Patent Description:
Aspects of the present disclosure relate to wireless communications, and more particularly, to techniques for frequency hopping enhancements for sounding reference signal (SRS) transmission.

<NPL>, discusses SRS transmission patterns when repetition, frequency hopping and antenna switching are activated. In any cases, it is suggested to perform repetition first, then frequency hopping, then antenna switching, and the SRS transmission pattern is repeated between antenna switching events and guard symbols are inserted between antenna switching occurrences.

<NPL>, discusses SRS transmission patterns when repetition, frequency hopping and antenna switching are activated. It is especially suggested that the SRS hopping pattern for a first antenna is repeated, with a cyclic shift, for a second antenna, with a guard symbol in between.

<NPL>, discusses the relationship linking the number of antenna switching, NAS, the number of frequency hops, NFH, the guard symbol for antenna switching, GSAS, the guard symbol for frequency hopping, GSNH, the SRS repetition R and the Number N of additional SRS symbols.

Independent claim <NUM> defines a user equipment apparatus according to the invention. Independent claim <NUM> defines the corresponding base station apparatus according to the invention. Independent claim <NUM> defines the corresponding method at the user equipment apparatus according to the invention. Independent claim <NUM> defines the corresponding method at the base station apparatus according to the invention. Independent claim <NUM> defines the corresponding computer program according to the invention.

Certain aspects provide a method, performed by a user equipment (UE), for wireless communication. The method generally includes determining a first sounding reference signal (SRS) frequency hopping pattern for transmitting one or more SRSs; determining an antenna switch will occur during the transmission of the one or more SRSs; determining a second SRS frequency hopping pattern for transmitting the one or more SRSs, wherein determining the second SRS frequency hopping pattern comprises using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern based on the determined antenna switch; and transmitting a first set of SRSs of the one or more SRSs according to the first SRS frequency hopping pattern and transmitting a second set of SRSs of the one or more SRSs according to the second SRS frequency hopping pattern.

Certain aspects provide an apparatus for wireless communications by a user equipment. The apparatus generally includes at least one processor configured to determine a first sounding reference signal (SRS) frequency hopping pattern for transmitting one or more SRSs; determine an antenna switch will occur during the transmission of the one or more SRSs; determine a second SRS frequency hopping pattern for transmitting the one or more SRSs, wherein determining the second SRS frequency hopping pattern comprises using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern based on the determined antenna switch; and transmit a first set of SRSs of the one or more SRSs according to the first SRS frequency hopping pattern and transmitting a second set of SRSs of the one or more SRSs according to the second SRS frequency hopping pattern. The apparatus also generally includes a memory coupled with the at least one processor.

Certain aspects provide an apparatus for wireless communications by a user equipment in a network. The apparatus generally includes means for determining a first sounding reference signal (SRS) frequency hopping pattern for transmitting one or more SRSs; means for determining an antenna switch will occur during the transmission of the one or more SRSs; means for determining a second SRS frequency hopping pattern for transmitting the one or more SRSs, wherein determining the second SRS frequency hopping pattern comprises using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern based on the determined antenna switch; and means for transmitting a first set of SRSs of the one or more SRSs according to the first SRS frequency hopping pattern and transmitting a second set of SRSs of the one or more SRSs according to the second SRS frequency hopping pattern.

Certain aspects provide a non-transitory computer-readable medium for wireless communications by a user equipment in a network. The non-transitory computer-readable medium generally includes instructions that, when executed by at least one processor, cause the at least one processor to determine a first sounding reference signal (SRS) frequency hopping pattern for transmitting one or more SRSs; determine an antenna switch will occur during the transmission of the one or more SRSs; determine a second SRS frequency hopping pattern for transmitting the one or more SRSs, wherein determining the second SRS frequency hopping pattern comprises using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern based on the determined antenna switch; and transmit a first set of SRSs of the one or more SRSs according to the first SRS frequency hopping pattern and transmitting a second set of SRSs of the one or more SRSs according to the second SRS frequency hopping pattern.

Certain aspects provide a method for wireless communications by a base station (BS). The method generally includes receiving a first set of SRSs of one or more SRSs in a subframe according to a first SRS frequency hopping pattern and receiving a second set of SRSs of one or more SRSs in the subframe according to a second SRS frequency hopping pattern, wherein the second SRS frequency hopping pattern is generated from the first SRS frequency hopping pattern based on an antenna switch in the subframe.

Certain aspects provide an apparatus for wireless communications by a base station (BS). The apparatus generally includes at least one processor configured to receive a first set of SRSs of one or more SRSs in a subframe according to a first SRS frequency hopping pattern and receive a second set of SRSs of one or more SRSs in the subframe according to a second SRS frequency hopping pattern, wherein the second SRS frequency hopping pattern is generated from the first SRS frequency hopping pattern based on an antenna switch in the subframe. The apparatus also generally includes a memory coupled with the at least one processor.

Certain aspects provide an apparatus for wireless communications by a base station (BS). The apparatus generally includes means for receiving a first set of SRSs of one or more SRSs in a subframe according to a first SRS frequency hopping pattern and means for receiving a second set of SRSs of one or more SRSs in the subframe according to a second SRS frequency hopping pattern, wherein the second SRS frequency hopping pattern is generated from the first SRS frequency hopping pattern based on an antenna switch in the subframe.

Certain aspects provide a non-transitory computer-readable medium for wireless communications by a base station (BS). The non-transitory computer-readable medium generally includes instructions that, when executed by at least one processor, cause the at least one processor to receive a first set of SRSs of one or more SRSs in a subframe according to a first SRS frequency hopping pattern and receive a second set of SRSs of one or more SRSs in the subframe according to a second SRS frequency hopping pattern, wherein the second SRS frequency hopping pattern is generated from the first SRS frequency hopping pattern based on an antenna switch in the subframe.

Certain aspects of the present disclosure also provide various apparatus, means, and computer readable medium configured to perform (or cause a processor to perform) the operations described herein.

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for frequency hopping enhancements for sounding reference signal (SRS) transmission.

The following description provides examples of frequency hopping SRS transmission, and is not limiting of the scope, applicability, or examples set forth in the claims.

According to certain aspects, the BSs <NUM> and UEs <NUM> may be configured for aperiodic SRS transmission on additional SRS symbol as described herein. As shown in <FIG>, the BS 110a includes a sounding reference signal (SRS) module <NUM>. The SRS manager <NUM> may be configured to perform the operations illustrated in one or more of <FIG>, as well as other operations disclosed herein for frequency hopping enhancements for SRS transmission, in accordance with aspects of the present disclosure. Additionally, as shown in <FIG>, the UE 120a includes a SRS manager <NUM>. The SRS manager <NUM> may be configured to perform the operations illustrated in one or more of <FIG> and <FIG>-<NUM>, as well as other operations disclosed herein for frequency hopping enhancements for SRS transmission, in accordance with aspects of the present disclosure.

Wireless communication network <NUM> may also include relay stations (e.g., relay station <NUM>10r), also referred to as relays or the like, that receive a transmission of data and/or other information from an upstream station (e.g., a BS 110a or a UE 120r) and sends a transmission of the data and/or other information to a downstream station (e.g., a UE <NUM> or a BS <NUM>), or that relays transmissions between UEs <NUM>, to facilitate communication between devices.

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 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) in transceivers 232a-232t. Each modulator in transceivers 232a-232t may process a respective output symbol stream (e.g., for OFDM, etc.) to obtain an output sample stream. Downlink signals from modulators in transceivers 232a-232t may be transmitted via the antennas 234a-234t, respectively.

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

On the uplink, at UE 120a, 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 symbols from the transmit processor <NUM> may be precoded by a TX MIMO processor <NUM> if applicable, further processed by the demodulators in transceivers 254a-254r (e.g., for SC-FDM, etc.), and transmitted to the BS 110a. At the BS <NUM>10a, the uplink signals from the UE 120a may be received by the antennas <NUM>, processed by the modulators in transceivers 232a-232t, 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 120a.

The controller/processor <NUM> and/or other processors and modules at the UE 120a may perform or direct the execution of processes for the techniques described herein. For example, as shown in <FIG>, the controller/processor <NUM> of the BS 110a includes an SRS manager <NUM> that may be configured to perform the operations illustrated in one or more of <FIG>, as well as other operations disclosed herein for frequency hopping enhancements for SRS transmission, according to aspects described herein. As shown in <FIG>, the controller/processor <NUM> of the UE 120a includes SRS manager <NUM> that may be configured to perform the operations illustrated in one or more of <FIG> and <FIG>-<NUM>, as well as other operations disclosed herein for frequency hopping enhancements for SRS transmission, according to aspects described herein. Although shown at the Controller/Processor, other components of the UE 120a and BS 110a may be used performing the operations described herein.

In wireless communication systems, such as the wireless communication network <NUM> described above, user equipments (UEs) may transmit sounding reference signals (SRSs) so that the network/base station (e.g., eNBs, gNB, etc.) can measure uplink channel quality. Conventionally, one SRS is transmitted by the UE in a last symbol of a normal uplink subframe. However, more recently, additional symbols have been introduced for transmitting SRSs in a normal uplink (UL) subframe. These 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 as a mixed DL/UL subframe with three fields including a downlink pilot time slot (DwPTS) field, guard period (GP) field, and an uplink pilot time slot (UpPTS) field. Further, "special subframes" may be placed between "normal DL subframes" and "normal UL subframes" and may allow a UE to switch between receive and transmit processing in TDD system.

In some cases, SRS capacity and coverage enhancements may be supported by introducing more than one symbol for SRS in an UL normal subframe. For example, this may involve introducing more than one symbol for SRS for one UE or for multiple UEs in the 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, for example, when more than one symbol in a normal subframe is allocated for SRS for the cell. As noted above, a virtual cell ID may be introduced for SRS, allowing different SRS transmissions to be distinguished.

Additionally, in some cases, intra-subframe frequency hopping (FH) and repetition may be supported for aperiodic SRS in the additional SRS symbols of a normal uplink subframe. Intra-subframe frequency hopping for aperiodic SRS transmission may involve transmitting aperiodic SRSs on different frequency bands on a symbol-by-symbol basis in a subframe. Additionally, aperiodic SRS repetition may involve repeating transmission of an aperiodic SRS. For example, aperiodic SRS transmission may involve repeating transmission of an aperiodic SRS, 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 (AS) may be supported for aperiodic SRS in the additional SRS symbols. Intra-subframe antenna switching for aperiodic SRS transmission may involve transmitting aperiodic SRSs using different antennas on a symbol-by-symbol basis in a subframe. For example, in some case, 1T2R, 1T4R, and 2T4R antenna switching may be supported, where T represents the number of transmit antennas and R represents the number of receive antennas, allowing a UE with R antennas greater than T SRS tx antenna ports (e.g., R>T) to switch (R/T) antennas or antenna pairs on each SRS transmit instance/opportunity.

In some cases, intra-subframe frequency hopping/repetition and intra-subframe antenna switching may be concurrently configured. In this case, frequency hopping may be performed before antenna switching. In certain cases, there may be a restriction on the number of antenna switches and frequency hops that may occur in a single subframe. For example, in some cases, the number of antenna switches may be limited to two for 1T2R or when the number of antenna pairs is configured as two for 2T4R (e.g., antenna pairs {<NUM>, <NUM>} and {<NUM>, <NUM>}). Additionally, in some cases, the number of antenna switches may be limited to three if the number of antenna pairs is configured as three for 2T4R (e.g., antenna pairs {<NUM>, <NUM>}, {<NUM>, <NUM>} and {<NUM>, <NUM>}). Additionally, in some cases, the number of antenna switches may be limited to four for 1T4R.

For intra-subframe frequency hopping, the number of frequency hops, NFH (e.g., an integer value), for additional SRS may be determined according to N = RNFH + (NFH - <NUM>)GFH if antenna switching is not configured for additional SRS, and according to equation one if antenna switching is configured for additional SRS: <MAT> where N is a total duration in terms of OFDM symbols for transmission of the additional SRS symbols given by the higher-layer parameter additionalSRS-duration, R is a repetition factor associated with the transmission of the additional SRS symbols given by higher-layer parameter additionaSRS-RepNum, NAS is a number of antenna switches associated with the transmission of the additional SRS symbols, NFH is a number of frequency hops associated with transmission of the additional SRS symbols, GAS is a guard symbol configuration value for antenna switching given by the higher-layer parameter additionalSRS-GuardSymbolAS, and GFH is a guard symbol configuration value for frequency hopping given by the higher-layer parameter additionalSRS-GuardSymbolFH. In some cases, GFH ∈ {<NUM>, <NUM>} and GAS ∈ {<NUM>, <NUM>}. In some cases, if a UE is configured by the higher layer parameter additionalSRS-GuardSymbolFH a guard symbol may be added between every frequency hop.

If a full set of subbands is used for SRS frequency hopping on additional SRS symbols within a subframe, it may be straightforward that the same group of subband indices are used per antenna. However, if only a subset of subbands is used for SRS frequency hopping on additional SRS symbols within a subframe, NFH may be counted as the number of frequency hops on same antenna index while keeping the same group of subband indices to be used per antenna. Otherwise the part "R*NAS*NFH" in the equation one may not be correct no matter if GFH = <NUM> or <NUM> and GAS = <NUM> or <NUM>. For example, there are <NUM> subbands in total within SRS bandwidth configured for additional SRS. If no antenna switching is enabled, NFH=<NUM> subbands can be sounded on N=<NUM> additional SRS symbols(e.g., N=<NUM>, R=<NUM>, GFH=<NUM>, GAS=<NUM>, NFH=<NUM>) with a subset of subbands {<NUM>, <NUM>, <NUM>, <NUM>, <NUM>, <NUM>} on additional SRS symbols. However, if SRS 1T2R is enabled, only NFH=<NUM> subbands can be sounded on N=<NUM> additional SRS symbols (e.g., N=<NUM>, R=<NUM>, GFH=<NUM>, GAS=<NUM>, NAS=<NUM>, NFH=<NUM>) with a subset of subbands {<NUM>, <NUM>, <NUM>} per antenna over N=<NUM> SRS symbols.

In other aspects, in the cases of when GFH = <NUM> and Gas= <NUM> or <NUM>, the part "(NFH-<NUM>)*GFH" in equation one above may not be correct, as explained below. Additionally, in the case of GFH = <NUM> and GAS = <NUM>, if a frequency hopping pattern (e.g., a subband order) is repeated after switching antenna, and additional gap symbol may be required since the last subband index of previous antenna is different from the starting subband index. Since Gas = <NUM>, the part of "(NAS -<NUM>)*GAS" in equation one above is equal to <NUM>, which does not count the above additional gap symbol between antenna switches if the frequency hopping pattern is repeated per antenna. For example, assuming that the subband order for additional SRS transmission is subband <NUM> → subband <NUM> → subband <NUM>, if this subband order is repeated after an antenna switch, an additional symbol gap may be required since the UE may need to switch from subband <NUM> to subband <NUM>.

Thus, aspects of the present disclosure provide techniques for correcting the above issues described above when transmitting SRSs using intra-subframe frequency hopping, repetition, and/or antenna switching. For example, if SRS antenna switching and frequency hopping are both enabled, some aspects include techniques for setting a same group of subband indices to be used per antenna index. Additionally, some aspects include techniques for determining the number of frequency hops (NFH) (e.g., when GFH = <NUM> and GAS = <NUM> or <NUM>) as well as helping to alleviate the need for an additional gap symbol when switching antennas. For example, in some cases, techniques presented herein involve modifying a first SRS frequency hopping pattern used for transmitting a first set of SRSs in response to a determination that an antenna switch will occur. The modified hopping pattern may alleviate the need for the additional gap symbol, as explained below.

<FIG> illustrates example operations <NUM> for wireless communications in a network in a network, for example, for transmitting sounding reference signals (SRSs) to the network. The operations <NUM> may be performed, for example, by UE (e.g., such as a UE 120a in the wireless communication network <NUM>). The operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor <NUM> of <FIG>). Further, the transmission and reception of signals by the apparatus in operations <NUM> may be enabled, for example, by one or more antennas (e.g., antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the apparatus may be implemented via a bus interface of one or more processors (e.g., controller/processor <NUM>) obtaining and/or outputting signals.

The operations <NUM> may begin at <NUM> by determining a first sounding reference signal (SRS) frequency hopping pattern for transmitting one or more SRSs.

At <NUM>, the UE determines an antenna switch will occur during the transmission of the one or more SRSs.

At <NUM>, the UE determines a second SRS frequency hopping pattern for transmitting the one or more SRSs, wherein determining the second SRS frequency hopping pattern comprises using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern based on the determined antenna switch.

At <NUM>, the UE transmits a first set of SRSs of the one or more SRSs according to the first SRS frequency hopping pattern and transmitting a second set of SRSs of the one or more SRSs according to the second SRS frequency hopping pattern.

<FIG> illustrates example operations <NUM> for wireless communications in a network, for example, for receiving SRSs. The operations <NUM> may be performed, for example, by a network entity, such as a BS (e.g., BS 110a in the wireless communication network <NUM>). Operations <NUM> may be implemented as software components that are executed and run on one or more processors (e.g., controller/processor <NUM> of <FIG>). Further, the transmission and reception of signals by the BS in operations <NUM> may be enabled, for example, by one or more antennas (e.g., antennas <NUM> of <FIG>). In certain aspects, the transmission and/or reception of signals by the BS may be implemented via a bus interface of one or more processors (e.g., controller/processor <NUM>) obtaining and/or outputting signals.

The operations <NUM> may begin, at <NUM>, by receiving a first set of SRSs of one or more SRSs in a subframe according to a first SRS frequency hopping pattern.

At <NUM>, the network entity receives a second set of SRSs of one or more SRSs in the subframe according to a second SRS frequency hopping pattern, wherein the second SRS frequency hopping pattern is generated from the first SRS frequency hopping pattern based on an antenna switch in the subframe.

As noted above, aspects of the present disclosure provide techniques for helping correct issues with determining the number of frequency hops for transmitting additional SRS and reducing symbol gaps when intra-subframe frequency hopping and intra-subframe antenna switching are configured/activated.

For example, as noted above, Equation <NUM> above for determining the number of frequency hops may not be correct. For example, if SRS antenna switching and frequency hopping are both enabled on additional SRS symbols, the parameter {nSRS = <NUM>,. NFH - <NUM>} may used to calculate subband index for first antenna index, where nSRS = <MAT>, l is the index of the OFDM symbol number carrying additional SRS within the subframe not counting guard symbol(s), and l<NUM> is starting OFDM symbol within the subframe is given by the higher-layer parameter additionalSRS-startPos. For the subband index on other antenna index, the same group of subband indices as the first antenna index may be used instead of using nSRS > NFH to calculate the subband index.

Additionally, when GFH = <NUM> and GAS = <NUM> or <NUM>, to fix the issue of counting the gap symbols for possible frequency hops and/or antenna switches in Equation <NUM> with the determination of the number of frequency hops, aspects of the present disclosure provide techniques for repeating an SRS frequency subband order of a previous antenna when switching to a different antenna and adding a gap symbol per antenna switch in the case of GFH = <NUM> and GAS = <NUM>.

For example, in some cases, the UE may determine a first SRS frequency hopping pattern for transmitting one or more SRSs. According to aspects, the first SRS frequency hopping pattern may include an order of subbands for transmitting a first set of SRSs of the one or more SRSs. The UE may also determine that an antenna switch will occur during the transmission of the one or more SRSs. In response to the determined antenna switch, the UE may determine a second SRS frequency hopping pattern for transmitting the one or more SRSs using (e.g., based on) the first SRS frequency hopping pattern. According to aspects, the second SRS frequency hopping pattern may include an order of subbands for transmitting a second set of SRSs of the one or more SRSs. In some cases, the first set of SRSs may be transmitted using a first antenna while the second set of SRSs may be transmitted using a second antenna different from the first antenna used for transmitting the first set of SRSs (e.g., based on the determined antenna switch).

In some cases, determining the first SRS frequency hopping pattern and the second SRS frequency hopping pattern may be based on a gap symbol configuration for transmitting the one or more SRSs. For example, in some cases, the gap symbol configuration may comprise GFH = <NUM> and GAS = <NUM>.

According to the claimed invention, using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern comprises repeating the order of subbands used for transmitting a first set of SRSs on the first antenna. In other words, the subband order of the second set of SRSs may be the same as the subband order of the first set of SRSs. Additionally, since repeating the same subband order for both the first antenna and the second antenna will result in a frequency change between a last SRS of the first set of SRSs and a first SRS of the second set of SRSs, a gap symbol may be included between the last SRS of the first set of SRSs and a first SRS of the second set of SRSs. Accordingly, after receiving the first set of SRSs according to an order of subbands, the BS may receive the second set of SRSs according to the same order of subbands as the first SRS frequency hopping pattern.

According to the claimed invention, to achieve this subband repetition and gap symbol between the first set of SRSs and the second set of SRSs, the UE determines the first SRS frequency hopping pattern and the second frequency hopping pattern according to equation two: <MAT> where N is a total duration in terms of OFDM symbols for transmission of the additional SRS symbols given by the higher-layer parameter additionalSRS-duration, R is a repetition factor associated with the transmission of the additional SRS symbols given by higher-layer parameter additionaSRS-RepNum, NAS is a number of antenna switches associated with the transmission of the additional SRS symbols, NFH is a number of frequency hops with the same antenna/antenna pair associated with transmission of the additional SRS symbols, GAS ∈ {<NUM>,<NUM>} is a guard symbol configuration value for antenna switching given by the higher-layer parameter additionalSRS-GuardSymbolAS, and GFH E {<NUM>,<NUM>} is a guard symbol configuration value for frequency hopping given by the higher-layer parameter additionalSRS-GuardSymbolFH.

<FIG> illustrates repeating a subband order for transmitting one or more SRSs, according to certain aspects. For example, as illustrated, the UE may transmit a first set of SRSs of one or more SRSs according to a first SRS frequency hopping pattern using a first antenna (e.g., antenna <NUM>). As shown the first SRS frequency hopping pattern may include a subband order for transmitting the first set of SRSs, which includes, for example, transmitting a first SRS <NUM> on subband <NUM> in symbol <NUM>, transmitting a second SRS <NUM> on subband <NUM> in symbol <NUM>, and transmitting a third SRS <NUM> on subband <NUM> in symbol <NUM>. As shown, since the UE changes subbands between SRS transmissions of the first set of SRSs, a gap symbol may be configured between each SRS transmission (e.g., in symbols <NUM> and <NUM>) to accommodate an antenna switch. After transmitting the first set of SRSs, the UE may switch to antenna <NUM> and transmit a second set of SRSs of the one or more SRSs.

As illustrated, the second set of SRSs may be transmitted according to a second SRS frequency hopping pattern, which may include repeating the subband order of the first set of SRSs. For example, as illustrated, a first subband (e.g., subband <NUM>) of the second SRS frequency hopping pattern used for transmitting the second set of SRSs is the same as a first subband (e.g., subband <NUM>) of the first frequency hopping pattern used for transmitting the first set of SRSs. Similarly, as illustrated, a last subband (e.g., subband <NUM>) of the second SRS frequency hopping pattern used for transmitting the second set of SRSs is the same as a last subband (e.g., subband <NUM>) of the first frequency hopping pattern used for transmitting the first set of SRSs. As noted, an antenna switch may occur between transmission of a last SRS (e.g., <NUM>) of the first set of SRSs transmitted using the last subband (e.g., subband <NUM>) of the first frequency hopping pattern and transmission of a first SRS (e.g., <NUM>) of the second set of SRSs transmitted using the first subband (e.g., subband <NUM>) of the second frequency hopping pattern. To accommodate the antenna switch between the last SRS (e.g., <NUM>) of the first set of SRSs and the first SRS (e.g., <NUM>) of the second set of SRSs, a gap symbol may be configured between the last SRS (e.g., <NUM>) of the first set of SRSs and the first SRS (e.g., <NUM>) of the second set of SRSs.

For example, as illustrated, to accommodate the switch from antenna <NUM> to antenna <NUM>, a gap symbol may be configured in symbol <NUM> after which the UE may transmit SRS <NUM> on subband <NUM> in symbol <NUM>, SRS <NUM> on subband <NUM> in symbol <NUM>, and SRS <NUM> on subband <NUM> in symbol <NUM>, using the same subband order as the first set of SRSs. Similarly, since the UE changes subbands between SRS transmissions of the second set of SRSs, a gap symbol may be included between each SRS transmission (e.g., in symbols <NUM> and <NUM>). Accordingly, the BS may receive the first set of SRSs (e.g., SRS <NUM>, SRS <NUM>, and SRS <NUM>) transmitted from a first antenna and receive the second set of SRSs (e.g., SRS <NUM>, SRS <NUM>, and SRS <NUM>) transmitted from a second antenna.

In some cases, the first frequency hopping pattern may different from the second frequency hopping pattern. For example, in some cases, using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern may comprise reversing an order of subbands in the first SRS frequency hopping pattern, as illustrated in <FIG> and explained below. For example, assuming a subband order of subband <NUM> → subband <NUM> → subband <NUM> for the first SRS frequency hopping pattern, using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern may include reversing the subband order of the first SRS frequency hopping pattern such that the subband order for the second frequency hopping pattern is subband <NUM> → subband <NUM> → subband <NUM>. Accordingly, after receiving the first set of SRSs according to a subband order for the first set of SRSs, the base station may receive the second set of SRSs according to a reversed subband order for the first set of SRSs.

Further in another example, SRS 1T4R with antenna indices {<NUM>, <NUM>, <NUM>, <NUM>} may be configured together with frequency hopping assuming a subband order of subband <NUM> → subband <NUM> → subband <NUM> for the first SRS frequency hopping pattern on antenna index <NUM>. In this case, for the frequency hopping pattern on antenna index <NUM>, using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern may include reversing the subband order of the first SRS frequency hopping pattern such that the subband order for the second frequency hopping pattern is subband <NUM> → subband <NUM> → subband <NUM>, so that the last subband index on antenna <NUM> is same as the starting subband index on antenna <NUM>.

Additionally, in some cases, for the frequency hopping pattern on antenna index <NUM>, using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern may include repeating the subband order of the first SRS frequency hopping pattern such that the subband order for the second frequency hopping pattern is subband <NUM> → subband <NUM> → subband <NUM>, so that the last subband index on antenna <NUM> is same as the starting subband index on antenna <NUM>.

Additionally, in some cases, for the frequency hopping pattern on antenna index <NUM>, using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern may include reversing the subband order of the first SRS frequency hopping pattern such that the subband order for the second frequency hopping pattern is subband <NUM> → subband <NUM> → subband <NUM>, so that the last subband index on antenna <NUM> is same as the starting subband index on antenna <NUM>.

In other cases, using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern may comprise applying a cyclic shift to the subband order of the first SRS frequency hopping pattern. According to aspects, applying the cyclic shift to the subband order of the first SRS frequency hopping pattern may change the subband order for SRSs after the first SRS of the second set of SRSs, as illustrated in <FIG> and explained below. For example, again assuming a subband order of subband <NUM> → subband <NUM> → subband <NUM> for the first SRS frequency hopping pattern, applying the cyclic shift to the subband order of the first SRS frequency hopping band to generate the second SRS frequency hopping band may result in a subband order for the second SRS frequency hopping pattern of subband <NUM> → subband <NUM> → subband <NUM>, so that the last subband index on previous antenna index is same as the starting subband index on next antenna index. Accordingly, after receiving the first set of SRSs according to a subband order for the first set of SRSs, the base station may receive the second set of SRSs according to cyclically-sifted subband order for the first set of SRSs.

In another example, SRS 1T4R with antenna indices {<NUM>, <NUM>, <NUM>, <NUM>} may be configured together with frequency hopping assuming a subband order of subband <NUM> → subband <NUM> → subband <NUM> for the first SRS frequency hopping pattern on antenna index <NUM>. In this case, for the frequency hopping pattern on antenna index <NUM>, using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern may include adding a cyclic-shift offset on the subband order of the first SRS frequency hopping pattern such that the subband order for the second frequency hopping pattern is subband <NUM> → subband <NUM> → subband <NUM>, so that the last subband index on antenna <NUM> is same as the starting subband index on antenna <NUM>.

Additionally, in some cases, for the frequency hopping pattern on antenna index <NUM>, using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern may include adding a cyclic-shift offset on the subband order the subband order of the first SRS frequency hopping pattern such that the subband order for the second frequency hopping pattern is subband <NUM> → subband <NUM> → subband <NUM>, so that the last subband index on antenna <NUM> is same as the starting subband index on antenna <NUM>.

According to aspects, in either case of reversing the subband order or applying a cyclic shift, a first SRS of the second set of SRSs may be transmitted on a same subband as a last SRS of the first set of SRSs. According to aspects, since the first SRS of the second set of SRSs and the last SRS of the first set of SRSs are transmitted on the same subband, when an antenna switch occurs, the UE may not need a gap symbol since the UE does not need to change frequency bands.

Additionally, in either case of reversing the subband order or applying a cyclic shift, the first SRS frequency hopping pattern and the second SRS frequency hopping pattern may be determined according to equation <NUM>: <MAT> where N is a total duration in terms of OFDM symbols for transmission of the additional SRS symbols given by the higher-layer parameter additionalSRS-duration, R is a repetition factor associated with the transmission of the additional SRS symbols given by higher-layer parameter additionaSRS-RepNum, NAS is a number of antenna switches associated with the transmission of the additional SRS symbols, NFH is a number of frequency hops with a same antenna associated with transmission of the additional SRS symbols, GAS is a guard symbol configuration value for antenna switching given by the higher-layer parameter additionalSRS-GuardSymbolAS, and GFH is a guard symbol configuration value for frequency hopping given by the higher-layer parameter additionalSRS-GuardSymbolFH.

Alternatively, Equation <NUM> may be changed to Equation <NUM>, but the SRS frequency hopping pattern may be repeated per antenna without modification. To avoid the additional gap, the UE may regard the configuration of GFH=<NUM> and GAS=<NUM> as an error case (e.g., UE is not expected to be configured with GFH=<NUM> and Gas=<NUM>).

<FIG> illustrates reversing a subband order for transmitting one or more SRSs, according to certain aspects. For example, as illustrated the UE may transmit a first set of SRSs of one or more SRSs according to a first SRS frequency hopping pattern using a first antenna (e.g., antenna <NUM>). As shown the first SRS frequency hopping pattern may include a subband order for transmitting the first set of SRSs, which includes, for example, transmitting a first SRS <NUM> on subband <NUM> in symbol <NUM>, transmitting a second SRS <NUM> on subband <NUM> in symbol <NUM>, and transmitting a second SRS <NUM> on subband <NUM> in symbol <NUM>. As shown, since the UE changes subbands between SRS transmissions of the first set of SRSs, a gap symbol may be included between each SRS transmission (e.g., in symbols <NUM> and <NUM>). Thereafter, the UE may switch to antenna <NUM> and transmit a second set of SRSs of the one or more SRSs. As illustrated, the second set of SRSs may be transmitted according to a second SRS frequency hopping pattern, which may include reversing the subband order of the first set of SRSs. For example, as illustrated, after switching to antenna <NUM>, the UE may transmit SRS <NUM> on subband <NUM> in symbol <NUM>, SRS <NUM> on subband <NUM> in symbol <NUM>, and SRS <NUM> on subband <NUM> in symbol <NUM>. Accordingly, the BS may receive the first set of SRSs (e.g., SRS <NUM>, SRS <NUM>, and SRS <NUM>) transmitted from a first antenna and receive the second set of SRSs (e.g., SRS <NUM>, SRS <NUM>, and SRS <NUM>) transmitted from a second antenna.

According to aspects, since the last symbol of the first set of SRSs (e.g., SRS <NUM>) and a first symbol of the second set of SRSs (e.g., SRS <NUM>) are transmitted on the same subband (e.g., subband <NUM>), the UE may not require a gap symbol between SRS <NUM> and SRS <NUM> since the UE does not have to switch frequencies (e.g., subbands). Removing the need for this gap symbol may improve network efficiency (e.g., using symbols more efficiently) and saves power at the UE (e.g., since the UE does not need to expend energy retuning between antenna switches).

<FIG> illustrates applying a cyclic shift to a subband order for transmitting one or more SRSs, according to certain aspects. For example, as illustrated the UE may transmit a first set of SRSs of one or more SRSs according to a first SRS frequency hopping pattern using a first antenna (e.g., antenna <NUM>). As shown the first SRS frequency hopping pattern may include a subband order for transmitting the first set of SRSs, which includes, for example, transmitting a first SRS <NUM> on subband <NUM> in symbol <NUM>, transmitting a second SRS <NUM> on subband <NUM> in symbol <NUM>, and transmitting a second SRS <NUM> on subband <NUM> in symbol <NUM>. As shown, since the UE changes subbands between SRS transmissions of the first set of SRSs, a gap symbol may be included between each SRS transmission (e.g., in symbols <NUM> and <NUM>). Thereafter, the UE may switch to antenna <NUM> and transmit a second set of SRSs of the one or more SRSs. As illustrated, the second set of SRSs may be transmitted according to a second SRS frequency hopping pattern, which may include applying a cyclic shift to the subband order of the first set of SRSs. For example, as illustrated, after switching to antenna <NUM>, the UE may transmit SRS <NUM> on subband <NUM> in symbol <NUM>, SRS <NUM> on subband <NUM> in symbol <NUM>, and SRS <NUM> on subband <NUM> in symbol <NUM>. Accordingly, the BS may receive the first set of SRSs (e.g., SRS <NUM>, SRS <NUM>, and SRS <NUM>) transmitted from a first antenna and receive the second set of SRSs (e.g., SRS <NUM>, SRS <NUM>, and SRS <NUM>) transmitted from a second antenna.

<FIG> illustrates a communications device <NUM> that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in <FIG> as well as other operations disclosed herein for frequency hopping enhancements for SRS transmission.

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., 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 for frequency hopping enhancements for SRS transmission. In certain aspects, computer-readable medium/memory <NUM> stores code for performing the operations illustrated in one or more of <FIG> as well as other operations disclosed herein for frequency hopping enhancements for SRS transmission. For example, computer-readable medium/memory <NUM> stores code <NUM> for determining, code <NUM> for transmitting, code <NUM> for using, code <NUM> for reversing, code <NUM> for applying, and code <NUM> for repeating.

In some cases, the code <NUM> for determining may include code for determining a first sounding reference signal (SRS) frequency hopping pattern for transmitting one or more SRSs.

In some cases, the code <NUM> for determining may include code for determining an antenna switch will occur during the transmission of the one or more SRSs.

In some cases, the code <NUM> for determining may include code for determining a second SRS frequency hopping pattern for transmitting the one or more SRSs.

In some cases, the code <NUM> for transmitting may include code for transmitting a first set of SRSs of the one or more SRSs according to the first SRS frequency hopping pattern and transmitting a second set of SRSs of the one or more SRSs according to the second SRS frequency hopping pattern.

In some cases, the code <NUM> for using may include code for using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern based on the determined antenna switch.

In some cases, code <NUM> for reversing may include code for reversing an order of subbands in the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern.

In some cases, code <NUM> for applying may include code for applying a cyclic shift to an order of subbands in the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern.

In some cases, code <NUM> for repeating may include code for repeating the order of subbands in the first SRS frequency hopping pattern at least for a subset of antenna indices to generate the second SRS frequency hopping pattern.

In some cases, code <NUM> for determining may include code for determining at least one of the first SRS frequency hopping pattern or the second SRS frequency hopping pattern according to equation <NUM> described above.

In some cases, code <NUM> for transmitting may include code for transmitting a first SRS of the second set of SRSs in a symbol immediately after a last SRS of the first set of SRSs.

In some cases, code <NUM> for transmitting may include code for transmitting the first set of SRSs using a first antenna.

In some cases, code <NUM> for transmitting may include code for switching to a second antenna and transmitting the second set of SRSs using the second antenna.

In certain aspects, 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 disclosed herein for frequency hopping enhancements for SRS transmission. For example, the processor <NUM> includes circuitry <NUM> for determining, circuitry <NUM> for transmitting, circuitry <NUM> for using, circuitry <NUM> for reversing, circuitry <NUM> for applying, and circuitry <NUM> for repeating.

In some cases, the circuitry <NUM> for determining may include circuitry for determining a first sounding reference signal (SRS) frequency hopping pattern for transmitting one or more SRSs.

In some cases, the circuitry <NUM> for determining may include circuitry for determining an antenna switch will occur during the transmission of the one or more SRSs.

In some cases, the circuitry <NUM> for determining may include circuitry for determining a second SRS frequency hopping pattern for transmitting the one or more SRSs.

In some cases, the circuitry <NUM> for transmitting may include circuitry for transmitting a first set of SRSs of the one or more SRSs according to the first SRS frequency hopping pattern and transmitting a second set of SRSs of the one or more SRSs according to the second SRS frequency hopping pattern.

In some cases, the circuitry <NUM> for using may include circuitry for using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern based on the determined antenna switch.

In some cases, circuitry <NUM> for reversing may include circuitry for reversing an order of subbands in the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern.

In some cases, circuitry <NUM> for applying may include circuitry for applying a cyclic shift to an order of subbands in the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern.

In some cases, circuitry <NUM> for repeating may include circuitry for repeating the order of subbands in the first SRS frequency hopping pattern at least for a subset of antenna indices to generate the second SRS frequency hopping pattern.

In some cases, circuitry <NUM> for determining may include circuitry for determining at least one of the first SRS frequency hopping pattern or the second SRS frequency hopping pattern according to equation <NUM> described above.

In some cases, circuitry <NUM> for transmitting may include circuitry for transmitting a first SRS of the second set of SRSs in a symbol immediately after a last SRS of the first set of SRSs.

In some cases, circuitry <NUM> for transmitting may include circuitry for transmitting the first set of SRSs using a first antenna.

In some cases, circuitry <NUM> for transmitting may include circuitry for switching to a second antenna and transmitting the second set of SRSs using the second antenna.

<FIG> illustrates a communications device <NUM> that may include various components (e.g., corresponding to means-plus-function components) configured to perform operations for the techniques disclosed herein, such as the operations illustrated in <FIG>, as well as other operations disclosed herein for frequency hopping enhancements for SRS transmission.

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., 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 for frequency hopping enhancements for SRS transmission. In certain aspects, computer-readable medium/memory <NUM> stores code for performing the operations illustrated in one or more of <FIG> as well as other operations disclosed herein for frequency hopping enhancements for SRS transmission. For example, computer-readable medium/memory <NUM> stores code <NUM> for receiving.

In some cases, code <NUM> for receiving may include code for receiving a first set of SRSs of one or more SRSs in a subframe according to a first SRS frequency hopping pattern.

In some cases, code <NUM> for receiving may include code for receiving a second set of SRSs of one or more SRSs in the subframe according to a second SRS frequency hopping pattern.

In some cases, code <NUM> for receiving may include code for receiving the second set of SRSs on subbands according to a reversed order.

In some cases, code <NUM> for receiving may include code for receiving the second set of SRSs on subbands according to a cyclic shift.

In some cases, code <NUM> for receiving may include code for receiving the second set of SRSs on subbands according to a same order of subbands as the first SRS frequency hopping pattern.

In some cases, code <NUM> for receiving may include code for receiving a first SRS of the second set of SRSs in a symbol immediately after a last SRS of the first set of SRSs.

In some cases, code <NUM> for receiving may include code for receiving the first set of SRSs transmitted from a first antenna and receiving the second set of SRSs transmitted from a second antenna.

In certain aspects, 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 disclosed herein for frequency hopping enhancements for SRS transmission. For example, the processor <NUM> includes circuitry <NUM> for receiving.

In some cases, circuitry <NUM> for receiving may include circuitry for receiving a first set of SRSs of one or more SRSs in a subframe according to a first SRS frequency hopping pattern.

In some cases, circuitry <NUM> for receiving may include circuitry for receiving a second set of SRSs of one or more SRSs in the subframe according to a second SRS frequency hopping pattern.

In some cases, circuitry <NUM> for receiving may include circuitry for receiving the second set of SRSs on subbands according to a reversed order.

In some cases, circuitry <NUM> for receiving may include circuitry for receiving the second set of SRSs on subbands according to a cyclic shift.

In some cases, circuitry <NUM> for receiving may include circuitry for receiving the second set of SRSs on subbands according to a same order of subbands as the first SRS frequency hopping pattern.

In some cases, circuitry <NUM> for receiving may include circuitry for receiving a first SRS of the second set of SRSs in a symbol immediately after a last SRS of the first set of SRSs.

In some cases, circuitry <NUM> for receiving may include circuitry for receiving the first set of SRSs transmitted from a first antenna and receiving the second set of SRSs transmitted from a second antenna.

In the case of a user equipment120 (see <FIG>), a user interface (e.g., keypad, display, mouse, joystick, etc.) may also be connected to the bus.

Claim 1:
An apparatus for wireless communication by a user equipment, UE (<NUM>), comprising:
means for determining a first sounding reference signal, SRS, frequency hopping pattern for transmitting one or more SRSs;
means for determining an antenna switch will occur during transmission of the one or more SRSs;
means for determining a second SRS frequency hopping pattern for transmitting the one or more SRSs, wherein determining the second SRS frequency hopping pattern comprises using the first SRS frequency hopping pattern to generate the second SRS frequency hopping pattern based on the determined antenna switch and by repeating an order of subbands in the first SRS frequency hopping pattern at least for a subset of antenna indices; and
means for transmitting a first set of SRSs of the one or more SRSs according to the first SRS frequency hopping pattern and transmit a second set of SRSs of the one or more SRSs according to the second SRS frequency hopping pattern;
characterized in that at least one of the first SRS frequency hopping pattern or the second SRS frequency hopping pattern is determined according to: <MAT> where N is a total duration associated with the one or more SRSs, R is a repetition factor associated with the one or more SRSs, NAS is a number of antenna switches associated with the one or more SRSs, NFH is a number of frequency hops with a same antenna or antenna pair associated with the one or more SRSs, GAS ∈ {<NUM>,<NUM>} is a guard symbol configuration value for antenna switching, and GFH ∈ {<NUM>,<NUM>} is a guard symbol configuration value for frequency hopping of the one or more SRSs.