Technical Field

The invention relates to sidelink (SL) based ccooperative positioning (CoP) using estimated positions. Examples of the invention provides a client device configured to in addition to an estimated position of another client device provide a quality metric associated with the estimated position. Examples of the invention further provides a network node configured to determine a position of a client device based on estimated positions of the client device and quality metrics associated with the estimated positions. Furthermore, the invention relates to corresponding methods and a computer program.

Background

CoP has emerging interests in coming vehicle-to-everything (V2X) and internet-of-things (loT) applications in new-radio (NR), where accurate locations are essential for these applications to succeed. In particular, radio based CoP is considered where global navigation satellite systems (GNSS) or the next generation NodeB (gNB) is not available, or to further decrease positioning errors even when GNSS or gNB is available.

CoP can be implemented inside a CoP group (CoPG), which typically contains a number of anchor nodes (ANs) such as gNBs, transmit and receive points (TRPs) or some terminal nodes whose locations are known, and a number of target nodes (TNs) whose locations are unknown and need to be estimated. To estimate the location of a TN, radio links (RLs) between the gNB and nodes, and SLs between two different nodes are setup for measuring distances between them with transmitted positioning reference signals (PRSs). The estimation can be based on radio-ranging techniques such as measuring time of arrival (ToA), observed time difference of arrival (OTDoA), round trip time (RTT), reference signal received power (RSRP), angle-of- departure and arrival (AoD and AoA), etc.

These location estimates can be handled in a centralized or distributed manner. In a centralized manner, all distance estimates are reported to a location server (LCS), which can then detect the locations of TNs in a joint manner and send back these locations. In a distributed manner, each node can broadcast information about its own location estimates for other nodes to be able to estimate their locations using observations on SLs, and these location estimates are iteratively exchanged and updated until they are converged. For both manners, the location information is obtained based on a number of distance estimates on different RLs and SLs. Summary

An objective of examples of the invention is to provide a solution which mitigates or solves the drawbacks and problems of conventional solutions such as problems related to positioning accuracy for CoP.

Another objective of examples of the invention is to improve positioning accuracy for SL based CoP by providing quality metrics associated with estimated positions of client devices.

The above and further objectives are solved by the subject matter of the independent claims. Further examples of the invention can be found in the dependent claims.

According to a first aspect of the invention, the above mentioned and other objectives are achieved with a first client device for a communication system, the first client device being configured to estimate a position of a second client device based on a measured sidelink positioning reference signal received from the second client device; determine a quality metric associated with the estimated position of the second client device based on the measured sidelink positioning reference signal; and transmit a positioning message to a network node, the positioning message indicating the estimated position of the second client device and the quality metric.

An advantage of the first client device according to the first aspect is that when a position is estimated for a second client device, an indication of the quality of this estimation is also determined and shared together with the estimated position. By sharing the quality of the estimation with the network node, the network node can determine the position of the second client device more accurately. The network node may e.g. weight different estimated positions of the second client device from different first client devices based on the qualities of the respective estimations. The accuracy of the positioning can thereby be improved, and the positioning can be made more robust such that it can be used under varying channel conditions and with nodes equipped with different positioning accuracy-capabilities.

In an implementation form of a first client device according to the first aspect, the quality metric indicates a positioning accuracy of the estimated position of the second client device.

An advantage with this implementation form is that it allows the network node to compare the positioning accuracy of different estimated positions and give a higher weight to estimated positions with higher positioning accuracy. The accuracy of the positioning can thereby be improved, and the cooperative positioning can be made more robust.

In an implementation form of a first client device according to the first aspect, the positioning accuracy is based on one or more in the group comprising: a signal-to-noise ratio, a signal-to- interference plus noise ratio, and a normalized noise power of the measured sidelink positioning reference signal.

An advantage with this implementation form is that the positioning accuracy can be based on well-known quality measurements, thereby simplifying the implementation.

In an implementation form of a first client device according to the first aspect, the first client device is further configured to receive a configuration message from the network node, the configuration message indicating that the quality metric is to be reported to the network node.

An advantage with this implementation form is that the network node can configure the first client device to provide quality metrics, thereby improving the flexibility of the present solution.

In an implementation form of a first client device according to the first aspect, the configuration message further indicates a set of allowed quality metric types to be reported to the network node; and the first client device is further configured to select a quality metric type among the set of allowed quality metric types to be reported to the network node.

An advantage with this implementation form is that that the network node can further dynamically configure the types of quality metric which can be report, while giving the first client device the freedom to select among the allowed types, thereby further improving the flexibility of the present solution.

In an implementation form of a first client device according to the first aspect, the first client device and/or the second client device is an anchor node or a target node.

According to a second aspect of the invention, the above mentioned and other objectives are achieved with a network node for a communication system, the network node being configured to receive a set of positioning messages from a set of first client devices configured to communicate in a set of sidelinks, each positioning message indicating an estimated position of a second client device and a quality metric associated with the estimated position of the second client device; and determine a position of the second client device based on the set of positioning messages.

An advantage of the network node according to the second aspect is that the network node for each estimated position of the second client device also receives an indication of the quality of the estimation. By considering the quality of each estimation, the network node can determine the position of the second client device more accurately. The network node may e.g. weigh the estimated positions of the second client device from the set of first client devices based on the quality of the respective estimations. The accuracy of the positioning can thereby be improved, and the positioning can be made more robust such that it can be used in varying channel conditions.

In an implementation form of a network node according to the second aspect, the network node is further configured to determine a set of weights based on the set of positioning messages, each weight indicating a weight factor for each estimated position of the second client device; and determine the position of the second client device based on the set of weights and the set of positioning messages.

An advantage with this implementation form is that it allows the network node to compare the different estimated positions based on the set of weights. The accuracy of the positioning can thereby be improved, and the positioning can be made more robust.

In an implementation form of a network node according to the second aspect, each quality metric indicates a positioning accuracy of an estimated position of the second client device.

An advantage with this implementation form is that it allows the network node to compare the positioning accuracy of different estimated positions and give a higher weight to estimated positions with higher positioning accuracy. The accuracy of the positioning can thereby be improved, and the positioning can be made more robust.

In an implementation form of a network node according to the second aspect, the positioning accuracy is based on one or more in the group comprising: a signal-to-noise ratio, a signal-to- interference plus noise ratio, and a normalized noise power of a measured sidelink positioning reference signal received from the second client device.

An advantage with this implementation form is that the positioning accuracy can be based on well-known quality measurements, thereby simplifying the implementation.

In an implementation form of a network node according to the second aspect, the network node is further configured to transmit a configuration message to a first client device in the set of first client devices, the configuration message indicating that the quality metric is to be reported to the network node.

An advantage with this implementation form is that the network node can configure the first client device to provide quality metrics, thereby improving the flexibility of the present solution.

In an implementation form of a network node according to the second aspect, the configuration message further indicates a set of allowed quality metric types to be reported to the network node.

An advantage with this implementation form is that the network node can further dynamically configure the types of quality metric which can be report, thereby further improving the flexibility of the present solution.

In an implementation form of a network node according to the second aspect, the network node is further configured to activate or deactivate a sidelink in the set of sidelinks based on the set of positioning messages.

An advantage with this implementation form is that the number of sidelinks and hence the associated time-frequency resources needed can be optimized based on the reported quality metrics. The overall transmission-reporting latency in the positioning procedure can thereby be reduced.

In an implementation form of a network node according to the second aspect, the network node is further configured to adapt a transmission power for a sidelink in the set of sidelinks based on the set of positioning messages. An advantage with this implementation form is that the transmission powers for sidelinks can be optimized based on the reported quality metrics. The overall interference situation in the system can thereby be improved. Further, the power consumption in the client device can also be reduced.

In an implementation form of a network node according to the second aspect, the network node is further configured to allocate a sidelink to the set of sidelinks based on the set of positioning messages.

An advantage with this implementation form is that the number of sidelinks and hence the associated time-frequency resources needed can be optimized based on the reported quality metrics. The overall transmission-reporting latency in the positioning procedure can thereby be reduced.

In an implementation form of a network node according to the second aspect, the network node comprises a location server.

In an implementation form of a network node according to the second aspect, the network node is a gNB or a transmitting and receiving point.

According to a third aspect of the invention, the above mentioned and other objectives are achieved with a method for a first client device, the method comprises estimating a position of a second client device based on a measured sidelink positioning reference signal received from the second client device; determining a quality metric associated with the estimated position of the second client device based on the measured sidelink positioning reference signal; and transmitting a positioning message to a network node, the positioning message indicating the estimated position of the second client device and the quality metric.

The method according to the third aspect can be extended into implementation forms corresponding to the implementation forms of the first client device according to the first aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the first client device.

The advantages of the methods according to the third aspect are the same as those for the corresponding implementation forms of the first client device according to the first aspect. According to a fourth aspect of the invention, the above mentioned and other objectives are achieved with a method for a network node, the method comprises receiving a set of positioning messages from a set of first client devices configured to communicate in a set of sidelinks, each positioning message indicating an estimated position of a second client device and a quality metric associated with the estimated position of the second client device; and determining a position of the second client device based on the set of positioning messages.

The method according to the fourth aspect can be extended into implementation forms corresponding to the implementation forms of the network node according to the second aspect. Hence, an implementation form of the method comprises the feature(s) of the corresponding implementation form of the network node.

The advantages of the methods according to the fourth aspect are the same as those for the corresponding implementation forms of the network node according to the second aspect.

The invention also relates to a computer program, characterized in program code, which when run by at least one processor causes said at least one processor to execute any method according to examples of the invention. Further, the invention also relates to a computer program product comprising a computer readable medium and said mentioned computer program, wherein said computer program is included in the computer readable medium, and comprises of one or more from the group: ROM (Read-Only Memory), PROM (Programmable ROM), EPROM (Erasable PROM), Flash memory, EEPROM (Electrically EPROM) and hard disk drive.

Further applications and advantages of the examples of the invention will be apparent from the following detailed description.

Brief Description of the Drawings

The appended drawings are intended to clarify and explain different examples of the invention, in which:

- Fig. 1a-b show an example of a cooperative positioning group and a hidden node;

- Fig. 2 shows a client device according to an example of the invention;

- Fig. 3 shows a method for a first client device according to an example of the invention;

- Fig. 4 shows a network node according to an example of the invention; - Fig. 5 shows a method for a network node according to an example of the invention;

- Fig. 6 shows a communication system according to an example of the invention;

- Fig. 7 shows signaling for positioning according to an example of the invention;

- Fig. 8 shows signaling for configuration of positioning according to an example of the invention.

Detailed Description

Conventional cooperative positioning (CoP) procedures comprise three phases:

• An initial phase including exchanging positioning capabilities from nodes to a location server (LCS), transferring assistance data from the LCS to nodes, and resource allocations for transmission and reception.

• A second phase including transmitting positioning reference signals (PRSs) and measuring PRSs to estimate e.g. time of arrival (ToA), observed time difference of arrival (OTDoA), round trip time (RTT), reference signal received power (RSRP), angle-of-departure and arrival (AoD and AoA) etc.

• A third phase including reporting of measurements and/or position estimates to the LCS for processing.

Although conventional solutions have considered CoP procedures, how a LCS, or a node implementing similar functionality, uses the measured and reported distance estimates (or other measurements that can be transferred into distances) from cooperative nodes to accurately determine the position of a target node has not been addressed.

A potential issue is that distance estimates from different nodes can yield quit different error levels, even for the same distance between two nodes. These errors can depend on interference levels caused by e.g. a hidden node and/or channel fadings on the SLs, and/or the type of estimation algorithms implemented in different nodes etc. If these differences in estimation errors are not considered at the LCS in a centralized CoP scheme, the positioning accuracy can be degraded. Further, the same issue exists when the CoP is implemented in a distributed scheme, where each node is estimating its own locations with many different distance measurements obtained on RLs and SLs, but with different error levels.

An effect of interference from a hidden node on distance estimates is illustrated with reference to Figs. 1a-b. The example in Figs. 1a-b shows a CoP group (CoPG) comprising of a pico radio resource unit pRUU, an anchor node AN with known location, and a target node TN to be located. A hidden node is located close to the target node TN, causing interference in the area where the target node TN is located. In this example, one can have four distance estimates: d ₂₀ and d ₂₁ are estimates for distance d ₂ between the pico radio resource unit pRRU and the target node TN, d ₃₀ and d ₃₁ are estimates for distance d ₃ between the target TN and the anchor node AN: d _2k = d ₂ + n _2k , d ₂ = (x ₀ - x ₂ + (To - T2) ² ,

Due to the existing hidden node, estimates d ₂₀ and d ₃₀ can bear larger estimation errors than estimates d ₂₁ and d ₃₁ .

A maximum likelihood (ML) estimation of the target node TN location is to solve,

( Z ₂ ,y 17 ₂ _ Eq. 2 -

As seen, variances of effective estimation errors, e.g. o _2k and o _3k , play an important role in the cost function to be minimized, and the inverses1/o- _2k and 1/o- _3k are denoted as weights. If these weights are not reported to the LCS, without any priori information, the LCS may treat the reported estimates with equal importance, and implement a suboptimal estimate according to x ₂ ,y ₂ ) = argmin{(d ₂ - d ₂₀ ) ² + (d ₂ - d ₂₁ ) ² + (d ₃ - d ₃₀ ) ² + (d ₃ - d ₃₁ ) ² }. Eq. 3

Since Eq.3 is suboptimal, this may cause significant estimation errors, especially when the weights are quite different. Thus, only reporting distance estimates without any indication their qualities may not be enough to accurately determine the location of a target node TN.

An objective of examples of the invention is therefore to provide a solution which mitigates or solves these problems related to positioning accuracy for CoP. According to examples of the invention a solution is provided which allows client devices to provide both an estimated position for another client device and a quality metric associated with the estimated position. The quality metric may indicate the accuracy of the estimated position and can thereby help a network node to determine the position of the other client device more accurately.

Fig. 2 shows a client device according to an example of the invention. The client device may what in this disclosure is denoted a first client device 100 or a second client device 100'. In the example shown in Fig. 2, the client device 100, 100' comprises a processor 102, a transceiver 104 and a memory 106. The processor 102 is coupled to the transceiver 104 and the memory 106 by communication means 108 known in the art. The client device 100, 100' further comprises an antenna or antenna array 110 coupled to the transceiver 104, which means that the client device 100, 100' is configured for wireless communications in a communication system.

The processor 102 may be referred to as one or more general-purpose CPU, one or more digital signal processor (DSP), one or more application-specific integrated circuit (ASIC), one or more field programmable gate array (FPGA), one or more programmable logic device, one or more discrete gate, one or more transistor logic device, one or more discrete hardware component, one or more chipset. The memory 106 may be a read-only memory, a random access memory, or a non-volatile random access memory (NVRAM). The transceiver 104 may be a transceiver circuit, a power controller, an antenna, or an interface which communicates with other modules or devices. In examples, the transceiver 104 may be a separate chipset, or it is integrated with processor in one chipset. While in some implementations, the transceiver 104 the memory 106 and the processor 102 are integrated in one chipset.

That the client device 100, 100' is configured to perform certain actions can in this disclosure be understood to mean that the client device 100, 100' comprises suitable means, such as e.g. the processor 102 and the transceiver 104, configured to perform said actions.

With reference to Fig. 2 and 6, according to examples of the invention the first client device 100 is configured to estimate a position of a second client device 100' based on a measured sidelink positioning reference signal (SL-PRS) 510 received from the second client device 100'. The first client device 100 is further configured to determine a quality metric associated with the estimated position of the second client device 100' based on the measured SL-PRS 510. The first client device 100 is further configured to transmit a positioning message 520 to a network node 300, the positioning message 520 indicating the estimated position of the second client device 100' and the quality metric.

Fig. 3 shows a flow chart of a corresponding method 200 which may be executed in a first client device 100, such as the one shown in Fig. 2. The method 200 comprises estimating 202 a position of a second client device 100' based on a measured SL-PRS 510 received from the second client device 100'. The method 200 further comprises determining 204 a quality metric associated with the estimated position of the second client device 100' based on the measured SL-PRS 510. The method 200 further comprises transmitting 206 a positioning message 520 to a network node 300, the positioning message 520 indicating the estimated position of the second client device 100' and the quality metric. Fig. 4 shows a network node 300 according to an example of the invention. In the example shown in Fig. 4, the network node 300 comprises a processor 302, a transceiver 304 and a memory 306. The processor 302 is coupled to the transceiver 304 and the memory 306 by communication means 308 known in the art. The network node 300 may be configured for both wireless and wired communications in a communication system. The wireless communication capability is provided with an antenna or antenna array 310 coupled to the transceiver 304, while the wired communication capability is provided with a wired communication interface 312 coupled to the transceiver 304.

The processor 302 may be referred to as one or more general-purpose CPU, one or more digital signal processor (DSP), one or more application-specific integrated circuit (ASIC), one or more field programmable gate array (FPGA), one or more programmable logic device, one or more discrete gate, one or more transistor logic device, one or more discrete hardware component, one or more chipset. The memory 306 may be a read-only memory, a random access memory, or a non-volatile random access memory (NVRAM). The transceiver 304 may be a transceiver circuit, a power controller, an antenna, or an interface which communicates with other modules or devices. In examples, the transceiver 304 may be a separate chipset, or it is integrated with processor in one chipset. While in some implementations, the transceiver 304 the memory 306 and the processor 302 are integrated in one chipset.

That the network node 300 is configured to perform certain actions can in this disclosure be understood to mean that the network node 300 comprises suitable means, such as e.g. the processor 302 and the transceiver 304, configured to perform said actions.

With reference to Fig. 4 and 6, according to examples of the invention the network node 300 is configured to receive a set of positioning messages 520a, 520b,..., 520n from a set of first client devices 100a, 100b,..., 100n configured to communicate in a set of SLs Sa, Sb,..., Sn. Each positioning message 520n indicating an estimated position of a second client device 100' and a quality metric associated with the estimated position of the second client device 100'. The network node 300 is further configured to determine a position of the second client device 100' based on the set of positioning messages 520a, 520b,..., 520n.

Fig. 5 shows a flow chart of a corresponding method 400 which may be executed in a network node 300, such as the one shown in Fig. 4. The method 400 comprises receiving 402 a set of positioning messages 520a, 520b,..., 520n from a set of first client devices 100a, 100b,..., 100n configured to communicate in a set of SLs Sa, Sb,... , Sn. Each positioning message 520n indicating an estimated position of a second client device 100' and a quality metric associated with the estimated position of the second client device 100'. The method 400 further comprises determining 404 a position of the second client device 100' based on the set of positioning messages 520a, 520b,..., 520n.

Fig. 6 shows a communication system 500 according to an example of the invention. The communication system 500 comprises a network node 300, a set of first client devices 100a, 100b,..., 100n and a second client device 100' configured to communicate with each other over air interfaces, e.g. over air interfaces as defined according to 3GPP new radio. With reference to Fig. 6, the network node 300 may be a gNB or a TRP and may communicate with the set of first client devices 100a, 100b,..., 100n and the second client device 100' over Uu links, while the set of first client devices 100a, 100b,..., 100n and the second client device 100' may communicate with each other over SLs Sa, Sb,..., Sn.

The network node 300, the set of first client devices 100a, 100b, ... , 10On and the second client device 100' may belong to a CoP group (CoPG) and may have different roles in the CoPG. The network node 300 may comprise a location server and be configured to determine a position of a client device in the CoPG based on CoP information from the other client devices in the CoPG. A client device with an unknown position/location may be referred to as a target node TN, while a client device with a known position may be referred to as an anchor node AN. Any one of the first client devices 100a, 100b, ..., 100n and the second client device 100' may be an anchor node AN or a target node TN.

In the example shown in Fig. 6, it is assumed that the set of first client devices 100a, 100b,..., 100n are anchor nodes ANs and the second client device 100' is a target node TN for which a position is to be estimated by the network node 300 based on input from the set of first client devices 100a, 100b,... , 100n. According to examples of the invention each first client device 100 determines an estimated position of the second client device 100' and a quality metric associated with the estimated position based on a measured SL-PRS 510 transmitted by the second client device 100'. Each first client device 100 further transmits a positioning message 520 to the network node 300 indicating the determined estimated position and associated quality metric. In this way, the network node 300 receives a set of positioning messages 520a, 520b,..., 520n from the set of first client devices 100a, 100b,..., 100n. Based on the received set of positioning messages 520a, 520b,..., 520n, the network node 300 determines a position of the second client device 100'. The network node 300 may consider each indicated estimated position, as well as its respective quality metric, when determining the position of the second client device 100'. This allows the network node 300 to e.g. weight the different estimated positions based on their quality and give a higher weight to estimated positions with higher quality. The position of the second client device 100' can thereby be determined with higher accuracy.

Fig. 7 shows signaling between a first client device 100, a second client device 100', and a network node 300 for positioning of the second client device 100' according to an example of the invention. The first client device 100 is an anchor node AN and the second client device 100' is a target node TN. However, as described with reference to Fig. 6, the first client device 100 and/or the second client device 100' may in examples be an anchor node AN or a target node TN. Furthermore, the network node 300 may comprise a location server and/or be a gNB or a TRP.

In step I in Fig. 7, the second client device 100' transmits a SL-PRS 510. The SL-PRS 510 may be configured and transmitted in a conventional way, e.g. transmitted using broadcast or groupcast and further be transmitted periodically

In step II in Fig. 7, the first client device 100 receives and measures the SL-PRS 510 transmitted by the second client device 100'. Based on the measured SL-PRS 510, the first client device 100 estimates a position of the second client device 100' and determines a quality metric associated with the estimated position of the second client device 100', in step III in Fig. 7.

The first client device 100 may estimate the position of the second client device 100' based on the measured SL-PRS 510 in a conventional way, e.g. using an estimation algorithm configured or implemented in the first client device 100. The estimation may be based on one or more estimations of ToA and TDoA, AoA, AoD, RSRP, RTT etc. from the SL-PRS 510.

The first client device 100 may determine the quality metric associated with the estimated position based on information indicating the quality of the measured SL-PRS 510, e.g. information indicating channel conditions and/or interference associated with the SL-PRS 510. The determined quality metric may indicate a positioning accuracy of the estimated position of the second client device 100'. In examples, the positioning accuracy is based on one or more in the group comprising: a signal-to-noise ratio (SNR), a signal-to-interference plus noise ratio (SINR), and a normalized noise power of the measured SL-PRS 510 received from the second client device 100'. The first client device 100 may e.g. determine the SNR, the SINR and/or the normalized noise power of the measured SL-PRS 510 and then determine the quality metric based on these signal to noise related measurements. In step IV in Fig. 7, the first client device 100 transmits a positioning message 520 to the network node 300. The positioning message 520 indicates the estimated position of the second client device 100' and the quality metric associated with the estimated position of the second client device 100' determined in step III.

The network node 300 receives the positioning message 520 from the first client device 100 in step V in Fig. 7. The network node 300 hence obtains the estimated position of the second client device 100' and the quality metric associated with the estimated position of the second client device 100' as determined by the first client device 100. In a similar way, the network node 300 can receive further positioning messages 520 from other first client devices 100 indicating their estimated positions and quality metrics for the second client device 100', as shown in Fig. 7. Thus, the network node 300 receives a set of positioning messages 520a, 520b, ... , 520n from a set of first client devices 100a, 100b, ... , 10On configured to communicate in a set of SLs Sa, Sb,..., Sn. Each positioning message 520n indicates an estimated position of the second client device 100' and a quality metric associated with the estimated position of the second client device 100'.

In step VI in Fig. 7, the network node 300 determines a position of the second client device 100' based on the set of positioning messages 520a, 520b,..., 520n. Step VI may comprise the network node 300 determining the position of the second client device 100' based on the estimated positions of the second client device 100' indicated in the set of positioning messages 520a, 520b,..., 520n, while considering the quality metrics also indicated in the set of positioning messages 520a, 520b,..., 520n.

In examples, the network node 300 first determines a set of weights based on the set of positioning messages 520a, 520b,..., 520n, each weight indicating a weight factor for each estimated position of the second client device 100'.. The network node 300 then determines the position of the second client device 100' based on the set of weights and the set of positioning messages 520a, 520b,..., 520n. The weight factor for each estimated position may be determined from one or more of the quality metrics associated with the estimated positions in current transmissions and also previous transmissions.

The set of positioning messages 520a, 520b,..., 520n provides the network node 300 with valuable information about the condition of the SLs Sa, Sb,..., Sn. The network node 300 may use this information to e.g. change SL configuration for one or more client devices, as indicated by the optional step VII in Fig. 7. In optional step VII in Fig. 7, the network node 300 may e.g. activate or deactivate a SL in the set of SLs Sa, Sb,..., Sn based on the set of positioning messages 520a, 520b,..., 520n. The network node 300 may further adapt a transmission power for a SL in the set of SLs Sa, Sb, ... , Sn based on the set of positioning messages 520a, 520b,..., 520n. The network node 300 may further allocate a SL to the set of SLs Sa, Sb,..., Sn based on the set of positioning messages 520a, 520b,..., 520n. Depending on the type of action taken and the affected client devices, the network node 300 may provide information about the change to the relevant client devices, as indicated with dashed arrows in Fig. 7. For example, if the quality metric provided by the first client device 100 indicates that the quality of the SL between the first client device 100 and the second client device 100' is poor, the network node 300 may deactivate the SL between the first client device 100 and the second client device 100' or increase the transmission power for the SL.

Fig. 8 shows signaling between a first client device 100 and a network node 300 for configuration of positioning according to an example of the invention. Although only the first client device 100 is shown in Fig. 8, the network node 300 may use the same signaling to configure a set of first client devices 100a, 100b,..., 100n and/or the second client device 100'.

In step I in Fig. 8, the network node 300 transmits a configuration message 530 to the first client device 100. The configuration message 530 indicates that the quality metric is to be reported to the network node 300, i.e. that when the first client device 100 provides an estimated position, the quality metric associated with the estimated position should also be provided. In examples, the configuration message 530 further indicates a set of allowed quality metric types to be reported to the network node 300. In this way, the network node 300 can configure the first client device 100 to provide one or more specific quality metric types. The set of allowed quality metric types may be specified by the 3GPP standard, calculated by the node itself, or similar.

The indication in the configuration message 530 may be implemented using one or more bits. For example, using one bit, a “0” may indicate that the quality metric is not to be reported and a “1” may indicate that the quality metric is to be reported. Using m number of bits, a “0” may indicate that the quality metric is not to be reported, while n (0<n<2m-1) may indicate the type of quality metric to be reported.

The first client device 100 receive the configuration message 530 from the network node 300 in step II in Fig. 8, and hence obtains the indication that the quality metric is to be reported to the network node 300. In step III in Fig. 8, the first client device 100 estimates a position of a second client device 100' and further determines a quality metric associated with the estimated position of the second client device 100' based on the indication that the quality metric is to be reported. The estimation of the position and the determination of the quality metric may be performed as described with reference to step III in Fig. 7. When the configuration message 530 further indicates a set of allowed quality metric types to be reported to the network node 300. The first client device 100 further selects a quality metric type among the set of allowed quality metric types to be reported to the network node 300. The first client device 100 then determines the quality metric based on the selected type.

In step IV in Fig. 8, the first client device 100 transmits the positioning message 520 to the network node 300 indicating the estimated position of the second client device 100' and the quality metric associated with the estimated position of the second client device 100'. When the network node 300 has indicates a set of allowed quality metric types to be reported, the first client device 100 reports the selected type of quality metric. In examples, the quality metric indicated in the positioning message 520 may hence be one of the quality metric types in the set of allowed quality metric types.

A number of different types of quality metrics may be used without deviating from the scope of the invention. Below follows a description of one type of quality metric.

Considering the received signal model at one receiving node, where time delay A=0 represent the first received path, i.e. line-of-sight (LoS), and other values of A>0 denote non-line-of-sight (NLoS) paths:

This node can estimate a distance d, denoted as d , and with which, the reconstructed signal can be subtracted from received signal as

Depending on interference plus noise power, and this node’s capability of estimating other parameters including /t _A , {A} and d, the effective noise power E'{||n|| ² } can vary, where £"{■} denotes the expectation operator which averages the noise power over all received PRS samples. Advanced network nodes may estimate all NLoS components and subtract them from the received signal, which yields a smaller residual power from Eq. 5. On the other hand, low-cost network nodes with simple estimation algorithms may only estimate the strongest path and then subtract it, which can yield a higher residual power. According to this, a quality metric can be specified as the effective noise power E'{||n|| ² }, which is further normalized by the received signal power E'{||r|| ² }:

The normalization factor, i.e., the denominator in Eq. 6 can be replaced by other metrics such as the total channel power£ _s |/i _s | ² , or even the power of the strongest channel tap that equals

Other types of quality metric can also be used including but not limited to e.g. the inverse of estimate SNR, or the inverse of estimated SINR

The first client device 100 and the second client device 100' herein may be denoted as a user device, a user equipment (UE), a mobile station, a transmission and reception point (TRP), a road side unit (RSU), an internet of things (loT) device, a sensor device, a wireless terminal and/or a mobile terminal, is enabled to communicate wirelessly in a wireless communication system, sometimes also referred to as a cellular radio system. The UEs may further be referred to as mobile telephones, cellular telephones, computer tablets or laptops with wireless capability. The UEs in this context may be, for example, portable, pocket-storable, hand-held, computer-comprised, or vehicle-mounted mobile devices, enabled to communicate voice and/or data, via the radio access network, with another entity, such as another receiver or a server. The UE can be a Station (STA), which is any device that contains an IEEE 802.11- conformant Media Access Control (MAC) and Physical Layer (PHY) interface to the Wireless Medium (WM). The UE may also be configured for communication in 3GPP related LTE and LTE-Advanced, in WiMAX and its evolution, and in fifth generation (5G) wireless technologies, such as New Radio (NR). The network node 300 herein may be denoted as a radio network access node, an access network access node, an access point, or a base station, e.g. a Radio Base Station (RBS), which in some networks may be referred to as transmitter, “gNB”, “gNodeB”, “eNB”, “eNodeB”, “NodeB” or “B node”, depending on the technology and terminology used. The radio network access nodes may be of different classes such as e.g. macro eNodeB, home eNodeB or pico base station, based on transmission power and thereby also cell size. The radio network access node can be a Station (STA), which is any device that contains an IEEE 802.11- conformant Media Access Control (MAC) and Physical Layer interface to the Wireless Medium. The radio network access node may also be a base station (BS) corresponding to the 5G wireless systems.

Furthermore, any method according to examples of the invention may be implemented in a computer program, having code means, which when run by processing means causes the processing means to execute the steps of the method. The computer program is included in a computer readable medium of a computer program product. The computer readable medium may comprise essentially any memory, such as a ROM (Read-Only Memory), a PROM (Programmable Read-Only Memory), an EPROM (Erasable PROM), a Flash memory, an EEPROM (Electrically Erasable PROM), or a hard disk drive.

Moreover, it is realized by the skilled person that examples of first client device 100, the second client device 100' and the network node 300 comprise the necessary communication capabilities in the form of e.g., functions, means, units, elements, etc., for performing the solution. Examples of other such means, units, elements and functions are: processors, memory, buffers, control logic, encoders, decoders, rate matchers, de-rate matchers, mapping units, multipliers, decision units, selecting units, switches, interleavers, de-interleavers, modulators, demodulators, inputs, outputs, antennas, amplifiers, receiver units, transmitter units, DSPs, MSDs, TCM encoder, TCM decoder, power supply units, power feeders, communication interfaces, communication protocols, etc. which are suitably arranged together for performing the solution.

Especially, the processor(s) of the first client device 100, the second client device 100' and the network node 300 may comprise, e.g., one or more instances of a Central Processing Unit (CPU), a processing unit, a processing circuit, a processor, an Application Specific Integrated Circuit (ASIC), a microprocessor, or other processing logic that may interpret and execute instructions. The expression “processor” may thus represent a processing circuitry comprising a plurality of processing circuits, such as, e.g., any, some or all of the ones mentioned above. The processing circuitry may further perform data processing functions for inputting, outputting, and processing of data comprising data buffering and device control functions, such as call processing control, user interface control, or the like.

Finally, it should be understood that the invention is not limited to the examples described above, but also relates to and incorporates all examples within the scope of the appended independent claims.