Patent Description:
The present application relates to wireless devices, and more particularly to systems, methods, and apparatuses for reducing power consumption by opportunistically depowering one or more receiver chains.

Wireless communication systems are rapidly growing in usage. Additionally, there exist numerous different wireless communication technologies and standards. Some examples of wireless communication standards include GSM, UMTS (associated with, for example, WCDMA or TD-SCDMA air interfaces), LTE, LTE Advanced (LTE-A), <NUM> New Radio (NR), HSPA, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), IEEE <NUM> (WLAN or Wi-Fi), IEEE <NUM> (WiMAX), Bluetooth, and others.

Mobile electronic devices may take the form of smart phones or tablets that a user typically carries. Wearable devices (also referred to as accessory devices) are a newer form of mobile electronic device, one example being smart watches. Typically, mobile electronic devices have relatively limited energy storage capabilities, e.g., battery capacity. In general, it would be desirable to reduce the power requirements of communication devices, including both wearable devices and more traditional wireless devices such as smart phones. For example, powering a larger number of receiver chains for multi-layer communication may result in greater power use than powering a smaller number of receiver chains. Therefore, improvements in the field are desired. <CIT> discloses techniques that can facilitate mapping of codewords to Multiple Input Multiple Output layers for <NUM> New Radio systems. Codeword(s) can be mapped to MIMO layers based on predefined mappings. Configuration signaling can be generated or processed that can comprise an indication of an indicated maximum number of Multiple Input Multiple Output layers for a Component Carrier. <NPL> discloses new radio assistance from gNB to the UE regarding the maximum number of MIMO layers to be used for the downlink/uplink transmission. The signaling assistance can be also used at the UE to reduce power consumption, by autonomous turning on/off of the RF chains.

Embodiments are presented herein of, inter alia, systems, methods, and apparatuses for reducing power requirements of a wireless device by opportunistically depowering one or more receiver chains.

A wireless device may comprise a plurality of receiver chains which may be used for receiving information using one or more wireless technologies. In some embodiments, the plurality of receiver chains may be configured for multiple-input, multiple-output (MIMO) communication. Each of the plurality of receiver chains may be configured to be separately powered down.

The wireless device may exchange communication parameters with a base station. Based on the communication parameters, and possibly other factors such as one or more inactivity timers, the wireless device may dynamically determine a maximum number of MIMO layers. The wireless device may adjust a number of active receiver chains based on the number of MIMO layers.

Note that the techniques described herein may be implemented in and/or used with a number of different types of devices, including but not limited to, base stations, access points, cellular phones, portable media players, tablet computers, wearable devices, and various other computing devices.

This summary is intended to provide a brief overview of some of the subject matter described in this document. Accordingly, it will be appreciated that the above-described features are merely examples and should not be construed to narrow the scope or spirit of the subject matter described herein in any way.

A better understanding of the present subject matter can be obtained when the following detailed description of the embodiments is considered in conjunction with the following drawings, in which:.

While the features described herein may be susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the drawings and detailed description thereto are not intended to be limiting to the particular form disclosed, but on the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the subject matter as defined by the appended claims.

<FIG> illustrates an exemplary (and simplified) wireless communication system, according to some embodiments. It is noted that the system of <FIG> is merely one example of a possible system, and embodiments may be implemented in any of various systems, as desired.

As shown, the exemplary wireless communication system includes a base station 102A which communicates over a transmission medium with one or more user devices 106A, 106B, etc., through 106N.

The base station 102A may be a base transceiver station (BTS) or cell site, and may include hardware that enables wireless communication with the UEs 106A through 106N. The base station 102A may also be equipped to communicate with a network <NUM> (e.g., a core network of a cellular service provider, a telecommunication network such as a public switched telephone network (PSTN), and/or the Internet, among various possibilities).

The communication area (or coverage area) of the base station may be referred to as a "cell. " The base station 102A and the UEs <NUM> may be configured to communicate over the transmission medium using any of various radio access technologies (RATs), also referred to as wireless communication technologies, or telecommunication standards, such as GSM, UMTS (WCDMA, TD-SCDMA), LTE, LTE-Advanced (LTE-A), <NUM> NR, HSPA 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), Wi-Fi, WiMAX etc..

Such cells may also be capable of facilitating communication between user devices and/or between user devices and the network <NUM>, according to the same wireless communication technology as base station 102A and/or any of various other possible wireless communication technologies.

Note that a UE <NUM> may be capable of communicating using multiple wireless communication standards. For example, a UE <NUM> may be configured to communicate using a wireless networking (e.g., Wi-Fi) and/or peer-to-peer wireless communication protocol (e.g., BT, Wi-Fi peer-to-peer, etc.) in addition to at least one cellular communication protocol (e.g., NR, GSM, UMTS (WCDMA, TD-SCDMA), LTE, LTE-A, HSPA, 3GPP2 CDMA2000 (e.g., 1xRTT, 1xEV-DO, HRPD, eHRPD), etc.). The UE <NUM> may also or alternatively be configured to communicate using one or more global navigational satellite systems (GNSS, e.g., GPS or GLONASS), one or more mobile television broadcasting standards (e.g., ATSC-M/H or DVB-H), and/or any other wireless communication protocol, if desired. Other combinations of wireless communication standards (including more than two wireless communication standards) are also possible.

<FIG> illustrates user equipment <NUM> (e.g., one of the devices 106A through 106N) in communication with a base station <NUM> (e.g., one of the base stations 102A through 102N), according to some embodiments. The UE <NUM> may be a device with cellular communication capability such as a mobile phone, a hand-held device, a wearable device, a computer or a tablet, or virtually any type of wireless device.

The UE <NUM> may include one or more antennas and one or more radios for communicating using one or more wireless communication protocols or technologies. In one embodiment, the UE <NUM> might be configured to communicate using one or more of NR, CDMA2000 (1xRTT / 1xEV-DO / HRPD / eHRPD), or LTE using a single shared radio and/or GSM or LTE using the single shared radio. The shared radio may couple to a single antenna, or may couple to multiple antennas (e.g., for MIMO) for performing wireless communications. In general, a radio may include any combination of a baseband processor, analog RF signal processing circuitry (e.g., including filters, mixers, oscillators, amplifiers, etc.), or digital processing circuitry (e.g., for digital modulation as well as other digital processing). Similarly, the radio may implement one or more receive and transmit chains using the aforementioned hardware. For example, the UE <NUM> may share one or more parts of a receive and/or transmit chain between multiple wireless communication technologies, such as those discussed above. Further, in some embodiments, the UE <NUM> may comprise multiple receiver chains, e.g., for MIMO communication.

In some embodiments, the UE <NUM> may include separate (and possibly multiple) transmit and/or receive chains (e.g., including separate RF and/or digital radio components) for each wireless communication protocol with which it is configured to communicate. For example, the UE <NUM> might include a shared radio for communicating using any of NR, LTE, and/or 1xRTT (or UMTS or GSM), and separate radios for communicating using each of Wi-Fi and Bluetooth.

<FIG> illustrates one possible block diagram of a UE device, such as UE device <NUM>. As shown, the UE device <NUM> may include a system on chip (SOC) <NUM>, which may include portions for various purposes. For example, as shown, the SOC <NUM> may include processor(s) <NUM> which may execute program instructions, and display circuitry <NUM> which may perform graphics processing and provide display signals to the display <NUM>. The processor(s) <NUM> may also be coupled to memory management unit (MMU) <NUM>, which may be configured to receive addresses from the processor(s) <NUM> and translate those addresses to locations in memory (e.g., memory <NUM>, read only memory (ROM) <NUM>, Flash memory <NUM>). The MMU <NUM> may be configured to perform memory protection and page table translation or set up. In some embodiments, the MMU <NUM> may be included as a portion of the processor(s) <NUM>.

The UE device <NUM> may also include other circuits or devices, such as the display circuitry <NUM>, receiver chains <NUM>, dock/connector I/F <NUM>, and/or display <NUM>.

In the embodiment shown, ROM <NUM> may include a bootloader, which may be executed by the processor(s) <NUM> during boot up or initialization. As also shown, the SOC <NUM> may be coupled to various other circuits of the accessory device <NUM>. For example, the UE device <NUM> may include various types of memory, a connector interface <NUM> (e.g., for coupling to a computer system), the display <NUM>, and wireless communication circuitry/receiver chain(s) <NUM> (e.g., for communication using cellular, Wi-Fi, Bluetooth, NFC, GPS, etc.). In some embodiments, one or more of wireless communication circuitry/receiver chain(s) <NUM> may perform both send (e.g., transmission) and receive functions.

The UE device <NUM> may include at least one receiver chain <NUM> (e.g., receiver chain 330a, as illustrated), and in some embodiments multiple receiver chains (e.g., including any number of receiver chains 330b-330n), for performing wireless communication with base stations and/or other devices. UE device <NUM> may perform communications with base stations and other devices implementing different wireless technologies in some embodiments. In particular, UE device <NUM> may employ multiple receiver chains 330a-330n for MIMO communications, e.g. using cellular. Each receiver (Rx) chain 330a-330n may include baseband circuitry <NUM> and RF processing circuitry <NUM>, and an antenna <NUM>, among various possibilities. In some embodiments, some components may be shared between multiple receiver chains. For example, the baseband circuitry may be implemented as a shared processor handling multiple Rx chain signals simultaneously. In some embodiments, not all illustrated components of a receiver chain 330a-330n may be included. Individual receiver chains may be separately powered, e.g., so that one subset of receiver chains <NUM> may be powered or active while another subset may be depowered or inactive. Note that the term depowered as used herein may include a variety of possible states, including low power states, fully depowered states, sleep states, etc. Additionally, the receiver chains may be configured so that individual elements/components of a receiver chain may be separately powered or depowered. For example, in some embodiments it may be possible to more quickly power/depower one element (e.g., baseband processor <NUM>) relative to other components of the receiver chain; e.g., a baseband processor <NUM> may have a shorter "power-off time" or "cycle time" than the other elements. Thus, under some circumstances, an opportunity may exist to save power by temporarily depowering one or more elements without depowering the remainder of the chain (e.g., because the amount of time to depower and repower the remaining components may exceed the amount of time before those components may be needed). In other words, specific elements may be selected to power off based on a comparison of the power-off time and a transmission time interval (TTI) associated with an active communication session. In some embodiments, a single receiver chain may include multiple antennas.

For example, the UE device <NUM> may use antenna(s) <NUM> to perform wireless communication. As noted above, the UE may in some embodiments be configured to communicate wirelessly using a plurality of wireless communication standards or radio access technologies (RATs).

As described herein, receiver chain(s) <NUM> may include hardware and software components for implementing embodiments of this disclosure. The receiver chain(s) <NUM> of the UE device <NUM> may be configured to implement part or all of the methods described herein, e.g., by a processor executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium), a processor configured as an FPGA (Field Programmable Gate Array), and/or using dedicated hardware components, which may include an ASIC (Application Specific Integrated Circuit).

The receiver chains <NUM> may also include elements such as Wi-Fi Logic and Bluetooth Logic that are not illustrated. The Wi-Fi Logic may enable the UE device <NUM> to perform Wi-Fi communications on an <NUM> network. The Bluetooth Logic may enable the UE device <NUM> to perform Bluetooth communications.

As described further subsequently herein, the UE <NUM> may include hardware and software components for implementing features for controlling a number of active receiver chains <NUM>, such as those features described herein with reference to, inter alia, <FIG>. The processor <NUM> of the UE device <NUM> may be configured to implement part or all of the methods described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). In other embodiments, processor <NUM> may be configured as a programmable hardware element, such as an FPGA (Field Programmable Gate Array), or as an ASIC (Application Specific Integrated Circuit). Alternatively (or in addition) the processor <NUM> of the UE device <NUM>, in conjunction with one or more of the other components may be configured to implement part or all of the features described herein, such as the features described herein with reference to, inter alia, <FIG>.

<FIG> illustrates an exemplary block diagram of a base station <NUM>, according to some embodiments.

The antenna(s) <NUM> may be configured to operate as a wireless transceiver and may be further configured to communicate with UE devices <NUM> via radio <NUM>. The radio <NUM> may be configured to communicate via various wireless telecommunication standards, including, but not limited to, NR, LTE, LTE-A, UMTS, CDMA2000, Wi-Fi, etc..

The BS <NUM> may be configured to communicate wirelessly using multiple wireless communication standards. For example, as one possibility, the base station <NUM> may include an NR radio for performing communication according to NR as well as a Wi-Fi radio for performing communication according to Wi-Fi. In such a case, the base station <NUM> may be capable of operating as both an LTE base station and a Wi-Fi access point. As another possibility, the base station <NUM> may include a multi-mode radio which is capable of performing communications according to any of multiple wireless communication technologies (e.g., NR, LTE and Wi-Fi). The BS <NUM> may be referred to as a gNB.

The BS <NUM> may be configured to communicate according to MIMO techniques. For example, the BS <NUM> may use multiple antennas <NUM> to communicate with UE <NUM> using its one or more transmit chains and/or receiver chains 330a-330nnn. For example, there may be one or more transmit chains and/or receiver chains contained within the communication chain <NUM>. Technical standards may describe a variety of modes for communication between these devices, e.g., LTE standards may describe various transmission modes (TM) which may specify different transmission schemes for physical downlink shared channel (PDSCH) messages. For example, TM1 may utilize only a single antenna, while other (e.g., higher numbered) modes may utilize additional antennas. One or more physical downlink control channel (PDCCH) messages may include control information. The control info may include an allocated rank (e.g., rank indication or RI) and modulation and coding scheme (MCS). The nature of the control information may differ between different transmission modes. For example, according to TM3 and TM4, a pre-coding matrix indicator (PMI), may be included, but according to TM9, PMI may not be included.

The BS <NUM> may include hardware and software components for implementing or supporting implementation of features described herein. The processor <NUM> of the base station <NUM> may be configured to implement part or all of the methods described herein, e.g., by executing program instructions stored on a memory medium (e.g., a non-transitory computer-readable memory medium). Alternatively (or in addition) the processor <NUM> of the BS <NUM>, in conjunction with one or more of the other components <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM> may be configured to implement part or all of the features described herein.

<FIG> is a block diagram illustrating an exemplary set of receiver chains (e.g., receiver chains <NUM>) of a wireless device (such as one of the UEs <NUM> illustrated in <FIG>). It should be noted that the exemplary details illustrated in and described with respect to <FIG> are not intended to be limiting to the disclosure as a whole: numerous variations and alternatives to the details provided herein below with respect to <FIG> are possible and should be considered within the scope of the disclosure.

As illustrated, the UE <NUM> (e.g., receiver chains <NUM>) may include an RF portion <NUM> and a baseband (BB) portion <NUM>. The RF portion <NUM> may be connected to one or more antennas <NUM>. In some embodiments, the UE may include multiple RF portions <NUM> and/or multiple BB portions <NUM>. Either or both of RF <NUM> and BB <NUM> may include elements of one or more receiver (Rx) chains <NUM>. Further, either or both of RF <NUM> and BB <NUM> may include elements of one or more transmitter chains. Receiver and transmitter (Tx) chains may share some or all elements, or may be entirely independent (e.g., may not share any elements). In the illustrated example, two Rx chains are shown, but it will be appreciated that any number of Rx chains are possible.

A receiver chain may comprise one antenna and various elements within the RF <NUM> and BB <NUM>. As illustrated, a receiver chain may include the following elements in RF <NUM>: a band pass filter (BPF), low noise amplifier (LNA), mixer, low pass filter (LPF), and automatic gain control (AGC). The RF components of a receiver chain may be a single integrated circuit (IC), according to some embodiments. An RF IC may include multiple parallel chains of signal processing blocks (e.g., the illustrated elements and/or additional or alternative elements). Each chain may correspond to one physical antenna.

The features of the receiver chain included in BB <NUM> may vary in different embodiments. The receiver chain may also include an analog to digital converter (ADC), which may be included in BB <NUM>. It should be noted that the ADC may be included in RF <NUM> rather than BB <NUM>, according to some embodiments. The BB <NUM> may include one or more elements (or perform logical functions corresponding to such elements) that may be shared between any number of Rx chains. For example, as illustrated, BB <NUM> may include equalization and channel estimation functions, which may be performed for any number of corresponding signals (e.g., Rx chains) using shared or dedicated processing and/or memory. Further functions of BB <NUM> may include signal buffering; the BB <NUM> may perform buffering for any number of signals/Rx chains using shared or dedicated processing and/or memory. The BB <NUM> may include multiple paths of signal processing chain (e.g., Rx chain). Note that in some embodiments of BB <NUM>, the Rx chain could be a logical concept. In other words, the BB <NUM> may be shared processing circuitry which may be configured to handle multiple Rx chain signals simultaneously.

In some embodiments, one antenna may correspond to one Rx chain (e.g., one IC) in RF <NUM>. The Rx chain may further include an ADC, which may be included in BB <NUM> or RF <NUM>. The Rx chain may include any number of ICs performing RF and/or BB functions.

In some embodiments, multiple antennas may correspond to one Rx chain or multiple Rx chains may correspond to a single antenna. In some embodiments, an antenna switch block may be included to switch or modify the connections between one or more antennas and one or more Rx chains. In some embodiments, some or all components of RF <NUM> may be shared by one or more Rx chains.

A UE <NUM> may be configured to power or depower one or more receiver chains independently. Depowering a receiver chain may include powering off LNA, mixer, BPF, and LPF, among various possibilities. Depowering a receiver chain may further include reducing the use of ADC, signal buffering, channel estimation, and equalization, e.g., in shared BB processing circuitry. Further, reducing the number of active receiver chains may reduce the use of memory, processors, or other shared resources, which may further reduce power consumption. Such reduced use may reduce the power consumption of shared circuitry.

In some embodiments, a wireless device (e.g., UE <NUM>) may have a limited power supply (e.g., a battery). Further, extended battery life may be a valuable feature to the user of the device. Powering each receiver chain may incur a significant power demand. Accordingly, depowering as many receiver chains as possible, when those chains are unused or under-used, may extend the battery life of the device.

According to some technical specifications, e.g., NR, the number of antennas and/or receiver chains utilized to receive data may vary over time. For example, multiple-input, multiple-output (MIMO) communication-capable UE devices may use up to eight antennas and/or receiver chains, among various possibilities. A BS <NUM> may use a variety of techniques to transmit data to a UE; these techniques may require different numbers of active (e.g. powered) receiver chains for the UE (e.g., UE <NUM>) to successfully receive and decode the data. For example, in MIMO communications, transmissions from the BS <NUM> may include various numbers of MIMO layers. The UE may use one receiver chain (and a corresponding antenna) to receive each transmitted MIMO layer. In current NR, a network may support up to <NUM> MIMO layers, for single user MIMO (SU-MIMO), according to some embodiments. It should be noted that the techniques described herein may be applied to other numbers of layers and other types of transmissions, e.g., MU-MIMO.

During radio resource control (RRC) configuration, a maximum number of MIMO layers to be supported may be determined based on a number of codewords (e.g., and/or the related concept of transport blocks) supported by the UE, according to some embodiments. For example, the number of codewords may be indicated by a parameter called maxNrofCodeWordsScheduledByDCI. If maxNrofCodeWordsScheduledByDCI = <NUM>, then network may send up to <NUM> layer(s) for a single codeword during a transmission time interval (TTI) for which the parameter is applicable. If maxNrofCodeWordsScheduledByDCI = <NUM>, then network may send up to <NUM> layer(s) for two codewords during the TTI. In other words, the network may send <NUM>-<NUM> layers for codeword <NUM> and layers <NUM>-<NUM> for codeword <NUM> (e.g., up to a first <NUM> layers may be transmitted for a first codeword and up to a second <NUM> layers may be transmitted for a second codeword). For example, if <NUM> layers are transmitted, layers <NUM>-<NUM> may be for codeword <NUM> and layer <NUM> may be for codeword <NUM>. In some embodiments, this maxNrofCodeWordsScheduledByDCI parameter, and corresponding maximum number of MIMO layers, may remain in effect for the duration of the RRC connection. This maximum number of layers may accordingly be referred to as a static maximum.

For a UE in RRC-Connected mode, the actual (as opposed to maximum) number of MIMO layers may be dynamically indicated and adjusted by downlink control information (DCI) transmitted during a physical downlink control channel (PDCCH) for a physical downlink shared channel (PDSCH). For example, an "Antenna port field" value in DCI may indicate how many MIMO layers are transmitted for corresponding PDSCH. If maxNrofCodeWordsScheduledByDCI = <NUM>, then the network/BS may indicate one of <NUM>, <NUM>, <NUM>, or <NUM> layer(s) to transmit a single codeword. If maxNrofCodeWordsScheduledByDCI = <NUM>, then network can indicate one of <NUM>, <NUM>, <NUM>, or <NUM> layer(s) to transmit two codewords. These numbers of layers and codewords are exemplary only, and other numbers may be used.

Note that as the number of MIMO layers to be supported increases, the UE power consumption may increase (e.g., because each active Rx chain may use power). The UE (e.g., modem) may take time for decoding DCIs. For example, DCI decoding may end around the <NUM>th - <NUM>th orthogonal frequency-division multiplexing (OFDM) symbol in a slot. Until DCI decoding finishes, the UE may not know how many MIMO layers are being transmitted for the potential PDSCH in the slot. Thus, the UE may turn on multiple receiver chains to process received signal samples corresponding to a maximum number of layers it could support (e.g., according to RRC configuration via maxNrofCodeWordsScheduledByDCI) instead of based on the actual number of MIMO layers being transmitted. Thus, the UE may consume a significant amount power for processing signal samples which may not be actually used for the UE. For instance, when only two layers are scheduled with a maximum number of layers equal to <NUM> layers (e.g., <NUM> codeword), the UE may buffer all <NUM> layers of streams until the UE finishes DCI decoding (to determine the actual number of layers scheduled). Accordingly, there may be significant power saving benefits to turning off any unneeded receiver components or circuitry as early as possible during a slot.

<FIG> illustrates a method for controlling the number of MIMO layers and accordingly selectively powering and depowering receiver chains, according to some embodiments. In various embodiments, some of the elements of the method shown may be performed concurrently, in a different order than shown, may be substituted for by other method elements, or may be omitted. Additional method elements may also be performed as desired. Aspects of the method of <FIG> may be implemented by a wireless device, such as the UEs <NUM> and/or BS <NUM> illustrated in and described with respect to the preceding Figures, or more generally in conjunction with any of the computer systems or devices shown in the Figures, among other devices, as desired. For example, one or more processors of a UE <NUM> and/or BS <NUM> (e.g., such as processors <NUM>, one or more processors included in receiver chains <NUM>, processors <NUM>, etc.) may cause such a device to perform any or all of the aspects of the method of <FIG>, according to some embodiments. Note that while at least some elements of the method of <FIG> are described in a manner relating to the use of communication techniques and/or features associated with 3GPP specification documents, such description is not intended to be limiting to the disclosure, and aspects of the method of <FIG> may be used in any suitable wireless communication system, as desired. For example, although aspects of the method of <FIG> are described relating to MIMO communications in NR, it should be noted that the method may apply to other types of communications and wireless networks. Further, although aspects of the method of <FIG> are described relating to downlink transmission, it should be noted that the method may apply to uplink transmission as well. As shown, the method may operate as follows.

A UE (e.g., UE <NUM>) establishes communication with a base station (e.g., BS <NUM>) and exchange one or more communication parameters with the BS (<NUM>), according to some embodiments. The BS may provide one or more cells of a (e.g., cellular) wireless network and the UE may communicate with the base station using NR and/or other radio access technologies. In some embodiments, the BS may provide a WLAN network, e.g., according to <NUM>.

The UE and BS may be configured to communicate using MIMO. The one or more communication parameters may be usable by the UE and/or BS to determine how many MIMO layers may be used for communication during one or more time periods, among various possibilities. The UE may use any number of transmitter and/or receiver chains to exchange communication parameters (and possibly other data) with the BS. For example, the UE and BS may exchange application and/or control data in the uplink and/or downlink directions.

The UE and BS may perform configuration, e.g., RRC configuration. For example, the UE may indicate (e.g., to the BS) how many codewords it supports and/or the BS may indicate (e.g., to the UE) a maximum number of MIMO layers. Such indications may be communicated in any way, e.g., by sending corresponding messages between the UE and BS. The BS may explicitly indicate a first maximum number of MIMO layers based on the number of codewords (e.g., via maxNrofCodeWordsScheduledByDCI).

In some embodiments, the BS may determine and indicate a second (or third, etc.) maximum number of MIMO layers or adjust the first maximum based on additional information. Such second (and possibly subsequent) or adjusted maximum numbers of MIMO layers may be used to dynamically restrict/adjust the maximum number of MIMO layers in effect to more closely match the number of MIMO layers that the BS is likely to transmit to the UE in upcoming time periods/slots. Such adjustments to the maximum may be determined based on various additional factors, e.g., channel conditions, preferences of the UE, etc., and may be explicitly or implicitly indicated in various ways as explained below. The adjusted/second and subsequent maximum number of MIMO layers may be less than or equal to the first maximum number of layers. For example, if the first maximum is <NUM> layers (e.g., because two codewords are enabled), the BS may determine a dynamic adjustment to the maximum in order to adjust the maximum to <NUM> layers in response to channel conditions. If channel conditions improve, the BS may further determine an adjustment the maximum back to <NUM> layers. As an alternative example, if the first maximum is <NUM> layers (e.g., because two codewords are enabled), the BS may set a conditional maximum of <NUM> layers, e.g., to use based on an inactivity timer, e.g., during CDRX on durations. The BS may indicate to the UE to use such a conditional maximum when the condition(s) (e.g., expiration of the inactivity timer) is (are) satisfied. Any such dynamically adjusted or conditional maximum may be referred to as an adjusted maximum, configured maximum, or second maximum, among various possibilities and/or may be referred to as making an adjustment to the (e.g., first) maximum.

In some embodiments, the BS configures, via the one or more communication parameters, the UE to use one or more bandwidth parts (BWP). A bandwidth part may be a contiguous region of frequency/spectrum that the UE may monitor for transmissions from the BS. The BS may configure the UE to use one or multiple BWPs concurrently. The BS may dynamically change the assignment of BWPs to the UE, e.g., via RRC signaling, via one or more media access control (MAC) control elements (CE) or via Downlink Control Information (DCI). A BWP assignment may last until it is reconfigured, or may remain in effect for a preconfigured amount of time.

In some embodiments, specific BWPs is defined to use specific maximum numbers of MIMO layers. For example, a configuration of BWPk may include a configured maximum number of MIMO layers to be supported on that BWP (e.g., Nmax_L_k). For example, for <NUM> codeword, Nmax_L_k could be <NUM>-<NUM>. For <NUM> codewords, Nmax_L_k could be <NUM>-<NUM>. Alternatively, for <NUM> codewords, Nmax_L_k could be limited to <NUM>-<NUM>, according to some embodiments. Other values are possible. The actual number of layers to be transmitted is limited by Nmax_L_k in BWPk. This may allow the UE turn on only Nmax_L_k receiver chains to receive up to Nmax_L_k layers in BWPk or to depower receiver chains so that only Nmax_L_k receiver chains are powered. In other words, the UE is able to determine how many receiver chains may be used based on an assigned BWP. Thus, for as long as the UE is assigned to BWPk, the UE may use Nmax_L_k. Such an assignment may remain in effect for any number of slots. In other words, Nmax_L_k may be a conditional maximum for a UE assigned to BWPk.

Some example BWP configurations are enumerated below. Note that these configurations are exemplary only and that other configurations may be used.

A first BWP, BWP1, may be a default or initial (narrow) BWP with Nmax_L_k = <NUM>. A UE may use and/or switch to this default BWP when a BWP inactivity timer expires, e.g., when there was no traffic arrival for a duration of an inactivity timer. In this case, UE may monitor mainly or only for control signals. In order to save power, UE may operate with small number of receive chains, e.g., <NUM> receive chain in the illustrated example.

BWP2 may be a medium size BWP with Nmax_L_k = <NUM>. This BWP may be used when traffic arrival is moderate, e.g., for VoLTE or web browsing.

BWP3 may be a large size BWP with Nmax_L_k = <NUM>. This BWP may be used when there are only a few users in the cell, and network can assign enough resources to a UE in low signal to noise ratio (SNR) conditions. In other words, this BWP may be used near a cell edge where more energy per layer may be helpful for reception.

BWP4 may be a large size BWP with Nmax_L_k = <NUM>. This BWP may be used when there is heavy traffic arrival such as FTP or video streaming for UE in high SNR conditions. In other words, this BWP may be used in a high SNR region (e.g., near a cell center) where more layers may provide higher throughput.

In some embodiments, the one or more communication parameters may include a parameter for the maximum number of layers to receive during a connected mode discontinuous reception (CDRX) on duration. Such a parameter may be referred to as NCDRX_L. Thus, NCDRX_L may be a conditional maximum for a UE operating in a CDRX on duration. In other words, while operating in CDRX mode in a BWP, the maximum number of layers may be limited to NCDRX_L. In some embodiments, the maximum number of layers may be determined based on the lower of NCDRX_L or the maximum number of layers for the UE's current BWP, e.g., Nmax_L_k. In other words, the number of layers may be given by: min(NCDRX_L, Nmax_L_k). In other embodiments, the maximum number of layers may be determined based on the lower of NCDRX_L or the number of layers associated with the number of supported code words (e.g., <NUM> for <NUM> codeword, <NUM> for <NUM> codewords). In other words, maximum layers may be given by: min(NCDRX_L, <NUM> or <NUM> - depending on number of codewords). NCDRX_L may be configured by RRC or by MAC CE.

In some embodiments, the communication parameters may include a dynamic indication of a maximum number of MIMO layers. Such a dynamic indication may be may be more flexible than RRC signaling (e.g., which may be limited to indicating a maximum of <NUM> layers for <NUM> codeword or <NUM> layers for <NUM> codewords, as noted above). For example, such a dynamic indication may be accomplished through MAC CE signaling, among various possibilities. Thus, the number of MIMO layers may be changed without changing the BWP. The dynamic signaling may allow for any number of MIMO layers to be selected as a maximum. For example, if <NUM> codeword is enabled, then <NUM>-<NUM> layers may be indicated; if <NUM> codewords are enabled, then <NUM>-<NUM> layers may be indicated. The number of layers may vary with channel conditions (e.g., based on channel rank). The number of layers indicated may remain in effect for a fixed period of time, until some condition is met, or until changed. In other words, if a MAC CE indicating a maximum number of layers is received, the UE may use this maximum number for future slots until an indication of a changed number is received or other condition is met.

In some embodiments, the UE may indicate one or more preferred maximum number of layers to the BS. A preferred number of layers may be specific to a BWP. The UE may indicate BWP specific preferred numbers for any number of BWPs. In some embodiments, the UE may indicate a preferred number of layers by indicating a preferred BWP, e.g., which may be associated with a number of layers. A number of layers may be indicated for CDRX operation. These indications may remain in effect for a fixed period of time, until some condition is met, or until changed. The indications may be sent through MAC CE or RRC messages. For example, the UE may transmit the indications as UEAssistanceInformation. The BS (e.g., the network) may not honor the UE's indicated preference for number of layers in some circumstances.

The UE may select the preferred maximum number of layers to indicate to the BS based on any of various considerations. For example, the UE may consider any or all of: measurements of channel conditions taken by the UE, measurements of channel conditions taken by the BS or other devices, rank, motion of the UE, expected traffic to or from the UE, status of any applications executing on the UE, activity of the user, battery level, charging status, connection to (or status of connections with) one or more other RATs or networks, connection to (or status of) a companion or accessory device, congestion, throughput in recent time periods, etc..

In some embodiments, the BS may respond to an indication from the UE of a preferred maximum number of layers. For example, the BS may indicate to the UE that the preferred maximum number of layers will (or will not) be used during one or more time periods.

The UE and/or BS may select a preferred number of layers based on channel conditions, e.g., as determined based on one or more measurements. The measurements may occur on any frequency or combination of frequencies, e.g., including licensed and/or unlicensed spectrum. The communication and measurements may continue (e.g., periodically, randomly, as needed, etc.) for any amount of time. For example, the measurements may occur over any number of slots, subframes and/or symbols. The measurements may include any radio link measurements such as signal-noise ratio (SNR), signal to interference and noise ratio (SINR), reference signal received power (RSRP), reference signal received quality (RSRQ), received signal strength indicator (RSSI), channel quality indicator (CQI), rank indicator (RI), precoding matrix indicator (PMI), etc. The UE and/or BS may retain a history of measurement values. The UE/BS may compare the measurement values, or metrics calculated based on the measured values, to one or more thresholds. The UE/BS may use various parameters, e.g., for hysteresis, in such comparisons. The measurements, thresholds, and/or parameters may be configured by the BS (e.g., by the network) and/or by the UE. The UE and/or BS may report measurement values, comparison results, etc. to each other and/or to the network at any time.

Better channel conditions (e.g., higher measurement values of SNR, RSRP, etc. and/or higher channel rank) may be associated with higher numbers of MIMO layers. For example, a better channel may support more layers. In contrast, under worse channel conditions, devoting more resources (e.g., transmit power, bandwidth, etc.) to a smaller number of layers may achieve better performance, according to some embodiments.

The UE may dynamically determine an adjusted, dynamic, or conditional maximum number of MIMO layers (<NUM>), according to some embodiments. The UE may determine the adjusted maximum number of MIMO layers based on the communication parameters exchanged with the BS. The UE may also determine the number of MIMO layers based on other conditions. For example, the UE may use one or more inactivity timers (e.g., in conjunction with the communication parameters) to determine a conditional maximum number of layers in effect at any given time, as explained in more detail below with respect to <FIG> and <FIG>. The UE may use any combination of communication parameters exchanged with the BS and information about other conditions to determine the adjusted number of communication layers. For example, the UE may consider channel conditions in combination with any indications received from the BS.

The UE may adjust a number of active receiver chains (<NUM>), according to some embodiments. The UE may determine the (e.g., adjusted) number of receiver chains based on the (e.g., adjusted) number of MIMO layers. For example, the UE may adjust the number of active receiver chains to be equal to the number of MIMO layers. In particular, if the number of active receiver chains is greater than the number of MIMO layers, the UE may depower one or more receiver chains or vice versa.

In some embodiments, the UE may further determine which individual receiver chains to power (e.g., or depower) in order to adjust the number of active receiver chains. For example, based on a determination that the adjusted number of receiver chains is <NUM>, the UE may consult a look up table to determine which <NUM> receiver chains to power (and correspondingly, which other receiver chains should be depowered).

In some embodiments, the UE may determine not to reduce a number of active receiver chains or not to deactivate all components of a receiver chain based on an amount of time associated with repowering the receiver chains. For example, if communication parameters indicate that a higher number of MIMO layers may be used at a future time, there may not be sufficient time to power off and power back on some or all components of a receiver chain (e.g., if the time to repower the chain or one or more chain components is as long (e.g., within a threshold amount of time) of the time that the chain would be used). Accordingly, the UE may not depower components for which the repower time is too long, relative to the amount of time until the component would be used next.

The UE may receive data (<NUM>), according to some embodiments. The UE may use a subset of active receiver chains (e.g., the receiver chains that were not depowered) to receive data from the BS or sending device. The subset of the active receiver chains used to receive the data may be determined based on an actual number of layers indicated in DCI. The subset of the active receiver chains may include some or all of the active receiver chains. The data may include payload data and/or further communication signaling or other control information, among various possibilities. The data may be received in one or more PDSCH messages, among other possibilities, during one or more slots or TTIs.

The UE may further adjust the number of active receiver chains for future time periods based on previously received communication parameters, additional communication parameters (e.g., possibly received as part of the data received in <NUM>), and/or on other factors (e.g., changing conditions, inactivity timers, etc.). The timing of further adjusting the number of active receiver chains may depend on the communication parameters received in <NUM> and/or on further parameters received in <NUM>, among various possibilities.

In various embodiments, the UE may repower (e.g., power back on) some or all of the depowered receiver chains. Such repowering may occur at a time associated with further downlink data (e.g., based on communication parameters indicating a different number of MIMO layers) and/or may occur periodically. For example, the UE may repower some or all receiver chains after receiving the data and prior to performing any of various measurements e.g., channel state information (CSI) measurement, or maximum supportable rank computation. Alternatively, or under other circumstances, the UE may not repower any receiver chains. Further, the UE may depower additional receiver chains. Thus, in any number of future time periods, the UE may receive further data with different (e.g., larger or smaller) subsets of active receiver chains.

Although the description of the methods relating to <FIG> focuses on the UE receiving information, it should be appreciated that the UE may also transmit data. Such transmissions may occur simultaneously, before, or, after any of the actions described herein. The UE may use some or all of the same elements (e.g., antennas) for transmission as well as for reception, or may use different/additional elements. The techniques of <FIG> may be applied to transmission as well as reception, or to a combination of transmission and reception functions/chains.

Adjusting the number of receiver chains may require turning on or off of receiver chains (which may include part of RF components and/or component blocks in baseband). This changing may require a certain amount of switching time, which may be referred to as T_mimo_layer_switch. There may be another kind of switching time required to support BWP switching denoted as T_bwp_switch. The BWP switching time, T_bwp_switch, may vary depending on the subcarrier spacing of target BWP and UE processing capability. When BWP switching is involved with MIMO layer switch, the above mentioned two switching times may be considered together. In other words, in selecting what receiver chain(s) (or components of a receiver chain(s)) may be switched off, the UE may consider both the time to switch receiver chains and the time to switch BWPs. For example, the UE may consider the longer of the two switching times. For example, if there is no MIMO layer switching during BWP switching, then the UE may finish BWP switching during a given time T_bwp_switch. However, if BWP switching is involved with MIMO layer switching (e.g., a current BWP's MIMO layer is different from a target BWP's MIMO layer), then the UE may consider the longer switching time (e.g., max(T_mimo_layer_switch, T_bwp_switch)) to finish BWP switching. In other words, if T_mimo_layer_switch is smaller than or equal to T_bwp_switch, then the receiver chain switching time may be considered as equal to T_bwp_switch.

<FIG> illustrates the power consumption of a UE's receiver chains over the course of a slot, according to some embodiments. In the illustrated example, <NUM> codeword may be enabled, and a maximum number of <NUM> receiver (Rx) chains may be needed, e.g., according to existing technical specifications.

At the beginning of the slot (time <NUM> to <NUM>), the UE may receive PDCCH using <NUM> Rx chains. The power consumption, illustrated by the shaded area, may be relatively high. The PDCCH may include DCI, including an indication of how many layers will be used for a PDSCH transmission later in the slot. The indication may be included in an antenna port field. The duration of the PDCCH reception may vary, but in some embodiments, the duration may be <NUM>-<NUM> OFDM symbols.

PDCCH reception may end and PDSCH reception may begin (time <NUM>). The UE may continue to receive with <NUM> Rx chains and may continue to buffer the streams associated with <NUM> layers. The UE may decode PDCCH and DCI. PDSCH reception may continue for the remaining time of the slot (e.g., until time <NUM>).

The UE may finish decoding PDCCH (time <NUM>), completing a PDCCH decoding delay. At this time, the UE may determine that, in the illustrated example, the antenna port field indicates that two layers are included in PDSCH. In other words, the UE may determine that only two layers are actually scheduled. Accordingly, the UE may begin to depower two receiver chains in order to save power. Depowering receiver chain components may take some time, as illustrated by the declining power consumption.

The process of depowering two receiver chains may complete (time <NUM>), resulting in a relatively low power consumption for the remainder of the slot (e.g., until time <NUM>). The UE may then repower the depowered receiver chains for (at least the beginning of) a subsequent slot or slots.

<FIG> is similar to <FIG>. However, in comparison to <FIG>, <FIG> illustrates some potential advantages of the techniques of <FIG>, according to some embodiments. <FIG> illustrates the power consumption of a UE's receiver chains over the course of a slot, according to some embodiments. In the illustrated example, <NUM> codeword may be enabled, and a maximum number of <NUM> receiver (Rx) chains may be needed, e.g., according to existing technical specifications.

In contrast to <FIG>, based on previously exchanged communication parameters, the UE may begin the slot illustrated in <FIG> with only two Rx chains active (<NUM>). The previously exchanged communication parameters may include an assignment to a BWP with a configured (e.g., adjusted, conditional) maximum of two MIMO layers, among various possibilities. In other words, Nmax_L_k may be two. Thus, the UE may receive PDCCH using <NUM> Rx chains (during time <NUM> to <NUM>). The power consumption, illustrated by the shaded area, may be relatively low, e.g., approximately half of the corresponding power consumption illustrated in <FIG>. The PDCCH may include DCI, including an indication of how many layers will be used for a PDSCH transmission later in the slot. The indication may be included in an antenna port field. The duration of the PDCCH reception may vary, but in some embodiments, the duration may be <NUM>-<NUM> OFDM symbols.

The UE may finish decoding PDCCH (time <NUM>), completing a PDCCH decoding delay. At this time, the UE may determine that, in the illustrated example, the antenna port field indicates that two layers are included in PDSCH. In other words, the UE may determine that two layers are actually scheduled. Accordingly, the UE may determine that no adjustment to the number of active receiver chains is necessary to receive the scheduled layers. Thus, the number of active receiver chains (e.g., <NUM>) and corresponding power consumption may remain (e.g., approximately) constant for the remainder of the slot (e.g., until time <NUM>).

Although not shown in the illustrated example, it will be appreciated that the number of layers actually scheduled (e.g., as determined after the PDCCH decoding delay) may be less than Nmax_L_k, in some circumstances. In such cases, the number of active receiver chains may be reduced following the PDCCH decoding delay until the end of the slot. The UE may then repower the depowered receiver chains for (at least a portion of) a subsequent slot or slots.

It will be appreciated that the relative timing and power consumption illustrated in <FIG> and <FIG> is exemplary only.

In some embodiments, there may be one or more inactivity timers involved during BWP and CDRX operation in RRC connected mode. For example, a DRX inactivity timer (e.g., drx-InactivityTimer) may represent a length of time (e.g., a number of subframes) that the UE must remain active (e.g., continuously) following an uplink or downlink grant. A BWP inactivity timer (e.g., bwp-InactivityTimer) may represent the amount of time that a UE must use a first BWP (e.g., larger) BWP following an uplink or downlink grant prior to transitioning to a second (e.g., smaller) BWP. Note that the two BWPs may have different numbers of layers, e.g., the second BWP may be a default BWP, and may be configured for fewer layers than the first BWP. These timers may be configured separately (e.g., independently of each other, e.g., either timer may be shorter or longer than the other, or the timers may have the same duration). Note that additional or different timers may also be employed or that either of these timers may be employed without the other, according to some embodiments. For example, multiple BWP inactivity timers may be used, e.g., to schedule a series of steps to smaller BWPs, among various possibilities.

<FIG> and <FIG> are timing diagrams (e.g., time may proceed from left to right) illustrating bandwidth parts and conditional maximum numbers of MIMO layers in relation to inactivity timers, according to some embodiments.

<FIG> illustrates a first case, in which a DRX inactivity timer may be longer than a BWP inactivity timer.

A first (e.g., most recent) grant may occur, and the DRX inactivity timer and BWP inactivity timers may be initiated (<NUM>). The UE may operate on a first BWP. The first BWP may be BWP2, e.g., as in the exemplary BWPs discussed above with respect to <FIG>. Accordingly, the Nmax_L_2 may be <NUM> and the UE may actively receive with <NUM> layers.

The BWP inactivity timer may expire (<NUM>). In response to expiration of the BWP inactivity timer, the UE may switch to a second BWP, e.g., BWP1, which may be a default BWP. Accordingly, the Nmax_L_1 may be <NUM> and the UE may actively receive with a single layer. In other words, Layer <NUM> may continue to be used, but Layer <NUM> may no longer be used.

The DRX inactivity timer may expire (<NUM>). Accordingly, the UE may then begin operating in CDRX mode with repeating on durations and off durations according to DRX configurations. The UE may continue to operate on BWP1 using Layer <NUM>. Note that the number of layers to be used may be expressed as min(Nmax_L_1, NCDRX_L). In the illustrated example, this expression may be equal to <NUM>, e.g., because Nmax_L_1 = <NUM>. However, it should be appreciated that in some embodiments, expiration of the DRX inactivity may result in a reduction in the number of active layers, e.g., if NCDRX_L is less than Nmax_L_K.

<FIG> illustrates a second case, in which a DRX inactivity timer may be shorter than a BWP inactivity timer.

The DRX inactivity timer may expire (<NUM>). In response to expiration of the DRX inactivity timer, the UE may begin operating in CDRX mode with repeating on durations and off durations according to DRX configurations. The UE may continue to operate on BWP2, and may use a single layer (Layer <NUM>) during the on durations. Again, the number of layers to be used may be determined as min(Nmax_L_1, NCDRX_L). In the case illustrated in <FIG>, NCDRX_L may equal <NUM>. Thus, NCDRX_L may be lower than Nmax_L_1, and may therefore determine the number of layers. During a DRX On duration, data arrival may be sparse. Therefore, it may be advantageous to power only the minimum required number of Rx chains (<NUM>, in the illustrated example) to save power.

The BWP inactivity timer may expire (<NUM>). Accordingly, the UE may then switch to a second BWP, e.g., BWP1, which may be a default BWP. Accordingly, the Nmax_L_1 may be <NUM> and the UE may use a single layer to receive during CDRX on durations. The UE may continue to operate on BWP1. Thus, the number of layers used may not change, but the size of the BWP may decrease, in the illustrated example.

It will be appreciated that the relative timing, BWPs, and number of layers illustrated in <FIG> and <FIG> is exemplary only.

<FIG> is a timing diagram illustrating techniques for dynamically changing the maximum number of layers to be supported. In some embodiments, the number of layers may be adjusted without changing BWP. The maximum number of layers may be signaled from the BS to the UE using a MAC CE, or other suitable signaling mechanism (e.g., RRC, DCI, etc.). The maximum number of layers may remain in effect for any length of time, typically including more than one slot. DCI may also be used to indicate the actual number of layers used for any individual slot. Thus, some slots may still use fewer layers than the dynamically adjusted maximum number of layers. However, these techniques may allow the dynamically adjusted maximum number of layers and the number of layers used in at least some individual slots to track more closely, e.g., because the maximum can be adjusted independently of the number of codewords. For example, if one codeword is enabled, then one of <NUM>, <NUM>, <NUM>, or <NUM> layers could be indicated as a dynamically adjusted maximum. If two codewords are enabled, then one of <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, or <NUM> layers could be indicated.

As illustrated, channel conditions (e.g., channel rank) may vary over time. Other indicators of channel quality or signal strength may be used (e.g., RSRP, SNR, etc.). At a first time, <NUM>, the BS may transmit a MAC CE to the UE dynamically setting a maximum number of layers to <NUM> (e.g., Nmax_L=<NUM>). Such an indication may be transmitted in response to declining channel rank, among various possibilities. Such an indication may be transmitted in response to a preference for a maximum number of layers indicated by the UE. Following the first indication, the BS may transmit any number of indications to the UE setting an actual number of layers for particular time periods (e.g., slots) (<NUM>). For example, the indications may be DCI with antenna port fields. These indications may indicate <NUM> or <NUM> layers for each of the respective slots.

At a later time <NUM>, the BS may transmit a second indication (e.g., MAC CE) to the UE dynamically setting a maximum number of layers to <NUM> (e.g., Nmax_L=<NUM>). Such an indication may be transmitted in response to improving channel conditions, among various possibilities. Following the second indication, the BS may transmit any number of indications to the UE setting an actual number of layers for particular time periods (e.g., slots) (<NUM>). For example, the indications may be DCI with antenna port fields. These indications may indicate <NUM>-<NUM> layers for each of the respective slots.

It will be appreciated that <FIG> is exemplary only, and that any number of indications may be transmitted and that other indicators may be used.

In the following, exemplary embodiments are provided.

In a first set of embodiments, a method for operating a base station may comprise:
at the base station: establishing a wireless communication link with a user equipment device (UE); determining a first maximum number of multiple-input multiple-output (MIMO) layers for communication with the UE, wherein the first maximum number of MIMO layers is based on a number of codewords enabled for the UE; transmitting a first communication parameter to the UE, wherein the first communication parameter indicates the first maximum number of MIMO layers; determining an adjusted maximum number of MIMO layers for communication with the UE; transmitting a second communication parameter to the UE, wherein the second communication parameter indicates the adjusted maximum number of MIMO layers; and transmitting data to the UE using an actual number of MIMO layers less than or equal to the adjusted maximum number of MIMO layers.

In some embodiments, the second communication parameter may comprise an indication to the UE to use a first bandwidth part, wherein a configured maximum number of MIMO layers of the first bandwidth part is equal to the adjusted maximum number of MIMO layers.

In some embodiments, the first bandwidth part is a default bandwidth part, wherein the configured maximum number of MIMO layers of the first bandwidth part is equal to one.

In some embodiments, the second communication parameter comprises a maximum number of layers to receive during a connected mode discontinuous reception (CDRX) on duration.

In some embodiments, the adjusted maximum number of MIMO layers is based at least in part on one or more of: channel conditions; or a preference indication received from the UE.

In some embodiments, the second communication parameter comprises a media access control (MAC) control element (CE), wherein the adjusted maximum number of MIMO layers is based at least in part on channel conditions.

In some embodiments, the MAC CE is transmitted to the UE during a first slot, wherein the adjusted maximum number of MIMO layers is applicable to one or more second slots after the first slot, the method may further comprise: determining a third maximum number of MIMO layers for communication with the UE, wherein the third maximum number of MIMO layers is determined based at least in part on a change in channel conditions; transmitting a third communication parameter to the UE, wherein the third communication parameter indicates the third maximum number of MIMO layers, wherein the third maximum number of MIMO layers is applicable to one or more third slots after the one or more second slots; and transmitting data to the UE using a second actual number of MIMO layers less than or equal to the third maximum number of MIMO layers during the one or more third slots.

In some embodiments, the method may further comprise: transmitting downlink control information (DCI) to the UE, wherein the DCI comprises an indication of the actual number of MIMO layers.

In a second set of embodiments, a user equipment device (UE) configured for multiple-input multiple-output (MIMO) wireless communications, may comprise: a plurality of receiver chains configured to receive MIMO communications; a non-transitory computer-readable memory medium; and a processing element coupled to the plurality of receiver chains and the memory medium, wherein the processing element is configured to cause the UE to: establish communication with a base station; receive a first communication parameter from the base station; determine a maximum number of MIMO layers based on the first communication parameter; receive a second communication parameter from the base station; determine an adjustment to the maximum number of MIMO layers based on the second communication parameter; and adjust a number of active receiver chains based on the adjustment to the maximum number of MIMO layers.

In some embodiments, the UE may be further configured to: receive downlink control information (DCI) from the base station during a first slot, wherein the DCI comprises an indication of an actual number of MIMO layers from the base station, wherein the actual number of MIMO layers is less than or equal to the adjusted maximum number of MIMO layers; further adjust the number of active receiver chains based on the actual number of MIMO layers during the first slot, wherein said further adjusting comprises reducing the number of active receiver chains by depowering at least one active receiver chain; and repowering the at least one active receiver chain for at least a portion of a subsequent slot.

In some embodiments, the UE may be further configured to: receive data from the base station using the number of active receiver chains.

In some embodiments, the UE may be further configured to: indicate to the base station a number of codewords supported by the UE, wherein the first maximum number of MIMO layers is associated with the number of codewords.

In some embodiments, the UE may be further configured to: indicate to the base station a preferred maximum number of MIMO layers, wherein the adjusted maximum number of MIMO layers is equal to the preferred maximum number of MIMO layers.

In some embodiments, the UE may be further configured to: perform one or more measurements of channel conditions, wherein the preferred maximum number of MIMO layers is based on the one or more measurements of channel conditions.

In some embodiments, an apparatus, may comprise a processing element configured to cause a wireless device to: establish communication with a base station; receive at least one communication parameter from the base station; dynamically determine a maximum number of multiple-input multiple-output (MIMO) layers based on the at least one communication parameter; depower at least a first receiver chain of a plurality of receiver chains based on the maximum number of MIMO layers, wherein a first subset of the plurality of receiver chains remain powered; and receive data from the base station using the first subset of the plurality of receiver chains.

In some embodiments, the maximum number of MIMO layers is further based on at least one inactivity timer.

In some embodiments, the at least one inactivity timer may comprise: a discontinuous reception (DRX) inactivity timer; and a bandwidth part (BWP) inactivity timer.

In some embodiments, the at least one communication parameter comprises: a maximum number of layers for a first BWP; and a maximum number of layers for a second BWP.

In some embodiments, the at least one communication parameter comprises: a maximum number of layers for a connected mode discontinuous reception (CDRX) on duration.

In some embodiments, the processing element may be further configured to cause the wireless device to: receive a second communication parameter from the base station, wherein the second communication parameter is received via a media access control (MAC) control element (CE); dynamically determine a second maximum number of MIMO layers based on the second communication parameter; depower at least a further receiver chain of the plurality of receiver chains based on the second maximum number of MIMO layers; and receive second data from the base station using at least a second subset of the plurality of receiver chains, wherein the second subset contains fewer receiver chains than the first subset.

For example some embodiments may be realized as a computer-implemented method, a computer-readable memory medium, or a computer system.

In some embodiments, a device (e.g., a UE <NUM>) may be configured to include a processor (or a set of processors) and a memory medium, where the memory medium stores program instructions, where the processor is configured to read and execute the program instructions from the memory medium, where the program instructions are executable to implement any of the various method embodiments described herein (or, any combination of the method embodiments described herein, or, any subset of any of the method embodiments described herein, or, any combination of such subsets). The device may be realized in any of various forms.

Claim 1:
A method for operating a base station (<NUM>), the method comprising:
at the base station (<NUM>):
establishing a wireless communication link with a user equipment device, UE, (<NUM>);
configuring a first Bandwidth Part, BWP, for the UE, wherein a configuration of the first BWP includes a configured first maximum number of multiple-input multiple-output, MIMO, layers specific to the first BWP;
changing from the first BWP to a second BWP for the UE, wherein a configuration of the second BWP includes a configured second maximum number of MIMO layers specific to the second BWP, wherein the second maximum number of MIMO layers is different than the first maximum number of MIMO layers;
indicating the change from the first BWP to the second BWP to the UE via downlink control information; and
transmitting (<NUM>) data to the UE (<NUM>) on the second BWP using an actual number of MIMO layers less than or equal to the second maximum number of MIMO layers.