Patent Description:
<NPL>, relates to a discussion for Rel-<NUM> additional SRS symbols from various perspectives. <NPL>, relates to a discussion on the enhancements on SRS, and provides observations and proposals. <NPL>, relates to views on design considerations for the introduction of additional SRS symbols in normal UL subframes. <NUM>rd Generation Partnership Project, <NPL>, describes the physical channels for evolved UTRA. <NPL>, relates to various observations and proposals related to antenna switching. <NPL> relates to views on UL SRS design with the consideration of using SRS for CSI acquisition and beam management.

Aspects of the present disclosure provide apparatus, methods, processing systems, and computer readable mediums for radio resource control (RRC) configuration for aperiodic sounding reference signal (A-SRS) on additional SRS symbols.

The following description provides examples of RRC configuration for A-SRS on additional SRS symbols, 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 module <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 configuring aperiodic SRS transmission on additional SRS symbols, in accordance with aspects of the present disclosure. Additionally, as shown in <FIG>, the UE 120a includes a SRS module <NUM>. The SRS module <NUM> may be configured to perform the operations illustrated in one or more of <FIG>, as well as other operations disclosed herein for configuring aperiodic SRS on additional SRS symbols, in accordance with aspects of the present disclosure.

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 110a, 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 module <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 aperiodic SRS transmission on additional SRS symbols, according to aspects described herein. As shown in <FIG>, the controller/processor <NUM> of the UE 120a includes SRS module <NUM> that may be configured to perform the operations illustrated in one or more of <FIG>, as well as other operations disclosed herein for aperiodic SRS transmission on additional SRS symbols, 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 system 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 which 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 the 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 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 on UL normal subframe. This may involve introducing more than one symbol for SRS for one UE or for multiple UEs in 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 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 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 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.

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) transmitted in last symbol of a normal uplink subframe. The additional SRS symbols may be the non-legacy SRS symbols in a normal uplink subframe. In another case, the additional SRS symbols may be configured in all symbols, including last symbol, of a normal uplink subframe. Additionally, in some cases, the additional SRS may be aperiodically triggered. In some cases, a UE may be allowed to transmit periodic legacy SRS and aperiodic additional SRS in the same normal uplink 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 uplink subframe. Thus, aspects of the present disclosure provide techniques for improving the transmission of only one of legacy SRS or additional SRS symbol(s) in a same normal uplink subframe as well as techniques for the transmission of both legacy SRS and additional SRS symbols in a same normal uplink subframe.

<FIG> illustrates example operations <NUM> for wireless communications by a network entity. In some cases, the network entity may include a base station (e.g., gNB) configured to configure a UE for A-SRS transmission in accordance with aspects of the present disclosure.

According to aspects, the base station may include one or more components as illustrated in <FIG>, which may be configured to perform the operations described herein. For example, the antenna <NUM>, transceivers <NUM>, controller/processor <NUM>, and/or memory <NUM> as illustrated in <FIG> may perform the operations described herein.

Operations <NUM> begin, at <NUM>, by transmitting, to a user equipment, signaling indicating, for a set of uplink subframes, a first configuration for transmitting one or more SRS transmissions of a first type and a second configuration for transmitting one or more SRS transmission of a second type.

At <NUM>, the network entity receives, within at least one uplink subframe of the set of uplink subframes, at least one of the one or more SRS transmissions of the first type or the one or more SRS transmissions of the second type based, at least in part, on the signaling.

<FIG> illustrates example operations <NUM> for wireless communications by a network entity in a network. For example, operations <NUM> may be performed by a UE for configuration and transmission of A-SRS in accordance with aspects of the present disclosure.

According to aspects, the UE may include one or more components as illustrated in <FIG> which may be configured to perform the operations described herein. For example, the antenna <NUM>, transceivers <NUM>, controller/processor <NUM>, and/or memory <NUM> as illustrated in <FIG> may perform the operations described herein.

Operations <NUM> begin, at <NUM>, by receiving, from the network, signaling indicating, for a set of uplink subframes, a first configuration for transmitting one or more SRS transmissions of a first type and a second configuration for transmitting one or more SRS transmission of a second type.

At <NUM>, the UE transmits, within at least one uplink subframe of the set of uplink subframes, at least one of the one or more SRS transmissions of the first type or the one or more SRS transmissions of the second type based, at least in part, on the signaling.

As noted above, aspects of the present disclosure provide techniques for configuring UEs to transmit SRSs in an uplink subframe. For example, aspects of the present disclosure provide techniques for configuring a non-legacy UE to be able to transmit both SRSs of a first type and SRSs of a second type in a same or different uplink subframe, while also remaining backwards compatible to legacy UEs that are only capable of transmitting SRSs of a second type in an uplink subframe. According to aspects, SRSs of the first type may include non-legacy SRSs while SRSs of the second type may include legacy SRSs. In this context, legacy SRSs may refer to SRS transmitted in a last symbol of a normal UL subframe while non-legacy SRSs may refer to additional SRSs transmitted in symbols of the subframe other than the last symbol of the subframe.

According to aspects, a resource configuration for the SRS transmissions of the first type may be different from that of the SRS transmissions of the second type in at least one uplink subframe. For example, in some cases, the SRSs of the first type, also known as "additional SRSs" (e.g., SRSs added to a subframe in addition to the legacy SRSs) may include SRS transmissions not located in a last symbol of an uplink, while SRSs of the second type may include SRS transmissions located in at least one of the last symbol. Additionally, in some cases, the SRS transmissions of the first type may be triggered in same or different way from that of the SRS transmissions of the second type, as explained below.

According to aspects, the SRS transmissions of the first type may include at least one of one of periodic SRS transmissions or aperiodic SRS transmissions. Additionally, the SRS transmissions of the second type may also include at least one of periodic SRS transmissions or aperiodic SRS transmissions.

As noted above, the base station may transmit signaling to the UE, indicating a first configuration for transmitting one or more SRS transmissions of the first type and a second configuration for transmitting one or more SRS transmission of the second type. In some cases, the first configuration and/or the second configuration may be transmitted/received in at least one of a radio resource control (RRC) message or downlink control information (DCI).

For example, in some cases, the first configuration for transmitting the one or more SRS transmissions of the first type may include a subframe configuration for transmitting, for example, aperiodic SRSs, and may be configured by indicating the higher-layer parameter srs-ConfigIndexAP. According to aspects, the first configuration may include a periodicity and a subframe offset for transmitting the one or more SRS transmissions of the first type, which may be the same or different from that of the SRS transmissions of the second type. For example, the UE may receive the first configuration and determine which subframes and the periodicity for transmitting the SRSs of the first type based on the subframe offset information and the periodicity information. If no explicit indication of srs-ConfigIndexAP for the SRS transmission of the first type, the UE may use the same srs-ConfigIndexAP of the SRS transmission of the second type for the SRS transmission of the first type by default.

In some cases, the subframes in which SRSs of the first type are configured to be transmitted may be the same or different as the subframes in which SRSs of the second type are configured to be transmitted. For example, in some cases, the base station may configure the SRS transmissions of the first type in a different normal uplink subframe than SRS transmissions of the second type. Thus, in this case, the SRS transmissions of the first type and the SRS transmissions of the second type may not overlap in a same subframe. Additionally, in this case, SRS resources for the SRS transmissions of the first type may thus include a last symbol of a normal uplink subframe. For example, when the UE receives signaling with a configuration indicating that SRS transmissions of the first type do not overlap with SRS transmissions of the second type in a same normal uplink subframe, the UE may transmit SRS transmissions of the first type in a last symbol of the normal uplink subframe. In such cases, the UE may assume a same configuration for the SRS transmission of the first type, which may be different from that of the SRS transmission of the second type even when SRS transmissions of the first type overlap or are configured for transmission in the last symbol of the normal uplink subframe.

However, if the base station configures both SRS transmissions of the first type and SRS transmissions of the second type for transmission in the same normal uplink subframe, the SRS resources for the SRS transmissions of the first type may include different alternatives. For example, as illustrated in <FIG>, in a first alternative (Alt <NUM>), when SRS transmissions of the first type (e.g., "Additional SRS"/"New SRS" in <FIG>) and SRS transmissions of the second type (e.g., "Legacy SRS" in FIG. <NUM>) are configured in a same normal uplink subframe <NUM>, the SRS resources (e.g., as indicated in the first configuration) for the SRS transmissions of the first type may not include a last symbol <NUM> of the normal uplink subframe. According to aspects, however, if only SRS transmissions of the first type are scheduled for transmission in a normal uplink subframe <NUM>, the SRS resources for the SRS transmission of the first type may include the last symbol <NUM> of the normal uplink subframe.

In a second alternative (Alt <NUM>), as illustrated in <FIG>, when SRS transmissions of the first type and SRS transmissions of the second type are configured in a same normal uplink subframe <NUM> (e.g., as indicated by the first configuration and second configuration), the SRS resources for the SRS transmissions of the first type may include a last symbol <NUM> of the normal uplink subframe <NUM> (e.g., in which the SRS transmissions of the second type are also configured/scheduled). However, in this case, since the SRS transmissions of the first type and the SRS transmissions of the second type may collide in the last symbol <NUM> of the normal uplink subframe <NUM>, the UE may determine which of the SRS transmissions of the first type or the SRS transmissions of the second type to transmit in the last symbol of the same uplink subframe based, at least in part, on a priority order, such as new A-SRS → legacy A-SRS → new P-SRS (if defined) → legacy P-SRS. With respect to this priority order, "new" may refer to SRS transmissions of the first type, "legacy" may refer to SRS transmissions of the second type, A-SRS may refer to aperiodic SRS, and P-SRS may refer to periodic SRS. For example, in some cases, as illustrated in <FIG>, based on the priority order, when SRS transmissions of the first type and SRS transmissions of the second type are configured in a same normal uplink subframe <NUM>, the UE may drop the SRS transmission of the second type <NUM> in the last symbol <NUM> of the normal uplink subframe <NUM> in favor of an SRS transmission of the first type.

According to aspects, in addition to the first configuration and second configuration indicating a subframe configuration for the SRS transmissions of the first type and the SRS transmissions of the second type, the first configuration may also indicate a symbol configuration within a subframe or a slot and/or a symbol configuration within the slot for the SRS transmissions of the first type. The second configuration may include an SRS symbol configuration that is fixed on the last symbol of a normal uplink subframe and, in some cases, a symbol configuration for special UpPTS SRS transmission of the second type.

For example, in some cases, the first configuration (e.g., for transmission of SRS transmissions of the first type) may include a slot index (e.g., <NUM> or <NUM>) and a number of symbols (e.g., <NUM>-<NUM> symbols in second slot of a normal uplink subframe if excluding last symbol, or <NUM>-<NUM> symbols in the first slot or a second slot if including last symbol) for SRS transmissions of the first type in a normal uplink subframe.

Additionally, in some cases, the first configuration may include a list of SRS configurations per SRS symbol within a slot of a normal uplink subframe. In some cases, the first configuration (e.g., for transmission of SRS transmissions of the first type) may include a number of symbols in a normal uplink subframe (e.g., <NUM>-<NUM> symbols if excluding last symbol or <NUM>-<NUM> symbols if including last symbol). According to aspects, each of the SRS configurations in the list may indicate the symbol index, in the normal uplink subframe, for each symbol of the number of symbols to transmit the SRS transmissions of the first type.

Additionally, in some cases, each of the SRS configurations in the list may indicate the parameter sets for SRS transmission. The parameter sets for each SRS symbol may, in some cases, be independently indicated. In some cases, the first configuration may include a list of symbol indices, start symbol and symbol duration, or a symbol bitmap indicating the symbols in the normal uplink subframe to transmit the SRS transmissions of the first type. The first configuration may include the parameter sets for SRS transmission, which are common for SRS symbols. In some cases, the start symbol indicates an index from <NUM>st to <NUM>th symbol in a normal uplink subframe. Further, in some cases, the symbol duration indicates the number of the non-legacy SRS symbols configured between <NUM> to <NUM> symbols, which may also include the guard symbol if configured for the UE with SRS antenna switching and/or frequency hopping.

In some cases, the bitmap may include <NUM> bits or <NUM> bits that each correspond to a different symbol within a slot of the normal uplink subframe (e.g., <NUM> bits if SRS transmissions of the first type are not allowed within the last symbol of the second slot of the normal uplink subframe, otherwise <NUM> bits maximum). In some cases, the bitmap may include 13bits or 14bits that correspond to a different symbol within a normal uplink subframe (e.g., <NUM> bits if SRS transmissions of the first type are not allowed within the last symbol of the normal uplink subframe, otherwise <NUM> bits maximum). In some cases, the slot configuration may be predefined to be the first slot or the second slot, if not explicitly indicated by the base station.

According to aspects, the UE may use the slot/symbol configuration within the first configuration to determine where and when to transmit the SRS transmissions of the first type within a normal uplink subframe.

Additionally, in some cases, the first configuration may include configuration information for one or more of SRS antenna switching, frequency hopping, or repetition for transmitting the SRS transmissions of the first type. For example, in some cases, the first configuration may include SRS repetition pattern for the one or more SRS transmissions of the first type, which the UE may use when transmitting the SRS transmissions of the first type. According to aspects, the SRS repetition pattern may indicate a first SRS transmission of one or more SRS transmissions of the first type is to be repeated in a number of symbols (e.g., a number of SRS repetition symbols) of a normal uplink subframe using a same antenna transmission port, antenna, subband, and transmission power. In some cases, the number of SRS repetition symbols may be no larger than total number of SRS symbols in the normal uplink subframe. According to aspects, a repetition pattern may be used when intra-subframe SRS antenna switching/frequency hopping is enabled, where the repetition pattern may be predefined as, for example, first repeat SRS on same antenna transmission port/antenna/subband/transmission power and then switch antenna and/or subband. In some cases, by default, if the base station does not include specific signaling in the first configuration indicating a repetition pattern, the UE may understand that the number of repetitions is <NUM> (e.g., no repetition). In some case, if SRS antenna switching/frequency hopping is not enabled, the SRS may be transmitted over wideband on same antenna port/antenna, and therefore same SRS transmissions may be repeated on each SRS symbol. In this case, there may be no need to indicate the number of SRS repetition symbols. As noted, the UE may transmit the SRS transmissions of the first type according to the repetition pattern received in the first configuration.

As noted, the first configuration may include configuration information for intra-subframe antenna switching for transmitting the SRS transmissions of the first type within a normal uplink subframe. For example, the first configuration may include an indication of whether intra-subframe antenna switching is enabled or disabled in a normal uplink subframe (e.g., for transmitting the SRS transmissions of the first type). According to aspects, if intra-subframe antenna switching is enabled, the UE may use a first antenna or a first antenna group for transmitting a first SRS transmission of the first type in the normal uplink subframe (e.g., in a first symbol of the normal uplink subframe). Thereafter, the UE may then switch to using a second antenna or a second antenna group for transmitting a second SRS transmission of the first type in the normal uplink subframe (e.g., in a second symbol of the normal uplink subframe). It should be noted that the first symbol of the normal uplink subframe and second symbol of the normal uplink subframe may refer to any symbol with normal uplink subframe and not necessarily to the actual first and second symbols of the normal uplink subframe.

According to aspects, if antenna switching is enabled, the base station may receive a first SRS transmission of the first type in the at least one uplink subframe to obtain channel information of a first antenna at the UE or a first antenna group at the UE. The base station may then receive a second SRS transmission of the first type in the at least one uplink subframe to obtain channel information of a second antenna at the UE or a second antenna group at the UE.

According to aspects, if antenna switching is disabled, the UE may not switch antennas while transmitting the SRS transmissions of the first type in the normal uplink subframe. Additionally, according to aspects, the configuration information for antenna switching for SRS transmission of the first type may include configuration information for SRS antenna switching 1T2R, 1T4R, and/or 2T4R, which may be different from that of SRS transmission of the second type, where, for example, xT refers to the number (x) of transmit antennas T and xR refers to the number (x) of receive antennas R. In some cases, a UE could be configured with SRS antenna switching 1T2R or 1T4R, which selects one antenna among two or four antennas, or SRS antenna switching 2T4R, which selects one a pair of two antenna ports among predefined two pairs or three pairs of antennas, depending on the UE capability per band. In some cases, a UE may be configured with a guard period, such as a symbol between every antenna switching for UE processing. For the SRS transmission of the first type (e.g., aperiodic non-legacy SRS transmission), the number of the antenna switches (e.g., the number of times that an antenna/antenna group switches) in a normal uplink subframe may be a full set of SRS antenna switching, such as <NUM> for SRS 1T2R or SRS 2T4R with <NUM> pairs of antennas, <NUM> for SRS 2T4R with <NUM> pairs of antennas, or <NUM> for SRS 1T4R.

In some cases, by default, if the base station does not include explicit signaling indicating the antenna switching configuration information (e.g., related to 1T2R, 1T4R, and/or 2T4R) for the second type, the UE may use the same configuration as for SRS antenna switching of the first type. In some cases, the base station may include explicit signaling indicating the antenna switching configuration information (e.g., related to 1T2R, 1T4R, and/or 2T4R) for A-SRS only, which may be different from that of the SRS antenna switching of P-SRS. Otherwise, the UE may assume the same configuration of SRS antenna switching for A-SRS and P-SRS.

In some cases, the first configuration may include a starting antenna index (e.g., for 1T2R or 1T4R) or an antenna group index (e.g., for 2T4R) for intra-subframe SRS antenna switching. According to aspects, in some cases, by default, the UE may start from antenna <NUM> (zero) or antenna group <NUM> (zero) if the number of symbols within the normal uplink subframe is equal to the number of antennas as the UE.

As noted, the first configuration may include configuration information for intra-subframe frequency hopping for transmitting the SRS transmissions of the first type within a normal uplink subframe. For example, the first configuration may include an indication of whether intra-subframe frequency hopping is enabled or disabled in a normal uplink subframe (e.g., for transmitting the SRS transmissions of the first type). According to aspects, if frequency hopping is enabled, the UE may use a first subband for transmitting a first SRS transmission of the first type in a normal uplink subframe (e.g., in a first symbol of the normal uplink subframe). Thereafter, the UE may then switch to using a second subband for transmitting a second SRS transmission of the first type in the at least one uplink subframe (e.g., in a second symbol of the normal uplink subframe). Similarly, if frequency hopping is enabled, the base station may receive a first SRS transmission of the first type in the at least one uplink subframe to obtain channel information on a first subband and receive a second SRS transmission of the first type in the at least one uplink subframe to obtain channel information on a second subband.

Further, according to aspects, if intra-subframe frequency hopping is enabled, the first configuration may include an indication of a hopping bandwidth for the UE to perform frequency hopping during transmission of the SRS transmissions of the first type in the normal uplink subframe. In some cases, the hopping bandwidth may be indicated as a total SRS bandwidth divided by a configured number of SRS transmissions of the first type in the normal uplink subframe. In some cases, the hopping bandwidth configured for the SRS transmission of the first type may be the same or different from that of SRS transmission of the second type. If the BS does not provide an explicit indication of hopping bandwidth, by default, the UE may assume the same hopping bandwidth for the first and second type of SRS transmissions. Additionally, the first configuration may include an indication of a starting frequency location in the hopping bandwidth to perform the frequency hopping during transmission of the SRS transmissions of the first type in the normal uplink subframe. According to aspects, the starting frequency location may include at least one of a subband index or a physical resource block. The UE may then transmit SRS transmissions of the first type according to, for example, the hopping bandwidth indication and the starting frequency location. In some cases, a UE could be configured with a guard period, such as a guard symbol between every frequency hopping for UE processing. For the SRS transmission of the first type (e.g., aperiodic non-legacy SRS transmission) the number of the frequency hops in a normal uplink subframe can be a full set of SRS subbands or a subset of SRS subbands. The total number of SRS subbands may be dependent on the configured SRS bandwidth and the subband size of hopping bandwidth configured for the non-legacy SRS symbols. Additionally, the number of SRS subbands within a normal uplink subframe for intra-subframe aperiodic SRS transmission of the first type may be dependent on the total number of OFDM symbols configured and the guard symbol (if configured) for frequency hopping. Further, if antenna switching and frequency hopping are enabled for intra-subframe aperiodic SRS transmission of the first type, the number of SRS subbands within a normal uplink subframe may also be dependent on a number of antenna switches (if configured) and the guard symbol (if configured) for antenna switching.

In some cases, if intra-subframe frequency hopping is disabled (e.g., as indicated in the first configuration) the UE may not change subbands while transmitting SRS transmissions of the first type. If the hopping bandwidth is smaller than an SRS bandwidth, whether the UE changes the frequency subbands per symbol or per subframe may be configured by using the enable/disable bit for intra-subframe frequency hopping. Note that the enable/disable bit for intra-subframe frequency hopping and enable/disable bit for intra-subframe antenna switching may be independently configured or combined together by the base station. If using a combined bit, the intra-subframe frequency hopping and antenna switching may be concurrently enabled or disabled. It is also dependent on the guard period configuration for SRS antenna switching and frequency hopping, respectively. For example, if a UE is configured with no guard period for SRS frequency hopping but guard period for SRS antenna switching, the UE carries out the frequency hopping before the antenna switching; if a UE is configured with guard period for SRS frequency hopping but no guard period for SRS antenna switching, the UE carries out the antenna switching before frequency hopping; if a UE with configured with no guard symbol or guard symbol same for SRS antenna switching and frequency hopping, the UE concurrently carries out the frequency hopping and antenna switching, i.e., switch the antenna and subband at same time.

In some cases, when SRS transmissions of the first type and SRS transmissions of the second type are configured/scheduled within a same subframe, the UE may determine whether the first configuration for SRS transmissions of the first type and the second configuration for SRS transmissions of the second type are complimentary to each other. In some cases, the UE's determination of whether the first configuration and the second configuration are complementary to each other may be based on signaling received from the base station.

For example, when SRS transmissions of the first type (e.g., non-legacy aperiodic SRS transmission) and SRS transmissions of the second type (e.g., legacy periodic/aperiodic SRS transmissions) are configured to be transmitted in the same subframe, the base station may transmit signaling (e.g., srs-ConfigComplementaryAp) to enable/disable configuration of a symbol number and pattern for SRS transmissions of the first type taking into account the SRS transmissions of the second type in the same subframe.

For example, if the UE determines that the first configuration and the second configuration are complementary to each other, the UE may take the SRS transmissions of the second type into account when determining how to transmit the SRS transmissions of the first type. That is, for example, the UE may adjust configuration parameters for the SRS transmissions of the first type depending on those of second type, such as a number of symbols for the SRS transmissions of the first type, an antenna index/antenna group index, and/or subband.

<FIG> illustrate different examples of adjusting configuration parameters for SRS transmissions of the first type depending on those of second type, according to aspects presented herein. For example, as illustrated at 602A in <FIG>, if the first configuration and second configuration are determined not to be complementary to each other, the UE may consider the SRS transmissions of the first type and the SRS transmissions of the second type to be independent from each other. For example, as illustrated at 604A, if the first configuration and second configuration are not complementary to each other (e.g., in some cases determined based on an indication from the base station), the UE may transmit the SRS transmissions of the first type (e.g., aperiodic additional SRS symbols, as shown in <FIG>) and the SRS transmissions of the second type (e.g., periodic legacy SRS symbols, as shown in <FIG>) in the same normal uplink subframe independently from each other (e.g., configuration parameters of the SRS transmissions of the first type are not adjusted by the UE based on configuration parameters of the SRS transmissions of the second type).

Additionally, as illustrated at 606A in <FIG>, if the first configuration and the second configuration are determined to be complementary to each other and if the UE is configured with N symbols for the SRS transmissions of the first type, the UE may select N SRS symbols 608A for the SRS transmissions of the first type in the case of no SRS transmissions of the second type are configured in a same subframe or may select (N-<NUM>) SRS symbols 610A for the SRS transmissions of the first type in the case that there is one SRS transmission of the second type configured in a same subframe.

For example, if the first configuration and the second configuration are determined to be complementary to each other (e.g., based on an indication provided by the base station), the UE may determine a number of the SRS transmissions of the first type to transmit in the same uplink subframe based on, for example, a number SRS transmissions of the second type configured for transmission in the same normal uplink subframe. In some cases, determining the number of SRS transmissions of the first type to transmit may include reducing the one or more SRS transmissions of a first type by the number of SRS transmissions of the second type configured for transmission in the same uplink subframe, for example, as illustrated at 610A in <FIG>. Thereafter, the UE may transmit the SRS transmissions of the first type according to the determined number of SRS transmissions of the first type and transmit the SRS transmissions of the second type according to the determined number of SRS transmissions of the second type.

It should be noted that <FIG> relates to configuring legacy (e.g., SRS transmissions of the second type) periodic SRS transmissions without antenna switching/frequency hopping enabled in a same normal uplink subframe in which SRS transmissions of the first type are configured (e.g., aperiodic SRS transmissions of the first type). <FIG> illustrates the case of configuring legacy (e.g., SRS transmissions of the second type) aperiodic SRS transmissions without antenna switching/frequency hopping enabled in a same normal uplink subframe in which SRS transmissions of the first type (e.g., aperiodic SRS transmissions of the first type) are configured.

In some cases, a repetition pattern may be enabled for the SRS transmissions of the first type in <FIG>. In this case, an SRS transmission of the first type may be repeated a plurality of times, while still taking into account the SRS transmission of the second type in the same normal uplink subframe. For example, in some cases, as illustrated at 610A, a first SRS transmission of the first type may be repeated three times in a normal uplink subframe while still allowing for an SRS transmission of the second type in the same normal uplink subframe.

Additionally, as noted above, if the first configuration and the second configuration are determined to be complementary, the UE may take into account at least one of an antenna or an antenna group used for transmitting the SRS transmissions of the second type when configuring/transmitting the SRS transmissions of the first type. For example, <FIG> illustrates configuring a legacy (e.g., SRS transmissions of the second type) periodic SRS with inter-subframe AS 1T4R and new (e.g., SRS transmissions of the first type) aperiodic SRS intra-subframe AS 1T4R in a normal uplink subframe, according to certain aspects herein.

As illustrated, when antenna switching is enabled and the first configuration and the second configuration are complimentary (e.g., as illustrated at 602C), the UE may take into account the antenna used for transmitting the SRS transmissions of the second type when transmitting the SRS transmissions of the first type. For example, as illustrated, if the SRS transmission of the second type is configured for transmission on antenna <NUM> as illustrated at 604C, the SRS transmissions of the first type may be configured for transmission on antennas other than antenna <NUM> (e.g., antennas <NUM>, <NUM>, and <NUM>) as illustrated at 606C. In other words, if the first configuration and the second configuration are complementary, the UE may determine not to use a same antenna or same antenna group used for transmitting the SRS transmissions of the second type when transmitting the SRS transmissions of the first type.

However, if the first configuration and the second configuration are not complimentary (e.g., as illustrated at 608C) and if the SRS transmission of the second type is configured for transmission on antenna <NUM> as illustrated at 610C, the UE may not take this antenna information into account and may still transmit the SRS transmissions of the first type using antenna <NUM>, for example, as illustrated at 612C.

Additionally, as noted above, if the first configuration and the second configuration are determined to be complementary, the UE may take into account a subband used for transmitting the SRS transmissions of the second type when configuring/transmitting the SRS transmissions of the first type. For example, <FIG> illustrates configuring a legacy (e.g., SRS transmissions of the second type) periodic with inter-subframe frequency hopping and new (e.g., SRS transmissions of the first type) aperiodic SRS intra-subframe frequency hopping in a normal uplink subframe, according to certain aspects herein. As illustrated, when frequency hopping is enabled and the first configuration and the second configuration are complimentary as illustrated at 602D, the UE may take the subband used for transmitting the SRS transmissions of the second type into account when transmitting the SRS transmissions of the first type. For example, as illustrated, if the SRS transmission of the second type is configured for transmission on subband <NUM>, the SRS transmissions of the first type may be configured for transmission on subbands other than subband <NUM>, such as subbands <NUM>, <NUM>, and <NUM>. In other words, if the first configuration and the second configuration are complementary, the UE may determine not to use a same subband used for transmitting the SRS transmissions of the second type when transmitting the SRS transmissions of the first type.

However, if the first configuration and the second configuration are not complimentary (e.g., as illustrated at 604D) and if the SRS transmission of the second type is configured for transmission on subband <NUM>, the UE may not take this subband information into account and may still transmit the SRS transmissions of the first type using subband <NUM>, as illustrated.

According to aspects, on the base station side, after the SRS transmissions of the first type and the SRS transmissions of the second type have been transmitted by the UE, the base station may receive and combine the SRS transmissions of the first type with the SRS transmission of the second type in the same normal uplink subframe (e.g., in some cases, with same or different power control). According to aspects, aperiodic SRS repetition on (N-<NUM>) new SRS symbols together with one legacy symbol may achieve similar combining gain of N SRS repetitions. Additionally, aperiodic SRS antenna switching on additional SRS symbols may only need to switch the antennas not used for the legacy SRS symbol. The transmission power for SRS transmissions of the first type may also be aligned with that for SRS transmissions of the second type if the higher layer signaling (e.g., srs-ConfigComplementaryAp) is indicated to enable complementary configuration, so that the unnecessary power change may be reduced at the UE side and it is easier for the base station to combine/merge the SRS transmissions of the first and second type together.

According to aspects, in some cases, the UE may receive signaling from the base station that includes a trigger indication of whether the one or more SRS transmissions of the first type and the one or more SRS transmissions of the second type are allowed to be transmitted in a same normal uplink subframe. In some cases, the trigger indication may be received in downlink control information signaling or a radio resource control message transmitted by the base station.

For example, in some cases, the UE may receive a trigger indication from the base station indicating that SRS transmissions of the first type and SRS transmissions of the second type are not allowed (e.g., are disabled) in a same normal uplink subframe. In this case, if SRS transmissions of the first type and SRS transmissions of the second type are scheduled to be transmitted in the same normal uplink subframe (e.g., based on the first configuration and second configuration), the UE may determine which of the first configuration or the second configuration to use for transmitting SRSs, for example, based on a priority order. For example, in some cases, the UE may determine to use the first configuration and transmit SRS transmissions of the first type in the normal uplink subframe and to drop SRS transmissions of the second type in the normal uplink subframe (e.g., based on the UE receiving a trigger indication, indicating SRS transmissions of the first type and SRS transmissions of the second type are not allowed to both occur within the same normal uplink subframe).

In some cases, the UE may receive a trigger indication from the base station indicating that both SRS transmissions of the first type and SRS transmissions of the second type are allowed (e.g., are enabled) to be transmitted in a same normal uplink subframe. In this case, the UE may determine to use both the first configuration and the second configuration to transmit the SRS transmissions of the first type and the SRS transmissions of the second type in the same normal uplink subframe. For example, in this case, the UE may transmit the SRS transmissions of the first type according to the first configuration and transmit the SRS transmissions of the second type according to the second configuration. In some cases, SRS transmission of the first type and SRS transmission of the second type cannot be configured or triggered in the same subframe. For example, when the UE is supporting carrier aggregation, the SRS transmission of the first type may be configured to be transmitted in the secondary (SCell) without PUSCH/PUCCH and the SRS transmission of the second type may be configured to be transmitted in the SCell without PUSCH/PUCCH (e.g., for SRS carrier switching). In this case, the UE may not be expected to be configured or triggered to transmit the SRS of the first type and SRS of the second type at the same time.

According to certain aspects, when the UE receives a trigger indication from the base station, the UE may determine a first valid normal uplink subframe to commence transmission of SRSs. For example, upon detection of a positive SRS request in subframe n (e.g., the UE receives a trigger indication in subframe n enabling SRS transmission of the first type in a normal uplink subframe), the UE may determine the first valid subframe for transmitting SRSs according to: n+k, where k >= kp, and where kp may be predefined (e.g., kp=<NUM>). In other words, the UE may determine the timing of the one or more SRS transmissions of the first type with the latency no less than that a minimum value after its corresponding trigger indication, which is similar as that of the one or more SRS transmissions of the second type. According to aspects, if the first valid subframe is at subframe n+kp, the SRS may be transmitted by the UE with minimum latency of kp subframes, which may be the minimum processing time for preparing SRS transmission after the trigger indication. According to aspects, if the first valid subframe is at subframe n+k, later than subframe n+kp, the SRS may be transmitted by the UE with latency of more than kp subframes, still satisfying the processing time for preparing SRS transmission after the trigger indication received from the base station. In certain cases, some UEs, for example, who inform the base station of the capability of the UE that is less than the required minimum processing time after the trigger indication, may be configured by the BS to transmit SRS in the first valid subframe according to n+k, where k >= kp, and where kp may be configurable based on the reported minimum processing time to be a value smaller than <NUM>.

In some cases, the determination of the valid subframe for commencing transmission of SRS may satisfy (kSRS+Toffset,<NUM>)mod TSRS,<NUM>=<NUM>, where TSRS,<NUM> and Toffset,<NUM> are the periodicity and subframe offset configured for the SRS transmission of the first type, e.g., aperiodic SRS for non-legacy SRS symbols. In some cases, by default, the parameters can be same as those of the SRS transmission of the second type (e.g., aperiodic SRS for legacy SRS symbols.

According to aspects, the UE may have a power change limitation defined as a limited number of power changes within a subframe within a normal uplink subframe that may be taken into account when transmitting SRS transmissions of the first type and SRS transmissions of the second type within the same normal uplink subframe. For example, in some cases, the base station may take into account the UE's capability when configuring the number of SRS transmissions of the first type satisfying the power change requirement. For example, when configuring the number of SRS transmission of the first type in a normal uplink subframe that does not include any SRS transmissions of the second type, the base station may take into account a power change of the SRS transmissions of the first type due to SRS antenna switching/frequency hopping. According to aspects, when the normal uplink subframe includes both SRS transmissions of the first type and SRS transmissions of the second type, a difference in power between SRS transmissions of the first type and SRS transmissions of the second type may still result in power change even without antenna switching/frequency hopping that may need to be taken into account by the base station.

Thus, according to aspects, the base station may configure a similar power control for SRS transmissions of the first type and SRS transmissions of the second type to reduce a power change. For example, the base station may determine a first indication of a transmission power for transmitting the SRS transmissions of the first type and a second indication of a transmission power for transmitting the SRS transmissions of the second type. In some cases, the base station may configure the first indication of the transmission power and the second indication of the transmission power to reduce a power change between SRS transmissions of the first type and SRS transmission of the second type. According to aspects, the base station may then transmit signaling to the UE indicating the first indication of the transmission power for transmitting the SRS transmissions of the first type and the second indication of the transmission power for transmitting the SRS transmissions of the second type.

In some cases, however, if the power change between the SRS transmissions of the first type and the SRS transmissions of the second type is out of the UE's capability, the UE may determine which of the first configuration or the second configuration to use to transmit SRSs. In some cases, this determination may be based on a priority order (e.g., new/additional A-SRS → legacy A-SRS → legacy P-SRS). For example, in some cases, if the power change between the SRS transmissions of the first type and the SRS transmissions of the second type is out of the UE's capability, the UE may determine to use the first configuration to transmit SRS transmissions of the first type (e.g., new A-SRS corresponds to the SRS transmissions of the first type) while dropping SRS transmissions of the second type (e.g., legacy A-SRS or legacy P-SRS corresponds to the SRS transmissions of the second type).

According to aspects, in some cases, the first configuration for SRS transmission of the first type may be indicated on a per-component-carrier (e.g., PCell and SCell) or per-component-carrier-group basis. According to aspects, some parameters for SRS transmission of the first type on multiple CCs may have additional restriction for SRS carrier switching (CS). In some cases, for SRS CS (e.g., for TDD serving cell configured for PUSCH/PUCCH) intra-subframe SRS FH/AS in UpPTS for legacy UEs configured with srs-UpPtsAdd may be supported. Thus, by default, for SRS CS, the UE configured with new/additional SRS symbols (e.g., SRS transmissions of the first type) may support intra-subframe SRS frequency hopping/antenna switching (SRS FH/AS) in normal uplink subframes and may follow the same behaviors as that of UEs configured with SRS CS and srs-UpPtsAdd.

According to aspects, in some cases, periodic SRS on additional SRS symbols can be regarded as the SRS of first type and the legacy periodic or aperiodic SRS on last symbol in normal uplink subframes and symbol(s) in UpPTS may correspond to the SRS of the second type. The SRS of the first type and second type may be transmitted in the same or different subframes. Some RRC configuration parameters for aperiodic SRS on additional SRS symbols in normal uplink may be similar as those of periodic SRS, such as srs-ConfigIndex for periodicity and subframe offset, slot/symbol index configuration, antenna configuration for SRS antenna switching, hopping bandwidth for SRS frequency hopping, number of SRS repetition, enabling/disabling bit for intra-subframe SRS antenna switching/frequency hopping, enabling/disabling bit for complementary configuration of SRS first type and second type, and the like. Different from aperiodic SRS transmission, the periodic SRS transmission may not need to be triggered by using DCI bits.

<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 aperiodic SRS transmission on additional SRS symbols.

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 aperiodic SRS transmission on additional SRS symbols. 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 aperiodic SRS transmission on additional SRS symbols. For example, computer-readable medium/memory <NUM> stores code <NUM> for transmitting, code <NUM> for receiving, and code <NUM> for triggering.

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 aperiodic SRS transmission on additional SRS symbols. For example, the processor <NUM> includes circuitry <NUM> for transmitting, circuitry <NUM> for receiving, and circuitry <NUM> for triggering.

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 aperiodic SRS transmission on additional SRS symbols. 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 aperiodic SRS transmission on additional SRS symbols. For example, computer-readable medium/memory <NUM> stores code <NUM> for receiving, code <NUM> for transmitting, code <NUM> for determining, code <NUM> for dropping, code <NUM> for taking into account, and code <NUM> for selecting.

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 aperiodic SRS transmission on additional SRS symbols. For example, the processor <NUM> includes circuitry <NUM> for receiving, circuitry <NUM> for transmitting, circuitry <NUM> for determining, circuitry <NUM> for dropping, circuitry <NUM> for taking into account, and circuitry <NUM> for selecting.

In some examples, a UE may function as a scheduling entity in a peerto-peer (P2P) network, and/or in a mesh network.

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.

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:
A method (<NUM>) of wireless communications by a user equipment, UE, in a network, the method (<NUM>) comprising:
receiving (<NUM>), from the network, signaling indicating, for a set of uplink subframes, a first configuration for transmitting a number of SRS transmissions of a first type and a second configuration for transmitting a number of SRS transmissions of a second type;
receiving from a base station a trigger indication indicating that the number of SRS transmissions of the first type and the number of SRS transmissions of the second type are allowed to be transmitted in a same uplink subframe;
reducing the number of SRS transmissions of the first type to transmit by the number of SRS transmissions of the second type configured for transmission in the same uplink subframe; and
transmitting (<NUM>), within the same uplink subframe, the reduced number of SRS transmissions of the first type and the number of SRS transmissions of the second type based at least in part on the trigger indication..