Patent Description:
Examples of such multiple-access systems include 3rd Generation Partnership Project (3GPP) Long Term Evolution (LTE) systems, LTE Advanced ((LTE-A) systems, code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, orthogonal frequency division multiple access (OFDMA) systems, single-carrier frequency division multiple access (SC-FDMA) systems, and time division synchronous code division multiple access (TD-SCDMA) systems, to name a few.

In some examples, a wireless multiple-access communication system may include a number of base stations (BSs), which are each capable of simultaneously supporting communication for multiple communication devices, otherwise known as user equipment (UEs). In other examples (e.g., in a next generation, new radio (NR), or <NUM> network), a wireless multiple access communication system may include a number of distributed units (DUs) (e.g., edge units (EUs), edge nodes (ENs), radio heads (RHs), smart radio heads (SRHs), transmission reception points (TRPs), etc.) in communication with a number of central units (CUs) (e.g., central nodes (CNs), access node controllers (ANCs), etc.), where a set of one or more DUs, in communication with a CU, may define an access node (e.g., which may be referred to as a NR BS, <NUM> NB, a next generation NB (gNB), a transmission reception point (TRP), etc.). A BS or DU may communicate with a set of UEs on downlink channels (e.g., for transmissions from a BS or to a UE) and uplink channels (e.g., for transmissions from a UE to a BS or DU).

NR is an example of an emerging telecommunication standard.

The paper discusses high layer impacts on SRS Carrier Based Switching for LTE, and contributes proposals to address the observed issues.

The paper simply details a chronological list of agreements in relation to 'SRS Carrier-Based Switching'.

Certain aspects provide a method for wireless communication by a user equipment (UE). The method generally includes determining one or more band combinations that share an antenna switch. The UE sends a list of one or more bands in the one or more band combinations to a base station (BS).

Certain aspects provide a method for wireless communication by a BS. The method generally includes receiving, from a UE, a list of one or more bands of one or more band combinations that share an antenna switch. The BS schedules the UE based on the received list.

Certain aspects provide an apparatus for wireless communication, such as a UE. The apparatus generally includes means for determining one or more band combinations that share an antenna switch. The apparatus includes means for sending a list of one or more bands in the one or more band combinations to a BS.

Certain aspects provide an apparatus for wireless communication, such as a BS. The apparatus generally includes means for receiving, from a UE, a list of one or more bands of one or more band combinations that share an antenna switch. The apparatus includes means for scheduling the UE based on the received list.

Certain aspects provide an apparatus for wireless communication, such as a UE. The apparatus generally includes at least one processor coupled with a memory and configured to determine one or more band combinations that share an antenna switch. The apparatus includes a transmitter configured to send a list of one or more bands in the one or more band combinations to a BS.

Certain aspects provide an apparatus for wireless communication, such as a BS. The apparatus generally includes a receiver configured to receive, from a UE, a list of one or more bands of one or more band combinations that share an antenna switch. The apparatus includes at least one processor coupled with a memory and configured to schedule the UE based on the received list.

Certain aspects provide a computer readable medium having computer executable code stored thereon for wireless communication. The computer readable medium generally includes code for determining one or more band combinations that share an antenna switch. The computer readable medium includes code for sending a list of one or more bands in the one or more band combinations to a BS.

Certain aspects provide a computer readable medium having computer executable code stored thereon for wireless communication. The computer readable medium generally includes code for receiving, from a UE, a list of one or more bands of one or more band combinations that share an antenna switch. The computer readable medium includes code for scheduling the UE based on the received list.

Aspects of the present disclosure provide methods and apparatus for improving performance for sounding reference signal (SRS) antenna switching in carrier aggregation (CA). The SRS antenna switching may be for a time division duplexed (TDD) component carrier (CC) (e.g., band) and a shared switch or a shared filter on the transmit or receive side, or both, may affect communications on another CC (e.g., configured for frequency division duplexing (FDD) or <NUM> communications) configured for CA with the TDD CC and that shares the antenna switch with the TDD CC. According to certain aspects, the user equipment (UE) can determine bands that can be affected by the SRS antenna switch and send a list of the affected bands to the base station (BS). The BS can use the list of affected bands to determine scheduling for the UE, for example, to avoid or mitigate the effect of antenna switching on those bands. For example, the BS can schedule SRS switching in special subframes only, refrain from scheduling SRS switching in affected subframes/band combinations, schedule SRS switching to be aperiodic or at a reduced periodicity, avoid scheduling transmissions in affected subframes, schedule shorter TTIs in those subframes, and/or scheduling a particular modulation scheme or data pattern for those subframes.

The techniques described herein may be used for various wireless communication technologies such as LTE, CDMA, TDMA, FDMA, OFDMA, SC-FDMA and other networks.

NR is an emerging wireless communications technology under development in conjunction with the <NUM> Technology Forum (SGTF).

NR 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). These services may also have different transmission time intervals (TTI) to meet respective quality.

<FIG> illustrates an example wireless communication network <NUM>, such as a new radio (NR) or <NUM> network, in which aspects of the present disclosure may be performed, for example, for improving performance for sounding reference signal (SRS) antenna switching in carrier aggregation (CA) as described in more detail below.

A user equipment (UE) <NUM> may be configured for CA and SRS antenna switching for a time division duplexed (TDD) component carrier (CC) (e.g., band). The antenna switch may affect communications on another CC (e.g., configured for frequency division duplexing (FDD) or <NUM> communications) configured for CA with the TDD CC and that shares the antenna switch with the TDD CC. According to certain aspects, the UE <NUM> can determine bands affected (e.g., potentially affected) by the SRS antenna switch (e.g., bands that share the antenna switch) and send a list of the affected bands to a base station (BS) <NUM>. The BS <NUM> can use the list of affected bands to determine scheduling for the UE <NUM>, for example, to avoid or mitigate the effect of antenna switching on those bands.

As illustrated in <FIG>, the wireless communication network <NUM> may include a number of BSs <NUM> and other network entities. A BS may be a station that communicates with UEs. Each BS <NUM> may provide communication coverage for a particular geographic area. In NR systems, the term "cell" and NR BS, next generation NB (gNB), transmission reception point (TRP), etc., may be interchangeable. In some examples, the BSs may be interconnected to one another and/or to one or more other BSs or network nodes (not shown) in the 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 RAT may also be referred to as a radio technology, an air interface, etc. A frequency may also be referred to as a carrier, a subcarrier, a tone, a subband, a frequency channel, etc. Each frequency may support a single RAT in a given geographic area in order to avoid interference between wireless networks of different RATs.

The wireless communication network <NUM> may also include relay stations.

The wireless communication network <NUM> may be a heterogeneous network that includes BSs of different types, e.g., macro BS, pico BS, femto BS, relays, etc. These different types of BSs 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.

The BSs <NUM> may also communicate with one another, e.g., directly or indirectly via wireless or wireline backhaul.

Some UEs may be considered machine-type communication (MTC) devices or evolved/enhanced MTC (eMTC) devices. Some UEs may be considered Intermet-of-Things (IoT) devices which may be narrowband IoT (NB-IoT) devices.

For example, the spacing of the subcarriers may be <NUM> and the minimum resource allocation (called a resource block (RB)) may be <NUM> subcarriers (or <NUM>). Consequently, the nominal Fast Fourier Transform (FFT) size may be equal to <NUM>, <NUM>, <NUM>, <NUM> or <NUM> for system bandwidth of <NUM>, <NUM>, <NUM>, <NUM> or <NUM> megahertz (MHz), respectively. For example, a subband may cover <NUM> (i.e., <NUM> resource blocks), and there may be <NUM>, <NUM>, <NUM>, <NUM> or <NUM> subbands for system bandwidth of <NUM>, <NUM>, <NUM>, <NUM> or <NUM>, respectively.

For example, a scheduling entity (e.g., a base station) allocates resources for communication among some or all devices and equipment within its service area or cell. In some examples, for scheduled communication, subordinate entities utilize resources allocated by the scheduling entity. BSs are not the only entities that may function as a scheduling entity. For examples, a UE may function as a scheduling entity and may schedule resources for one or more subordinate entities (e.g., one or more other UEs) and the other UEs utilize the resources scheduled by the UE for wireless communication. 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 may communicate directly with one another in addition to communicating with the scheduling entity.

<FIG> illustrates an example logical architecture <NUM> of a distributed radio access network (RAN), which may be implemented in the wireless communication network <NUM> illustrated in <FIG>. The ANC <NUM> may be a CtJ of the distributed RAN. The 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 TRP <NUM> may be connected to more than one ANC. 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 <NUM> may support fronthauling solutions across different deployment types. For example, the logical architecture <NUM> may be based on transmit network capabilities (e.g., bandwidth, latency, and/or jitter).

The logical architecture <NUM> may share features and/or components with LTE. For example, the NG-AN <NUM> may support dual connectivity with NR and may share a common fronthaul for LTE and NR.

The logical architecture <NUM> may enable cooperation between and among TRPs <NUM>. No inter-TRP interface may be present.

Logical functions may be dynamically distributed in the logical architecture <NUM>.

<FIG> illustrates an example physical architecture <NUM> of a distributed RAN, according to aspects of the present disclosure. The C-CU <NUM> may be centrally deployed.

In some examples, the C-RU <NUM> hosts core network functions locally.

<FIG> illustrates example components of the BS <NUM> and UE <NUM> illustrated in <FIG>, which may be used to implement aspects of the present disclosure, such as the operations described herein and illustrated with reference to <FIG> and <FIG>.

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), etc. The data may be for the Physical Downlink Shared Channel (PDSCH), etc. 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. The transmit processor <NUM> may also generate reference symbols, such as for the primary synchronization signal (PSS), secondary synchronization signal (SSS), and cell-specific reference signal (CRS). A transmit (TX) multiple-input multiple-output (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 the modulators (MODs) 432a through 432t.

At the UE <NUM>, the antennas 452a through 452r may receive the downlink signals from the BS <NUM> and may provide received signals to the demodulators (DEMODs) 454a through 454r, respectively.

On the uplink, at the UE <NUM>, a transmit processor <NUM> may receive and process data (e.g., for the Physical Uplink: Shared Channel (PUSCH)) from a data source <NUM> and control information (e.g., for the Physical Uplink Control Channel (PUCCH) from the controller/processor <NUM>. The transmit processor <NUM> may also generate reference symbols for a reference signal (RS). The symbols from the transmit processor <NUM> may be precoded by a TX MIMO processor <NUM> if applicable, further processed by the modulators 454a through 454r (e.g., for SC-FDM, etc.), and transmitted to the BS <NUM>. At the BS <NUM>, the uplink signals from the UE <NUM> may be received by the antennas <NUM>, processed by the demodulators <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 processor <NUM> and/or other processors and modules at the BS <NUM> may perform or direct, e.g., the execution of the functional blocks illustrated in <FIG>, and/or other processes for the techniques described herein. The processor <NUM> and/or other processors and modules at the UE <NUM> may also perform or direct, e.g., the execution of the functional blocks illustrated in <FIG>, and/or other processes for the techniques described herein. The memories <NUM> and <NUM> may store data and program codes for the BS <NUM> and the UE <NUM>, respectively.

The illustrated communications protocol stacks may be implemented by devices operating in a wireless communication system (e.g., wireless communication network <NUM>), such as in an NR system. 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>.

The second option <NUM>-b may be useful, for example, in a femto cell deployment.

A mini-slot is a subslot structure (e.g., <NUM>, <NUM>, or <NUM> symbols).

The PBCH carries some basic system information (SI), such as downlink 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 (RMS), system information blocks (SIBs), other system information (OSI) can be transmitted on a PDSCH in certain subframes.

Carrier aggregation (CA) is used in certain systems (e.g., LTE-Advanced) in order to increase the bandwidth, and thereby increase the bitrate. CA can be used for both FDD and TDD. <FIG> and <FIG> illustrate examples of FDD CA. Each aggregated carrier is referred to as a component carrier (CC).

In certain systems (e.g., LTE-Advanced), UEs may use spectrum of up to <NUM> bandwidths allocated in a carrier aggregation of up to a total of <NUM> (<NUM> CCs) used for transmission in each direction. Two types of CA include contiguous CA and non-contiguous CA. In contiguous CA, multiple available CCs are adjacent to each other as shown in <FIG>. In non-contiguous CA multiple available CCs are separated along the frequency band as shown in <FIG>. Both non-contiguous and contiguous CA aggregate multiple CCs to serve a single UE.

In some cases, a UE operating in a multicarrier system (a system supporting CA) can be configured to aggregate certain functions of multiple carriers, such as control and feedback functions, on the same carrier, which may be referred to as a "primary carrier" (PCC). The remaining carriers that depend on the primary carrier for support are referred to as associated secondary carriers (SCC).

Aggregated CCs may be intra-band-CCs within the same operating frequency band or can be inter-band, in which case the CCs belong to different operating frequency bands.

According to certain aspects, TDD and FDD carriers can be jointly aggregated. TDD-FDD CA may allow the network to boost user throughput by aggregating both TDD and FDD for the same UE. TDD-FDD CA may allow the load to be divided between the TDD and FDD frequencies. TDD-FDD CA allows CA to be applied even when the spectrum is allocated in both TDD and FDD bands. Thus, the benefits of CA (e.g., flexibility and efficient resource utilization) can be achieved for TDD and FDD bands.

According to certain aspects, CA can be applied jointly to LTE TDD bands and bands configured to <NUM> communications.

In some communications systems (e.g., long term evolution (LTE) and/or new radio (NR) systems), the frequency spectrum may include bands configured for time division duplexing (TDD) and bands configured for frequency division duplexing (FDD). Certain systems, such as NR systems (e.g., wireless communication network <NUM>) may also include bands configured for NR (e.g., <NUM>) communications. As described above, carrier aggregation (CA) may be configured jointly for TDD and FDD or <NUM> configured bands.

In some cases, front end (FE) components in a device, such as a user equipment (UE), are shared. For example, some FE components may be shared between TDD bands and FDD band, and/or shared between LTE configured bands and <NUM> configured bands. For example, the FE components could be shared by a TDD tx and FDD Rx, by the TDD Tx and a FDD Tx, or by the TDD Tx, FDD Rx, and FDD Tx. <FIG> is block diagram illustrating an example UE architecture <NUM> with shared components for some frequency bands, in accordance with certain aspects of the present disclosure. As shown in <FIG>, the UE architecture <NUM> includes a combined FDD and TDD filter <NUM>. The combined FDD and TDD filter <NUM> has a single output to the antenna ports <NUM> (Ant0) and <NUM> (Ant1) to support CA. The FDD bands (e.g., FDD LNA <NUM> and FDD Tx <NUM>) and TDD bands (e.g., TDD Tx <NUM> and TDD LNA <NUM>) may share all of the FE components following the combined FDD and TDD filter <NUM>. It is noted that while <FIG> shows one example of the UE architecture, other UE architectures may be used within the scope of this disclosure. For example, although <FIG> illustrates shared components for FDD and TDD bands, in other examples, a UE architecture may include shared components for TDD bands and <NUM> communication bands.

The UE may be configured for antenna switching/selection. In some examples, the UE is configured for sounding reference signal (SRS) switching (e.g., antenna selection) for the TDD bands for uplink transmission. The UE may switch between the antenna ports <NUM> and <NUM> using the antenna switch <NUM> (SW A). Because the antenna switch <NUM> is shared by the TDD and FDD bands, when the antenna switch <NUM> switches antennas, for example from antenna <NUM> to antenna <NUM> or from antenna <NUM> to antenna <NUM>, the antenna is switched for the FDD band also.

The SRS antenna switching for the TDD band(s) may result in a performance loss for the other band sharing the antenna, i.e., the FDD or <NUM> band. For example, an uplink or downlink communication on the FDD or <NUM> band may be affected by the SRS antenna switching for the TDD band. SRS may be transmitted in the last symbol of a subframe. SRS antenna switching can be performed periodically. For a different CA band (e.g., the FDD or <NUM> configured band), the last symbol in the subframe could be scheduled on a different antenna; thus, the communication for that symbol may be interrupted by the SRS antenna switching for the TDD band. In the case of a timing advance (TA) for the other band (e.g., the FDD or <NUM> band), two symbols could be affected by the SRS antenna switching for the TDD band. As shown in <FIG>, the CC0 is configured as a TDD band and the CC1 is configured as a FDD band with a TA relative to the TDD band. As shown in <FIG>, the antenna is switched from the antenna <NUM> to the antenna <NUM> for transmission of SRS on the CC0 configured for TDD in the last symbol of the subframe. As shown in <FIG>, due to the TA, the symbol boundaries for the CC0 and CC1 are not aligned and, therefore, the antenna switch in the last symbol of CC0 affects the last two symbols of the CC1.

Due to different channel conditions between the switched antennas (e.g., Ant <NUM> and Ant <NUM>), the phase of the affected symbols (e.g., in the FDD CC1) may be different than the phase of the other symbols in that subframe. The phase difference may result in increased block error rate (BLER), which could affect throughput (e.g., DL throughput for the DL Rx subframe of CC1). In some cases, only particular FDD bands that are aggregated with particular TDD bands will be affected by the antenna switching. Thus, it may desirable for the BS to know of the bands that could be affected by antenna switching.

Aspects of the present disclosure provide methods for improved performance for SRS switching in CA. According to certain aspects, the UE determines bands that can be affected by the SRS antenna switching and sends a list of the affected bands to the BS. These lists could be for various band combinations, such as TDD Tx and FDD Rx, TDD Tx and FDD Tx, and/or TDD Tx and FDD Rx and Tx. The BS can use the list of affected bands to determine (e.g., optimize) scheduling for the UE, for example, to avoid or mitigate the effects of antenna switching on those bands.

<FIG> illustrates example operations <NUM> for wireless communications, in accordance with aspects of the present disclosure. Operations <NUM> may be performed by a UE, for example, such as a UE <NUM> in the wireless communication network <NUM> shown in <FIG>.

Operations <NUM> begin, at block <NUM>, by determining one or more band combinations (e.g., TDD + FDD CA and/or TDD + <NUM> CA configured band combinations) that share an antenna switch. The bands may be for uplink, downlink, or both uplink and downlink. The bands may share other components such as a filter. The shared filter can be for the receiver, transmitter, or both between the bands.

At block <NUM>, the UE sends a list of one or more bands in the one or more band combinations to a BS. For example, for each uplink band, the UE can send a list of all bands having an uplink communication affected by antenna switching and/or a list of all bands having a downlink communication affected by antenna switching. For each uplink band (e.g., configured for TDD), the UE can send a list of all bands configured for CA with that band.

According to certain aspects, the UE can decide whether to support antenna switching for the one or more bands in the list of one or more band combinations. For example, the UE can decide to ignore (e.g., not obey) an antenna selectivity command. Thus, the UE may refrain from performing antenna switching for the one or more band combinations in certain subframes. According to certain aspects, the UE can send the BS an indication of the decision. For example, the UE can send the indication in the list, indicating whether antenna selection is supported. Alternatively, the UE can send the indication of the decision separately from the list. Alternatively, the UE can the indication of the decision rather than sending the list.

According to certain aspects, the UE can report the list of the affected bands and/or the decision of whether antenna selection is supported for the bands at initialization of the UE or after (e.g., in response to) the UE is assigned the band combinations. The UE may report the information at another time.

In some examples, for each band combination, the UE signals which bands support Tx antenna selection. For each of the uplink bands that support Tx antenna selection, the UE signals all the bands for which the UL switches together (e.g., for which the same port has to be enforced) and/or all the bands for which DL switches together (e.g., introducing a "glitch" in the DL reception).

According to certain aspects, the UE may receive scheduling information from the BS based on the list of bands provided to the BS, as described in more detail below.

<FIG> illustrates example operations <NUM> for wireless communications, in accordance with aspects of the present disclosure. Operations <NUM> may be performed by a BS, for example, such as a BS <NUM> in the wireless communication network <NUM> shown in <FIG>. Operations <NUM> may be complementary operations by the BS to the operations <NUM> performed by the UE.

Operations <NUM> begin, at block <NUM>, by receiving, from a UE, a list of one or more bands of one or more band combinations that share an antenna switch.

At block <NUM>, the BS schedules the UE based on the received list. For example, the BS may avoid scheduling the UE in collision subframes in which the one or more band combinations are configured for communicating (e.g., and in which SRS antenna switching occurs).

In another example, the BS can schedule shorter transmission time intervals (TTIs) in the collision subframes. For example, if the UE supports a shortened TTI (sTTI), the BS can schedule sTTI (e.g., <NUM>) for those affected subframes/band combinations. If sTTI is assigned in the collision subfames, then in some cases only one of six possible sTTI might be lost.

According to certain aspects, the BS may reduce the rate of SRS antenna switching to reduce outage. For example, the BS may schedule the UE for multiple antenna switching for SRS only in special subframes (e.g., TDD subframe configuration "special" subframes). Alternatively, the BS may schedule the UE for aperiodic SRS antenna switching. The BS may schedule the UE for SRS antenna switching at a reduced periodicity. In another example, the BS may refrain from scheduling the UE for SRS antenna switching (e.g., in the collision subframes and/or for certain band combinations).

In another example, the BS may schedule UE with a modulation scheme and/or data that is more robust, to mitigate the effect of the affected (e.g., lost) symbols. For example, even at a lower data rate, overall throughput can be increased if a lower modulation scheme or a specific data patterns is used for those subframes with collision.

Advantageously, techniques provided herein may enable an apparatus (e.g., a BS, such as a NB, gNB, etc.) to intelligently schedule a UE based on information received from the UE regarding bands and/or band combinations affected by SRS antenna switching. Further aspects provide for the UE and/or BS to decide whether or not SRS antenna switching should be performed (e.g., supported/scheduled) at all for the subframes/bands affected by the SRS antenna switching. Thus, performance can be improved, such as a higher throughput.

Thus, the claims are not intended to be limited to the aspects shown herein, but is to be accorded the full scope consistent with the language of the claims.

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

Claim 1:
A method (<NUM>) for wireless communications by a base station, BS, comprising:
receiving (<NUM>), from a user equipment, UE, a list of one or more bands of one or more band combinations that share an antenna switch, and are affected by antenna switching; and
scheduling (<NUM>) the UE based on the received list,
wherein scheduling the UE based on the list comprises avoiding scheduling the UE in subframes in which the one or more band combinations are configured for communicating a sounding reference signal, SRS, at the same time as at least one other communication.