WO2021090239A1

WO2021090239A1 - Triggering of sounding reference signal transmission

Info

Publication number: WO2021090239A1
Application number: PCT/IB2020/060430
Authority: WO
Inventors: Jari Lindholm
Original assignee: Nokia Technologies Oy
Priority date: 2019-11-08
Filing date: 2020-11-05
Publication date: 2021-05-14

Abstract

An example method, apparatus, and computer-readable storage medium are provided for triggering SRS from a UE. In an example implementation, the method may include transmitting, by a user equipment, UE, sounding reference signal, SRS, capability information to a network node, the SRS capability information indicating that the UE supports transmission of an additional SRS in addition to a basic SRS and receiving, by the UE, SRS configuration from the network node, the SRS configuration indicating sub-frames in which the additional SRS can be transmitted to the network node. The method may further include receiving, by the UE, downlink control information, DCI, via a downlink control channel from the network node, the DCI including information for triggering transmission of the additional SRS from the UE and transmitting, by the UE, the additional SRS based at least on the DCI received from the network node.

Description

TRIGGERING OF SOUNDING REFERENCE SIGNAL TRANSMISSION

PRIORITY CLAIM

[0001] This application claims priority to U.S. Provisional Patent Application No. 62/933,087, filed November 8, 2019, entitled “Triggering of Sounding Reference Signal Transmission,” which is hereby incorporated by reference in its entirety.

TECHNICAL FIELD

[0002] This description relates to wireless communications, and in particular, to sounding reference signal (SRS) in wireless networks.

BACKGROUND

[0003] A communication system may be a facility that enables communication between two or more nodes or devices, such as fixed or mobile communication devices. Signals can be carried on wired or wireless carriers.

[0004] An example of a cellular communication system is an architecture that is being standardized by the 3rd Generation Partnership Project (3GPP). A recent development in this field is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. E-UTRA (evolved UMTS Terrestrial Radio Access) is the air interface of 3GPP's Long Term Evolution (LTE) upgrade path for mobile networks. In LTE, base stations or access points (APs), which are referred to as enhanced Node AP or Evolved Node B (eNBs), provide wireless access within a coverage area or cell. In LTE, mobile devices, or mobile stations are referred to as user equipments (UE). LTE has included a number of improvements or developments.

[0005] 5G New Radio (NR) is part of a continued mobile broadband evolution process to meet the requirements of 5G, similar to earlier evolution of 3G & 4G wireless networks.

In addition, 5G is also targeted at the new emerging use cases in addition to mobile broadband. A goal of 5G is to provide significant improvement in wireless performance, which may include new levels of data rate, latency, reliability, and security. 5G NR may also scale to efficiently connect the massive Internet of Things (IoT), and may offer new types of mission-critical services. Ultra-reliable and low-latency communications (URLLC) devices may require high reliability and very low latency. SUMMARY

[0006] An example method, apparatus, and computer-readable storage medium are provided for triggering of SRS from a UE. In an example implementation, the method may include transmitting, by a user equipment, UE, sounding reference signal, SRS, capability information to a network node, the SRS capability information indicating that the UE supports transmission of an additional SRS in addition to a basic SRS; and receiving, by the UE, SRS configuration from the network node, the SRS configuration indicating sub- frames in which the additional SRS can be transmitted to the network node. The method may further include receiving, by the UE, downlink control information, DCI, via a downlink control channel from the network node, the DCI including information for triggering transmission of the additional SRS from the UE; and transmitting, by the UE, the additional SRS based at least on the DCI received from the network node.

[0007] In another example implementation, the method may include receiving, by a network node, sounding reference signal, SRS, capability information from a user equipment, UE, the SRS capability information indicating that the UE supports transmission of an additional SRS in addition to a basic SRS; and transmitting, by the network node, SRS configuration to the UE, the SRS configuration indicating sub-frames in which the additional SRS can be received by the network node. The method may further include transmitting, by the network node, downlink control information (DCI) via a downlink control channel to the UE, the DCI including information for triggering transmission of the additional SRS from the UE; and receiving, by the network node, the additional SRS based at least on the DCI transmitted from the network node.

BRIEF DESCRIPTION OF THE DRAWINGS

[0008] FIG. 1 is a block diagram of a wireless network according to an example implementation.

[0009] FIG. 2 is a message flow diagram illustrating triggering of SRS transmission from a UE, according to an example implementation.

[0010] FIG. 3 is a block diagram illustrating additional SRS and basic SRS, according to an example implementation.

[0011] FIG. 4 is a block diagram illustrating additional SRS, basic SRS, and a traffic channel, according to additional example implementation. [0012] FIG. 5 is a block diagram illustrating triggering of SRS with DCI, according to an example implementation.

[0013] FIG. 6 is a block diagram illustrating triggering of SRS with DCI and cross carrier scheduling, according to an additional example implementation.

[0014] FIG. 7 is a flow chart illustrating transmission of SRS, according to an example implementation.

[0015] FIG. 8 is a flow chart illustrating transmission of SRS, according to an additional example implementation.

[0016] FIG. 9 is a block diagram of a node or wireless station (e.g., base station/access point or mobile station/user device/UE), according to an example implementation.

DETAILED DESCRIPTION

[0017] FIG. 1 is a block diagram of a wireless network 130 according to an example implementation. In the wireless network 130 of FIG. 1, user devices (UDs) 131, 132, 133 and 135, which may also be referred to as mobile stations (MSs) or user equipment (UEs), may be connected (and in communication) with a base station (BS) 134, which may also be referred to as an access point (AP), an enhanced Node B (eNB), a next generation Node B (gNB), or a network node. At least part of the functionalities of an access point (AP), base station (BS), or eNB/gNB may also be carried out by any node, server or host which may be operably coupled to a transceiver, such as a remote radio head. BS (or AP) 134 provides wireless coverage within a cell 136, including to user devices 131, 132, 133 and 135. Although only four user devices are shown as being connected or attached to BS 134, any number of user devices may be provided. BS 134 is also connected to a core network 150 via an interface 151. This is merely one simple example of a wireless network, and others may be used.

[0018] A user device (user terminal, user equipment (UE)) may refer to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (MS), a mobile phone, a cell phone, a smartphone, a personal digital assistant (PDA), a handset, a device using a wireless modem (alarm or measurement device, etc.), a laptop and/or touch screen computer, a tablet, a phablet, a game console, a notebook, and a multimedia device, as examples, or any other wireless device. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network.

[0019] In LTE (as an example), core network 150 may be referred to as Evolved Packet Core (EPC), which may include a mobility management entity (MME) which may handle or assist with mobility/handover of user devices between BSs, one or more gateways that may forward data and control signals between the BSs and packet data networks or the Internet, and other control functions or blocks.

[0020] In addition, by way of illustrative example, the various example implementations or techniques described herein may be applied to various types of user devices or data service types, or may apply to user devices that may have multiple applications running thereon that may be of different data service types. New Radio (5G) development may support a number of different applications or a number of different data service types, such as for example: machine type communications (MTC), enhanced machine type communication (eMTC), narrowband Internet of Things (NB-IoT), Internet of Things (IoT), and/or narrowband IoT user devices, enhanced mobile broadband (eMBB), and ultra-reliable and low-latency communications (URLLC).

[0021] IoT may refer to an ever-growing group of objects that may have Internet or network connectivity, so that these objects may send information to and receive information from other network devices. For example, many sensor type applications or devices may monitor a physical condition or a status, and may send a report to a server or other network device, e.g., when an event occurs. Machine Type Communications (MTC or machine to machine communications) may, for example, be characterized by fully automatic data generation, exchange, processing and actuation among intelligent machines, with or without intervention of humans. Enhanced mobile broadband (eMBB) may support much higher data rates than currently available in LTE.

[0022] Ultra-reliable and low-latency communications (URLLC) is a new data service type, or new usage scenario, which may be supported for New Radio (5G) systems. This enables emerging new applications and services, such as industrial automations, autonomous driving, vehicular safety, e-health services, and so on. 3GPP targets in providing up to e.g., 1 ms U-Plane (user/data plane) latency connectivity with l-le-5 reliability, by way of an illustrative example. Thus, for example, URLLC user devices UEs may require a significantly lower block error rate than other types of user devices UEs as well as low latency. Thus, for example, a URLLC UE (or URLLC application on a UE) may require much shorter latency, as compared to an eMBB UE (or an eMBB application running on a UE).

[0023] The various example implementations may be applied to a wide variety of wireless technologies or wireless networks, such as LTE, LTE-A, 5G, IoT, MTC, eMTC, NB-IoT, eMBB, URLLC, etc., or any other wireless network or wireless technology.

These example networks, technologies or data service types are provided only as illustrative examples. Multiple Input, Multiple Output (MIMO) may refer to a technique for increasing the capacity of a radio link using multiple transmit and receive antennas to exploit multipath propagation. MIMO may include the use of multiple antennas at the transmitter and/or the receiver. MIMO may include a multi-dimensional approach that transmits and receives two or more unique data streams through one radio channel. For example, MIMO may refer to a technique for sending and receiving more than one data signal simultaneously over the same radio channel by exploiting multipath propagation. According to an illustrative example, multi-user multiple input, multiple output (multi-user MIMIO, or MU-MIMO) enhances MIMO technology by allowing a base station (BS) or other wireless node to simultaneously transmit or receive multiple streams to different user devices or UEs, which may include simultaneously transmitting a first stream to a first UE, and a second stream to a second UE, via a same (or common or shared) set of physical resource blocks (PRBs) (e.g., where each PRB may include a set of time-frequency resources).

[0024] Also, a BS may use precoding to transmit data to a UE (based on a precoder matrix or precoder vector for the UE). For example, a UE may receive reference signals or pilot signals, and may determine a quantized version of a DL channel estimate, and then provide the BS with an indication of the quantized DL channel estimate. The BS may determine a precoder matrix based on the quantized channel estimate, where the precoder matrix may be used to focus or direct transmitted signal energy in the best channel direction for the UE. Also, each UE may use a decoder matrix may be determined, e.g., where the UE may receive reference signals from the BS, determine a channel estimate of the DL channel, and then determine a decoder matrix for the DL channel based on the DL channel estimate. For example, a precoder matrix may indicate antenna weights (e.g., an amplitude/gain and phase for each weight) to be applied to an antenna array of a transmitting wireless device. Likewise, a decoder matrix may indicate antenna weights (e.g., an amplitude/gain and phase for each weight) to be applied to an antenna array of a receiving wireless device.

This applies to UL as well when a UE is transmitting data to a BS.

[0025] For example, according to an example aspect, a receiving wireless user device may determine a precoder matrix using Interference Rejection Combining (IRC) in which the user device may receive reference signals (or other signals) from a number of BSs (e.g., and may measure a signal strength, signal power, or other signal parameter for a signal received from each BS), and may generate a decoder matrix that may suppress or reduce signals from one or more interferers (or interfering cells or BSs), e.g., by providing a null (or very low antenna gain) in the direction of the interfering signal, in order to increase a signal-to interference plus noise ratio (SINR) of a desired signal. In order to reduce the overall interference from a number of different interferers, a receiver may use, for example, a Linear Minimum Mean Square Error Interference Rejection Combining (LMMSE-IRC) receiver to determine a decoding matrix. The IRC receiver and LMMSE-IRC receiver are merely examples, and other types of receivers or techniques may be used to determine a decoder matrix. After the decoder matrix has been determined, the receiving UE/user device may apply antenna weights (e.g., each antenna weight including amplitude and phase) to a plurality of antennas at the receiving UE or device based on the decoder matrix.

Similarly, a precoder matrix may include antenna weights that may be applied to antennas of a transmitting wireless device or node. This applies to a receiving BS as well.

[0026] A sounding reference signal (SRS) is a reference signal is transmitted by a user equipment (UE) on an uplink to a network node (e.g., eNB, gNB, etc.). The SRS allows the network node to estimate the quality of the uplink channel. In 3GPP Rel-16, an agreement was reached on the following: i) only aperiodic SRS transmission is supported in additional symbols of a subframe. This means that the SRS is triggered dynamically using downlink control information (DCI). ii) only Rel-15 DCI formats that support SRS triggering can be used to trigger the new Rel-16 SRS transmissions iii) the size of the SRS request field is the same as in the current DCI formats and should be used to trigger the SRS existing prior to Rel-16 (now referred to as a basic SRS), additional SRS transmitted in additional symbols of a sub-frame (in Rel-16 and later), or both of them within the same subframe. This implies that DCI formats that support 2-bit SRS request field may be used and the suitable DCI formats may be 4, 4A, 4B, 3B and 7_0B.

[0027] The DCI format 3B is originally intended to schedule SRS and transmit TPC command for SRS in the carrier that is not used for PUSCH or PUCCH. The DCI format 3B may be used to trigger SRS in the additional symbols in Rel-16 for carriers that do not carry physical uplink control channel (PUCCH)/physical uplink shared channel (PUSCH). The rest of the DCI formats that have 2-bit SRS request fields may be used to schedule PUSCH transmissions and an agreement was reached to use them to trigger the SRS in additional symbols.

[0028] However, the simultaneous transmission of SRS in additional symbols and PUSCH in the same subframe and in the same carrier is not supported. This means that if DCI schedules SRS in additional symbols and PUSCH in the same subframe, most of the DCI contents that are intended to schedule PUSCH are transmitted unnecessarily and adds interference to the system. An agreement was reached that fully independent power control (e.g., open and closed loop) may be supported for SRS in additional symbols. The method to send closed loop TPC commands for the SRS in additional symbols need to be defined.

[0029] As an agreement was reached that periodic transmission of SRS in additional symbols is not supported, and triggering of the new SRS in additional symbols of a subframe may become a bottleneck and efficient usage of DCI formats should be considered. In addition, the agreements made so far in 3GPP RAN 1 seem to preclude the use of some DCI formats for triggering SRS in additional symbols because some DCI formats have only 1-bit SRS request field. On the other hand, the work item has an objective to improve DL performance and in typical scenario DL transmissions and DCI formats are sent more often than UL grants.

[0030] Therefore, there is a desire/need to overcome the above limitations. The present disclosure, in an example implementation, describes a method for transmitting, by a user equipment, UE, sounding reference signal, SRS, capability information to a network node, the SRS capability information indicating that the UE supports transmission of an additional SRS and a basic SRS; receiving, by the UE, SRS configuration from the network node, the SRS configuration indicating sub-frames in which the additional SRS can be transmitted to the network node; receiving, by the UE, downlink control information, DCI, via a downlink control channel from the network node, the DCI including information for triggering transmission of the additional SRS and the basic SRS from the UE; and transmitting, by the UE, the additional SRS and the basic SRS based at least on the DCI received from the network node.

[0031] The present disclosure, in another example implementation, describes an additional method for receiving, by a network node, sounding reference signal, SRS, capability information from a user equipment, UE, the SRS capability information indicating that the UE supports transmission of an additional SRS and a basic SRS; transmitting, by the network node, SRS configuration to the UE, the SRS configuration indicating sub-frames in which the additional SRS can be received by the network node; transmitting, by the network node, downlink control information (DCI) via a downlink control channel to the UE, the DCI including information for triggering transmission of the additional SRS from the UE; and receiving, by the network node, the additional SRS and the basic SRS based at least on the DCI transmitted from the network node.

[0032] FIG. 2 is a message flow diagram 200 illustrating triggering of SRS transmission, according to an example implementation.

[0033] In an example implementation, FIG. 2 illustrates UE, e.g., UE 202 in communication with a network node, e.g., eNB 204. In some implementations, for example, eNB 204 may be an LTE eNB. In some other implementations, for example, eNB 204 may be a base station in a wireless communication network that provides cellular services, which may include a gNB (5G/NR node) or some other base station.

[0034] At 210, UE 202 may transmit SRS capability information to eNB 204. In some implementations, for example, the SRS capability information, also referred to as capability signaling, may indicate that UE 202 is capable of transmitting an additional SRS, with or without the transmission of a basic SRS. The capability signaling may indicate that two types of SRSs may be configured: i) a basic SRS signal; and ii) an additional SRS, and that the additional SRS may span one or more orthogonal frequency division multiplexing (OFDM) symbols in a time domain. It should be noted that the additional SRS may be counted as one signal even if the additional SRS spans multiple OFDM symbols. In some implementations, for example, the eNB may rely on the SRS capability information transmitted from the UE before the eNB can configure and trigger the transmission of additional SRS.

[0035] At 220, eNB 204 may transmit SRS configuration to UE 202. In some implementations, for example, the SRS configuration transmitted from eNB 204 may indicate the sub-frames and/or the symbols in which the additional SRS may be transmitted from the UE.

[0036] In an example implementation, the SRS configuration may indicate that the additional SRS may be transmitted for every 5^th sub-frame or every 10^th sub-frame from the UE. In an additional example implementation, the SRS configuration may indicate that the additional SRS may be transmitted in symbols X, Y, or X and Y of a sub-frame (e.g., symbols 8 and 9 of a sub-frame), as illustrated in FIG. 3. In another additional example implementation, the SRS configuration may indicate the starting and ending symbols the UE may transmit the additional SRS, for example, starting symbol 8 and ending symbol 9, as illustrated in FIG. 3.

[0037] In some implementations, for example, the SRS configuration may be transmitted from the eNB to the UE via RRC signaling and may be considered as semi-static. Upon receiving the SRS configuration, in some implementations, for example, the UE may transmit the additional SRS in the next valid uplink sub-frame and/or symbol after receiving triggering in the DCI. [0038] In some implementations, for example, the basic SRS may be transmitted in a last symbol of a sub-frame, as illustrated in FIG. 3. In some implementations, for example, the configuration of the basic SRS may be indicated to the UE in the SRS configuration if basic SRS is to be transmitted in any symbol of a sub-frame.

[0039] At 230, eNB 204 may transmit downlink control information (DCI) to UE 202.

In some implementations, for example, the DCI may include information for triggering transmission of the additional SRS and/or basic SRS from the UE. It should be noted that 220 of FIG.2 refers to the configuration of the SRS by the eNB (e.g., additional SRS and/or basic SRS) and 230 of FIG. 2 refers to the triggering of SRS (e.g., triggering transmission of additional SRS and/or basic SRS). Although, SRS configuration may be considered as semi static, the triggering of SRS may be considered dynamic.

[0040] At 240, UE 202 may transmit additional SRS and/or basic SRS to eNB 204.

In some implementations, for example, UE 202 may transmit SRS based on the DCI received from the eNB.

[0041] In some implementations, the additional SRS and/or basic SRS may be transmitted in several ways. In an example implementation, UE 202 may transmit the additional SRS and the basic SRS. In another example implementation, UE 202 may transmit only the additional SRS. In another example implementation, UE 202 may transmit only the basic SRS.

[0042] FIG. 3 is a block diagram 300 illustrating additional SRS and basic SRS, according to an example implementation.

[0043] In FIG. 3, the additional SRS 310 is illustrated as being transmitted in additional symbols 8 and 9 of a sub-frame (e.g., subframe n) and the basic SRS is illustrated as being transmitted in a last symbol, symbol 13 of the sub-frame. It should be noted that the additional SRS may be transmitted in any symbol of a sub-frame as indicated by the SRS configuration. It some implementations, the additional SRS may be transmitted in any symbol of a sub-frame, except the last symbol of a sub-frame, as indicated by the SRS configuration.

[0044] FIG. 4 is a block diagram 400 illustrating additional SRS, basic SRS, and a traffic channel, according to additional example implementation.

[0045] In some implementations, UE 202 may be configured with multiple carriers, e.g., two carriers. In such an example implementation, when the UE is configured with two carriers, a first carrier 402 and a second carrier 404, the additional SRS may be transmitted using first carrier 402 and an uplink traffic channel 430 may be transmitted using second carrier 404 (or vice versa). In an example implementation, the uplink traffic channel may be a physical uplink shared channel (PUSCH). The basic SRS, 420 and 422, may be respectively transmitted in first carrier 402 and second carrier 404.

[0046] FIG. 5 is a block diagram 500 illustrating triggering of SRS with DCI, according to an example implementation.

[0047] In an example implementation, FIG. 5 illustrates an uplink-downlink configuration (uplink-downlink configuration 4) with a downlink-to-uplink switch-point periodicity of 10 ms. In such an example implementation, DCI in sub-frame 8 may trigger basic SRS and another DCI in sub-frame 7 may trigger additional SRS. As described above in reference to FIGs. 3 and 4, for example, the basic SRS may be transmitted in a last symbol of a sub-frame and the additional SRS may be transmitted in other symbols of the sub-frame. In other words, the additional SRS may be triggered via DCI sent in sub-frame 7 and the basic SRS may be triggered via DCI sent in sub-frame 8. The SRSs may be transmitted in the next valid sub-frame, e.g., sub-frame 2.

[0048] FIG. 6 is a block diagram 600 illustrating triggering of SRS with DCI and cross carrier scheduling, according to an additional example implementation.

[0049] In an example implementation, FIG. 6 illustrates an uplink-downlink configuration (e.g., uplink-downlink configuration 4) with a downlink-to-uplink switch-point periodicity of 10 ms, similar to FIG. 5, but configured with multiple carriers. In an example implementation as illustrated in FIG. 6, DCI may trigger additional SRS in carrier # 1 (402) and configure uplink traffic channel in carrier # 2 (404). This provides flexibility to transmit both the additional SRS and uplink traffic channel when multiple carriers are configured.

[0050] FIG. 7 is a flow chart 700 illustrating transmission of SRS, according to an example implementation.

[0051] At block 710, a UE, e.g., UE 202, may transmit SRS capability information to a network node, e.g., eNB 204. In some implementations, for example, the SRS capability information may indicate that the UE supports transmission of an additional SRS in addition to a basic SRS. That is, the SRS capability information may indicate that the UE supports transmission of an additional SRS and/or a basic SRS. In some implementations, the UE may transmit the SRS capability information to the network node at registration time.

[0052] At block 720, the UE may receive SRS configuration from the network node.

In some implementations, for example, the SRS configuration may indicate sub-frames in which the additional SRS can be transmitted to the network node. In some implementations, for example, the UE may receive SRS configuration via RRC signaling from the eNB. [0053] In some implementations, the SRS configuration may include (or indicate) transmission patterns of the additional SRS. In an example implementation, the transmission patterns may include one or more of frequency hopping, antenna switching, and repetition patterns.

[0054] At block 730, the UE may receive DCI via a downlink control channel from the network node. In some implementations, for example, the DCI may include information for triggering transmission of the additional SRS from the UE.

[0055] In some implementations, the triggering may be based on a parameter included in the DCI received from the eNB. In an example implementation, the parameter may be an SRS request field.

[0056] In some implementations, for example, the SRS request field may be a two-bit field or a one-bit field. In an example two-bit implementation, the values of the SRS request field may indicate which SRSs are triggered. For example, a value of “00” may indicate that no SRSs have been triggered; a value of “01” may indicate that the transmission of basic SRS has been triggered; a value of “10” may indicate that the transmission of additional SRS has been triggered; and/or a value of “11” may indicate the transmission of additional SRS and basic SRS has been triggered.

[0057] In an example one-bit implementation, the values of SRS request field in different sub-frames may indicate which SRS has been triggered. For example, the transmission of the additional SRS and the basic SRS may be based on SRS request fields received in DCIs of different sub-frames.

[0058] In some implementations, for example, when the SRS request field is received in a DCI format such that a traffic channel and the additional SRS are scheduled in a same sub-frame, the traffic channel may be dropped.

[0059] In some implementations, for example, when the UE is configured with two carriers, a first carrier and a second carrier, the additional SRS may be transmitted using the first carrier and the uplink traffic channel may be transmitted using the second carrier, or vice versa.

[0060] In some implementations, for example, the transmit power of the additional SRS may be adjusted based on a TPC command associated with power control of an uplink traffic channel. In other words, the power control bits of DCI formats may be used for adjusting power control of additional SRS. [0061] At block 740, the UE may transmit the additional SRS based at least on the DCI received from the network node. In some implementations, for example, the UE may transmit the basic SRS in a last symbol of a sub-frame and the additional SRS in any other (one or more) symbols of the sub-frame.

[0062] Thus, the DCI may be used to efficiently trigger the additional SRS.

[0063] Additional example implementations are described herein.

[0064] Example 1. A method of communications, comprising: transmitting, by a user equipment, UE, sounding reference signal, SRS, capability information to a network node, the SRS capability information indicating that the UE supports transmission of an additional SRS in addition to a basic SRS; receiving, by the UE, SRS configuration from the network node, the SRS configuration indicating sub-frames in which the additional SRS can be transmitted to the network node; receiving, by the UE, downlink control information, DCI, via a downlink control channel from the network node, the DCI including information for triggering transmission of the additional SRS from the UE; and transmitting, by the UE, the additional SRS based at least on the DCI received from the network node.

[0065] Example 2. The method of Example 1, wherein the SRS configuration is received via radio resource control signaling from the network node.

[0066] Example 3. The method of any of Examples 1-2, wherein the SRS configuration indicates transmission patterns of the additional SRS, the transmission patterns of the additional SRSs including one or more of frequency hopping, antenna switching, and repetition patterns.

[0067] Example 4. The method of any of Examples 1-3, wherein the triggering is based on a parameter included in the DCI received from the network node.

[0068] Example 5. The method of any of Examples 1-4, wherein the parameter includes an SRS request field.

[0069] Example 6. The method of any of Examples 1-5, wherein when the SRS request field is one bit in length, the transmission of the additional SRS comprises transmitting the additional SRS and the basic SRS based on SRS request fields received in DCIs of different sub-frames.

[0070] Example 7. The method of any of Examples 1-5, wherein the SRS request field is received in a DCI format such that a traffic channel and the additional SRS are scheduled in a same sub-frame, and wherein the traffic channel is dropped. [0071] Example 8. The method of any of Examples 1-7, wherein the UE is configured with two carriers, a first carrier and a second carrier, wherein the additional SRS is transmitted using the first carrier, and further comprising: transmitting, from the UE, an uplink traffic channel using the second carrier.

[0072] Example 9. The method of any of Examples 1-8, further comprising: adjusting power of the additional SRS, instead of the power of the uplink traffic channel, based on a transmit power control, TPC, command, received from the network node.

[0073] Example 10. The method of any of Examples 1-9, wherein the basic SRS is transmitted in a last symbol of a sub-frame and/or the additional SRS is transmitted in any one or more symbols of a sub-frame.

[0074] Example 11. The method of any of Examples 1-10, wherein the network node is an eNB or gNB.

[0075] Example 12. An apparatus comprising at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to perform a method of any of Examples 1-11.

[0076] Example 13. An apparatus comprising means for performing a method of any of Examples 1-11.

[0077] Example 14. A non-transitory computer-readable storage medium having stored thereon computer executable program code which, when executed on a computer system, causes the computer system to perform the steps of any of Examples 1-11.

[0078] FIG. 8 is a flow chart 800 illustrating reception of SRS, according to an additional example implementation.

[0079] At block 810, a network node, e.g., eNB 204, may receive SRS capability information from a user equipment, UE, e.g., UE 202.

[0080] At block 820, eNB 204 may transmit SRS configuration to the UE. In some implementations, the SRS configuration may indicate sub-frames in which the additional SRS may be received by the network node.

[0081] At block 830, eNB 204 may transmit DCI via a downlink control channel to the UE. In some implementations, for example, the DCI may include information for triggering transmission of the additional SRS from the UE.

[0082] At block 840, eNB 204 may receive the additional SRS based at least on the DCI transmitted from the network node.

[0083] Thus, the DCI may be used to efficiently trigger the additional SRS.

[0084] Additional example implementations are described herein. [0085] Example 15. A method of communications, comprising: receiving, by a network node, sounding reference signal, SRS, capability information from a user equipment, UE, the SRS capability information indicating that the UE supports transmission of an additional SRS in addition to a basic SRS; transmitting, by the network node, SRS configuration to the UE, the SRS configuration indicating sub-frames in which the additional SRS can be received by the network node; transmitting, by the network node, downlink control information (DCI) via a downlink control channel to the UE, the DCI including information for triggering transmission of the additional SRS from the UE; and receiving, by the network node, the additional SRS based at least on the DCI transmitted from the network node.

[0086] Example 16. The method of Example 16, wherein the SRS configuration is transmitted via radio resource control signaling from the network node.

[0087] Example 17. The method of any of Examples 15-16, wherein the SRS configuration indicates transmission patterns of the additional SRS, the transmission patterns of the additional SRS including one or more of frequency hopping, antenna switching, and repetition patterns.

[0088] Example 18. The method of any of Examples 15-17, wherein the triggering is based on a parameter included in the DCI transmitted from the network node.

[0089] Example 19. The method of any of Examples 15-18, wherein the parameter includes an SRS request field.

[0090] Example 20. The method of any of Examples 15-19, wherein the basic SRS is received in a last symbol of a sub-frame and/or the additional SRS is received in any one or more symbols of the sub-frame.

[0091] Example 21. The method of any of Examples 15-20, wherein the network node is an eNB or gNB.

[0092] Example 22. An apparatus comprising at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to perform a method of any of Examples 15-21.

[0093] Example 23. An apparatus comprising means for performing a method of any of Examples 15-21.

[0094] Example 24. A non-transitory computer-readable storage medium having stored thereon computer executable program code which, when executed on a computer system, causes the computer system to perform the steps of any of Examples 15-21.

[0095] The triggering of SRS transmission in additional symbols using DCI formats may be performed, in some implementations, as described below. [0096] When SRS transmission in additional symbols is triggered with DCI so that the SRS and the traffic channel, such as for example, PUSCH, would be transmitted in the same subframe, only SRS is transmitted and PUSCH may be dropped, e.g., the fields in the DCI that define PUSCH transmission are ignored, except the power control bits. The power control bits may be interpreted so that they control the power of the SRS in additional symbols and not the power control of the PUSCH. If carrier indicator field is present in the DCI, it is supported to have operation where PUSCH is transmitted in the carrier defined by carrier indicator field of the DCI but the SRS in additional symbols is transmitted in the same carrier where the DCI was transmitted. The power control bits in the DCI are used to control PUSCH power control, and not SRS.

[0097] For DCI formats that have 1-bit SRS request field, it is supported that this bit may be used to trigger SRS in additional symbols at least in the case that TDD radio frame has more DL subframes than UL subframes. This can be done so that depending on subframes within radio frame, where DCI triggering SRS is transmitted, basic SRS or the additional SRS in additional symbols may be selected/triggered for transmission. Operations can be, e.g., such that SRS request field in the DCI in even numbered subframes triggers basic SRS and DCI in odd numbered subframes triggers the additional SRS in additional subframes, or vice versa.

[0098] The DCI formats that allocate DL transmissions and have SRS request field may also include TPC command field that control the power of a control channel, such as for example, PUCCH. The PUCCH TPC bits in the DCI, that triggers the new SRS in the additional symbols, may be used to control the power of additional SRS instead of PUCCH.

[0099] For power control of SRS in the additional symbols, if the TPC command of DCI format triggering the new SRS is already specified to be used for PUSCH/PUCCH power control, transmission of TPC commands can be done using DCI formats 3/3A/3B. Modifications/additions to specification may be done so that 3/3A/3B has separate fields for the new SRS in additional symbols.

[0100] For use of 1-bit SRS request field of DCI formats to trigger the new SRS, typically the number of DL subframes in the radio frame is configured to be bigger than the number of UL subframes because in DL-MIMO operations the target is to have good DL throughput. This means that there may be more than one SRS triggering opportunity at least for some of the UL subframes and this makes it possible to have dynamic selection between basic SRS, the new SRS or both in the same subframe. [0101] It is beneficial to use DCIs/DCI formats that schedule/allocate DL transmissions for triggering SRS in DL heavy configuration because those DCIs need to be transmitted often while the DCIs/DCI formats for UL grant are only needed infrequently. Using the DCI that is anyway transmitted instead of the infrequently transmitted DCI that may be sent only to trigger SRS, reduces the load in the PDCCH. Otherwise, PDCCH resources may be the bottleneck of the system.

[0102] The operations/procedures proposed above for DCI triggered SRS is intended for the case when SRS request field has 2 bits. Some of the DCI formats for UL grant have 1-bit SRS request field e. g., 0/0A/0B/0C, 6_0A and 7_0A. For these cases, similar operations as proposed for other DCI formats with 1-bit SRS request field above could be used, e.g., in some of the subframes DCI triggers basic SRS and in some other subframes DCI triggers the new SRS in additional symbols. Depending on RRC configuration it is then possible to have basic and the new SRS simultaneously in the same subframe.

[0103] FIG. 9 is a block diagram 900 of a wireless station (e.g., user equipment (UE)/user device or AP/gNB/MgNB/SgNB) according to an example implementation. The wireless station 900 may include, for example, one or more RF (radio frequency) or wireless transceivers 902 A, 902B, where each wireless transceiver includes a transmitter to transmit signals and a receiver to receive signals. The wireless station also includes a processor or control unit/entity (controller) 904/908 to execute instructions or software and control transmission and receptions of signals, and a memory 906 to store data and/or instructions.

[0104] Processor 904 may also make decisions or determinations, generate frames, packets or messages for transmission, decode received frames or messages for further processing, and other tasks or functions described herein. Processor 904, which may be a baseband processor, for example, may generate messages, packets, frames or other signals for transmission via wireless transceiver 902 (902A or 902B). Processor 904 may control transmission of signals or messages over a wireless network, and may control the reception of signals or messages, etc., via a wireless network (e.g., after being down-converted by wireless transceiver 902, for example). Processor 904 may be programmable and capable of executing software or other instructions stored in memory or on other computer media to perform the various tasks and functions described above, such as one or more of the tasks or methods described above. Processor 904 may be (or may include), for example, hardware, programmable logic, a programmable processor that executes software or firmware, and/or any combination of these. Using other terminology, processor 904 and transceiver 902 together may be considered as a wireless transmitter/receiver system, for example. [0105] In addition, referring to FIG. 9, a controller (or processor) 908 may execute software and instructions, and may provide overall control for the station 900, and may provide control for other systems not shown in FIG. 9, such as controlling input/output devices (e.g., display, keypad), and/or may execute software for one or more applications that may be provided on wireless station 900, such as, for example, an email program, audio/video applications, a word processor, a Voice over IP application, or other application or software. Moreover, a storage medium may be provided that includes stored instructions, which when executed by a controller or processor may result in the processor 904, or other controller or processor, performing one or more of the functions or tasks described above.

[0106] According to another example implementation, RF or wireless transceiver(s) 902A/902B may receive signals or data and/or transmit or send signals or data. Processor 904 (and possibly transceivers 902A/902B) may control the RF or wireless transceiver 902 A or 902B to receive, send, broadcast or transmit signals or data.

[0107] The aspects are not, however, restricted to the system that is given as an example, but a person skilled in the art may apply the solution to other communication systems. Another example of a suitable communications system is the 5G concept.

It is assumed that network architecture in 5G will be quite similar to that of the LTE- advanced. 5G is likely to use multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and perhaps also employing a variety of radio technologies for better coverage and enhanced data rates. In one example implementation, the smaller station may be a small cell operating at a lower power or at a higher frequency (e.g., above 6GHz). In another example implementation, the smaller station may be a small cell that may be used as a secondary cell (SCell) for a UE (instead of a primary cell (PCell) or mobility anchor).

[0108] It should be appreciated that future networks will most probably utilize network functions virtualization (NFV) which is a network architecture concept that proposes virtualizing network node functions into “building blocks” or entities that may be operationally connected or linked together to provide services. A virtualized network function (VNF) may comprise one or more virtual machines running computer program codes using standard or general type servers instead of customized hardware. Cloud computing or data storage may also be utilized. In radio communications this may mean node operations may be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. It should also be understood that the distribution of labor between core network operations and base station operations may differ from that of the LTE or even be non-existent.

[0109] Implementations of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Implementations may be implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., in a machine-readable storage device or in a propagated signal, for execution by, or to control the operation of, a data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. Implementations may also be provided on a computer readable medium or computer readable storage medium, which may be a non-transitory medium. Implementations of the various techniques may also include implementations provided via transitory signals or media, and/or programs and/or software implementations that are downloadable via the Internet or other network(s), either wired networks and/or wireless networks. In addition, implementations may be provided via machine type communications (MTC), and also via an Internet of Things (IOT).

[0110] The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer readable medium, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, photoelectrical and/or electrical carrier signal, telecommunications signal, and software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer or it may be distributed amongst a number of computers.

[0111] Furthermore, implementations of the various techniques described herein may use a cyber-physical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers,...) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals. The rise in popularity of smartphones has increased interest in the area of mobile cyber-physical systems. Therefore, various implementations of techniques described herein may be provided via one or more of these technologies. [0112] A computer program, such as the computer program(s) described above, can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a stand-alone program or as a module, component, subroutine, or other unit or part of it suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

[0113] Method steps may be performed by one or more programmable processors executing a computer program or computer program portions to perform functions by operating on input data and generating output. Method steps also may be performed by, and an apparatus may be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0114] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processors of any kind of digital computer, chip or chipset. Generally, a processor will receive instructions and data from a read only memory or a random access memory or both. Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer also may include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magneto optical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non volatile memory, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto optical disks; and CD ROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in, special purpose logic circuitry.

Claims

WHAT IS CLAIMED IS:

1. A method of communications, comprising: transmitting, by a user equipment, UE, sounding reference signal, SRS, capability information to a network node, the SRS capability information indicating that the UE supports transmission of an additional SRS in addition to a basic SRS; receiving, by the UE, SRS configuration from the network node, the SRS configuration indicating sub-frames in which the additional SRS can be transmitted to the network node; receiving, by the UE, downlink control information, DCI, via a downlink control channel from the network node, the DCI including information for triggering transmission of the additional SRS from the UE; and transmitting, by the UE, the additional SRS based at least on the DCI received from the network node.

2. The method of claim 1, wherein the SRS configuration is received via radio resource control signaling from the network node.

3. The method of any of claims 1-2, wherein the SRS configuration indicates transmission patterns of the additional SRS, the transmission patterns of the additional SRSs including one or more of frequency hopping, antenna switching, and repetition patterns.

4. The method of any of claims 1-3, wherein the triggering is based on a parameter included in the DCI received from the network node.

5. The method of any of claim 4, wherein the parameter includes an SRS request field.

6. The method of any of claim 5, wherein when the SRS request field is one bit in length, the transmission of the additional SRS comprises transmitting the additional SRS and the basic SRS based on SRS request fields received in DCIs of different sub-frames.

7. The method of claim 5 or 6, wherein the SRS request field is received in a DCI format such that an uplink traffic channel transmission and the additional SRS are scheduled in a same sub-frame, and wherein the uplink traffic channel is dropped.

8. The method of any of claims 1-7, wherein the UE is configured with two carriers, a first carrier and a second carrier, wherein the additional SRS is transmitted using the first carrier, and further comprising: transmitting, from the UE, an uplink traffic channel using the second carrier.

9. The method of any of claims 1-8, further comprising: adjusting power of the additional SRS, instead of the power of the uplink traffic channel or an uplink control channel, based on a transmit power control, TPC, command, received from the network node.

10. The method of any of claims 1-9, wherein the basic SRS is transmitted in a last symbol of a sub-frame and/or the additional SRS is transmitted in any one or more symbols of a sub-frame.

11. The method of any of claims 1-10, wherein the network node is an eNB or gNB.

12. The method of claim 1, wherein the triggering transmission of the additional SRS is based on a SRS request field included in the DCI, the DCI also configuring a physical uplink shared channel (PUSCH) transmission, such that the PUSCH and the additional SRS are scheduled in a same sub-frame, and wherein the PUSCH is dropped.

13. An apparatus comprising at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to perform a method of any of claims 1-12.

14. An apparatus comprising means for performing a method of any of claims 1-12.

15. A non-transitory computer-readable storage medium having stored thereon computer executable program code which, when executed on a computer system, causes the computer system to perform the steps of any of claims 1-12.

16. A method of communications, comprising: receiving, by a network node, sounding reference signal, SRS, capability information from a user equipment, UE, the SRS capability information indicating that the UE supports transmission of an additional SRS in addition to a basic SRS; transmitting, by the network node, SRS configuration to the UE, the SRS configuration indicating sub-frames in which the additional SRS can be received by the network node; transmitting, by the network node, downlink control information (DCI) via a downlink control channel to the UE, the DCI including information for triggering transmission of the additional SRS from the UE; and receiving, by the network node, the additional SRS based at least on the DCI transmitted from the network node.

17. The method of claim 16, wherein the SRS configuration is transmitted via radio resource control signaling from the network node.

18. The method of any of claims 16-17, wherein the SRS configuration indicates transmission patterns of the additional SRS, the transmission patterns of the additional SRS including one or more of frequency hopping, antenna switching, and repetition patterns.

19. The method of any of claims 16-18, wherein the triggering is based on a parameter included in the DCI transmitted from the network node.

20. The method of claim 19, wherein the parameter includes an SRS request field.

21. The method of any of claims 16-20, wherein the basic SRS is received in a last symbol of a sub-frame and/or the additional SRS is received in any one or more symbols of the sub-frame.

22. The method of any of claims 16-21, wherein the network node is an eNB or gNB.

23. An apparatus comprising at least one processor and at least one memory including computer instructions, when executed by the at least one processor, cause the apparatus to perform a method of any of claims 16-22.

24. An apparatus comprising means for performing a method of any of claims 16-22.

25. A non-transitory computer-readable storage medium having stored thereon computer executable program code which, when executed on a computer system, causes the computer system to perform the steps of any of claims 16-22.

26. An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: transmit, by a user equipment, UE, sounding reference signal, SRS, capability information to a network node, the SRS capability information indicating that the UE supports transmission of an additional SRS in addition to a basic SRS; receive, by the UE, SRS configuration from the network node, the SRS configuration indicating sub-frames in which the additional SRS can be transmitted to the network node; receiving, by the UE, downlink control information, DCI, via a downlink control channel from the network node, the DCI including information for triggering transmission of the additional SRS from the UE; and transmit, by the UE, the additional SRS based at least on the DCI received from the network node.

27. The apparatus of claim 26, wherein the SRS configuration is received via radio resource control signaling from the network node.

28. The apparatus of any of claims 26-27, wherein the SRS configuration indicates transmission patterns of the additional SRS, the transmission patterns of the additional SRSs including one or more of frequency hopping, antenna switching, and repetition patterns.

29. The apparatus of any of claims 26-28, wherein the triggering is based on a parameter included in the DCI received from the network node.

30. The apparatus of claim 29, wherein the parameter includes an SRS request field.

31. The apparatus of claim 30, wherein when the SRS request field is one bit in length, the transmission of the additional SRS comprises transmitting the additional SRS and the basic SRS based on SRS request fields received in DCIs of different sub-frames.

32. The apparatus of any of claims 30-31, wherein the SRS request field is received in a DCI format such that an uplink traffic channel transmission and the additional SRS are scheduled in a same sub-frame, and wherein the uplink traffic channel is dropped.

33. The apparatus of any of claims 26-32, wherein the UE is configured with two carriers, a first carrier and a second carrier, wherein the additional SRS is transmitted using the first carrier, and wherein the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: transmit, from the UE, an uplink traffic channel using the second carrier.

34. The apparatus of any of claims 26-33, wherein the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: adjust power of the additional SRS, instead of the power of the uplink traffic channel or an uplink control channel, based on a transmit power control, TPC, command, received from the network node.

35. The apparatus of any of claims 26-34, wherein the basic SRS is transmitted in a last symbol of a sub-frame and/or the additional SRS is transmitted in any one or more symbols of a sub-frame.

36. The apparatus of any of claims 26-35, wherein the network node is an eNB or gNB.

37. The apparatus of claim 26, wherein the triggering transmission of the additional SRS is based on a SRS request field included in the DCI, the DCI also configuring a physical uplink shared channel (PUSCH) transmission, such that the PUSCH and the additional SRS are scheduled in a same sub-frame, and wherein the PUSCH is dropped.

38. An apparatus comprising: at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to: receive, by a network node, sounding reference signal, SRS, capability information from a user equipment, UE, the SRS capability information indicating that the UE supports transmission of an additional SRS in addition to a basic SRS; transmit, by the network node, SRS configuration to the UE, the SRS configuration indicating sub-frames in which the additional SRS can be received by the network node; transmit, by the network node, downlink control information (DCI) via a downlink control channel to the UE, the DCI including information for triggering transmission of the additional SRS from the UE; and receive, by the network node, the additional SRS based at least on the DCI transmitted from the network node.

39. The apparatus of claim 38, wherein the SRS configuration is transmitted via radio resource control signaling from the network node.

40. The apparatus of any of claims 38-39, wherein the SRS configuration indicates transmission patterns of the additional SRS, the transmission patterns of the additional SRS including one or more of frequency hopping, antenna switching, and repetition patterns.

41. The apparatus of any of claims 38-40, wherein the triggering is based on a parameter included in the DCI transmitted from the network node.

42. The apparatus of claim 41, wherein the parameter includes an SRS request field.

43. The apparatus of any of claims 38-42, wherein the basic SRS is received in a last symbol of a sub-frame and/or the additional SRS is received in any one or more symbols of the sub-frame.