Patent Description:
A base station (BS) or distributed unit may communicate with a set of UEs on downlink (DL) channels (e.g., for transmissions from a base station or to a UE) and uplink (UL) channels (e.g., for transmissions from a UE to a BS or DU).

New Radio (NR) (e.g., <NUM>th generation (<NUM>)) is an example of an emerging telecommunication standard. It is designed to better support mobile broadband Internet access by improving spectral efficiency, lowering costs, improving services, making use of new spectrum, and better integrating with other open standards using OFDMA with a cyclic prefix (CP) on a DL and on an UL.

<CIT> and <CIT> discloses a method for sending and receiving a Sounding Reference Signal (SRS) is provided. The method includes: receiving, by a user equipment (UE), a control signaling from a Base Station (BS), wherein a first field in the control signaling indicates the UE transmitting data or sending the SRS, a second field in the control signaling indicates a frequency-hopping mode for the UE transmitting the data or sending the SRS, and a third field in the control signaling indicates frequency-band.

Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for indicating capability of a user equipment (UE) to support multiple sounding reference signals (SRSs) with a single subframe, with at least one of frequency hopping, different bandwidths, or antenna switching for the multiple SRSs in the same subframe.

The following description provides examples of supporting multiple SRSs with a same subframe, and is not limiting of the scope, applicability, or examples set forth in the claims.

The techniques described herein may be used for various wireless communication technologies, such as long term evolution (LTE), code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal frequency division multiple access (OFDMA), single-carrier frequency division multiple access (SC-FDMA) and other networks. An OFDMA network may implement a radio technology such as new radio (NR) (e.g. <NUM> RA), Evolved UTRA (E-UTRA), Ultra Mobile Broadband (UMB), IEEE <NUM> (Wi-Fi), IEEE <NUM> (WiMAX), IEEE <NUM>, Flash-OFDMA, etc. UTRA and E-UTRA are part of Universal Mobile Telecommunication System (UMTS).

3GPP LTE and LTE-Advanced (LTE-A) are releases of the UMTS that use E-UTRA.

NR access (e.g., <NUM> technology) may support various wireless communication services, such as enhanced mobile broadband (eMBB) targeting wide bandwidth (e.g., <NUM> or beyond), millimeter wave (mmW) targeting high carrier frequency (e.g., <NUM> or beyond), massive machine type communications MTC (mMTC) targeting non-backward compatible MTC techniques, and/or mission critical targeting ultra-reliable low-latency communications (URLLC).

NR supports beamforming and beam direction may be dynamically configured. Multiple input multiple output (MIMO) transmissions with precoding may also be supported. MIMO configurations in a downlink (DL) may support up to <NUM> transmit antennas with multi-layer DL transmissions up to <NUM> streams and up to <NUM> streams per UE.

For example, the wireless communication network <NUM> may include one or more base stations (BSs) <NUM> and/or one or more user equipments (UEs) 120a-y configured for supporting multiple sounding reference signals (SRSs) with a same subframe. As shown in <FIG>, a UE 120a includes a SRS manager <NUM> that may be configured to report their capability information to support multiple SRS transmissions in a single subframe in accordance with operations <NUM> of <FIG>. A BS 110a includes a SRS manager <NUM> that may be configured to perform operations <NUM> of <FIG> to configure UEs <NUM> for the SRS transmissions, based on their reported capability information.

The wireless communication network <NUM> may be a new radio (NR) system (e.g., a <NUM>th generation (<NUM>) NR network). As shown in <FIG>, the wireless communication network <NUM> may be in communication with a core network <NUM>. The core network <NUM> may in communication with one or more BSs 110a-z (each also individually referred to herein as a BS <NUM> or collectively as BSs <NUM>) and/or UEs 120a-y (each also individually referred to herein as a UE <NUM> or collectively as UEs <NUM>) in the wireless communication network <NUM> via one or more interfaces.

As illustrated in <FIG>, the wireless network <NUM> may include a number of BSs <NUM> and other network entities. A BS <NUM> may be a station that communicates with UEs <NUM>. Each BS <NUM> may provide communication coverage for a particular geographic area. In 3GPP, the term "cell" can refer to a coverage area of a Node B (NB) and/or a Node B subsystem serving this coverage area, depending on the context in which the term is used. In NR systems, the term "cell" and next generation NodeB (gNB), NR BS, <NUM> NB, access point (AP), or transmission reception point (TRP) may be interchangeable. In some examples, a cell may not necessarily be stationary, and the geographic area of the cell may move according to the location of a mobile BS <NUM>. In some examples, the base stations may be interconnected to one another and/or to one or more other base stations or network nodes (not shown) in wireless communication network <NUM> through various types of backhaul interfaces, such as a direct physical connection, a wireless connection, a virtual network, or the like using any suitable transport network.

A BS <NUM> may provide communication coverage for a macro cell, a pico cell, a femto cell, and/or other types of cells. A macro cell may cover a relatively large geographic area (e.g., several kilometers in radius) and may allow unrestricted access by UEs <NUM> with service subscription. A pico cell may cover a relatively small geographic area and may allow unrestricted access by UEs <NUM> with service subscription. A femto cell may cover a relatively small geographic area (e.g., a home) and may allow restricted access by UEs <NUM> having an association with the femto cell (e.g., UEs <NUM> in a Closed Subscriber Group (CSG), UEs <NUM> for users in the home, etc.). A BS <NUM> for a macro cell may be referred to as a macro BS. A BS <NUM> for a femto cell may be referred to as a femto BS or a home BS. A BS <NUM> may support one or multiple (e.g., three) cells.

The wireless communication network <NUM> may also include relay stations. A relay station is a station that receives a transmission of data and/or other information from an upstream station (e.g., a BS <NUM> or a UE <NUM>) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE <NUM> or a BS <NUM>). A relay station may also be a UE <NUM> that relays transmissions for other UEs <NUM>.

The wireless communication network <NUM> may be a heterogeneous network that includes BSs <NUM> of different types, e.g., macro BS, pico BS, femto BS, relays, etc. These different types of BSs <NUM> may have different transmit power levels, different coverage areas, and different impact on interference in the wireless communication network <NUM>.

The wireless communication network <NUM> may support synchronous or asynchronous operation. For synchronous operation, the BSs <NUM> may have similar frame timing, and transmissions from different BSs <NUM> may be approximately aligned in time. For asynchronous operation, the BSs <NUM> may have different frame timing, and transmissions from different BSs <NUM> may not be aligned in time.

A UE <NUM> may also be referred to as a mobile station, a terminal, an access terminal, a subscriber unit, a station, a customer premises equipment (CPE), a cellular phone, a smart phone, a personal digital assistant (PDA), a wireless modem, a wireless communication device, a handheld device, a laptop computer, a cordless phone, a wireless local loop (WLL) station, a tablet computer, a camera, a gaming device, a netbook, a smartbook, an ultrabook, an appliance, a medical device or medical equipment, a biometric sensor/device, a wearable device such as a smart watch, smart clothing, smart glasses, a smart wrist band, smart jewelry (e.g., a smart ring, a smart bracelet, etc.), an entertainment device (e.g., a music device, a video device, a satellite radio, etc.), a vehicular component or sensor, a smart meter/sensor, industrial manufacturing equipment, a global positioning system device, or any other suitable device that is configured to communicate via a wireless or wired medium. Some UEs <NUM> may be considered machine-type communication (MTC) devices or evolved MTC (eMTC) devices.

Certain wireless networks (e.g., LTE) utilize orthogonal frequency division multiplexing (OFDM) on a downlink (DL) and single-carrier frequency division multiplexing (SC-FDM) on an uplink (UL).

NR may utilize OFDM with a CP on the UL and DL and include support for half-duplex operation using TDD. Multiple input multiple output (MIMO) transmissions with precoding may also be supported.

In some examples, access to the air interface may be scheduled, wherein a scheduling entity (e.g., a BS <NUM>) allocates resources for communication among some or all devices and equipment within its service area or cell. BSs <NUM> are not the only entities that may function as a scheduling entity. In some examples, a UE <NUM> may function as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs <NUM>), and the other UEs <NUM> may utilize the resources scheduled by the UE <NUM> for wireless communication. In some examples, a UE <NUM> may function as a scheduling entity in a peer-to-peer (P2P) network, and/or in a mesh network. In a mesh network example, UEs <NUM> may communicate directly with one another in addition to communicating with a scheduling entity.

In <FIG>, a solid line with double arrows indicates desired transmissions between a UE <NUM> and a serving BS <NUM>, which is a BS <NUM> designated to serve the UE <NUM> on the DL and/or the UL. A finely dashed line with double arrows indicates interfering transmissions between a UE <NUM> and a BS <NUM>.

<FIG> illustrates an example logical architecture of a distributed radio access network (RAN) <NUM>, which may be implemented in the wireless communication network <NUM> illustrated in <FIG>. The ANC <NUM> may be a central unit (CU) of the distributed RAN <NUM>. A backhaul interface to the Next Generation Core Network (NG-CN) <NUM> may terminate at the ANC <NUM>. The backhaul interface to neighboring next generation access Nodes (NG-ANs) <NUM> may terminate at the ANC <NUM>. The ANC <NUM> may include one or more TRPs <NUM> (e.g., cells, BSs, gNBs, etc.).

The TRPs <NUM> may be connected to a single ANC (e.g., ANC <NUM>) or more than one ANC (not illustrated). For example, for RAN sharing, radio as a service (RaaS), and service specific AND deployments, the TRPs <NUM> may be connected to more than one ANC. The TRPs <NUM> may each include one or more antenna ports. The TRPs <NUM> may be configured to individually (e.g., dynamic selection) or jointly (e.g., joint transmission) serve traffic to a UE.

The logical architecture of the distributed RAN <NUM> may support fronthauling solutions across different deployment types.

The logical architecture of the distributed RAN <NUM> may share features and/or components with LTE.

The logical architecture of the distributed RAN <NUM> may enable cooperation between and among TRPs <NUM>, for example, within a TRP and/or across TRPs via ANC <NUM>.

Logical functions may be dynamically distributed in the logical architecture of the distributed RAN <NUM>. As will be described in more detail with reference to <FIG>, a radio resource control (RRC) layer, a packet data convergence protocol (PDCP) layer, a radio link control (RLC) layer, a medium access control (MAC) layer, and a physical (PHY) layers may be adaptably placed at the DU (e.g., TRP <NUM>) or CU (e.g., ANC <NUM>).

<FIG> illustrates an example physical architecture of a distributed radio access network (RAN) <NUM>, according to aspects of the present disclosure. The C-CU <NUM> may be centrally deployed. The C-CU <NUM> functionality may be offloaded (e.g., to advanced wireless services (AWS)), in an effort to handle peak capacity.

The C-RU <NUM> may be close to a network edge.

The DU <NUM> may be located at edges of the network with radio frequency (RF) functionality.

<FIG> illustrates example components of a BS <NUM> and a UE <NUM> (e.g., in the wireless communication network <NUM> of <FIG>).

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

The transmit processor <NUM> may process (e.g., encode and symbol map) the data and control information to obtain data symbols and control symbols, respectively. A transmit MIMO processor <NUM> may perform spatial processing (e.g., precoding) on the data symbols, the control symbols, and/or the reference symbols, if applicable, and may provide output symbol streams to modulators (MODs) in transceivers 432a through 432t. Each MOD in transceivers <NUM> may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Each MOD in transceivers 432may further process (e.g., convert to analog, amplify, filter, and upconvert) the output sample stream to obtain a DL signal. The DL signals from the MODs in transceivers 432a through 432t may be transmitted via antennas 434a through 434t, respectively.

At the UE 120a, antennas 452a through 452r may receive the DL signals from the BS <NUM> and may provide received signals to demodulators (DEMODs) in transceivers 454a through 454r, respectively. Each DEMOD in the transceiver <NUM> may condition (e.g., filter, amplify, downconvert, and digitize) a respective received signal to obtain input samples. Each DEMOD in the transceiver <NUM> may further process the input samples (e.g., for OFDM, etc.) to obtain received symbols. A MIMO detector <NUM> may obtain received symbols from all the DEMODs in the transceivers 454a through 454r, perform MIMO detection on the received symbols if applicable, and provide detected symbols.

On the UL, at UE 120a, a transmit processor <NUM> may receive and process data (e.g., for the physical uplink shared channel (PUSCH)) transmission from a data source <NUM> and control information (e.g., for the physical uplink control channel (PUCCH) from the controller/processor <NUM>. The symbols from the transmit processor <NUM> may be precoded by a transmit MIMO processor <NUM> if applicable, further processed by the DEMODs in transceivers 454a through 454r (e.g., for SC-FDM, etc.), and transmitted to the BS <NUM>. At the BS <NUM>, the UL signals from the UE <NUM> may be received by the antennas <NUM>, processed by the MOD in transceivers <NUM>, detected by a MIMO detector <NUM> if applicable, and further processed by a receive processor <NUM> to obtain decoded data and control information sent by the UE <NUM>.

The memories <NUM> and <NUM> may store data and program codes for the BS 110a and the UE 120a, respectively. A scheduler <NUM> may schedule UEs for data transmission on the DL and/or the UL.

Antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the UE 120a and/or antennas <NUM>, processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the BS 110a may be used to perform various techniques and methods described herein. For example, as shown in <FIG>, the controller/processor <NUM> of the BS 110a has a SRS manager <NUM> that may be configured to perform the operations illustrated in <FIG>, as well as other operations disclosed herein. As shown in <FIG>, the controller/processor <NUM> of the UE 120a has a SRS manager <NUM> that may be configured to perform the operations illustrated in <FIG>, as well as other operations disclosed herein, in accordance with aspects of the present disclosure. Although shown at the controller/processor, other components of the UE 120a and the BS 110a may be used performing the operations described herein.

The NR may support half-duplex operation using time division duplexing (TDD). The NR may support a base subcarrier spacing (SCS) of <NUM> and other SCS may be defined with respect to the base SCS (e.g., <NUM>, <NUM>, <NUM>, <NUM>, etc.).

The diagram <NUM> illustrates a communications protocol stack including a RRC layer <NUM>, a PDCP layer <NUM>, a RLC layer <NUM>, a MAC layer <NUM>, and a PHY layer <NUM>.

A first option <NUM>-a shows a split implementation of a protocol stack, in which implementation of the protocol stack is split between a centralized network access device (e.g., an ANC <NUM> in <FIG>) and distributed network access device (e.g., a DU such as TRP DU <NUM> in <FIG>).

The NR may support a base subcarrier spacing of <NUM> and other subcarrier spacing may be defined with respect to the base subcarrier spacing, for example, <NUM>, <NUM>, <NUM>, <NUM>, etc. The symbol and slot lengths scale with the subcarrier spacing.

The transmission timeline for each of a DL and an UL may be partitioned into units of radio frames. A sub-slot structure may refer to a transmit time interval having a duration less than a slot (e.g., <NUM>, <NUM>, or <NUM> symbols). Each symbol in a slot may be configured for a link direction (e.g., DL, UL, or flexible) for data transmission and the link direction for each subframe may be dynamically switched.

In NR, a synchronization signal block (SSB) is transmitted. In certain aspects, SSBs may be transmitted in a burst where each SSB in the burst corresponds to a different beam direction for UE-side beam management (e.g., including beam selection and/or beam refinement). The SSBs includes a PSS, a SSS, and a two symbol PBCH. The SSB can be transmitted in a fixed slot location, such as the symbols <NUM>-<NUM> as shown in <FIG>. The PBCH carries some basic system information, such as DL system bandwidth, timing information within radio frame, SS burst set periodicity, system frame number, etc. The SS blocks may be organized into SS bursts to support beam sweeping. Further system information such as, remaining minimum system information (RMSI), system information blocks (SIBs), other system information (OSI) can be transmitted on a PDSCH in certain subframes. The SSB may be transmitted up to sixty-four times, for example, with up to sixty-four different beam directions for mmW. The multiple transmissions of the SSB are referred to as a SS burst set. SSBs in an SS burst set may be transmitted in the same frequency region, while SSBs in different SS bursts sets can be transmitted at different frequency regions.

In wireless communication systems (e.g., <NUM>th generation (<NUM>) new radio (NR)), a user equipment (UE) (e.g., such as the UE 120a in the wireless communication network <NUM>) may transmit one or more sounding reference signals (SRSs) so that a network entity (e.g., such as the BS 110a in the wireless communication network <NUM>). can measure uplink (UL) channel quality. Conventionally, one SRS is transmitted by the UE in a last symbol of a normal UL subframe. However, more recently, additional symbols have been introduced for transmitting the SRSs in a normal UL subframe.

The additional SRS symbols may be identified based on a flexible SRS symbol location configuration and/or a virtual cell ID associated with the UE that transmitted the (additional) SRSs. In this context, a "normal subframe" is contrasted with a "special subframe" such as those defined and placed between "normal downlink (DL) subframes" and "normal UL subframes" that are designed to allow the UE sufficient time to switch between receive and transmit processing.

Increasing SRS capacity by introducing more than one symbol for the SRSs on an UL normal subframe may be part of an overall support of and advance of coverage enhancements. Increasing the SRS capacity may involve introducing more than one symbol for the SRSs for one UE or for multiple UEs on a UL normal subframe. As a baseline, a minimum SRS resource allocation granularity for a cell may be one slot (e.g., one of two time slots of a subframe) or a subframe, when more than one symbol in a normal subframe is allocated for the SRSs for the cell. As noted above, a virtual cell ID may be introduced for the SRSs, allowing different SRSs transmissions to be distinguished.

Additionally, in some cases, intra-subframe frequency hopping and repetition may be supported for aperiodic SRSs in the additional SRS symbols of a normal UL subframe. The intra-subframe frequency hopping for the aperiodic SRSs transmission may involve transmitting aperiodic SRSs on different frequency bands on a symbol-by-symbol basis in a subframe. Additionally, the aperiodic SRSs repetition may involve repeating transmission of the aperiodic SRSs, transmitted in a first additional symbol of a subframe (e.g., using a first antenna, frequency band, etc.), in a second additional symbol of the subframe.

Further, intra-subframe antenna switching may be supported for the aperiodic SRSs in the additional SRS symbols. The intra-subframe antenna switching for the aperiodic SRSs transmission may involve transmitting the aperiodic SRSs using different antennas on a symbol-by-symbol basis in a subframe.

Both legacy SRS and additional SRS symbol(s) may be configured for the same UE. In some cases, the legacy SRS may be a periodic SRS (P-SRS) or an aperiodic SRS (A-SRS). Additionally, in some cases, the additional SRSs may be aperiodically triggered. Currently, the UE may be allowed to transmit periodic legacy SRSs and aperiodic additional SRSs in the same normal UL subframe. In the case of aperiodic legacy SRS, a UE may transmit only one of legacy SRS or additional SRS symbol(s) in a normal UL subframe.

The time location of possible additional SRS symbols in one normal UL subframe for a cell may be selected from various options. According to a first option, all symbols in only one slot of one subframe may be used for the SRSs from the cell perspective. According to a second option, all symbols in one subframe may be used for the SRSs from the cell perspective. In some cases, cell-specific configurations of SRS resources in slot-level granularity may be implemented.

As noted above, in certain wireless communication systems (e.g., In LTE Rel-<NUM>), multiple sounding reference signals (SRSs) transmissions in a single uplink (UL) subframe may be supported. In contrast, in earlier (legacy) releases of LTE, only a single SRS in a normal UL subframe is supported.

The configuration of multiple SRSs may be quite flexible, allowing for various features and enhancements, such as repetition, frequency hopping, and antenna switching. With the repetition, a SRS is transmitted with a same antenna in contiguous symbols. With the frequency hopping, the SRS is transmitted in a first bandwidth in a first symbol and in a second bandwidth in a second symbol. With the antenna switching, the SRS is transmitted from a first antenna in a first symbol and from a second antenna in a second symbol.

The features, such as the repetition, the frequency hopping, and the antenna switching may be combined for the SRSs transmissions. One example of the SRSs transmissions with the repetition, the frequency hopping, and the antenna switching is illustrated in <FIG>. For example, <FIG> shows repetition of two (R=<NUM>), frequency hopping across three different bandwidths, and antenna switching across two antennas (such as Antenna <NUM> and Antenna <NUM>).

Another example of the SRSs transmissions with the frequency hopping and the antenna switching but no repetition is illustrated in <FIG>. For example, <FIG> shows frequency hopping across three different bandwidths and antenna switching across two antennas (such as Antenna <NUM> and Antenna <NUM>), but without repetition.

Additionally, while not shown in <FIG>, gaps (symbols) may be introduced to allow sufficient time for retuning (for the frequency hopping) or changing antennas (for the antenna switching). The gaps may be needed, for example, if a carrier frequency needs to be changed to transmit the one or more SRSs in a different part of a frequency band when hopping frequencies (e.g., the frequency hopping is not digital). These gaps are configurable by a network entity.

The availability of several advanced features and configurable gaps results in a large number of possible SRS configurations, which presents a challenge in terms of a user equipment (UE) implementation. For example, some configurations that are likely to occur infrequently (corner cases) may be very difficult to implement and, for full support, the UE might have to support these configurations anyway (even when no operator is likely to support them). Further, it may be practically impossible to test all the possible combinations, especially the full range of combinations of the repetition, the antenna switching, the frequency hopping, and configurable gaps.

Aspects of the present disclosure, however, provide techniques that may allow a UE, via expanded UE capability signaling, to indicate limitations that might prevent the UE from supporting all possible SRSs configuration combinations.

<FIG> is a flow diagram illustrating example operations <NUM> for wireless communications, in accordance with certain aspects of the present disclosure. The operations <NUM> may be performed by a UE (e.g., such as the UE 120a in the wireless communication network <NUM>) to indicate its capability to support multiple SRS transmissions in a single subframe and with what advanced features. The operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., the controller/processor <NUM> of <FIG>). Further, the transmission and reception of signals by the UE in operations <NUM> may be enabled, for example, by one or more antennas (e.g., the antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the UE may be implemented via a bus interface of one or more processors (e.g., the controller/processor <NUM>) obtaining and/or outputting signals.

The operations <NUM> begin, at <NUM>, by reporting, to a network entity (e.g., such as the BS 110a in the wireless communication network <NUM>), capability information indicating a capability of the UE to support multiple SRSs in a same subframe. The capability information includes one or more parameters indicating capability of the UE to support at least one of frequency hopping, different bandwidths, or antenna switching for the multiple SRSs in the same subframe.

At <NUM>, the UE transmits the SRSs to the network entity in accordance with the capability information. For example, the network entity determines an SRS configuration for the UE based on the capability information of the UE, and configure the UE accordingly. The UE then transmits the SRSs to the network entity.

<FIG> is a flow diagram illustrating example operations <NUM> for wireless communications. The operations <NUM> may be configured complementary to the operations <NUM> of <FIG>. The operations <NUM> may be performed by a network entity (e.g., such as the BS 110a in the wireless communication network <NUM>) to configure the UE 120a 110a in the wireless communication network <NUM> based on its capability to support multiple SRSs transmissions in a single subframe (reported in accordance with operations <NUM> of <FIG>). The operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., the controller/processor <NUM> of <FIG>). Further, the transmission and reception of signals by the network entity in operations <NUM> may be enabled, for example, by one or more antennas (e.g., the antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the network entity may be implemented via a bus interface of one or more processors (e.g., the controller/processor <NUM>) obtaining and/or outputting signals.

The operations <NUM> begin, at <NUM>, by receiving, from a UE, capability information indicating a capability of the UE to support multiple SRSs in a same subframe. The capability information includes one or more parameters indicating capability of the UE to support at least one of frequency hopping, different bandwidths, or antenna switching for the multiple SRSs in the same subframe.

At <NUM>, the network entity configures the UE for transmitting the SRSs in accordance with the capability information. The network entity monitors for the SRSs transmissions sent by the UE, in accordance with the capability configuration.

In certain aspects, the UE may report various types of parameters to the network entity to indicate the capability information associated with the UE to support the frequency hopping, the different bandwidths, or the antenna switching for the multiple SRSs in the same subframe. The parameters may be reported per band, per band combination, and/or per band of band combination.

According to the invention, a parameter ( reported by the UE to the network entity) may indicate a maximum number of SRS symbols the UE supports per subframe. The parameter may be useful for the network entity as one of the potential limitations of the UE is that, when configured with the frequency hopping or the antenna switching, the UE may need to change power/frequency of the SRSs after every frequency hop or antenna switch. The radio frequency of the UE may not have the capability to process all these changes (e.g. a limitation of number of the frequency hopping or the antenna switching per subframe).

For example, considering an example with <NUM> symbols and frequency hopping in different bandwidths in each symbol, the UE may need to adjust transmit power (e.g., power amplifier setting) to match each frequency band. The UE radio frequency components may be designed to only handle a certain number of power levels per subframe, such as <NUM> power levels (which may allow for <NUM> physical uplink control channel (PUCCH) transmissions with the frequency hopping and <NUM> for SRS). A gap may be one symbol (or multiple symbols) long and generally, may not be included when counting a number of power changes.

Similarly, repetition generally uses the same power and frequency resources (and, thus, do not require a power change). Referring back to <FIG>, the illustrated example may effectively count as <NUM> SRS symbols, not <NUM> (adjusting for the repetition).

For these reasons, when the UE determines what maximum number of SRS symbols per subframe it is to report, there are various alternatives for considering the gaps and/or the repetition. According to a first alternative, if the UE is configured with the gaps between the SRS symbols, the gaps are not counted towards a total of the maximum number of SRS symbols the UE supports per subframe (e.g. <NUM> antennas + <NUM> gap counts as <NUM> symbols). According to a second alternative, the gaps are counted towards the total (e.g. <NUM> antennas + <NUM> gap counts as <NUM> symbols). According to a third alternative, if the repetition is used for transmitting the SRSs, the repetition is not counted towards the total. According to a fourth alternative, the repetitions are counted towards the total.

In some cases, this limitation regarding a maximum number of SRS symbols (and/or other reported limitations) may only apply if the UE is configured with the frequency hopping and/or the antenna switching (otherwise any number of SRSs may be supported). Further the limitation regarding a maximum number of SRS symbols (and/or other reported limitations) may be reported per band, per band combination, or per band of band combination.

In certain aspects, a parameter may indicate different number of antennas (such as transmit antennas and receive antennas) that a UE may support for transmitting the multiple SRSs in the same subframe than for a single SRS in the same subframe. In current (legacy) systems, the UE is only able to indicate one capability. For example, in a given frequency band in a frequency band combination, the UE reports whether the UE supports 1T2R (<NUM> transmit and <NUM> receive antennas), 1T4R (<NUM> transmit and <NUM> receive antennas), and/or 2T4R (<NUM> transmit and <NUM> receive antennas). This antenna switching capability is for a single SRS in a normal UL subframe, and for the SRS in an UL pilot time slot (UpPTS).

Aspects of the present disclosure, however, allow the UE to report different antenna switching capabilities, for example, to accommodate the additional complications of multiple SRSs in a normal UL subframe. For example, the UE may report separate capabilities (e.g. per band of band combination) of the support of different combinations of antenna selection. For example, the UE may support 1T4R with single SRS, but only 1T2R with multiple SRS.

In certain aspects, a parameter may indicate support of frequency hopping such as an intra-subframe frequency hopping. This may help address one of the main complications of supporting the frequency hopping, which depends on whether a UE has to do "analog" or "digital" hopping. In analog frequency hopping, a local oscillator (LO) is tuned to a center of a SRS band. In such cases, after a frequency hop, the LO has to be retuned (to the center of a new SRS band). In digital hopping, the LO is tuned to the center of a component carrier. In such cases, a baseband processor performs the digital frequency hopping just by placing data in different subcarriers.

In some cases, the analog frequency hopping may be the only option, for example, due to issues with the digital frequency hopping. For example, with the digital frequency hopping, "mirror emissions" may appear due to a small allocation being placed far away from the DC subcarrier. The usage of digital versus analog frequency hopping may depend on a variety of factors, such as a SRS bandwidth or a particular band of operation (as different bands may have different emission requirements).

In certain aspects, a UE may indicate support of the intra-subframe frequency hopping. For example, the UE may decide to indicate support (or lack of support) for the intra-subframe frequency hopping, depending on a band (in a band combination), depending on a SRS bandwidth, and/or depending on a configuration (or not) of gaps in the subframe.

In some cases, the UE can report (for a band of band combination), for different values of bandwidth of SRSs, whether the UE supports frequency hopping and, if so, whether the UE needs gaps or not. For example, this may be signaled by zero or more thresholds of bandwidths Xi and one or more indications for support of capabilities Yi. One or both of Xi and Yi may be signaled by the UE or fixed in a specification. For example, if X = [<NUM>, <NUM>] and Y = [notSupport, supportWithGaps, supportWithoutGaps], this may mean that:.

In some cases, such signaling may be simplified. For example, one simplification is for the UE to signal two values of X, and the values of Y are always assumed to be [notSupport, supportWithGaps, supportWithoutGaps]. In this case, X can include values <NUM> and <NUM> (or larger). As another example of simplification, the support of the gaps by the UE may be signaled by a separate capability. In such cases, the UE may only signal a single threshold X. This may be interpreted as meaning that if SRS bandwidth is below a first bandwidth threshold, the UE does not support intra-subframe FH, while if the SRS bandwidth is above a second bandwidth threshold, the UE does support intra-frame FH. The UE may support the intra-subframe frequency hopping without the gaps if the SRS bandwidth is above the second bandwidth threshold. The UE may support the intra-subframe frequency hopping with the gaps if the SRS bandwidth is between the first bandwidth threshold and the second bandwidth threshold.

In certain aspects, the capability information to support the frequency hopping may depend on a number of repetitions used for the SRSs transmissions.

In certain aspects, the capability information may indicate a number of symbols between frequency hops for the UE to support the frequency hopping without gaps.

In certain aspects, the UE may indicate support of antenna switching such as intra-subframe antenna switching. One potential complication of the antenna switching is to program a radio frequency front end to perform the switch in a certain time. In many cases, the radio frequency hardware (card) may not have the capability to perform very fast switches (e.g., to switch back to back for many symbols).

In certain aspects, a UE may be able to report, for each frequency band in a frequency band combination, whether the UE should be configured with gaps for antenna switching. This may provide flexibility, for example, to accommodate when it may be easier for the UE to perform the frequency hopping and the antenna switching if they are not performed back to back (in adjacent symbols). For example, referring to <FIG>, with repetition (R=<NUM>), it may be easier for the UE to perform the frequency hopping and the antenna switching, than without repetition (as in the example of <FIG>), since the UE has more time to prepare for each frequency hop and/or antenna switch.

There are various alternatives for the UE to report the support of the frequency hopping and/or the antenna switching with or without the gaps, and may report different support for different repetition values.

In one example, the frequency hopping and/or the antenna switching capabilities may be reported separately, for example, once for R=<NUM> (no repetition) and once for R><NUM> (with repetition).

In another example, with R><NUM>, a UE may support the frequency hopping and/or the antenna switching without gaps, and with R=<NUM> the UE may report the capability (with gaps).

In another example, a UE may report multiple values of repetition and multiple capabilities for the frequency hopping, the antenna switching, and/or the gaps corresponding to each of the values of R. As an alternative, the UE may report a value of R (as a threshold) and two capabilities (or sets of capabilities) for the frequency hopping, the antenna switching, and/or the gaps (one for repetitions below R, one above R).

In certain aspects, a UE may report a number of symbols the UE should be configured with between antenna switches (or frequency hops) to operate without gaps. For example, assuming the UE reports N=<NUM> (that the UE should be configured with at least <NUM> symbols between consecutive the frequency hopping and/or the antenna switching ), the UE may support a first two configurations shown in <FIG> without gaps, and a third configuration in <FIG> (with a gap between antenna switching). A fourth configuration may not be supported, however, as there is not <NUM> symbols between the antenna switching.

In certain aspects, if a UE performs frequency hopping and antenna switching in a same symbol, then the UE may be configured with a gap IF (the UE reports that) either frequency hopping or antenna switching requires a gap.

In certain aspects, the capability information may indicate whether a UE is able to support different types of SRS in a same subframe. For example, legacy SRSs and additional SRSs can be configured in the same subframe, with potentially different power control parameters. To accommodate such cases, the UE may be configured to report whether legacy P-SRS and/or AP-SRS can be configured together with the additional SRSs in the same subframe. If the UE does report that legacy P-SRS and/or AP-SRS can be configured together with the additional SRSs in the same subframe, the UE may also report whether a gap is needed between legacy and additional SRSs if different power due to frequency hopping, antenna switching, and/or power control. As an alternative or in addition, the UE may report whether there is power restriction between power level of legacy SRSs and additional SRSs in the same subframe.

The communications device <NUM> includes a processing system <NUM> coupled to a transceiver <NUM> (e.g., a transmitter and/or a receiver). The processing system <NUM> is configured to perform processing functions for the communications device <NUM>, including processing signals received and/or to be transmitted by the communications device <NUM>.

The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium/memory <NUM> via a bus <NUM>. In certain aspects, the computer-readable medium/memory <NUM> is configured to store instructions (e.g., a computer-executable code) that when executed by the processor <NUM>, cause the processor <NUM> to perform the operations illustrated in <FIG>, or other operations for performing the various techniques discussed herein. In certain aspects, computer-readable medium/memory <NUM> stores code <NUM> for reporting and code <NUM> for transmitting. The code <NUM> for reporting may include code for reporting, to a network entity, capability information indicating a capability of the UE to support multiple SRSs in a same subframe where the capability information includes one or more parameters indicating capability of the UE to support at least one of frequency hopping, different bandwidths, or antenna switching for the multiple SRSs in the same subframe. The code <NUM> for transmitting may include code for transmitting the SRSs in accordance with the reported capability information.

The processor <NUM> may include circuitry configured to implement the code stored in the computer-readable medium/memory <NUM>, such as for performing the operations illustrated in <FIG>, as well as other operations for performing the various techniques discussed herein. For example, the processor <NUM> includes circuitry <NUM> for reporting and circuitry <NUM> for transmitting. The circuitry <NUM> for reporting may include circuitry for reporting, to a network entity, capability information indicating a capability of the UE to support multiple SRSs in a same subframe where the capability information includes one or more parameters indicating capability of the UE to support at least one of frequency hopping, different bandwidths, or antenna switching for the multiple SRSs in the same subframe. The circuitry <NUM> for transmitting may include circuitry for transmitting the SRSs in accordance with the reported capability information.

The processing system <NUM> includes a processor <NUM> coupled to a computer-readable medium/memory <NUM> via a bus <NUM>. In certain aspects, the computer-readable medium/memory <NUM> is configured to store instructions (e.g., a computer-executable code) that when executed by the processor <NUM>, cause the processor <NUM> to perform the operations illustrated in <FIG>, or other operations for performing the various techniques discussed herein. In certain aspects, computer-readable medium/memory <NUM> stores code <NUM> for receiving and code <NUM> for configuring. The code <NUM> for receiving may include code for receiving from a UE capability information indicating a capability of the UE to support multiple SRSs in a same subframe where the capability information includes one or more parameters indicating capability of the UE to support at least one of frequency hopping, different bandwidths, or antenna switching for the multiple SRSs in the same subframe. The code <NUM> for configuring may include code for configuring the UE for transmitting the SRSs in accordance with the reported capability information.

The processor <NUM> may include circuitry configured to implement the code stored in the computer-readable medium/memory <NUM>, such as for performing the operations illustrated in <FIG>, as well as other operations for performing the various techniques discussed herein. For example, the processor <NUM> includes circuitry <NUM> for receiving and circuitry <NUM> for configuring. The circuitry <NUM> for receiving may include circuitry for receiving from a UE capability information indicating a capability of the UE to support multiple SRSs in a same subframe where the capability information includes one or more parameters indicating capability of the UE to support at least one of frequency hopping, different bandwidths, or antenna switching for the multiple SRSs in the same subframe. The circuitry <NUM> for configuring may include circuitry for configuring the UE for transmitting the SRSs in accordance with the reported capability information.

For example, various operations shown in <FIG> and <FIG> may be performed by various processors shown in <FIG>. More particularly, operations <NUM> of <FIG> may be performed by processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the BS <NUM> shown in <FIG> while operations <NUM> of <FIG> may be performed by one or more of processors <NUM>, <NUM>, <NUM>, and/or controller/processor <NUM> of the UE <NUM>.

In the case of a user equipment <NUM> (see <FIG>), a user interface (e.g., keypad, display, mouse, joystick, etc.) may also be connected to the bus.

For example, instructions for performing the operations described herein and illustrated in <FIG> and <FIG>.

Claim 1:
A method for wireless communications by a user equipment, UE (<NUM>), comprising:
reporting (<NUM>), to a network entity (<NUM>), capability information indicating a capability of the UE (<NUM>) to support multiple sounding reference signals, SRSs in a same subframe, wherein the capability information comprises one or more parameters indicating capability of the UE (<NUM>) to support at least one of frequency hopping, different bandwidths, or antenna switching for the multiple SRSs in the same subframe, wherein the one or more parameters comprises: a maximum number of SRS symbols the UE (<NUM>) supports per subframe; and
transmitting (<NUM>) the SRSs in accordance with the capability information.