TRANSMIT POWER CONTROL TO AVOID RADIO FREQUENCY SATURATION

Abstract

Certain aspects of the present disclosure provide techniques and apparatus for controlling transmit power to avoid radio frequency (RF) saturation. An example method of wireless communication includes obtaining a transmit power budget associated with a time interval. The method further includes determining a first transmit power based at least in part on the transmit power budget and a receive power associated with a communication link. The method further includes transmitting a signal at the first transmit power in the time interval.

Description

BACKGROUND

Field of the Disclosure

Aspects of the present disclosure relate to wireless communications, and more particularly, to transmit power control.

Description of Related Art

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) are generally mandated to meet radio frequency (RF) exposure limits set by certain governments and international standards and regulations. To ensure compliance with the standards, such devices may undergo an extensive certification process prior to being shipped to market. To ensure that a wireless communication device complies with an RF exposure limit, techniques have been developed to enable the wireless communication device to assess RF exposure from the wireless communication device and adjust the transmit power of the wireless communication device accordingly to comply with the RF exposure limit. In some cases, the wireless communication device may adjust the transmit power in response to other transmit power controls, such as RF emission controls, interference controls, automatic gain control, etc.

SUMMARY

Some aspects provide a method of wireless communication by a wireless device. The method includes obtaining a transmit power budget associated with a time interval. The method further includes determining a first transmit power based at least in part on the transmit power budget and a receive power associated with a communication link. The method further includes transmitting a signal at the first transmit power in the time interval.

Some aspects provide an apparatus for wireless communication. The apparatus includes a memory and a processor coupled to the memory. The processor is configured to obtain a transmit power budget associated with a time interval, determine a first transmit power based at least in part on the transmit power budget and a receive power associated with a communication link, and control transmission of a signal at the first transmit power in the time interval.

Some aspects provide an apparatus for wireless communication. The apparatus includes means for obtaining a transmit power budget associated with a time interval. The apparatus further includes means for determining a first transmit power based at least in part on the transmit power budget and a receive power associated with a communication link. The apparatus further includes means for transmitting a signal at the first transmit power in the time interval.

Some aspects provide a non-transitory computer-readable medium. The computer-readable medium includes instructions stored thereon for obtaining a transmit power budget associated with a time interval, determining a first transmit power based at least in part on the transmit power budget and a receive power associated with a communication link, and transmitting a signal at the first transmit power in the time interval.

Other aspects provide: an apparatus operable, configured, or otherwise adapted to perform any one or more of the aforementioned methods and/or those described elsewhere herein; a non-transitory, computer-readable medium comprising instructions that, when executed by a processor of an apparatus, cause the apparatus to perform the aforementioned methods as well as those described elsewhere herein; a computer program product embodied on a computer-readable storage medium comprising code for performing the aforementioned methods as well as those described elsewhere herein; and/or an apparatus comprising means for performing the aforementioned methods as well as those described elsewhere herein. By way of example, an apparatus may comprise a processing system, a device with a processing system, or processing systems cooperating over one or more networks.

To the accomplishment of the foregoing and related ends, the one or more aspects comprise the features hereinafter fully described and particularly pointed out in the claims. The following description and the appended drawings set forth in detail certain illustrative features of the one or more aspects. These features are indicative, however, of but a few of the various ways in which the principles of various aspects may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the present disclosure can be understood in detail, a more particular description, briefly summarized above, may be had by reference to aspects, some of which are illustrated in the drawings. It is to be noted, however, that the appended drawings illustrate only certain typical aspects of this disclosure and are therefore not to be considered limiting of its scope, for the description may admit to other equally effective aspects.

FIG. 1 is a block diagram conceptually illustrating an example wireless communication system exhibiting radio frequency (RF) exposure to a human.

FIG. 2 is a block diagram conceptually illustrating a design of an example wireless communication device communicating with another device.

FIG. 3 is a graph illustrating examples of transmit powers over time in compliance with an RF exposure limit.

FIG. 4 is a diagram illustrating an example wireless device having multiple radios.

FIG. 5 is a diagram illustrating an example logical architecture for controlling the RF exposure associated with one or more radios.

FIG. 6 is a flow diagram illustrating example operations for wireless communication by a wireless device.

FIG. 7 illustrates a communications device that may include various components configured to perform operations for the techniques disclosed herein.

To facilitate understanding, identical reference numerals have been used, where possible, to designate identical elements that are common to the figures. It is contemplated that elements disclosed in one aspect may be beneficially utilized in other aspects without specific recitation.

DETAILED DESCRIPTION

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer-readable mediums for controlling transmit power to avoid radio frequency (RF) saturation.

A wireless communication device may be capable of communicating via multiple radio access technologies (RATs), such as wireless wide area network (WWAN) RAT(s) (e.g., 5G New Radio, Evolved Universal Terrestrial Radio Access (E-UTRA), Universal Mobile Telecommunications System (UMTS) and/or code division multiple access (CDMA)), wireless local area network (WLAN) RATs (e.g., IEEE 802.11), short-range communications (e.g., Bluetooth), non-terrestrial communications, device-to-device (D2D) communications, vehicle-to-everything (V2X) communications, and/or other communications (e.g., future RAT(s)). In some cases, the wireless device may control RF exposure using a centralized controller that controls the transmit power (and hence, the RF exposure) associated with particular radios for one or more RATs.

To control the RF exposure associated with multiple radios (e.g., WLAN, WWAN (E-UTRA/5G), and Bluetooth), a time-averaged evaluation may have two components: an outer loop (OL) that periodically determines the transmit power limit for each of the radios, and an inner loop (IL) for each of the radios that uses the respective transmit power limit to determine its transmit power for a specific time interval of a running time window or for each packet. The OL may compute the transmit power limit based on a transmit power history report provided by the IL associated with each of the radios, where the transmit power history report may indicate the transmit powers used over time in the previous time interval(s).

In some cases, the OL may provide a generous transmit power limit to certain radio(s), for example, when no other radio systems are transmitting. For example, the transmit power limit may correspond to a relatively high transmit power, such as the maximum transmit power the wireless device is capable of outputting. In certain cases, the wireless device may be located close to the receiver (e.g., an access point or peer device). The excessive transmit power can cause RF saturations at the receiver, which can result in an increased packet error rate leading to a drop in throughput, for example.

Aspects of the present disclosure provide apparatus and methods for controlling the transmit power to avoid RF saturation. The wireless device may obtain a transmit power budget and determine if the transmit power budget can cause RF saturation at a receiver. If the transmit power budget can cause RF saturation at the receiver, the wireless device may reduce the transmit power associated with the transmit power budget and use that new transmit power for a transmission. If the transmit power budget avoids RF saturation at the receiver, the wireless device may use the transmit power budget to determine the transmit power.

The apparatus and methods for controlling transmit power(s) described herein may provide various advantages. For example, the apparatus and methods for controlling transmit power(s) described herein may allow for improved wireless communication performance including, for example, an increased throughput, decreased latency, and/or increased transmission range, where the improved performance may be attributable to a transmit power that avoids RF saturation at a receiver.

As used herein, a radio may refer to a physical or logical transmission path associated with one or more frequency bands (carriers, channels, bandwidths, subdivisions thereof, etc.), transceivers, and/or radio access technologies (RATs) (e.g., wireless wide area network (WWAN), wireless local area network (WLAN), short-range communications (Bluetooth), non-terrestrial communications, vehicle-to-everything (V2X) communications, etc.) used for wireless communications. For example, for uplink carrier aggregation (or multi-connectivity) in WWAN communications, each of the active component carriers used for wireless communications may be treated as a separate radio. Similarly, multi-band transmissions for IEEE 802.11 may be treated as separate radios for each frequency band (e.g., 2.4 GHz, 5 GHZ, or 6 GHz).

Example RF Exposure Compliance

FIG. 1 illustrates an example wireless communication system 100 in which aspects of the present disclosure may be performed. For example, the wireless communication system 100 may include a wireless wide area network (WWAN) and/or a wireless local area network (WLAN). For example, a WWAN may include a New Radio system (e.g., a 5G NR 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), a code division multiple access (CDMA) system (e.g., a 2G/3G network), any future WWAN system, or any combination thereof. A WLAN may include a wireless network configured for communications according to an IEEE standard such as one or more of the 802.11 standards, etc. In some cases, the wireless communication system 100 may include a device-to-device (D2D) communications network or a short-range communications system, such as Bluetooth communications.

As illustrated in FIG. 1, the wireless communication system 100 may include a first wireless device 102 communicating with any of various second wireless devices 104a-f (a second wireless device 104) via any of various radio access technologies (RATs), where a wireless device may refer to a wireless communication device. The RATs may include, for example, WWAN communications (e.g., E-UTRA and/or 5G NR), WLAN communications (e.g., IEEE 802.11), vehicle-to-everything (V2X) communications, non-terrestrial network (NTN) communications, short-range communications (e.g., Bluetooth), etc.

The first wireless device 102 may be emitting RF signals in proximity to a human 108, who may be the user of the first wireless device 102 and/or a bystander. As an example, the first wireless device 102 may be held in the hand of the human 108 and/or positioned against or near the head of the human 108. In certain cases, the first wireless device 102 may be positioned in a pocket or bag of the human 108. In some cases, the first wireless device 102 may be positioned proximate to the human 108 as a mobile hotspot. To ensure the human 108 is not overexposed to RF emissions from the first wireless device 102, the first wireless device 102 may control the transmit power associated with the RF signals in accordance with an RF exposure limit, as further described herein, where the RF exposure limit may depend on corresponding exposure scenario (e.g., head exposure, extremity (e.g., hand) exposure, body (body-worn) exposure, hotspot exposure, etc.). Extremities may include, for example, hands, wrists, feet, ankles, and pinnae.

The first wireless device 102 may include any of various wireless communication devices including a user equipment (UE), a wireless station, an access point, a customer-premises equipment (CPE), etc. In certain aspects, the first wireless device 102 includes an RF exposure manager 106 that controls transmit power to avoid RF saturation at the second wireless device 104, in accordance with aspects of the present disclosure.

The second wireless devices 104a-f may include, for example, a base station 104a, an aircraft 104b, a satellite 104c, a vehicle 104d, an access point (AP) 104e, and/or a UE 104f. Further, the wireless communication system 100 may include terrestrial aspects, such as ground-based network entities (e.g., the base station 104a and/or access point 104e), and/or non-terrestrial aspects, such as the aircraft 104b and the satellite 104c, which may include network entities on-board (e.g., one or more base stations) capable of communicating with other network elements (e.g., terrestrial base stations) and/or user equipment.

The base station 104a may generally include: a NodeB, enhanced NodeB (eNB), next generation enhanced NodeB (ng-eNB), next generation NodeB (gNB or gNodeB), access point, base transceiver station, radio base station, radio transceiver, transceiver function, transmission reception point, and/or others. The base station 104a may provide communications coverage for a respective geographic coverage area, which may sometimes be referred to as a cell, and which may overlap in some cases (e.g., a small cell may have a coverage area that overlaps the coverage area of a macro cell). A base station may, for example, provide communications coverage for a macro cell (covering relatively large geographic area), a pico cell (covering relatively smaller geographic area, such as a sports stadium), a femto cell (relatively smaller geographic area (e.g., a home)), and/or other types of cells.

The first wireless device 102 and/or the UE 104f may generally include: a cellular phone, smart phone, session initiation protocol (SIP) phone, laptop, personal digital assistant (PDA), satellite radio, global positioning system, multimedia device, video device, digital audio player, camera, game console, tablet, smart device, wearable device, vehicle, electric meter, gas pump, large or small kitchen appliance, healthcare device, implant, sensor/actuator, display, internet of things (IoT) devices, always on (AON) devices, edge processing devices, or other similar devices. A UE may also be referred to more generally as a mobile device, a wireless device, a wireless communications device, a wireless station (STA), a mobile station, a subscriber station, a mobile subscriber station, a mobile unit, a subscriber unit, a wireless unit, a remote unit, a remote device, an access terminal, a mobile terminal, a wireless terminal, a remote terminal, a handset, and other terms.

According to some aspects, the wireless communication system 100 can include a WLAN, such as a Wi-Fi network. For example, the wireless communication system 100 can be a network implementing at least one of the IEEE 802.11 family of wireless communication protocol standards (such as that defined by the IEEE 802.11-2020 specification or amendments thereof including, but not limited to, 802.11ay, 802.11ax, 802.11az, 802.11ba, 802.11bd, 802.11be, 802.11bf, and the 802.11 amendment associated with Wi-Fi 8). The wireless communication system 100 may include numerous wireless communication devices such as wireless AP(s) and STAs. For example, the first wireless device 102, the second wireless device 104, and the UE 104f may be representative of an AP and/or STA. As an example, in some cases, the first wireless device 102 may operate as an AP and/or a STA. The wireless communication system 100 can include multiple APs, including the AP 104e and/or the first wireless device 102. The AP can represent various different types of APs including but not limited to enterprise-level APs, single-frequency APs, dual-band APs, standalone APs, software-enabled APs (soft APs), and multi-link APs. The coverage area and capacity of a cellular network (such as E-UTRA, 5G NR, etc.) can be further improved by a small cell which is supported by an AP serving as a miniature base station. Furthermore, private cellular networks also can be set up through a wireless area network using small cells.

A single AP and an associated set of STAs may be referred to as a basic service set (BSS), which is managed by the respective AP. The coverage area of the AP may represent a basic service area (BSA) of the wireless communication system 100. The BSS may be identified or indicated to users by a service set identifier (SSID), as well as to other devices by a basic service set identifier (BSSID), which may be a medium access control (MAC) address of the AP. The AP may periodically broadcast beacon frames (“beacons”) including the BSSID to enable any STAs within wireless range of the AP to “associate” or re-associate with the AP to establish a respective communication link 110, or to maintain a communication link 110, with the AP. For example, the beacons can include an identification or indication of a primary channel used by the respective AP as well as a timing synchronization function for establishing or maintaining timing synchronization with the AP. The AP may provide access to external networks to various STAs in the WLAN via respective communication links 110.

To establish a communication link 110 with an AP, each of the STAs is configured to perform passive or active scanning operations (“scans”) on frequency channels in one or more frequency bands (for example, the 2.4 GHZ, 5 GHZ, 6 GHZ or 60 GHz bands). To perform passive scanning, a STA listens for beacons, which are transmitted by respective APs at a periodic time interval referred to as the target beacon transmission time (TBTT) (measured in time units (TUs) where one TU may be equal to 1024 microseconds (μs)). To perform active scanning, a STA generates and sequentially transmits probe requests on each channel to be scanned and listens for probe responses from APs. Each STA may identify, determine, ascertain, or select an AP with which to associate in accordance with the scanning information obtained through the passive or active scans, and to perform authentication and association operations to establish a communication link 110 with the selected AP. The AP assigns an association identifier (AID) to the STA at the culmination of the association operations, which the AP uses to track the STA.

As a result of the increasing ubiquity of wireless networks, a STA may have the opportunity to select one of many BSSs within range of the STA or to select among multiple APs that together form an extended service set (ESS) including multiple connected BSSs. An extended network station associated with the wireless communication system 100 may be connected to a wired or wireless distribution system that may allow multiple APs to be connected in such an ESS. As such, a STA can be covered by more than one AP and can associate with different APs at different times for different transmissions. Additionally, after association with an AP, a STA also may periodically scan its surroundings to find a more suitable AP with which to associate. For example, a STA that is moving relative to its associated AP may perform a “roaming” scan to find another AP having more desirable network characteristics such as a greater received signal strength indicator (RSSI) or a reduced traffic load.

In some cases, STAs may form networks without APs or other equipment other than the STAs themselves. One example of such a network is an ad hoc network (or wireless ad hoc network). Ad hoc networks may alternatively be referred to as mesh networks or peer-to-peer (P2P) networks. In some cases, ad hoc networks may be implemented within a larger wireless network such as the wireless communication system 100. In such examples, while the STAs may be capable of communicating with each other through the AP using communication links 110, STAs also can communicate directly with each other via direct wireless communication links 110. For example, the first wireless device 102 may communicate directly with the UE 104f via WLAN communications (or other P2P communications, e.g., Bluetooth). Additionally, two STAs may communicate via a direct wireless communication link 110 regardless of whether both STAs are associated with and served by the same AP. In such an ad hoc system, one or more of the STAs may assume the role filled by the AP in a BSS. Such a STA may be referred to as a group owner (GO) and may coordinate transmissions within the ad hoc network. Examples of direct wireless communication links 110 include Wi-Fi Direct connections, connections established by using a Wi-Fi Tunneled Direct Link Setup (TDLS) link, and other P2P group connections. In some cases, the first wireless device 102 may be capable of communicating with multiple peers including STA(s) and/or AP(s).

The APs and STAs may function and communicate (via the respective communication links 110) according to one or more of the IEEE 802.11 family of wireless communication protocol standards. These standards define the WLAN radio and baseband protocols for the physical (PHY) and medium access control (MAC) layers. The APs and STAs transmit and receive wireless communications (hereinafter also referred to as “wireless packets”) to and from one another in the form of PHY protocol data units (PPDUs). The APs and STAs in the wireless communication system 100 may transmit PPDUs over an unlicensed or shared spectrum, which may be a portion of spectrum that includes frequency bands used by WLAN technology, such as the 2.4 GHz band, the 5 GHz band, the 60 GHz band, the 3.6 GHz band, and the 900 MHz band. Some examples of the APs and STAs described herein also may communicate in other frequency bands, such as the 5.9 GHZ and the 6 GHZ bands, which may support both licensed and unlicensed communications. The APs and STAs also can communicate over other frequency bands such as shared licensed frequency bands, where multiple operators may have a license to operate in the same or overlapping frequency band or bands.

Each of the frequency bands may include multiple sub-bands or frequency channels. For example, PPDUs conforming to the IEEE 802.11n, 802.11ac, 802.11ax and 802.11be standard amendments may be transmitted over the 2.4 GHZ, 5 GHZ or 6 GHZ bands, each of which is divided into multiple 20 MHz channels. As such, these PPDUs are transmitted over a physical channel having a minimum bandwidth of 20 MHZ, but larger channels can be formed through channel bonding. For example, PPDUs may be transmitted over physical channels having bandwidths of 40 MHZ, 80 MHZ, 160 MHz or 320 MHz by bonding together multiple 20 MHz channels.

Each PPDU is a composite structure that includes a PHY preamble and a payload in the form of a PHY service data unit (PSDU). The information provided in the preamble may be used by a receiving device to decode the subsequent data in the PSDU. In instances in which PPDUs are transmitted over a bonded channel, the preamble fields may be duplicated and transmitted in each of the multiple component channels. The PHY preamble may include both a legacy portion (or “legacy preamble”) and a non-legacy portion (or “non-legacy preamble”). The legacy preamble may be used for packet detection, automatic gain control and channel estimation, among other uses. The legacy preamble also may generally be used to maintain compatibility with legacy devices. The format of, coding of, and information provided in the non-legacy portion of the preamble is associated with the particular IEEE 802.11 protocol to be used to transmit the payload.

In certain cases, the first wireless device 102 may control the transmit power used to emit RF signals in compliance with an RF exposure limit. RF exposure may be expressed in terms of a specific absorption rate (SAR), which measures energy absorption by human tissue per unit mass and may have units of watts per kilogram (W/kg). RF exposure may also be expressed in terms of power density (PD), which measures energy absorption per unit area and may have units of milliwatts per square centimeter (mW/cm²). In certain cases, a maximum permissible exposure (MPE) limit in terms of PD may be imposed for wireless communication devices using transmission frequencies above 6 GHz. Frequency bands of 24 GHz to 71 GHz are sometimes referred to as a “millimeter wave” (“mmW” or “mmWave”). The MPE limit is a regulatory metric for exposure based on area, e.g., an energy density limit defined as a number, X, watts per square meter (W/m2) averaged over a defined area and time-averaged over a frequency-dependent time window in order to prevent a human exposure hazard represented by a tissue temperature change. Certain RF exposure limits may be specified based on a maximum RF exposure metric (e.g., SAR or PD) averaged over a specified time window (e.g., 100 or 360 seconds for sub-6 GHz frequency bands or 2 seconds for 60 GHz bands).

SAR may be used to assess RF exposure for transmission frequencies less than 6 GHz, which cover wireless communication technologies such as 2G/3G (e.g., CDMA), 4G (e.g., E-UTRA), 5G (e.g., NR in sub-6 GHz bands), IEEE 802.11 (e.g., a/b/g/n/ac), etc. PD may be used to assess RF exposure for transmission frequencies higher than 6 GHz, which cover wireless communication technologies such as IEEE 802.11ad, 802.11ay, 5G in mmWave bands, etc. Thus, different metrics may be used to assess RF exposure for different wireless communication technologies.

A wireless device (e.g., the first wireless device 102) may be capable of transmitting signals using multiple wireless communication technologies and/or frequency bands, and in some cases, capable of simultaneous transmission of such signals. For example, the wireless device may transmit signals using a first wireless communication technology operating at or below 6 GHZ (e.g., 3G, 4G, 5G, 802.11a/b/g/n/ac, etc.) and a second wireless communication technology operating above 6 GHz (e.g., mm Wave 5G in 24 to 60 GHz bands, IEEE 802.11ad or 802.11ay). In certain aspects, the wireless device may transmit signals using the first wireless communication technology (e.g., 3G, 4G, 5G in sub-6 GHz bands, IEEE 802.11ac, etc.) in which RF exposure may be measured in terms of SAR, and the second wireless communication technology (e.g., 5G in 24 to 71 GHz bands, IEEE 802.11ad, 802.11ay, etc.) in which RF exposure may be measured in terms of PD.

FIG. 2 illustrates example components of the first wireless device 102, which may be used to communicate with any of the second wireless devices 104, in some cases, in proximity to human tissue as represented by the human 108.

The first wireless device 102 may be, or may include, a chip, system on chip (SoC), chipset, package or device that includes one or more modems 212. In some cases, the modem(s) 212 may include, for example, any of a WWAN modem (e.g., a modem configured to communicate via E-UTRA and/or 5G NR standards), a WLAN modem (e.g., a modem configured to communicate via 802.11 standards), a Bluetooth modem, a NTN modem, etc. In certain aspects, the first wireless device 102 also includes one or more radios (collectively “the radio 250”). In some aspects, the first wireless device 102 further includes one or more processors, processing blocks or processing elements (collectively “the processor 210”) and one or more memory blocks or elements (collectively “the memory 240”).

In certain aspects, the processor 210 may include a processor representative of an application processor that generates information (e.g., application data such as content requests) for transmission and/or receives information (e.g., requested content) via the modem 212. In some cases, the processor 210 may include a microprocessor associated with the modem 212, which may implement the RF exposure manager 106 and/or process any of certain protocol stack layers associated with a radio access technology (RAT). For example, the processor 210 may process any of an application layer, packet layer, WLAN protocol stack layers (e.g., a link or MAC layer), and/or WWAN protocol stack layers (e.g., a radio resource control (RRC) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, and a MAC layer). In some cases, at least one of the modems 212 (e.g., the WWAN modem) may be in communication with one or more of the other modems 212 (e.g., the WLAN modem and/or Bluetooth modem). For example, the processor 210 may be representative of at least one of the modems 212 in communication with one or more of the other modems 212.

The modem 212 may generally be configured to implement a physical (PHY) layer. For example, the modem 212 may be configured to modulate packets and to output the modulated packets to the radio 250 for transmission over a wireless medium. The modem 212 is similarly configured to obtain modulated packets received by the radio 250 and to demodulate the packets to provide demodulated packets. In addition to a modulator and a demodulator, the modem 212 may further include digital signal processing (DSP) circuitry, automatic gain control (AGC), a coder, a decoder, a multiplexer and a demultiplexer (not shown).

As an example, while in a transmission mode, the modem 212 may obtain data from the processor 210. The data obtained from the processor 210 may be provided to a coder, which encodes the data to provide encoded bits. The encoded bits may be mapped to points in a modulation constellation (e.g., using a selected modulation and coding scheme) to provide modulated symbols. The modulated symbols may be mapped, for example, to spatial stream(s) or space-time streams. The modulated symbols may be multiplexed, transformed via an inverse fast Fourier transform (IFFT) block, and subsequently provided to DSP circuitry for transmit windowing and filtering. The digital signals may be provided to a digital-to-analog converter (DAC) 222. In certain aspects involving beamforming, the modulated symbols in the respective spatial streams may be precoded via a steering matrix prior to provision to the IFFT block.

The modem 212 may be coupled to the radio 250 including a transmit (TX) path 214 (also known as a transmit chain) for transmitting signals via one or more antennas 218 and a receive (RX) path 216 (also known as a receive chain) for receiving signals via the antennas 218. When the TX path 214 and the RX path 216 share an antenna 218, the paths may be connected with the antenna via an interface 220, which may include any of various suitable RF devices, such as a switch, a duplexer, a diplexer, a multiplexer, and the like. As an example, the modem 212 may output digital in-phase (I) and/or quadrature (Q) baseband signals representative of the respective symbols to the DAC 222.

Receiving I or Q baseband analog signals from the DAC 222, the TX path 214 may include a baseband filter (BBF) 224, a mixer 226 (which may include one or several mixers), and a power amplifier (PA) 228. The BBF 224 filters the baseband signals received from the DAC 222, and the mixer 226 mixes the filtered baseband signals with a transmit local oscillator (LO) signal to convert the baseband signal to a different frequency (e.g., upconvert from baseband to a radio frequency). In some aspects, the frequency conversion process produces the sum and difference frequencies between the LO frequency and the frequencies of the baseband signal. The sum and difference frequencies are referred to as the beat frequencies. Some beat frequencies are in the RF range, such that the signals output by the mixer 314 are typically RF signals, which may be amplified by the PA 228 before transmission by the antenna 218. The antennas 218 may emit RF signals, which may be received at the second wireless device 104. While one mixer 226 is illustrated, several mixers may be used to upconvert the filtered baseband signals to one or more intermediate frequencies and to thereafter upconvert the intermediate frequency signals to a frequency for transmission.

The RX path 216 may include a low noise amplifier (LNA) 230, a mixer 232 (which may include one or several mixers), and a baseband filter (BBF) 234. RF signals received via the antenna 218 (e.g., from the second wireless device 104) may be amplified by the LNA 230, and the mixer 232 mixes the amplified RF signals with a receive local oscillator (LO) signal to convert the RF signal to a baseband frequency (e.g., downconvert). The baseband signals output by the mixer 232 may be filtered by the BBF 234 before being converted by an analog-to-digital converter (ADC) 236 to digital I or Q signals for digital signal processing. The modem 212 may receive the digital I or Q signals and further process the digital signals, for example, demodulating the digital signals.

Certain transceivers may employ frequency synthesizers with a voltage-controlled oscillator (VCO) to generate a stable, tunable LO frequency with a particular tuning range. Thus, the transmit LO frequency may be produced by a frequency synthesizer 238, which may be buffered or amplified by an amplifier (not shown) before being mixed with the baseband signals in the mixer 226. Similarly, the receive LO frequency may be produced by the frequency synthesizer 238, which may be buffered or amplified by an amplifier (not shown) before being mixed with the RF signals in the mixer 232. Separate frequency synthesizers may be used for the TX path 214 and the RX path 216.

While in a reception mode, the modem 212 may obtain digitally converted signals via the ADC 236 and RX path 216. As an example, in the modem 212, digital signals may be provided to the DSP circuitry, which is configured to acquire a received signal, for example, by detecting the presence of the signal and estimating the initial timing and frequency offsets. The DSP circuitry is further configured to digitally condition the digital signals, for example, using channel (narrowband) filtering, analog impairment conditioning (such as correcting for I/Q imbalance), and applying digital gain to ultimately obtain a narrowband signal. The output of the DSP circuitry may be fed to the AGC, which is configured to use information extracted from the digital signals, for example, in one or more received training fields, to determine an appropriate gain. The output of the DSP circuitry also may be coupled with the demodulator, which is configured to extract modulated symbols from the signal and, for example, compute the logarithm likelihood ratios (LLRs) for each bit position of each subcarrier in each spatial stream. The demodulator may be coupled with the decoder, which may be configured to process the LLRs to provide decoded bits. The decoded bits from all of the spatial streams may be fed to the demultiplexer for demultiplexing. The demultiplexed bits may be descrambled and provided to a medium access control layer (e.g., the processor 210) for processing, evaluation, or interpretation.

The processor 210 and/or modem 212 may control the transmission of signals via the TX path 214 and/or reception of signals via the RX path 216. In some aspects, the processor 210 and/or modem 212 may be configured to perform various operations, such as those associated with any of the methods described herein. The processor 210 and/or the modem 212 may include a microcontroller, a microprocessor, an application processor, a baseband processor, a MAC processor, a neural network 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. In some cases, aspects of the processor 210 may be integrated with (incorporated in and/or shared with) the modem 212, such as the RF exposure manager 106, a microcontroller, a microprocessor, a baseband processor, a medium access control (MAC) processor, a digital signal processor, etc. For example, the processor 210 may be representative of a co-processor (e.g., a microprocessor) associated with the modem 212, and the modem 212 may be representative of an ASIC including the baseband processor, MAC processor, DSP, and/or neural network processor. The memory 240 may store data and program codes (e.g., computer-readable instructions) for performing wireless communications as described herein. The memory 240 may be external to the processor 210 and/or the modem 212 (as illustrated) and/or incorporated therein. In certain cases, the RF exposure manager 106 (as implemented via the processor 210 and/or modem 212) may determine a transmit power (e.g., corresponding to certain levels of gain(s) applied to the TX path 214 including the BBF 224, the mixer 226, and/or the PA 228) that complies with an RF exposure limit set by country-specific regulations and/or international guidelines (e.g., International Commission on Non-Ionizing Radiation Protection (ICNIRP) guidelines) as described herein.

FIG. 2 shows an example transceiver design. It will be appreciated that other transceiver designs or architectures may be applied in connection with aspects of the present disclosure. For example, while examples discussed herein utilize I and Q signals (e.g., quadrature modulation), those of skill in the art will understand that components of the transceiver may be configured to utilize any other suitable modulation, such as polar modulation. As another example, circuit blocks may be arranged differently from the configuration shown in FIG. 2, and/or other circuit blocks not shown in FIG. 2 may be implemented in addition to or instead of the blocks depicted.

In certain cases, compliance with an RF exposure limit may be performed as a time-averaged RF exposure evaluation within a specified running (moving) time window associated with the RF exposure limit. The RF exposure limit may specify a time-averaged RF exposure metric (e.g., SAR and/or PD) over the running time window. As an example, the Federal Communications Commission (FCC) specifies that certain SAR limits (general public exposure) are 0.08 W/kg, as averaged over the whole body, and a peak spatial-average SAR of 1.6 W/kg, averaged over any 1 gram of tissue (defined as a tissue volume in the shape of a cube) for sub-6 GHz bands, whereas certain PD limits are 1 mW/cm², as averaged over the whole body, and a peak spatial-average PD of 4 mW/cm², averaged over any 1 cm². The FCC also specifies the corresponding averaging time may be six minutes (360 seconds) for sub-6 GHz bands, whereas the averaging time may be 2 seconds for mm Wave bands (e.g., 60 GHz frequency bands), under a proposed regulation, for example.

The RF exposure limit and/or corresponding averaging time window may vary based on the frequency band. In certain aspects, the RF exposure limit(s) and/or corresponding averaging time window(s), if applicable, may be specific to a particular geographic region or country, such as the United States, Canada, China, or European Union. In some cases, the RF exposure limit(s) may specify the maximum allowed RF exposure that can be encountered without time averaging. In such cases, the maximum allowed RF exposure may correspond to a maximum output or transmit power that can be used by the wireless device.

FIG. 3 is a graph 300 of a transmit power over time (P(t)) that varies over a running (e.g., rolling or moving) time window (T) associated with the RF exposure limit. The wireless device (e.g., the first wireless device 102) may evaluate RF exposure compliance over the running time window 302 (T) based on past RF exposure (e.g., a transmit power report) in a past time interval 304 of the time window 302 and a future time interval 306. The wireless device may determine the maximum allowed transmit power for the future time interval 306 that satisfies the time-averaged RF exposure limit based on the past RF exposure used in the past time interval 304. The wireless device may perform such a time-averaging evaluation as the time window 302 moves over time, for example, in the next future time interval 308, where the past time interval 304 now includes the previous future time interval 306.

The maximum time-averaged transmit power limit (P_limit) represents the maximum transmit power the wireless device can transmit continuously for the duration of the running time window 302 (T) in compliance with the RF exposure limit. For example, the wireless device is transmitting continuously at P_limit in the third time window 302c such that the time-averaged transmit power over the time window (e.g., the third time window 302c) is equal to P_limit in compliance with the time-averaged RF exposure limit.

In certain cases, an instantaneous transmit power may exceed P_limit in certain transmission occasions, for example, as shown in the first time window 302a and the second time window 302b. In some cases, the wireless device may transmit at P_max, which may be the maximum instantaneous transmit power supported by the wireless device, the maximum instantaneous transmit power the wireless device is capable of outputting, or the maximum instantaneous transmit power allowed by a standard or regulatory body (e.g., the maximum output power, P_CMAX). In some cases, the wireless device may transmit at a transmit power less than or equal to P_limit in certain transmission occasions, for example, as shown in the first time window 302a.

In certain cases, a reserve power may be used to enable a continuous transmission within a time window (T) when transmitting above P_limit in the time window or to enable a certain level of quality for certain transmissions. As shown in the second time window 302b, the transmit power may be backed off from P_max to a reserve power (Preserve) so that the wireless device can maintain a continuous transmission during the time window (e.g., maintain a radio connection with a receiving entity) in compliance with the time-averaged RF exposure limit. In the third time window 302c, the wireless device may increase the transmit power to P_limit in compliance with the time-averaged RF exposure limit. In some cases, Preserve may allow for a certain level of transmission quality for certain transmissions (e.g., control signaling, high priority communications, low latency communications, highly reliable communications, etc.). Preserve may be used to reserve transmit power for at least a portion of the time window 302 for certain transmissions (e.g., control signaling). Preserve may also be referred to as a “control power level” or “control level.”

In the second time window 302b, the area between P_max and Preserve for the time duration of transmitting at P_max may be equal to the area between P_limit and Preserve for the time window T, such that the total area of transmit power (P(t)) in the second time window 302b is equal to the area of P_limit for the time window T. Such an area may be considered using 100% of the energy (transmit power or exposure) to remain compliant with the time-averaged RF exposure limit. Without the reserve power Preserve, the transmitter may transmit at P_max for a portion of the time window with the transmitter turned off for the remainder of the time window to ensure compliance with the time-averaged RF exposure limit.

In some aspects, the wireless device may transmit at a power that is higher than P_limit, but less than P_max in the time-average mode illustrated in the second time window 302b. While a single transmit burst is illustrated in the second time window 302b, it will be understood that the wireless device may instead utilize a plurality of transmit bursts within the time window (T), where the transmit bursts are separated by periods during which the transmit power is maintained at or below Preserve. Further, it will be understood that the transmit power of each transmit burst may vary (either within the burst and/or in comparison to other bursts), and that at least a portion of the burst may be transmitted at a power above P_limit.

In certain aspects, the wireless device may transmit at a power less than or equal to a fixed power limit (e.g., P_limit) without considering past exposure and/or past transmit powers in terms of a time-averaged RF exposure. For example, the wireless device may transmit at a power less than or equal to P_limit using a look-up table (comprising one or more values of P_limit depending on an RF exposure scenario). The look-up table may provide one or more values of P_limit depending on the transmit frequency, transmit antenna, radio configuration (single-radio or multi-radio) and/or RF exposure scenario (e.g., a device state index corresponding to head exposure, body or torso exposure, extremity or hand exposure, and/or hotspot exposure) encountered by the wireless device. Examples of RF exposure scenarios include cases where the wireless device is emitting RF signals proximate to human tissue, such as a user's head, hand, or body (e.g., torso), or where the wireless device is being used as a hotspot away from human tissue. Therefore, the RF exposure can be managed as a time-averaged RF exposure evaluation (e.g., illustrated in FIG. 3), managed using a look-up table or flat or maximum value, or using another strategy or algorithm, where a particular process of managing the RF exposure may be referred to herein as an RF exposure control scheme.

For certain aspects, a wireless device may exhibit or be configured with a transmission duty cycle. The wireless device may determine transmit power level(s) and/or reserve power level(s) in compliance with the time-averaged RF exposure limit based on the duty cycle. The transmission duty cycle may be indicative of a share (e.g., 100 ms) of a specific period (e.g., 500 ms) in which the wireless device transmits RF signals. The duty cycle may be a ratio of the share to the specific period (e.g., 100 ms/500 ms), where the duty cycle may be represented as a number from zero to one. The duty cycle may be an effective duty cycle associated with the total transmit time of one or more transmissions in the time period. For example, in the first time window 302a, the duty cycle may be greater than 50% of the duration of the time window (T), whereas in the second time window 302b, the duty cycle may be equal to 100% of the duration of the time window (T). In certain cases, the duty cycle may be standardized (e.g., predetermined) with a specific RAT and/or vary over time, for example, due to changes in radio conditions, mobility, and/or user behavior.

As an example, certain RATs may specify the uplink duty cycle in the form of a time division duplexing (TDD) configuration, such as a TDD uplink-downlink (UL-DL) slot pattern in 5G NR or similar TDD patterns in E-UTRA or UMTS. In 5G NR, the TDD UL-DL slot pattern may specify the number of uplink slots and corresponding position in time associated with the uplink slots in a sequence of slots, such that the total number of uplink slots with respect to the total number of slots in the sequence is indicative of the duty cycle. In certain aspects, the duty cycle may correspond to the actual duration for past transmissions scheduled or used, for example, within the TDD UL-DL slot pattern. For example, although the wireless device may be configured with a TDD UL-DL slot pattern, the wireless device may use a portion or subset of the UL slots for transmitting RF signals. Thus, the duty cycle for the wireless device may be less than the maximum available duty cycle corresponding to the TDD UL-DL slot pattern.

Example Transmit Power Control to Avoid Radio Frequency Saturation

Aspects of the present disclosure provide apparatus and methods for controlling the transmit power to avoid RF saturation. The wireless device may obtain a transmit power budget and determine if the transmit power budget can cause RF saturation at a receiver. If the transmit power budget can cause RF saturation at the receiver (for example, based on a path loss between the wireless device and the receiver), the wireless device may reduce the transmit power associated with the transmit power budget and use that new transmit power for a transmission. For example, the wireless device may estimate the received power of the signal at the receiver based on the transmit power budget and the path loss. If the transmit power budget avoids RF saturation at the receiver, the wireless device may use the transmit power budget.

The apparatus and methods for controlling transmit power(s) described herein may provide various advantages. For example, the apparatus and methods for controlling transmit power(s) described herein may allow for improved wireless communication performance including, for example, an increased throughput, decreased latency, and/or increased transmission range, where the improved performance may be attributable to a transmit power that avoids RF saturation at a receiver.

FIG. 4 is a diagram illustrating an example wireless device 402 (e.g., the first wireless device 102) having multiple radios 450a-d (e.g., the radios 250). In this example, the radios 450a-d may be associated with any of various RATs and/or frequency bands, channels, bandwidths, carriers, etc. For example, the first radio 450a may communicate via WWAN RAT(s) (e.g., E-UTRA and/or 5G NR) in sub-6 GHz frequency bands. The second radio 450b may communicate via WWAN RAT(s) (e.g., 5G NR) in mmWave frequency bands. The third radio 450c may communicate via WLAN RAT(s) in sub-6 GHz (e.g., 2.4 GHz, 5 GHZ, and/or 6 GHZ) frequency bands. The fourth radio 450d may communicate via short-range communications (e.g., Bluetooth) in a 2.4 GHz frequency band. While this example shows a wireless device having four radios, a wireless device may have any number of radios for wireless communications, such as a radio per one or more frequency bands associated with WWAN and/or WLAN communications, a radio per RAT, and/or a radio capable of communicating via multiple RATs.

FIG. 5 is a diagram illustrating an example logical architecture 500 for controlling the transmit power (and hence, the RF exposure) associated with one or more radios 506 (e.g., the radio(s) 450a-d) of a wireless device (e.g., the wireless device 402). As the outer loop 502 and the inner loop(s) 504 control transmit power(s) applied at the radio(s) 506 to be in compliance with an RF exposure limit, aspects of the outer loop 502 and/or the inner loop(s) 504 may be representative of the RF exposure manager 106. In certain aspects, the outer loop 502 may be representative of a centralized RF exposure manager, and the inner loop(s) may be representative of transmit power manager(s) associated with the radio(s) 506, as further described herein. As an example, the outer loop 502 may be implemented in a WWAN modem, and at least one of the inner loops 504 may be implemented in a WLAN modem or a multi-RAT modem (e.g., WLAN and Bluetooth). With respect to FIG. 2, the outer loop 502 may be implemented in the processor 210 (which as described herein may include or be representative of, in some cases, a modem—e.g., a WWAN modem), and the inner loop 504 may be implemented in the modem 212—e.g., another modem, such as a WLAN modem.

In this example, the outer loop 502 operates as a centralized controller for controlling the RF exposure associated with the radios 506. The outer loop 502 may determine the maximum allowed transmit powers that can be used for a future time interval based on the past transmit powers associated with all (or some) of the radios 506. For example, the outer loop 502 may periodically (e.g., every 500 milliseconds) receive first information 508 from the inner loop(s) 504 associated with the radios 506. In some cases, the outer loop 502 may obtain the first information 508 in response to certain criteria (e.g., a triggering event including a change in channel conditions, quality of service (QOS), etc.). The periodicity in which the first information 508 is obtained at the outer loop 502 may correspond to a time interval cycle, such as following each future time interval 306, 308 of the rolling time window 302.

The first information 508 may include an indication of a transmit power report and/or an indication of a transmit power request associated with a respective inner loop 504. The indication of the transmit power request may include a requested transmit power or exposure margin for a future time interval (e.g., the time interval 306, 308). The indication of the transmit power report may include past transmit power history or an average transmit power associated with a time interval (e.g., a past time interval in a rolling time window, such as the past time interval 304 or the previous future time interval). A particular inner loop 504 may be associated with one or more radios (e.g., any of the radios 450a-d), and thus, the first information 508 may be associated with such radio(s). As an example, at least one of the inner loops 504 may provide the first information 508 associated with a WLAN radio to the outer loop 502.

The outer loop 502 may determine separate transmit power budgets for the inner loops 504, for example, based on the first information 508 and/or other information (e.g., a particular transmit power budget allocation for an inner loop). In some aspects, the outer loop 502 may determine the transmit power budgets without the first information 508, for example, when an inner loop 504 is not configured to provide the first information 508. The transmit power budgets may be associated with a time interval, such as the future time interval 306, 308, in which to apply the transmit power budgets. The transmit power budgets for the inner loops 504 may comply with an RF exposure limit. For example, the inner loop(s) 504 may obtain the respective transmit power budgets before the future time interval occurs, and the inner loop(s) 504 may determine particular transmit power(s) to use in compliance with the respective transmit power budget(s).

In certain aspects, the outer loop 502 may periodically provide second information 510 to the inner loop(s) 504, where the second information 510 may indicate the transmit power budgets associated with the inner loops 504. In some cases, each of the inner loops 504 may obtain the second information 510, which may indicate a portion of the total transmit power budget for each of the inner loops 504. For example, the outer loop 502 may provide a first transmit power budget to a first inner loop and a second transmit power budget to a second inner loop, where the first transmit power budget and the second transmit power budget are portions of the total transmit power budget distributed among the inner loops 504. In certain cases, a subset of the inner loops 504 may be assigned transmit power budgets, for example, when certain radio(s) are disabled (e.g., in an idle mode or sleep mode) and not expected to communicate in the respective time interval. In such cases, the outer loop 502 may provide the second information 510 to only the subset of the inner loops 504.

For certain aspects, the inner loop 504 may operate in a standalone mode, where the inner loop 504 determines its own transmit power budget in compliance with the RF exposure limit. In standalone mode, the inner loop 504 may determine the transmit power budget without periodic updates from the outer loop 502 and/or other inner loops 504. The inner loop 504 may not communicate with the outer loop 502 while operating in standalone mode. As an example, the inner loop 504 may temporarily stop communications with the outer loop 502 due to the outer loop 502 being in an idle mode or sleep mode, and as such, the inner loop 504 may operate in a standalone mode for purposes of determining RF exposure compliant transmit powers. In some cases, the inner loop 504 may permanently operate in a standalone mode without the updates from the outer loop 502. For example, a WLAN modem and/or a Bluetooth modem may operate in a standalone mode separated from an outer loop and/or inner loop associated with WWAN communications. In such cases of standalone mode, obtaining the transmit power budget may involve the inner loop 504 generating the transmit power budget. In some cases, exposure for one or more RATs (e.g., WWAN) may be managed by a first exposure manager 502 while one or more other RATs (e.g., WLAN, Bluetooth, and/or NTN) are managed by a second exposure manager 502.

A transmit power budget may indicate the maximum allowed time-averaged transmit power that one or more radio(s) can use for the future time interval in compliance with an RF exposure limit. The maximum allowed time-averaged transmit power may correspond to a portion of a rolling time window (e.g., the future time interval), whereas the maximum time-averaged transmit power (e.g., P_limit) may correspond to the entire duration of such a time window associated with the RF exposure limit. A total transmit power budget of a wireless device may be shared among multiple RATs, for example, including WWAN, WLAN, NTN, V2X, D2D, and/or short-range (e.g., Bluetooth) communications. In some cases, the total transmit power budget may be allocated to a single RAT.

The inner loop 504 may determine a transmit power 512 for the future time interval based at least in part on the transmit power budget. As an example, based on the transmit power budget supplied by the outer loop 502 and a current duty cycle, the inner loop 504 may determine the transmit power (P_TX) according to the following expression:

$\begin{array}{cc}{P}_{\mathrm{TX}}=P_{\mathrm{limit}}+{\mathrm{OL}}_{\mathrm{limit}}+P_{\mathrm{DC}}& \left(1\right)\end{array}$

where P_limit may be the maximum time-averaged transmit power limit, corresponding to an RF exposure limit (e.g., a SAR limit and/or PD limit); OL_limit is a power adjustment provided by the outer loop (which may be positive or negative to increase or decrease P_limit); and P_DC is the additional power obtained by exploiting low duty cycle. Thus, in some cases, the second information 510 may be indicative of a transmit power budget, for example, as the power adjustment OL_limit. In some cases, P_limit may be selected from a look-up table with various transmit power limits corresponding to various transmission scenarios (e.g., any combination of RAT, carrier frequency, frequency band, antenna, antenna group, beam, etc.) and/or exposure scenarios (e.g., head exposure, body-word exposure, extremity or hand exposure, hotspot exposure, etc.). The inner loop 504 may provide an indication of transmit power(s) 512 to the radios 506 to be used for transmission(s) in the time interval. The indication of the transmit powers 512 may include a maximum allowed transmit power that can be used for the time interval, where the maximum allowed transmit power is in compliance with the RF exposure limit according to the transmit power budget.

In certain aspects, the inner loop 504 may determine the transmit power(s) 512 based on other transmit power control(s) 514, such as RF emission controls, RF interference controls, RF conformance control, data rate specific power control, etc., in addition to or instead of the RF exposure controls described herein. The transmit power control(s) 514 may be stored in memory, such as the memory 240. In some cases, the transmit power control(s) 514 may provide an additional or alternative transmit power budget and/or limit the maximum transmit power determined, such as to control interference or RF emissions. The transmit power controls 514 may provide one or more maximum allowed transmit powers, and the inner loop 504 may select the smallest value among multiple transmit power levels, including the maximum allowed transmit power for RF compliance, for RF emission controls, RF interference controls, automatic gain control, etc. For example, the transmit power(s) 512 for the time interval may be determined according to an expression that selects the smallest value among multiple maximum allowed values as follows:

$\begin{array}{cc}{P}_{\mathrm{TX}}=\min \left(P_{\mathrm{TX}1},\dots ,P_{\mathrm{TXN}}\right)& \left(2\right)\end{array}$

where P_TX1 through P_TXN may represent N number of maximum allowed transmit powers associated with various transmit power controls. As an example, at least one of P_TX1 through P_TXN includes the maximum allowed transmit power determined according to the RF exposure controls as described herein. In certain aspects, the inner loop 504 may apply any suitable transmit power control(s), such as an RF emission limit, interference limit, RF saturation limit, etc., in addition to or instead of the RF-exposure-based transmit power budget, where such transmit power control may provide a transmit power budget that may be checked for RF saturation at the receiver and adjusted if RF saturation is detected as described herein. Thus, the transmit power(s) 512 may comply with the RF exposure controls and/or other transmit power controls.

To avoid RF saturations being encountered at a receiver (e.g., the second wireless device 104), the inner loop 504 may check whether the transmit power budget (or any other transmit power control) can cause RF saturation at the receiver. For example, the wireless device may determine a path loss between the wireless device and the receiver, and the wireless device may use the path loss to estimate the received power of a signal received at the receiver and transmitted from the wireless device. The received power may be determined using the path loss and the transmit power used at the wireless device based on the transmit power budget. If the received power exceeds a threshold indicative of RF saturation, the wireless device may reduce the transmit power corresponding to the transmit power budget. The saved power due to the reduced transmit power may be used by another radio or for a future transmission, for example (and may be known to the outer loop 502 or reported back to the outer loop 502, for example as first information 508). If the received power satisfies the threshold indicative of RF saturation, the wireless device may use the transmit power corresponding to the transmit power budget.

As an example, the path loss may be determined assuming there is channel reciprocity between the wireless device (e.g., the first wireless device 102) and another wireless device (e.g., the second wireless device 104). The path loss (pathloss) may be determined according to the following expression:

$\begin{array}{cc}\mathrm{pathloss}=P_{\mathrm{TX},2}-\mathrm{RSSI}& \left(3\right)\end{array}$

where P_TX,2 is a transmit power used at the other wireless device and RSSI is the received signal strength indicator (RSSI) associated with a signal received at the wireless device from the other wireless device. In some cases, P_TX,2 may be assumed to be a particular value or provided to the wireless device (e.g., via feedback by the other wireless device). For example, in a WLAN, P_TX,2 may be assumed to be the maximum transmit power that an AP is allowed to transmit at 30 dBm.

In certain aspects, the path loss may be identified using any suitable estimation or determination associated with the path loss. For example, the path loss may be determined using a moving (running or rolling) average or a finite impulse response (FIR) filter of signal strengths over a particular time window. The signal strengths may be associated with signals received at the wireless device, and the signal strengths may include RSSI measurements of the received signals. An FIR filter may be used to compute the average path loss, and the average path loss may be used in the transmit power determination as further described herein. In some cases, weights associated with each of the signal strengths may be used in the computation of the average path loss. For example, a weighted signal strength may be equal to the product of the respective weight and the respective strength. In certain cases, the value of a weight can be used to give more preference to certain signal strengths, such as the most-recently measured RSSI or the first measured RSSI. The RSSI to compute the path loss may be measured from any suitable received signal, for example, including a beacon, a management frame, a pilot signal, a synchronization signal, a reference signal, etc. In certain aspects, the path loss may be determined using any suitable characteristic associated with the communication link between the wireless device and the other wireless device, such as a channel quality indicator, a signal-to-noise ratio (SNR), a signal-to-interference-plus-noise ratio (SINR), a signal-to-noise-plus-distortion ratio (SNDR), a reference signal received power (RSRP), a reference signal received quality (RSRQ), and/or a data error rate or ratio. In some cases, the wireless device may obtain an (explicit or implicit) indication of the path loss from another wireless device.

For certain aspects, the wireless device may apply a separate path loss for certain devices and/or communication links. For example, a separate path loss may be determined for each of the other wireless devices (e.g., the second wireless device 104) or a subset thereof in communication with the wireless device. In some cases, the wireless device may communicate with another wireless device via multiple communication links, for example, due to different beams, reflections, and/or transmission/propagation paths. A path loss may be determined for each of the communication links (or a subset thereof) associated with the other wireless devices in communication with the wireless device. As an example, the path loss may be maintained with respect to each peer or virtual device, and the wireless device may use the path losses to adjust the power per peer or communication link. Thus, the transmit power adjustment described herein may apply to the communication links and/or peers associated other suitable protocols, such as P2P and neighbor awareness networking (NAN).

If the transmit power to be used at the wireless device may lead to RF saturation at the other wireless device, the wireless device may adjust the transmit power to avoid the RF saturation. For example, the wireless device may estimate the received power of the signal received at the other wireless device, and the wireless device may determine if that received power exceeds a threshold indicative of RF saturation. The threshold may correspond to a maximum input level (MIL), for example, as provided in 802.11 standards or any other wireless communication standard (e.g., 3GPP standards). As an example, the MIL may be −20 dBm for orthogonal frequency-division multiplexing (OFDM) in the 2.4 GHz frequency band, −30 dBm for OFDM in the 5 GHz frequency band, or −30 dBm for OFDM in the 6 GHz frequency band.

The wireless device may determine if the transmit power may lead to RF saturation according to the following expression:

$\begin{array}{cc}{P}_{\mathrm{TX}}-\mathrm{pathloss}>P_{\mathrm{sat}}& \left(4\right)\end{array}$

where P^TX is the transmit power to be used at the wireless device—for example, as determined according to Expression (1) or Expression (2); pathloss is the path loss between the wireless device and the other wireless device—for example, as determined according to Expression (3); and P_sat is representative of a power threshold indicative of RF saturation, such as the MIL.

If Expression (4) is satisfied (e.g., P_TX−pathloss>P_sat), the wireless device may determine a new transmit power to use for the time interval. For example, the wireless device may determine the transmit power according to the following expression:

$\begin{array}{cc}{P}_{\mathrm{TX}}=P_{\mathrm{sat}}+\mathrm{pathloss}+P_{\mathrm{buffer}}& \left(5\right)\end{array}$

where P_buffer may optionally be added and represent a buffer (or leeway or tolerance) to account for any errors or discrepancy in determining the path loss or P_sat. If Expression (4) is not satisfied (e.g., P_TX−pathloss≤P_sat), the wireless device may proceed with using the originally determined transmit power for the time interval—for example, as determined according to Expression (1) or Expression (2).

FIG. 6 is a flow diagram illustrating example operations 600 for wireless communication. The operations 600 may be performed, for example, by a wireless device (e.g., the first wireless device 102 in the wireless communication system 100). The operations 600 may be implemented as software components that are executed and run on one or more processors (e.g., the processor 210 and/or the modem 212 of FIG. 2). Further, the transmission and/or reception of signals by the wireless device in the operations 600 may be enabled, for example, by one or more antennas (e.g., antennas 218 of FIG. 2). In certain aspects, the transmission and/or reception of signals by the wireless device may be implemented via a bus interface of one or more processors (e.g., the processor 210 and/or the modem 212) obtaining and/or outputting signals for reception or transmission.

The operations 600 may begin, at block 602, where the wireless device obtains a transmit power budget (or an indication thereof) associated with a time interval (e.g., the future time interval 306). For example, an inner loop (e.g., the inner loop 504) of the wireless device may obtain a transmit power budget associated with a future time interval. The transmit power budget may include, correspond to, or be indicative of a maximum allowed time-averaged transmit power based on an RF exposure limit, for example, as described herein with respect to FIGS. 3 and 5. A transmit power budget may indicate the maximum allowed time-averaged transmit power that one or more radio(s) can use for the future time interval within a time averaging time window in compliance with the time-averaged RF exposure limit. As a total transmit power budget of the wireless device may be shared among multiple radios across a rolling time window, the transmit power budget may indicate a time-averaged power that is less than or equal to P_max. In some cases, to obtain the transmit power budget, the wireless device may obtain the transmit power budget from a controller (e.g., the outer loop 502) that controls RF exposure associated with one or more RATs. In certain cases, the inner loop may generate the transmit power budget, for example, when the inner loop is operating in a standalone mode without the periodic information (e.g., the second information 510) from the outer loop. In such cases, to obtain the transmit power budget, the wireless device may generate the transmit power budget in a standalone mode.

At block 604, the wireless device may determine a first transmit power (e.g., P_TX) based at least in part on the transmit power budget and a receive power associated with a communication link. The receive power may be associated with a receiver of another device (e.g., the second wireless device 104), and to determine the first transmit power, the wireless device may determine the first transmit power to avoid RF saturation at the receiver of the other device.

At block 606, the wireless device may transmit a signal at the first transmit power in the time interval. For example, the wireless device may transmit the signals to a second wireless communication device (e.g., any of the second wireless devices 104 depicted in FIG. 1). The signals may indicate (or carry) any of various information, such as data or control information.

To determine the first transmit power, the wireless device may determine if a transmit power may lead to an RF saturation at another wireless device (e.g., the second wireless device 104), for example, as described herein with respect to Expressions (4) and (5). As an example, the wireless device may select a second transmit power (e.g., the transmit power determined according to Expression (5)) as the first transmit power in response to the receive power satisfying a first criterion (e.g., P_TX−pathloss>P_sat), or the wireless device may select a third transmit power (e.g., the transmit power as determined according to Expression (1) or (2)) as the first transmit power in response to the receive power satisfying a second criterion (e.g., P_TX−pathloss≤ P_sat) different than the first criterion. In certain aspects, the wireless device may select the second transmit power (e.g., the transmit power determined according to Expression (5)) as the first transmit power in response to the receive power satisfying a criterion (e.g., P_TX−pathloss>P_sat); otherwise, the wireless device may select the third transmit power (e.g., the transmit power as determined according to Expression (1) or (2)) as the first transmit power.

The wireless device may determine the third transmit power based at least in part on the transmit power budget, for example, according to Expression (1) and/or Expression (2). The wireless device may determine the receive power based at least in part on the third transmit power, for example, according to Expressions (3) and (4).

The wireless device may determine the second transmit power based at least in part on one or more properties (e.g., RSSI, MIL, and/or path loss) associated with the communication link, for example, according to Expression (5). For example, the wireless device may determine the second transmit power as a sum of at least a maximum input level (MIL) and a path loss associated with the communication link. The sum may be the sum of the maximum input level, the path loss, and a buffer value (e.g., P_buffer), for example, according to Expression (5). The properties may include a path loss associated with the communication link, a signal strength associated with the communication link, a maximum input level associated with the communication link, or any combination thereof. The path loss may correspond to the communication link between the wireless device and another device (e.g., the second wireless device 104). The signal strength (e.g., RSSI) may be associated with a wireless signal received at the wireless device and transmitted from the other device. The maximum input level may be associated with the other device as described herein.

In certain aspects, the wireless device may determine the path loss associated with the communication link. As an example, the wireless device may determine the path loss based at least in part on the signal strength (e.g., the RSSI) and a fourth transmit power (e.g., P_TX,2) associated with another device, for example, according to Expression (3). In certain cases, the wireless device may assume the fourth transmit power is a particular transmit power level, e.g., the maximum transmit power that an AP is allowed to transmit at 30 dBm. In some cases, the wireless device may determine the path loss based at least in part on a moving average of the signal strength, such as an FIR filter operation. For certain aspects, the wireless device may determine the path loss based at least in part on a weighted average of the signal strength. In certain aspects, the wireless device may select the path loss among a plurality of path losses associated with a plurality of connections corresponding to one or more peers or one or more communication links.

For certain aspects, the wireless device may apply the transmit power controls described herein for any of various RATs, such as WWAN, WLAN, short-range communications (e.g., Bluetooth), V2X, NTN, etc. For example, the communication link may be associated with WLAN communications or WWAN communications. In some cases, the wireless device may transmit the signal via one or more frequency bands in a shared spectrum (e.g., unlicensed spectrum) and/or a licensed spectrum. In certain cases, the frequency bands may include a 2.4 GHz frequency band, a 5 GHz frequency band, a 6 GHz frequency band, or any combination thereof.

Aspects of the present disclosure may be applied to any of various wireless communication devices (wireless devices) that may emit RF signals causing exposure to human tissue, such as a base station and/or a CPE, performing the RF exposure compliance described herein.

Example Communications Device

FIG. 7 depicts aspects of an example communications device 700. In some aspects, communications device 700 is a wireless communication device, such as the first wireless device 102 described above with respect to FIGS. 1 and 2.

The communications device 700 includes a processing system 702 coupled to a transceiver 708 (e.g., a transmitter and/or a receiver). The transceiver 708 is configured to transmit and receive signals for the communications device 700 via an antenna 710, such as the various signals as described herein. The processing system 702 may be configured to perform processing functions for the communications device 700, including processing signals received and/or to be transmitted by the communications device 700.

The processing system 702 includes one or more processors 720. In various aspects, the one or more processors 720 may be representative of any of the processor 210 and/or the modem 212, as described with respect to FIG. 2. The one or more processors 720 are coupled to a computer-readable medium/memory 730 via a bus 706. In certain aspects, the computer-readable medium/memory 730 is configured to store instructions (e.g., computer-executable code) that when executed by the one or more processors 720, cause the one or more processors 720 to perform the operations 600 described with respect to FIG. 6, or any aspect related to the operations described herein. Note that reference to a processor performing a function of communications device 700 may include one or more processors performing that function of communications device 700. Reference to one or more processors performing multiple functions may include any one of the one or more processors performing any one of the multiple functions.

In the depicted example, computer-readable medium/memory 730 stores code (e.g., executable instructions) for obtaining 731, code for determining 732, code for transmitting 733, code for selecting 734, or any combination thereof. Processing of the code 731-734 may cause the communications device 700 to perform the operations 600 described with respect to FIG. 6, or any aspect related to operations described herein.

The one or more processors 720 include circuitry configured to implement (e.g., execute) the code stored in the computer-readable medium/memory 730, including circuitry for obtaining 721, circuitry for determining 722, circuitry for transmitting 723, circuitry for selecting 724, or any combination thereof. Processing with circuitry 721-72[!] may cause the communications device 700 to perform the operations 600 described with respect to FIG. 6, or any aspect related to operations described herein.

Various components of the communications device 700 may provide means for performing the operations 600 described with respect to FIG. 6, or any aspect related to operations described herein. For example, means for transmitting, sending or outputting for transmission may include the TX path 214 and/or antenna(s) 218 of the first wireless device 102 illustrated in FIG. 2 and/or transceiver 708 and antenna 710 of the communications device 700 in FIG. 7. Means for receiving or obtaining may include the RX path 216 and/or antenna(s) 218 of the first wireless device illustrated in FIG. 2 and/or transceiver 708 and antenna 710 of the communications device 700 in FIG. 7. Means for obtaining, means for determining, and/or means for selecting may include a processor, such as the processor 210 and/or modem 212 depicted in FIG. 2 and/or the processor(s) 720 in FIG. 7.

Example Aspects

Implementation examples are described in the following numbered clauses:

Aspect 1: A method of wireless communication by a wireless device, comprising: obtaining a transmit power budget associated with a time interval; determining a first transmit power based at least in part on the transmit power budget and a receive power associated with a communication link; and transmitting a signal at the first transmit power in the time interval.

Aspect 2: The method of Aspect 1, wherein the receive power is associated with a receiver of another device.

Aspect 3: The method of Aspect 1 or 2, wherein determining the first transmit power comprises determining the first transmit power to avoid radio frequency (RF) saturation at a receiver of another device.

Aspect 4: The method according to any of Aspects 1-3, wherein determining the first transmit power comprises: selecting a second transmit power as the first transmit power in response to the receive power satisfying a first criterion; or selecting a third transmit power as the first transmit power in response to the receive power satisfying a second criterion different than the first criterion.

Aspect 5: The method of Aspect 4, wherein determining the first transmit power comprises: determining the third transmit power based at least in part on the transmit power budget; and determining the receive power based at least in part on the third transmit power.

Aspect 6: The method of Aspect 4 or 5, wherein determining the first transmit power comprises determining the second transmit power based at least in part on one or more properties associated with the communication link.

Aspect 7: The method of Aspect 6, wherein determining the second transmit power comprises determining the second transmit power as a sum of at least a maximum input level and a path loss associated with the communication link.

Aspect 8: The method of Aspect 7, wherein the sum is the sum of the maximum input level, the path loss, and a buffer value.

Aspect 9: The method according to any of Aspects 1-8, wherein the transmit power budget comprises a maximum allowed transmit power based on a radio frequency (RF) exposure limit.

Aspect 10: The method according to any of Aspects 6-9, wherein the one or more properties comprise: a path loss associated with the communication link; a signal strength associated with the communication link; a maximum input level associated with the communication link; or any combination thereof.

Aspect 11: The method of Aspect 10, wherein: the path loss corresponds to the communication link between the wireless device and another device; the signal strength is associated with a wireless signal received at the wireless device and transmitted from the other device; and the maximum input level is associated with the other device.

Aspect 12: The method of Aspect 10 or 11, further comprising determining the path loss based at least in part on the signal strength and a fourth transmit power associated with another device.

Aspect 13: The method of Aspect 12, wherein determining the path loss comprises determining the path loss based at least in part on a moving average of the signal strength.

Aspect 14: The method of Aspect 12 or 13, wherein determining the path loss comprises determining the path loss based at least in part on a weighted average of the signal strength.

Aspect 15: The method according to any of Aspects 12-14, wherein determining the path loss comprises selecting the path loss among a plurality of path losses associated with a plurality of connections.

Aspect 16: The method according to any of Aspects 1-15, wherein transmitting the signal comprises transmitting the signal via one or more frequency bands in a shared spectrum.

Aspect 17: The method of Aspect 16, wherein the frequency bands include a 2.4 GHz frequency band, a 5 GHz frequency band, a 6 GHz frequency band, or any combination thereof.

Aspect 18: The method according to any of Aspects 1-17, wherein the communication link is associated with wireless local area network (WLAN) communications or wireless wide area network (WWAN) communications.

Aspect 19: The method according to any of Aspects 1-18, wherein obtaining the transmit power budget comprises obtaining the transmit power budget from a controller that controls RF exposure associated with a plurality of radio access technologies including a radio access technology associated with the communication link.

Aspect 20: An apparatus for wireless communication, comprising: a memory; and a processor coupled to the memory, the processor being configured to: obtain a transmit power budget associated with a time interval, determine a first transmit power based at least in part on the transmit power budget and a receive power associated with a communication link, and control transmission of a signal at the first transmit power in the time interval.

Aspect 21: The apparatus of Aspect 20, further comprising a transmitter configured to transmit the signal at the first transmit power, wherein the receive power is associated with a receiver of another device.

Aspect 22: The apparatus of Aspect 20 or 21, wherein to determine the first transmit power, the processor is further configured to determine the first transmit power to avoid radio frequency (RF) saturation at a receiver of another device.

Aspect 23: The apparatus according to any of Aspects 20-22, wherein to determine the first transmit power, the processor is further configured to: select a second transmit power as the first transmit power in response to the receive power satisfying a first criterion; or select a third transmit power as the first transmit power in response to the receive power satisfying a second criterion different than the first criterion.

Aspect 24: The apparatus of Aspect 23, wherein to determine the first transmit power, the processor is further configured to: determine the third transmit power based at least in part on the transmit power budget; and determine the receive power based at least in part on the third transmit power.

Aspect 25: The apparatus of Aspect 23 or 24, wherein to determine the first transmit power, the processor is further configured to determine the second transmit power based at least in part on one or more properties associated with the communication link.

Aspect 26: The apparatus of Aspect 25, wherein to determine the second transmit power, the processor is further configured to determine the second transmit power as a sum of at least a maximum input level and a path loss associated with the communication link.

Aspect 27: The apparatus of Aspect 26, wherein the sum is the sum of the maximum input level, the path loss, and a buffer value.

Aspect 28: The apparatus according to any of Aspects 25-27, wherein the one or more properties comprise: a path loss associated with the communication link; a signal strength associated with the communication link; a maximum input level associated with the communication link; or any combination thereof.

Aspect 29: The apparatus of Aspect 28, wherein: the path loss corresponds to the communication link between the apparatus and a wireless device; the signal strength is associated with a wireless signal received at the apparatus and transmitted from the wireless device; and the maximum input level is associated with the wireless device.

Aspect 30: A non-transitory computer-readable medium having instructions stored thereon for: obtaining a transmit power budget associated with a time interval; determining a first transmit power based at least in part on the transmit power budget and a receive power associated with a communication link; and transmitting a signal at the first transmit power in the time interval.

Aspect 31: An apparatus, comprising: a memory comprising computer-executable instructions; and one or more processors configured to execute the computer-executable instructions and cause the apparatus to perform a method in accordance with any of Aspects 1-19.

Aspect 32: An apparatus, comprising means for performing a method in accordance with any of Aspects 1-19.

Aspect 33: A non-transitory computer-readable medium comprising computer-executable instructions that, when executed by one or more processors of a processing system, cause the processing system to perform a method in accordance with any of Aspects 1-19.

Aspect 34: A computer program product embodied on a computer-readable storage medium comprising code for performing a method in accordance with any of Aspects 1-19.

Additional Considerations

The preceding description is provided to enable any person skilled in the art to practice the various aspects described herein. The examples discussed herein are not limiting of the scope, applicability, or aspects set forth in the claims. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other aspects. For example, changes may be made in the function and arrangement of elements discussed without departing from the scope of the disclosure. Various examples may omit, substitute, or add various procedures or components as appropriate. For instance, the methods described may be performed in an order different from that described, and various actions may be added, omitted, or combined. Also, features described with respect to some examples may be combined in some other examples. For example, an apparatus may be implemented or a method may be practiced using any number of the aspects set forth herein. In addition, the scope of the disclosure is intended to cover such an apparatus or method that is practiced using other structure, functionality, or structure and functionality in addition to, or other than, the various aspects of the disclosure set forth herein. It should be understood that any aspect of the disclosure disclosed herein may be embodied by one or more elements of a claim.

The various illustrative logical blocks, modules and circuits described in connection with the present disclosure may be implemented or performed with a microcontroller, a microprocessor, a general purpose processor, a digital signal processor (DSP), a neural network processor, 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 may be a microprocessor, but in the alternative, the processor may be any commercially available processor, controller, microcontroller, or state machine. A processor may 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, a system on a chip (SoC), or any other such configuration.

As used herein, a phrase referring to “at least one of” a list of items refers to any combination of those items, including single members. As an 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 with 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).

As used herein, the term “determining” encompasses a wide variety of actions. For example, “determining” may 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” may include receiving (e.g., receiving information), accessing (e.g., accessing data in a memory), and the like. Also, “determining” may include resolving, selecting, identifying, mapping, applying, choosing, establishing, and the like.

The methods disclosed herein comprise one or more actions for achieving the methods. The method actions may be interchanged with one another without departing from the scope of the claims. In other words, unless a specific order of actions is specified, the order and/or use of specific actions may be modified without departing from the scope of the claims. Further, the various operations of methods described above may be performed by any suitable means capable of performing the corresponding functions. The means may include various hardware and/or software component(s) and/or module(s), including, but not limited to a circuit, an application specific integrated circuit (ASIC), or processor.

The following claims are not intended to be limited to the aspects shown herein, but are to be accorded the full scope consistent with the language of the claims. Within a claim, reference to an element in the singular is not intended to mean “one and only one” unless specifically so stated, but rather “one or more.” The use of a definite article (e.g., “the” or “said”) before an element is not intended to impart a singular meaning (e.g., “one and only one”) on an otherwise plural meaning (e.g., “one or more”) associated with the element unless specifically so stated. Unless specifically stated otherwise, the term “some” refers to one or more. No claim element is to be construed under the provisions of 35 U.S.C. § 112 (f) unless the element is expressly recited using the phrase “means for.” All structural and functional equivalents to the elements of the various aspects described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims.

Claims

1. A method of wireless communication by a wireless device, comprising: obtaining a transmit power budget associated with a time interval;determining a first transmit power based at least in part on the transmit power budget and a receive power associated with a communication link; andtransmitting a signal at the first transmit power in the time interval.

2. The method of claim 1, wherein the receive power is associated with a receiver of another device.

3. The method of claim 1, wherein determining the first transmit power comprises determining the first transmit power to avoid radio frequency (RF) saturation at a receiver of another device.

4. The method of claim 1, wherein determining the first transmit power comprises: selecting a second transmit power as the first transmit power in response to the receive power satisfying a first criterion; orselecting a third transmit power as the first transmit power in response to the receive power satisfying a second criterion different than the first criterion.

5. The method of claim 4, wherein determining the first transmit power comprises: determining the third transmit power based at least in part on the transmit power budget; anddetermining the receive power based at least in part on the third transmit power.

6. The method of claim 4, wherein determining the first transmit power comprises determining the second transmit power based at least in part on one or more properties associated with the communication link.

7. The method of claim 6, wherein determining the second transmit power comprises determining the second transmit power as a sum of at least a maximum input level and a path loss associated with the communication link.

8. The method of claim 7, wherein the sum is the sum of the maximum input level, the path loss, and a buffer value.

9. The method of claim 1, wherein the transmit power budget comprises a maximum allowed transmit power based on a radio frequency (RF) exposure limit.

10. The method of claim 6, wherein the one or more properties comprise: a path loss associated with the communication link;a signal strength associated with the communication link;a maximum input level associated with the communication link; orany combination thereof.

11. The method of claim 10, wherein: the path loss corresponds to the communication link between the wireless device and another device;the signal strength is associated with a wireless signal received at the wireless device and transmitted from the other device; andthe maximum input level is associated with the other device.

12. The method of claim 10, further comprising determining the path loss based at least in part on the signal strength and a fourth transmit power associated with another device.

13. The method of claim 12, wherein determining the path loss comprises determining the path loss based at least in part on a moving average of the signal strength.

14. The method of claim 12, wherein determining the path loss comprises determining the path loss based at least in part on a weighted average of the signal strength.

15. The method of claim 12, wherein determining the path loss comprises selecting the path loss among a plurality of path losses associated with a plurality of connections.

16. The method of claim 1, wherein transmitting the signal comprises transmitting the signal via one or more frequency bands in a shared spectrum.

17. The method of claim 16, wherein the frequency bands include a 2.4 GHZ frequency band, a 5 GHz frequency band, a 6 GHz frequency band, or any combination thereof.

18. The method of claim 1, wherein the communication link is associated with wireless local area network (WLAN) communications or wireless wide area network (WWAN) communications.

19. The method of claim 1, wherein obtaining the transmit power budget comprises obtaining the transmit power budget from a controller that controls RF exposure associated with a plurality of radio access technologies including a radio access technology associated with the communication link.

20. An apparatus for wireless communication, comprising: a memory configured to store instructions; andone or more processors coupled to the memory and configured to execute the instructions to cause the one or more processors to: obtain a transmit power budget associated with a time interval,determine a first transmit power based at least in part on the transmit power budget and a receive power associated with a communication link, andcontrol transmission of a signal at the first transmit power in the time interval.

21. The apparatus of claim 20, further comprising a transmitter configured to transmit the signal at the first transmit power, wherein the receive power is associated with a receiver of another device.

22. The apparatus of claim 20, wherein to determine the first transmit power, the one or more processors are further configured to execute the instructions to further cause the one or more processors to determine the first transmit power to avoid radio frequency (RF) saturation at a receiver of another device.

23. The apparatus of claim 20, wherein to determine the first transmit power, the one or more processors are configured to execute the instructions to further cause the one or more processors to: select a second transmit power as the first transmit power in response to the receive power satisfying a first criterion; orselect a third transmit power as the first transmit power in response to the receive power satisfying a second criterion different than the first criterion.

24. The apparatus of claim 23, wherein to determine the first transmit power, the one or more processors are configured to execute the instructions to further cause the one or more processors to: determine the third transmit power based at least in part on the transmit power budget; anddetermine the receive power based at least in part on the third transmit power.

25. The apparatus of claim 23, wherein to determine the first transmit power, the one or more processors are further configured to execute the instructions to further cause the one or more processors to determine the second transmit power based at least in part on one or more properties associated with the communication link.

26. The apparatus of claim 25, wherein to determine the second transmit power, the one or more processors are further configured to execute the instructions to further cause the one or more processors to determine the second transmit power as a sum of at least a maximum input level and a path loss associated with the communication link.

27. The apparatus of claim 26, wherein the sum is the sum of the maximum input level, the path loss, and a buffer value.

28. The apparatus of claim 25, wherein the one or more properties comprise: a path loss associated with the communication link;a signal strength associated with the communication link;a maximum input level associated with the communication link; orany combination thereof.

29. The apparatus of claim 28, wherein: the path loss corresponds to the communication link between the apparatus and a wireless device;the signal strength is associated with a wireless signal received at the apparatus and transmitted from the wireless device; andthe maximum input level is associated with the wireless device.

30. A non-transitory computer-readable medium having instructions stored thereon for: obtaining a transmit power budget associated with a time interval;determining a first transmit power based at least in part on the transmit power budget and a receive power associated with a communication link; andtransmitting a signal at the first transmit power in the time interval.