Configuration of round trip time measurements for positioning

Abstract

The claims disclose a method performed by a first communication node (320) of a communication network for supporting round trip time (RTT) measurements for positioning, the method comprising: obtaining a message (341) indicating a timing target for transmitting a second position reference signal (302) with respect to communication of a first position reference signal (301); a first position reference signal (301; 301 ') is received at a first reception time (t321). 401, 402; 501), and transmitting a second position reference signal (302) at a second transmission time (t322) according to the timing target. In addition, the claims disclose a first communication node, a second communication node and a method performed by the second communication node.

Description

Technical Field

[0001] Various examples are generally directed to methods of facilitating round trip time measurements for positioning. Background Art

[0002] Measuring the round trip time (RTT) of a location reference signal (LRS) has been shown to be a useful method for determining the location of a wireless device (or user equipment, UE) by determining the distance of the wireless device (or user equipment, UE) from one or more access nodes (ANs) of a communication network, wherein the communication network includes multiple communication nodes, including ANs and UEs, communicating according to a predefined protocol.

[0003] The accuracy of the RTT measurement may depend on the clock signal used by the various communication nodes participating in the RTT measurement. The clocks of different communication nodes may not always be synchronized with each other and / or experience different clock drifts. Summary of the invention

[0004] Techniques allowing more accurate RTT measurements may be needed. The above needs have been solved by the subject matter of the independent claims. Advantageous embodiments are described in the dependent claims.

[0005] An example discloses a method performed by a first communication node of a communication network to support round-trip time measurement for positioning, the method comprising: obtaining a message indicating a timing target for sending a second location reference signal relative to a communication of a first location reference signal; receiving the first location reference signal at a first receiving time point; and sending a second location reference signal at a second sending time point according to the timing target.

[0006] Additionally, an example discloses a method performed by a second communication node of a communication network for supporting round trip time measurements for positioning, the method comprising providing a message to a first communication node indicating a timing target between communication of a first location reference signal and transmission of a second location reference signal.

[0007] Furthermore, an example discloses a first communication node of a communication network, the first communication node comprising a control circuit, wherein the control circuit is configured to perform the aforementioned method.

[0008] Furthermore, an example discloses a second communication node of the communication network, the second communication node comprising a control circuit, wherein the control circuit is configured to perform the aforementioned method. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 RTT measurements for positioning are schematically shown.

[0010] Figure 2 Communication between a first communication node and a second communication node is shown.

[0011] Figure 3 shows a method for supporting RTT measurements for positioning.

[0012] Figure 4 shows a method for supporting RTT measurements for positioning.

[0013] Figure 5 shows a method for supporting RTT measurements for positioning.

[0014] Figure 6 shows a method for supporting RTT measurements for positioning.

[0015] Figure 7 shows a method for supporting RTT measurements for positioning.

[0016] Figure 8 shows the selection of resources for supporting RTT measurements.

[0017] Figure 9 shows the selection of resources for supporting RTT measurements. DETAILED DESCRIPTION

[0018] Some examples of the present disclosure generally provide multiple circuits or other electrical devices. All references to circuits and other electrical devices and the functions provided by each electrical device are not intended to be limited to only what is shown and described herein. While specific labels may be assigned to the various circuits or other electrical devices disclosed, these labels are not intended to limit the scope of operation of the circuits and other electrical devices. Such circuits and other electrical devices may be combined and / or separated from each other in any manner based on the desired specific type of electrical implementation. It should be recognized that any circuit or other electrical device disclosed herein may include any number of microcontrollers, graphics processing units (GPUs), integrated circuits, memory devices (e.g., flash memory, random access memory (RAM), read-only memory (ROM), electrically programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), or other suitable variations thereof), and software that cooperate with each other to perform the operations disclosed herein. In addition, any one or more of the electrical devices may be configured to execute program code that is implemented in a non-transitory computer-readable medium that is programmed to perform any number of functions and / or methods as disclosed.

[0019] Hereinafter, examples of the present disclosure will be described in detail with reference to the accompanying drawings. It should be understood that the following description of the examples should not be considered restrictive. The scope of the present disclosure is not intended to be limited by the examples or drawings described below, and the examples and drawings are only considered illustrative.

[0020] The accompanying drawings should be regarded as schematic representations, and the elements shown in the drawings are not necessarily shown to scale. Instead, the various elements are represented such that their functions and general purposes become apparent to those skilled in the art. Any connections or couplings between the functional blocks, devices, components, or other physical or functional units shown in the drawings or described herein may also be implemented by indirect connections or couplings. The couplings between components may also be established by wireless connections. The functional blocks may be implemented in hardware, firmware, software, or a combination thereof.

[0021] Figure 1 RTT measurements for positioning are shown. The RTT measurements involve communication between a Location Server Node (LN) 140, an AN 110, and a UE 120. In some examples, the LN may be implemented by a Location Management Function (LMF). In some scenarios, the AN may be implemented by a gNB. In additional scenarios, the AN may be implemented by a TRP. The LN 140, AN 110, and UE 120 may be part of a communication network. The communication network may include multiple communication nodes that communicate according to a predefined protocol, including the AN 110 and UE 120. The predefined protocol may be a protocol defined by the 3rd Generation Partnership Project (3GPP).

[0022] The AN 120 transmits a first Location Reference Signal (LRS) 101 at time point t 110 The first LRS may be a Downlink Positioning Reference Signal (DL-PRS). The UE 120 receives the first LRS 101 at time point t 121 In response to receiving the first LRS 101, the UE 120 transmits a second LRS 102 at time point t 122 The second LRS 102 may be an Uplink Sounding Reference Signal (UL-SRS). The AN 110 receives the second LRS 102 at time point t 113 The AN 110 provides a message 141 to the LN 140 indicating the time interval t 113 -t 110 The time interval t 113 -t 110 may also be referred to as the Rx-Tx time difference of the AN. The message 141 may be provided to the LN 140 using the NRPPa protocol specified in 3GPP TS 38.455 v17.2.0. Similarly, the UE 120 provides a message 142 to the LN 140 indicating the time interval t 122 -t 121 The time interval t 122 -t 121It may also be referred to as the Tx-Rx time difference of the UE. The Rx-Tx time difference of the UE may be due to the fact that the UE 120 has to wait for the UL resources to become available for transmitting the second location reference signal 102. Specifically, the UE 120 may have to align the start of the transmission of the second location reference signal 102 with the start of the UL time slot. The LTE positioning protocol (LPP) specified in 3GPP TS37.355 v17.2.0 may be used to provide the message 142. Thereafter, the LN 142 may calculate the RTT, which indicates the time range t between the AN 110 and the UE 120 range twice that of, such as RTT = 2·t range =(t 121 -t 110 )+(t 113 -t 122 )=(t 113 -t 110 )-(t 122 -t 121 ), as indicated by the box 151.

[0023] Therefore, the UE 120 performs the following actions. The UE 120 measures the first reception time point t of receiving the first LRS 121 , the UE 120 transmits the second LRS, and the UE 120 provides an indication of the time interval t 122 -t 121 (i.e., the transmission time t of the second LRS 102 122 relative to the reception time t of the first LRS 101 121 ) of the message.

[0024] The channel access procedure for multi-RTT positioning technology based on downlink and uplink is disclosed in 3GPP TR 38.305 v17.2.0.

[0025] Generally, TOA measurement can also be used to determine the time range t between the AN 110 and the UE 120 range , that is, measure the time interval t 121 -t 110 =t range . However, it may be advantageous to use RTT measurement instead of TOA measurement for positioning, as will be explained below with reference to Figure 2 explained.

[0026] Figure 2 shows the communication between the first communication node (CN) 220 and the second CN 210 of the communication network. The communication network may include multiple CNs that communicate according to a predefined protocol, including the first CN 220 and the second CN 210. The predefined protocol may be a protocol defined by 3GPP.

[0027] The first CN 220 and the second CN 210 can each use their own clocks to measure the time points of signal transmission or reception. The clocks of the first CN 220 and the second CN 210 may not be completely synchronized with each other. Specifically, as Figure 2 indicated, there may be an offset between the clock of the first CN 220 and the clock of the second CN 210.

[0028] The offset between the clocks will affect the time range t between the first CN 220 and the second CN 210 based on the TOA measurement of the first LRS201 range measurement accuracy, that is, t range = t 221 - t 210 , because t 221 ≠ t 211 (and t 220 ≠ t 210 ). In the RTT measurement using the first LRS201 and the second LRS202 to determine t range = 1 / 2*RTT = 1 / 2((t 213 - t 210 ) - (t 222 - t 221 ))), the offset error is canceled.

[0029] Therefore, using RTT measurement for positioning may be particularly useful for CNs that are not fully synchronized, especially for CNs that communicate with each other using sidelink (SL) communication.

[0030] In addition to the offset error, the clocks of the CNs participating in the RTT measurement may experience random clock drift. The larger values of t 221 - t 222 and / or t 210 - t 213 can increase the timing error caused by clock drift and thus reduce the positioning accuracy.

[0031] Therefore, there is a need to improve positioning techniques, especially for CNs that communicate with each other using SL communication.

[0032] Therefore, an example discloses a method performed by a first CN of a communication network, supporting RTT measurement for positioning, wherein the method includes: obtaining a message indicating a timing target for communicating a second LRS relative to a first position reference signal, receiving the first position reference signal at a first reception time point, and transmitting the second position reference signal at a second transmission time point according to the timing target.

[0033] Another example discloses a method performed by a second CN of a communication network that supports RTT measurements for positioning, wherein the method includes providing a message indicating a timing target for communicating a second LRS relative to a first position reference signal.

[0034] Aspects of SL communication have been specified in 3GPP TR 37.985 v17.1.1, clauses 5.2.1 and 6.3, in particular with respect to vehicle-to-everything (V2X) communication. For SL communication, two channel access modes (mode 1 and mode 2) for resource selection are specified. In mode 1, the AN (i.e., gNB) allocates and manages SL resources for V2X communication under the NR Uu interface. This means that when operating in mode 1, the UE must be within network coverage. Additionally, depending on the transport block (TB) type, mode 1 has two variants: dynamic grant (DG) and semi-persistent scheduling grant (SG). DG can be used for the transmission of a single TB, and SG can be used for periodic transmissions. In mode 2, the UE can autonomously select their SL resources from a resource pool by sensing and selecting. To avoid resource conflicts, the UE operating in mode 2 first needs to sense the resource pool by measuring the power in each sub-channel in a sensing window and filtering out the occupied sub-channels. The candidate sub-channels remaining from this step can undergo further selection in the resource selection phase. Within the resource selection window, the transmitting UE further selects one or more sub-channels to be used for TB transmission.

[0035] Figure 3 A method for supporting RTT measurements for positioning in a communication network is shown. The communication network includes a plurality of communication nodes, the plurality of communication nodes including a first communication node 320, a second communication node 340, and a first position reference signal transmitting communication node 310. The communication nodes of the communication network can communicate according to a predefined protocol. In particular, the communication nodes of the communication network can use mode 1 SL communication as described above. In Figure 3 the example, the first communication node 320 can be implemented by a UE, the second communication node 340 can be implemented by an AN, and the first position reference signal transmitting communication node 310 can be implemented by a UE.

[0036] The first communication node 320 obtains from the second communication node 340 a message 341 indicating a timing target for communicating a second position reference signal 302 relative to the first position reference signal 301. The first position reference signal transmitting communication node 310 transmits the first position reference signal 301 at a first transmission time point t 310 The first communication node 320 receives the first position reference signal 301 at a first reception time point t according to the timing target, and at a second transmission time point t 321 322 ​Transmit the second location reference signal 302. The first location reference signal transmitting communication node 310 transmits at the second reception time point t 313 Receive the second location reference signal 302.

[0037] The first communication node 320 can optionally, in particular, provide the first location reference signal transmitting communication node 310 with a message 343 indicating the time difference between the second transmission time point t 322 and the first reception time point t 321 Based on the first transmission time point t 310 , the second reception time point t313, and the second transmission time point t 322 and the first reception time point t 321 The time difference between them, the first location reference signal transmitting communication node 310 can derive the RTT.

[0038] The timing target for transmitting the second location reference signal 302 relative to the first location reference signal 301 can improve the accuracy of the RTT measurement for positioning. In particular, the timing target can reduce the impact of clock drift on positioning accuracy. In some scenarios, the first communication node 320 and the first location reference signal transmitting communication node 310 can move relative to each other at a relative speed. Therefore, the first location reference signal 301 and the second location reference signal 302 can travel different distances. Setting the timing target for transmitting the second location reference signal 302, in particular a relatively short timing target, can allow reducing the impact of the relative speed on positioning accuracy.

[0039] In some examples, the timing target defines a time window for transmitting the second location reference signal 302 relative to the first location reference signal 301. For example, the time window can specify the maximum (and optionally minimum) time for the first communication node 320 to transmit the second location reference signal 302.

[0040] In some examples, the timing target defines the offset of the second transmission time point t 322 for communication relative to the first location reference signal 301.

[0041] In some scenarios, the timing target can be defined relative to the transmission of the first location reference signal, that is, relative to the first transmission time point t 310 . Other scenarios can specify that the timing target is defined relative to the reception of the first location reference signal (i.e., relative to the first reception time point t 321 ).

[0042] When the timing target defines the offset of the second transmission time point t 322 relative to the first reception time point t 321 , providing an indication of the second transmission time point t can be omitted.322 and the time difference between the first reception time point t 321 of the message, since the information will already be available to the communication node to derive the RTT, as it has defined such a parameter in the timing target.

[0043] For example, the first location reference signal transmitting communication node 310 may also obtain a message 342 indicating the timing target from the second communication node 340. Thus, the use of limited radio resources can be reduced.

[0044] Figure 4 FIG. shows another method for supporting RTT measurement for positioning in a communication network. The communication network includes a plurality of communication nodes, and the plurality of communication nodes include a first communication node 420 and a second communication node 410. The communication nodes of the communication network can communicate according to a predefined protocol. For example, the communication nodes of the communication network can use the mode 2SL communication as described above. Both the first communication node 410 and the second communication node 420 can be implemented by a UE.

[0045] The first communication node 420 obtains a message 441 from the second communication node 410 indicating the timing target for transmitting the second location reference signal 402 relative to the first location reference signal 401. The second communication node 410, which can also be considered as the first location reference signal transmitting communication node 310, transmits the first location reference signal 401 at the first transmission time point t 310 The first communication node 420 receives the first location reference signal 401 at the first reception time point t according to the timing target, and transmits the second location reference signal 402 at the second transmission time point t 421 The second communication node 410 receives the second location reference signal 402 at the second reception time point t 422 and transmits the second location reference signal 402 at the second transmission time point t 413 The second communication node 410 receives the second location reference signal 402 at the second reception time point t.

[0046] The first communication node 420 may optionally provide, in particular, to the second communication node 410 a message 443 indicating the time difference between the second transmission time point t 422 and the first reception time point t 421 Based on the first transmission time point t 410 the second reception time point t 414 and the second transmission time point t 422 and the time difference between the first reception time point t 421 the second communication node 410 can derive the RTT.

[0047] The timing target for communicating the second position reference signal 402 relative to the first position reference signal 401 can improve the accuracy of RTT measurements for positioning. In particular, the timing target can reduce the impact of clock drift on positioning accuracy. According to an example, the first communication node 420 and the second communication node 410 can move relative to each other at a relative speed. Accordingly, the first position reference signal 401 and the second position reference signal 402 can travel different distances. Setting the timing target for transmitting the second position reference signal 402, particularly a relatively short timing target, can allow reducing the impact of the relative speed on positioning accuracy.

[0048] In some scenarios, the timing target defines a time window for communicating the second position reference signal 402 relative to the first position reference signal 401. For example, the time window can specify the maximum (and optionally minimum) time for the first communication node 420 to transmit the second position reference signal 402.

[0049] According to some scenarios, the timing target defines a second transmission time point t 422 offset with respect to the communication of the second communication node 410.

[0050] In some examples, the timing target can be defined relative to the transmission of the first position reference signal (i.e., relative to the first transmission time point t 410 ). Other scenarios can specify that the timing target is defined relative to the reception of the first position reference signal (relative to the first reception time point t 421 ).

[0051] In the case where the timing target defines an offset of the second transmission time point t 422 relative to the first reception time point t 421 , the message providing the time difference between the second transmission time point t 422 and the first reception time point t 421 can be omitted, because the information will already be available to the communication nodes to derive the RTT. Accordingly, the use of limited radio resources can be reduced.

[0052] In some examples, the first communication node 410 may not be able to transmit the second LRS according to the timing target. In such a scenario, the first communication node 410 can still provide a message indicating the time difference between the second transmission time point t 422 and the first reception time point t 421 to allow derivation of the RTT. The time difference can also be indicated relative to the timing target, e.g., how much longer the time difference is than the expected offset.

[0053] In Figure 5In it, another method for supporting RTT measurements for positioning in a communication network is shown. The communication network includes a plurality of communication nodes, and the plurality of communication nodes includes a first communication node 520 and a second communication node 510. The communication nodes of the communication network can communicate according to a predefined protocol. For example, the communication nodes of the communication network can use the mode 2SL communication as described above. Both the first communication node 510 and the second communication node 520 can be implemented by a UE.

[0054] As explained with respect to Figure 2 the clocks of the first communication node 520 and the second communication node 510 may be out of sync or at least not fully synchronized. Therefore, t 51？ refers to a time point relative to the clock of the second communication node 510, and t 52？ refers to a time point relative to the clock of the first communication node 520.

[0055] The first communication node 520 obtains from the second communication node 510 a message 541 indicating a timing target for transmitting a second positioning reference signal 502 with respect to the first positioning reference signal 501 for communication. The second communication node 501 transmits the first positioning reference signal 501 at a first transmission time point t 510 The first transmission time point t 510 may correspond to the start of the first symbol. The first communication node 520 receives the first positioning reference signal 501 at a first reception time point t 521

[0056] The timing target may specify that the second positioning reference signal 502 is to be transmitted at a second transmission time point t 521 defined as an offset relative to the first reception time point t 522 The offset may be represented in the form of a plurality of symbols (e.g., N symbols).

[0057] At 551, the first communication node 520 may estimate the signal propagation delay d = t 521 - t 520 and modify the second positioning reference signal to be transmitted in the Nth symbol by applying the delay d. This can be done in the frequency domain. The modified second positioning reference signal sequence S’ 502 can be expressed as

[0058]

[0059] where S corresponds to the unmodified second positioning reference signal sequence in the time domain, IFT(*) corresponds to the inverse Fourier transform operation, FT(*) corresponds to the Fourier transform, and T C corresponds to the sampling time.

[0060] ​Then, the first communication node 520 may transmit a second position reference signal 502 with a modified second position reference signal sequence S′(t) in the Nth symbol. The second communication node 510 receives the second position reference signal 502 at the second reception time point t 513 and may calculate the RTT = t 513 - t 510 - N T symb , where T symb corresponds to a symbol duration such as an OFDM symbol duration.

[0061] Figure 6 FIG. shows a method for supporting RTT measurement for positioning in a communication network. The communication network includes a plurality of communication nodes, the plurality of communication nodes including a first communication node 620, a second communication node 640, and a first position reference signal transmitting communication node 610. The first communication node 620 and the first position reference signal transmitting communication node 610 may be implemented by a UE, and the second communication node 640 may be implemented by an AN of the communication network. The communication nodes of the communication network may communicate according to a predefined protocol. For example, the communication nodes of the communication network may use the mode 1 SL communication as described above. More specifically, a dynamic grant (DG) procedure may be used. Figure 6 Particularly shown is a mechanism for allocating resources for communicating the first position reference signal 601 and for communicating the second position reference signal 602.

[0062] The second communication node 640 may obtain a message 661 from the first location reference signal transmitting communication node 610 indicating a request for resources 671 allocated for communicating the first location reference signal 601. The second communication node 640 may provide a message 662 to the first location reference signal transmitting communication node 610 indicating the resources 671 allocated for communicating the first location reference signal 601. So far, downlink control information (DCI) signaling may be used. The first location reference signal transmitting communication node 610 may provide a message 663 to the first communication node 620 indicating a timing target for transmitting a second location reference signal 602 with respect to the first location reference signal 601. The message 663 may also trigger the first communication node 620 to measure a first reception time point at which the first location reference signal 601 is received. The message 663 may be provided to the first communication node 620 using sidelink control information (SCI). The first location reference signal transmitting communication node 610 may use the resources 671 allocated by the second communication node 640 for communicating the first location reference signal 601 to transmit the first location reference signal 601. A single transport block (TB) may be used to transmit the first location reference signal 601. After receiving the first location reference signal 601, the first communication node 620 may provide a message 664 to the second communication node 640 indicating a request for resources 672 allocated for communicating the second location reference signal 602. The second communication node 640 may provide a message 665 to the first communication node 620 indicating the resources 672 allocated for communicating the second location reference signal 602. DCI signaling may be used to provide the message 665. The first communication node 620 may provide a message 666 to the first reference signal transmitting communication node 610 that guides the first location reference signal transmitting node 610 to measure a second reception time point at which the second location reference signal 602 is received. Thereafter, the first communication node 620 may use the resources 672 allocated by the second communication node 640 to transmit the second location reference signal 602.

[0063] Figure 7 Further aspects supporting round-trip time (RTT) measurements for positioning in a communication network are shown. The communication network includes a plurality of communication nodes, which includes a first communication node 720, a second communication node 740, and a first location reference signal transmitting communication node 710. The first communication node 720 and the first location reference signal transmitting communication node 710 may be implemented by a user equipment (UE), and the second communication node 740 may be implemented by an access network (AN) of the communication network. The communication nodes of the communication network may communicate according to a predefined protocol. For example, the communication nodes of the communication network may use mode 1 sidelink communication as described above.

[0064] The second communication node 740 may obtain, from the first position reference signal transmitting communication node 710, a message 761 indicating a request for resources 771 allocated for communicating the first position reference signals 701, 703 and resources 772 allocated for communicating the second position reference signals 702, 704. The second communication node 740 may have full knowledge of the resources that have been occupied. Thus, for the purpose of RTT measurement, the second communication node 740 may optimize the allocation of resources 771 and 772. For example, the second communication node 740 may allocate contiguous resources for communicating the first position reference signal and the second position reference signal. Resources for communicating the first position reference signals 701, 703 and the second position reference signals 702, 704 may be allocated jointly. Compared with the scenario described with respect to Figure 6 the resources 772 for communicating the second position reference signal 702 are allocated before the first communication node 720 receives the first position reference signal 701. Thus, the time interval between receiving the first position reference signal 701 and transmitting the second position reference signal 702 may be shorter, thereby improving the accuracy of RTT measurement. Specifically, as Figure 6 shown, the time interval between receiving the first position signal 701 and transmitting the second position reference signal 702 may be shorter than the time interval between receiving the first position reference signal 601 and transmitting the second position reference signal 602 because no additional signaling is required between the two position reference signal transmissions.

[0065] The second communication node 740 may provide messages 762, 766 indicating the resources 771 and 772 to the first position reference signal transmitting node 710 and the first communication node 720, respectively. Radio resource control (RRC) signaling may be used to transmit the messages 762, 766. The messages 762, 766 may indicate several preconfigured sets of resources 771 and 772.

[0066] The second communication node 740 may provide messages 781, 782 to the first position reference signal transmitting communication node 710 and the first communication node 720 to activate RTT measurement. Lower layer signaling may be used to provide the messages 781, 782. For example, DCI signaling may be used to provide the messages 781, 782. The messages 781, 782 may indicate the preconfigured sets of resources 771, 772 to be used for performing the RTT measurement (i.e., communicating the first position reference signal 701 and the second position reference signal 702). The lower layer signaling may be addressed to each UE individually (unicast) or via multicast, where the DCI may be scrambled with a specific radio network temporary identifier (RNTI) (such as the RTT RNTI).

[0067] After that, the first location reference signal transmitting communication node 710 can use a preconfigured set of resources 771 to transmit the first location reference signal. The first communication node 720 uses the preconfigured set of resources 772 to receive the first location reference signal 701 and transmit the second location reference signal 702.

[0068] The second communication node 740 can provide messages 783, 784 to the first location reference signal transmitting communication node 710 and the first communication node 720 to deactivate RTT measurement.

[0069] The second communication node 740 can provide a message 767 to the first location reference signal transmitting communication node 710, the message indicating the time difference between the second transmission time point at which the second location reference signal 702 has been transmitted and the first reception time point at which the first location reference signal 701 has been received.

[0070] Before deactivating the RTT measurement, not only one pair of the first location reference signal 701 and the second location reference signal 702 may have been communicated, but several pairs. Specifically, several first location reference signals 701 may have been communicated periodically, followed by corresponding communications of the second location reference signal 702.

[0071] The second communication node 740 can provide messages 785, 786 for reactivating the RTT measurement. The messages 785, 786 can indicate that the preconfigured resource set for communicating the first location reference signal 703 and the second location reference signal 704 is different from the resource set for communicating the first location reference signal 701 and the second location reference signal 702.

[0072] In some scenarios, the first communication node (e.g., communication node 420) and the second communication node (e.g., communication node 410) of the communication network can operate in mode 2 as described above. When operating in mode 2, the second communication node can assist the first communication node in configuring resources for communicating the second location reference signal. In particular, the second communication node can have full control over the configuration. The second communication node can be configured to sense and / or select and / or allocate resources for communicating the second location reference signal. The second communication node can provide a message to the first communication node indicating the resources for communicating the second location reference signal.

[0073] In some examples, the second communication node can provide a message to the first communication node indicating a set of candidate resources for communicating the second location reference signal. Then, the first communication node can select resources from the set of candidate resources. The second communication node can assist the first communication node in finding resources for transmitting the second location reference signal in the operation of the inter-UE coordination class (IUC).

[0074] As Figure 8As shown, the second communication node 810 can measure the power in each sub-channel in the sensing window 804 and filter out the occupied resources 803. The candidate sub-channels remaining from this step can undergo further selection in the resource selection phase. The second communication node 810 can select the (candidate) resources for communicating both the first position reference signal and the second position reference signal. Preferably, the second communication node 810 can select the resources 801, 802 for communicating the first position reference signal and the second position reference signal in two consecutive time slots. The time slots can start with automatic gain control (AGC) symbols 811, 812 and end with guard symbols 821, 822. The resources 801, 802 can be selected to use the same frequency pattern as indicated in Figure 8 . For example, the second communication node can use the same combSize and the same combOffset, as specified in 3GPP TS 38.211 v17.3.0 for both the first position reference signal and the second position reference signal, but in different time slots.

[0075] As previously mentioned, the first communication node can obtain a message indicating the set of candidate resources for communicating the second position reference signal. The resources actually used by the first communication node to communicate the second position reference signal can be pre-allocated. In other scenarios, the first communication node can autonomously select the resources to be used based on its UE-ID. In some examples, the first communication node can perform a random selection among the candidate resources. For example, it can be stipulated that the first communication node performs sensing to derive the resources to be actually used to communicate the second positioning symbol.

[0076] As Figure 9 shown, the communication of the first position reference signal and the second position reference signal can be performed at the symbol level. For example, symbol 901 can be used to communicate the first position reference signal, and symbol 902 can be used to communicate the second position reference signal. The time slots can start with AGC symbols 911, 912 and end with guard symbols 921, 922. The guard symbols can allow the communication node to switch from the received signal to the transmitted signal (and vice versa).

[0077] In some scenarios, the first communication node (i.e., the communication node that receives the first position reference signal and transmits the second position reference signal) can derive the (candidate) resources for transmitting the first position reference signal and transmitting the second position reference signal.

[0078] In other words, the communication node that derives the (candidate) resources can choose to be the communication node that transmits the first position reference signal or the communication node that receives the first position reference signal. This can enhance the flexibility for deriving the (candidate) resources for communicating the first position reference signal and the second position reference signal.

[0079] In some examples, a first communication node receives a message indicating a plurality of resources (opportunities) for communicating a first location reference signal. The first communication node monitors the plurality of resources to detect the first location reference signal. Once the first communication node has detected the first location reference signal, the first communication node may stop monitoring the remaining opportunities. If the first communication node does not detect the first location reference signal, the first communication node may continue to monitor the remaining opportunities.

[0080] In some scenarios, the first communication node may be unable to send a second location reference signal according to a timing target. In such a scenario, the first communication node may perform a fallback selection. Specifically, the first communication node may perform a two-sided RTT measurement. The two-sided RTT measurement may stipulate the transmission of a first location reference signal, a second location reference signal, and a third location reference signal. The third location reference signal may be required to correct clock drifts at two communication nodes.

[0081] The timing target as described herein may be selected based on the clock accuracy of the communication node. In other examples, the timing target may be selected based on the relative speed of the first communication node with respect to the communication node transmitting the first location reference signal.

[0082] In summary, at least the following examples have been described above:

[0083] Example 1. A method performed by a first communication node (320, 420, 520) of a communication network for supporting round-trip time RTT measurements for positioning, the method comprising

[0084] - obtaining a message (341, 441, 541) indicating a timing target for communicating a second location reference signal (302, 402, 502) relative to a first location reference signal (301, 401, 501);

[0085] - receiving the first location reference signal (301, 401, 501) at a first reception time point (t 321 ; t 421 ; t 521 );

[0086] - transmitting the second location reference signal (302, 402, 502) at a second transmission time point (t 322 ; t 422 ; t 522 ) according to the timing target.

[0087] Example 2. The method according to Example 1,

[0088] Among them, the timing target defines a time window for transmitting the second position reference signal (302; 402; 502).

[0089] Example 3. The method according to Example 1,

[0090] wherein the timing target defines an offset of the communication of the second transmission time point (t 322 ; t 422 ; t 522 ) with respect to the first position reference signal (302; 402; 502).

[0091] Example 4. The method according to any one of Examples 1 to 3,

[0092] wherein the message (341; 441; 541) indicating the timing target for transmitting the second position reference signal (302; 402; 502) indicates the timing target with respect to the first reception time point (t 321 ; t 421 ; t 521 ).

[0093] Example 5. The method according to any one of Examples 1 to 3,

[0094] wherein the message (341, 441, 541) indicating the timing target for transmitting the second position reference signal (302; 402; 502) indicates the timing target with respect to the transmission of the first position reference signal (301; 401; 501) at the first transmission time point (t 310 ; t 410 ; t 510 ).

[0095] Example 6. The method according to any one of Examples 1 to 5, further comprising

[0096] - providing a message (343, 443) indicating a time difference between the second transmission time point (t 322 ; t 422 ) and the first reception time point (t 321 ; t 421 ).

[0097] Example 7. The method according to any one of Examples 1 to 6, further comprising at least one of the following:

[0098] - obtaining a message indicating one or more resources allocated for transmitting the second position reference signal (302; 402; 502).

[0099] - Obtain a message indicating one or more resources allocated for receiving the first position reference signal (301; 401; 501).

[0100] Example 8. The method according to Example 7,

[0101] - wherein the message (341; 441; 541) indicating the timing target indicates the resources allocated for receiving the first position reference signal (301; 401; 501) and / or the resources for transmitting the second position reference signal (302; 402; 502).

[0102] Example 9. The method according to any one of Examples 1 to 8, wherein the message (341; 441; 541) indicating the timing target and / or the message indicating the resources for transmitting the second position reference signal (302; 402; 502) is part of a sidelink control information SCI message.

[0103] Example 10. The method according to any one of Examples 1 to 9, further comprising:

[0104] - Providing a message indicating that the first communication node (320; 420; 520) cannot meet the timing target.

[0105] Wherein, providing a message indicating that the first communication node (320; 420; 520) cannot meet the timing target includes transmitting a third position reference signal.

[0106] Example 11. A method performed by a second communication node (340; 410; 510) of a communication network for supporting round-trip time RTT measurements for positioning, the method comprising

[0107] - Providing a message (341; 441; 541) to a first communication node (320; 420; 520) indicating a timing target between the communication of a first position reference signal (301; 401; 501) and the transmission of a second position reference signal (302; 402; 502).

Claims

1. A method performed by a first communication node (320, 420, 520) of a communication network, the method supporting round-trip time RTT measurements for positioning, the method comprises: - obtaining a message (341, 441, 541) indicating a timing target for communicating a second position reference signal (302, 402, 502) relative to a first position reference signal (301, 401, 501); - At a first reception time point (t 321 ; t 421 ; t 521 ), receive the first position reference signal (301; 401; 501); - Transmit the second position reference signal (302; 402; 502) at the second transmission time point (t 322 ; t 422 ; t 522 ) according to the timing target.

2. The method according to claim 1, wherein, the timing target defines a time window for transmitting the second position reference signal (302, 402, 502).

3. The method according to claim 1, wherein, The timing target defines the offset of the communication with respect to the first position reference signal (302; 402; 502) for the second transmission time point (t 322 ; t 422 ; t 522 ).

4. The method according to any one of claims 1 to 3, wherein, The message (341; 441; 541) indicating the timing target for transmitting the second position reference signal (302; 402; 502) indicates the timing target relative to the first reception time point (t 321 ; t 421 ; t 521 ).

5. The method according to any one of claims 1 to 3, wherein, The message (341, 441, 541) indicating the timing target for transmitting the second position reference signal (302; 402; 502) indicates the timing target relative to the transmission of the first position reference signal (301; 401; 501) at a first transmission time point (t 310 ; t 410 ; t 510 ).

6. The method according to any one of claims 1 to 5, further comprises: - Provide an indication of the second transmission time point (t 322 ; t 422 ) and the time difference with the first reception time point (t 321 ; t 421 ). The message (343, 443) 7. The method according to any one of claims 1 to 6, further comprises: - obtaining a message indicating one or more resources allocated for transmitting the second position reference signal (302; 402, 502).

8. The method according to any one of claims 1 to 7, further comprises: - obtaining a message indicating one or more resources allocated for receiving the first position reference signal (301; 401, 501).

9. The method according to any one of claims 7 and 8, - wherein the message (341, 441, 541) indicating the timing target indicates the resources allocated for receiving the first position reference signal (301, 401, 501) and / or the resources for transmitting the second position reference signal (302, 402, 502).

10. The method according to any one of claims 1 to 9, wherein, the message (341, 441, 541) indicating the timing target and / or the message indicating the resources for transmitting the second position reference signal (302, 402, 502) is part of a sidelink control information SCI message.

11. The method according to any one of claims 1 to 10, further comprises: - providing a message indicating that the first communication node (320, 420, 520) cannot meet the timing target.

12. The method according to claim 11, wherein, providing a message indicating that the first communication node (320, 420, 520) cannot meet the timing target includes transmitting a third position reference signal.

13. A method performed by a second communication node (340 ； 410, 510) of a communication network, the method supporting round-trip time RTT measurements for positioning, the method comprises: - providing to a first communication node (320, 420, 520) a message (341, 441, 541) indicating a timing target between communication of a first position reference signal (301, 401, 501) and transmission of a second position reference signal (302, 402, 502).

14. The method according to claim 13, wherein, The timing target defines a time window for transmitting the second position reference signal (302; 402; 502).

15. The method according to claim 13, wherein, The timing target defines an offset for a second transmission time point (t 322 ; t 422 ; t 522 ) for transmitting the second location reference signal (302; 402; 502).

16. The method according to any one of claims 13 to 15, wherein, The message (341; 441; 541) indicating the timing target for transmitting the second position reference signal (302; 402; 502) indicates the timing target relative to a first reception time point (t 321 ; t 421 ; t 521 ), at which the first communication node (310; 410; 510) receives the first position reference signal (301; 401; 501) at the first reception time point (t 321 ; t 421 ; t 521 ).

17. The method according to any one of claims 13 to 16, wherein, The message (341; 441; 541) indicating the timing target for transmitting the second position reference signal (302; 402; 502) indicates the timing target for the transmission of the first position reference signal (301; 401; 501) relative to a first transmission time point (t 310 ; t 410 ; t 510 ).

18. The method according to any one of claims 13 to 17, further comprising: - Obtain a message indicating a time difference between the second transmission time point (t 422 ) and the first reception time point (t 421 ) at which the first communication node (310; 410; 510) receives the first position reference signal (401).

19. The method according to any one of claims 13 to 18, further comprising: - At the second reception time point (t 413 ; t 513 ) Receive the second position reference signal (402; 502) from the first communication device (420; 520).

20. The method according to any one of claims 13 to 19, further comprising: - Providing a message (341; 441; 541) to the first communication node (320; 420; 520) indicating one or more resources allocated for transmitting the second position reference signal (302, 402, 502).

21. The method according to any one of claims 13 to 20, further comprising: - Providing a message (341; 441; 541) to the first communication node (320; 420; 520) indicating one or more resources allocated for receiving the first position reference signal (301; 401; 501).

22. The method according to any one of claims 20 and 21, wherein, The message (341; 441; 541) indicating the timing target indicates the resources allocated for receiving the first position reference signal (301; 401; 501) and / or the resources for transmitting the second position reference signal (302; 402; 502).

23. The method according to any one of claims 13 to 22, further comprising: - Providing a message (342) to the first position reference signal transmitting communication node (310) indicating one or more resources allocated for transmitting the first position reference signal (301).

24. The method according to any one of claims 13 to 23, further comprising: - Providing a message (342) to the first position reference signal transmitting communication node (310) indicating one or more resources allocated for receiving the second position reference signal (320).

25. The method according to any one of claims 13 to 24, further comprising: - Providing a message (342) to the first position reference signal transmitting communication node (310) indicating the timing target.

26. A first communication node (320; 420; 520) of a communication network, the first communication node (320; 420; 520) includes a control circuit, wherein, The control circuit is configured to execute the method according to any one of claims 1 to 10.

27. A second communication node (340; 410; 510) of a communication network, the second communication node (340; 410; 510) includes a control circuit, wherein, The control circuit is configured to execute the method according to any one of claims 11 to 23.

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