ignore movement of pets. Further, the ceiling-mounted occupant detection sensor  180  may determine the locations of the occupants  202  as X-Y-Z coordinates in a three-dimensional coordinate system. 
     The wall-mounted occupant detection sensor  182  may be mounted to a wall of the room  102  and may be configured to use distance data from the occupant detection circuit to determine the locations of the occupants of the room  102 .  FIG.  2 B  is an example view of the wall-mounted occupant sensor  182  illustrating a coverage area  210  (e.g., a range) and a plurality of occupants  212  within the coverage area. As shown in  FIG.  2 B , the coverage area  210  of the wall-mounted occupant detection sensor  182  may have a wedge shape. Since the coverage area  210  may be wedge-shaped, the wall-mounted occupant detection sensor  182  may be mounted in a corner of the room  102 . The wall-mounted occupant detection sensor  182  may be configured to generate an occupant map, e.g., a two-dimensional (2D) radar image indicating the locations of the occupants  212  within the coverage area. The wall-mounted occupant detection sensor  182  may be configured to determine the locations of occupants  212  as coordinates (e.g., X-Z coordinates) in a two-dimensional coordinate system  214  associated with (e.g., defined by) the occupant detection circuit of the ceiling-mounted occupant detection sensor  180 . For example, the wall-mounted occupant detection sensor  182  may ignore (e.g., discard) the Y-coordinate information determined by the occupant detection circuit. In addition, the wall-mounted occupant detection sensor  182  may set the Y-coordinate to a value (e.g., a constant value) and determine the X-Z coordinates of the occupants  202  at that particular value of the Y-coordinate. For example, the wall-mounted occupant detection sensor  182  may set the Y-coordinate to a value that corresponds to a particular height (e.g., approximately 2.5-3 feet) so as to ignore movement of pets. Further, the wall-mounted occupant detection sensor  182  may determine the locations of the occupants  212  as X-Y-Z coordinates in a three-dimensional coordinate system. 
     The occupant detection sensors  180 ,  182  may each transmit one or more messages (e.g., digital messages) to the system controller  110  via the RF signals  108  (e.g., using the proprietary protocol described herein) in response to determining an occupant count (e.g., a sensor occupant count) of the room  102  and/or an occupant count of a region of interest (e.g., an area of interest) of the room  102  (e.g., including a change thereof). The system controller  110  may be configured to maintain the occupant count for the room  102  (e.g., a room occupant count) and/or the occupant count for a region of interest of the room  102 . Based on the occupant count, the system controller  110  may be further configured to determine an occupancy condition and/or a vacancy condition of the room  102 . For example, when the occupant count is greater than zero, the system controller  110  may determine that the room  102  or a region of interest of the room  102  is occupied, and when the occupant count reaches zero, the system controller  110  may determine that the room  102  or the region of interest of the room  102  is vacant. It should be noted that the terms “area of interest” and “region of interest” are used interchangeably in the description provided herein. 
     The operation of the occupant detection sensors  180 ,  182  may be configured, for example, during the commissioning procedure of the load control system  100 . Each of the occupant detection sensors  180 ,  182  may comprise one or more configuration buttons for setting operational characteristics (e.g., sensitivity, coverage area, etc.) of the occupant detection sensor. In addition, each occupant detection sensor  180 ,  182  may adjust the operational characteristics in response to receiving one or more messages via the RF signals  108 . For example, the mobile device  140  may execute design software installed on the mobile device to allow for adjusting the operational characteristics of the occupant detection sensors  180 ,  182 , and may transmit (e.g., directly transmit) messages including the operational characteristics to the occupant detection sensors, for example, via a short-range RF technology (e.g., BLUETOOTH®, near field communication (NFC), WIFI®, Thread, etc.). The mobile device  140  may also transmit messages including the operational characteristics to the occupant detection sensors  180 ,  182  via the system controller  110 . Further, each occupant detection sensor  180 ,  182  may be configured to learn and/or automatically adjust the operational characteristics of the occupant detection sensor (e.g., as will be described in greater detail below). Each occupant detection sensor  180 ,  182  may also be configured to acquire knowledge (e.g., bounds, dimensions, shape, etc.) of the room  102  and/or a region of interest of the room  102  (e.g., as will be described in greater detail below). 
     As previously mentioned, the occupant detection sensor  180 ,  182  may each transmit one or more messages including a determined occupant count (e.g., a sensor occupant count) to the system controller  110 , which may maintain the occupant count for the room  102  (e.g., a room occupant count). The system controller  110  may be configured to receive messages transmitted by the ceiling-mounted occupant detection sensor  180  and/or the wall-mounted occupant detection sensor  182  (e.g., as well as other occupant detection sensors), and aggregate the occupant counts (or change thereof) indicated in those messages. The system controller  110  may be capable of resolving discrepancies between information reported by the ceiling-mounted occupant detection device  180  and the wall-mounted occupant detection sensor  182  (e.g., and information gathered from other devices in the load control system  100 ). The system controller  110  may be configured to gather and/or store room occupant count data over time and thus maintain a historical view of the occupancy status of a room. 
     Each of the occupant detection sensor  180 ,  182  may be configured to perform some or all of the functions of the system controller  110 . For example, the ceiling-mounted occupant counting detection sensor  180  may be capable of receiving information (e.g., digital messages) from the wall-mounted detection sensor  182  (e.g., or other occupant detection sensors) regarding an occupant count (or a change thereof) or an occupancy status of room  102 . The ceiling-mounted occupant counting detection sensor  180  may be configured to process the received occupant count in conjunction with the occupant count determined by the ceiling-mounted occupant counting detection sensor  180  itself, and determine and maintain the room occupant count for the room  102 . Similar to the system controller  110 , each occupant detection sensor  180 ,  182  may be capable of resolving mismatches among various pieces of information received or derived by the occupant detection sensor. 
     The occupant detection circuit of each of the occupant detection sensors  180 ,  182  may be configured to determine locations of occupants within the respective coverage area  200 ,  210 .  FIG.  2 C  illustrates an example coverage area  221  of a ceiling-mounted occupant detection sensor  220  (e.g., the ceiling-mounted occupant detection sensor  180 ). The ceiling-mounted occupant detection sensor  220  may be configured to determine the locations of occupants as X-Y coordinates in a coordinate system, e.g., a global coordinate system  222  associated with (e.g., defined by) the occupant detection circuit of the ceiling-mounted occupant detection sensor  220 , as shown in  FIG.  4   . For example, the occupant detection circuit of the ceiling-mounted occupant detection sensor  220  may include a radar detection circuit characterized by a boresight (e.g., that may be set by the antennas of the radar detection circuit). The direction of the boresight of the radar detection circuit may establish the x-axis of the global coordinate system  222  of the ceiling-mounted occupant detection sensor  220 . The global coordinate system  222  may have an origin  224  (e.g., the (0, 0) coordinate) that may be located at the center of the coverage area  221  of the occupant detection sensor  220  (e.g., at a center point of the occupant detection sensor). The occupant detection sensor  220  may be configured to determine the number of occupants in a room  230  (e.g., the room  102 ) and/or movements of the occupants in response to the X-Y coordinates of the occupants as determined by the occupant detection circuit. 
     The ceiling-mounted occupant detection sensor  220  may comprise one or more coordinate system indicators (e.g., boresight indicators) to indicate the direction of the respective coordinate system (e.g., the directions of the x-axis and the y-axis of the global coordinate system  222 ).  FIGS.  3 A- 3 C  are perspective views of example ceiling mounted-mounted occupant detection sensors  300 ,  310 ,  320  (e.g., that may be deployed as the ceiling-mounted occupant detection sensor  180  and/or the ceiling-mounted occupant detection sensor  220 ). For example, a perimeter of the occupant detection sensor  300  shown in  FIG.  3 A  may be marked with coordinate system indicators in the form of directional indicia  302 , which may include the letters “F”, “B”, “R”, and “L” indicating the front side, back side, right side, and left side of the occupant detection sensor, respectively. The directional indicia  302  may be formed as part of the occupant detection sensor  300  and/or may be printed on the occupant detection sensor. The occupant detection sensor  300  may be characterized by a global coordinate system having an x-axis that may originate from the center of the occupant detection sensor and extend through the front of the occupant detection sensor (e.g., marked with the letter “F” as shown), for example, as shown by a line  304  in  FIG.  3 A . The direction indicia  302  may include the letters “N”, “S”, “E”, and “W” indicating north, south, east, and west directions, respectively, of the occupant detection sensor (e.g., of the global coordinate system  222 ). The directional indicia  302  may also include the letters “X” and “Y” to indicate the direction of the x-axis and the y-axis of the global coordinate system  222 . 
     Referring to  FIG.  3 B , the ceiling-mounted occupant detection sensor  310  may be marked with a coordinate system indicator in the form of a single indicium, such as an arrow  312 . The occupant detection sensor  310  may be characterized by a global coordinate system having an x-axis that may extend from the side of the occupant detection sensor marked by the directional indicium (e.g., from the side of the occupant detection sensor on which the arrow  312  is located and/or in the direction indicated the arrow  312 ), for example, as shown by a line  314  in  FIG.  3 B . The arrow  312  may be located on a downward-facing surface  316  of the occupant detection sensor  310  (e.g., so as to be easily viewed from below). The arrow  312  may be formed as part of the occupant detection sensor  310  and/or may be printed on the occupant detection sensor. The coordinate system indicator may comprise an indium, such as a triangle or dot, and/or other component, such as an illuminated element (e.g., a light-emitting diode). If the coordinate system indicator is a single indicium that indicates a direction (e.g., such as the arrow  312  or a triangle), the coordinate system indicator may also be centrally located on the downward-facing surface  316  of the occupant detection sensor  310 . 
     As shown in  FIG.  3 C , the ceiling-mounted occupant detection sensor  320  may comprise multiple (e.g., a pair of) coordinate system indicators, such as first and second light sources  322 ,  323 , e.g., light-emitting diodes (LEDs). For example, the first light source  322  may comprise a green LED and the second light source  323  may comprise a red LED. The occupant detection sensor  320  may be characterized by a coordinate system having an x-axis that may extend from the side of the occupant detection sensor on which the first light source  322  (e.g., the green LED) is located, for example, as shown by a line  324  in  FIG.  3 C . The first light source  322  may indicate the positive direction of the x-axis of the global coordinate system  222  and the second light source  323  may indicate the negative direction of the x-axis of the global coordinate system  222 . The first and second light sources  322 ,  323  may be located on a downward-facing surface  326  of the occupant detection sensor  320  (e.g., so as to be easily viewed from below the occupant detection sensor  320 ). The first and second light sources  322 ,  323  may be located on the sides of the occupant detection sensor  320 . 
     The coordinate system indicators of the occupant detection sensor  220  (e.g., as shown on the occupant detection sensors  300 - 320  of  FIGS.  3 A- 3 C ) may be used during installation/configuration of the occupant detection sensors (e.g., during the commissioning procedure of the load control system  100 ). For example, the coordinate system indicators may be used to position the x-axis of the global coordinate system  222  of the occupant detection sensor  220  to be aligned with (e.g., parallel or perpendicular to) the walls of the room  230 . 
     The occupant detection sensor  220  may be configured to detect (e.g., only detect) occupants in a region of interest (ROI)  240  within the coverage area  221  (e.g., within the room  230 ). The region of interest  240  may be associated with (e.g., characterized by) a coordinate system, e.g., a local coordinate system  242 , having an origin  244  (e.g., the (0,0) coordinate) that may be located at one of the corners of the region of interest. The boundaries of the region of interest  240  may be aligned with the walls of the room  230  (e.g., the x-axis and the y-axis of the local coordinate system  242  may be parallel and/or perpendicular to the walls of the room). In addition, the occupant detection sensor  220  may be configured to ignore data regarding occupants in a masked region  250  within the region of interest  240 . Among other purposes, the use of the region of interest(s)  240  and/or masked region(s)  250  may allow the occupant detection sensor  220  to focus on the occupants of just the room  230  and ignore moving bodies in other areas, for example, in a hallway outside of a doorway (e.g., the doorway  106 ). The term “marked region” may be used interchangeably herein with the term “masked area.” 
     The occupant detection sensor  220  may be configured to determine the locations (e.g., X-Y coordinates) of the occupants within the local coordinate system  242  associated with (e.g., defined by) the region of interest  240 . The global coordinate system  222  of the occupant detection sensor  220  may or may not be aligned with the local coordinate system  242  of the region of interest  240 , for example, in terms of orientations and/or origins of the coordination systems. The occupant detection sensor  220  may be configured to determine and/or store a relationship between the global coordinate system  222  and local coordinate system  242 . For example, if the local coordinate system  242  is not aligned with the global coordinate system  222  in terms of orientations of the coordinate systems, the occupant detection sensor  220  may be configured to determine a rotation angle φR between the x-axis (or y-axis) of the global coordinate system  222  of the occupant detection sensor  220  and the x-axis (or y-axis) of the local coordinate system  242  of the region of interest  240 . If the origin of the local coordinate system  242  is not aligned with the origin of the global coordinate system  222 , the occupant detection sensor  220  may be configured to determine an offset vector (x OFF , y OFF ) between the origin  224  of the global coordinate system  222  and the origin  244  of the local coordinate system  242 . The occupant detection sensor  220  may be configured to use the relationship between the global coordinate system  222  and the local coordinate system  242  (e.g., which may comprise the rotation angle φ R  and/or the offset vector (x OFF , y OFF )) to transform a location (x, y) from the global coordinate system  222  (e.g., as determined by the antennas of a radar detection circuit of the occupant detection sensor) into a location (x′, y′) in the local coordinate system  242 . The ceiling-mounted occupant detection sensor  180  may be configured to use the location in the local coordinate system  242  and dimensions X ROI , Y ROI  of the region of interest  240  to determine if occupants are within the region of interest. 
     The region of interest  240  may be configured, for example, during a commissioning procedure of the load control system  100 , and the occupant detection sensor  220  may acquire knowledge (e.g., learn) of the region of interest  240  during the commissioning procedure (e.g., by entering a learning mode). For example, a shape and/or dimensions of the region of interest may be selected using the configuration buttons on the occupant detection sensor  220  and/or design software executed on a programming device (e.g., the mobile device  140 ). For example, the shape of the region of interest may be selected from a list of standard shapes (e.g., circle, square, rectangle, etc.). The dimensions of the selected shape may be entered via the programming device (e.g., a radius for a circular region of interest, an edge length for a square region of interest, and/or a length and width for a rectangular region of interest). The shape and/or dimension information may then be transmitted (e.g., via wireless communication) to the occupant detection sensor  220 . The occupant detection sensor  220  may be configured to determine the rotation angle φ R  between the x-axis of the global coordinate system  222  of the occupant detection sensor and the x-axis of the region of interest  240 , the offset vector (x OFF , y OFF ), and/or the bounds/dimensions of the region of interest  242 . For example, the coordinate system indicators may be used to establish and/or determine the rotation angle φR between the x-axis of the global coordinate system of the occupant detection sensor  220  and the x-axis of the region of interest  240  (e.g., as will be described in greater detail below). 
     The occupant detection sensor  220  may be configured to learn the shape, boundaries, and/or dimensions of the region of interest. For example, the occupant detection sensors  220  may be placed into a learning mode (e.g., in response to an actuation of one of the configuration buttons and/or a message received from the mobile device  140 ) and an installer may walk around the perimeter of the room to identify the bounds of the region of interest while the occupant detection sensor is in the learning mode. The occupant detection sensor  220  may monitor the movements of the installer in the learning mode and use the locations of the installer to set the shape, boundaries, and/or dimensions of the region of interest. 
     The occupant detection sensor  220  may be configured to focus on a small region of interest within a large region of interest. For example, the occupant detection sensor  220  may be configured to detect movements of occupants within a room (e.g., within a large region of interest) using a first sensitivity level, and detect movements around a desk or keyboard (e.g., within a small region of interest within the room) using a second sensitivity level that may be greater than the first sensitivity level. The large and small regions of interest and/or the sensitivity levels used in each region may be configured, for example, during the commissioning procedure. Multiple small regions of interest may be configured within a single large region of interest. 
     The occupant detection sensor  220  may be configured to detect when an occupant enters or exits a region of interest (e.g., the room  230 ) and use this information to maintain and/or adjust the occupant count for the region of interest. The occupant detection sensor  220  may be configured to learn and/or store knowledge about an entry location (e.g., a doorway) within the region of interest  240 . The occupant detection sensor  220  may be configured to track the movements of the occupants to and from the entry location in order to determine when an occupant enters or exits the room  230 . The occupant counting sensor  220  may be configured to increase the occupant count when a person enters the room  230  and decrease the occupant count when a person leaves the room. The entry location may be set during the commissioning procedure of the occupant detection sensor  220 . For example, the occupant counting sensor  220  may be placed in a learning mode (e.g., in response to an actuation of one of the configuration buttons and/or a message received from the programming device), and the installer may stand at the entry location in order to indicate the entry location to the occupant counting sensor. In addition, the occupant counting sensor  220  may each be configured to automatically learn the entry location, for example, in response to detecting occupants repetitively moving to and from a certain location along the perimeter of the coverage area and/or region of interest during normal operation. The occupant counting sensor  220  may be configured to set more than one entry location for a single room. 
     The occupant detection sensor  220  may be configured to detect one or more “noise” sources (e.g., a fan) in the coverage area and/or region of interest, and ignore these noise sources when determining the occupant count for the room  230  or a region of interest in the room  230 . For example, the occupant detection sensor  220  may be configured to detect a noise source by identifying a harmonic target by its Doppler signature during normal operation. The occupant detection sensor  220  may set or be configured with a masked region over the identified noise source so that the noise source may be ignored when determining the occupant count for the room  230  during normal operation. 
     The occupant detection sensor  220  may each be configured to track specific occupants (e.g., record and update locations of the occupants) while those occupants are in the room  230 . For example, the occupant detection sensor  220  may be configured to detect when a new occupant enters the room  230  (e.g., by detecting that the new occupant has a new tracking number and/or detecting that the new occupant is moving into the room from the entry location). When the new occupant is first detected, the occupant detection sensor  220  may assign the occupant a tracking number and/or an occupant identifier. The occupant detection sensor  220  may be configured to track the occupant as the occupant moves around the room  230  (e.g., using the tracking number and/or the occupant identifier), and track the occupant to a stationary location (e.g., if the occupant sits down at a desk or table). If the occupant “disappears” from the occupant data received from the occupant detection circuit while at the stationary location (e.g., due to minimal or no movement), the occupant detection sensor  220  may be configured to maintain the occupant count for the room  230  and location of the occupant. When the occupant disappears from the occupant data and then reappears (e.g., with a new tracking number), the occupant detection circuit may assign the occupant a new tracking number and/or occupant identifier. However, the occupant detection sensor  220  may be configured to maintain the occupant identifiers for occupants that had been or are presently stationary. The occupant detection sensor  220  may be configured to detect that the occupant has exited the room  230  and cease tracking the occupant (e.g., by deleting the occupant identifier and location information of the occupant from a memory of the occupant detection sensor  220 ). 
     The occupant detection sensor  220  may also be configured to determine if the occupant has entered a static area, for example, an area surrounding a desk chair, where the occupant may sit for long periods of time (e.g., may be a stationary occupant). The occupant detection sensor  220  may be configured to maintain the occupant identified and occupant location for occupants that have moved into a static area. A static area may be defined (e.g., during the commissioning procedure) by identifying a location within the region of interest and/or the corners or perimeter of the static area. Multiple static areas may be configured within the region of interest. The occupant detection sensor  220  may be configured to operate in a different mode of operation when the occupant has entered the static area. For example, the occupant detection sensor  220  may be configured to detect occupants in the room (e.g., a large region of interest) using a first sensitivity level when an occupant is not in the static area. When the occupant enters the static area, the occupant detection sensor  220  may then be configured to detect occupants in the room using the first sensitivity level and detect occupants in the static area (e.g., a small region of interest around a keyboard) using a second sensitivity level that is greater than the first sensitivity level. 
       FIG.  4    is an example block diagram of an example sensor, such as an occupant detection sensor  400  (e.g., the ceiling-mounted occupant detection sensor  180  and/or the wall-mounted occupant detection sensor  182  of  FIG.  1   ). The occupant detection sensor  400  may comprise a sensing circuit such as an occupant detection circuit, e.g., an image sensing circuit, such as a radar detection circuit  410  having a radar detection processor  412 . The radar detection processor  412  may comprise, for example, one or more of a microprocessor, a microcontroller, a digital signal processor (DSP), a programmable logic device (PLD), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any suitable processing device. The occupant detection circuit may comprise a visible image sensing circuit (e.g., including a camera), a thermal imaging circuit (e.g., including a thermopile array), a time-of-flight image sensing circuit, and/or any other sensing or imaging circuit capable of generating a two-dimensional or three-dimensional image or map of the locations of occupants in a room (e.g., the room  102 ,  230 ). An example of a visible light sensing circuit is described in greater detail in commonly-assigned U.S. Patent Application Publication No. 2017/0171941, published Jun. 15, 2017, entitled LOAD CONTROL SYSTEM HAVING A VISIBLE LIGHT SENSOR, the entire disclosure of which is hereby incorporated by reference. 
     The radar detection circuit  410  may also comprise a transmitting antenna array  414  (e.g., a phased array) coupled to the radar occupant detection processor  412  via a radar transmitter circuit  415 , and a receiving antenna array  416  (e.g., a phased array) coupled to the radar detection processor  412  via a radar receiver circuit  417 . For example, the radar detection circuit  410  may operate using a frequency-modulated continuous wave (FMCW) radar technology. The radar detection circuit  410  may also operate using other types of radar technology, such as, for example, pulsed radar, continuous wave radar, side aperture radar, phased-array radar, mono-static radar, multi-static radar, or other radar technology. The radar detection processor  412  may be configured to build a radar image (e.g., an occupant map) of the coverage area from the signals received from the receiving antenna array  416  (e.g., the phased array) via the radar receiver circuit  417 . 
     The radar detection processor  412  may be configured to transmit a radar signal (e.g., a chirp) via the transmitting antenna array  414 , and receive a reflected signal via the receiving antenna array  416 . The radar signal may be a frequency-modulated continuous waveform (FMCW) that increases in frequency over a chirp interval TCHIRP. The radar detection processor  412  may be configured to process the reflected signal (e.g., as compared to the transmitted radar signal) to determine a Doppler shift of the reflected signal and data regarding a moving body in the room, such as the distance to the moving body, a direction of movement of the moving body, and/or an acceleration of the moving body. The radar detection processor  412  may be configured to transmit a number N CHIRP  of chirps during a radar detection event to determine the Doppler shift of the reflected signals due to the moving body in the room. Each radar detection event may last for a radar detection interval (e.g., approximately 5 milliseconds). For example, each radar detection even may include approximately 128 chirps, which may be equally spaced apart (e.g., having a constant frequency). The radar detection events may be spaced apart from each other by, for example, tens of milliseconds. 
     If two occupant detection sensors  400  are located near each other, the radar detection events of each occupant detection sensor may overlap, which may cause interference with the chirps of each radar detection event. The radar detection processor  412  may be configured to randomize a start time of each radar detection event to avoid consistent overlap of the radar detection events of nearby occupant detection sensors. For example, the radar detection processor  412  may be configured randomize the start time of each radar detection event in increments of 5 milliseconds. 
     The radar detection processor  412  may be configured to control the transmitting antenna array  414  and/or the receiving antenna array  416  to adjust an angle from the occupant detection sensor  400  at which the moving bodies may be detected. The radar detection processor  412  may be configured to sweep through (e.g., periodically step through) various detection angles and determine data regarding the moving body at each detection angle. At each detection angle, the radar detection processor  412  may transmit a radar signal and receive a reflected signal to process. The radar detection processor  412  may be configured to build a map or image (e.g., a two-dimensional or three-dimensional map or image) of the moving objects in the room from the determined data regarding the moving bodies at each detection angle. The radar detection processor  412  may be configured to determine an occupant count for the room as well as the locations (e.g., X-Y coordinates) of the occupants in the room (e.g., in the global coordinate system  222 ). The radar detection processor  412  may assign a unique tracking number to each detected occupant in the space. 
     The occupant detection sensor  400  may also comprise a control circuit  420  that may be connected to the radar detection processor  412  of the radar detection circuit  410  via a communication bus  422 . The control circuit  420  may comprise, for example, a microprocessor, a programmable logic device (PLD), a microcontroller, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or any suitable processing device. The control circuit  420  may be configured to receive the occupant count for the room as well as the tracking numbers and the locations (e.g., X-Y coordinates) of the occupants in the room from the radar detection processor  412  via the communication bus  422 . Any of the functions and/or procedures executed by the control circuit  420  as described herein could also be implemented (e.g., fully implemented) by the radar detection processor  412 . 
     The occupant detection sensor  400  may comprise one or more memory circuits for storing the occupant count, occupant identifiers, occupant locations, and/or occupancy status (e.g., whether an occupant is stationary). The memory circuit(s) may be implemented as an external integrated circuit (IC) coupled to the control circuit  420  or as an internal circuit of the control circuit  420  and/or the radar detection processor  412 . For example, the control circuit  420  may comprise an internal memory  429  and/or the radar detection processor  412  may comprise an internal memory  419 . The control circuit  420  may be configured to save different occupant counts that are associated with different time periods in the memory circuit(s) so that a historical view of the occupancy condition of the room (e.g., a usage history) may be derived. 
     The occupant detection sensor  400  may comprise a user interface  424  including one or more actuators that may be used to configure the occupant detection sensor (e.g., during the commissioning procedure of the load control system  100  of  FIG.  1   ). For example, the user interface  424  may comprise one or more configuration buttons configured to be actuated to cycle through options that define the region of interest of the occupant detection sensor  400 . In addition, the user interface  424  may comprise a potentiometer having a knob and/or a digital rotary switch configured to be rotated to adjust a value that defines the region of interest of the occupant detection sensor  400  (e.g., such as the rotation angle φ R ). Further, the user interface  424  may comprise other input devices, such as a digital DIP switch. The occupant detection sensor  400  may also comprise a compass (e.g., an electronic compass  426 ) for determining the direction of true north, which may be used to configure the occupant detection sensor, for example, during the commissioning procedure of the load control system  100 . In addition, a potentiometer and/or digital rotary switch of the user interface  624  may be used to determine the direction of true north. 
     The occupant detection sensor  400  may comprise a communication circuit  428  configured to transmit and/or receive messages (e.g., digital messages) via a communication link using a communication protocol. For example, the communication link may comprise a wireless communication link and the communication circuit  428  may comprise an RF transceiver coupled to an antenna. The communication link may comprise a wired digital communication link and the communication circuit  428  may comprise a wired communication circuit. The communication protocol may comprise a proprietary protocol, such as, for example, the ClearConnect protocol. The control circuit  420  may be configured to transmit and/or receive digital messages via the communication link during normal operation of the occupant detection sensor  400 . For example, the control circuit  420  may be configured to transmit an indication of a determined occupant count (or a change thereof) of the room to a system controller (e.g., the system controller  110  of  FIG.  1   ). The control circuit  420  may also be able to receive an indication of an occupant count (or a change thereof) of the room determined by another occupant detection sensor. In the latter case, the occupant detection sensor  400  may perform some or all of the functions of a system controller, as described herein. 
     The occupant detection sensor  400  may comprise a power source  430  for producing a DC supply voltage V CC  for powering the radar detection circuit  410 , the control circuit  420 , the communication circuit  428 , and other low-voltage circuitry of the occupant detection sensor  400 . The power source  430  may comprise a power supply configured to receive an external supply voltage from an external power source (e.g., an AC mains line voltage power source and/or an external DC power supply). In addition, the power source  430  may comprise a battery for powering the circuitry of the occupant detection sensor  400 . 
     The occupant detection sensor  400  may further comprise a low-power detection circuit  440  (e.g., a low-power occupancy detection circuit), such as a passive infrared (PIR) detector circuit. The low-power detection circuit  440  may generate a PIR detect signal V PIR  (e.g., a low-power occupancy signal) that may indicate an occupancy and/or vacancy condition in the space in response to detected passive infrared energy in the room. The low-power detection circuit  440  may consume less power than the radar detection circuit  410 . However, the control circuit  420  may be configured to more accurately determine the occupant count in the room using the radar detection circuit  410  (e.g., rather than the low-power detection circuit  440 ). For example, when the power source  430  is a battery, the control circuit  420  may be configured to disable the radar detection circuit  410  when the low-power detection circuit  440  indicates that the room is vacant. The control circuit  420  may detect an occupancy condition in the space in response to the PIR detect signal V PIR  and may subsequently enable the radar detection circuit  410  to determine the occupant count of the room. The control circuit  420  may enable the radar detection circuit  410  after detecting an occupancy condition in the space in response to the PIR detect signal V PIR . The control circuit  420  may also keep the radar detection circuit  410  enabled after detecting an occupancy condition in the space (e.g., in response to the PIR detect signal V PIR ). The control circuit  420  may keep the radar detection circuit  410  enabled until the PIR detect signal V PIR  indicates that the space is vacant. 
     The control circuit  420  may configure the operation of the radar detection circuit  410 , for example, by transmitting signals to the radar detection processor  412  via the communication bus  422 . The control circuit  420  may configure the operation of the radar detection circuit  410  in response to actuation of the configuration buttons of the user interface  424  and/or receiving messages via the communication circuit  428 . For example, the control circuit  420  may be configured to adjust a sensitivity of the occupant detection sensor  400  by adjusting a radar signal-to-noise ratio (SNR) threshold of the radar detection processor  412 . In addition, the radar detection processor  412  and/or the control circuit  420  may be configured to adjust the sensitivity of the occupant detection sensor  400  by adjusting a required size of an identified moving body (e.g., to filter out small moving bodies). 
     The control circuit  420  may be configured to detect occupants within a region of interest of a coverage area of the occupant detection sensor  400 . For example, the control circuit may increase the occupant count in response to occupants having a location (e.g., X-Y coordinate) that falls with the region of interest. The region of interest may be defined by one or more X-Y coordinates, for example, of the corners of a square or rectangle, or by the center of a circle of a prescribed radius. The control circuit  420  may also be configured to detect occupancy in a small region of interest within a large region of interest. For example, the control circuit  420  may be configured to detect movement within a room (e.g., within a large region of interest) using a first detection threshold, and detect movement around a keyboard (e.g., within a small region of interest within the room) using a second detection threshold that may be lower than the first detection threshold or by adjusting the velocity threshold of the Doppler processing (e.g., filter out slow or fast moving objects). 
       FIG.  5    is a simplified flowchart of an example configuration procedure  500  that may be executed to configure an occupant detection sensor  600  (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ).  FIG.  6    is a top-down view of an example room  610  for illustrating the operation of the configuration procedure  500  for the occupant detection sensor  600 . For the example in  FIG.  6   , the example room  610  is rectangular and has four walls  610   a - 610   d . While not shown in  FIG.  6   , the coverage area of the occupant detection sensor  600  may extend beyond the extents of the room  610 , such that the room is fully encompassed by the coverage area. The coverage area of the occupant detection sensor  600  may be characterized by a global coordinate system  602  (e.g., a polar coordinate system) having an origin  604  located at a center point of the occupant detection sensor. The occupant detection sensor  600  may also be characterized by a region of interest  620  that may be circular in shape and may be centered at the origin  604  of the occupant detection sensor  600 . The region of interest  620  may be smaller than the coverage area of the occupant detection sensor  600 . 
     The configuration procedure  500  may begin at  510 . At  512 , bounds (e.g., dimensions or boundaries) of the region of interest may be established. For example, the bounds may be defined by a radius r ROI  of the region of interest  620 . The radius r ROI  of the region of interest  620  may be adjusted by actuating an actuator of a user interface (e.g., the user interface  424 ). In addition, the radius r ROI  of the region of interest  620  may be adjusted using the programming device. For example, the radius r ROI  of the region of interest  620  may be received from the programming device in a message (e.g., a digital message received via the communication circuit  428 ). At  514 , the configuration data (e.g., the radius r ROI  of the region of interest  620 ) determined at  512  may be stored in the occupant detection sensor  600 . At  516 , the configuration procedure  500  may exit. During normal operation of the occupant detection sensor, the control circuit may use the dimensions of the region of interest to determine if the location of the occupant is with the bounds of the region of interest. For example, the control circuit may determine if the distance from the occupant detection circuit to the occupant (e.g., the Z-coordinate defining the location of the occupant as determined by the occupant detection circuit) is less than the radius r ROI  of the region of interest  620  to determine if the location of the occupant is with the bounds of the region of interest. 
       FIG.  7    is a simplified flowchart of an example configuration procedure  700  that may be executed to configure an occupant detection sensor (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ). The configuration procedure  700  may be used to define at least one region of interest (e.g., at least one rectangular region of interest) in a space (e.g., a room) in which the occupant detection sensor is installed. For example, the region of interest may be set to be the entire extents of the room (e.g., within the periphery of the room) or a section of the room. The region of interest may be characterized by a local coordinate system that may or may not be aligned with a global coordinate system of the occupant detection sensor (e.g., the x-axis of the local coordinate system may not be parallel to the x-axis of the global coordinate system). If the room includes multiple regions of interest, the configuration procedure  700  may be repeated multiple times to configure each region of interest. 
     The configuration procedure  700  may begin at  710 . At  712 , configuration data regarding the region of interest may be collected, e.g., by a programming device or by the occupant detection sensor itself. For example, a shape of the region of interest (e.g., circle, square, rectangle, or other polygon), dimensions of the region of interest (e.g., radius or diameter if the shape is a circle, length of sides if the shape is as square, or length and width if the shape is a rectangle), and/or information regarding one or more defining features (e.g., corners) of the region of interest may be collected at  712 . The configuration data may be collected before or after the occupant detection sensor is installed (e.g., as will be described in greater detail below). 
     At  714 , a rotation angle φ R  between the x-axis of the global coordinate system of the occupant detection sensor and the x-axis of the local coordinate system of the region of interest may be established. For example, to establish the rotation angle φ R , the occupant detection sensor may be installed with the x-axis of the global coordinate system aligned with (e.g., parallel and/or perpendicular to) one or more walls of the room (e.g., parallel to the x-axis of the region of interest), such that the rotation angle φ R  is approximately 0°. The x-axis of the global coordinate system of the occupant detection sensor may be determined from one or more coordinate system indicators on the occupant detection sensor (e.g., as shown in  FIGS.  3 A- 3 C ). The rotation angle φ R  may be established at  714  when the shape of the region of interest is a polygon such as a rectangle (e.g., the operation at  714  may be skipped if the shape of the region of interest is a circle). 
     The occupant detection sensor may also be installed with the coordinate system indicator not aligned with the one of the walls of the room (e.g., the global coordinate system of the occupant detection sensor may not be aligned with the local coordinate system of the region of interest). In such a case, a programming device, such as the mobile device  140  (e.g., a smart phone) or other suitable programming tool, may be used to establish the rotation angle φ R  between the x-axis of the global coordinate system and the x-axis of the local coordinate system at  714  of the configuration procedure  700 . For example, the programming device may comprise an internal compass (e.g., an electronic compass). The programming device may be configured to use the electronic compass to determine an angle of the x-axis of the global coordinate system of the occupant detection sensor (e.g., from a recorded image of the coordinate system indicators on the occupant detection sensor) with relation to true north. The programming device may then use the electronic compass to determine the angle of the x-axis of the local coordinate system of the region of interest with relation to true north (e.g., while being held square against one of the walls of the room). The programming device may then calculate the rotation angle (R between the x-axis of the global coordinate system of the occupant detection sensor and the x-axis of the local coordinate system of the region of interest based on a difference in the respective deviations of the two x-axes from true north. 
     Further, at  714 , the occupant detection sensor may itself be configured to determine the rotation angle φ R  (e.g., as part of a self-configuration procedure). For example, commissioning devices or location markers, e.g., radar commissioning devices, such as Doppler phantoms (e.g., a person or object), may be placed in two or more corners of the room or a region of interest. The Doppler phantoms may continuously move (e.g., rotate) in fixed locations during the self-configuration procedure, such that the occupant detection sensor is able to automatically determine the locations of the two or more corners of the room. For example, the Doppler phantoms may be located in one location for a circular region of interest, two corners for a square room, three corners for a rectangular room, and additional corners for a complex-shaped room. Multiple Doppler phantoms may all be located in corners of the room at the same time or a single Doppler phantom may move or may be moved between the corners of the room one at a time. The occupant detection sensor may be configured to calculate the rotation angle φ R  using the locations (e.g., X-Y coordinates) of the corners of the room as determined from the Doppler phantoms. In addition, the occupant detection sensor may be configured to determine the locations of the corners of the room in response to an installer tracing (e.g., walking) the perimeter of the room and/or standing while moving slightly in the corners of the room during the self-configuration procedure. 
     At  716 , an offset vector between an origin of the global coordinate system of the occupant detection sensor and an origin of the local coordinate system of the region of interest may be established. For example, the region of interest may include the extents of the room and may be defined by the locations of vertices (e.g., the corners) of the room. The origin of the local coordinate system of the region of interest may be set at a vertex (e.g., a corner) of the room. An installer may measure the distances from the center of the ceiling-mounted occupant detection sensor to each of the walls (e.g., four walls) of the room in which the occupant detection sensor is installed by counting ceiling tiles, using a tape measure, using a laser range finder or using an ultrasonic range finder. The installer may enter the measurements into a configuration application running on the programming device. For example, if the global coordinate system of the occupant detection sensor is aligned with the local coordinate system of the room and/or region of interest, the installer may enter the measurement into the configuration application running on the programming device in a particular order so that the programming device can properly determine the dimensions of the room and/or region of interest as well as the offset vector between the origin of the global coordinate system and the origin of the local coordinate system of the region of interest. 
     In addition, the programming device may be configured to measure the distances between the occupant detection sensor and the walls of the room at  716 , for example, using a distance measuring application or technology of the programming device, such as an optical displacement sensing technique. Further, other measurement tools may be used to measure the distances between the occupant detection sensor and the walls, such as a laser rangefinder and/or a tripod rangefinder. Using the measurements of the room and/or region of interest, the programming device may be configured to calculate the dimensions of the room and/or region of interest as well as the offset vector between the origin of the global coordinate system and the origin of the local coordinate system of the region of interest at  716 . In addition, the occupant detection sensor itself may be configured to determine the offset vector in response to the locations (e.g., X-Y coordinates) of the corners of the room (e.g., as determined from one or more Doppler phantoms and/or an installer tracing the perimeter of the room during the self-configuration procedure). 
     At  718 , bounds (e.g., dimensions or boundaries) of the region of interest may be established. For example, the bounds may be set equal to and/or determined from the configuration data collected at  712  (e.g., by the programming device). If the region of interest is a rectangle or square, the bounds may be calculated from the distances between the occupant detection sensor and the walls determined at  716  (e.g., the dimensions of the room). In addition, the occupant detection sensor itself may be configured to calculate the bounds using the locations (e.g., X-Y coordinates) of the corners of the room (e.g., as determined from one or more Doppler phantoms and/or an installer tracing the perimeter of the room during the self-configuration procedure). 
     At  718 , the configuration data (e.g., the rotation angle φ R , the offset vector, and/or the dimensions of the region of interest) determined at  712 - 716  may be stored in the occupant detection sensor. If the configuration data is determined using the programming device, the programming device may be configured to transmit the configuration data to the occupant detection sensor prior to the occupant detection sensor storing the configuration data at  718 . Note that if the x-axis of the global coordinate system is aligned with (e.g., parallel and/or perpendicular to) one or more walls of the room (e.g., parallel to the x-axis of the region of interest), the rotation angle φ R  may be included in the configuration data and set to 0°, or the rotation angle may not be included in the configuration data. In the latter case, the occupant detection sensor may determine that the rotation angle is 0°. At  720 , the configuration procedure  700  may exit. 
     During normal operation of the occupant detection sensor, the control circuit may use the rotation angle φ R  and/or the offset vector to convert (e.g., transform) a location in the global coordinate system of the occupant detection sensor (e.g., as determined by the occupant detection circuit) to a location in the local coordinate system of the region of interest (as will be described in greater detail below). The control circuit may use the dimensions of the region of interest to determine if the location in the local coordinate system is with the bounds of the region of interest. During the configuration procedure  700 , the control circuit may also transform locations of the vertices (e.g., corners) of the region of interest in the global coordinate system into locations of the vertices of the region of interest in the local coordinate system. For example, the control circuit may use the locations of the vertices of the region of interest in the local coordinate system for further configuration of the occupant detection sensor (e.g., during normal operation). 
       FIG.  8    is a simplified flowchart of an example configuration procedure  800  that may be executed to configure an occupant detection sensor  900  (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ).  FIG.  9    is a top-down view of an example room  910  for illustrating the operation of the configuration procedure  800  for the occupant detection sensor  900 . For the example in  FIG.  9   , the example room  910  is rectangular and has four walls  910   a - 910   d . While not shown in  FIG.  9   , the coverage area of the occupant detection sensor  900  may extend beyond the extents of the room  910 , such that the room is fully encompassed by the coverage area. The coverage area of the occupant detection sensor  900  may be characterized by a global coordinate system  902  having an origin  904  located at a center point of the occupant detection sensor. The occupant detection sensor  900  may comprise a coordinate system indicator  906  (e.g., an arrow) for indicating the direction of the x-axis and/or y-axis of the global coordinate system  902 . The occupant detection sensor  900  may also be characterized by an initial region of interest  908  (e.g., an out-of-box region of interest with which the occupant detection sensor  900  may be configured when first installed and powered on). The initial region of interest  908  may be rectangular in shape with the longer sides parallel to the x-axis of the global coordinate system  902 . 
     The configuration procedure  800  may be executed to configure a desired region of interest  920 , which may be, for example, the extents of the room  910 . The desired region of interest  920  may be characterized by a local coordinate system  922  having an origin  924  located at one of the corners of the desired region of interest. The desired region of interest  920  may be aligned with the walls of the room  910 . As shown in  FIG.  9   , the x-axis of the local coordinate system  922  of the desired region of interest  920  may be aligned with (e.g., parallel to) the x-axis of the global coordinate system  902  of the occupant detection sensor  900 . The local coordinate system  922  may be offset from the global coordinate system  902  by an offset vector  930 . 
     The configuration procedure  800  may begin at  810 . At  812 , an installer may install the occupant detection sensor  900  with the coordinate system indicator  906  directed towards one of the walls  910   a - 910   b  of the room  910 . For example, the coordinate system indicator  914  may be directed to one of the shorter walls  910   a  of the room  910 , such that the x-axis of the global coordinate system  902  is perpendicular to the shorter walls  910   a ,  910   c  and parallel with the longer walls  910   b ,  910   d . Since the x-axis of the global coordinate system  902  is parallel to the x-axis of the local coordinate system  922 , the rotation angle φ R  between the x-axis of the global coordinate system  902  and the x-axis of the local coordinate system  922  may be established as approximately 0° at  812  due to the installation of the occupant detection sensor with the coordinate system indicator  906  directed towards one of the walls  910   a - 910   b  of the room  910 . In addition, the global coordinate system  902  and the local coordinate system  922  may be aligned (e.g., having x-axes and y-axes extending in the same directions), and may be offset from one another by the offset vector  930 . For example, the occupant detection sensor  900  may be rotatably mounted to a base portion, such that the respective the occupant detection sensor  900  may be easily rotated to direct the coordinate system indicator  906  in the appropriate direction (e.g., towards one of the walls  901   a - 910   d ). An example of a sensor that is rotatable is described in greater detail in commonly-assigned U.S. Pat. No. 9,568,356, issued Feb. 14, 2017, entitled SENSOR HAVING A ROTATABLE ENCLOSURE, the entire disclosure of which is hereby incorporated by reference. 
     At  814 , the installer may start a sensor configuration software (e.g., a sensor configuration app) on a programming device, such as the mobile device  140  (e.g., a smart phone). At  816 , the installer may determine the center point of the occupant detection sensor  900  (e.g., the origin  904  of the global coordinate system  902 ). For example, the installer may determine the location on the floor immediately below the location at which the occupant detection sensor  900  is located on the ceiling. In addition, the installer may hang a plumb bob from the occupant detection sensor  900  (e.g., aligned with the boresight) to identify the center point of the occupant detection sensor. For example, the occupant detection sensor  900  may comprise an attachment mechanism, such as a hook (not shown), at the center of the downward-facing surface of the occupant detection sensor for connecting to a cord of the plumb bob. Further, the occupant detection sensor  900  may comprise a laser emitter circuit (not shown) that may be located at the center of the occupant detection sensor and aligned with the boresight. The laser emitter circuit may shine a laser beam onto the floor below the center of the occupant detection sensor. The programming device may transmit a digital message to the occupant detection sensor  900  to cause the occupant detection sensor to enable the laser emitting circuit in response the sensor configuration software starting at  814 . In addition, the occupant detection sensor  900  may enable the laser emitting circuit in response to the installer actuating a button on the occupant detection sensor. 
     At  818 , the installer may measure a distance between the center point of the occupant detection sensor  900  and one of the walls  910   a - 910   d . For example, the installer may first measure a distance D 1  (e.g., as shown in  FIG.  9   ) between the center point of the occupant detection sensor  900  and the wall  910   a  to which the coordinate system indicator  906  is pointing. At  820 , the installer may then enter the measurement of the distance (e.g., the distance D 1  between the center point of the occupant detection sensor  900  and the wall  910   a ) into the sensor configuration software running on the programming device. If there are more walls to which to measure the distance from the center of the occupant detection sensor  900  at  822  (e.g., the installer is not done measuring distances), the installer may once again measure a distance between the center point of the occupant detection sensor  900  and one of the other walls  910   a - 910   d  at  818 , and enter the measurement into the sensor configuration software running on the programming device at  820 . For example, the second time that  818  is completed, the installer may measure a distance D 2  between the center point of the occupant detection sensor  900  and the wall  910   b . The installer may continue to measure the distances D 3 , D 4  between the center point of the occupant detection sensor  900  and the walls  910   c ,  910   d  at  818  and enter the measurement into the sensor configuration software running on the programming device at  820 , until there are no more walls to which to measure the distance from the center of the occupant detection sensor  900  at  822 . For example, the installer may move between the walls  910   a - 910   d  in a clockwise manner in order to measure and store the distance D 1 -D 4  into the sensor configuration software in that order. 
     When the installer is done measuring distances at  822 , the programming device (e.g., the sensor configuration software running on the programming device) may determine an offset vector (x OFF , y OFF ) (e.g., the offset vector  930  shown in  FIG.  9   ) at  824 . For example, the programming device may calculate the offset vector (x OFF , y OFF ) from two of the distances D 1 -D 4  measured at  818 , e.g., x OFF =−D 3  and y OFF =−D 2 . At  826 , the programming device may determine dimensions X ROI , Y ROI  of the region of the interest (e.g., the desired region of interest  920 ). For example, the programming device may calculate the dimensions X ROI , Y ROI  of the region of interest  920  from the distances D 1 -D 4  measured at  818 , e.g., X ROI =D 1 +D 3  and Y ROI =D 2 +D 4 . 
     At  828 , the programming device may transmit (e.g., directly transmit) the sensor configuration data to the occupant detection sensor  900 . For example, the sensor configuration data may include the rotation angle φ R  (e.g., approximately 0°), the offset vector (x OFF , y OFF ), and/or the dimensions X ROI , Y ROI  of the region of the interest. In addition, the programming device may transmit the sensor configuration data to another control device (e.g., the system controller  110  of the load control system  100 ), which may then transmit the sensor configuration data to the occupant detection sensor  900 . At  830 , the occupant detection sensor  900  may store the sensor configuration data in memory, before the configuration procedure  800  exits. 
       FIG.  10    is a simplified flowchart of an example configuration procedure  1000  that may be executed to configure an occupant detection sensor  1100  (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ).  FIG.  11    is a top-down view of an example room  1110  for illustrating the operation of the configuration procedure  1000  for the occupant detection sensor  1100 . For the example of  FIG.  11   , the example room  1110  may be rectangular with four walls  1110   a - 1110   d , and the coverage area of the occupant detection sensor  1100  may extend beyond the extents of the room  1110 , such that the room is fully encompassed by the coverage area. The coverage area of the occupant detection sensor  1100  may be characterized by a global coordinate system  1102  having an origin  1104  located at a center point of the occupant detection sensor. The occupant detection sensor  1100  may comprise coordinate system indicators  1106   a ,  1106   b  (e.g., light sources) for indicating the direction of the x-axis of the global coordinate system  1102 . For example, the first coordinate system indicator  1106   a  may comprise a green LED and the second coordinate system indicator  1106   b  may comprise a red LED. The occupant detection sensor  1100  may also be characterized by an initial region of interest  1108  (e.g., an out-of-box region of interest with which the occupant detection sensor  1100  may be configured when first installed and powered on). 
     The configuration procedure  1000  may be executed to configure a desired region of interest  1120 , which may be, for example, the extents of the room  1110 . The desired region of interest  1120  may be characterized by a local coordinate system  1122  having an origin  1124  located at one of the corners of the desired region of interest. The desired region of interest  1120  may be aligned with the wall of the room  1110 . As shown in  FIG.  11   , the x-axis of the global coordinate system  1102  of the occupant detection sensor  1100  may not be aligned with the x-axis of the local coordinate system  1122  of the desired region of interest  1120 . For example, a rotation angle φ R  may exist between the x-axis of the global coordinate system  1102  and the x-axis of the local coordinate system  1122 . The local coordinate system  1122  may also be offset from the global coordinate system  1102  by an offset vector  1130 . 
     The configuration procedure  1000  may be executed using a programming device  1140 , such as the mobile device  140  (e.g., a smart phone). The programming device  1140  may comprise a visible light sensing circuit (e.g., a camera) for recording images (e.g., of the room  1110  and/or the occupant detection sensor  1100 ). In addition, the programming device  1140  may comprise an internal compass (e.g., an electronic compass) for determining the direction of true north (e.g., as indicated by a north indicator  1114  on  FIG.  11   ). The programming device  1140  may be characterized by a programming device axis  1142  that may extend from one of the sides of the programming device (e.g., a top side). The programming device  1140  may be configured to use the internal electronic compass to the determine a programming device angle (PP between the programming device axis  1142  and a true north axis  1118  (e.g., that extends towards true north as indicated by the north indicator  1114  on  FIG.  11   ). 
     The configuration procedure  1000  may begin at  1010 . At  1012 , an installer may start a sensor configuration software (e.g., a sensor configuration app) on the programming device  1140 . At  1014 , the installer may position the programming device  1140  below (e.g., approximately below) the occupant detection sensor  1100 . At  1016 , the programming device  1140  (e.g., the sensor configuration software running on the programming device) may determine a sensor angle φ S  between the x-axis of the global coordinate system  1102  of the occupant detection sensor  1100  and a true north axis  1116  (e.g., that extends towards true north as indicated by the north indicator  1114  on  FIG.  11   ). For example, the programming device  1140  may be configured to record an image of the occupant detection sensor  1100  using the camera (e.g., while the programming device is located under the occupant detection sensor). The programming device  1140  may be configured to determine the x-axis of the global coordinate system  1102  of the occupant detection sensor  1100  by determining the location of the coordinate system indicators  1106   a ,  1106   b  in the image. For example, the programming device may  1140  be configured to process the image to determine location of the x-axis of the global coordinate system  1102  along a line extending between the coordinate system indicators  1106   a ,  1106   b  with the first coordinate system indicator  1106   a  located on the side of the occupant detection sensor in which the x-axis of the global coordinate system  1102  extends (e.g., the position direction of the x-axis of the global coordinate system  1102 ). The occupant detection sensor  1110  may be configured to turn on the coordinate system indicators  1106   a ,  1106   b  in response receiving a digital message from the programming device  1140  (e.g., when the sensor configuration app is started at  1012 ) and/or in response to an actuation of a button on the occupant detection sensor. The programming device  1140  may be configured to use the internal electronic compass to determine the sensor angle φ S  between the x-axis of the global coordinate system  1102  of the occupant detection sensor  1100  and the true north axis  1116 . At  1018 , the programming device  1140  may store the sensor angle φ S  in memory. 
     At  1020 , the installer may place the edge of the programming device  1140  square against one of the walls  1110   a - 1110   d  of the room. For example, the installer may first place the programming device  1140  against the wall  1110   a  to which the first coordinate system indicator  1106   a  is closest. The installer may place the programming device  1140  against the wall  1110   a  with one of the sides and/or surfaces of the programming device (e.g., the top side) flat and square against the wall, such that the programming device axis  1142  is parallel with the x-axis of the local coordinate system  1122  of the region of interest  1120 . In addition, the installer may place the programming device  1140  against the wall  1110   a  with the camera facing upwards to enable the programming device to record an image of the occupant detection sensor  1100  while the programming device is against the wall. 
     If the programming device  1140  has not already established the rotation angle φ R  between the x-axis of the global coordinate system  1102  and the x-axis of the local coordinate system  1122  at  1022 , the programming device may use the internal electronic compass to determine the programming device angle (PP between the programming device axis  1142  and the true north axis  1118  at  1024 . Since the programming device  1140  is being held against the wall such that the programming device axis  1142  is parallel to the x-axis of the local coordinate system  1122 , the programming device angle (PP may be representative of a room angle between the x-axis of the local coordinate system  1122  and the true north axis  1118 . At  1026 , the programming device  1140  may calculate the rotation angle φ R  between the x-axis of the global coordinate system  1102  and the x-axis of the local coordinate system  1122  by subtracting the sensor angle φ S  from the programming device angle φ P , e.g., φ R =φ P −φ S . At  1028 , the programming device  1140  may store the programming device angle φ P  in memory. 
     At  1030 , the programming device  1140  may determine the distance (e.g., the distance D 1 ) between the wall  1110   a  and the center point of the occupant detection sensor  1100 . For example, the programming device  1140  may record an image of the occupant detection sensor  1100  and use an optical displacement sensing technique to measure the distance between the wall  1110   a  and the center point of the occupant detection sensor  1100  (e.g., using the locations of the first and second coordinate system indicators  1106   a ,  1106   b  in the recorded image). At  1032 , the programming device  1140  may store the measurement of the distance (e.g., distance D 1 ) in memory. If there are more walls to which to measure the distance from the center of the occupant detection sensor  1100  at  1034  (e.g., the programming device  1140  is not done measuring distances), the installer may place the programming device  1140  against one of the other walls  1110   a - 1110   d  of the room at  1020 . For example, the second time that  1020  is completed, the installer may place the programming device  1040  against the second wall  1110   b . Since the programming device  1040  has already established the rotation angle φ R  at  1022 , the programming device may next measure a distance D 2  between the wall  1110   b  and the center point of the occupant detection sensor  1100  at  1030  and store the measurement in memory at  1032 . The programming device  1140  may be placed against the other walls  1110   c ,  110   d  in order to measure and store the distances D 3 , D 4  between the walls and the center point of the occupant detection sensor  1100 , until there are no more walls to which to measure the distance from the center of the occupant detection sensor  1100  at  1034 . For example, the installer may place the programming device  1140  against the walls  1110   a - 1110   d  in a clockwise manner to measure and store the distances D1-D4 in that order. 
     When the programming device  1140  is done measuring distances at  1034 , the programming device  1140  may determine an offset vector (x OFF , y OFF ) (e.g., the offset vector  1130  shown in  FIG.  11   ) at  1036 . For example, the programming device  1140  may determine the offset vector (x OFF , y OFF ) from two of the distances D 1 -D 4  measured at  1030 , e.g., x OFF =−D 3  and y OFF =−D 2 . At  1038 , the programming device may determine dimensions X ROI , Y ROI  of the region of the interest (e.g., the desired region of interest  1120 ). For example, the programming device may calculate the dimensions X ROI , Y ROI  from the distances D 1 -D 4  measured at  1030 , e.g., X ROI =D 1 +D 3  and Y ROI =D 2 +D 4 . 
     At  1040 , the programming device  1140  may transmit (e.g., directly transmit) the sensor configuration data to the occupant detection sensor  1100 . For example, the sensor configuration data may include the rotation angle φ R , the offset vector (x OFF , y OFF ), and/or the dimensions X ROI , Y ROI  of the desired region of the interest  1120 . In addition, the programming device  1140  may transmit the sensor configuration data to another control device (e.g., the system controller  110  of the load control system  100 ), which may then transmit the sensor configuration data to the occupant detection sensor  1100 . At  1042 , the occupant detection sensor  1100  may store the sensor configuration data in memory, before the configuration procedure  1000  exits at  1044 . 
       FIG.  12    is a simplified flowchart of an example configuration procedure  1200  that may be executed to configure an occupant detection sensor  1300  (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ).  FIG.  13    is a top-down view of an example room  1310  for illustrating the operation of the configuration procedure  1200  for the occupant detection sensor  1300 . For the example of  FIG.  13   , the example room  1310  may be rectangular with four walls  1310   a - 1310   d , and the coverage area of the occupant detection sensor  1300  may extend beyond the extents of the room  1310 , such that the room is fully encompassed by the coverage area. The coverage area of the occupant detection sensor  1300  may be characterized by a global coordinate system  1302  having an origin  1304  located at a center point of the occupant detection sensor. The occupant detection sensor  1300  may also be characterized by an initial region of interest (not shown) similar to the initial region of interest  1108  shown in  FIG.  11   . 
     The configuration procedure  1200  may be executed to configure a desired region of interest  1320 , which may be, for example, the extents of the room  1310 . The desired region of interest  1320  may be characterized by a local coordinate system  1322  having an origin  1324  located at one of the corners of the desired region of interest. The desired region of interest  1320  may be aligned with the walls of the room  1310 . As shown in  FIG.  13   , the x-axis of the global coordinate system  1302  of the occupant detection sensor  1300  may not be aligned with the x-axis of the local coordinate system  1322  of the desired region of interest  1320 . For example, a rotation angle φ R  may exist between the x-axis of the global coordinate system  1302  and the x-axis of the local coordinate system  1322 . The local coordinate system  1322  may also be offset from the global coordinate system  1302  by an offset vector  1330 . 
     The configuration procedure  1200  may be primarily executed by a control circuit of the occupant detection sensor  1300  (e.g., the radar detection processor  412  and/or the control circuit  420  of the occupant detection sensor  400 ), for example, as part of a self-configuration procedure. The configuration procedure  1200  may be executed with one or more commissioning devices or location markers, such as Doppler phantoms  1350   a ,  1350   b ,  1350   c , located in two or more corners of the room  1310 . Since the room  1310  is rectangularly shaped, the room  1310  may have Doppler phantoms  1350   a ,  1350   b ,  1350   c  in three corners. 
     The configuration procedure  1200  may begin at  1210 . At  1212 , an installer may place the Doppler phantoms  1350  in two or more corners of the room  1310  (e.g., three corners as shown in  FIG.  13   ). At  1214 , an installer may cause the occupant detection sensor to enter a sensor configuration mode (e.g., a self-configuration mode). The installer may cause the occupant detection sensor to enter the sensor configuration mode while the installer is not located in the room  1310  (e.g., such that the occupant detection sensor  1300  may not mistake the installer for one of the Doppler phantoms  1350   a - 1350   c ). For example, the installer may use a sensor configuration software (e.g., a sensor configuration app) running on a programming device, such as the mobile device  140  (e.g., a smart phone) to transmit (e.g., directly transmit) a message to the occupant detection sensor to cause the occupant detection sensor to enter the sensor configuration mode. In addition, the installer may shine a laser pointer on a laser receiving circuit (not shown) in the occupant detection sensor  1300  to cause the occupant detection sensor to enter the sensor configuration mode. 
     At  1216 , the occupant detection sensor (e.g., the control circuit of the occupant detection sensor) may determine locations (x a , y a ), (x b , y b ), (x c , y c ) of the respective Doppler phantoms  1350   a ,  1350   b ,  1350   c  in the global coordinate system  1302 . At  1218 , the occupant detection sensor  1300  may be configured to calculate the rotation angle φ R  using the locations of two of the Doppler phantoms  1350   a - 1350   c . For example, the occupant detection sensor  1300  may be configured use the locations (x a , y a ), (x b , y b ) of the Doppler phantoms  1350   a ,  1350   b  to calculate the rotation angle φ R , e.g., 
     
       
         
           
             
               φ 
               R 
             
             = 
             
               
                 
                   tan 
                   
                     - 
                     1 
                   
                 
                 ⁡ 
                 
                   ( 
                   
                     
                       
                         y 
                         a 
                       
                       - 
                       
                         y 
                         b 
                       
                     
                     
                       
                         x 
                         a 
                       
                       - 
                       
                         x 
                         b 
                       
                     
                   
                   ) 
                 
               
               . 
             
           
         
       
     
     For example, the control circuit of the occupant detection sensor  1300  may be configured to calculate the arctangent function (e.g., tan −1 ) and/or may have the solutions to the arctangent function stored in memory. At  1220 , the occupant detection sensor  1300  may determine an offset vector (x OFF , y OFF ) (e.g., the offset vector  1330  shown in  FIG.  13   ). For example, the occupant detection sensor  1300  may be configured to determine the offset vector (x OFF , y OFF ) from the locations (x a , y a ) of one of the Doppler phantoms  1350   a , e.g., x OFF =−x a  and y OFF =−y a . 
     At  1222 , the occupant detection sensor  1300  may determine dimensions X ROI , Y ROI  of the region of the interest (e.g., the desired region of interest  1320 ). For example, the occupant detection sensor  1300  may be configured to calculate the dimensions X ROI , Y ROI  using the locations (x a , y a ), (x b , y b ), (x a , y c ) of all three Doppler phantoms  1350   a ,  1350   b ,  1350   c , e.g.,
 
 X   ROI =sqrt[( y   a   −y   b ) 2 +( x   a   −x   b ) 2 ]; and
 
 Y   ROI =sqrt[( y   b   −y   c ) 2 +( x   b   −x   c ) 2 ].
 
At  1224 , the occupant detection sensor  1200  may store the sensor configuration data in memory. For example, the sensor configuration data may include the rotation angle φ R , the offset vector (x OFF , y OFF ), and/or the dimensions X ROI , Y ROI  of the desired region of the interest  1320 . At  1226 , the occupant detection sensor  1300  may exit the sensor configuration mode, before the configuration procedure  1200  exits at  1228 .
 
       FIG.  14    is a simplified flowchart of an example configuration procedure  1400  that may be executed to configure an occupant detection sensor (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ). For example, the configuration procedure  1400  may be executed to configure a region of interest that has a rectangular shape (e.g., such as the desired region of interest  1320  shown in  FIG.  13   ). In addition, the configuration procedure  1400  may be executed to configure regions of interest that have complex shapes, such as an L-shape, a C-shape, or other polygon having four or more sides. 
     At  1410 , an installer may start the configuration procedure  1400 , for example, by opening a sensor configuration application on a programming device, such as the mobile device  140  (e.g., a smart phone) and/or selecting a “start configuration” option and/or button on the configuration application. The programming device may subsequently transmit a message (e.g., a digital message) to the occupant detection sensor to start the configuration procedure  1400 . In addition, the installer may start the configuration procedure  1400  at  1410  by shining a laser pointer onto a laser receiving circuit (not shown) on the occupant detection sensor or otherwise signaling to the occupant detection sensor to start the configuration procedure  1400  (e.g., by actuating a button on the occupant detection sensor). 
     At  1412 , the occupant detection sensor may enter a configuration mode. At  1414 , the occupant detection sensor may determine a starting location (e.g., X-Y coordinates) of the installer and store the starting location of the installer in memory as a doorway location. While the occupant detection sensor is in the configuration mode, the installer may walk around the perimeter of the room at  1416  and the occupant detection sensor may periodically store (e.g., automatically or after being prompted by the installer) the location of the installer in memory (e.g., in separate memory locations) at  1418 . For example, the occupant detection sensor may store the locations in memory as X-Y coordinates. The occupant detection sensor may continue to store locations of the installer at  1418  until the installer returns to the starting location at  1420 . 
     After the installer returns to the starting location at  1420 , the occupant detection sensor may process the locations of the installer that were stored in memory during the configuration mode to determine the locations of the corners and/or the perimeter of the room at  1422 . For example, if the room is rectangular, the occupant detection sensor may determine the locations (x a , y a ), (x b , y b ), (x a , y c ), (x d , y d ) of the four corners of the room at  1422 . The occupant detection sensor may be configured to perform a least squares rectangular fit on the locations of the installer that were stored in the memory during the configuration mode to estimate the best fit for the walls and/or corners of the room based on the stored data. For example, the occupant detection sensor may ensure that lines defining the walls of the rooms are perpendicular to each other and form a square or rectangle. At  1424 , the occupant detection sensor may be configured to determine the rotation angle φ R  using the locations of two of the corners of the room. For example, if the room is rectangular, the occupant detection sensor may be configured to calculate the rotation angle φ R  in a similar manner as at  1218  of the configuration procedure  1200  shown in  FIG.  12   . At  1426 , the occupant detection sensor may determine an offset vector (x OFF , y OFF ) using location of one of the corners of the room (e.g., which may be set as the origin of the local coordinate system associated with the region of interest). For example, if the room is rectangular, the occupant detection sensor may be configured to determine the offset vector (x OFF , y OFF ) in a similar manner as at  1220  of the configuration procedure  1200  shown in  FIG.  12   . 
     At  1428 , the occupant detection sensor may be configured to determine bounds of the region of interest for the occupant detection sensor. The bounds of the region of interest may be defined by the perimeter and/or dimensions of the room and/or region of interest. If the room is rectangular, the occupant detection sensor may be configured to determine the bounds by determining dimensions X ROI , Y ROI  of the region of interest, for example, in a similar manner as at  1222  of the configuration procedure  1200  shown in  FIG.  12   . At  1430 , the occupant detection sensor may store the sensor configuration data in memory. For example, the sensor configuration data may include the rotation angle φ R , the offset vector (x OFF , y OFF ), and/or the bounds (e.g., the dimensions X ROI , Y ROI ) of the region of the interest. At  1432 , the occupant detection sensor may exit the sensor configuration mode, before the configuration procedure  1400  exits at  1434 . 
       FIG.  15    is a simplified flowchart of another example configuration procedure  1500  that may be executed to configure an occupant detection sensor (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ). For example, the configuration procedure  1500  may be executed to configure a region of interest that has a rectangular shape (e.g., such as the desired region of interest  1320  shown in  FIG.  13   ). In addition, the configuration procedure  1500  may be executed to configure regions of interest that have complex shapes, such as an L-shape, a C-shape, or other polygon having four or more sides. Throughout the configuration procedure  1500 , an installer may utilize a configuration application running on a programming device, such as the mobile device  140  (e.g., a smart phone), which may be in communication with (e.g., direct communication with) the occupant detection sensor for configuring the occupant detection sensor. At  1510 , the installer may start the configuration procedure  1500 , for example, by opening a configuration application running on the network device and/or selecting a “start configuration” option and/or button on the configuration application. 
     At  1512 , the occupant detection sensor may enter a configuration mode. At  1514 , the installer may walk to a location in the room. At  1516 , the installer may select a location type using the programming device. For example, the location may indicate a part of the room and/or an object in the room (e.g., a corner, a doorway, a desk chair, etc.). The programming device may then transmit an indication of the selected location type to the occupant detection sensor at  1518 , and the occupant detection sensor may store the location type and the location (e.g., X-Y coordinates) in memory at  1520 . If the installer is not done identifying locations in the room at  1522 , the installer may walk to a different location at  1514  and select the appropriate location type at  1516 . If the installer is done identifying locations in the room (e.g., in the installer selected a “done” option and/or button on the programming device) at  1522 , the occupant detection sensor may be configured to determine the rotation angle φ R  using the locations of two of the corners of the room at  1524  (e.g., using the locations of the corners of the room determined at  1518 - 1522 ). For example, if the room is rectangular, the occupant detection sensor may be configured to calculate the rotation angle φ R  in a similar manner as at  1218  of the configuration procedure  1200  shown in  FIG.  12   . At  1526 , the occupant detection sensor may determine an offset vector (x OFF , y OFF ) using location of one of the corners of the room (e.g., which may be set as the origin of the location coordinate system associated with the region of interest). For example, if the room is rectangular, the occupant detection sensor may be configured to determine the offset vector (x OFF , y OFF ) in a similar manner as at  1220  of the configuration procedure  1200  shown in  FIG.  12   . 
     At  1530 , the occupant detection sensor may be configured to determine bounds of the region of interest for the occupant detection sensor (e.g., as defined by the perimeter and/or dimensions of the room and/or region of interest). If the room is rectangular, the occupant detection sensor may be configured to determine the bounds by determining dimensions X ROI , Y ROI  of the region of interest, for example, in a similar manner as at  1222  of the configuration procedure  1200  shown in  FIG.  12   . At  1532 , the occupant detection sensor may store the sensor configuration data in memory. For example, the sensor configuration data may include the rotation angle φ R , the offset vector (x OFF , y OFF ), the bounds (e.g., the dimensions X ROI , Y ROI ) of the region of the interest, and/or locations determined at  1518 - 1522  that may define masked areas or static areas. At  1534 , the occupant detection sensor may exit the sensor configuration mode, before the configuration procedure  1500  exits at  1536 . 
     While the configuration procedure  1500  as shown in  FIG.  15    allows the installer to identify the locations of corners, doorways, and desk chairs in the room, the configuration procedure could also allow the installer to identify other locations in the room, such as, for example, corners of a desk, corners of a table, a keyboard of a computer, and/or a noise source (e.g., such as a fan or other moving object that is not an occupant of the room). Rather than (or in addition to) identifying the corners of the room to identify the perimeter of the room, the configuration application  1500  may allow the installer to identify the perimeter or the room by walking around the perimeter of the room (e.g., as in the configuration procedure  1400  shown in  FIG.  14   ). In addition, the configuration procedure  1500  of  FIG.  15    may be used to identify the location of multiple corners, doorways, desks, desk chairs, etc. of the room. Further, the configuration procedure  1500  may allow an installer to define a region of interest having a complex shape, such as a polygon having more than four sides. 
       FIG.  16    is a simplified flowchart of an example configuration procedure  1600  that may be executed to configure an occupant detection sensor  1700  (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ).  FIG.  17 A  is a top-down view of an example room  1710  for illustrating the operation of the configuration procedure  1600  for the occupant detection sensor  1700 . The coverage area of the occupant detection sensor  1700  may be characterized by a global coordinate system  1702  having an origin  1704  located at a center point of the occupant detection sensor. 
     The configuration procedure  1600  may be executed to configure multiple regions of interest  1720   a - 1720   e  (e.g., multiple rectangular regions of interest) in the room  1710 . For example, the room  1710  may include five rectangular regions of interest as shown in  FIG.  17 A . The regions of interest  1720   a - 1720   e  may overlap with each other. The regions of interest  1720   a - 1720   e  may be rotated and sized so as to cover the extents of the room  1710 . In other words, the combined area of the multiple regions of interest  1720   a - 1702   e  (e.g., including both overlapping and non-overlapping areas) may be, for example, the extents of the room  1710 . Each of the regions of interest  1720   a - 1720   e  may be characterized by a respective local coordinate system  1722   a - 1722   e  having a respective origin  1724   a - 1724   e  (e.g., located at one of the corners of the region of interest). As shown in  FIG.  17 A , the x-axis of the global coordinate system  1702  of the occupant detection sensor  1700  may not be aligned with any of the x-axes of the local coordinate systems  1722   a - 1722   e  of the regions of interest  1720   a - 1720   e . For example, a respective rotation angle (not shown in  FIG.  17 A ) may exist between the x-axis of the global coordinate system  1702  and each of the x-axes of the respective local coordinate systems  1722   a - 1722   e . Each of the local coordinate systems  1722   a - 1722   e  may also be offset from the global coordinate system  1702  by a respective offset vector  1730   a - 1730   e.    
     Multiple rectangular regions of interest may be provided in the room  1710  since rectangular regions of interest may simplify configuration and operation of the occupant detection sensor  1700 . To specify and/or configure rectangular regions of interest, the rotation angle, the offset vector, and/or the bounds (e.g., the dimensions) for each rectangular region of interest may be established using one or more of the methods disclosed herein. Multiple rectangular regions of interest may be assembled together to create a region of interest having a complex shape. During normal operation, rectangular regions of interest may allow for quick determination (e.g., via simple computation) of whether an occupant is within the bounds of a complex-shaped region formed by multiple rectangular regions of interest. For example, the occupant detection sensor  1700  may determine that a particular occupant is within one of the rectangular regions of interest to determine that the occupant is within the complex-shaped region of interest. 
     The configuration procedure  1600  may begin at  1610 . At  1612 , a rotation angle between the x-axis of the global coordinate system  1702  of the occupant detection sensor  1700  and the x-axis of a local coordinate system of a first one of the regions of interest (e.g., the local coordinate system  1722   a  of the region of interest  1720   a ) may be established. At  1614 , an offset vector (e.g., the offset vector  1730   a ) between the origin  1704  of the global coordinate system  1702  of the occupant detection sensor  1700  and an origin of the local coordinate system of the first one of the regions of interest (e.g., the origin  1724   a ) may be established. At  1616 , bounds (e.g., dimensions or boundaries) of the first one of the regions of interest may be established. The rotation angle, offset vector, and bounds of the first one of the regions of interest may be established at  1612 - 1616  using any of the techniques used in the configuration procedures of  FIGS.  7 - 15   . Once established, the configuration information including the rotation angle, offset vector, and bounds of the region of interest may be stored at  1618 . If there are more regions of interest to configure at  1620 , the configuration procedure  1600  may loop around to establish the rotation angle, offset vector, and bounds of the next region of interest (e.g., the region of interest  1720   b ) at  1612 - 1616 . When all of the regions of interest in the room  1710  (e.g., all of the regions of interest  1720   a - 1720   e ) have been configured at  1620 , the configuration procedure  1600  may exit at  1720 . 
       FIGS.  17 B and  17 C  are top-down views of other example rooms  1710 ′,  1710 ″ that each have multiple regions of interest and may be configured using the configuration procedure  1600  of  FIG.  16    for the occupant detection sensor  1700 . For example, the room  1710 ′ in  FIG.  17 B  may be a C-shaped room and may include three rectangular regions of interest. The room  1710 ″ of  FIG.  17 C  may have a curved façade and may include four rectangular regions of interest. 
       FIG.  18    is a simplified flowchart of an example configuration procedure  1800  that may be executed to configure an occupant detection sensor  1900  (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ).  FIGS.  19 A and  19 B  are top-down views of an example room  1910  for illustrating the operation of the configuration procedure  1800  for the occupant detection sensor  1900 . The coverage area of the occupant detection sensor  1900  may be characterized by a global coordinate system  1902  having an origin  1904  located at a center point of the occupant detection sensor. The room  1910  may comprise a plurality of work spaces  1912  (e.g., “hot-desk” work spaces). Each work space  1910  may comprise a computer monitor  1914  and a respective keyboard  1916 , as well as a desk chair  1918  in which an occupant may sit to use the respective computer monitor  1914  and respective keyboard  1916 . 
     The configuration procedure  1800  may be executed to configure multiple regions of interest  1920   a - 1920   d  in the room  1910 . In the example of  FIG.  19 A , each of the regions of interest  1920   a - 1920   d  may be a circle. In the example of  FIG.  19 B , each of the regions of interest  1920   e - 1920   h  may be a square. In addition, each of the regions of interest may be a rectangle. Each of the regions of interest shown in  FIGS.  19 A and  19 B  may surround an area of the respective workspace  1912  in which the occupant may be located (e.g., around the keyboard  1916  and/or the desk chair  1918 ). Each of the circular regions of interest  1920   a - 1920   d  shown in  FIG.  19 A  may be characterized by a respective local coordinate system  1922   a - 1922   d  having a respective origin  1924   a - 1924   d  (e.g., located at the center of each circular region of interest). For example, the local coordinate system  1922   a - 1922   d  of each of the circular regions of interest  1920   a - 1920   d  may be a cylindrical coordinate system (e.g., having coordinates defined by a distance from the respective origin  1924   a - 1924   d  and an angle from a respective reference angle between a line through the center of each circular region of interest  1920   a - 1920   d  and the x-axis of the global coordinate system  1902 ). 
     Each of the square regions of interest  1920   e - 1920   h  shown in  FIG.  19 B  may be characterized by a respective local coordinate system  1922   e - 1922   h  having a respective origin  1924   e - 1924   h  (e.g., located at a corner of each square region of interest). For example, the local coordinate system  1922   e - 1922   h  of each of the square regions of interest  1920   e - 1920   h  may be a Cartesian coordinate system (e.g., having coordinates defined distances along an x-axis and a y-axis). As shown in  FIG.  19 B , the x-axes of the local coordinate systems  1922   e - 1922   h  of the square region of interests  1920   e - 1920   h  may not be aligned with (e.g., parallel to) the x-axis of the global coordinate system  1902  of the occupant detection sensor  1900 . For example, a rotation angle φ R  may exist between the x-axis of the global coordinate system  1902  and the x-axis of each of the local coordinate systems  1922   e - 1922   h . The local coordinate systems  1922   e - 1922   h  may also be offset from the global coordinate systems  1902  by respective offset vectors  1930   a - 1930   d  (e.g., with only the offset vectors  1930   a  and  1930   d  shown in  FIG.  19 B ). The origin  1924   e - 1924   h  of each of local coordinate systems  1922   e - 1922   h  may also be located at respective centers  1926   e - 1926   h  of the square regions of interest  1920   e - 1920   h . The exact location of the origins of  1924   e - 1924   h  of each of local coordinate systems  1922   e - 1922   h  should not affect the applicability of the techniques described herein. 
     Throughout the configuration procedure  1800 , an installer may utilize a configuration application running on a programming device, such as the mobile device  140  (e.g., a smart phone), which may be in communication with (e.g., direct communication with) the occupant detection sensor for configuring the occupant detection sensor. At  1810 , the installer may start the configuration procedure  1800 , for example, by opening a configuration application running on the network device and/or selecting a “start configuration” option and/or button on the configuration application. 
     At  1812 , the occupant detection sensor may enter a configuration mode. At  1814 , the installer may enter the shape and/or size (e.g., dimensions) of each of the multiple regions of interest to be configured. For example, the shape may be entered as circle (e.g., to configure the circular regions of interest  1922   a - 1922   d ), square (e.g., to configure the square regions of interest  1922   e - 1922   h ), rectangle, or other polygon at  1814 . In addition, the dimensions of the multiple regions of interest may also be entered, e.g., as a radius or diameter when the shape is a circle, as a side length when the shape is a square, or as a length and width when the shape is a rectangle at  1814 . Each of the multiple regions of interest may be configured with the same shape and dimensions. 
     At  1816 , the installer may walk to the location of one of the workspaces  1912  in the room  1910  (e.g., to the location of one of the desk chairs  1918 ). For example, the installer may walk to approximately the center of the desired region of interest for that workspace  1912  (e.g., the center of one of the circular regions of interest  1922   a - 1922   d  or the center  1926   e - 1926   h  of one of the square regions of interest  1922   e - 1922   h ). At  1818 , the installer may confirm that the installer is located at the proper location, for example, by actuating a “confirmation” option and/or button on the configuration application running on the programming device. At  1818 , the programming device may transmit the configuration data (e.g., the shape and/or dimensions) as well as an indication that the installer is presently at the center of one of the regions of interest to the occupant detection sensor. At  1820 , the occupant detection sensor may store the configuration data (e.g., the shape and/or dimensions) and the location (e.g., X-Y coordinates) of the centers in memory at  1822 . If the installer is not done identifying locations in the room at  1824 , the installer may walk to the location of a different workspace  1912  at  1816  to configure another region of interest. Since the configuration data (e.g., the shape and/or dimensions) of each region of interest may be the same, the programming device may not transmit the configuration data to the occupant detection sensor during subsequent executions of  1820  and/or the occupant detection sensor may not store the configuration data during subsequent executions of  1822 . In those cases, the occupant detection sensor may reuse the configuration data transmitted and/or stored previously for an identical region of interest. 
     If the installer is done identifying locations in the room (e.g., in the installer selected a “done” option and/or button on the programming device) at  1824  and the shape of each of the regions of interest is a circle at  1826 , the occupant detection sensor may simply exit the configuration mode at  1828  and the configuration procedure  1800  may exit at  1842 . If the shape of each of the regions of interest is not a circle (e.g., is a square, rectangle, or other polygon) at  1826 , the occupant detection sensor may use the stored locations of the installer during the configuration procedure  1800  to perform a least squares fit to determine a center line  1940  (e.g., as shown in  FIG.  19 B ) that may extend as close as possible through the centers  1926   e - 1926   h  of the regions of interest  1922   e - 1922   h  at  1830 . For example, if the room  1910  has multiple rows of workspaces  1912 , the occupant detection sensor may perform the least squares fit multiple times at  1830  to determine multiple center lines. 
     At  1832 , the occupant detection sensor may be configured to determine the rotation angle φ R  between the x-axis of the global coordinate system  1902  and the x-axis of each of the local coordinate systems  1922   e - 1922   h . For example, the calculate the rotation angle φ R  determining an angle between x-axis of the global coordinate system  1902  and the center line  1940  of the regions of interest  1922   e - 1922   h  at  1832  (e.g., in a similar manner as at  1218  of the configuration procedure  1200  shown in  FIG.  12   ). The occupant detection sensor may determine multiple the rotation angles φ R  if there are multiple rows of workspaces  1910  and thus multiple center lines  1940 . At  1834 , the occupant detection sensor may determine an offset vector for each of the regions of interest  1922   e - 1922   h  using the locations of the centers  1926   e - 1926   h  of the regions of interest  1922   e - 1922   h , the dimension of the region of interest, and the rotation angle (DR. At  1836 , the occupant detection sensor may be configured to determine bounds of each of the regions of interest  1922   e - 1922   h  (e.g., as defined by the dimensions of each of the region of interests). At  1838 , the occupant detection sensor may store the sensor configuration data (e.g., the rotation angle(s) φ R , the offset vectors for each of the regions of interest  1922   e - 1922   h , and/or the bounds of each of the regions of interest). At  1840 , the occupant detection sensor may exit the sensor configuration mode, before the configuration procedure  1800  exits at  1842 . 
       FIG.  20    is a simplified flowchart of a control procedure  2000  that may be executed by an occupant detection sensor (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ) during normal operation. For example, the control procedure  2000  may be executed by a control circuit of the occupant detection sensor (e.g., the radar detection processor  412  and/or the control circuit  420 ). The control circuit may execute (e.g., periodically execute) the control procedure  2000  at  2010  to process occupant data determined and/or generated by an occupant detection circuit (e.g., the radar detection circuit  410 ). The occupant data may comprise a location (e.g., a Z-coordinate) of the occupant in a global coordinate system (e.g., a polar coordinate system) of the occupant detection sensor for each occupant in a coverage area of the occupant detection sensor. For example, the Z-coordinate of the occupant data may define a distance between the occupant detection sensor and the occupant. The control procedure  2000  may be executed to determine, for example, an occupant count (e.g., a sensor occupant count) of the number of occupants in a region of interest (e.g., a circular region of interest  620  as shown in  FIG.  6   ). 
     At  2012 , the control circuit may clear the sensor occupant count. At  2014 , the control circuit may determine the Z-coordinate for an occupant from an occupant detection circuit (e.g., the radar detection circuit  410 ). At  2016 , the control circuit may determine if the occupant is within the bounds of the region of interest. For example, when the region of interest is a circle, the control circuit may determine if the Z-coordinate is less than the radius r ROI  for the region of interest at  2016  to determine if the location of the occupant is within the bounds of the region of interest. If the occupant is within the region of interest at  2016 , the control circuit may increment the sensor occupant count by one at  2018 . If the occupant is not within the region of interest at  2016 , the control circuit may not increment the sensor occupant count by one. If the control circuit is not done processing occupants received from the occupant detection circuit (e.g., occupants within the coverage area of the occupant detection sensor) at  2020 , the control procedure  2000  may loop around to determine the Z-coordinate of the next occupant at  2014 . When the control circuit is done processing occupants received from the occupant detection circuit at  2020 , the control procedure  2000  may exit at  2022 . 
       FIG.  21    is a simplified flowchart of a control procedure  2100  that may be executed by an occupant detection sensor (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ) during normal operation. For example, the control procedure  2100  may be executed by a control circuit of the occupant detection sensor (e.g., the radar detection processor  412  and/or the control circuit  420 ). The control circuit may execute (e.g., periodically execute) the control procedure  2100  at  2110  to process occupant data determined by an occupant detection circuit (e.g., the radar detection circuit  410 ). The occupant data may comprise a tracking number and a location (e.g., an X-Y coordinate) in a global coordinate system of the occupant detection sensor for each occupant in a coverage area of the occupant detection sensor. For example, the control procedure  2100  may be executed to determine an occupant count (e.g., a sensor occupant count) of the number of occupants in a region of interest (e.g., one of the rectangular regions of interest  920 ,  1120 ,  1320  shown in  FIGS.  9 ,  11 , and  13   , respectively). 
     At  2112 , the control circuit may use the occupant data received from the occupant detection circuit to determine the locations of the occupants within a region of interest. For example, the control circuit may transform the locations of each occupant in the global coordinate system into the local coordinate system of the occupant sensor. If the locations of the occupants in the local coordinate system fall within the bounds of the region of interest, the control circuit may store the location of the respective occupant and the corresponding tracking number in memory for further processing. At  2114 , the control circuit may track the locations of the occupants in the region of interest. For example, the control circuit may be configured to continue to track occupants that have become stationary at  2114  even though the occupants may not be detected by the occupant detection circuit of the occupant detection sensor. At  2116 , the control circuit may determine a sensor occupant count (e.g., by counting the number of occupants determined to be within the region of interest at  2114 ), before the control procedure  2100  exits at  2118 . 
       FIG.  22    is a simplified flowchart of a location determination procedure  2200  that may be executed by an occupant detection sensor (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ) during normal operation. The location determination procedure  2200  may be executed by a control circuit of the occupant detection sensor (e.g., the radar detection processor  412  and/or the control circuit  420 ). For example, the location determination procedure  2200  may be executed at  2112  of the control procedure  2100  shown in  FIG.  21   . 
     The location determination procedure  2200  may begin at  2210 . At  2212 , the control circuit may determine the location (x, y) of an occupant in the global coordinate system and a tracking number of the occupant from an occupant detection circuit (e.g., the radar detection circuit  410 ). At  2214 , the control circuit may transform the location (x, y) of the occupant in the global coordinate system to a location (x′, y′) in the local coordinate system. For example, the control circuit may use a linear transformation to determine the location (x′, y′) in the local coordinate system, e.g., 
                 [           x   ′               y   ′           ]     =         [           cos   ⁡     (     φ   R     )             sin   ⁡     (     φ   R     )                 -     sin   ⁡     (     φ   R     )               cos   ⁡     (     φ   R     )             ]     ⁡     [         x           y         ]       -     [           x   off   ′               y   off   ′           ]         ;   or                   x   ′     =       x   ·     cos   ⁡     (     φ   R     )         +     y   ·     sin   ⁡     (     φ   R     )         -     x   off   ′         ;   and                   y   ′     =       x   ·     -     sin   ⁡     (     φ   R     )           +     y   ·     cos   ⁡     (     φ   R     )         -     y   off   ′         ;                   where   ⁢           [           x   off   ′               y   off   ′           ]     =       [           cos   ⁡     (     φ   R     )             sin   ⁡     (     φ   R     )                 -     sin   ⁡     (     φ   R     )               cos   ⁡     (     φ   R     )             ]     ⁡     [           x   off               y   off           ]         ;   or                   x   off   ′     =         x   off     ·     cos   ⁡     (     φ   R     )         +       y   off     ·     sin   ⁡     (     φ   R     )             ;   and                 y   off   ′     =         x   off     ·     -     sin   ⁡     (     φ   R     )           +       y   off     ·       cos   ⁡     (     φ   R     )       .               
φ R  may represent a rotation angle between the global coordinate system and the local coordinate system, and x off  and y off  may represent an offset vector between respective origins of the two coordinate systems, as described herein. At  2216 , the control circuit may determine if the location (x′, y′) in the local coordinate system is within the bounds of the region of interest. For example, when the region of interest is a rectangle, the control circuit may determine if the coordinates of the location (x′, y′) in the local coordinate system are less than the respective maximum dimensions X ROI , Y ROI  of the region of the interest at  2216  to determine if the location of the occupant is within the bounds of the region of interest.
 
     If the location (x′, y′) in the local coordinate system is within the bounds of the region of interest at  2216 , the control circuit may determine if the location (x′, y′) is within a masked area at  2218 . If the location (x′, y′) is not within a masked area at  2218 , the control circuit may store the location (x′, y′) in the local coordinate system and the tracking number in memory at  2220 . In addition, the control circuit may store the location (x, y) in the global coordinate system and the tracking number in memory at  2220 . If the location (x′, y′) is not within the bounds of the region of interest at  2216  or the location (x′, y′) is within a masked area at  2218 , the control circuit may not store the location (x′, y′) or the tracking number in memory at  2220 . If there are more regions of interest in the present room at  2222 , the location determination procedure  2200  may loop around to allow the control circuit to determine if the occupant location is in the next region of interest. The control circuit may continue to determine if the occupant location is in each region of interest in the room until the control circuit determines that the occupant location is in one of the regions of interest at  2218  or there are no more regions of interest at  2222 . If the control circuit does not determine that the occupant location is in any of the regions of interest, the control circuit may not store the location (x′, y′) or the tracking number in memory at  2220 . If the control circuit is not done processing the locations of occupants received from the occupant detection circuit at  2224 , the location determination procedure  2200  may loop around to determine the location of the next occupant and associated tracking number at  2212 . When the control circuit is done processing the locations of occupants received from the occupant detection circuit at  2224 , the location determination procedure  2200  may exit at  2226 . 
     The control circuit may use the transformation shown above (e.g., at  2214  of the location determination procedure  2200 ) to transform a location (x, y) in the global coordinate system to a location (x′, y′) in the local coordinate system when the region of interest is a polygon, such as a square or rectangle. When the region of interest is a circle, the control circuit may transform a location (x, y) in the global coordinate system to a location (x′, y′) in the local coordinate system by subtracting an offset vector from the location (x, y) in the global coordinate system. The bounds of a circular region of interest may be a dimension of the region of interest, as indicated by a diameter or radius. For example, the control circuit may be configured to determine if the location (x′, y′) in the local coordinate system is within the bounds of the region of interest (e.g., at  2216  of the location determination procedure  2200 ) by determining if a distance between an origin of the circular region of interest and the location (x′, y′) is less than the radius. When the region of interest is a circle, the control circuit may be configured to determine if the location of an occupant is within the bounds of the region of interest without transforming the location of the occupant to a local coordinate system. For example, the control circuit may calculate a distance between the occupant and the center of the circular region of interest using locations of the occupant and the center of the circular region of interest in the global coordinate system. The control circuit may then determine that the occupant is within the bounds of the circular region of interest if the distance is smaller than the radius of the circle and that the occupant is outside the bounds of the circular region of interest if the distance is greater than the radius of the circle. 
       FIGS.  23 A and  23 B  show a simplified flowchart of an example occupant tracking procedure  2300  that may be executed by an occupant detection sensor (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ) during normal operation. The occupant tracking procedure  2300  may be executed by a control circuit of the occupant detection sensor (e.g., the radar detection processor  412  and/or the control circuit  420 ) at  2310 . For example, the occupant tracking procedure  2300  may be executed at  2114  of the control procedure  2100  shown in  FIG.  21   . The control circuit may track the occupants during the occupant tracking procedure  2300  using the occupant data determined and/or generated by the location determination procedure  2200  shown in  FIG.  22   . For example, the occupant data may comprise a tracking number and a location (e.g., X-Y coordinate) in the local coordinate system for each occupant in the region of interest. In addition, the occupant data may comprise a tracking number and a location (e.g., X-Y coordinate) in the global coordinate system for each occupant in the region of interest. 
     As shown in  FIG.  23 A , the control circuit may process each occupant in the occupant data one at a time (e.g., for only those occupants in the region of interest as determined by the location determination procedure  2200 ). At  2312 , the control circuit may determine if the occupant is a new occupant by determining if the tracking number of the occupant is new (e.g., the tracking number is new if the tracking number is not the same as any tracking number stored by the occupant detection sensor). If the tracking number is new at  2312 , the control circuit may determine if the new occupant is at substantially the same location as (e.g., within a predetermined range of) a previously-identified stationary occupant at  2314  (e.g., the new occupant is the same as the stationary occupant). If the new occupant is not at substantially the same location as a stationary occupant at  2314 , but is located near a doorway at  2316 , the control circuit may determine if the size of the new occupant exceeds a size threshold at  2318 . If the size of the new occupant exceeds the size threshold at  2318 , the control circuit may assign the new occupant a new occupant identifier at  2320  and store the occupant identifier along with the tracking number and the occupant location (e.g., as received from the occupant detection circuit) at  2322 . The size threshold may be preconfigured for the occupant detection sensor, for example, during a commissioning procedure. 
     If the new occupant is at substantially the same location as a stationary occupant at  2314 , the control circuit may maintain the previous occupant identifier for the stationary occupant at  2324 , and update the occupant location for the stationary occupant at  2326  with the newly determined location (e.g., so that slight movements of the occupant may not accumulate over time to cause erroneous conditions). The control circuit may update the stored tracking number for the stationary occupant with the new tracking number at  2324 . If the tracking number for the occupant is not new at  2312  (e.g., the tracking number is not new if the tracking number is the same as a tracking number stored by the occupant detection sensor), the control circuit may determine if the previously-identified occupant (e.g., identified by the tracking number) has moved at  2328 . If the occupant has moved at  2328 , the control circuit may update the occupant location for the moving occupant at  2330 . If there are more occupants at  2332 , the occupant detection procedure  2300  may loop around to process the next occupant. 
     Referring to  FIG.  23 B , if there are not more occupants to process at  2332 , the control circuit may determine if one of the previously-identified occupants is missing (e.g., no longer in the room) at  2340 . For example, the control circuit may determine that an occupant is missing at  2340  if the occupant is no longer in the region of interest (e.g., if the occupant is not in the occupant data as determined by the location determination procedure  2200 ). If an occupant is missing at  2340  and the last known location of the occupant was near a doorway at  2342 , the control circuit may delete the occupant identifier and occupant location from memory at  2344 . If the last known location of the missing occupant was not near a doorway at  2342 , the control circuit may mark the occupant as stationary at  2344 . If there are more missing occupants at  2348 , the occupant detection procedure  2300  may loop around to process the next missing occupant. If there are not more missing occupants at  2348 , the occupant detection procedure may exit at  2350 . The location of the doorway may be learned/determined by the control circuit, for example, during the commissioning procedure described herein. 
       FIG.  24    is a simplified flowchart of a control procedure  2400  that may be executed by an occupant detection sensor (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ) during normal operation. For example, the control procedure  2400  may be executed by a control circuit of the occupant detection sensor (e.g., the radar detection processor  412  and/or the control circuit  420 ). The control circuit may execute (e.g., periodically execute) the control procedure  2400  at  2410  to process occupant data determined by an occupant detection circuit (e.g., the radar detection circuit  410 ). The occupant data may comprise a tracking number and a location (e.g., X-Y coordinate) in a global coordinate system if the occupant detection sensor for each occupant in a coverage area of the occupant detection sensor. For example, the control procedure  2400  may be executed to determine whether one or more regions of interest in a room are occupied or vacant (e.g., such as the circular regions of interest  1920   a - 1920   d  and the square regions of interest  1920   e - 1920   h  shown in  FIG.  17   ). 
     At  2412 , the control circuit may determine a location (x n , y n ) in the global coordinate system and a tracking number of an occupant from the occupant detection circuit. If the regions of interest of the room are circular at  2414 , the control circuit may calculate a distance d OCC  (e.g., a magnitude of a vector) between the location (x n , y n ) of the occupant and the center (x n , y n ) of the circular region of interest (e.g., in the global coordinate system), e.g.,
 
 d   OCC =sqrt[( y   n   −y   c ) 2 +( x   n   −x   n ) 2 ].
 
     At  2418 , the control circuit may determine if the location (x n , y n ) of the occupant is within the circular region of interest, for example, by determining if the distance d OCC  between the location (x n , y n ) of the occupant and the center (x c , y c ) of the circular region of interest is less than or equal to a dimension, such as a radius r ROI , of the circular region of interest. If the location (x n , y n ) of the occupant is inside of the circular region of interest (e.g., if d OCC ≤r ROI ) at  2418 , the control circuit may mark the region of interest as occupied at  2420 . If the location (x n , y n ) of the occupant is not inside of the circular region of interest (e.g., if d OCC &gt;r ROI ) at  2418 , the control circuit may not mark the region of interest as occupied at  2420 . 
     If the regions of interest of the room are not circular at  2414  (e.g., are square, rectangular, or other polygon), the control circuit may transform the location (x n , y n ) of the occupant in the global coordinate system to a location (x′n, y′n) in the local coordinate system at  2422 . The control circuit may use a linear transformation to determine the location (x′, y′) in the local coordinate system at  2414 , for example, in a similar manner as at  2414  of the location determination procedure  2400  of  FIG.  24   . At  2424 , the control circuit may determine if the location (x n , y n ) of the occupant is within the region of interest. For example, if the region of interest is a square, the control circuit may determine if the coordinates of the location (x′n, y′n) in the local coordinate system are each less than the side length of the region of the interest at  2424  to determine if the location of the occupant is within the region of interest. If the location (x′n, y′n) of the occupant in the local coordinate system is inside of the region of interest at  2424 , the control circuit may mark the region of interest as occupied at  2420 . If the location (x′ n , y′ n ) of the occupant is not inside of the circular region of interest at  2424 , the control circuit may not mark the region of interest as occupied at  2420 . 
     If there are more regions of interest in the room to process at  2426 , the control procedure  2400  may loop around to determine if the occupant located in the region of interest at  2418  or  2424 . If there are not more regions of interest in the room to process at  2426 , but there are more occupant locations to process at  2428 , the control procedure  2400  may loop around to determine a location (x n , y n ) in the global coordinate system and a tracking number of the next occupant at  2412 . If there are not more occupant locations to process at  2428 , the control procedure may exit at  2430 . 
       FIG.  25    is a simplified flowchart of a location determination procedure  2500  may that be executed by an occupant detection sensor  2600  (e.g., the ceiling-mounted occupant detection sensor  180 , the wall-mounted occupant detection sensor  182 , and/or the occupant detection sensor  400 ) during normal operation.  FIG.  26 A  is a top-down view of an example room  2610  for illustrating the operation of the occupant detection sensor  2600  during the location determination procedure  2500 . The location determination procedure  2500  may be executed by a control circuit of the occupant detection sensor  2600  (e.g., the radar detection processor  412  and/or the control circuit  420 ). For example, the location determination procedure  2500  may be executed at  2112  of the control procedure  2100  shown in  FIG.  21   . 
     For the example of  FIG.  26 A , the room  2610  may be rectangular with four walls  2610   a - 2610   d , and the coverage area of the occupant detection sensor  2600  may extend beyond the extents of the room  2610 , such that the room is fully encompassed by the coverage area. The coverage area of the occupant detection sensor  2600  may be characterized by a global coordinate system  2602  having an origin  2604  located at a center point of the occupant detection sensor. The room  2610  may be characterized by a desired region of interest  2620 , which may be, for example, the extents of the room. The x-axis of the global coordinate system  2602  of the occupant detection sensor  2600  may not be aligned with an x-axis of a local coordinate system (not shown) of the desired region of interest  2620 . The control circuit of the occupant detection sensor  2600  may be configured to determine the locations (x 1 , y 1 ), (x 2 , y 2 ), (x 3 , y 3 ), (x 4 , y 4 ) of the corners of the desired region of interest  2620  in a global coordinate system associated with the occupant detection sensor  2500 , for example, during a configuration procedure (e.g., the configuration procedure  1400  shown in  FIG.  14    and/or the configuration procedure  1500  shown in  FIG.  15   ). The locations (x 1 , y 1 ), (x 2 , y 2 ), (x 3 , y 3 ), (x 4 , y 4 ) of the corners may define the bounds of the desired region of interest  2620 . The control circuit may store in memory the locations (x 1 , y 1 ), (x 2 , y 2 ), (x 3 , y 3 ), (x 4 , y 4 ) of the corners in order (e.g., moving counter-clockwise around the region of interest  2620 ). The control circuit may not need to establish a relationship between the global coordinate system  2602  and a local coordinate system of the desired region of interest  2620  in order to execute the location determination procedure  2500  of  FIG.  25   . For example, the control circuit may not need to determine a rotation angle or an offset vector between the x-axis of the global coordinate system  2602  and the x-axis of the local coordinate system of the desired region of interest  2620  in order to execute the location determination procedure  2500  of  FIG.  25   . The control circuit may not need to transform a location of an occupant in the global coordinate system  2602  to a location in the local coordinate system of the desired region of interest  2620  when executing the location determination procedure  2500 . 
     As shown in  FIG.  26 A , a first occupant A may be located inside of the desired region of interest  2620  and a second occupant B may be located outside of the desired region of interest  2620 . To determine if a location of an occupant that is within the coverage area of the occupant detection sensor  2600  is within the desired region of interest  2620 , the occupant detection sensor may determine if respective vectors extending from each corner of the desired region of interest  2620  to the occupant are all directed into the desired region of interest. The occupant detection sensor  2600  may determine that the location of the occupant is within the desired region of interest if all of the vectors are directed into the region of interest. The occupant detection sensor  2600  may determine that the location of the occupant is not within the desired region of interest if at least one of the vectors is not directed into the region of interest. 
     To determine if the respective vectors extending from each corner to the occupant are directed into the desired region of interest  2620 , the occupant detection sensor  2600  may perform a test at each corner of the desired region of interest  2620 . To perform the test at one of the corners, the occupant detection sensor  2600  may determine if a slope m O  of a line between that corner and the occupant is greater than or equal to a slope m C  of a line between that corner and the next corner. For example, at the first corner having the location (x 1 , y 1 ), the occupant detection sensor  2600  may determine if the slope m O  of a line L O:A  between the first corner and occupant A is greater than or equal to the slope m C  of a line L C:1-2  between the first corner and the second corner having the location (x 2 , y 2 ). At the second corner having the location (x 2 , y 2 ), the occupant detection sensor  2600  may determine if the slope m O  of a line (not shown) between the second corner and occupant A is greater than or equal to the slope m C  of a line L C:2-3  between the second corner and the third corner having the location (x 3 , y 3 ). If the slope m O  is greater than or equal to the slope m C  at each corner of the desired region of interest  2620 , the occupant detection sensor  2600  may conclude that the occupant is inside of the desired region of interest  2620 . For example, for occupant A as shown in  FIG.  26   , the slope m O  is greater than or equal to the slope m C  at each corner of the desired region of interest  2620 . If the slope m O  is less than the slope m C  at any of the corners of the desired region of interest  2620 , the occupant detection sensor  2600  may conclude that the occupant is outside of the desired region of interest  2620 . For example, for occupant B as shown in  FIG.  26 A , the slope m O  is less than the slope m C  at at least the first corner of the desired region of interest  2620 . 
     Referring back to  FIG.  25   , the location determination procedure  2500  may begin at  2510 . At  2512 , the control circuit may determine a location (x O , y O ) in the global coordinate system  2602  and a tracking number of an occupant from an occupant detection circuit (e.g., the radar detection circuit  410 ). At  2514 , the control circuit may start at the first corner of the desired region of interest  2620  that has the location (x 1 , y 1 ). At  2516 , the control circuit may calculate the slope m C  from a present corner (e.g., the first corner) to a next corner (e.g., the second corner having the location (x 2 , y 2 )) of the desired region of interest  2620 , e.g.,
 
 m   C =( y   2   −y   1 )/( x   2   −x   1 ).
 
At  2518 , the control circuit may calculate the slope m O  from the present corner (e.g., the first corner) to the occupant, e.g.,
 
 m   O =( y   O   −y   1 )/( x   O   −x   1 ).
 
If the slope m O  is greater than or equal to the slope m C  at  2520 , the control circuit may determine if there are more corners of the desired region of interest  2620  to analyze at  2522 . If there are more corners at  2522 , the control circuit may move to the next corner at  2524  (e.g., the second corner), calculate the slope m C  from second corner to the third corner at  2516 , and calculate the slope m O  from the second corner to the occupant at  2518 . If the slope m O  is greater than or equal to the slope m C  at  2520  for each corner of the desired region of interest  2620  (e.g., there are no more corners to analyze at  2522 ), the control circuit may store the location (x O , y O ) and the tracking number of the occupant in memory at  2526 . If the control circuit is not done processing the locations of occupants received from the occupant detection circuit at  2528 , the location determination procedure  2500  may loop around to determine the location of the next occupant and associated tracking number at  2512 . If the slope m O  is not greater than or equal to the slope m C  at  2520  at any of the corners of the desired region of interest  2620 , the control circuit may move on to process the location of the next occupant without storing the location (x O , y O ) and the tracking number of the current occupant in memory. When the control circuit is done processing the locations of occupants received from the occupant detection circuit at  2528 , the location determination procedure  2500  may exit at  2530 .
 
     While the desired region of interest  2620  shown in  FIG.  26 A  is rectangular in shape, the location determination procedure  2500  may be executed on regions of interest having any shape and any number of corners (e.g., regions of interest having complex shapes and/or polygons of any shape or size) without modification as long as the corners of the desired region of interest are analyzed in order (e.g., a counterclockwise order). The control circuit may learn/determine the locations of the corners using the techniques described herein, e.g., during a commissioning procedure.  FIGS.  26 B and  26 C  are top-down views of other example rooms  2610 ′,  2610 ″ that have complex shapes and respective regions of interest  2620 ′,  2620 ″ that are polygons with, for example, greater than four sides and corners. These regions of interest  2620 ′,  2620 ″ may be configured using the configuration procedure  2500  of  FIG.  25    for the occupant detection sensor  2600 . For example, the room  2610 ′ (and corresponding region of interest  2620 ′) of  FIG.  26 B  may be L-shaped (e.g., having six sides and corners). The room  2610 ″ (and corresponding region of interest  2620 ″) of  FIG.  26 C  may have a hexagon shape (e.g., having six sides that are not all parallel and/or perpendicular to each other). 
     Although features and elements are described herein in particular combinations, each feature or element can be used alone or in any combination with the other features and elements. The methods described herein may be implemented in a computer program, software, or firmware that may be incorporated in a computer-readable medium for execution by a computer or processor. Examples of computer-readable media include electronic signals (transmitted over wired or wireless connections) and computer-readable storage media. Examples of computer-readable storage media include, but are not limited to, a read only memory (ROM), a random access memory (RAM), removable disks, and optical media such as CD-ROM disks, and digital versatile disks (DVDs).