Method and apparatus for probing and control signaling enhancements

Abstract

In one embodiment, a user equipment (UE) receives, from an access node (AN), a downlink control information (DCI) triggering transmission of a sounding reference signal (SRS) for a set of SRS resources. The DCI indicates a time domain resource of available time domain resources for transmission of the set of SRS resources. The UE determines a location of the time domain resource in the available time domain resources according to the DCI, and transmits the SRS according to the location of the time domain resource. In another embodiment, the UE receives control information indicating frequency resources in a carrier for transmission of one or more SRSs. The UE determines, based thereon, to divide the frequency resources into segments each comprising contiguous physical resource blocks (PRBs), and to transmit the SRS in an orthogonal frequency division multiplexing (OFDM) symbol on a first segment but not a second segment.

Description

[0001] This patent application claims priority to U.S. Provisional Application No. 63 / 104,374, filed October 22, 2020, entitled “Methods and Apparatus for Sounding and Control Signaling Enhancements,” and U.S. Provisional Application No. 63 / 138,220, filed January 15, 2021, entitled “Methods and Apparatus for Sounding and Control Signaling Enhancements.” The above applications are hereby incorporated by reference into this application as if reproduced in full herein. TECHNICAL FIELD

[0002] The present disclosure relates generally to wireless communications, and in particular embodiments, to methods and apparatus for sounding and control signaling enhancements. BACKGROUND

[0003] A sounding reference signal (SRS) is a reference signal transmitted by a user equipment (UE) on the uplink with the purpose of enabling uplink channel estimation over a wide bandwidth. As a result, the network is able to communicate with the UE based on the uplink channel estimation. Furthermore, due to channel reciprocity between uplink and downlink in time division duplex (TDD) communication systems, the network can utilize the SRS for dynamic scheduling. That is, the network can utilize channel dependent scheduling. In this case, time and frequency resources are dynamically scheduled taking into account different traffic priorities and quality of service requirements. Typically, the UE monitors a number of physical downlink control channels (PDCCHs) to obtain scheduling decisions communicated by the network to the UE. When a valid PDCCH is detected, the UE follows the scheduling decision and receives (or transmits) data.

[0004] SRS-related parameters (e.g., SRS transmission port, SRS transmission bandwidth, SRS resource set, transmission comb, and cyclic shift, etc.) of SRS to be transmitted in uplink are essentially semi-statically configured, which can be provided through high layer signaling such as radio resource control signaling. A more dynamic technique is needed to indicate the configuration to better associate SRS parameters (e.g., SRS transmission bandwidth and / or port) with physical data shared channel (PDSCH) parameters. In addition, it is desirable to convey the association between downlink reference signals such as channel state information reference signal (CSI-RS) or demodulation reference signal (DMRS) and uplink SRS to the UE to accurately reflect the interference situation and perform optimal beamforming. Therefore, there is a need for an apparatus and method for conveying control information that accurately indicates the more dynamic (rather than semi-static) configuration of the above-mentioned parameters, such as, for example, a portion of the transmission bandwidth required to transmit a subset of SRS resource sets using a subset of transmission ports associated with a particular set of downlink reference signals (thus implicitly indicating the transmission comb and cyclic shift). The conveyance of control information can be closely linked to the actual data transmission. As configured by the layer 3 RRC configuration signaling, SRS transmission can be periodic (i.e., periodic SRS, P-SRS or PSRS), semi-persistent (i.e., semi-persistent SRS, SP-SRS or SP SRS) as activated / deactivated by layer 2 MAC CE, or aperiodic (i.e., aperiodic SRS, A-SRS or AP-SRS or ASRS or AP SRS) as indicated by layer 1 downlink control information (DCI) in PDCCH. SUMMARY

[0005] Technical advantages are generally realized by the embodiments of the disclosure describing methods and apparatuses for sounding and control signaling enhancements.

[0006] According to one aspect of the disclosure, a method is provided, comprising: receiving, by a user equipment (UE) from an access node (AN), a downlink control information (DCI) triggering transmission of sounding reference signal (SRS) of a SRS resource set, the DCI including first information indicating a first time domain resource of available time domain resources for transmission of the SRS resource set; determining, by the UE, the available time domain resources for transmission of the SRS resource set according to a first time slot of receiving the DCI; determining, by the UE, a position of the first time domain resource in the available time domain resources according to the first information of the DCI; and transmitting, by the UE to the AN, the SRS according to the position of the first time domain resource.

[0007] Optionally, in any of the above aspects, determining the available time domain resources comprises: determining, by the UE, a reference time slot of the available time domain resources according to a position of the first time slot of the DCI and a high layer parameter slotoffset; and determining, by the UE, the position of the available time domain resources according to the reference time slot.

[0008] Optionally, in any of the above aspects, the reference slot is a first slot in which the DCI is received when a higher layer parameter slotoffset is not configured.

[0009] Optionally, in any of the above aspects, the reference slot is located n slots after the first slot, n is configured by a higher layer parameter slotoffset, and n is greater than or equal to zero (0).

[0010] Optionally, in any of the above aspects, the available time domain resources include time domain resources located in or after the reference slot in the time domain and configured as uplink (UL) or flexible, wherein the time domain resources are in units of slots, mini-slots, or OFDM symbols.

[0011] Optionally, in any of the above aspects, the DCI includes an index of the first time domain resource in the available time domain resources.

[0012] Optionally, in any of the above aspects, the method further includes: determining, by the UE, that the transmission of the SRS conflicts with another transmission / reception in the first time domain resource; and transmitting, by the UE, the SRS in a next time domain resource of the first time domain resource in the available time domain resources without transmitting the SRS in the first time domain resource.

[0013] Optionally, in any of the above aspects, the method further includes: determining, by the UE, that the transmission of the SRS conflicts with another transmission / reception in the first time domain resource; and transmitting, by the UE, the SRS in the first time domain resource when a priority of the transmission of the SRS is higher than a priority of the another transmission / reception.

[0014] Optionally, in any of the above aspects, the method further includes: receiving, by the UE, the priority of the SRS.

[0015] Optionally, in any of the above aspects, the SRS has at least one transmission parameter shared with a data transmission or a high-priority data transmission associated with the SRS.

[0016] According to another aspect of the present disclosure, a method is provided, comprising: receiving, by a user equipment (UE), control information for transmission of one or more sounding reference signals (SRSs), the control information including information indicating frequency resources in a carrier for the transmission of the one or more SRSs; determining, by the UE, to divide the frequency resources into a plurality of segments according to the control information, each segment including a plurality of contiguous physical resource blocks (PRBs); and transmitting, by the UE, a first SRS of the one or more SRSs in a first orthogonal frequency division multiplexing (OFDM) symbol on a first segment of the plurality of segments according to the control information without transmitting the first SRS on a second segment of the plurality of segments.

[0017] Optionally, in any of the above aspects, the transmitting includes: transmitting, by the UE, the SRSs on the plurality of segments with different OFDM symbols, respectively, according to the control information.

[0018] Optionally, in any of the preceding aspects, the transmitting includes transmitting, by the UE, the second SRS on the second segment in the second OFDM symbol according to the control information.

[0019] Optionally, in any of the preceding aspects, the first SRS on the first segment and the second SRS on the second segment are transmitted according to a frequency hopping pattern.

[0020] Optionally, in any of the preceding aspects, the control information includes information indicating that the SRS is transmitted according to the frequency hopping pattern.

[0021] Optionally, in any of the preceding aspects, the control information is downlink control information (DCI) or radio resource control (RRC) configuration information.

[0022] Optionally, in any of the preceding aspects, the control information includes information indicating that the frequency resources are divided into the plurality of segments for transmitting the SRS.

[0023] Optionally, in any of the preceding aspects, the control information includes information indicating a number of the plurality of segments.

[0024] Optionally, in any of the preceding aspects, the determining that the frequency resources are divided into the plurality of segments includes determining, by the UE, that the frequency resources are divided into the plurality of segments when the plurality of segments are discontinuous from each other.

[0025] Optionally, in any of the preceding aspects, the transmitting the first SRS includes repeatedly transmitting, by the UE, the first SRS on the first segment of the plurality of segments in the plurality of OFDM symbols.

[0026] Optionally, in any of the preceding aspects, the control information includes information indicating that the first SRS is repeatedly transmitted.

[0027] Optionally, in any of the preceding aspects, the method further includes receiving, by the UE, a physical downlink shared channel (PDSCH) on the frequency resources in the carrier.

[0028] Optionally, in any of the preceding aspects, the control information includes information indicating an index of a first time domain resource of available time domain resources for transmitting the SRS resource set; wherein the method further includes determining, by the UE, the available time domain resources for transmitting the SRS resource set according to a slot in which the control information is received, and determining, by the UE, a location of the first time domain resource in the available time domain resources according to the index of the first time domain resource of the available time domain resources, the first time domain resource including the first OFDM symbol.

[0029] According to another aspect of the present disclosure, a method is provided, comprising: transmitting, by an access node (AN) to a user equipment (UE), a downlink control information (DCI) triggering transmission of sounding reference signals (SRS) for a set of SRS resources, wherein the DCI comprises information indicating a location of a first time domain resource in available time domain resources for transmission of the set of SRS resources, and the available time domain resources for transmission of the set of SRS resources are based on a first time slot in which the DCI is transmitted; and receiving, by the AN from the UE, the SRS according to the location of the first time domain resource.

[0030] Optionally, in any of the above aspects, the method further comprises determining the available time domain resources for transmission of the set of SRS resources according to the first time slot in which the DCI is transmitted, the determining comprising: determining, by the AN, a reference time slot of the available time domain resources according to the location of the first time slot of the DCI and a higher layer parameter slotoffset; and determining, by the UE, the location of the available time domain resources for transmission of the set of SRS resources according to the reference time slot.

[0031] Optionally, in any of the above aspects, the reference time slot is the first time slot in which the DCI is transmitted when the UE is not configured with the higher layer parameter slotoffset.

[0032] Optionally, in any of the above aspects, the reference time slot is located n time slots after the first time slot, n being specified by a higher layer parameter slotoffset configured for the UE, n being greater than or equal to 0.

[0033] Optionally, in any of the above aspects, the available time domain resources comprise time domain resources located in or after the reference time slot in the time domain and configured as uplink (UL) or flexible, wherein the time domain resources are in units of time slots, mini-slots, or OFDM symbols.

[0034] Optionally, in any of the above aspects, the DCI comprises an index of the first time domain resource in the available time domain resources.

[0035] Optionally, in any of the above aspects, the receiving the SRS comprises: receiving, by the AN, the SRS in a next time domain resource of the first time domain resource in the available time domain resources without receiving the SRS in the first time domain resource when the transmission of the SRS collides with another transmission / reception in the first time domain resource.

[0036] Optionally, in any of the above aspects, the receiving the SRS comprises: receiving, by the AN, the SRS on the first time domain resource.

[0037] Optionally, in any of the above aspects, the SRS has at least one transmission parameter shared by a data transmission or a high priority data transmission associated with the SRS.

[0038] According to another aspect of the present disclosure, a method is provided, comprising: transmitting, by an access node (AN) to a user equipment (UE), control information for transmission of one or more sounding reference signals (SRSs), the control information including information indicating frequency resources in a carrier for transmission of the SRSs; in response to transmitting the control information, receiving, by the AN from the UE, a first SRS of the one or more SRSs in a first orthogonal frequency division multiplexing (OFDM) symbol on a first segment of a plurality of segments segmented by the frequency resources, without receiving the first SRS on a second segment of the plurality of segments, each segment including a plurality of contiguous physical resource blocks (PRBs).

[0039] Optionally, in any of the above aspects, the receiving includes receiving, by the AN from the UE, the SRS on the plurality of segments in different OFDM symbols, respectively.

[0040] Optionally, in any of the above aspects, the receiving includes receiving, by the AN from the UE, a second SRS on the second segment in a second OFDM symbol.

[0041] Optionally, in any of the above aspects, the first SRS on the first segment and the second SRS on the second segment are received according to a frequency hopping pattern.

[0042] Optionally, in any of the above aspects, the control information includes information indicating that the SRSs are transmitted according to the frequency hopping pattern.

[0043] Optionally, in any of the above aspects, the control information is downlink control information (DCI) or radio resource control (RRC) configuration information.

[0044] Optionally, in any of the above aspects, the control information includes information indicating that the frequency resources are segmented into the plurality of segments for transmission of the SRSs.

[0045] Optionally, in any of the above aspects, the control information includes information indicating a number of the plurality of segments.

[0046] Optionally, in any of the above aspects, the plurality of segments are non-contiguous to each other.

[0047] Optionally, in any of the above aspects, the receiving the first SRS includes repeatedly receiving, by the AN from the UE, the first SRS on the first segment of the plurality of segments in a plurality of OFDM symbols.

[0048] Optionally, in any of the above aspects, the control information includes information indicating that the first SRS is repeatedly transmitted.

[0049] Optionally, in any of the above aspects, the method further includes transmitting, by the AN to the UE, a physical downlink shared channel (PDSCH) on the frequency resources in the carrier.

[0050] According to another aspect of the present disclosure, there is provided an apparatus comprising: a non-transitory memory storing instructions; one or more processors in communication with the memory, wherein the instructions, when executed by the one or more processors, cause the apparatus to perform the method of any of the above aspects.

[0051] According to another aspect of the present disclosure, there is provided a non-transitory computer-readable medium storing computer instructions, which when executed by one or more processors of an apparatus, cause the apparatus to perform the method of any of the above aspects.

[0052] According to another aspect of the present disclosure, there is provided a system comprising an access node (AN) and a user equipment (UE), wherein the AN is configured to perform: transmitting, to the UE, a downlink control information (DCI) triggering sounding reference signal (SRS) transmission of a SRS resource set, wherein the DCI comprises information indicating a location of a first time domain resource in available time domain resources for transmitting the SRS resource set, and the available time domain resources for transmitting the SRS resource set are based on a first time slot in which the DCI is transmitted; receiving, from the UE, the SRS according to the location of the first time domain resource; wherein the UE is configured to perform: receiving, from the AN, the DCI; determining, according to a first time slot in which the DCI is received, the available time domain resources for transmitting the SRS resource set; determining, according to the DCI, the location of the first time domain resource in the available time domain resources; transmitting, to the AN, the SRS according to the location of the first time domain resource.

[0053] According to another aspect of the present disclosure, there is provided a system comprising an access node (AN) and a user equipment (UE), wherein the AN is configured to perform: transmitting, to the UE, control information for transmitting one or more sounding reference signals (SRSs), the control information comprising information indicating frequency resources in a carrier for transmitting the one or more SRSs; in response to transmitting the control information, receiving, from the UE, a first SRS of the one or more SRSs in a first orthogonal frequency division multiplexing (OFDM) symbol on a first segment of a plurality of segments segmented by the frequency resources, without receiving the first SRS in OFDM symbols on a second segment of the plurality of segments, each segment comprising a plurality of contiguous physical resource blocks (PRBs); wherein the UE is configured to perform: receiving the control information; determining, according to the control information, that the frequency resources are segmented into the plurality of segments; transmitting, according to the control information, the first SRS of the one or more SRSs in the first OFDM symbol on the first segment of the plurality of segments, without transmitting the first SRS in OFDM symbols on the second segment of the plurality of segments.

[0054] An advantage of the above aspects is that SRS transmission can be triggered flexibly, SRS resources can be configured dynamically, SRS transmission can be more closely associated with data transmission to be performed, and channel interference conditions can be more accurately reflected. This can significantly reduce SRS transmission collisions, reduce SRS overhead, reduce the impact of interference on data communication, improve the spectral efficiency (SE) of the network and terminal devices, and improve user experience. BRIEF DESCRIPTION OF DRAWINGS

[0055] For a more complete understanding of the present disclosure and its advantages, reference is now made to the following description taken in conjunction with the accompanying drawings in which:

[0056] Figure 1 A diagram illustrating an example wireless communication system is shown;

[0057] Figure 2 A diagram illustrating an example communication system is shown, providing mathematical expressions for signals transmitted in the communication system;

[0058] Figure 3 A flow diagram illustrating operations performed in an interference sounding procedure according to example embodiments presented herein is shown;

[0059] Figure 4 A time slot diagram highlighting existing SRS triggering and transmission schemes;

[0060] Figure 5 A time slot diagram highlighting SRS triggering and transmission according to example embodiments presented herein;

[0061] Figure 6 and Figure 7 An example mapping of resource block groups (RBGs) and SRS resources and ports according to example embodiments presented herein is shown;

[0062] Figure 8 A diagram illustrating messages exchanged by a communication device performing interference sounding according to example embodiments presented herein is shown;

[0063] Figure 9 A first example DCI according to example embodiments presented herein is shown;

[0064] Figure 10 A second example DCI according to example embodiments presented herein is shown;

[0065] Figure 11 A third example DCI according to example embodiments presented herein is shown;

[0066] Figure 12 A fourth example DCI according to example embodiments presented herein is shown;

[0067] Figure 13a flow diagram illustrating example operations in a UE, in accordance with example embodiments presented herein;

[0068] Figure 14 a flow diagram illustrating example operations in an access node, in accordance with example embodiments presented herein;

[0069] Figure 15 a flow diagram illustrating example operations in an access node configuring uplink SRS, in accordance with example embodiments presented herein;

[0070] Figure 16 a flow diagram illustrating example operations in a UE transmitting uplink SRS, in accordance with example embodiments presented herein;

[0071] Figure 17 an example of GC DCI for A-SRS transmission, in accordance with example embodiments presented herein;

[0072] Figure 18 a diagram illustrating an example BIT based on partial frequency sounding with dynamic indication of A-SRS triggering, in accordance with example embodiments presented herein;

[0073] Figure 19 a diagram illustrating partitioning of frequency resources for SRS transmission, in accordance with example embodiments presented herein;

[0074] Figure 20A an example single-shot BIT operation flow, in accordance with example embodiments presented herein;

[0075] Figure 20B and Figure 20C a communication system highlighting example interference conditions, in accordance with example embodiments presented herein;

[0076] Figure 21A and Figure 21B a data plot illustrating example BIT performance, in accordance with example embodiments presented herein;

[0077] Figure 22 a diagram illustrating information exchanged between a gNB and a UE when the gNB configures UL SRS sounding and then performs DL transmission based on the UL SRS sounding results, in accordance with example embodiments presented herein;

[0078] Figure 23 a diagram illustrating an RGB with example mapping of SRS resources and ports, in accordance with example embodiments presented herein;

[0079] Figure 24A , Figure 24B , Figure 24C and Figure 24DFIG. 1 is a diagram illustrating different PRB sounding patterns according to example embodiments presented herein;

[0080] Figure 25A FIG. 2 is a diagram illustrating complementary cumulative distribution function (CCDF) of PAPR in scenario 4 according to example embodiments presented herein;

[0081] Figure 25B FIG. 3 is a diagram illustrating CCDF of PAPR in scenario 5 according to example embodiments presented herein;

[0082] Figure 26 FIG. 4 is a flowchart of a wireless communication method embodiment;

[0083] Figure 27 FIG. 5 is a flowchart of another wireless communication method embodiment;

[0084] Figure 28 FIG. 6 is a flowchart of another wireless communication method embodiment;

[0085] Figure 29 FIG. 7 is a flowchart of another wireless communication method embodiment;

[0086] Figure 30 An example communication system is shown in accordance with example embodiments presented herein;

[0087] Figure 31A and Figure 31B An example device that can implement the methods and teachings of the present disclosure is shown;

[0088] Figure 32 A block diagram of a computing system that can be used in implementing devices and methods disclosed herein. DETAILED DESCRIPTION

[0089] The structure and use of the disclosed embodiments is discussed in detail below. It should be appreciated, however, that the disclosure provides many applicable concepts that can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative of specific structures of the embodiments and utilization, and do not limit the scope of the disclosure.

[0090] A sounding reference signal (SRS) is a reference signal transmitted by a user equipment (UE) in the uplink (UL) for enabling, for example, uplink channel estimation, sounding channel interference, etc. Based on the SRS, the network can communicate with the UE through dynamic scheduling. SRS plays a vital role in wireless communications, for example, in time division duplex (TDD) downlink (DL) full multiple-input multiple-output (MIMO) channel state information (CSI) acquisition, TDD / frequency division duplex (FDD) UL CSI acquisition, beam management, frequency selective scheduling, UL timing advance (TA) maintenance, positioning, etc.

[0091] The configuration of SRS transmission is typically semi-static, which limits the practicality of SRS. Embodiments of the present disclosure provide dynamic triggering and configuration mechanisms for SRS transmission.

[0092] In some embodiments, a user equipment (UE) can receive a downlink control information (DCI) triggering transmission of SRS of a SRS resource set. The DCI indicates a time domain resource of available time domain resources for transmission of the SRS resource set. The UE can determine the location of the time domain resource in the available time domain resources according to the DCI, e.g., the DCI includes an index of the time domain resource in the available time domain resources, and transmit the SRS according to the location of the time domain resource. In one embodiment, when the transmission of the SRS in the time domain resource collides with transmission or reception of other signals, the next time domain resource in the available time domain resources can be used for transmission of the SRS.

[0093] In some embodiments, a UE can receive control information indicating frequency resources in a carrier for transmission of one or more SRS. The UE can determine to divide the frequency resources into segments according to the control information, where each segment includes contiguous physical resource blocks (PRBs), and transmit the SRS in an orthogonal frequency division multiplexing (OFDM) symbol on a first segment but not a second segment. In one embodiment, the SRS can be repeatedly transmitted in different OFDM symbols on one or more segments. In another embodiment, the SRS can be transmitted on different segments according to a frequency hopping pattern. In 5G NR, uplink supports OFDM and single carrier frequency division multiplexing (SC-FDM). A symbol in the present disclosure can be an OFDM symbol or an SC-FDM symbol. Embodiments of the present disclosure are exemplified with OFDM symbols only. One of ordinary skill in the art will recognize that embodiments are also applicable to SC-FDM symbols.

[0094] The present embodiments enable flexible triggering of SRS transmission, and dynamic configuration of SRS resources. The embodiments also enable tighter association of SRS transmission with data transmission to be performed, and allow more accurate reflection of channel interference situation. The present embodiments can significantly reduce the impact of interference on communication, reduce SRS transmission collision, reduce SRS overhead, improve spectral efficiency (SE) of the network and individual devices overall, and improve user experience.

[0095] Figure 1 An example wireless communication system 100 is shown. The communication system 100 includes an access node 110 having a coverage area 111. The access node 110 serves a plurality of user equipments (UEs), including UE 120 and UE 122. Transmissions from the access node 110 to the UEs are referred to as downlink (DL) transmissions and occur on a downlink channel (shown as solid arrow lines in FIG. 1), while transmissions from the UEs to the access node 110 are referred to as uplink (UL) transmissions and occur on an uplink channel (shown as dashed arrow lines in FIG. 1). Figure 1 Figure 1 ​The service can be provided to multiple UEs by a service provider connected to the access node 110 through a backhaul network 130 (e.g., the Internet). The wireless communication system 100 can include multiple distributed access nodes 110.

[0096] In a typical communication system, there are several modes of operation. In a cellular mode of operation, communication with multiple UEs is through an access node 110, while in a device-to-device mode of communication, such as in a Proximity Service (ProSe) mode of operation, direct communication between UEs is possible. An access node can also be commonly referred to as a Node B, an evolved Node B (eNB), a next generation (NG) Node B (gNB), a master eNB (MeNB), a secondary eNB (SeNB), a master gNB (MgNB), a secondary gNB (SgNB), a network controller, a controlling node, a base station, an access point, a transmission point (TP), a reception point (TRP), a cell, a carrier, a macro cell, a femto cell, a pico cell, a relay, a customer premises equipment (CPE), etc. A UE can also be commonly referred to as a mobile station, a mobile device, a terminal, a user, a subscriber, a station, a communication device, a CPE, a relay, an integrated access and backhaul (IAB) relay, etc. It is noted that when using relays (relay-based, pico, CPE, etc.), and in particular when using multi-hop relays, the boundary between a controller and a node controlled by the controller can become blurred, and a two-node (e.g., a controller or a node controlled by the controller) deployment in which a first node provides configuration or control information to a second node is considered to be a controller. Likewise, the concepts of UL and DL transmission can also be extended.

[0097] A cell can include one or more bandwidth parts (BWPs) allocated for UL or DL for a UE. Each BWP can have its own BWP-specific parameters and configurations. Note that not all BWPs need to be activated for a UE at the same time. One cell can correspond to one or more carriers. Typically, one cell (e.g., a primary cell (PCell) or a secondary cell (SCell)) is a component carrier (e.g., a primary component carrier (PCC) or a secondary CC (SCC)). For certain cells, each cell can include multiple carriers in UL, one carrier is referred to as a UL carrier with an associated DL or a non-supplemental UL (non-SUL) carrier, and the other carriers are referred to as supplemental UL (SUL) carriers without an associated DL. A cell or carrier can be configured with a slot or subframe format composed of DL and UL symbols, and the cell or carrier is considered to operate in a time division duplex (TDD) mode. Typically, for unpaired spectrum, a cell or carrier is in TDD mode, and for paired spectrum, a cell or carrier is in frequency division duplex (FDD) mode. An access node can provide wireless access according to one or more wireless communication protocols, such as Long Term Evolution (LTE), LTE-Advanced (LTE-A), 5G, 5G LTE, 5G NR, 6G, High Speed Packet Access (HSPA), Wi-Fi 802.11a / b / g / n / ac, etc. For simplicity, only one access node and two UEs are shown, but it is understood that a communication system can employ multiple access nodes capable of communicating with multiple UEs.

[0098] In standard antenna element-to-element channel estimation, a channel between two devices is estimated by having a first device transmit a known signal to a second device at a known time or frequency resource, the signal received at the second device can be represented as:

[0099] y = Hx + n (1)

[0100] where y is the signal received at the second device, x is the known signal (which can be a reference signal, pilot, or pilot signal), H is the channel model or response, and n is the noise (and interference for certain communication channels). Since x is known to the second device, the second device can determine or estimate H from y.

[0101] Note that the concepts of antennas, antenna elements, and antenna ports can generally be interchangeable, but in certain specific scenarios, they can mean different but related subjects. For example, a transmit (Tx) antenna port can be formed (or virtualized) by multiple antenna elements or antennas, and a receiver sees only this one Tx antenna port, not each of the multiple antenna elements or antennas. Virtualization can be achieved, for example, through beamforming.

[0102] Figure 2An example communication system 200 is shown, providing mathematical expressions for signals transmitted in the communication system. The communication system 200 includes an access node 205 communicating with a UE 210. As Figure 2 shown, the access node 205 uses a transmit filter v and the UE 210 uses a receive filter w. Both the access node 205 and the UE 210 use linear precoding or combining. It is assumed that H is an N rx x N tx matrix of a MIMO system, i.e. with N tx transmit antennas and N rx receive antennas. The transmit filter v, of size N tx x Ns, enables the transmitter to precode or beamform the transmitted signal, where Ns is the number of layers, streams, symbols, pilots, messages or known sequences transmitted. The receive filter w of the multi-antenna system, of size N rx x Ns, represents a combining matrix. It is noted that the above description is for a transmission from the access node 205 to the UE 210, i.e. a downlink transmission. The transmission can also occur in the reverse direction (uplink), for which the channel matrix becomes H H , which is the Hermitian of the channel model H, w can be seen as a transmit filter and v as a receive filter. w for transmission and w for reception can or can not be the same, as can be the case for v.

[0103] The downlink (or forward) channel 215 between the access node 205 and the UE 210 has a channel model or response H, while the uplink (or backward, or reverse) channel 220 between the UE 210 and the access node 205 has a channel model or response H H , which is the Hermitian of the channel model H. Although Figure 2 only one access node and one UE are depicted, it is not limited to this case. Multiple UEs can be served by the access node on different time-frequency resources (e.g. FDM-TDM, as in a typical cellular system) or on the same time-frequency resources (e.g. MU-MIMO, where multiple UEs are paired together, each UE precoded individually). In paired UEs, there is intra-cell interference. There can also be multiple access nodes in the network, some of which can serve the UE 210 in a joint transmission manner (e.g. coherent joint transmission, non-coherent joint transmission, coordinated multipoint transmission, etc.), dynamic point switching manner, etc. Some other access nodes can not serve the UE 210, and their transmissions to their UEs can cause inter-cell interference to the UE 210. The scenario considered herein is a multiple access node and multiple UE scenario, where the access nodes serve the UEs and have multiple user multiple input multiple output (MU-MIMO), and the example embodiments of bidirectional training are applicable to this scenario.

[0104] In Release 17, as agreed in 3GPP TSG RAN Meeting #86, 3GPP TM The Work Item Description (WID)“Further Enhancements on NR MIMO” as specified in 3GPP

[0105] 1. SRS enhancements, for both FR1 and FR2:

[0106] - Determine and specify enhancements of aperiodic SRS triggering to facilitate more flexible triggering and / or DCI overhead / usage reduction.

[0107] - Specify SRS switching for up to 8 antennas (e.g., xTyR, x = {1, 2, 4} and y = {6, 8}).

[0108] - Evaluate and specify, if needed, the following mechanisms to enhance SRS capacity and / or coverage: SRS time bundling, increased SRS repetition, partial sounding across frequencies.

[0109] 2. Motivation for flexible triggering includes:

[0110] - Limited triggering information in DCI (only 1, 2, or 3 bits).

[0111] - Unflexible triggering delay.

[0112] - Important role of SRS in DL full-MIMO CSI acquisition, BM, UL frequency diversity, and MIMO support, etc.

[0113] - New addition: Important role of A-SRS through DL interference sounding and mitigation in TDD coordinated MIMO

[0114] - UE-to-Tx SRS based on DL (pre)scheduling results so that the gNB can estimate the DL interference and then adjust through precoder adjustment to mitigate the DL interference.

[0115] - Some similarity with DL NZP CSI-RS based interference sounding to get better MCS. This is also after scheduling and before PDSCH, but UL SRS is used to get better precoding (hence better bi-directional training (BiT or BIT)).

[0116] - Also closely related to SRS coverage / capacity enhancement.

[0117] According to one example embodiment, precoded, unprecoded, or precoded and unprecoded uplink SRS are transmitted by the UE to the access node to assist dynamic scheduling. These uplink SRS include certain transmission parameters (e.g., certain transmission ports, transmission comb, cyclic shift, transmission bandwidth (related to SRS resource), etc.) that can be configured through higher layer signaling (e.g., through radio resource control (RRC) or medium access control (MAC) control element (CE) signaling). In some cases, the uplink SRS can be unprecoded to support uplink channel estimation and assist network prescheduling. The network preschedules the UE when performing uplink channel estimation. The prescheduling of the UE can involve selecting a UE from a plurality of UEs configured by the access node, where the selected UE includes a UE that is suitable to receive (or transmit) data. Thus, the selected UE includes a subset of the plurality of UEs configured by the access node. The selected UE can be referred to as a prescheduled UE. The suitability of the UE can be determined based on channel quality, signal quality, error rate, data transmission history, quality of service constraints, etc.

[0118] The prescheduling of the UE can precede the actual scheduling of data transmission (or reception) and actual data transmission (or reception). In general, the scheduling is unpredictable. That is, the number of UEs and which subset of UEs to preschedule is unknown during the higher layer configuration. Thus, after the prescheduling, the network can decide to reconfigure the semi-statically configured SRS parameters based on the subset of UEs selected for prescheduling. Thus, there is a need for apparatus and methods that support more dynamic configuration of control signals.

[0119] Interference sounding and prescheduling can be performed by the network after the UE transmits the uplink SRS. As mentioned previously, prescheduling is the process of the access node selecting a subset of UEs that the access node has configured for data transmission or reception. The selected UEs can be used to transmit precoded SRS. These precoded SRS can be referred to as triggered SRS. The access node can use the precoded SRS to determine the downlink precoder (referred to above as transmit filter v). The prescheduling can precede the actual scheduling of data transmission (or reception) and can be performed during a training phase (e.g., during bi-directional training (BiT or BIT)) to determine the downlink precoder (and combiner).

[0120] BIT, also known as forward-backward training, is a low-complexity general distributed training procedure for training and updating transmit precoders and receive combiners without explicitly estimating CSI. BIT can be adapted to transmit beamformers in TDD MIMO communication systems, which can also be generally referred to as transmit precoders, transmit filters, spatial transmit filters, analog precoders, etc., and receive combiners (also generally referred to as receive filters, spatial receive filters, analog combiners, etc.). In BIT, the devices participating in the BIT (transmit devices or receive devices) do not have a priori knowledge of CSI, in particular detailed information about the channel, such as the channel matrix H or the covariance matrix of the channel, where the channel can be the channel between a UE and its serving access node, or the channel between a UE and its interfering access node (which typically requires exchange of information between access nodes, such as channel information or RS information about the interfering link, so that the UE or access node can estimate the interfering link). Iterative versions of BIT include forward training (e.g., in the downlink direction) and backward training (e.g., in the uplink direction), which are repeated until convergence is achieved. A single BIT includes a single forward training step and a single backward training step. BIT is able to accommodate unknown interference, can suppress interference without requiring any channel estimation or CSI feedback, and is therefore less sensitive to the orthogonality of the training sequences. More detailed discussion of BIT is given in U.S. Patent Application No. 15 / 983,692, entitled “System and Method for Communications System Training,” filed May 18, 2018, which is incorporated by reference herein in its entirety.

[0121] Uplink sounding includes estimating the uplink channel between an access node and a UE served by the access node upon receiving an uplink SRS, reflecting the interference situation of the neighbor cell.

[0122] Figure 3 A flowchart showing operations 300 performed during interference sounding is shown. Operations 300 can be indicative of operations performed during interference sounding involving an access node and one or more UEs.

[0123] Operations 300 begin with one or more UEs transmitting uplink SRS (block 305). The uplink SRS can be transmitted by active UEs configured by the access node, and can be used for uplink channel estimation of the uplink channel between the configured UEs and the access node. The uplink SRS, in addition to being used for uplink channel estimation, can also be used by the access node to select UEs for pre-scheduling. As previously described, a pre-scheduled UE is a UE selected by the access node from among its configured UEs to transmit a trigger-based uplink SRS that is used by the access node to determine a downlink precoder. In one embodiment, the uplink SRS transmitted by the one or more UEs in block 305 can be unprecoded. In one embodiment, feedback transmitted by the one or more UEs is used by the access node to select UEs for pre-scheduling, rather than using the uplink SRS. The access node performs uplink channel estimation (block 307). For example, the uplink channel is estimated using the uplink SRS transmitted by the one or more UEs. Alternatively, the uplink channel is estimated using feedback transmitted by the one or more UEs.

[0124] The access node pre-schedules the UEs (block 309). The access node can pre-schedule the UEs based on uplink SRSs or feedback received from one or more UEs. For example, the access node selects the UEs associated with uplink SRSs (or feedback) received with the highest signal quality metrics. Examples of signal quality metrics include SINR, SNR, RSRP, RSRQ, received signal power, etc. The access node can select the UEs associated with uplink SRSs received with signal quality metrics exceeding a specified threshold. The specified threshold can be specified by a technical standard, by an operator of the communication system, or by coordination between the access node and the UEs. The access node can select a specified number of UEs associated with uplink reference signals received with signal quality metrics exceeding a specified threshold. The specified number can be specified by an operator of the communication system in a technical standard, or by coordination between the access node and the UEs. For example, the access node can pre-schedule the UEs based on channel quality indicators (CQIs) of uplink channels or precoding matrix indicators (PMIs) associated with the UEs. The access node transmits downlink control information (DCI) for pre-scheduling the UEs to trigger SRS transmission with specific parameters and to assist the UEs in measuring (e.g., using) downlink ports. The downlink control information can provide the pre-scheduled UEs with SRS parameters and related downlink associations. In other words, the downlink control information configures the SRS parameters and related downlink associations. The downlink control information can indicate to the pre-scheduled UEs which downlink CSI-RSs are assigned to the pre-scheduled UEs for proper measurement and determination of downlink combiners and / or uplink precoders. In one embodiment, the DCI can be group-based DCI addressed to a group of UEs (e.g., all active UEs or a subset of active UEs). In another embodiment, the DCI can be unicast DCI (e.g., 5G NR DCI) addressed to a UE. The DCI (in either case) includes modified or added fields that indicate the SRS parameters. The access node can transmit CSI-RSs (block 311). The CSI-RSs (if any are to be transmitted by the access node) can be transmitted with precoding or without precoding. The UEs can perform downlink channel estimation (block 313). In the case that the access node transmits CSI-RSs, the UEs perform downlink channel estimation based on the received CSI-RSs. In one embodiment, only the UEs that receive the downlink control signal (i.e., the pre-scheduled UEs) perform downlink channel estimation.

[0125] The pre-scheduled UE transmits triggered uplink SRS (block 315). The pre-scheduled UE transmits uplink SRS according to the configuration of the downlink control signal. In one embodiment, the uplink SRS can be precoded or unprecoded (where no information is contained). The uplink SRS is transmitted according to the SRS configuration. For example, the pre-scheduled UE transmits its uplink SRS in the configured SRS resource, through the configured transmission port, using the configured sub-band, comb and cyclic shift, and using the configured transmission bandwidth, as configured by the downlink control signal.

[0126] The SRS configuration can include configuration of SRS parameters. Configuration of SRS parameters, such as SRS resource set (SRS resources within the set), SRS transmission bandwidth, SRS transmission port, SRS transmission comb and cyclic shift, etc., can be performed using higher layer configuration. The SRS resource set can include one or more SRS resources, the SRS resource set is triggered as a whole. The SRS resource can specify one or more parameters of SRS transmission, such as port number, RE to be used for transmitting SRS, sequence to be used for SRS, whether SRS is aperiodic or periodic or semi-persistent, associated DL signal of SRS, etc. TS 38.214 v16.5.0 (2021-04), incorporated by reference, specifies SRS parameters configured by higher layer parameters SRS-Resource or SRS-PosResource and SRS-ResourceSet. TS 38.331 v16.4.1 (2021-04), incorporated by reference, specifies SRS-Resource and SRS-ResourceSet information elements. The arrangement of SRS resources or ports can be defined by the network, which can configure the UE with different arrangements. In addition, the network can configure different mappings (e.g., relationships, associations) between downlink ports, layers, reference signals (such as DMRS, CSI-RS) and uplink ports or layers (SRS) for the UE.

[0127] One key to support BiT and various SRS enhancements is to improve the flexibility of aperiodic SRS (A-SRS, A SRS, AP-SRS, or AP SRS) triggering, in addition to the BiT related motivation, at least including the following motivations. That is, the flexible A-SRS triggering can be designed and used beyond the BiT application. For example, the design to support BiT can also be used for the special case of Zero Forcing (ZF) without any inter-cell cooperation, such as semi-static coordination. A-SRS can be used to probe the DL channel / interference of paired UEs within a cell. That is, a UE transmits A-SRS on the PRBs indicated by the network for PDSCH, and the network adjusts the PDSCH precoding based on these partial bandwidth A-SRS instead of the persistent / semi-persistent SRS (P / SP SRS, or P / SP-SRS), which is periodically sent by a UE to cover the entire wideband with a longer period in a typical ZF scheme. The conventional ZF is generally based on P / SP SRS. The SRS has to cover the wideband (with or without frequency hopping), and all active UEs have to be probed. Therefore, the period of P / SP SRS cannot be small for all UEs, otherwise the SRS would cause a huge overhead. In fact, when the inter-cell interference (or the covariance matrix of inter-cell interference) is ignored, the above scheme simplifies to a single-cell massive MIMO, i.e., ZF, but the probing for ZF is based on A-SRS, whose frequency domain resources, ports, and beamforming are tied to PDSCH. Only the UEs scheduled with PDSCH in the next few Transmission Time Intervals (TTIs) will transmit A-SRS. The A-SRS PRB, port, and beamforming are the same as the intended PDSCH. The A-SRS is used by the network to adjust the ZF precoder for PDSCH. Therefore, the aging of A-SRS does not exceed a few TTIs, which guarantees a high precision of precoding / beamforming, thus achieving a high spectral efficiency (SE). With these A-SRS, the P / SP SRS period can be increased, thus reducing the overall SRS overhead. Therefore, the A-SRS based ZF has downlink interference probing without any inter-cell coordination, thus outperforming the P / SP-SRS based ZF in terms of beamforming precision, interference suppression, and overhead reduction. The key standard component needed to support this enhancement is still the flexible A-SRS triggering, similar to BiT.

[0128] The triggering information in the existing DCI is limited (only 1, 2, or 3 bits):

[0129] SRS transmission is associated with many parameters, such as comb, cyclic shift, transmission bandwidth expressed in number of PRBs on UL or SUL with serving cell, antenna port, etc. In existing standards, A-SRS can be triggered by SRS request field in DCI, which can include 1, 2, or 3 bits. These bits can indicate: 1) certain SRS resource set(s) on the current serving cell, or 2) certain SRS resource set(s) on the serving cell, or 3) one of UL and SUL. However, many other SRS transmission parameters cannot be indicated in DCI, only specified in RRC configuration signaling. For example, due to DCI bit-width limitation, the network can have to configure several SRS resource sets together, or several serving cells together, i.e. these sets have to be triggered together, which is very undesirable. In general, the limited triggering information leads to lack of flexibility for many applications, as described below, and thus its motivation is to improve A-SRS triggering flexibility.

[0130] Lack of flexibility for triggering offset (delay):

[0131] In existing standards, A-SRS triggering offset is configured by RRC field slotOffset of 1 ~ 32 slots, if this field is not configured, 0 slot offset is applied. Figure 4 For the figure of time slots 400, the existing SRS triggering and transmission scheme is highlighted. In this example, the A-SRS triggering offset configured for the UE by RRC signaling is 4. The gNB can send a DCI at time slot 402 to trigger the transmission of SRS by the UE. According to the A-SRS triggering offset, the UE is to transmit the SRS at time slot 404, which is 4 slots after time slot 402.

[0132] In some cases, this can be restrictive. For example, when using group common (GC) DCI format 2_3 to trigger SRS on one or more serving cells for a group of UEs, all SRS transmissions will occur after their preconfigured offset from the same DCI triggering time slot. For example, all SRS transmissions will be performed 4 slots after the DCI triggering time slot. This can impose a significant restriction on the time slot in which the network decides to send the GC DCI. For another example, SRS triggering by DL DCI can collide with acknowledgement / non-acknowledgement (A / N) associated with the DL DCI, and SRS triggering by UL DCI can collide with PUSCH associated with the UL DCI, especially in TDD when UL slots are less frequent. In general, the main purpose of A-SRS triggering is to provide flexibility in SRS timing, but the predetermined timeline in the triggering offset and mostly fixed slot structure does not work well for this purpose. Enhancements are needed. For another example, if the SRS transmission in time slot 404 collides with transmission or reception of another signal, the UE can not be able to transmit the SRS even if the UE is triggered to transmit the SRS. In addition, existing schemes limit the use of SRS transmissions to other available time slots. For example, since the UE can only transmit SRS in time slots configured based on the fixed A-SRS triggering offset, the UE cannot use time slot 408 to transmit SRS even if there is another time slot available for SRS transmission, e.g., time slot 408 (uplink slot). In addition, existing schemes limit the selection of available time slots for SRS triggering. For example, time slot 406 (downlink slot) can be used for downlink transmission, but time slot 406 cannot be used to trigger SRS transmission because 4 slots after time slot 406 (i.e., time slot 410) is not an uplink slot and cannot be used to transmit SRS according to the fixed A-SRS triggering offset.

[0133] Various important roles of A-SRS:

[0134] A-SRS plays a vital role in TDD DL full-MIMO CSI acquisition, TDD / FDD UL CSI acquisition, FR2 beam management, frequency-selective scheduling, UL timing advance (TA) maintenance, positioning, etc. It is also vital for FDD DL performance. However, the lack of flexibility in the above SRS triggering limits the practicality of SRS. For example, if SRS is dropped due to collision caused by inflexible triggering offset, CSI acquisition and frequency-selective scheduling can be impacted. Note that CSI acquisition and frequency-selective scheduling can be highly dynamic, thus P / SP-SRS is not suitable. In LTE Rel-14 SRS carrier switching, autonomous A-SRS retransmission is introduced, such that dropped A-SRS (i.e., colliding with A / N) triggered by DL DCI will be autonomously retransmitted at the next configured SRS transmission occasion, but 5G NR does not support this feature yet. To make P / SP-SRS and A-SRS complement each other well, P / SP-SRS can be configured with long periodicity (to avoid excessive overhead and excessive complexity), and the network relies on A-SRS for fast response to traffic load and CSI (especially dynamic interference). Therefore, due to the various important roles played by A-SRS, flexible A-SRS triggering is beneficial in many cases and should be supported.

[0135] Closely related to SRS capacity / coverage enhancement:

[0136] SRS coverage / capacity enhancement can include, but is not limited to: 1) enhancing SRS capacity by SRS on partial bandwidth, where the bandwidth can be dynamically indicated by DCI; 2) enhancing SRS capacity by SRS on PRBs / symbols not used in PUSCH / PDSCH region, where the SRS time-frequency resources can be dynamically indicated by DCI based on the unused resources of the TTI; 3) enhancing SRS capacity by multiplexing (on the same symbol) SRS with other signals (e.g., A / N) to accommodate flexible SRS multiplexing to maximize SRS capacity; 4) enhancing SRS coverage by narrowband transmission based on frequency selectivity (rather than pre-configured PRBs), etc. Some enhancements are also applicable to P / SP-SRS, however, especially for capacity enhancement, SRS needs to have sufficient flexibility, e.g., when the network identifies that A-SRS has the opportunity to fill in the gaps of time-frequency resources (e.g., unoccupied symbols in a slot, some unoccupied PRBs, etc.), it can trigger the UE to perform A-SRS. Therefore, flexible triggering of A-SRS is also useful for SRS capacity / coverage enhancement.

[0137] To effectively convey information about dynamic interference conditions to the network, the gNB can indicate how the UE transmits the SRS, including time / frequency resource allocation and port selection of the SRS corresponding to the intended PDSCH. This means that the network needs to dynamically adjust more SRS transmission parameters (such as PRB allocation, port selection) than traditional SRS transmission. Embodiments are provided for SRS transmission, the parameters of which are bound to DL transmission, including PRB allocation, time domain resource allocation, and port allocation.

[0138] One embodiment is for A-SRS PRB / port allocation indication. The SRS PRB / port allocation can be the same as the intended PDSCH, and can be dynamically indicated.

[0139] One embodiment is for A-SRS beamforming indication. The SRS beamforming can be based on DL channel measurement resources (CMR), and to better reflect the potential DL interference, it is more desirable to be based on DL CMR and IMR, one or both of which can be dynamically indicated. One embodiment is for A-SRS trigger offset. To utilize A-SRS to estimate interference, to mitigate interference by precoding adjustment, the gNB does not need to detect the SRS sequence of each UE. The accumulated received SRS power on each gNB receive antenna port should be sufficient. Therefore, A-SRS can be transmitted on overlapping resources to reduce overhead. However, the A-SRS trigger can be sent to different UEs at different times. To enable A-SRS overlap, the A-SRS trigger offset can be dynamically indicated to different UEs. The trigger offset can be similar to the k0 and start and length indicator (SLIV) (i.e., time domain resource allocation (TDRA)) design of PDSCH. To further reduce overhead, k0 and start and length indicator (SLIV) can not refer to absolute slot / symbol offset, but to slot / symbol offset based on configured SRS slot / symbol. The TDRA overhead can be further reduced, for example, instead of indicating the slot, only the symbol is indicated. The TDRA of SRS can be omitted in DCI and based on RRC / MAC.

[0140] The time domain resources that can be used by A-SRS will be clarified below. According to the time domain resources that can be used by A-SRS, the design and indication of the trigger offset are discussed.

[0141] The time-domain resources that can be used by A-SRS with flexible triggering can be defined to avoid potential ambiguity. For example, one example suggests that A-SRS transmission can be delayed to the next “available” slot, but error can occur if the network and the UE have different interpretations of “available” slot. The possible A-SRS time-domain resources can include time-domain resources that do not exclude SRS transmission, such as all slots and orthogonal frequency-division multiplexing (OFDM) symbols that are not configured by RRC configuration as DL. In other words, the possible A-SRS time-domain resources can be a set of potential A-SRS transmission opportunities in time domain. For example, all slots and OFDM symbols that are for UL or flexible according to TDD-UL-DL-ConfigCommon or TDD-UL-DL-ConfigDedicated can be considered as possible A-SRS time-domain resources. For another example, all slots and OFDM symbols, regardless of whether they are configured as DL, UL, or flexible, can be considered as possible A-SRS time-domain resources. The advantage of the former approach is, for example, reduced overhead of triggering offset indication (as the indication can need to refer to a subset of slots / symbols, rather than all slots / symbols), but its major disadvantage is that it can be complicated to determine whether a slot / symbol is DL, UL, or flexible, and it can change over time, which can lead to confusion. On the other hand, the latter approach can need more bits to cover the same time duration, or the same bits but cover a shorter time duration, but it greatly simplifies the design. The latter approach does not create ambiguity if the transmission direction of a slot / symbol is overridden by DCI. The latter approach provides the same A-SRS time-domain resources for FDD and TDD, which is advantageous for the case of aggregation for both FDD and TDD. The latter approach can also make some unused DL slots / symbols potentially available for A-SRS with appropriate UL / DL switching gap, which further improves the triggering flexibility of A-SRS. Therefore, in one embodiment, all slots / symbols can be designated as possible A-SRS time-domain resources. For either approach, if the parameter changes between the received DCI and the A-SRS transmission, the A-SRS will be discarded.

[0142] As used herein, the possible A-SRS time-domain resources can also be referred to as available time-domain resources for transmission of SRS of A-SRS, or available time-domain resources for SRS transmission of A-SRS, or available time-domain resources for A-SRS. As used herein, SRS of A-SRS refers to SRS in the aperiodic SRS resource set. In the art, A-SRS generally refers to the aperiodic SRS resource set. Other terms can be used without departing from the spirit and principles of the disclosure, such as valid time-domain resources for transmission of SRS, or acceptable time-domain resources for transmission of SRS. It is also noted that when referring to SRS, “transmission of SRS” and “transmission of SRS resource” can also be used.

[0143] When explicit or implicit indication is assigned to time-domain resources of flexible A-SRS, resource allocation granularity can also be defined. For example, the resource indication in DCI can be slot-based, in which case the OFDM symbols to be used by A-SRS are based on RRC configuration, i.e., the DCI can flexibly indicate in which slot A-SRS will be transmitted (e.g., 2 slots later than the current DCI slot), but no symbol information is provided (e.g., provided in RRC to reduce DCI overhead). For another example, the DCI indication can be mini-slot (non-slot) based, e.g., on the 5th mini-slot of the 2nd slot after the current DCI slot, or on the 10th mini-slot after the current DCI mini-slot. This can be particularly useful for ultra-reliable low-latency communication (URLC) which already works with mini-slots. For yet another example, the DCI indication can be OFDM symbol based, e.g., on the 10th symbol of the 2nd slot after the current DCI slot, or on the 20th symbol after the current DCI symbol. Generally, finer granularity requires higher indication overhead, but also provides higher flexibility.

[0144] In some embodiments, the reference time (starting point) of the SRS trigger offset can be clarified. The reference time is the point used to start the calculation of the SRS trigger offset. One approach is to define the starting point according to the current DCI slot / minislot / symbol in which the DCI is transmitted to trigger the SRS transmission. It is noted that the reference time granularity should generally be consistent with the A-SRS time domain resource allocation granularity. Other approaches can also be considered, e.g., relative to the current DCI slot plus a slot offset (if already configured by RRC), or relative to the next flexible / UL slot / symbol. If the granularity is slot, the current DCI slot is considered as the reference time (slot 0) of the A-SRS trigger offset. In this case, the reference time can also be referred to as the reference slot. If the granularity is minislot, the minislot immediately after the current DCI minislot is considered as the reference time (minislot 0) of the A-SRS trigger offset. If the granularity is symbol, the symbol immediately after the last symbol of the current DCI is considered as the reference time (symbol 0) of the A-SRS trigger offset. If the A-SRS is used for CSI acquisition of a specific UL / DL data transmission (for URLLC, etc.), the A-SRS time can be relative to the associated data transmission (before that). In general, this design can be easily extended to the case where the trigger offset is relative to a reference timing, and the reference timing can be specified in the standard, RRC configuration, MAC signaling, or a DCI field (e.g., indicating slot / symbol).

[0145] Therefore, the following designs and any combination thereof can also be used for A-SRS:

[0146] Flexible A-SRS time domain resource

[0147] • Option A1: on all slots / OFDM symbols not configured for DL in TDD-UL-DL-ConfigCommon or TDD-UL-DL-ConfigDedicated

[0148] • Option A2: on all slots / OFDM symbols

[0149] Flexible A-SRS time domain resource allocation. The allocation granularity can be:

[0150] • Option B1: based on slot

[0151] • Option B2: based on slot, is minislot

[0152] • Option B3: based on slot and OFDM symbol

[0153] Flexible reference time of SRS trigger offset.

[0154] • Option C1: The reference time is based on the slot / minislot of the current DCI. When the granularity is slot, the current DCI slot can be considered as the reference time (slot 0) for the A-SRS time-domain resource and the trigger offset. When the granularity is minislot, the minislot immediately after the current DCI minislot can be considered as the reference time (minislot 0) for the A-SRS trigger offset reference point.

[0155] • Option C2: If the reference point is based on symbol, the symbol immediately after the last symbol of the current DCI can be considered as the reference point.

[0156] • If the A-SRS is for CSI acquisition of a specific UL / DL data transmission, the A-SRS time can be relative to (e.g., before) the associated data transmission (for URLLC, etc.). If the A-SRS is joint with data, the slot before the data with UL symbol available for SRS can be the reference time. In some cases, these can require negative A-SRS trigger offset.

[0157] • Option C3: The reference point is based on the next UL / flexible slot / symbol.

[0158] When combining different options, some consistency should be adopted in general. For example, if considering symbol-based option A2, symbol-based option B3 should be used, and symbol-based option C3 should be used. Similarly, they can all be based on minislot, slot, etc.

[0159] With the above clarifications, we can proceed with the A-SRS trigger offset indication design. We provide the following example proposals for indicating the A-SRS trigger offset. The following embodiments are described with slot-based time resource granularity. Other granularities can also be easily used for those skilled in the art.

[0160] - Proposal 1: Delay the SRS transmission to the available slot after the trigger offset defined in the current specification according to the parameter slotoffset (see TS 38.214 v16.5.0 (2021-04), TS 38.331 v16.4.1 (2021-04)), including possible redefinition of the trigger offset.

[0161] There are at least several cases where it would be useful to delay SRS transmission to the next transmission opportunity (e.g., the next available time-domain resource for SRS transmission). In the existing design, when SRS is triggered for a group of UEs on their one or more serving cells using group-common (GC) DCI format 2_3, all SRS transmissions will occur after their pre-configured offset with respect to the same DCI triggering slot. This can impose significant restrictions on the slot in which the network decides to send the GC DCI. For example, SRS triggering by DL DCI can collide with A / N associated with the DL DCI, and SRS triggering by UL DCI can collide with PUSCH associated with the UL DCI, especially in TDD when UL slots are less frequent. In LTE Rel-14 SRS carrier switching, autonomous A-SRS retransmission is introduced so that dropped A-SRS (i.e., colliding with A / N) triggered by DL DCI will be retransmitted autonomously at the next configured SRS transmission occasion. Along this line, design can provide more opportunities for dropped A-SRS to be transmitted later. In the context of specifying A-SRS time-domain resource and granularity, A-SRS colliding with another transmission can be autonomously delayed to the nth transmission opportunity, e.g., the nth slot / minislot / symbol within the A-SRS time-domain resource, n > 0, if the resource on the nth transmission opportunity is not occupied by other transmissions of the same or higher priority, then the A-SRS can be transmitted there, but if the resource is occupied by other transmissions of higher priority, then the A-SRS should not be transmitted there (possibly further delayed or dropped). Some rules can be specified to drop the A-SRS, e.g., maximum duration in terms of milliseconds or slots, maximum number of delay operations (i.e., trials) before a certain slot (e.g., before the next slot, which is the intra-slot delay for low latency purpose), etc.

[0162] Closely related to this issue is the priority of flexible A-SRS. At least in some cases, A-SRS can be treated with higher priority and should not be dropped in the first place. The higher priority can be explicitly assigned by the network with a priority flag, or implicitly assigned in the case that A-SRS is associated with URLLC transmission or certain data transmission (e.g., A-SRS is used for interference sounding for certain data transmission, rather than general CSI acquisition purpose).

[0163] For the redefinition of the triggering offset, several options can be considered, which can also depend on how the A-SRS time domain resource is specified. The triggering offset can be indicated as a slot offset and a symbol position, similar to the k0 and SLIV design for PDSCH or the k2 and SLIV design for PUSCH. To further reduce the overhead, k0, k2 and SLIV can not refer to absolute slot / symbol offsets, but to slot / symbol offsets within the A-SRS time domain resource. If the indicated A-SRS symbol length is larger than the RRC configured A-SRS symbol length, the A-SRS can be repeated, hopped or split in time domain to fill the indicated symbol. More details on the splitting will be provided below. If the indicated symbol length crosses the slot boundary, the indicated A-SRS symbol can also cross the slot boundary and enter the next slot, similar to the existing PUSCH design. If the parameters change across the slot boundary, the A-SRS on the next slot can be cancelled. In general, the A-SRS triggering offset can be indicated reusing / enhancing the UL / DL TDRA field design.

[0164] Proposal 2: Explicit or implicit indication of the triggering offset in DCI

[0165] For the explicit indication of the triggering offset, a triggering offset field can be added in the A-SRS triggering DCI, or more generally, the UL / DL TDRA field can be reused or enhanced for A-SRS.

[0166] The implicit trigger offset can be the next SRS transmission opportunity within the A-SRS time domain resource, e.g., the available time resource such as the slot in which SRS can be transmitted. That is, the UE can autonomously find the next block in the A-SRS time domain resource that is available for transmitting all configured or indicated A-SRS symbols. This design can be considered as autonomous delaying and combined with the explicit trigger offset method. For example, if the SRS TDRA field is missing or the symbol indicated by SRS TDRA is occupied, the UE will autonomously find the next available opportunity to transmit SRS. This mode of operation can be enabled / disabled by a flag in RRC (similar to the design of LTE Rel-14 soundingRS-FlexibleTiming configuration) or in DCI. The UE can start searching from the slot carrying the DCI, but if a slot offset value is configured in RRC and / or indicated by DCI, the UE can start searching from the slot with the configured / indicated offset. In one embodiment, if the reference slot (based on the slot carrying the DCI, optionally also the RRC configured slot offset; see other embodiments below) is slot n, and the DCI indicates a slot offset t, the UE starts searching from slot n + t. If slot n + t is an available slot for the indicated A-SRS (see other embodiments below), the UE transmits A-SRS in that slot. However, when slot n + t is not an available slot for A-SRS, if autonomous delaying is configured / activated in the case of a conflict that results in A-SRS not being able to be sent in slot n + t, the UE will start searching from slot n + t for the next available slot and transmit in the next available slot. The search can extend up to k slots, i.e., up to slot n + t + k, and if the UE does not find an available slot, the A-SRS is dropped. Note that a conflict occurs if the symbol in the slot that SRS is supposed to occupy is occupied by other higher priority transmission / reception, so SRS cannot be sent.

[0167] An embodiment is provided for assigning higher priority to A-SRS with newly introduced flexibility. A-SRS with at least one parameter newly introduced in the SRS request field in this application to support BiT and other enhanced A-SRS can be assigned higher priority so that when it conflicts with other SRS / UL transmissions, the other transmissions are dropped.

[0168] In some embodiments, reference slot design and available slot design are provided. The reference slot is the slot in which the UE / gNB starts counting for the slot offset value. A given aperiodic SRS resource set is transmitted in the (t+1)th available slot starting from the reference slot, where t is indicated by DCI or RRC, and the candidate values of t include at least 0.

[0169] There can be two options for the reference slot:

[0170] • Option 1: The reference slot is the slot of the triggering DCI.

[0171] • Option 2: The reference slot is the slot indicated by a legacy triggering offset.

[0172] Option 1 and Option 2 have their own pros and cons. Since the A-SRS resource set is only transmitted after the reference slot, for example, if the configured legacy RRC slot offset value is 4, Option 2 can only trigger A-SRS after 4 slots. Therefore, if the network wants to trigger A-SRS after 2 slots (e.g., the UL slot occurs after 2 slots), only Option 1 can meet the requirement. In this sense, Option 1 is more flexible than Option 2. On the other hand, for the non-zero slot offset value configured by RRC, Option 2 can allow the UE to have more time to prepare A-SRS transmission, and can allow the network to trigger A-SRS at a later time in the future with the same DCI overhead than Option 1. Comparing the pros and cons, Option 1 is more suitable because the enhancement for SRS in Rel-17 is to improve the triggering flexibility.

[0173] The existing minimum triggering offset and UE capability for the minimum offset must be considered. According to the existing standard, the minimum time interval between the last symbol of the PDCCH triggering the aperiodic SRS transmission and the first symbol of the SRS resource is N2(or N2+14) symbols and an additional duration T switch , where N2in symbols is determined according to UE processing capability, and T switch represents the uplink switching gap. These requirements defined in the existing standard can be considered when specifying the enhancement, or can be considered by gNB implementation by gNB.

[0174] Regarding the above "in the (t+1)th available slot", this can be interpreted as counting "the first available slot", "the second available slot", until "the (t+1)th available slot". In other words, only the slot resources that can potentially be used for SRS, including UL slots and flexible slots, can be counted. Alternatively, it can be interpreted as counting "the first slot", "the second slot", until "the (t+1)th slot", if the "the (t+1)th slot" is available, then the A-SRS resource set is transmitted. Therefore, a given aperiodic SRS resource set is transmitted in the (t+1)th slot, which is counted from the reference slot if it is an available slot.

[0175] For the definition of "available slot", it is also useful to consider that having contiguous slots with contiguous symbols available for SRS transmission, instead of restricting the symbols to be within one slot. If this is supported, it is more likely to accommodate SRS transmission without collision. Thus, in one embodiment, the following definition of "available slot" can be adopted:

[0176] Based on RRC configuration only, an "available slot" is a slot that satisfies the following: in one or contiguous slots of all SRS resources in a resource set, there are available contiguous UL and / or flexible symbols in the configured / indicated time domain locations, and it satisfies the minimum timing requirement between the triggering PDCCH and all SRS resources in the resource set.

[0177] RRC configuration configures different number of slot offset values. For positioning related SRS, a resource set is configured with multiple slot offset values by RRC, i.e., slot level offset is defined for each SRS resource in the resource set by higher layer parameter slotOffset. But for all other SRS, a resource set is configured with only one slot offset value by RRC. The description of available slot above can be further extended as: a given aperiodic SRS resource within a given aperiodic SRS resource set is transmitted in the (t+1)th available slot counting from the reference slot, where t is indicated by DCI or RRC, candidate values of t include at least 0, and only based on RRC configuration, an “available slot” is a slot that satisfies: in one or contiguous slots of all SRS resources in the resource set, there are available contiguous UL and / or flexible symbols in the configured / indicated time domain location, and it satisfies the minimum timing requirement between the triggering PDCCH and all SRS resources in the resource set. Some other embodiments are provided here. If an SRS resource set is associated with different slot offsets for different resources, multiple available slots can be used for the SRS resource set. In one embodiment, the relative timing relationship between resources configured by slot offset is maintained in the available slot, e.g., if the slot offset makes resource 2 3 slots later than resource 1, the available slot for a set of n resources should satisfy that in n single or contiguous slot sets of all SRS resources in the resource set, there are available contiguous UL and / or flexible symbols in the configured / indicated time domain location, and satisfy the minimum timing requirement between the triggering PDCCH and all SRS resources in the resource set, and n resources are located on the slots (only count for the first slot in each set), the relative slot offset is the same as the configured slot offset. This embodiment can be quite complex, and if one resource cannot fit, the whole set must be discarded or delayed. In another embodiment, each resource in the set is processed independently to be sent on the available slot, and there is no limit to their relative timing. If one resource cannot accommodate the slot n+t associated with this resource, it can be discarded or delayed according to the configuration, but other resources are not affected.

[0178] Figure 5For a diagram of a slot 500 according to embodiments of the application, SRS triggering and transmission are highlighted. A gNB can transmit a DCI in slot 502 to trigger transmission of a set of A-SRS resources by a UE. If no A-SRS triggering offset is configured for the UE, the reference slot (slot 0) used to determine the available time-domain resources for SRS transmission can be the slot 502 in which the DCI is transmitted. If the minimum timing requirement between the triggering DCI in slot 502 and all SRS resources is 0-2 slots (i.e., the SRS cannot be transmitted 0-2 slots after the DCI), the available time-domain resources for SRS transmission after 0-2 slots (i.e., in this example, the available slots) can include slots 504, 506, 508, and 510. Each of these slots can be used by the UE to transmit SRS. Slots 504, 506, 508, and 510 can be labeled / indexed as available slots 1-4. The DCI can indicate which of the available slots 1-4 the UE can use for SRS transmission. For example, the DCI can indicate the index / number of the slot in the available slots that the UE is to use to transmit SRS, e.g., number 2. The UE, upon being triggered by the DCI, can determine the location of the indicated slot (i.e., slot 506) based on the index / number and the available slots, and transmit SRS in the determined slot 506. In one embodiment, if slot 506 is occupied by another transmission / reception, the UE can look for the next time-domain resource in the available time-domain resources, i.e., slot 508 (slot number 3), and transmit SRS in slot 508. If the transmission of SRS has a higher priority than the other transmission / reception, the UE can transmit SRS in slot 506 without regard to the other transmission / reception.

[0179] In the case where an A-SRS triggering offset (e.g., 4) is configured for the UE, the UE can determine the reference slot from the A-SRS triggering offset and the slot in which the DCI is transmitted, in which case the reference slot will be slot 506, and the available time-domain resources for SRS transmission can include slots 508, 510, 512, and 514. Similarly, these four slots can be numbered as slots 1-4. The DCI can indicate the index / number of the slot in the available slots that the UE is to use to transmit SRS, e.g., number 2. The UE, upon being triggered by the DCI, can determine the location of the indicated slot (i.e., slot 510) based on the indicated index / number and the available slots, and transmit SRS in the determined slot 510. Note that alternatively, the offset numbered 1-4 can map to 0-3. This example shows only D slots and U slots; in general, certain slots can be configured with downlink OFDM symbols at the beginning portion of the slot and uplink OFDM / SC-FDM symbols, and each of these slots can still be an available time-domain resource for A-SRS if A-SRS is possible to be transmitted on the slot.

[0180] In one embodiment, after receiving the uplink SRS, the access node pre-schedules the UE and signals to the pre-scheduled UE through signaling which of the following are allocated to it: which part of the SRS transmission bandwidth, which SRS resources or ports from different SRS resource or port arrangements, transmission comb, cyclic shift, and which of the downlink CSI-RS ports (and / or DMRS). In addition to the listed parameters, the indication communicated to the pre-scheduled UE can also include an association (e.g., mapping, relationship) between the uplink ports, downlink ports, or bandwidth. The downlink ports can be composed of DMRS and / or CSI-RS ports. In one embodiment, the network uses a group DCI message to dynamically configure the SRS parameters. In another embodiment, a unicast DCI message is used to dynamically configure the SRS parameters. The SRS transmitted by the pre-scheduled UE can be referred to as triggered SRS to distinguish them from the uplink SRS transmitted by the UE for uplink channel estimation, for example, in Figure 3 In block 305 of FIG. 3. The uplink reference signals (e.g., SRS) are used to convey the interference situation in the neighbor cells, as well as the UE's interference mitigation receiver capability description to the serving access node. Subsequently, the access node determines the downlink precoder (e.g., from the received precoded SRS (i.e., triggered SRS)) and transmits the downlink data with the downlink precoder.

[0181] More details will be provided below regarding the indication of the SRS transmission parameters.

[0182] Regarding the indication of the SRS resources or ports, the network indicates to the UE which of the SRS resources or ports are allocated to the UE. In other words, the UE needs to know which resource in the pool of SRS resources or subset of SRS configured resources to transmit on the uplink.

[0183] In one embodiment, the network configures different arrangements of resources or ports for the UE. For example, different arrangements of resources or ports can differ in cyclic shift, transmission comb, number of symbols (e.g., orthogonal frequency division multiplexing (OFDM) symbols), etc. Different arrangements represent different mechanisms by which the network can pack the UE's SRS resources or ports. In one embodiment, the different resource or port arrangements are predefined. The overhead needed to indicate the predefined arrangement of resources or ports can be less than indicating different values of cyclic shift, transmission comb, number of symbols (e.g., OFDM symbols), etc. For example, if there are 8 predefined arrangements, indicating any one of the 8 can be done by indicating a 3-bit index, while the overhead needed to indicate different values can be much more than 3 bits. The predefined arrangements can be defined in the 3GPP standards and / or higher layers of configuration, the network can downsize (further select and indicate) the size of the particular configuration after pre-scheduling (or scheduling), and can indicate the downsized arrangement to the UE using DCI.

[0184] As an illustrative example of SRS resource or port signaling, consider a communication system with 8 Type 1 Demodulation Reference Signal (DMRS) ports. In an embodiment, 12 DMRS ports can be used as an illustrative example. 8 uplink SRS resources (e.g., ports) are provided for all UEs operating within a single cell, and 8 UEs are prescheduled. The UEs need to know which of the 8 uplink SRS resources to transmit on. Thus, there is a need to indicate to the UEs in an efficient manner in an attempt to inform the UEs which uplink SRS resource(s) to use, minimizing the impact on overall communication system performance. Informing the UEs which uplink SRS resources to use can involve indicating which comb, symbol, cyclic shift, number of OFDM symbols, etc. to use. As previously mentioned, in one embodiment, the UEs can be configured with different arrangements of these SRS resources or ports. For example, the arrangements can be specified by an operator of the communication system in a technical standard, or determined through coordination between the communication devices. Example arrangements include:

[0185] - 1 physical resource with 8 ports for 8 UEs, cyclic shift of 8 (for orthogonality between ports), and comb of 2;

[0186] - 1 physical resource with 8 ports for 8 UEs, cyclic shift of 8, and comb of 4;

[0187] - 8 physical resources with 1 port for each of the 8 UEs;

[0188] - 2 physical resources with 4 ports each, using cyclic shift 4.

[0189] In a first example embodiment, there is 1 physical resource with 8 ports for 8 UEs served within a cell, cyclic shift of 8 (to ensure orthogonality of SRS transmissions), comb of 2, and repeated over a specified number of symbols (e.g., the specified number of symbols can be specified by an operator of the communication system in a technical standard, or determined through coordination between the communication devices). To indicate to the UEs which of the 8 resources to use, a 3-bit indication is sufficient.

[0190] In a second example embodiment, there is 1 physical resource with 8 ports for 8 UEs operating within a cell, cyclic shift of 8, and comb of 4. To indicate to the UEs which of the 8 resources to use, a 3-bit indication is sufficient.

[0191] In a third example embodiment, for each UE operating within a cell, there are 8 physical resources with 1 port each, and OFDM symbol multiplexing. To indicate to the UEs which of the 8 resources to use, a 3-bit indication is sufficient.

[0192] In a fourth example embodiment, for each UE operating within a cell, there are 2 physical resources, each with 4 ports, and a cyclic shift of 4. In order to indicate to the UE which of the 8 resources to use, if certain UEs are allocated multiple ports, for example, a UE can be allocated 2 ports, a 4-bit indication is sufficient.

[0193] These different resource or port arrangements can be predefined, and the network can configure the UE with different arrangements. The network can use DCI to indicate one or more of these arrangements for a subset of (pre-scheduled, scheduled, active) UEs.

[0194] The examples given above are just examples of resource configurations, and the actual configuration can not be limited to the above. In this case, the network can use a certain number of bits (e.g., 3 to 4 bits) in the DCI to indicate to the UE which of the arrangements of resources or ports it is allocated (implicit indication of transmission layer, comb, and cyclic shift).

[0195] In one embodiment, the network can define a complete set of SRS resources / ports and use an indication to indicate a subset. Such a design is similar to the DMRS port indication in 5G NR. In another embodiment, the network can define a subset of SRS resources / ports and use an indication to indicate a subset from the configured subset. In any of these embodiments, a table can be used to summarize all possible resource sets / subsets, where the ports (rank) can be bound to cyclic shift, comb, OFDM symbol, offset.

[0196] The network can define a DCI bit indication, which can have a one-to-one mapping to the port indication for SRS, which can be bound to cyclic shift, comb, offset, OFDM symbol. The value indicated in the DCI will map to the ports that can be used for SRS transmission. In one embodiment, one port can be used, e.g., port 0. In another embodiment, multiple ports can be used, e.g., two ports can be used for SRS transmission. This field can be referred to as the number of antenna ports and layers for SRS, and a fixed number of bits can be used in the DCI to indicate it.

[0197] In another embodiment, an access node transmits configuration information for a plurality of SRS resources to a user equipment (UE). The configuration information includes a plurality of SRS resource sets for the UE, each SRS resource set including one or more SRS resources. The access node then transmits an indication of one of the plurality of SRS resource sets to the UE.

[0198] The antenna ports to be used for SRS transmission should be determined according to the order of SRS ports given by a pre-defined configuration, which can be represented by a table. The number of bits indicated in the DCI defined by the group indicates the ports of the transmission that are bound to physical resources (e.g., cyclic shift, comb, and OFDM symbol).

[0199] In the case where group DCI is used to communicate SRS configuration, indication of the layer or port of the UE within the pre-defined SRS port resource is possible. As an example for each cell (e.g., sector, transmission point, etc.), a pre-defined number of SRS port resources are allocated, e.g., 8 or 12 ports. In the group DCI, the network indicates the layer or port of the UE within the pre-defined SRS port resource. For example, the network configures SRS resources for all active UEs within the cell, and the SRS resources have the same 8 ports. The group DCI indicates which of the 8 ports is allocated to the UE. The pre-defined SRS port resource can be specified in the technical specification, or communicated to the UE from the network by RRC configuration signaling, MAC signaling, and in some embodiments, DCI. For example, RRC signaling configures SRS port resources with indices 0~7 for UE1 as SRS ports 0~7 for UE1, SRS port resources with indices 0~7 for UE2 as SRS ports 0~7 for UE2, SRS port resources with indices 8~15 for UE3 as SRS ports 0~7 for UE3, SRS port resources with indices 8~15 for UE4 as SRS ports 0~7 for UE4. And so on. This design can also be used for UE-specific DCI (e.g., DCI format 1-1, 1-1 enhancements (discussed in detail below), etc.) for A-SRS triggering. The DCI can have an antenna port indication field for A-SRS, which in some embodiments, can also be used for antenna port indication of PDSCH, and the UE maps the ports indicated in the field to the pre-defined SRS port resource allocated to the UE. For example, UE1 can receive an enhanced DCI of 1-1, where the antenna port indication field for PDSCH and SRS indicates value 25 (as shown in Table 7.3.1.2.2-2 of TS 38.212, v16.2.0, 2020-06 (which is incorporated by reference herein), reproduced below; where dmrs-Type = 1, maxLength = 2, which are also communicated to the UE for PDSCH), which corresponds to PDSCH DMRS ports 2 and 6 and SRS ports 2 and 6, which are further mapped to SRS port resources 2 and 6. As another example, UE3 can receive an enhanced DCI of 1-1, where the antenna port indication field for PDSCH and SRS indicates value 25, which corresponds to PDSCH DMRS ports 2 and 6 and SRS ports 2 and 6, which are further mapped to SRS port resources 10 and 14.

[0200] Table 7.3.1.2.2-2: Antenna ports (1000 + DMRS ports), dmrs-Type = 1, maxLength = 2 in TS 38.212 v16.2.0

[0201]

[0202]

[0203] In one example, consider a communication system with 4 UEs, the network can allocate a first port for a first UE, two subsequent ports for a second UE, and so on. In another embodiment, the network can reuse the DMRS port mapping or CSI-RS port mapping.

[0204] In one embodiment, SRS resources are configured for all resource block groups (RBGs), but scheduling or group DCI allows different UEs to be scheduled on different RBGs.

[0205] Related to UE identification, UE identification is used to reduce DCI signaling overhead. In one embodiment, to further reduce the DCI size, a unique but shorter UE identification is assigned to a pre-scheduled UE. Instead of using a long UE identification, such as a radio network temporary identification (RNTI), which can be 10 or more bits in length, a unique short UE identification is assigned to each pre-scheduled UE. For example, if there are at most 16 pre-scheduled UEs, the short UE identification can be as short as 4 bits, and if there are at most 8 pre-scheduled UEs, the short UE identification can be as short as 3 bits. In one embodiment, the short UE identification can be assigned by the access node and delivered to the pre-scheduled UE using RRC messaging, MAC CE messaging, higher layer messaging, and the like.

[0206] Related to indicating UE identification, the access node can send a DCI trigger to the pre-scheduled UEs. The indication of the pre-scheduled UEs can be included in a dedicated field of the DCI. In addition, the UE identification and UE identification field in the DCI can be configured using higher layer signaling.

[0207] By using the UE identification, the pre-scheduled UEs are able to decode the DCI identified by the UE ID. Those pre-scheduled UEs that are able to decode the DCI identified with their UE ID are considered triggered UEs. UEs that are configured but not triggered can also attempt to decode the DCI, but they will fail because the DCI is not addressed to them, so they will not be triggered.

[0208] As new UEs are pre-scheduled or there is an additional set of active UEs, for example, the UE identification can be updated and reconfigured through higher layer configuration.

[0209] As mentioned before, there can be a correlation between SRS and DL reference signals. In order for a UE to receive precoded (or unprecoded) CSI-RS, the UE needs to know which CSI-RS ports have been allocated, thus a CSI-RS port indication needs to be sent to the UE. After the UE receives the CSI-RS port indication, the UE can infer (e.g., from the CSI-RS port indication) the preconfigured CSI-RS ports for measuring the downlink channel and the SRS ports for transmitting SRS, since the SRS resources and CSI-RS resources have been preconfigured and there is a correlation between SRS and CSI-RS resources.

[0210] Similarly, the UE needs to know which of the DMRS ports have been allocated to it. A DMRS port indication needs to be sent to the UE. After the UE receives the DMRS port indication, the UE can infer (e.g., from the DMRS port indication) the preconfigured DMRS ports for measuring the downlink channel and the SRS ports for transmitting SRS, since the SRS resources and DMRS resources have been preconfigured and there is a correlation between SRS and DMRS resources.

[0211] In one embodiment, the SRS indication field used to indicate the specific arrangement of SRS resources or ports is also used to indicate to the UE the mapping between uplink ports and downlink ports (e.g., DMRS or CSI-RS ports). Since the SRS ports for each UE are identified, the UE can infer the associated ports in the downlink from the configuration (mapping). In this case, the association between uplink ports and downlink ports can be configured by higher layers. A fixed mapping that can identify the association can be defined, e.g., a one-to-one mapping between uplink ports and downlink ports can be configured. In another embodiment, the arrangement between uplink ports and downlink ports can be used as the mapping. The arrangement can be specified in the technical standard by the operator of the communication system or specified through coordination between the network and the UE. Thus, both the network and the UE are aware of the arrangement. When the UE determines the SRS port or layer indicated to the UE, the UE can measure the corresponding CSI-RS and / or DMRS for channel estimation and use the measurement results to determine the precoder for precoding the uplink SRS.

[0212] In one embodiment, the indication can be implicit. In this case, indicating the SRS resources or ports can be sufficient to indicate the association due to the fixed mapping between the resources. In another embodiment, the indication can be explicit. In this case, a dedicated field can be used that explicitly identifies the downlink CSI-RS or DMRS used to schedule the UE.

[0213] The DCI can have a dedicated field to indicate the DMRS-SRS association. It can also have a field to indicate the CSI-RS-DMRS association. A table can be defined in the specification that has a one-to-one mapping of uplink ports to downlink ports.

[0214] The number of bits used to indicate the association between downlink ports and SRS ports can be used to indicate the transmission of one or more downlink ports and SRS ports, which can be indicated by the SRS resource / port indication field.

[0215] In one embodiment, the association is used not only to indicate port association, but also to indicate bandwidth association (active bandwidth part).

[0216] In addition to the above parameters (e.g., UE identity, association, and SRS resource indication), the group DCI can also include some or all of the following:

[0217] - Resource allocation field to indicate time and frequency resources (e.g., resource block group of the UE);

[0218] - Explicit indication of CSI-RS or DMRS ports using a dedicated field in the DCI, which can indicate the downlink ports. This can also be used by the UE to determine the rank of the transmission. In one embodiment, the UE can infer the rank of the transmission in the uplink from the downlink reception;

[0219] - Transmission power command for SRS transmission power control.

[0220] Figure 6 and 7FIGS. 600 and 700 show example mappings of RGBs 605, 607, 705, and 707, and SRS resources and ports. FIG. 600 shows RGBs 605 and 607 in a communication system with the following configuration: assuming DMRS Type 1 (8 ports per cell per RGB for all paired UEs); in another embodiment, 12-port DMRS can be considered, and 8 ports are associated with 8 SRS port resources selected from n available port resources (e.g., n = 48 for comb-4, n = 16 for comb-2). The SRS port resources can be arranged in a similar manner as shown for RBG1 605 and RBG2 607, and each port resource can be assigned a global index, e.g., (2, 9) for (COMB shift = 2, cyclic shift = 9) for different RBGs, i.e., the global index can be the same for different RBGs, or (1, 2, 9) for (RBG = 1, COMB shift = 2, cyclic shift = 9), i.e., the global index is RBG-specific index. In some embodiments, other time / frequency resource groups can be used instead of RBGs, e.g., (RBG, OFDM symbol), PRB, every 4 RBGs, etc. SRS from neighboring cells should be multiplexed on n SRS port resources. The bits to indicate which 1, 2, or 4 SRS port resources out of n available SRS port resources are needed for a UE are more than the bits available in a DCI message.

[0221] FIG. 700 shows RGBs 705 and 707 with the same configuration as discussed in FIG. 600. Figure 6 In one embodiment, the UE-group CSI-RS or DMRS design is applied to SRS. For each cell, there are only 8 predefined SRS port resources (in Figure 7The different shaded and patterned blocks in the SRS port resource area (shown as RGB) are then used. Then, in a DCI message (such as a group DCI message or a UE-specific DCI message), a tier or port allocation for the UE is performed within the eight predefined SRS port resources, and indicated accordingly. For example, SRS resources are configured for all active UEs in cell 1 (shown as unshaded blocks in the SRS port resource area as RGB), and the SRS resources have the same eight ports. That is, the SRS ports assigned to the UEs configured with SRS port resources are mapped to the SRS port resources one-to-one. The group DCI message indicates which of the eight ports are assigned to a specific UE. For example, the rank [1, 2, 4, 1] is indicated for UEs 1, 2, 3, and 4, without indicating the tier index. Another example is the use of DMRS port mapping for resources. SRS resources are configured for all RGB, but scheduling or group DCI allows different UEs to be scheduled on different RGB. In one embodiment, the SRS port resources allocated to a UE (or cell) are discontinuous, as shown in the figure. Specifically, a UE in CELL1 may not be allocated COMB shift = 1 and cyclic shifts from 1 to 12. Instead, the UE's port resources are distributed (spread out) in the figure, for example, (COMB shift = 1, cyclic shift = 1), (COMB shift = 1, cyclic shift = 7), (COMB shift = 2, cyclic shift = 1), (COMB shift = 2, cyclic shift = 7), (COMB shift = 3, cyclic shift = 1), (COMB shift = 3, cyclic shift = 7), (COMB shift = 4, cyclic shift = 1), and (COMB shift = 4, cyclic shift = 7). The advantage is that the ports of a UE or cell are more dispersed across potential SRS port resources, reducing potential interference / overlap between cyclic shifts that are close to each other.

[0222] Alternative designs for the group DCI used to transmit SRS control information are possible. In one embodiment, UEs identified in the group DCI share a resource allocation field (type 0 or type 1 indication). This may occur in a multi-user multiple-input multiple-output (MU-MIMO) setup where UEs can share resource blocks or RBGs. In this case, pre-configured UEs that have not been pre-scheduled have a field in the group DCI with a trigger set to zero.

[0223] In another embodiment, the UEs identified in the group DCI have a separate field indicating the resource allocation field for each UE. In this case, pre-configured UEs that have not been pre-scheduled have a field with the trigger set to zero.

[0224] In any of the preceding embodiments, the UE identity can be used to identify the pre-scheduled UE. In this way, only the pre-scheduled UE can decode the DCI. However, the UE will attempt to decode the DCI to check if the DCI is triggered (pre-scheduled). For example, all UEs detecting the DCI can attempt to decode the DCI.

[0225] In any of the preceding embodiments, the DCI includes a combination of the listed fields or a subset of the above fields.

[0226] In another embodiment, a modified DCI format, such as DCI format 0_1 (UL grant) or DCI format 1_1, can be used to dynamically configure the triggering (pre-scheduling) of the UE with the above SRS parameters and associated downlink PDSCH and / or CSI-RS parameters.

[0227] Any 5G NR DCI design can be used to indicate the necessary above, such as adding / modifying the necessary fields to the DCI.

[0228] Figure 8 A diagram 800 showing messages exchanged by a communication device performing interference sounding is shown. The diagram 800 shows messages exchanged by an access node 805 and UEs 810 and 812 when the communication device performs interference sounding (which can also be referred to as training or BIT).

[0229] The UEs 810 and 812 transmit uplink SRS (blocks 815 and 817). The uplink SRS can be unprecoded and periodic. The uplink SRS is transmitted to the access node 805. The access node 805 estimates the uplink channel (block 820). The estimation of the uplink channel is made from the uplink SRS transmitted by the UEs. The access node pre-schedules the UEs (block 825). The pre-scheduling of the UEs can be based on a signal quality metric, CQI, PMI, or feedback, as discussed earlier. In Figure 8 In the example shown, the UEs 810 and 812 are also pre-scheduled UEs.

[0230] The access node 805 transmits control information configuring the uplink SRS for the pre-scheduled UEs (block 830). For example, the control information can be transmitted in a group DCI or a unicast DCI. In one embodiment, the group DCI can contain the UE identity of the pre-scheduled UEs. The control information can include (a subset of which is also possible) configuration information for the UEs, such as the transmission bandwidth of the uplink SRS, or a portion of the transmission bandwidth, an indication of the transmission port of the uplink SRS, an indication of the SRS resource or port of the uplink SRS, an implicit or explicit indication of the cyclic shift and comb, a subband of the uplink SRS, an SRS trigger, a CSI-RS trigger, a DMRS trigger, an indication of the mapping between the CSI-RS and the SRS, the mapping between the DMRS and the SRS, etc.

[0231] If the access node 805 is to transmit CSI-RS, the access node 805 transmits CSI-RS (block 835). The UEs 810 and 812 can perform downlink channel estimation (blocks 840 and 842). The downlink channel estimation can be performed based on the CSI-RS transmitted by the access node 805.

[0232] The UEs 810 and 812 transmit uplink SRS (blocks 845 and 847). The uplink SRS is transmitted according to the configuration information transmitted by the access node 805. The uplink SRS can be precoded, e.g., based on a singular value decomposition (SVD) precoder. The access node 805 determines an interference covariance matrix (block 850). The interference covariance matrix is determined based on the uplink SRS transmitted by the UEs 810 and 812 (i.e., the pre-scheduled UEs). The access node 805 determines a downlink precoder (block 855). The downlink precoder is determined according to the interference covariance matrix. The access node 805 transmits downlink data to the UEs 810 and 812 (block 860). For example, the access node 805 precodes the downlink data for each pre-scheduled UE using the downlink precoder associated with the pre-scheduled UE. The precoded downlink data is transmitted through a physical downlink shared channel (PDSCH).

[0233] In the Third Generation Partnership Project (3GPP) Fifth Generation (5G) New Radio (NR) standards related to existing DCI formats, the DCI size is minimized to reduce communication overhead. For example, in DCI format 2_3 used to transmit group transmit power control (TPC) commands used by one or more UEs for SRS transmission, the DCI size is less than or equal to the DCI size of DCI format 1_0. Therefore, the number of bits available for transmitting uplink SRS configuration is limited. However, the existing DCI formats do not support dynamic signaling of SRS configuration. In addition, control information must be provided for all configured UEs, even those that are not triggered (i.e., not pre-scheduled) to transmit uplink SRS, and therefore, the number of UEs that can be configured using the existing DCI formats is limited due to the limitation in the number of bits.

[0234] According to an example embodiment, a DCI format for transmitting SRS configuration information is provided. In one embodiment, the DCI includes SRS configuration information only for pre-scheduled UEs. Existing DCI formats include control information for all configured UEs, even those that are not pre-scheduled. Making the DCI include only SRS configuration information for pre-scheduled UEs reduces the size of the DCI, thereby allowing for a reduction in DCI size or the inclusion of more SRS configuration information.

[0235] Figure 9 The first example DCI 900 is shown. Figure 9 As shown, DCI 900 is an example of a DCI, where the DCI includes SRS configuration information used only for pre-scheduled UEs, and a short UE identifier is used to identify the UE. DCI 900 includes an identification field 905, which identifies that the DCI is used to transmit SRS configuration information to the pre-scheduled UEs. DCI 900 also includes SRS configuration information for each pre-scheduled UE, such as a first pre-scheduled UE 910, a second pre-scheduled UE 912, and an Nth pre-scheduled UE 914.

[0236] As an example of the savings achievable by using a short UE identifier and transmitting information only for pre-scheduled UEs, consider a scenario where an access node is serving 20 UEs, of which only 5 are pre-scheduled. If a 10-bit long RNTI is used, the DCI format would require transmitting at least 20 * 10 = 200 bits of identification information separately. However, by using a short UE identifier and pre-scheduled UEs, the DCI format 700 would only require transmitting 5 * 4 = 20 bits of identification information.

[0237] For each prescheduled UE, such as the first prescheduled UE 910, the DCI 900 includes a UE ID field 920, a resource allocation field 922, an SRS TPC command field 924, and an SRS indication field 926. The UE ID field 920 includes a short UE identity of the prescheduled UE and can be, for example, 4 bits in size. The resource allocation field 922 includes time and frequency resource blocks or groups for the prescheduled UE. The size of the resource allocation field 922 can depend on the type of resource allocation and the bandwidth part (BWP) size, where the size also depends on, for example, the resource allocation type. The SRS TPC command field 924 includes a power control command for SRS and can be, for example, 2 bits in size. The SRS indication field 926 includes SRS resources, SRS ports, SRS transmission bandwidth, etc. The values in the SRS indication field 926 can be preconfigured with a set of different possible arrangements of SRS resources or ports, SRS transmission bandwidth, etc. values and only save an index to a particular set of possible SRS resources, SRS ports, SRS transmission bandwidth, etc. in the SRS indication field 926 to reduce the size. The SRS indication field 926 can also be used to indicate a mapping to DL ports (layer, reference signal, etc.). An example size of the SRS indication field 926 is 4 bits. The SRS indication field 926 supports uplink SRS port indication for transmission of SRS. SRS cyclic shift, SRS subband, SRS comb, etc. are also implicitly indicated. Precoded CSI-RS ports (e.g., same ports) assigned to the prescheduled UE in the downlink are also implicitly indicated. The example sizes of the various fields of the DCI 900 are for discussion purposes only. The example embodiments presented herein can operate with other field sizes.

[0238] In relation to the resource allocation field, such as the resource allocation field 922, resource type 1 can be used for frequency allocation. Alternatively, resource type 2 can be used for frequency allocation. A resource block group can be used for the UE. In addition, the frequency allocation can include an allocation for SRS transmission.

[0239] In relation to the downlink antenna port, the indication to the UE can be for a downlink port or a downlink layer. As an example, the indication can be a bitmap. As another example, the indication can be a value. The UE can be able to determine the CSI-RS or DMRS port to use based on the SRS port assigned to the UE. As an example, the indication can use the SRS indication field. In another embodiment, the indication to the SRS port can use a bitmap.

[0240] Information associated with the configured UEs that are not prescheduled is not included in the DCI format 900. The prescheduled UEs can process the DCI to determine if the access node has triggered the prescheduled UE for SRS transmission.

[0241] In one embodiment, to further reduce the DCI size, the SRS configuration information for each prescheduled UE is arranged in order (e.g., in increasing order or decreasing order) such that the short UE identity does not need to be included in the DCI. Thus, a further reduction in the DCI size is achieved.

[0242] In one embodiment, time and frequency resource blocks or groups are configured for the prescheduled UEs. In Figure 9 In one embodiment, each prescheduled UE can be configured with a different allocation of time and frequency resource blocks or groups. In this embodiment, a single allocation of time and frequency resource blocks or groups is configured for the prescheduled UEs indicated in the DCI. In one embodiment, a single DCI is used to transmit SRS configuration information for the prescheduled UEs of the access node. In this case, the DCI includes the SRS TPC command and the SRS indication for each prescheduled UE. The SRS TPC command and the SRS indication for each prescheduled UE can be arranged according to the short UE identity assigned to each prescheduled UE. For example, the SRS TPC command and the SRS indication for each prescheduled UE can be arranged in increasing short UE identity or decreasing short UE identity.

[0243] In one embodiment, a single DCI is used to transmit SRS configuration information for a subset of the prescheduled UEs of the access node. In this case, the DCI includes the SRS TPC command and the SRS indication for each prescheduled UE in the subset. For example, a first DCI includes the SRS TPC command and the SRS indication for a first subset of prescheduled UEs, a second DCI includes the SRS TPC command and the SRS indication for a second subset of prescheduled UEs, and so on. The SRS TPC command and the SRS indication for each prescheduled UE in the subset can be arranged according to the short UE identity assigned to each prescheduled UE in the subset. For example, the SRS TPC command and the SRS indication for each prescheduled UE in the subset can be arranged in increasing short UE identity or decreasing short UE identity.

[0244] Figure 10 A second example DCI 1000 is shown. As Figure 10As shown, DCI 1000 is an example of a DCI in which a single allocation of time and frequency resource blocks or groups is configured for a pre-scheduled UE. DCI 1000 includes an identification field 1005 that identifies that the DCI is a DCI that is used to communicate SRS configuration information to a pre-scheduled UE, and a resource allocation field 1010. Resource allocation field 1010 includes the time and frequency resource blocks or groups for the pre-scheduled UE indicated in DCI 1000. DCI 1000 also includes an SRSTPC command and an SRS indication for each pre-scheduled UE (e.g., first pre-scheduled UE 1015, second pre-scheduled UE 1017, and Nth pre-scheduled UE 1019).

[0245] For each pre-scheduled UE, such as first pre-scheduled UE 1015, DCI 1000 includes an SRS TPC command field 1025 and an SRS indication field 1027. SRS TPC command field 1025 includes a power control command for SRS, and can be, for example, 2 bits in size. SRS indication field 1027 includes SRS resources, SRS ports, SRS transmission bandwidth, etc. The values in SRS indication field 1027 can be pre-configured with a set of possible values for SRS resources, SRS ports, SRS transmission bandwidth, etc., and only an index to a particular set of possible SRS resources, SRS ports, SRS transmission bandwidth, etc. is saved in SRS indication field 1027 to reduce size. The size of example SRS indication field 1027 is 4 bits. SRS indication field 1027 supports SRS port indication in uplink for transmission of SRS. It also implicitly indicates the precoding CSI-RS ports (e.g., same ports) allocated to the pre-scheduled UE in downlink. It also implicitly indicates SRS cyclic shift, SRS subband, SRS comb, etc.

[0246] In one embodiment, to further reduce DCI size, an allocation of time and frequency resource blocks or groups is configured for a pre-scheduled UE. An allocation of time and frequency resource blocks or groups can be configured for a pre-scheduled UE that is scheduled for SRS transmission. Thus, in this case, an allocation of time and frequency resource blocks or groups is included for each pre-scheduled UE that is scheduled for SRS transmission, and an allocation of time and frequency resource blocks or groups is omitted for each pre-scheduled UE that is not scheduled for SRS transmission.

[0247] Figure 11 A third example DCI 1100 is shown. As Figure 11As shown, DCI 1100 is an example of a DCI in which time and frequency resource blocks or groups are allocated for each pre-scheduled UE that is scheduled for SRS transmission. DCI 1100 includes an identification field 1105 that identifies that the DCI is a DCI that is conveying SRS configuration information to the pre-scheduled UEs. DCI 1100 also includes information for each pre-scheduled UE (e.g., first pre-scheduled UE 1110, second pre-scheduled UE 1112, and Nth pre-scheduled UE 1114). The information can be different for pre-scheduled UEs that are scheduled for SRS transmission as compared to pre-scheduled UEs that are not scheduled for SRS transmission.

[0248] For each pre-scheduled UE that is scheduled for SRS transmission, such as first pre-scheduled UE 1110, DCI 1100 includes a resource allocation field 1120, an SRS TPC command field 1122, and an SRS indication field 1124. Resource allocation field 1120 includes the time and frequency resource blocks or groups for the pre-scheduled UE. The size of resource allocation field 1120 can depend on the type of resource allocation and the BWP size, and can be, for example, 10 bits in size. SRS TPC command field 1122 includes a power control command for SRS, and can be, for example, 2 bits in size. SRS indication field 1124 includes the SRS resource, SRS port, SRS transmission bandwidth, etc. The values in SRS indication field 1124 can be pre-configured with a set of possible values for the SRS resource, SRS port, SRS transmission bandwidth, etc., and only an index to the set of possible SRS resource, SRS port, SRS transmission bandwidth, etc. is saved in SRS indication field 1124 to reduce the size. The size of example SRS indication field 1124 is 4 bits. SRS indication field 1124 supports SRS port indication in uplink for SRS transmission. It also implicitly indicates the precoding CSI-RS port (e.g., same port) allocated to the pre-scheduled UE in downlink. It also implicitly indicates SRS cyclic shift, SRS subband, SRS comb, etc. The example sizes of the various fields of DCI 1100 are for discussion purposes only. The example embodiments presented herein can operate with other field sizes.

[0249] For each pre-scheduled UE that is not scheduled for SRS transmission, such as Nth pre-scheduled UE 1114, resource allocation field 1130, SRS TPC command field 1132, and SRS indication field 1134 are set to zero or some other designated value. Although Figure 11 While Nth pre-scheduled UE 1114 is shown as an example of a pre-scheduled UE that is not scheduled for SRS transmission, any of the N pre-scheduled UEs in DCI 1100 can be a pre-scheduled UE that is not scheduled for SRS transmission.

[0250] Figures 9-11 The example embodiments shown are for group DCI. However, the example embodiments presented herein can also be used for unicast DCI. In unicast DCI, the DCI is specifically addressed to a single UE. Addressing the DCI to a specific UE can be accomplished by encoding the DCI using the UE's identifier. When the DCI is encoded using the UE's identifier, only that UE can decode the DCI, while other UEs will detect the encoded DCI as noise. Since the DCI is specifically addressed to the UE using the UE's identifier, the DCI does not need to include the UE's unique identifier. Therefore, the size of the DCI is reduced.

[0251] Figure 12 The fourth example, DCI 1200, is shown. (As...) Figure 12 As shown, DCI 1200 is an example of a DCI used in unicast DCI. DCI 1200 includes an identification field 1205, a resource allocation field 1210, an SRS TPC command field 1215, and an SRS indication field 1220. The identification field 1205 identifies that the DCI is used to transmit SRS configuration information to the pre-scheduled UE. The resource allocation field 1210 includes time and frequency resource blocks or groups for the pre-scheduled UE. The size of the resource allocation field 1210 can depend on the type of resource allocation and the BWP size, and can be, for example, 10 bits. The SRS TPC command field 1215 includes power control commands for SRS, and can be, for example, 2 bits. The SRS indication field 1220 includes SRS resources, SRS port, SRS transmission bandwidth, etc. The values ​​in the SRS indication field 1220 can be pre-configured with a set of possible SRS resources, SRS ports, SRS transmission bandwidth, etc., and the SRS indication field 1220 only stores indices for a set of possible SRS resources, SRS ports, SRS transmission bandwidth, etc., to reduce size. The example SRS indication field 1220 is 4 bits in size. The SRS indication field 1220 supports uplink SRS port indication for transmitting SRS. It also implicitly indicates the precoded CSI-RS port (e.g., the same port) assigned to the pre-scheduled UE in the downlink. It also implicitly indicates SRS cyclic shift, SRS subband, SRS comb, etc. The example sizes of the various fields of DCI 1200 are for illustrative purposes only. The example embodiments presented herein can operate with other field sizes.

[0252] In another embodiment, dynamic signaling using fields (or fields) in the DCI can be used to transmit the identifier of a reference downlink resource (or resources). Higher-layer signaling can be used to configure dedicated fields for transmitting mappings from a configured fixed mapping.

[0253] Figure 13A flow chart of example operations 1300 performed in a UE is shown. Operations 1300 can indicate operations performed in a UE when the UE participates in interference sounding and receives downlink data. The UE can be a pre-scheduled UE.

[0254] Operations 1300 begin when the UE transmits an uplink SRS (block 1305). The uplink SRS can be unprecoded. The uplink SRS can be periodic in nature. The UE receives a DCI from an access node (block 1307). The DCI can include SRS configuration information for the UE. The SRS configuration information configures the UE to transmit an SRS. The DCI can also include CSI-RS configuration. The DCI can be part of a group DCI message. The DCI can be a unicast DCI message. The UE estimates a downlink channel (block 1309). The UE estimates the downlink channel using a CSI-RS transmitted by the access node. The UE transmits a precoded SRS (block 1311). The precoded SRS is transmitted according to the SRS configuration information received in the DCI. The UE receives downlink data (block 1313). The downlink data is received from the access node. The downlink data is precoded using a precoder determined according to the precoded SRS transmitted by the UE.

[0255] Figure 14 A flow chart of example operations 1400 performed in an access node is shown. Operations 1400 can indicate operations performed in an access node when the access node participates in interference sounding and transmits downlink data.

[0256] Operations 1400 begin when the access node estimates an uplink channel (block 1405). For example, the access node estimates the uplink channel using SRSs transmitted by UEs. The SRSs can be precoded or unprecoded. The access node pre-schedules UEs (block 1407). The access node pre-schedules UEs according to SRSs transmitted by the UEs. For example, the access node pre-schedules UEs associated with SRSs having a signal quality that exceeds a specified threshold. The access node transmits a DCI to the pre-scheduled UEs to trigger SRS transmission (block 1409). The DCI transmitted by the access node can also cause the UEs to measure a downlink CSI-RS or DMRS. The access node configures SRSs for the pre-scheduled UEs and sends SRS configuration information to the pre-scheduled UEs in the DCI. The SRS configuration information can also include CSI-RS information. The DCI can be a group DCI or a unicast DCI.

[0257] The access node can transmit a CSI-RS (block 1411). The CSI-RS can be used for downlink channel estimation. The access node receives a precoded SRS (block 1413). The precoded SRS can be received according to the SRS configuration information. The access node determines an interference covariance matrix (block 1415). The interference covariance matrix is determined according to the precoded SRS. The access node determines a downlink precoder (block 1417). The downlink precoder is determined according to the interference covariance matrix. The access node transmits downlink data (block 1419). The downlink data is precoded according to the downlink precoder.

[0258] Figure 15 A flow diagram illustrating example operations 1500 performed in an access node configuring uplink SRS is shown. Operations 1500 can be indicative of operations performed in an access node when the access node configures uplink SRS and receives uplink SRS transmissions.

[0259] Operations 1500 begin when the access node transmits an SRS configuration (block 1505). The SRS configuration can be transmitted in downlink control information, e.g., in a group DCI or a unicast DCI. In the case of using a group DCI, the group DCI can be addressed to the UE (e.g., the pre-scheduled UE) using a UE identity that is unique in the UE group but shorter than a typical UE identity, thus saving signaling overhead. In one embodiment, the SRS configuration includes information about the arrangement of SRS port resources (e.g., comb, offset, cyclic shift, symbol, etc.). The SRS port resources can also be divided into multiple resource groups. In one embodiment, the SRS configuration includes a set of SRS ports in the SRS resource. In one embodiment, the SRS configuration includes information about the association between the SRS port resources and downlink port resources (e.g., CSI-RS ports, DMRS ports, etc.). Information about the mapping between the ports can also be included.

[0260] The access node transmits an indication of SRS resources (block 1507). In one embodiment, the indication of SRS resources indicates a group of SRS resources for uplink SRS transmission. In one embodiment, the indication of SRS resources indicates a subset of SRS ports in the SRS resource for uplink SRS transmission. In one embodiment, the indication of SRS resources indicates an association for determining SRS ports for uplink SRS transmission. The indication of SRS resources can be transmitted in downlink control information, e.g., in a group DCI or a unicast DCI. When a group DCI is used, a UE identity is used (as described above). The indication of SRS resources can be included in a message transmitted after the transmission of the SRS configuration. The message in which the indication of SRS resources is included can be the first message transmitted after the transmission of the SRS configuration. The access node receives uplink SRS (block 1509). The uplink SRS is received according to the indicated SRS resources.

[0261] Figure 16 A flow chart illustrating example operations 1600 made in a UE that transmits uplink SRS is shown. Operations 1600 can be indicative of operations made in a UE when the UE receives an uplink SRS configuration and transmits uplink SRS.

[0262] Operations 1600 begin with the UE receiving an SRS configuration (block 1605). The SRS configuration can be received in downlink control information, e.g., in a group DCI or a unicast DCI. In the case of using a group DCI, the group DCI can be addressed to the UE (e.g., a pre-scheduled UE) using a UE identity that is unique in the group of UEs but shorter than a typical UE identity, thus saving signaling overhead. In one embodiment, the SRS configuration includes information about the arrangement of SRS port resources (e.g., comb, offset, cyclic shift, symbol, etc.). The SRS port resources can also be grouped into multiple resource groups. In one embodiment, the SRS configuration includes a set of SRS ports in the SRS resource. In one embodiment, the SRS configuration includes information about the association between the SRS port resources and downlink port resources (e.g., CSI-RS ports, DMRS ports, etc.). Information about the mapping between the ports can also be included. The UE receives the downlink control information and attempts to decode the downlink control information even if the UE is not the intended recipient of the SRS configuration.

[0263] The UE receives an indication of SRS resources (block 1607). In one embodiment, the indication of SRS resources indicates a group of SRS resources for uplink SRS transmission. In one embodiment, the indication of SRS resources indicates a subset of SRS ports in the SRS resource for uplink SRS transmission. In one embodiment, the indication of SRS resources indicates an association for determining SRS ports for uplink SRS transmission. The indication of SRS resources can be received in downlink control information, e.g., in a group DCI or a unicast DCI. When a group DCI is used, a UE identity is used (as described above). The indication of SRS resources can be included in a message received after the reception of the SRS configuration. The message in which the indication of SRS resources is included can be the first message received after the transmission of the SRS configuration. The UE transmits uplink SRS (block 1609). The uplink SRS is transmitted according to the indicated SRS resources.

[0264] Some embodiments of flexible A-SRS triggering for BiT described above can result in higher DCI overhead as it contains more bits in the SRS request field. In addition, A-SRS triggering can occur more frequently, e.g., at every occurrence of MU scheduling. To reduce DCI overhead, several embodiments are provided. First, a more flexible framework for splitting SRS transmission parameter information among RRC configuration signaling, MAC CE, and DCI would be useful. The minimum impact would be to keep as much SRS transmission parameter information in RRC and MAC as possible, and DCI contains only the minimum parameter information needed for dynamic signaling. In addition, the existing DCI can be enhanced to include new fields and associated with new UE behavior.

[0265] Embodiments of overhead reduction based on group common DCI are provided.

[0266] BiT sounding is to support PDSCH with MU-MIMO, where multiple UEs are paired together in PDSCH and its DMRS. Therefore, BiT sounding should be "mirrored" with PDSCH DMRS. For example, we know that for PDSCH DMRS Type 1, up to 8 DMRS ports / RBG / cell can be supported. Accordingly, 8 SRS port resources can be split and indicated to multiple UEs, where SRS port resource is in terms of OFDM symbol for cyclic shift, comb and shift, possibly RBG of a cell. Then, DL DMRS port to SRS port resource mapping (i.e., association) can be designed, and port information can be conveyed to UEs through SRS trigger. This can be done in an overhead efficient way through GC DCI, which is sent to a group of UEs that can be paired for MU transmission in a slot. The GC DCI can trigger SRS to be sent from UEs simultaneously, i.e., a common trigger offset can be used. In addition, other fields such as CMR / IMR indication can also be included, and the design can be similar to the CSI request field in DCI format 0_1. One embodiment is a GC DCI for overhead reduced flexible A-SRS triggering, and the GC DCI is sent to a group of UEs that can be paired for MU transmission in a slot, they have a common trigger offset, and each UE is allocated a UE-specific frequency domain resource allocation (FDRA), a port allocation (in terms of available SRS port resources of its serving cell, e.g., cyclic shift, comb and shift), and a CMR / IMR indication. In one embodiment, a new field of A-SRS trigger offset with slot offset k0 and symbol location is included in the GC DCI. In one embodiment, a new field of A-SRS beamforming with dynamically indicated DL CMR and / or IMR is included in the GC DCI, similar to the CSI request field in DCI format 0_1. In one embodiment, if A-SRS is allocated with FDRA and / or port allocation, the UE assumes higher priority of A-SRS in the GC DCI. In one embodiment, UE-specific port allocation field is used to replace group-common (joint) port allocation field for all UEs that are paired on a RBG (or associated frequency domain unit) by indicating only the rank (number of layers of data or number of ports of SRS / DMRS) of the paired UEs (the ordering of UEs can be indicated elsewhere, or UE ID is also included to accompany the rank allocation). In this embodiment, the ports of UEs must follow a certain pattern, such as consecutive or uniform distribution, but as long as the rank is indicated, each UE can determine its SRS port resource.

[0267] The following Table 1 provides enhancements to DCI 1-1 for SRS sounding.

[0268] Table 1

[0269]

[0270] The restrictions for enhanced DCI 1-1 include:

[0271] - Some fields are "used for PDSCH". It is now also possible to apply to SRS".

[0272] - However, it is not clear under what conditions these PDSCH fields also apply to SRS.

[0273] - DCI has no CSI request. However, for BiT with DL sounding for improved link adaptation, a CSI request is needed.

[0274] - In addition, there is no detailed description of enhancing UL DCI 0_1 for SRS sounding.

[0275] Embodiments of UE-specific DCI based overhead reduction are provided. To reduce DCI overhead, one embodiment uses DL DCI format 1_0 / 1_1 for both A-SRS triggering and PDSCH scheduling, and SRS and PDSCH have the same PRB / port allocation. In DCI format 1_0 or 1_1, it already has fields for: 1) A-SRS trigger, 2) PDSCH PRB allocation dynamically indicated by DL FDRA field, 3) dynamically indicated PDSCH port, 4) possible PRB bundling size indicated field (as in DCI format 1_1), etc. These fields can be used (reused) by the UE for SRS triggering. New fields for BiT purposes are also added, such as SRS resource indication, SRS trigger offset (similar to PDSCH SLIV), CMR / IMR indication field, which can be similar to CSI request field as in DCI format 0_1. The UE assumes that the FDRA and port are also applicable to the triggered SRS, which can greatly reduce the DCI overhead. For port indication, a mapping (association) of DCI DL port indication to SRS port (in terms of cyclic shift, comb and shift) can be defined in Rel-17. One embodiment is to reuse UE-specific DCI (e.g., format 1_1) and introduce new fields for overhead reduced flexible A-SRS triggering, and the UE first performs A-SRS transmission according to the existing fields of FDRA, port indication, and PRB bundling size indication, and the new fields of SRS resource indication, SRS trigger offset, and CMR / IMR indication. Then, the UE performs PDSCH reception according to at least the same FDRA and port indication in the same DCI. In one embodiment, a new field of A-SRS trigger offset with slot offset k0 and symbol location is included in the UE-specific DCI. In one embodiment, a new field of A-SRS beamforming with dynamically indicated DL CMR and / or IMR is included in the UE-specific DCI, similar to the CSI request field in DCI format 0_1. In one embodiment, the UE assumes higher priority of A-SRS in the UE-specific DCI if A-SRS is allocated with FDRA and / or port allocation. In one embodiment, the UE supports more receive antenna ports (e.g., for PDSCH and its DMRS) than transmit antenna ports (e.g., for SRS). For example, the UE can only probe on one port. In this case, the UE should ignore the PDSCH port indication and only probe on one port. For another example, the UE can only probe on two ports but can receive on up to four ports. In this case, the UE can still utilize the PDSCH port indication information, i.e., probe on one port if the PDSCH is one layer, but probe on two ports if the PDSCH is two or more layers.In one embodiment, port indication for SRS is not supported, but rank (number of ports or number of layers) indication is supported. That is, the UE uses the rank indication of SRS (or PDSCH) for SRS transmission. The ports associated with this rank are pre-determined according to the standard or RRC configuration.

[0276] Embodiments are provided for flexible A-SRS triggering for interference sounding with overhead reduction based on UE-specific DCI and overhead reduction based on GC DCI. In one embodiment, the GC DCI is an enhanced GC DCI format 2_3 with UE FDRA and port indication. In one embodiment, the UE-specific DCI is an enhanced DL DCI format 1_0 / 1_1 for re-interpreting the existing FDRA / port indication field for SRS transmission. In one embodiment, both of the above embodiments are supported. In one embodiment, the enhanced GC DCI and / or UE-specific DCI is supported and becomes a new DL DCI format. In any embodiment, a new field of A-SRS triggering offset with slot offset k0 and symbol location can be included. In any embodiment, a new field of A-SRS beamforming with dynamically indicated DL CMR and / or IMR can be included, similar to the CSI request field in DCI format 0_1. In any embodiment, if A-SRS is assigned with FDRA and / or port allocation, the UE assumes higher priority of A-SRS.

[0277] In one embodiment, the GC DCI and / or UE-specific DCI is for TDD where UL works in OFDM (instead of SC-FDMA). In order to properly utilize BiT or SRS sounding for DL, UL and DL should be as symmetric as possible. Since DL is just OFDM, it is more suitable for UL to be OFDM as well. This can also be more suitable if PDSCH / SRS transmission is not contiguous in frequency domain, e.g., with PRB skipping, FDRA type 0 with non-contiguous RBGs, interleaved VRB-to-PRB mapping, etc.

[0278] In one embodiment, the GC DCI and / or UE-specific DCI reuses the PDSCH TDRA design for its SRS trigger offset design. In one embodiment, the GC DCI and / or UE-specific DCI reuses the PUSCH TDRA for its SRS trigger offset design. In one embodiment, the GC DCI and / or UE-specific DCI reuses the PUSCH / PDSCH TDRA for its SRS trigger offset design, but modifies the L value configuration and range to be suitable for SRS transmission. For example, the network can configure SRS to be only on 8~14 OFDM symbols, thus, the current range of L for PUSCH 4~14 or 1~14 can be modified to 8~14 so that the L value can be indicated using fewer bits.

[0279] In the embodiment of GC DCI and / or UE-specific DCI, a new field of A-SRS beamforming with dynamically indicated DL CMR and / or IMR is included. This field can be similar to the CSI request field in DCI format 0_1, or reuse the same indication / configuration as the CSI request field. In one embodiment, the A-SRS beamforming field is the same as the CSI request field with 0, 1, 2, 3, 4, 5, or 6 bits determined by the higher layer parameter reportTriggerSize. When all bits of the field in the DCI are set to zero, the SRS is not beamformed. Non-zero codepoints of the field in the DCI map to the CMR / IMR associated with the CSI trigger states according to the order of the associated positions of the highest trigger state in CSI-AperiodicTriggerStateList, where codepoint “1” maps to the trigger state in the first position. After the UE determines the CMR from this field, the UE also selects the CMR port according to the antenna port indication field, and the UE generates SRS beamforming for each SRS port using the selected CMR port and the indicated / associated IMR.

[0280] In some embodiments, a flag / switch is introduced to specify whether the A-SRS triggered by the DCI reuses some fields from another scheduled / triggered transmission. The main purpose of this flag is to make the DCI useful for both BiT purposes and non-BiT purposes while redesigning the minimum. For example, when the flag is set, the UE shall assume that the A-SRS triggered in the DCI reuses the fields (e.g., FDRA) of the PDSCH scheduled by this DCI or another DCI, but when the flag is not set, the UE shall not assume that the A-SRS reuses the fields of another transmission. In other words, this flag serves as an indication to the UE whether to assume the association of the A-SRS parameters with another transmission.

[0281] In one embodiment, the flag / switch is a field in DCI, that is, the association can be dynamically indicated for full flexibility. In one embodiment, the flag is turned on / off by MAC CE. In one embodiment, the flag is turned on / off by RRC configuration in DCI format.

[0282] In one embodiment, the flag is used for DCI that can be used to schedule PUSCH transmission. One example can be DCI format 0_1, etc., which schedules PUSCH and includes fields for PUSCH transmission, such as PUSCH FDRA, antenna port, with or without frequency hopping, on UL (uplink carrier) or SUL (supplemental uplink carrier), on which BWP, etc. In one embodiment, the flag is used for association of A-SRS with PUSCH. When the flag is set, A-SRS is triggered and PUSCH is scheduled, the UE uses parameters obtained from certain PUSCH fields for SRS transmission, and these fields can include at least one or more of PUSCH FDRA, PUSCH antenna port indication, PUSCH frequency hopping, UL / SUL indication, BWP indication, closed loop TPC command, etc. PUSCH and A-SRS have different timing, so they do not collide, i.e., A-SRS can have its own TDRA, or have an offset relative to PUSCH, such as n slots earlier than PUSCH. However, when the flag is not set and A-SRS is triggered, the UE does not use these PUSCH fields for A-SRS transmission. In one embodiment, the flag is a field associated with SRS request field in DCI format. In one embodiment, the flag field contains multiple bits to indicate which PUSCH fields should be used by the UE for associated A-SRS, such as bits to indicate whether A-SRS reuses PUSCH FDRA / BWP, and bits to indicate whether A-SRS reuses PUSCH TPC command, etc. In one embodiment, the flag is used for association of A-SRS with PDSCH. When the flag is set and A-SRS is triggered, the UE uses parameters obtained from certain PDSCH fields for SRS transmission, and these fields can include at least one or more of PDSCH FDRA, PDSCH antenna port indication, PDSCH frequency hopping, BWP indication, PRB to VRB interleaving, etc. However, when the flag is not set and A-SRS is triggered, the UE does not use these PDSCH fields for A-SRS transmission. The associated PDSCH is not scheduled using this DCI, but the association is designated to the UE so that the UE can link to the correct PDSCH, which can be achieved by a common ID (e.g., a field with ID or DCI RNTI, etc.) for SRS and PDSCH or by their timing relationship (e.g., triggered at the same time, triggered within 2 slots, PDSCH scheduled n slots after A-SRS, n being 1, 2, etc.).

[0283] In one embodiment, the flag is for DCI that can be used to schedule PDSCH transmission. One example can be DCI format 1_1, etc., which schedules PDSCH and includes fields for PDSCH transmission, such as PDSCH FDRA, antenna port, PRB bundling size, etc. In one embodiment, the flag is for association of A-SRS with PDSCH for the same DCI. When the flag is set, A-SRS is triggered, and PDSCH is scheduled, the UE uses the parameters obtained from certain PDSCH fields for SRS transmission, and these fields can include at least one or more of PDSCH FDRA, PDSCH antenna port indication, PDSCH PRB bundling size, etc. However, when the flag is not set and A-SRS is triggered, the UE does not use these PDSCH fields for A-SRS transmission. In one embodiment, the flag is a field associated with SRS request field in DCI format. In one embodiment, the flag field contains multiple bits to indicate which PDSCH fields should be used by the UE for the associated A-SRS, such as a bit to indicate whether A-SRS reuses PDSCH FDRA / BWP, and a bit to indicate whether A-SRS reuses PDSCH antenna port, etc.

[0284] In one embodiment, the DCI that can schedule PUSCH or PDSCH or trigger A-SRS can also have a CSI request field. The flag or bits of the flag indicate to the UE whether A-SRS is also associated with the CSI request field. When the flag is set, the UE can use the CMR and optional IMR associated with the CSI request for A-SRS beamforming. The DCI can be an extension of format 0_1 or 1_1. In DCI embodiments with PDSCH scheduling, SRS triggering, and CSI request, A-SRS can be tied to the scheduled PDSCH (e.g., reuse PDSCH FDRA) and / or CSI request (reuse CMR / IMR for beamforming). The CSI request can be associated with aperiodic CSI-RS transmission. This is particularly useful for BiT, as one DCI indicates DL RS for A-SRS beamforming, A-SRS parameters shared with PDSCH, and PDSCH. The DL RS can also be used for DL sounding for MCS adjustment, i.e., the UE reports CQI to the gNB without reporting PMI, so that the gNB can link-adapt the PDSCH.

[0285] In one embodiment, uplink DCI (e.g., 0_1) that schedules PUSCH can indicate no scheduling of PUSCH by UL-SCH, i.e., UL-SCH bits are zero. A-SRS trigger parameters can redefine the fields designed for PUSCH. For example, A-SRS trigger offset or TDRA can use several bits. A-SRS port indication can use several bits. A-SRS FDRA can use several bits. And so on.

[0286] In one embodiment, downlink DCI (e.g., 1_1) that schedules PDSCH can indicate no scheduling of PDSCH. No PDSCH can be indicated by DL-SCH indication, i.e., DL-SCH bits are zero, or by setting several bits in original PDSCH fields to zero, e.g., downlink assignment index bits, FDRA / TDRA bits, etc. A-SRS trigger parameters can redefine the fields designed for PUSCH. For example, A-SRS trigger offset or TDRA can use several bits. A-SRS port indication can use several bits. A-SRS FDRA can use several bits. And so on.

[0287] In summary, UL DCI can be used for SRS triggering with or without PUSCH, with or without CSI request, SRS bound to PUSCH (e.g., FDRA, etc.) or not bound to PUSCH, SRS bound to PDSCH or not bound to PDSCH, SRS bound to CSI request field or not bound to CSI request field. DL DCI can be used for SRS triggering with or without PDSCH, with or without CSI request, SRS bound to PDSCH (e.g., FDRA, etc.) or not bound to PDSCH, SRS bound to CSI request field or not bound to CSI request field.

[0288] Embodiments of GC DCI triggering SRS are provided. One embodiment is to enhance current GC DCI format 2_3. The enhanced DCI format 2_3 does not have FDRA field to reduce overhead. The DCI can include multiple SRS blocks, each SRS block can be used to trigger one or multiple SRS transmissions. Each block includes SRS request field (optional), one or multiple SRS TPC command field (if the block can trigger multiple SRS transmissions). These blocks can be used for the same UE or for multiple UEs. Each UE receiving the SRS trigger in the block in the DCI assumes to receive another DCI with FDRA and uses that FDRA for the triggered SRS. The other DCI can be UL DCI, e.g., 0_1 or enhanced 0_1 or 0_1, etc., in which case the FDRA and possibly other fields, like BWP indication, UL / SUL indication, frequency hopping indication, antenna port indication, etc., are also used by the UE for A-SRS transmission. The other DCI can be DL DCI, e.g., 1_1 or enhanced 1_1 or 1_0, etc., in which case the FDRA and possibly other fields, like antenna port indication, PRB bundling size indication, etc., are also used by the UE for A-SRS transmission. In one embodiment, each UE's block in the GC DCI is associated with a flag / switch, when the flag is set, the UE uses the linked DCI fields for A-SRS, when the flag is not set, the UE does not look for the linked DCI fields for A-SRS. The flag can be a field in the GC DCI, can be activated / deactivated by MAC CE, or can be configured by RRC signaling. The linked DCI is designated to the UE so that the UE can link to the correct DCI, which can be achieved by a common ID (e.g., a field with ID or DCI RNTI, etc.) for SRS and PDSCH or by their timing relationship (e.g., triggered at the same time, triggered within 2 slots, PDSCH scheduled n slots after A-SRS, n is 1, 2, etc.). In one embodiment, the GC DCI does not have to be used only for paired UEs. Each UE's block and the fields within the block are pre-configured by RRC signaling, when all bits of the SRS request field of a UE are 0, the UE does not trigger SRS, when the SRS request field of a UE is not all 0, A-SRS is triggered.

[0289] In one embodiment, in GC DCI, all triggered SRSs in GC DCI use the same TDRA field. That is, each UE does not have a UE-specific TDRA field, which saves overhead. In one embodiment, in GC DCI, several TDRA options are provided for all UEs using DCI, and each TDRA is associated with an ID. Then, in each UE's block, a field is used to indicate to the UE which TDRA should be applied based on the ID. In one embodiment, a separate TDRA field is configured for each SRS block, that is, each triggered SRS can be associated with a different TDRA. In one embodiment, SRS triggered by DCI are transmitted on the same time slot, but may be transmitted on different OFDM symbols. Then, DCI includes a group common TDRA field (e.g., k0 of the time slot offset) applied to all triggered SRS from that DCI, and a single TDRA field for each SRS block (e.g., OFDM symbol position, SLIV, etc.).

[0290] In some embodiments, if additional time-domain related parameters are required, one or two more bits can be added to the new field to indicate time-domain probe behavior, such as repetition, skipping, or splitting, across the allocated multiple OFDM symbols (if applicable). The A-SRS time-domain resource allocation field can indicate not only the trigger offset but also the duration of the SRS transmission based on the number of OFDM symbols, as well as other time-domain behavior-related parameters, such as repetition, whether discontinuous symbols are allowed, etc. For example, if the indicated A-SRS symbol length is greater than the A-SRS symbol length configured by the RRC, the A-SRS can be indicated to repetite, skip, or split in the time domain to fill the indicated symbol. One motivation for splitting the SRS into multiple symbols is to pre-schedule data transmission or probe data transmission with reduced SRS PAPR, as described below. Another motivation might be to reduce the SRS bandwidth per transmission, since UE power is typically limited, and therefore the bandwidth for SRS transmission is limited. The UE may not be aware of the probe intent or other intents determined by the network. Therefore, the impact of necessary standards may be to specify how the UE transmits SRS across multiple symbols.

[0291] If the same DCI is to trigger n individual probes on n A-SRS resource sets, then n such TDRA fields can be included. However, to avoid significant redesign of existing DCIs, at least an upper limit should be imposed on n for UE-specific DCIs. For example, UE-specific DCIs should only allow n = 1, 2, or 3. If a larger n is required, GC DCIs are more suitable than using UE-specific DCIs. The n individual probes can be on one or more time slots, on one or more carriers, etc.

[0292] According to some embodiments, the following DCI enhancements can be considered.

[0293] - Increase A-SRS time domain resource allocation field

[0294] See above for detailed discussion. This can apply to UE-specific DCI and / or GC DCI.

[0295] - Allow dynamically indicated frequency domain allocation, port allocation, and beamforming, reuse existing DCI field design as much as possible, reuse existing DCI field as much as possible

[0296] Dynamically indicated A-SRS frequency domain resource allocation can be beneficial in many cases. For example, this can significantly improve PDSCH spectral efficiency for interference sounding in TDD massive MIMO. For another example, A-SRS can be used for CSI acquisition for PUSCH transmission, so A-SRS can be transmitted only on a set of PRBs that can be scheduled for PUSCH, instead of on a wideband that consumes too many resources and energy or on a preconfigured bandwidth where gNB cannot acquire relevant CSI for PUSCH transmission. Furthermore, dynamically indicated A-SRS frequency domain resource allocation can also be used for SRS coverage / capacity enhancement related to partial frequency sounding. Similarly, dynamically indicated A-SRS port allocation and beamforming are also useful and should be supported.

[0297] To support flexible A-SRS triggering with dynamically indicated frequency domain allocation, we note that existing DCI formats already provide well-designed PUSCH / PDSCH FDRA fields, so they can be reused or enhanced for A-SRS. Furthermore, if A-SRS is used for CSI acquisition for co-scheduled PUSCH / PDSCH transmission (instead of general purpose, not tied to a specific transmission), A-SRS can be transmitted on the same PRBs as PUSCH / PDSCH. In this case, gNB can indicate UE to reuse PUSCH / PDSCH FDRA field for A-SRS, which helps to avoid high DCI overhead.

[0298] Similarly, to support flexible A-SRS triggering with dynamic indication of port allocation, we can reuse / enhance the existing PUSCH / PDSCH port indication field design, and if A-SRS is used for CSI acquisition for co-scheduled PUSCH / PDSCH transmission, we can reuse the PUSCH / PDSCH port indication field. To support flexible A-SRS triggering with dynamic indication of beamforming, for non-codebook-based SRS beamforming, we can reuse / enhance the existing design of CMR / IMR indication in the CSI request field of DCI format 0_1, and for codebook-based SRS beamforming, we can reuse / enhance the existing TPMI field design, and reuse the TPMI field if SRS is used for CSI acquisition for co-scheduled PUSCH transmission.

[0299] If n separate sounding on n A-SRS resource sets are to be triggered using the same DCI, n such FDRA fields, n such port indication fields, etc. should be included. However, to avoid significant redesign of existing DCI, at least an upper limit of n should be imposed on UE-specific DCI. For example, UE-specific DCI can only be allowed n = 1, 2, [3].

[0300] - UE-specific UL DCI and DL DCI to enhance A-SRS

[0301] UE-specific UL DCI (e.g., DCI format 0-1, 0-2) can be enhanced for A-SRS. For example, we can extend the DCI for A-SRS triggering without co-scheduled PUSCH by adding fields in the free PUSCH fields to indicate SRS TDRA, FDRA, port, and beamforming. In addition, if SRS is used for CSI acquisition for co-scheduled PUSCH transmission, UL power control information acquisition, UL beam acquisition, etc., we can extend the DCI for A-SRS triggering by reusing the PUSCH fields to indicate SRS FDRA, port, and beamforming. In this case, the UE first performs A-SRS transmission according to the existing fields of FDRA and port indication, as well as the new fields of SRS resource indication, SRS triggering offset, and CMR / IMR indication. Then, the UE performs PUSCH transmission according to at least the same FDRA and port indication in the same DCI, and possibly follows the TPC command sent for the UE in GC DCI based on the power received by gNB from A-SRS.

[0302] On the other hand, UE-specific DL DCI (e.g., DCI format 1-1) can be enhanced for A-SRS. If SRS is used for CSI acquisition for co-scheduled PDSCH transmission, we can extend the DL DCI for A-SRS triggering with co-scheduled PDSCH by reusing the PDSCH fields indicating SRS FDRA, port and beamforming. In this case, the UE first performs A-SRS transmission according to the existing fields of FDRA, PRB bundling size indication and port indication, as well as new fields of SRS resource indication, SRS trigger offset and CMR / IMR indication. Then, the UE performs PDSCH reception according to at least the same FDRA and port indication in the same DCI.

[0303] - GC DCI for enhanced A-SRS

[0304] GC DCI can be enhanced for A-SRS (e.g., DCI format 2-3 with multiple blocks, each block can be used to trigger one A-SRS transmission).

[0305] The basic design principle for GC DCI for A-SRS can be that A-SRS transmissions scheduled by GC DCI can be approximately the same time, e.g., in the same slot or a pair of adjacent slots. Based on this principle, we can consider adding a group common field in the GC DCI to indicate the slot / symbol location applicable to all A-SRS transmissions triggered by the DCI, as well as UE-specific fields for UE-specific symbol offset (which can span slots) of the UE, or block-specific fields for block-specific symbol offset of the SRS block.

[0306] In addition, since A-SRS transmissions can be on the same slot, preconfigured SRS transmission resources (e.g., symbol location, PRB, comb / shift, cyclic shift) can not be suitable and there can be resource conflicts, resulting in some SRS transmissions being discarded. To solve this problem, the GC DCI can indicate SRS multiplexing through UE-specific SRS port resources (symbols, combs / comb shifts and cyclic shifts).

[0307] Figure 17 An example of this aspect is shown. Figure 17An example of SRS resource configuration 1700 for A-SRS transmission. The SRS region 1702 can be indicated by SRS GC DCI. The indication of the SRS region can include the starting symbol and optional length (in terms of number of symbols, e.g., TDRA field; and the SRS region can span across slot boundary, e.g., the boundary of slot n and slot n+1) and frequency domain allocation in a slot (e.g., slot n). The SRS region starting symbol can be indicated as a field common to all SRS blocks. Each SRS block can also be allocated with a subset of port resources within the SRS region 1702. All SRS port resources within the SRS region are indicated by the GC DCI. The GC DCI common timing field can only indicate the reference symbol and reference PRB / RBG. Then, all block-specific resource allocation are relative to the reference symbol and reference PRB / RBG. The port resources in time domain can include symbol location, comb and comb shift, cyclic shift. Each SRS block in the GC DCI is allocated with a subset of port resources that are orthogonal to the port resources allocated to other SRS blocks.

[0308] In some embodiments, the following can be considered for time offset and TDRA indication:

[0309] - UL / DL TDRA

[0310] - Non-slot-based (2, 4, 7 symbols of SRS in UL slot even DL slot of TDD). SRS triggering time offset and time domain resource can use non-slot-based structure

[0311] - Even pre-emption (for eMBB / other UEs) can be used to allow very flexible SRS to insert SRS and optional UL / DL URLLC data

[0312] - PDCCH schedules URLLC data (UL / DL) and CSI acquisition RS (SRS / CSI-RS) on different symbols, which can all be in the same slot

[0313] In some embodiments, the DCI can support the following aspects:

[0314] 1. At least support the following flexible A-SRS triggering enhancements in UE-specific DCI:

[0315] - Add A-SRS time domain resource allocation field.

[0316] - Allow dynamic indication of frequency domain allocation, port allocation, and beamforming, reuse existing DCI field design as much as possible, reuse existing DCI field as much as possible.

[0317] - UE-specific UL DCI and DL DCI for A-SRS enhancement

[0318] 2. At least support flexible A-SRS triggering enhancement in the following group common DCI:

[0319] - Design principle: A-SRS transmission scheduled by GC DCI is in the same slot or adjacent slot.

[0320] • Add one group-common field for the slot / symbol location common for all SRS transmissions

[0321] • Indicate SRS multiplexing by UE-specific SRS port resources (symbols, comb / comb shift, and cyclic shift)

[0322] 3. For UL DCI 0_1 and 0_2 triggering aperiodic SRS without data without CSI, reuse the unused fields for SRS parameter indication, including adding new fields for A-SRS and reusing the design of A-SRS part of the unused fields:

[0323] - Reuse the unused PUSCH TDRA field for A-SRS time domain resource allocation on one or multiple OFDM symbols and reuse the PUSCH TDRA field design as much as possible.

[0324] • Also add a new field to indicate the sounding behavior on the allocated multiple OFDM symbols: repetition, hopping, or splitting

[0325] - Reuse the unused PUSCH FDRA field, port allocation field, beamforming field, TPC command field, etc. for A-SRS and reuse the same field design as much as possible.

[0326] - Redesign the SRS request field to include more bits for indicating SRS resources / resource sets.

[0327] 4. For UL DCI 0_1 and 0_2 with data and DL DCI 1_1 and 1_2 with data triggering aperiodic SRS:

[0328] - Add one A-SRS TDRA field for A-SRS time domain resource allocation on one or multiple OFDM symbols and reuse the PUSCH / PDSCH TDRA field design as much as possible (up to 4 bits).

[0329] • Also add a new field to indicate the sounding behavior on the allocated multiple OFDM symbols: repetition, hopping, or splitting

[0330] - Add a flag to indicate whether A-SRS also uses PUSCH / PDSCH field for its parameter indication, including FDRA field, port allocation field, beamforming field, etc.

[0331] 5. Enhance GC DCI 2_3 to optionally include at least TDRA field in SRS trigger block for flexible trigger offset, and increase bits for indicating SRS resource / resource set.

[0332] If DL coverage of the UE is not an issue, SRS coverage can be limited by the transmission power of the UE. To overcome the power limitation, the following embodiments are provided.

[0333] One embodiment is to concentrate power on a narrower bandwidth or fewer subcarriers to improve UL reception SNR. Current sounding already supports non-wideband transmission (at least 4 RBs), but in the case of coverage limited, narrowband sounding can be further split into multiple partial soundings to cover the bandwidth of one narrowband sounding. This is also useful to exploit frequency selectivity and reduce interference between SRS from different UEs. In addition, this also improves frequency-selective precoding of SRS.

[0334] To support partial bandwidth sounding, the standard can allow 1~2 PRB sounding, PRB skipping, larger comb (i.e., RE skipping), etc.

[0335] However, a potential issue with partial bandwidth sounding is that since each sounding transmission is typically associated with an unknown random phase, the gNB can not be able to combine multiple partial bandwidth sounding transmissions to obtain wideband CSI. This needs to be addressed.

[0336] One embodiment is to repeat in time domain, including multiple symbols in the same slot and across multiple slots. Simple repetition can be supported. It can also be allowed to use different combs / comb shifts (or repetition with different density in RE / PRB or interleaved).

[0337] One embodiment is to allow TD-OCC in SRS. In CSI-RS, TD-OCC is supported in order to leverage multiple OFDM symbols to strengthen CSI-RS transmission. This can also be adopted in SRS.

[0338] To increase SRS capacity, embodiments should allow more UEs to sound simultaneously, and allow more sounding opportunities / resources as well as SRS transmission multiplexed with other signals.

[0339] One embodiment is to use less time / frequency resources for each SRS transmission. If each SRS transmission occupies fewer subcarriers and / or OFDM symbols, then more UEs can be sounded and the SRS capacity is increased. For example, the SRS comb can be increased to 8 or 12. As another example, PRB hopping or narrower bandwidth for SRS can be considered, which can also improve the SRS coverage as mentioned above.

[0340] One embodiment is to allow non-orthogonal low-correlation sequences. The number of orthogonal sequences for SRS is limited. To allow more SRS transmissions to be multiplexed on overlapping time / frequency resources, non-orthogonal low-correlation sequences can be employed. The network can configure / trigger transmission of non-orthogonal sequences when needed, e.g., when SRS capacity becomes a limiting factor for operation, but orthogonal sequences can still be used at other times.

[0341] One embodiment is to allow SRS to use more time / frequency resources. For example, all 14 symbols in a UL slot can be used for SRS, which is already supported in NR-U. To provide this flexibility, flexible configuration and triggering of SRS needs to be standardized. This also motivates flexible A-SRS triggering to dynamically / opportunistically utilize unused UL symbols / PRBs, or even DL symbols / PRBs in TDD. To support the latter, SRS switching gap (due to RF retuning) similar to SRS carrier-based switching can be used to harvest some unused DL symbols, i.e., the UE switches from DL reception to SRS transmission on one or more OFDM symbols according to the network configuration / indication after the SRS switching gap, and switches back to DL reception after the SRS transmission and another SRS switching gap. In addition, concurrent SRS+PUCCH, or even SRS+PUSCH, can be considered to allow more SRS opportunities.

[0342] Regarding Category 1 enhancements on time bundling, this can improve SRS coverage. One issue that can exist is the potential phase discontinuity issue. Further analysis shows that while this can be an issue in general, there are at least some scenarios where the phase change between SRS transmissions is small enough, e.g., when SRS transmissions are close enough in time, when Doppler is small, or when the UE’s transmit chain can maintain the phase well between transmissions. In any case, the gNB can decide whether the phase discontinuity is severe, and if not, it can configure the UE to sound in a time bundle, and then the gNB performs joint processing. This can depend on the gNB implementation. As long as the standard provides sufficient support for the configuration and / or indication of SRS transmissions in a time bundle, the rest can be standard-transparent. The current SRS configuration seems to be sufficient in general, and the SRS indication by DCI can be enhanced to trigger time-bundled transmissions.

[0343] In some embodiments, for SRS coverage / capacity enhancement related to time bundling, the following can be considered:

[0344] - At least in some cases, the potential phase discontinuity is small enough and can support time bundling.

[0345] - Provide standard support for time bundling by more flexible SRS transmission configuration / indication, and make time bundling transparent to UE.

[0346] For 2-type enhancement with increased repetition, this can be the most direct method to improve SRS coverage and should be supported. The current standard already allows the configuration of repetition factor values of n1, n2, n4 and nrofSymbols values of n1, n2, n4, n8, n12. To enhance, repetition factor values of n3, n6, n8, etc. can be added, and nrofSymbols values of n3 (to complement n4 in a half-slot), n5 (to complement n2 in a half-slot), n6 (to complement n1 in a half-slot and n8 in a slot), n10 (to complement n2 in a slot), and n14 can be added. One SRS occasion can also extend to the next slot, for example, for nrofSymbols of n6, SRS can use the last 2 symbols in a slot and 4 symbols in the next slot, which can be at the beginning of the slot in the case of available SRS time domain resources, or can be at different time domain locations based on available SRS time domain resources. RRC configuration and DCI indication of SRS transmission repetition / symbols can be enhanced.

[0347] Increased repetition can result in a reduction in signals / UEs that can be multiplexed simultaneously. This negative impact can be partially compensated for by partial frequency sounding, which will be discussed below. However, this means that the standard can need to consider joint design of time domain repetition and partial frequency sounding, for example, when time domain repetition is increased, the frequency domain resources can become more sparse or less.

[0348] In some embodiments, for SRS coverage / capacity enhancement 2-type (increased repetition), the following can be considered:

[0349] - Allow configuration / indication of more repetition factor values and more nrofSymbols values;

[0350] - Allow cross-slot resource mapping;

[0351] - Allow joint design of partial frequency sounding and increased repetition to compensate for the negative impact on SRS capacity.

[0352] The following provides candidate scheme embodiments for partial frequency sounding:

[0353] - Scheme 3-1: RB-level partial frequency sounding

[0354] - Scheme 3-2: Subcarrier-level partial frequency sounding

[0355] - Scheme 3-3: Subband-level partial frequency sounding

[0356] - Scheme 3-4: Partial frequency sounding scheme with CSI-RS assistance, where SRS is transmitted in RB subsets of the original SRS frequency resource

[0357] - Scheme 3-5: Dynamic variation of SRS bandwidth scaling with RB-level subband size

[0358] The 3 types of enhancements for partial frequency sounding mainly include more flexibility on SRS frequency resource to allow transmission of SRS on partial frequency resource within the original SRS frequency resource. Regarding the 3 types of enhancements for partial frequency sounding, this is useful to concentrate power on a narrower bandwidth or fewer subcarriers to improve UL reception SNR. Current sounding already supports non-wideband transmission (at least 4 PRBs), but in the case of coverage limited, narrowband sounding can be further split into multiple partial soundings to cover the bandwidth of one narrowband sounding. This is also useful to exploit frequency selectivity and reduce interference between SRS from different UEs. In addition, this also improves the frequency-selective precoding of SRS. The partial bandwidth granularity can be modified to 1-2 PRBs. However, to reduce signaling overhead, some restrictions can be considered. If A-SRS is associated with a specific PDSCH / PUSCH transmission, the SRS can have the same granularity as the PDSCH / PUSCH frequency domain resource allocation granularity. For example, for resource block group (RBG) based resource allocation Type 0, SRS can also follow the same RBG based granularity (RBG of 2 / 4 / 8 / 16 PRBs). For example, when PDSCH / PUSCH is transmitted in multiple non-contiguous RBGs, SRS can also be transmitted in multiple non-contiguous RBGs. For PRB based resource allocation Type 1 (contiguous allocation in frequency domain, i.e., the frequency resource allocated to the transmission occupies contiguous PRB frequency resources), the SRS bandwidth can also be as small as one PRB. For example, when PDSCH / PUSCH is transmitted in contiguous PRBs, SRS can also be transmitted in contiguous PRBs.

[0359] Figure 18 Figure 1800 is a diagram of an example BiT for A-SRS triggering based on partial frequency sounding with dynamic indication. In Figure 18In this example, each block represents a PRB. In this example, the gNB can pre-schedule a subset of PRBs (e.g., PRBs 1802 and 1804) for data transmission in TTI m. To probe the interference of the subset of PRBs pre-scheduled for data, the UE can only need to probe on the subset of PRBs, e.g., on PRBs 1802 and 1804 in TTI m+n. The data transmission can then be completed, e.g., in TTI m+n+k, with precoders adjusted according to the SRS-based interference probing. Since the SRS transmission is tied to a specific data transmission, a flexible A-SRS trigger can be used.

[0360] Partial frequency probing can also be achieved by extending the transmission of one SRS resource (or resource set) to multiple hop transmissions. For example, an SRS resource on 8 PRBs (PRBs 1~8) can be completed in 2 hop transmissions, the first hop on PRBs 1~4 and the second hop on 5~8. The hop can be configured / indicated based on frequency domain granularity, e.g., PRB (i.e., n PRBs per hop) or RBG (i.e., n RBGs per hop). Different hops can also have different combs and / or different comb shifts. For example, an SRS resource of comb 4 and shift 0 can be split into 2 hops, the first hop with comb 8 and shift 0 and the second hop with comb 8 and shift 4.

[0361] In addition to Scheme 3-2, the above candidate schemes all belong to this category, where the granularity of N consecutive PRBs can be different. For example, for Scheme 3-1, N=1; for Scheme 3-3, N=4 or N can be the same as the PDSCH / PUSCH frequency domain resource allocation granularity (i.e., N=2, 4, 8, 16); for Scheme 3-4, N=1, 2, 4, 8, etc.; for Scheme 3-5, N=2 or 4. Although the motivations of these schemes can be different, their standard impact can be similar, and a unified design can be used to support all these schemes.

[0362] In summary, Schemes 3-1, 3-3, 3-4, and 3-5 belong to Category A: partial frequency probing with granularity of N PRBs can be supported by one unified design, where N=1, 2, 4, 8, 16, etc.

[0363] Partial frequency probing can also be achieved if each SRS transmission occupies fewer subcarriers, then more UEs can be probed, SRS capacity is increased, which can also improve SRS coverage while more power is concentrated. For example, the SRS comb can be increased to 6, 8, or 12. Scheme 3-2 belongs to this category, referred to as Category B: partial frequency probing with larger comb.

[0364] Note that Category A and Category B can be merged in some cases.

[0365] For legacy sounding, SRS occupies one contiguous segment of bandwidth, which can prevent the peak to average power ratio (PAPR) from becoming too high. Depending on the specific proposal / design / implementation, several candidate solutions (e.g., solutions 3-1, 3-2, and 3-3) consider transmitting SRS on non-contiguous segments in the frequency domain, which typically results in some small increase in PAPR. According to our evaluation, the PAPR can increase by about 0.5 dB to 3 dB if two or more non-contiguous SRS segments are transmitted on the same OFDM symbol. Further analysis on the non-contiguous sounding PAPR will be described later in this disclosure.

[0366] There can be several solutions to address the PAPR issue, as described below:

[0367] - First, since the increase in PAPR is not significant and can be estimated in advance by both gNB and UE, gNB can decide some non-contiguous SRS transmission for certain cell-center UEs only. This is an implementation-oriented solution that does not require any standard support.

[0368] - Second, when K non-contiguous SRS segments are to be transmitted, gNB can indicate UE to autonomously split K segments over K OFDM symbols, so that on each OFDM symbol, SRS transmission is only on one contiguous PRB. This can prevent PAPR increase and further reduce SRS transmission bandwidth, suitable for cell-center and cell-edge UEs. This requires some standard support, e.g., the splitting can be indicated in the triggering DCI as part of the time-domain behavior of SRS on multiple OFDM symbols.

[0369] Non-contiguous SRS segments can still be supported without significant PAPR increase.

[0370] Figure 19 A diagram 1900 is shown to illustrate splitting of frequency resources for SRS transmission. In Figure 19In this case, the gNB can pre-schedule data transmission to the UE on frequency resources including a first set of contiguous PRBs 1902 and a second set of contiguous PRBs 1904. The two sets are not contiguous in the frequency domain. The gNB can trigger the UE to perform sounding on the same frequency resources and configure the UE with the same frequency resources for SRS transmission. The UE can transmit SRS on the configured frequency resources upon the trigger. In one example, the UE can split the configured frequency resources into two segments (based on the two non-contiguous sets), segment 1902 and segment 1904, and transmit SRS on the two segments 1902 and 1904 on two different OFDM / SC-FDM symbols 1906 and 1908. The UE can split the frequency resources into more segments, which can be indicated by the gNB or can depend on how many non-contiguous segments the frequency resources include. In one OFDM / SC-FDM symbol, the SRS can be transmitted on only a portion of the frequency resources indicated by RRC configuration or DCI indication, from the gNB to the UE. In one embodiment, the UE can transmit SRS according to a frequency hopping pattern in the two OFDM symbols. In another embodiment, the UE can repeatedly transmit SRS on one segment in different OFDM symbols. For example, the SRS can be transmitted three times on the same segment 1902 in three different symbols. The gNB can indicate whether SRS transmission is to be performed on split frequency resources, whether to hop across OFDM symbols on a segment, and / or to repeat in OFDM symbols on one or more segments. Upon receiving the SRS, the gNB can adjust the precoder for data transmission on the frequency resources according to the received SRS.

[0371] In some embodiments, standard support can be provided for Type A schemes with possible repetition / splitting.

[0372] All schemes in Type A can be supported by a unified design, which can also include possible repetition / splitting / hopping across multiple OFDM symbols. The DCI triggering partial frequency sounding includes an FDRA field with a bitmap, each bit indicating sounding on N contiguous PRBs. Another field in the DCI can be used to indicate whether the sounding is repeated across the indicated multiple OFDM symbols, is hopped across the indicated multiple OFDM symbols, or is split across the indicated multiple OFDM symbols.

[0373] Type 3 SRS coverage / capacity enhancement (partial frequency sounding) can consider the following:

[0374] - Support SRS partial bandwidth granularity based on PDSCH / PUSCH resource allocation granularity;

[0375] - Support SRS comb 6, 8, 12;

[0376] - Support of multi-hop SRS resources (one SRS resource is done by multiple hops of PRB / RBG and / or comb shift).

[0377] In 3GPP Release 17, further enhanced MIMO (FeMIMO) probing reference signal enhancements include:

[0378] - Identify and specify enhancements of aperiodic SRS triggering to facilitate more flexible triggering and / or DCI overhead / usage reduction;

[0379] - Specify SRS switching for up to 8 antennas (e.g., xTyR, x = {1, 2, 4} and y = {6, 8});

[0380] - Evaluate and, if necessary, specify the following mechanisms to enhance SRS capacity and / or coverage: SRS time bundling, increased SRS repetition, partial probing across frequencies.

[0381] Motivations for flexible triggering include:

[0382] - Limited triggering information in DCI (only 1, 2, or 3 bits);

[0383] - Triggering delay is not flexible;

[0384] - Important role of SRS in DL full-MIMO CSI acquisition, BM, UL frequency diversity, and MIMO support, etc.

[0385] - New addition: Important role of aperiodic SRS (A-SRS) in TDD coordinated MIMO for DL interference probing and mitigation includes:

[0386] - UE-to-Tx SRS based on DL (pre-)scheduling results so that gNB can estimate DL interference and then adjust through precoder adjustment to mitigate DL interference,

[0387] - Some similarity with DL NZP CSI-RS based interference probing for better MCS. This is also after scheduling and before PDSCH, but UL SRS is used for better precoding (hence better BiT).

[0388] - Also closely related to SRS coverage / capacity enhancement.

[0389] Figure 20A An example single BIT operation flow 2000 is shown. In BIT, precoded SRS is based on PDSCH scheduling and then based on PDSCH itself. Precoded probing is based on gNB’s MU pre-scheduling to cooperatively probe DL interference conditions in UL.

[0390] AsFigure 20A Cov(Y) captures inter / intra-cell interference in UL, (Cov(Y)) is the covariance of the received signal at the UE. –1 h enabling UL interference avoidance. Then, by reciprocity, DL Tx with this precoding enables cooperative DL interference avoidance. Theoretical guidance stems from global optimization.

[0391] Figure 20B and 20C A communication system is shown highlighting example interference conditions. Figure 20B A communication system 2030 shows a case where UL SRS transmission by UE 2005 using transmit beamforming results in weak interference at first BS 2007, while second BS 2009 sees strong interference. Figure 20C A communication system 2050 shows a case where beamforming can be used to reduce interference to a UE. First BS 2057 can use beamforming in the direction of UE 2055, but second BS 2059 avoids using beamforming in the direction of UE 2055 because such transmission can cause high interference at UE 2055.

[0392] Figure 21A and 21B Data graphs 2100 and 2150 are shown highlighting example BIT performance.

[0393] Regarding flexible A-SRS triggering for BIT, SRS can include enhancements with dynamic indication parameters associated with corresponding DL transmissions. Enhancements can include:

[0394] - A-SRS triggering with dynamic indication of PRB allocation (e.g. FDRA) and port allocation;

[0395] - A-SRS triggering with dynamic indication of DL channel measurement resources (CMR) and / or interference measurement resources (IMR);

[0396] - A-SRS triggering with flexible triggering delay.

[0397] Related to reducing DCI overhead for flexible triggering, motivations include:

[0398] - All flexible triggering can result in higher DCI overhead;

[0399] - BiT can also require more A-SRS triggers.

[0400] Example solutions can include:

[0401] - UE-specific DCI with FDRA and port indication for A-SRS (same as PDSCH). However, FDRA can generally need 5-19 bits and port indication can need 4-6 bits;

[0402] - Group common DCI to a group of UEs that can be paired for MU transmission in a slot, with FDRA and port indication. However, SRS trigger offset can not be equal for this group of UEs.

[0403] According to example embodiments, methods and apparatuses are provided on how to trigger SRS transmission with all required SRS parameters in DCI but with reduced DCI overhead, and associated UE assumptions / behaviors / configurations to support this. Table 2 below shows the current DCI 1-1 format used for scheduling PDSCH in one cell. Table 3 below shows the antenna ports.

[0404] Table 2

[0405]

[0406]

[0407] Table 3

[0408] dmrs-Type maxLength bit field length Table in 38.212 1 1 4 Table 7.3.1.2.2-1 1 2 5 Table 7.3.1.2.2-2 2 1 5 Table 7.3.1.2.2-3 2 1 6 Table 7.3.1.2.2-4

[0409] According to example embodiments, an enhanced DCI 1-1 format is provided. The enhanced DCI 1-1 format supports PDSCH scheduling in one cell, as well as associated SRS sounding. Table 4 below provides detailed information on the enhanced DCI 1-1 format.

[0410] Table 4

[0411]

[0412]

[0413] The enhanced DCI 1-1 format includes the following beneficial features:

[0414] - SRS sounding requires fields FDRA and antenna port indication, but with high overhead. The enhanced DCI 1-1 design reuses the existing fields for FDRA and antenna port indication in the associated PDSCH scheduling DCI, and adds a new SRS trigger offset, so that one DCI can be used for both operations (e.g. SRS transmission and PDSCH reception).

[0415] - The GC DCI can also add a new SRS trigger offset field so that all SRS are transmitted on overlapping resources for BiT purposes.

[0416] Not all new or optional fields need to be present in the enhanced DCI 1-1 format.

[0417] Table 5 below shows further examples of enhancements for DCI 1-1.

[0418] Table 5

[0419]

[0420] Further enhancements for DCI 2-3 and 0-1 can include: SRS triggered by DCI can be linked to another DL DCI and SRS reuses fields (e.g. FDRA, antenna ports) from the linked DCI.

[0421] Figure 22 Figure 2200 illustrates information exchanged between a gNB and a UE when the gNB configures UL SRS sounding and then performs DL transmission based on the UL SRS sounding results.

[0422] According to example embodiments, an enhanced DCI 0-1 format is provided. The enhanced DCI 0-1 format supports scheduling of PUSCH in one cell, as well as associated SRS sounding. Table 6 below provides detailed information about the enhanced DCI 0-1 format. Table 7 below shows example fields in DCI format 0_1 that are reused for A-SRS triggering.

[0423] Table 6

[0424]

[0425]

[0426] Not all new or optional fields need to be present in the enhanced DCI 0-1 format.

[0427] Table 7

[0428]

[0429]

[0430]

[0431] For all other SRS parameters not indicated in the DCI, RRC / MAC signaling can be used to determine these parameters.

[0432] Table 8 below shows example fields in DCI format 1_1 that are reused for A-SRS triggering.

[0433] Table 8

[0434]

[0435]

[0436] As Figure 22 illustrated, A-SRS can also be based on a carrier indication field, a bandwidth part indication field, a VRB-PRB mapping field, a PRB bundling size field, a TPC command for PUCCH field, or a TPC command for SRS field in DCI. Further, a SRS triggering offset can be indicated in a TDRA field (e.g., reuse from PUSCH or PDSCH design). A CMR and optional IMR can be included for the UE to determine SRS precoding, e.g., the design of CSI request field can be reused.

[0437] An example of SRS mapping of resources and ports can be as follows (refer to Figure 6 ):

[0438] - Assume DMRS Type 1 is used, i.e., 8 ports per paired UE / RBG / cell;

[0439] - These 8 ports are associated with 8 SRS port resources selected from n available port resources:

[0440] - For comb-4, n = 48,

[0441] - For comb-2, n = 16.

[0442] - SRS from neighboring cells should be multiplexed on n SRS port resources.

[0443] - Then, indicate to the UE which 1, 2, or 4 SRS port resources out of the n available SRS port resources are needed, which takes too many bits.

[0444] Figure 23 A diagram 2300 showing RGBs 2305 and 2307, and example mapping of SRS resources and ports. In one embodiment, the UE group CSI-RS / DMRS design is applied to the SRS design. For example, for each cell, limit the cell to a specified number of predefined SRS port resources (e.g., 8, but other values are possible). Then, in the group DCI, indicate the UE’s layer / port from within the specified number (e.g., 8) of predefined SRS port resources. For example, configure SRS resources for all active UEs in cell 1, all SRS resources have the same 8 ports. The group DCI indicates which of the 8 ports is for a particular UE. For example, indicate rank [1, 2, 4, 1] for UEs 1, 2, 3, 4. No layer index needs to be indicated. As another example, reuse the DMRS port mapping. As another example, the SRS resources can be configured for all RBGs, but the scheduling / group DCI allows different UEs to be scheduled on different RBGs.

[0445] In TS 38.331, the usage of SRS resource is as follows:

[0446] with ENUMERATED{beam-management, codebook, non-codebook, antenna-switching},

[0447] In TS 38.214, procedures are specified for SRS resources for different usages. Some procedures are the same for “codebook” and “antenna-switching”, but some are not, as follows:

[0448] - The UE receives a command based on a downlink DCI, a group common DCI, or an uplink DCI, where the codepoint of the DCI can trigger one or more SRS resource sets. For SRS in a resource set with usage set to “codebook” or “antenna-switching”, the minimum time duration between the last symbol of the PDCCH triggering the aperiodic SRS transmission and the first symbol of the SRS resource is N2+T switch . Otherwise, the minimum time duration between the last symbol of the PDCCH triggering the aperiodic SRS transmission and the first symbol of the SRS resource is N2+T switch + 14. The minimum time duration in OFDM symbols is calculated according to the minimum subcarrier spacing between the PDCCH and the aperiodic SRS.

[0449] - When the UE receives a spatial relation update command for a SRS resource as specified in [10, TS 38.321] clause 6.1.3.26, and when the HARQ-ACK corresponding to the PDSCH carrying the update command is transmitted in slot n, the corresponding actions in [10, TS 38.321] and the UE assumptions regarding the updated spatial relation for the SRS resource shall apply to the SRS transmission starting from the first slot after slot n+1. The update command contains spatial relation assumptions provided by a reference list of reference signal IDs, each element in the updated SRS resource set has one reference signal ID. Each ID in the list refers to: a reference SS / PBCH block; a NZP CSI-RS resource configured on the serving cell indicated by the resource serving cell ID field in the update command, if present, which is otherwise the same as the SRS resource set; or a SRS resource configured on the serving cell and uplink bandwidth part indicated by the resource serving cell ID field and resource BWP ID field in the update command, if present, which is otherwise the same as the SRS resource set. When the UE is configured with the higher layer parameter usage set to “antenna-switching” in a SRS-ResourceSet, the UE shall not expect to be configured with a different spatial relation for a SRS resource in the same SRS-ResourceSet.

[0450] - When the UE is configured with the higher layer parameter usage in SRS-ResourceSet set to "antenna switching" and is configured with a guard period of Y symbols according to clause 6.2.1.2, the UE shall use the same priority rules as defined above within the guard period as configured for SRS in general.

[0451] Generally, there are more restrictions for "antenna switching" than for "codebook". In specific operational scenarios, if the same procedure applies for different usage, the network can configure one SRS resource with either usage, but the network can use it for both usage purposes without standard impact, or the network can configure two SRS resources which are almost identical except for "usage" (without standard impact), or the network can configure one SRS resource with two "usage" values (change to TS 38.331 is needed). In general operational scenarios, different procedures can be needed for different usage, so different SRS resources have to be configured. This is up to the network. Overall, the use cases for this potential enhancement seem to be limited, and the potential benefits can include some minor RRC overhead reduction and avoiding reaching the UE's SRS resource limit of 64. Based on the analysis, we tend to stick to the implementation approach rather than the enhancement, unless some other strong reasons are identified.

[0452] Therefore, in one embodiment, the system relies on the implementation approach to reuse SRS resources for more than one usage, e.g., "antenna switching" and "codebook".

[0453] Regarding whether to support the related enhancement of indicating Tx / Rx antenna subset in SRS antenna switching, we point out that some CSI measurement related issues have not been considered in the existing discussion. When the UE Tx / Rx antenna number changes in a more dynamic way, the MIMO channel properties also change more dynamically and abruptly. Therefore, the UL / DL CSI will change. The existing RI / PMI / CQI, etc. need to support fast adaptation, such as time domain limited based CSI measurement (single CSI-RS or multiple CSI-RS but cannot be averaged / filtered outside the time window). That is, at the time slot when the UE antenna configuration changes, all the CSI measurements need to be reset, and the new measurement is performed without averaging / filtering any measurement before the time slot.

[0454] If the network wants to dynamically switch between two or more UE antenna configurations, the network needs to configure multiple sets of CSI measurement / reporting, and averaging on the CSI measurement resource is not allowed. If n different UE antenna configurations are configured, each of the n antenna configurations is configured with at least one set of CSI measurement and reporting configuration, which is separate / independent from the other UE antenna configurations.

[0455] For more details on the PAPR of the discontinuous sounding, see below. Some evaluations were done on the discontinuous (frequency) sounding segments to show the degree of PAPR increase. The evaluations took into account the following:

[0456] - To describe the SRS pattern, we use a bitmap of PRBs, where a PRB is marked with 1 if there is sounding on that PRB and 0 if there is no sounding on that PRB. For example, [0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1] for 16 PRBs in a partial bandwidth, transmitting 4 discontinuous segments, where each segment contains 2 consecutive PRBs for sounding and 2 PRBs not for sounding. See Figure 24A .

[0457] - On each PRB, a comb-4 is assumed, i.e. 3 subcarriers are used per PRB.

[0458] - When sounding over multiple discontinuous segments, different sequences can be used on different segments or the same sequence can be used. Both were evaluated.

[0459] We considered the following cases when doing the evaluations:

[0460] 1. Scenario 1: Periodic segments with pattern [0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1...]. Figure 24A An example of this pattern is shown. Figure 24A is a plot 2410 showing an example of discontinuous sounding over 16 PRBs, denoted as [0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1]. In this pattern, we considered:

[0461] 1) Case 1: 8 PRBs ([0 0 1 1 0 0 1 1]; same sequence).

[0462] 2) Case 2: 16 PRBs ([0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1]; same or different sequence; see Figure 24A ).

[0463] 3) Case 3: 32 PRBs ([0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1 0 0 1 1] same or different sequence).

[0464] 2. Scenario 2: Periodic segments with pattern [0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1...]. Figure 24BAn example of this pattern is shown. Figure 24B is a diagram 2430 showing an example of non-contiguous sounding on 16 PRBs, denoted as [0 00 1 0 0 0 1 0 0 0 1 0 0 0 1]. In this pattern, we consider:

[0465] 1) Case 1: 8 PRBs ([0 0 0 1 0 0 0 1]; same sequence);

[0466] 2) Case 2: 16 PRBs ([0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1]; same or different sequence; see Figure 24B );

[0467] 3) Case 3: 32 PRBs ([0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 0 0 0 1 0 00 1 0 0 0 1] same or different sequence).

[0468] 3. Scenario 3: Periodic segments of pattern [0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1…]. Figure 24C An example of this pattern is shown. Figure 24C is a diagram 2450 showing an example of non-contiguous sounding on 16 PRBs, denoted as [0 10 1 0 1 0 1 0 1 0 1 0 1 0 1]. In this pattern, we consider:

[0469] 1) Case 1: 8 PRBs ([0 1 0 1 0 1 0 1]; same sequence);

[0470] 2) Case 2: 16 PRBs ([0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1]; same or different sequence; see Figure 24C );

[0471] 3) Case 3: 32 PRBs ([0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 1 0 10 1 0 1 0 1] same or different sequence).

[0472] 4. Scenario 4: Aperiodic 2 segments, in the form of [000011111111000000001111…], with random location of segments. Figure 24D An example of this pattern is shown. Figure 24Dis a graph 2470 showing an example of discontinuous sounding on PRB, denoted as [0000111111110000000011111111111111110000]. For this scenario, we consider the cases shown in Table 9 below.

[0473] Table 9

[0474]

[0475] 5. Scenario 5: Aperiodic 3 segments, in the form of [0000111100001111000000001111…], with random positions of segments.

[0476] For this scenario, we consider the cases shown in Table 10 below.

[0477] Table 10

[0478] Case 1 Case 2 Case 3 Number of subbands (in 4 PRBs) Number of subbands (in 4 PRBs) Number of subbands (in 4 PRBs) 1st paragraph 1 2 4 2nd paragraph 2 4 4 3rd paragraph 1 6 4

[0479] The evaluation results for scenarios 1-3 are shown in Table 11 below.

[0480] Table 11

[0481] Scenario Case Sequence PAPR increment (dB) Scenario 1 Case 1 Same sequence 1.97 Scenario 1 Case 2 Same sequence 2.59 Scenario 1 Case 2 Different sequence 3.23 Scenario 1 Case 3 Same sequence 0.82 Scenario 1 Case 3 Different sequence 1.94 Scenario 2 Case 1 Same sequence 2.05 Scenario 2 Case 2 Same sequence 2.71 Scenario 2 Case 2 Different sequence 4.36 Scenario 3 Case 1 Same sequence 1.57 Scenario 3 Case 2 Same sequence 2.85 Scenario 3 Case 2 Different sequence 4.19 Scenario 3 Case 3 Same sequence 1.50 Scenario 3 Case 3 Different sequence 1.92

[0482] From Table 11 above, for scenarios 1-3, the PAPR increment is roughly in the range of 0.8dB to 4.3dB, and using the same sequence is better than using different sequences. When focusing on the same sequence test, the PAPR increment is in the range of 0.8dB to 2.9dB.

[0483] Figure 25A is a graph 2500 showing the complementary cumulative distribution function (CCDF) of PAPR for discontinuous sounding cases 1-4 of scenario 4, with the same or different sequences. From Figure 25A we can see that for scenario 4, the PAPR increment is roughly in the range of 0.5dB to 1.5dB, and using the same sequence can be better or worse than using different sequences.

[0484] Figure 25B is a graph 2550 showing the CCDF of PAPR for discontinuous sounding cases 1-3 of scenario 5, with the same or different sequences. We can see that for scenario 5, the PAPR increment is also roughly in the range of 0.5dB to 1.5dB, and using the same sequence is better than using different sequences in the tested cases.

[0485] Evaluations show that in most cases, for non-contiguous sounding, the UE would like to transmit SRS using the same sequence even if the sounding PRBs are not contiguous. For example, if one sequence is [s1 s2 s3 s4 s5 s6 s7 s8 s9 s 10 s 11 s 12 …], then it can be transmitted as [s1 s2 s3 gap s4 s5 s6 s7 s8 s9 gap s 10 s 11 s 12 …], where the gap is a PRB with no sounding, i.e., the elements in the sequence are not skipped over the PRBs with no sounding, they are just transmitted in different PRBs. Alternatively, it can be transmitted as [s1 s2 s3 gap s7 s8 s9 gap s 10 s 11 s 12 …], where the gap is a PRB with no sounding. That is, some elements in the sequence are skipped over the PRBs with no sounding. The network can configure / indicate to the UE which way of transmission it intends to use. Moreover, in a few cases, using different sequences over non-contiguous segments results in lower PAPR than using the same sequence. In these cases, the network can configure / indicate to the UE which sequence to use by the index of the sequence. When SRS is contiguous in the frequency domain, the UE can generate a first pseudo-random sequence for SRS according to the configured parameters (e.g., a first total sequence length of SRS based on the total number of PRBs allocated for SRS). However, over the first contiguous segment of frequency resources, the UE can generate a second pseudo-random sequence for SRS, e.g., a second sequence length of SRS is determined by the number of PRBs of the first contiguous segment, and the second sequence is generated with the second sequence length as a parameter. In some embodiments, in the A-CSI triggering DCI, the DCI indicates SRS whose resources are over non-contiguous PRBs, and the SRS will be transmitted on the same OFDM symbol. The gNB can also convey to the UE one or more sequence indices of SRS, and the length for each sequence. For example, 2 sequences can be indicated, for the first sequence, 12 elements will be used (e.g., 1 subband according to the SRS configuration), and for the second sequence, 24 elements will be used (e.g., 2 subbands according to the SRS configuration). The UE then transmits SRS accordingly.

[0486] Figure 26A flowchart for a wireless communication method embodiment 2600 is shown. The method 2600 can indicate operations performed by a UE. The UE can receive, from an access node (AN), downlink control information (DCI) triggering sounding reference signal (SRS) transmissions of a set of SRS resources, where the DCI includes information indicating a first time domain resource of available time domain resources for transmitting the set of SRS resources (step 2602). The UE can determine the available time domain resources for transmitting the set of SRS resources according to a first time slot in which the DCI is received (step 2604). The UE can determine a location of the first time domain resource in the available time domain resources according to the information of the DCI (step 2606), and transmit an SRS to the AN according to the location of the first time domain resource (step 2608).

[0487] Figure 27 A flowchart for another wireless communication method embodiment 2700 is shown. The method 2700 can indicate operations performed by a UE. The UE can receive control information for transmitting one or more sounding reference signals (SRSs), where the control information includes information indicating frequency resources in a carrier for transmitting the one or more SRSs (step 2702). The UE can determine, based on the control information, to divide the frequency resources into a plurality of segments, each segment including one or more contiguous physical resource blocks (PRBs) (step 2704). The UE can transmit, based on the control information, a first SRS of the one or more SRSs in a first orthogonal frequency division multiplexing (OFDM) symbol on a first segment of the plurality of segments and not on a second segment of the plurality of segments (step 2706).

[0488] Figure 28A flowchart of another wireless communication method embodiment 2800 is shown. The method 2800 can indicate operations performed by a base station, such as operations performed by an access node (AN). The AN can transmit, to a user equipment (UE), downlink control information (DCI) triggering sounding reference signal (SRS) transmission of a set of SRS resources, where the DCI includes information indicating a location of a first time-domain resource among available time-domain resources for transmitting the set of SRS resources (step 2802). The available time-domain resources for transmitting the set of SRS resources can be based on a first slot in which the DCI is transmitted. The AN can receive the SRS from the UE based on the location of the first time-domain resource (step 2804).

[0489] Figure 29 A flowchart of another wireless communication method embodiment 2900 is shown. The method 2900 can indicate operations performed by a base station, such as operations performed by an access node (AN). The AN can transmit, to a user equipment (UE), control information for transmitting one or more sounding reference signals (SRSs), where the control information includes information indicating frequency resources in a carrier for transmitting the SRSs (step 2902). The AN can then receive, from the UE, a first SRS of the one or more SRSs in a first orthogonal frequency division multiplexing (OFDM) symbol on a first segment of a plurality of segments segmented by the frequency resources in response to transmitting the control information, and not receive the first SRS on a second segment of the plurality of segments (step 2904). Each segment includes a plurality of contiguous physical resource blocks (PRBs).

[0490] An advantage of this embodiment is that control information, such as SRS transmission bandwidth, SRS transmission port, and a set of SRS resources including SRS transmission comb and cyclic shift, is dynamically signaled to pre-scheduled (or scheduled) UEs after being configured by higher layer signaling, such as radio resource control (RRC) or media access control (MAC) control element (CE) signaling.

[0491] Yet another advantage of this embodiment is that dynamic signaling of control information does not significantly increase communication overhead, thereby minimizing impact on overall performance of a communication system.

[0492] In yet another advantage, embodiments of the present disclosure associate parameters of SRS configuration (SRS transmission bandwidth and / or ports) with physical downlink shared control channel (PDSCH) parameters (bandwidth and / or ports) and / or CSI-RS parameters (bandwidth and / or ports).

[0493] Figure 30 An example communication system 3000 is shown. In general, the system 3000 enables multiple wireless or wireline users to transmit and receive data and other content. The system 3000 can implement one or more channel access methods, such as code division multiple access (CDMA), time division multiple access (TDMA), frequency division multiple access (FDMA), orthogonal FDMA (OFDMA), single-carrier FDMA (SC-FDMA), or non-orthogonal multiple access (NOMA).

[0494] In the present example, the communication system 3000 includes electronic devices (EDs) 3010a-3010c, radio access networks (RANs) 3020a-3020b, a core network 3030, a public switched telephone network (PSTN) 3040, the Internet 3050, and other networks 3060. While the Figure 30 A certain number of these components or elements are shown in the system 3000, but any number of these components or elements can be included in the system 3000.

[0495] EDs 3010a-3010c are configured to operate or communicate in system 3000. For example, EDs 3010a-3010c are configured to transmit or receive over wireless or wired communication channels. Each of EDs 3010a-3010c represents any suitable end user device and can include (or can be referred to as) a user equipment (UE), a wireless transmit or receive unit (WTRU), a mobile station, a fixed or mobile subscriber unit, a cell phone, a personal digital assistant (PDA), a smartphone, a laptop, a computer, a tablet, a wireless sensor, or a consumer electronics device.

[0496] RANs 3020a-3020b include base stations 3070a-3070b, respectively. Each base station 3070a-3070b is configured to wirelessly interface with one or more EDs 3010a-3010c to enable access to core network 3030, PSTN 3040, Internet 3050, or other networks 3060. Base stations 3070a-3070b can include (or be) one or more of a base transceiver station (BTS), a Node-B, an evolved NodeB (eNodeB), a next generation (NG) NodeB (gNB), a Home NodeB, a Home eNodeB, a site controller, an access point (AP), or a wireless router, among other well-known devices. EDs 3010a-3010c are configured to interface and communicate with Internet 3050, and can access core network 3030, PSTN 3040, or other networks 3060.

[0497] In Figure 30 In the illustrated embodiment, base station 3070a forms part of RAN 3020a, which can include other base stations, elements, or devices. Further, base station 3070b forms part of RAN 3020b, which can include other base stations, elements, or devices. Each of base stations 3070a-3070b is configured to transmit or receive wireless signals in a particular geographic area, sometimes referred to as a “cell.” In some embodiments, multiple-input multiple-output (MIMO) technology can be used, with multiple transceivers for each cell.

[0498] The base stations 3070a-3070b communicate with one or more EDs 3010a-3010c over one or more air interfaces 3090 using wireless communication links. The air interfaces 3090 can utilize any suitable wireless access technology.

[0499] It is contemplated that the system 3000 can use multi-channel access functionality, including schemes as described above. In particular embodiments, the base stations and EDs implement 5G New Radio (NR), LTE, LTE-A, or LTE-B. Of course, other multiple access schemes and wireless protocols can be utilized.

[0500] The RANs 3020a-3020b are in communication with the core network 3030 to provide the EDs 3010a-3010c with voice, data, application, voice over internet protocol (VoIP), or other services. Understandably, the RANs 3020a-3020b or core network 3030 can be in direct or indirect communication with one or more other RANs (not shown). The core network 3030 can also serve as a gateway for the other networks (for example, PSTN 3040, Internet 3050, and other networks 3060) to

[0501] Although Figure 30 Various changes can be made to the communication system Figure 30 illustrated. For example, the communication system 3000 can include any number of EDs, base stations, networks, or other components in any suitable configuration.

[0502] Figure 31A and Figure 31B Example devices that can implement the methods and teachings herein are illustrated. In particular, Figure 31A An example ED 3110 is illustrated, Figure 31B An example base station 3170 is illustrated. These components can be used in the system 3000 or any other suitable system.

[0503] As Figure 31AAs shown, the ED 3110 includes at least one processing unit 3100. The processing unit(s) 3100 implement various processing operations of the ED 3110. For example, the processing unit(s) 3100 can perform signal coding, data processing, power control, input / output processing, or any other functionality enabling the ED 3110 to operate in the system 3000. The processing unit(s) 3100 also support the methods and teachings described in detail above. Each processing unit 3100 includes any suitable processing or computing device configured to perform one or more operations. Each processing unit 3100 maybe, for example, a microprocessor, a microcontroller, a digital signal processor, a field programmable gate array, or application specific integrated circuit, among others.

[0504] The ED 3110 also includes at least one transceiver 3102. The transceiver 3102 is used to modulate data or other content for transmission by at least one antenna or network interface controller (NIC) 3104. The transceiver 3102 is also configured to demodulate data or other content received by the at least one antenna 3104. The at least one antenna 3104 is configured to transmit or receive wireless signals 3190. Each transceiver 3102 includes any suitable structure for generating a signal for transmission or processing a received signal. Each antenna 3104 includes any suitable structure for transmitting or receiving a wireless signal or a wired signal. One or more transceivers 3102 can be used in the ED 3110, and one or more antennas 3104 can be used in the ED 3110. Although the transceiver 3102 is shown as a single functional unit, it can also be implemented using at least one transmitter and at least one separate receiver.

[0505] The ED 3110 also includes one or more input / output devices 3106 or interfaces (e.g., wired interfaces to the Internet 3050). The input / output devices 3106 facilitate interaction with users or other devices (network communications) within the network. Each input / output device 3106 includes any suitable structure for providing information to or from a user, such as a speaker, microphone, keypad, keyboard, display, or touch screen, including network interface communications.

[0506] In addition, ED 3110 includes at least one memory 3108. Memory 3108 stores instructions and data used, generated, or collected by ED 3110. For example, memory 3108 may store software or firmware instructions executed by processing unit 3100, as well as data used to reduce or eliminate interference in incoming signals. Each memory 3108 includes any suitable volatile or non-volatile storage and retrieval device. Any suitable type of memory can be used, such as random access memory (RAM), read-only memory (ROM), hard disk, optical disk, subscriber identity module (SIM) card, memory stick, secure digital (SD) card, etc.

[0507] like Figure 31B As shown, base station 3170 includes at least one processing unit 3150, at least one transceiver 3152 (including transmitter and receiver functions), one or more antennas 3156, at least one memory 3158, and one or more input / output devices or interfaces 3166. A scheduler, as understood by those skilled in the art, is coupled to processing unit 3150. The scheduler may be included within base station 3170 or may operate separately from base station 3170. Processing unit 3150 implements various processing operations of base station 3170, such as signal encoding, data processing, power control, input / output processing, or any other functions. Processing unit 3150 may also support the methods and teachings described in detail above. Each processing unit 3150 includes any suitable processing or computing device configured to perform one or more operations. Each processing unit 3150 may include a microprocessor, microcontroller, digital signal processor, field-programmable gate array, or application-specific integrated circuit, etc.

[0508] Each transceiver 3152 includes any suitable structure for generating signals for wireless or wired transmission to one or more EDs or other devices. Each transceiver 3152 also includes any suitable structure for processing signals received via wireless or wired transmission from one or more EDs or other devices. Although shown as combined into a single unit for transceivers 3152, a transmitter and a receiver can be separate components. Each antenna 3156 includes any suitable structure for transmitting or receiving wireless or wired signals 3190. Although a common antenna 3156 is shown coupled to transceivers 3152, one or more antennas 3156 can be coupled to transceivers 3152, enabling individual antennas 3156 to be coupled to transmitters and receivers if configured as separate components. Each memory 3158 includes any suitable volatile or non-volatile storage and retrieval devices. Each input / output device 3166 facilitates interaction with a user or other devices (network communications) via a network. Each input / output device 3166 includes any suitable structure for providing information to or from a user, including network interface communications.

[0509] Figure 32 A block diagram of a computing system 3200 that can be used to implement the devices and methods disclosed herein. For example, the computing system can be any entity in a UE, access network (AN), mobility management (MM), session management (SM), user plane gateway (UPGW), or access stratum (AS). A particular device can use all or only a subset of the components shown, and different devices can have different levels of integration. For example, some devices can be implemented using a single integrated circuit, while others can include a number of integrated circuits or other components. Additionally, a device can contain multiple instances of a component, such as multiple processing units, processors, memories, transmitters, receivers, etc. The computing system 3200 includes a processing unit 3202. The processing unit includes a central processing unit (CPU) 3214, a memory 3208, and can also include a mass storage device 3204, a video adapter 3210, and an I / O interface 3212, all of which are connected to a bus 3220.

[0510] Bus 3220 can be one or more of several types of bus architecture including a memory bus or memory controller, a peripheral bus, or a video bus. CPU 3214 can include any type of electronic data processor. Memory 3208 can include any type of non-transitory system memory such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), or a combination thereof. In an embodiment, memory 3208 can include ROM for use at boot-up and DRAM for program and data storage for use when executing programs.

[0511] Mass storage device 3204 can include any type of non-transitory storage device for storing data, programs, and other information and making such data, programs, and other information accessible via bus 3220. Mass storage device 3204 can include one or more of a solid state hard drive, a hard disk drive, a disk drive, or an optical disk drive.

[0512] Video adapter 3210 and I / O interface 3212 provide interfaces to couple external input and output devices to processing unit 3202. As illustrated, examples of input and output devices include a display 3218 coupled to video adapter 3210 and a mouse, keyboard, or printer 3216 coupled to I / O interface 3212. Other devices can be coupled to processing unit 3202, and additional or fewer interface cards can be utilized. For example, a serial interface such as Universal Serial Bus (USB) (not shown) can be used to provide interface for external devices.

[0513] Processing unit 3202 also includes one or more network interfaces 3206, which can comprise a wired link (e.g., an Ethernet cable) or a wireless link to an access node or different networks. Network interfaces 3206 support communication to and from remote units via a network. For example, network interfaces 3206 can provide wireless communication via one or more transmitters / transmit antennas and one or more receivers / receive antennas. In one embodiment, processing unit 3202 is coupled to a local-area network 3222 or a wide-area network for communication with remotely located devices, such as other processing units, the Internet, or remote storage facilities.

[0514] It should be understood that one or more steps in the example methods provided herein can be performed by corresponding units or modules. For example, a signal can be transmitted by a transmitting unit or a transmitting module. A signal can be received by a receiving unit or a receiving module. A signal can be processed by a processing unit or a processing module. Other steps can be performed by an indicating unit or module, a determining unit or module, a configuring unit or module, a dividing unit or module, and / or a scheduling unit or module. The corresponding units / modules can be hardware, software, or a combination thereof. For example, one or more of the units / modules can be an integrated circuit, such as a field programmable gate array (FPGA) or an application-specific integrated circuit (ASIC).

[0515] While the disclosure and the advantages thereof have been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the scope of the disclosure as defined by the appended claims.

Claims

1. A method of communication, comprising: receiving, by a user equipment (UE) from an access node (AN), a downlink control information (DCI) triggering transmission of sounding reference signal (SRS) of a SRS resource set, the DCI comprising a first information indicating a first time domain resource of available time domain resources for transmission of the SRS resource set; determining, by the UE, the available time domain resources for transmission of the SRS resource set according to a first time slot in which the DCI is received; determining, by the UE, a location of the first time domain resource in the available time domain resources according to the first information of the DCI; and transmitting, by the UE, the SRS to the AN according to the location of the first time domain resource. The determining of the available time domain resources comprises:

2. The method of claim 1, wherein, determining, by the UE, the available time domain resources according to the first time slot of the DCI and a higher layer parameter slotoffset configured for the UE. 3.The method of claim 2, wherein: determining, by the UE, a reference time slot of the available time domain resources according to the first time slot and the higher layer parameter slotoffset, the reference time slot being located n time slots after the first time slot, n being configured by the higher layer parameter slotoffset, and n being greater than or equal to zero (0). the available time domain resources comprise time domain resources located in or after the reference time slot in time domain and configured as uplink (UL) or flexible, the time domain resources being in units of time slots, mini-slots or OFDM symbols.

4. The method of claim 3, wherein, the available time domain resources comprise time domain resources located in or after the first time slot in time domain and configured as UL or flexible, the time domain resources being in units of time slots, mini-slots or OFDM symbols.

5. The method of claim 1, wherein, the DCI comprises an index of the first time domain resource in the available time domain resources.

6. The method of claim 1, wherein, 7.The method of claim 1, further comprising: determining, by the UE, that the transmission of the SRS conflicts with another transmission / reception in the first time domain resource; and transmitting, by the UE, the SRS in a next time domain resource of the first time domain resource in the available time domain resources, instead of in the first time domain resource. 8.The method of any one of claims 1-6, further comprising: determining, by the UE, that the transmission of the SRS conflicts with another transmission / reception in the first time domain resource; and transmitting, by the UE, the SRS in the first time domain resource when the transmission of the SRS has a priority higher than a priority of the another transmission / reception. 9.The method of claim 8, further comprising: receiving, by the UE, the priority of the SRS. the SRS has at least one transmission parameter shared by a data transmission or a high priority data transmission associated with the SRS. 11.A method of communication, comprising: transmitting, by an access node (AN) to a user equipment (UE), a downlink control information (DCI) triggering transmission of sounding reference signal (SRS) of a SRS resource set, wherein 10. The method of claim 8, wherein, ​ ​ ​ The DCI includes information indicating a location of a first time domain resource in available time domain resources for transmission of the SRS resource set; The available time domain resources for transmission of the SRS resource set correspond to a first slot in which the DCI is transmitted; and receiving, by the AN from the UE, the SRS according to the location of the first time domain resource.

12. The method of claim 11, wherein, The available time domain resources correspond to a location of the first slot of the DCI and a higher layer parameter slotoffset.

13. The method of claim 12, wherein: The available time domain resources correspond to a reference slot located at a location n slots after the first slot, n being specified by the higher layer parameter slotoffset configured for the UE, and n being greater than or equal to 0.

14. The method of claim 13, wherein, The available time domain resources include time domain resources located in or after the reference slot in time domain and configured as uplink (UL) or flexible time domain resources, the time domain resources being in units of slots, mini-slots, or OFDM symbols.

15. The method of claim 11, wherein, The available time domain resources include time domain resources located in or after the first slot in time domain and configured as uplink (UL) or flexible time domain resources, the time domain resources being in units of slots, mini-slots, or OFDM symbols.

16. The method of claim 11, wherein, The DCI includes an index of the first time domain resource in the available time domain resources.

17. The method according to any one of claims 11-16, characterized in that, Receiving the SRS includes: when the transmission of the SRS collides with another transmission / reception in the first time domain resource, receiving, by the AN, the SRS in a next time domain resource of the first time domain resource in the available time domain resources, instead of in the first time domain resource.

18. The method according to any one of claims 11-16, characterized by, Receiving the SRS includes: receiving, by the AN, the SRS in the first time domain resource.

19. The method of claim 18, wherein, The SRS has at least one transmission parameter shared by a data transmission or a high priority data transmission associated with the SRS.

20. An apparatus for communication, comprising: a non-transitory memory storing computer-executable instructions; and one or more processors in communication with the memory, wherein the instructions, when executed by the one or more processors, cause the apparatus to perform: receiving, from an access node (AN), a downlink control information (DCI) triggering transmission of a sounding reference signal (SRS) resource set, the DCI including first information indicating a first time domain resource in available time domain resources for transmission of the SRS resource set; determining the available time domain resources for transmission of the SRS resource set according to a first slot in which the DCI is received; determining a location of the first time domain resource in the available time domain resources according to the first information of the DCI; and transmitting, to the AN, the SRS according to the location of the first time domain resource.

21. An apparatus for communication, comprising: a non-transitory memory storing computer-executable instructions; and one or more processors in communication with the memory, wherein the instructions, when executed by the one or more processors, cause the apparatus to perform: transmitting, by an access node, AN, to a user equipment, UE, downlink control information, DCI, triggering transmission of sounding reference signal, SRS, for a set of SRS resources, wherein the DCI comprises information indicating a location of a first time domain resource among available time domain resources for transmission of the set of SRS resources, the available time domain resources for transmission of the set of SRS resources correspond to a first time slot in which the DCI is transmitted; and receiving, by the AN from the UE, the SRS in accordance with the location of the first time domain resource.

22. A system for communication, comprising an apparatus according to claim 20 and an apparatus according to claim 21. the computer instructions, when executed by one or more processors of an apparatus, cause the apparatus to perform operations of:

23. A non-transitory computer readable medium storing computer instructions, wherein, receiving, from an access node, AN, downlink control information, DCI, triggering transmission of sounding reference signal, SRS, for a set of SRS resources, the DCI comprising first information indicating a first time domain resource among available time domain resources for transmission of the set of SRS resources; determining the available time domain resources for transmission of the set of SRS resources in accordance with a first time slot in which the DCI is received; determining a location of the first time domain resource among the available time domain resources in accordance with the first information of the DCI; and transmitting, to the AN, the SRS in accordance with the location of the first time domain resource. the computer instructions, when executed by one or more processors of an apparatus, cause the apparatus to perform operations of: transmitting, by an access node, AN, to a user equipment, UE, downlink control information, DCI, triggering transmission of sounding reference signal, SRS, for a set of SRS resources, wherein 24. A non-transitory computer-readable medium storing computer instructions, wherein, the DCI comprises information indicating a location of a first time domain resource among available time domain resources for transmission of the set of SRS resources, the available time domain resources for transmission of the set of SRS resources correspond to a first time slot in which the DCI is transmitted; and receiving, by the AN from the UE, the SRS in accordance with the location of the first time domain resource. ​ ​ ​

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