Transmission power reduction based on spatial distribution of radio frequency exposure in multi-transmitter scenarios

Abstract

According to certain aspects, a wireless device includes a transmitter and a processor coupled to the transmitter. The processor is configured to determine a radio frequency (RF) exposure value at a peak location based on a transmission power level of the transmitter, determine a contribution of each of the transmitters to the RF exposure value at the peak location, and reduce the transmission power level of each of one or more of the transmitters based on the contribution of the transmitters to the RF exposure value at the peak location.

Description

[0001] Cross Reference to Related Applications

[0002] This patent application claims priority to and benefit of Non-Provisional Patent Application No. 17 / 376,067 filed in the U.S. Patent Office on July 14, 2021, and Provisional Patent Application No. 63 / 052,371 filed in the U.S. Patent and Trademark Office on July 15, 2020, the entire contents of both of which are incorporated herein by reference as if fully set forth below in their entirety and for all applicable purposes. TECHNICAL FIELD

[0003] Aspects of the disclosure relate generally to wireless devices, and more particularly to reducing transmission power to meet radio frequency (RF) exposure compliance. BACKGROUND

[0004] Modern wireless devices (e.g., cellular telephones) often need to limit user exposure to RF radiation according to radio frequency (RF) exposure limits set by domestic and international regulatory bodies. To ensure that wireless devices comply with the RF exposure limits, techniques have been developed for enabling wireless devices to assess RF exposure from the wireless devices in real-time and adjust transmission power of the wireless devices accordingly to comply with the RF exposure limits. SUMMARY

[0005] The following is a simplified summary of one or more embodiments in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of all contemplated embodiments, and is intended to neither identify key or critical elements of all embodiments nor delineate the scope of any or all embodiments. Its sole purpose is to present some concepts of one or more embodiments in a simplified form as a prelude to the more detailed description that is presented later.

[0006] According to certain aspects, a wireless device includes a transmitter and a processor coupled to the transmitter. The processor is configured to determine a radio frequency (RF) exposure value at a first location based on a transmission power level of the transmitter, determine a contribution of each of the transmitters to the RF exposure value at the first location, and reduce the transmission power level of each of one or more of the transmitters based on the contribution of the transmitters to the RF exposure value at the first location.

[0007] According to certain aspects, a method implemented in a wireless device having transmitters and a processor includes determining an RF exposure value at a first location based on transmission power levels of the transmitters, determining a contribution of each of the transmitters to the RF exposure value at the first location, and reducing the transmission power level of each of one or more of the transmitters based on the contribution of the transmitters to the RF exposure value at the first location.

[0008] According to certain aspects, an apparatus for wireless communication includes transmitters and a processor, means for determining an RF exposure value at a first location based on transmission power levels of the transmitters, means for determining a contribution of each of the transmitters to the RF exposure value at the first location, and means for reducing the transmission power level of each of one or more of the transmitters based on the contribution of the transmitters to the RF exposure value at the first location.

[0009] In certain aspects, the RF exposure value is a specific absorption rate (SAR) value, a power density (PD) value, or a combined SAR and PD value.

[0010] In one aspect, the processor is configured to reduce the transmission power level of each of one or more of the transmitters by, for each transmitter, determining a proportion of the RF exposure value at the first location attributable to each transmitter, and reducing the transmission power level of each transmitter in accordance with the proportion of the RF exposure value attributable to each transmitter, where the RF exposure value at the first location corresponds to a peak RF exposure value.

[0011] In one aspect, the processor is configured to reduce the transmission power level of each of one or more of the transmitters by, for each transmitter, determining a proportion of the RF exposure value at the first location attributable to each transmitter, and reducing the transmission power level of each transmitter in accordance with the proportion of the RF exposure value attributable to each transmitter, where the RF exposure value at the first location corresponds to a peak RF exposure value.

[0012] In some aspects, the processor is configured to determine a reduction of the RF exposure value at the first location to satisfy an RF exposure limit, and the processor is configured to reduce the transmission power level of each of one or more of the transmitters based further on the determined reduction of the RF exposure value at the first location.

[0013] In some aspects, each transmitter is assigned a respective priority, and the processor is configured to reduce the transmission power level of each of one or more of the transmitters based further on the priority of the transmitters.

[0014] In one aspect, the processor is configured to reduce the transmission power level of each of one or more of the transmitters such that the contribution of two or more of the transmitters to the RF exposure value at the first location is approximately equal after the reduction. The processor can be configured to reduce the transmission power level of each of one or more of the transmitters such that the contribution of all of the transmitters to the RF exposure value at the first location is approximately equal after the reduction.

[0015] In one aspect, after the reduction, the processor is configured to set a transmission power limit for each transmitter based on the transmission power level of the transmitter.

[0016] In one aspect, the processor is configured to determine the RF exposure value at the first location by: for each transmitter, scaling a respective RF exposure distribution based on the transmission power level of the transmitter; combining the scaled RF exposure distributions to obtain a combined RF exposure distribution; and determining the RF exposure value at the first location in the combined RF exposure distribution, wherein the RF exposure value at the first location corresponds to the peak RF exposure value.

[0017] To the accomplishment of the foregoing and related aspects, one or more embodiments comprise the features recited in the following claims, and the following description and the annexed drawings teach by way of example the best mode presently contemplated for carrying out the embodiments. The following description and drawings are illustrative of the principles of one or more embodiments and should not be construed as limiting the scope of the embodiments. BRIEF DESCRIPTION OF DRAWINGS

[0018] Figure 1 An example of a wireless device in which aspects of the disclosure can be implemented is shown.

[0019] Figure 2 An example of a normalized specific absorption rate (SAR) distribution in combination with a normalized power density (PD) distribution in accordance with certain aspects of the disclosure is shown.

[0020] Figure 3 is a flowchart showing an exemplary method for determining a transmission power level that complies with an RF exposure limit for simultaneous transmissions using multiple wireless communication technologies in accordance with certain aspects of the disclosure.

[0021] Figure 4 is a flowchart showing an exemplary method for determining a transmission power level that complies with a PD limit in accordance with certain aspects of the disclosure.

[0022] Figure 5 An example of a time-averaged SAR distribution in accordance with certain aspects of the disclosure is shown.

[0023] Figure 6 FIG. 1 is a flow diagram illustrating an exemplary method for determining a transmission power level that complies with a time-averaged SAR limit, in accordance with certain aspects of the present disclosure.

[0024] Figure 7 An example of a time-averaged PD profile is shown, in accordance with certain aspects of the present disclosure.

[0025] Figure 8 FIG. 1 is a flow diagram illustrating an exemplary method for determining a transmission power level that complies with a time-averaged SAR limit, in accordance with certain aspects of the present disclosure.

[0026] Figure 9 An example of a time-averaged SAR profile combined with a time-averaged PD profile is shown, in accordance with certain aspects of the present disclosure.

[0027] Figure 10 FIG. 1 is a flow diagram illustrating an exemplary method for determining a transmission power level that complies with a time-averaged SAR limit, in accordance with certain aspects of the present disclosure.

[0028] Figure 11 An example is shown in which multiple time-averaging windows are used for different frequency bands to determine a time-averaged PD profile, in accordance with certain aspects of the present disclosure.

[0029] Figure 12 An example is shown in which a time-averaged PD profile is determined for simultaneous transmissions at different frequency bands, in accordance with certain aspects of the present disclosure.

[0030] Figure 13 An example of a time-averaged SAR profile combined with a PD profile is shown, in accordance with certain aspects of the present disclosure.

[0031] Figure 14 An example of a wireless device including multiple transmitters is shown, in accordance with certain aspects of the present disclosure.

[0032] Figure 15 FIG. 1 is a flow diagram illustrating an exemplary method for determining a transmission power level that complies with a time-averaged SAR limit, in accordance with certain aspects of the present disclosure.

[0033] Figure 16 FIG. 1 is a flow diagram illustrating an exemplary method for determining a transmission power level that complies with a time-averaged SAR limit, in accordance with certain aspects of the present disclosure.

[0034] Figure 17 FIG. 1 is a flow diagram illustrating an exemplary method for determining a transmission power level that complies with a time-averaged SAR limit, in accordance with certain aspects of the present disclosure. DETAILED DESCRIPTION

[0035] The detailed description set forth below, in connection with the appended drawings, is intended as a description of various configurations and is not intended to represent the only configurations in which the concepts described herein can be practiced. The detailed description includes specific details for the purpose of providing a thorough understanding of various concepts. However, it will be apparent to those skilled in the art that these concepts can be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form in order to avoid obscuring such concepts.

[0036] Figure 1 An example of a wireless device 100 in which aspects of the disclosure described herein can be implemented is shown. The wireless device 100 can comprise a mobile wireless device (e.g., a cellular phone, a tablet, a laptop, etc.), a wireless access point, a customer premises equipment (CPE), or some other wireless device.

[0037] The wireless device 100 includes a processor 110 and a memory 115 coupled to the processor 110. The memory 115 can store instructions that, when executed by the processor 110, cause the processor 110 to perform one or more of the operations described herein. The processor 110 can be implemented with a general purpose processor, a digital signal processor (DSP), a baseband modem, an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate logic, discrete hardware components, or any combination thereof, configured to perform one or more of the operations described herein. In some examples, multiple processors 110 and / or multiple memories 115 are implemented. One or more of the operations described herein can be performed by two or more of the processors 110, e.g., by executing instructions stored in one or more of the memories 115.

[0038] The wireless device 100 also includes a first transmitter 120, a first plurality of antennas 122-1 through 122-N (where N is a positive integer) coupled to the first transmitter 120, and a first bus 140 coupled between the first transmitter 120 and the processor 110. In certain aspects, the first transmitter 120 is configured to transmit signals via one or more of the first plurality of antennas 122-1 through 122-N using one or more wireless communication techniques, including but not limited to third generation (3G) techniques (e.g., CDMA), fourth generation (4G) techniques (also referred to as Long Term Evolution (LTE)), fifth generation (5G) techniques, one or more techniques based on one or more IEEE 802.11 protocols (e.g., IEEE 802.11ac, IEEE 802.11n, IEEE 802.11ad, IEEE 802.11ax, IEEE 802.11ay, etc.), and / or one or more other techniques. In some aspects, the first transmitter 120 can be configured to transmit signals via the plurality of antennas 122-1 through 122-N using multiple-input multiple-output (MIMO) transmission to increase the capacity of a radio link between the wireless device 100 and another wireless device (not shown). In some aspects, the first transmitter 120 can be configured to transmit signals via the plurality of antennas 122-1 through 122-N using beamforming to direct the transmission toward another wireless device (not shown). In these aspects, the transmission can be electrically steered by adjusting the relative phase and / or amplitude of the transmission signals of the different antennas 122-1 through 122-N.

[0039] The processor 110 interfaces with the first transmitter 120 via the first bus 140. The first bus 140 can include one or more signal lines between the processor 110 and the first transmitter 120. To transmit data, the processor 110 can process the data into one or more signals (e.g., baseband signals or intermediate frequency signals). The processing performed by the processor 110 can include encoding the data and modulating the encoded data (e.g., using any of a variety of different modulation schemes, including BPSK, QPSK, QAM, etc.). The processor 110 can output the one or more signals to the first transmitter 120 via the first bus 140. The first transmitter 120 can then process the one or more signals from the processor 110 into one or more RF signals for transmission via one or more of the antennas 122-1 through 122-N. The processing performed by the first transmitter 120 can include upconversion, power amplification, etc.

[0040] In some aspects, the processor 110 can adjust the transmission power of one or more of the antennas 122-1 through 122-N. For example, the first transmitter 120 can include a plurality of amplifiers (not shown), where each amplifier is coupled to a respective one of the antennas. For each amplifier, the processor 110 can output a respective control signal to the amplifier via the first bus 140 to control the gain of the amplifier. In this example, the processor 110 can adjust the transmission power of the antennas by adjusting the gain of the respective amplifiers accordingly. In another example, the processor 110 can output one or more signals to the first transmitter 120, where each of the one or more signals corresponds to a respective one of the antennas 122-1 through 122-N. In this example, the processor 110 can adjust the transmission power of the antennas by adjusting the amplitude of the respective signals accordingly. It should be understood that the present disclosure is not limited to the above examples, and the processor 110 can employ other techniques to adjust the transmission power.

[0041] In some aspects, the processor 110 can adjust the transmission power of one or more of the antennas 122-1 through 122-N using an open power control loop and / or a closed power control loop. For an example of an open power control loop, the wireless device 100 can receive a pilot signal from another wireless device (not shown) via a receiver (not shown). In this example, the processor 110 estimates the channel conditions between the wireless device 100 and the other wireless device based on the received pilot signal, and adjusts the transmission power of one or more of the antennas 122-1 through 122-N based on the estimated channel conditions. For an example of a closed power control loop, the wireless device 100 receives a feedback signal from another wireless device via a receiver (not shown), where the feedback signal indicates the channel conditions between the wireless device 100 and the other wireless device. In this example, the processor 110 adjusts the transmission power of one or more of the antennas 122-1 through 122-N based on the indicated channel conditions.

[0042] The processor 110 can also adjust the transmission power of one or more of the antennas 122-1 through 122-N based on the data rate. For example, the processor 110 can increase (boost) the transmission power to transmit a short burst of data.

[0043] Furthermore, the processor 110 can adjust the transmission power of one or more of the antennas 122-1 through 122-N to keep the RF exposure from the wireless device 100 within the RF exposure limit set by a regulator (e.g., the FCC), as discussed further below. In this case, the transmission power is constrained by the RF exposure limit.

[0044] In the illustrated example, the wireless device 100 also includes a second transmitter 130, a second plurality of antennas 132-1 through 132-M coupled to the second transmitter 130, and a second bus 150 coupled between the second transmitter 130 and the processor 110. In certain aspects, the second transmitter 130 is configured to transmit signals via one or more of the second plurality of antennas 132-1 through 132-M using one or more wireless communication techniques, including but not limited to 3G techniques, 4G techniques, 5G techniques, one or more techniques based on one or more IEEE 802.11 protocols (e.g., IEEE 802.11 ac, IEEE 802.11 n, IEEE 802.11 ad, IEEE 802.11 ax, IEEE 802.11 ay, etc.), and / or one or more other techniques. The second transmitter 130 can transmit signals via the plurality of antennas 132-1 through 132-M using MIMO transmission, beamforming, and / or other methods. In certain aspects, the first transmitter 120 and the second transmitter 130 can transmit signals simultaneously using different wireless communication techniques, as discussed further below.

[0045] The processor 110 interfaces with the second transmitter 130 via the second bus 150, which can include one or more signal lines between the processor 110 and the second transmitter 130. To transmit data, the processor 110 can process the data into one or more signals (e.g., baseband or intermediate frequency signals). The processing performed by the processor 110 can include encoding the data and modulating the encoded data (e.g., using any of a variety of different modulation schemes, including BPSK, QPSK, QAM, etc.). The processor 110 can output the one or more signals to the second transmitter 130 via the second bus 150. The second transmitter 130 can then process the one or more signals from the processor 110 into one or more RF signals for transmission via one or more of the antennas 132-1 through 132-M. The processing performed by the second transmitter 130 can include frequency upconversion, power amplification, etc.

[0046] The processor 110 can adjust the transmission power of one or more of the antennas 132-1 through 132-M. For example, the second transmitter 130 can include a plurality of amplifiers (not shown), where each amplifier is coupled to a respective one of the antennas 132-1 through 132-M. For each amplifier, the processor 110 can output a respective control signal to the amplifier via the second bus 150 to control the gain of the amplifier. In this example, the processor 110 can adjust the transmission power of the antennas by adjusting the gain of the respective amplifiers accordingly. In another example, the processor 110 can output one or more signals to the second transmitter 130, where each of the one or more signals corresponds to a respective one of the antennas 132-1 through 132-M. In this example, the processor 110 can adjust the transmission power of the antennas by adjusting the amplitude of the respective signals accordingly. It should be appreciated that the present disclosure is not limited to the above examples, and the processor 110 can employ other techniques to adjust the transmission power.

[0047] As described above, the processor 110 can use an open power control loop and / or a closed power control loop to adjust the transmission power of one or more of the antennas 132-1 through 132-M. The processor 110 can also adjust the transmission power of one or more of the antennas 132-1 through 132-M to keep RF exposure from the wireless device 100 within an RF exposure limit set by a regulator, as discussed further below.

[0048] It should be appreciated that, in addition to the first transmitter 120 and the second transmitter 130 shown, the wireless device 100 can include one or more additional transmitters. Although in the example shown in Figure 1 It should be appreciated that, in addition to the first transmitter 120 and the second transmitter 130 shown, the wireless device 100 can include one or more additional transmitters. Although in the example shown in Figure 1 It should be appreciated that, in addition to the first transmitter 120 and the second transmitter 130 shown, the wireless device 100 can include one or more additional transmitters. Although in the example shown in

[0049] Modern wireless devices (e.g., cellular phones) often need to limit user exposure to radio frequency (RF) radiation according to exposure limits set by domestic and international regulatory agencies. RF exposure can be expressed in terms of specific absorption rate (SAR), which measures the absorption of energy per unit mass of human tissue, and the unit can be in watts per kilogram (W / kg). RF exposure can also be expressed in terms of power density (PD), which measures the absorption of energy per unit area, and the unit can be in mW / cm 2 .

[0050] SAR can be used to evaluate RF exposure for transmission frequencies below 10 GHz, which encompasses wireless communication technologies such as 3G (e.g., CDMA), 4G, IEEE 802.11ac, etc. PD can be used to evaluate RF exposure for transmission frequencies above 10 GHz, which encompasses wireless communication technologies such as IEEE 802.11ad, 5G, etc. Thus, different metrics can be used to evaluate RF exposure for different wireless communication technologies.

[0051] Wireless device 100 can transmit signals simultaneously using multiple wireless communication technologies. For example, wireless device 100 can transmit signals simultaneously using a first wireless communication technology (e.g., 3G, 4G, etc.) that operates below 10 GHz and a second wireless communication technology (e.g., 5G, IEEE 802.11ad) that operates above 10 GHz or a first wireless communication technology and a second wireless communication technology in similar or overlapping frequency bands (e.g., WWAN and WLAN). Since wireless device 100 transmits signals simultaneously using the first technology and the second technology, a user of the device is exposed to RF radiation from the transmissions using both technologies. Thus, techniques for determining RF exposure compliance are needed for cases where wireless device 100 transmits signals simultaneously using multiple wireless communication technologies.

[0052] As discussed further below, aspects of the present disclosure enable wireless device 100 to evaluate RF exposure (in real-time) for cases where wireless device 100 transmits signals simultaneously using multiple wireless communication technologies.

[0053] In certain aspects, the wireless device 100 can simultaneously transmit signals using a first wireless communication technology (e.g., 3G, 4G, IEEE 802.11ac, etc.) in which RF exposure is measured according to SAR and a second wireless communication technology (e.g., 5G, IEEE 802.11ad) in which RF exposure is measured according to PD. In these aspects, the first transmitter 120 can transmit a first signal according to the first wireless communication technology and the second transmitter 130 can transmit a second signal according to the second wireless communication technology. As discussed further below, when the wireless device 100 simultaneously transmits the first and second signals using the first and second technologies, respectively, the processor 110 can evaluate combined RF exposure from the first and second technologies to ensure compliance with RF exposure limits. In other aspects, both the first wireless communication technology and the second wireless communication technology are associated with SAR measurements or both are associated with PD measurements. In other aspects, techniques as described herein can be used to combine communications from different transmitters and / or antennas that are communicating using the same wireless communication technology. While certain descriptions below refer to a first wireless technology, a second wireless technology, SAR, and / or PD, it should be understood that these descriptions can equally apply to the various transmissions described in this paragraph.

[0054] To evaluate RF exposure from transmissions using a first technology (e.g., 3G, 4G, IEEE 802.11ac, etc.), the wireless device 100 can include a plurality of SAR profiles for the first technology stored in the memory 115. Each of the SAR profiles can correspond to a respective one of a plurality of transmission scenarios supported by the wireless device 100 for the first technology. As discussed further below, the transmission scenarios can correspond to various combinations of antennas 122-1 through 122-N, frequency bands, channels, and / or body positions.

[0055] The SAR profile (also referred to as a SAR map) for each transmission scenario can be generated based on measurements (e.g., electric field measurements) performed in a test laboratory using a human body model. After the SAR profiles are generated, the SAR profiles are stored in the memory 115 to enable the processor 110 to evaluate (e.g., in real-time) RF exposure as discussed further below. Each SAR profile includes a set of SAR values, where each SAR value can correspond to a different location (e.g., on a model of a human body). Each SAR value can include an average SAR value over a 1 g or 10 g mass at the respective location.

[0056] The SAR values in each SAR distribution correspond to a particular transmission power level (e.g., the transmission power level at which the SAR values were measured in a test lab). Since SAR scales with transmission power level, the processor 110 can scale the SAR distribution for any transmission power level by multiplying each SAR value in the SAR distribution by the following transmission power scaling factor:

[0057]

[0058] where Tx c is the current transmission power level for the respective transmission scenario, and Tx SAR is the transmission power level corresponding to the SAR values in the stored SAR distribution (e.g., the transmission power level at which the SAR values were measured in a test lab).

[0059] As described above, the wireless device 100 can support multiple transmission scenarios for a first technology. In certain aspects, a transmission scenario can be specified by a set of parameters. The set of parameters can include one or more of an antenna parameter indicating one or more antennas (i.e., active antennas) used for transmission, a frequency band parameter indicating one or more frequency bands (i.e., active frequency bands) used for transmission, a channel parameter indicating one or more channels (i.e., active channels) used for transmission, a body position parameter indicating a position of the wireless device 100 relative to a user body position (head, torso, away from body, etc.), and / or other parameters. In cases where the wireless device 100 supports a large number of transmission scenarios, it can be very time consuming and expensive to perform measurements for each transmission scenario in a test setting (e.g., a test lab). To reduce testing time, measurements can be performed for a subset of the transmission scenarios to generate SAR distributions for the subset of transmission scenarios. As discussed further below, in this example, a SAR distribution for each of the remaining transmission scenarios can be generated by combining two or more of the SAR distributions for the subset of transmission scenarios.

[0060] For example, SAR measurements can be performed for each of the antennas 122-1 through 122-N to generate a SAR distribution for each of the antennas 122-1 through 122-N. In this example, a SAR distribution for a transmission scenario in which two or more of the antennas 122-1 through 122-N are active can be generated by combining the SAR distributions for the two or more active antennas.

[0061] In another example, SAR measurements can be performed for each of a plurality of frequency bands to generate a SAR profile for each of the plurality of frequency bands. In this example, a SAR profile for a transmission scenario in which two or more frequency bands are active can be generated by combining the SAR profiles for the two or more active frequency bands.

[0062] In certain aspects, the SAR profiles can be normalized with respect to a SAR limit by dividing each SAR value in the SAR profile by the SAR limit. In this case, when a normalized SAR value is greater than 1, the normalized SAR value exceeds the SAR limit, and when a normalized SAR value is less than 1, the normalized SAR value is below the SAR limit. In these aspects, each of the SAR profiles stored in the memory 115 can be normalized with respect to the SAR limit.

[0063] In certain aspects, a normalized SAR profile for a transmission scenario can be generated by combining two or more normalized SAR profiles. For example, a normalized SAR profile for a transmission scenario in which two or more antennas are active can be generated by combining the normalized SAR profiles for the two or more active antennas. For cases in which different transmission power levels are used for the active antennas, the normalized SAR profile for each active antenna can be scaled by the respective transmission power level before the normalized SAR profiles for the active antennas are combined. The normalized SAR profile for simultaneous transmissions from multiple active antennas can be given by:

[0064]

[0065] where SAR lim is the SAR limit, SAR norm_combined is the combined normalized SAR profile for simultaneous transmissions from active antennas, i is an index of an active antenna, SAR i is the SAR profile for the ith active antenna, Tx i is the transmission power level for the ith active antenna, Tx SARi is the transmission power level for the SAR profile of the ith active antenna, and K is the number of active antennas. Equation (2) can be rewritten as follows:

[0066]

[0067] where SAR norm_i is the normalized SAR profile for the ith active antenna. In cases in which multiple active antennas at the same transmission frequency are simultaneously transmitting (e.g., multiple-input multiple-output (MIMO)), the combined normalized SAR profile is obtained by summing the square roots of the individual normalized SAR profiles and computing the square of the sum, as follows:

[0068]

[0069] In another example, normalized SAR distributions for different frequency bands can be stored in the memory 115. In this example, the normalized SAR distribution for a transmission scenario in which two or more frequency bands are active can be generated by combining the normalized SAR distributions for the two or more active frequency bands. For cases in which the transmission power level is different for the active frequency bands, the normalized SAR distribution for each active frequency band can be scaled by the respective transmission power level before combining the normalized SAR distributions for the active frequency bands. In this example, the combined SAR distribution can also be calculated using Equation (3a), where i is an index of an active frequency band, SAR norm_i is the normalized SAR distribution for the i-th active frequency band, Tx i is the transmission power level for the i-th active frequency band, and Tx SARi is the transmission power level for the normalized SAR distribution for the i-th active frequency band.

[0070] To evaluate RF exposure from transmissions using a second technology (e.g., 5G, IEEE 802.11ad, etc.), the wireless device 100 can include a plurality of PD distributions for the second technology stored in the memory 115. Each of the PD distributions can correspond to a respective one of a plurality of transmission scenarios supported by the wireless device 100 for the second technology. As discussed further below, the transmission scenarios can correspond to various combinations of the antennas 132-1 through 132-M, frequency bands, channels, and / or body positions.

[0071] The PD distribution (also referred to as a PD map) for each transmission scenario can be generated based on measurements (e.g., electric field measurements) performed in a test laboratory using a human body model. After the PD distributions are generated, the PD distributions are stored in the memory 115 to enable the processor 110 to evaluate (e.g., in real-time) RF exposure, as discussed further below. Each PD distribution includes a set of PD values, where each PD value can correspond to a different position (e.g., on a model of a human body).

[0072] The PD values in each PD distribution correspond to a particular transmission power level (e.g., the transmission power level at which the PD values were measured in the test laboratory). Since the PD is scaled with the transmission power level, the processor 110 can scale the PD distribution for any transmission power level by multiplying each PD value in the PD distribution by the following transmission power scaling factor:

[0073]

[0074] where Txc is a current transmission power level for the respective transmission scenario, and Tx PD is a transmission power level corresponding to a PD value in the PD distribution (e.g., a transmission power level at which the PD value was measured in a test lab).

[0075] As described above, the wireless device 100 can support multiple transmission scenarios for the second technology. In certain aspects, a transmission scenario can be specified by a set of parameters. The set of parameters can include one or more of an antenna parameter indicating one or more antennas (i.e., active antennas) used for transmission, a frequency band parameter indicating one or more frequency bands (i.e., active frequency bands) used for transmission, a channel parameter indicating one or more channels (i.e., active channels) used for transmission, a body position parameter indicating a position of the wireless device 100 relative to a user body position (head, torso, away from body, etc.), and / or other parameters. In cases where the wireless device 100 supports a large number of transmission scenarios, it can be very time consuming and expensive to perform measurements in a test setting (e.g., a test lab) for each transmission scenario. To reduce test time, measurements can be performed for a subset of the transmission scenarios to generate PD distributions for the subset of transmission scenarios. As discussed further below, in this example, a PD distribution for each of the remaining transmission scenarios can be generated by combining two or more PD distributions in the subset of PD distributions.

[0076] For example, PD measurements can be performed for each of the antennas 132-1 through 132-M to generate a PD distribution for each of the antennas 132-1 through 132-M. In this example, a PD distribution for a transmission scenario in which two or more of the antennas 132-1 through 132-M are active can be generated by combining PD distributions for the two or more active antennas.

[0077] In another example, PD measurements can be performed for each of a plurality of frequency bands to generate a PD distribution for each of the plurality of frequency bands. In this example, a PD distribution for a transmission scenario in which two or more of the frequency bands are active can be generated by combining PD distributions for the two or more active frequency bands.

[0078] In certain aspects, the PD distributions can be normalized with respect to the PD limit by dividing each PD value in the PD distribution by the PD limit. In this case, when a normalized PD value is greater than 1, the normalized PD value exceeds the PD limit, and when a normalized PD value is less than 1, the normalized PD value is below the PD limit. In some examples, each of the PD distributions stored in the memory 115 can be normalized with respect to the PD limit.

[0079] In certain aspects, the normalized PD profile of a transmission scenario can be generated by combining two or more normalized PD profiles. For example, the normalized PD profile of a transmission scenario in which two or more antennas are active can be generated by combining the normalized PD profiles of the two or more active antennas. For cases in which different transmission power levels are used for active antennas, the normalized PD profile of each active antenna can be scaled by the respective transmission power level before combining the normalized PD profiles of the active antennas. The normalized PD profile of simultaneous transmissions from multiple active antennas can be given by:

[0080]

[0081] where PD lim is the PD limit, PD norm_combined is the combined normalized PD profile of simultaneous transmissions from active antennas, i is an index of an active antenna, PD i is the PD profile of the i-th active antenna, Tx i is the transmission power level of the i-th active antenna, Tx PDi is the transmission power level of the PD profile of the i-th active antenna, and L is the number of active antennas. Equation (5) can be rewritten as follows:

[0082]

[0083] where PD norm_i is the normalized PD profile of the i-th active antenna. In cases in which multiple active antennas at the same transmission frequency are simultaneously transmitting (e.g., MIMO), the combined normalized PD profile is obtained by summing the square roots of the individual normalized PD profiles and computing the square of the sum, as follows:

[0084]

[0085] In another example, the normalized PD profiles of different frequency bands can be stored in the memory 115. In this example, the normalized PD profile of a transmission scenario in which two or more frequency bands are active can be generated by combining the normalized PD profiles of the two or more active frequency bands. For cases in which the transmission power levels differ for active frequency bands, the normalized PD profile of each active frequency band can be scaled by the respective transmission power level before combining the normalized PD profiles of the active frequency bands. In this example, the combined PD profile can also be computed using equation (6a), where i is an index of an active frequency band, PD norm_i is the normalized PD profile of the i-th active frequency band, Tx i is the transmission power level of the i-th active frequency band, and Tx PDiis a normalized PD profile of the ith active band.

[0086] As described above, the wireless device 100 can simultaneously transmit signals using a first technology (e.g., 3G, 4G, IEEE 802.11ac, etc.) and a second technology (e.g., 5G, IEEE 802.11ad, etc.), where different metrics are used to measure RF exposure for the first and second technologies (e.g., SAR is used for the first technology, and PD is used for the second technology). In this case, the processor 110 can determine a first maximum allowed power level for the first technology and a second maximum allowed power level for the second technology for transmissions in future time slots that comply with the RF exposure limit. During the future time slots, the transmission power levels of the first and second technologies are constrained (i.e., bounded) by the determined first and second maximum allowed power levels, respectively, to ensure compliance with the RF exposure limit, as described below. In this disclosure, the term “maximum allowed power level” refers to the “maximum allowed power level” imposed by the RF exposure limit, unless otherwise specified. It should be understood that the “maximum allowed power level” does not necessarily equal the absolute maximum power level that complies with the RF exposure limit, and can be less than the absolute maximum power level that complies with the RF exposure limit (e.g., to provide a safety margin). The “maximum allowed power level” can be used to set a power level limit for transmissions at a transmitter, such that transmission power levels that exceed the “maximum allowed power level” are not allowed, to ensure RF exposure compliance.

[0087] The processor 110 can determine the first and second maximum allowed power levels as follows. The processor can determine a normalized SAR profile of the first technology at the first transmission power level, determine a normalized PD profile of the second technology at the second transmission power level, and combine the normalized SAR profile and the normalized PD profile to generate a combined normalized RF exposure profile (hereinafter referred to simply as a combined normalized profile). The value at each location in the combined normalized profile can be determined by combining the normalized SAR value at that location with the normalized PD value at that location, or by another technique.

[0088] The processor 110 can then determine whether the first and second transmission power levels comply with the RF exposure limits by comparing the peak in the combined normalized distribution to 1. If the peak is equal to or less than 1 (i.e., the condition ≤ 1 is satisfied), the processor 110 can determine that the first and second transmission power levels comply with the RF exposure limits (e.g., the SAR limit and the PD limit) and use the first and second transmission power levels as the first and second maximum allowed power levels, respectively, during future time slots. If the peak is greater than 1, the processor 110 can determine that the first and second transmission power levels do not comply with the RF exposure limits. To avoid non-compliance during future time slots, the processor 110 can reduce one or more of the first and second transmission power levels such that the peak in the combined normalized distribution is equal to or less than 1. In this case, the processor 110 can use the first and second transmission power levels that comply with the RF exposure limits as the first and second maximum allowed power levels, respectively, during future time slots. The condition for RF exposure compliance for simultaneous transmissions using the first and second techniques can be given by:

[0089] SAR norm + PD norm ≤ 1 (7).

[0090] During future time slots, the processor 110 limits (constrains) the transmission power level of the first transmitter 120 with the first maximum allowed power level. For example, if a power control loop is used for the first technique, the power control loop is allowed to set the transmission power level of the first transmitter 120 to a power level that is equal to or lower than the first maximum allowed power level, but not to a power level that exceeds the first maximum allowed power level. During future time slots, the processor 110 also limits (constrains) the transmission power level of the second transmitter 130 with the second maximum allowed power level. For example, if a power control loop is used for the second technique, the power control loop is allowed to set the transmission power level of the second transmitter 130 to a power level that is equal to or lower than the second maximum allowed power level, but not to a power level that exceeds the second maximum allowed power level.

[0091] Figure 2 A visual representation of the normalized SAR distribution 210 and the normalized PD distribution 220 is shown, where the normalized SAR distribution 210 and the normalized PD distribution 220 are combined to generate a combined normalized distribution 230. Figure 2 The condition that the peak in the combined normalized distribution 230 is equal to or less than 1 for RF exposure compliance is also shown. Although each of the distributions 210, 220, and 230 is shown as a Gaussian distribution, the distributions 210, 220, and 230 can be any distribution that represents the SAR and PD values for the first and second techniques, respectively. Figure 2The distribution is depicted as a two-dimensional distribution, but it should be understood that this disclosure is not limited to this example.

[0092] The normalized SAR distribution in Equation (7) can be generated by combining two or more normalized SAR distributions as described above (e.g., for transmission scenarios using multiple active antennas). Similarly, the normalized PD distribution in Equation (7) can be generated by combining two or more normalized PD distributions as described above (e.g., for transmission scenarios using multiple active antennas). In this case, the RF exposure compliance condition in Equation (7) can be rewritten using Equations (3a) and (6a) as follows:

[0093]

[0094] For the MIMO case, equations (3b) and (6b) can be combined alternatively. As shown in equation (8), the combined normalized distribution can be a function of the transmission power levels of the first and second technologies. All points in the combined normalized distribution should satisfy the normalization limit of one of equations (8). Furthermore, when combining SAR and PD distributions, the SAR and PD distributions should be spatially aligned or aligned with their peak locations such that the combined distribution given by equation (8) represents the combined RF exposure of a given location of the human body.

[0095] When wireless device 100 transmits signals simultaneously using both the first and second technologies, processor 110 can determine one or more maximum allowable power levels for the first technology and one or more maximum allowable power levels for the second technology for transmission in future time slots as follows: Based on the transmission scenario of the first technology in future time slots, processor 110 retrieves one or more normalized SAR distributions of the first technology from memory 115, and based on the transmission scenario of the second technology in future time slots, retrieves one or more normalized PD distributions of the second technology from memory 115. For example, if the transmission scenario of the first technology uses multiple active antennas, processor 110 can retrieve the normalized SAR distribution for each active antenna. Similarly, if the transmission scenario of the second technology uses multiple active antennas, processor 110 can retrieve the normalized PD distribution for each active antenna.

[0096] Processor 110 can then execute Figure 3 The exemplary method 300 shown determines the maximum permissible power levels of a first and a second technology that meet RF exposure limits (e.g., SAR limits and PD limits).

[0097] At block 310, the processor 110 initializes the transmission power levels for the first technology and the second technology based on the transmission scenarios for the first technology and the second technology in the future time slot. If the transmission scenario for the first technology uses multiple active antennas, the transmission power levels can include a transmission power level for each active antenna of the first technology. Similarly, if the transmission scenario for the second technology uses multiple active antennas, the transmission power levels can include a transmission power level for each active antenna of the second technology.

[0098] The transmission power levels for the first technology and the second technology can be initialized based on one or more power control loops, one or more desired data rates, one or more desired beam directions or sectors, etc. In one example, the transmission power levels can be initialized to a set of default transmission power levels.

[0099] At block 320, the processor 110 determines a combined normalized distribution based on the transmission power levels in block 310, the retrieved normalized SAR distribution, and the retrieved normalized PD distribution (e.g., according to equation (8) discussed above).

[0100] At block 330, the processor 110 compares a peak value in the combined normalized distribution to 1. If the peak value in the combined normalized distribution is equal to or less than 1 (i.e., satisfies the condition ≤ 1), the processor 110 determines that the transmission power levels comply with the RF exposure limit. In this case, the method 300 ends at block 350, and the processor 110 uses the transmission power levels as the maximum allowed power levels for the future time slot.

[0101] If the peak value in the combined normalized distribution is greater than 1, the processor 110 adjusts the transmission power levels at block 340. For example, the processor 110 can adjust the transmission power levels by reducing one or more of the transmission power levels.

[0102] The processor 110 then repeats blocks 320 and 330 using the adjusted transmission power level (i.e., determines the combined normalized distribution in block 320 using the adjusted transmission power level). The processor 110 can repeat blocks 340, 320, and 330 until the peak in the combined normalized distribution is equal to or less than 1, at which point the transmission power level complies with the RF exposure limit. The transmission power level that complies with the RF exposure limit is then used as the maximum allowed power level for future time slots. The maximum allowed power level includes one or more maximum allowed power levels for the first technology and one or more maximum allowed power levels for the second technology. For examples in which multiple active antennas are used for the first technology (e.g., two or more of the antennas 122-1 through 122-N), the maximum allowed power level includes a maximum allowed power level for each active antenna. For examples in which multiple active antennas are used for the second technology (e.g., two or more of the antennas 132-1 through 132-M), the maximum allowed power level includes a maximum allowed power level for each active antenna.

[0103] After the processor 110 determines the maximum allowed power level, the processor 110 constrains the transmission power of the first transmitter 120 during future time slots by the one or more maximum allowed power levels determined for the first technology. For examples in which the first transmitter 120 transmits signals during future time slots using multiple antennas (e.g., two or more of the antennas 122-1 through 122-N), the maximum allowed power level includes a maximum allowed power level for each active antenna. In this example, the processor 110 constrains the transmission power level of each active antenna by the respective maximum allowed power level. The processor 110 also constrains the transmission power of the second transmitter 130 during future time slots by the one or more maximum allowed power levels determined for the second technology. For examples in which the second transmitter 130 transmits signals during future time slots using multiple antennas (e.g., two or more of the antennas 132-1 through 132-M), the maximum allowed power level includes a maximum allowed power level for each active antenna. In this example, the processor 110 constrains the transmission power level of each active antenna by the respective maximum allowed power level.

[0104] It should be appreciated that the present disclosure is not limited to Figure 3 The exemplary method 300 shown, and other methods can be employed to determine maximum allowed power levels for the first technology and the second technology that comply with the RF exposure limit. For example, the processor 110 can determine a maximum allowed power level that causes the peak in the combined normalized distribution to be equal to or less than a value less than 1 for a conservative approximation analysis to determine the maximum allowed power level with fewer calculations. Thus, the value less than 1 can be used as a condition for evaluating RF exposure compliance.

[0105] In some cases, the wireless device 100 can transmit signals using the second technology (e.g., 5G, IEEE 802.11ad, etc.) when the first technology is inactive. In these cases, RF exposure compliance can be evaluated without considering RF exposure of the first technology.

[0106] In these cases, the processor 110 can determine a maximum allowed power level for the second technology that complies with the PD limit in the future time slot, as shown below. First, the processor 110 can retrieve a normalized PD distribution for the second technology from the memory 115 based on a transmission scenario for the second technology in the future time slot. For example, if the transmission scenario for the second technology in the future time slot uses multiple active antennas, the processor 110 can retrieve a normalized PD distribution for each active antenna. In this example, the active antennas can be selected, for example, based on an expected beam direction or sector for transmissions by the wireless device 100 in the future time slot.

[0107] Then, the processor 110 can determine the maximum allowed power level for the second technology that complies with the PD limit by performing the example method shown below. Figure 4

[0108] At block 410, the processor 110 initializes transmission power levels for the second technology according to a transmission scenario for the second technology. If the transmission scenario for the second technology uses multiple active antennas, the transmission power levels can include a transmission power level for each active antenna. The transmission power levels can be initialized according to a power control loop, an expected data rate, an expected beam direction or sector, etc. In one example, the transmission power levels can be initialized to a set of default transmission power levels.

[0109] At block 420, the processor 110 determines a combined normalized PD distribution based on the transmission power levels in block 410 and the retrieved normalized PD distribution (e.g., according to equation (6a) or (6b) discussed above).

[0110] At block 430, the processor 110 compares a peak in the combined normalized PD distribution to 1. If the peak in the combined normalized PD distribution is equal to or less than 1 (i.e., satisfies the condition ≤ 1), the processor 110 determines that the transmission power levels comply with the PD limit. In this case, the method 400 ends at block 450, and the processor 110 uses the transmission power levels as the maximum allowed power levels for the second transmitter 130.

[0111] If the peak in the combined normalized PD distribution is greater than 1, the processor 110 adjusts the transmission power levels at block 440. For example, the processor 110 can adjust the transmission power levels by reducing one or more of the transmission power levels initialized in block 410.

[0112] ​Then, the processor 110 repeats blocks 420 and 430 using the adjusted transmission power level (i.e., determines the combined normalized PD distribution in block 420 using the adjusted transmission power level). The processor 110 can repeat blocks 440, 420, and 430 until the peak in the combined normalized PD distribution is equal to or less than 1, at which point the transmission power level complies with the PD limit. Then, the processor 110 uses the transmission power level that complies with the PD limit as the maximum allowed power level for the second transmitter 130. After the processor 110 determines the maximum allowed power level that complies with the PD limit, the processor 110 constrains the transmission power of the second transmitter 130 during future time slots according to the determined maximum allowed power level. For examples in which the second transmitter 130 transmits signals during future time slots using multiple active antennas (e.g., two or more of the antennas 132-1 through 132-M), the maximum allowed power level of the second technique includes a maximum allowed power level for each active antenna. In this example, the processor 110 constrains the transmission power level of each active antenna by the respective maximum allowed power level.

[0113] It should be appreciated that the present disclosure is not limited to Figure 4 The exemplary method 400 shown, and other methods can be employed to determine the maximum allowed power level that complies with the PD limit. For example, the processor 110 can determine the maximum allowed power level that causes the peak to be equal to or less than a value less than 1 to perform a conservative approximation analysis to determine the maximum allowed power level with fewer calculations.

[0114] In some cases, RF exposure regulations require that the time-averaged RF exposure over a time window not exceed an RF exposure limit. This allows a wireless device 100 to briefly exceed the RF exposure limit as long as the time-averaged RF exposure does not exceed the limit.

[0115] In this regard, the processor 110 can determine RF exposure compliance in the case where the first technique is active and the second technique is not active as follows. The processor 110 can compute a time-averaged normalized SAR distribution over a first time window (e.g., 6 minutes) and compare the peak in the time-averaged normalized SAR distribution to 1 to evaluate RF exposure compliance. If the peak is equal to or less than 1 (i.e., satisfies the condition ≤ 1), the processor 110 can determine that the RF exposure is compliant.

[0116] In this regard, Figure 5 An example is shown in which the processor 110 computes a time-averaged normalized SAR distribution over a first time window 505 (e.g., 6 minutes). In this example, the first time window 505 is divided into multiple time slots (i.e., time intervals). For example, a 6-minute time window can be divided into 5-second time slots. In this example, the processor 110 computes the normalized SAR distribution for each time slot and then computes the time-averaged normalized SAR distribution by averaging the normalized SAR distributions for the time slots in the first time window 505. Figure 5In the illustrated example, there are p time slots 515(1)-515(p) and p normalized SAR distributions 510(1)-510(p). Although each of the distributions 510(1)-510(p) is depicted as a two-dimensional distribution in Figure 5 the example, it should be understood that the present disclosure is not limited to this example.

[0117] The processor 110 can determine a normalized SAR distribution for each time slot (e.g., according to equation (3a) or (3b)). The normalized SAR distribution for a time slot can be generated by combining two or more SAR distributions. For example, if two or more antennas are active during a time slot, the processor 110 can combine the normalized SAR distributions for the two or more active antennas to generate the normalized SAR distribution for the time slot. For cases in which different transmission power levels are used for active antennas, the processor 110 can scale the normalized SAR distribution for each active antenna by the transmission power level for the antenna.

[0118] In certain aspects, the transmission scenario and / or the transmission power level of the first technique can vary within the first time window 505. In these aspects, the transmission scenario can be approximately constant within a time slot, but can vary from time slot to time slot within the first time window 505. The processor 110 can determine a normalized SAR distribution for each time slot based on the transmission scenario for the time slot and the time-averaged transmission power level (e.g., according to equation (3a) or 3(b)).

[0119] The processor 110 can average the normalized SAR distributions 510(1)-510(p) over the first time window 505 to generate a time-averaged normalized SAR distribution 520. For example, the processor 110 can compute the time-averaged normalized SAR distribution 520 by combining the normalized SAR distributions 510(1)-510(p) for the time slots 515(1)-515(p) and dividing the resulting combined normalized SAR distribution by the number of time slots, as follows:

[0120]

[0121] where SAR norm_j jthtime slot 515(j). As described above, the normalized SAR distribution for a time slot can be a combination of multiple SAR distributions for the time slot (e.g., for cases of multiple active antennas). The processor 110 can then compare the peak value in the time-averaged normalized SAR distribution 520 to 1 to evaluate RF exposure compliance. If the peak value is equal to or less than 1 (i.e., satisfies the condition ≤ 1), the processor 110 can determine that the RF exposure is compliant.

[0122] In certain aspects, the processor 110 can determine a maximum allowed power level for a future time slot to ensure time-averaged RF exposure compliance. In this regard, Figure 5 The time slots 515(1)-515(p-1) in the vector can correspond to previous transmissions by the wireless device 100, and the time slot 515(p) can correspond to a future time slot. In this regard, the time slot 515(p) is referred to hereinafter as the future time slot. Equation (9a) can be written as follows:

[0123]

[0124] where SAR norm_p is the SAR profile for the future time slot 515(p).

[0125] In this example, it is assumed that the transmission power levels for the normalized SAR profiles 510(1)-510(p-1) are known to the processor 110 because they correspond to previous transmissions by the wireless device 100. For example, the processor 110 can record in the memory 115 the transmission power levels and transmission scenarios for each of the time slots 515(1)-515(p-1), and use the recorded transmission power levels and transmission scenarios for the time slots 515(1)-515(p-1) to determine the normalized SAR profiles 510(1)-510(p-1) for these time slots. For the time slots 515(1)-515(p-1), the normalized SAR profile for the jth time slot 515(j) can be determined using equation (3a) or (3b) for all transmission scenarios and power levels that are active during the jth time slot 515(j).

[0126] In this example, the transmission power level of the normalized SAR profile 510(p) corresponding to the future time slot 515(p) is the variable to be solved by the processor 110. To determine the maximum allowed power level of the future time slot 515(p), the processor 110 can calculate a time-averaged normalized SAR profile 520, where the transmission power level of the future time slot 515(p) is a variable in the time-averaged normalized SAR profile (i.e., the time-averaged normalized SAR profile is a function of the transmission power level of the future time slot 515(p)). The processor 110 can then determine the transmission power level of the future time slot 515(p) such that the peak in the time-averaged normalized SAR profile is equal to or less than 1 (i.e., satisfies the condition ≤ 1 in equation (9b)). The processor 110 uses the transmission power level that satisfies the RF exposure compliance condition as the maximum allowed power level of the future time slot 515(p) and sets the transmission power limit of the future time slot 515(p) according to the determined maximum allowed power level. The processor 110 can determine the maximum allowed power level of the future time slot 515(p) during the time slot 515(p-1) such that the maximum allowed power level of the future time slot 515(p) is ready at the beginning of the future time slot 515(p) for the processor 110 to implement the maximum allowed power level.

[0127] According to Figure 6 According to the example method 600 shown, the processor 110 can determine the maximum allowed power level of the future time slot 515(p). At block 610, the processor 110 initializes the transmission power level of the future time slot 515(p) according to the transmission scenario of the future time slot 515(p). The transmission power level can be initialized according to a power control loop, a desired data rate, a desired beam direction or sector, etc. In one example, the transmission power level can be initialized to a set of default transmission power levels.

[0128] At block 620, the processor 110 determines a time-averaged normalized SAR profile for the future time slot 515(p) based on the transmission scenario and the transmission power level at block 610. Note that the transmission power levels of the previous time slots 515(1)-515(p-1) are known, as described above.

[0129] At block 630, the processor 110 compares the peak in the time-averaged normalized SAR profile to 1 to evaluate RF exposure compliance. If the peak is equal to or less than 1, the method 600 ends at block 650. In this case, the processor 110 uses the transmission power level initialized at block 610 as the maximum allowed power level of the future time slot 515(p).

[0130] If the peak is greater than 1, at block 640, the processor 110 adjusts the transmission power levels of the future time slots. The processor 110 can adjust the transmission power levels of the future time slots by reducing one or more of the transmission power levels of the future time slots. The processor 110 then repeats blocks 620 and 630 using the adjusted transmission power levels. The processor 110 can repeat blocks 640, 620, and 630 until the peak in the time-averaged normalized SAR profile is equal to or less than 1, at which point the transmission power levels comply with the SAR limit and the processor 110 uses the transmission power levels that comply with the SAR limit as the maximum allowed power levels for the future time slots 515(p).

[0131] For examples in which the first transmitter 120 transmits a signal using multiple active antennas (e.g., two or more of the antennas 122-1 through 122-N) during the future time slots 515(p), the maximum allowed power levels can include a maximum allowed power level for each active antenna. In this example, the processor 110 limits (constrains) the transmission power level of each active antenna by the respective maximum allowed power level.

[0132] It should be appreciated that the present disclosure is not limited to Figure 6 The exemplary method 600 shown, and other methods can be employed to determine the transmission power levels for the future time slots 515(p) such that the time-averaged normalized SAR profile complies with the SAR limit. For example, the processor 110 can determine the maximum allowed power levels that cause the peak of the time-averaged normalized SAR profile to be equal to or less than a value less than 1 to perform a conservative approximation analysis to determine the maximum allowed power levels with fewer calculations.

[0133] In some cases, the adjuster can require that the time-averaged PD profile for the second technology not exceed the PD limit for the second technology. This allows the wireless device 100 to briefly exceed the PD limit as long as the time-averaged PD profile does not exceed the PD limit.

[0134] In this regard, the processor 110 can determine RF exposure compliance in cases in which the second technology is active and the first technology is not active as follows. The processor 110 can calculate a time-averaged normalized PD profile over a second time window (e.g., 2 minutes) and compare a peak in the time-averaged normalized PD profile to 1 to evaluate RF exposure compliance. If the peak is equal to or less than 1 (i.e., satisfies the condition ≤ 1), the processor 110 can determine RF exposure compliance.

[0135] In this regard, Figure 7An example is shown in which the processor 110 computes a time-averaged normalized PD distribution over a second time window 705 (e.g., 2 minutes). In this example, the second time window 705 is divided into a plurality of time slots (i.e., time intervals). For example, a 2-minute time window can be divided into 5-second time slots. In this example, the time-averaged normalized PD distribution is computed over the second time window 705. Figure 7 In the example shown, there are q time slots 715(1)-715(q) and q normalized PD distributions 710(1)-710(q). Although each of the distributions 710(1)-710(q) is depicted as a two-dimensional distribution in Figure 7 It is understood that the present disclosure is not limited to this example.

[0136] The processor 110 can determine the normalized PD distribution for each time slot (e.g., according to equation (6a) or (6b)). The normalized PD distribution for a time slot can be generated by combining two or more PD distributions. For example, if two or more antennas are active during a time slot, the processor 110 can combine the normalized PD distributions for the two or more active antennas to generate the normalized PD distribution for the time slot. For cases in which different transmission power levels are used for active antennas, the processor 110 can scale the normalized PD distribution for each active antenna by the respective transmission power level.

[0137] In certain aspects, the transmission scenario and / or the transmission power level of the second technique can vary over the second time window 705. In these aspects, the transmission scenario can be approximately constant over one time slot, but can vary from time slot to time slot over the second time window 705. The processor 110 can determine the normalized PD distribution for each time slot based on the transmission scenario and the time-averaged transmission power level during the time slot (e.g., according to equation (6a) or (6b)).

[0138] The processor 110 can average the normalized PD distributions 710(1)-710(q) over the second time window 705 to generate a time-averaged normalized PD distribution 720. For example, the processor 110 can compute the time-averaged normalized PD distribution 720 by combining the normalized PD distributions 710(1)-710(q) for the time slots 715(1)-715(q) and dividing the resulting combined normalized PD distribution by the number of time slots, as follows:

[0139]

[0140] where PD norm_jrepresents the normalized PD profile of the jth time slot 715(j). As described above, the normalized PD profile of a time slot can be a combination of multiple normalized PD profiles of the time slot (e.g., for the case of multiple active antennas). The processor 110 can then compare the peak value in the time-averaged normalized PD profile 720 to 1 to evaluate the RF exposure compliance. If the peak value is equal to or less than 1 (i.e., the condition ≤ 1 is satisfied), the processor 110 can determine that the RF exposure compliance.

[0141] In certain aspects, the processor 110 can determine the maximum allowed power level for a future time slot to ensure time-averaged RF exposure compliance. In this regard, Figure 7 The time slots 715(1)-715(q-1) in (10a) can correspond to previous transmissions of the wireless device 100, and the time slot 715(q) can correspond to a future transmission. In this regard, the time slot 715(q) is referred to hereinafter as a future time slot. Equation (10a) can be rewritten as follows:

[0142]

[0143] where PD norm_q is the normalized PD profile of the future time slot 715(q).

[0144] In this example, it is assumed that the transmission power levels of the normalized PD profiles 710(1)-710(q-1) are known to the processor 110 because they correspond to previous transmissions of the wireless device 100. For example, the processor 110 can record the transmission power levels and transmission scenarios for each of the time slots 715(1)-715(q-1) in the memory 115, and use the recorded transmission power levels and transmission scenarios of the time slots 715(1)-715(q-1) to determine the normalized PD profiles 710(1)-710(q-1) of these time slots. For the time slots 715(1)-715(q-1), the normalized PD profile of the jth time slot 715(j) can be determined using equation (6a) or (6b) for all transmission scenarios and power levels that are active during the jth time slot 715(j).

[0145] In this example, the transmission power level of the normalized PD profile 710(q) corresponding to future time slot 715(q) is a variable to be solved by the processor 110. To determine the maximum allowed power level for future time slot 715(q), the processor 110 can calculate a time-averaged normalized PD profile 720, where the transmission power level of future time slot 715(q) is a variable in the time-averaged normalized PD profile 720 (i.e., the time-averaged normalized PD profile 720 is a function of the transmission power level of future time slot 715(q)). The processor 110 can then determine the transmission power level of future time slot 715(q) such that the peak in the time-averaged normalized PD profile is equal to or less than 1 (i.e., satisfies the condition ≤ 1 in equation (10b)). The determined transmission power level that complies with the RF exposure level is used as the maximum allowed power level for future time slot 715(q). In this regard, the processor 110 sets the transmission power limit for future time slot 715(q) according to the determined maximum allowed power level. The processor 110 can determine the maximum allowed power level for future time slot 715(q) during time slot 715(q-1) such that the maximum allowed power level for future time slot 715(q) is ready at the beginning of future time slot 715(q) for the processor 110 to implement the maximum allowed power level.

[0146] The processor 110 can determine the maximum allowed power level for future time slot 715(q) according to the exemplary method 800 shown. At block 810, the processor 110 initializes a transmission power level for future time slot 715(q) according to a transmission scenario for future time slot 715(q). For example, the transmission power level can be initialized according to a power control loop, a desired data rate, a desired beam direction or sector, etc. In one example, the transmission power level can be initialized to a set of default transmission power levels. Figure 8 The processor 110 can determine the maximum allowed power level for future time slot 715(q) according to the exemplary method 800 shown. At block 810, the processor 110 initializes a transmission power level for future time slot 715(q) according to a transmission scenario for future time slot 715(q). For example, the transmission power level can be initialized according to a power control loop, a desired data rate, a desired beam direction or sector, etc. In one example, the transmission power level can be initialized to a set of default transmission power levels.

[0147] At block 820, the processor 110 determines a time-averaged normalized PD profile for future time slot 715(q) based on the transmission scenario and the transmission power level at block 810. Note that the transmission power levels of the previous time slots 715(1)-715(q-1) are known, as described above.

[0148] At block 830, the processor 110 compares the peak in the time-averaged normalized PD profile to 1 to evaluate RF exposure compliance. If the peak is equal to or less than 1, the method 800 ends at block 850. In this case, the processor 110 uses the transmission power level initialized at block 810 as the maximum allowed power level for future time slot 715(q).

[0149] If the peak is greater than 1, at block 840, the processor 110 adjusts the transmission power levels 810 of the future time slots. The processor 110 can adjust the transmission power levels of the future time slots 715(q) by reducing one or more of the transmission power levels of the future time slots 715(q). The processor 110 then repeats blocks 820 and 830 using the adjusted transmission power levels. The processor 110 can repeat blocks 840, 820, and 830 until the peak in the time-averaged PD profile is equal to or less than 1, at which point the transmission power levels comply with the PD limit and the processor 110 uses the transmission power levels as the maximum allowed power levels for the future time slots 715(q).

[0150] For examples in which the second transmitter 130 transmits a signal during the future time slots 715(q) using multiple active antennas (e.g., two or more of the antennas 132-1 through 132-M), the maximum allowed power levels can include a maximum allowed power level for each active antenna. In this example, the processor 110 limits (constrains) the transmission power level of each active antenna by the respective maximum allowed power level.

[0151] It should be appreciated that the present disclosure is not limited to Figure 8 The exemplary method 800 shown, and other methods can be employed to determine the transmission power levels for the future time slots 715(q) such that the time-averaged normalized PD profile complies with the PD limit. For example, the processor 110 can determine a maximum allowed power level for the future time slots 715(q) that causes the peak in the time-averaged normalized PD profile to be approximately equal to or less than a value less than 1.

[0152] The processor 110 can also determine the time-averaged RF exposure compliance in the case where both the first technology and the second technology are active (i.e., the wireless device is simultaneously transmitting signals using the first technology and the second technology). To do so, as Figure 9 shown, the processor 110 can combine the time-averaged normalized SAR profile 520 and the time-averaged normalized PD profile 720 to generate a combined time-averaged normalized profile 920. The processor 110 can then compare the peak in the combined time-averaged normalized profile 920 to 1 to evaluate the time-averaged RF exposure compliance. If the peak is equal to or less than 1 (i.e., satisfies the condition ≤ 1), the processor 110 can determine that the wireless device 100 is compliant. The compliance condition can be given by the following combined equations (9b) and (10b):

[0153]

[0154] The length of the first time window 505 of the time-averaged normalized SAR distribution and the second time window 705 of the time-averaged normalized PD distribution can be different. In this regard, Figure 9 An example is shown in which the first time window 505 is longer than the second time window 705. For example, the length of the first time window 505 can be about 6 minutes and the length of the second time window 705 can be about 2 minutes. The length of the first and second time windows can be dictated by the respective RF exposure regulations (e.g., established by the FCC or other regulatory body). Note that the length of the time windows 505 and 705 are not drawn to scale in Figure 9

[0155] In certain aspects, the processor 110 can determine the maximum allowed power levels for future time slots 515(p) and 715(q) of the first and second technologies to ensure time-averaged RF exposure compliance. In these aspects, the future time slots 515(p) and 715(q) can be approximately aligned in time, as shown in the example in Figure 9 To determine the maximum allowed power levels for the future time slots 515(p) and 715(q), the processor 110 can calculate a combined time-averaged normalized distribution 920 in which the transmission power levels of the future time slots 515(p) and 715(q) are variables in the combined time-averaged normalized distribution 920 (i.e., the combined time-averaged normalized distribution 920 is a function of the transmission power levels of the future time slots 515(p) and 715(q)). The processor 110 can then determine the maximum allowed power levels for the future time slots 515(p) and 715(q) such that the peak in the combined time-averaged normalized distribution 920 is equal to or less than 1 (i.e., satisfies the condition ≤ 1 in equation (11)). The processor 110 can then set the transmission power limits for the future time slots 515(p) and 715(q) according to the determined maximum allowed power levels.

[0156] According to the example method 1000 shown in Figure 10

[0157] ​​At block 1010, the processor 110 initializes transmission power levels for the future time slots 515(p) and 715(q) based on transmission scenarios for the future time slots 515(p) and 715(q). If the transmission scenario for the future time slots 515(p) of the first technology uses multiple active antennas, the transmission power levels can include a transmission power level for each active antenna. Similarly, if the transmission scenario for the future time slots 715(q) of the second technology uses multiple active antennas, the transmission power levels can include a transmission power level for each active antenna.

[0158] The transmission power levels can be initialized based on one or more power control loops, one or more desired data rates, one or more desired beam directions or sectors, etc. In one example, the transmission power levels can be initialized to a set of default transmission power levels.

[0159] At block 1020, the processor 110 determines a combined time-averaged normalized profile 920 based on the transmission power levels for the future time slots 515(p) and 715(q). Note that, as described above, the transmission power levels in the previous time slots 515(1)-515(p-1) of the first technology and the transmission power levels in the previous time slots 715(1)-715(q-1) of the second technology are known.

[0160] At block 1030, the processor 110 compares a peak value in the combined time-averaged normalized profile to 1 to evaluate RF exposure compliance. If the peak value is equal to or less than 1, the method 1000 ends at block 1050. In this case, the processor 110 uses the transmission power levels initialized at block 1010 as the maximum allowed power levels for the future time slots 515(p) and 715(q).

[0161] If the peak value is greater than 1, at block 1040, the processor 110 adjusts the transmission power levels for the future time slots. The processor 110 can adjust the transmission power levels for the future time slots by reducing one or more of the transmission power levels. The processor 110 then repeats blocks 1020 and 1030 using the adjusted transmission power levels. The processor 110 can repeat blocks 1040, 1020, and 1030 until the peak value in the combined time-averaged normalized profile is equal to or less than 1, at which point the transmission power levels for the future time slots are compliant, and the processor 110 uses the transmission power levels as the maximum allowed power levels. The determined maximum allowed power levels include a first maximum allowed power level for the first technology and a second maximum allowed power level for the second technology. In this regard, the processor 110 sets a transmission power limit for the first transmitter 120 according to the first maximum allowed power level and sets a transmission power limit for the second transmitter 130 according to the second maximum allowed power level.

[0162] It should be understood that this disclosure is not limited to Figure 10 The exemplary method 1000 shown can be used, and other methods can be employed to determine the maximum permissible power levels for future time slots 515(p) and 715(q) such that the combined time-averaged normalized distribution 920 conforms to the RF exposure limit.

[0163] In some respects, the time-averaged PD window depends on the transmission frequency (e.g., approximately 2 minutes in the 28 GHz band and approximately 1 minute in the 60 GHz band). In these respects, when the second transmitter 130 transmits signals across multiple frequency bands, the time-averaged PD distribution can be calculated using different time windows for each band. For example, if the second transmitter 130 transmits signals in a first frequency band (e.g., 28 GHz) and a second frequency band (e.g., 60 GHz), the time-averaged PD distribution can be given by:

[0164]

[0165] Where q is the number of time slots in the first frequency band (e.g., the 28 GHz band), and r is the number of time slots in the second frequency band (e.g., the 60 GHz band). Because different time windows are used for the first and second frequency bands, the number of time slots in the first frequency band is different from the number of time slots in the second frequency band (i.e., q and r are different).

[0166] Figure 11 An example of two time-averaging windows used for the PD is shown. In this example, the second time window 705 discussed above is used for the first frequency band (e.g., the 28 GHz band), and the third time window 1105 is used for the second frequency band (e.g., the 60 GHz band). The third time window 1105 is shorter than the second time window 705. For example, the second time window 705 may be approximately two minutes long, while the third time window 1105 may be approximately one minute long.

[0167] like Figure 11 As shown, the third time window 1105 is divided into r time slots 1115(1) to 1115(r). For the second frequency band, there are r normalized PD distributions 1110(1) to 1110(r), where each normalized PD distribution corresponds to a corresponding time slot in time slots 1115(1) to 1115(r). In this example, time slots 1115(1) to 1115(r-1) correspond to previous time slots, and time slot 1115(r) corresponds to a future time slot that is approximately aligned with future time slots 515(p) and 715(q).

[0168] In this example, the normalized PD profile for each of the previous time slots 715(1) through 715(q-1) in the second time window 705 can be determined based on the transmission scenario and transmission power level of the first frequency band during the time slots. The normalized PD profile for the future time slot 715(q) is a function of the transmission power level of the first frequency band in the future time slot 715(q). Similarly, the normalized PD profile for each of the previous time slots 1115(1) through 1115(r-1) in the third time window 1105 can be determined based on the transmission scenario and transmission power level of the second frequency band during the time slots. The normalized PD profile for the future time slot 1115(r) is a function of the transmission power level of the second frequency band in the future time slot 1115(r).

[0169] The time-averaged normalized PD profile 720 can be computed according to equation (12) above, where the time-averaged normalized PD profile is a function of the transmission power level of the first frequency band in the future time slot 715(q) and the transmission power level of the second frequency band in the future time slot 1115(r).

[0170] In this example, the time-averaged normalized PD profile 720 is a combination of the time-averaged normalized PD profile for the first frequency band corresponding to the second time window 705 and the time-averaged normalized PD profile for the second frequency band corresponding to the third time window 1105. In this regard, the time-averaged PD profile 720 can be considered a combined time-averaged PD profile.

[0171] For examples in which the wireless device 100 also transmits signals using the first technology, the time-averaged normalized PD profile can be combined with the time-averaged normalized SAR profile to obtain the combined time-averaged normalized profile described above. In this example, the combined time-averaged normalized profile is a function of the transmission scenario and transmission power level of the first technology in the future time slot 515(p), the transmission scenario and transmission power level of the first frequency band in the future time slot 715(q), and the transmission scenario and transmission power level of the second frequency band in the future time slot 1115(r). The maximum allowed power level can be determined by determining a transmission power level that causes the peak of the combined time-averaged normalized profile to be equal to or less than 1 (e.g., according to the method 1000 shown). In this example, the maximum allowed power level includes a maximum allowed power level for the first technology, a maximum allowed power level for the first frequency band, and a maximum allowed power level for the second frequency band. During the future time slots 515(p), 715(q), and 1115(r), the processor 110 sets a transmission power limit for the first technology according to the maximum allowed power level for the first technology, sets a transmission power limit for the first frequency band according to the maximum allowed power level for the first frequency band, and sets a transmission power limit for the second frequency band according to the maximum allowed power level for the second frequency band. Figure 10 In this example, the time-averaged normalized PD profile 720 is a combination of the time-averaged normalized PD profile for the first frequency band corresponding to the second time window 705 and the time-averaged normalized PD profile for the second frequency band corresponding to the third time window 1105. In this regard, the time-averaged PD profile 720 can be considered a combined time-averaged PD profile.

[0171] For examples in which the wireless device 100 also transmits signals using the first technology, the time-averaged normalized PD profile can be combined with the time-averaged normalized SAR profile to obtain the combined time-averaged normalized profile described above. In this example, the combined time-averaged normalized profile is a function of the transmission scenario and transmission power level of the first technology in the future time slot 515(p), the transmission scenario and transmission power level of the first frequency band in the future time slot 715(q), and the transmission scenario and transmission power level of the second frequency band in the future time slot 1115(r). The maximum allowed power level can be determined by determining a transmission power level that causes the peak of the combined time-averaged normalized profile to be equal to or less than 1 (e.g., according to the method 1000 shown). In this example, the maximum allowed power level includes a maximum allowed power level for the first technology, a maximum allowed power level for the first frequency band, and a maximum allowed power level for the second frequency band. During the future time slots 515(p), 715(q), and 1115(r), the processor 110 sets a transmission power limit for the first technology according to the maximum allowed power level for the first technology, sets a transmission power limit for the first frequency band according to the maximum allowed power level for the first frequency band, and sets a transmission power limit for the second frequency band according to the maximum allowed power level for the second frequency band.

[0172] While in the above example, two time average windows 705 and 1105 are used for PD, it should be appreciated that more than two time average windows can be used depending on the number of active frequency bands above 10 GHz. In general, the number of time average windows used for PD can be equal to the number of active frequency bands above 10 GHz, where each time average window corresponds to a respective one of the active frequency bands.

[0173] In certain aspects, the wireless device 110 can simultaneously transmit signals in the first frequency band and the second frequency band (e.g., 28 GHz and 60 GHz) when the first technology is inactive. In this case, the processor 110 can determine the maximum allowed power level for the first frequency band and the second frequency band as follows. The processor can determine a time-averaged normalized PD profile in accordance with equation (12), where the time-averaged normalized PD profile is a function of the transmission power level in the first frequency band in the future time slot 715(q) and the transmission power level in the second frequency band in the future time slot 1115(r). Figure 12 This example is illustrated in FIG. 20, where the condition for RF exposure compliance is that the time-averaged normalized PD profile 720 is equal to or less than 1. Note that in this case, the time-averaged normalized PD profile is not combined with the time-averaged normalized SAR profile 520 because in this case, the first technology is inactive.

[0174] The processor 110 can then determine the transmission power levels for the first frequency band and the second frequency band that cause the peak in the time-averaged normalized PD profile to be equal to or less than 1, and use the determined transmission power levels as the maximum allowed power levels. In this example, the maximum allowed power levels include a maximum allowed power level for the first frequency band and a maximum allowed power level for the second frequency band. During the future time slots 715(q) and 1115(r), the processor 110 sets the transmission power limit for the first frequency band in accordance with the maximum allowed power level for the first frequency band, and sets the transmission power limit for the second frequency band in accordance with the maximum allowed power level for the second frequency band. It should be appreciated that the above techniques can be extended to three or more frequency bands to determine the maximum allowed power levels for the three or more frequency bands.

[0175] Certain RF exposure regulations can not require the time-averaged value of PD, or the time-averaging of PD can not be currently specified (this can change). In these cases, the time-averaged SAR profile can be combined with the normalized PD profile to evaluate RF exposure compliance. Figure 13 This example is illustrated in FIG. 20, where the time-averaged normalized SAR profile 520 is combined with the normalized PD profile for the future time slot 715(q) to obtain a combined normalized profile 920.

[0176] In this example, the processor 110 can determine the maximum allowed power levels for the first and second technologies as follows. The processor 110 combines the time-averaged normalized SAR distribution 520 with the normalized PD distribution 710 for the future time slot 715(q) to obtain a combined normalized distribution 920, where the combined normalized distribution 920 is a function of the transmission power level of the first technology in the future time slot 515(p) and the transmission power level of the second technology in the future time slot 715(q).

[0177] The processor 110 can then determine the transmission power levels for the first and second technologies that cause the peak in the normalized distribution 920 to be equal to or less than 1, and use the determined transmission power levels as the maximum allowed power levels. In this example, the maximum allowed power levels include a maximum allowed power level for the first technology and a maximum allowed power level for the second technology. During the future time slots 515(p) and 715(a), the processor 110 sets the transmission power limit for the first transmitter 120 according to the maximum allowed power level for the first technology, and sets the transmission power limit for the second transmitter 130 band according to the maximum allowed power level for the second technology.

[0178] It should be appreciated that the lengths of the above-mentioned time slots 515(1)-515(p) can be equal, or two or more of the time slots 515(1)-515(p) can have different lengths. The future time slot 515(p) can also be referred to as a time interval, and can have a length equal to or less than one-tenth of the length of the first time window 505. In one example, the future time slot 515(p) has a length of about 5 seconds, and the first time window 505 has a length of about 6 minutes.

[0179] It should be appreciated that the lengths of the above-mentioned time slots 515(1)-515(p) can be equal, or two or more of the time slots 515(1)-515(p) can have different lengths. The future time slot 515(p) can also be referred to as a time interval, and can have a length equal to or less than one-tenth of the length of the first time window 505. In one example, the future time slot 515(p) has a length of about 5 seconds, and the first time window 505 has a length of about 6 minutes.

[0180] It should be appreciated that the lengths of the above-mentioned time slots 515(1)-515(p) can be equal, or two or more of the time slots 515(1)-515(p) can have different lengths. The future time slot 515(p) can also be referred to as a time interval, and can have a length equal to or less than one-tenth of the length of the first time window 505. In one example, the future time slot 515(p) has a length of about 5 seconds, and the first time window 505 has a length of about 6 minutes.

[0181] The length of the first time window 505 can be at least 50% longer than the length of the second time window 705. In one example, the first time window 505 has a length of about 6 minutes and the second time window 705 has a length of about 2 minutes, where the lengths of the first and second time windows can be set by a regulation body. It should be appreciated that the lengths of the first time window 505 and the second time window 705 set by a regulation body can vary over time and can vary between different regulation bodies. As mentioned above, a regulation body can define time windows that depend on the transmission frequency, e.g., a time window length of 2 minutes for the 28 GHz band and a time window length of 1 minute for the 60 GHz band. In this case, it should also be appreciated that there can be one time window for SAR and two or more time windows for PD, each time window for PD corresponding to a given transmission band.

[0182] As used herein, the term “prior time slot” refers to a time slot that precedes a corresponding future time slot. For example, Figure 5 The time slots 515(1)-515(p-1) in the first time window 505 are prior time slots that precede the future time slot 515(p).

[0183] As used herein, the term “future time slot” refers to a time slot (i.e., a time interval or duration) that is future relative to the time at which the corresponding maximum allowed power level is determined. Determining the maximum allowed power level for a future time slot in advance of the future time slot helps to ensure RF exposure compliance during the future time slot. Since the future time slots 515(p), 715(q), and 1115(r) discussed above are approximately aligned in time, they can be collectively considered as one future time slot.

[0184] It should be appreciated that the above-described time windows (e.g., the time windows 505, 705, and 1105) can be moving time average windows. In this case, each time window is shifted by one time slot each time a new maximum allowed power level for a future time slot is determined. For example, in the above discussion of the time window 505, the time slot 515(p) is given as the future time slot. To determine the maximum allowed power level for the next future time slot 515(p+1), the processor 110 shifts the time window 505 by one time slot to cover the time slots 515(2) through 515(p+1). Note that the first time slot 515(1) in the previous determination of the maximum allowed power level is dropped from the time window 505 and the future time slot 515(p) in the previous determination of the maximum allowed power level becomes the last of the prior time slots in the time window 505.

[0185] It should be appreciated that the first communication technology discussed above can include multiple communication technologies for which SAR is used to assess RF exposure compliance. For example, the first technology can include WWAN, WLAN, Bluetooth, etc. In this regard, it should be appreciated that the first transmitter 120 can include multiple transmitters. Further, it should be appreciated that the SAR can have contributions from multiple sub-6 GHz communication technologies (e.g., simultaneous transmission of WWAN, WLAN, and Bluetooth).

[0186] It should be appreciated that the second communication technology discussed above can include multiple communication technologies for which PD is used to assess RF exposure compliance. For example, the second technology can include mmWave / 5G and mmWave / 802.11ad. In this regard, it should be appreciated that the second transmitter 130 can include multiple transmitters. Further, it should be appreciated that the PD can have contributions from multiple communication technologies (e.g., simultaneous transmission of mmWave / 5G and mmWave / 802.11ad).

[0187] In some examples given above, the normalized distribution is compared to 1 to assess RF exposure compliance. However, it should be appreciated that the present disclosure is not limited to these examples. For example, a distribution (e.g., a SAR distribution, a PD distribution, a combined RF exposure distribution, etc.) can be normalized with respect to any value, such that other limit values other than 1 can be used to define the condition of RF exposure compliance. In this example, the condition of RF compliance is that the normalized distribution is equal to or less than the limit value. Further, as described above, the limit value can be set to a value less than 1.

[0188] As described above, the processor 110 can determine a maximum allowed power level for a transmitter (e.g., the first transmitter 120 or the second transmitter 130) for a future time slot (e.g., according to any of the methods described herein) and set a transmission power limit for the transmitter based on the determined maximum allowed power level. In certain aspects, setting the transmission power limit based on the determined maximum allowed power level can prevent the power level of the transmitter from exceeding the maximum allowed power level at any time during the future time slot. In certain aspects, setting the transmission power limit based on the determined maximum allowed power level can prevent the time average of the power level of the transmitter from exceeding the maximum allowed power level over the future time slot. This allows the power level to temporarily exceed the maximum allowed power level over the future time slot, so long as the time average of the power level over the future time slot does not exceed the maximum allowed power level. In these aspects, the power level can exceed the maximum allowed power level over a time interval shorter than the future time slot. In these aspects, the maximum allowed power level is a maximum allowed time average power level over the future time slot.

[0189] It should be appreciated that the transmitting device need not compute the combined and / or normalized profile in all examples (e.g., as described in Figure 3 , Figure 4 , Figure 6 , Figure 8 and Figure 10 described above and with respect to other figures). In some aspects, the combined and / or normalized profile can be computed a priori in a laboratory or otherwise, and the transmitting device (e.g., device 100 or a device executing one or more of blocks 340, 440, 640, 840, 1040, etc.) can determine the power for transmission based thereon. In some aspects, one or more combined and / or normalized profiles can be stored in or otherwise represented in memory (e.g., memory 115). In some aspects, the transmitting device (or processor of such a device) can be allocated or determine an amount of power that will comply with any limits required to meet the combined and / or normalized profile as described above. However, in some examples, the device or processor itself can not compute the combined profile, but can use the amount of power to compute or determine the maximum allowed (time-averaged) power level for a future time slot. The device or processor can regulate its own transmission with respect to the particular amount of power. In some examples, the device or processor assumes that any other transmitters are simultaneously transmitting at full power. Thus, the time-averaging can be performed (e.g., by one or more processors associated with the transmitters) with respect to the particular amount of power, independent of and without knowledge of the actions of other transmitters and / or processors, in a manner that complies with all exposure requirements. It should be appreciated that the operations described in this paragraph can be used in all of the examples discussed above and throughout this document with respect to determining combined and / or normalized exposure.

[0190] As described above, the transmission power level can be reduced to meet RF exposure compliance for a future time slot. In this regard, according to certain aspects of the disclosure, exemplary methods for reducing the transmission power level to meet RF exposure compliance for a future time slot are discussed below. The exemplary methods can apply in situations where SAR exposure is evaluated, in situations where PD exposure is evaluated, and in situations where combined SAR and PD exposure is evaluated, as discussed further below.

[0191] In the following discussion, it is assumed that wireless device 100 is transmitting signals simultaneously using multiple transmitters, where each transmitter transmits at a respective transmission power level. In this regard, Figure 14An example is shown in which the first transmitter 120 for the first wireless technology (e.g., LTE) includes multiple transmitters 1410-1 through 1410-N. In this example, each of the transmitters 1410-1 through 1410-N is coupled to a respective one of the antennas 122-1 through 122-N (persistently or selectively / temporarily) and is configured to transmit a respective signal 1415-1 through 1415-N at a respective transmit power level. The signals 1415-1 through 1415-N can be generated by the processor(s) 110 (shown) and input to the transmitters 1410-1 through 1410-N via a first bus 140 (shown). The processing performed by each of the transmitters 1410-1 through 1410-N can include upconversion, power amplification, etc. The processor(s) 110 can individually set the transmit power levels of the transmitters 1410-1 through 1410-N. For example, each of the transmitters 1410-1 through 1410-N can include a respective power amplifier (PA), and the processor(s) 110 can set the transmit power level of each of the transmitters 1410-2 through 1410-N by respectively setting the gain of the respective PA. Figure 1 Figure 1

[0192] Figure 14 An example is also shown in which the second transmitter 130 for the second wireless technology (e.g., 5G) includes multiple transmitters 1420-1 through 1420-M. In this example, each of the transmitters 1420-1 through 1420-M is coupled to a respective one of the antennas 132-1 through 132-M (persistently or selectively / temporarily) and is configured to transmit a respective signal 1425-1 through 1425-M at a respective transmit power level. The signals 1425-1 through 1425-M can be generated by the processor(s) 110 (shown) and input to the transmitters 1420-1 through 1420-M via a second bus 150 (shown). The processing performed by each of the transmitters 1420-1 through 1420-M can include upconversion, power amplification, etc. The processor(s) 110 can individually set the transmit power levels of the transmitters 1420-1 through 1420-M. For example, each of the transmitters 1420-1 through 1420-M can include a respective power amplifier (PA), and the processor(s) 110 can set the transmit power level of each of the transmitters 1420-2 through 1420-M by respectively setting the gain of the respective PA. Figure 1 Figure 1

[0193] It should be understood that the present disclosure is not limited to Figure 14 ​​​​the example shown. For example, two transmitters can be coupled to the same antenna, with the two transmitters configured to transmit in different frequency bands. As another example, although the transmitters 120, 130 are configured for a first wireless technology and a second wireless technology as described above, the transmitters 120, 130 can be configured for the same wireless technology. Thus, it should be understood that the example methods discussed below are not limited to the example shown. Figure 14

[0194] At a given time, all of the transmitters 1410-1 to 1410-N and 1420-1 to 1420-M, or a subset of the transmitters 1410-1 to 1410-N and 1420-1 to 1420-M, can be active (e.g., depending on the transmission scenario). For the case where a subset of the transmitters 1410-1 to 1410-N and 1420-1 to 1420-M are active, other transmitters of the transmitters 1410-1 to 1410-N and 1420-1 to 1420-M are inactive (i.e., not transmitting). In the discussion below, RF exposure compliance for a future time slot is evaluated based on the active transmitters. As described above, in some cases, one or all other transmitters can be assumed to be active and transmit at full power when determining how to operate one or more particular transmitters.

[0195] To evaluate RF exposure compliance for a future time slot using multiple active transmitters transmitting simultaneously, the processor 110 can determine a combined RF exposure profile for the future time slot. The processor 110 can determine the combined RF exposure profile for the future time slot by scaling the RF exposure profile of each active transmitter based on the respective transmission power level, and combining the scaled RF exposure profiles of the active transmitters to obtain the combined RF exposure profile. For the case where SAR exposure is evaluated, the combined RF exposure profile is a combined SAR profile (e.g., determined based on equation (2), equation (3a), or equation (3b)). For the case where PD exposure is evaluated, the combined RF exposure profile is a combined PD profile (e.g., determined based on equation (5), equation (6a), or equation (6b)). For the case where combined SAR and PD exposure is evaluated, the combined RF exposure profile is a combined SAR and PD profile (e.g., determined based on equation (8)). As described above, SAR exposure can be evaluated when the first transmitter 120 is active and the second transmitter 130 is not active, PD exposure can be evaluated when the second transmitter 130 is active and the first transmitter 120 is not active, and combined SAR and PD exposure can be evaluated when both the first transmitter 120 and the second transmitter 130 are active. In the discussion below, the RF exposure value can be a SAR value, a PD value, or a combined SAR and PD value.

[0196] ​After determining the combined RF exposure profile for the future time slot, the processor 110 can determine whether the transmission power levels of the active transmitters satisfy RF exposure compliance. In one example, the processor 110 can determine whether compliance is satisfied by comparing the RF exposure value at the peak location in the combined RF exposure profile to the RF exposure limit. If the RF exposure value at the peak location is equal to or below the RF exposure limit, the processor 110 can determine RF exposure compliance for the future time slot. If the RF exposure value at the peak location exceeds the RF exposure limit, the processor 110 can determine non-compliance for the future time slot.

[0197] To evaluate time-averaged RF exposure compliance for the future time slot, the processor 110 can average the combined RF exposure profile discussed above with the combined RF exposure profile of the previous time slot to obtain a time-averaged combined RF exposure profile (e.g., based on equation (9a), equation (9b), equation (10a), equation (10b), or equation (11)). The processor 110 then compares the RF exposure value at the peak location in the time-averaged combined RF exposure profile to the RF exposure limit to evaluate time-averaged RF exposure compliance for the future time slot. If the RF exposure value at the peak location is equal to or below the RF exposure limit, the processor 110 can determine time-averaged RF exposure compliance for the future time slot. If the RF exposure value at the peak location exceeds the RF exposure limit, the processor 110 can determine non-compliance for the future time slot.

[0198] For examples in which RF exposure compliance is evaluated only within the future time slot, the peak location discussed above can simply correspond to the location of the peak RF exposure value in the combined RF exposure profile. For examples in which time-averaged RF exposure compliance is evaluated, the peak location discussed above can correspond to the location of the peak RF exposure value in the time-averaged combined RF exposure profile. Note that the location of the peak RF exposure value in the time-averaged combined RF exposure profile is not necessarily the same as the location of the peak RF exposure value in the combined RF exposure profile for the future time slot, as the time-averaged combined RF exposure profile is an average of the future time slot and the previous time slot, as discussed above. As further discussed above, a device and / or processor can not explicitly compute the combined and / or normalized profiles. In some such examples, determinations regarding future time slot or time-averaged RF exposure compliance can be made based on a combined and / or normalized profile computed by another device or processor or according to requirements needed from the combined and / or normalized profile. In some aspects, the peak location is not explicitly computed. In some such examples, it can be assumed that there is complete overlap between transmitters and / or that all locations can correspond to the peak.

[0199] In the following discussion, RF exposure compliance can refer to RF exposure compliance over only future time slots or time-averaged RF exposure compliance.

[0200] When the transmission power levels for future time slots do not satisfy RF exposure compliance, the processor 110 can reduce the transmission power levels to satisfy RF exposure compliance. In one approach, the processor 110 can incrementally reduce the transmission power levels for each active transmitter by a fixed step size (e.g., 0.5 dB) until RF exposure compliance is satisfied. However, in some cases, one of the active transmitters can contribute much more to the RF exposure value at the peak location than the other active transmitters. In these cases, reducing the transmission power levels for the active transmitters by the same amount will penalize the active transmitter that can contribute very little to the RF exposure value at the peak location.

[0201] To address this issue, various aspects of the present disclosure determine the contribution of each active transmitter to the RF exposure value at the peak location or another selected location, and reduce the transmission power levels for the active transmitters based on their contribution to the RF exposure value at that location to satisfy RF exposure compliance. In certain aspects, the transmission power levels for each active transmitter are reduced in proportion to their contribution to the RF exposure value at that location.

[0202] Figure 15 A method 1500 for reducing transmission power levels to satisfy RF exposure compliance in accordance with certain aspects of the present disclosure is shown. The method 1500 can be performed by the processor(s) 110. As described above, the initial transmission power levels for the active transmitters (i.e., the transmission power levels for the active transmitters at the start of the method 1500) can be determined based on one or more power control loops, one or more desired data rates, one or more desired beam directions or sectors, etc.

[0203] At block 1510, the processor(s) 110 determine a contribution of each active transmitter to the RF exposure value at a first peak location in the combined RF exposure distribution for the future time slots. The first location can be the peak location or other location. For example, the other location can be the location closest to the user. Compliance is ensured at the peak location, but the contribution at other locations can be used to determine a reduction amount as described below. In the following description, the peak location will be described for ease of description, but it should be understood that one or more other locations can be used. In one example, the processor 110 determines the contribution of each active transmitter based on the RF exposure value at the peak location in the scaled RF exposure distribution for the active transmitter and the RF exposure value at the peak location in the combined RF exposure distribution. As described above, the RF exposure distribution for each active transmitter is scaled based on the transmission power level of the active transmitter. The contribution of each active transmitter can be expressed as a ratio or percentage of the contribution of the transmitter to the RF exposure value at the peak location in the combined RF exposure distribution. For examples in which the contribution of each active transmitter is expressed as a ratio, the sum of the contributions of all active transmitters equals 1. For examples in which the contribution of each active transmitter is expressed as a percentage, the sum of the contributions of all active transmitters equals 100%. For examples in which the combined SAR and PD exposure is evaluated, the RF exposure distributions for the active transmitters can be normalized prior to combination as described above.

[0204] At block 1520, the processor(s) 110 reduce the transmission power level of each of one or more of the active transmitters based on the contribution of the active transmitters to the RF exposure value at the peak location in the combined RF exposure distribution such that RF exposure compliance is satisfied. For examples in which RF exposure compliance is evaluated only for the future time slots, RF exposure compliance can be satisfied when the RF exposure value at the peak location in the combined RF exposure distribution is equal to or below the RF exposure limit. For examples in which time-averaged RF exposure compliance is evaluated, RF exposure compliance can be satisfied when the RF exposure value at the peak location in the time-averaged combined RF exposure distribution is equal to or below the RF exposure limit. As described above, the RF exposure value at the peak location in the time-averaged combined RF exposure distribution is a function of the transmission power levels in the future time slots because the average includes the future time slots.

[0205] In certain aspects, the processor(s) 110 can reduce the transmission power level of each active transmitter according to its contribution to the RF exposure value at the peak location in the combined RF exposure distribution. Thus, in these aspects, the transmission power level of the active transmitter that contributes the most to the RF exposure value at the peak location is reduced the most, the transmission power level of the active transmitter that contributes the second most to the RF exposure value at the peak location is reduced the second most, and so on.

[0206] In certain aspects, the amount of reduction in the transmission power level of one or more transmitters can be determined by the processor(s) 110 using one or more other factors in addition to or in lieu of the contributions. For example, as described in further detail below, a priority of the transmitters can be used. In some aspects, it can be assumed that certain transmitters transmit at full power (or at another power determined) when determining how to reduce the power of one or more other transmitters. In such examples, the transmission power of certain transmitters (associated with the assumed transmission power) can not be adjusted, but the transmission power of one or more other transmitters can be adjusted according to the operations described below. In some such examples, the processor(s) 110 can consider that there is a complete overlap between the transmission area of certain transmitters and the transmission area of all of the one or more transmitters, such that the peak location (or selected location) can be determined with reference to the one or more other transmitters (e.g., independent of the certain transmitters).

[0207] Figure 16 An example method 1600 for reducing a transmission power level in block 1520 is shown in accordance with certain aspects of the present disclosure. For ease of discussion, the example method 1600 is discussed below using an example of three active transmitters labeled a, b, and c, where transmitter a contributes the most to the RF exposure value at the peak location, transmitter b contributes the second most to the RF exposure value at the peak location, and transmitter c contributes the least to the RF exposure value at the peak location. However, it should be understood that the method 1600 is not limited to this example.

[0208] At block 1610, the processor 110 determines an amount of reduction in the RF exposure value at the peak location in the combined RF exposure profile of the future time slots that satisfies the RF exposure compliance. The amount of reduction can be expressed as a percentage reduction. For example, an amount of reduction of 50% indicates that a 50% reduction in the RF exposure value at the peak location complies with the RF exposure compliance. For examples in which time-averaged RF exposure compliance is evaluated, the RF exposure compliance can be satisfied when the amount of reduction in the RF exposure value at the peak location in the combined RF exposure profile causes the RF exposure value at the peak location in the time-averaged combined RF exposure profile to be equal to or below the RF exposure limit. For examples in which RF exposure compliance is evaluated only within the future time slots, the RF exposure compliance can be satisfied when the RF exposure value at the peak location in the combined SAR profile is equal to or below the RF exposure limit.

[0209] At block 1620, the processor 110 determines a difference between a contribution of an active transmitter (e.g., transmitter a) that contributes most to the RF exposure value at the peak location and a contribution of an active transmitter (e.g., transmitter b) that contributes second most to the RF exposure value at the peak location. For example, if the contribution percentages of the transmitters a, b, and c are 60:25: 15, respectively, the difference between the contribution of the active transmitter (e.g., transmitter a) that contributes most to the RF exposure value at the peak location and the contribution of the active transmitter (e.g., transmitter b) that contributes second most to the RF exposure value at the peak location is 35% (i.e., 60% - 25%).

[0210] At block 1630, the processor 110 determines whether the difference in block 1620 is greater than or equal to the determined reduction (i.e., determined in block 1610) of the RF exposure value at the peak location. If the difference is greater than or equal to the determined reduction, the processor 110 proceeds to block 1640. If the difference is less than the determined reduction, the processor 110 proceeds to block 1650.

[0211] At block 1640, the processor 110 reduces the transmission power level of the active transmitter (e.g., transmitter a) that contributes most to the RF exposure value at the peak location to achieve the determined reduction of the RF exposure value at the peak location to satisfy the RF exposure compliance. In this case, the processor 110 keeps the transmission power levels of the other active transmitters (e.g., transmitters b and c) alone. For example, if the contribution percentages of the transmitters a, b, and c are 60:25: 15, respectively, and the determined reduction is 25%, the difference in block 1620 is 35% (i.e., 60% - 25%), which is greater than the determined reduction 25%. In this case, the processor 110 reduces the transmission power level of transmitter a to achieve the determined reduction of the RF exposure value at the peak location.

[0212] At block 1650, the processor 110 determines a sum of a first difference and a second difference, where the first difference is a difference between a contribution of the active transmitter (i.e., transmitter a) that contributes most to the RF exposure value at the peak location and a contribution of the active transmitter (e.g., transmitter c) that contributes third most to the RF exposure value at the peak location, and the second difference is a difference between a contribution of the active transmitter (e.g., transmitter b) that contributes second most to the RF exposure value at the peak location and a contribution of the active transmitter (e.g., transmitter c) that contributes third most to the RF exposure value at the peak location. For example, if the contribution percentages of the transmitters a, b, and c are 60:25: 15, respectively, the sum of the first difference and the second difference is 55% (i.e., (60% - 15%) + (25% - 15%)).

[0213] At block 1660, the processor 110 determines whether the sum of the first difference and the second difference in block 1650 is greater than or equal to the determined reduction in the RF exposure value at the peak location (i.e., the reduction determined in block 1610). If the sum of the first difference and the second difference is greater than or equal to the determined reduction, the processor 110 proceeds to block 1670. If the sum of the first difference and the second difference is less than the determined reduction, the processor 110 proceeds to block 1680.

[0214] At block 1670, the processor 110 reduces the transmission power levels of the two most and second most active transmitters (e.g., transmitters a and b) that contribute most to the RF exposure value at the peak location to achieve the determined reduction in the RF exposure value at the peak location. In this case, the processor 110 leaves only the transmission power level of the third most active transmitter (e.g., transmitter c) that contributes to the RF exposure value at the peak location. For example, the processor 110 can reduce the transmission power levels of transmitters a and b such that the contributions of transmitters a and b to the RF exposure value at the peak location are approximately equal after the reduction. In this example, the transmission power level of transmitter a is reduced by a greater amount than the transmission power level of transmitter b. This is because transmitter a contributed more than transmitter b before the reduction, and transmitters a and b contribute equally after the reduction. Thus, in this example, the transmission power levels of transmitters a and b are reduced based on their contributions to the RF exposure value at the peak location.

[0215] Block 1670 can be illustrated by the following example. If the contribution percentages of transmitters a, b, and c are 60:25: 15, respectively, and the determined reduction is 45%, the sum of the first difference and the second difference is 55% (i.e., (60% - 15%) + (25% - 15%)), which is greater than the determined reduction of 45%. In this case, the processor 110 reduces the transmission power levels of transmitters a and b to achieve the determined reduction in the RF exposure value at the peak location.

[0216] At block 1680, the processor 110 reduces the transmission power levels of the top three active transmitters (e.g., transmitters a, b, and c) that contribute the most, the second most, and the third most to the RF exposure value at the peak location to achieve the determined amount of reduction in the RF exposure value at the peak location. For example, the processor 110 can reduce the transmission power levels of transmitters a, b, and c such that the contributions of transmitters a, b, and c to the RF exposure value at the peak location are approximately equal after the reduction. In this case, the transmission power level of transmitter a is reduced the most and the transmission power level of transmitter c is reduced the least. This is because transmitter a contributed the most and transmitter c contributed the least before the reduction, and transmitters a, b, and c contribute equally after the reduction. Thus, in this example, the transmission power levels of transmitters a, b, and c are reduced based on their contributions to the RF exposure value at the peak location.

[0217] Block 1680 can be illustrated by the following example. If the contribution percentages of transmitters a, b, and c are 60:25: 15, respectively, and the determined amount of reduction is 70%, the sum of the first and second differences is 55% (i.e., (60% - 15%) + (25% - 15%)), which is less than the determined amount of reduction 70%. In this case, the processor 110 reduces the transmission power levels of transmitters a, b, and c to achieve the determined amount of reduction in the RF exposure value at the peak location. The processor 110 can reduce the transmission power levels of transmitters a, b, and c such that the contributions of transmitters a, c, and c to the RF exposure value at the peak location are approximately equal after the reduction.

[0218] If there are more than three transmitters, a block similar to block 1650 can be included between block 1660 and block 1680. In this case, the new block can involve three different differences (between the contributions of: the top active transmitter and the fourth top active transmitter that contribute to the RF exposure value at the peak location, the second top active transmitter and the fourth top active transmitter that contribute to the RF exposure value at the peak location, and the third top active transmitter and the fourth top active transmitter that contribute to the RF exposure value at the peak location). It can be determined (at another new block) whether the sum of the three differences is greater than or equal to the determined amount of reduction. If so, the transmission power of the top, second, third, and fourth active transmitters can be reduced. Further, block 1680 can be adjusted to refer to the top, second, third, and fourth active transmitters. If there are more than four additional transmitters, similar adjustments can be made to the method 1600.

[0219] Figure 16Method 1600 illustrates certain calculations and sequences that can be used to implement a reduction in transmission power level. It is contemplated that for the example used in relation to method 1600, various techniques for calculating and reducing transmission power levels can be used to achieve the desired or intended results. In some examples, a processor 110 in a system can determine the relative RF exposure contribution of a transmitter, where the relative contribution can be expressed as a percentage of the combined RF exposure.

[0220] In a first example, a solution is sought to obtain a reduction in the total RF exposure value at the peak location from the combined RF exposure of three transmitters (Tx1, Tx2, Tx3), where the contributions of the three transmitters at the peak location can be expressed as {a = 102, b = 42.5, c = 25.5} respectively. The contributions of the three transmitters can contribute to a combined RF exposure of 170 at the peak location. When the compliance limit is 100, a SAR reduction value of 70 is needed to meet the RF exposure limit.

[0221] A system configured in accordance with certain aspects of the present disclosure can calculate a set of transmission power level reductions that provide an RF exposure profile that meets the compliance limit. In a first example, the relative contributions of three transmitters to RF exposure can be expressed as {60%, 25%, 15%}. A proportional reduction in transmission power applied to each transmitter can be calculated based on the relative contributions of the transmitters to RF exposure. In the first example, the power reductions can be calculated to meet a reduction_needed of 70. Thus, in the first example, the reduction for each transmitter is: 0.6 x 70 = 42, 0.25 x 70 = 17.5, 0.15 x 70 = 10.5.

[0222] This mode of calculation can be referred to as equal priority reduction. For the example of {a = 102, b = 42.5, c = 25.5}, the reductions are as follows.

[0223] Reduction for Tx1 = 70 * 60% = 42.

[0224] Reduction for Tx1 in dB = 10*log 10 ((102 - 42) / 102) = -2.3 dB.

[0225] Reduction for Tx2 = 70 * 25% = 17.5.

[0226] Reduction for Tx2 in dB = 10*log 10 ((42.5 - 17.5) / 42.5) = -2.3 dB.

[0227] The reduction amount for Tx3 = 70 * 15% = 10.5.

[0228] The reduction amount for Tx3 in dB = 10*log 10 ((25.5-10.5) / 25.5) = -2.3 dB. However, as described above and further below, when determining the back-off, the priorities of the different transmitters and / or their reductions can be taken into account.

[0229] As described above, these reductions can be described as back-off values, and can be calculated in proportion to the respective contributions of the transmitters to the RF exposure at the peak position. As shown in this example, the percentage of Tx contribution at the peak position (TxN contrib ) is 60%:25%:15%. In some cases, the total back-off can be achieved by the cumulative back-off of each transmitter and / or past behavior (TxN backoff ). One such example of this approach can be represented as:

[0230] WHILE max(Total_exposure) > 100%

[0231] TxN backoff = TxN backoff - {reduction_needed} * TxN contrib

[0232] Total_exposure = past average exposure + Tx1 backoff + Tx2 backoff + Tx3 backoff

[0233] Recalculate max(Total_exposure), peak position, and all TxN contrib

[0234] END WHILE.

[0235] In the second example, which also includes the three transmitters and contributions of the first example, the processor 110 in the system can determine that the combined RF exposure contribution of the two secondary transmitters (Tx2 and Tx3) reaches a value of 68 (i.e., 42.5 + 25.5), indicating that the desired RF exposure compliance level cannot be achieved simply by reducing the transmission power levels of the secondary transmitters (Tx2 and Tx3). The processor 110 can be configured to reduce the transmission power of the highest contributing transmitter until it reaches the contribution level of the next highest contributing transmitter. The transmission power levels of these transmitters can be reduced until the contribution level of the next highest contributing transmitter is reached. These reductions continue for the potential increase group of transmitters with the largest contributions before a solution is achieved. This method of reducing transmission power levels can be expressed as:

[0236] IF(ab)>reduction_needed

[0237] Then only reduce the power of Tx1.

[0238] The reduction amount of the Tx1 transmitter = reduction_needed

[0239] Otherwise, if (ac) + (bc) > reduction_needed

[0240] Then only the power of Tx1 and Tx2 is reduced.

[0241] The reduction ratio is = (ab) + y:y

[0242] (ab)+2y=reduction_needed

[0243] Otherwise, if (a+b+c) > reduction_needed

[0244] This reduces the power of Tx1, Tx2, and Tx3.

[0245] The reduction ratio is = (ac) + x : (bc) + x : x

[0246] (ab)+(bc)*2+3x=reduction_needed

[0247] [If there are more than three transmitters, additional steps can be performed.]

[0248] END.

[0249] For the example {a = 102, b = 42.5, c = 25.5}, ​​the reduction ratio of the two largest contributing transmitters (Tx1, Tx2) is = (102 - 42.5) + y:y, where y = 5.25.

[0250] Reduction in Tx1 = (a - b) + y = 59.5 + 5.25 = 64.75.

[0251] Reduction in Tx1 (in dB) = 10*log 10 ((102 - 64.75) / 102) = -4.4 dB.

[0252] Reduction in Tx2 = y = 5.25.

[0253] Reduction in Tx1 (in dB) = 10*log 10 ((42.5 - 5.25) / 42.5) = -0.6 dB.

[0254] This operation can be an example of the method 1600 described above.

[0255] In a third example, a solution is sought to obtain a reduction in the total RF exposure value at the peak location from a combined RF exposure of three transmitters (Tx1, Tx2, Tx3), where the contributions of the three transmitters at the peak location can be represented as {a = 103.23, b = 4.44, c = 3.33} respectively. The contributions of the three transmitters can result in a combined RF exposure of 111 at the peak location. When the compliance limit is 100, a SAR reduction value of 11 is needed to meet the RF exposure limit. Here, the relative contributions of the three transmitters to the RF exposure can be represented as {93%, 4%, 3%}. In this example, Tx1 is the first priority contributor and Tx2 and Tx3 are both second priority contributors. In the second example, eliminating the second priority contributions is not enough to meet the desired SAR reduction. If the second priority contributions were already sufficient, the processor(s) 110 can determine to reduce the transmission power / contribution of only Tx2 and Tx3, or to reduce the transmission power / contribution of Tx2, or to reduce the transmission power / contribution of Tx2 in addition to Tx1 if a greater reduction is needed. But here, the reduction in RF exposure can be achieved by reducing the transmission power of Tx1 alone. In this example, there is no reduction in the transmission power of Tx2 and Tx3, but there can be a reduction in the transmission power of Tx1 to obtain a reduction of >= 11 in the contribution to the RF exposure. For example, a reduction of 0.5 dB in Tx1 = 103.23 * 10^(-0.5 / 10) = 92.0, which reduces by 11.23. This operation can be an example of the method 1700 described below.

[0256] In a fourth example, a solution is sought to obtain a reduction in the total RF exposure value at the peak location from a combined RF exposure of three transmitters (Tx1, Tx2, Tx3), where the contributions of the three transmitters at the peak location can be represented as {a = 103.23, b = 4.44, c = 3.33} respectively. The contributions of the three transmitters can result in a combined RF exposure of 111 at the peak location. When the compliance limit is 100, a SAR reduction value of 11 is needed to meet the RF exposure limit. Here, the relative contributions of the three transmitters to the RF exposure can be represented as {93%, 4%, 3%}. In this example, Tx1 is the first priority contributor, Tx2 and Tx3 are both second priority contributors, similar to the third example described above. However, in the fourth example, the priority can be ignored. The reduction or fallback can be made in accordance with any of the examples or methods described herein without prioritizing any transmitter over another.

[0257] Therefore, in some cases:

[0258] Reduction in Tx1 = 11 * 93% = 10.23.

[0259] Reduction in Tx1 in dB = 10*log 10 ((103.23 - 10.23) / 10.23) = -0.45 dB

[0260] Reduction in Tx2 = 11 * 4% = 0.44.

[0261] Reduction in Tx2 in dB = 10*log 10 ((4.44 - 0.44) / 4.44) = -0.45 dB.

[0262] Reduction in Tx3 = 11 * 3% = 0.33.

[0263] Reduction in Tx3 in dB = 10*log 10 ((3.33 - 0.33) / 3.33) = -0.45 dB.

[0264] As noted above, in certain aspects, the active transmitters can be assigned a priority. For example, the active transmitters can be assigned a priority based on the priority of the signals being transmitted by the active transmitters. For example, voice can be assigned a higher priority than data. Thus, a transmitter transmitting voice can be assigned a higher priority than a transmitter transmitting data. In one example, the memory 115 can include an arbitration list specifying the priority of different types of signals. In this example, the processor(s) 110 can assign a priority to each active transmitter based on the priority of the corresponding signal specified in the arbitration list. It will be appreciated that two or more active transmitters can be assigned the same priority (e.g., when two or more active transmitters are transmitting the same type of signal).

[0265] In certain aspects, in addition to or instead of the contribution of the active transmitters to the RF exposure value at the peak location, the priority of the active transmitters is considered by the processor(s) 110 in block 1520. In this regard, Figure 17 An example method 1700 for reducing the transmission power level in block 1520 according to certain aspects of the disclosure is shown. For ease of discussion, the example method 1700 is discussed below using the example of three active transmitters labeled a, b, and c, where transmitter a is assigned a primary priority and transmitters b and c are assigned a secondary priority that is lower than the primary priority. However, it will be appreciated that the method 1700 is not limited to this example.

[0266] At block 1710, the processor(s) 110 determine an amount of reduction in the RF exposure value at the peak location in the combined RF exposure profile of the future time slots that satisfies RF exposure compliance. The processor(s) 110 can determine the amount of reduction in a similar manner as discussed above for block 1610.

[0267] At block 1720, the processor(s) 110 determine the contribution of the secondary active transmitters to the RF exposure value at the peak location. Secondary active transmitters refer to active transmitters that are assigned a secondary (or lower) priority (i.e., transmitters b and c in the example above). The processor(s) 110 can determine the contribution of the secondary active transmitters by summing the contribution of each secondary active transmitter. For the example where transmitters b and c are secondary active transmitters, the contribution of the secondary active transmitters is the sum of the contributions of the active transmitters b and c. For example, if the contribution percentages of transmitters a, b, and c are 90:6:4, respectively, then the contribution of the secondary active transmitters is 10% (i.e., 6% + 4%). For the case where there is only one secondary active transmitter, then the contribution is only the contribution of that secondary active transmitter.

[0268] At block 1730, the processor(s) 110 determine whether the contribution of the secondary active transmitter in block 1720 is greater than or equal to the determined reduction in the RF exposure value at the peak location (i.e., the reduction determined in block 1710). If the contribution is greater than or equal to the determined reduction, the processor(s) 110 proceed to block 1740. If the contribution is less than the determined reduction, the processor(s) 110 proceed to block 1750.

[0269] At block 1740, the processor(s) 110 reduce the transmission power level of the secondary active transmitter to achieve the determined reduction in the RF exposure value at the peak location to satisfy the RF exposure compliance. In this case, the processor(s) 110 can leave the transmission power level of the primary active transmitter (e.g., transmitter a) unchanged. For example, if the contribution percentages of the secondary transmitters b and c are 6:4, respectively, and the determined reduction is 5%, the contribution of the secondary active transmitter is 10%, which is greater than the determined reduction of 5%. In this case, the processor(s) 110 can reduce the transmission power level of the transmitters b and c to achieve the determined reduction in the RF exposure value at the peak location. The processor(s) 110 can use the example method 1600 to reduce the transmission power level of the secondary active transmitter.

[0270] At block 1750, the processor(s) 110 reduce the transmission power level of the primary active transmitter. This is because the contribution of the secondary active transmitter is not enough to achieve the determined reduction in the RF exposure value at the peak location. For example, the processor(s) 110 can reduce the transmission power level of the primary active transmitter such that the remaining reduction in the RF exposure value at the peak location needed to achieve the determined reduction in the RF exposure value at the peak location is less than the contribution of the secondary active transmitter. In this way, by reducing the transmission power level of the secondary active transmitter, the remaining reduction in the RF exposure value at the peak location needed to satisfy the RF exposure compliance can be achieved.

[0271] Block 1750 can be illustrated by the following example. If the contribution percentages of the transmitters a, b, and c are 90:6:4, respectively, and the determined reduction to meet RF exposure compliance is 11%, the contribution of the secondary active transmitter (i.e., 10%) is not enough to achieve the determined reduction of 11%. In this example, the processor 110 can reduce the transmission power level of the primary active transmitter (i.e., transmitter a) by the minimum reduction amount (e.g., 0.5 dB), which results in a reduction of 9%. By reducing the transmission power level of the secondary active transmitter, the remaining 2% reduction needed to reach 11% can be achieved. The minimum reduction amount can correspond to the minimum step in dB by which the processor 110 can reduce the transmission power level of the primary active transmitter.

[0272] At block 1760, the processor 110 reduces the transmission power level of the secondary active transmitter to further reduce the RF exposure value at the peak location to achieve the determined reduction of the RF exposure value at the peak location. The processor 110 can use the example method 1600 to reduce the transmission power level of the secondary active transmitter.

[0273] In certain aspects, the method for reducing the transmission power level in block 1520 includes Figure 17 The illustrated method 1700 can be used to modify or optimize the power reduction calculation, which can otherwise result in full or near-full deprivation of power for low-priority transmitters.

[0274] In some cases, the processor(s) 110 can be configured to ensure or guarantee at least some transmission power for the secondary transmitters when applying the power reduction based on the RF exposure value. In one example, a minimum power level can be configured or defined for each transmitter, and the processor 110 can calculate the power reduction that maintains these pre-configured or pre-defined minimum values for each secondary transmitter. For example, the processor(s) 110 can use the contribution of the secondary transmitter corresponding to the pre-configured or pre-defined minimum value for the secondary transmitter.

[0275] In other cases, when applying the power reduction based on the RF exposure value, the processor(s) 110 can be configured to reduce the transmission power of the secondary transmitters to zero before reducing the highest priority transmitter. In some examples, the reduction of the transmission power of one or more secondary transmitters can result in a transmission power level that is insufficient to allow the secondary transmitters to operate effectively. In these examples, the following minimum transmission power that would be provided to the one or more secondary transmitters can be allocated to the higher priority primary transmitter and / or other secondary transmitters.

[0276] In some cases, when applying a power reduction based on the RF exposure value, the processor(s) 110 can be configured to use a variable step size to reduce the power of one or more transmitters. In one example, the processor(s) 110 can be configured to use a minimum and / or fixed step size in all calculations. In another example, the processor(s) 110 can be configured to use a minimum and / or fixed step size in calculations until the transmission power of one or more secondary transmitters approaches a preconfigured or predefined minimum value or exceeds a threshold defined or configured for the transmitters. The processor(s) 110 can be configured to use a minimum and / or fixed step size in calculations for certain transmitters and a variable step size for other transmitters, including, for example, for secondary transmitters that approach a preconfigured or predefined minimum value.

[0277] In certain aspects, the combined RF exposure distribution or the time-averaged combined RF exposure distribution can include two or more hot spot regions. Each hot spot region can include a respective peak RF exposure value that exceeds the RF exposure limit and can correspond to a respective antenna. In these aspects, the processor(s) 110 can perform the above-described method 1500 for each hot spot region, where the peak location of each hot spot region corresponds to the location of the respective peak RF exposure value. After the processor(s) 110 performs the method 1500 for one of the hot spot regions, the processor(s) 110 can use the determined transmission power level as the initial transmission power level for performing the method 1500 for the next one of the hot spot regions. This helps to ensure that the final determined transmission power level after performing the method 1500 for all of the hot spot regions satisfies RF exposure compliance for all of the hot spot regions. Similarly, the method 1500 can be performed multiple times for a selected plurality of locations of interest other than the peak location(s).

[0278] After determining the transmission power levels of the active transmitters for the future time slot, the processor(s) 110 can do one or more of the following. The processor(s) 110 can set the transmission power limits of one or more (e.g., each) active transmitter for the future time slot based on the determined corresponding transmission power levels. For example, the processor(s) 110 can set the transmission power levels of one or more (e.g., each) active transmitter for the future time slot to the corresponding determined transmission power levels. In one example, the transmission power level of each active transmitter is constrained by the corresponding transmission power limit during the future time slot (e.g., not allowed to exceed the transmission power level at any time during the future time slot). In another example, the time-averaged transmission power level of each active transmitter over the future time slot is constrained by the corresponding transmission power limit during the future time slot. In this example, the transmission power level of an active transmitter is allowed to temporarily exceed the corresponding transmission power limit over the future time slot as long as the time-averaged value of the transmission power level over the future time slot does not exceed the transmission power limit. In yet another example, the processor 110 can set the transmission power level of each active transmitter for the future time slot to the corresponding determined transmission power level.

[0279] In certain aspects, the memory 115 can include a computer-readable medium comprising instructions stored thereon that, when executed by the processor(s) 110, cause the processor(s) 110 to perform any of the methods described herein. For example, the computer-readable medium can include RAM (Random Access Memory), flash memory, ROM (Read Only Memory), PROM (Programmable Read Only Memory), EPROM (Erasable Programmable Read Only Memory), EEPROM (Electrically Erasable Programmable Read Only Memory), registers, magnetic disks, optical disks, hard drives, or any other tangible non-transitory storage medium, or any combination thereof.

[0280] In certain aspects, an apparatus can include means for performing the methods 1500, 1600, or 1700. In one example, the apparatus can include means for determining a specific absorption rate (SAR) distribution for a first wireless communication technology, means for determining a power density (PD) distribution for a second wireless communication technology, and means for combining the SAR distribution and the PD distribution to generate a combined RF exposure distribution. The apparatus can also include means for determining at least one first maximum allowed power level and at least one second maximum allowed power level for a future time slot based on the combined RF exposure distribution, means for setting at least one transmission power limit for a first transmitter in the future time slot based on the at least one first maximum allowed power level, and means for setting at least one transmission power limit for a second transmitter in the future time slot based on the at least one second maximum allowed power level.

[0281] In another example, the apparatus can include a transmitter, a means for determining a RF exposure value at a peak location based on a transmission power level of the transmitter, a means for determining a contribution of each of the transmitters to the RF exposure value at the peak location, and a means for reducing the transmission power level of each of one or more of the transmitters based on the contribution of the transmitters to the RF exposure value at the peak location. The RF exposure value can be a SAR value, a PD value, or a combined SAR and PD value. The means for reducing the transmission power level of each of one or more of the transmitters can be configured to, for each transmitter, determine a proportion of the RF exposure value at a first location attributable to each of the transmitters, and reduce the transmission power level of each of the transmitters according to the proportion of the RF exposure value attributable to each of the transmitters, where the RF exposure value at the first location corresponds to the peak RF exposure value. The means for reducing the transmission power level of each of one or more of the transmitters can be configured to determine one of the transmitters that contributes most to the RF exposure value at the peak location, and reduce the transmission power level of the one of the transmitters by a greatest amount among the transmitters. The means for reducing the transmission power level of each of one or more of the transmitters can be configured to determine a reduction amount of the RF exposure value at the peak location to satisfy an RF exposure limit. The reduction of the transmission power level of each of one or more of the transmitters can also be based on the determined reduction amount of the RF exposure value at the peak location. Each of the transmitters can be assigned a respective priority, and the means for reducing the transmission power level of each of one or more of the transmitters can be configured to reduce one or more of the transmission power levels based on the priority of the transmitters. The means for reducing the transmission power level of each of one or more of the transmitters can be configured to reduce the transmission power level of each of one or more of the transmitters such that a contribution of two or more of the transmitters to the RF exposure value at the peak location is approximately equal after the reduction. The means for reducing the transmission power level of each of one or more of the transmitters can be configured to reduce the transmission power level of each of one or more of the transmitters such that a contribution of all of the transmitters to the RF exposure value at the peak location is approximately equal after the reduction. The means for reducing the transmission power level of each of one or more of the transmitters can be configured to set a transmission power limit for each of the transmitters based on the transmission power level of the transmitters. The means for determining the RF exposure value at the peak location can be configured to, for each of the transmitters, scale a respective RF exposure profile based on the transmission power level of the transmitter, and determine the RF exposure value at the peak location in a combined RF exposure profile.

[0282] Some implementation examples are described in the following numbered clauses:

[0283] 1. A wireless device comprising transmitters and a processor coupled to the transmitters, wherein the processor is configured to: determine an RF exposure value at a first location based on a transmission power level of the transmitters; determine a contribution of each of the transmitters to the RF exposure value at the first location; and reduce the transmission power level of each of one or more of the transmitters based on the contribution of the transmitters to the RF exposure value at the first location.

[0284] 2. The wireless device of clause 1, wherein the RF exposure value is a SAR value, a PD value, or a combined SAR and PD value.

[0285] 3. The wireless device of clause 1 or 2, wherein the processor is configured to reduce the transmission power level of each of the one or more of the transmitters by: for each transmitter, determining a proportion of the RF exposure value at the first location attributable to the each transmitter; and reducing the transmission power level of the each transmitter according to the proportion of the RF exposure value attributable to the each transmitter, wherein the RF exposure value at the first location corresponds to a peak RF exposure value.

[0286] 4. The wireless device of clause 1 or 2, wherein the processor is configured to reduce the transmission power level of each of the one or more of the transmitters by: when the RF exposure value at the first location corresponds to a peak RF exposure value, determining one of the transmitters that contributes most to the RF exposure value at the first location; and reducing the transmission power level of the one of the transmitters by a maximum amount among the transmitters.

[0287] 5. The wireless device of clause 1 or 2, wherein: the processor is configured to determine a reduction amount of the RF exposure value at the first location to satisfy an RF exposure limit; and the processor is configured to reduce the transmission power level of each of the one or more of the transmitters based also on the determined reduction amount of the RF exposure value at the first location.

[0288] 6. The wireless device of clause 1 or 2, wherein: each transmitter is assigned a respective priority; and the processor is configured to reduce the transmission power level of each of the one or more of the transmitters based also on the priority of the transmitters.

[0289] 7. The wireless device of clause 1 or 2, wherein the processor is configured to reduce the transmission power level of each of the one or more of the transmitters such that the contributions of two or more of the transmitters to the RF exposure value at the first location are approximately equal after the reduction.

[0290] 8. The wireless device of clause 7, wherein the processor is configured to reduce the transmission power level of each of the one or more of the transmitters such that the contributions of all of the transmitters to the RF exposure value at the first location are approximately equal after the reduction.

[0291] 9. The wireless device of any of clauses 1-8, wherein after the reduction, the processor is configured to set a transmission power limit for each transmitter based on the transmission power level of the transmitter.

[0292] 10. The wireless device of any of clauses 1-9, wherein the processor is configured to determine the RF exposure value at the first location by: for each transmitter, scaling a respective RF exposure distribution based on the transmission power level of the transmitter; combining the scaled RF exposure distributions to obtain a combined RF exposure distribution; and determining the RF exposure value at the first location in the combined RF exposure distribution, wherein the RF exposure value at the first location corresponds to a peak RF exposure value.

[0293] 11. A method implemented in a wireless device comprising transmitters, comprising: determining an RF exposure value at a first location based on transmission power levels of the transmitters; determining a contribution of each of the transmitters to the RF exposure value at the first location; and reducing the transmission power level of each of one or more of the transmitters based on the contribution of the transmitters to the RF exposure value at the first location.

[0294] 12. The method of clause 11, wherein the RF exposure value is a SAR value, a PD value, or a combined SAR and PD value.

[0295] 13. The method of clause 11 or 12, wherein reducing the transmission power level of each of the one or more of the transmitters comprises, for each transmitter, determining a proportion of the RF exposure value at the first location attributable to the each transmitter, and reducing the transmission power level of the each transmitter according to the proportion of the RF exposure value attributable to the each transmitter, wherein the RF exposure value at the first location corresponds to a peak RF exposure value.

[0296] 14. The method of clause 11 or 12, wherein reducing the transmission power level of each of the one or more of the transmitters comprises, when the RF exposure value at the first location corresponds to a peak RF exposure value, determining one of the transmitters that contributes most to the RF exposure value at the first location, and reducing the transmission power level of the one of the transmitters by a maximum amount among the transmitters.

[0297] 15. The method of clause 11 or 12, further comprising determining an amount of reduction of the RF exposure value at the first location to meet an RF exposure limit, wherein reducing the transmission power level of each of the one or more of the transmitters is further based on the determined amount of reduction of the RF exposure value at the first location.

[0298] 16. The method of clause 11 or 12, wherein: each transmitter is assigned a respective priority; and reducing the transmission power level of each of the one or more of the transmitters is further based on the priority of the transmitter.

[0299] 17. The method of clause 11 or 12, wherein reducing the transmission power level of each of the one or more of the transmitters comprises reducing the transmission power level of each of the one or more of the transmitters such that a contribution of two or more of the transmitters to the RF exposure value at the first location is approximately equal after the reduction.

[0300] 18. The method of clause 17, wherein reducing the transmission power level of each of the one or more of the transmitters comprises reducing the transmission power level of each of the one or more of the transmitters such that a contribution of all of the transmitters to the RF exposure value at the first location is approximately equal after the reduction.

[0301] 19. The method of any of clauses 11-18, further comprising, after the reducing, setting a transmission power limit for each of the transmitters based on the transmission power level of the transmitter.

[0302] 20. The method of any of clauses 11-19, wherein determining the RF exposure value at the first location comprises, for each transmitter, scaling a respective RF exposure profile based on the transmission power level of the transmitter; combining the scaled RF exposure profiles to obtain a combined RF exposure profile; and determining the RF exposure value at the first location in the combined RF exposure profile, wherein the RF exposure value at the first location corresponds to a peak RF exposure value.

[0303] 21. An apparatus for wireless communication, comprising: a transmitter; means for determining an RF exposure value at a first location based on a transmission power level of the transmitter; means for determining a contribution of each of the transmitters to the RF exposure value at the first location; and means for reducing the transmission power level of each of one or more of the transmitters based on the contribution of the transmitters to the RF exposure value at the first location.

[0304] 22. The apparatus of clause 21, wherein the RF exposure value is a SAR value, a PD value, or a combined SAR and PD value.

[0305] 23. The apparatus of clause 21, wherein the means for reducing the transmission power level of each of the one or more of the transmitters is configured to, for each transmitter, determine a proportion of the RF exposure value at the first location attributable to the each transmitter; and reduce the transmission power level of the each transmitter in accordance with the proportion of the RF exposure value attributable to the each transmitter, wherein the RF exposure value at the first location corresponds to a peak RF exposure value.

[0306] 24. The apparatus of clause 21, wherein the means for reducing the transmission power level of each of the one or more of the transmitters is configured to, when the RF exposure value at the first location corresponds to a peak RF exposure value, determine one of the transmitters that contributes most to the RF exposure value at the first location; and reduce the transmission power level of the one of the transmitters by a maximum amount among the transmitters.

[0307] 25. The apparatus of clause 21, wherein the means for reducing the transmission power level of each of the one or more of the transmitters is configured to determine a reduction in the RF exposure value at the first location to meet an RF exposure limit, wherein reducing the transmission power level of each of the one or more of the transmitters is further based on the determined reduction in the RF exposure value at the first location.

[0308] 26. The apparatus of clause 21, wherein: each transmitter is assigned a respective priority; and the means for reducing the transmission power level of each of the one or more of the transmitters is configured to reduce one or more transmission power levels based on the priority of the transmitters.

[0309] 27. The apparatus of clause 21, wherein the means for reducing the transmission power level of each of the one or more of the transmitters is configured to reduce the transmission power level of each of the one or more of the transmitters such that a contribution of two or more of the transmitters to the RF exposure value at the first location is approximately equal after the reduction.

[0310] 28. The apparatus of clause 27, wherein the means for reducing the transmission power level of each of the one or more of the transmitters is configured to reduce the transmission power level of each of the one or more of the transmitters such that a contribution of all of the transmitters to the RF exposure value at the first location is approximately equal after the reduction.

[0311] 29. The apparatus of clause 21, wherein the means for reducing the transmission power level of each of the one or more of the transmitters is configured to set a transmission power limit for each transmitter based on the transmission power level of the transmitters.

[0312] 30. The apparatus of clause 21, wherein the means for determining the RF exposure value at the first location is configured to: for each transmitter, scale a respective RF exposure profile based on the transmission power level of the transmitter; combine the scaled RF exposure profiles to obtain a combined RF exposure profile; and determine the RF exposure value at the first location in the combined RF exposure profile, wherein the RF exposure value at the first location corresponds to a peak RF exposure value.

[0313] It should be appreciated that the present disclosure is not limited to the exemplary terminology used to describe aspects of the present disclosure and that the present disclosure encompasses equivalent terminology. For example, it should be appreciated that a distribution can also be referred to as a map, a scan, or another term. In another example, it should be appreciated that an antenna can also be referred to as an antenna element or another term. In yet another example, it should be appreciated that a maximum allowed power level can also be referred to as a power level limit or another term.

[0314] The term “about,” “approximately” used in reference to a value or attribute herein is intended to mean within 10% of the stated value or attribute.

[0315] Any reference to an element herein using a designation such as “first,” “second,” and so forth does not generally limit the quantity or order for or between elements. Rather, these designations are used herein as a convenient method of distinguishing between two or more elements or instances of an element. Thus, a reference to first and second elements does not mean that only two elements can be employed, or that the first element must precede the second element.

[0316] In the present disclosure, the word “exemplary” is used to mean “serving as an example, instance, or illustration.” Any implementation or aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects of the disclosure. Likewise, the term “aspects” does not require that all aspects of the disclosure include the discussed feature, advantage or mode of operation.

[0317] The previous description of the present disclosure is provided to enable any person skilled in the art to make or use the present disclosure. Various modifications to the present disclosure will be clear to those skilled in the art, and the generic principles defined herein can be applied to other variations without departing from the spirit or scope of the present disclosure. Thus, the present disclosure is not intended to be limited to the examples described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A wireless device, comprising: Transmitter; as well as A processor, coupled to the transmitter, wherein the processor is configured to: The radio frequency (RF) exposure value at the first location is determined based on the transmission power level of the transmitter; Determine the contribution of each transmitter in the transmitters to the RF exposure value at the first location, the contribution including the proportion of the RF exposure value at the first location that can be attributed to each transmitter in the transmitters; as well as The transmission power level of each transmitter is reduced based on the proportion of the RF exposure value at the first location that can be attributed to each of one or more of the transmitters. The processor is configured to determine the RF exposure value at the first location by: For each transmitter, the corresponding RF exposure distribution is scaled based on the transmitter's transmission power level, and each RF exposure distribution includes a set of RF exposure values, where each RF exposure value corresponds to a different location; The scaled RF exposure distributions are combined to obtain a combined RF exposure distribution; and Determine the RF exposure value at the first location in the combined RF exposure distribution, wherein the RF exposure value at the first location corresponds to the peak RF exposure value.

2. The wireless device of claim 1, wherein the RF exposure value is a specific absorption rate (SAR) value, a power density (PD) value, or a combination of SAR and PD values.

3. The wireless device of claim 1, wherein the proportion of the RF exposure value at the first location attributable to each of the transmitters is calculated as a percentage of the sum of the contributions of all the transmitters in the RF exposure value at the first location, and The RF exposure value at the first location corresponds to the peak RF exposure value.

4. The wireless device of claim 1, wherein the processor is configured to reduce the transmission power level of each of the one or more transmitters by: When the RF exposure value at the first location corresponds to the peak RF exposure value, determine the transmitter among the transmitters that contributes the most to the RF exposure value at the first location; and Reduce the transmission power level of one of the transmitters by the maximum amount among the transmitters.

5. The wireless device according to claim 1, wherein: The processor is configured to determine the amount by which the RF exposure value at the first location is reduced to meet an RF exposure limit; as well as The processor is configured to further reduce the transmission power level of each of the one or more transmitters based on a determined reduction amount of the RF exposure value at the first location.

6. The wireless device according to claim 1, wherein: Each transmitter is assigned a corresponding priority; and The processor is configured to further reduce the transmission power level of each of the one or more transmitters based on the priority of the transmitter.

7. The wireless device of claim 1, wherein the processor is configured to: reduce the transmission power level of each of the one or more transmitters such that the contributions of two or more transmitters to the RF exposure value at the first location are approximately equal after the reduction.

8. The wireless device of claim 7, wherein the processor is configured to: reduce the transmission power level of each of the one or more transmitters in the transmitters such that the contribution of all transmitters in the transmitters to the RF exposure value at the first location is approximately equal after the reduction.

9. The wireless device of claim 1, wherein after the reduction, the processor is configured to set a transmission power limit for each transmitter based on the transmission power level of the transmitter.

10. A method implemented in a wireless device including a transmitter, comprising: The radio frequency (RF) exposure value at the first location is determined based on the transmission power level of the transmitter; Determine the contribution of each transmitter in the transmitters to the RF exposure value at the first location, the contribution including the proportion of the RF exposure value at the first location that can be attributed to each transmitter in the transmitters; as well as The transmission power level of each transmitter is reduced based on the proportion of the RF exposure value at the first location that can be attributed to each of one or more of the transmitters. Determining the RF exposure value at the first location includes: For each transmitter, the corresponding RF exposure distribution is scaled based on the transmitter's transmission power level, and each RF exposure distribution includes a set of RF exposure values, where each RF exposure value corresponds to a different location; The scaled RF exposure distributions are combined to obtain a combined RF exposure distribution; and Determine the RF exposure value at the first location in the combined RF exposure distribution, wherein the RF exposure value at the first location corresponds to the peak RF exposure value.

11. The method of claim 10, wherein the RF exposure value is a specific absorption rate (SAR) value, a power density (PD) value, or a combination of SAR and PD values.

12. The method of claim 10, wherein the proportion of the RF exposure value at the first location attributable to each of the transmitters is calculated as a percentage of the sum of the contributions of all the transmitters in the plurality of transmitters to the RF exposure value at the first location, and The RF exposure value at the first location corresponds to the peak RF exposure value.

13. The method of claim 10, wherein reducing the transmission power level of each of the one or more transmitters comprises: When the RF exposure value at the first location corresponds to the peak RF exposure value, the transmitter that contributes the most to the RF exposure value at the first location is determined. as well as Reduce the transmission power level of one of the transmitters by the maximum amount among the transmitters.

14. The method of claim 10, further comprising: Determine the amount by which the RF exposure value at the first location is reduced to meet the RF exposure limit. The reduction in the transmission power level of each of the one or more transmitters is also based on a reduction amount determined by the RF exposure value at the first location.

15. The method of claim 10, wherein: Each transmitter is assigned a corresponding priority; and The reduction of the transmission power level of each of the one or more transmitters is also based on the priority of the transmitter.

16. The method of claim 10, wherein reducing the transmission power level of each of the one or more transmitters comprises: Reduce the transmission power level of each of the one or more transmitters in the transmitters such that the contribution of two or more transmitters in the transmitters to the RF exposure value at the first location is approximately equal after the reduction.

17. The method of claim 16, wherein reducing the transmission power level of each of the one or more transmitters comprises: Reduce the transmission power level of each of the one or more transmitters in the transmitters such that the contribution of all transmitters in the transmitters to the RF exposure value at the first location is approximately equal after the reduction.

18. The method of claim 10, further comprising: After the reduction, a transmission power limit is set for each transmitter based on the transmission power level of the transmitter.

19. An apparatus for wireless communication, comprising: Transmitter; Components for determining the radio frequency (RF) exposure value at a first location based on the transmission power level of the transmitter; Components for determining the relative contribution of the transmitter to the RF exposure value at the first location, the contribution including the proportion of the RF exposure value at the first location that can be attributed to each of the transmitters; as well as Components for reducing the transmission power level of each transmitter based on a proportion of the RF exposure value at the first location that can be attributed to each of the one or more transmitters. The component used to determine the RF exposure value at the first location is configured as follows: For each transmitter, the corresponding RF exposure distribution is scaled based on the transmitter's transmission power level, and each RF exposure distribution includes a set of RF exposure values, where each RF exposure value corresponds to a different location; The scaled RF exposure distributions are combined to obtain a combined RF exposure distribution; and Determine the RF exposure value at the first location in the combined RF exposure distribution, wherein the RF exposure value at the first location corresponds to the peak RF exposure value.

20. The apparatus of claim 19, wherein the RF exposure value is a specific absorption rate (SAR) value, a power density (PD) value, or a combination of SAR and PD values.

21. The apparatus of claim 19, wherein the proportion of the RF exposure value at the first location attributable to each of the transmitters is calculated as a percentage of the sum of the contributions of all the transmitters in the plurality of transmitters to the RF exposure value at the first location, and The RF exposure value at the first location corresponds to the peak RF exposure value.

22. The apparatus of claim 19, wherein the component for reducing the transmission power level of each of the one or more transmitters is configured to: When the RF exposure value at the first location corresponds to the peak RF exposure value, determine the transmitter among the transmitters that contributes the most to the RF exposure value at the first location; and Reduce the transmission power level of one of the transmitters by the maximum amount among the transmitters.

23. The apparatus of claim 19, wherein the component for reducing the transmission power level of each of the one or more transmitters is configured to: Determine the amount by which the RF exposure value at the first location is reduced to meet the RF exposure limit. The reduction in the transmission power level of each of the one or more transmitters is also based on a reduction amount determined by the RF exposure value at the first location.

24. The apparatus according to claim 19, wherein: Each transmitter is assigned a corresponding priority; as well as The component for reducing the transmission power level of each of the one or more transmitters is configured to reduce one or more transmission power levels based on the priority of the transmitter.

25. The apparatus of claim 19, wherein the component for reducing the transmission power level of each of the one or more transmitters in the transmitters is configured to: reduce the transmission power level of each of the one or more transmitters in the transmitters such that the contributions of two or more transmitters in the transmitters to the RF exposure value at the first location are approximately equal after the reduction.

26. The apparatus of claim 25, wherein the component for reducing the transmission power level of each of the one or more transmitters in the transmitters is configured to reduce the transmission power level of each of the one or more transmitters in the transmitters such that the contribution of all transmitters in the transmitters to the RF exposure value at the first location is approximately equal after the reduction.

27. The apparatus of claim 19, wherein the component for reducing the transmission power level of each of the one or more transmitters is configured to set a transmission power limit for each transmitter based on the transmission power level of the transmitter.

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