Patent Publication Number: US-2023132977-A1

Title: Systems and methods for configuring transmission power level based on body proximity

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Application No 63/272,807, filed Oct. 28, 2021, entitled “Systems and Methods for Configuring Transmission Power Level Based on Body Proximity,” the disclosure of which is incorporated by reference in its entirety for all purposes. 
    
    
     BACKGROUND 
     The present disclosure relates generally to wireless communication, and more specifically to transmission power of user equipment. 
     To transmit signals over a greater distance and/or with less data loss, user equipment may use greater transmission power. However, to reduce an effect of radio frequency exposure on a user, transmission power may be limited. 
     SUMMARY 
     A summary of certain embodiments disclosed herein is set forth below. It should be understood that these aspects are presented merely to provide the reader with a brief summary of these certain embodiments and that these aspects are not intended to limit the scope of this disclosure. Indeed, this disclosure may encompass a variety of aspects that may not be set forth below. 
     In one embodiment, one or more non-transitory, tangible, computer-readable media stores instructions that cause processing circuitry to receive a probability of detection of a body by a body proximity sensor, receive a first transmission power level based on a radio frequency exposure limit, and determine a second transmission power level based on the first transmission power level and the probability of detection of the body by the body proximity sensor. The instructions also cause the processing circuitry to cause a transmitter to transmit at the first transmission power level based on detecting the body by the body proximity sensor, and cause the transmitter to transmit at the second transmission power level based on not detecting the body by the body proximity sensor. 
     In another embodiment, a method includes receiving, at processing circuitry, a probability of detection of a body by a body proximity sensor. The method also includes receiving, at the processing circuitry, a first transmission power level based on a radio frequency exposure limit. The method further includes determining, at the processing circuitry, a second transmission power level based on the first transmission power level and the probability of detection of the body by the body proximity sensor. The method also includes storing, in a memory or storage device, the first transmission power level and the second transmission power level. 
     In yet another embodiment, user equipment includes a body proximity sensor that detects a body with a probability of detection, one or more antennas, and a transmitter that transmits radio frequency signals via the one or more antennas at a first transmission power level based on the body proximity sensor detecting the body and the probability of detection, and at a second transmission power level based on the body proximity sensor not detecting the body and the probability of detection. 
     Various refinements of the features noted above may exist in relation to various aspects of the present disclosure. Further features may also be incorporated in these various aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to one or more of the illustrated embodiments may be incorporated into any of the above-described aspects of the present disclosure alone or in any combination. The brief summary presented above is intended only to familiarize the reader with certain aspects and contexts of embodiments of the present disclosure without limitation to the claimed subject matter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of this disclosure may be better understood upon reading the following detailed description and upon reference to the drawings described below in which like numerals refer to like parts. 
         FIG.  1    is a block diagram of user equipment, according to embodiments of the present disclosure; 
         FIG.  2    is a schematic diagram of the user equipment of  FIG.  1   , according to embodiments of the present disclosure; 
         FIG.  3    is a schematic diagram of a body proximity sensor of the user equipment of  FIG.  1   , according to embodiments of the present disclosure; 
         FIG.  4    is a timing diagram of configuring transmission power based on body proximity sensor detection, according to embodiments of the present disclosure; 
         FIG.  5    is a flowchart of a method for determining and applying transmission power levels based on a Probability of Detection, while ensuring compliance with regulatory radio frequency (RF) exposure limits, according to embodiments of the present disclosure; 
         FIG.  6    is a timing diagram illustrating False Alarms decreasing an average transmission power gain, according to embodiments of the present disclosure; 
         FIG.  7    is a flowchart of a method for determining and applying transmission power levels based on the Probability of Detection (P d ) and a presence of a human target as detected by the body proximity sensor of  FIG.  3   , while ensuring compliance with regulatory RF exposure limits, according to embodiments of the present disclosure; and 
         FIG.  8    is a flowchart of a method for determining and applying transmission power levels based on the Probability of Detection (P d ) and frequency of detection of a human target as detected by the body proximity sensor of  FIG.  3   , while ensuring compliance with regulatory RF exposure limits, according to embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     One or more specific embodiments will be described below. In an effort to provide a concise description of these embodiments, not all features of an actual implementation are described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers’ specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure. 
     When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” and “the” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. Additionally, it should be understood that references to “one embodiment” or “an embodiment” of the present disclosure are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Furthermore, the particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. Use of the terms “approximately,” “near,” “about,” “close to,” and/or “substantially” should be understood to mean including close to a target (e.g., design, value, amount), such as within a margin of any suitable or contemplatable error (e.g., within 0.1% of a target, within 1% of a target, within 5% of a target, within 10% of a target, within 25% of a target, and so on). Moreover, it should be understood that any exact values, numbers, measurements, and so on, provided herein, are contemplated to include approximations (e.g., within a margin of suitable or contemplatable error) of the exact values, numbers, measurements, and so on. 
     Wireless devices, such as user equipment, may maintain their radio frequency (RF) exposure within limits defined by regulatory bodies, such as the Federal Communications Commission (FCC). The RF exposure caused to a human body or part of a human body depends on a distance between a transmitter of the user equipment and the human target. 
       FIG.  1    is a block diagram of user equipment  10  (e.g., an electronic device), according to embodiments of the present disclosure. The user equipment  10  may include, among other things, one or more processors  12  (collectively referred to herein as a single processor for convenience, which may be implemented in any suitable form of processing circuitry), memory  14 , nonvolatile storage  16 , a display  18 , input structures  22 , an input/output (I/O) interface  24 , a network interface  26 , and a power source  29 . The various functional blocks shown in  FIG.  1    may include hardware elements (including circuitry), software elements (including machine-executable instructions) or a combination of both hardware and software elements (which may be referred to as logic). The processor  12 , memory  14 , the nonvolatile storage  16 , the display  18 , the input structures  22 , the input/output (I/O) interface  24 , the network interface  26 , and/or the power source  29  may each be communicatively coupled directly or indirectly (e.g., through or via another component, a communication bus, a network) to one another to transmit and/or receive data between one another. It should be noted that  FIG.  1    is merely one example of a particular implementation and is intended to illustrate the types of components that may be present in the user equipment  10 . 
     By way of example, the user equipment  10  may include any suitable computing device, including a desktop or notebook computer (e.g., in the form of a MacBook®, MacBook® Pro, MacBook Air®, iMacⓇ, MacⓇ mini, or Mac ProⓇ available from Apple Inc. of Cupertino, California), a portable electronic or handheld electronic device such as a wireless electronic device or smartphone (e.g., in the form of a model of an iPhone® available from Apple Inc. of Cupertino, California), a tablet (e.g., in the form of a model of an iPad® available from Apple Inc. of Cupertino, California), a wearable electronic device (e.g., in the form of an Apple Watch® by Apple Inc. of Cupertino, California), and other similar devices. It should be noted that the processor  12  and other related items in  FIG.  1    may be embodied wholly or in part as software, hardware, or both. Furthermore, the processor  12  and other related items in  FIG.  1    may be a single contained processing module or may be incorporated wholly or partially within any of the other elements within the user equipment  10 . The processor  12  may be implemented with any combination of general-purpose microprocessors, microcontrollers, digital signal processors (DSPs), field programmable gate array (FPGAs), programmable logic devices (PLDs), controllers, state machines, gated logic, discrete hardware components, dedicated hardware finite state machines, or any other suitable entities that may perform calculations or other manipulations of information. The processors  12  may include one or more application processors, one or more baseband processors, or both, and perform the various functions described herein. 
     In the user equipment  10  of  FIG.  1   , the processor  12  may be operably coupled with a memory  14  and a nonvolatile storage  16  to perform various algorithms. Such programs or instructions executed by the processor  12  may be stored in any suitable article of manufacture that includes one or more tangible, computer-readable media. The tangible, computer-readable media may include the memory  14  and/or the nonvolatile storage  16 , individually or collectively, to store the instructions or routines. The memory  14  and the nonvolatile storage  16  may include any suitable articles of manufacture for storing data and executable instructions, such as random-access memory, read-only memory, rewritable flash memory, hard drives, and optical discs. In addition, programs (e.g., an operating system) encoded on such a computer program product may also include instructions that may be executed by the processor  12  to enable the user equipment  10  to provide various functionalities. 
     In certain embodiments, the display  18  may facilitate users to view images generated on the user equipment  10 . In some embodiments, the display  18  may include a touch screen, which may facilitate user interaction with a user interface of the user equipment  10 . Furthermore, it should be appreciated that, in some embodiments, the display  18  may include one or more liquid crystal displays (LCDs), light-emitting diode (LED) displays, organic light-emitting diode (OLED) displays, active-matrix organic light-emitting diode (AMOLED) displays, or some combination of these and/or other display technologies. 
     The input structures  22  of the user equipment  10  may enable a user to interact with the user equipment  10  (e.g., pressing a button to increase or decrease a volume level). As illustrated, the input structures  22  may include a body proximity sensor (BPS)  23 . The BPS  23  may determine if a body, such as human target or user, is within close proximity (e.g., within a threshold range, such as within one or more millimeters (mm), including within 1 mm, within 2 mm, within 3 mm, within 5 mm, within 10 mm, within 20 mm, and so on) of an antenna of the user equipment  10 , or if no human target is present in close proximity. In additional or alternative embodiments, the BPS  23  may determine if other objects (e.g., obstructions, trees, rocks, buildings, and so on) or non-human targets (e.g., dogs, cats, horses, livestock, and so on) are within close proximity of the antenna, or if no other object or non-human target is within close proximity of the antenna. 
     The I/O interface  24  may enable the user equipment  10  to interface with various other electronic devices, as may the network interface  26 . In some embodiments, the I/O interface  24  may include an I/O port for a hardwired connection for charging and/or content manipulation using a standard connector and protocol, such as the Lightning connector provided by Apple Inc. of Cupertino, California, a universal serial bus (USB), or other similar connector and protocol. The network interface  26  may include, for example, one or more interfaces for a personal area network (PAN), such as an ultra-wideband (UWB) or a BLUETOOTH® network, a local area network (LAN) or wireless local area network (WLAN), such as a network employing one of the IEEE 802.11x family of protocols (e.g., WI-FI®), and/or a wide area network (WAN), such as any standards related to the Third Generation Partnership Project (3GPP), including, for example, a 3 rd  generation (3G) cellular network, universal mobile telecommunication system (UMTS), 4 th  generation (4G) cellular network, long term evolution (LTE®) cellular network, long term evolution license assisted access (LTE-LAA) cellular network, 5 th  generation (5G) cellular network, and/or New Radio (NR) cellular network, a satellite network, a non-terrestrial network, and so on. In particular, the network interface  26  may include, for example, one or more interfaces for using a Release-15 cellular communication standard of the 5G specifications that include the millimeter wave (mmWave) frequency range (e.g., 24.25-300 gigahertz (GHz)) and/or any other cellular communication standard release (e.g., Release-16, Release-17, any future releases) that define and/or enable frequency ranges used for wireless communication. The network interface  26  of the user equipment  10  may allow communication over the aforementioned networks (e.g., 5G, Wi-Fi, LTE-LAA, and so forth). 
     The network interface  26  may also include one or more interfaces for, for example, broadband fixed wireless access networks (e.g., WIMAX®), mobile broadband Wireless networks (mobile WIMAX®), asynchronous digital subscriber lines (e.g., ADSL, VDSL), digital video broadcasting-terrestrial (DVB-T®) network and its extension DVB Handheld (DVB-H®) network, ultra-wideband (UWB) network, alternating current (AC) power lines, and so forth. As illustrated, the network interface  26  may include a transceiver  30 . In some embodiments, all or portions of the transceiver  30  may be disposed within the processor  12 . The transceiver  30  may support transmission and receipt of various wireless signals via one or more antennas, and thus may include a transmitter and a receiver. The power source  29  of the user equipment  10  may include any suitable source of power, such as a rechargeable lithium polymer (Li-poly) battery and/or an alternating current (AC) power converter. 
       FIG.  2    is a functional diagram of the user equipment  10  of  FIG.  1   , according to embodiments of the present disclosure. As illustrated, the processor  12 , the memory  14 , the BPS  23 , the transceiver  30 , a transmitter  52 , a receiver  54 , and/or antennas  55  (illustrated as  55 A- 55 N, collectively referred to as an antenna  55 ) may be communicatively coupled directly or indirectly (e.g., through or via another component, a communication bus, a network) to one another to transmit and/or receive data between one another. 
     The user equipment  10  may include the transmitter  52  and/or the receiver  54  that respectively enable transmission and reception of data between the electronic device  10  and an external device via, for example, a network (e.g., including base stations) or a direct connection. As illustrated, the transmitter  52  and the receiver  54  may be combined into the transceiver  30 . The user equipment  10  may also have one or more antennas  55 A- 55 N electrically coupled to the transceiver  30 . The antennas  55 A- 55 N may be configured in an omnidirectional or directional configuration, in a single-beam, dual-beam, or multi-beam arrangement, and so on. Each antenna  55  may be associated with a one or more beams and various configurations. In some embodiments, multiple antennas of the antennas  55 A- 55 N of an antenna group or module may be communicatively coupled a respective transceiver  30  and each emit radio frequency signals that may constructively and/or destructively combine to form a beam. The user equipment  10  may include multiple transmitters, multiple receivers, multiple transceivers, and/or multiple antennas as suitable for various communication standards. In some embodiments, the transmitter  52  and the receiver  54  may transmit and receive information via other wired or wireline systems or means. 
     As illustrated, the various components of the user equipment  10  may be coupled together by a bus system  56 . The bus system  56  may include a data bus, for example, as well as a power bus, a control signal bus, and a status signal bus, in addition to the data bus. The components of the user equipment  10  may be coupled together or accept or provide inputs to each other using some other mechanism. 
       FIG.  3    is a schematic diagram of the BPS  23 , according to embodiments of the present disclosure. The BPS  23  may determine a direction and/or distance between the user equipment  10  and a subject  102  (e.g., a human target, a user). The BPS  23  may facilitate meeting a maximum permissible exposure (MPE) of RF waves as defined for the user equipment  10 . In particular, the BPS  23  may determine the direction and/or distance to the subject  102  within a range of the user equipment  10 , which may be used to determine an amount of RF exposure to the subject  102  from the user equipment  10 . The BPS  23  may include a first oscillator  104 , a first interface  106 , a first antenna  108 , a second oscillator  109 , a second interface  110 , a second antenna  112 , and/or signal processing circuitry  114 . In some embodiments, the first oscillator  104 , the first interface  106 , the first antenna  108 , the second oscillator  109 , the second interface  110 , the second antenna  112 , and/or the signal processing circuitry  114  may be implemented within the user equipment  10 , and may be coupled to one or more other components within the user equipment  10 . For example, in some embodiments, the first oscillator  104  and the second oscillator  109  may each comprise or share a local oscillator of the user equipment  10 , the first and second antennas  108 ,  112  may be included in the antennas  55  as shown in  FIG.  2   , and/or the signal processing circuitry  114  may be part of the processor  12  as shown in  FIG.  2   . 
     In operation, the first oscillator  104  and/or the second oscillator  109  may each receive a signal output by another component of the user equipment  10  (as represented by the frequency graphs  116 A,  116 B), and may themselves output signals with frequencies defined by the signal received from the other component of the user equipment  10 . For example, a voltage and/or current of the signal received from the other component may define a frequency of the signal output by the oscillators  104 ,  109 . The oscillators  104 ,  109  may each output (either through generation of a signal or modification of a signal) the signal having the defined frequency. In some embodiments, the oscillators  104 ,  109  may share a single input signal (e.g.,  116 A or  116 B). 
     The first interface  106  may receive the signal output by the first oscillator  104  and output a signal to be output by the first antenna  108  based on the signal received from the first oscillator  104 . For example, the first interface  106  may receive the signal output by the first oscillator  104  and itself output a signal with the frequency of the signal output by the first oscillator  104 . The signal output by the first interface  106  may be in a format to facilitate wireless transmission of the signal by the first antenna  108 . In particular, in response to receiving the signal from the first interface  106 , the antenna  108  may wirelessly transmit the signal into the area around the user equipment  10 . In some embodiments, the signal transmitted by the antenna  108  may have a low power spectrum density and a wide bandwidth. The wireless transmission of the signal by the first antenna  108  may be part of a BPS operation for determining a direction and/or distance between the user equipment  10  and the subject  102 . 
     A portion of the signal emitted by the first antenna  108  may encounter the subject  102 . The portion of the signal that encounters the subject  102  may be reflected from the subject  102 . Characteristics of the portion of the signal reflected back may differ from the signal emitted by the first antenna  108  due to encountering the subject  102 . For example, the portion of the signal reflected back may have a lower amplitude than the signal emitted from the first antenna  108 . 
     The second antenna  112  may receive the portion of the signal reflected back from the subject  102  and provide the portion of the signal to the second interface  110 . The second interface  110  may output an electrical signal based on the portion of the signal received from the second antenna  112  for signal processing. The second interface  110  may receive the signal output by the second oscillator  109  and produce a signal based on the signal received from the second oscillator  109 . For example, the second interface  110  may receive the signal output by the second oscillator  109  and output a signal with the frequency of the signal output by the second oscillator  109 . The signal output by the second interface  110  based on the signal received from the second oscillator  109  may be equivalent to, or at least similar to, the signal output by the first interface  106  based on the signal received from the first oscillator  104 . 
     The second interface  110  may provide the signal produced based on the reflected signal received by the second antenna  112  and the signal produced based on the output signal of the second oscillator  109  to the signal processing circuitry  114 . The signal processing circuitry  114  may process the signal produced based on the reflected signal and the signal produced based on the output signal of the second oscillator  109  to determine a direction and/or distance between the user equipment  10  and the subject  102 . For example, the signal processing circuitry  114  may include one or more filters, one or more analog-to-digital converters (ADCs), one or more fast Fourier transform (FFTs) circuits, and/or other circuitry to perform signal processing of the signals to determine the direction and/or distance between user equipment  10  and the subject  102 . 
     Based on the determined direction and/or distance of the user equipment  10  from the subject  102 , one or more operations of the user equipment  10  may be adjusted. For example, MPE limits may be defined for transmissions from the antenna  55  (e.g., based on the subject  102  being within close proximity to the user equipment  10 ). That is, based on the determined direction and/or distance of the user equipment  10  from the subject  102 , or portion thereof, the user equipment  10  may modify certain operations from standard operation to meet the MPE limits. In some embodiments, if the distance between the user equipment  10  and the subject  102  is less than a threshold distance, operational characteristics of transmissions may be adjusted from standard values or settings. In some embodiments, the transmissions of the user equipment  10  adjusted from the standard transmission may be the transmissions emitted toward the subject  102 . In particular, transmission power of the transmitter  52  may be reduced from standard transmission power levels to meet MPE limits. 
     Based on detection of a human target within a close proximity (e.g., within a threshold range, such as within one or more millimeters (mm), including within 1 mm, within 2 mm, within 3 mm, within 5 mm, within 10 mm, within 20 mm, and so on) of the antenna  55  by the BPS  23 , the user equipment  10  may adjust transmission power of the transmitter  52  to ensure RF exposure compliance.  FIG.  4    is a timing diagram of configuring transmission power based on BPS  23  detection, according to embodiments of the present disclosure. As illustrated, when no human target is detected by the BPS  23  or a human target is not in close proximity to the antenna  55 , such as in time period  130 , the user equipment  10  may transmit with a high or higher transmission power level (e.g., a transmission power level of X1). That is, because a human target is beyond an RF exposure critical or threshold distance, transmitting with the high transmission power level of X1 may not cause any human target to exceed the RF exposure limit. The user equipment  10  may operate using the high transmission power level X1 until a next BPS  23  detection. The high transmission power level X1 may be at or above a limit defined by a regulatory body, such as the Federal Communications Commission (FCC). For example, X1 may equal 21 decibel-milliwatts (dBm) or greater, 22 dBm or greater, 23 dBm or greater, 26 dBm or greater, 28 dBm or greater, and so on. 
     When the BPS  23  detects a human target in close proximity to the antenna  55 , such as in time period  132 , because the high transmission power level X1 may cause a high amount of RF exposure to the human target, the user equipment  10  may apply a low or lower transmission power level (e.g., a reduced transmission power level of X2) to maintain RF exposure within regulatory limits. The low transmission power level X2 may be at or below a limit defined by a regulatory body, such as the Federal Communications Commission (FCC). For example, X2 may equal 21 dBm or less, 20 dBm or less, 19 dBm or less, 18 dBm or less, and so on. The user equipment  10  may operate using the low transmission power level X2 until a next BPS  23  detection. In the case where the BPS  23  may be deactivated or turned off, the user equipment  10  may also operate using the low transmission power level X2. 
     However, the BPS  23  may not have 100% accuracy, and may, at times, detect the presence of a subject  102  when there is no subject  102  present (e.g., a false alarm), or not detect the presence of a subject  102  when there a subject  102  is present (e.g., a missed detection). The probability of detection or rate of correctly detecting a human target (e.g., the subject  102 ) when it is in close proximity to the BPS  23  may be characterized as a Probability of Detection (P d ), which may be calculated using Equation 1 below. 
     
       
         
           
             
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     Under at least some regulations, RF exposure limits may not only be enforced for a point in time, but also over a time domain. That is, the user equipment  10  may ensure that average RF exposure over a range of time also meets the RF exposure limits. As discussed above, if the BPS  23  does not detect a human target within close proximity of the antenna  55 , the user equipment  10  may cause the transmitter  52  to transmit using the high transmission power level of X1. However, in the case of a missed detection (e.g., where there is a human target within close proximity of the antenna  55  but the BPS  23  does not detect the human target), the human target may be exposed to the high transmission power level of X1, which may exceed the regulatory RF exposure limits. On the other hand, each correct BPS  23  detection results in the transmission power level set to the low transmission power level of X2, which exposes the human target to instantaneous low RF exposure below the regulatory limits. If the human target is exposed to a sufficient number of high power transmissions due to BPS  23  missed detections over a time period, then, over that time period, the human target may be exposed to an RF exposure (e.g., an average RF exposure) that exceeds the regulatory limits. 
     The presently disclosed embodiments determine and apply transmission power levels (e.g., X1 and X2) based on the BPS Probability of Detection (P d ), while considering the regulatory RF exposure limits. X1 and X2 may be determined or optimized to achieve a maximum average transmission power gain (e.g., over a time period) when operating with the BPS  23  while ensuring that the maximum RF exposure caused during the entire transmission does not exceed regulatory limits. 
       FIG.  5    is a flowchart of a method  140  for determining and applying transmission power levels based on the Probability of Detection (P d ), while ensuring compliance with regulatory RF exposure limits, according to embodiments of the present disclosure. Any suitable device (e.g., a controller) that may control components of the user equipment  10 , such as the processor  12 , may perform the method  140 . In some embodiments, the method  140  may be implemented by executing instructions stored in a tangible, non-transitory, computer-readable medium, such as the memory  14  or storage  16 , using the processor  12 . For example, the method  140  may be performed at least in part by one or more software components, such as an operating system of the user equipment  10 , one or more software applications of the user equipment  10 , and the like. While the method  140  is described using steps in a specific sequence, it should be understood that the present disclosure contemplates that the described steps may be performed in different sequences than the sequence illustrated, and certain described steps may be skipped or not performed altogether. 
     In process block  142 , the processor  12  receives the RF exposure limit. For example, the RF exposure limit may be set by a regulatory entity, such as the FCC. In some embodiments, the RF exposure limit may be received from a base station or communication network, and/or may vary from geographical region to geographical region. In process block  144 , the processor  12  determines the low transmission (TX) power level X2 relative to the RF exposure limit. In some embodiments, the processor  12  may set the low transmission power level X2 to (or cause the antenna  55  to emit) the RF exposure limit. In additional or alternative embodiments, an exposure buffer or margin may be implemented when defining the low transmission power level X2. That is, the low transmission power level X2 may be defined by a sum of the RF exposure limit and the exposure buffer. This exposure margin may correspond to a transmission power backoff to be applied relative to the RF exposure limit to ensure regulatory compliance. The transmission power backoff may be fixed, and may include 1 decibel-milliwatts (dBm) or less, 1.5 dBm or less, 2 dBm or less, 5 dBm or less, and so on. In particular, the transmission power backoff may include any suitable value that compensates for factors that may change the transmission power (e.g., and thus cause the transmission power to exceed the RF exposure limit), such as RF impairments and/or transmission power changes due to temperature variations, among others. 
     In process block  146 , the processor  12  determines the BPS Probability of Detection and False Alarm Rate. This may be performed during, for example, a manufacturing or testing phase of the user equipment  10  (e.g., prior to shipping or delivering the user equipment  10  to a customer or consumer). In particular, a human target or a phantom (e.g., an object that simulates a human target) may be placed in close proximity (e.g., within a threshold range, such as within one or more millimeters (mm), including within 1 mm, within 2 mm, within 3 mm, within 5 mm, within 10 mm, within 20 mm, and so on) to the antenna  55  of the user equipment  10 . The processor  12  may operate the BPS  23  to detect the target, and for each BPS detection attempt, the processor  12  determines whether the target was detected or not. Based on the overall number of detection attempts and the number of correct detections, the processor  12  may determine the Probability of Detection (e.g., using Equation 1 above). 
     The processor  12  may also determine a False Alarm Rate of the BPS  23 . Again, the processor  12  may operate the BPS  23  (e.g., this time with no human target or phantom in close proximity of the antenna  55 ), and for each BPS detection attempt, the processor  12  determines whether the target was detected (e.g., a False Alarm) or not (e.g., a Correct Detection result). Based on the overall number of detection attempts and the number of False Alarms, the processor  12  may determine the False Alarm rate (e.g., using Equation 1 above). 
     In process block  148 , the processor  12  determines the high transmission power level X1 based on the Probability of Detection. In particular, the processor  12  may have determined the BPS Probability of Detection in process block  146  and may have determined the low transmission power level X2 relative to the RF exposure limit in process block  144 . The processor  12  may then determine a transmission power level difference between the high transmission power level and the low transmission power level (e.g., X1-X2) that simulates the RF exposure for the BPS Probability of Detection based on these inputs, without exceeding the RF exposure limit. That is, the processor  12  may determine the transmission power level difference X1-X2, and thus the high transmission power level X1, to ensure that the RF exposure limit is not exceeded (e.g., over time), while increasing or maximizing the transmission power difference (e.g., to increase or maximize the high transmission power level X1 to ensure superior communication performance). 
     For example, the processor  12  may determine the transmission power difference by assuming that a human target is in close proximity 100% of the time for a given time period (e.g., a regulatory averaging period). The regulatory averaging period may be any suitable time period to measure RF exposure values, such as 1 second or less, 4 seconds or less, 10 seconds or less, 30 seconds or less, and so on. The processor  12  may then average the low transmission power level X2 for the time that the BPS  23  correctly detects a human target according to the BPS Probability of Detection and the high transmission power level X1 for the time that the BPS  23  misses detecting a human target according to the BPS Probability of Detection, and ensure that the average is within the RF exposure limit. The processor  12  may then determine the transmission power level difference X1-X2. For example, if the BPS Probability of Detection is 70%, the processor  12  may apply the low transmission power level X2 for 70% of the applicable time range, and apply the high transmission power level X1 for 30% of the applicable time range, and ensure that the average transmission power over the applicable time range is within the RF exposure limit. The processor  12  may then determine the transmission power level difference X1-X2. 
     In some cases, simulation may be performed for different values of the high transmission power level X1 to find a transmission power difference (e.g., an increased or maximum transmission power difference) that is still RF exposure compliant. For example, the simulation may include performing BPS  23  detection to generate target detection results at fixed intervals, and applying the Probability of Detection that was determined in process block  146 . Based on the BPS detection result, the transmission power levels and/or RF exposure value are selected and recorded. In particular, if no target is detected, the high transmission power level X1 is selected and the corresponding RF exposure is stored for RF exposure time domain averaging. On the other hand, if a target is detected, the low transmission power level X2 is selected and the corresponding RF exposure is stored for RF exposure time domain averaging. 
     The RF exposure values recorded during the simulation may be set relative to RF exposure limit. For example, the low transmission power level X2 may have been determined relative to RF exposure limit, as discussed above. As such, for the low transmission power level X2, the RF exposure may be determined using Equation 3 below: 
     
       
         
           
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     The high transmission power level X1 may have been determined per simulation run relative to the low transmission power level X2, where simulations were performed for different transmission power difference X1-X2 values, as discussed above. As such, for the high transmission power level X1, the RF exposure may be determined using Equation 4 below: 
     
       
         
           
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     Based on the BPS detection-dependent RF exposure values determined through the simulation, the processor  12  may determine the time domain averaged RF exposure values (e.g., according to regulatory averaging periods). The processor  12  may determine a time domain RF exposure (e.g., a maximum RF exposure over time) for each combination of transmission power level difference X1-X2. The processor  12  may then determine a transmission power difference X1-X2 value (e.g., a maximum transmission power difference X1-X2 value) for which RF exposure is within regulatory limits. This determined maximum RF exposure compliant transmission power difference X1-X2 value defines a net transmission power gain for BPS operation when a human target is close by the antenna  55 . 
     In process block  150 , the processor  12  determines a transmission power gain based on the low transmission power, the high transmission power, and the false alarm rate. That is, the processor  12  may determine the transmission power gain that may be achieved due to BPS  23  operation over time. The processor  12  may determine the transmission power gain by applying the False Alarm Rate, which corresponds to False Alarms, where a human target is detected in close proximity to the antenna  55  when there is no actual human target in close proximity to the antenna  55 . During these False Alarms, the transmitter  52  may use the low transmission power level X2 for transmission (e.g., instead of the proper high transmission power level X1). As such, False Alarms further decrease the average achievable transmission power gain. 
       FIG.  6    is a timing diagram illustrating False Alarms decreasing the average transmission power gain, according to embodiments of the present disclosure. As illustrated, the BPS  23  determines, for certain time periods  160 , that there is no human target in close proximity to the antenna  55 . During these time periods  160 , the processor  12  causes the transmitter to use the high transmission power level X1 for transmission. However, for other time periods  162 , the BPS  23  also mistakenly determines that there is a human present when there is not, resulting in a False Alarm. During these time periods  162 , the processor  12  causes the transmitter to use the low transmission power level X2 for transmission. As such, the average transmission power  164  is decreased due to the False Alarms, and the average transmission power gain  166  (e.g., as based on or measured from the low transmission power level X2) is also decreased. The processor  12  may determine the average transmission power gain  166  using Equation 5 below, where b is the False Alarm Rate as determined in Equation 2 above: 
     
       
         
           
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     In process block  152 , the processor  12  selects and/or stores the high transmission power level X1 and the low transmission power level X2 based on the average transmission power gain  166  and/or a rate of detection. In particular, the processor  12  may select a larger or maximum average transmission power gain  166 , and store the high transmission power level X1 and the low transmission power level X2 corresponding to the larger or maximum average transmission power gain  166  (e.g., in the memory  14  and/or the storage  16 ). That is, the transmission power gain  166  may be used as a performance indicator of pairs of the high transmission power level X1 and the low transmission power level X2. In process block  154 , the processor  12  applies the stored high transmission power X1 and the low transmission power level X2 during transmission based on a desired transmission power gain (e.g., a desired average transmission power gain  166 ). In particular, the processor  12  may apply the high transmission power X1 in response to the BPS  23  detecting there is no human target, and the low transmission power level X2 in response to the BPS  23  detecting there is a human target. In this manner, the method  140  enables the user equipment  10  to determine and apply transmission power levels based on the BPS  23  Probability of Detection, while ensuring compliance with regulatory RF exposure limits. 
     In additional or alternative embodiments, rather than determining the low transmission power level X2 relative to the RF exposure limit as shown in process block  144 , the processor  12  may determine the low transmission power level X2 based on other factors, in place of or in addition to the RF exposure limit. For example, the processor  12  may determine the low transmission power level X2 based on presence of a human target as detected by the BPS  23 .  FIG.  7    is a flowchart of a method  170  for determining and applying transmission power levels based on the Probability of Detection (P d ) and a presence of a human target as detected by the BPS  23 , while ensuring compliance with regulatory RF exposure limits, according to embodiments of the present disclosure. Any suitable device (e.g., a controller) that may control components of the user equipment  10 , such as the processor  12 , may perform the method  170 . In some embodiments, the method  170  may be implemented by executing instructions stored in a tangible, non-transitory, computer-readable medium, such as the memory  14  or storage  16 , using the processor  12 . For example, the method  170  may be performed at least in part by one or more software components, such as an operating system of the user equipment  10 , one or more software applications of the user equipment  10 , and the like. While the method  170  is described using steps in a specific sequence, it should be understood that the present disclosure contemplates that the described steps may be performed in different sequences than the sequence illustrated, and certain described steps may be skipped or not performed altogether. 
     In decision block  172 , the processor  12  determines whether an indication has been received from the BPS  23  that a human target is detected. If so, then, in process block  174 , the processor  12  applies a decreased low transmission power level X2 (e.g., beyond what is determined in process block  144  of  FIG.  5   ) to account for missed detections. That is, because a human target is exposed to the high transmission power level X1 in the case of a missed detection, the processor  12  may decrease the low transmission power level X2 to drive the average transmission power over time down to compensate for the high transmission power level X1 exposure. The decreased low transmission power level X2 may be stored in the memory  14  and/or the storage  16 , or the processor  12  may decrease the low transmission power level X2 that is stored in the memory  14  and/or the storage  16 . It should be understood that the decreased low transmission power level X2 and/or the low transmission power level X2 that is decreased by the processor  12  may be determined using the method  140  shown in  FIG.  5   , which may be determined based on the BPS Probability of Detection and False Alarm Rate as described in the method  140 . 
     If the processor  12  determines that an indication has not been received from the BPS  23  that a human target is detected, then, in process block  176 , the processor  12  applies an increased high transmission power level X1 (e.g., beyond what is determined in process block  144  of  FIG.  5   ) to compensate for the decreased low transmission power level X2 applied in process block  174 . Indeed, in some embodiments, the processor  12  may set the high transmission power level X1 to meet the RF exposure limit, such that no exposure margin is applied. In additional or alternative embodiments, the processor  12  may apply a default high transmission power level X1 (e.g., that determined in process block  144  of  FIG.  5   ). As with the decreased low transmission power level X2 applied in process block  174 , the increased high transmission power level X1 may be stored in the memory  14  and/or the storage  16 , or the processor  12  may decrease the default high transmission power level X1 that is stored in the memory  14  and/or the storage  16 . It should be understood that the increased high transmission power level X1 and/or the default increased high transmission power level X1 that is increased by the processor  12  may be determined using the method  140  shown in  FIG.  5   , which may be determined based on the BPS Probability of Detection and False Alarm Rate as described in the method  140 . In this manner, the method  170  enables the user equipment  10  to determine and apply transmission power levels based on the BPS  23  Probability of Detection and a presence of a human target as detected by the BPS  23 , while ensuring compliance with regulatory RF exposure limits. 
     Moreover, in some embodiments, the processor  12  may store multiple pairs of high and low transmission power levels (X1, X2) in the memory  14  and/or the storage  16  to be selected and used based on, for example, a frequency or rate that a human target is detected by the BPS  23 .  FIG.  8    is a flowchart of a method  190  for determining and applying transmission power levels based on the Probability of Detection (P d ) and frequency of detection of a human target as detected by the BPS  23 , while ensuring compliance with regulatory RF exposure limits, according to embodiments of the present disclosure. Any suitable device (e.g., a controller) that may control components of the user equipment  10 , such as the processor  12 , may perform the method  190 . In some embodiments, the method  190  may be implemented by executing instructions stored in a tangible, non-transitory, computer-readable medium, such as the memory  14  or storage  16 , using the processor  12 . For example, the method  190  may be performed at least in part by one or more software components, such as an operating system of the user equipment  10 , one or more software applications of the user equipment  10 , and the like. While the method  190  is described using steps in a specific sequence, it should be understood that the present disclosure contemplates that the described steps may be performed in different sequences than the sequence illustrated, and certain described steps may be skipped or not performed altogether. 
     In process block  192 , the processor  12  receives a detection rate or frequency of a human target by the BPS  23 . In particular, the BPS  23  may detect a human target over at least a portion of a time window (e.g., 1 second or less, 4 seconds or less, 10 seconds or less, 30 seconds or less, and so on), and the processor  12  may determine a rate of the detection over the time window (e.g., between 0 to 100% of the time window). In decision block  194 , the processor  12  determines whether the detection rate exceeds a threshold. That is, the processor  12  may determine whether the detection rate indicates that a human target is more frequently detected. The threshold detection rate may include 30% or greater, 50% or greater, 70% or greater, or any other suitable detection rate that indicates that the human target is more frequently detected. 
     If so, then, in process block  196 , the processor  12  applies a decreased low transmission power level X2 (e.g., beyond what is determined in process block  144  of  FIG.  5   ) and an increased high transmission power level X1 (e.g., beyond what is determined in process block  144  of  FIG.  5   ). That is, because there is a human target detected that may be more frequently exposed to RF signals emitted by the antenna  55 , the processor  12  may apply the decreased low transmission power level X2 to ensure that the regulatory RF exposure limits are met and/or not exceeded. Moreover, because the decreased low transmission power level X2 may drive down the average transmission power of the transmitter  52 , the processor  12  may apply the increased high transmission power level X1 to compensate. Advantageously, a human target may not be exposed to the increased high transmission power level X1, as it may be implemented when the BPS  23  detects that there is no human target. 
     The decreased low transmission power level X2 and the increased high transmission power level X1 may be stored in the memory  14  and/or the storage  16 , or the processor  12  may decrease the low transmission power level X2 and increase the high transmission power level X1 that are stored in the memory  14  and/or the storage  16 . It should be understood that the decreased low transmission power level X2 and/or the low transmission power level X2 that is decreased by the processor  12 , and the increased high transmission power level X1 and/or the high transmission power level X1 that is increased by the processor  12  may be determined using the method  140  shown in  FIG.  5   , which may be determined based on the BPS Probability of Detection and False Alarm Rate as described in the method  140 . 
     If the processor  12  determines that the detection rate does not exceed the threshold, then, in process block  198 , the processor  12  applies an increased low transmission power level X2 (e.g., beyond what is determined in process block  144  of  FIG.  5   ) and a decreased high transmission power level X1 (e.g., beyond what is determined in process block  144  of  FIG.  5   ). That is, because there is a human target detected that may be less frequently exposed to RF signals emitted by the antenna  55 , the processor  12  may apply the increased low transmission power level X2. Moreover, because the increased low transmission power level X2 may drive up the average transmission power of the transmitter  52 , the processor  12  may apply the decreased high transmission power level X1 to compensate. 
     The increased low transmission power level X2 and the decreased high transmission power level X1 may be stored in the memory  14  and/or the storage  16 , or the processor  12  may increase the low transmission power level X2 and decrease the high transmission power level X1 that are stored in the memory  14  and/or the storage  16 . It should be understood that the increased low transmission power level X2 and/or the low transmission power level X2 that is increased by the processor  12 , and the decreased high transmission power level X1 and/or the high transmission power level X1 that is decreased by the processor  12  may be determined using the method  140  shown in  FIG.  5   , which may be determined based on the BPS Probability of Detection and False Alarm Rate as described in the method  140 . In this manner, the method  170  enables the user equipment  10  to determine and apply transmission power levels based on the BPS  23  Probability of Detection and frequency of detection of a human target as detected by the BPS  23 , while ensuring compliance with regulatory RF exposure limits. 
     In some embodiments, there may be a default or medium pair of high and low transmission power levels (X1, X2) (e.g., where the default low transmission power level is between the decreased and increased low transmission power levels, and the high transmission power level is between the decreased and increased high transmission power levels) that may be stored, selected, and/or applied by the processor  12  when the detection rate of a human target within a threshold proximity to the antenna  55  is between a lower threshold percentage of time (e.g., 20% or less, 30% or less, 40% or less, and so on) and a higher threshold percentage of time (e.g., 60% or more, 70% or more, 80% or more, and so on). 
     The specific embodiments described above have been shown by way of example, and it should be understood that these embodiments may be susceptible to various modifications and alternative forms. It should be further understood that the claims are not intended to be limited to the particular forms disclosed, but rather to cover all modifications, equivalents, and alternatives falling within the spirit and scope of this disclosure. 
     The techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function]...” or “step for [perform]ing [a function]...,” it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). However, for any claims containing elements designated in any other manner, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f). 
     It is well understood that the use of personally identifiable information should follow privacy policies and practices that are generally recognized as meeting or exceeding industry or governmental requirements for maintaining the privacy of users. In particular, personally identifiable information data should be managed and handled so as to minimize risks of unintentional or unauthorized access or use, and the nature of authorized use should be clearly indicated to users.