Real-time estimation of radio frequency (RF) exposure

Abstract

The disclosure relates to estimating radio frequency (RF) exposure in real time. In certain aspects, a method implemented in a wireless device includes determining a specific absorption rate (SAR) distribution for a first wireless communication technology, determining a power density (PD) distribution for a second wireless communication technology, and combining the SAR distribution and the PD distribution to generate a combined RF exposure distribution. The method further includes determining at least one first maximum allowable power level and at least one second maximum allowable power level for a future time slot based on the combined RF exposure profile, setting at least one transmit power limit for the first transmitter in the future time slot based on the at least one first maximum allowable power level, and setting at least one transmit power limit for the second transmitter in the future time slot based on the at least one second maximum allowable power level.

Description

[0001] This application is a divisional application of the Chinese invention patent application with an international application date of July 3, 2019, a national application number of 201980057688.8, and an invention name of “Real-time Estimation of Radio Frequency (RF) Exposure”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to and the benefit of Non-Provisional Application No. 16 / 460,894 filed in the U.S. Patent and Trademark Office on July 2, 2019, Provisional Application No. 62 / 694,405 filed in the U.S. Patent and Trademark Office on July 5, 2018, and Provisional Application No. 62 / 696,687 filed in the U.S. Patent and Trademark Office on July 11, 2018, the entire contents of which are incorporated herein by reference as if fully set forth in their entirety and for all applicable purposes below. Technical Field

[0004] Aspects of the present disclosure relate generally to wireless devices, and more particularly to assessing radio frequency (RF) exposure from wireless devices. Background Art

[0005] Modern wireless devices (e.g., cellular phones) are generally required to limit user exposure to radio frequency (RF) radiation according to RF exposure limits set by domestic and international regulatory agencies. In order to ensure that wireless devices comply with RF exposure limits, technologies have been developed that enable wireless devices to assess RF exposure from wireless devices in real time and adjust the transmit power of the wireless devices accordingly to comply with the RF exposure limits. Summary of the invention

[0006] A simplified summary of one or more embodiments is presented below in order to provide a basic understanding of such embodiments. This summary is not an extensive overview of all contemplated embodiments, and is neither intended to identify key or important elements of all embodiments nor to define 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 a more detailed description that is presented later.

[0007] A first aspect relates to a wireless device. The wireless device includes: a first transmitter configured to transmit a first signal according to a first wireless communication technology, a second transmitter configured to transmit a second signal according to a second wireless communication technology, and a processor coupled to the first transmitter and the second transmitter. The processor is configured to: determine a specific absorption rate (SAR) distribution for the first wireless communication technology, determine a power density (PD) distribution for the second wireless communication technology, combine the SAR distribution and the PD distribution to generate a combined RF exposure distribution, determine at least one first maximum allowable power level and at least one second maximum allowable power level for a future time slot based on the combined RF exposure distribution, set at least one transmit power limit for the first transmitter in the future time slot based on the at least one first maximum allowable power level, and set at least one transmit power limit for the second transmitter in the future time slot based on the at least one second maximum allowable power level.

[0008] A second aspect relates to a method implemented in a wireless device. The method includes determining a specific absorption rate (SAR) distribution for a first wireless communication technology, determining a power density (PD) distribution for a second wireless communication technology, and combining the SAR distribution and the PD distribution to generate a combined RF exposure distribution. The method also includes determining at least one first maximum allowable power level and at least one second maximum allowable power level for a future time slot based on the combined RF exposure distribution, setting at least one transmit power limit for a first transmitter in the future time slot based on the at least one first maximum allowable power level, and setting at least one transmit power limit for a second transmitter in the future time slot based on the at least one second maximum allowable power level.

[0009] A third aspect relates to a computer-readable medium. The computer-readable medium includes instructions stored thereon for determining a specific absorption rate (SAR) distribution for a first wireless communication technology, determining a power density (PD) distribution for a second wireless communication technology, and combining the SAR distribution and the PD distribution to generate a combined RF exposure distribution. The computer-readable medium also includes instructions stored thereon for determining at least one first maximum allowable power level and at least one second maximum allowable power level for a future time slot based on the combined RF exposure distribution, setting at least one transmit power limit for a first transmitter in a future time slot based on the at least one first maximum allowable power level, and setting at least one transmit power limit for a second transmitter in a future time slot based on the at least one second maximum allowable power level.

[0010] A fourth aspect relates to a wireless device. The wireless device includes a transmitter and a processor coupled to the transmitter. The processor is configured to: determine a specific absorption rate (SAR) distribution for a first wireless communication technology, determine a power density (PD) distribution for a second wireless communication technology, combine the SAR distribution and the PD distribution to generate a combined RF exposure distribution, and determine a maximum allowable time-averaged power level for a future time slot based on the combined RF exposure distribution, wherein the future time slot includes a plurality of sub-time slots. The processor is also configured to: determine a maximum allowable power level for each of the plurality of sub-time slots based on the maximum allowable time-averaged power level for the future time slot, and set a transmit power limit for the transmitter in each of the sub-time slots based on the corresponding maximum allowable power level.

[0011] A fifth aspect relates to a wireless device. The wireless device includes a transmitter and a processor coupled to the transmitter. The processor is configured to: determine a specific absorption rate (SAR) distribution for a first wireless communication technology, determine a power density (PD) distribution for a second wireless communication technology, combine the SAR distribution and the PD distribution to generate a combined RF exposure distribution, and determine a PD limit for a future time slot based on the combined RF exposure distribution, wherein the future time slot includes a plurality of sub-time slots. The processor is also configured to: determine a maximum allowable power level for each of the plurality of sub-time slots based on the PD limit for the future time slot, and set a transmit power limit for the transmitter in each of the sub-time slots based on the corresponding maximum allowable power level.

[0012] A sixth aspect relates to a wireless device. The wireless device includes a transmitter and a processor coupled to the transmitter. The processor is configured to: determine a maximum allowable time-averaged power level for a future time slot, determine a maximum allowable transmit duty cycle for the future time slot based on the determined maximum allowable time-averaged power level and the maximum allowable power level, and set a transmit duty cycle limit for the transmitter in the future time slot based on the maximum allowable transmit duty cycle.

[0013] A seventh aspect relates to a wireless device. The wireless device includes a transmitter and a processor coupled to the transmitter. The processor is configured to: determine a maximum allowable time average power level for a future time slot, determine a maximum allowable peak power level for the future time slot based on the determined maximum allowable time average power level and a maximum allowable duty cycle, and set a peak power limit for the transmitter in the future time slot based on the maximum allowable peak power level.

[0014] To achieve the foregoing and related purposes, one or more embodiments include the features fully described below and particularly pointed out in the claims. The following description and the accompanying drawings set forth in detail certain illustrative aspects of one or more embodiments. However, these aspects are only indicative of a few of the various ways in which the principles of the various embodiments may be employed, and the described embodiments are intended to include all such aspects and their equivalents. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 One example of a wireless device in which aspects of the present disclosure may be implemented is shown.

[0016] Figure 2 An example of a normalized specific absorption rate (SAR) distribution combined with a normalized power density (PD) distribution in accordance with certain aspects of the present disclosure is shown.

[0017] Figure 3 is a flow chart illustrating an example method for determining a transmit power level that complies with RF exposure limits for simultaneous transmission using multiple wireless communication technologies in accordance with certain aspects of the present disclosure.

[0018] Figure 4 is a flow chart illustrating an example method for determining a transmit power level that complies with PD limits in accordance with certain aspects of the present disclosure.

[0019] Figure 5 An example of a time-averaged SAR distribution in accordance with certain aspects of the present disclosure is shown.

[0020] Figure 6 is a flow chart illustrating an example method for determining a transmit power level for a future time slot that complies with a time-averaged SAR limit in accordance with certain aspects of the present disclosure.

[0021] Figure 7 An example of a time-averaged PD distribution in accordance with certain aspects of the present disclosure is shown.

[0022] Figure 8 is a flow chart illustrating an example method for determining a transmit power level that complies with a time-averaged PD limit in accordance with certain aspects of the present disclosure.

[0023] Fig. 9 An example of a time-averaged SAR distribution combined with a time-averaged PD distribution in accordance with certain aspects of the present disclosure is shown.

[0024] Fig.10 is a flow chart illustrating an example method for determining a transmit power level that complies with time-averaged RF exposure limits in accordance with certain aspects of the present disclosure.

[0025] Fig.11 An example in accordance with certain aspects of the present disclosure is shown in which a time-averaged PD distribution is determined using multiple time-averaged windows for different frequency bands.

[0026] Fig.12 An example in accordance with certain aspects of the present disclosure is shown in which a time-averaged PD distribution is determined for simultaneous transmissions at different frequency bands.

[0027] Fig.13 An example of a time-averaged SAR distribution combined with a PD distribution in accordance with certain aspects of the present disclosure is shown.

[0028] Fig.14 is a flow chart illustrating one example of a method implemented in a wireless device in accordance with certain aspects of the present disclosure.

[0029] Fig.15 An example in accordance with certain aspects of the present disclosure is shown in which maximum allowable power levels are determined at different rates for different technologies.

[0030] Fig.16 An example of PD over time for the inner loop is shown in accordance with certain aspects of the present disclosure.

[0031] Fig.17 An example of a used portion of a PD allocation and a portion of a PD allocation reserved for future transmissions in accordance with certain aspects of the present disclosure is shown.

[0032] Fig.18 An example table for converting allowed PDs to maximum allowable power levels in accordance with certain aspects of the present disclosure is shown. DETAILED DESCRIPTION

[0033] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of various configurations and is not intended to represent the only configuration in which the concepts described herein may be practiced. For the purpose of providing a thorough understanding of the various concepts, the detailed description includes specific details. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some instances, well-known structures and components are shown in block diagram form to avoid obscuring these concepts.

[0034] Figure 1 One example of a wireless device 100 in which aspects of the disclosure described herein may be implemented is shown. The wireless device 100 may include a mobile wireless device (eg, a cellular phone), a laptop computer, a wireless access point, or some other wireless device.

[0035] The wireless device 100 includes a processor 110 and a memory 115 coupled to the processor 110. The memory 115 may 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 may 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.

[0036] The wireless device 100 also includes a first transmitter 120, a first plurality of antennas 122-1 through 122-N 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 technologies, including but not limited to third generation (3G) technologies (e.g., CDMA), fourth generation (4G) technologies (also referred to as long term evolution (LTE)), fifth generation (5G) technologies, one or more technologies 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 technologies. In some aspects, the first transmitter 120 can be configured to transmit signals via the multiple antennas 122-1 to 122-N using multiple-input multiple-output (MIMO) transmissions 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 multiple antennas 122-1 to 122-N using beamforming to direct the transmissions to another wireless device (not shown). In these aspects, the transmissions can be electrically steered by adjusting the relative phase and / or amplitude of the transmitted signals for the different antennas 122-1 to 122-N.

[0037] The processor 110 interfaces with the first transmitter 120 via the first bus 140. The first bus 140 may include one or more signal lines between the processor 110 and the first transmitter 120. In order to transmit data, the processor 110 may process the data into one or more signals (e.g., baseband signals or intermediate frequency signals). The processing performed by the processor 110 may 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 may output the one or more signals to the first transmitter 120 via the first bus 140. The first transmitter 120 may then process the one or more signals from the processor 110 into one or more RF signals to be transmitted via one or more of the antennas 122-1 to 122-N. The processing performed by the first transmitter 120 may include frequency up-conversion, power amplification, etc.

[0038] In some aspects, the processor 110 may adjust the transmit power for one or more of the antennas 122-1 to 122-N. For example, the first transmitter 120 may include a plurality of amplifiers (not shown), each of which is coupled to a corresponding antenna in the antenna. For each amplifier, the processor 110 may output a corresponding control signal to the amplifier via the first bus 140 to control the gain of the amplifier. In this example, the processor 110 may adjust the transmit power for the antenna by adjusting the gain of the corresponding amplifier accordingly. In another example, the processor 110 may output one or more signals to the first transmitter 120, each of which corresponds to a corresponding antenna in the antennas 122-1 to 122-N. In this example, the processor 110 may adjust the transmit power for the antenna by adjusting the amplitude of the corresponding signal accordingly. It should be understood that the present disclosure is not limited to the above examples, and the processor 110 may use other techniques to adjust the transmit power.

[0039] In certain aspects, the processor 110 may use a power control open loop and / or a power control closed loop to adjust the transmit power for one or more of the antennas 122-1 to 122-N. For the example of power control open loop, the wireless device 100 may receive a pilot signal from another wireless device (not shown) via a receiver (not shown). In this example, the processor 110 estimates a channel condition between the wireless device 100 and the other wireless device based on the received pilot signal, and adjusts the transmit power for one or more of the antennas 122-1 to 122-N based on the estimated channel condition. For the example of power control closed loop, the wireless device 100 receives a feedback signal from another wireless device via a receiver (not shown), wherein the feedback signal indicates a channel condition between the wireless device 100 and the other wireless device. In this example, the processor 110 adjusts the transmit power for one or more of the antennas 122-1 to 122-N based on the indicated channel condition.

[0040] Processor 110 may also adjust transmit power for one or more of antennas 122-1 through 122-N based on the data rate. For example, processor 110 may increase (boost) transmit power to transmit short data bursts.

[0041] In addition, as discussed further below, processor 110 can adjust the transmit power for one or more of antennas 122-1 through 122-N to keep RF exposure from wireless device 100 within RF exposure limits set by a regulatory body (e.g., FCC). In this case, the transmit power is constrained by the RF exposure limits.

[0042] The wireless device 100 also includes a second transmitter 130, a second plurality of antennas 132-1 to 132-M coupled to the second transmitter 130, and a second bus 150, the second bus 150 being 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 to 132-M using one or more wireless communication technologies, including but not limited to 3G technology, 4G technology, 5G technology, one or more technologies based on one or more IEEE 802.11 protocols (e.g., IEEE 802.11ac, IEEE 802.11n, IEEE802.11ad, IEEE 802.11ax, IEEE 802.11ay, etc.), and / or one or more other technologies. The second transmitter 130 may transmit signals via the plurality of antennas 132-1 to 132-M using MIMO transmission, beamforming, and / or other methods. In certain aspects, as discussed further below, the first transmitter 120 and the second transmitter 130 may simultaneously transmit signals using different wireless communication technologies.

[0043] The processor 110 interfaces with the second transmitter 130 via a second bus 150, which may include one or more signal lines between the processor 110 and the second transmitter 130. In order to transmit data, the processor 110 may process the data into one or more signals (e.g., baseband signals or intermediate frequency signals). The processing performed by the processor 110 may 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 may output the one or more signals to the second transmitter 130 via the second bus 150. The second transmitter 130 may then process the one or more signals from the processor 110 into one or more RF signals to be transmitted via one or more of the antennas 132-1 to 132-M. The processing performed by the second transmitter 130 may include frequency up-conversion, power amplification, etc.

[0044] The processor 110 may adjust the transmit power for one or more of the antennas 132-1 to 132-M. For example, the second transmitter 130 may include a plurality of amplifiers (not shown), each of which is coupled to a corresponding antenna of the antennas 132-1 to 132-M. For each amplifier, the processor 110 may output a corresponding control signal to the amplifier via the second bus 150 to control the gain of the amplifier. In this example, the processor 110 may adjust the transmit power for the antenna by adjusting the gain of the corresponding amplifier accordingly. In another example, the processor 110 may output one or more signals to the second transmitter 130, each of which corresponds to a corresponding antenna of the antennas 132-1 to 132-M. In this example, the processor 110 may adjust the transmit power for the antenna by adjusting the amplitude of the corresponding signal accordingly. It should be understood that the present disclosure is not limited to the above examples, and the processor 110 may use other techniques to adjust the transmit power.

[0045] As discussed above, processor 110 may adjust transmit power for one or more of antennas 132-1 through 132-M using a power control open loop and / or a power control closed loop. As discussed further below, processor 110 may also adjust transmit power for one or more of antennas 132-1 through 132-M to keep RF exposure from wireless device 100 within RF exposure limits set by regulatory agencies.

[0046] It should be understood that, in addition to Figure 1 The first transmitter 120 and the second transmitter 130 are shown, the wireless device 100 may also include one or more additional transmitters. Figure 1 In the example shown, the first transmitter 120 and the second transmitter 130 are coupled to separate antenna groups, but it should be understood that the first transmitter 120 and the second transmitter 130 can share one or more antennas. Moreover, in some embodiments, the first transmitter 120 can transmit on only one antenna, and / or the second transmitter 130 can transmit on only one antenna.

[0047] Modern wireless devices (e.g., cellular phones) are generally required 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 the specific absorption rate (SAR), which measures the energy absorbed per unit mass of human tissue and has units of watts per kilogram (W / kg). RF exposure can also be expressed in terms of power density (PD), which measures the energy absorbed per unit area and has units of mW / cm 2 .

[0048] SAR can be used to assess RF exposure for transmission frequencies less than 10 GHz, which covers wireless communication technologies such as 3G (e.g., CDMA), 4G, IEEE 802.11ac, etc. PD can be used to assess RF exposure for transmission frequencies above 10 GHz, which covers wireless communication technologies such as IEEE 802.11ad, 5G, etc. Therefore, different metrics can be used to assess RF exposure for different wireless communication technologies.

[0049] The wireless device 100 may transmit signals simultaneously using multiple wireless communication technologies. For example, the wireless device 100 may transmit signals simultaneously using a first wireless communication technology (e.g., 3G, 4G, etc.) operating below 10 GHz and a second wireless communication technology (e.g., 5G, IEEE 802.11ad) operating above 10 GHz. Since the wireless device 100 transmits signals simultaneously using the first technology and the second technology, the user of the device is exposed to RF radiation from transmissions using both technologies. Accordingly, for situations where the wireless device 100 transmits signals simultaneously using multiple wireless communication technologies, techniques for determining RF exposure compliance are needed.

[0050] As discussed further below, aspects of the present disclosure enable the wireless device 100 to assess RF exposure in real time for situations where the wireless device 100 is transmitting signals simultaneously using multiple wireless communication technologies.

[0051] In some aspects, the wireless device 100 may simultaneously transmit signals using a first wireless communication technology (e.g., 3G, 4G, IEEE802.11ac, etc.) and a second wireless communication technology (e.g., 5G, IEEE 802.11ad, etc.), in which RF exposure is measured in terms of SAR, and in which RF exposure is measured in terms of PD. In these aspects, the first transmitter 120 may transmit the first signal according to the first wireless communication technology, and the second transmitter 130 may transmit the second signal according to the second wireless communication technology. As discussed further below, when the wireless device 100 simultaneously transmits the first signal and the second signal using the first technology and the second technology, respectively, the processor 110 may evaluate the combined RF exposure from the first technology and the second technology to ensure compliance with the RF exposure limit.

[0052] To assess RF exposure from transmissions using a first technology (e.g., 3G, 4G, IEEE 802.11ac, etc.), the wireless device 100 may include a plurality of SAR distributions for the first technology stored in the memory 115. Each of the SAR distributions may correspond to a respective transmission scenario of a plurality of transmission scenarios supported by the wireless device 100 for the first technology. As discussed further below, the transmission scenarios may correspond to various combinations of antennas 122-1 to 122-N, frequency bands, channels, and / or body locations.

[0053] A SAR distribution (also referred to as a SAR map) for each emission scenario may be generated based on measurements (e.g., electric field measurements) performed using a human body model in a test lab. As discussed further below, after the SAR distribution is generated, the SAR distribution is stored in memory 115 to enable processor 110 to assess RF exposure in real time. Each SAR distribution includes a set of SAR values, where each SAR value may correspond to a different location (e.g., on a human body model). Each SAR value may include a SAR value averaged over a mass of 1 g or 10 g at the corresponding location.

[0054] The SAR values ​​in each SAR distribution correspond to a particular transmit power level (e.g., the transmit power level at which the SAR values ​​were measured in a test lab). Since SAR scales with transmit power level, processor 110 may scale the SAR distribution for any transmit power level by multiplying each SAR value in the SAR distribution by the following transmit power scaling factor:

[0055]

[0056] Among them, Tx c is the current transmit power level for the corresponding transmit scenario, and Tx SAR is the transmit power level corresponding to the SAR value in the stored SAR distribution (eg, the transmit power level at which the SAR value was measured in a test laboratory).

[0057] As discussed above, the wireless device 100 may support multiple transmission scenarios for the first technology. In some aspects, the transmission scenario may be specified by a set of parameters. The set of parameters may include one or more of the following: antenna parameters indicating one or more antennas (i.e., active antennas) used for transmission, band parameters indicating one or more frequency bands (i.e., active bands) used for transmission, channel parameters indicating one or more channels (i.e., active channels) used for transmission, body position parameters indicating the position of the wireless device 100 relative to the user's body position (head, torso, away from the body, etc.), and / or other parameters. In the case where the wireless device 100 supports a large number of transmission scenarios, it may be very time-consuming and expensive to perform measurements for each transmission scenario in a test setting (e.g., a test laboratory). In order to reduce the test time, measurements may be performed for a subset of transmission scenarios to generate a SAR distribution for the subset of transmission scenarios. In this example, as discussed further below, a SAR distribution for each remaining transmission scenario may be generated by combining two or more SAR distributions for a subset of transmission scenarios in the SAR distribution.

[0058] For example, SAR measurement may be performed for each of the antennas 122-1 to 122-N to generate a SAR distribution for each of the antennas 122-1 to 122-N. In this example, for a transmission scenario in which two or more of the antennas 122-1 to 122-N are active, a SAR distribution for the transmission scenario may be generated by combining the SAR distributions for the two or more active antennas.

[0059] In another example, SAR measurement may be performed for each of the plurality of frequency bands to generate a SAR distribution for each of the plurality of frequency bands. In this example, for a transmission scenario in which two or more frequency bands are active, a SAR distribution for the transmission scenario may be generated by combining the SAR distributions for the two or more active frequency bands.

[0060] In some aspects, the SAR distribution can be normalized relative to the SAR limit by dividing each SAR value in the SAR distribution by the SAR limit. In this case, when the normalized SAR value is greater than 1, the normalized SAR value exceeds the SAR limit, and when the normalized SAR value is less than 1, the normalized SAR value is below the SAR limit. In these aspects, each SAR distribution stored in the memory 115 can be normalized relative to the SAR limit.

[0061] In certain aspects, a normalized SAR distribution for a transmission scenario may be generated by combining two or more normalized SAR distributions. For example, for a transmission scenario in which two or more antennas are active, a normalized SAR distribution for the transmission scenario may be generated by combining the normalized SAR distributions for the two or more active antennas. For the case where different transmit power levels are used for the active antennas, the normalized SAR distribution for each active antenna may be scaled by the corresponding transmit power level before combining the normalized SAR distributions for the active antennas. The normalized SAR distribution for simultaneous transmission from multiple active antennas may be given by:

[0062]

[0063] SAR lim is the SAR limit, SAR norm combined is the combined normalized SAR distribution for simultaneous transmissions from active antennas, i is the index for the active antenna, and SAR i is the SAR distribution for the i-th active antenna, Tx i is the transmit power level for the ith active antenna, Tx SARi is the transmit power level of the SAR distribution for the i-th active antenna, and K is the number of active antennas. Equation (2) can be rewritten as follows:

[0064]

[0065] SAR norm_i is the normalized SAR distribution for the i-th active antenna. In the case of using multiple active antennas for simultaneous transmission at the same transmit frequency (e.g., multiple-input multiple-output (MIMO)), the combined normalized SAR distribution is obtained by summing the square roots of the individual normalized SAR distributions and calculating the square of the sum, as given by:

[0066]

[0067] In another example, the normalized SAR distributions for different frequency bands may be stored in the memory 115. In this example, for a transmission scenario in which two or more frequency bands are active, a normalized SAR distribution for the transmission scenario may be generated by combining the normalized SAR distributions for the two or more active frequency bands. For situations where the transmit power levels for the active frequency bands are different, the normalized SAR distribution for each active frequency band may be scaled by the corresponding transmit power level before combining the normalized SAR distributions for the active frequency bands. In this example, the combined SAR distribution may also be calculated using equation (3a), where i is the index for the active frequency band, and SARnorm_i is the normalized SAR distribution for the ith active frequency band, Tx i is the transmit power level for the ith active band, and Tx SARi is the transmit power level of the normalized SAR distribution for the ith active frequency band.

[0068] To assess RF exposure from transmissions using a second technology (e.g., 5G, IEEE 802.11ad, etc.), the wireless device 100 may include a plurality of PD distributions for the second technology stored in the memory 115. Each of the PD distributions may correspond to a respective transmission scenario of a plurality of transmission scenarios supported by the wireless device 100 for the second technology. As discussed further below, the transmission scenarios may correspond to various combinations of antennas 132-1 to 132-M, frequency bands, channels, and / or body locations.

[0069] A PD distribution (also referred to as a PD map) for each emission scenario may be generated based on measurements (e.g., electric field measurements) performed using a human body model in a test lab. As discussed further below, after the PD distribution is generated, the PD distribution is stored in memory 115 to enable processor 110 to assess RF exposure in real time. Each PD distribution includes a set of PD values, where each PD value may correspond to a different location (e.g., on a human body model).

[0070] The PD values ​​in each PD distribution correspond to a particular transmit power level (e.g., the transmit power level at which the PD values ​​were measured in a test lab). Since PD scales with transmit power level, processor 110 can scale the PD distribution for any transmit power level by multiplying each PD value in the PD distribution by the following transmit power scaling factor:

[0071]

[0072] Among them, Tx c is the current transmit power level for the corresponding transmit scenario, and Tx PD is the transmit power level corresponding to the PD value in the PD distribution (eg, the transmit power level at which the PD value was measured in a test lab).

[0073] As discussed above, the wireless device 100 may support multiple transmission scenarios for the second technology. In some aspects, the transmission scenario may be specified by a set of parameters. The set of parameters may include one or more of the following: antenna parameters indicating one or more antennas (i.e., active antennas) for transmission, band parameters indicating one or more frequency bands (i.e., active bands) for transmission, channel parameters indicating one or more channels (i.e., active channels) for transmission, body position parameters indicating the position of the wireless device 100 relative to the user's body position (head, torso, away from the body, etc.), and / or other parameters. In the case where the wireless device 100 supports a large number of transmission scenarios, it may be very time-consuming and expensive to perform measurements for each transmission scenario in a test setting (e.g., a test laboratory). In order to reduce test time, measurements may be performed for a subset of transmission scenarios to generate a PD distribution for a subset of transmission scenarios. In this example, as discussed further below, a PD distribution for each remaining transmission scenario may be generated by combining two or more PD distributions for a subset of transmission scenarios in the PD distribution.

[0074] For example, PD measurement may be performed for each of the antennas 132-1 to 132-M to generate a PD distribution for each of the antennas 132-1 to 132-M. In this example, for a transmission scenario in which two or more of the antennas 132-1 to 132-M are active, a PD distribution for the transmission scenario may be generated by combining the PD distributions for the two or more active antennas.

[0075] In another example, PD measurement may be performed for each of the plurality of frequency bands to generate a PD distribution for each of the plurality of frequency bands. In this example, for a transmission scenario in which two or more frequency bands are active, a PD distribution for the transmission scenario may be generated by combining the PD distributions for the two or more active frequency bands.

[0076] In some aspects, the PD distribution can be normalized relative to the PD limit by dividing each PD value in the PD distribution by the PD limit. In this case, when the normalized PD value is greater than 1, the normalized PD value exceeds the PD limit, and when the normalized PD value is less than 1, the normalized PD value is below the PD limit. In these aspects, each PD distribution stored in the memory 115 can be normalized relative to the PD limit.

[0077] In certain aspects, a normalized PD distribution for a transmission scenario may be generated by combining two or more normalized PD distributions. For example, for a transmission scenario in which two or more antennas are active, a normalized PD distribution for the transmission scenario may be generated by combining the normalized PD distributions for the two or more active antennas. For the case where different transmit power levels are used for the active antennas, the normalized PD distribution for each active antenna may be scaled by the corresponding transmit power level before combining the normalized PD distributions for the active antennas. The normalized PD distribution for simultaneous transmission from multiple active antennas may be given by:

[0078]

[0079] Among them PD lim is the PD limit, PD norm_combined is the combined normalized PD distribution for simultaneous transmissions from active antennas, i is the index for the active antenna, and PD i is the PD distribution for the i-th active antenna, Tx i is the transmit power level for the ith active antenna, Tx PDi is the transmit power level of the PD distribution for the i-th active antenna, and L is the number of active antennas. Equation (5) can be rewritten as follows:

[0080]

[0081] Among them PD norm_i is the normalized PD distribution for the i-th active antenna. In the case of using multiple active antennas for simultaneous transmission at the same transmit frequency (e.g., MIMO), the combined normalized PD distribution is obtained by summing the square roots of the individual normalized PD distributions and calculating the square of the sum, as given by:

[0082]

[0083] In another example, the normalized PD distributions for different frequency bands may be stored in the memory 115. In this example, for a transmission scenario in which two or more frequency bands are active, a normalized PD distribution for the transmission scenario may be generated by combining the normalized PD distributions for the two or more active frequency bands. For situations where the transmit power levels for the active frequency bands are different, the normalized PD distribution for each active frequency band may be scaled by the corresponding transmit power level before combining the normalized PD distributions for the active frequency bands. In this example, the combined PD distribution may also be calculated using equation (6a), where i is the index for the active frequency band, and PD norm_i is the normalized PD distribution for the ith active frequency band, Tx iis the transmit power level for the ith active band, and Tx PDi is the transmit power level of the normalized PD distribution for the ith active frequency band.

[0084] As discussed above, the wireless device 100 may transmit signals simultaneously using a first technology (e.g., 3G, 4G, IEEE 802.11ac, etc.) and a second technology (e.g., 5G, IEEE 802.11ad, etc.), wherein different metrics are used to measure RF exposure for the first technology and the second technology (e.g., SAR for the first technology and PD for the second technology). In this case, the processor 110 may determine: a first maximum allowable power level for the first technology and a second maximum allowable power level for the second technology for transmission that complies with the RF exposure limit in a future time slot. As further described below, during the future time slot, the transmission power levels for the first technology and the second technology are constrained (i.e., bounded) by the determined first maximum allowable power level and the second maximum allowable power level, respectively, to ensure compliance with the RF exposure limit. In the present disclosure, unless otherwise stated, the term "maximum allowable power level" refers to the "maximum allowable power level" imposed by the RF exposure limit. It should be understood that the "maximum allowable power level" is not necessarily equal to 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 allowable power level" can be used to set a power level limit for transmissions at the transmitter, such that the power level of the transmission is not allowed to exceed the "maximum allowable power level" to ensure RF exposure compliance.

[0085] The processor 110 may determine the first maximum allowable power level and the second maximum allowable power level as follows. The processor may determine a normalized SAR distribution at a first transmit power level for the first technology, determine a normalized PD distribution at a second transmit power level for the second technology, and combine the normalized SAR distribution and the normalized PD distribution to generate a combined normalized RF exposure distribution (hereinafter referred to as a combined normalized distribution). The value at each location in the combined normalized distribution may be determined by combining the normalized SAR value at the location with the normalized PD value at the location or another technique.

[0086] The processor 110 may then determine whether the first transmit power level and the second transmit power level comply with the RF exposure limit by comparing the peak value in the combined normalized distribution to 1. If the peak value is equal to or less than 1 (i.e., the condition ≤ 1 is satisfied), the processor 110 may determine that the first transmit power level and the second transmit power level comply with the RF exposure limit (e.g., SAR limit and PD limit), and use the first transmit power level and the second transmit power level as the first maximum allowable power level and the second maximum allowable power level, respectively, during the future time slot. If the peak value is greater than 1, the processor 110 may determine that the first transmit power level and the second transmit power level do not comply with the RF exposure limit. To avoid noncompliance during the future time slot, the processor 110 may reduce one or more of the first transmit power level and the second transmit power level so that the peak value in the combined normalized distribution is equal to or less than 1. In this case, the processor 110 may use the first transmit power level and the second transmit power level that comply with the RF exposure limit as the first maximum allowable power level and the second maximum allowable power level, respectively, during the future time slot. The RF exposure compliance condition for simultaneous transmission using the first technology and the second technology may be given by the following formula:

[0087] SAR norm +PD norm ≤1 (7).

[0088] During the future time slots, the processor 110 limits (constrains) the transmit power level of the first transmitter 120 by the first maximum allowable power level. For example, if the power control loop is used for the first technology, the power control loop is allowed to set the transmit power level of the first transmitter 120 to a power level equal to or lower than the first maximum allowable power level, but not to a power level that exceeds the first maximum allowable power level. During the future time slots, the processor 110 also limits (constrains) the transmit power level of the second transmitter 130 by the second maximum allowable power level. For example, if the power control loop is used for the second technology, the power control loop is allowed to set the transmit power level of the second transmitter 130 to a power level equal to or lower than the second maximum allowable power level, but not to a power level that exceeds the second maximum allowable power level.

[0089] Figure 2 A visual representation of a normalized SAR distribution 210 and a 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 Also shown is the condition where the peak value in the combined normalized distribution 230 is equal to or less than 1 to achieve RF exposure compliance. Figure 2Each of the distributions 210, 220, and 230 is depicted as a two-dimensional distribution, but it should be understood that the present disclosure is not limited to this example.

[0090] As discussed above, the normalized SAR distribution in equation (7) can be generated by combining two or more normalized SAR distributions (e.g., for a transmission scenario using multiple active antennas). Similarly, as discussed above, the normalized PD distribution in equation (7) can be generated by combining two or more normalized PD distributions (e.g., for a transmission scenario 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:

[0091]

[0092] For the MIMO case, instead, equations (3b) and (6b) may be combined. As shown in equation (8), the combined normalized distribution may be a function of the transmit power level for the first technology and the transmit power level for the second technology. All points in the combined normalized distribution should satisfy the normalization limit of 1 in equation (8). In addition, when combining the SAR and PD distributions, the SAR and PD distributions should be aligned spatially or with their peak positions so that the combined distribution given by equation (8) represents the combined RF exposure for a given location on the human body.

[0093] For the case where the wireless device 100 transmits signals simultaneously using the first technology and the second technology, the 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.

[0094] The processor 110 retrieves one or more normalized SAR distributions for the first technology from the memory 115 based on the transmission scenario for the first technology in the future time slot, and retrieves one or more normalized PD distributions for the second technology from the memory 115 based on the transmission scenario for the second technology in the future time slot. For example, if the transmission scenario for the first technology uses multiple active antennas, the processor 110 can retrieve the normalized SAR distribution for each active antenna. Similarly, if the transmission scenario for the second technology uses multiple active antennas, the processor 110 can retrieve the normalized PD distribution for each active antenna.

[0095] Then, the processor 110 can execute Figure 3 An exemplary method is illustrated for determining maximum allowable power levels for a first technology and a second technology that comply with RF exposure limits (eg, SAR limits and PD limits).

[0096] At block 310, processor 110 initializes transmit power levels for the first technology and the second technology based on transmit scenarios for the first technology and the second technology in future time slots. If the transmit scenario for the first technology uses multiple active antennas, the transmit power level may include a transmit power level for each active antenna of the first technology. Similarly, if the transmit scenario for the second technology uses multiple active antennas, the transmit power level may include a transmit power level for each active antenna of the second technology.

[0097] The transmit power levels for the first and second technologies may 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 transmit power levels may be initialized to a set of default transmit power levels.

[0098] At block 320, processor 110 determines a combined normalized distribution based on the transmit power level in block 310, the retrieved normalized SAR distribution, and the retrieved normalized PD distribution (eg, according to equation (8) discussed above).

[0099] At block 330, processor 110 compares the 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., condition ≤ 1 is satisfied), processor 110 determines that the transmit power level complies with the RF exposure limit. In this case, method 300 ends at block 350, and processor 110 uses the transmit power level as the maximum allowable power level for future time slots.

[0100] If the peak in the combined normalized distribution is greater than 1, then processor 110 adjusts the transmit power level at block 340. For example, processor 110 may adjust the transmit power level by decreasing one or more of the transmit power levels.

[0101] The processor 110 then repeats blocks 320 and 330 using the adjusted transmit power level (i.e., determines the combined normalized distribution in block 320 using the adjusted transmit power level). The processor 110 may 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 transmit power level complies with the RF exposure limit. The transmit power level that complies with the RF exposure limit is then used as the maximum allowable power level for future time slots. The maximum allowable power level includes one or more maximum allowable power levels for the first technology and one or more maximum allowable power levels for the second technology. For examples where multiple active antennas (e.g., two or more of antennas 122-1 to 122-N) are used for the first technology, the maximum allowable power level includes the maximum allowable power level for each active antenna. For examples where multiple active antennas (e.g., two or more of antennas 132-1 to 132-M) are used for the second technology, the maximum allowable power level includes the maximum allowable power level for each active antenna.

[0102] After the processor 110 determines the maximum allowable power level, the processor 110 constrains the transmit power of the first transmitter 120 during the future time slot by the determined one or more maximum allowable power levels for the first technology. For examples in which the first transmitter 120 transmits signals during the future time slot using multiple antennas (e.g., two or more of the antennas 122-1 to 122-N), the maximum allowable power level includes a maximum allowable power level for each active antenna. In this example, the processor 110 constrains the transmit power level for each active antenna by the corresponding maximum allowable power level. The processor 110 also constrains the transmit power of the second transmitter 130 during the future time slot by the determined one or more maximum allowable power levels for the second technology. For examples in which the second transmitter 130 transmits signals during the future time slot using multiple antennas (e.g., two or more of the antennas 132-1 to 132-M), the maximum allowable power level includes a maximum allowable power level for each active antenna. In this example, the processor 110 constrains the transmit power level for each active antenna by the corresponding maximum allowable power level.

[0103] It should be understood that the present disclosure is not limited to Figure 3The exemplary method 300 is illustrated, and other methods may be used to determine the maximum allowable power level for the first technology and the second technology that complies with the RF exposure limit. For example, the processor 110 may determine the maximum allowable power level that causes the peak in the combined normalized distribution to be equal to or less than a value less than 1 to perform a conservative approximation analysis, thereby determining the maximum allowable power level with fewer calculations. Therefore, a value less than 1 can be used as a condition for evaluating RF exposure compliance.

[0104] In some cases, when the first technology is inactive, the wireless device 100 may transmit signals using a second technology (e.g., 5G, IEEE 802.11ad, etc.) In these cases, RF exposure from the first technology does not need to be considered to assess RF exposure compliance.

[0105] In these cases, the processor 110 may determine the maximum allowable power level for the second technology in the future time slot that complies with the PD limit as follows. First, the processor 110 may retrieve the normalized PD distribution for the second technology from the memory 115 based on the 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 may retrieve the normalized PD distribution for each active antenna. In this example, the active antenna may be selected for transmission by the wireless device 100 in the future time slot, for example, based on a desired beam direction or sector.

[0106] Then, the processor 110 can execute Figure 4 An exemplary method is illustrated for determining a maximum allowable power level for a second technology that complies with PD limits.

[0107] At block 410, processor 110 initializes a transmit power level for the second technology based on a transmit scenario for the second technology. If the transmit scenario for the second technology uses multiple active antennas, the transmit power level may include a transmit power level for each active antenna. The transmit power level may be initialized based on a power control loop, a desired data rate, a desired beam direction or sector, etc. In one example, the transmit power level may be initialized to a set of default transmit power levels.

[0108] At block 420, processor 110 determines a combined normalized PD distribution based on the transmit power level and the retrieved normalized PD distribution in block 410 (eg, according to equation (6a) or (6b) discussed above).

[0109] At block 430, processor 110 compares the peak value in the combined normalized PD distribution to 1. If the peak value in the combined normalized PD distribution is equal to or less than 1 (i.e., condition ≤ 1 is satisfied), processor 110 determines that the transmit power level complies with the PD limit. In this case, method 400 ends at block 450, and processor 110 uses the transmit power level as the maximum allowable power level for second transmitter 130.

[0110] If the peak in the combined normalized PD distribution is greater than 1, processor 110 adjusts the transmit power level at block 440. For example, processor 110 may adjust the transmit power level by reducing one or more of the transmit power levels initialized in block 410.

[0111] The processor 110 then repeats blocks 420 and 430 using the adjusted transmit power level (i.e., determines the combined normalized PD distribution in block 420 using the adjusted transmit power level). The processor 110 may 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 transmit power level complies with the PD limit. The processor 110 then uses the transmit power level that complies with the PD limit as the maximum allowable power level for the second transmitter 130. After the processor 110 determines the maximum allowable power level that complies with the PD limit, the processor 110 constrains the transmit power for the second transmitter 130 during future time slots based on the determined maximum allowable power level. For examples in which the second transmitter 130 transmits signals using multiple active antennas (e.g., two or more of the antennas 132-1 to 132-M) during future time slots, the maximum allowable power level for the second technology includes the maximum allowable power level for each active antenna. In this example, processor 110 constrains the transmit power level for each active antenna by a respective maximum allowable power level.

[0112] It should be understood that the present disclosure is not limited to Figure 4 The exemplary method 400 is illustrated, and other methods may be used to determine the maximum allowable power level that complies with the PD limit. For example, the processor 110 may determine the maximum allowable power level that results in a peak value equal to or less than a value less than 1 to perform a conservative approximation analysis, thereby determining the maximum allowable power level with fewer calculations.

[0113] In some cases, RF exposure regulations require that the time average RF exposure within a time window does not exceed the RF exposure limit. This allows the wireless device 100 to briefly exceed the RF exposure limit as long as the time average RF exposure does not exceed the limit.

[0114] In this regard, for a case where the first technology is active and the second technology is inactive, the processor 110 may determine RF exposure compliance as follows. The processor 110 may calculate a time-averaged normalized SAR distribution within a first time window (e.g., 6 minutes) and compare a peak value in the time-averaged normalized SAR distribution with 1 to evaluate RF exposure compliance. If the peak value is equal to or less than 1 (i.e., a condition of ≤1 is satisfied), the processor 110 may determine that the RF exposure is compliant.

[0115] At this point, Figure 5 An example is shown in which the processor 110 calculates a time-averaged normalized SAR distribution within a first time window 505 (e.g., 6 minutes). In this example, the first time window 505 is divided into a plurality of time slots (i.e., time intervals). For example, a 6-minute time window may be divided into 5-second time slots. Figure 5 In the example shown, there are p number of time slots 515(1)-515(p) and p number of normalized SAR distributions 510(1)-510(p). Figure 5 Each of the distributions 510(1)-510(p) is depicted as a two-dimensional distribution in FIG. 5 , but it should be understood that the present disclosure is not limited to this example.

[0116] The processor 110 may determine a normalized SAR distribution for each time slot (e.g., according to equation (3a) or (3b)). The normalized SAR distribution for the time slot may be generated by combining two or more SAR distributions. For example, if two or more antennas are active during the time slot, the processor 110 may combine the normalized SAR distributions for the two or more active antennas to generate a normalized SAR distribution for the time slot. For situations where different transmit power levels are used for the active antennas, the processor 110 may scale the normalized SAR distribution for each active antenna by the transmit power level used for the antenna.

[0117] In certain aspects, the transmission scenario and / or the transmission power level for the first technology may vary within the first time window 505. In these aspects, the transmission scenario may be approximately constant within a time slot, but may vary between time slots within the first time window 505. The processor 110 may determine a normalized SAR distribution for each time slot (e.g., according to equation (3a) or 3(b)) based on the transmission scenario and the time-averaged transmission power level for the time slot.

[0118] The processor 110 may average the normalized SAR distributions 510(1)-510(p) within the first time window 505 to generate a time-averaged normalized SAR distribution 520. For example, the processor 110 may calculate 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 given by:

[0119]

[0120] SAR norm_j 510(j) represents the normalized SAR distribution for the j-th time slot 510(j). As discussed above, the normalized SAR distribution for a time slot may be a combination of multiple SAR distributions for the time slot (e.g., for the case of multiple active antennas). The processor 110 may then compare the peak value in the time-averaged normalized SAR distribution 520 with 1 to assess RF exposure compliance. If the peak value is equal to or less than 1 (i.e., the condition ≤ 1 is satisfied), the processor 110 may determine that the RF exposure is compliant.

[0121] In some aspects, processor 110 may determine a maximum allowable power level for future time slots to ensure time-averaged RF exposure compliance. In this regard, Figure 5 The time slots 515(1)-515(p-1) in may correspond to previous transmissions of the wireless device 100, and the time slot 515(p) may correspond to a future time slot. In this regard, the time slot 515(p) is referred to below as a future time slot. Equation (9a) may be written as follows:

[0122]

[0123] SAR norm_p is the SAR distribution for the future time slot 515(p).

[0124] In this example, it is assumed that the transmit power levels for the normalized SAR distributions 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 may record the transmit power levels and transmission scenarios for each of the time slots 515(1)-515(p-1) in the memory 115 and use the recorded transmit power levels and transmission scenarios for the time slots 515(1)-515(p-1) to determine the normalized SAR distributions 510(1)-510(p-1) for these time slots. For the time slots 515(1)-515(p-1), the normalized SAR distribution for the jth time slot 515(j) may be determined using equations (3a) or (3b) for all transmission scenarios and power levels active during the jth time slot 515(j).

[0125] In this example, the transmit power level for the normalized SAR distribution 510(p) corresponding to the future time slot 515(p) is a variable to be solved by the processor 110. To determine the maximum allowable power level for the future time slot 515(p), the processor 110 may calculate a time-averaged normalized SAR distribution 520, where the transmit power level for the future time slot 515(p) is a variable in the time-averaged normalized SAR distribution 520 (i.e., the time-averaged normalized SAR distribution is a function of the transmit power level for the future time slot 515(p)). The processor 110 may then determine the transmit power level for the future time slot 515(p) such that the peak value in the time-averaged normalized SAR distribution is equal to or less than 1 (i.e., satisfies the condition ≤ 1 in equation (9b)). The processor 110 uses the transmit power level that satisfies the condition for RF exposure compliance as the maximum allowable power level for the future time slot 515(p), and sets the transmit power limit for the future time slot 515(p) based on the determined maximum allowable power level. The processor 110 can determine the maximum allowable power level for the future time slot 515(p) during the time slot 515(p-1) so that at the beginning of the future time slot 515(p), the maximum allowable power level for the future time slot 515(p) is ready for the processor 110 to enforce the maximum allowable power level.

[0126] The processor 110 may Figure 6The illustrated exemplary method 600 is used to determine the maximum allowable power level for the future time slot 515(p). At block 610, the processor 110 initializes the transmit power level for the future time slot 515(p) based on the transmission scenario for the future time slot 515(p). The transmit power level may be initialized based on a power control loop, a desired data rate, a desired beam direction or sector, etc. In one example, the transmit power level may be initialized to a set of default transmit power levels.

[0127] At block 620, processor 110 determines a time-averaged normalized SAR distribution based on the transmit power level and the transmit scenario at block 610 for the future time slot 515(p). Note that, as discussed above, the transmit power levels for the previous time slots 515(1)-515(p-1) are known.

[0128] At block 630, the processor 110 compares the peak value in the time-averaged normalized SAR distribution to 1 to assess RF exposure compliance. If the peak value is equal to or less than 1, the method 600 ends at block 650. In this case, the processor 110 uses the transmit power level initialized at block 610 as the maximum allowable power level for future time slots 515(p).

[0129] If the peak value is greater than 1, the processor 110 adjusts the transmit power level for the future time slot at block 640. The processor 110 may adjust the transmit power level for the future time slot by reducing one or more of the transmit power levels for the future time slot. The processor 110 then repeats blocks 620 and 630 using the adjusted transmit power levels. The processor 110 may repeat blocks 640, 620, and 630 until the peak value in the time-averaged normalized SAR distribution is equal to or less than 1, at which point the transmit power level complies with the SAR limit, and the processor 110 uses the transmit power level that complies with the SAR limit as the maximum allowable power level for the future time slot 515(p).

[0130] For an example in which the first transmitter 120 transmits signals using multiple active antennas (e.g., two or more of the antennas 122-1 through 122-N) during the future time slot 515(p), the maximum allowable power level may include a maximum allowable power level for each active antenna. In this example, the processor 110 limits (constrains) the transmit power level for each active antenna by the corresponding maximum allowable power level.

[0131] It should be understood that the present disclosure is not limited to Figure 6The exemplary method 600 is illustrated, and other methods may be used to determine the transmit power level for the future time slot 515(p) so that the time-averaged normalized SAR distribution complies with the SAR limit. For example, the processor 110 may determine the maximum allowable power level that causes the peak value of the time-averaged normalized SAR distribution to be equal to or less than a value less than 1 to perform a conservative approximation analysis, thereby determining the maximum allowable power level with fewer calculations.

[0132] In some cases, regulatory agencies may require that the time averaged PD distribution for the second technology does 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 distribution does not exceed the PD limit.

[0133] In this regard, for the case where the second technology is active and the first technology is inactive, the processor 110 may determine RF exposure compliance as follows. The processor 110 may calculate a time-averaged normalized PD distribution within a second time window (e.g., 2 minutes) and compare a peak value in the time-averaged normalized PD distribution with 1 to evaluate RF exposure compliance. If the peak value is equal to or less than 1 (i.e., a condition of ≤1 is satisfied), the processor 110 may determine that the RF exposure is compliant.

[0134] At this point, Figure 7 An example is shown in which the processor 110 calculates a time-averaged normalized PD distribution within 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 may be divided into 5-second time slots. Figure 7 In the example shown, there are q number of time slots 715(1)-715(q) and q number of normalized PD distributions 710(1)-710(q). Figure 7 Each of distributions 710(1)-710(q) is depicted as a two-dimensional distribution in FIG. 1 , but it should be understood that the present disclosure is not limited to this example.

[0135] The processor 110 may determine a normalized PD distribution for each time slot (e.g., according to equation (6a) or (6b)). The normalized PD distribution for a time slot may be generated by combining two or more PD distributions. For example, if two or more antennas are active during the time slot, the processor 110 may combine the normalized PD distributions for the two or more active antennas to generate a normalized PD distribution for the time slot. For the case where different transmit power levels are used for the active antennas, the processor 110 may scale the normalized PD distribution for each active antenna by the corresponding transmit power level.

[0136] In certain aspects, the transmission scenario and / or the transmission power level for the second technology may vary within the second time window 705. In these aspects, the transmission scenario may be approximately constant within a time slot, but may vary between time slots within the second time window 705. The processor 110 may determine a normalized PD distribution for each time slot (e.g., according to equation (6a) or (6b)) based on the transmission scenario and the time-averaged transmission power level during the time slot.

[0137] The processor 110 may average the normalized PD distributions 710(1)-710(q) within the second time window 705 to generate a time-averaged normalized PD distribution 720. For example, the processor 110 may calculate the time-averaged normalized PD distribution 720 by combining the normalized PD distributions 710(1)-710(q) for time slots 715(1)-715(q) and dividing the resulting combined normalized PD distribution by the number of time slots, as given by:

[0138]

[0139] Among them PD norm_j denoted the normalized PD distribution for the j-th time slot 710(j). As discussed above, the normalized PD distribution for a time slot may be a combination of multiple normalized PD distributions for the time slot (e.g., for the case of multiple active antennas). The processor 110 may then compare the peak value in the time-averaged normalized PD distribution 720 with 1 to assess RF exposure compliance. If the peak value is equal to or less than 1 (i.e., the condition ≤ 1 is satisfied), the processor 110 may determine that the RF exposure is in compliance.

[0140] In some aspects, processor 110 may determine a maximum allowable power level for future time slots to ensure time-averaged RF exposure compliance. In this regard, Figure 7 The time slots 715(1)-715(q-1) in may correspond to previous transmissions of the wireless device 100, and the time slot 715(q) may correspond to future transmissions. In this regard, the time slot 715(q) is referred to below as a future time slot. Equation (10a) may be rewritten as follows:

[0141]

[0142] Among them PD norm_q is the normalized PD distribution for the future time slot 715(q).

[0143] In this example, it is assumed that the transmit power levels for the normalized PD distributions 710(1)-710(q-1) are known to the processor 110 because they correspond to previous transmissions by the wireless device 100. For example, the processor 110 may record the transmit power levels and transmission scenarios for each of the time slots 715(1)-715(q-1) in the memory 115 and use the recorded transmit power levels and transmission scenarios for the time slots 715(1)-715(q-1) to determine the normalized PD distributions 710(1)-710(q-1) for these time slots. For the time slots 715(1)-715(q-1), the normalized PD distribution 710(j) for the jth time slot 715(j) may be determined using equations (6a) or (6b) for all transmission scenarios and power levels active during the jth time slot 715(j).

[0144] In this example, the transmit power level for the normalized PD distribution 710(q) corresponding to the future time slot 715(q) is a variable to be solved by the processor 110. In order to determine the maximum allowable power level for the future time slot 715(q), the processor 110 can calculate the time-averaged normalized PD distribution 720, where the transmit power level for the future time slot 715(q) is a variable in the time-averaged normalized PD distribution 720 (i.e., the time-averaged normalized PD distribution 720 is a function of the transmit power level for the future time slot 715(q)). The processor 110 can then determine the transmit power level for the future time slot 715(q) so that the peak value in the time-averaged normalized PD distribution is equal to or less than 1 (i.e., satisfies the condition ≤1 in equation (10b)). The determined transmit power level that complies with the RF exposure level is used as the maximum allowable power level for the future time slot 715(q). In this regard, the processor 110 sets the transmit power limit for the future time slot 715(q) based on the determined maximum allowable power level. The processor 110 may determine the maximum allowable power level for the future time slot 715(q) during the time slot 715(q-1) such that at the start of the future time slot 715(q), the maximum allowable power level for the future time slot 715(q) is ready for the processor 110 to enforce the maximum allowable power level.

[0145] The processor 110 may Figure 8The illustrated exemplary method 800 is used to determine the maximum allowable power level for the future time slot 715 (q). At block 810, the processor 110 initializes the transmit power level for the future time slot 715 (q) based on the transmission scenario for the future time slot 715 (q). For example, the transmit power level can be initialized based on a power control loop, a desired data rate, a desired beam direction or sector, etc. In one example, the transmit power level can be initialized to a set of default transmit power levels.

[0146] At block 820, processor 110 determines a time-averaged normalized PD distribution based on the transmit power level and transmit scenario at block 810 for the future time slot 715(q). Note that, as discussed above, the transmit power levels for the previous time slots 715(1)-715(q-1) are known.

[0147] At block 830, the processor 110 compares the peak value in the time-averaged normalized PD distribution to 1 to assess RF exposure compliance. If the peak value is equal to or less than 1, the method 800 ends at block 850. In this case, the processor 110 uses the transmit power level initialized at block 810 as the maximum allowable power level for future time slots 715(q).

[0148] If the peak value is greater than 1, the processor 110 adjusts the transmit power level 810 for the future time slot at block 840. The processor 110 may adjust the transmit power level for the future time slot 715(q) by reducing one or more of the transmit power levels for the future time slot 715(q). The processor 110 then repeats blocks 820 and 830 using the adjusted transmit power levels. The processor 110 may repeat blocks 840, 820, and 830 until the peak value in the time-averaged PD distribution is equal to or less than 1, at which point the transmit power level complies with the PD limit and the processor 110 uses the transmit power level as the maximum allowable power level for the future time slot 715(q).

[0149] For an example in which the second transmitter 130 transmits signals using multiple active antennas (e.g., two or more of the antennas 132-1 through 132-M) during the future time slot 715(q), the maximum allowable power level may include a maximum allowable power level for each active antenna. In this example, the processor 110 limits (constrains) the transmit power level for each active antenna by the corresponding maximum allowable power level.

[0150] It should be understood that the present disclosure is not limited to Figure 8The exemplary method 800 is illustrated, and other methods may be used to determine the transmit power level for the future time slot 715 (q) so that the time-averaged normalized PD distribution complies with the PD limit. For example, the processor 110 may determine the following maximum allowable power level for the future time slot 715 (q) that causes the peak in the time-averaged normalized PD distribution to be approximately equal to or less than a value less than 1.

[0151] For situations where both the first technology and the second technology are active (i.e., the wireless device transmits signals using the first technology and the second technology simultaneously), the processor 110 may also determine time-averaged RF exposure compliance. Fig. 9 As illustrated, the processor 110 may combine the time-averaged normalized SAR distribution 520 and the time-averaged normalized PD distribution 720 to generate a combined time-averaged normalized distribution 920. The processor 110 may then compare the peak value in the combined time-averaged normalized distribution 920 with 1 to assess the time-averaged RF exposure compliance. If the peak value is equal to or less than 1 (i.e., the condition ≤ 1 is satisfied), the processor 110 may determine that the wireless device 100 is compliant. The compliance condition may be given by combining equations (9b) and (10b) as follows:

[0152]

[0153] The lengths of the first time window 505 for the time-averaged normalized SAR distribution and the second time window 705 for the time-averaged normalized PD distribution may be different. Fig. 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 may be approximately 6 minutes, and the length of the second time window 705 may be approximately 2 minutes. The lengths of the first time window and the second time window may be specified by corresponding RF exposure regulations (e.g., established by the FCC or other regulatory authorities). Note that the lengths of the time windows 505 and 705 are different in length. Fig. 9 Not drawn to scale.

[0154] In some aspects, the processor 110 may determine the maximum allowable power levels for the first technology and the second technology for future time slots 515(p) and 715(q) to ensure time-averaged RF exposure compliance. Fig. 9As shown in the example in , the future time slots 515 (p) and 715 (q) can be approximately aligned in time. In order to determine the maximum allowable power level for the future time slots 515 (p) and 715 (q), the processor 110 can calculate the combined time average normalized distribution 920, where the transmit power level for the future time slots 515 (p) and 715 (q) is a variable in the combined time average normalized distribution 920 (i.e., the combined time average normalized distribution 920 is a function of the transmit power level for the future time slots 515 (p) and 715 (q)). Then, the processor 110 can determine the maximum allowable power level for the future time slots 515 (p) and 715 (q) so that the peak value in the combined time average normalized distribution 920 is equal to or less than 1 (i.e., the condition ≤ 1 in equation (11) is satisfied). Then, the processor 110 can set the transmit power limit for the future time slots 515 (p) and 715 (q) based on the determined maximum allowable power level.

[0155] The processor 110 may Fig.10 The illustrated exemplary method 1000 determines maximum allowable power levels for future time slots 515(p) and 715(q). The maximum allowable power levels may include a first maximum allowable power level for a first technology and a second maximum allowable power level for a second technology.

[0156] At block 1010, processor 110 initializes transmit power levels for future time slots 515(p) and 715(q) based on the transmit scenarios for the future time slots 515(p) and 715(q). If the transmit scenario for the future time slot 515(p) of the first technology uses multiple active antennas, the transmit power levels may include transmit power levels for each active antenna. Similarly, if the transmit scenario for the future time slot 715(q) of the second technology uses multiple active antennas, the transmit power levels may include transmit power levels for each active antenna.

[0157] The transmit power level may 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 transmit power level may be initialized to a set of default transmit power levels.

[0158] At block 1020, processor 110 determines a combined time-averaged normalized distribution 920 based on the transmit power levels for future time slots 515(p) and 715(q). Note that, as discussed above, the transmit power levels in previous time slots 515(1)-515(p-1) for the first technology and the transmit power levels in previous time slots 715(1)-715(q-1) for the second technology are known.

[0159] At block 1030, processor 110 compares the peak value in the combined time-averaged normalized distribution to 1 to assess RF exposure compliance. If the peak value is equal to or less than 1, method 1000 ends at block 1050. In this case, processor 110 uses the transmit power level initialized at block 1010 as the maximum allowable power level for future time slots 515(p) and 715(q).

[0160] If the peak value is greater than 1, the processor 110 adjusts the transmit power level for the future time slot at block 1040. The processor 110 may adjust the transmit power level for the future time slot by reducing one or more of the transmit power levels for the future time slot. The processor 110 then repeats blocks 1020 and 1030 using the adjusted transmit power level. The processor 110 may repeat blocks 1040, 1020, and 1030 until the peak value in the combined time-averaged normalized distribution is equal to or less than 1, at which point the transmit power level for the future time slot is compliant and the processor 110 uses the transmit power level as the maximum allowable power level. The determined maximum allowable power level includes a first maximum allowable power level for the first technology and a second maximum allowable power level for the second technology. At this point, the processor 110 sets a transmit power limit for the first transmitter 120 according to the first maximum allowable power level, and sets a transmit power limit for the second transmitter 130 according to the second maximum allowable power level.

[0161] It should be understood that the present disclosure is not limited to Fig.10 The illustrated exemplary method 1000, and other methods may be employed to determine the maximum allowable power levels for future time slots 515(p) and 715(q) such that the combined time-averaged normalized distribution 920 complies with the RF exposure limits.

[0162] In some aspects, the time-average window used for PD depends on the transmission frequency (e.g., ~2 minutes in the 28 GHz band and ~1 minute in the 60 GHz band). In these aspects, when the second transmitter 130 transmits signals at multiple frequency bands, a different time window can be used for each frequency band to calculate the time-averaged PD distribution. For example, if the second transmitter 130 transmits signals at 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:

[0163]

[0164] Where q is the number of time slots for a first frequency band (e.g., 28 GHz band), and r is the number of time slots for a second frequency band (e.g., 60 GHz band). Since different time windows are used for the first frequency band and the second frequency band, the number of time slots for the frequency band is different from the number of time slots for the second frequency band (i.e., q and r are different).

[0165] Fig.11 An example is shown in which two time averaging windows are used for PD. In this example, the second time window 705 discussed above is used for a first frequency band (e.g., a 28 GHz band), and the third time window 1105 is used for a second frequency band (e.g., a 60 GHz band), where the third time window 1105 is shorter than the second time window 705. For example, the second time window 705 may have a length of approximately two minutes, and the third time window 1105 may have a length of approximately one minute.

[0166] like Fig.11 As shown, the third time window 1105 is divided into a number r of time slots 1115(1) to 1115(r). For the second frequency band, there are a number r of normalized PD distributions 1110(1) to 1110(r), where each normalized PD distribution corresponds to a corresponding time slot in the time slots 1115(1) to 1115(r). In this example, the time slots 1115(1) to 1115(r-1) correspond to previous time slots, and the time slot 1115(r) corresponds to a future time slot approximately aligned with the future time slots 515(p) and 715(q).

[0167] In this example, a normalized PD distribution for each of the previous time slots 715(1) to 715(q-1) in the second time window 705 may be determined based on the transmission scenario and the transmission power level for the first frequency band during the time slot. The normalized PD distribution for the future time slot 715(q) is a function of the transmission power level for the first frequency band in the future time slot 715(q). Similarly, a normalized PD distribution for each of the previous time slots 1115(1) to 1115(r-1) in the third time window 1105 may be determined based on the transmission scenario and the transmission power level for the second frequency band during the time slot. The normalized PD distribution for the future time slot 1115(r) is a function of the transmission power level for the second frequency band in the future time slot 1115(r).

[0168] The time-averaged normalized PD distribution 720 may be calculated according to equation (12) above, where the time-averaged normalized PD distribution is a function of the transmit power level for the first frequency band in future time slots 715(q) and the transmit power level for the second frequency band in future time slots 1115(r).

[0169] In this example, the time-averaged normalized PD distribution 720 is a combination of the time-averaged normalized PD distribution for the first frequency band corresponding to the second time window 705 and the time-averaged normalized PD distribution for the second frequency band corresponding to the third time window 1105. In this regard, the time-averaged PD distribution 720 may be considered a combined time-averaged PD distribution.

[0170] For examples where the wireless device 100 also transmits signals using the first technology, the time-averaged normalized PD distribution can be combined with the time-averaged normalized SAR distribution to obtain the combined time-averaged normalized distribution discussed above. In this example, the combined time-averaged normalized distribution is a function of the transmission scenario and transmit power level for the first technology in the future time slot 515 (p), the transmission scenario and transmit power level for the first frequency band in the future time slot 715 (q), and the transmission scenario and transmit power level for the second frequency band in the future time slot 1115 (r). The maximum allowable power level can be determined by determining the transmit power level that causes the peak of the combined time-averaged normalized distribution to be equal to or less than 1 (e.g., based on Fig.10 1000). In this example, the maximum allowable power levels include: a maximum allowable power level for a first technology, a maximum allowable power level for a first frequency band, and a maximum allowable power level for a second frequency band. During future time slots 515(p), 715(q), and 1115(r), processor 110 sets a transmit power limit for the first technology based on the maximum allowable power level for the first technology, sets a transmit power limit for the first frequency band based on the maximum allowable power level for the first frequency band, and sets a transmit power limit for the second frequency band based on the maximum allowable power level for the second frequency band.

[0171] Although two time averaging windows 705 and 1105 are used for PD in the above example, it should be understood that more than two time averaging windows may be used depending on the number of different frequency bands above 10 GHz that are active. In general, the number of time averaging windows used for PD may be equal to the number of active frequency bands above 10 GHz, with each time averaging window corresponding to a respective one of the active frequency bands.

[0172] In some aspects, when the first technology is not active, the wireless device 110 can transmit signals simultaneously at the first frequency band and the second frequency band (e.g., 28 GHz and 60 GHz). In this case, the processor 110 can determine the maximum allowable power levels for the first frequency band and the second frequency band as follows. The processor can determine the time-averaged normalized PD distribution according to equation (12), where the time-averaged normalized PD distribution is a function of the transmit power level for the first frequency band in the future time slot 715 (q) and the transmit power level for the second frequency band in the future time slot 1115 (r). An example of this situation is Fig.12 The middle figure shows where the condition for compliance with RF exposure is that the time-averaged normalized PD distribution 720 is equal to or less than 1. Note that the time-averaged normalized PD distribution is not combined with the time-averaged normalized SAR distribution 520 in this case since the first technique is not active in this case.

[0173] The processor 110 may then: determine the transmit power levels for the first frequency band and the second frequency band that result in a peak in the time-averaged normalized PD distribution being equal to or less than 1, and use the determined transmit power levels as the maximum allowable power levels. In this example, the maximum allowable power levels include the maximum allowable power level for the first frequency band and the maximum allowable power level for the second frequency band. During future time slots 715(q) and 1115(r), the processor 110 sets the transmit power limit for the first frequency band based on the maximum allowable power level for the first frequency band, and sets the transmit power limit for the second frequency band based on the maximum allowable power level for the second frequency band. It should be understood that the above techniques can be extended to three or more frequency bands to determine the maximum allowable power levels for the three or more frequency bands.

[0174] Some RF exposure regulations may not require time averaging of PD, or may not currently specify time averaging for PD (this may change). In these cases, the time-averaged SAR distribution can be combined with the normalized PD distribution to assess RF exposure compliance. An example of this is in Fig.13 The middle figure shows that the time-averaged normalized SAR distribution 520 is combined with the normalized PD distribution for the future time slot 715 ( q ) to obtain a combined normalized distribution 920 .

[0175] In this example, the processor 110 may determine the maximum allowable power levels for the first technology and the second technology 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 transmit power level for the first technology in the future time slot 515(p) and the transmit power level for the second technology in the future time slot 715(q).

[0176] Processor 110 may then determine transmit power levels for the first technology and the second technology that result in a peak in normalized distribution 920 equal to or less than 1, and use the determined transmit power levels as maximum allowable power levels. In this example, the maximum allowable power levels include a maximum allowable power level for the first technology and a maximum allowable power level for the second technology. During future time slots 515(p) and 715(q), processor 110 sets a transmit power limit for first transmitter 120 based on the maximum allowable power level for the first technology, and sets a transmit power limit for second transmitter 130 based on the maximum allowable power level for the second technology.

[0177] It should be understood that the lengths of the time slots 515(1)-515(p) discussed above 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 that is equal to or less than one-tenth the length of the first time window 505. In one example, the length of the future time slot 515(p) is approximately 5 seconds, and the length of the first time window 505 is approximately 6 minutes.

[0178] It should be understood that the lengths of the time slots 715(1)-715(q) discussed above may be equal, or two or more of the time slots 715(1)-715(q) may have different lengths. The future time slot 715(q) may also be referred to as a time interval, and may have a length equal to or less than one-fifth of the length of the second time window 705. In one example, the length of the future time slot 715(q) is approximately 5 seconds, and the length of the second time window 705 is approximately 2 minutes.

[0179] It should be understood that the lengths of the time slots 1115(1)-1115(r) discussed above can be equal, or two or more of the time slots 1115(1)-1115(r) can have different lengths. The future time slot 1115(r) can also be referred to as a time interval, and can have a length equal to or less than one-fifth of the length of the third time window 1105. In one example, the length of the future time slot 1115(r) is approximately 5 seconds, and the length of the third time window 1105 is approximately one minute.

[0180] 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 length of the first time window 505 is approximately 6 minutes, and the length of the second time window 705 is approximately 2 minutes, wherein the lengths of the first time window and the second time window can be set by the regulatory authority. It should be understood that the lengths of the first time window 505 and the second time window 705 set by the regulatory authority can change over time and can vary between different regulatory authorities. As discussed above, the regulatory authority can define a time window that depends on the transmit frequency, for example, for the 28 GHz band, the time window length is 2 minutes, and for the 60 GHz band, the time window length is 1 minute. In that case, it should also be understood that there may be one time window for SAR, and there may be two or more time windows for PD, wherein each time window for PD corresponds to a given transmit frequency band.

[0181] As used herein, the term "previous time slot" refers to a time slot before a corresponding future time slot. Figure 5 The time slots 515(1)-515(p-1) in are previous time slots, which precede the future time slot 515(p).

[0182] As used herein, the term "future time slot" refers to a time slot (i.e., time interval or duration) in the future relative to the time when the corresponding maximum allowable power level is determined. Determining the maximum allowable power level for the future time slot in advance of the future time slot helps ensure RF exposure compliance during the future time slot. Because the future time slots 515 (p), 715 (q), and 1115 (r) discussed above are approximately aligned in time, they can be collectively considered to be one future time slot.

[0183] It should be understood that the time windows discussed above (e.g., time windows 505, 705, and 1105) can be moving time average windows. In this case, each time the maximum allowable power level for a new future time slot is determined, each time window is shifted by one time slot. For example, in the above discussion of time window 505, time slot 515(p) is given as a future time slot. In order to determine the maximum allowable power level for the next future time slot 515(p+1), processor 110 shifts time window 505 by one time slot to cover time slots 515(2) to 515(p+1). Note that the first time slot 515(1) in the previously determined maximum allowable power level is discarded from time window 505, and the future time slot 515(p) in the previously determined maximum allowable power level becomes the last of the previous time slots in time window 505.

[0184] It should be understood that the first communication technology discussed above may include multiple communication technologies in which SAR is used to assess RF exposure compliance. For example, the first technology may include WWAN, WLAN, Bluetooth, etc. In this regard, it should be understood that the first transmitter 120 may include multiple transmitters. Likewise, it should be understood that SAR may have contributions from multiple sub-6 GHz communication technologies (e.g., simultaneous transmissions of WWAN, WLAN, and Bluetooth).

[0185] It should be understood that the second communication technology discussed above may include multiple communication technologies in which the PD is used to assess RF exposure compliance. For example, the second technology may include mmWave / 5G and mmWave / 802.11ad. In this regard, it should be understood that the second transmitter 130 may include multiple transmitters. Likewise, it should be understood that the PD may have contributions from multiple communication technologies (e.g., simultaneous transmission of mmWave / 5G and mmWave / 802.11ad).

[0186] In some of the examples given above, the normalized distribution is compared to 1 to assess RF exposure compliance. However, it should be understood 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.) may be normalized relative to any value so that a limit value other than 1 may be used to define a condition for RF exposure compliance. In this example, the condition for RF compliance is that the normalized distribution is equal to or less than the limit value. Similarly, as discussed above, the limit value may be set to a value less than 1.

[0187] As discussed above, the processor 110 may determine a maximum allowable 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 transmit power limit for the transmitter based on the determined maximum allowable power level. In some aspects, setting the transmit power limit based on the determined maximum allowable power level prevents the power level of the transmitter from exceeding the maximum allowable power level at any time during the future time slot. In some aspects, setting the transmit power limit based on the determined maximum allowable power level prevents the time average of the power level of the transmitter in the future time slot from exceeding the maximum allowable power level. This allows the power level to temporarily exceed the maximum allowable power level in the future time slot, as long as the time average of the power level in the future time slot does not exceed the maximum allowable power level. In these aspects, the power level may exceed the maximum allowable power level for a time interval shorter than the future time slot. In these aspects, the maximum allowable power level is the maximum allowable time average power level in the future time slot.

[0188] Fig.14 An example method 1400 implemented in a wireless device (eg, wireless device 100 ) in accordance with certain aspects of the present disclosure is illustrated.

[0189] At block 1410, a specific absorption rate (SAR) distribution is determined for a first wireless communication technology. For example, the SAR distribution may include a time-averaged SAR distribution corresponding to a time-averaged window (e.g., time window 505). The first wireless communication technology may include one or more of: WWAN, WLAN, 3G, 4G, Bluetooth, etc.

[0190] At block 1420, a power density (PD) distribution for a second wireless communication technology is determined. For example, the PD distribution may include a time-averaged PD distribution corresponding to one or more time-averaged windows (e.g., time windows 705 and / or 1105). The second wireless communication technology may include one or more of the following: 5G, IEEE 802.11ad, etc.

[0191] At block 1430 , the SAR distribution and the PD distribution are combined to generate a combined RF exposure distribution.

[0192] At block 1440, at least one first maximum allowable power level and at least one second maximum allowable power level for the future time slot are determined based on the combined RF exposure distribution. For example, the combined RF exposure distribution may be a function of the transmit power level in the future time slot. In this example, the at least one first maximum allowable power level and at least one second maximum allowable power level may be determined by determining a power level for the transmit power level that results in a peak value of the combined RF exposure distribution being equal to or less than a limit value (e.g., a limit value of 1) that ensures RF exposure compliance.

[0193] At least one transmit power limit for a first transmitter in a future time slot is set based on the at least one first maximum allowable power level at block 1450. Setting at least the transmit power limit for a first transmitter (e.g., first transmitter 120) based on the at least one first maximum allowable power level may limit the transmit power level of the first transmitter in the future time slot to the at least one first maximum allowable power level or limit the time-averaged transmit power level of the first transmitter in the future time slot to the at least one first maximum allowable power level.

[0194] At block 1460, at least one transmit power limit for a second transmitter in a future time slot is set based on the at least one second maximum allowable power level. Setting at least the transmit power limit for a second transmitter (e.g., second transmitter 130) based on the at least one second maximum allowable power level may limit the transmit power level of the second transmitter in the future time slot to the at least one second maximum allowable power level or limit the time-averaged transmit power level of the second transmitter in the future time slot to the at least one second maximum allowable power level.

[0195] It should be understood that method 1400 is not limited to Fig.14 The exemplary order shown. For example, block 1420 can be performed before block 1410, or both blocks 1410 and 1420 can be performed simultaneously. Similarly, block 1460 can be performed before block 1450, or both blocks 1450 and 1460 can be performed simultaneously.

[0196] In the above reference Fig. 9In the exemplary time averaging method discussed, the processor 110 determines a time-averaged SAR distribution 505 for a first technology within a first time window 505, and determines a time-averaged PD distribution 705 for a second technology within a second time window 705, wherein the first time window 505 and the second time window 705 have different durations (i.e., different lengths). The processor 110 then combines the time-averaged SAR distribution 505 and the time-averaged PD distribution 705 to obtain a combined time-averaged distribution 920, and determines a maximum allowable power level for the first technology and a maximum allowable power level for the second technology for a future time slot based on the combined time-averaged distribution 920. The processor 110 may make this determination every Δt seconds, where Δt seconds (e.g., 5 seconds) is the duration of one time slot. In this case, the processor 110 updates the maximum allowable power level for the first technology and the maximum allowable power level for the second technology every Δt seconds (e.g., 5 seconds), and as discussed above, the first time window 505 and the second time window 705 are moving time averaging windows. In Fig. 9 In the example shown, the same slot duration (eg, 5 seconds) is used for the first technology and the second technology.

[0197] The maximum peak-to-average ratio (PAR) for each technology in the future time slot can be given by:

[0198] PAR max =10*log10(time_window / Δt) (13)

[0199] PAR max is the maximum allowable PAR, time_window is the duration of the corresponding time averaging window (e.g., the first time window 505 for the first technology and the second time window 705 for the second technology), and Δt is the duration of the future time slot. Here, the average transmit power level for each technology in the future time slot is given by the corresponding maximum allowable power level determined for the future time slot.

[0200] For example, if the first time window 505 for the first technology is 100 seconds and Δt is 5 seconds, the maximum allowable PAR for the first technology is equal to 20 dB. If the second time window 705 for the second technology is 30 seconds and Δt is 5 seconds, the maximum allowable PAR for the second technology is equal to 7.8 dB. The problem with this is that the second technology (e.g., millimeter wave communication) may require a high PAR. For example, for millimeter wave communication, the average transmit power may be approximately 8 dBm, and a transmit power of more than 23 dBm may be required to maintain a radio link at the cell edge, which translates to a PAR of more than 15 dB.

[0201] By reducing Δt (i.e., the duration of one time slot), the maximum PAR for one technology (e.g., the second technology) may be increased. Reducing Δt causes the processor 110 to update the maximum allowable power level for the first technology and the maximum allowable power level for the second technology more frequently, which consumes more computing resources for both technologies. However, for another technology (e.g., the first technology) that has already met its PAR requirement, it may not be necessary to reduce Δt in order to meet the PAR requirement for one technology (e.g., the second technology). In this case, reducing Δt (i.e., the duration of one time slot) results in an unnecessary increase in computing resources for the other technology (e.g., the first technology).

[0202] To address this issue, aspects of the present disclosure allow the maximum allowable power levels for different technologies to be updated at different rates while still meeting overall RF exposure compliance, as discussed further below.

[0203] In some aspects, the maximum allowable power level for the second technology is updated at a smaller time interval than the first technology so as to increase the maximum allowable PAR for the second technology without increasing the computational load for the first technology. Fig.15 As shown, the future time slot 715(q) for the second technology is further divided (split) into smaller time slots 1515(1) to 1515(N). As discussed further below, the processor 110 can determine a normalized PD distribution 1520(1) to 1520(N) for each of the smaller time slots 1515(1) to 1515(N). In the following description, for ease of discussion, the smaller time slots 1515(1) to 1515(N) are referred to as sub-time slots.

[0204] In these aspects, the processor 110 determines the maximum allowable power level for future time slots 715 (q) in an outer loop. In the outer loop, the processor 110 determines the maximum allowable power level for future time slots 715 (q) based on the combined time-averaged RF exposure profile 920 as discussed above to ensure overall RF exposure compliance. As discussed above, the processor 110 updates the maximum allowable power level for future time slots 715 (q) every Δt seconds (i.e., the duration of one time slot). For example, if the duration of one time slot is 5 seconds, the processor 110 determines the maximum allowable power level for future time slots 715 (q) every 5 seconds. Note that in the outer loop, the same time slot duration is used for the first technology and the second technology to meet overall RF exposure compliance. Reference above Fig. 9 The operation of the outer loop is discussed in greater detail according to certain aspects.

[0205] In the inner loop, processor 110 determines the maximum allowable power level for sub-time slots 1515(1) through 1515(N), one at a time, at a rate of approximately 1 per Δt / N seconds, where N is the number of sub-time slots in future time slot 715(q) and Δt is the duration of future time slot 715(q). For example, if N equals 50 and Δt equals 5 seconds, processor 110 determines the maximum allowable power level for one of sub-time slots 1515(1) through 1515(N) approximately every 100 milliseconds. Thus, the inner loop increases the update rate by a factor of N. As discussed above, the higher update rate increases the PAR for the second technology (e.g., millimeter wave communications).

[0206] For the inner loop, the processor 110 may use the normalized PD distribution calculated in the outer loop for the future time slot 715(q) as the normalized PD limit for the inner loop. For example, in equation (11) discussed above, the normalized PD distribution for the future time slot 715(q) is given by PD norm_q Given, PD norm_q It may be scaled by the maximum allowable power level determined for the future time slot 715(q).

[0207] In the inner loop, the processor 110 may determine the maximum allowable power level for the nth sub-time slot based on the following equation:

[0208]

[0209] Where N is the total number of sub-slots 1515(1) to 1515(N), i is the index for the sub-slot, and PD norm_i is the normalized PD distribution for the ith sub-time slot, PD norm_n is the normalized PD distribution for the nth sub-time slot, and PD norm_lim is the PD limit for the inner loop. As discussed above, the PD limit for the inner loop may be given by the normalized PD distribution computed in the outer loop for the future time slot 715(q).

[0210] In equation (14), sub-slots 1515(1) to 1515(1-n) are past sub-slots relative to sub-slot 1515(n) (i.e., prior in time to sub-slot 1515(n)) and, therefore, correspond to previous transmissions of second transmitter 130. Sub-slot 1515(n) may be considered to be future sub-slots relative to sub-slots 1515(1) to 1515(1-n). Since sub-slots 1515(1) to 1515(n-1) correspond to previous transmissions, processor 110 may determine the normalized PD distribution for sub-slots 1515(1) to 1515(n-1) in equation (14) based on the previous transmission power levels for sub-slots 1515(1) to 1515(n-1). For example, processor 110 may record the transmit power levels for subslots 1515(1) through 1515(n-1) and use the recorded transmit power levels to determine a normalized PD distribution for subslots 1515(1) through 1515(n-1).

[0211] Processor 110 may then determine the transmit power level for sub-time slot 1515(n) such that the expression on the left side of equation (14) is equal to or less than PD norm_lim (i.e., satisfying the condition ≤PD norm_lim ). For example, if the peak value in the left expression is equal to or less than PD norm_lim , the processor 110 may determine that the condition is satisfied. The processor 110 may then use the determined transmit power level for the sub-time slot 1515(n) as the maximum allowable power level for the sub-time slot 1515(n). In this regard, the processor 110 may set a transmit power limit for the second transmitter 130 based on the maximum allowable power level for the sub-time slot 1515(n) such that the transmit power level of the second transmitter 130 during the sub-time slot 1515(n) is constrained by the maximum allowable power level for the sub-time slot 1515(n).

[0212] The processor 110 may determine the maximum allowable power level for the sub-time slot 1515(n) before the sub-time slot 1515(n) begins so that the maximum allowable power level is ready in time to enforce the maximum allowable power level for the sub-time slot 1515(n) (e.g., by setting a transmit power limit for the second transmitter 130 based on the maximum allowable power level). Thus, at the time when the processor 110 determines the maximum allowable power level for the sub-time slot 1515(n), the sub-time slot 1515(n) may be considered to be a future sub-time slot.

[0213] The processor 110 may determine the maximum allowable power level for each sub-time slot 1515(1) to 1515(N) based on equation (14), where n is 1 for the first sub-time slot 1515(1) and N for the last sub-time slot 1515(N). In equation (14), the expression on the left side is a cumulative average given by the combination of the normalized PD distributions for the sub-time slots 1515(1) to 1515(n) divided by N. For the example where the duration of the future time slot 715(q) in the outer cycle is 5 seconds and the duration of one sub-time slot is 100 milliseconds, N is equal to 50. Note that as n increases from 1 for the first sub-time slot to N for the last sub-time slot (i.e., as the processor 110 progresses through the sub-time slots 1515(1) to 1515(N)), the cumulative average accumulates more sub-time slots.

[0214] Thus, the processor 110 may perform the above operations in an inner loop to update the maximum allowable power level for the second technology at a higher rate than the outer loop (i.e., updating the maximum allowable power level for the second technology every Δt / N seconds). The processor 110 may accomplish this without increasing the update rate for the first technology, and therefore without increasing the computational load for the first technology. For example, if the duration of a time slot in the outer loop is 5 seconds and the duration of a sub-time slot in the inner loop is 100 milliseconds, the maximum allowable power level for the first technology is updated every 5 seconds, and the maximum allowable power level for the second technology is updated every 100 milliseconds. Thus, the processor 110 is able to update the maximum allowable power levels for the first technology and the second technology at different rates (i.e., different time intervals between updates).

[0215]

[00136] Additional examples for determining maximum allowable power levels for subslots 1515(1) through 1515(N) in an inner loop will now be discussed in accordance with certain aspects of the present disclosure.

[0216] Fig.16 A time averaging window 1605 is illustrated for an inner loop corresponding to a future time slot 715(q) in an outer loop. The duration of the time averaging window 1605 is equal to the duration of one time slot in the outer loop (labeled "T1"). The time averaging window 1605 can be aligned in time with the future time slot 715(q) in the outer loop. In one example, the duration T1 of one time slot in the outer loop is equal to 0.5 seconds (i.e., T1=0.5 seconds). The time averaging window 1605 includes N sub-time slots, where the duration of each sub-time slot is equal to T1 / N (labeled "T2"). In one example, N is equal to 50 and T1 is equal to 0.5 seconds. In this example, the duration of one sub-time slot in the inner loop is equal to 10ms (i.e., T2=10ms).

[0217] exist Fig.16 In the example of FIG. 1 , the inner loop receives the PD limit (labeled “PD lim ”). The PD limit may correspond to the normalized PD distribution PD determined for the future time slot 715(q) discussed above. norm_lim The PD peak value in Fig.16 In the example of FIG. 7 , the PD limit is greater than 1. This is possible because the outer loop determines RF exposure compliance within the time averaging window 705 including the plurality of time slots 715(1)-715(q). This allows the PD limit to exceed 1 as long as the average RF exposure within the time averaging window 705 in the outer loop meets RF exposure compliance. In general, the PD limit from the outer loop can be greater or less than 1.

[0218] Fig.16 A point in time is shown where a maximum allowable power level is being determined for a sub-time slot 1620 within a time averaging window 1605 . Fig.16 1620 (hereinafter referred to as past subslots) within the time averaging window 1605. The past subslots correspond to the PD (eg, PD peak) with respect to Fig.16 The PD of the sub-slots following sub-slot 1620 within the time averaging window 1605 is Fig.16 , since these sub-slots correspond to Fig.16 Future launch with respect to the time point shown.

[0219] In this example, the PD limit is met when the PD averaged within the time averaging window 1605 is equal to or lower than the PD limit. Graphically, this condition is met when the area under the PD curve 1610 across the entire time averaging window 1605 is equal to or less than the area under the PD limit line 1630 across the entire time averaging window 1605.

[0220] In some aspects, the processor 110 may determine the maximum allowable power level for the i-th sub-time slot within the time averaging window 1605 based on the following equation:

[0221]

[0222] Among them PD allowed,i is the allowed PD (eg, allowed PD peak) for the i-th sub-time slot in the time averaging window 1605, and the expression N·PD lim is the PD allocation for the time averaging window 1605, PD Ris the retained PD, and the summation term sums the PD of past sub-slots within the time averaging window 1605. Equation (15) can be rewritten as the following equivalent equation:

[0223]

[0224] In equation (15), the sum of the PDs of the past subslots represents the used portion of the PD allocation for the time averaging window 1605. The past subslots include the first subslot to the i-1th subslot in the time averaging window 1605. The used portion of the PD allocation is subtracted from the PD allocation for the time averaging window 1605 because the used portion of the PD allocation is not available for the i-th subslot.

[0225] Item (Ni) · PD P represents the portion of the PD allocation for the time averaging window 1605 that is reserved for future sub-time slots (i.e., sub-time slots after the i-th sub-time slot within the time averaging window 1605). The reserved PD R Multiply by (Ni), (Ni) is the number of future subslots after the i-th subslot. The portion of the PD allocation reserved for future subslots is subtracted from the PD allocation for the time averaging window 1605 because the portion of the PD allocation reserved for future subslots is not available for the i-th subslot. In some aspects, the reserved PD R Given by:

[0226] PD R =PD lim PD_reserve_ratio (17)

[0227] Where PD_reserve_ratio is the reservation ratio. Thus, the portion of the PD allocation that is reserved for future sub-time slots can be set by setting the reservation ratio. Examples of factors for setting the reservation ratio are further discussed below according to certain aspects.

[0228] Thus, when determining the allowed PD for the i-th subslot, processor 110 takes into account the portion of the PD allocation for the time averaging window 1605 that has been exhausted by past subslots. Processor 110 also reserves a portion of the remaining PD allocation for future subslots. Fig.17 A graphical representation of the portion of the PD allocation that has been used up by past sub-timeslots 1710, the allowed PDs for the ith sub-timeslot 1720, and the portion of the remaining PD allocation that is reserved for future sub-timeslots 1730 is shown. Fig.17 , the PD distribution for the time averaging window 1605 is represented by the area under the PD limit line 1630.

[0229] As discussed above, the processor 110 can set the portion of the PD allocation that is reserved for future sub-time slots by setting a reservation ratio. In one example, the processor 110 can set the reservation ratio based on the channel conditions between the wireless device 100 (e.g., a mobile wireless device) and another wireless device (e.g., a base station) that receives transmissions from the wireless device 100. For example, if the channel conditions are good (e.g., low interference and / or a short distance between wireless devices), the processor 110 can set the reservation ratio to be higher to more evenly spread the transmit power across the time averaging window 1605. In this case, spreading the transmit power can result in higher throughput. Setting the reservation ratio to be higher spreads the transmit power more evenly by reserving a larger portion of the PD allocation for future sub-time slots.

[0230] If channel conditions are poor (e.g., high interference and / or long distances between wireless devices), the processor 110 may set the reservation ratio to be lower. Setting the reservation ratio to be lower reduces the portion of the PD allocation that is reserved for future sub-time slots. This relaxes the constraints on the transmit power of the current sub-time slot imposed by the portion of the PD allocation that is reserved for future sub-time slots, thereby allowing the transmitter 130 to transmit at a higher power for the current sub-time slot. In this case, transmitting at a higher power (e.g., in short bursts) may be necessary to ensure that data transmitted from the wireless device 100 is successfully received by another wireless device.

[0231] In another example, the processor 110 may set the reservation ratio based on the data traffic pattern. For example, if the wireless device 100 is scheduled to transmit data toward the end of the time averaging window 1605, the processor 110 may set the reservation ratio to be higher to reserve a sufficient amount of PD allocation for the scheduled data transmission. This can help prevent the transmitter 130 from using up all or most of the PD allocation before the scheduled data transmission and not leaving enough PD allocation for the scheduled data transmission. In another example, if the wireless device 100 is scheduled to transmit data for a short duration toward the beginning of the time averaging window 1605, and there are no other scheduled data transmissions for the remainder of the time averaging window 1605, the processor 110 may set the reservation ratio to be lower because it may not be necessary to reserve a portion of the PD allocation for another data transmission in this example. In another example, the processor 110 may predict future transmissions and / or frequencies based on past transmissions and / or upper layer information. The processor 110 may then set the reservation ratio based on the predicted future transmissions and / or frequencies. For example, if data packets (e.g., data packets of a certain size) were transmitted at a certain time interval in the past, processor 110 can use this information to predict that data packets will be transmitted at this time interval in the future and set the reservation ratio accordingly (e.g., set the reservation ratio to provide sufficient reservation for the predicted data packet transmission within the time averaging window 1605).

[0232] Processor 110 may determine an allowed PD for each sub-time slot within the time averaging window 1605 for the inner loop (e.g., based on equation (15)). For the first sub-time slot, the portion of the PD allocation that has been used is zero because there are no sub-time slots before the first sub-time slot within the time averaging window 1605. For the last sub-time slot, the portion of the PD allocation that is reserved for future sub-time slots is zero because there are no sub-time slots after the last sub-time slot within the time averaging window 1605. After determining the allowed PD for each sub-time slot, processor 110 may determine a maximum allowable power level for the sub-time slot and set a transmit power limit of transmitter 130 for the sub-time slot based on the determined maximum allowable power level.

[0233] In some aspects, the processor 110 may use a table to determine the maximum allowable power level for a sub-time slot based on the allowed PD for the sub-time slot. In this regard, Fig.18 One example of a table 1810 for converting allowed PDs for a sub-time slot to a maximum allowable power level is shown. The table 1810 may be stored in the memory 115.

[0234] In this example, table 1810 includes indices for n different transmission scenarios for transmitter 130. The n transmission scenarios may correspond to different beams, different user locations relative to wireless device 100, etc. For each transmission scenario in table 1810, table 1810 includes a corresponding transmit power level at a reference PD (labeled “Tx1” through “Tx2”). n ”). The transmit power levels for different transmit scenarios at the reference PD may be predetermined by performing simulations and / or measurements on the wireless device 110 and may be pre-stored in table 1810.

[0235] To determine the maximum allowable power level for the sub-time slot based on the corresponding allowed PD, the processor 110 may determine a transmission scenario for the sub-time slot and retrieve a transmission power level corresponding to the determined transmission scenario in the table 1810. For example, if the transmission scenario in the table 1810 corresponds to a different beam, the processor 110 may determine the beam for the sub-time slot and retrieve a transmission power level corresponding to the determined beam in the table 1810.

[0236] After retrieving the transmit power level from the table 1810, the processor 110 may determine the maximum allowable power level for the sub-time slot by scaling the transmit power level from the table 1810 based on the allowed PD and the reference PD for the sub-time slot (e.g., scaling the transmit power level from the table 1810 by a ratio of the allowed PD to the reference PD). For example, if the allowed PD is 50% less than the reference PD, the processor 110 may reduce the transmit power level from the table 1810 by 50% to obtain the maximum allowable power level for the sub-time slot. If the transmit power levels in the table 1810 are in decibels (dB), in this example, the maximum allowable power level is obtained by subtracting 3 dB from the transmit power in the table 1810. Therefore, the maximum allowable power level for any allowed PD may be obtained by scaling the transmit power level in the table 1810 based on the allowed PD and the reference PD. As discussed above, this is possible because the PD scales with the transmit power.

[0237] As discussed above, when determining the allowed PD for a sub-time slot, the processor 110 may take into account the portion of the PD allocation that has been used up by the past sub-time slot. In the example of equation (15), the portion of the PD allocation that has been used up by the past sub-time slot is determined by summing the PD of the past sub-time slot. In one example, the PD of the past sub-time slot may correspond to the allowed PD determined for the past sub-time slot. In another example, the PD of the past sub-time slot may correspond to the actual PD for the past sub-time slot. The actual PD for the past sub-time slot may be a PD corresponding to the actual transmit power level used during the past sub-time slot, which may be equal to or less than the maximum allowable power level determined for the past sub-time slot. In this example, the processor 110 may record the actual transmit power level used for the past sub-time slot and determine the actual PD for the past sub-time slot based on the actual transmit power level for the past sub-time slot.

[0238] It should be understood that the present disclosure is not limited to one inner loop. For example, the processor 110 may use two inner loops including a first inner loop and a second inner loop to determine the maximum allowable power level. In this example, the inner loop discussed above may correspond to a first inner loop that receives a PD limit for a future time slot 715 (q) from an outer loop and adjusts the PD within the future time slot in the sub-time slot so that when the PD is averaged within the future time slot, the PD limit from the outer loop is satisfied.

[0239] In this example, the second inner loop is below the first inner loop. The second inner loop divides each sub-time slot in the first inner loop into smaller sub-time slots. For each sub-time slot of the first inner loop, the second inner loop receives a PD limit from the first inner loop (e.g., an allowed PD for the sub-time slot of the inner loop) and adjusts the maximum allowable power level within the sub-time slot so that the PD limit is met. Within the sub-time slot of the first inner loop, the second inner loop determines the maximum allowable power level for each sub-time slot of the second inner loop within the sub-time slot of the first inner loop (e.g., based on equation (15), where the PD limit is provided by the first inner loop). In this example, the maximum allowable power level is determined for each sub-time slot of the second inner loop.

[0240] In some aspects, the processor 110 may determine the maximum allowable power level for different sub-6 GHz technologies at different rates using any of the techniques discussed above. For example, the processor 110 may update the maximum allowable power level for LTE every 100 milliseconds, but update the maximum allowable power level for GSM every 5 seconds, depending on how frequently or infrequently the technology changes. In this example, the processor 110 may determine the maximum allowable power level for LTE and the maximum allowable power level for GSM every 5 seconds in the outer loop. For LTE, the processor 110 may further divide the future time slots in the outer loop into sub-time slots (e.g., 50 sub-time slots) and determine the maximum allowable power level for each sub-time slot in the inner loop. The processor 110 may use the normalized SAR distribution for the future time slots in the outer loop as the normalized SAR limit in the inner loop for determining the maximum allowable power level for each sub-time slot in the inner loop.

[0241] In some aspects, the techniques discussed above can be extended to run more than two different time intervals (i.e., at more than two different update rates to update the maximum allowable power level for different technologies). To this end, the processor 110 can run different inner loops for different technologies, where the duration of a sub-time slot in each inner loop is different. In this example, the duration of a sub-time slot for each inner loop can be selected based on the desired time interval (i.e., update rate) of the corresponding technology. In some cases, each technology can run at a specific time interval that is different from other technologies.

[0242] As discussed above, processor 110 may determine the maximum allowable power level for the technology for future time slots, and set the transmit power limit of the corresponding transmitter (e.g., transmitter 120 or 130) based on the determined maximum allowable power level. The future time slot may be a future time slot in an outer loop (e.g., a future time slot of 5 seconds) or a future sub-time slot in an inner loop (e.g., a future sub-time slot of 100 milliseconds). In some aspects, the maximum allowable power level discussed above is used as the maximum allowable time-averaged power level for future time slots, and therefore in these aspects, may be considered to be the maximum allowable time-averaged power level for future time slots. In the following discussion, the maximum allowable power level discussed above is referred to as the maximum allowable time-averaged power level.

[0243] In the above aspects, setting the transmit power limit of the transmitter based on the determined maximum allowable time average power level prevents: the time average of the transmit power level of the transmitter in future time slots from exceeding the maximum allowable time average power level. The instantaneous transmit power level of the transmitter is allowed to exceed the maximum allowable time average power level during future time slots as long as the time average of the power level in the future time slots does not exceed the maximum allowable time average power level.

[0244] In the above example, the maximum allowable time average power level for a future time slot is used to set the maximum power limit of the corresponding transmitter so that the time average of the transmit power level within the future time slot does not exceed the maximum allowable time average power level.

[0245] In some aspects, processor 110 may convert the maximum allowable time-averaged power level for a future time slot to a maximum allowable duty cycle for the future time slot as follows:

[0246] Max_duty_cycle=Max_avg_P / P max (18)

[0247] where Max_duty_cycle is the maximum allowable duty cycle for future time slots, Max_avg_P is the maximum allowable time-averaged power level for future time slots, and P max is the maximum allowable power level. max It can be the limit of the maximum allowable instantaneous power level or peak power level of the corresponding transmitter. max May be defined by standards or regulatory authorities. In this example, the transmitter may operate at a duty cycle approximately equal to the maximum allowable duty cycle and at a duty cycle approximately equal to P during future time slots. max The maximum duty cycle can be between 0 and 1.

[0248] In certain aspects, after determining the maximum allowable time-averaged power level for the future time slot (e.g., using any of the methods discussed above), the processor 110 may determine a corresponding maximum allowable duty cycle for the future time slot based on equation (18). The processor 110 may then set a transmit duty cycle limit for the corresponding transmitter (e.g., transmitter 120 or 130) for the future time slot based on the determined maximum allowable duty cycle. In this example, setting the transmit duty cycle limit based on the determined maximum allowable duty cycle prevents the transmit duty cycle of the transmitter from exceeding the maximum allowable duty cycle for the future time slot. In other words, the transmit duty cycle of the transmitter for the future time slot is constrained by the determined maximum allowable duty cycle.

[0249] In some aspects, processor 110 may convert the maximum allowable time-averaged power level for a future time slot to a maximum allowable peak power for a future time slot as follows:

[0250] Max_peak_power=Max_avg_P / Max_duty_cycle (19)

[0251] Wherein Max_peak_power is the maximum allowable peak power for future time slots, Max_duty_cycle is the maximum allowable duty cycle for future time slots, and Max_avg_P is the maximum allowable time-averaged power level for future time slots. The maximum allowable duty cycle may be provided by a radio frequency (RF) system (e.g., through an uplink grant provided by a network), defined by a standard, etc.

[0252] In certain aspects, after determining the maximum allowable time-averaged power level for the future time slot (e.g., using any of the methods discussed above), the processor 110 may determine a corresponding maximum peak power for the future time slot based on equation (19). The processor 110 may then set a peak power limit for the corresponding transmitter (e.g., transmitter 120 or 130) for the future time slot based on the determined maximum allowable peak power. In this example, setting the peak power limit for the transmitter for the future time slot based on the determined maximum allowable peak power prevents the peak power of the transmitter from exceeding the maximum allowable peak power. In other words, the instantaneous power level of the transmitter during the future time slot is constrained by the maximum allowable peak power such that the peak power during the future time slot does not exceed the maximum allowable peak power.

[0253] The processor 110 may also generate a table based on the maximum allowable time average power level for the future time slot, the table including different combinations of the maximum allowable duty cycle and the maximum allowable peak power for the future time slot. For example, the processor 110 may generate the table by inputting different maximum allowable duty cycles into equation (19) and determining the maximum allowable peak power for each different maximum allowable duty cycle. In this example, the processor may use the table to dynamically adjust the duty cycle based on the peak power during the future time slot, or use the table to dynamically adjust the peak power based on the transmit duty cycle during the future time slot.

[0254] Therefore, the processor 110 may convert the maximum allowable time average power level for the future time slot into the maximum allowable duty cycle for the future time slot, and set the transmit duty cycle limit of the corresponding transmitter based on the maximum allowable duty cycle. The processor 110 may also convert the maximum allowable time average power level for the future time slot into the maximum allowable peak power for the future time slot, and set the peak power limit of the corresponding transmitter based on the maximum allowable peak power. The maximum allowable time average power level for the future time slot may be determined using any of the methods discussed above. For examples in which the future time slot is a future time slot in an outer loop, the maximum allowable time average power level may correspond to the maximum allowable power level calculated for the future time slot. For examples in which the future time slot is a future sub-time slot in an inner loop, the maximum allowable time average power level may correspond to the maximum allowable power level calculated for a future sub-time slot (e.g., a 100 millisecond sub-time slot). It should be understood that the present disclosure is not limited to these examples, and the maximum allowable time average power level for the future time slot may be determined using other methods.

[0255] For example, transmitters (e.g., transmitters 120 and 130) may be configured to transmit signals in time slots that are divided (discretized) into N time slots (not to be confused with Fig.18 In this example, the maximum allowable time-averaged power level for future time slots can be determined by the following formula:

[0256]

[0257] Where P limit is the time-averaged transmitted power that results in an RF exposure corresponding to the regulatory agency’s SAR limit or PD limit, avgP tk is the average transmit power in the kth time slot, the Nth time slot is a future time slot, and Max_avgP tN is the maximum permissible time-averaged power level for future time slots. In equation (20), relative to P limit The average transmit power level is normalized. The time window may be a moving time average window, where the maximum allowable time average power level for future time slots is updated every time_window / N seconds, where time_window is the duration of the time window. In this example, the first time slot to the kth time slot in equation (20) correspond to previous transmissions of the transmitter. Therefore, the average transmit power level for these time slots is known. In this example, the processor 110 may determine the maximum allowable time average power level Max_avgP that satisfies the condition in equation (20) tk , to determine the maximum allowable time average power level Max_avgP for future time slotstk The processor 110 may determine the maximum allowable time-averaged power level Max_avgP that results in the normalized time-averaged power on the left side of equation (20) being equal to or less than 1. tk , to do this.

[0258] In the above example, the processor 110 may set the maximum allowable time average power level Max_avgP for the future time slot to tk Convert to the maximum allowable duty cycle for future time slots (e.g., based on equation (18), convert Max_avgP tk The processor 110 may also set the maximum allowable time average power level Max_avgP for future time slots to Max_avgP tk Convert to the maximum allowable peak power for the future time slot (e.g., based on equation (19), convert Max_avgP tk Max_avg_P) in equation (19), and sets the peak power limit of the corresponding transmitter based on the maximum allowable peak power.

[0259] In some aspects, the memory 115 may include a computer-readable medium including instructions stored thereon that, when executed by the processor 110, cause the processor 110 to perform the method 1400 and / or any other method described herein. By way of example, the computer-readable medium may 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.

[0260] In certain aspects, an apparatus may include means for performing method 1400. The apparatus may 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 may also include means for determining at least one first maximum allowable power level and at least one second maximum allowable power level for a future time slot based on the combined RF exposure distribution, means for setting at least one transmit power limit for a first transmitter in a future time slot based on the at least one first maximum allowable power level, and means for setting at least one transmit power limit for a second transmitter in a future time slot based on the at least one second maximum allowable power level.

[0261] It should be understood that the present disclosure is not limited to the exemplary terms used above to describe aspects of the present disclosure, and the present disclosure encompasses equivalent terms. For example, it should be understood that a distribution may also be referred to as a map, a scan, or another term. In another example, it should be understood that an antenna may also be referred to as an antenna element or another term. In yet another example, it should be understood that a maximum allowable power level may also be referred to as a power level limit or another term.

[0262] The term "approximately" as used herein with respect to a stated value or property is intended to mean within 10% of the stated value or property.

[0263] Any reference to an element using names such as "first", "second" etc. in this article does not generally limit the quantity or order of those elements. Rather, these names are used as a convenient way to distinguish two or more elements or element instances in this article. Therefore, reference to a first and a second element does not mean that only two elements can be used, or that the first element must be before the second element.

[0264] Within this 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.

[0265] The previous description of the disclosure is provided to enable any person skilled in the art to make or use the disclosure. Various modifications to the disclosure will be apparent to those skilled in the art, and the general principles defined herein may be applied to other variations without departing from the spirit or scope of the disclosure. Therefore, the disclosure is not intended to be limited to the examples described herein, but to be given the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A wireless device comprising: A first transmitter configured to transmit a first signal according to a first wireless communication technology; a second transmitter configured to transmit a second signal according to a second wireless communication technology; as well as a processor coupled to the first transmitter and the second transmitter, wherein the processor is configured to: averaging a specific absorption rate, SAR, for the first wireless communication technology over a first time averaging window, the first time averaging window being divided into a first plurality of time slots, the first plurality of time slots comprising a future time slot and a first plurality of previous time slots for the first wireless communication technology, the averaged SAR being based on a transmit power level for each time slot in the first plurality of time slots; averaging a power density PD for the second wireless communication technology within a second time averaging window, the second time averaging window being divided into a second plurality of time slots, the second plurality of time slots comprising a future time slot and a second plurality of previous time slots for the second wireless communication technology, the averaged PD being based on a transmit power level for each time slot in the second plurality of time slots; determining at least one first maximum allowable power level and at least one second maximum allowable power level based on a combination of the averaged SAR and the averaged PD; setting at least one transmit power limit for the first transmitter in the future time slot for the first wireless communication technology based on the at least one first maximum allowable power level; as well as At least one transmit power limit for the second transmitter in the future time slot for the second wireless communication technology is set based on the at least one second maximum allowable power level.

2. The wireless device of claim 1, wherein the averaged SAR is normalized with respect to a SAR limit, and the averaged PD is normalized with respect to a PD limit.

3. The wireless device of claim 2, wherein the processor is configured to: Based on a combination of the normalized averaged SAR and the normalized averaged PD, the at least one first maximum allowable power level and the at least one second maximum allowable power level are determined. 4 . The wireless device of claim 1 , wherein the first time averaging window and the second time averaging window have different lengths.

5. The wireless device of claim 1, wherein during the future time slot for the first wireless communication technology, the first transmitter is configured to transmit the first signal based on the at least one first maximum allowable power level.

6. The wireless device of claim 5, wherein during the future time slot for the first wireless communication technology, the first transmitter is configured to limit a power level of the first transmitter based on the at least one transmit power limit for the first transmitter.

7. The wireless device of claim 5 , wherein during the future time slot for the first wireless communication technology, the first transmitter is configured to limit an average value of a power level of the first transmitter within the future time slot for the first wireless communication technology based on the at least one transmit power limit for the first transmitter.

8. The wireless device of claim 5, wherein during the future time slot for the second wireless communication technology, the second transmitter is configured to transmit the second signal based on the at least one second maximum allowable power level.

9. The wireless device of claim 8, wherein during the future time slot for the second wireless communication technology, the second transmitter is configured to limit a power level of the second transmitter based on the at least one transmit power limit for the second transmitter.

10. The wireless device of claim 8, wherein during the future time slot for the second wireless communication technology, the second transmitter is configured to limit an average value of a power level of the second transmitter within the future time slot for the second wireless communication technology based on the at least one transmit power limit for the second transmitter.

11. The wireless device of claim 1, wherein the first wireless communication technology comprises Long Term Evolution (LTE), and the second wireless communication technology comprises fifth generation (5G).

12. The wireless device according to claim 1, wherein the first wireless communication technology comprises a wireless local area network (WLAN), and the second wireless communication technology comprises fifth generation (5G).

13. The wireless device of claim 1 , wherein the processor is configured to: The at least one first maximum allowable power level and the at least one second maximum allowable power level are updated, wherein the at least one second maximum allowable power level is updated at a smaller time interval than the at least one first maximum allowable power level.

14. The wireless device of claim 1, wherein the SAR for the first wireless communication technology comprises a combination of a plurality of SARs, and each SAR of the plurality of SARs is for a corresponding antenna of a plurality of antennas.

15. The wireless device of claim 1, wherein the SAR for the first wireless communication technology comprises a combination of a plurality of SARs, and each of the plurality of SARs is for a corresponding frequency band of a plurality of frequency bands.

16. The wireless device of claim 1, wherein the PD for the second wireless communication technology comprises a combination of a plurality of PDs, and each of the plurality of PDs is for a corresponding antenna of a plurality of antennas.

17. The wireless device of claim 1, wherein the PD for the second wireless communication technology comprises a combination of a plurality of PDs, and each of the plurality of PDs is for a corresponding combination of antennas.

18. The wireless device of claim 1, wherein the PD for the second wireless communication technology comprises a combination of a plurality of PDs, and each of the plurality of PDs is for a corresponding frequency band of a plurality of frequency bands.

19. The wireless device according to claim 1, wherein the second wireless communication technology includes multiple wireless communication technologies, the PD for the second wireless communication technology includes a combination of multiple PDs, and each of the multiple PDs is for a corresponding wireless communication technology among the multiple wireless communication technologies.

20. The wireless device of claim 1, wherein the second transmitter comprises a plurality of transmitters, the PD for the second wireless communication technology comprises a combination of a plurality of PDs, and each of the plurality of PDs is for a corresponding transmitter of the plurality of transmitters.

21. The wireless device of claim 1, wherein the processor is configured to: averaging the PD for the second wireless communication technology over a third time averaging window; and The at least one first maximum allowable power level and the at least one second maximum allowable power level are determined based on a combination of the PD averaged within the second time averaging window and the PD averaged within the third time averaging window and a combination of the averaged SAR.

22. The wireless device of claim 21, wherein the second time averaging window is for a first frequency band and the third time averaging window is for a second frequency band.

23. A method implemented in a wireless device, comprising: averaging a specific absorption rate, SAR, for a first wireless communication technology over a first time averaging window, the first time averaging window being divided into a first plurality of time slots, the first plurality of time slots comprising a future time slot and a first plurality of previous time slots for the first wireless communication technology, the averaged SAR being based on a transmit power level for each time slot in the first plurality of time slots; averaging a power density PD for a second wireless communication technology within a second time averaging window, the second time averaging window being divided into a second plurality of time slots, the second plurality of time slots comprising a future time slot and a second plurality of previous time slots for the second wireless communication technology, the averaged PD being based on a transmit power level for each time slot in the second plurality of time slots; determining at least one first maximum allowable power level and at least one second maximum allowable power level based on a combination of the averaged SAR and the averaged PD; setting at least one transmit power limit for a first transmitter in the future time slot for the first wireless communication technology based on the at least one first maximum allowable power level; as well as At least one transmit power limit for a second transmitter in the future time slot for the second wireless communication technology is set based on the at least one second maximum allowable power level.

24. A computer-readable medium comprising instructions stored thereon, the instructions being for: averaging a specific absorption rate, SAR, for a first wireless communication technology over a first time averaging window, the first time averaging window being divided into a first plurality of time slots, the first plurality of time slots comprising a future time slot and a first plurality of previous time slots for the first wireless communication technology, the averaged SAR being based on a transmit power level for each time slot in the first plurality of time slots; averaging a power density PD for a second wireless communication technology within a second time averaging window, the second time averaging window being divided into a second plurality of time slots, the second plurality of time slots comprising a future time slot and a second plurality of previous time slots for the second wireless communication technology, the averaged PD being based on a transmit power level for each time slot in the second plurality of time slots; determining at least one first maximum allowable power level and at least one second maximum allowable power level based on a combination of the averaged SAR and the averaged PD; setting at least one transmit power limit for a first transmitter in the future time slot for the first wireless communication technology based on the at least one first maximum allowable power level; as well as At least one transmit power limit for a second transmitter in the future time slot for the second wireless communication technology is set based on the at least one second maximum allowable power level.

25. A wireless device comprising: Transmitter; as well as a processor coupled to the transmitter, wherein the processor is configured to: receiving a power density PD limit for a time slot, the time slot comprising a sub-time slot; determining a PD allocation for the time slot based on the PD limit; determining, for one of the sub-timeslots, a maximum allowable power level based on a portion of the PD allocation exhausted by one or more of the sub-timeslots preceding the one of the sub-timeslots; as well as A transmit power limit for the transmitter is set based on the maximum allowable power level.

26. The wireless device of claim 25, wherein during the one of the sub-timeslots, the transmitter is configured to transmit a signal at a transmit power level that is equal to or less than the transmit power limit.

27. The wireless device of claim 25, wherein determining, by the processor, the PD allocation for the time slot comprises: The PD limit is multiplied by the number of sub-timeslots.

28. The wireless device of claim 25, wherein the processor is configured to determine the PD allocation exhausted by the one or more of the sub-timeslots preceding the one of the sub-timeslots.

29. The wireless device of claim 28, wherein determining, by the processor, the PD allocation exhausted by the one or more of the subslots preceding the one of the subslots comprises: The PDs of the one or more sub-slots in the sub-slots preceding the one of the sub-slots are summed.

30. The wireless device of claim 25, wherein the processor is further configured to: determining a portion of the PD allocation reserved for one or more of the subslots following the one of the subslots; and The maximum allowable power level for the one of the sub-timeslots is also determined based on the portion of the PD allocation reserved for the one or more of the sub-timeslots that follow the one of the sub-timeslots.

31. The wireless device of claim 30, wherein determining, by the processor, the portion of the PD allocation reserved for the one or more of the subslots following the one of the subslots comprises: The reserved PD is multiplied by the number of the one or more of the subslots that follow the one of the subslots.

32. The wireless device of claim 31, wherein the processor is configured to determine the reserved PD based on the PD limit and a reservation ratio.

33. The wireless device of claim 32, wherein determining, by the processor, the reserved PD comprises: Multiply the PD limit by the retention ratio.

34. The wireless device of claim 32, wherein the processor is configured to set the reservation ratio based on at least one of: a channel condition between the wireless device and another wireless device, or a data transmission scheduled for the wireless device.

35. The wireless device of claim 25, wherein determining, by the processor, the maximum allowable power level for the one of the subslots comprises: determining an allowed PD for the one of the sub-timeslots based on the portion of the PD allocation exhausted by the one or more of the sub-timeslots preceding the one of the sub-timeslots; retrieving a transmit power level from a memory, the transmit power level corresponding to a reference PD; as well as The maximum allowable power level for the one of the sub-timeslots is determined based on the retrieved transmit power level, the allowed PD, and the reference PD.

36. The wireless device of claim 35, wherein determining, by the processor, the maximum allowable power level for the one of the subslots based on the retrieved transmit power level, the allowed PD, and the reference PD comprises: The retrieved transmit power level is scaled by a ratio of the allowed PD to the reference PD.

37. The wireless device of claim 25, wherein the processor is configured to: Determining the time-averaged RF exposure distribution; and The PD limit for the time slot is determined based on the time average RF exposure distribution.

38. The wireless device of claim 37, wherein determining, by the processor, the time-averaged RF exposure profile comprises: determining a time-averaged specific absorption SAR distribution within a first time window; Determine the time average power density PD distribution in the second time window; as well as The time-averaged SAR distribution and the time-averaged PD distribution are combined to generate the time-averaged RF exposure distribution.

39. The wireless device of claim 38, wherein the first time window and the second time window have different lengths.

40. The wireless device of claim 37, wherein the time-averaged RF exposure profile comprises a time-averaged power density (PD) profile.

41. A method implemented in a wireless device, comprising: receiving a power density PD limit for a time slot, the time slot comprising a sub-time slot; determining a PD allocation for the time slot based on the PD limit; determining, for one of the sub-timeslots, a maximum allowable power level based on a portion of the PD allocation exhausted by one or more of the sub-timeslots preceding the one of the sub-timeslots; as well as Based on the maximum allowable power level, a transmit power limit for the transmitter is set.

42. The method of claim 41 further comprising: Determine the time-averaged RF exposure distribution; as well as The PD limit for the time slot is determined based on the time average RF exposure distribution.

43. The method of claim 42, wherein determining the time-averaged RF exposure distribution comprises: determining a time-averaged specific absorption SAR distribution within a first time window; Determine the time average power density PD distribution in the second time window; as well as The time-averaged SAR distribution and the time-averaged PD distribution are combined to generate the time-averaged RF exposure distribution.

44. A wireless device comprising: Transmitter; as well as a processor coupled to the transmitter, wherein the processor is configured to: determining a time-averaged RF exposure distribution within the time slot; determining an RF exposure limit for one of the time slots based on the time-averaged RF exposure profile within the time slots, the one of the time slots comprising a sub-time slot; determining a time-averaged RF exposure profile within said one of said time slots; determining a maximum allowable power level for one of the sub-time slots based on the RF exposure limit and the time-averaged RF exposure distribution within the one of the time slots; as well as A transmit power limit for the transmitter is set based on the maximum allowable power level.

45. The wireless device of claim 44, wherein determining, by the processor, the time-averaged RF exposure profile within the time slot comprises: determining a time-averaged specific absorption SAR distribution within a first time window; Determine the time average power density PD distribution in the second time window; as well as The time-averaged SAR distribution and the time-averaged PD distribution are combined to generate the time-averaged RF exposure distribution within the time slot.

46. ​​The wireless device of claim 45, wherein the first time window and the second time window have different lengths.

47. The wireless device of claim 45, wherein the time-averaged SAR distribution corresponds to a first technology and the time-averaged PD distribution corresponds to a second technology.

48. The wireless device of claim 47, wherein the first technology comprises sub-6 GHz technology and the second technology comprises millimeter wave technology.

49. The wireless device of claim 47, wherein the same slot duration is used for the first technology and the second technology.

50. The wireless device of claim 45, wherein the time-averaged SAR distribution is normalized with respect to a SAR limit and the time-averaged PD distribution is normalized with respect to a PD limit.

51. The wireless device of claim 45, wherein the RF exposure limits comprise PD limits.

52. The wireless device of claim 44, wherein the time-averaged RF exposure profile within the time slot comprises a time-averaged power density (PD) profile, and the RF exposure limit comprises a PD limit.

53. The wireless device of claim 52, wherein the sub-slots are normalized with respect to the PD limit.

54. The wireless device of claim 44, wherein the time-averaged RF exposure profile within the time slot comprises a time-averaged Specific Absorption Rate (SAR) profile, and the RF exposure limit comprises a SAR limit.

55. The wireless device of claim 54, wherein the sub-time slots are normalized with respect to the SAR limit.

56. The wireless device of claim 44, wherein the one of the subslots comprises a second subslot, and the processor is configured to: determining a second RF exposure limit for the one of the sub-time slots; determining a time-averaged RF exposure profile within said one of said sub-time slots; and A maximum allowable power level for one of the second sub-time slots is determined based on the second RF exposure limit and the time-averaged RF exposure distribution within the one of the sub-time slots.

57. The wireless device of claim 44, wherein the processor is configured to: determining a second RF exposure limit for a second one of the time slots based on the time-averaged RF exposure profile within the time slots, the second one of the time slots comprising a second sub-time slot; determining a time-averaged RF exposure profile within said second one of said time slots; and A maximum allowable power level for one of the second sub-time slots is determined based on the second RF exposure limit and the time-averaged RF exposure distribution within the second ones of the time slots.

58. The wireless device of claim 57, wherein the first sub-time slot and the second sub-time slot have different time intervals.

59. The wireless device of claim 44, wherein the RF exposure limit comprises a power density (PD) limit, and the processor is configured to: determining a PD allocation based on the PD limit; determining a portion of the PD allocation reserved for one or more of the subslots following the one of the subslots; and The maximum allowable power level for the one of the sub-timeslots is also determined based on the portion of the PD allocation reserved for the one or more of the sub-timeslots that follow the one of the sub-timeslots.

60. The wireless device of claim 59, wherein the time-averaged RF exposure distribution within the one of the time slots is averaged in the sub-time slots over one or more sub-time slots preceding the one of the time slots.

61. The wireless device of claim 59, wherein determining, by the processor, the portion of the PD allocation reserved for the one or more of the subslots following the one of the subslots comprises: The reserved PD is multiplied by the number of the one or more of the subslots that follow the one of the subslots.

62. The wireless device of claim 61, wherein the processor is configured to determine the reserved PD based on the PD limit and a reservation ratio.

63. The wireless device of claim 62, wherein determining, by the processor, the reserved PD comprises: Multiply the PD limit by the retention ratio.

64. The wireless device of claim 62, wherein the processor is configured to set the reservation ratio based on at least one of: a channel condition between the wireless device and another wireless device, or a data transmission scheduled for the wireless device.

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