WO2025078430A1

WO2025078430A1 - Method and wireless communications device for transmitting srs in a wireless communications network

Info

Publication number: WO2025078430A1
Application number: PCT/EP2024/078400
Authority: WO
Inventors: Behrooz MAKKI; Andreas Nilsson; Sven JACOBSSON; Xinlin ZHANG; Fredrik Athley; Siva Muruganathan
Original assignee: Telefonaktiebolaget LM Ericsson AB
Current assignee: Telefonaktiebolaget LM Ericsson AB
Priority date: 2023-10-10
Filing date: 2024-10-09
Publication date: 2025-04-17
Anticipated expiration: 2026-04-10

Abstract

There is presented a method performed by a wireless communications device (121) of a wireless communications network (100), for transmitting SRS. The method comprises receiving (511) an SRS configuration, wherein the SRS configuration indicates information 5 on a mapping between one or more SRS ports of the wireless communications device to two or more RAPGs of the wireless communications device. The method comprises transmitting (512) SRS to a network node (111) according to the indicated mapping between the SRS ports and the RAPGs.

Description

METHOD AND WIRELESS COMMUNICATIONS DEVICE FOR TRANSMITTING SRS IN

A WIRELESS COMMUNICATIONS NETWORK

TECHNICAL FIELD

Embodiments presented herein relate to methods, a wireless communications device, a network node, computer programs, and a computer program product for transmission of sounding reference signals from the wireless communications device and for reception of the sounding reference signals at the network node.

BACKGROUND

In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or User Equipments (UE), communicate via a Local Area Network such as a Wi-Fi network or a Radio Access Network (RAN) to one or more core networks (CN). The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to as a beam or a beam group, with each service area or cell area being served by a radio access node such as a radio access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a NodeB, eNodeB (eNB), or gNB as denoted in 5G. A service area or cell area is a geographical area where radio coverage is provided by the radio access node. The radio access node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio access node.

Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases, for example to specify a Fifth Generation (5G) network also referred to as 5G New Radio (NR). The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E- UTRAN/LTE is a variant of a 3GPP radio access network wherein the radio access nodes are directly connected to the EPC core network rather than to RNCs used in 3G networks. In general, in E-UTRAN/LTE the functions of a 3G RNC are distributed between the radio access nodes, e.g. eNodeBs in LTE, and the core network. As such, the RAN of an EPS has an essentially “flat” architecture comprising radio access nodes connected directly to one or more core networks, i.e. they are not connected to RNCs. To compensate for that, the E-UTRAN specification defines a direct interface between the radio access nodes, this interface being denoted the X2 interface.

Aspects of wireless communication systems in 3GPP will be disclosed next.

Figure 1 illustrates a simplified wireless communication system. Consider the simplified wireless communication system in Figure 1 , with a UE 12, which communicates with one or multiple access nodes 103-104, which in turn is connected to a network node 106. The access nodes 103-104 are part of the radio access network 10.

For wireless communication systems pursuant to 3GPP Evolved Packet System, (EPS), also referred to as Long Term Evolution, LTE, or 4G, standard specifications, such as specified in 3GPP TS 36.300 and related specifications, the access nodes 103-104 corresponds typically to a Evolved NodeBs (eNBs) and the network node 106 corresponds typically to either a Mobility Management Entity (MME) and/or a Serving Gateway (SGW). The eNB is part of the radio access network 10, which in this case is the E-UTRAN (Evolved Universal Terrestrial Radio Access Network), while the MME and SGW are both part of the EPC (Evolved Packet Core network). The eNBs are interconnected via the X2 interface, and connected to EPC via the S1 interface, more specifically via S1-C to the MME and S1-U to the SGW.

For wireless communication systems pursuant to 3GPP 5G System, 5GS (also referred to as New Radio, NR, or 5G) standard specifications, such as specified in 3GPP TS 38.300 and related specifications, on the other hand, the access nodes 103-104 corresponds typically to an 5G NodeB (gNB) and the network node 106 corresponds typically to either a Access and Mobility Management Function (AMF) and/or a User Plane Function (UPF). The gNB is part of the radio access network 10, which in this case is the NG-RAN (Next Generation Radio Access Network), while the AMF and UPF are both part of the 5G Core Network (5GC). The gNBs are inter-connected via the Xn interface, and connected to 5GC via the NG interface, more specifically via NG-C to the AMF and NG-U to the UPF.

To support fast mobility between NR and LTE and avoid change of core network, LTE eNBs may also be connected to the 5G-CN via NG-U/NG-C and support the Xn interface. An eNB connected to 5GC is called a next generation eNB (ng-eNB) and is considered part of the NG-RAN. LTE connected to 5GC will not be discussed further in this document; however, it should be noted that most of the solutions/features described for LTE and NR in this document also apply to LTE connected to 5GC. In this document, when the term LTE is used without further specification it refers to LTE-EPC. Multiple-input multiple-output (MIMO) is one of key physical layer technologies in 5G. A gNB equipped with many, e.g., 64 or more, antennas provide large array gains and/or performs spatial multiplexing of many users on the same time-frequency resources. Particularly, the spectral efficiency may be increased or, equivalently, the required power to satisfy a quality-of-service requirement may be decreased as the number of antennas increases.

Note: In the following, the “device” may refer to a UE node, a CPE (for FWA) node, or nodes with similar functionalities.

Note: In the following, the terms “Rx chain” and “Rx port” may be used interchangeably. Also, the terms “Tx chain” and “Tx port” may be used interchangeably.

Due to the success of MIMO, it is expected that systems beyond 5G and 6G systems will make use of even larger arrays, not only at the gNB side, but also at the UE side. Indeed, equipping a UE with more antenna elements enables the UE to, in the DL, receive more Physical Downlink Shares Channel (PDSCH) layers, provide additional beamforming gain (via spatial combining) and/or perform interference mitigation. For this reason, support for receiving up to 8 PDSCH layers per UE was introduced in NR Rel-16.

Layer mapping distributes modulated symbols across one or multiple layers for transmission using multiple antennas. It aims to improve spectral efficiency, reliability, and capacity of the wireless communication system by utilizing advanced antenna techniques such as MIMO and beamforming. The number of layers depends on the availability of physical antenna, UE capability, and channel conditions.

Sounding Reference Signal (SRS) antenna switching enhancements to support reciprocity-based DL precoding for a UE with 6Rx or 8Rx chains (and up to 4Tx chains) was introduced in NR Rel-17. SRS is a kind of reference signal for Uplink so that the gNB may perform channel quality estimation for uplink. In TDD, the gNB may utilize the channel estimation result from SRS not only for UL scheduling but also for DL scheduling as well based on channel reciprocity in TDD.

Furthermore, even though UEs typically have more Rx chains than Tx chains, support for 8Tx UL transmission was introduced in NR Rel-18 for high-end UEs (e.g., an advanced CPE device for FWA deployments). As mentioned above, 6 Rx and 8Rx UEs may be supported already in previous 3GPP releases. However, due to complexity and cost, it may be difficult to use such a large number of Rx chains for real-world UEs (e.g., for handheld devices). Therefore, to enable practical implementations of 6Rx or 8Rx (or, even higher number of Rx chains) UEs, it is desirable to reduce the associated complexity and cost.

With this motivation, in the initial discussions for the topics of interest in Rel-19, it has been suggested to support lower-complexity 6Rx and 8 Rx UEs, where the Rx chains are divided into receive antenna port groups (RAPGs) (see, e.g., 3gpp RP-231928). Figure 2 shows an example of such a setup for the cases with Q receive antenna port groups and N Rx chains. In general, one can consider different numbers of Rx chains per RAPG. Here, the N-Rx receiver is divided into Q sub-receivers for independent Ml MO detection. That is, each sub-receiver has dedicated and separated processing capability, and it corresponds to a limited number of Rx chains, i.e. , a receive antenna port group. In Figure 2, the number of Rx ports per receive antenna port group is M = N/Q. In general, one can consider different numbers of Rx chains per receive antenna port group.

Aspects of SRS antenna switching will be disclosed next.

As mentioned above, for reciprocity-based DL precoding, SRS is used to obtain CSI in the UL. It is desirable for the network (NW) to sound all UE antennas (where sounding an antenna implies that SRS is transmitted from that antenna) but costly to equip the UE with many Tx chains (UEs typically have more Rx chains than Tx chains). Therefore, NR supports SRS antenna switching for UEs equipped with more Rx chains than Tx chains. If a UE supports antenna switching, it will report so by means of UE-capability signaling (see, e.g., Table 1).

Table 1. SRS antenna-switching capabilities supported by the UE (copied from 3GPP TS 38.306).

The left column of Table 1 lists UE capabilities for SRS antenna-switching that may be reported by a UE in NR Rel-15. For example, if a UE reports t1r2 it means that it has two antennas (it has two Rx chains) but can only transmit from one of those antennas at a time (it has one Tx chain). In this case, the NW can configure 1T2R antenna switching with two one-port SRS resources in an SRS resource set with usage antennaSwitching. The two SRS resources must be configured in different OFDM symbols and separated, at least, by a guard period that depends on the SCS (see Clause 6.2.1.2 of 3GPP TS 38.214 for further details) such that both antennas can be sounded, with an antenna switch in between.

In general, xTyR SRS antenna switching may be configured for a UE with x Tx chains and y Rx chains. Figure 3 shows examples of xTyR SRS antenna switching for UE architectures with x = y/2 Tx chains and y Rx chains.

In NR Rel-16, additional UE capabilities for SRS antenna-switching were introduced, which are shown in the right column of Table 1. Here, a UE may indicate support for sounding only a subset of Rx antennas, which may save UE power consumption and SRS overhead at the cost of reduced channel knowledge at the gNB. For example, the UE capability Hr1-t1r2 indicates that the gNB may configure one singleport SRS resource (no antenna switching) or two single-port SRS resources (same as for the capability 11r2 described above) per SRS resource set with usage antennaSwitching.

In NR Rel-17, antenna switching was extended to up to 6 or 8 Rx ports, and 1 , 2, or 4 Tx chains. The UE may indicate support for antenna-switching configurations beyond 4 Rx via higher-layer parameter srs-AntennaSwitchingBeyond4RX-r17 (see 3GPP TS 38.306 for further details).

In NR Rel-18, support for up to 8 Tx at a UE was introduced, where the capability for t8r8 antenna switching was added.

SUMMARY

To enable proper DL reciprocity-based communication with a low-complexity wireless communications device, such as a UE, using receive antenna port groups (RAPGs), it is beneficial that the gNB is aware of which SRSs are associated with which RAPGs, since it is important for the network to know how to suppress inter-layer interference in the DL transmission. The wireless communications device may not be able to perform complete inter-layer interference rejection across RAPGs. Thus, the network needs to suppress such interference itself by proper nulling using appropriate DL precoders. An object of embodiments herein may be to obviate some of the problems related to DL-reciprocity based communication with a low-complexity device having a plurality of antennas.

Embodiments discloses herein comprises methods for how a wireless communications device should map SRS ports to RAPGs, using either explicit methods indicated by the network or using implicit methods pre-defined in a specification.

According to an aspect, the object is achieved by a method for transmitting SRS. The method may include associating SRS ports with receive antenna port groups, RAPGs. The method is performed by a wireless communications device, such as a UE, which uses receive antenna port groups. The method comprises: receiving an SRS configuration, where the SRS configuration indicates information a mapping between one or more SRS ports of the wireless communications device to two or more RAPGs of the wireless communications device; and transmitting SRS to a network node according to the indicated mapping between the SRS ports and the RAPGs.

According to a further aspect, the object is achieved by a wireless communications device configured to perform the method according to the previous aspect.

According to a further aspect, the object is achieved by a method performed by a network node for receiving SRS from a wireless communications device which uses receive antenna port groups for communicating with the network node. The method comprises: transmitting an SRS configuration to the wireless communications device, where the SRS configuration indicates how the wireless communications device should map SRS ports to two or more RAPGs; and receiving SRS from the wireless communications device according to the indicated mapping of SRS ports and RAPGs.

According to a further aspect, the object is achieved by a network node configured to perform the method according to the previous aspect. According to a further aspect, the object is achieved by a computer program comprising instructions, which when executed by a processor, causes the processor to perform actions according to any of the aspects above.

According to a further aspect, the object is achieved by a carrier comprising the computer program of the aspect above, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

Embodiments herein enable the network to determine DL precoders such that interlayer interference may be handled properly by the network for devices with multiple RAPGs. Since the UE cannot perform inter-layer interference very easily between layers received at different RAPGs, the network should preferably design precoders for the layers targeting a first RAPG such that the interference of these layers received at the second RAPG is as small as possible, similarly as is done for MU -Ml MO. The different RAPGs may be seen as different UEs. For the network to know which antenna ports that belongs to which RAPG, the UE needs to know which SRS ports belongs to which RAPG.

In some embodiments, the method performed by the wireless communications device further comprises: indicating that the wireless communications device has several RAPGs and/or a capability for a low-complexity receiver.

In some embodiments, the method performed by the network node further comprises: receiving indication that the wireless communications device has several RAPGs and/or a capability for a low-complexity receiver.

In some embodiments, the SRS configuration comprises an implicit mapping between SRS ports and RAPG.

In some embodiments, the implicit mapping is based on a predefined rule (i.e. , a specified rule).

In some embodiments, the rule is based on one or more of a. An SRS resource set ID, b. An SRS resource ID, c. An SRS port index.

In some embodiments, a first set of the SRS ports in an SRS resource belongs to the first RAPG, and a second set of the SRS ports in the same SRS resource belongs to the second RAPG.

In some embodiments, the first set of the SRS ports contains the same number of SRS ports as the second set of SRS ports.

In some embodiments, the first set of the SRS ports in an SRS resource is the SRS ports with lowest SRS port index in that SRS resource.

In some embodiments, a first number of SRS resources, or SRS resource sets, belongs to the first RAPG, and a second number of SRS resources, or SRS resource sets, belongs to the second RAPG.

In some embodiments, the first number of SRS resources/SRS resource sets contains the same number of SRS ports as the second number of SRS resources/SRS resource sets.

In some embodiments, a first half of the SRS ports is mapped to a first RAPG, and a second half of the SRS ports is mapped to a second RAPG.

In some embodiments, the SRS ports are mapped to RAPGs based on the order of the SRS resource ID compared to other SRS resource IDs associated with their respective SRS resource.

In some embodiments, the first half of the SRS ports mapped to the first RAPG comprises even SRS ports and wherein the second half of the SRS ports mapped the second RAPG comprises odd SRS ports.

In some embodiments, the first and second half of the SRS ports are determined based on an order of the SRS ports, wherein the first half of SRS ports consists of the first half of the SRS port according to the order of the SRS ports, and the second part of the SRS ports consists of the last half of the SRS ports according to the order of the SRS ports.

In some embodiments, the SRS ports are ordered according to a. First consider the lowest SRS resource set ID in case multiple SRS resource sets are used, b. Then consider the lowest SRS resource IDs per SRS resource set in case multiple SRS resources are used per SRS resource set, and c. Then consider lowest SRS port index within per SRS resource in case multiple SRS Ports are used per SRS resource.

In some embodiments, a first bundle of SRS resources are mapped to a first RAPG, and a second bundle of SRS resources are mapped to a second RAPG.

In some embodiments, the SRS ports are ordered according to SRS transmission occasion.

In some embodiments, there is: a) sequential mapping between SRS transmission occasions and RAPGs, or b) cyclical mapping between SRS transmission occasions and RAPGs.

Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a/an/the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

When using the word "comprise" or “comprising” it shall be interpreted as nonlimiting, i.e. meaning "consist at least of".

The embodiments herein are not limited to the above described preferred embodiments. Various alternatives, modifications and equivalents may be used. BRIEF DESCRIPTION OF THE DRAWINGS

The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 illustrates a simplified wireless communication system;

Figure 2 shows an example of such a setup for the cases with Q receive antenna port groups and N Rx chains;

Figure 3 shows examples of xTyR SRS antenna switching for UE architectures with x=y/2 Tx chains and y Rx chains;

Figure 4 is a schematic overview depicting a wireless communications network 100 wherein embodiments herein may be implemented;

Figure 5a is a combined signalling diagram and flow chart and illustrates example methods for transmitting SRS and DL reciprocity-based communication based on the SRS;

Figure 5b illustrates example methods performed by the UE;

Figure 5c illustrates example methods performed by the network node;

Figure 6a illustrates a device with two RAPGs with 3Rx chains each;

Figure 6b illustrates a device with two RAPGs with 4RX per RAPG;

Figure 6c illustrates a device with two 2 Tx chains and 6 Rx chains divided into two RAPGs;

Figure 6d illustrates a device with two 3 Tx chains and 6 Rx chains divided into two RAPGs;

Figure 7 shows an example of a wireless communications device;

Figure 8 shows an example of a network node;

Figure 9 shows a communication system in accordance with an embodiment;

Figure 10 shows example implementations of a UE, a base station, and a host computer in accordance with an embodiment;

Figure 11 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment;

Figure 12 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment;

Figure 13 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment; and

Figure 14 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. DETAILED DESCRIPTION

Examples of network nodes are NodeB, base station (BS), multi-standard radio (MSR) radio node such as MSR BS, eNodeB, gNodeB, MeNB, SeNB, location measurement unit (LMU), integrated access backhaul (IAB) node, network controller, radio network controller (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), Central Unit (e.g. in a gNB), Distributed Unit (e.g. in a gNB), Baseband Unit, Centralized Baseband, C-RAN, access point (AP), transmission points, transmission nodes, transmission reception point (TRP), RRU, RRH, nodes in distributed antenna system (DAS), core network node (e.g. MSC, MME etc), O&M, OSS, SON, positioning node (e.g. E-SMLC),etc.

The non-limiting term UE refers to any type of wireless device communicating with a network node and/or with another UE in a cellular or mobile communication system. Examples of UE are target device, device to device (D2D) UE, vehicular to vehicular (V2V), machine type UE, MTC UE or UE capable of machine to machine (M2M) communication, PDA, tablet, mobile terminals, smart phone, laptop embedded equipment (LEE), laptop mounted equipment (LME), USB dongles etc.

The term radio access technology, or RAT, may refer to any RAT e.g. UTRA, E- UTRA, narrow band internet of things (NB-loT), WiFi, Bluetooth, next generation RAT, New Radio (NR), 4G, 5G, 6G, future generation RAT etc. Any of the equipment denoted by the term node, network node or radio network node may be capable of supporting a single or multiple RATs.

The term signal or radio signal used herein may be any physical signal or physical channel. Examples of DL physical signals are reference signal (RS) such as PSS, SSS, CSI-RS, DM RS signals in SS/PBCH block (SSB), discovery reference signal (DRS), CRS, PRS etc. RS may be periodic e.g. RS occasion carrying one or more RSs may occur with certain periodicity e.g. 20 ms, 40 ms etc. The RS may also be aperiodic. Each SSB carries NR-PSS, NR-SSS and NR-PBCH in 4 successive symbols. One or multiple SSBs are transmit in one SSB burst which is repeated with certain periodicity e.g. 5 ms, 10 ms, 20 ms, 40 ms, 80 ms and 160 ms. The UE is configured with information about SSB on cells of certain carrier frequency by one or more SS/PBCH block measurement timing configuration (SMTC) configurations. The SMTC configuration comprising parameters such as SMTC periodicity, SMTC occasion length in time or duration, SMTC time offset wrt reference time (e.g. serving cell’s SFN) etc. Therefore, SMTC occasion may also occur with certain periodicity e.g. 5 ms, 10 ms, 20 ms, 40 ms, 80 ms and 160 ms. Examples of UL physical signals are reference signal such as SRS, DM RS etc. The term physical channel refers to any channel carrying higher layer information e.g. data, control etc. Examples of physical channels are PBCH, NPBCH, PDCCH, PDSCH, sPUCCH, sPDSCH. sPUCCH. sPUSCH, MPDCCH, NPDCCH, NPDSCH, E-PDCCH, PUSCH, PUCCH, NPUSCH etc.

The term time resource used herein may correspond to any type of physical resource or radio resource expressed in terms of length of time. Examples of time resources are: symbol, time slot, subframe, radio frame, TTI, interleaving time, slot, subslot, mini-slot, etc.

Embodiments herein relate to wireless communication networks in general. Figure 4 is a schematic overview depicting a wireless communications network 100 wherein embodiments herein may be implemented. The wireless communications network 100 comprises one or more RANs and one or more CNs. The wireless communications network 100 may use a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, 5G, New Radio (NR), Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. Embodiments herein relate to recent technology trends that are of particular interest in a 5G context and 6G context and beyond, however, embodiments are also applicable in further development of the existing wireless communication systems such as e.g. WCDMA and LTE.

Network nodes operate in the wireless communications network 100. The network nodes may for example be access nodes such as a first radio access node 111. The first radio access node 111 provides radio coverage over a geographical area, a service area referred to as a cell 115, which may also be referred to as a beam or a beam group of a first radio access technology (RAT), such as 5G, LTE, Wi-Fi or similar. There may also be further cells, such as a second cell 116.

The first radio access node 111 may be a NR-RAN node, transmission and reception point e.g. a base station, a radio access node such as a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access controller, a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), a gNB, a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit capable of communicating with a wireless device within the service area depending e.g. on the radio access technology and terminology used. The first radio access node 111 may be referred to as a serving radio access node and communicates with a UE with Downlink (DL) transmissions to the UE and Uplink (UL) transmissions from the UE.

A number of wireless communications devices operate in the wireless communication network 100, such as a wireless communications device 121. The wireless communications device 121 may be a UE. The wireless communications device 121 may further be a mobile station, a non-access point (non-AP) STA, a STA, a user equipment and/or a wireless terminal, that communicate via one or more Access Networks (AN), e.g. RAN, e.g. via the first radio access node 111 to one or more core networks (CN) e.g. comprising a CN node 130, for example comprising an Access Management Function (AMF). It should be understood by the skilled in the art that “UE” is a non-limiting term which means any terminal, wireless communication terminal, user equipment, Machine Type Communication (MTC) device, Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a small base station communicating within a cell.

Methods herein may in a first aspect be performed by the wireless communications device 121 and in a second aspect by a network node, such as the first radio access node 111. As an alternative, a Distributed Node (DN) and functionality, e.g., comprised in a cloud 140 as shown in Figure 4, may be used for performing or partly performing the methods.

As explained above, the network performance is improved by increasing the number of antennas at the gNB and/or the devices. While it is probable that soon the number of gNB antennas will increase, it may be challenging to increase the number of antennas on the devices, due to cost and complexity. For this reason, it is beneficial to develop low- complexity receivers for devices with a large number of receive antennas using the receive antenna port group concept, as explained above.

Embodiments herein will now be described in more detail. Embodiments herein will be described for the cases with two receive antenna port groups (RAPGs). However, the method may be extended to cases with more than two RAPGs. Below, methods will be presented for associating Rx ports, sounded via an antennaswitching procedure, with RAPGs. Such an association is needed for the NW to perform DL precoding and rank adaptation for low complexity 8Rx devices. For example, the association may be implicit according to a predetermined set of rules and known to both the NW and the device, or the association is explicitly configured by the NW to the device. The below is based on that the device, in a previous step (see, (optional) actions 510, 520), has indicated that it has several RAPGs and/or indicated capability for low- complexity receiver.

Figure 5a is a combined signalling diagram and flow chart and illustrates example methods for transmitting SRS and DL reciprocity-based communication based on the SRS. The signaling is between a wireless communications device, such as the UE 121 , and a network node, such as the first radio access node 111.

The actions may be performed in any suitable order, for example in another order than given below.

Action 500 (optional)

In the optional action 500, the UE, such as the wireless communications device 121 , transmits a capability report to the NW node, such as the first radio access node 111., indicating the UE has several RAPGs and/or a capability for a low-complexity receiver.

Action 501

The NW node, such as the first radio access node 111 , may transmit an SRS configuration to the wireless communications device 121. The SRS configuration indicates how the wireless communications device 121 should map SRS ports to two or more RAPGs

Typically, the UE determines the mapping but with certain constraints indicated by the network or the specification. For example, the specification may indicate that a first 4 SRS ports should be transmitted from a first RAPG, and the last 4 SRS ports should be transmitted from a second RAPG. However, which RAPG that is "the first RAPG" is up to UE implementation. I.e., the spec only indicates how the SRS ports should be grouped w r t the RAPGs.

Thus, the wireless communications device 121 receives an SRS configuration, where the SRS configuration indicates how the wireless communications device 121 should map SRS ports to two or more RAPGs. In other words, the SRS configuration indicates a mapping (i.e., how the wireless communications device should map) between one or more SRS ports, such as a multiple of SRS ports, of the wireless communications device to two or more RAPGs of the wireless communications device. In some embodiments disclosed herein the mapping maps an SRS port out of a multiple of SRS ports to a respective RAPG out of a multiple of RAPG.

Action 502

The wireless communications device 121 transmits SRS to a network node 111 according to the indicated mapping of SRS ports and RAPGs.

Action 503:

Based on the received SRS, the NW determines DL precoders for the layers targeting a first RAPG such that the interference of these layers received at the second RAPG is as small as possible, similarly as is done for MU -Ml MO.

Action 504:

Based on the determined precoders the network node 111 transmits DL communication to the UE 121.

Figure 5b illustrates example methods performed by the UE 121.

The methods comprises one or more of the following actions, which actions may be taken in any suitable order.

The UE 121 is configured to communicate with the network node 111.

In (optional) Action 510, the wireless communications device 121 indicates that the wireless communications device 121 has several RAPGs and/or a capability for a low- complexity receiver.

In Action 511, the wireless communications device 121 receives an SRS configuration, where the SRS configuration indicates how the wireless communications device should map SRS ports to two or more RAPGs. That is, the SRS configuration indicates a mapping of how the wireless communications device should map one or more SRS ports, such as a multiple of SRS ports, to two or more RAPGs. In Action 512, the wireless communications device 121 transmits SRS to a network node 111 according to the indicated mapping of SRS ports and RAPGs.

Figure 5c illustrates example methods performed by the network node 111.

In (optional) Action 520, the network node 111 receives an indication that the wireless communications device 121 has several RAPGs and/or a capability for a low- complexity receiver.

In Action 521 , the network node 111 transmits an SRS configuration to the wireless communications device. The SRS configuration indicates how the wireless communications device should map SRS ports to two or more RAPGs.

In Action 522, the network node 111 receives SRS from the wireless communications device 121.

Further aspects of different SRS ports per each SRS resource being associated with different RAPGs will be disclosed next.

Some embodiments are described with reference to Figure 6a, for a device with two RAPGs with 3Rx chains each, and where there is one TX chain per RAPG that may be switched to sound Rx antennas associated with the same RAPG (i.e. , no antenna switching across RAPGs).

In some embodiments, the device maps the first half of the SRS ports of one or multiple SRS resource(s) to a first RAPG, and the last half of the SRS ports of each SRS resource to a second RAPG (assuming a device with two RAPGs). This convention is reasonable if each RAPG is associated with different Tx chains, as it minimizes SRS overhead since Tx chains associated with different RAPGs may be sounded in a same OFDM symbol (note that multiple SRS resources in a same OFDM symbol is not supported for antenna switching).

For the example in Figure 6a, the 6Rx device is configured with three two-port SRS resources (i.e., 2T6R antenna switching), and the device may map the first SRS port of each SRS resource to a first RAPG, and the device may map the last SRS port of each SRS resource to a second RAPG.

In some embodiments, the first half and the second half of the SRS ports per SRS resource are the SRS ports with lowest and highest SRS port number:

• For a two-port SRS resource, SRS port 1000 and 1001 are associated with a first and a second RAPG, respectively.

• For a four-port SRS resource, SRS ports {1000, 1001} and {1002, 1003} are associated with a first and second RAPG, respectively.

In some embodiments, for a four-port SRS resource the first half and second half of the SRS ports per SRS resource are SRS port numbers {1000, 1002} and {1001 , 1003}, respectively.

In NR Rel-18, partially coherent precoding was introduced for 8 Tx UEs with N_g = 2 groups of 4 coherent antenna ports and for 8Tx UEs with N_g = 4 groups of 2 coherent antenna ports (but no coherence across groups can be guaranteed). Such UEs support sounding 8 Rx in a single 8-port SRS resource (i.e. , 8T8R antenna switching). Within said 8-port SRS resource:

• For the case N_g = 2, SRS ports numbered {1000, 1001 , 1004, 1005} are assumed to be coherent, and SRS ports numbered {1002, 1003, 1006, 1007} are assumed to be coherent.

• For the case N_g = 4, SRS ports numbered {1000, 1004} are assumed to be coherent, SRS ports numbered {1001, 1005} are assumed to be coherent, SRS ports numbered {1002, 1006} are assumed to be coherent, and SRS ports numbered {1003, 1007} are assumed to be coherent.

In some embodiments, since it is likely that a UE with 8Tx and 8Rx, where the 8Rx are split over multiple RAPGs cannot precode coherently over antenna ports associated with different RAPGs, the set of SRS ports (over one or multiple SRS resource sets) are numbered as follows:

• For the case of 2 RAPGs, a first set of SRS ports, which are associated with a first RAPG, are {1000, 1001, 1004, 1005} and the second set of SRS ports, which are associated with a second RAPG, are {1002, 1003, 1006, 1007}. • For the case of 4 RAPGs, a further first set of SRS ports, which are associated with a first RAPG, are {1000, 1004}, the second set of SRS ports, which are associated with a second RAPG, are {1001 , 1005}, the third set of SRS ports, which are associated with a third RAPG, are {1002, 1006}, and the fourth set of SRS ports, which are associated with a fourth RAPG, are {1003, 1007}.

Further aspects of different SRS resources/resource sets being associated with different RAPGs will be disclosed next.

In the above embodiments, different SRS ports of a same SRS resource are mapped to different RAPGs. This convention is reasonable, e.g., if the number of Tx chains equals the number of Rx chains (e.g., for 8T8R antenna switching). This convention is reasonable if each RAPG is associated with a different set of Tx chains. For instance, device with 8Rx, 2 RAPGs, and 2Tx chains per RAPG may sound all 8Rx ports in 4 SRS transmission using 2T8R antenna switching. The downside with this approach is that in the case of SRS dropping (e.g., if SRS transmission occasion collides with other UL transmission with higher priority), NW will have partial CSI for all RAPGs (instead of full CSI for, at least, one RAPGS). Furthermore, it is unclear how to support asymmetric UE architectures.

Therefore, in other embodiments, for antenna switching configured with more than one SRS resource sets and/or multiple SRS resources in an SRS resource set, all SRS ports of a same SRS resource are mapped to a same RAPG, and different SRS resources/SRS resource sets are mapped to different RAPGs.

Some embodiments are described with reference to Figure 6b, for a device with two RAPGs with 4RX per RAPG, and where two TX chains may be switched across both RAPG using 2T8R antenna switching. Thus, the same TX chains may be switched across all RAPGs.

In some embodiments, a first part of the SRS ports may be mapped to a first RAPG, and a second part of the SRS ports may be mapped to a second RAPG. The first and second parts of the SRS ports may be determined based on an order of the SRS ports, such that the first part of SRS ports consists, e.g., of the first half of the SRS ports according to the order of the SRS ports, and the second part of the SRS ports consists of the last half of the SRS ports according to the order of the SRS ports. In some embodiments, the SRS port order is based on the following rules: 1. First, consider the lowest SRS resource set ID (if multiple SRS resource sets are used)

2. Then, consider the lowest SRS resource IDs per SRS resource set (if multiple SRS resources are used per SRS resource set)

3. Then, consider lowest SRS port index within per SRS resource (if multiple SRS Ports are used per SRS resource)

Note, in what follows, for the case when different SRS ports over multiple SRS resources/SRS resource sets are in the first and the second half of SRS ports, the term “bundle” (instead of “set”) of SRS resources associated with an RAPG may be used. This is so because SRS resource set is a term that exists already in legacy specification and since the SRS resources that are associated with a RAPG may not overlap with the SRS resources that are associated with an SRS resource set.

In some embodiments, a first bundle of SRS resources is mapped to a first RAPG, a second bundle of SRS resources are mapped to a second RAPG, and so on.

• (“Based on SRS resource ID”) In some embodiments, for xTyR antenna switching and two RAPGs, a first bundle of SRS resources is the y/(2x) SRS resources with lowest SRS resource ID, and a second bundle of SRS resources are the y/(2x) SRS resources with lowest SRS resource ID

• (“Based on SRS transmission occasion-sequential mapping”) In some embodiments, for xTyR antenna switching and two RAPGs, a first and second bundle of SRS resources are the y/(2x) SRS resources that are transmitted first and last, respectively. o E.g., if all SRS resources are transmitted in a same slot, the first and second bundle of SRS resources are the SRS resources that are transmitted first and last in the slot, respectively (configured with the highest and lowest value of the RRC-parameter ‘startPosition’ in SRS- Config IE, respectively). o E.g., if different SRS resources are transmitted in different slots, the first and second bundle of SRS resources are the SRS resources that are transmitted in slots with lowest and highest slot index, respectively.

• (“Based on SRS transmission occasion-cyclical mapping”) In some embodiments, for xTyR antenna switching and two RAPGs, the first bundle of SRS resources is the y/(2x) SRS resources transmitted in a first, third, etc. SRS transmission occasion, and the second bundle of SRS resources is the y/(2x) SRS resources transmitted in a second, fourth, etc. SRS transmission occasion. SRS transmission occasions may be in a same slot or in different slots (e.g., for aperiodic SRS, in a same SRS resource set or different SRS resource sets).

Some examples (where first and last SRS resources may be according to the above):

• E.g., for 1T6R antenna switching, the first three SRS resources are associated with a first RAPG and the last three SRS resources are associated with a second RAPG.

• E.g., for 2T8R antenna switching, the first two SRS resources are associated with a first RAPG and the last two SRS resources are associated with a second RAPG.

• E.g., for 4T8R antenna switching, the first SRS resource is associated with a first RAPG and the last SRS resource is associated with a second RAPG.

In some embodiments, if SRS resources are spread over multiple SRS resource sets, all SRS resource(s) in a first bundle of SRS resource sets are associated with a first RAPG, all SRS resource(s) in a second bundle of SRS resource sets are associated with a second RAPG, and so on.

• (“Based on SRS resource set ID”) In some embodiments, the SRS resource set with lowest SRS resource set ID are associated with a first RAPG, the SRS resource(s) belonging to the SRS resource set with second lowest SRS resource set ID are associated with a second RAPG, and so on. Thus, association may be performed based on an order of SRS resource set ID.

• (“Based on SRS transmission occasion-sequential mapping”) In some embodiments, a first and second bundle of SRS resource sets are the SRS resource sets that are transmitted in the first and last slots, respectively.

• (“Based on SRS transmission occasion-cyclical mapping”) In some embodiments, the first bundle of SRS resource sets are the SRS resource sets transmitted in a first, third, etc. slot, and the second bundle of SRS resource sets are the SRS resource sets in a second, fourth, etc. slot.

In some embodiments, in case an SRS resource set contains multiple SRS resources, within each SRS resource set, either of the above rules for SRS port numbering applies. • E.g. , if the first and second SRS resource set each contains a pair of SRS resources, in some embodiments SRS ports {1000, 1001} belong to the first SRS resource, and SRS ports {1002, 1003} belong to a second SRS resource in the first SRS resource set, and SRS ports {1004, 1005} belong to the first SRS resource, and SRS ports {1006, 1007} belong to a second SRS resource in the second SRS resource set.

• E.g., if the first and second SRS resource set contains a pair of SRS resources, in some embodiments SRS ports {1000, 1004} belong to the first SRS resource, and SRS ports {1001 , 1005} belong to a second SRS resource in the first SRS resource set, and SRS ports {1002, 1006} belong to the first SRS resource, and SRS ports {1003, 1007} belong to a second SRS resource in the second SRS resource set.

Some embodiments will now be described with reference to Figure 6c, where the device in total has two 2 Tx chains and 6 Rx chains which are divided into two RAPGs. The first RAPG has 4 Rx chains and 1 Tx chain while the second RAPG has 2 Rx chains and 1 Tx chain. Thus, in Figure 6c each RAPG has its own corresponding Tx chains. To support such devices, the first and second bundle of SRS resources should not contain the same amount of SRS ports. For example, if 1T6R antenna switching is configured for the device in Figure 6c, the first four SRS resources belong to the first RAPG and the last two SRS resources belong to the second RAPG. The first and last SRS resources may be determined according to above rules (e.g., based on SRS resource ID or SRS transmission occasion).

Further aspects of i mplicit/expl icit mapping of SRS ports/SRS resources/SRS resource sets to RAPGs will be disclosed next.

In some embodiments, there is an implicit mapping between SRS transmissions and RAPG based on if the transmitted SRS resources are overlapping in time or not.

In some embodiments, if two SRS resources are configured by the NW such that they are overlapping in time, the device maps each of the overlapping SRS resources to separate RAPG. In one related embodiment, if two SRS resources are configured by the NW such that they are overlapping in time, the SRS resource with lowest SRS resource ID belongs to a first RAPG, and the SRS resource with highest SRS resource ID belongs to the second RAPG. Thus, the wireless communications device 121 may map a respective SRS resource to an RAPG based on the SRS resource ID, more particularly based on the order of the SRS resource ID compared to other SRS resource IDs associated with their respective SRS resource to be mapped to RAPGs. Thus, in some embodiments, the SRS ports are mapped to RAPGs based on the order of the SRS resource ID compared to other SRS resource IDs associated with their respective SRS resource. Or it may be, e.g., that SRS ports with even port number in an SRS resource belongs to a first RAPG and SRS ports with odd port number in an SRS resource belongs to a second RAPG. Thus, in some embodiments, the first half of the SRS ports mapped to the first RAPGH comprises even SRS ports and the second half of the SRS ports mapped the second RAPG comprises odd SRS ports.

In some embodiments, considering an explicit mapping, RRC configuration is used to associate SRS resource sets (or SRS resources in an SRS resource set) to RAPG.

• In some embodiments, a bitfield is RRC configured per SRS resource set or SRS resource to indicate which SRS ports (belonging to the SRS resource or the one or more SRS resources in an SRS resource set) belongs to which RAPG (all the SRS ports belonging to the indicated SRS resource set and/or SRS resource should be mapped to an associated RAPG). In a related embodiment, the bitfield indicates a new RAPG index. An SRS resource configured with a certain RAPG index may be transmitted from antenna ports associated with that RAPG.

• In some embodiments, a single bit indicator is RRC configured per SRS resource set or SRS resource to indicate which SRS ports (belonging to the SRS resource or the one or more SRS resources in an SRS resource set) belongs to which RAPG (assuming the device has two RAPGs).

One benefit with explicitly configuring the association between SRS ports (belonging to one or more SRS resources in one or more SRS resource sets) is that it supports device architectures for which the number Rx ports or Tx ports per RAPG may vary over RAPGs.

An example of asymmetric device architecture is shown in Figure 6d, where the UE in total has two 3 Tx chains and 6 Rx chains which are divided into two RAPGs. The first RAPG has 4 Rx chains and 2 Tx chains while the second RAPG has 2 Rx chains and 1 Tx chain.

To support an asymmetric device architecture (e.g., as in Figure 6d), in some embodiments, each RAPG is associated with a separate antenna switching configuration. For example, in Figure 6d, 2T4R antenna switching is configured for the first RAPG and 1T2R is configured for the second RAPG. In some embodiments, SRS resources and/or SRS resource sets associated with different RAPGs may be transmitted simultaneously.

In some embodiments, simultaneous transmission of different SRS resources and/or SRS resource sets associated with different RAPGs is an optional UE capability.

Further aspects of dynamic/Semi-persistent signaling of association between SRS ports and RAPGs will be disclosed next.

In some other embodiments, when the configured SRS resource(s) and/or SRS resource set(s) are configured for the purpose of aperiodic SRS triggering, then which SRS ports that belong to which RAPG may be indicated via the DCI triggering the SRS. For instance, a codepoint of a field of the DCI may indicate an SRS trigger state which contains information on which SRS ports belong to which RAPG. In one example, when the codepoint in the field of the DCI indicates an SRS trigger state that triggers an SRS resource set, then all the SRS ports belonging to the triggered SRS resource set may be mapped to the associated RAPG. In another example, when the codepoint in the field of the DCI indicates an SRS trigger state that triggers an SRS resource set, then

• a first set of SRS ports in a first SRS resource in the triggered SRS resource set may be mapped to a first associated RAPG; and

• a second set of SRS ports in a second SRS resource in the triggered SRS resource set may be mapped to a second associated RAPG.

In yet some other embodiments, when the configured SRS resource(s) and/or SRS resource set(s) are configured for the purpose of semi-persistent SRS activation, then which SRS ports that belong to which RAPG may be indicated via a MAC CE activating/deactivating the SRS. For instance, a field in the MAC CE may contain information on which SRS ports belong to which RAPG. In one example, when the MAC CE activates an SRS resource set, then all the SRS ports belonging to the activated SRS resource set may be mapped to the associated RAPG. In another example, when the MAC CE activates an SRS resource set, then

• a first set of SRS ports in a first SRS resource in the activated SRS resource set may be mapped to a first associated RAPG; and

• a second set of SRS ports in a second SRS resource in the activated SRS resource set may be mapped to a second associated RAPG.

In the above embodiments, the SRS ports and the associated RAPG may be indicated via any one of the following non-limiting ways: • a predefined set of SRS ports and associated RAPGs may be predefined in specifications, such as 3GPP specifications, and an index to one of the predefined SRS ports to RAPG associations may be configured to an SRS resource set/SRS resource, or triggered along with an SRS resource set/SRS resource, or activated along with an SRS resource set/SRS resource.

• A finite set of SRS ports to RAPG associations may be higher layer configured (e.g., RRC configured) and an index to one of the predefined SRS ports to RAPG associations may be configured to an SRS resource set/SRS resource, or triggered along with an SRS resource set/SRS resource, or activated along with an SRS resource set/SRS resource.

In this way, the proposed scheme enables DL-reciprocity based communication with a low-complexity device using RAPGs where the network may determine DL precoders such that inter-layer interference may be properly handled.

Figure 7 shows an example of the wireless communications device 121. Figure 8 shows an example of the network node 111.

The wireless communications device 121 and the network node 111 may comprise a respective input and output interface, IF, 706, 806 configured to communicate with each other, see Figures 7-8. The input and output interface may comprise a wireless receiver (not shown) and a wireless transmitter (not shown).

The embodiments herein may be implemented through a respective processor or one or more processors, such as the respective processor 704 and 804, of a processing circuitry in the wireless communications device 121 and the network node 111 and depicted in Figures 7-8 together with computer program code for performing the functions and actions of the embodiments herein. The program code mentioned above may also be provided as a computer program product, for instance in the form of a data carrier carrying computer program code for performing the embodiments herein when being loaded into the respective wireless communications device 121 and the network node 111. One such carrier may be in the form of a CD ROM disc. It is however feasible with other data carriers such as a memory stick. The computer program code may furthermore be provided as pure program code on a server and downloaded to the respective wireless communications device 121 and network node 111. The wireless communications device 121 and the network node 111 may further comprise a respective memory 702 and 802 comprising one or more memory units. The memory comprises instructions executable by the processor in the wireless communications device 121 and the network node 111.

Each respective memory 702 and 802 is arranged to be used to store e.g. information, data, configurations, and applications to perform the methods herein when being executed in the respective wireless communications device 121 and the network node 111.

In some embodiments, a respective computer program 703 and 803 comprises instructions, which when executed by the at least one processor, cause the at least one processor of the respective wireless communications device 121 and network node 111 to perform the actions above.

In some embodiments, a respective carrier 705 and 805 comprises the respective computer program, wherein the carrier is one of an electronic signal, an optical signal, an electromagnetic signal, a magnetic signal, an electric signal, a radio signal, a microwave signal, or a computer-readable storage medium.

Those skilled in the art will also appreciate that the units in the units described above may refer to a combination of analog and digital circuits, and/or one or more processors configured with software and/or firmware, e.g. stored in the respective wireless communications device 121 and network node 111 described above. One or more of these processors, as well as the other digital hardware, may be included in a single Application-Specific Integrated Circuitry (ASIC), or several processors and various digital hardware may be distributed among several separate components, whether individually packaged or assembled into a system-on-a-chip (SoC).

With reference to Figure 9, in accordance with an embodiment, a communication system includes a telecommunication network 3210, such as a 3GPP-type cellular network, which comprises an access network 3211 , such as a radio access network, and a core network 3214. The access network 3211 comprises a plurality of base stations 3212a, 3212b, 3212c, such as the source and target access node 111 , 112, AP STAs NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 3213a, 3213b, 3213c. Each base station 3212a, 3212b, 3212c is connectable to the core network 3214 over a wired or wireless connection 3215. A first user equipment (UE) such as a Non-AP STA 3291 located in coverage area 3213c is configured to wirelessly connect to, or be paged by, the corresponding base station 3212c. A second UE 3292 such as a Non-AP STA in coverage area 3213a is wirelessly connectable to the corresponding base station 3212a. While a plurality of UEs 3291 , 3292 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 3212.

The telecommunication network 3210 is itself connected to a host computer 3230, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 3230 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections 3221, 3222 between the telecommunication network 3210 and the host computer 3230 may extend directly from the core network 3214 to the host computer 3230 or may go via an optional intermediate network 3220. The intermediate network 3220 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 3220, if any, may be a backbone network or the Internet; in particular, the intermediate network 3220 may comprise two or more subnetworks (not shown).

The communication system of Figure 9 as a whole enables connectivity between one of the connected UEs 3291 , 3292 such as e.g. the UE 121, and the host computer 3230. The connectivity may be described as an over-the-top (OTT) connection 3250. The host computer 3230 and the connected UEs 3291 , 3292 are configured to communicate data and/or signaling via the OTT connection 3250, using the access network 3211, the core network 3214, any intermediate network 3220 and possible further infrastructure (not shown) as intermediaries. The OTT connection 3250 may be transparent in the sense that the participating communication devices through which the OTT connection 3250 passes are unaware of routing of uplink and downlink communications. For example, a base station 3212 may not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 3230 to be forwarded (e.g., handed over) to a connected UE 3291. Similarly, the base station 3212 need not be aware of the future routing of an outgoing uplink communication originating from the UE 3291 towards the host computer 3230.

Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to Figure 10. In a communication system 3300, a host computer 3310 comprises hardware 3315 including a communication interface 3316 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 3300. The host computer 3310 further comprises processing circuitry 3318, which may have storage and/or processing capabilities. In particular, the processing circuitry 3318 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer 3310 further comprises software 3311 , which is stored in or accessible by the host computer 3310 and executable by the processing circuitry 3318. The software 3311 includes a host application 3312. The host application 3312 may be operable to provide a service to a remote user, such as a UE 3330 connecting via an OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the remote user, the host application 3312 may provide user data which is transmitted using the OTT connection 3350.

The communication system 3300 further includes a base station 3320 provided in a telecommunication system and comprising hardware 3325 enabling it to communicate with the host computer 3310 and with the UE 3330. The hardware 3325 may include a communication interface 3326 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 3300, as well as a radio interface 3327 for setting up and maintaining at least a wireless connection 3370 with a UE 3330 located in a coverage area (not shown in Figure 10) served by the base station 3320. The communication interface 3326 may be configured to facilitate a connection 3360 to the host computer 3310. The connection 3360 may be direct or it may pass through a core network (not shown in Figure 10) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware 3325 of the base station 3320 further includes processing circuitry 3328, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station 3320 further has software 3321 stored internally or accessible via an external connection.

The communication system 3300 further includes the UE 3330 already referred to. Its hardware 3335 may include a radio interface 3337 configured to set up and maintain a wireless connection 3370 with a base station serving a coverage area in which the UE 3330 is currently located. The hardware 3335 of the UE 3330 further includes processing circuitry 3338, which may comprise one or more programmable processors, applicationspecific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE 3330 further comprises software 3331, which is stored in or accessible by the UE 3330 and executable by the processing circuitry 3338. The software 3331 includes a client application 3332. The client application 3332 may be operable to provide a service to a human or non-human user via the UE 3330, with the support of the host computer 3310. In the host computer 3310, an executing host application 3312 may communicate with the executing client application 3332 via the OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the user, the client application 3332 may receive request data from the host application 3312 and provide user data in response to the request data. The OTT connection 3350 may transfer both the request data and the user data. The client application 3332 may interact with the user to generate the user data that it provides. It is noted that the host computer 3310, base station 3320 and UE 3330 illustrated in Figure 10 may be identical to the host computer 3230, one of the base stations 3212a, 3212b, 3212c and one of the UEs 3291 , 3292 of Figure 9, respectively. This is to say, the inner workings of these entities may be as shown in Figure 10 and independently, the surrounding network topology may be that of Figure 9.

In Figure 10, the OTT connection 3350 has been drawn abstractly to illustrate the communication between the host computer 3310 and the use equipment 3330 via the base station 3320, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE 3330 or from the service provider operating the host computer 3310, or both. While the OTT connection 3350 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

The wireless connection 3370 between the UE 3330 and the base station 3320 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE 3330 using the OTT connection 3350, in which the wireless connection 3370 forms the last segment. More precisely, the teachings of these embodiments may improve the data rate, latency, power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime.

A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 3350 between the host computer 3310 and UE 3330, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 3350 may be implemented in the software 3311 of the host computer 3310 or in the software 3331 of the UE 3330, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 3350 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 3311, 3331 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 3350 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station 3320, and it may be unknown or imperceptible to the base station 3320. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer’s 3310 measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software 3311, 3331 causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 3350 while it monitors propagation times, errors etc.

Figure 11 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 9 and Figure 10. For simplicity of the present disclosure, only drawing references to Figure 11 will be included in this section. In a first action 3410 of the method, the host computer provides user data. In an optional subaction 3411 of the first action 3410, the host computer provides the user data by executing a host application. In a second action 3420, the host computer initiates a transmission carrying the user data to the UE. In an optional third action 3430, the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional fourth action 3440, the UE executes a client application associated with the host application executed by the host computer.

Figure 12 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 9 and Figure 10. For simplicity of the present disclosure, only drawing references to Figure 12 will be included in this section. In a first action 3510 of the method, the host computer provides user data. In an optional subaction (not shown) the host computer provides the user data by executing a host application. In a second action 3520, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third action 3530, the UE receives the user data carried in the transmission.

Figure 13 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figure 9 and Figure 10. For simplicity of the present disclosure, only drawing references to Figure 13 will be included in this section. In an optional first action 3610 of the method, the UE receives input data provided by the host computer. Additionally or alternatively, in an optional second action 3620, the UE provides user data. In an optional subaction 3621 of the second action 3620, the UE provides the user data by executing a client application. In a further optional subaction 3611 of the first action 3610, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in an optional third subaction 3630, transmission of the user data to the host computer. In a fourth action 3640 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

Figure 14 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station such as a AP STA, and a UE such as a Non-AP STA which may be those described with reference to Figures 9 and 10. For simplicity of the present disclosure, only drawing references to Figure 14 will be included in this section. In an optional first action 3710 of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In an optional second action 3720, the base station initiates transmission of the received user data to the host computer. In a third action 3730, the host computer receives the user data carried in the transmission initiated by the base station.

The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

NUMBERED EMBODIMENTS

1. A method, performed by a wireless communications device 121 of a wireless communications network 100, for transmitting SRS, the method comprises: receiving an SRS configuration, wherein the SRS configuration indicates information on a mapping (i.e. , how the wireless communications device should map) between one or more SRS ports, such as a multiple of SRS ports, of the wireless communications device to two or more RAPGs of the wireless communications device; and transmitting SRS to a network node 111 according to the indicated mapping between the SRS ports and the RAPGs.

2. The method of embodiment 1 , wherein the SRS configuration comprises an implicit mapping between SRS ports and RAPG. 3. The method of embodiment 2, wherein the implicit mapping is based on a predefined rule (i.e., a specified rule).

4. The method of embodiment 3, wherein the rule is based on one or more of a. An SRS resource set ID, b. An SRS resource ID, c. An SRS port index.

5. The method of any of embodiments 1-4, wherein a first set of the SRS ports in an SRS resource belongs to the first RAPG, and a second set of the SRS ports in the same SRS resource belongs to the second RAPG.

6. The method of embodiment 5, wherein the first set of the SRS ports contains the same number of SRS ports as the second set of SRS ports.

7. The method of embodiment 5, wherein the first set of the SRS ports contains more SRS ports than the second set of SRS ports.

8. The method of embodiment 7, wherein if there is an odd number, M, of SRS ports in an SRS resource, the first M/2 + 1 SRS ports belongs to the first RAPG.

9. The method of any of embodiments 5-8, wherein the first set of the SRS ports in an SRS resource is the SRS ports with lowest SRS port index in that SRS resource.

10. The method of any of embodiments 5-8, wherein the first set of the SRS ports is SRS port 1000, 1001, 1004, and 1005 and the second set of SRS ports in is SRS port 1002, 1003, 1006, and 1007.

11. The method of any of embodiments 1-4, wherein a first number of SRS resources/SRS resource sets belongs to the first RAPG, and a second number of SRS resources/SRS resource sets belongs to the second RAPG. 12. The method of embodiment 11 , wherein the first number of SRS resources/SRS resource sets contains the same number of SRS ports as the second number of SRS resources/SRS resource sets.

13. The method of embodiment 11, wherein the first number of SRS resources/SRS resource sets contains more SRS ports than the second number of SRS resources/SRS resource sets.

14. The method of embodiment 11, wherein the SRS ports are ordered according to a. First consider the lowest SRS resource set ID (if multiple SRS resource sets are used) b. Then consider the lowest SRS resource IDs per SRS resource set (if multiple SRS resources are used per SRS resource set) c. Then consider lowest SRS port index within per SRS resource (if multiple SRS Ports are used per SRS resource).

15. The method of embodiment 11, wherein the SRS ports are ordered according to SRS transmission occasion.

16. The method of embodiment 15, wherein there is: a) sequential mapping between SRS transmission occasions and RAPGs, or b) cyclical mapping between SRS transmission occasions and RAPGs.

17. The method of any of embodiments 1-16, wherein the SRS configuration comprises an explicit mapping between SRSs and RAPG.

18. The method of embodiment 17, wherein a bitfield is RRC configured per SRS resource set or SRS resource to indicate which SRS ports belongs to which RAPG.

19. The method of embodiment 18, wherein all the SRS ports belonging to the indicated SRS resource set or SRS resource are transmitted from the indicated RAPG.

20. The method of embodiment 19, wherein the bitfield is an RAPG index.

21. The method of embodiment 20, wherein there is a separate antenna switching configuration per RAPG. 22. The method of any of embodiments 1-21 , wherein DCI triggering an aperiodic SRS transmission also indicates mapping between SRS ports (in different SRS resources and/or SRS resource sets) and RAPGs.

23. The method of any of embodiments 1-22, wherein MAC CE activating/deactivating a semi-persistent SRS transmission also indicates mapping between SRS ports (in different SRS resources and/or SRS resource sets) and RAPGs.

24. A wireless communications device, such as a UE, adapted for transmitting SRS to a network node. The wireless communications device is adapted to perform the method of any of embodiments 1-23.

25. A method, performed by a network node 111 for receiving SRS from a wireless communications device which uses receive antenna port groups for communicating with the network node, the method comprises: transmitting an SRS configuration to the wireless communications device, where the SRS configuration indicates how the wireless communications device should map SRS ports to two or more RAPGs; and receiving SRS from the wireless communications device according to the indicated mapping of SRS ports and RAPGs.

26. A network node 111 , adapted for receiving SRS from a wireless communications device, such as a UE, which uses receive antenna port groups. The network node 111 is adapted to perform the method of embodiment 25.

ABBREVIATIONS

Claims

1. A method, performed by a wireless communications device (121) of a wireless communications network (100), for transmitting SRS, the method comprises: receiving (511) an SRS configuration, wherein the SRS configuration indicates information on a mapping between one or more SRS ports of the wireless communications device to two or more RAPGs of the wireless communications device; and transmitting (512) SRS to a network node (111) according to the indicated mapping between the SRS ports and the RAPGs.

2. The method of claim 1 , wherein the method further comprises: indicating (510) that the wireless communications device (121) has several RAPGs and/or a capability for a low-complexity receiver.

3. The method of claim 1 or 2, wherein the SRS configuration comprises an implicit mapping between SRS ports and RAPG.

4. The method of claim 3, wherein the implicit mapping is based on a predefined rule.

5. The method of claim 4, wherein the rule is based on one or more of a. An SRS resource set ID, b. An SRS resource ID, c. An SRS port index.

6. The method of any of claims 1-5, wherein a first set of the SRS ports in an SRS resource belongs to the first RAPG, and a second set of the SRS ports in the same SRS resource belongs to the second RAPG.

7. The method of claim 6, wherein the first set of the SRS ports contains the same number of SRS ports as the second set of SRS ports.

8. The method of any of claims 6-7, wherein the first set of the SRS ports in an SRS resource is the SRS ports with lowest SRS port index in that SRS resource.

9. The method of any of claims 1-5, wherein a first number of SRS resources, or SRS resource sets, belongs to the first RAPG, and a second number of SRS resources, or SRS resource sets, belongs to the second RAPG.

10. The method of claim 9, wherein the first number of SRS resources/SRS resource sets contains the same number of SRS ports as the second number of SRS resources/SRS resource sets.

11. The method of claim 9, wherein a first half of the SRS ports is mapped to a first RAPG, and a second half of the SRS ports is mapped to a second RAPG.

12. The method of claim 9 or 10, wherein the SRS ports are mapped to RAPGs based on the order of the SRS resource ID compared to other SRS resource IDs associated with their respective SRS resource.

13. The method of claim 11 , wherein the first half of the SRS ports mapped to the first RAPG comprises even SRS ports and wherein the second half of the SRS ports mapped the second RAPG comprises odd SRS ports.

14. The method of claim 11 , wherein the first and second half of the SRS ports are determined based on an order of the SRS ports, wherein the first half of SRS ports consists of the first half of the SRS port according to the order of the SRS ports, and the second part of the SRS ports consists of the last half of the SRS ports according to the order of the SRS ports.

15. The method of claim 9, wherein the SRS ports are ordered according to a. First consider the lowest SRS resource set ID in case multiple SRS resource sets are used, b. Then consider the lowest SRS resource IDs per SRS resource set in case multiple SRS resources are used per SRS resource set, and c. Then consider lowest SRS port index within per SRS resource in case multiple SRS Ports are used per SRS resource.

16. The method of claim 9, wherein a first bundle of SRS resources are mapped to a first RAPG, and a second bundle of SRS resources are mapped to a second RAPG.

17. The method of claim 9, wherein the SRS ports are ordered according to SRS transmission occasion.

18. The method of claim 15, wherein there is: a) sequential mapping between SRS transmission occasions and RAPGs, or b) cyclical mapping between SRS transmission occasions and RAPGs.

19. A wireless communications device for transmitting SRS to a network node according to the method of any of claims 1-16.

20. A computer program (703) for transmitting SRS to a network node (111), the computer program (703) comprising instructions, which when executed by a processor (704) of a wireless communication device (121), causes the processor (704) to perform actions according to the method of any of claims 1-16.

21. A method, performed by a network node (111) for receiving SRS from a wireless communications device (121) which uses receive antenna port groups for communicating with the network node (111), the method comprises: transmitting (521) an SRS configuration to the wireless communications device, where the SRS configuration indicates how the wireless communications device should map SRS ports to two or more RAPGs; and receiving (522) SRS from the wireless communications device according to the indicated mapping of SRS ports and RAPGs.

22. The method of claim 19, wherein the method further comprises: receiving (520) indication that the wireless communications device (121) has several RAPGs and/or a capability for a low-complexity receiver.

23. The method of claim 19 or 20, wherein the SRS configuration comprises an implicit mapping between SRS ports and RAPG.

24. The method of claim 21 , wherein the implicit mapping is based on a predefined rule.

25. The method of claim 22, wherein the rule is based on one or more of a. An SRS resource set ID, b. An SRS resource ID, c. An SRS port index.

26. The method of any of claims 19-23, wherein a first set of the SRS ports in an SRS resource belongs to the first RAPG, and a second set of the SRS ports in the same SRS resource belongs to the second RAPG.

27. The method of any of claims 19-23, wherein a first number of SRS resources, or SRS resource sets, belongs to the first RAPG, and a second number of SRS resources, or SRS resource sets, belongs to the second RAPG.

28. A network node (111) for receiving SRS from a wireless communications device (121) according to the method of any of claims 19-25.

29. A computer program (803) for receiving SRS from a wireless communications device (121), the computer program (803) comprising instructions, which when executed by a processor (804) of a network node (111), causes the processor (804) to perform actions according to the method of any of claims 19-25.