Dynamic CRS rate-matching for NR ues

Abstract

There is provided techniques for dynamic CRS rate-matching for NR UEs. A spectrum in which the NR UEs are served at least partly overlaps with a spectrum in which LTE UEs are served. A method is performed by a network node. The method comprises obtaining MBSFN configuration pertaining to a change in an MBSFN 5 pattern for the LTE UEs. The MBSFN configuration specifies at least one non- MBSFN subframe being replaced by an MBSFN subframe, and / or at least one MBSFN subframe being replaced by a non-MBSFN subframe in the MBSFN pattern. The method comprises adapting the dynamic downlink CRS rate-matching for the NR UEs in the at least one non-MBSFN subframe or MBSFN subframe that was 10 replaced. Either dynamic downlink CRS rate-matching is switched on or switched off in the at least one non-MBSFN frame or MBSFN subframe that was replaced depending on the change in the MBSFN pattern.

Description

[0001] DYNAMIC CRS RATE-MATCHING FOR NR UES

[0002] TECHNICAL FIELD

[0003] Embodiments presented herein relate to a method, a network node, a computer program, and a computer program product for dynamic cell-specific reference signal rate matching for New Radio user equipment.

[0004] BACKGROUND

[0005] NR (New Radio) is the air interface specified for the fifth generation (5G) telecommunications systems according to the third-generation partnership project (3GPP). NR might be regarded as a further development, with enhanced functionality and performance, of the Long-Term Evolution (LTE) air interface.

[0006] Mobile network operators that deploy NR typically have access to, or have been allocated, existing frequency spectrum on multiple frequency bands where LTE signalling is currently deployed. Initially, the fraction of NR capable user equipment (UEs) might be limited compared to LTE capable user equipment and therefore a large part of the existing frequency spectrum might still need to be allocated for LTE signalling.

[0007] There are several architecture options for how to deploy NR together with LTE.

[0008] One option is to use LTE as the main air interface whilst NR is added using dual connectivity in non-standalone mode. With dual connectivity, both the LTE air interface and the NR air interface can be used in parallel for data transmission (and reception). In the downlink (i.e., in the direction from a radio access network node on the network side towards UEs on the user side) the data transmission is split at the Packet Data Convergence Protocol (PDCP) layer and can use either one of the air interfaces (i.e., LTE or NR) or both. In uplink (i.e., in the direction from the UE on the user side towards a radio access network node on the network side) the data received from the two air interfaces are combined in the PDCP layer at the radio access network node.

[0009] To have an efficient frequency spectrum utilization, it is possible to overlay an NR carrier in the same frequency spectrum as an LTE carrier. This is made possible by flexible locations of control channels and signals, and by NR rate matching around LTE reference signals, such as cell-specific reference signal (CRS), channel state information reference signal (CSI-RS), and synchronization signals (such as primary synchronization signal (PSS), secondary synchronization signal (SSS)), and physical broadcast channel (PBCH) that are transmitted in an LTE carrier.

[0010] A side effect of dynamically sharing the spectrum using CRS rate matching is that the NR Physical Downlink Control Channel (PDCCH) becomes constrained to only the symbols where CRS does not exist. This significantly caps the number of simultaneous scheduled UEs and hampers the efficient use of the spectrum.

[0011] Further, relying on radio resource control (RRC) signaling for configuring the NR UEs with CRS rate matching causes overhead. For example, RRC signaling is needed each time a new Multimedia Broadcast multicast service Single Frequency Network (MBSFN) configuration is selected. This signaling consumes air interface resources and can create connection issues especially for poor radio condition UEs.

[0012] Hence, there is still a need for improved joint downlink NR and LTE transmissions.

[0013] SUMMARY

[0014] An object of embodiments herein is to provide efficient joint downlink NR and LTE transmission that does not suffer from the issues noted above, or at least where the issues noted above are mitigated or reduced.

[0015] According to a first aspect there is presented a method for dynamic CRS ratematching for NR UEs. A spectrum in which the NR UEs are served at least partly overlaps with a spectrum in which LTE UEs are served. The method is performed by a network node. The method comprises obtaining MBSFN configuration pertaining to a change in an MBSFN pattern for the LTE UEs. The MBSFN pattern specifies which subframes are MBSFN subframes and which subframes are non-MBSFN subframes. There are separate MBSFN patterns for the NR UEs and the LTE UEs. The MBSFN configuration specifies at least one non-MBSFN subframe being replaced by an MBSFN subframe, and / or at least one MBSFN subframe being replaced by a non- MBSFN subframe in the MBSFN pattern. The method comprises adapting the dynamic downlink CRS rate-matching for the NR UEs in the at least one non-MBSFN subframe or MBSFN subframe that was replaced. Either dynamic downlink CRS rate- matching is switched on or switched off in the at least one non-MBSFN frame or MBSFN subframe that was replaced depending on the change in the MBSFN pattern.

[0016] According to a second aspect there is presented a network node for dynamic CRS rate-matching for NR UEs. A spectrum in which the NR UEs are served at least partly overlaps with a spectrum in which LTE UEs are served. The network node comprises processing circuitry. The processing circuitry is configured to cause the network node to obtain MBSFN configuration pertaining to a change in an MBSFN pattern for the LTE UEs. The MBSFN pattern specifies which subframes are MBSFN subframes and which subframes are non-MBSFN subframes. There are separate MBSFN patterns for the NR UEs and the LTE UEs. The MBSFN configuration specifies at least one non- MBSFN subframe being replaced by an MBSFN subframe, and / or at least one MBSFN subframe being replaced by a non-MBSFN subframe in the MBSFN pattern. The processing circuitry is configured to cause the network node to adapt the dynamic downlink CRS rate-matching for the NR UEs in the at least one non-MBSFN subframe or MBSFN subframe that was replaced. Either dynamic downlink CRS ratematching is switched on or switched off in the at least one non-MBSFN frame or MBSFN subframe that was replaced depending on the change in the MBSFN pattern.

[0017] According to a third aspect there is presented a network node for dynamic CRS ratematching for NR UEs. A spectrum in which the NR UEs are served at least partly overlaps with a spectrum in which LTE UEs are served. The network node comprises an obtain module configured to obtain MBSFN configuration pertaining to a change in an MBSFN pattern for the LTE UEs. The MBSFN pattern specifies which subframes are MBSFN subframes and which subframes are non-MBSFN subframes. There are separate MBSFN patterns for the NR UEs and the LTE UEs. The MBSFN configuration specifies at least one non-MBSFN subframe being replaced by an MBSFN subframe, and / or at least one MBSFN subframe being replaced by a non- MBSFN subframe in the MBSFN pattern. The network node comprises an adapt module configured to adapt the dynamic downlink CRS rate-matching for the NR UEs in the at least one non-MBSFN subframe or MBSFN subframe that was replaced. Either dynamic downlink CRS rate-matching is switched on or switched off in the at least one non-MBSFN frame or MBSFN subframe that was replaced depending on the change in the MBSFN pattern. According to a fourth aspect there is presented a computer program for dynamic CRS rate-matching for NR UEs. The computer program comprises computer code which, when run on processing circuitry of a network node, causes the network node to perform actions. One action comprises the network node to obtain MBSFN configuration pertaining to a change in an MBSFN pattern for the LTE UEs. The MBSFN pattern specifies which subframes are MBSFN subframes and which subframes are non-MBSFN subframes. There are separate MBSFN patterns for the NR UEs and the LTE UEs. The MBSFN configuration specifies at least one non- MBSFN subframe being replaced by an MBSFN subframe, and / or at least one MBSFN subframe being replaced by a non-MBSFN subframe in the MBSFN pattern. One action comprises the network node to adapt the dynamic downlink CRS ratematching for the NR UEs in the at least one non-MBSFN subframe or MBSFN subframe that was replaced. Either dynamic downlink CRS rate-matching is switched on or switched off in the at least one non-MBSFN frame or MBSFN subframe that was replaced depending on the change in the MBSFN pattern.

[0018] According to a fifth aspect there is presented a computer program product comprising a computer program according to the fourth aspect and a computer readable storage medium on which the computer program is stored. The computer readable storage medium could be a non-transitory computer readable storage medium.

[0019] Advantageously, these aspects enable efficient joint downlink NR and LTE transmission.

[0020] Advantageously, these aspects enable joint downlink NR and LTE transmission that does not suffer from the issues noted above.

[0021] Advantageously, these aspects do not require any additional RRC signaling for configuring the NR UEs with dynamic CRS rate-matching, even when the MBSFN pattern changes. In turn, these aspects therefore increase the spectral efficiency for the NR UEs.

[0022] Other objectives, features and advantages of the enclosed embodiments will be apparent from the following detailed disclosure, from the attached dependent claims as well as from the drawings. Generally, all terms used in the claims are to be interpreted according to their ordinary meaning in the technical field, unless explicitly defined otherwise herein. All references to "a / an / the element, apparatus, component, means, module, step, etc." are to be interpreted openly as referring to at least one instance of the element, apparatus, component, means, module, step, etc., unless explicitly stated otherwise. The steps of any method disclosed herein do not have to be performed in the exact order disclosed, unless explicitly stated.

[0023] BRIEF DESCRIPTION OF THE DRAWINGS

[0024] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

[0025] Fig. 1 is a schematic diagram illustrating a communications network according to embodiments;

[0026] Fig. 2 is a block diagram of a network node according to an embodiment;

[0027] Fig. 3 is a flowchart of methods according to embodiments;

[0028] Fig. 4 schematically illustrates MBSFN patterns according to embodiments;

[0029] Fig. 5 schematically is a signaling diagram according to an embodiment;

[0030] Fig. 6 is a flowchart of a method according to an embodiment;

[0031] Fig. 7 is a schematic diagram showing structural units of a network node according to an embodiment;

[0032] Fig. 8 is a schematic diagram showing functional modules of a network node according to an embodiment; and

[0033] Fig. 9 shows one example of a computer program product comprising computer readable storage medium according to an embodiment.

[0034] DETAILED DESCRIPTION

[0035] The inventive concept will now be described more fully hereinafter with reference to the accompanying drawings, in which certain embodiments of the inventive concept are shown. This inventive concept may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided by way of example so that this disclosure will be thorough and complete, and will fully convey the scope of the inventive concept to those skilled in the art. Like numbers refer to like elements throughout the description. Any step or feature illustrated by dashed lines should be regarded as optional.

[0036] Fig. 1 is a schematic diagram illustrating a communications network loo where embodiments presented herein can be applied. The communications network 100 comprises a network node 200 configured to provide network access to user equipment, as represented by user equipment 150a, 150b, 150c, isod, in a radio access network 110. The radio access network 110 is operatively connected to a core network 120. The core network 120 is in turn operatively connected to a service network 130, such as the Internet. The user equipment 150a, 150b, 150c, isod are thereby enabled to, via the network node 200, access services of, and exchange data with, the service network 130. Some of the user equipment might be configured to communicate with the network node 200 using only LTE signalling, some of the user equipment might be configured to communicate with the network node 200 only using NR signalling, and some of the user equipment might be configured to communicate with the network node 200 using both LTE signalling and NR signalling. User equipment 150c, isod configured to communicate with the network node 200 using LTE signalling are hereinafter denoted LTE user equipment. User equipment 150a, 150b configured to communicate with the network node 200 using NR signalling are hereinafter denoted NR user equipment.

[0037] The network node 200 comprises, is collocated with, is integrated with, or is in operational communications with, an antenna system comprising co-sited antenna arrays 140a, 140b. Each of the antenna arrays 140a, 140b might comprise a plurality of individual antennas, or antenna elements. In some implementations, one antennas antenna array 140b might be configured for LTE signalling whereas the other antennas antenna array 140a might be configured for NR signalling. In other implementations, both antenna arrays 140a, 140b are configured for both LTE signalling and NR signalling. Examples of network nodes 200 are radio access network nodes, radio base stations, base transceiver stations, Node Bs, evolved Node Bs, gNBs, access points, access nodes, transmission and reception points, and integrated access and backhaul nodes. Examples of user equipment 150a, 150b, 150c, isod are terminal devices, wireless devices, mobile stations, mobile phones, handsets, wireless local loop phones, smartphones, laptop computers, tablet computers, network equipped sensors, network equipped vehicles, and so-called Internet of Things devices.

[0038] As noted above there is still a need for improved joint downlink NR and LTE transmissions.

[0039] The embodiments disclosed herein therefore relate to techniques for dynamic CRS rate-matching for NR UEs 150a, 150b. In order to obtain such techniques, there is provided a network node 200, a method performed by the network node 200, a computer program product comprising code, for example in the form of a computer program, that when run on a network node 200, causes the network node 200 to perform the method.

[0040] Fig. 2 schematically illustrates a block diagram of a network node 200 having a shared resource allocator 240, an LTE scheduler 242, and an NR scheduler 244, together with an LTE transmitter 246 and an NR transmitter 248. The LTE transmitter 246 might comprise, or be operatively connected to, at least antenna array 140b. The NR transmitter 248 might comprise, or be operatively connected to, at least antenna array 140a. The shared resource allocator 240 is configured to, based on input from the LTE scheduler 242 and the NR scheduler 244 take a decision in terms of determining when to perform dynamic CRS RM for the NR UEs 150a, 150b, as in below step S104. Transmission of downlink subframes is initiated by the shared resource allocator 240 providing output to the LTE scheduler 242 and the NR scheduler 244. The output to the LTE scheduler 242 is defined by a scheduling decision for the LTE UEs. The output to the NR scheduler 244 is defined by the information in step S104. The LTE scheduler 242 is configured to, based on the output received from the shared resource allocator 240, schedule the LTE transmission and initiate transmission of the LTE transmission from the LTE transmitter 246. The NR scheduler 244 is configured to, based on the output received from the shared resource allocator 240, schedule NR transmission and initiate transmission of the NR transmission from the NR transmitter 248.

[0041] Fig. 3 is a flowchart illustrating embodiments of methods for dynamic CRS ratematching for NR UEs 150a, 150b. A spectrum in which the NR UEs 150a, 150b are served at least partly overlaps with a spectrum in which LTE UEs 150c, isod are served. The methods are performed by the network node 200. The methods are advantageously provided as computer programs 920.

[0042] It is assumed that an initial MBSFN pattern is configured for the NR UEs 150a, 150b and the LTE UEs 150c, isod. For the LTE UEs 150c, isod, MBSFN subframes are subframes where LTE PDSCH is not transmitted. Three examples of MBSFN patterns 400a, 400b, 400c are illustrated in Fig. 4. The LTE UEs 150c, isod might be configured with the initial MBSFN pattern via System Information Broadcast, and the NR UEs 150a, 150b might be configured with the initial MBSFN pattern during UE connection setup signaling.

[0043] It is further assumed that a decision is made that the MBSFN allocation should be changed for the LTE UEs 150c, isod. In some aspects, the decision is made by the shared resource allocator 240.

[0044] S102: The network node 200 therefore obtains MBSFN configuration pertaining to a change in an MBSFN pattern 400a, 400b, 400c for the LTE UEs 150c, isod.

[0045] The MBSFN pattern 400a, 400b, 400c specifies which subframes are MBSFN subframes 420 and which subframes are non-MBSFN subframes 410. As further can be seen in Fig. 4, the NR UEs 150a, 150b and the LTE UEs 150c, isod do not necessarily share the same view of the MBSFN pattern. There are therefore separate MBSFN patterns 400a, 400b, 400c for the NR UEs 150a, 150b and the LTE UEs 150c, isod.

[0046] The MBSFN configuration specifies at least one non-MBSFN subframe 410 being replaced by an MBSFN subframe 420, and / or at least one MBSFN subframe 420 being replaced by a non-MBSFN subframe 410 in the MBSFN pattern 400a, 400b, 400c.

[0047] Both the LTE scheduler 242 and the NR scheduler 244 are informed of the change. S104: The network node 200 adapts the dynamic downlink CRS rate-matching for the NR UEs 150a, 150b in the at least one non-MBSFN subframe 410 or MBSFN subframe 420 that was replaced. Depending on the change in the MBSFN pattern 400a, 400b, 400c, either dynamic downlink CRS rate-matching is switched on or switched off in the at least one non-MBSFN frame 410 or MBSFN subframe 420 that was replaced.

[0048] In general terms, rate-matching is effected by the use of downlink control information (DCI; such as a scheduling assignment) to instruct the NR UEs 150a, 150b whether to perform or not to perform rate-matching around a certain resource element (RE). When the NR UEs 150a, 150b are configured to not perform ratematching, the NR UEs 150a, 150b know that the REs comprises PDSCH data and the NR UEs 150a, 150b therefore decode these REs accordingly.

[0049] Embodiments relating to further details of dynamic CRS rate-matching for NR UEs 150a, 150b as performed by the network node 200 will now be disclosed.

[0050] There may be different ways in which the MBSFN pattern 400a, 400b, 400c is changed. In some embodiments, the MBSFN pattern 400a, 400b, 400c for the LTE UEs 150c, isod only is changed in any of the subframes where the MBSFN pattern 400a, 400b, 400c for the NR UEs 150a, 150b comprises MBSFN subframes 420. This is the case for the example in Fig. 4.

[0051] Aspects of how the network node 200 adapts the dynamic downlink CRS ratematching for the NR UEs 150a, 150b in the at least one non-MBSFN subframe 410 or MBSFN subframe 420 that was replaced will be disclosed next.

[0052] In some aspects, the number of MBSFNs is increased (thus changing from MBSFN pattern 400a to MBSFN pattern 400b, or from MBSFN pattern 400b to MBSFN pattern 400c). The NR UEs 150a, 150b are then without dynamic CRS rate-matching over the new MBSFN subframes 420. That is, in some embodiments, in response to at least one non-MBSFN subframe 410 being replaced by an MBSFN subframe 420, the adapting comprises switching off the dynamic CRS rate-matching for the NR UEs 150a, 150b in the at least one non-MBSFN subframe 410 being replaced by the MBSFN subframe 420. In this respect, it takes some time for all LTE UEs 150c, 150c! to be configured with the new MBSFN pattern, and the NR UEs 150a, 150b can meanwhile be configured to use dynamic CRS rate-matching over the new MBSFN subframes. When all LTE UEs 150c, isod have been informed of the new MBSFN pattern, the NR UEs 150a, 150b are in these MBSFN subframes scheduled without dynamic CRS rate-matching. Hence, in some aspects, dynamic CRS rate-matching is only to be used over the new MBSFN subframes 420 during the time the LTE UEs 150c, isod get configured with the new MBSFN configuration. That is, in some embodiments, the dynamic CRS ratematching for the NR UEs 150a, 150b in the at least one non-MBSFN subframe 410 that was replaced remains switched on during a time period it takes for the LTE UEs 150c, isod to be configured with the MBSFN configuration and then is switched off.

[0053] In some aspects, the number of MBSFNs is decreased (thus changing from MBSFN pattern 400c to MBSFN pattern 400b, or from MBSFN pattern 400b to MBSFN pattern 400a). Dynamic CRS rate-matching for the NR UEs 150a, 150b can then be started over the new non-MBSFN subframes 410. That is, in some embodiments, in response to at least one MBSFN subframe 420 being replaced by a non-MBSFN subframe 410, the adapting comprises switching on the dynamic CRS rate-matching for the NR UEs 150a, 150b in the at least one MBSFN subframe 420 being replaced by the non-MBSFN subframe 410.

[0054] In some aspects, dynamic CRS rate-matching is only to be started once the new MBSFN configuration is effective in the LTE UEs 150c, isod. That is, in some embodiments, the dynamic CRS rate-matching for the NR UEs 150a, 150b in the at least one MBSFN subframe 420 that was replaced remains switched off until after a time period it takes for the LTE UEs 150c, isod to be configured with the MBSFN configuration and then is switched on.

[0055] Aspects of spectrum sharing between NR UEs 150a, 150b and LTE UEs 150c, isod will be disclosed next.

[0056] In some aspects, the NR UEs 150a, 150b are in a non-MBSFN subframe allocated a spectrum share which is more than half of the bandwidth. In particular, in some embodiments, the non-MBSFN subframe 410 occupies a bandwidth in the spectrum, and the NR UEs 150a, 150b are allocated at least a share of the spectrum, and the share is more than half of the bandwidth of the non-MBSFN subframe 410. Further, in some embodiments, in case at least one LTE UE 150c, isod is served, time / frequency resources are allocated to the at least one LTE UE 150c, isod from a part of the spectrum where the dynamic CRS rate-matching is performed. There can be different strategies to allocate the time / frequency resources. One strategy is to maximize NR efficiency. Then the time / frequency resources for the NR UEs 150a, 150b are placed in the part of the spectrum where rate-matching is not performed and the time / frequency resources for the LTE UEs 150c, isod are placed in the part of the spectrum where rate-matching is performed. Another strategy is to maximize the CRS. Then the time / frequency resources for the NR UEs 150a, 150b are placed in the part of the spectrum where rate-matching is performed and the time / frequency resources for the LTE UEs 150c, isod are placed in the part of the spectrum where rate-matching is not performed. In other words, when CRS is transmitted over the whole of the spectrum but rate-matching in NR is performed over just part of the spectrum, the NR UEs 150a, 150b are scheduled in the part of the spectrum where rate-matching is performed whilst LTE UEs 150c, isod are scheduled in the other part of the spectrum. Further in this respect, in some embodiments, in case at least one NR UE 150a, 150b and at least one LTE UE 150c, isod is served, CRSs allocated for the at least one LTE UE 150c, isod are punctured in a part of the spectrum where the dynamic CRS rate-matching is not performed.

[0057] In some aspects it is ensured that the LTE UEs 150c, isod always have enough PRBs to perform their receiver operations. This can be achieved by the CRS being transmitted over a sufficient range of PRBs, where the minimum value of this range of PRBs can be adaptively determined. Therefore, in some embodiments, in case at least one NR UE 150a, 150b and at least one LTE UE 150c, isod is served, a minimum number of time / frequency resources for CRSs allocated for the at least one LTE UE 150c, isod is adaptively determined. There can be different adaptive approaches. For example, the adaptive approach could involve trying LTE PDSCH transmissions over a range of PRBs and observing HARQ feedback from the LTE UEs 150c, isod. Particularly, in some embodiments, adaptively determining the minimum number of time / frequency resources comprises observing HARQ feedback from the at least one LTE UE 150c, isod in response to downlink data or control transmissions to the at least one LTE UE 150c, isod.

[0058] Aspects of how to implement the dynamic rate-matching will be disclosed next. In general terms, the NR UEs 150a, 150b need to perform rate-matching around the CRS that LTE transmits in normal subframes (irrespective of whether these have been normal subframes (i.e., non-MBSFN subframes) for long or whether they have recently been turned into normal subframes from MBSFN subframes). But the capacity for NR to signal alternative rate-matching patterns to the NR UEs 150a, 150b is limited. By coordinating the NR CSI-RS pattern to at least partly overlap with that of the LTE CRS, NR rate-matching around the LTE CRS can be performed by ZP-CSI- RS (where ZP is short for zero power). Hence, in some embodiments, using the dynamic CRS rate-matching comprises using ZP-CSI-RS rate-matching. In this way, the NR UEs 150a, 150b can be configured to perform dynamic rate-matching around LTE CRS using ZP-CSI-RS such that it can cover the maximum possible number of CRS REs. In some embodiments, using the dynamic CRS rate-matching comprises using rateMatchingResrcSetDynamic (UE feature 5-27) rate-matching and / or separateCRS-RateMatching-ri6 (UE feature 16-23-5) rate-matching, if this is supported by the NR UEs 150a, 150b. Further, depending on the value of the LTE minimum CRS PRBs, it can be determined whether to trigger rateMatchingResrcSetDynamic or separateCRS-RateMatching-ri6. Hence, in some embodiments, whether to trigger rateMatchingResrcSetDynamic rate-matching or separateCRS-RateMatching-ri6 rate-matching is dependent on the aforementioned determined minimum number of time / frequency resources. A variation is to additionally configure the NR UEs 150a, 150b with static CRS rate-matching as well but only over CRS Port_o, or over all ports for middle 6 PRBs. A yet further variation is to configure the NR UEs 150a, 150b with maximum CRS rate-matching and / or with ZP-CSI-RS rate-matching.

[0059] Reference is next made to the signaling diagram of Fig. 5.

[0060] S20ia, S20ib: The LTE scheduler and the NR scheduler are configured with initial MBSFN patterns and the shared resource allocator is made aware of these MBSFN patterns. The LTE scheduler informs the LTE UEs of the (LTE) MBSFN pattern via system information broadcast. The NR scheduler configures the NR UEs with the (NR) MBSFN pattern and configures the NR UEs with dynamic rate-matching. S202: The shared resource allocator decides that dynamic rate-matching is to be used or not used and sends a dynamic rate-matching decision to the NR scheduler. The NR scheduler transmits PDSCH with or without dynamic rate-matching.

[0061] S203: The shared resource allocator decides to change the MBSFN pattern for the LTE UEs and communicates the new MBSFN pattern to the LTE scheduler. The MBSFN pattern is changed such that at least one non-MBSFN subframe is replaced by an MBSFN subframe, and / or at least one MBSFN subframe is replaced by a non- MBSFN subframe in the MBSFN pattern used by the LTE UEs. The LTE scheduler informs the LTE UEs of the new MBSFN pattern via system information broadcast.

[0062] S204: The shared resource allocator, based on the changed MBSFN pattern, adapts the dynamic downlink CRS rate-matching for the NR UEs in the at least one non- MBSFN subframe or MBSFN subframe that was replaced and informs the NR scheduler about this. The NR scheduler adapts its transmission of PDSCH with or without dynamic rate-matching accordingly.

[0063] S205: Based on HARQ feedback received from the LTE UEs, the LTE scheduler updates the minimum number of PRBs for CRS and informs the shared resource allocator about this.

[0064] S206: The shared resource allocator, based on the information received from the LTE scheduler, decides to update the CRS transmission and the dynamic rate-matching. The shared resource allocator informs the LTE scheduler about the CRS transmission and the NR scheduler about the dynamic rate-matching. The LTE scheduler schedules CRS transmission accordingly. The NR scheduler transmits PDSCH according to the dynamic rate-matching decision.

[0065] In general terms, rateMatchingResrcSetDynamic or separateCRS-RateMatching-ri6 or any similar rate matching capability can allow CRS transmission over the full LTE bandwidth. In a scenario when NR UE does not support any of these optional capabilities and is allocated a spectrum share which is more than half of the bandwidth in a non-MBSFN subframe, the procedure according to the flowchart of Fig. 6 can be applied. S30i:The LTE scheduler initializes a minimum number of PRBs over which CRS will be transmitted. The minimum number can be zero if there are no LTE UEs 150c, i5od. Feedback from LTE UEs 150c, isod is analyzed. This can be HARQ feedback on control or data channels or Channel State Information (CSI) or any other UE reported parameter.

[0066] S302: Based on the feedback received, the minimum number of PRBs over which CRS will be transmitted is adjusted. If the HARQ feedback is an acknowledgment (ACK), the number can be reduced. If the feedback is not an ACK (i.e., a negative acknowledgement, NACK), the number can be increased. Similar actions may be performed on other types of received feedback.

[0067] S303: It is checked whether or not the minimum number of PRBs over which CRS will be transmitted is less than or equal to the number of PRBs covered by ZP-CSI-RS rate-matching Seti. Seti is a set of ZP-CSI-RS resources which cover only the REs of LTE CRS. This set however, is limited to half of the LTE bandwidth, either above or below the LTE DC carrier.

[0068] S304: The NR scheduler transmits PDSCH with dynamic rate-matching using ZP- CSI-RS rate-matching Seti. The LTE scheduler does not transmit CRS over the PRBs which are not covered by ZP-CSI-RS rate-matching Seti.

[0069] S305: If the minimum number of PRBs over which CRS will be transmitted, is greater than PRBs covered by ZP-CSI-RS rate-matching Seti, it is checked if the NR UEs 150a, 150b are configured with any other dynamic rate-matching capabilities, such as rateMatchingResrcSetDynamic, or separateCRS-RateMatching-ri6, or any similar rate matching capability that can allow CRS transmission over the full LTE bandwidth.

[0070] S306: It is checked whether or not the NR UEs 150a, 150b are configured with any such dynamic rate-matching capabilities and NR PDSCH can maximize its transport block size (TBS) with such capabilities compared with ZP-CSI-RS rate-matching Set2. Set2 is a set of ZP-CSI-RS resources which cover additional REs than LTE CRS. This set however, can cover entire LTE bandwidth. S307: The NR scheduler uses dynamic rate-matching capabilities to perform CRS rate-matching. The LTE scheduler transmits CRS over all LTE PRBs.

[0071] S308: It is checked whether or not the NR UEs 150a, 150b are configured with any other dynamic rate-matching capabilities and NR PDSCH maximizes its TBS through ZP-CSI-RS rate-matching Set2 compared with ZP-CSI-RS rate-matching Seti.

[0072] S309: The NR scheduler uses ZP-CSI-RS rate-matching Set2 to perform CRS ratematching. The LTE scheduler transmits CRS over all LTE PRBs.

[0073] S310: The NR scheduler uses ZP-CSI-RS rate-matching Seti to perform CRS ratematching and is restricted to use PRBs covered by ZP-CSI-RS rate-matching Seti. The LTE scheduler transmits CRS over all LTE PRBs.

[0074] Fig. 7 schematically illustrates, in terms of a number of structural units, the components of a network node 200 according to an embodiment. Processing circuitry 210 is provided using any combination of one or more of a suitable central processing unit (CPU), multiprocessor, microcontroller, digital signal processor (DSP), etc., capable of executing software instructions stored in a computer program product 910 (as in Fig. 9), e.g. in the form of a storage medium 230. The processing circuitry 210 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0075] Particularly, the processing circuitry 210 is configured to cause the network node 200 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 230 may store the set of operations, and the processing circuitry 210 may be configured to retrieve the set of operations from the storage medium 230 to cause the network node 200 to perform the set of operations. The set of operations may be provided as a set of executable instructions.

[0076] Thus the processing circuitry 210 is thereby arranged to execute methods as herein disclosed. The storage medium 230 may also comprise persistent storage, which, for example, can be any single one or combination of magnetic memory, optical memory, solid state memory or even remotely mounted memory. The network node 200 may further comprise a communications (comm.) interface 220 at least configured for communications other entities, functions, nodes, and devices, as in Fig. 1. As such the communications interface 220 may comprise one or more transmitters and receivers, comprising analogue and digital components. The processing circuitry 210 controls the general operation of the network node 200 e.g. by sending data and control signals to the communications interface 220 and the storage medium 230, by receiving data and reports from the communications interface 220, and by retrieving data and instructions from the storage medium 230. Other components, as well as the related functionality, of the network node 200 are omitted in order not to obscure the concepts presented herein.

[0077] Fig. 8 schematically illustrates, in terms of a number of functional modules, the components of a network node 200 according to an embodiment. The network node 200 of Fig. 8 comprises a number of functional modules; an obtain module 210a configured to perform step S102, and an adapt module 210b configured to perform step S104. The network node 200 of Fig. 8 may further comprise a number of optional functional modules, as represented by functional module 210c. In general terms, each functional module 210a: 210c may in one embodiment be implemented only in hardware and in another embodiment with the help of software, i.e., the latter embodiment having computer program instructions stored on the storage medium 230 which when run on the processing circuitry makes the network node 200 perform the corresponding steps mentioned above in conjunction with Fig 8. It should also be mentioned that even though the modules correspond to parts of a computer program, they do not need to be separate modules therein, but the way in which they are implemented in software is dependent on the programming language used. Preferably, one or more or all functional modules 210a: 210c maybe implemented by the processing circuitry 210, possibly in cooperation with the communications interface 220 and / or the storage medium 230. The processing circuitry 210 may thus be configured to from the storage medium 230 fetch instructions as provided by a functional module 210a: 210c and to execute these instructions, thereby performing any steps as disclosed herein.

[0078] The network node 200 may be provided as a standalone device or as a part of at least one further device. For example, the network node 200 may be provided in a node of the radio access network or in a node of the core network. Alternatively, functionality of the network node 200 may be distributed between at least two devices, or nodes. These at least two nodes, or devices, may either be part of the same network part (such as the radio access network or the core network) or may be spread between at least two such network parts. In general terms, instructions that are required to be performed in real time may be performed in a device, or node, operatively closer to the cell than instructions that are not required to be performed in real time. Thus, a first portion of the instructions performed by the network node 200 may be executed in a first device, and a second portion of the of the instructions performed by the network node 200 may be executed in a second device; the herein disclosed embodiments are not limited to any particular number of devices on which the instructions performed by the network node 200 may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a network node 200 residing in a cloud computational environment. Therefore, although a single processing circuitry 210 is illustrated in Fig. 7 the processing circuitry 210 may be distributed among a plurality of devices, or nodes. The same applies to the functional modules 210a: 210c of Fig. 8 and the computer program 920 of Fig. 9.

[0079] Some (radio) access network architectures define network nodes (or gNBs) comprising multiple component parts or nodes: a central unit (CU), one or more distributed units (DUs), and one or more radio units (RUs). The protocol layer stack of the network node is divided between the CU, the DUs and the RUs, with one or more lower layers of the stack implemented in the RUs, and one or more higher layers of the stack implemented in the CU and / or DUs. The CU is coupled to the DUs via a fronthaul higher layer split (HLS) network; the CU / DUs are connected to the RUs via a fronthaul lower-layer split (LLS) network. The DU may be combined with the CU in some embodiments, where a combined DU / CU may be referred to as a CU or simply a baseband unit. A communication link for communication of user data messages or packets between the RU and the baseband unit, CU, or DU is referred to as a fronthaul network or interface. Messages or packets may be transmitted from the network node 200 in the downlink (i.e., from the CU to the RU) or received by the network node 200 in the uplink (i.e., from the RU to the CU).

[0080] Fig. 9 shows one example of a computer program product 910 comprising computer readable storage medium 930. On this computer readable storage medium 930, a computer program 920 can be stored, which computer program 920 can cause the processing circuitry 210 and thereto operatively coupled entities and devices, such as the communications interface 220 and the storage medium 230, to execute methods according to embodiments described herein. The computer program 920 and / or computer program product 910 may thus provide means for performing any steps as herein disclosed.

[0081] In the example of Fig. 9, the computer program product 910 is illustrated as an optical disc, such as a CD (compact disc) or a DVD (digital versatile disc) or a Blu-Ray disc. The computer program product 910 could also be embodied as a memory, such as a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM), or an electrically erasable programmable read-only memory (EEPROM) and more particularly as a non-volatile storage medium of a device in an external memory such as a USB (Universal Serial Bus) memory or a Flash memory, such as a compact Flash memory. Thus, while the computer program 920 is here schematically shown as a track on the depicted optical disk, the computer program 920 can be stored in any way which is suitable for the computer program product 910.

[0082] The inventive concept has mainly been described above with reference to a few embodiments. However, as is readily appreciated by a person skilled in the art, other embodiments than the ones disclosed above are equally possible within the scope of the inventive concept, as defined by the appended patent claims.

Claims

CLAIMS1. A method for dynamic CRS rate-matching for NR UEs (150a, 150b), wherein a spectrum in which the NR UEs (150a, 150b) are served at least partly overlaps with a spectrum in which LTE UEs (150c, isod) are served, wherein the method is performed by a network node (200), and wherein the method comprises: obtaining (S102) MBSFN configuration pertaining to a change in an MBSFN pattern (400a, 400b, 400c) for the LTE UEs (150c, isod), wherein the MBSFN pattern (400a, 400b, 400c) specifies which subframes are MBSFN subframes (420) and which subframes are non-MBSFN subframes (410), wherein there are separate MBSFN patterns (400a, 400b, 400c) for the NR UEs (150a, 150b) and the LTE UEs (150c, isod), and wherein the MBSFN configuration specifies at least one non-MBSFN subframe (410) being replaced by an MBSFN subframe (420), and / or at least one MBSFN subframe (420) being replaced by a non-MBSFN subframe (410) in the MBSFN pattern (400a, 400b, 400c); and adapting (S104) the dynamic downlink CRS rate-matching for the NR UEs (150a, 150b) in the at least one non-MBSFN subframe (410) or MBSFN subframe (420) that was replaced, wherein either dynamic downlink CRS rate-matching is switched on or switched off in the at least one non-MBSFN frame (410) or MBSFN subframe (420) that was replaced depending on the change in the MBSFN pattern (400a, 400b, 400c).

2. The method according to claim 1, wherein the MBSFN pattern (400a, 400b, 400c) for the LTE UEs (150c, isod) only is changed in any of the subframes where the MBSFN pattern (400a, 400b, 400c) for the NR UEs (150a, 150b) comprises MBSFN subframes (420).

3. The method according to claim 1 or 2, wherein in response to at least one non- MBSFN subframe (410) being replaced by an MBSFN subframe (420), the adapting comprises switching off the dynamic CRS rate-matching for the NR UEs (150a, 150b) in the at least one non-MBSFN subframe (410) being replaced by the MBSFN subframe (420).4- The method according to claim 3, wherein the dynamic CRS rate-matching for the NR UEs (150a, 150b) in the at least one non-MBSFN subframe (410) that was replaced remains switched on during a time period it takes for the LTE UEs (150c, i50d) to be configured with the MBSFN configuration and then is switched off.

5. The method according to claim 1 or 2, wherein in response to at least one MBSFN subframe (420) being replaced by a non-MBSFN subframe (410), the adapting comprises switching on the dynamic CRS rate-matching for the NR UEs (150a, 150b) in the at least one MBSFN subframe (420) being replaced by the non- MBSFN subframe (410).

6. The method according to claim 5, wherein the dynamic CRS rate-matching for the NR UEs (150a, 150b) in the at least one MBSFN subframe (420) that was replaced remains switched off until after a time period it takes for the LTE UEs (150c, isod) to be configured with the MBSFN configuration and then is switched on.

7. The method according to any preceding claim, wherein the non-MBSFN subframe (410) occupies a bandwidth in the spectrum, wherein the NR UEs (150a, 150b) are allocated at least a share of the spectrum, wherein the share is more than half of the bandwidth of the non-MBSFN subframe (410).

8. The method according to claim 7, wherein, in case at least one LTE UE (150c, isod) is served, time / frequency resources are allocated to the at least one LTE UE (150c, isod) from a part of the spectrum where the dynamic CRS rate-matching is performed.

9. The method according to claim 7, wherein, in case at least one NR UE (150a, 150b) and at least one LTE UE (150c, isod) is served, CRSs allocated for the at least one LTE UE (150c, isod) are punctured in a part of the spectrum where the dynamic CRS rate-matching is not performed.

10. The method according to any of claims 7 to 9, wherein, in case at least one NR UE (150a, 150b) and at least one LTE UE (150c, isod) is served, a minimum number of time / frequency resources for CRSs allocated for the at least one LTE UE (150c, isod) is adaptively determined.

11. The method according to claim io, wherein adaptively determining said minimum number comprises observing HARQ feedback from the at least one LTE UE (150c, isod) in response to downlink data or control transmissions to the at least one LTE UE (150c, isod).

12. The method according to any preceding claim, wherein using the dynamic CRS rate-matching comprises using ZP-CSI-RS rate-matching.

13. The method according to any preceding claim, wherein using the dynamic CRS rate-matching comprises using rateMatchingResrcSetDynamic rate-matching or separateCRS-RateMatching-ri6 rate-matching.

14. The method according to a combination of claim 10 and claim 13, wherein whether to trigger rateMatchingResrcSetDynamic rate-matching or separateCRS- RateMatching-ri6 rate-matching is dependent on said minimum number.

15. A network node (200) for dynamic CRS rate-matching for NR UEs (150a, 150b), wherein a spectrum in which the NR UEs (150a, 150b) are served at least partly overlaps with a spectrum in which LTE UEs (150c, isod) are served, the network node (200) comprising processing circuitry (210), the processing circuitry being configured to cause the network node (200) to: obtain MBSFN configuration pertaining to a change in an MBSFN pattern (400a, 400b, 400c) for the LTE UEs (150c, isod), wherein the MBSFN pattern (400a, 400b, 400c) specifies which subframes are MBSFN subframes (420) and which subframes are non-MBSFN subframes (410), wherein there are separate MBSFN patterns (400a, 400b, 400c) for the NR UEs (150a, 150b) and the LTE UEs (150c, isod), and wherein the MBSFN configuration specifies at least one non-MBSFN subframe (410) being replaced by an MBSFN subframe (420), and / or at least one MBSFN subframe (420) being replaced by a non-MBSFN subframe (410) in the MBSFN pattern (400a, 400b, 400c); and adapt the dynamic downlink CRS rate-matching for the NR UEs (150a, 150b) in the at least one non-MBSFN subframe (410) or MBSFN subframe (420) that wasreplaced, wherein either dynamic downlink CRS rate-matching is switched on or switched off in the at least one non-MBSFN frame (410) or MBSFN subframe (420) that was replaced depending on the change in the MBSFN pattern (400a, 400b, 400c).

16. A network node (200) for dynamic CRS rate-matching for NR UEs (150a, 150b), wherein a spectrum in which the NR UEs (150a, 150b) are served at least partly overlaps with a spectrum in which LTE UEs (150c, isod) are served, the network node (200) comprising: an obtain module (210a) configured to obtain MBSFN configuration pertaining to a change in an MBSFN pattern (400a, 400b, 400c) for the LTE UEs (150c, isod), wherein the MBSFN pattern (400a, 400b, 400c) specifies which subframes are MBSFN subframes (420) and which subframes are non-MBSFN subframes (410), wherein there are separate MBSFN patterns (400a, 400b, 400c) for the NR UEs (150a, 150b) and the LTE UEs (150c, isod), and wherein the MBSFN configuration specifies at least one non-MBSFN subframe (410) being replaced by an MBSFN subframe (420), and / or at least one MBSFN subframe (420) being replaced by a non-MBSFN subframe (410) in the MBSFN pattern (400a, 400b, 400c); and an adapt module (210b) configured to adapt the dynamic downlink CRS ratematching for the NR UEs (150a, 150b) in the at least one non-MBSFN subframe (410) or MBSFN subframe (420) that was replaced, wherein either dynamic downlink CRS rate-matching is switched on or switched off in the at least one non-MBSFN frame (410) or MBSFN subframe (420) that was replaced depending on the change in the MBSFN pattern (400a, 400b, 400c).

17. The network node (200) according to claim 15 or 16, further being configured to perform the method according to any of claims 2 to 14.

18. A computer program (920) for dynamic CRS rate-matching for NR UEs (150a, 150b), wherein a spectrum in which the NR UEs (150a, 150b) are served at least partly overlaps with a spectrum in which LTE UEs (150c, isod) are served, thecomputer program comprising computer code which, when run on processing circuitry (210) of a network node (200), causes the network node (200) to: obtain (S102) MBSFN configuration pertaining to a change in an MBSFN pattern (400a, 400b, 400c) for the LTE UEs (150c, isod), wherein the MBSFN pattern (400a, 400b, 400c) specifies which subframes are MBSFN subframes (420) and which subframes are non-MBSFN subframes (410), wherein there are separate MBSFN patterns (400a, 400b, 400c) for the NR UEs (150a, 150b) and the LTE UEs (150c, isod), and wherein the MBSFN configuration specifies at least one non-MBSFN subframe (410) being replaced by an MBSFN subframe (420), and / or at least one MBSFN subframe (420) being replaced by a non-MBSFN subframe (410) in the MBSFN pattern (400a, 400b, 400c); and adapt (S104) the dynamic downlink CRS rate-matching for the NR UEs (150a, 150b) in the at least one non-MBSFN subframe (410) or MBSFN subframe (420) that was replaced, wherein either dynamic downlink CRS rate-matching is switched on or switched off in the at least one non-MBSFN frame (410) or MBSFN subframe (420) that was replaced depending on the change in the MBSFN pattern (400a, 400b, 400c).

19. A computer program product (910) comprising a computer program (920) according to claim 18, and a computer readable storage medium (930) on which the computer program is stored.

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