Cross link interference-sounding reference signal (CLI-SRS) measurements

Abstract

A method performed by a first user equipment, UE, for Cross-Link Interference- Sounding Reference Signal, CLI-SRS, in a wireless communication system is provided. Configuration information for transmitting CLI-SRS, the configuration information comprising a first timing advance, TA, that is specific to CLI signaling is received from a network node. A second TA for the CLI-SRS, based on the first TA is applied.

Description

[0001] CROSS LINK INTERFERENCE-SOUNDING REFERENCE SIGNAL (CLLSRS)

[0002] MEASUREMENTS FIELD

[0003] The present disclosure relates to wireless communications, and in particular, to high accuracy cross link interference (CLI)-sounding reference signal (SRS) measurements.

[0004] BACKGROUND

[0005] The Third Generation Partnership Project (3GPP) has developed and is developing standards for Fourth Generation (4G) (also referred to as Long Term Evolution (LTE)) and Fifth Generation (5G) (also referred to as New Radio (NR)) wireless communication systems. Such systems provide, among other features, broadband communication between network nodes, such as base stations, and mobile user equipments (UE), as well as communication between network nodes and between UEs. The 3GPP is also developing standards for Sixth Generation (6G) wireless communication networks.

[0006] FDD and TDD systems

[0007] Transmission and reception from a node, e.g., a terminal in a cellular system, may be multiplexed in the frequency domain or in the time domain (or combinations thereof). Frequency Division Duplex (FDD) as illustrated to the left in example of FIG. 1 implies that downlink and uplink transmission take place in different, sufficiently separated, frequency bands. Time Division Duplex (TDD), as illustrated to the right in FIG. 1 implies that downlink and uplink transmission take place in different, non-overlapping time slots. Thus, TDD may operate in unpaired spectrum, whereas FDD requires paired spectrum.

[0008] Typically, the structure of the transmitted signal in a communication system is organized in the form of a frame structure.

[0009] In more detail, the following two information elements (IES) are defined in current specifications. The TDD pattern is typically configured with at least the first IE and optionally the 2ndIE:

[0010] • TDD-DL-UL-ConfigCommon (cell-specific); and • TDD-DL-UL-ConfigDedicated (UE-specific).

[0011] The first IE is cell specific (common to all UEs) and is provided by broadcast signaling. It provides the number of slots in the TDD pattern via a reference subcarrier spacing and a periodicity such that the S-slot pattern repeats every S slots. This IE allows for very flexible configuration of the pattern characterized as follows:• A number of full downlink slots at the beginning of the pattern configured by the parameter nDownlinkSlots

[0012] • A number of full uplink slots at the end of the pattern configured by the parameter nlplinkSlots

[0013] • A number of downlink ('D') symbols following the full downlink slots configured by the parameter n ownlinkSymbols

[0014] • A number of uplink ('U') symbols preceding the full downlink slots configured by the parameter nUplinkSlots

[0015] • If there is a gap between the last downlink symbol and the first uplink symbol, then all symbols in the gap are characterized as flexible ('F'). A symbol classified as 'F' may be used for downlink or uplink. A UE determines the direction in one of the following two ways:

[0016] o Detecting a downlink control information (DCI) that schedules / triggers aDL signal / channel, e.g., physical downlink shared channel (PDSCH), channel state information reference signal (CSI-RS) or schedules / triggers an UL signal / channel, e.g., physical uplink shared channel (PUSCH), sounding reference signal (SRS), etc.; and

[0017] o By dedicated (UE-specific) signaling of the IE TDD-DL-UL- ConfigDedicated. This parameter overrides some or all of the 'F' symbols in the pattern, thus providing a semi-static indication of whether a symbol is classified as 'D' or 'U'; and • Optionally, a 2ndpattern that is concatenated to the first pattern may be configured as above. If a 2ndpattern is configured, the constraint is that the sum of the periodicities of the two patterns must evenly divide 20 ms.

[0018] FIG. 2 shows an example TDD DL / UL pattern configured by TDD-DL-UL-ConfigCommon. It consists of 3 full 'D' slots, 1 full 'U' slot, with a mixed slot in between consisting of 4 'D' symbols and 3 'U' symbols. The remaining 7 symbols in the mixed slot are classified as 'F.'

[0019] If a UE is not configured with TDD-DL-UL-ConfigDedicated, then the pattern at the top of the diagram is what it assumes. As stated above, the network node may make use of the 'F' symbols flexibly, by scheduling / triggering either an uplink or a downlink signal / channel in a UE specific manner. This allows for very dynamic behavior: the direction is not known to the UE a priori; rather, the direction becomes known once the UE detects a DCI scheduling / triggering a particular DL or UL signal / channel.In contrast, the DL / UL direction for some or all of the 'F' symbols in a particular slot may be provided to the UE in a semi-static manner by radio resource control (RRC) configuring the UE with DD-DL-UL-ConfigDedicated. The lower part of FIG. 2 shows 3 example configurations for overriding 'F' symbols in Slot 3. If the IE indicates 'allDownlink' or 'allUplink' for a particular slot (or slots), then all 'F' symbols in the slot are converted to either 'D' or U,' respectively. If the IE indicates 'explicit,' then a number of symbols at the beginning of the slot and / or a number of symbols at the end of the slot are indicated as 'D' and U,' respectively. In the example below, the first 7 and the last 5 are indicated as 'D' and U', which converts some of the 'F' symbols (but not all in this example) to 'D' and U.'

[0020] A behavior is that the UE-specific IE TDD-DL-UL-ConfigDedicated may only override (i.e., specify 'D' or 'U') for symbols that are configured as 'F' by the cell-specific IE TDD-DL-UL-ConfigCommon. In other words, a UE does not expect to have a 'D' symbol converted to 'U or vice versa.

[0021] Subband full duplex

[0022] As described above, in a conventional TDD system, an entire carrier bandwidth (BW) or all carriers in the same frequency band should use the same DL transmission or UL reception directions. This is illustrated in FIG. 3 for a single carrier and in FIG. 4 for multiple carriers.

[0023] For the 3GPP Technical Release 18 (3GPP Rel-18) evolution of the NR system, 3GPP has decided to study the technical feasibilities and potential benefits of subband full duplex (SBFD) systems.

[0024] • In such a system, a portion of a wide bandwidth carrier may be used for a different direction than that of the rest of the carrier. This is illustrated in FIG. 5. That is, unlike a conventional TDD system as shown in FIG. 3 where the entire bandwidth is used for DL transmission in the first three slots, the center portion of the SBFD carrier is used for UL reception while the rest of the carrier continues to be used for DL transmission as shown in FIG. 5,

[0025] • Similarly, instead of utilizing all carriers for the same DL or UL directions in a conventional TDD system as shown in FIG. 4, some carriers in the SBFD system may be used for a different direction than that of the other carriers as shown in FIG. 6.In the 3 GPP Rel-18 study, the scope has been limited such that in SBFD operation, only network nodes transmit DL and receive UL simultaneously. An individual UE is scheduled in only one direction (DL or UL) at a time.

[0026] A 3GPP Rel-18 work item agreed on 2 types of the SBFD sub band configuration. One is DU configuration which is in frequency domain DL subbands are continuous in frequency domain, as shown in FIG. 7. Another one is DUD configuration in frequency domain the DL subbands are discontinuous due to the UL sub band, as shown in FIG. 8.

[0027] UE to UE CLI measurements and handling

[0028] When a network node operates in SBFD duplex modes, UEs transmitting UL during a symbol or slot that is used for DL by the same or other base stations (BS), i.e., network nodes, of the same or other operators, may interfere with other UEs receiving DL in the same network, and / or in adjacent channels / bands. This generates UE-to-UE Cross-Link Interference (CLI). This interference is usually less disruptive than the BS-to-BS interference, due to the relatively lower UE transmit power compared to the gNB (network node) transmit power. However, if two UEs happen to be at a close mutual distance and the first one is scheduled UL while the 2ndone is scheduled DL at the same time, CLI from the 1stUE may impact DL performance of the 2nd UE. Such UE-to-UE CLI may be:

[0029] Co-channel UE-UE CLI: The UL from the UEs in the SBFD / SFFD / DTDD network interferes with other UEs attempting to receive DL in the same network:

[0030] o In cases of SBFD / single frequency full duplex (SFFD) networks, UE-to-UE CLI may come from the same cell or from a different cell, as shown in FIGS. 9 and 10; o In cases of dynamic TDD (DTDD), UE-to-UE CLI comes only from another cell 18; and

[0031] o Adjacent channel UE-UE CLI: The UL from the UEs in one SBFD / SFFD / DTDD network interferes with other UEs receiving DL in adjacent channels / bands / networks. See FIG. 11.

[0032] In results reported in 3GPP Technical Report (TR) 38.858, where adjacent channel UE-to-UE CLI is specifically studied, it was shown that if users are uniformly distributed in a wide coverage area, their chance to be close to each other and be scheduled in opposite directions at the same time is low, and UE-to-UE CLI does not damage DL performance. However, if UEs are close to each other and clustered in such a way that their distance is e.g., always less than 50 m, DL performance of legacy TDD UEs may be impacted by UE-to-UE CLI, especially DL edge users’ performance (5% throughput).As a result, the UE-to-UE CLI does not only impact DL UEs in DTDD / SBFD / SFFD networks, but also in TDD networks, in case said TDD network is neighbor to a DTDD / SBFD / SFFD second network.

[0033] An option for detecting if a UE is affected by UE-to-UE CLI is to analyze measurement reports from the UE in terms of RS SI (Received Signal Strength Indicator) (CLI-RSSI). This is an indicator that includes the co-channel non-serving cell signal, adjacent channel interference and even the thermal noise within the specified band.

[0034] However, even if a UE reports a low RSSI, it is not possible to know if this is caused by UE-to-UE CLI, and by what aggressor UE. More information like the relative position with respect to other UEs would provide more insight about if the UE may be victim of UE-to-UE CLI, before making scheduling decisions.

[0035] For purpose of UE-UE CLI measurement in a SBFD or Dynamic TDD network node, the network node may configure a potential aggressor UE to transmit CLI SRS and configure one or multiple potential victim UEs to measure the CLLSRS. The aggressor UE is assumed to transmit the CLI SRS with the same UL timing as PUSCH which is derived based on Timing Advance (NTA) and TA offset (NTA, offset) configuration in relation to the DL reference timing. The victim UEs are assumed to receive the CLLSRS based on their own DL reference timing, possibly with certain proprietary timing error compensation schemes. In the current 3GPP specification, Timing Advance (NTA) for a UE is calculated and maintained based on the propagation delay of the serving link between the serving network node and the UE. With proper configuration of NTA for connected UEs in a cell, UL synchronization may be achieved in the sense that concurrent UL signals transmitted from different UEs in the cell may arrive at the network node roughly at the same time. The legacy TA doesn't not at all reflect the propagation delay between two UEs. Applying such legacy TA to CLLSRS transmission may lead to large residual timing error at the receiver at the victim UE, causing degradation in measurement performance.

[0036] The timing error for receiving CLLSRS at a victim UE is dependent on the propagation delay between the aggressor UE and its serving network node, the propagation delay between the victim UE and its serving network node, and the propagation delay between the aggressor and the victim UEs. FIG. 12 presents the timing analysis for CLLSRS reception at a victim UE, where the aggressor UE (UE1) and the victim UE (UE2) are assumed to be served by the same network node. As may be seen from FIG. 12, the timing error for CLI SRS reception at the victim UE may be calculatedas

[0037]

[0038] where Tprop land Tprop 2are the propagation delays between UE1 and the network node, UE2 and the network node respectively; TprOp:a2vis the propagation delay from UE1 to UE2; TTA offSet= Tc* NTAOffSetis a constant timing offset between UL reception timing and DL transmission timing at the network node to account for RX / TX switching processing time, wherein NTA o^setis configured by higher layer configured parameter n-TimingAdvanceOffset and Tcis the basic time unit defined in clause 4.1 of 3GPP Technical Standard (TS) 38.211.

[0039] The timing error in CLI-SRS reception may manifest as either a delay or a time advance. FIG. 13 illustrates measurement timing error for several examples of typical SRS transmission occurring in the last orthogonal frequency division multiplexed (OFDM) symbols of a slot. In the most relevant use case for CLI-SRS measurement, where the aggressor UE and the victim UE are in close proximity, the timing error typically appears as time advance. This is because the propagation delay between the UEs is much shorter compared to the propagation delay between the UEs and their serving network node.

[0040] FIG. 14 provides example link level simulation results with TDL C channel model in FR2 to demonstrate performance degradation for CLI-SRS measurement caused by the residual timing error at the victim UE. It may be observed that the measurement accuracy degrades as the timing error increases. It may also be observed that the measurement accuracy is also dependent on the length of OFDM Cyclic Prefix (CP). Longer CP length provides better protection to timing error. For instance, with 0.68 us timing error the performance for 60kHz subcarrier spacing (SCS) overlaps with the ideal case (i.e., zero timing error), while the performance for 120kHz degrades for about 0.5 dB compared to the ideal case.

[0041] Currently, this residual timing error is being considered as a fix value from the 3GPP standard specification and different level of measurement requirement relaxation was being considered for the 3GPP Rel-16 L3 sounding reference signal reference signal received power (SRS-RSRP) measurement. For the 3GPP Rel-19 SBFD work item, a similar approach is being considered by the 3GPP working group. However, the 3GPP Rel-19 LI SRS-RSRP introduces a faster measurement procedure to enable faster CLI mitigation schemes. The methods to improve the measurement accuracy need to be further addressed.SUMMARY

[0042] Some embodiments advantageously provide methods, network nodes, and UEs for high accuracy cross link interference (CLI)-sounding reference signal (SRS)-measurements.

[0043] Some embodiments include methods for CLI measurements to achieve higher accuracy in a delay uncertain environment. A first set of embodiments includes method for determining timing advance for CLI-SRS transmission at a first UE (aggressor UE). A second set of embodiments includes methods for calculating and adjusting CLI-SRS receive timing at a second UE (victim UE).

[0044] Some embodiments include methods for timing advance determination at a first UE (an aggressor UE) for transmission of CLI-SRS and methods for delay compensation at the second UE (victim UE) to tackle residual timing error for reception of CLI-SRS. Some embodiments reduce the CLI-SRS reception timing error at the second UE (victim UE) and hence improve the CLI-SRS-RSRP measurement accuracy.

[0045] According to one aspect of the present disclosure, a method performed by a first user equipment, UE, for Cross-Link Interference-Sounding Reference Signal, CLI-SRS, in a wireless communication system is provided. The method includes receiving, from a network node, configuration information for transmitting CLI-SRS, the configuration information comprising a first timing advance, TA, that is specific to CLI signaling, and applying a second TA for the CLI-SRS, based on the first TA.

[0046] According to one or more embodiments of this aspect, the first TA is based on one or more of: serving link propagation delays; path losses; directions and UE positions of the first UE and a second UE; inter-UE propagation delays.

[0047] According to one or more embodiments of this aspect, the applying of the second TA is based on a third TA that is associated with downlink reference timing between the first UE and the network node.

[0048] According to one or more embodiments of this aspect, the applying of the second TA is based on a TA offset.

[0049] According to one or more embodiments of this aspect, the first TA is different from the second TA.

[0050] According to one or more embodiments of this aspect, the first TA has a TA value of zero.According to one or more embodiments of this aspect, the method further comprises transmitting the CLI-SRS using the second TA.

[0051] According to one or more embodiments of this aspect, the first TA is for CLI-SRS transmission toward a second UE.

[0052] According to another aspect of the present disclosure, a first user equipment, UE, for Cross-Link Interference-Sounding Reference Signal, CLI-SRS, in a wireless communication system is provided. The first UE is configured to: receive, from a network node, configuration information for transmitting CLI-SRS, the configuration information comprising a first timing advance, TA, that is specific to CLI signaling; and apply a second TA for the CLI-SRS, based on the first TA.

[0053] According to one or more embodiments of this aspect, the first TA is based on one or more of: serving link propagation delays; path losses; directions and UE positions of the first UE and a second UE; inter-UE propagation delays.

[0054] According to one or more embodiments of this aspect, the applying of the second TA is based on a third TA that is associated with downlink reference timing between the first UE and the network node.

[0055] According to one or more embodiments of this aspect, the applying of the second TA is based on a TA offset.

[0056] According to one or more embodiments of this aspect, the first TA is different from the second TA.

[0057] According to one or more embodiments of this aspect, the first TA has a TA value of zero.

[0058] According to one or more embodiments of this aspect, the first UE is configured to transmit the CLI-SRS using the second TA.

[0059] According to one or more embodiments of this aspect, the first TA is for CLI-SRS transmission toward a second UE.

[0060] According to another aspect of the present disclosure, a method implemented by a network node is provided. The method includes configuring a first user equipment, UE, with configuration information for the first UE to transmit Cross-Link Interference-Sounding Reference Signal, CLI-SRS by applying a second timing advance, TA, based on a first TA, and the first TA is specific to CLI signaling.

[0061] According to one or more embodiments of this aspect, the method further includes determining one or more of: serving link propagation delays; path losses; directions andUE positions of the first UE and a second UE; inter-UE propagation delays; wherein the first TA is based on the determination.

[0062] According to one or more embodiments of this aspect, the method further includes configuring a second UE with a configuration for performing measurements of CLI-SRS, the CLI-SRS being associated with the second TA.

[0063] According to another aspect of the present disclosure, a network node is provided. The network node is configured to: configure a first user equipment, UE, with configuration information for the first UE to transmit Cross-Link Interference-Sounding Reference Signal, CLI-SRS by applying a second timing advance, TA, based on a first TA; and the first TA being specific to CLI signaling.

[0064] According to one or more embodiments of this aspect, the network node is configured to: determine one or more of: serving link propagation delays; path losses; directions and UE positions of the first UE and a second UE; inter-UE propagation delays; whrein the first TA is based on the determination.

[0065] According to one or more embodiments of this aspect, the network node is further configured to: configure a second UE with a configuration for performing measurements of CLI-SRS, the CLI-SRS being associated with the second TA.

[0066] BRIEF DESCRIPTION OF THE DRAWINGS

[0067] A more complete understanding of the present embodiments, and the attendant advantages and features thereof, will be more readily understood by reference to the following detailed description when considered in conjunction with the accompanying drawings wherein:

[0068] FIG. 1 illustrates frequency and time division duplex;

[0069] FIG. 2 illustrates an example TDD DL / UL pattern consisting of S = 5 slots;

[0070] FIG. 3 illustrates a conventional single carrier subband time division duplex (TDD) system;

[0071] FIG. 4 illustrates a conventional multi-carrier TDD system;

[0072] FIG. 5 illustrates a single carrier subband full duplex (SBFD) system;

[0073] FIG. 6 illustrates a multi-carrier SBFD system;

[0074] FIG. 7 illustrates a downlink-uplink configuration;

[0075] FIG. 8 illustrates a downlink-uplink-downlink configuration;

[0076] FIG. 9 illustrates co-channel UE-to-UE CLI in one cell;

[0077] FIG. 10 illustrates co-channel UE-to-UE CLI from different cells;FIG. 11 illustrates adj acent channel UE-to-UE CLI;

[0078] FIG. 12 shows timing error for SLI SRS at a victim UE receiver;

[0079] FIG. 13 shows CLI SRS receiving timing error as advance and delay;

[0080] FIG. 14 is an example of FR2 SRS-RSRP measurement accuracy variation as timing error increases;

[0081] FIG. 15 is a schematic diagram of an example network architecture illustrating a communication system according to principles disclosed herein;

[0082] FIG. 16 is a block diagram of a network node in communication with a user equipment over a wireless connection according to some embodiments of the present disclosure;

[0083] FIG. 17 is a schematic diagram of another example network architecture illustrating a communication system according to principles disclosed herein;

[0084] FIG. 18 is a flowchart of an example process in a network node for high accuracy cross link interference (CLI)-sounding reference signal (SRS)-reference signal received power (RSRP) according to some embodiments of the present disclosure;

[0085] FIG. 19 is a flowchart of an example process in a user equipment for high accuracy cross link interference (CLI)-sounding reference signal (SRS)-reference signal received power (RSRP) according to some embodiments of the present disclosure;

[0086] FIG. 20 is a flowchart of another example process in a network node according to some embodiments of the present disclosure;

[0087] FIG. 21 is a flowchart of another example process in a first UE (e.g., aggressor UE) according to some embodiments of the present disclosure;

[0088] FIG. 22 is a flow chart of another example process in a second UE (e.g., victim UE) according to some embodiments of the present disclosure;

[0089] FIG. 23 is an example of timing error for CLI SRS reception at a victim UE according to principles disclosed herein;

[0090] FIG. 24 is another example of timing error for CLI SRS reception at a victim UE according to principles disclosed herein;

[0091] FIG. 25 is an example of a first search variant;.

[0092] FIG. 26 is an example of a second search variant;

[0093] FIG. 27 is a first example of SRS-RSRP measurement accuracy improvement; and FIG. 28 is a second example of SRS-RSRP measurement accuracy improvement.DETAILED DESCRIPTION

[0094] Before describing in detail example embodiments, it is noted that the embodiments reside primarily in combinations of apparatus components and processing steps related to high accuracy cross link interference (CLI)-sounding reference signal (SRS) measurements. Accordingly, components have been represented where appropriate by conventional symbols in the drawings, showing only those specific details that are pertinent to understanding the embodiments so as not to obscure the disclosure with details that will be readily apparent to those of ordinary skill in the art having the benefit of the description herein.

[0095] As used herein, relational terms, such as “first” and “second,” “top” and “bottom,” and the like, may be used solely to distinguish one entity or element from another entity or element without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises,” “comprising,” “includes” and / or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0096] In embodiments described herein, the joining term, “in communication with” and the like, may be used to indicate electrical or data communication, which may be accomplished by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling or optical signaling, for example. One having ordinary skill in the art will appreciate that multiple components may interoperate and modifications and variations are possible of achieving the electrical and data communication.

[0097] In some embodiments described herein, the term “coupled,” “connected,” and the like, may be used herein to indicate a connection, although not necessarily directly, and may include wired and / or wireless connections.

[0098] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the concepts described herein. As used herein, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood thatthe terms “comprises,” “comprising,” “includes” and / or “including” when used herein, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0099] The term “network node” used herein may be any kind of network node comprised in a radio network which may further comprise any of base station (BS), radio base station, base transceiver station (BTS), base station controller (BSC), radio network controller (RNC), g Node B (gNB), evolved Node B (eNB or eNodeB), Node B, multistandard radio (MSR) radio node such as MSR BS, multi -cell / multicast coordination entity (MCE), relay node, donor node controlling relay, radio access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU) Remote Radio Head (RRH), a core network node (e.g., mobile management entity (MME), self-organizing network (SON) node, a coordinating node, positioning node, MDT node, etc.), an external node (e.g., 3rd party node, a node external to the current network), nodes in distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also comprise test equipment. The term “radio node” used herein may be used to also denote a user equipment (UE) such as a wireless device (WD) or a radio network node.

[0100] In some embodiments, the non-limiting terms wireless device (WD) or a user equipment (UE) are used interchangeably. The UE herein may be any type of user equipment capable of communicating with a network node or another UE over radio signals, such as a wireless device (WD). The UE may also be a radio communication device, target device, device to device (D2D) UE, aggressor UE, victim UE, machine type UE or UE capable of machine to machine communication (M2M), low-cost and / or low-complexity UE, a sensor equipped with UE, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles, Customer Premises Equipment (CPE), an Internet of Things (loT) device, or a Narrowband loT (NB-IOT) device etc.

[0101] Also, in some embodiments the generic term “radio network node” is used. It may be any kind of a radio network node which may comprise any of base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, Multi-cell / multicast Coordination Entity (MCE), relay node, access point, radio access point, Remote Radio Unit (RRU) Remote Radio Head (RRH).Note that although terminology from one particular wireless system, such as, for example, 3GPP LTE and / or New Radio (NR) and / or 6G, may be used in this disclosure, this should not be seen as limiting the scope of the disclosure to only the aforementioned system. It is contemplated that other 3GPP systems may make use of the concepts and arrangements disclosed herein. For example, a disclosure relating to NR may also be implementable in a 6G system and / or an LTE system, a disclosure relating to 6G may also be implementable in a NR and / or LTE system, and a disclosure relating to LTE may also be implementable in a NR and / or 6G system. Other wireless systems, including without limitation Wide Band Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB) and Global System for Mobile Communications (GSM), may also benefit from exploiting the ideas covered within this disclosure.

[0102] Note further, that functions described herein as being performed by a user equipment or a network node may be distributed over a plurality of user equipments and / or network nodes. In other words, it is contemplated that the functions of the network node and user equipment described herein are not limited to performance by a single physical device and, in fact, may be distributed among several physical devices.

[0103] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs. It will be further understood that terms used herein should be interpreted as having a meaning that is consistent with their meaning in the context of this specification and the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein.

[0104] While the present disclosure uses certain terminology to describe one or more embodiments, it is foreseeable that the exact terminology regarding the applicable technology / equipment / methods may change over time, but that the technical features and their functions described herein remain unchanged.

[0105] Some embodiments are directed to high accuracy cross link interference (CLI)-sounding reference signal (SRS) measurements.

[0106] Returning to the drawing figures, in which like elements are referred to by like reference numerals, there is shown in FIG. 15 a schematic diagram of a communication system 10, according to an embodiment, such as a 3 GPP -type cellular network that may support standards such as LTE and / or NR (5G) and / or 6G, which comprises an access network 12, such as a radio access network, and a core network 14. The core network 14includes one or more network nodes 15. The access network 12 comprises a plurality of network nodes 16a, 16b, 16c (referred to collectively as network nodes 16), such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 18a, 18b, 18c (referred to collectively as coverage areas 18). Each network node 16a, 16b, 16c is connectable to the core network 14 over a wired or wireless connection 20. A first user equipment (UE) 22a located in coverage area 18a is configured to wirelessly connect to, or be paged by, the corresponding network node 16a. A second UE 22b in coverage area 18b is wirelessly connectable to the corresponding network node 16b. While a plurality of UEs 22a, 22b (collectively referred to as user equipments 22) 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 network node 16. Note that although only two UEs 22 and three network nodes 16 are shown for convenience, the communication system may include many more UEs 22 and network nodes 16.

[0107] As one example, in certain embodiments, access network 12 may contain some access network nodes 16 that support 3 GPP radio access technologies (RAT), such as LTE or NR, while other access network nodes 16 support (or the same access network nodes 16 additionally support) non-3GPP RATs, such as Wi-Fi or a proprietary RAT. As another example, communication system 10 may support multiple generations of related communication standards (e.g., 4G, 5G and 6G 3 GPP communication standards) and, as a result, may include an access network 12 and / or a core network 14 that supports multiple different standard generations or may include multiple access networks 12 and / or multiple core networks 14 with individual networks supporting different standards generations.

[0108] Also, it is contemplated that a UE 22 may be in simultaneous communication and / or configured to separately communicate with more than one network node 16 and more than one type of network node 16. For example, a UE 22 may have dual connectivity with a network node 16 that supports LTE and the same or a different network node 16 that supports NR. As an example, UE 22 may be in communication with an eNB for LTEZE-UTRAN, a gNB for NR / NG-RAN (i.e. being configured for multiradio dual connectivity (MR-DC), such as E-UTRAN (Evolved-UMTS Terrestrial Radio Access Network) New Radio - Dual Connectivity (EN-DC) and / or Wi-Fi.

[0109] A network node 16 (eNB or gNB) is configured to include a NN TA unit 24 which may be configured to perform one or more network node 16 functions that are described herein, such as, for example, determining a timing advance for cross link interferencesounding reference signal (CLI-SRS) transmission. A user equipment 22 is configured to include a UE TA unit 26 which may be configured to perform one or more UE 22 functions that are described herein such as, for example, determining a second timing advance for the CLI-SRS transmission, the second timing advance being determined based at least in part on the first timing advance.

[0110] Example implementations, in accordance with an embodiment, of the UE 22 and network node 16 discussed in the preceding paragraphs will now be described with reference to FIG. 16.

[0111] The communication system 10 includes a network node 16 provided in a communication system 10 and including hardware 28 enabling it to communicate with the UE 22. The hardware 28 may include a communication interface 29 comprising a radio interface 30 for setting up and maintaining at least a wireless connection 32 with a UE 22 located in a coverage area 18 served by the network node 16. The radio interface 30 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 30 includes an array of antennas 34 to radiate and receive signal(s) carrying electromagnetic waves.

[0112] In the embodiment shown, the hardware 28 of the network node 16 further includes processing circuitry 36. The processing circuitry 36 may include a processor 38 and a memory 40. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 36 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 38 may be configured to access (e.g., write to and / or read from) the memory 40, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0113] Thus, the network node 16 further has software 42 stored internally in, for example, memory 40, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the network node 16 via an external connection. The software 42 may be executable by the processing circuitry 36. The processing circuitry 36 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by network node 16.

[0114] Processor 38 corresponds to one or more processors 38 for performing network node 16functions described herein. The memory 40 is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 42 may include instructions that, when executed by the processor 38 and / or processing circuitry 36, causes the processor 38 and / or processing circuitry 36 to perform the processes described herein with respect to network node 16. For example, processing circuitry 36 of the network node 16 may include a NN TA unit 24 which may be configured to perform one or more network node 16 functions that are described herein such as, for example, determining a timing advance for cross link interference sounding reference signal (CLI-SRS) transmission.

[0115] The network node 16 may be composed of multiple distinct network entities (e.g., a NodeB entity and a RNC entity, or a BTS entity and a BSC entity, etc.), which may each have or utilize their own respective physical components. In certain scenarios in which the network node 16 comprises multiple such entities (e.g., BTS and BSC), one or more of the separate entities may be shared among several network nodes. For example, a single RNC may control multiple NodeBs. In such a scenario, each unique NodeB and RNC pair, may in some instances be considered a single separate network node. In some embodiments, the network node 16 may be configured to support multiple radio access technologies (RATs). In such embodiments, some components may be duplicated (e.g., separate memories 40 or portions of memory 40 for different RATs) and some components may be reused (e.g., a same antenna may be shared by different RATs). The network node 16 may also include multiple sets of the various illustrated components for different wireless technologies integrated into network node 16, for example GSM, WCDMA, LTE, NR, Wi-Fi (e.g., according to an IEEE 802.11 family standard), Zigbee, Z-wave, LoRaWAN, Radio Frequency Identification (RFID) or Bluetooth wireless technologies. These wireless technologies may be integrated into the same or different chip or set of chips and other components within network node 16.

[0116] In certain alternative embodiments, network node 16 may be capable of wireless communication but does not include separate radio front-end circuitry, instead, the processing circuitry 36 includes radio front-end circuitry and is connected to the antenna 34. Similarly, in some embodiments, all or some of the RF receivers, transmitters and / or transceivers are part of the radio interface 30. In still other embodiments, the communication interface 29 includes one or more ports or terminals, the radio interface 30, and the RF receiver, transmitter and / or transceiver, and the communication interface31 communicates with baseband processing circuitry, which is part of a digital unit (not shown).

[0117] The antenna 34 may include one or more antennas, or antenna arrays, configured to send and / or receive wireless signals. The antenna 34 may be coupled to the radio front-end circuitry in radio interface 30 and may be any type of antenna capable of transmitting and receiving data and / or signals wirelessly. In certain embodiments, the antenna 34 is separate from the network node 16 and connectable to the network node 16 through one or more interfaces or ports.

[0118] Network node 15 may include one or more components described above with respect to network node 16, e.g., communication interface 29, radio interface 30, antenna 34, ports, processing circuitry 36, processor 38, memory 40 and software 42. These elements of network node 15 may be arranged such that network node 15 may perform various core network functions. Network node 15 may communicate wirelessly or via a wired connection with network nodes 16 via communication link 59.

[0119] The communication system 10 further includes the UE 22 already referred to. The UE 22 may have hardware 44 that may include a radio interface 46 configured to set up and maintain a wireless connection 32 with a network node 16 serving a coverage area 18 in which the UE 22 is currently located. The radio interface 46 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The radio interface 46 includes an array of antennas 48 to radiate and receive signal(s) carrying electromagnetic waves.

[0120] Communication functions of the radio interface 46 may include cellular communication, Wi-Fi communication (e.g., according to an IEEE 802.11 family standard), LPWAN communication, data communication, voice communication, multimedia communication, short-range communications such as Bluetooth, near-field communication, location-based communication such as the use of the global positioning system (GPS) to determine a location, another like communication function, or any combination thereof. Communications may be implemented according to one or more communication protocols and / or standards, such as IEEE 802.11, Code Division Multiplexing Access (CDMA), Wideband Code Division Multiple Access (WCDMA), GSM, LTE, New Radio (NR), UMTS, WiMax, Ethernet, transmission control protocol / internet protocol (TCP / IP), synchronous optical networking (SONET), Asynchronous Transfer Mode (ATM), QUIC, Hypertext Transfer Protocol (HTTP), and so forth.The hardware 44 of the UE 22 further includes processing circuitry 50. The processing circuitry 50 may include a processor 52 and memory 54. In particular, in addition to or instead of a processor, such as a central processing unit, and memory, the processing circuitry 50 may comprise integrated circuitry for processing and / or control, e.g., one or more processors and / or processor cores and / or FPGAs (Field Programmable Gate Array) and / or ASICs (Application Specific Integrated Circuitry) adapted to execute instructions. The processor 52 may be configured to access (e.g., write to and / or read from) memory 54, which may comprise any kind of volatile and / or nonvolatile memory, e.g., cache and / or buffer memory and / or RAM (Random Access Memory) and / or ROM (Read-Only Memory) and / or optical memory and / or EPROM (Erasable Programmable Read-Only Memory).

[0121] Thus, the UE 22 may further comprise software 56, which is stored in, for example, memory 54 at the UE 22, or stored in external memory (e.g., database, storage array, network storage device, etc.) accessible by the UE 22. The software 56 may be executable by the processing circuitry 50. The software 56 may include a client application 58. The client application 58 may be operable to provide a service to a human or non-human user via the UE 22.

[0122] The processing circuitry 50 may be configured to control any of the methods and / or processes described herein and / or to cause such methods, and / or processes to be performed, e.g., by first UE 22. The processor 52 corresponds to one or more processors 52 for performing UE 22 functions described herein. The UE 22 includes memory 54 that is configured to store data, programmatic software code and / or other information described herein. In some embodiments, the software 56 and / or the client application 58 may include instructions that, when executed by the processor 52 and / or processing circuitry 50, causes the processor 52 and / or processing circuitry 50 to perform the processes described herein with respect to UE 22. For example, the processing circuitry 50 of the user equipment 22 may include a UE TA unit 26 which may be configured to perform one or more UE 22 functions that are described herein with respect to, for example, the aggressor UE 22 and / or victim UE 22. In one example, UE 22 is configured to determine a second timing advance for the CLI-SRS transmission, the second timing advance being determined based at least in part on the first timing advance.

[0123] In some embodiments, the inner workings of the network node 16 and UE 22 may be as shown in FIG. 16 and independently, the surrounding network topology may be that of FIG. 15.The wireless connection 32 between the UE 22 and the network node 16 is in accordance with the teachings of the embodiments described throughout this disclosure. More precisely, the teachings of some of these embodiments may improve the data rate, latency, and / or power consumption and thereby provide benefits such as reduced user waiting time, relaxed restriction on file size, better responsiveness, extended battery lifetime, etc. In some embodiments, 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.

[0124] Although FIGS. 15 and 16 show various “units” such as NN TA unit 24 and UE TA unit 26 as being within a respective processor, it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuitry. In other words, the units may be implemented in hardware or in a combination of hardware and software within the processing circuitry.

[0125] FIG. 17 is another example of a communication system 10 according to some embodiments. As used herein, the communication system 10 of FIG. 17 includes multiple access points (APs) 60 (with four example APs 60a, 60b, 60c, and 60d being depicted) and multiple wireless devices, referred to in the context of communication system 10 of FIG. 3 as stations (STAs) 62 (referred to individually as STA 62a, STA 62b, STA 62c, STA 62d, and STA 62e). STA 62a is served by AP 60a in a first basic service set (BSS) 64a. STA 62b and STA 62c are served by AP 60b in a second BSS, BSS 64b. STA 62d is served by AP 60c in a third BSS, BSS 64c. STA 62e is served by AP 60d in a fourth BSS, BSS 64d. Stations 62 may be non-AP STAs and correspond to various kinds of wireless devices, for example, user terminals, such as mobile or stationary computing devices like smartphones, laptop computers, desktop computers, tablet computers, gaming devices, head-mounted displays (HMDs) for Augmented Reality (AR) or Virtual Reality (VR), or the like, including UEs 22 that are shown and described with respect to FIGS. 15 and 16. In other words, in some embodiment, STA 62 is a UE 22. Further, stations 62 could, for example, correspond to other kinds of equipment like smart home devices, printers, multimedia devices, data storage devices, or the like.

[0126] Each of STAs 62 may connect through a radio link to one of APs 60. For example, depending on location or channel conditions experienced by a given STA 62, the STA may select an appropriate AP and BSS for establishing the radio link. The radio link may be based on one or more orthogonal frequency-division multiplexing (OFDM) carriers from a frequency spectrum that is shared on the basis of a contention-based mechanism,e.g., an unlicensed or license exempt band like 2.4 GHz Industrial, Scientific, and Medical (ISM) band, the 5 GHz band, the 6 GHz band, or the 60 GHz band.

[0127] Each AP 60 may provide data connectivity to STAs 62 connected to a particular AP 60. As illustrated, APs 60 may be connected to a data network 66. In this way, APs 60 may also provide data connectivity between STAs 62 and other entities, e.g., to one or more servers, service providers, data sources, data sinks, user terminals, or the like.

[0128] Accordingly, the radio link established between a given STA 62 and its serving AP 60 may be used for providing various kinds of services to STA 62, e.g., a voice service, a multimedia service, or other data service. Such services may be based on applications that are executed on STA 62 and / or on a device linked to STA 62. By way of example, FIG. 3 illustrates an application service platform 68 provided in data network 66. The application(s) executed on STA 62 and / or on one or more other devices linked to STA 62 may use the radio link for data communication with one or more other STA 62 and / or the application service platform 68, thereby enabling utilization of the corresponding service(s) at STA 62.

[0129] FIG. 18 is a flowchart of an example process in a network node 16 for high accuracy cross link interference (CLI)-sounding reference signal (SRS)-reference signal received power (RSRP). One or more blocks described herein may be performed by one or more elements of network node 16 such as by one or more of processing circuitry 36 (including the NN TA unit 24), processor 38, and / or radio interface 30. Network node 16 such as via processing circuitry 36 and / or processor 38 and / or radio interface 30 is configured to determine a timing advance for cross link interference sounding reference signal (CLI-SRS) transmission (Block S10). The process includes configuring the UE 22 to transmit CLI-SRS according to the timing advance (Block S12).

[0130] In some embodiments, the timing advance is further based at least in part on a timing offset between uplink and downlink transmissions. In some embodiments, the timing advance is determined based at least in part on a serving link propagation delay. In some embodiments, the timing advance is determined based at least in part on path loss. In some embodiments, the timing advance is determined based at least in part on at least one of positions of the UE 22 and a victim UE 22 and a direction between the UE 22 and the victim UE 22.

[0131] FIG. 19 is a flowchart of an example process in a user equipment 22 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of user equipment 22 such as by one or more ofprocessing circuitry 50 (including the UE TA unit 26), processor 52, and / or radio interface 46. User equipment 22 such as via processing circuitry 50 and / or processor 52 and / or radio interface 46 is configured to receive from the network node 16 a configuration for cross link interference sounding reference signal (CLI-SRS) transmission, the configuration including a first timing advance (Block S14). The process also includes determining a second timing advance for the CLI-SRS transmission, the second timing advance being determined based at least in part on the first timing advance (Block SI 6).

[0132] In some embodiments, the second timing advance is further based at least in part on a timing offset between uplink and downlink transmissions. In some embodiments, the method includes transmitting the CLI-SRS transmission with a zero timing advance. In some embodiments, the method includes measuring CLI-SRS with different starting positions within a search window and determining a CLI-SRS reference signal received power (RSRP) based at least in part on a highest CLI-SRS of the measured CLI-SRS. In some embodiments, the method includes collecting a set of time-domain samples within a discrete Fourier transform (DFT) window for each measurement. In some embodiments, the measurements are performed according to a sparse search grid corresponding to a number of DFT windows. In some embodiments, the different starting positions correspond to different circular shifts of a discrete Fourier transform window. In some embodiments, the measurements correspond to a non-sparse search grid corresponding to a range of circular shift. In some embodiments, a starting position and an ending position of the search window are configured relative to a downlink reference timing. In some embodiments, a starting position of the search window is based at least in part on the first timing advance. In some embodiments, a step size between starting positions within the search window is variable.

[0133] FIG. 20 is a flowchart of another example process in a network node 16 according to some embodiments of the present disclosure. Network node 16 is configured to configure (Block SI 8) a first user equipment, UE 22, with configuration information for the first UE 22 to transmit Cross-Link Interference- Sounding Reference Signal, CLI-SRS by applying a second timing advance, TA, based on a first TA, where the first TA is specific to CLI signaling.

[0134] According to one or more embodiments, the network node 16 is configured to: determine one or more of serving link propagation delays; path losses; directions and UE positions of the first UE and a second UE; and inter-UE propagation delays; and the first TA is based on the determination.According to one or more embodiments, the network node 16 is further configured to: configure a second UE with a configuration for performing measurements of CLI-SRS, the CLI-SRS being associated with the second TA.

[0135] FIG. 21 is a flowchart of another example process in a first UE 22 (e.g., aggressor UE) according to some embodiments of the present disclosure. The first UE 22 is configured to receive (Block S20), from a network node 16, configuration information for transmitting CLI-SRS, where the configuration information comprises a first timing advance, TA, that is specific to CLI signaling, as described herein. The first UE 22 is configured to apply (Block S22) a second TA for the CLI-SRS, based on the first TA, as described herein.

[0136] According to one or more embodiments, the first TA is based on one or more of: serving link propagation delays; path losses; directions and UE positions of the first UE 22 and a second UE 22; and inter-UE propagation delays.

[0137] According to one or more embodiments, the applying of the second TA is based on a third TA that is associated with downlink reference timing between the first UE 22 and the network node 16.

[0138] According to one or more embodiments, the applying of the second TA is based on a TA offset.

[0139] According to one or more embodiments, the first TA is different from the second TA.

[0140] According to one or more embodiments, the first TA has a TA value of zero.

[0141] According to one or more embodiments, the first UE 22 is configured to transmit the CLI-SRS using the second TA.

[0142] According to one or more embodiments, the first TA is for CLI-SRS transmission toward a second UE 22.

[0143] FIG. 22 is a flowchart of another example process in a second UE 22 (e.g., victim UE) according to some embodiments of the present disclosure. The second UE 22 is configured to perform (Block S24) measurements of a signal metric of CLI-SRS at a plurality of starting positions within at least a first window, where the CLI-SRS is associated with a second timing advance, TA, that is different from a first TA that is specific to CLI signaling, as described herein. The second UE 22 is configured to select (Block S26) one of the plurality of starting positions associated with a highest signal metric of the measurements, as described herein. The second UE 22 is configured to process (Block S28) the CLI-SRS at the selected starting position as described herein.According to one or more embodiments, the performing of measurements comprises detecting the CLI-SRS using a CLI-SRS sequence for each of the plurality of starting positionings within the at least first window.

[0144] According to one or more embodiments, for each starting position corresponds to a detection attempt; and the performing of the measurements comprises: for each detection attempt, collect K time samples within a DFT window for each hypothesized position where K represents an FFT size of an OFDM demodulator at the second UE 22; and the second UE 22 is configured to: evaluate detection power based on the collected time samples; determine a hypothesis position having a highest signal metric of the detection attempts based on the evaluation, the selection being based on the determination.

[0145] According to one or more embodiments, the at least first window is a time domain window associated with a plurality of DFT windows.

[0146] According to one or more embodiments, the at least first window is a plurality of DFT window based on multiple shift hypotheses of a single DFT window, where each shift hypothesis corresponds to a detection attempt.

[0147] According to one or more embodiments, the shift hypotheses of the single DFT correspond to circular shift hypotheses of the single DFT.

[0148] According to one or more embodiments, the shift hypotheses of the single DFT correspond to shifts in zeros instead of samples.

[0149] According to one or more embodiments, the second UE 22 is configured to receive a measurement configuration from the network node 16, where the measurement configuration configures the second UE 22 to perform measurements of the signal metric of CLI-SRS at the plurality of starting positions within at least the first window.

[0150] According to one or more embodiments, the first TA is a CLI-SRS specific TA. Having described the general process flow of arrangements of the disclosure and having provided examples of hardware and software arrangements for implementing the processes and functions of the disclosure, the sections below provide details and examples of arrangements for high accuracy cross link interference (CLI)-sounding reference signal (SRS) measurements.

[0151] One or more network node 16 functions described below may be performed by one or more of processing circuitry 36, processor 38, NNTA unit 24, communication interface 29, etc. One or more UE 22 (e.g., aggressor UE 22a, victim UE 22b) functions described below may be performed by one or more of processing circuitry 50, processor 52, UE TA unit 26, radio interface 46, etc.Embodiment 1: Timing advance setting at aggressor UE 22a (e.g., first UE 22a) Embodiment la

[0152] In some embodiments, when a UE 22 is configured by the network node 16 to transmit CLI-SRS, the UE 22 is also provided with another timing advance (TTA, CLI-SRS) specifically for the CLI-SRS transmission. The UE 22 should derive a timing advance (e.g., second TA) based on the indicated TTA, CLI-SRS instead of the legacy Timing Advance TTA and TTA, offset and apply it to the corresponding CLI-SRS transmission. FIG. 23 demonstrates the first UE (aggressor UE 22 (UE1)) applying a different timing advance to the transmission of CLI-SRS for the same application example as in FIG. 12. As may be observed in FIG. 23, thanks to the CLI-SRS specific timing advance the residual timing error for CLI-SRS reception at the second UE (victim UE 22) may be significantly reduced.

[0153] In some embodiments, the first UE 22a (aggressor UE) determines the timing advance (e.g., second TA) for the corresponding CLI-SRS transmission solely based on the indicated TTA, CLI-SRS. In some embodiments, the aggressor UE 22a calculates the timing advance for the corresponding CLI-SRS transmission using both the indicated TTA, CLI-SRS and TTA, offset.

[0154] The serving network node 16 may employ various methods to determine the timing advance (TA) value for the first UE 22a (aggressor UE) to transmit CLI-SRS. In one illustrative example, the network node 16 may calculate the TA value for CLI-SRS transmission based on the available data, such as serving link propagation delays, path losses, directions and UE positions of both the first UE 22a (aggressor UE) and the second UE 22b (victim UE), as well as the inter-UE propagation delays, path losses and directions.

[0155] Embodiment lb

[0156] In some embodiments, when a UE 22 is configured by network node 16 to transmit CLI-SRS, the UE 22 does not apply the legacy timing advance (TTA) to the CLI-SRS transmission. In some embodiments, the UE 22 determines the timing advance (e.g., second TA) for the CLI-SRS transmission based on the configured TTA, offset with respect to the downlink reference timing. In some embodiments, the UE 22 applies zero timing advance for the CLI-SRS transmission. FIG. 24 illustrates the timing error for CLI-SRS reception at the second UE 22b (victim UE) when the CLI-SRS is transmitted with timing advance solely based on TTA, offset for the same example as in FIG. 12 and FIG. 23.Embodiment 2: Determination of starting position for CLI SRS reception at victim UE

[0157] In some embodiments, the second UE 22b (victim UE) measures CLI-SRS using a search window with a predefined length. The UE 22 measures the power of CLI-SRS with different CLI-SRS starting positions within the search window and determines the CLI-SRS RSRP based on the highest detected power.

[0158] Variant 1: In some embodiments, the second UE 22b (victim UE) detects the CLI-SRS using the configured CLI-SRS sequence multiple times, beginning at different positions (timing hypotheses) within the pre-defined search window. For each CLI-SRS detection attempt (i.e. each timing hypothesis) at a given position, the second UE 22b (victim UE) collects K time-domain samples within the discrete Fourier transform (DFT) window for the hypothesized position and evaluate the detection power. K represents the fast Fourier transform (FFT) size of the OFDM demodulator at the UE receiver. See FIG. 25 for an illustration. The hypothesis with the highest estimated power (or analogous measure, e.g., highest correlation peak) may be considered optimal and used for further receiver processing, e.g., to compensate for the delay before performing a final channel and power estimation. Due to synchronization error between the UEs, the CLI-SRS sequence may begin at the Ithtime sample in the refence OFDM symbol, with I being unknown to the second UE 22b (victim UE). Note that I may be either negative or positive. Note that the first DFT window hypothesis may start even before the cyclic prefix (CP) of the reference OFDM symbol, and the last DFT window hypothesis may start even after the end of the reference OFDM symbol, as illustrated in FIG. 25.

[0159] Variant 2: In some embodiments, the second UE 22b (victim UE) again detects the CLI-SRS using the configured CLI-SRS sequence but using just a single DFT window. The timing search is then instead performed by hypothesizing different circular shifts of the samples within that single DFT window. Such a circular time shift may be achieved e.g., by applying a phase ramp to the frequency-domain representation of the signal (i.e. the signal after applying a DFT). See FIG. 26. Again, the hypothesis with the highest estimated power (or correlation peak etc.) is considered optimal and used in further processing as described above. In one sub-variant, the circular shift is replaced by a shift operation that shifts in zeros instead of samples from the end.Variants 1 and 2 may be combined. For example, variant 1 may be performed using a sparse search grid (i.e. large step size) to keep the number of DFTs that must be performed to a minimum, while variant 2 may subsequently be performed with a smaller search window and finer step size only around the optimal hypothesis found using variant 1.

[0160] In some embodiments, the search window starting position and end position is expressed as offsets from the second UE’s 22b (victim UE’s) own DL reference timing, possibly adjusted by proprietary timing compensation schemes. For example, the search window may be centered around this reference time or shifted towards either side. The determination for the search window starting position may consider whether the first UE 22a (aggressor UE) transmits the CLI-SRS with or without timing advance based on network node indication.

[0161] In some embodiments, the search window is defined by the starting position expressed as an offset from the DL reference timing and the window size in number of time-domain samples. The size of the search window may be either fixed or variable.

[0162] In some embodiments, the search window start is also based on timing advance information from the network node 16.

[0163] In some embodiments, the step size in the search window is 1 time-domain sample. In some embodiments, the step size in the search window is larger than 1 timedomain sample, with the possibility to refine the search with a smaller step size around the most promising position or positions. Note that while all step sizes for DFT window sweeping are the same in the illustration in FIG. 25, they may vary in size in the general case.

[0164] FIGS. 27 and 28 show some simulation results which demonstrates that the method proposed in this embodiment improves the CLLSRS-RSRP measurement accuracy significantly. In FIGS. 27 and 28, the bars labeled “A” correspond to an RSRP error not greater than 2 dB. Bars labeled “B” correspond to an RSRP error not less than 6 dB. The bar labeled “C” corresponds to an RSRP error between 2 and 6 dB.

[0165] The detailed estimation steps are as follow.

[0166] • Step 1: The second UE22b (victim UE) defines a time domain search window, starting at the “starting position” and ending at the “end position”.

[0167] • Step 2: For each candidate position, i, in the search window, the second UE 22b (victim UE) computes a corresponding signal quality. In one example embodiment, this is accomplished as follows:o The signal quality may for example be computed as the detected power of samples i, i + 1, i + 2 ... , i + S — 1, where S is a configured integer number 0 < S < K representing the length of the detection window. The signal quality may also be defined as other meaningful metrics, such as total power, average power or SNR. The computation of the signal quality may involve finer timing search by hypothesizing different circular shifts of the samples;

[0168] • Step 3: The second UE 22b (victim UE) finds the candidate position I' and possibly the optimal circular shift I” with the highest signal quality; and

[0169] • Step 4: The second UE 22b (victim UE) assumes that the CSI-SRS starts at sample I = I' + I” and calculates CLI-SRS RSRP based on the DFT window starting at that position.

[0170] To better handle the case that CLI-SRS sequences are heavily delayed, the UE 22 may extend the search window by including samples received after the SRS receiving window.

[0171] To better handle the cases that SRS sequences arrive earlier than the SRS receiving window, the second UE 22b (victim UE) may extend the search window by including samples arrived before the SRS receiving window.

[0172] In some embodiments, the search window length is adjusted to improve the SRS-RSRP measurement accuracy, either with more candidate positions before the first candidate position or with more candidate positions after the last candidate position. This may be if the signal quality peak is at any of the search window endpoints.

[0173] Examples

[0174] Example Al . A network node 16 configured to communicate with a user equipment (UE 22), the network node 16 configured to, and / or comprising a radio interface 30 and / or comprising processing circuitry 36 configured to:

[0175] determine a timing advance for cross link interference sounding reference signal (CLI-SRS) transmission; and

[0176] configure the UE 22 to transmit CLI-SRS according to the timing advance.

[0177] Example A2. The network node 16 of Example Al, wherein the timing advance is further based at least in part on a timing offset between uplink and downlink transmissions.

[0178] Example A3. The network node 16 of any of Examples Al and A2, wherein the timing advance is determined based at least in part on a serving link propagation delay.Example A4. The network node 16 of any of Examples Al and A2, wherein the timing advance is determined based at least in part on path loss.

[0179] Example A5. The network node 16 of any of Examples Al and A2, wherein the timing advance is determined based at least in part on at least one of positions of the first UE 22a and a second UE 22b (victim UE) and a direction between the first UE 22a and the second UE 22b.

[0180] Example Bl. A method implemented in a network node 16 that is configured to communicate with a user equipment 22, the method comprising:

[0181] determining a timing advance for cross link interference sounding reference signal (CLI-SRS) transmission; and

[0182] configuring the UE to transmit CLI-SRS according to the timing advance.

[0183] Example B2. The method of Example Bl, wherein the timing advance is further based at least in part on a timing offset between uplink and downlink transmissions.

[0184] Example B3. The method of any of Examples Bl and B2, wherein the timing advance is determined based at least in part on a serving link propagation delay.

[0185] Example B4. The method of any of Examples B 1 and B2, wherein the timing advance is determined based at least in part on path loss.

[0186] Example B5. The method of any of Examples B 1 and B2, wherein the timing advance is determined based at least in part on at least one of positions of the first UE 22a (aggressor UE) and a second UE 22b (victim UE) and a direction between the first UE 22a (aggressor UE) and the second UE 22b (victim UE).

[0187] Example Cl . A user equipment (UE 22) configured to communicate with a network node 16, the UE 22 configured to, and / or comprising a radio interface 46 and / or processing circuitry 50 configured to:

[0188] receive from the network node 16 a configuration for cross link interference sounding reference signal (CLI-SRS) transmission, the configuration including a first timing advance; and

[0189] determine a second timing advance for the CLI-SRS transmission, the second timing advance being determined based at least in part on the first timing advance.

[0190] Example C2. The UE 22 of Example Cl, wherein the second timing advance is further based at least in part on a timing offset between uplink and downlink

[0191] transmissions.Example C3. The UE 22 of Example Cl, wherein the UE 22, radio interface 46 and / or processing circuitry 50 is configured to transmit the CLI-SRS transmission with a zero timing advance.

[0192] Example C4. The UE 22 of any of Examples C1-C3, wherein the UE 22, radio interface 46 and / or processing circuitry 50 are configured to measure CLI-SRS with different starting positions within a search window and determining a CLI-SRS reference signal received power (RSRP) based at least in part on a highest CLI-SRS of the measured CLI-SRS.

[0193] Example C5. The UE 22 of Example C4, wherein the UE, radio interface 46 and / or processing circuitry 50 are configured to collect a set of time-domain samples within a discrete Fourier transform (DFT) window for each measurement.

[0194] Example C6. The UE 22 of Example C5, wherein the measurements are performed according to a sparse search grid corresponding to a number of DFT windows.

[0195] Example C7. The UE 22 of Example C4, wherein the different starting positions correspond to different circular shifts of a discrete Fourier transform window.

[0196] Example C8. The UE 22 of Example C7, wherein the measurements correspond to a non-sparse search grid corresponding to a range of circular shift.

[0197] Example C9. The UE 22 of any of Examples C4-C8, wherein a starting position and an ending position of the search window are configured relative to a downlink reference timing.

[0198] Example CIO. The UE 22 of any of Examples C4-C9, wherein a starting position of the search window is based at least in part on the first timing advance.

[0199] Example Cl 1. The UE 22 of any of Examples C4-C10, wherein a step size between starting positions within the search window is variable.

[0200] Example DI . A method implemented in a user equipment (UE 22) that is configured to communicate with a network node 16, the method comprising:

[0201] receiving from the network node 16 a configuration for cross link interference sounding reference signal (CLI-SRS) transmission, the configuration including a first timing advance; and

[0202] determining a second timing advance for the CLI-SRS transmission, the second timing advance being determined based at least in part on the first timing advance.

[0203] Example D2. The method of Example DI, wherein the second timing advance is further based at least in part on a timing offset between uplink and downlink

[0204] transmissions.Example D3. The method of Example DI, further comprising transmitting the CLI-SRS transmission with a zero timing advance.

[0205] Example D4. The method of any of Examples D1-D3, further comprising measuring CLI-SRS with different starting positions within a search window and determining a CLI-SRS reference signal received power (RSRP) based at least in part on a highest CLI-SRS of the measured CLI-SRS.

[0206] Example D5. The method of Example D4, further comprising collecting a set of time-domain samples within a discrete Fourier transform (DFT) window for each measurement.

[0207] Example D6. The method of Example D5, wherein the measurements are performed according to a sparse search grid corresponding to a number of DFT windows.

[0208] Example D7. The method of Example D4, wherein the different starting positions correspond to different circular shifts of a discrete Fourier transform window.

[0209] Example D8. The method of Example D7, wherein the measurements correspond to a non-sparse search grid corresponding to a range of circular shift.

[0210] Example D9. The method of any of Examples D4-D8, wherein a starting position and an ending position of the search window are configured relative to a downlink reference timing.

[0211] Example DIO. The method of any of Examples D4-D9, wherein a starting position of the search window is based at least in part on the first timing advance.

[0212] Example Dll. The method of any of Examples D4-D10, wherein a step size between starting positions within the search window is variable.

[0213] As will be appreciated by one of skill in the art, the concepts described herein may be embodied as a method, data processing system, computer program product and / or computer storage media storing an executable computer program. Accordingly, the concepts described herein may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects all generally referred to herein as a “circuit” or “module.” Any process, step, action and / or functionality described herein may be performed by, and / or associated to, a corresponding module, which may be implemented in software and / or firmware and / or hardware. Furthermore, the disclosure may take the form of a computer program product on a tangible computer usable storage medium having computer program code embodied in the medium that may be executed by a computer. Any suitable tangible computerreadable medium may be utilized including hard disks, CD-ROMs, electronic storage devices, optical storage devices, or magnetic storage devices.

[0214] Some embodiments are described herein with reference to flowchart illustrations and / or block diagrams of methods, systems and computer program products. It will be understood that each block of the flowchart illustrations and / or block diagrams, and combinations of blocks in the flowchart illustrations and / or block diagrams, may be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer (to thereby create a special purpose computer), special purpose computer, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0215] These computer program instructions may also be stored in a computer readable memory or storage medium that may direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer readable memory produce an article of manufacture including instruction means which implement the function / act specified in the flowchart and / or block diagram block or blocks.

[0216] The computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions / acts specified in the flowchart and / or block diagram block or blocks.

[0217] It is to be understood that the functions / acts noted in the blocks may occur out of the order noted in the operational illustrations. For example, two blocks shown in succession may in fact be executed substantially concurrently or the blocks may sometimes be executed in the reverse order, depending upon the functionality / acts involved. Although some of the diagrams include arrows on communication paths to show a primary direction of communication, it is to be understood that communication may occur in the opposite direction to the depicted arrows.

[0218] Computer program code for carrying out operations of the concepts described herein may be written in an object oriented programming language such as Python, Java®or C++. However, the computer program code for carrying out operations of the disclosure may also be written in conventional procedural programming languages, such as the "C" programming language. The program code may execute entirely on the user's computer, partly on the user's computer, as a stand-alone software package, partly on the user's computer and partly on a remote computer or entirely on the remote computer. In the latter scenario, the remote computer may be connected to the user's computer through a local area network (LAN) or a wide area network (WAN), or the connection may be made to an external computer (for example, through the Internet using an Internet Service Provider).

[0219] Many different embodiments have been disclosed herein, in connection with the above description and the drawings. It will be understood that it would be unduly repetitious and obfuscating to literally describe and illustrate every combination and subcombination of these embodiments. Accordingly, all embodiments may be combined in any way and / or combination, and the present specification, including the drawings, shall be construed to constitute a complete written description of all combinations and subcombinations of the embodiments described herein, and of the manner and process of making and using them, and shall support claims to any such combination or subcombination.

[0220] Abbreviations that may be used in the preceding description include:

[0221] Abbreviation Explanation

[0222] CLI Cross Link Interference

[0223] SRS Sounding Reference Signal

[0224] TA Timing Advance

[0225] It will be appreciated by persons skilled in the art that the embodiments described herein are not limited to what has been particularly shown and described herein above. In addition, unless mention was made above to the contrary, it should be noted that all of the accompanying drawings are not to scale. A variety of modifications and variations are possible in light of the above teachings without departing from the scope of the following claims.

Claims

CLAIMS1. A method performed by a first user equipment, UE (22a), for Cross-Link Interference- Sounding Reference Signal, CLLSRS, in a wireless communication system, the method comprising:receiving (S20), from a network node (16), configuration information for transmitting CLLSRS, the configuration information comprising a first timing advance, TA, that is specific to CLI signaling; andapplying (S22) a second TA for the CLLSRS, based on the first TA.

2. The method of Claim 1, wherein the first TA is based on one or more of serving link propagation delays; path losses; directions and UE positions of the first UE (22a) and a second UE (22b); inter-UE propagation delays.

3. The method of any one of Claims 1-2, wherein the applying of the second TA is based on a third TA that is associated with downlink reference timing between the first UE (22a) and the network node (16).

4. The method of any one of Claims 1-3, wherein the applying of the second TA is based on a TA offset.

5. The method of any one of Claims 1-4, wherein the first TA is different from the second TA.

6. The method of Claim 1, wherein the first TA has a TA value of zero.

7. The method of any one of Claims 1-6, further comprising transmitting the CLLSRS using the second TA.

8. The method of any one of Claims 1-7, wherein the first TA is for CLLSRS transmission toward a second UE (22b).

9. A first user equipment, UE (22a), for Cross-Link Interference-Sounding Reference Signal, CLI-SRS, in a wireless communication system, the first UE (22a) configured to:receive, from a network node (16), configuration information for transmitting CLI-SRS, the configuration information comprising a first timing advance, TA, that is specific to CLI signaling; andapply a second TA for the CLI-SRS, based on the first TA.

10. The first UE (22a) of Claim 9, wherein the first TA is based on one or more of serving link propagation delays; path losses; directions and UE positions of the first UE (22a) and a second UE (22b); inter-UE propagation delays.

11. The first UE (22a) of any one of Claims 9-10, wherein the applying of the second TA is based on a third TA that is associated with downlink reference timing between the first UE (22a) and the network node (16).

12. The first UE (22a) of any one of Claims 9-11, wherein the applying of the second TA is based on a TA offset.

13. The first UE (22a) of any one of Claims 9-12, wherein the first TA is different from the second TA.

14. The first UE (22a) of Claim 9, wherein the first TA has a TA value of zero.

15. The first UE (22a) of any one of Claims 9-14, wherein the first UE (22a) is configured to transmit the CLI-SRS using the second TA.

16. The first UE (22a) of any one of Claims 9-15, wherein the first TA is for CLI-SRS transmission toward a second UE (22b).

17. A method implemented by a network node (16), the method comprising: configuring (SI 8) a first user equipment, UE (22a), with configuration information for the first UE (22a) to transmit Cross-Link Interference- Sounding Reference Signal, CLI-SRS by applying a second timing advance, TA, based on a first TA; andthe first TA being specific to CLI signaling.

18. The method of Claim 17, further comprising:determining one or more of serving link propagation delays; path losses; directions and UE positions of the first UE (22a) and a second UE (22b); inter-UE propagation delays; wherein the first TA is based on the determination.

19. The method of any one of Claims 17-18, further comprising: configuring a second UE (22b) with a configuration for performing measurements of CLI-SRS, the CLI-SRS being associated with the second TA.

20. A network node (16) configured to:configure a first user equipment, UE (22), with configuration information for the first UE (22) to transmit Cross-Link Interference- Sounding Reference Signal, CLI-SRS by applying a second timing advance, TA, based on a first TA; and the first TA being specific to CLI signaling.

21. The network node (16) of Claim 20, wherein the network node (16) is configured to:determine one or more of: serving link propagation delays; path losses; directions and UE positions of the first UE (22a) and a second UE (22b); inter-UE propagation delays; wherein the first TA is based on the determination.

22. The network node (16) of any one of Claims 20-21, wherein the network node (16) is further configured to:configure a second UE (22b) with a configuration for performing measurements of CLI-SRS, the CLI-SRS being associated with the second TA.

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