WO2023141986A1

WO2023141986A1 - Client device and network access node for reception of prs and pdcch/pdsch

Info

Publication number: WO2023141986A1
Application number: PCT/CN2022/074783
Authority: WO
Inventors: Thorsten Schier; Jun Li; Yan Cheng
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2022-01-28
Filing date: 2022-01-28
Publication date: 2023-08-03

Abstract

The disclosure relates to a client device (100) and a corresponding network node (200). The client device (100) for a communication system (500), comprises a processor configured to receive, from a network node, a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in a same cell that overlap in time with the PRS; and to extract from the plurality of OFDM symbols the one or more additional channels that overlap in time with the PRS.

Description

CLIENT DEVICE AND NETWORK ACCESS NODE FOR RECEPTION OF PRS AND PDCCH/PDSCH

Technical Field

Embodiments of the disclosure relate to a client device and a network access node for positioning reference signal transmission and reception as well as control and data channel transmission and reception. Furthermore, embodiments of the disclosure also relate to corresponding methods and a computer program.

Background

In 3GPP 5G communication systems, also called new radio (NR) , as part of the ongoing standardization work for ultra-reliable low latency communication (URLLC) , features and mechanisms for enhanced propagation delay compensation (PDC) are defined in the 3GPP specifications of Release-17. These features will be helpful to achieve a tighter synchronisation between different nodes in the network. Many wide area or factory automation applications and use cases, such as electrical utilities, network and UE test devices, some VIAPA services as seen in TS22.263, trading and payment systems, 5G smart watches, etc., can be enabled with help of these advanced features.

The 3GPP working group RAN1 studied various concepts to achieve an enhanced propagation delay compensation and in the RAN1#107-e meeting, two methods have been agreed:

1. Support RTT-based PDC method

2. Support PDC method based on legacy TA-based mechanism

Prior to the above decision, 3GPP made an extensive evaluation of the achievable accuracy with different methods. It was found that the second approach above only can deliver sufficient performance in basic scenarios with loose requirements. For all applications with higher synchronisation demands, the first method (RTT-based PDC) should be used, where RTT is an abbreviation for round trip time.

In RTT-based PDC, the User Equipment (UE) can measure the Rx-Tx time difference with help of a downlink reference signal and then report the measured time difference back to the network for network based PDC. In RAN1#104b-e it has been agreed that as reference signal, the positioning reference signal (PRS) or the channel state information reference signal (CSI-RS) for tracking can be used.

To employ PRS would be a more obvious and a straight forward choice compared to CSI-RS for tracking, since it has been designed from the beginning with the purpose facilitate Rx-Tx time difference measurements. However, since the PRS has been specified in a different sub-topic of NR, i.e. in NR positioning, there will come up problems when applying the existing procedures around PRS directly for PDC and especially when URLLC services have to be supported with their stringent requirements on latency and reliability.

In positioning, the UE needs to receive PRSs from different cells in order to obtain multiple Rx-Tx time differences, which are required for enabling the positioning calculations. Therefore, in NR positioning, the UE generally receives PRS not only from the serving cell, but also from neighbouring cells. The 3GPP specification has therefore defined measurement gaps for the reception of the various PRSs. During these gaps, the UE will only measure PRS and will not receive any other DL signals or channels, such as PDCCH (physical downlink control channel) or PDSCH (physical downlink shared channel) . In NR positioning it is also possible that the UE measures PRS outside a measurement gap, but also here multiple PRS need to be received (which typically are located on different frequencies) and it is not possible to receive signals or channels other than PRS at those time-instances (i.e. at those OFDM symbols) when PRS is received. The reception of such signals and channels is precluded by the 3GPP specifications. This is illustrated in the example of Figure 1, where PRS is located on symbol #4 and during this symbol #4, no other reception is possible i.e. the PDSCH that is scheduled orthogonally in frequency to the PRS cannot be received during symbol #4 (this in indicated with an “x” on the corresponding resources) if the PRS priority configured by gNB in Rel-17 positioning is higher. Otherwise, the PRS on symbol #4 will not be measured by the UE.

For PDC, if PRS is used to measure the Rx-Tx time difference at the UE side, it is common understanding that PRS only needs to be received from the serving cell since PRS measurement from neighbor cells is only used for positioning, it is not useful for PDC. Therefore no measurements on PRS from neighbor cells are needed and consequently, measurement gaps are not required. This can be seen from an agreement in RAN1#107b-e, which says that “Measurement gaps should not be mandatory for a UE to process PRS for PDC purposes” . Without measurement gaps, other signals and channels as e.g. PDCCH or PDSCH could be scheduled to overlap in time with PRS. But the current specification in positioning (as shown by the example of Figure 1) would preclude their reception at a given OFDM symbol, if this OFDM symbol also contains PRS and if positioning procedure is reused exactly without any changes.

Summary

An objective of embodiments of the disclosure is to provide a solution for positioning reference signal transmission and reception as well as control and data channel transmission and reception will be apparent from the following detailed description.

It is an objective of the present disclosure to provide improved devices and methods for positioning reference signal transmission and reception as well as control and data channel transmission and reception. The foregoing and other objectives are achieved by the subject matter of the independent claims. Further implementation forms are apparent from the dependent claims, the description and the figures.

According to a first aspect, a client device 100 is provided for a communication system, wherein the client device comprises a processor configured to receive, from a network node, a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in the same cell overlapping in time with the PRS. The client device is further configured to extract from the plurality of OFDM symbols the one or more additional channels that overlap in time with the PRS.

According to another embodiment the one or more additional channels are one or more of a Physical Downlink Control Channel, PDCCH, and Physical Downlink Shared Channel, PDSCH. This allows services with demanding requirements, such as very high reliability, to be supported together with propagation delay compensation enhancements based on RRT methods.

According to another embodiment the client device of any preceding claim is further configured to receive a trigger message comprising instructions for the client device to receive PRS instead of one or more of the additional channels. This allows with low implementation cost and low specification effort to dynamically switch between the receptions of the additional channel and the PRS. The network device can trigger the reception of the PRS on demand when it is needed, in example when propagation delay compensation calculations shall be performed. Without the trigger the UE can by default receive the additional channel that can be carrying an important URLLC service.

According to another embodiment the trigger message is a Downlink Control Information (DCI) , message. This gives the network the possibility to explicitly control when the PRS shall be received and the reception of the trigger is then decoupled from other operations which gives flexibility when and where to transmit the trigger.

According to another embodiment the trigger message is a Rx-Tx time difference report request. This is allows for an implicit triggering which is re-using an existing signalling mechanism and does therefore not increase the signalling overhead and has no significant impact on the specification effort.

According to another embodiment the client device is further configured to extract both the PRS and the one or more other channels from the plurality of OFDM symbols. This allows for a parallel reception of PRS and the additional channel (this is understand that both the additional channel and the PRS can be received together) . When the PRS signal needs to be received, e.g. for calculations needed for propagation delay compensation, also the additional channel can be correctly decoded. This allows the additional channel to carry URLLC services with ultra-high reliability requirements that are sensitive to decoding errors.

According to another embodiment the PRS and the other one or more overlapping channels overlap in time but not in frequency. This allows for a reception of the additional channel and PRS on the time-overlapping symbols with low implementation cost and low specification effort.

According to another embodiment the PRS and the one or more overlapping channels overlap in time and in frequency. This allows for a reception of the additional channel and PRS on the time-overlapping symbols and gives the network scheduler more freedom where the additional channel can be scheduled. It facilitates and efficient utilization of the available radio resources.

According to another embodiment the one or more overlapping channels comprise a demodulation reference signal, DMRS, wherein the DMRS is not overlapping in time and frequency with the PRS, further configured to perform rate matching around the PRS. This allows the scheduler to schedule the additional channel overlapping with PRS at relatively low implementation and specification cost. Both the PRS and the additional channel can be received by the UE without interfering each other.

According to another embodiment the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is not overlapping in time and frequency with the PRS, further configured to superimpose the PRS and the one or more overlapping channels. This allows the scheduler to schedule the additional channel overlapping with PRS at relatively low implementation and specification cost. Both the PRS and the additional channel can be received by the UE on the same resources.

According to another embodiment the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to prioritize the reception of the DMRS. The embodiment allows the scheduler full flexibility where to schedule the additional channel with respect to the locations of PRS, since the DMRS positions within the additional channel do not need impose a scheduling restriction. And the prioritization rule also resolves a potential ambiguity whether to transmit DMRS or PRS if they appear on the same resource.

According to another embodiment the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to prioritize the reception of the PRS. The embodiment allows the scheduler full flexibility where to schedule the additional channel with respect to the locations of PRS, since the DMRS positions within the additional channel do not impose a scheduling restriction. And the prioritization rule also resolves a potential ambiguity whether to transmit DMRS or PRS if they appear on the same resource.

According to another embodiment the client device is further configured to prioritize depending upon static rules. The static rules can be pre-defined in the specification and require little implementation and specification effort.

According to another embodiment the client device is further configured to prioritize depending upon semi-static rules, which can be signalled by radio resource control (RRS) parameters. This allows to adapt the prioritization but requires more specification effort and has also slightly more implementation impact as the static rules.

According to another embodiment the client device is further configured to prioritize depending upon dynamic rules, which can be explicitly signalled by DCI. This allows for very fast adaption of the prioritization but requires more effort in its realization than the semi-static rules.

According to another embodiment the client device is further configured to prioritize depending upon implicit rules. The benefit with this embodiment is that existing signalling methods are used, thus the specification and implementation effort is low and also there should not be extra signalling overhead needed.

According to another embodiment of the client device the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to not receive the PRS on any resource that is overlapping with the one or more overlapping channels

According to a second aspect, a network node 200 is provided for a communication system, wherein the network node comprises a processor configured to transmit, to a client device a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in a same cell that overlap in time with the PRS.

According to another embodiment the one or more additional channels are one or more of a Physical Downlink Control Channel, PDCCH, and Physical Downlink Shared Channel, PDSCH. This allows services with demanding requirements, such as very high reliability, to be supported together with propagation delay enhancements.

According to another embodiment the network node is further configured to transmit a trigger message comprising instructions for the client device (100) to receive PRS instead of one or more of the additional channels. The network device can trigger the reception of the PRS on demand when it is needed, in example when it needs to a perform propagation delay compensation calculation. Without the trigger the UE can by default receive the additional channel that can be carrying an important URLLC service.

According to another embodiment of the network node the trigger message is a Downlink Control Information (DCI) , message. This gives the network the possibility to explicitly control when the PRS shall be received and the reception of the trigger is then decoupled from other operation which gives flexibility when and where to transmit the trigger.

According to another embodiment of the network node the trigger message is a Rx-Tx time difference report request. This allows for an implicit triggering which is re-using an existing signalling mechanism and does therefore not increase the signalling overhead.

According to another embodiment of the network node, the network node being further configured to instruct the client device (100) to extract both the PRS and the one or more other channels from the plurality of OFDM symbols. This allows for a parallel reception of PRS and the additional channel. When the PRS signal needs to be received, e.g. for calculations needed for propagation delay compensation, the additional channel can then still be correctly decoded. This allows the additional channel to carry URLLC services with ultra-high reliability requirements.

According to another embodiment of the network node the PRS and the other one or more overlapping channels overlap in time but not in frequency. This allows for a transmission of the additional channel and PRS on the time-overlapping symbols. And their reception can be realized with low implementation cost and low specification effort.

According to another embodiment of the network node wherein the PRS and the one or more overlapping channels overlap in time and in frequency. This gives the scheduler flexibility and the available radio resources can be efficiently utilized.

According to another embodiment of the network node the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is not overlapping with the PRS, further configured to perform rate matching around the PRS. This gives the scheduler quite some flexibility since in general the additional channel and PRS can overlap, which facilities an efficient resource utilization. The network only needs to ensure that DMRS and PRS do not overlap. This kind of transmission enables very simple and cost efficient receivers while the utilization of the radio resource still is very good.

According to another embodiment of the network node the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is not overlapping in time and frequency with the PRS, further configured to superimpose the PRS and the one or more overlapping channels. This gives the scheduler quite some flexibility since in general the additional channel and PRS can overlap, which facilities an efficient resource utilization. The network only needs to ensure that DMRS and PRS do not overlap. This kind of transmission enables very simple and cost efficient receivers while the utilization of the radio resource still is very good.

According to another embodiment of the network node the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to prioritize the transmission of the DMRS and to instruct the client device (100) to prioritize the reception of the DMRS. This gives the scheduler the most flexibility since in general the additional channel and PRS can overlap, without the need to avoid DMRS overlapping with PRS. This kind of transmission enables very simple scheduling algorithms and optimum resource utilization. The receivers and the specification effort, on the other hand, are not expected to be as cost efficient as for the case where DMRS and PRS do not overlap.

According to another embodiment of the network node the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to prioritize the transmission of the PRS and to instruct the client device (100) to prioritize the reception of the PRS. This gives the scheduler the most flexibility since in general the additional channel and PRS can overlap, without the need to avoid DMRS overlapping with PRS. This kind of transmission enables very simple scheduling algorithms and optimum resource utilization. The receivers and the specification effort, on the other hand, are not expected to be as cost efficient as for the case where DMRS and PRS do not overlap.

According to another embodiment the network node is further configured to prioritize and to instruct the client device (100) depending upon static rules. The static rules can be pre-defined in the specification and require little implementation and specification effort.

According to another embodiment the network node is further configured to prioritize and to instruct the client device (100) depending upon semi-static rules, which can be signalled by radio resource control (RRS) parameters. This allows to adapt the prioritization but requires more specification effort and has also slightly more implementation impact as the static rules. According to another embodiment the network node is further configured to prioritize and to instruct the client device (100) depending upon dynamic rules, which can be explicitly signalled by DCI. This allows for very fast adaption of the prioritization but requires more effort in its realization than the semi-static rules.

According to another embodiment the network node is further configured to prioritize and to instruct the client device (100) depending upon implicit rules. The benefit with this embodiment is that existing signalling methods are used, thus the specification and implementation effort is low and also there should not be extra signalling overhead needed.

According to another embodiment of the network node the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to not transmit the PRS on any resource that is overlapping in time and frequency with the one or more time-overlapping channels.

According to a third aspect, a method 1100 of operating a client device 100 is provided wherein the method comprises receiving, from a network node, a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in a same cell that overlap in time with the PRS. The method further comprises extracting from the plurality of OFDM symbols the one or more additional channels that overlap in time with the PRS. Further embodiments are provided that allow the method 1100 to perform different methods comprising the different embodiments of the client device discussed above.

According to a fourth aspect, a method 1200 of operating a network node 200 is provided, wherein the method comprises transmitting, to a client device 100, a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in a same cell that overlap in time with the PRS. Further embodiments are provided that allow the method 1100 to perform different methods comprising the different embodiments of the network node discussed above.

According to fifth and sixth aspects, a computer program product comprising a computer-readable storage medium for storing program code which causes a computer or a processor to perform the method 1100 and the method 1200, when the program code is executed by the computer or the processor.

Brief Description of the Drawings

In the following, embodiments of the present disclosure are described in more detail with reference to the attached figures and drawings, in which:

Explanation: In figures 1-10, time frequency resources are illustrated by the rectangle grid between the horizontal time-axis and the vertical frequency-axis.

Fig. 1 illustrates the state of the art according to the current specification. For a given bandwidth part (BWP) , if one or more symbols contain PRS (as it is symbol #4 in the example) , no other signals and channels can be received in these symbol (s) . These non-receivable resources are market with “x” in this example. Furthermore, examples for time-frequency resources are depicted. These examples are also applicable for other figures;

Fig. 2a illustrates the client device behaviour for the received overlapping PDSCH;

Fig. 2b illustrates an attempt to avoid the demodulation performance degradation described by the example of Figure 2a.

Fig. 3 illustrates a selective reception of either PDSCH or PRS;

Fig. 4 illustrates a parallel transmission and reception of PRS and PDSCH when they are overlapping in time but not in frequency;

Fig. 5 illustrates the ambiguity when information bits of a PDSCH or PDCCH overlap with in time and frequency with PRS;

Fig. 6 illustrates the situation that the other channel (e.g. a PDSCH or a PDCCH) overlap in time and frequency with PRS, but the channel’s DMRS does not overlap with DMRS;

Fig. 7 illustrates the situation that some PRS overlap with data bits from the PDSCH and some other PRS overlap with DMRS from the PDSCH.

Fig. 8 illustrates one example to resolve the situation when some PRS overlap with data bits from the other channel and some other PRS overlap with DMRS from the other channel;

Fig. 9 shows another example to resolve the overlap between PRS and another channel such as PDCCH or PDSCH;

Fig. 10 gives a schematic overview of the embodiments disclosed in this invention.

Fig. 11 shows a workflow of a method of this invention.

Fig. 12 shows a workflow of another method of this invention.

In the following, identical reference signs refer to identical or at least functionally equivalent features.

Detailed Description of the embodiments

The reception restrictions when other channels such as a PDSCH or a PDCCH overlap in time with PRS, as described in the background, may be acceptable for positioning applications but for PDC with URLLC services there will be significant drawbacks. It should be noted that when in this disclosure the “reception of a PDCCH” or “reception of a PDSCH” is addressed, it is understood that this can also mean the reception of a part of the PDSCH or PDCCH. As illustrated in the example of figure 2a, the entire PDSCH lasts from symbol#3 until symbol #8, and in symbol #4 the PDSCH is overlapping with PRS, hence the PDSCH (or it can also be said the part of the PDSCH which coincides with symbol #4) is not received. A general clarification to the figures used in this disclosure is given: In figures 1-10, time frequency resources are illustrated by the rectangle grid between the horizontal time-axis and the vertical frequency-axis.

A first disadvantage is the waste of resources. A PRS could be configured as often as every 4 ^th slot and its bandwidth could be configured to only occupy a small chunk of the entire bandwidth part. Then, the number of non-usable resources will be significant.

Another critical disadvantage is that the reception reliability will be decreased significantly, which is not acceptable for URLLC applications. As shown in Figure 2a, when the scheduled channel overlaps in time with PRS, the resources during that overlap will not be used for the decoding of the channel. As a consequence, the probability for a decoding failure increases. And even worse, if the channel’s DMRS happens to coincide with the PRS, then the DMRS will not be received which will make it almost impossible to decode the channel correctly.

One way to get around the above problem of degraded decoding performance is that the gNB only schedules channels that do not overlap in time with PRS, as illustrated in Figure 2b. But this approach increases the delay which is not desired or not even acceptable for URLLC applications. As it is shown in the example for Figure 2b, the starting time is delayed by 2 OFDM symbols, which is not acceptable for URLLC with stringent latency requirements. Also, the whole bandwidth on symbol #4 can still not be utilized for other reception than PRS. For this resource waste there does not exist any solution.

As analyzed above, when utilizing the existing PRS procedures for PDC, significant drawbacks will be encountered that are not acceptable for URLLC services. In order to overcome these drawbacks, the following steps are disclosed:

It shall be allowed that for the same cell, PRS and other channels e.g. PCCCH or PDSCH, can occur overlapping in time. To process the received signals or channels during the OFDM symbols when the overlap occurs, different types of client devices (UEs) with different capabilities are defined. One UE capability (which is further addressed as the low capability) is to process only one channel or signal at a time, i.e. either the PRS or the other channel (e.g. PDCCH or PDSCH) is received during the overlapping symbol (s) . Another UE capability (which is further addressed as the high capability) is to process both PRS and the other channel during the overlapping OFDM symbol (s) . That means that both PRS and the overlapping channel are received.

Embodiment 1 is disclosed for a UE being capable to at least perform reception according to the low capability. Note that it typically is the case that there are some UEs that only can support the low capability and also that there are other UEs that can support both the low and the high capability. In this first embodiment the UE prioritizes by default the other channel or signal (e.g. the PDSCH or PDCCH carrying e.g. data for an URLLC service) that is overlapping in time with PRS. This is the case unless the UE is triggered to prioritize the PRS. One example to perform triggering is an explicit trigger by a DCI. And another example to perform the triggering is an implicit trigger, for example if the UE is requested to measure the Rx-Tx time difference by a DCI or MAC CE or RRC. This concept of a prioritized reception is illustrated in Figure 3. T he advantage of this embodiment is that it results in less implementation complexity than for a parallel reception in the high capability UE, but on the downside it will also result in non-received PDCCHs or PDSCHs, which degrades the URLLC performance. It should be noted that this embodiment is not restricted to the case when the PRS and the other channels (e.g. PDSCH or PDCCH) are only overlapping in time but are not in frequency. This embodiment also applies when the PRS and the other channel are overlapping frequency as for example for the situation illustrated in Figure 5. If PRS and another channel overlap in time and frequency, the same or different prioritization methods as for the case where the overlap only is in time can be applied.

Embodiment 2 is disclosed. That is if the PRS and another channel (e.g. a PDSCH or a PDCCH) only overlap in time but not in frequency, then both the PRS and the other channel are received during the overlapping symbols. More specifically, if a frequency resource (RB) contains PRS then this resource cannot be used for PDCCH or PDSCH in the same OFDM symbol. This is illustrated in Figure 4 where the PDSCH is located on other RBs that do not contain PRS. The advantage of the second embodiment is that it allows a reception of PRS and other signals and channels together, but the implementation complexity at the UE side is a bit larger than in the first embodiment.

For the high capability UE, i.e. a UE that is able to receive other channels and PRS in the same symbol, when the gNB schedules the other channels, e.g. PDCCH or PDSCH, overlapping in time and frequency with PRS, new problems arise. This is because when PRS is overlapping in time and frequency with another channel on some time-frequency resource (a time-frequency can for example be one PRB for the duration of one OFDM symbol, another example could be a single sub-carrier for the duration of one OFDM symbol) , it is not clear if PRS or the other channel shall be transmitted by the gNB (and received by the UE) . This ambiguity is illustrated in Figure 5. When information bits of a PDSCH or PDCCH overlap with PRS in time and frequency, it has to be decided what to transmit on the time-frequency resources that are intended for PRS. These resources are encircled in Figure 5. A major part of the subsequent embodiments in this invention escribe rules and methods to resolve the possible ambiguity on colliding resources whether to send and receive PRS, the other channel (e.g. the PDSCH or PDCCH) or both. Note, that the low capability and high capability UE does not mean that the specification will define these capabilities, it is also feasible to have no capability reporting in the specification.

Firstly, two sub-cases for the overlap in frequency are distinguished. In general, a PDCCH and also a PDSCH contains data bits that are conveying the actual information to be transmitted and it contains demodulation reference signal (DMRS) that is required for channel estimation of the channel which facilitates a proper demodulation of the received channel. In the first sub-case, the UE is not expected to be scheduled in such way that the DMRS overlaps with PRS in one or some time-frequency resources, only data can overlap in a time-frequency resource with PRS. In the second sub-case, also the DMRS may overlap in a time-frequency resource with PRS.

The first sub-case can be achieved by specification, e.g. the UE is not expected to scheduled that a channel’s (e.g. PDSCH or PDCCH) DMRS overlap with PRS (in other words, DMRS and PRS do not collide on the same resources) . Another way to avoid the DMRS/PRS overlap is by network configuration or dynamic scheduling decisions. The network can ensure that the DMRS and PRS do not collide in the same time-frequency resources.

Embodiment 3 is for the first sub-case of the invention. In this embodiment rate matching is applied. That means that the channel (e.g. the PDCCH or the PDSCH) will be rate-matched around the resources occupied by PRS and resources occupied by PRS cannot be used for the PDSCH or PDCCH. As a result, PRS is transmitted on its configured resources and the encoded data bits are mapped around the overlapping PRS locations. One option to prohibit that DMRS and PRS overlap and to enable rate matching accordingly is to include the PRS pattern in the information element that is specifying the rate matching pattern, for example the PRS pattern and the resources defined in the rate matching information element can be configured in such a way that PRS is fully covered. By doing so, no resource occupied by PRS can be used for PDSCH or PDCCH. Both PRS and the other channel (e.g. PDCCH or PDSCH) are transmitted and can be correctly received. This is illustrated in Figure 6. The advantage with this embodiment is that it gives the gNB scheduler more flexibility on which time-frequency resources to allocate channels such as PDCCH and PDSCH, since it does not strictly need to take into account where the PRS is located. In one example of rate matching, the number of encoded data bits which would be mapped on the resources is based on the resources that can be used for transmission (i.e. does not include PRS resources) .

Another variant of embodiment 3 is to apply puncturing. That means that the channel (e.g. the PDCCH or the PDSCH) will be punctured around the time-frequency resources occupied by PRS and the time-frequency resources occupied by PRS cannot be used for the PDSCH or PDCCH. As a result, PRS is transmitted on its configured resources and the encoded data bits are mapped around the overlapping PRS locations. In one example of puncturing, the number of encoded data bits which would be mapped on the resources is based on the PDSCH resources including PRS resources, but do not map if overlaps with PRS in time frequency domain.

Embodiment 4 of the invention applies to the same channel constellation as shown in Figure 6, that means the PCCCH or PDSCH is overlapping with PRS, but its DMRS is not overlapping with PRS. Instead of rate matching according to embodiment 3, PRS and other signals or channels are superimposed on the overlapping resources. The superposition of data and PRS can be achieved with proper power scaling. An advantage of such an embodiment 4 is that it is simple for the gNB scheduler and utilizes all allocated resources for transmission.

For the second sub-case (i.e. the channel’s DMRS may overlap on a time-frequency resource with PRS) , rate matching (i.e. embodiment 3) or superposition (i.e. embodiment 4) can still be applied when data of the channel is colliding with PRS. Note that only because it is allowed in this second sub-case that DMRS and PRS may collide, it does not mean that they have to collide. This is up to the gNB scheduler or the network configuration, and in situations where there is overlap between the channel’s data and PRS the same embodiments can be applied as for the situation where the UE is not expected to be scheduled with overlapping DMRS and PRS on time-frequency resources (i.e. embodiment 3 and embodiment 4) .

For the second sub-case, when the other channel’s DMRS collide on with the PRS, rate matching is not applied for the resources in which the overlap between DMRS and PRS occurs, since it would significantly degrade the possibility for the UE to perform channel estimation and to correctly demodulate the received signal. In that case a different procedure can be used.

Embodiment 5 of the invention is for the second sub-case for the situation when the channel’s DMRS and PRS overlap. That means that the one or more of the PDSCH resources that are indicated as DMRS in figure 6 overlap with PRS. This embodiment is hence not exactly represented by figure 6, but figure 6 can be used as a starting point to describe this embodiment. In this embodiment, to resolve a collision between PRS and DMRS from another channel (such as PDCCH or PDSCH) , a priority level is given to the DMRS. If the DMRS has higher priority than the PRS, then DMRS is transmitted on the colliding resources and is received by the UE, but no PRS. If the priority of DRMS is lower than PRS, then PRS is transmitted on the colliding resources and PRS is received by the UE. This_enables a correct reception and processing of the prioritized channel or signal (e.g. correct reception PDSCH or PDCCH if DMRS is prioritized and correct measurement of Rx- Tx time difference if PRS is prioritized) . In one variant of this embodiment, the remaining de-prioritized signal still is transmitted on the non-overlapping resources and in another sub-variant, the entire de-prioritized signal is dropped also on the non-overlapping parts. The priority level of the DMRS can be statically defined, which mean for example pre-defined in the specification, or it can be semi-statically configured by RRC, or can be explicitly dynamically indicated by DCI or implicitly derived from triggering a Rx-Tx time difference measurement report. Note, that in an equivalent realization of this embodiment, the priority level can also be assigned to the PRS instead of the DMRS . The advantage of this embodiment 5 is that it enables a correct reception and processing of the prioritized channel or signal for a low cost. And depending in the prioritization mechanism, the priority levels and hence the reception of whether DMRS or PRS can be quickly adapted.

Embodiment 6 of the invention also resolves a collision between DMRS and PRS in the second sub-case that is addressed by Embodiment 5. But instead of prioritization, DMRS is shifted to non-colliding resources, such as other time or frequency locations where no PRS is configured. The advantage of this embodiment is that it enable a parallel reception of DMRS and PRS.

An embodiment 7 of the invention also resolves a collision between DMRS and PRS that is addressed in embodiment 5. The PRS is transmitted and the DMRS is dropped. The UE uses the PRS to perform the channel estimation for the demodulation of the overlapping channel such as PDCCH or PDSCH. This can be utilized when the PRS and DMRS are quasi co-located (QCLed, e.g. typeC as defined in TS 38.214 section 5.1.5, where the average delay and Doppler shift are assumed to be the same which may be helpful for the UEs demodulation) . It should be noted that under the listed QCL conditions, PRS can also be used for the demodulation of the channel if it does not overlap with DMRS. In this situation it can be seen as an extra reference signal in addition to DMRS that facilitates and further improves the demodulation of the received channel. If PRS can also be used for PDSCH or PDCCH demodulation, then it may also be needed to signal the power ratio between PRS and PDSCH, or between PRS and DMRS . An advantage of this embodiment is that it preserves the UE’s possibility to correctly demodulate the PDSCH while it is not sacrificing performance on the PRS measurement.

In embodiment 8 also a collision between DMRS and PRS that is addressed in embodiment 5 is resolved. PRS and DMRS are superimposed and both are transmitted and received. An advantage of this embodiment is that it is simple for the gNB scheduler and that both the channel and PRS have the chance to be received without performance loss (under favorable conditions) .

The previously described embodiments, when PRS is overlapping with another channel in time and frequency, use examples where PRS either is overlapping only with data from the other channel (e.g. with data from a PDCCH or from a PDSCH) or when PRS is overlapping only with the DMRS from the other channel (e.g. with DMRS from a PDCCH or from a PDSCH) . It is understood that this does not preclude cases, where among the overall time-frequency resources in which PRS and the other channel (such as a PDCCH or a PDSCH) overlap, in some of these resources there is an overlap between PRS and data from the other channel and in some other of these resources there is an overlap between PRS and the DMRS of the other channel. This overlapping situation is illustrated in Figure 7.

The

embodiments

9, 10, 11, 12, 13, 14, 15 and 16 of the invention solve the situation when in some time-frequency resources there is an overlap between PRS and the other channel’s data and in some other time-frequency resources there is an overlap between PRS and the other channel’s DMRS. Different combinations of the previously described embodiments for the collision between channel’s data and PRS and between channel’s DMRS and PRS are applied. Figure 8 illustrates one example to resolve the situation when some PRS overlap with data bits from the other channel and some other PRS overlap with DMRS from the other channel. In Figure 8, data overlapping with PRS is resolved by rate matching (i.e. embodiment 3) and the overlap between DMRS and PRS is resolved by prioritization (embodiment 5) . Different previously described embodiments can be applied separately for the resources where there is an overlap between DMRS and PRS and where this is an overlap between data and PRS. Figure 8 describes embodiment 9, where the data of the other channel is rate matched around PRS (i.e. embodiment 3) and for collisions between DMRS and PRS, prioritization rules are applied (embodiment 5) . Embodiments 9-16 comprise therefore combinations of the previously described

embodiment

3, 4, 5, 6, 7, and 8. Example embodiments for different combinations are listed below (it is understand that this list is not necessarily to the combinations listed below) . The advantages described for the single embodiments are also valid for the combined embodiments 9 to 16 in which they the single embodiments are comprised.

● Embodiment 9: Embodiment 3 for data vs PRS and Embodiment 5 for DMRS vs PRS

● Embodiment 10: Embodiment 3 for data vs PRS and Embodiment 6 for DMRS vs PRS

● Embodiment 11: Embodiment 3 for data vs PRS and Embodiment 7 for DMRS vs PRS

● Embodiment 12: Embodiment 3 for data vs PRS and Embodiment 8 for DMRS vs PRS

● Embodiment 13: Embodiment 4 for data vs PRS and Embodiment 5 for DMRS vs PRS

● Embodiment 14: Embodiment 4 for data vs PRS and Embodiment 6 for DMRS vs PRS

● Embodiment 15: Embodiment 4 for data vs PRS and Embodiment 7 for DMRS vs PRS

● Embodiment 16: Embodiment 4 for data vs PRS and Embodiment 8 for DMRS vs PRS

It is understood that the embodiments 9 to 16 are not mutual exclusive, but that multiple embodiments can be supported.

Embodiment 17 is another variant to resolve to resolve the overlap between PRS and another channel such as PDCCH or PDSCH. An example is given in Figure 9. In this example, in total 4 time-frequency resources carrying PRS overlap with the PDSCH. In two of them there is an overlap with data and in two other there is an overlap with DMRS. In this embodiment PRS is dropped and not received in any of the overlapping time-frequency resources, i.e. not received where DMRS overlaps with PRS and not received where the other channel’s data overlap with PRS. Thus, the other channel is received as if no PRS was configured. The advantage of this embodiment is that it is simple for implementation. In one realization of this embodiment, the PRS also on the non-overlapping resources is not received, as seen in the right-hand drawing of Figure 9. And in another realization of this embodiment, the non-overlapping PRS are still received (as seen in the center-drawing) . The first realization corresponds to a lower capability UE as illustrated in Figure 3 and the second realization corresponds to a higher capability UE as illustrated in Figure 4.

Embodiment 18 is another method to resolve the overlap between another channel (e.g. a PDCCH or a PDSCH) and PRS. It is a combination of embodiment 3 and embodiment 17. If only the channel’s data overlap with PRS, the channel is rate matched around PRS as described for embodiment 3. But if at least one DMRS overlaps with PRS, PRS is dropped according to embodiment 17. The advantage of this embodiment is that is gives the gNB full flexibility where the allocate the other channel and at the time makes it very likely to result in scheduling decisions that guarantee a correct reception of both PRS and the other channel.

The various embodiments disclosed in this invention and their relationship is illustrated in Figure 10.

It should be noted that even if the invention is described for PDC, its application is not only applicable to PDC. For example in future positioning scenarios, PRS might also only be measured from just one cell. Then the above described invention can also be applied for positioning which enables the concurrent reception of PRS and other channels for an even broader set of use cases.

It should also be noted that the embodiments can be applied separately for a PDSCH and PDCCH and different solutions can be adopted for the overlap in time or time and frequency depending on whether the overlap is between PDSCH and PRS or PDCCH and PRS. It shall also be noted that one or multiple of the described embodiments can also be applied for just one channel type, e.g. for the overlap between PDSCH and PRS while the overlap between PDCCH and PRS is avoided by configuration. For example, the UE is configured in such way that CORESET (control-resource set) do not overlap with PRB (s) that carry PRS in the symbols occupied by search space set (s) . PRB (physical resource block) includes 12 subcarriers in the frequency domain. RE (resource element) includes one subcarrier in the frequency domain and one symbol in the time domain.

method (1100) of operating a client device (100) for a communication system (500) , wherein the method comprises:

receiving, from a network node, a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in a same cell that overlap in time with the PRS;

extracting from the plurality of OFDM symbols the one or more additional channels that overlap in time with the PRS.

Figure 11 shows a flow diagram illustrating steps of a method 1100 of operating a client device. The method 1100 comprises a first step 1110 of receiving, from a network node, a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in a same cell that overlap in time with the PRS. Another step 1120 comprises extracting from the plurality of OFDM symbols the one or more additional channels that overlap in time with the PRS. Other implementations of this method include the features and characteristics of the embodiments disclosed above.

Figure 12 shows a flow diagram illustrating steps of a method 1200 of operating a client device. The method 1200 comprises a first step 1210 of transmitting, to a client device, a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in a same cell that overlap in time with the PRS. Other implementations of this method include the features and characteristics of the embodiments disclosed above.

Furthermore, any method according to embodiments of the disclosure 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 embodiments of the client device 100 and the network access node 200 comprises 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 client device 100 and the network access node 200 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 disclosure is not limited to the embodiments described above, but also relates to and incorporates all embodiments within the scope of the appended independent claims.

It should also be understood that the here disclosed mechanisms can be applied for both PDSCH and PDCCH or for just one of them.

Claims

A client device (100) for a communication system (500) , wherein the client device comprises:

a processor configured to:

receive, from a network node, a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in a same cell that overlap in time with the PRS;

extract from the plurality of OFDM symbols the one or more additional channels that overlap in time with the PRS.
The client device (100) of claim 1, wherein the one or more additional channels are one or more of a Physical Downlink Control Channel, PDCCH, and Physical Downlink Shared Channel, PDSCH.
The client device of any preceding claim further configured to receive a trigger message comprising instructions for the client device to receive PRS instead of one or more of the additional channels.
The client device of claim 4, wherein the trigger message is a Downlink Control Information, DCI, message.
The client device of claim 4, wherein the trigger message is a Rx-Tx time difference report request.
The client device of any preceding claim, the client device being further configured to extract both the PRS and the one or more other channels from the plurality of OFDM symbols.
The client device of claim 6, wherein the PRS and the other one or more overlapping channels overlap in time but not in frequency.
The client device of claim 6, wherein the PRS and the one or more overlapping channels overlap in time and in frequency.
The client device of claim 8, wherein the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is not overlapping in time and frequency with the PRS, further configured to perform rate matching around the PRS.
The client device of claim 8, wherein the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is not overlapping in time and frequency with the PRS, further configured to superimpose the PRS and the one or more overlapping channels.
The client device of claim 8, wherein the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to prioritize the reception of the DMRS.
The client device of claim 8, wherein the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to prioritize the reception of the PRS.
The client device of any of claims 11 or 12, further configured to prioritize depending upon static rules.
The client device of any of claims 11 or 12, further configured to prioritize depending upon semi-static rules.
The client device of any of claims 11 or 12, further configured to prioritize depending upon dynamic rules.
The client device of any of claims 11 or 12, further configured to prioritize depending upon implicit rules.
The client device of claim 8, wherein the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to not receive the PRS on any resource that is overlapping with the one or more overlapping channels.
A network node (200) for a communication system (500) , wherein the network node comprises:

a processor configured to:

transmit, to client device (100) , a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in a same cell that overlap in time with the PRS.
The network node (200) of claim 18, wherein the one or more additional channels are one or more of a Physical Downlink Control Channel, PDCCH, and Physical Downlink Shared Channel, PDSCH.
The network node of any of claims 18 or 19, further configured to transmit a trigger message comprising instructions for the client device (100) to receive PRS instead of one or more of the additional channels.
The network node of claim 20, wherein the trigger message is a Downlink Control Information, DCI, message.
The network node of any of claim 20, wherein the trigger message is a Rx-Tx time difference report request.
The network node of any of claims 18 to 22, the network node being further configured to instruct the client device (100) to extract both the PRS and the one or more other channels from the plurality of OFDM symbols.
The network node of any of claims 18 to 23, wherein the PRS and the other one or more overlapping channels overlap in time but not in frequency.
The network node of any of claims 18 to 24, wherein the PRS and the one or more overlapping channels overlap in time and in frequency.
The network node of claim 25, wherein the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is not overlapping in time and frequency with the PRS, further configured to perform rate matching around the PRS
The network node of claim 25, wherein the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is not overlapping in time and frequency with the PRS, further configured to superimpose the PRS and the one or more overlapping channels.
The network node of claim 25, wherein the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to prioritize the transmission of the DMRS and to instruct the client device (100) to prioritize the reception of the DMRS.
The network node of claim 25, wherein the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to prioritize the transmission of the PRS and to instruct the client device (100) to prioritize the reception of the PRS.
The network node of any of claims 28 or 29, further configured to prioritize and to instruct the client device (100) depending upon static rules.
The network node of any of claims 28 or 29, further configured to prioritize and to instruct the client device (100) depending upon semi-static rules.
The network node of any of claims 28 or 29, further configured to prioritize and to instruct the client device (100) depending upon dynamic rules.
The network node of any of claims 28 or 29, further configured to prioritize and to instruct the client device (100) depending upon implicit rules.
The network node of claim 26, wherein the one or more overlapping channels comprise a demodulation reference signal DMRS, wherein the DMRS is overlapping in time and frequency with the PRS, further configured to not transmit the PRS on any resource that is overlapping in time and frequency with the one or more time-overlapping channels.
A method (1100) of operating a client device (100) for a communication system (500) , wherein the method comprises:

receiving, from a network node, a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in a same cell that overlap in time with the PRS;

extracting from the plurality of OFDM symbols the one or more additional channels that overlap in time with the PRS.
A method (1200) of operating a network node (200) for a communication system (500) , wherein the method comprises:

transmitting, to client device (100) , a plurality of OFDM symbols, wherein the plurality of OFDM symbols contain a position reference signal, PRS, and one or more additional channels in a same cell that overlap in time with the PRS.
A computer program product comprising a computer-readable storage medium for storing program code which causes a computer or a processor to perform the method (1100) of claim 35, when the program code is executed by the computer or the processor.
A computer program product comprising a computer-readable storage medium for storing program code which causes a computer or a processor to perform the method (1200) of claim 36, when the program code is executed by the computer or the processor.