Abnormal robust time average radio frequency exposure compliance continuity

Abstract

Certain aspects of the present disclosure provide techniques for anomaly-robust time-averaged radio frequency (RF) exposure compliance continuity. A method that can be performed by a user equipment (UE) generally includes transmitting, at a first transmission power, a first signal based on time-averaged RF exposure measurements during a time window, and storing RF exposure information associated with the time window. The method can also include detecting that an anomaly event associated with the UE has occurred, and in response to the detection of the event, transmitting, at a second transmission power, a second signal based at least in part on the stored RF exposure information.

Description

[0001] Cross Reference to Related Applications

[0002] This patent application claims priority to U.S. Application No. 17 / 392,442, filed August 3, 2021, which claims priority to U.S. Provisional Application No. 63 / 077,377, filed September 11, 2020, both of which are hereby expressly incorporated by reference in their entirety herein. TECHNICAL FIELD

[0003] Aspects of the disclosure relate to wireless communications, and more particularly, to techniques for providing radio frequency (RF) exposure compliance continuity. BACKGROUND

[0004] Wireless communication systems are widely deployed to provide various telecommunication services such as telephony, video, data, messaging, broadcasts, etc. Modern wireless communication devices, such as cellular telephones, typically need to meet radio frequency (RF) exposure limits prescribed by domestic and international standards and regulations. To ensure compliance with the standards, such devices currently must go through extensive certification processes before they can be shipped to the market. To ensure that wireless communication devices comply with the RF exposure limits, techniques have been developed that enable wireless communication devices to assess RF exposure from the wireless communication devices in real-time and adjust the wireless communication device transmission power accordingly to comply with the RF exposure limits. SUMMARY

[0005] The systems, methods, and devices of the disclosure each have several aspects, no one aspect of which is solely responsible for its desirable attributes. Without limiting the scope of this disclosure as expressed by the claims which follow, some features will now be discussed briefly. The detailed description, taken with the drawings, affords the best understanding of the features of the disclosure. Upon considering this discussion, one will understand how the features of the disclosure provide advantages, including ensuring compliance with radio frequency exposure limits after various abnormal events.

[0006] Certain aspects of the subject matter described in this disclosure can be implemented in a method of wireless communication by a user equipment (UE). The method generally includes transmitting, at a first transmission power, a first signal based on a time-averaged radio frequency (RF) exposure measurement during a time window, and storing RF exposure information associated with the time window. The method can also include detecting that an abnormal event associated with the UE has occurred, and transmitting, at a second transmission power, a second signal in response to the detection of the event based at least in part on the stored RF exposure information.

[0007] Certain aspects of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication. The apparatus generally includes a transmitter, a memory, and a processor. The transmitter is configured to transmit a first signal at a first transmission power based on a time-averaged RF exposure measurement during a time window. The processor is coupled to the memory such that the processor and the memory are configured to store RF exposure information associated with the time window and detect that an abnormal event associated with the apparatus has occurred. The transmitter is further configured to transmit a second signal at a second transmission power based at least in part on the stored RF exposure information in response to the detection of the event.

[0008] Certain aspects of the subject matter described in this disclosure can be implemented in an apparatus for wireless communication. The apparatus generally includes a transmitter, a memory, and a processor. The transmitter is configured to transmit a first signal at a first transmission power based on a time-averaged RF exposure measurement during a time window. The processor is coupled to the memory such that the processor and the memory are configured to store RF exposure information associated with the time window and detect that an abnormal event associated with the apparatus has occurred. The transmitter is further configured to transmit a second signal at a second transmission power based at least in part on the stored RF exposure information in response to the detection of the event.

[0009] Certain aspects of the subject matter described in this disclosure can be implemented in a computer-readable medium having instructions stored thereon for transmitting a first signal at a first transmission power based on a time-averaged RF exposure measurement during a time window; storing RF exposure information associated with the time window; detecting that an abnormal event associated with the UE has occurred; and transmitting a second signal at a second transmission power based at least in part on the stored RF exposure information in response to the detection of the event.

[0010] Certain aspects of the subject matter described in this disclosure can be implemented in a method of wireless communication by a UE. The method generally includes transmitting a first signal at a first transmission power based on a time-averaged RF exposure measurement during a time window; storing RF exposure information associated with the time window; detecting that an abnormal event associated with the UE has occurred; determining that a timestamp corresponding to a most recent time-averaged RF exposure measurement is not within a current time window or determining that a check value fails a cyclic redundancy check (CRC) of the RF exposure information; and transmitting a second signal at a second transmission power in a fail-safe mode based on the determination.

[0011] To the accomplishment of the foregoing and related aspects, one or more aspects comprise the features recited in the following description and the claims, both of which are incorporated by reference in their entirety. The foregoing and other aspects are explained in detail by way of example in the following description and accompanying drawings. BRIEF DESCRIPTION OF DRAWINGS

[0012] For a detailed understanding of the above-described features of the present disclosure, reference can be made to the following detailed description (which is to be read in connection with the accompanying drawings) wherein certain representative aspects (some of which are illustrated in the figures) are described. It should be understood, however, that the brief summary and the following detailed description are merely representative and are not intended to narrow the scope of the present disclosure, as the scope of the present disclosure can be embodied in other specific forms.

[0013] Figure 1 is a block diagram conceptually illustrating an example wireless communication network, in accordance with certain aspects of the present disclosure.

[0014] Figure 2 is a block diagram conceptually illustrating a design of an example base station (BS) and user equipment (UE), in accordance with certain aspects of the present disclosure.

[0015] Figure 3 is a block diagram of an example radio frequency (RF) transceiver, in accordance with certain aspects of the present disclosure.

[0016] Figure 4 is a flow diagram illustrating example operations for wireless communication by a UE, in accordance with certain aspects of the present disclosure.

[0017] Figure 5 is a graph illustrating time-averaged RF exposure during a time window, in accordance with certain aspects of the present disclosure.

[0018] Figure 6 is a block diagram illustrating a design of an example wireless communication device to enable RF exposure continuity, in accordance with certain aspects of the present disclosure.

[0019] Figure 7 is a signaling flow diagram illustrating example signaling for RF exposure continuity, in accordance with aspects of the present disclosure.

[0020] Figure 8 A communication device (e.g., a UE) in accordance with aspects of the present disclosure can include various components configured to perform operations for the techniques disclosed herein.

[0021] To facilitate understanding, like reference numerals have been used, where possible, to designate like elements across the figures. It is contemplated that elements disclosed in one aspect can be beneficially utilized on other aspects without specific recitation. DETAILED DESCRIPTION

[0022] Aspects of the disclosure provide apparatuses, methods, processing systems, and computer readable media for controlling radio frequency (RF) exposure after an exceptional event, such as an error, reset, crash, or restart of a user equipment (UE) or modem of the UE, or an event that results in exposure to an unknown or indeterminate portion of time therebetween or detection thereof. In certain aspects, a UE can periodically store RF exposure information, such as time-averaged RF exposure measurements of a transmit power history, in memory, preferably unharmed by damage from exceptional events. When an exceptional event occurs, such as a UE restart or a modem reset of the UE, or the UE determines that an unknown or indeterminate portion of time therebetween has passed, the UE can use the stored RF exposure information to determine a reflected power that complies with RF exposure limits. The techniques described herein for providing RF exposure continuity can enable a UE to remain in compliance with RF exposure limits without potentially exposing a user to excessive RF fields after the UE encounters an exceptional event. In other words, the techniques described herein for providing RF exposure continuity can provide a safe operating condition in terms of RF exposure for a user after an exceptional event. The techniques described herein for providing RF exposure continuity can provide a low-power consumption solution that consumes an acceptable amount of power to store RF exposure information without significantly impacting battery life of the UE.

[0023] The following description provides examples of RF exposure compliance management in a communication system and does not limit the scope, applicability, or examples set forth in the claims. Changes can be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples can omit, substitute, or add various procedures or components as appropriate. For instance, the methods described can be performed in an order different from that described, and various steps can be added, omitted, or combined. Also, features described with respect to some examples can be combined in some other examples. For example, an apparatus or a method can be implemented using any number of the aspects set forth herein. Also, the scope of the disclosure is intended to cover an apparatus or method which is implemented using other structure, functionality, or structure and functionality in addition to, or other than, the various aspects of the disclosure described herein. It is understood that any aspect of the disclosure disclosed herein can be embodied by one or more elements of a claim. The word “exemplary” is used herein to mean “serving as an example, instance, or illustration.” Any aspect described herein as “exemplary” is not necessarily to be construed as preferred or advantageous over other aspects.

[0024] In general, any number of wireless networks can be deployed in a given geographic area. Each wireless network can support a particular radio access technology (RAT) and can operate on one or more frequencies. A RAT can also be referred to as a radio technology, an air interface, etc. A frequency can also be referred to as a carrier, a subcarrier, a frequency channel, an audio tone, a subband, etc. Each frequency can support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs and / or to support simultaneous communication of multiple RATs on the same frequency by different wireless networks.

[0025] The techniques described herein can be used for various wireless networks and radio technologies. While aspects can be described herein using terminology commonly associated with 3G, 4G, and / or new radio (e.g., 5GNR) wireless technologies, aspects of the present disclosure can be applied in other generation-based communication systems and / or according to other radio technologies, such as IEEE 802.11, Bluetooth, etc.

[0026] NR access can support various wireless communication services, such as Enhanced Mobile Broadband (eMBB) targeting wide bandwidth (e.g., 80 MHz or beyond), millimeter wave (mmW) targeting high carrier frequency (e.g., 24 GHz to 53 GHz or beyond), massive Machine Type Communications (MTC) (mMTC) targeting non-backward compatible MTC techniques, and / or mission critical communications targeting ultra-reliable low-latency (URLLC). These services can include latency and reliability requirements. These services can also have different transmission time intervals (TTI) to meet respective quality of service (QoS) requirements. In addition, these services can co-exist in the same subframe. NR supports beamforming and beam direction can be dynamically configured. MIMO transmissions with precoding can also be supported. The aggregation of multiple cells can be supported.

[0027] Figure 1 An example wireless communication network 100 in which aspects of the present disclosure can be performed is shown. For example, the wireless communication network 100 can be an NR system (e.g., a 5GNR network), an Evolved Universal Terrestrial Radio Access (E-UTRA) system (e.g., a 4G network), a Universal Mobile Telecommunications System (UMTS) (e.g., a 2G / 3G network), or a Code Division Multiple Access (CDMA) system (e.g., a 2G / 3G network), or can be configured for communication according to an IEEE standard, such as one or more of the 802.11 standards, etc. As shown, the wireless communication network 100 includes a number of base stations 110 (including one or more base stations 110a, 110b, 110c, and 110d) and a number of UEs 120 (including one or more UEs 120a, 120b, 120c, and 120d). A base station can communicate with UEs within its coverage area using wireless communication links. A UE can communicate with a base station within its coverage area using a wireless communication link. Figure 1 As shown, the UE 120a includes an RF exposure manager 122 that provides RF exposure continuity (e.g., after an anomaly event), in accordance with aspects of the present disclosure.

[0028] As shown, the UE 120a includes an RF exposure manager 122 that provides RF exposure continuity (e.g., after an anomaly event), in accordance with aspects of the present disclosure. Figure 1As shown, the wireless communication network 100 can include a number of BSs 1 lOa-z (also individually referred to as BS 110 or collectively as BSs 110) and other network entities. A BS 110 can provide communication coverage for a particular geographic area, which can be fixed or can also move according to the location of a mobile BS 110. In some examples, BSs 110 can be interconnected to one another and / or the wireless communication network 100 through various types of backhaul interfaces (e.g., a direct physical connection, a wireless connection, a virtual network, or the like) using any suitable transport network. Figure 1 In the example shown, BSs 110a, 110b, and 110c can be macro BSs for macro cells 102a, 102b, and 102c, respectively. BS 110x can be a pico BS for a pico cell 102x. BSs 110y and 110z can be femto BSs for femto cells 102y and 102z, respectively. A BS can support one or multiple cells.

[0029] BSs 110 communicate with UEs 120a-y (also referred to individually as UE 120 or collectively as UEs 120) in the wireless communication network 100. UEs 120 (e.g., 120x, 120y, etc.) can be dispersed throughout the wireless communication network 100, and each UE 120 can be stationary or mobile. Wireless communication network 100 can also include relay stations or relays (e.g., relay 110r), also referred to as relays, etc., that receive a transmission of data and / or other information from an upstream station (e.g., a BS 110a or a UE 120r) and send a transmission of the data and / or other information to a downstream station (e.g., a UE 120 or a BS 110), or that relay transmissions between UEs 120, to facilitate communication between devices.

[0030] A network controller 130 can be in communication with a set of BSs 110 and provide coordination and control for these BSs 110 (e.g., via the backhaul). In some cases, the network controller 130 can include a centralized unit (CU) and / or a distributed unit (DU), for example, in a 5G NR system. In some aspects, the network controller 130 can be in communication with a core network 132 (e.g., a 5G core network (5GC)), which provides various network functions such as access and mobility management, session management, user plane function, policy control function, authentication server function, unified data management, application function, network exposure function, network repository function, network slice selection function, and the like.

[0031] Figure 2FIG. 3 illustrates an example wireless communication network 100 in which aspects of the present disclosure can be practiced; Figure 1 The components of wireless communication network 100 can include, for example, a BS 110a and a UE 120a that can be used to implement aspects of the present disclosure.

[0032] At BS 110a, a transmit processor 220 can receive data from a data source 212 and control information from a controller / processor 240. The control information can be for the physical broadcast channel (PBCH), physical control format indicator channel (PCFICH), physical hybrid ARQ indicator channel (PHICH), physical downlink control channel (PDCCH), group common PDCCH (GC PDCCH), etc. The data can be for the physical downlink shared channel (PDSCH), etc. A medium access control (MAC) control element (MAC-CE) is a MAC layer communication structure that can be used for control command exchange between wireless nodes. The MAC-CE can be carried in a shared channel such as a physical downlink shared channel (PDSCH), a physical uplink shared channel (PUSCH), or a physical sidelink shared channel (PSSCH), etc.

[0033] The processor 220 can process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. The transmit processor 220 can also generate reference symbols, such as for the primary synchronization signal (PSS), secondary synchronization signal (SSS), PBCH demodulation reference signal (DMRS), and channel state information reference signal (CSI-RS). A transmit (TX) multiple-input multiple-output (MIMO) processor 230 can perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and / or the reference symbols, if applicable, and can provide output symbol streams to the modulators (MODs) of the transceivers 232a-232t. Each modulator transceiver 232a-232t can process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each modulator can further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a downlink signal. Downlink signals from modulator transceivers 232a-232t can be transmitted via the antennas 234a-234t, respectively.

[0034] At the UE 120a, the antennas 252a-252r can receive the downlink signals from the BS 110a and can provide received signals to the demodulators (DEMODs) in transceivers 254a-254r, respectively. Each demodulator in the transceivers 254a-254r can condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each demodulator can further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector 256 can obtain received symbols from all the demodulators in the transceivers 254a-254r, perform MIMO detection on the received symbols if applicable, and provide detected symbols. A receive processor 258 can process (e.g., demodulate, deinterleave, and decode) the detected symbols, providing decoded data for the UE 120a to a data sink 260, and provide decoded control information to a controller / processor 280.

[0035] On the uplink, at the UE 120a, a transmit processor 264 can receive and process data (e.g., for the physical uplink shared channel (PUSCH)) from a data source 262 and receive and process control information (e.g., for the physical uplink control channel (PUCCH)) from the controller / processor 280. The transmit processor 264 can also generate reference symbols for a reference signal (e.g., for the sounding reference signal (SRS)). The symbols from the transmit processor 264 can be precoded by a TX MIMO processor 266 if applicable, further processed by the modulators (MODs) in transceivers 254a-254r (e.g., for SC-FDM, etc.), and transmitted to the BS 110a. At the BS 110a, the uplink signals from the UE 120a can be received by the antennas 234, processed by the modulators in transceivers 232a-232t, detected by a MIMO detector 236 if applicable, and further processed by a receive processor 238 to obtain decoded data and control information sent by the UE 120a. The receive processor 238 can provide the decoded data to a data sink 239 and the decoded control information to a controller / processor 240.

[0036] The memory 242 and 282 can store data and program codes for the BS 110a and the UE 120a, respectively. A scheduler 244 can schedule UEs for data transmission on the downlink and / or uplink.

[0037] Antennas 252, processors 266, 264, and / or controller / processor 280 of the UE 120a and / or antennas 234, processors 220, 230, and / or controller / processor 240 of the BS 110a can be used to perform the various techniques and methods described herein. As Figure 2 illustrated, the controller / processor 280 of the UE 120a has an RF exposure manager 281 that provides RF exposure continuity (e.g., after an exceptional event), in accordance with aspects described herein. The RF exposure manager 281 can be an example of the RF exposure manager 122 Figure 1 described herein. Although illustrated at the controller / processor, other components of the UE 120a and BS 110a can be used to perform the operations described herein. In some embodiments, the BS 110a (e.g., controller / processor 240) includes an exposure manager configured to provide RF exposure continuity for the BS 110a.

[0038] NR can utilize orthogonal frequency division multiplexing (OFDM) with a cyclic prefix (CP) on the uplink and downlink. NR can support half-duplex

[0039] Although the UE 120a is described with reference to Figure 1 and Figure 2 communicate / directly transmit with another UE 120, or directly with another wireless device, without relaying communications through a network. In some embodiments, the BS 110a, illustrated and described above, is an example of another UE 120. Figure 2

[0040] Example RF transceiver

[0041] Figure 3 ​is a block diagram of an example RF transceiver circuit 300 according to certain aspects of the present disclosure. In some embodiments, the RF transceiver circuit 300 is an example of the transceiver 232 and / or 254, or a portion thereof. The RF transceiver circuit 300 includes at least one transmit (TX) path 302 (also referred to as a transmit chain) for transmitting signals via one or more antennas 306, which can be examples of the antennas 234 and / or 252, and at least one receive (RX) path 304 (also referred to as a receive chain) for receiving signals via the antennas 306. When the TX path 302 and the RX path 304 share an antenna 306, the paths can connect with the antenna via an interface 308, which can include any of a variety of suitable RF devices, such as switches, duplexers, diplexers, and multiplexers, among others.

[0042] The TX path 302 can include a baseband filter (BBF) 312, a mixer 314, a driver amplifier (DA) 316, and a power amplifier (PA) 318, from which in-phase (I) or quadrature (Q) baseband analog signals are received from a digital-to-analog converter (DAC) 310. The BBF 312, the mixer 314, and the DA 316 can be included in one or more radio frequency integrated circuits (RFICs). In some embodiments, the mixer (e.g., 314), the DA 316, and / or the PA 318 can be included in an RFIC.

[0043] The BBF 312 filters the baseband signal received from the DAC 310, and the mixer 314 mixes the filtered baseband signal with a transmit local oscillator (LO) signal to convert the baseband signal of interest to a different frequency (e.g., upconvert from baseband to radio frequency). This frequency conversion process produces sum and difference frequencies between the LO frequency and the frequency of the baseband signal of interest. The sum and difference frequencies are referred to as beat frequencies. The beat frequencies are typically in the RF range, such that the signal output by the mixer 314 is typically an RF signal, which can be amplified by the DA 316 and / or the PA 318 before transmission by the antenna 306. While one mixer 314 is shown, several mixers can be used to upconvert the filtered baseband signal to one or more intermediate frequencies (IFs), and then upconvert the IF signal to the frequency for transmission. Moreover, while the examples discussed herein utilize I and Q signals, those skilled in the art will understand that the elements of the RF transceiver circuit 300 can be configured to utilize polar modulation.

[0044] The RX path 304 can include a low noise amplifier (LNA) 324, a mixer 326, and a baseband filter (BBF) 328. The LNA 324, mixer 326, and optionally the BBF 328 can be included in one or more RFICs, which can or can not be the same RFIC(s) that include the TX path components. RF signals received via the antenna 306 can be amplified by the LNA 324, and the mixer 326 mixes the amplified RF signals with a receive local oscillator (LO) signal to convert the RF signals of interest to a different baseband frequency (e.g., downconvert). The baseband signals output by the mixer 326 can be filtered by the BBF 328 before being converted to digital I or Q signals by an analog-to-digital converter (ADC) 330 for digital signal processing. While one mixer 326 is shown, several mixers can be used to downconvert the amplified RF signals to one or more intermediate frequencies, and then downconvert the intermediate frequency signals to baseband.

[0045] Certain transceivers can employ a frequency synthesizer with a voltage controlled oscillator (VCO) to generate a stable tunable LO signal with a particular tuning range. Thus, a transmit LO signal can be generated by a TX frequency synthesizer 320, which can be buffered or amplified by an amplifier 322 before being mixed with a baseband (or IF) signal in the mixer 314. Similarly, a receive LO signal can be generated by an RX frequency synthesizer 332, which can be buffered or amplified by an amplifier 334 before being mixed with an RF (or IF) signal in the mixer 326.

[0046] A controller 336 can direct the operation of the RF transceiver circuit 300, such as transmitting signals via the TX path 302 and / or receiving signals via the RX path 304. The controller 336 can be a general purpose processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof. The controller 336 can be an example of, or can be implemented with, the controller / processor 240 or 280, or a portion thereof, or can be implemented separately from the controller / processor 240, 280. A memory 338 can store data and program codes for operating the RF transceiver circuit 300. The memory 338 can be an example of, or can be implemented with, the memory 242 or 282, or a portion thereof, or can be implemented separately from the memory 242, 282. The controller 336 and / or the memory 338 can include control logic. In certain cases, the controller 336 can determine a time-averaged RF exposure measurement based on a transmission power level (e.g., certain gain levels at the PA 318) set by the TX path 302 to set a transmission power level for a time slot that complies with RF exposure limits set by domestic and international regulations as further described herein.

[0047] Example RF exposure measurements

[0048] RF exposure can be expressed in terms of specific absorption rate (SAR), which measures the absorption of energy per unit mass of human tissue, and can have units of watts per kilogram (W / kg). RF exposure can also be expressed in terms of power density (PD), which measures the absorption of energy per unit area and can have units of mW / cm 2 In certain cases, maximum permissible exposure (MPE) limits in terms of PD can be imposed for wireless communication devices that use transmission frequencies above 6 GHz. MPE limits are regulatory measures for area-based exposure, e.g., an energy density limit defined as a number X of watts per square meter (W / m 2 ) averaged over a defined area and a time to prevent human exposure hazards represented by tissue temperature changes, averaged over a frequency-dependent time window.

[0049] SAR can be used to evaluate RF exposure for transmission frequencies below 6 GHz, which covers wireless communication technologies such as 2G / 3G (e.g., CDMA), 4G (e.g., LTE), 5G (e.g., NR in 6 GHz bands), IEEE 802.11ac, etc. PD can be used to evaluate RF exposure for transmission frequencies above 10 GHz, which covers wireless communication technologies such as IEEE 802.11ad, 802.11ay, 5G in mmWave bands, etc. Thus, different metrics can be used to evaluate RF exposure for different wireless communication technologies.

[0050] A wireless communication device (e.g., UE 120) can transmit signals using multiple wireless communication technologies simultaneously. For example, a wireless communication device can transmit signals using a first wireless communication technology (e.g., 3G, 4G, 5G, etc.) that operates at or below 6 GHz and a second wireless communication technology (e.g., mmWave 5G in 24-60 GHz bands, IEEE 802.11ad, or 802.11ay) that operates above 6 GHz simultaneously. In certain aspects, a wireless communication device can transmit signals using a first wireless communication technology (e.g., 3G, 4G, 5G, IEEE 802.11ac, etc.) in sub-6 GHz bands (where RF exposure is measured in terms of SAR) and a second wireless communication technology (e.g., 5G in 24-60 GHz bands, IEEE 802.11ad, 802.11ay, etc.) (where RF exposure is measured in terms of PD) simultaneously.

[0051] To evaluate RF exposure from transmissions using a first technology (e.g., 3G, 4G, 5G, IEEE 802.11ac, etc. in sub-6 GHz bands), a wireless communication device can include a plurality of SAR profiles for the first technology stored in memory (e.g., Figure 2 memory 242, 282, or Figure 3 memory 338) of the wireless communication device. Each of the SAR profiles can correspond to a respective transmission scenario of a plurality of transmission scenarios supported by the wireless communication device for the first technology. The transmission scenarios can correspond to various combinations of antennas (e.g., Figure 2 antennas 234a-t, 252a-r, or Figure 3 antennas 306) of the wireless communication device), frequency bands, channels, and / or body positions, as discussed further below.

[0052] The SAR profile (also referred to as a SAR map) for each transmission scenario can be generated based on measurements (e.g., electric field measurements) performed in a test laboratory using a human body model. After the SAR profiles are generated, the SAR profiles are stored in memory to enable a processor (e.g., Figure 2 processor 240, 280, or Figure 3 controller 336) of the wireless communication device to evaluate RF exposure in real-time, as discussed further below. Each SAR profile includes a set of SAR values, where each SAR value can correspond to a different location (e.g., on the human body model). Each SAR value can include a SAR value averaged over a certain mass (e.g., 1 g or 10 g) at the respective location.

[0053] The SAR values in each SAR profile correspond to a particular transmission power level (e.g., the transmission power level at which the SAR values were measured in the test laboratory). Since SAR scales with transmission power level, the processor can scale the SAR profile for any transmission power level by multiplying each SAR value in the SAR profile by a transmission power scaling factor: (1)

[0054] where Tx c is the current transmission power level for the respective transmission scenario, Tx SAR is the transmission power level corresponding to the SAR values in the stored SAR profile (e.g., the transmission power level at which the SAR values were measured in the test laboratory).

[0055] As described above, a wireless communication device can support multiple transmit scenarios for a first technology. In certain aspects, a transmit scenario can be specified by a set of parameters. The set of parameters can include one or more of an antenna parameter indicating one or more antennas (i.e., active antennas) used for transmission, a frequency band parameter indicating one or more frequency bands (i.e., active frequency bands) used for transmission, a channel parameter indicating one or more channels (i.e., active channels) used for transmission, a body position parameter indicating a position of the wireless communication device relative to a user body position (head, torso, away from body, etc.), a parameter indicating whether a device cover and / or a device cover type is on the device, and / or other parameters. In cases where a wireless communication device supports a large number of transmit scenarios, it can be very time consuming and expensive to perform measurements for each transmit scenario in a test setting (e.g., a test lab). To reduce test time, measurements can be performed for a subset of the transmit scenarios to generate SAR distributions for the subset of transmit scenarios. In this example, a SAR distribution for each of the remaining transmit scenarios can be generated by combining two or more SAR distributions for the subset of transmit scenarios, as discussed further below.

[0056] For example, SAR measurements can be performed for each antenna to generate a SAR distribution for each antenna. In this example, a SAR distribution for a transmit scenario in which two or more antennas are active can be generated by combining SAR distributions for the two or more active antennas.

[0057] In another example, SAR measurements can be performed for each of a plurality of frequency bands to generate a SAR distribution for each of the plurality of frequency bands. In this example, a SAR distribution for a transmit scenario in which two or more frequency bands are active can be generated by combining SAR distributions for the two or more active frequency bands.

[0058] In certain aspects, a SAR distribution can be normalized with respect to a SAR limit by dividing each SAR value in the SAR distribution by the SAR limit. In this case, when a normalized SAR value is greater than 1, the normalized SAR value exceeds the SAR limit, and when a normalized SAR value is less than 1, the normalized SAR value is below the SAR limit. In these aspects, each of the SAR distributions stored in the memory can be normalized with respect to the SAR limit.

[0059] In certain aspects, a normalized SAR distribution for a transmission scenario can be generated by combining two or more normalized SAR distributions. For example, a normalized SAR distribution for a transmission scenario in which two or more antennas are active can be generated by combining normalized SAR distributions for the two or more active antennas. For cases in which different transmission power levels are used for the active antennas, each active antenna's normalized SAR distribution can be scaled by the respective transmission power level before combining the normalized SAR distributions for the active antennas. A normalized SAR distribution for simultaneous transmission from multiple active antennas can be given by:

[0060] (2)

[0061] where SAR lim is the SAR limit, SAR norm_combined is the combined normalized SAR distribution for simultaneous transmission from the active antennas, i is an index for the active antennas, SAR i is the SAR distribution for the i-th active antenna, Tx i is the transmission power level for the i-th active antenna, Tx SARi is the transmission power level for the i-th active antenna's SAR distribution, and K is the number of active antennas.

[0062] Equation (2) can be rewritten as follows:

[0063] (3a)

[0064] where SAR norm_i is the normalized SAR distribution for the i-th active antenna. In cases of simultaneous transmission using multiple active antennas at the same transmission frequency (e.g., multiple-input multiple-output (MIMO)), the combined normalized SAR distribution can be obtained by summing the square roots of the individual normalized SAR distributions and computing the square of the sum, as follows:

[0065] (3b).

[0066] In another example, normalized SAR distributions for different frequency bands can be stored in memory. In this example, a normalized SAR distribution for a transmission scenario where two or more frequency bands are active can be generated by combining normalized SAR distributions for two or more active frequency bands. For cases where the transmission power level differs for the active frequency bands, the normalized SAR distribution for each active frequency band can be scaled by the corresponding transmission power level before combining the normalized SAR distributions for the active frequency bands. In this example, the combined SAR distribution can also be calculated using equation (3a), where i is the index for the active frequency band, and SAR... norm_i It is a normalized SAR distribution for the i-th active frequency band, Tx i This refers to the transmission power level of the i-th active frequency band, Tx SARi It is the transmission power level of the normalized SAR distribution for the i-th active frequency band.

[0067] To assess RF exposure from transmissions using a second technology (e.g., 5G in the 24-60 GHz band, IEEE 802.11ad, 802.11ay, etc.), the wireless communication device may include storage in memory (e.g., Figure 2 Memory 242, 282 or Figure 3 The memory 338 contains multiple PD distributions for the second technology. Each PD distribution may correspond to a specific transmission scenario among multiple transmission scenarios supported by the wireless communication device for the second technology. A transmission scenario may correspond to an antenna (e.g., Figure 2 Antennas 234a to 234t, 252a to 252r or Figure 3 Various combinations of antenna 306, frequency band, channel and / or body position, as discussed further below.

[0068] The PD distribution (also known as the PD map) for each launch scenario can be generated based on measurements (e.g., electric field measurements) performed in a test lab using a human model. After generating the PD distribution, it is stored in memory so that the processor (e.g., ...) can... Figure 2 Processor 240, 280 or Figure 3 The controller 336 is capable of assessing RF exposure in real time, as discussed further below. Each PD distribution includes a set of PD values, where each PD value may correspond to a different location (e.g., on a human model).

[0069] The PD values in each PD distribution correspond to a particular transmission power level (e.g., the transmission power level at which the PD values were measured in the test lab). Since PD scales with transmission power level, the processor can scale the PD distribution for any transmission power level by multiplying each PD value in the PD distribution by the following transmission power scaling factor:

[0070] (4)

[0071] where Tx c is the current transmission power level for the corresponding transmission scenario, Tx PD is the transmission power level corresponding to the PD values in the PD distribution (e.g., the transmission power level at which the PD values were measured in the test lab).

[0072] As described above, a wireless communication device can support multiple transmission scenarios for a second technology. In certain aspects, a transmission scenario can be specified by a set of parameters. The set of parameters can include one or more of the following: an antenna parameter indicating one or more antennas (i.e., active antennas) used for transmission, a frequency band parameter indicating one or more frequency bands (i.e., active frequency bands) used for transmission, a channel parameter indicating one or more channels (i.e., active channels) used for transmission, a body position parameter indicating a position of the wireless communication device relative to a user body position (head, torso, away from body, etc.), a parameter indicating whether a device cover and / or a device cover type is on the device, and / or other parameters. In cases where a wireless communication device supports a large number of transmission scenarios, it can be very time consuming and expensive to perform measurements in a test setting (e.g., a test lab) for each transmission scenario. To reduce test time, measurements can be performed for a subset of the transmission scenarios to generate PD distributions for the subset of transmission scenarios. In this example, the PD distribution for each of the remaining transmission scenarios can be generated by combining two or more of the PD distributions for the subset of transmission scenarios, as discussed further below.

[0073] For example, PD measurements can be performed for each antenna to generate a PD distribution for each antenna. In this example, the PD distribution for a transmission scenario in which two or more antennas are active can be generated by combining the PD distributions for the two or more active antennas.

[0074] In another example, PD measurements can be performed for each of a plurality of frequency bands to generate a PD distribution for each of the plurality of frequency bands. In this example, the PD distribution for a transmission scenario in which two or more frequency bands are active can be generated by combining the PD distributions for the two or more active frequency bands.

[0075] In certain aspects, the PD distribution can be normalized with respect to the PD limit by dividing each PD value in the PD distribution by the PD limit. In this case, when the normalized PD value is greater than 1, the normalized PD value exceeds the PD limit, and when the normalized PD is less than 1, the normalized PD value is below the PD limit. In these aspects, each of the PD distributions stored in the memory can be normalized with respect to the PD limit.

[0076] In certain aspects, the normalized PD distribution for a transmission scenario can be generated by combining two or more normalized PD distributions. For example, a normalized PD distribution for a transmission scenario in which two or more antennas are active can be generated by combining normalized PD distributions for the two or more active antennas. For cases in which different transmission power levels are used for the active antennas, the normalized PD distribution for each active antenna can be scaled by the respective transmission power level before combining the normalized PD distributions for the active antennas. The normalized PD distribution for simultaneous transmission from multiple active antennas can be given by:

[0077] (5)

[0078] where PD lim is the PD limit, PD norm_combined is the normalized PD distribution for the combination of simultaneous transmissions from active antennas, i is an index for an active antenna, PD i is the PD distribution for the i-th active antenna, Tx i is the transmission power level for the i-th active antenna, Tx PDi is the transmission power level for the PD distribution of the i-th active antenna, and L is the number of active antennas.

[0079] Equation (5) can be rewritten as follows:

[0080] (6a)

[0081] where PD norm_i is the normalized PD distribution for the i-th active antenna. In cases of simultaneous transmission using multiple active antennas at the same transmission frequency (e.g., MIMO), the combined normalized PD distribution can be obtained by summing the square roots of the individual normalized PD distributions and computing the square of the sum, as follows:

[0082] (6b).

[0083] In another example, normalized PD distributions for different frequency bands can be stored in memory. In this example, a normalized PD distribution for a transmission scenario in which two or more frequency bands are active can be generated by combining the normalized PD distributions for the two or more active frequency bands. For cases in which the transmission power level is different for the active frequency bands, each active frequency band's normalized PD distribution can be scaled by the respective transmission power level before combining the normalized PD distributions for the active frequency bands. In this example, the combined PD distribution can also be computed using Equation (6a), where i is an index for an active frequency band, PD norm_i is the normalized PD distribution for the i-th active frequency band, Tx i is the transmission power level for the i-th active frequency band, and Tx PDi is the transmission power level for the normalized PD distribution for the i-th active frequency band.

[0084] As described above, the UE 120 can simultaneously transmit signals using a first technology (e.g., 3G, 4G, IEEE 802.11ac, etc.) and a second technology (e.g., 5G, IEEE 802.11ad, etc.), where different metrics (e.g., SAR for the first technology and PD for the second technology) are used to measure RF exposure for the first and second technologies. In this case, the processor 280 can determine a first maximum allowed power level for the first technology and a second maximum allowed power level for the second technology for a transmission in a time slot that complies with the RF exposure limit. During the time slot, the transmission power levels for the first and second technologies are subject to (i.e., limited by) the determined first and second maximum allowed power levels, respectively, to ensure compliance with the RF exposure limit, as described below. In this disclosure, the term “maximum allowed power level” refers to the “maximum allowed power level” imposed by the RF exposure limit, unless otherwise specified. It should be understood that the “maximum allowed power level” does not necessarily equal the absolute maximum power level that complies with the RF exposure limit, and can be less than the absolute maximum power consumption level that complies with the RF exposure limit (e.g., to provide a safety margin). The “maximum allowed power level” can be used to set a power level limit for the transmission at the transmitter, such that the power level of the transmission does not exceed the “maximum allowed power level,” thereby ensuring RF exposure compliance.

[0085] The processor (e.g., 240, 280, 336) can determine the first maximum allowed power level and the second maximum allowed power level as follows. The processor can determine a normalized SAR distribution for the first technology at the first transmission power level, determine a normalized PD distribution for the second technology at the second transmission power level, 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 can be determined by combining the normalized SAR value at that location with the normalized PD value at that location or another technology.

[0086] The processor can then determine whether the first transmission power level and the second transmission power level comply with the RF exposure limit by comparing the peak value in the combined normalized distribution with 1. If the peak value is equal to or less than 1 (i.e., the condition ≤ 1 is satisfied), the processor 280 can determine that the first transmission power level and the second transmission power level comply with the RF exposure limit (e.g., the SAR limit and the PD limit), and use the first transmission power level and the second transmission power level as the first maximum allowed power level and the second maximum allowed power level, respectively, during the time slot. If the peak value is greater than 1, the processor can determine that the first transmission power level and the second transmission power level do not comply with the RF exposure limit. The condition for RF exposure compliance for simultaneous transmission using the first technology and the second technology can be given by the following equation:

[0087] (7).

[0088] The normalized SAR distribution in equation (7) can be generated by combining two or more normalized SAR distributions as described above (e.g., for a transmission scenario using multiple active antennas). Similarly, the normalized PD distribution in equation (7) can be generated by combining two or more normalized PD distributions as described above (e.g., for a transmission scenario using multiple active antennas). In this case, the condition for RF exposure compliance in equation (7) can be rewritten using equations (3a) and (6a) as follows:

[0089] (8). For the MIMO case, equations (3b) and (6b) can be combined instead. As shown in equation (8), the combined normalized distribution can be a function of the transmission power level for the first technology and the transmission power level for the second technology. All points in the combined normalized distribution can satisfy the normalized limit of 1 in equation (8). Furthermore, when combining the SAR distribution and the PD distribution, the SAR distribution and the PD distribution can be spatially aligned or aligned with their peak locations, such that the combined distribution given by equation (8) represents the combined RF exposure for a given location of the human body.

[0090] Example anomalous robust time average RF exposure compliance continuity

[0091] Time average RF exposure compliance (e.g., SAR or MPE / PD) can provide desired device performance, as well as ensure user safety at the device. In certain cases, such as normal runtime operation, a device (e.g., a UE) has an active system that always ensures RF exposure compliance based on a varying time window of power history. When the UE operation stops due to an anomalous condition, such as an assertion, crash, or reset, and then the UE subsequently returns to normal runtime operation, the UE can lose all recent RF exposure history used to ensure time average RF exposure compliance. For shorter RF exposure time windows (e.g., 4 seconds for NR frequency range (FR) 2), resetting the RF exposure history can be acceptable because the time it takes for the UE to restart and begin normal transmission operations can be longer than the time window over which the power history is to be averaged. However, for certain transmission frequencies (e.g., NR FR1 and legacy 2 / 3 / 4G wireless wide area network (WWAN)), and depending on the regulatory standard used, the time window can be longer (e.g., up to 360 seconds). Because the time window for determining RF exposure compliance for certain transmission frequencies is long, the UE can restart without transmit power history. Thus, the lack of transmit power history can disrupt the operation of software / components to ensure RF exposure compliance. For example, without proper procedures, the UE can transmit data using transmit power that exceeds the RF exposure limit for the time window due to the lack of transmit power history prior to the anomalous condition in the time window.

[0092] Aspects of the present disclosure provide various techniques for providing continuity of RF exposure information after various exceptional events, such as errors, resets, crashes, or reboots affecting the UE or the modem of the UE in particular, and / or events that result in RF exposure being unknown or uncertain for a portion of time in between. In certain aspects, a UE can periodically store RF exposure information, such as a time-averaged RF exposure measurement of transmit power and / or transmit power history, in a memory that can be immune to damage from exceptional events. When an exceptional event occurs, such as a UE reboot or a modem reset of the UE, or an event that causes the UE to experience or detect an amount of time for which RF exposure information is unknown or uncertain, the UE can use the stored RF exposure information to determine a transmit power that complies with RF exposure limits. The techniques described herein for providing RF exposure continuity can enable a UE to remain in compliance with RF exposure limits after encountering an exceptional event, and / or can allow a UE to transmit at a higher power in certain such cases while maintaining the safety of users after the exceptional event. The techniques described herein for providing RF exposure continuity can provide a low-power consumption solution that consumes an acceptable amount of power to store RF exposure measurements without significantly impacting the battery life of the UE. In certain cases, the techniques described herein for providing RF exposure continuity can facilitate desirable power consumption, e.g., due to a relatively higher transmit power used prior to the exceptional event that is taken into account when considering the stored RF exposure information (e.g., exceeding RF exposure limits). In certain cases, the techniques described herein for providing RF exposure continuity can enable desirable transmit power, e.g., due to a relatively lower transmit power used prior to the exceptional event that is taken into account when considering the stored RF exposure information (e.g., less than RF exposure limits).

[0093] Certain aspects of the present disclosure relate to using a UE's on-board power management integrated circuit (PMIC), which can include a counter. In certain cases, the counter can be based on a real-time clock (RTC). The RTC can monotonically count up even when the UE is reset or temporarily powered off. The RTC can allow UE software to periodically take a snapshot of the transmit power history using the PMIC RTC timestamp and save the transmit power history in internal static memory, which can be immune to damage due to abnormal events. After a reset or shortly after a reset, the UE software can check a memory location in the internal static memory for the RTC timestamp, an optional consistency / reliability indicator (e.g., a checksum such as a cyclic redundancy check (CRC)), and data indicating the most recent transmit power history (e.g., a CRC-protected data set). If the CRC passes, for example, the current (post-reset) RTC timestamp is used to determine how old the transmit power history is, and the compliance algorithm transmit power history accounting of the UE is updated accordingly. The techniques described herein for providing RF exposure continuity can ensure compliance at any time, even in the event of an unexpected reset or other abnormal event (e.g., if the most recent exposure record is lost or unknown for any reason). If the CRC passes, but the timestamp is too old to fall within the longest time averaging window, the transmit power history can not be used. If the CRC fails, the UE can enter a failsafe mode in which the transmit power is limited for an initial duration of the longest window, ensuring compliance at the expense of initial performance.

[0094] Figure 4 is a flowchart illustrating example operations 400 for wireless communication, in accordance with certain aspects of the present disclosure. The operations 400 can be performed, for example, by a UE (e.g., a UE 120a in the wireless communication network 100), a BS, or a customer premises equipment (CPE). The operations 400 can be implemented as software components that are run on one or more processors (e.g., controller / processors 240, 280, controller 336 of a UE, a BS, or a CPE) of a UE, a BS, or a CPE. Figure 2 Figure 3 Figure 2 Figure 3 Figure 3

[0095] ​​​​​Operations 400 can begin, at block 402, where the UE can transmit a first signal at a first transmission power based on time-averaged RF exposure measurements during a time window. At block 404, the UE can store RF exposure information associated with the time window. At block 406, the UE can detect that an exceptional event associated with the UE has occurred. At block 408, the UE can transmit a second signal at a second transmission power based at least in part on the stored RF exposure information in response to the detection of the event.

[0096] In some aspects, the UE (e.g., using components described in Figure 2 and / or Figure 3 described in the detailed description, and potentially in combination with the RF exposure manager 122, 281) can communicate with a base station, such as the BS 110. For example, at block 402 and / or block 408, the UE can transmit user data to the base station on a physical uplink shared channel (PUSCH) or various uplink feedback (e.g., uplink control information or hybrid automatic repeat request (HARQ) feedback) to the base station on a physical uplink control channel (PUCCH). In certain instances, the UE can communicate with another UE. For example, at block 402 and / or block 408, the UE can transmit user data and / or various feedback to another UE on a sidelink channel.

[0097] In some aspects, the RF exposure information can include a history of transmission powers and / or time-averaged RF exposure measurements. In certain instances, the RF exposure information can include a sum of the time-averaged RF exposure measurements, a sum of the transmission powers at times corresponding to time stamps within the time window, or an integral of the transmission power over time. In certain instances, the RF exposure information can include a separate value for each of the time-averaged RF exposure measurements or the transmission powers at times corresponding to time stamps within the time window.

[0098] At block 404, the UE (e.g., the RF exposure manager 122, 281) can periodically store the RF exposure information. That is, the UE can store the RF exposure information according to a periodicity, such as every 50 milliseconds (ms), 500 ms, or 1 second (s). In other words, the UE can store the RF exposure information at periodic intervals of, for example, 50 ms, 500 ms, or 1 s.

[0099] At block 404, the UE can store the RF exposure information in a memory that is impervious to damage from the exceptional event. That is, the memory can be configured to store data (such as the RF exposure information) prior to or at the time of the exceptional event, where the exceptional event does not damage the stored data. In certain cases, the UE can store the RF exposure information at the time of the exceptional event, for example, when the UE is still transmitting during the exceptional event. For example, the memory can be a non-volatile memory or static memory separate from the memory used for the file system, as described herein with respect to Figure 6 Further described. In certain cases, the memory used for the file system can consume too much power to provide a low-power memory solution for storing the RF exposure information. However, in certain aspects, the RF exposure information can be stored in the memory used for the file system.

[0100] At block 404, the UE can store the RF exposure information with a timestamp. The timestamp can correspond to a time at which the most recent time-averaged RF exposure measurement was generated or a time at which the UE transmitted the most recent transmission (e.g., absolute or relative time). In other words, the RF exposure information can include the most recent time-averaged RF exposure measurement or the most recent transmission power history.

[0101] In some aspects, the timestamp associated with the RF exposure information can be used to determine whether to use the RF exposure information in determining the second transmission power for the second signal. For example, at block 408, if the timestamp of the RF exposure information is within a current time window (e.g., in response to determining that the RF exposure information timestamp is within the current time window), the UE can transmit the second signal at the second transmission power based at least in part on the stored RF exposure information, where the current time window can look backward in time from, for example, a timestamp corresponding to a time at which the UE recovered from the abnormal event. In other words, if the timestamp of the RF exposure information is outside the current time window, the UE can not consider the RF exposure information in determining the second transmission power for the second signal. In certain cases, the UE can determine a time delta between the timestamp of the RF exposure information and a current timestamp (e.g., corresponding to when the UE recovered from the abnormal event), and if the time delta is greater than (or equal to) a duration of the (current or longest) time window, the UE can not consider the RF exposure information in determining the second transmission power for the second signal. Otherwise, if the time delta is less than (or equal to) the duration of the (current or longest) time window, the UE can use the RF exposure information in determining the second transmission power for the second signal. As noted above, the time window can vary based on frequency and / or regulation / standard; thus, in certain scenarios (e.g., transmission frequency, geographic location, etc.), a particular time delta can correspond to the UE using the RF exposure information in determining the second transmission power for the second signal, and in other scenarios, a particular time delta can correspond to the UE ignoring the RF exposure information.

[0102] In certain aspects, storing the RF exposure information can involve obtaining a timestamp from a counter or clock. For example, the UE can obtain the timestamp from a counter that is not damaged by the abnormal event. The counter can be impervious to damage by the abnormal event by being able to continue to provide timestamps independent of the abnormal event. That is, the counter can continue to monotonically count up during the abnormal event without losing any time delta. In certain cases, the counter can be based on a real-time clock.

[0103] For example, assume that the UE restarts and when the UE returns to normal operation, the UE checks whether the timestamp of the stored RF exposure information is within the current (or longest) time window. For example, the UE can obtain a current timestamp from a counter and compare the current timestamp to the timestamp of the RF exposure information. If the timestamp of the stored RF exposure information is within the current time window, the UE can use the stored RF exposure information in determining the second transmission power for the second signal. The UE can continue to use the RF exposure information to supplement RF exposure measurements until the timestamp is outside the current time window. If the timestamp of the RF exposure information is outside the current time window (i.e., too much time has passed since the abnormal event), the UE can not use the stored RF exposure information in determining the second transmission power for the second signal.

[0104] In certain cases, the RF exposure information and / or timestamp can be stored with a check value or other reliability or fidelity indicator that detects data inconsistency, such as a cyclic redundancy check (CRC) or checksum. In certain cases, the check value can include a remainder in a CRC of the RF exposure information and / or timestamp.

[0105] In certain aspects, determining whether to use the RF exposure information can depend on the check value passing the CRC or confirming the fidelity of the RF exposure information based on the reliability indicator. For example, if the CRC of the RF exposure information matches the check value (e.g., in response to determining that the CRC of the RF exposure information matches the check value), the UE can transmit the second signal at the second transmission power based on supplementing the current time-averaged RF exposure measurements during the time window with the stored RF exposure information. In certain aspects, if the CRC of the RF exposure information passes, the RF exposure information can be used to determine the second transmission power for the second signal. If the CRC of the RF exposure information fails, the UE can enter a fail-safe mode in which a lower RF exposure limit than the standard RF exposure limit can be used to determine the transmission power for the second signal. For example, the fail-safe mode can include using an assumed previous transmission power or exposure (e.g., the maximum transmission power or exposure over the duration of an earlier / previous portion of the current time window) to determine the transmission power for the second signal to ensure the safety of the user and compliance with any applicable exposure limit. In certain cases, the fail-safe mode can be used if the RF exposure information is outside the current time window when returning to normal operation after an abnormal event. However, in certain cases where the transmission power for the second signal is based on the stored RF exposure information, the stored RF exposure information would indicate a previous transmission power or exposure that is less than the transmission power assumed in the fail-safe mode, and thus, the transmission power for the second signal can be higher than the transmission power used in the fail-safe mode while still maintaining the safety of operation conditions for the user.

[0106] In certain cases, the second transmission power at block 408 can be based on supplementing the time-averaged RF exposure measurement with the stored RF exposure information. For example, assume that the time window is 100 seconds, such that the stored RF exposure information represents 100 seconds of transmission history. If the abnormal event only took 10 seconds, then there are still 90 seconds of RF exposure information available for a new RF exposure measurement taken during normal operation after the abnormal event.

[0107] In certain cases, the second transmission power at block 408 can be based at least in part on the stored RF exposure information when at least one RF exposure measurement is missing from the time window. For example, the UE can miss RF exposure measurements due to an abnormal event. That is, the UE can be unable to communicate with other wireless communication devices and transmit signals during the abnormal event. The UE can miss transmission power history during the abnormal event, and as a result, RF exposure measurements can be missing from the time window.

[0108] In some aspects, the UE can detect abnormal events (at block 406) in various ways. For example, the UE (e.g., RF exposure manager 122 281) can monitor certain logs, statistics, or interface states (enabled or disabled) associated with one or more wireless communication components of the UE, such as a modem, to determine whether the UE has encountered an abnormal event. Certain messages in the logs (e.g., error messages or directed messages) can indicate that an abnormal event has occurred, various transmission statistics (e.g., transmitted packets or transmission bytes) that are reset to zero can indicate that an abnormal event has occurred, or a switch of the modem from an enabled state (e.g., the modem is online and operational) to a disabled state (e.g., the modem is offline) can indicate that an abnormal event has occurred. In certain cases, the UE can monitor for a particular interrupt in the modem that indicates that an abnormal event has occurred. In some embodiments, the RF exposure manager is implemented in the modem, and the RF exposure manager can identify that the modem has been (temporarily) disabled by checking the above-mentioned logs or transmission statistics. Thus, software implemented separately from the modem can monitor the modem and / or its operation and perform the determination at block 406, or the modem can monitor itself to perform the determination at block 406. Such checking can be performed periodically (e.g., in the same order as the storage of RF exposure information, such as every 50 ms, 500 ms, or 1 s, or according to another period that is independent of the storage of RF exposure information), based on certain events (e.g., new data is loaded into a transmission buffer), and / or the like.

[0109] In some aspects, the abnormal event can include various events in which the UE temporarily stops communicating, or events that result in RF exposure of the UE that is unknown or uncertain for a portion of time during which. For example, the abnormal event can include a modem shutdown, modem reset, modem restart, modem crash, or modem encountering an error. In certain cases, the abnormal event can include an error, reset, crash, or restart that affects operation of the UE or a modem used to transmit the first signal and the second signal. For example, an error, reset, crash, or restart of the modem or another component can cause the UE to be temporarily inoperable from a perspective of wireless communication, or temporarily inoperable from a perspective of tracking RF exposure. That is, the error, reset, crash, or restart can prevent the UE from wirelessly communicating, such as transmitting a signal from the UE’s antenna(s), or prevent the UE from determining RF exposure for a period of time.

[0110] In some aspects, the second transmission power at block 408 can be based on a type of the abnormal event and / or a confidence in a likelihood of transmission during the portion of the time window corresponding to the missing RF exposure measurement. For example, if the RF exposure manager determines that communication (or at least transmission) stopped during the portion of the time window (e.g., based on the messages, logs, statistics, etc. described above), the RF exposure manager can assign zero transmission power to that portion of time when calculating the second transmission power. In other embodiments, the RF exposure manager assigns a minimum transmission power (e.g., the power required to maintain a particular link) to the portion of the time window corresponding to the missing RF exposure measurement when calculating the second transmission power, such as during a conservative operation. In other aspects, if a reason for the transmission stop or abnormal event occurring during the portion of the time window corresponding to the missing RF exposure measurement cannot be determined, the RF exposure manager can assign a maximum allowed power level (or other predetermined transmission power) to that portion of time to calculate the second transmission power. In some aspects, a confidence level regarding whether the device transmitted during the portion of the time window corresponding to the missing RF exposure measurement can be determined (e.g., based on data in a transmission buffer, a transmission log, a communication received from another device, etc.), and the second transmission power determined based on the confidence level. For example, a comparison of the confidence level to a threshold can determine whether zero or a minimum transmission power level is assigned, or whether a maximum allowed power level (or other power level) is assigned to the portion of the time window. In some embodiments, the confidence level can be used to proportionally assign transmission power to the portion of the time window.

[0111] In some aspects, the time-averaged RF exposure measurement (e.g., stored at block 404) can include at least one of a time-averaged SAR or a time-averaged PD. In some aspects, the time window can be in a range of 1 second to 360 seconds. For example, the time window can be 100 seconds or 360 seconds. The range of 1 second to 360 seconds is one example, and other suitable values of the time window can be used. In certain cases, the time window can be less than 1 second, such as 500 milliseconds. In certain cases, the time window can be greater than 360 seconds, such as 600 seconds.

[0112] Figure 5 FIG. 4B is a diagram illustrating time-averaged RF exposure during a time window Tl according to certain aspects of the present disclosure. The UE can determine the time- averaged RF exposure using time-averaged RF exposure measurements across the time window Tl (e.g., various RF measurements corresponding to intervals (i) through (i-m)). In certain cases, the UE can determine the RF exposure measurements based on a conversion model or scaling factor between SAR / PD and transmission power used at each transmission interval, such as intervals (i) through (i-m).

[0113] In this example, the RF exposure measurements 502 can have been stored as RF exposure information prior to the abnormal event, e.g., as described herein with respect to operations 400. In some aspects, the RF exposure information can be stored as a sum of the RF exposure measurements 502 or as individual values for each of the RF exposure measurements 502. Within the time window Tl, the UE can have encountered an abnormal event. After returning to normal operation or recovering from the abnormal event, if the RF exposure information is within the time window Tl, the UE can use the RF exposure information to represent RF exposure measurements prior to the abnormal event when determining the time-averaged RF exposure. In this example, the RF exposure information is within the time window Tl (e.g., the current time window can span from i-m to i), and thus, the UE can use the RF exposure information when determining transmission power that complies with the respective RF exposure requirements based on the time-averaged RF exposure. In certain cases, the UE can use a portion of the RF exposure information when determining the time-averaged RF exposure. For example, as the UE continues to determine the time-averaged RF exposure for the rolling time window Tl (e.g., the current time window can span from i-l to i+1, ahead (i.e., offset in time) by a certain time interval), the UE can use a portion of the RF exposure information corresponding to the remaining time intervals in the time window Tl (e.g., intervals (i-1) and (i-k)).

[0114] If the RF exposure information is outside of the time window T1, the UE can not use the RF exposure information in determining the transmission power, and in some cases, the UE can operate in a failsafe mode, e.g., as described herein with respect to operations 400. As an example, assume that the timestamp associated with the RF exposure information places the RF exposure information outside of the time window T1 by an interval (i-n). The UE can determine that the RF exposure information is outside of the time window by comparing the timestamp associated with the RF exposure information to the timestamp associated with the current interval (i). As described herein, if the time increment between the timestamp associated with the RF exposure information and the timestamp associated with the current interval (i) is greater than or equal to the duration of the time window T1, the UE can not use the RF exposure information in determining the transmission power.

[0115] Figure 6 is a block diagram illustrating a design of an example wireless communication device 600 (e.g., UE 120, BS 110) for implementing RF exposure continuity after an abnormal event in accordance with certain aspects of the present disclosure. As shown, the wireless communication device 600 can include a transceiver 602 (which can be an example of transceiver 232, 254, 300), one or more antennas 604 (which can be an example of antennas 234, 252, 306), a modem 606, a processor 608, a memory 610 (which can be an example of memory 242, 282, 338), and a counter 612. In certain cases, the counter 612 can be integrated with or included in a PMIC 614. In certain cases, the wireless communication device 600 can also include an application processor 616 and a file system memory 618. In some embodiments, one or both of the modem 606 and the processor 608 are implemented by Figure 2 components of the wireless communication device 600 (such as 212, 220, 230, 236, 238, 239, 240, 244, 256, 258, 260, 262, 264, 266, and / or 280) and / or Figure 3 implemented by the controller 336 of the wireless communication device 600, or within components of the wireless communication device 600 and / or Figure 2 implemented by the controller 336 of the wireless communication device 600, or within components of the wireless communication device 600 and / or Figure 3 implemented by the controller 336 of the wireless communication device 600, or within components of the wireless communication device 600 and / or

[0116] The wireless communication device 600 can transmit various signals from the transceiver 602 and one or more antennas 604 coupled to the transceiver 602. The modem 606 can provide modulated signals to the transceiver 602 and provide instructions to the transceiver 602 to adjust the transmission power of the signals to comply with various RF exposure limits. For example, the modem 606 can provide instructions to the transceiver 602 regarding a first transmission power and a second transmission power, as described herein with respect to operations 400. The processor 608 can obtain current RF exposure information from the modem 606 and periodically store the RF exposure information in the memory 610 along with a timestamp (and CRC), as described herein with respect to operations 400. In some aspects, the memory 610 can be tightly coupled with the modem 606 and / or the processor 608 and provide a lower power solution for repeatedly storing RF exposure information as compared to the file system memory 618. In certain aspects, the memory 610 can be impervious to damage due to abnormal events that affect the operation of the wireless communication device 600 or the modem 606 (e.g., electrically isolated from the modem 606 or certain components of the modem 606). Those skilled in the art will appreciate that the abnormal event that triggers the use of the stored RF exposure information can be associated with other components that affect the operability of the wireless communication device 600, such as various circuitry, memory, or processors. In certain cases, the processor 608 and / or the memory 610 can be integrated with the modem 606.

[0117] The processor 608 can obtain the timestamp from the counter 612, which can be integrated with the PMIC 614 such that when the wireless communication device 600 is turned off or restarted, which in turn can trigger an abnormal event associated with the modem 606, the counter 612 can continue to keep track of time. For example, the PMIC 614 can provide power to the counter 612 to continue tracking time when the wireless communication device 600 is turned off (i.e., in an off state), reset, or restarted. In certain cases, the counter 612 can be based on a real-time clock (RTC), which can be integrated with the PMIC. When the wireless communication device 600 returns to a normal operating state or at least recovers from the abnormal event, the processor 608 can obtain a current timestamp from the counter 612 and compare the current timestamp to the timestamp stored with the RF exposure information to determine whether the timestamp is within a time window associated with the RF exposure limit. If the timestamp of the RF exposure information is within the time window (e.g., T1) of the RF exposure limit, the wireless communication device 500 can use the stored RF exposure information to determine a transmission power that complies with the RF exposure limit. Figure 5

[0118] ​The application processor 616 can be a processor included in a system on a chip (SoC). For example, the application processor 616 can run an operating system that provides a graphical environment for user access to various applications, such as a web browser, a streaming media application, a social media application, and the like. The file system memory 618 can store the operating system, applications, and various user data. In some aspects, the memory 610 can be a non-volatile memory separate from the file system memory 618. In some cases, the application processor 616 and the file system memory 618 can store RF exposure information, in addition to or in place of the processor 608 and the memory 610. Further, in some cases, the counter 612 can be implemented on the SoC. For example, a monotonically increasing global counter on the SoC can be used when determining a timestamp. In some such cases, the counter on the SoC resets when the application processor 616 crashes or otherwise stops. In these cases, the RTC in the PMIC 614 can provide an advantage, as the RTC will continue to count when the application processor 616 is disabled (e.g., due to a reboot, shutdown, and the like).

[0119] Figure 7 is a signaling flow illustrating example operations for providing RF exposure continuity after an exceptional event, in accordance with certain aspects of the present disclosure. At 702, the UE 120 can transmit a first signal to the BS 110 at a first transmission power based on time-averaged RF exposure measurements during a time window (e.g., Figure 5 T1) of the UE 120. At 704, the UE 120 can periodically store RF exposure information associated with the time window. At 706, the UE 120 can encounter an exceptional event associated with the UE or modem (e.g., the modem 606). For example, the UE 120 can reboot, causing the modem to power up anew. In some cases, the modem can crash or encounter an error, e.g., due to a software bug or overheating. At 708, the UE 120 can detect that the exceptional event has occurred, e.g., as described herein with respect to operations 400. At 710, the UE 120 can transmit a second signal at a second transmission power in response to the detection of the event based at least in part on the stored RF exposure information, e.g., as described herein with respect to operations 400.

[0120] Figure 8 shows a communications device 800 (e.g., the UE 120), which can include operations for performing the techniques disclosed herein, such as Figure 4The components of communication device 800 may, individually or collectively, be constituted in whole or in part by one or more processors configured to perform the functions described herein. For example, the processor 804 may be configured to execute instructions stored in the computer-readable medium / memory 812 to perform the functions described herein. In some aspects, the processor 804 may be configured to operate with one or more peripherals (not shown) to perform the functions described herein. The components of communication device 800 may, individually or collectively, be constituted in whole or in part by one or more ASICs configured to perform the functions described herein. In some aspects, the processor 804 may be configured to operate with one or more peripherals (not shown) to perform the functions described herein. The components of communication device 800 may, individually or collectively, be constituted in whole or in part by one or more FPGAs configured to perform the functions described herein. In some aspects, the processor 804 may be configured to operate with one or more peripherals (not shown) to perform the functions described herein. The components of communication device 800 may, individually or collectively, be constituted in whole or in part by one or more circuits, such as corresponding to modules plus functions. The communication device 800 includes a processing system 802 coupled to a transceiver 808 (e.g., transmitter and / or receiver). The transceiver 808 is configured to transmit and receive signals for the communication device 800 via an antenna 810, such as the various signals as described herein. The processing system 802 can be configured to perform processing functions of the communication device 800, including processing signals received by and / or to be transmitted by the communication device 800.

[0121] The processing system 802 includes a processor 804 coupled to a computer- readable medium / memory 812 via a bus 806. In certain aspects, the computer-readable medium / memory 812 is configured to store instructions (e.g., computer-executable code) that, when executed by the processor 804, cause the processor 804 to perform Figure 4 The operations 400 illustrated, or other operations for performing the various techniques discussed herein for providing RF exposure continuity after an exceptional event. In certain aspects, the computer-readable medium / memory 812 stores code for transmitting 814, code for storing 816, and / or code for detecting 818. In certain aspects, the processing system 802 has circuitry 820 configured to implement code stored in the computer-readable medium / memory 812. In certain aspects, the circuitry 820 is coupled to the processor 804 and / or the computer-readable medium / memory 812 via the bus 806. For example, the circuitry 820 includes circuitry for transmitting 822, circuitry for storing 824, and / or circuitry for detecting 826. In other aspects, the circuitry 820 is integrated with the processor 804.

[0122] Example Aspects

[0123] In addition to the various aspects described above, specific combinations of aspects are within the scope of the present disclosure, some of which are as follows:

[0124] Aspect 1. A method of wireless communication by a user equipment (UE), comprising: transmitting, at a first transmission power, a first signal based on a time-averaged radio frequency (RF) exposure measurement during a time window; storing RF exposure information associated with the time window; detecting that an exceptional event associated with the UE has occurred; and in response to the detection of the event, transmitting, at a second transmission power, a second signal based at least in part on the stored RF exposure information.

[0125] Aspect 2. The method of aspect 1, wherein storing the RF exposure information comprises: periodically storing the RF exposure information.

[0126] Aspect 3. The method of any of aspects 1 or 2, wherein storing the RF exposure information comprises storing the RF exposure information in a memory that is impervious to damage from the abnormal event.

[0127] Aspect 4. The method of any of aspects 1-3, wherein: storing the RF exposure information comprises storing the RF exposure information with a timestamp corresponding to when a most recent time-averaged RF exposure measurement was generated, and obtaining the timestamp from a counter that is impervious to the abnormal event; and transmitting the second signal comprises transmitting the second signal at the second transmission power based at least in part on the stored RF exposure information in response to determining that the timestamp of the RF exposure information is within the time window.

[0128] Aspect 5. The method of any of aspects 1-4, wherein storing the RF exposure information comprises storing the RF exposure information with a check value comprising a remainder in a cyclic redundancy check (CRC) of the RF exposure information.

[0129] Aspect 6. The method of aspect 5, wherein transmitting the second signal comprises transmitting the second signal at the second transmission power based on supplementing a time-averaged RF exposure measurement for a current time window with the stored RF exposure information in response to determining that the CRC of the RF exposure information matches the check value.

[0130] Aspect 7. The method of any of aspects 1-6, wherein transmitting the second signal comprises transmitting the second signal at the second transmission power based on supplementing a time-averaged RF exposure measurement with the stored RF exposure information.

[0131] Aspect 8. The method of aspect 7, wherein transmitting the second signal comprises transmitting the second signal at the second transmission power based at least in part on the stored RF exposure information when at least one RF exposure measurement is missing in a current time window.

[0132] Aspect 9. The method of any of aspects 1-8, wherein the RF exposure information comprises a sum of the time-averaged RF exposure measurements or individual values for each of the time-averaged RF exposure measurements.

[0133] Aspect 10. The method of any of aspects 1-9, wherein the abnormal event comprises at least one of an error, a reset, a crash, or a restart affecting operation of the UE or a modem used to transmit the first and second signals.

[0134] Aspect 11. The method of any of aspects 1 through 10, wherein the time-averaged RF exposure measurement comprises at least one of a time-averaged specific absorption rate (SAR) or a time-averaged power density (PD).

[0135] Aspect 12. The method of any of aspects 1 through 11, wherein the transmitting the second signal is based on a determination of a type of the abnormal event.

[0136] Aspect 13. An apparatus for wireless communication, comprising a transmitter configured to transmit a first signal at a first transmission power based on a time-averaged radio frequency (RF) exposure measurement during a time window; a memory; and a processor coupled to the memory, the processor and the memory configured to store RF exposure information associated with the time window and to detect that an abnormal event associated with the apparatus has occurred; wherein the transmitter is further configured to transmit a second signal at a second transmission power based at least in part on the stored RF exposure information in response to the detection of the event.

[0137] Aspect 14. The apparatus of aspect 13, further comprising a modem coupled to the transmitter and the processor, the modem configured to provide instructions to the transmitter regarding the first transmission power and the second transmission power.

[0138] Aspect 15. The apparatus of any of aspects 13 or 14, wherein the processor and the memory are further configured to periodically store the RF exposure information.

[0139] Aspect 16. The apparatus of any of aspects 13 through 15, wherein the memory is not compromised by damage from the abnormal event.

[0140] Aspect 17. The apparatus of any of aspects 13 through 16, further comprising a counter configured to provide a time stamp and not be compromised by the abnormal event, wherein: the processor and the memory are further configured to obtain the time stamp from the counter and to store the RF exposure information with the time stamp, the time stamp corresponding to when a most recent time-averaged RF exposure measurement was generated; and the transmitter is further configured to transmit the second signal at the second transmission power based at least in part on the stored RF exposure information in response to a determination that the time stamp of the RF exposure information is within a current time window.

[0141] Aspect 18. The apparatus of any of aspects 13 through 17, further comprising a power management integrated circuit (PMIC), wherein the counter is integrated with the PMIC.

[0142] Aspect 19. The apparatus of any one of aspects 13 through 18, wherein the processor and the memory are further configured to store the RF exposure information with a check value, the check value comprising a remainder in a cyclic redundancy check (CRC) of the RF exposure information.

[0143] Aspect 20. The apparatus of aspect 19, wherein the transmitter is further configured to transmit the second signal at the second transmission power based on supplementing a time-averaged RF exposure measurement for a current time window with the stored RF exposure information in response to determining that the CRC of the RF exposure information matches the check value.

[0144] Aspect 21. The apparatus of any one of aspects 13 through 20, wherein the transmitter is further configured to transmit the second signal at the second transmission power based on supplementing a time-averaged RF exposure measurement with the stored RF exposure information.

[0145] Aspect 22. The apparatus of aspect 21, wherein the transmitter is further configured to transmit the second signal at the second transmission power based at least in part on the stored RF exposure information when at least one RF exposure measurement is missing in the time window.

[0146] Aspect 23. The apparatus of any one of aspects 13 through 22, wherein the RF exposure information comprises a sum of the time-averaged RF exposure measurements or individual values for each of the time-averaged RF exposure measurements.

[0147] Aspect 24. The apparatus of any one of aspects 13 through 23, wherein the abnormal event comprises at least one of an error, a reset, a crash, or a restart affecting operation of the apparatus or a modem used to transmit the first signal and the second signal.

[0148] Aspect 25. The apparatus of any one of aspects 13 through 24, wherein the time-averaged RF exposure measurement comprises at least one of a time-averaged specific absorption rate (SAR) or a time-averaged power density (PD).

[0149] Aspect 26. The apparatus of aspect 13, configured to perform the method of any one of aspects 1 through 12.

[0150] Aspect 27. An apparatus for wireless communication, comprising: means for transmitting a first signal at a first transmission power based on time-averaged radio frequency (RF) exposure measurements during a time window; means for storing RF exposure information associated with the time window; means for detecting that an abnormal event associated with the apparatus has occurred; and means for transmitting a second signal at a second transmission power based at least in part on the stored RF exposure information in response to the detection of the event.

[0151] Aspect 28. The apparatus of Aspect 27, further comprising means for generating time stamps that are not compromised by the abnormal event, wherein: the means for storing the RF exposure information comprises means for obtaining the time stamps from the means for generating the time stamps, means for storing the RF exposure information with the time stamps, the time stamps corresponding to when the most recent time-averaged RF exposure measurement was generated; and the means for transmitting the second signal comprises means for transmitting the second signal at the second transmission power based at least in part on the stored RF exposure information if the time stamp of the RF exposure information is within the time window.

[0152] Aspect 29. The apparatus of Aspect 27, comprising means for performing the method of any of Aspects 1-13.

[0153] Aspect 30. A computer-readable medium for wireless communication having computer- executable code stored thereon that, when executed by at least one processor, causes an apparatus to perform the method of any of Aspects 1-12.

[0154] Aspect 31. The method of any of Aspects 1-12, wherein transmitting the second signal at the second transmission power is based on a determination of a type of the abnormal event.

[0155] Aspect 32. The method of any of Aspects 1-12, wherein transmitting the second signal at the second transmission power is based on a determination that transmissions from the UE stopped for a portion of time corresponding to the abnormal event.

[0156] Aspect 33. The apparatus of any of Aspects 13-26, wherein the processor and the memory are configured to determine a type of the abnormal event, and wherein the transmitter is configured to transmit the second signal at the second transmission power based on the determination.

[0157] Aspect 34. The apparatus of any of aspects 13 to 26, wherein the processor and the memory are configured to determine that transmissions from the UE stopped for a portion of time corresponding to the abnormal event, and wherein the transmitter is configured to transmit the second signal at the second transmission power based on the determination.

[0158] Aspect 35. A method of wireless communication by a user equipment (UE), comprising: transmitting a first signal at a first transmission power based on time-averaged radio frequency (RF) exposure measurements during a time window; storing RF exposure information associated with the time window; detecting that an abnormal event associated with the UE has occurred; determining that a timestamp corresponding to a most recent time-averaged RF exposure measurement is not within a current time window, or determining that a check value fails a cyclic redundancy check (CRC) of the RF exposure information; and transmitting a second signal at a second transmission power in a fail-safe mode based on the determination.

[0159] Aspect 36. The method of aspect 35, comprising obtaining the timestamp from a counter that is not compromised by the abnormal event.

[0160] Aspect 37. The method of any of aspects 35 or 36, wherein the second transmission power is determined based on a transmission power or exposure that is at a maximum over a duration of a previous portion of the current time window.

[0161] Aspect 38. The method of any of aspects 35 to 37, wherein time-averaged RF exposure measurements for the current time window are not supplemented with the stored RF exposure information in the fail-safe mode.

[0162] Aspect 39. An apparatus for wireless communication, comprising: a transmitter configured to transmit a first signal at a first transmission power based on time-averaged radio frequency (RF) exposure measurements during a time window; a memory; and a processor coupled to the memory, the processor and the memory configured to: store RF exposure information associated with the time window, detect that an abnormal event associated with the apparatus has occurred, and determine that a timestamp corresponding to a most recent time-averaged RF exposure measurement is not within a current time window, or determine that a check value fails a cyclic redundancy check (CRC) of the RF exposure information; wherein the transmitter is further configured to transmit a second signal at a second transmission power in a fail-safe mode based on the determination.

[0163] Aspect 40. An apparatus for wireless communication, comprising: means for transmitting a first signal at a first transmission power based on time-averaged radio frequency (RF) exposure measurements during a time window; means for storing RF exposure information associated with the time window; means for detecting that an abnormal event associated with the UE has occurred; means for determining that a timestamp corresponding to a most recent time-averaged RF exposure measurement is not within a current time window, or means for determining that a check value fails a cyclic redundancy check (CRC) of the RF exposure information; and means for transmitting a second signal at a second transmission power in a fail-safe mode based on the determination.

[0164] The techniques described herein can be used for various wireless communication technologies, such as NR (e.g., 5G NR), 3GPP Long Term Evolution (LTE), LTE-Advanced (LTE-A), code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), single-carrier frequency division multiple access (SC-FDMA), time division synchronous code division multiple access (TD-SCDMA), and other networks. The terms “network” and “system” are often used interchangeably. A CDMA network can implement a radio technology such as Universal Terrestrial Radio Access (UTRA), cdma2000, and so on. UTRA includes Wideband-CDMA (WCDMA) and other variants of CDMA. cdma2000 covers IS-2000, IS-95 and IS-856 standards. A TDMA network can implement a radio technology such as Global System for Mobile Communications (GSM). An OFDMA network can implement a radio technology such as NR (e.g., 5G RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE 802.11 (Wi-Fi), IEEE 802.16 (WiMAX), IEEE 802.20, Flash-OFDMA, and so on. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS). LTE and LTE-A are releases of UMTS that use E-UTRA. UTRA, E-UTRA, UMTS, LTE, LTE-A and GSM are described in documents from an organization named “3rd Generation Partnership Project” (3GPP). cdma2000 and UMB are described in documents from an organization named “3rd Generation Partnership Project 2” (3GPP2). NR is an emerging wireless communications technology under development.

[0165] In 3GPP, the term "cell" can refer to a coverage area of a Node B (NB) and / or a NB subsystem serving the coverage area, depending on the context in which the term is used. In NR systems, the term "cell" and BS, next generation NodeB (gNB or g NodeB), access point (AP), distributed unit (DU), carrier or transmission reception point (TRP) can be used interchangeably. A BS can provide communication coverage for a macro cell, a pico cell, a femto cell, and / or other types of cells, and / or can be configured to provide communication coverage for a CPE. A macro cell can cover a relatively large geographic area (e.g., several kilometers in radius) and can allow unrestricted access by UEs with service subscriptions with the network provider. A pico cell can cover a relatively small geographic area and can allow restricted access by UEs with service subscriptions with the network provider. A femto cell can cover a relatively small geographic area (e.g., a home) and can allow restricted access by UEs with service subscriptions with the network provider. A BS for a macro cell can be referred to as a macro BS. A BS for a pico cell can be referred to as a pico BS. A BS for a femto cell can be referred to as a femto BS or a home BS.

[0166] A UE can also be referred to as and / or be configured as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a CPE, a cellular phone, a smart phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an electric appliance, a medical device or medical equipment, a biometric sensor / device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wristband, smart jewelry (e.g., a smart ring, a smart bracelet, etc.), an entertainment device (e.g., a music device, a video device, a satellite radio, etc.), a vehicular component or sensor, a smart meter / sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. Some UEs can be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices. MTC and eMTC UEs include, for example, robots, drones, remote devices, sensors, meters, monitors, location tags, etc., that can communicate with a BS, another device (e.g., remote device), or some other entity. A wireless node can provide, for example, connectivity for or to a network (e.g., a wide area network such as the Internet or a cellular network) via a wired or wireless communication link. Some UEs can be considered Internet-of-Things (IoT) devices, which can be narrowband IoT (NB-IoT) devices.

[0167] In some examples, access to the air interface can be scheduled. A scheduling entity (e.g., a BS) allocates resources for communications between pairs of devices and apparatuses within its serving area or cell. A scheduling entity can be responsible for scheduling, allocating, reconfiguring, and releasing resources for one or more subordinate entities. That is, for scheduled communications, a subordinate entity utilizes resources allocated by the scheduling entity. Base stations are not the only entities that can function as a scheduling entity. In some examples, a UE can function as a scheduling entity and can schedule resources for one or more subordinate entities (e.g., one or more other UEs), and the other UEs can utilize the resources scheduled by the UE for wireless communications. In some examples, a UE can function as a scheduling entity in a peer-to-peer (P2P) network and / or a mesh network. In a mesh network example, UEs can communicate directly with each other in addition to communicating with the scheduling entity.

[0168] The methods disclosed herein comprise one or more steps or actions for achieving the methods. The method steps and / or actions can be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of steps or actions is specified, the order and / or use of specific steps and / or actions can be modified without departing from the scope of the claims.

[0169] As used herein, the term “at least one” refers to any combination of one or more items, including single members. For example, “at least one of a, b, or c” is intended to cover a, b, c, a-b, a-c, b-c, and a-b-c, as well as any combination of multiples of the same element (e.g., a-a, a-a-a, a-a-b, a-a-c, a-b-b, a-c-c, b-b, b-b-b, b-b-c, c-c, and c-c-c, or any other ordering of a, b, and c).

[0170] As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” can include calculating, computing, processing, deriving, investigating, looking up (e.g., looking up in a table, a database or another data structure), ascertaining and the like. Also, “determining” can include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory) and the like. Also, “determining” can include resolving, selecting, choosing, establishing, and the like.

[0171] The above description is provided as an enabling teaching of the various aspects described herein. Those skilled in the art will recognize that many modifications are possible within the scope of the aspects described herein, and the generic principles defined herein can be applied to other aspects as well. Thus, the claims are not intended to be limited to the aspects shown herein, but instead have the true scope defined by the language of the claims, with equivalents of the scope to be intended to be covered herein. Unless otherwise stated, references to elements or layers in the claims are not intended to be disclaimed, but rather intended to be encompassed by the claims. Unless specifically stated otherwise, the term "some" refers to one or more. All structural and functional equivalents to elements described herein as well as technologies that are presently known or later developed that perform the same function described for elements described herein, are expressly incorporated by reference and are intended to be encompassed by the claims. Furthermore, any combination of the elements described herein can be used to practice the aspects described herein, unless specifically stated otherwise. Any claims that are presented of multiple dependent claims in a multiple dependent family member application may not resolve into multiple dependent claims in the application as filed, unless specifically stated to do so. None of the elements discussed herein are intended to be discretionary or not intended to be encompassed by the claims, unless specifically stated otherwise. Any claim element that is not specifically excluded by the phrase "means for" is intended to be encompassed by the claims, unless specifically stated otherwise. Any claim element that is not specifically excluded by the phrase "step for" is intended to be encompassed by the claims, unless specifically stated otherwise.

[0172] Various operations can be performed by any suitable means capable of performing the corresponding functions. The means can include various hardware and / or software components and / or modules, including but not limited to a circuit, an application specific integrated circuit (ASIC), or processor. Generally, where there are operations illustrated in figures, those operations can have corresponding counterpart means-plus-function components with similar numbering. The means can be implemented using any functionality described herein, or otherwise known to one of ordinary skill in the art.

[0173] The various illustrative logical blocks, modules, and circuits described in connection with the disclosure can be implemented or performed with a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA) or other programmable logic device (PLD), discrete gate or transistor logic, discrete hardware components, or any combination thereof designed to perform the functions described herein. A general purpose processor can be a microprocessor, but in the alternative, the processor can be any commercially available processor, controller, microcontroller, or state machine. A processor can also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0174] If implemented in hardware, an example hardware configuration can include a processing system in a wireless node. The processing system can be implemented with a bus architecture. The bus can include any number of interconnecting buses and bridges, depending on the specific application of the processing system and overall design constraints. The bus can link together various circuits such as a processor, machine-readable medium, and bus interface. The bus interface can be used to connect a network adapter to the processing system via the bus. The network adapter can be used to implement signal processing functionality of the PHY layer. In the case of a user terminal (see Figure 1 ), a user interface (e.g., keypad, display, mouse, joystick, etc.) can also be connected to the bus. The bus can also link various other circuits such as a timing source, peripherals, voltage regulators, power management circuits, and the like, which are well known in the art, and therefore will not be further described. The processor can be implemented with one or more general-purpose and / or special-purpose processors. Examples include microprocessors, microcontrollers, DSP processors, and other circuitry that can execute software. Those skilled in the art will recognize how to best implement the above-described functionality of the processing system depending on the particular application and general design constraints imposed on the overall system.

[0175] If implemented in software, the functions can be stored or transmitted over as one or more instructions or code on a computer-readable medium. Software shall be construed broadly to mean instructions, data, or any combination thereof, whether referred to as software, firmware, middleware, microcode, hardware description language, or otherwise. Computer-readable media include both computer storage media and communication media including any medium that facilitates transfer of a computer program from one place to another. The processor can be responsible for managing the bus and general processing, including the execution of software modules stored on the machine-readable storage media. A computer-readable storage medium can be coupled with the processor such that the processor can read information from, and write information to, the storage medium. In the alternative, the storage medium can be integral with the processor. By way of example, the machine-readable media can include a transmission line, a carrier wave modulated by data, and / or a computer readable storage medium with instructions stored thereon separate from the wireless node, all of which can be accessed via the bus. Alternatively, or in addition, the machine-readable media, or any portion thereof, can be integrated with the processor, such as the case can be with cache and / or general register files. Examples of machine-readable storage media can include RAM (random access memory), flash memory, ROM (read only memory), PROM (programmable read only memory), EPROM (erasable programmable read only memory), EEPROM (electrically erasable programmable read only memory), registers, magnetic disks, optical disks, hard drives, or any other suitable storage medium, or any combination thereof. The machine-readable media can be embodied in a computer-program product.

[0176] A software module can include a single instruction, or many instructions, and can be distributed over several different code segments, among different programs, and across multiple storage media. The computer-readable media can include a number of software modules. The software modules include instructions that, when executed by an apparatus such as a processor, cause the processing system to perform various functions. The software modules can include a transmission module and a receiving module. Each software module can reside in a single storage device or be distributed across multiple storage devices. By way of example, a software module can be loaded into RAM from a hard drive when a triggering event occurs. During execution of the software module, the processor can load some of the instructions into cache to increase access speed. One or more cache lines can then be loaded into a general register file for execution by the processor. When referring to the functionality of a software module below, it will be understood that such functionality is implemented by the processor when executing instructions from that software module.

[0177] Also, any connection is properly termed a computer-readable medium. For example, if the software is transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared (IR), radio, and microwave, then the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared (IR), radio, and microwave are included in the definition of medium. Disk and disc, as used herein, include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Thus, in some aspects computer-readable media can comprise non-transitory computer-readable media (e.g., tangible media). In addition, for other aspects computer-readable media can comprise transitory computer- readable media (e.g., signals). Combinations of the above should also be included within the scope of computer-readable media.

[0178] Thus, certain aspects can comprise a computer program product for performing the operations presented herein. For example, such a computer program product can comprise a computer-readable medium having instructions stored thereon, the instructions being executable by one or more processors to perform the operations described herein, for example, the operations described and illustrated in FIGS. 1-4. Figure 4 Thus, certain aspects can comprise a computer program product for performing the operations presented herein. For example, such a computer program product can comprise a computer-readable medium having instructions stored thereon, the instructions being executable by one or more processors to perform the operations described herein, for example, the operations described and illustrated in FIGS. 1-4.

[0179] Further, it should be appreciated that modules and / or other appropriate means for performing the methods and techniques described herein can be downloaded and / or otherwise obtained by a user terminal and / or base station as applicable. For example, such a device can be coupled to a server to facilitate the transfer of means for performing the methods described herein. Alternatively, various methods described herein can be provided via a storage means (e.g., RAM, ROM, a physical storage medium such as a compact disc (CD) or floppy disk, etc.), such that a user terminal and / or base station can obtain the various methods by coupling or physically

[0180] It is to be understood that the claims are not limited to the precise configuration and components illustrated above. Various modifications, changes, and variations can be made in the arrangement, operation, and details of the methods and apparatus described above without departing from the scope of the claims.

Claims

1. A method of wireless communication by a user equipment (UE), comprising: transmitting, at a first transmission power, a first signal based on time-averaged radio frequency (RF) exposure measurements during a time window; storing RF exposure information associated with the time window; detecting that an abnormal event associated with the UE has occurred; and transmitting, at a second transmission power, a second signal based at least in part on the stored RF exposure information, in response to the detection of the abnormal event and in response to determining that the RF exposure information passes a reliability check.

2. The method of claim 1, wherein storing the RF exposure information comprises: periodically storing the RF exposure information.

3. The method of claim 1, wherein storing the RF exposure information comprises: storing the RF exposure information in memory that is not compromised by damage from the abnormal event.

4. The method of claim 1, wherein: storing the RF exposure information comprises: storing the RF exposure information with a timestamp corresponding to when a most recent time-averaged RF exposure measurement was generated, and obtaining the timestamp from a counter that is not compromised by the abnormal event; and transmitting the second signal comprises transmitting the second signal at the second transmission power based at least in part on the stored RF exposure information, in response to determining that the timestamp of the RF exposure information is within a current time window.

5. The method of claim 1, wherein storing the RF exposure information comprises: storing the RF exposure information with a check value comprising a remainder in a cyclic redundancy check (CRC) of the RF exposure information.

6. The method of claim 5, wherein transmitting the second signal comprises: transmitting the second signal at the second transmission power based on supplementing a time-averaged RF exposure measurement for a current time window with the stored RF exposure information, in response to determining that the CRC of the RF exposure information matches the check value, wherein the passing the reliability check comprises a case where the CRC of the RF exposure information matches the check value.

7. The method of claim 1, wherein transmitting the second signal comprises: transmitting the second signal at the second transmission power based on supplementing a time-averaged RF exposure measurement with the stored RF exposure information.

8. The method of claim 7, wherein transmitting the second signal comprises: transmitting the second signal at the second transmission power based at least in part on the stored RF exposure information when at least one RF exposure measurement is missing in a current time window.

9. The method of claim 1, wherein the RF exposure information comprises: a sum of the time-averaged RF exposure measurements or an individual value for each of the time-averaged RF exposure measurements.

10. The method of claim 1, wherein the abnormal event comprises at least one of an error, a reset, a crash, or a restart affecting operation of the UE or a modem used to transmit the first signal and the second signal.

11. The method of claim 1, wherein the time-averaged RF exposure measurements comprise at least one of a time-averaged specific absorption rate (SAR) or a time-averaged power density (PD).

12. The method of claim 1, wherein transmitting the second signal is based on a determination of a type of the abnormal event.

13. An apparatus for wireless communication, comprising: a transmitter configured to transmit, at a first transmission power, a first signal based on time-averaged radio frequency (RF) exposure measurements during a time window; a memory; and a processor configured to: a processor coupled to the memory, the processor and the memory configured to: store RF exposure information associated with the time window, and detect that an abnormal event associated with the device has occurred; wherein the transmitter is further configured to transmit a second signal based at least in part on the stored RF exposure information at a second transmission power in response to the detection of the abnormal event and in response to determining that the RF exposure information passes a reliability check.

14. The device of claim 13, further comprising a modem coupled to the transmitter and the processor, the modem configured to provide instructions to the transmitter regarding the first transmission power and the second transmission power.

15. The device of claim 13, wherein the processor and the memory are further configured to store the RF exposure information periodically.

16. The device of claim 13, wherein the memory is not compromised by damage from the abnormal event.

17. The device of claim 13, further comprising a counter configured to provide a timestamp and not be compromised by the abnormal event, wherein: the processor and the memory are further configured to: obtain the timestamp from the counter, and store the RF exposure information with the timestamp corresponding to when a most recent time-averaged RF exposure measurement was generated; and the transmitter is further configured to transmit the second signal based at least in part on the stored RF exposure information at the second transmission power in response to determining that the timestamp of the RF exposure information is within a current time window.

18. The device of claim 17, further comprising a power management integrated circuit (PMIC), wherein the counter is integrated with the PMIC.

19. The device of claim 13, wherein the processor and the memory are further configured to store the RF exposure information with a check value, the check value comprising a remainder in a cyclic redundancy check (CRC) of the RF exposure information.

20. The apparatus of claim 19, wherein the transmitter is further configured to transmit the second signal at the second transmission power based on supplementing a time-averaged RF exposure measurement for a current time window with the stored RF exposure information in response to determining that the CRC of the RF exposure information matches the check value, wherein, the passing of the reliability check comprises a case where the CRC of the RF exposure information matches the check value.

21. The device of claim 13, wherein the transmitter is further configured to transmit the second signal at the second transmission power based on supplementing a time-averaged RF exposure measurement with the stored RF exposure information.

22. The device of claim 21, wherein the transmitter is further configured to transmit the second signal at the second transmission power based at least in part on the stored RF exposure information when at least one RF exposure measurement is missing in the time window.

23. The apparatus of claim 13, wherein the RF exposure information comprises: a sum of the time-averaged RF exposure measurements or an individual value for each of the time-averaged RF exposure measurements.

23. The device of claim 13, wherein the transmitter is further configured to transmit the second signal at the second transmission power based at least in part on the stored RF exposure information in response to determining that the RF exposure information passes a reliability check.

24. The apparatus of claim 13, wherein the abnormal event comprises at least one of an error, a reset, a crash, or a restart affecting operation of the apparatus or a modem used to transmit the first signal and the second signal, and wherein the time-averaged RF exposure measurement comprises at least one of a time-averaged specific absorption rate (SAR) or a time-averaged power density (PD).

25. The apparatus of claim 13, wherein the processor and the memory are configured to determine that transmissions from the apparatus stopped for a portion of time corresponding to the abnormal event, and wherein the transmitter is configured to transmit the second signal at the second transmission power based on the determination.

26. An apparatus for wireless communication, comprising: means for transmitting a first signal at a first transmission power based on a time-averaged radio frequency (RF) exposure measurement during a time window; means for storing RF exposure information associated with the time window; means for detecting that an abnormal event associated with the apparatus has occurred; and means for transmitting a second signal at a second transmission power based at least in part on the stored RF exposure information in response to the detection of the abnormal event and in response to a determination that the RF exposure information passes a reliability check.

27. A method of wireless communication by a user equipment (UE), comprising: transmitting a first signal at a first transmission power based on a time-averaged radio frequency (RF) exposure measurement during a time window; storing RF exposure information associated with the time window; detecting that an abnormal event associated with the UE has occurred; determining that the RF exposure information is outside a current time window or that the RF exposure information fails a reliability check; and transmitting a second signal at a second transmission power in a fail-safe mode based on the determination.

28. The method of claim 27, comprising obtaining the time stamp from a counter that is not compromised by the abnormal event, wherein the time stamp corresponds to a most recent time-averaged RF exposure measurement.

29. The method of claim 27, wherein the second transmission power is determined based on a transmission power or exposure that was at a maximum over a previous portion of the current time window.

30. The method of claim 27, wherein time-averaged RF exposure measurements for the current time window are not supplemented with the stored RF exposure information in the fail-safe mode.

31. An apparatus for wireless communication, comprising: a transmitter configured to transmit a first signal at a first transmission power based on a time-averaged radio frequency (RF) exposure measurement during a time window; a memory; and a processor coupled to the memory, the processor and the memory configured to: store RF exposure information associated with the time window; detect that an abnormal event associated with the apparatus has occurred; and determine that the RF exposure information is outside a current time window or that the RF exposure information fails a reliability check; and a transmitter configured to transmit a second signal at a second transmission power in a fail-safe mode based on the determination. wherein the transmitter is further configured to transmit the second signal at a second transmission power in a fail-safe mode based on the determination.

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