Reporting of reference signals from a user equipment

Abstract

There is provided techniques for reporting reference signal measurements from a user equipment. A method comprises receiving configuration from a network node. The configuration specifies a set of beams in which a reference signal is to be transmitted from the network node during a beam sweep. The method comprises performing measurements on the reference signal as received by the user equipment during the beam sweep. The measurements are performed for less than all beams in the specified set of beams by the user equipment skipping measuring the reference signal for a subset of beams during the beam sweep. The method comprises sending a measurement report of the performed measurements to the network node.

Description

[0001] REPORTING OF REFERENCE SIGNALS FROM A USER EQUIPMENT

[0002] TECHNICAL FIELD

[0003] Embodiments presented herein relate to a method, a user equipment, a computer program, and a computer program product for reporting reference signal measurements from the user equipment.

[0004] BACKGROUND

[0005] In general terms, reference signals, as transmitted between network nodes at the network-side and user equipment at the user-side in wireless telecommunication systems, can be used for different purposes, such as for providing synchronization, basic system information, and mobility measurements.

[0006] One non-limiting example of a downlink reference signal (i.e., a reference signal transmitted from the network nodes towards the user equipment) is the synchronization signal block (SSB) signal. The SSB consists of one Primary Synchronization Signal (PSS), one Secondary Synchronization Signal (SSS) and a Physical Broadcast Channel (PBCH). The PSS and SSS parts of the SSB are each transmitted over 127 sub-carriers, where the sub-carrier spacing could be 15 or 30 kHz for carrier frequencies below 6 GHz and 120 or 240 kHz for carrier frequencies above 6 GHz.

[0007] For low frequencies (e.g., carrier frequencies below 2-3 GHz) it is expected that in each cell, an SSB signal is transmitted in a beam that covers the whole cell. On the other hand, for higher frequencies (e.g., carrier frequencies above 2-3 GHz) several beamformed SSB signals are expected to be needed to attain coverage over the whole cell. In this respect, the maximum number of beams in which the SSB signal is transmitted per cell are: 4 for carrier frequencies below 3 GHz, 8 for carrier frequencies in the interval 3-6 GHz, and 64 for carrier frequencies above 6 GHz. Regardless of the number of beams, the SSB signal is transmitted in an SSB transmission burst, which could last up to 5 ms (i.e., span many slots). The periodicity of the SSB transmission burst can be configurable with the following options: 5, 10, 20, 40, 80, 160 ms.

[0008] Each user equipment is expected to measure on the SSB signals and report back the measurement results to its serving network node. Intermediate reference is here made to Fig. 1, in which is provided a schematic diagram illustrating a communications network 100 where embodiments presented herein can be applied. The communications network 100 comprises a network node no that, via a transmission and reception point (TRP) 120 is configured for transmission (and reception) of signals in beams 130. The network node 110 is thereby enabled to provide network access for one or more user equipment 140.

[0009] The network node no could be any of a (radio) access network node, radio base station, base transceiver station, node B (NB), evolved node B (eNB), gNB, access point, access node, integrated access and backhaul (IAB) node, etc. The TRP 120 could be any of an advanced (or adaptive) antenna system (AAS), antenna array, radio unit, distributed unit. The user equipment 140 might be any of a portable wireless device, mobile station, mobile phone, handset, wireless local loop phone, smartphone, laptop computer, tablet computer, wireless sensor device, Internet of Things device, network equipped vehicle, network equipped gaming control, etc. as long as the user equipment 140 is capable of implementing the herein disclosed embodiments.

[0010] As disclosed above, the SSB signal is just one example of a downlink reference signal. Other types of downlink reference signals, which the user equipment are expected to measure and (sometimes) report back to the serving network node, are channel state information reference signals (CSI-RS) and demodulation reference signals (DM-RS). Here, it is noted that, for example, CSI-RS, can be transmitted in larger number of beams than SSB signal.

[0011] Reporting measurements on downlink reference signals creates a reporting overhead for the user equipment. In this respect, efforts have been made to reduce the reporting overhead whilst maintaining the beam prediction accuracy. One way to reduce the reporting overhead is for the user equipment to only report the K beams with best measurements. One way to reduce the reporting overhead is for the user equipment to only report the beams for which the measurements are better than some threshold value. This can, at least potentially, save power in the user equipment and reduce the needed uplink resources. However, the measurements needed to be performed by the user equipment would still be same. That is, the user equipment would still need to measure on all beams in which the downlink reference signal is sent. Therefore, user equipment with high requirement on energy efficiency might still be negatively impacted. For example, for user equipment performing beam prediction using periodic downlink reference signals (such as SSB signals or CSI-RS), or a frequent use of aperiodic CSI-RS, the measurement overhead might be large for the user equipment. This generally holds regardless if the beam prediction is implemented in the user equipment or in the network node.

[0012] SUMMARY

[0013] An object of embodiments herein is to address the above issues and to provide reporting reference signal measurements where the above issues have been resolved, or at least mitigated or reduced.

[0014] A particular object is to lower the reporting overhead for the user equipment.

[0015] A particular object is to improve the energy efficiency of the user equipment.

[0016] According to a first aspect there is presented a method for reporting reference signal measurements. The method is performed by a user equipment. The method comprises receiving configuration from a network node. The configuration specifies a set of beams in which a reference signal is to be transmitted from the network node during a beam sweep. The method comprises performing measurements on the reference signal as received by the user equipment during the beam sweep. The measurements are performed for less than all beams in the specified set of beams by the user equipment skipping measuring the reference signal for a subset of beams during the beam sweep. The method comprises sending a measurement report of the performed measurements to the network node.

[0017] According to a second aspect there is presented a user equipment for reporting reference signal measurements. The user equipment comprises processing circuitry. The processing circuitry is configured to cause the user equipment to receive configuration from a network node. The configuration specifies a set of beams in which a reference signal is to be transmitted from the network node during a beam sweep. The processing circuitry is configured to cause the user equipment to perform measurements on the reference signal as received by the user equipment during the beam sweep. The measurements are performed for less than all beams in the specified set of beams by the user equipment skipping measuring the reference signal for a subset of beams during the beam sweep. The processing circuitry is configured to cause the user equipment to send a measurement report of the performed measurements to the network node.

[0018] According to a third aspect there is presented a user equipment for reporting reference signal measurements. The user equipment comprises a receive module configured to receive configuration from a network node. The configuration specifies a set of beams in which a reference signal is to be transmitted from the network node during a beam sweep. The user equipment comprises a measure module configured to perform measurements on the reference signal as received by the user equipment during the beam sweep. The measurements are performed for less than all beams in the specified set of beams by the user equipment skipping measuring the reference signal for a subset of beams during the beam sweep. The user equipment comprises a send module configured to send a measurement report of the performed measurements to the network node.

[0019] According to a fourth aspect there is presented a computer program for reporting reference signal measurements. The computer program comprises computer code which, when run on processing circuitry of a user equipment, causes the user equipment to perform actions. One action comprises the user equipment to receive configuration from a network node. The configuration specifies a set of beams in which a reference signal is to be transmitted from the network node during a beam sweep. One action comprises the user equipment to perform measurements on the reference signal as received by the user equipment during the beam sweep. The measurements are performed for less than all beams in the specified set of beams by the user equipment skipping measuring the reference signal for a subset of beams during the beam sweep. One action comprises the user equipment to send a measurement report of the performed measurements to the network node.

[0020] 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. Advantageously, these aspects provide reporting of reference signal measurements that does not suffer from the above issues.

[0021] Advantageously, these aspects enable the reporting overhead for the user equipment to be reduced.

[0022] Advantageously, these aspects enable the energy efficiency of the user equipment to be improved.

[0023] Advantageously, these aspects are applicable for both network-side and user-side beam prediction.

[0024] 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.

[0025] 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.

[0026] BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which:

[0028] Fig. 1 is a schematic diagram illustrating a communications network according to embodiments;

[0029] Figs. 2 and 3 schematically illustrate sets of beams according to examples;

[0030] Fig. 4 is a flowchart of methods according to embodiments;

[0031] Figs. 5 and 6 schematically illustrate sets of beams according embodiments;

[0032] Fig. 7 is a signaling diagram of a method according to an embodiment; Fig. 8 is a schematic diagram showing structural units of a user equipment according to an embodiment;

[0033] Fig. 9 is a schematic diagram showing functional modules of a user equipment according to an embodiment; and

[0034] Fig. io shows one example of a computer program product comprising computer readable storage medium according to an embodiment.

[0035] DETAILED DESCRIPTION

[0036] 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.

[0037] In general terms, spatial beam prediction could be performed either at the networkside (i.e., by the network node no) or at the user-side (i.e. , by the user equipment 140). In further detail, spatial beam prediction for a set A of beams can be performed based on measurement results of a Set B of beams. The Set B of beams could either consist of different beams compared to the Set A of beams (as in Fig. 2) or be a subset of the Set A of beams (as in Fig. 3).

[0038] In Fig. 2 is schematically illustrated a first set of beams 200a and a second set of beams 200b, where the second set of beams 200b comprises beams 220a, 220b that are comparatively wider than the beams 210a, 210b in the first set of beams 200a. For illustrative purposes it is assume that the first set of beams 200a is the aforementioned Set A of beams and that the second set of beams 200b is the aforementioned Set B of beams. In this example, a reference signal could by the network node be transmitted in the Set B of beams and based on measurements made by the user equipment 140 on the reference signal in these beams, a beam prediction can be made (either by the user equipment 140 or the network node) which beam in the Set A of beams is best for the network node to serve the user equipment 140.

[0039] In Fig. 3 is schematically illustrated a first set of beams 300a and a second set of beams 300b, where the second set of beams 300b comprises beams 320a, 320b that are a subset of the beams 310a, 310b, 310c in the first set of beams 300a. For illustrative purposes it is assume that the first set of beams 300a is the aforementioned Set A of beams and that the second set of beams 300b is the aforementioned Set B of beams. In this example, a reference signal could by the network node be transmitted in the Set B of beams and based on measurements made by the user equipment 140 on the reference signal in these beams, a beam prediction can be made (either by the user equipment 140 or the network node) which beam in the Set A of beams is best for the network node to serve the user equipment 140.

[0040] However, in the examples of both Fig. 2 and Fig. 3, the user equipment 140 still needs to perform measurements on the reference signal in all beams in which the reference signal is sent, i.e., for all the beams in the Set B of beams.

[0041] The embodiments disclosed herein therefore relate to techniques for reporting reference signal measurements. In order to obtain such techniques, there is provided a user equipment 140, a method performed by the user equipment 140, a computer program product comprising code, for example in the form of a computer program, that when run on a user equipment 140, causes the user equipment 140 to perform the method.

[0042] Hereinafter, unless otherwise stated, it is assumed that the beams are formed at the network-side (i.e., generated by the network node via the TRP) and that the user equipment 140 measures on signals, such as reference signals, transmitted on the beams. This can for example be an SSB signal transmitted on comparatively wide beams or an CSI-RS that is transmitted on comparatively narrow beams.

[0043] At least some of the herein disclosed embodiments are based on the user equipment 140, skipping measuring the reference signal on certain beams. This can be used to improve the energy efficiency of the user equipment 140, as well as to reduce the reporting overhead during both network-sided and user-side beam prediction. Fig. 4 is a flowchart illustrating embodiments of methods for reporting reference signal measurements. The methods are performed by the user equipment 140. The methods are advantageously provided as computer programs 1020.

[0044] S102: The user equipment 140 receives configuration from the network node 110. The configuration specifies a set of beams 130, 200b, 300b, 500a, 600a in which a reference signal is to be transmitted from the network node 110 during a beam sweep.

[0045] In this respect, each beam sweep thus represents one sweep as made by the network node 140 in the set of beams 130, 200b, 300b, 500a, 600a whilst transmitting the reference signal. However, this does not necessarily imply that the beam sweep is made in all beams in the set of beams 130, 200b, 300b, 500a, 600a. Rather, each beam sweep may be made only in a subset of these beams.

[0046] S108: The user equipment 140 performs measurements on the reference signal as received by the user equipment 140 during the beam sweep. The measurements are performed for less than all beams in the specified set of beams. This is achieved by the user equipment 140 skipping measuring the reference signal for a subset of beams during the beam sweep.

[0047] In general terms, the measurements are performed with respect to some performance metric, such as the received power of the reference signal, i.e., the reference signal received power (RSRP), the received quality of the reference signal, i.e., the reference signal received quality (RSRQ), the block error rate (BLER) of the reference signal, or the symbol error rate (SER) of the reference signal, etc.

[0048] S112: The user equipment 140 sends a measurement report of the performed measurements to the network node 110.

[0049] In this respect, there could be different types of measurement reports. In some examples, the measurement report includes beam identities of the beams for which the measurements were the best. In some examples, the measurement report includes all the beam identities, ordered from best measurement to worse measurement (or vice versa). In some examples, the measurement report further includes the measurements themselves, or at least some performance metric calculated from, or otherwise based on, the measurements (e.g., a probability for the reported beam being the best beam out of all beams in which the user equipment 140 received the reference signal, etc.). In general terms, which information to include in the measurement reports might depend on for what purpose the network node 110 is to use the measurement report. Therefore, in some examples the information the use equipment 140 is to include in the measurement report is specified by configuration received by the user equipment 140 from the network node 110.

[0050] Embodiments relating to further details of reporting reference signal measurements as performed by the user equipment 140 will now be disclosed with continued reference to Fig. 4.

[0051] There may be different types of information included in the configuration received from the network node 110. In some aspects, the configuration specifies that the user equipment 140 is to send a report of the measurements as made by the user equipment 140 on the reference signals to the network node 110. In other aspects, the user equipment 140 is separately configured by the network node 110 to report the measurements back to the network node 110. In some aspects, the measurement report of the performed measurements as sent by the user equipment 140 to the network node 110 is therefore regarded as a configured, expected, or requested, measurement report. In some aspects, the configuration specifies the number of beams the user equipment is to report. That is, in some embodiments, the configuration further specifies that the measurements are to be reported for K4> 1 number of beams. In some aspects, the configuration specifies whether the user equipment 140 is to use beam prediction (such as artificial intelligence or machine learning based beam prediction) or not. That is, in some embodiments, the configuration further specifies that beam prediction is to be performed by the user equipment 140. In some aspects, in case the user equipment 140 is to perform beam prediction, the configuration also includes a further (set A) of beams for which the user equipment 140 is to perform the beam prediction. Particularly, in some embodiments, the set of beams is a subset (denoted set B) of an available set of beams (denoted set A), at the network node 110, and the configuration further specifies the set A, and that the user equipment 140 is to predict a best beam in the set A based on the measurement performed on the reference signal as received in beams in a subset of the set B. Therefore, in some embodiments, the measurement report further comprises a predicted measurement for the best beam in set A based on the measurement performed on the reference signal as received in the beams in the subset of set B. Further aspects of beam prediction will be disclosed below.

[0052] As disclosed above, the user equipment 140 skips measuring the reference signal for a subset of beams during the beam sweep. Therefore, in some embodiments, the user equipment 140 is configured to perform (optional) step S106:

[0053] S106: The user equipment 140 determines the subset of beams to skip measuring the reference signal on during the beam sweep.

[0054] Different ways in which the user equipment 140 can determine which beams to skip measuring the reference signal on in a next beam sweep can be based on several different factors and methods, as disclosed next.

[0055] In some aspects, which beams the user equipment 140 is to skip measuring the reference signal on varies between different beam sweeps. That is, in some embodiments, the subset of beams to skip measuring the reference signal on differs between subsequent beam sweeps. In some examples, the user equipment 140 determines whether to skip measuring the reference signal on one or more of the beams per each beam sweep.

[0056] In some aspects, for each beam sweep, the user equipment 140 skips measuring the reference signal on one or more, or even all remaining beams if the reference signal as measured on the first K beams are capable to form the measurement report. That is, in some embodiments, the measurements per beam sweep are performed for as many beams in the set of beams as required for the measurement report to be completed. For example, by using only a subset of the beams as input to a beam prediction model implemented in the user equipment 140, the user equipment 140 can detect that the output of the beam prediction model gives a high enough probability that the predicted beam is the best beam, and the user equipment 140 can then stop measuring the reference signal on the remaining beams. In other words, the user equipment 140 measures on the reference signal in some number of beams and checks if the measurement report can be formed from these measurements. If the measurement report cannot be formed, then the user equipment 140 measures the reference signal on one or more additional beams. This is possible since for each transmission burst of the reference signal (such as an SSB transmission burst), the reference signal is transmitted during many slots, and the user equipment 140 will therefore have time to perform based beam prediction with measurements for only a subset of the beams as input, and then, if the measurement report can be formed from the thus far obtained measurements, stop measuring on the remaining SSBs in that transmission burst.

[0057] In some aspects, the user equipment 140 is capable of beamforming and for each beam sweep, the user equipment 140 skips measuring the reference signal on one or more of the beams in case the user equipment 140 could simultaneously use two or more receive beams for each beam in which the reference signal is transmitted. That is, in some embodiments, the user equipment 140 is capable of performing beamforming in at least two beams when receiving the reference signal, and the subset of beams to skip measuring the reference signal on during the beam sweep comprises beams in the set of beams that each is receivable in at least two of the at least two beams. This is that since for each beam in which the reference signal is transmitted, the user equipment 140 could attain measurements for two different receive beams (which could be used to improve beam prediction accuracy).

[0058] In some aspects, the user equipment 140 performs measurements on the reference signal as transmitted in all the beams during some beam sweep. That is, in some embodiments, the measurements are performed on less than all the beams in the set of beams in a second beam sweep, and the user equipment 140 is further configured to perform (optional) step S104.

[0059] S104: The user equipment 140 performs measurements on the reference signal during a first beam sweep in which the reference signal is transmitted in the set of beams from the network node 110. The measurements during the first beam sweep are performed on the reference signal as received in each of the beams in the set of beams.

[0060] In some aspects, the user equipment 140 determines whether to skips measuring the reference signal on one or more of the beams during some beam sweep T2 based on measurements of the reference signal as obtained during some previous beam sweep Ti. For example, the user equipment 140 might use one or more of the measurements obtained during the N>1 most recent beam sweep to determine for which of the beams the user equipment 140 shall (or shall not) measure the reference signal in a next upcoming beam sweep. Here, withiV > 1 it is thus possible for the user equipment 140 to use measurements from multiple previous beam sweeps to determine if a certain beam should be skipped during the next beam sweep. Hence, user equipment 140 might use the measurements for the previous beam sweep to determine which of beams to skip measuring the reference signal on in the next beam sweep. That is, in some embodiments, the subset of beams to skip measuring the reference signal on during the second beam sweep is determined based on the measurements performed during the first beam sweep.

[0061] Different examples of how the user equipment 140 can use one or more of the measurements obtained during the most recent beam sweep to determine for which of the beams the user equipment 140 shall (or shall not) measure the reference signal in a next upcoming beam sweep will be disclosed next.

[0062] In one example, the K beams yielding weakest measurements of the reference signal during beam sweep Ti are skipped during beam sweep T2. That is, in some embodiments, the subset of beams to skip measuring the reference signal on during the second beam sweep comprises > 1 beams with worst measurements in the first beam sweep. In case the performance metric of the measurements is the RSRP, RSRQ, or SINR, then the worst measurements are those with lowest RSRP, RSRQ, or SINR. On the other hand, in case the performance metric of the measurements is the BLER, or SER, then the worst measurements are those with highest BLER or SER. In one example, the beams yielding measurements being worse than some certain signal quality threshold during beam sweep Ti are skipped during beam sweep T2. In some examples, the signal quality threshold is the expected noise level. In some examples, the signal quality threshold is a certain value, for example selected in the interval from -150 dBm to -130 dBm.

[0063] In one example, the beams yielding measurements being more than a threshold worse than the best measurement obtained during beam sweep Ti are skipped during beam sweep T2. That is, in some embodiments, the subset of beams to skip measuring the reference signal on during the second beam sweep comprises K2> 1 beams for which the measurements performed during the first beam sweep were more than a threshold value worse than a best measurement of the first beam sweep. In some examples, the threshold takes a value in the interval from 30 dB to 50 dB. In some aspects, the user equipment 140 determines that different beams in which the reference signal is transmitted are spatially correlated. That is, in some embodiments, the subset of beams to skip measuring the reference signal on during the beam sweep comprises beams in the set of beams for which a spatial correlation is higher than a correlation threshold. The UE could determine this either through receiving information about the spatial correlation from the network node 110 or by determining correlation based on previous measurements. The information received from the network node 110 could here, for example, indicate that some of the beams might have the same quasi-collocation (QCL) information, and thus share the same transmission configuration indicator (TCI) state. The user equipment 140 could then determine to skips measuring the reference signal on one or more of the beams that are strongly spatially correlated. In some examples, the user equipment 140 predicts the measurements for the skipped beams by using the knowledge of the spatial correlation. In some examples, in case several beams share the same TCI state, the user equipment 140 only perform measurements on one of these beams, and (optionally) predicts measurements of the reference signal for one or more of the skipped beams.

[0064] In some aspects, the user equipment 140 skips measuring the reference signal on one or more beams during beam sweep T2 if all beams during beam sweep Ti that share the same TCI state were received with some performance metric below some threshold (for example, where the performance metric is the received power of the reference signal, i.e., RSRP, or the received quality of the reference signal, i.e., the RSRQ) and the threshold is an absolute value (e.g., an RSRP smaller than -140 dBm), or is relative to the strongest beam (e.g. 40 dB below best beam), etc. That is, in some embodiments, the subset of beams to skip measuring the reference signal on during the second measurement comprises K3> 1 beams that share TCI state, and for which the measurements performed during the first beam sweep were more than a threshold value worse than a best measurement of the first beam sweep. In some examples, the user equipment 140 is configured to apply a joint weighting function to all measurements of beams obtained during beam sweep Ti that share a TCI state, and based on the output of the function decide how large fraction of beams with the same TCI state at during beam sweep T2 the reference signal is to be measured on (e.g. no beam, some beams, or all beams). In some aspects, the user equipment 140 determines to skip measuring the reference signal on one or more beams for which measurements have been obtained within a time window T from the current time. That is, in some embodiments, the measurements are performed on the reference signal as received in less than all the beams in the set of beams during a second beam sweep, and the subset of beams to skip measuring the reference signal on during the second beam sweep comprises beams for which a respective previous measurement has been performed in a first beam sweep occurring within a predetermined time period T before the second beam sweep. Here, the value of T might depend on any, or any combination, of: the speed at which the user equipment 140 is moving, time domain channel correlation estimations, based on previous experiences of time domain correlation of measurements for different beams, etc. For example, the lower the speed is, the larger the value of T can be, etc.

[0065] In some aspects, when the measurements are made on a periodically transmitted reference signal with a periodicity of N slots (e.g. a DL-RS transmitted every N slots), the user equipment 140 only measure every X transmission burst of the reference signal. Further, during any transmission burst, the user equipment 140 might only measure the reference signal on a subset of the beams in which the reference signal is transmitted. The user equipment 140 might thereby measure the reference signal with a periodicity of X-N slots. That is, in some embodiments, the reference signal is transmitted in N±transmission bursts, and the subset of beams to skip measuring the reference signal on during at least one of the beam sweeps comprises all beams of N2of the transmission bursts, where 0 < N2< N±. Here, the value of might depend on any, or any combination, of: the speed at which the user equipment 140 is moving, time domain channel correlation estimations, previous experiences of time domain correlation of measurements for different beams, etc. For example, the lower the speed is, the larger the value of X can be, etc. In one non-limiting and illustrative example, for a user equipment 140 with speed of less than 3 km / h and a set of beams in which the reference signal is transmitted every 20 ms, the value of X can be = 5. That is, the user equipment 140 might perform measurements only every 100 ms for beam prediction purposes (and can thus turn off the transmitter and / or receiver during the remaining transmission bursts of the reference signal). In some aspects, when the measurements are made on a periodically transmitted reference signal with a periodicity of N slots (e.g. a DL-RS transmitted every N slots), the user equipment 140 selects a pattern among pre-determined patterns to determine when in time to skip (or perform) the measurements for beam sweep. That is, in some embodiments, in which beam sweep to skip the measuring is determined according to a first pattern selected from a first set of predefined patterns. As a nonlimiting and illustrative example, a pattern might specify the user equipment 140 to measure the reference signal in one or more beams in Y consecutive beam sweeps, and then skip Z consecutive beam sweeps. For example, in case Y = 2 and Z = 3, the user equipment 140 can perform measurements on reference signals transmitted in slot N, and 2N and then skip measurements in slot 3N, 4N and 5N, and then start performing measurements again in slots 6N, 7N and so on. Here, the values of Y and Z might depend on any, or any combination, of: the speed at which the user equipment 140 is moving, time domain channel correlation estimations, previous experiences of time domain correlation of measurements for different beams, etc. For example, the lower the speed is, the smaller the value of Y can be and the larger the value of T can be, etc.

[0066] In some aspects, when the measurements are made on a periodically transmitted reference signal with a periodicity of N slots (e.g. a DL-RS transmitted every N slots), the user equipment 140 selects a pattern among pre-determined patterns to determine for which beams the measurements shall (or shall not) be skipped for each beam sweep. That is, in some embodiments, the subset of beams to skip measuring the reference signal on during the beam sweep is determined according to a second pattern selected from a second set of predefined patterns. As a non-limiting and illustrative example, a pattern might specify the user equipment 140 to measure the reference signal on all the beams in the first X beam sweeps, and then measure the reference signal only in the K beams for which the measurements in the previous beam sweeps were worst whilst skipping measurements for the remaining beams. The user equipment 140 could be configured to predict measurements for the beams for which measurements are skipped, for example by adding some constant values to the measurements that are actually made. The pattern could further specify the user equipment 140 to perform measurements on the reference signal in all, or at least all the previously skipped, beams in the next beam sweep. This could reduce the uncertainty caused by the skipped measurements.

[0067] In some aspects, when the measurements are made on a periodically transmitted reference signal with a periodicity of N slots (e.g. a DL-RS transmitted every N slots), the user equipment 140 determines whether to skip measuring on the reference signal in one or more of the beams based on the measurement of some fixed set of beams. That is, in some embodiments, the measurements at least are performed on at least one fixed beam in the set of beams, and the subset of beams to skip measuring the reference signal on during the beam sweep is determined based on the measurements of the reference signal as transmitted in this at least one fixed beam. This fixed set of beams might include just a single beam, or might comprise several beams, and is hereinafter referred to as anchor beams. Examples of anchor beams are provided below. By comparing the relative difference of such anchor beams with the measurements in a previous beam sweep, the user equipment 140 could predict the measurements for the remaining beams in the current beam sweep by adding the relative difference for each beam. Below are some non-limiting examples of how anchor beams can be used for beam sweep T2 based on measurements of the reference signal as obtained during beam sweep Ti.

[0068] In one example, the anchor beams are the K beams for which the measurements are best based on the measurement in beam sweep Ti.

[0069] In one example, the anchor beams are the K beams for which the measurements are weakest based on the measurement in beam sweep Ti.

[0070] In one example, the anchor beams are the K beams for which the measurements are the best and the K beams for which the measurements are the weakest based on the measurement in beam sweep Ti.

[0071] In one example, the anchor beams are the K beams for which the measurements are the best, the K beams for which the measurements are worse than a threshold range from the / fbest beams, and the K beams for which the measurements are the weakest based on the measurement in beam sweep Ti. In one example, the anchor beams are the K beams for which the measurements are the best, the K beams for which the measurements are the weakest, and the K beams for which the measurements are better than a threshold range from the K worst beams based on the measurement in beam sweep Ti.

[0072] In one example, the relative difference of anchor beams between two consecutive beam sweeps might be lower than a certain signal quality threshold.

[0073] In one example, the relative difference of anchor beams between two non-consecutive beam sweep might be lower than a weighted signal quality threshold based on the gap between two non-consecutive beam sweeps.

[0074] Skipping measuring the reference signal on all the beams during a given beam sweep could for example be the case where the user equipment 140 implements a time domain beam prediction mode, and / or in case the user equipment 140 is stationary (i.e., not moving) and / or the radio propagation channel between the network node and the user equipment 140 is stationary.

[0075] In some aspects, the user equipment 140 is configured to predict the measurements for some or even all the beams for a given beam sweep based on previous measurements, and hence skip measuring the reference signal on these some or all the beams during this given beam sweep. In particular, in some embodiments, the user equipment 140 is configured to perform (optional) step S110.

[0076] S110: The user equipment 140 predicts measurements for beams in the subset of beams for which measurements on the reference signal were not performed. The measurement report might then further comprises at least some of the predicted measurements.

[0077] In some aspects, the user equipment 140 is configured to turn off one or more receive chains (or parts of receive chains) associated with the skipped measurements.

[0078] Reference is next made to the sets of beams in Figs. 5 and 6 for illustrating how the herein disclosed embodiments can be used for reporting reference signal measurements. In Fig. 5 is schematically illustrated a first set of beams 500a, a second set of beams 500b, and a third set of beams 500c. The network node is capable of transmitting signals in beams 510a, being all the 32 beams, but the network node actually only transmits the reference signal in a subset (defined by beams 610b) of these beams. Fig. 5 represents an example where the beams 510b for which the user equipment 140 is to report measurements is fixed, and thus is the same for all beam sweeps. In a first beam sweep (“Beam sweep 1”) the network node transmits a reference signal in beams 510b and the user equipment 140 measures the reference signal in these beams. In a second beam sweep (“Beam sweep 2”) the network node again transmits the reference signal in beams 510b but the user equipment 140 skips measuring the reference signal on beams 510c, where the beams 510c are a subset of the beams 510b. In a third beam sweep (“Beam sweep 3”) the network node again transmits the reference signal in beams 510b but the user equipment 140 now skips measuring the reference signal on beams 510c, where the beams 510c are a subset of the beams 510b but not the same beams as skipped in the second beam sweep. Hence, in both the second beam sweep and the third beam sweep the user equipment 140 skips measuring the reference signal on three beams, where one of the skipped beams is the same in the second beam sweep and the third beam sweep.

[0079] In Fig. 6 is schematically illustrated a first set of beams 600a, a second set of beams 600b, and a third set of beams 600c. The network node is capable of transmitting signals in beams 610a, being all the 32 beams, but the network node actually only transmits the reference signal in a subset (defined by beams 610b and 6iod) of these beams. Fig. 6 represents an example where the beams 610b for which the user equipment 140 is to report measurements is dynamic and thus changes from one beam sweep to the next. In a first beam sweep (“Beam sweep 1”) the network node transmits a reference signal in beams 610a and 6iod and the user equipment 140 measures the reference signal in these beams, but only reports the measurements for the beams 610b. In a second beam sweep (“Beam sweep 2”) the network node again transmits the reference signal in beams 610b and 6iod (which are not the same as for the first beam sweep) and the user equipment 140 skips measuring the reference signal on beams 610c, where the beams 610c are a subset of the beams 610a and 6iod. The user equipment 140 only reports the measurements for the beams 610b. In a third beam sweep (“Beam sweep 3”) the network node transmits the reference signal in beams 6ioa and 6iod (which are not the same as for the first or second beam sweeps) and the user equipment 140 now skips measuring the reference signal on beams 610c, where the beams 610c are a subset of the beams 610a and 6iod but not the same beams as skipped in the second beam sweep. The user equipment 140 only reports the measurements for the beams 610b. Hence, in both the second beam sweep and the third beam sweep the user equipment 140 skips measuring the reference signal on three beams, where two of the skipped beams are the same in the second beam sweep and the third beam sweep.

[0080] One particular embodiment for reporting reference signal measurements as performed by the network node 110 and the user equipment 140 will be disclosed next with reference to the signaling diagram of Fig. 7.

[0081] Step S201: The network node 110 provides configuration to the user equipment 140 for the user equipment 140 to report measurements on reference signals as transmitted by the network node 110 in a set (Set B) of beams. In some examples, the configuration also specifies that the user equipment 140 indeed is to report back to the network node 110 the measurements as made by the user equipment 140 on the reference signals. In some examples, the user equipment 140 is separately configured by the network node 110 to report back to the network node 110 the measurements as made by the user equipment 140 on the reference signals.

[0082] S202: The user equipment 140 is configured in accordance with the received configuration.

[0083] S203: The network node 110 performs a first transmission of the reference signal in the set (Set B) of beams.

[0084] S204: The user equipment 140 performs measurements on the reference signal in the different beams and reports the measurements back to the network node 110.

[0085] S205: The user equipment 140 determines which beams in the set (Set B) of beams that the user equipment 140 can skip measuring on during a next transmission of the reference signal in the set (Set B) of beams.

[0086] S206: The network node 110 performs a second transmission of the reference signal in the set (Set B) of beams. S207: The user equipment 140 performs measurements on the reference signals in a selected subset of the set (Set B) beams, and thus skips measuring on the reference signals in the remaining beams, in accordance with the determination in step S205.

[0087] S208: The user equipment 140, for example in case the configuration as received in step S202 specifies that the user equipment 140 is to report a measurement of the reference signal in one or more of the beams that the UE skipped measuring, predicts a measurement value for each such skipped beam. The prediction can, for example, be made on previous measurements, spatial correlation between the different beams, and / or an AI / ML based model.

[0088] S209: The user equipment 140 reports the measurements back to the network node 110.

[0089] Fig. 8 schematically illustrates, in terms of a number of structural units, the components of a user equipment 800 according to an embodiment. Processing circuitry 810 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 1010 (as in Fig. 10), e.g. in the form of a storage medium 830. The processing circuitry 810 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0090] Particularly, the processing circuitry 810 is configured to cause the user equipment 800 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 830 may store the set of operations, and the processing circuitry 810 may be configured to retrieve the set of operations from the storage medium 830 to cause the user equipment 800 to perform the set of operations. The set of operations may be provided as a set of executable instructions.

[0091] Thus the processing circuitry 810 is thereby arranged to execute methods as herein disclosed. The storage medium 830 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 user equipment 800 may further comprise a communications (comm.) interface 820 at least configured for communications with other entities, functions, nodes, and devices, as in Figs. 1, 4, and 7. As such the communications interface 820 may comprise one or more transmitters and receivers, comprising analogue and digital components. The processing circuitry 810 controls the general operation of the user equipment 800 e.g. by sending data and control signals to the communications interface 820 and the storage medium 830, by receiving data and reports from the communications interface 820, and by retrieving data and instructions from the storage medium 830. Other components, as well as the related functionality, of the user equipment 800 are omitted in order not to obscure the concepts presented herein.

[0092] Fig. 9 schematically illustrates, in terms of a number of functional modules, the components of a user equipment 900 according to an embodiment. The user equipment 900 of Fig. 9 comprises a number of functional modules; a receive module 910 configured to perform step S102, a measure module 940 configured to perform step S108, and a send module 960 configured to perform step S112. The user equipment 900 of Fig. 9 may further comprise a number of optional functional modules, such as any of a measure module 920 configured to perform step S104, a determine module 930 configured to perform step S106, and a predict module 950 configured to perform step S110.

[0093] In general terms, each functional module 910:960 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 830 which when run on the processing circuitry makes the user equipment 800 perform the corresponding steps mentioned above in conjunction with Fig 9. 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 910:960 maybe implemented by the processing circuitry 810, possibly in cooperation with the communications interface 820 and / or the storage medium 830. The processing circuitry 810 may thus be configured to from the storage medium 830 fetch instructions as provided by a functional module 910:960 and to execute these instructions, thereby performing any steps as disclosed herein. A first portion of the instructions performed by the user equipment 140, 800, 900 may be executed in a first device, and a second portion of the of the instructions performed by the user equipment 140, 800, 900 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 user equipment 140, 800, 900 may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to at least partly be performed by a user equipment 140, 800, 900 residing in, or operatively connected to, a cloud computational environment. Therefore, although a single processing circuitry 810 is illustrated in Fig. 8 the processing circuitry 810 may be distributed among a plurality of devices, or nodes. The same applies to the functional modules 910:960 of Fig. 9 and the computer program 1020 of Fig. 10.

[0094] Fig. 10 shows one example of a computer program product 1010 comprising computer readable storage medium 1030. On this computer readable storage medium 1030, a computer program 1020 can be stored, which computer program 1020 can cause the processing circuitry 810 and thereto operatively coupled entities and devices, such as the communications interface 820 and the storage medium 830, to execute methods according to embodiments described herein. The computer program 1020 and / or computer program product 1010 may thus provide means for performing any steps as herein disclosed.

[0095] In the example of Fig. 10, the computer program product 1010 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 1010 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 1020 is here schematically shown as a track on the depicted optical disk, the computer program 1020 can be stored in any way which is suitable for the computer program product 1010. 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 reporting reference signal measurements, the method being performed by a user equipment (140, 800, 900), the method comprising: receiving (S102) configuration from a network node (110), wherein the configuration specifies a set of beams (130, 200b, 300b, 500a, 600a) in which a reference signal is to be transmitted from the network node (110) during a beam sweep; performing (S108) measurements on the reference signal as received by the user equipment (140, 800, 900) during the beam sweep, wherein the measurements are performed for less than all beams in the specified set of beams by the user equipment (140, 800, 900) skipping measuring the reference signal for a subset of beams during the beam sweep; and sending (S112) a measurement report of the performed measurements to the network node (110).

2. The method according to claim 1, wherein the method further comprises: determining (S106) the subset of beams to skip measuring the reference signal on during the beam sweep.

3. The method according to claim 1 or 2, wherein the measurements are performed on less than all the beams in the set of beams in a second beam sweep, and wherein the method further comprises: performing (S104) measurements on the reference signal during a first beam sweep in which the reference signal is transmitted in the set of beams from the network node (110), wherein the measurements during the first beam sweep are performed on the reference signal as received in each of the beams in the set of beams.

4. The method according to claim 3, wherein the subset of beams to skip measuring the reference signal on during the second beam sweep is determined based on the measurements performed during the first beam sweep.

5. The method according to a combination of claims 3 and 4, wherein the subset of beams to skip measuring the reference signal on during the second beam sweep comprises> 1 beams with worst measurements in the first beam sweep.

6. The method according to a combination of claims 3 and 4, wherein the subset of beams to skip measuring the reference signal on during the second beam sweep comprises K2> 1 beams for which the measurements performed during the first beam sweep were more than a threshold value worse than a best measurement of the first beam sweep.

7. The method according to a combination of claims 3 and 4, wherein the subset of beams to skip measuring the reference signal on during the second measurement comprises K3> 1 beams that share transmission configuration indicator, TCI, state, and for which the measurements performed during the first beam sweep were more than a threshold value worse than a best measurement of the first beam sweep.

8. The method according to any preceding claim, wherein the measurements are performed on the reference signal as received in less than all the beams in the set of beams during a second beam sweep, and wherein the subset of beams to skip measuring the reference signal on during the second beam sweep comprises beams for which a respective previous measurement has been performed in a first beam sweep occurring within a predetermined time period T before the second beam sweep.

9. The method according to any preceding claim, wherein the reference signal is transmitted in N transmission bursts, and wherein the subset of beams to skip measuring the reference signal on during at least one of beam sweep comprises all beams of N2of the transmission bursts, where 0 < N2< N±.

10. The method according to any preceding claim, wherein the subset of beams to skip measuring the reference signal on during the beam sweep comprises beams in the set of beams for which a spatial correlation is higher than a correlation threshold.

11. The method according to any preceding claim, wherein the measurements per beam sweep are performed for as many beams in the set of beams as required for the measurement report to be completed.

12. The method according to any preceding claim, wherein the user equipment (140, 800, 900) is capable of performing beamforming in at least two beams when receiving the reference signal, and wherein the subset of beams to skip measuring the reference signal on during the beam sweep comprises beams in the set of beams that each is receivable in at least two of the at least two beams.

13. The method according to any preceding claim, wherein in which beam sweep to skip said measuring is determined according to a first pattern selected from a first set of predefined patterns.

14. The method according to any preceding claim, wherein the subset of beams to skip measuring the reference signal on during the beam sweep is determined according to a second pattern selected from a second set of predefined patterns.

15. The method according to any preceding claim, wherein the measurements at least are performed on at least one fixed beam in the set of beams, and wherein the subset of beams to skip measuring the reference signal on during the beam sweep is determined based on the measurements of the reference signal as transmitted in said at least one fixed beam.

16. The method according to any preceding claim, wherein the subset of beams to skip measuring the reference signal on differs between subsequent beam sweeps.

17. The method according to any preceding claim, wherein the configuration further specifies that the measurements are to be reported for K4> 1 number of beams.

18. The method according to any preceding claim, wherein the method further comprises: predicting (S110) measurements for beams in the subset of beams for which measurements on the reference signal were not performed, and wherein the measurement report further comprises at least some of the predicted measurements.

19. The method according to any preceding claim, wherein the configuration further specifies that beam prediction is to be performed by the user equipment (140, 800, 900)."2-120. The method according to any preceding claim, wherein the set of beams is a subset, set B, of an available set of beams, set A, at the network node (no), and wherein the configuration further specifies the set A, and that the user equipment (140, 800, 900) is to predict a best beam in the set A based on the measurement performed on the reference signal as received in beams in a subset of the set B.

21. The method according to claim 20, wherein the measurement report further comprises a predicted measurement for said best beam in set A based on the measurement performed on the reference signal as received in the beams in the subset of set B.

22. A user equipment (140, 800) for reporting reference signal measurements, the user equipment (140, 800) comprising processing circuitry (810), the processing circuitry being configured to cause the user equipment (140, 800) to: receive configuration from a network node (110), wherein the configuration specifies a set of beams (130, 200b, 300b, 500a, 600a) in which a reference signal is to be transmitted from the network node (110) during a beam sweep; perform measurements on the reference signal as received by the user equipment (140, 800) during the beam sweep, wherein the measurements are performed for less than all beams in the specified set of beams by the user equipment (140, 800) skipping measuring the reference signal for a subset of beams (510c, 610c, 6iod) during the beam sweep; and send a measurement report of the performed measurements to the network node (110).

23. A user equipment (140, 900) for reporting reference signal measurements, the user equipment (140, 900) comprising: a receive module (910) configured to receive configuration from a network node (110), wherein the configuration specifies a set of beams (130, 200b, 300b, 500a, 600a) in which a reference signal is to be transmitted from the network node (110) during a beam sweep;a measure module (940) configured to perform measurements on the reference signal as received by the user equipment (140, 900) during the beam sweep, wherein the measurements are performed for less than all beams in the specified set of beams by the user equipment (140, 900) skipping measuring the reference signal for a subset of beams (510c, 610c, 6iod) during the beam sweep; and a send module (960) configured to send a measurement report of the performed measurements to the network node (110).

24. The user equipment (140, 900) according to claim 22 or 23, further being configured to perform the method according to any of claims 2 to 21.

25. A computer program (1020) for reporting reference signal measurements, the computer program comprising computer code which, when run on processing circuitry (810) of a user equipment (140, 800), causes the user equipment (140, 800) to: receive (S102) configuration from a network node (110), wherein the configuration specifies a set of beams (130, 200b, 300b, 500a, 600a) in which a reference signal is to be transmitted from the network node (110) during a beam sweep; perform (S108) measurements on the reference signal as received by the user equipment (140, 800) during the beam sweep, wherein the measurements are performed for less than all beams in the specified set of beams by the user equipment (140, 800) skipping measuring the reference signal for a subset of beams (510c, 610c, 6iod) during the beam sweep; and send (S112) a measurement report of the performed measurements to the network node (110).

26. A computer program product (1010) comprising a computer program (1020) according to claim 25, and a computer readable storage medium (1030) on which the computer program is stored.

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