Configuration of uplink reference signal resources

Abstract

There is provided techniques for configuring a UE with uplink reference signal resources, where the UE is qualified for reciprocity assisted transmission. A method is performed by a network node. The method comprises allocating a bandwidth for the uplink reference signal resources to the UE. The bandwidth is allocated to the UE based on which one of at least two bandwidth groups the UE belongs to, as based on amount of buffered data of the UE. Each of the bandwidth groups is associated with its own allocation of bandwidth for the uplink reference signal resources. According to the bandwidth groups, the higher the amount of buffered data of the UE is, the smaller the bandwidth for the uplink reference signal resources the UE is allocated. The method comprises configuring the UE with the uplink reference signal resources in accordance with the allocated bandwidth.

Description

[0001] CONFIGURATION OF UPLINK REFERENCE SIGNAL RESOURCES

[0002] TECHNICAL FIELD

[0003] Embodiments presented herein relate to a method, a network node, a computer program, and a computer program product for configuring a user equipment with uplink reference signal resources.

[0004] BACKGROUND

[0005] Multiple-input, multiple-output (MIMO) communication is a communication technology where multiple antennas are deployed at both the transmitter and the receiver. MIMO communication can be used to increase quality, throughput, and capacity in wireless communication systems.

[0006] In MIMO based communication systems, transmissions in both the downlink (DL; from a transmission and reception point (TRP) at the network side to a user equipment (UE) at the user side) and the uplink (from a UE at the user side to a TRP at the network side) may experience inter-layer interference, inter-user interference, and inter-cell interference. For DL transmission, beamforming can be applied at the TRP to generate independent channels for multi-layer, or multi-user, transmission. This could reduce the complexity in the UE whilst also providing good performance.

[0007] The beamforming techniques that have been widely leveraged can be divided into two categories, namely UE feedback-based beamforming and reciprocity assisted transmission (RAT) based beamforming.

[0008] For UE feedback-based beamforming, the TRP typically uses channel state information (CSI) as fed back from UEs for downlink beamforming transmission. Here, the CSI is based on measurements made by the UE on downlink reference signals (such as channel state information reference signals (CSI-RSs)) transmitted from the TRP. For example, in prevalent wireless communication systems (e.g., based on the New Radio (NR) air interface, as in fifth-generation (5G) telecommunication system), the TRP can acquire CSI feedback in terms of channel quality information (CQI), precoding matrix index (PMI) and rank indicator (RI) as calculated by the UE. The TRP can then use the PMI together with the RI to form the beamforming for downlink transmission. For RAT-based beamforming, it is possible for the TRP to apply the physical channel property of reciprocity and use UL sounding and channel estimation (based on uplink reference signals, such as sounding reference signals (SRSs), transmitted by the UE) to obtain UL channel estimates. These UL channel estimates can then, based on the assumption of reciprocity, be used to calculate the precoding weight for the beamforming for the downlink transmission.

[0009] Generally, RAT-based beamforming can perform better than UE feedback-based beamforming for UEs which have good channel quality when the required CSI is available at the TRP and the beamforming algorithms are well designed. One prevalent way for such CSI measurement is to allocate SRS resources to the UEs. Considering the limitation of available uplink resources, it can be difficult, or even impossible, to assign all the UEs served by a given TRP with orthogonal SRS.

[0010] Typically, for UEs that are not allocated any SRS resources for RAT-based beamforming calculation, the TRP can serve these UEs using a codebook-based transmission scheme based on CSI as reported from these UEs (i.e., based on UE feedback-based beamforming).

[0011] With limited SRS resources, not all UEs served by the TRP can be allocated SRS resources in practice. Therefore, criteria for selecting UEs which can benefit most from being allocated SRS resources need to be considered. In this respect, existing schemes for allocating SRS resources for RAT-based beamforming generally consider the buffer size (or perhaps more correctly: the amount of buffered data) of the UEs and the channel quality in order to identify scenarios where RAT-based beamforming could be beneficial. The motivation for these criteria will be provided next. Typically, UEs with larger buffer size (i.e., larger amount of buffered data) tend to require a longer transmission time and to contribute more to the cell throughput. Therefore, improving the performance for these UEs is more beneficial from a cell throughput point-of-view. Moreover, good channel quality could ensure that RAT-based downlink transmission brings better performance than other transmission schemes, e.g., UE feedback-based downlink transmission. Thus, with a large buffer size and a good channel quality, a UE is more likely to be allocated SRS resources. On the other hand, with a smaller buffer size and / or bad channel quality, the UE is not likely to be allocated any SRS resources.

[0012] Generally, the SRS resources can have different allocations with respect to bandwidth. One straightforward way for allocating the bandwidth for the SRS resources is to allocate SRS resources in a narrow frequency band for UEs in poor coverage. One motivation for this is that concentrating the UE transmit power to a narrow bandwidth could enhance the accuracy of the channel estimation. Further, the complete bandwidth information could be obtained by frequency hopping of the bandwidth (in which the SRS resources are allocated) in different time domain transmission occasions. Likewise, for UEs in good coverage, allocating SRS resources in a wide frequency band could enable the channel characteristics for those UEs to be acquired on the full system bandwidth faster, possibly using only one single SRS transmission occasion.

[0013] In summary, one issue with the above-disclosed schemes is that UEs with relatively small buffer size but with good channel quality will not be allocated any SRS resources. These UEs will thereby lose the opportunity to be served with RAT-based beamforming, in turn leading to suboptimal performance in the network. This could be a particular issue in case a large amount of UEs has relatively small buffer size, which has also been proven to be the case in practice.

[0014] Hence, there is still a need for schemes with improved allocation of SRS resources, or other types of uplink reference signal resources.

[0015] SUMMARY

[0016] An object of embodiments herein is to address the above issues.

[0017] A particular object is to enable SRS resources, or other types of uplink reference signal resources, to be allocated to UEs in a manner that improves the performance in the network.

[0018] According to a first aspect there is presented a method for configuring a UE with uplink reference signal resources. The UE is qualified for reciprocity assisted transmission. The method is performed by a network node. The method comprises allocating a bandwidth for the uplink reference signal resources to the UE. The bandwidth is allocated to the UE based on which one of at least two bandwidth groups the UE belongs to, as based on amount of buffered data of the UE. Each of the bandwidth groups is associated with its own allocation of bandwidth for the uplink reference signal resources. According to the bandwidth groups, the higher the amount of buffered data of the UE is, the smaller the bandwidth for the uplink reference signal resources the UE is allocated. The method comprises configuring the UE with the uplink reference signal resources in accordance with the allocated bandwidth.

[0019] According to a second aspect there is presented a network node for configuring a UE with uplink reference signal resources. The UE is qualified for reciprocity assisted transmission. The network node comprises processing circuitry. The processing circuitry is configured to cause the network node to allocate a bandwidth for the uplink reference signal resources to the UE. The bandwidth is allocated to the UE based on which one of at least two bandwidth groups the UE belongs to, as based on amount of buffered data of the UE. Each of the bandwidth groups is associated with its own allocation of bandwidth for the uplink reference signal resources. According to the bandwidth groups, the higher the amount of buffered data of the UE is, the smaller the bandwidth for the uplink reference signal resources the UE is allocated. The processing circuitry is configured to cause the network node to configure the UE with the uplink reference signal resources in accordance with the allocated bandwidth.

[0020] According to a third aspect there is presented a computer program for configuring a UE with uplink reference signal resources, where the UE is qualified for reciprocity assisted transmission. 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 allocate a bandwidth for the uplink reference signal resources to the UE. The bandwidth is allocated to the UE based on which one of at least two bandwidth groups the UE belongs to, as based on amount of buffered data of the UE. Each of the bandwidth groups is associated with its own allocation of bandwidth for the uplink reference signal resources. According to the bandwidth groups, the higher the amount of buffered data of the UE is, the smaller the bandwidth for the uplink reference signal resources the UE is allocated. One action comprises the network node to configure the UE with the uplink reference signal resources in accordance with the allocated bandwidth.

[0021] According to a fourth aspect there is presented a computer program product comprising a computer program according to the third 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.

[0022] Advantageously, these aspects address the above issues.

[0023] Advantageously, these aspects enable SRS resources, or other types of uplink reference signal resources, to be allocated to UEs in a manner that improves the performance in the network.

[0024] Advantageously, by means of the herein disclosed embodiments, the uplink reference signal resources can be allocated in a manner that improves the cell throughput.

[0025] Advantageously, with a small bandwidth allocated to uplink reference signal resources for UEs with high amount of buffered data, some uplink reference signal resources can be saved to other UEs and thereby bring improvements to the cell throughput.

[0026] Advantageously, with a high bandwidth allocated to uplink reference signal resources for UEs with small amount of buffered data, this brings better user throughput for these UEs than if a low bandwidth is allocated to their uplink reference signal resources.

[0027] 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.

[0028] 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.

[0029] BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The inventive concept is now described, by way of example, with reference to the accompanying drawings, in which: Fig. 1 is a schematic diagram illustrating a communication network according to embodiments;

[0031] Fig. 2 is a flowchart of methods according to embodiments;

[0032] Fig. 3 schematically illustrates a schematic time-frequency resource grid for uplink reference signal resources as allocated to different UEs according to embodiments;

[0033] Fig. 4 shows simulation results according to embodiments;

[0034] Fig. 5 is a schematic diagram showing structural units of a network node according to an embodiment;

[0035] Fig. 6 is a schematic diagram showing functional modules of a network node according to an embodiment; and

[0036] Fig. 7 shows one example of a computer program product comprising computer readable storage medium according to an embodiment.

[0037] DETAILED DESCRIPTION

[0038] 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.

[0039] Fig. 1 is a schematic diagram illustrating a communication network 100 where embodiments presented herein can be applied. The communication network 100 comprises a network node 110 and a TRP 120. The network node 110 is configured to control the TRP 120. In this respect, although separated with respect to hardware, the network node 110 and the TRP 120 can be regarded as one logical unit and together form a (radio) access network node, (radio) base station, base transceiver station, node B (NB), evolved node (eNB), gNB, access node, access point, integrated access and backhaul (IAB) node, or the like. The network node 110 is, via the TRP 120, configured to serve UEs 130a, 130b, 130c. Non-limiting examples of UEs are portable wireless devices, mobile stations, mobile phones, handsets, wireless local loop phones, smartphones, laptop computers, tablet computers, network equipped vehicles, network equipped sensors, and Internet of Things (loT) devices. The TRP 120 is assumed of being capable of alternating between using UE feedback-based beamforming and RAT-based beamforming when transmitting signals to the UEs 130a, 130b, 130c, for example, depending on which of the UEs 130a, 130b, 130c are qualified for RAT-based beamforming.

[0040] As noted above, there is a need for schemes with improved allocation of SRS resources, or other types of uplink reference signal resources.

[0041] Further in this respect, another issue with the above-disclosed schemes is that the uplink reference signal resource utilization is less efficient. This is due to the abovedisclosed schemes not considering the relation between the buffer size (i.e., the amount of buffered data) and the bandwidth for the uplink reference signal allocation.

[0042] In general, for UEs in good coverage, allocating uplink reference signal resources in a wide frequency band is preferable from perspective of quick acquisition of the channel characteristics over the full system bandwidth. But considering the limitation of uplink reference signal resources and large number of active UEs, which is quite common for some time-division duplex (TDD) frame structure pattern with quite small number of uplink slots in a periodicity, it might still not be possible assign uplink reference signal resources in a wide frequency band for all UEs in good coverage.

[0043] On the other hand, if the buffer size (as above, and perhaps more correctly: the amount of buffered data) of the UE and the bandwidth allocation for the uplink reference signal resources can be jointly considered when allocating uplink reference signal resources to a UE, the uplink reference signal resource allocation can be more efficient in terms of ensuring that more UEs are allocated uplink reference signal resources. For RAT-based beamforming with so-called eigen based beamforming weight calculation, the performance of having either a wideband or a narrowband allocation of the uplink reference signal uplink reference signal is similar for UEs that have larger amount of buffered data. Uplink reference signal resources can thereby be saved by instead allocating uplink reference signal resources in a narrow frequency band instead of in a wide frequency band for UEs with large buffers. The thus saved uplink reference signal resources can then be allocated to UEs with a good channel quality and small amount of buffered data. Thus, the TRP will then be able to transmit data to those UEs using RAT-based beamforming instead of codebook-based beamforming, thus bringing better performance.

[0044] For RAT-based beamforming, different methods can be used to calculate the beamforming weights, for example using so-called eigen decomposition. Among the steps when so-called eigen decomposition, a covariance matrix for the whole DL frequency range is calculated from uplink reference signal resources which only occupy parts of the system bandwidth. The majority of the data based on which the beamforming weights are calculated is using the filtered covariance matrix calculated from different parts of the narrowband uplink reference signal resources, thereby capturing the channel characteristics for the whole system bandwidth.

[0045] Aspects of allocating uplink reference signal resources to UEs with different amounts of DL buffered data will be disclosed next, starting with UEs with a large amount of DL buffered data and then continuing with UEs having a small amount of buffered data. In this respect, buffered data represents the buffer size as given by Radio Link Control (RLC) or represents a predicted buffer size. Large buffered data has a larger size value than a predefined value and small buffered data has a smaller size value than the predefined value.

[0046] For UEs with large amounts of DL buffered data, the DL transmission in time domain would be long enough for channel characteristics to be collected for a wider frequency band. The uplink reference signal time interval determines how fast and how much the wider frequency band information can be collected for these UEs during the DL data transmission time. According to the herein disclosed embodiments, both the amount of buffered data and the uplink reference signal time interval can be considered when determining the bandwidth allocation of the uplink reference signal resources.

[0047] Since it takes longer time to serve these UEs, the channel characteristics for the wide frequency band (as obtained through uplink reference signal resources allocated in multiple time occasions) can be utilized before the buffers have been emptied. Simulation results as provided below shows that using uplink reference signal resources with a narrow frequency band allocation for those UEs can yield similar performance as when using uplink reference signal resources with a narrow frequency band allocation. Allocating uplink reference signal resources with a narrow frequency band to these UEs can thus save some uplink reference signal resources, which can be allocated to other UEs, and thus enable more UEs to be allocated uplink reference signal resources and served using RAT-based beamforming.

[0048] For UEs with a small amount of buffered data, the DL transmission in time domain would be shorter. If the uplink reference signal time interval is longer than the duration of the DL transmission, it is very likely that when frequency hopping is performed for the uplink reference signal resources, the data in the buffer has already been transmitted. This matters when the channel is frequency selectivity dominant. Uplink reference signal resources with a wide frequency band are allocated to UEs with small amounts of buffered data. With respect to the frequency domain, uplink reference signal resources with a wide frequency can be used for obtaining channel characteristics over a wider frequency band.

[0049] In view of the above, with a limited availability of uplink reference signal resources, uplink reference signal resources can be allocated with different bandwidths to balance uplink reference signal resource utilization and cell performance. Additionally, as will be described below, also other properties (such as the velocity of the UE) can be considered when allocating SRS resources to the UEs to further save uplink reference signal resources.

[0050] The embodiments disclosed herein in particular relate to techniques for configuring a UE 130a with uplink reference signal resources. In order to obtain such techniques, there is provided a network node 110, a method performed by the network node 110, a computer program product comprising code, for example in the form of a computer program, that when run on a network node 110, causes the network node 110, to perform the method.

[0051] In general terms, at least some of the herein disclosed embodiments are based on separating the UEs in different (uplink reference signal) bandwidth groups based on the amount of buffered data of the UEs. UEs with a large amount of buffered data are in groups with a small allocated bandwidth for the uplink reference signal resources, whereas UEs with a small amount of buffered data are in groups with large allocated bandwidth for the uplink reference signal resources. The uplink reference signal resources are then allocated to the UEs on a UE-level basis. Further, which bandwidth group each UE belongs to can be adaptively changed over time by the network node 110 monitoring the amount of buffered data of the different UEs over time.

[0052] Since the beamforming weights determined based on measurements on the uplink reference signals are applied at the TRP for DL transmission towards the UEs, the amount of buffered data of a given UE pertains to the amount of data to be transmitted to this given UE in the DL.

[0053] Fig. 2 is a flowchart illustrating embodiments of methods for configuring a UE 130a with uplink reference signal resources. The UE 130a is qualified for reciprocity assisted transmission. The methods are performed by the network node 110. The methods are advantageously provided as computer programs.

[0054] S106: The network node 110 allocates a bandwidth for the uplink reference signal resources to the UE 130a.

[0055] As disclosed above, the allocation of bandwidth for the uplink reference signal resources for a given UE qualified for RAT-based beamforming is based on which bandwidth group this given UE belongs to. Hence, the bandwidth is allocated to the UE 130a based on which one of at least two bandwidth groups the UE 130a belongs to, as based on amount of buffered data of the UE 130a. Further, each of the bandwidth groups is associated with its own allocation of bandwidth for the uplink reference signal resources. Also, according to the bandwidth groups, the higher the amount of buffered data of the UE 130a is, the smaller the bandwidth for the uplink reference signal resources the UE 130a is allocated. The UE 130a can then be configured accordingly.

[0056] S108: The network node 110 configures the UE 130a with the uplink reference signal resources in accordance with the allocated bandwidth.

[0057] This method thereby provides a criterion to determine the bandwidth for the uplink reference signal resources to be allocated to a given UE, namely the amount of buffered data for this given UE. In this way, the SRS resources can be efficiently and wisely allocated to more UEs, which in turn allows more UEs to be served using RAT- based beamforming.

[0058] Embodiments relating to further details of configuring a UE 130a with uplink reference signal resources as performed by the network node 110 will now be disclosed with continued reference to Fig. 2.

[0059] In some embodiments, the amount of buffered data of the UE 130a is either an actual amount of buffered data or a predicted amount of buffered data, and the network node 110 is configured to perform (optional) step S102:

[0060] S102: The network node 110 obtains the actual amount of buffered data or the predicted amount of buffered data.

[0061] Further, in some aspects, the network node 110 explicitly evaluates whether the UE 130a is RAT qualified or not. In particular, in some embodiments, the network node 110 is configured to perform (optional) step S104:

[0062] S104: The network node 110 verifies that the UE 130a is qualified for reciprocity assisted transmission before allocating the bandwidth for the uplink reference signal resources to the UE 130a.

[0063] In this respect, there could be different ways for the network node 110 to verify whether the UE is RAT qualified or not. In some aspects, the amount of buffered data, the channel quality, and / or the motion speed (or other type of time-domain channel variability, caused by movement, such as rotation) of the UE is evaluated to determine whether the UE is RAT qualified or not.

[0064] In a first example, the evaluation of the amount of buffered data is based on either long-time monitoring or instant monitoring of the actual amount of buffered data. In a second example, the amount of buffered data is evaluated based on the predicted amount of buffered data, which for example can be achieved using deep learning techniques. Then, the UE can be categorized as RAT qualified if the amount of buffered data (either actual or predicted) is larger than some threshold amount of buffered data. In a third example, the evaluation of the channel quality is based on either long-time monitoring or instant monitoring of the actual channel quality. In a fourth example, the channel quality is evaluated based on the predicted channel quality, which for example can be achieved using deep learning techniques. Then, the UE can be categorized as RAT qualified if the channel quality (either actual or predicted) is better than some channel quality threshold value. In a fifth example, the evaluation of the time-domain channel variability of the UE is based on either longtime monitoring or instant monitoring of the actual time-domain channel variability of the UE (e.g., as defined by time-domain channel properties (TDCP) reporting). In a sixth example, the time-domain channel variability of the UE is evaluated based on the predicted time-domain channel variability , which for example can be achieved using deep learning techniques. Then, the UE can be categorized as RAT qualified if the time-domain channel variability of the UE (either actual or predicted) is smaller than some variability threshold value. Hence, in some embodiments, verifying that the UE 130a is qualified for reciprocity assisted transmission comprises verifying at least one of: the amount of buffered data is larger than a threshold data amount, a channel quality of a wireless link to the UE 130a is better than a channel quality threshold value, a motion speed of the UE 130a is smaller than a velocity threshold.

[0065] Aspects of the network node determining the transmission time interval for the uplink reference signals for the UE will be disclosed next.

[0066] Generally, it is beneficial for the UE performance to allocate uplink reference signal resources with a small time interval and get more uplink reference signal measurement during traffic serving time. However, in practice, the transmission time interval of the uplink reference signal is set to consider a balance between the limited amount of uplink reference signal resources and the number of UEs served by the TRP to yield the largest cell performance benefit.

[0067] In some aspects, a generic value of the transmission time interval is set for all UEs, e.g., 20ms, 40ms, or 80ms. In particular, in some embodiments, the UE 130a is configured with a transmission time interval of the uplink reference signal resources that is independent of the amount of buffered data of the UE 130a. In this respect, a larger value of the transmission time interval will allow a higher number of UEs to be allocated uplink reference signal resources, but possibly yield worse UE performance, especially for RAT qualified UEs where the channel has some degree of time-varying property.

[0068] For UEs with large amount of buffered data, the time interval between the uplink reference signal transmissions might impact how fast and for how large portion of the frequency interval (i. e. , how much of the bandwidth) the channel characteristics can be collected.

[0069] In some aspects, if the transmission time interval is large, a larger bandwidth is used for the uplink reference signal resources for a larger portion of the frequency interval to be sensed for each uplink reference signal transmission. That is, in some embodiments, according to the bandwidth groups, the longer the transmission time interval is, the larger the bandwidth for the uplink reference signal resources the UE 130a is allocated.

[0070] Further aspects of the network node separating the UEs into different bandwidth groups will be disclosed next.

[0071] As disclosed above, according to the bandwidth groups, the higher the amount of buffered data of the UE 130a is, the smaller the bandwidth for the uplink reference signal resources the UE 130a is allocated. Here, the amount of buffered data could be compared to one or more buffer threshold values, depending on how many bandwidth groups. Generally, for K different bandwidth groups, there will be K-i buffer threshold values. In particular, in some embodiments, there are k =1, 2, ..., K different bandwidth groups with larger and larger bandwidth for the uplink reference signal resources, where bandwidth group k is associated with bandwidth k for the uplink reference signal resources, and the UE 130a belongs to bandwidth group k when the amount of buffered data of the UE 130a is lower than buffer threshold value k-i and higher or equal to buffer threshold value k, where buffer threshold value k-i > buffer threshold value k. Further in this respect, also other properties might influence the bandwidth allocated for the uplink reference signal resources. For example, also the transmission time interval of the uplink reference signal transmissions might impact how much bandwidth is allocated for the uplink reference signal resources. Particularly, UEs for which the transmission time interval of the uplink reference signal transmissions is smaller will belong to bandwidth where a small bandwidth is allocated for the uplink reference signal resources. In particular, in some embodiments, there are k =1, 2, ..., K different bandwidth groups with larger and larger bandwidth for the uplink reference signal resources, where bandwidth group k is associated with bandwidth k for the uplink reference signal resources, and the UE 130a belongs to bandwidth group k when the transmission time interval is larger or equal to transmission time interval threshold value k-1 and smaller than transmission time interval threshold value k, where transmission time interval threshold value k > transmission time interval threshold value k-1.

[0072] As a non-limiting and illustrative example, denote the amount of buffered data by BS, and denote the uplink reference signal transmission time interval by TI. Then, in case BS > buffer_threshold_i and TI < time_interval_threshold_i, then:

[0073] UE is in SRS bandwidth group_i

[0074] Else, if buffer_threshold_i > BS > buffer threshold_2, and time_interval_threshold_i < TI < time_interval_threshold_2 , then:

[0075] UE is in SRS bandwidth group_2 etc.

[0076] Here, buffer_threshold_i, buffer threshold_2, time_interval_threshold_i, and time_interval_threshold_2 are threshold values.

[0077] In a first non-limiting and illustrative example, the SRS time interval is TI = 10 ms, the buffer threshold for evaluating whether the UEs are qualified for reciprocity assisted transmission or not is 1 MB, buffer threshold_i = 20MB, buffer threshold_2 = 1 MB, time_interval_threshold_i = 10 ms, and time_interval_threshold_2 = 100 ms. Further, SRSs are allocated in 4 resource blocks (RBs) for UEs in SRS bandwidth group_i and in 272 RBs for UEs in SRS bandwidth group_2. In a second non-limiting and illustrative example, the threshold values are determined by downlink resource utilization in the cell. If the downlink resource utilization is larger than a certain given value, which indicate it takes longer time to schedule the UE due to large traffic load in this cell, buffer_threshold_i, buffer threshold_2 could be smaller, and / or time_interval_threshold_i, and time_interval_threshold_2 could be larger, to have more chance to allocate with smaller SRS bandwidth.

[0078] Further aspects of the network node allocating the uplink reference signal resources with corresponding bandwidth to the UEs will be disclosed next.

[0079] As disclosed above, which bandwidth group each UE belongs to can be adaptively changed over time by the network node 110 monitoring the amount of buffered data of the different UEs over time. Hence, in some embodiments, the network node 110 is configured to perform (optional) steps S110 and S112.

[0080] S110: The network node 110 monitors the amount of buffered data of the UE 130a.

[0081] S112: The network node 110 updates the bandwidth for the uplink reference signal resources to the UE 130a and configures the UE 130a with the thus updated bandwidth for the uplink reference signal resources, responsive to a change of the amount of buffered data of the UE 130a fulfilling an updating condition. In the flowchart of Fig. 2 this is represented by the network node 110 again entering step S104 that in case the updating condition is fulfilled.

[0082] In some examples, the updating condition is based on the amount of buffered data of the UE 130a. For example, the updating condition maybe fulfilled in case the amount of buffered data has changed (increased or decreased) more than some threshold value. This could indicate that it could be beneficial to configure the UE 130a with an updated bandwidth for the uplink reference signal resources. Further, in order to have smoot transitions and to avoid oscillations between two different configuration, a further updating condition could be that some predetermined amount of time has passed since the previous time the bandwidth for the uplink reference signal resources was updated. Generally, the UEs could be triggered to transmit the uplink reference signal according to different time schemes. In particular, in some embodiments, the UE 130a is configured (by the network node 110 in step S108) to transmit the uplink reference signal resources in accordance with the allocated bandwidth either periodically, a-periodically, or semi-persistently.

[0083] Further in this respect, whether to use periodic or a-periodic transmissions of the uplink reference signal might be based on the monitoring interval. Hence, in some embodiments, whether the UE 130a is configured to transmit the uplink reference signal resources in accordance with the allocated bandwidth periodically or a- periodically depends on a monitoring interval at which the amount of buffered data of the UE 130a is monitored.

[0084] Generally, the longer the monitoring interval is, the more suitable it is to use periodic transmissions of the uplink reference signal. Hence, in some embodiments, the UE 130a is configured to transmit the uplink reference signal resources in accordance with the allocated bandwidth periodically in case the monitoring interval is longer than a monitoring length threshold value. This is due to the longer time required for the UE to be configured via radio resource control (RRC) signaling. Conversely, the shorter the monitoring interval is, the more suitable it is to use a-periodic transmissions of the uplink reference signal. Hence, in some embodiments, the UE 130a is configured to transmit the uplink reference signal resources in accordance with the allocated bandwidth a-periodically in case the monitoring interval is shorter than the monitoring length threshold value. This is due to a-periodic transmissions of the uplink reference signal can be more flexible to configure than periodic transmissions of the uplink reference signal.

[0085] Fig. 3 provides a schematic time-frequency resource grid for uplink reference signal resources as allocated to two different UEs; a first UE (denoted “UE-i”) with a small amount of buffered data and a second UE (denoted “UE-2”) with a high amount of buffered data. As can be seen, uplink reference signal resources (denoted “resource block with SRS”) is allocated a higher number of RBs for UE-i than for UE-2.

[0086] Simulation results will be disclosed next with reference to Fig. 4. In Fig. 4 is shown the total downlink throughput (“dl throughput sum”) in Mbps as a function of the amount of served traffic in Mbps. The simulations were performed for a network with 21 served cells, 10000 served UEs in total, and with a-periodic SRS transmissions triggered for each 10 ms. The UEs were separated into two groups, based on their amount of buffered data; 20 MB and 1 MB, respectively (denoted “20 MB packet per UE” and “1 MB packet per UE” in Fig. 4). For the 20 MB case, the mean serving time is 600 ms (60% resource utilization). With SRS allocated in 4 RBs, in average 88% of the frequency band information is collected for each UE during the downlink data transmission time. For the 1 MB case, the mean serving time is 40 ms (60% resource utilization). With RBs allocated to SRS over the full system bandwidth (i.e., 272 RBs), the complete frequency band information is obtained already at the first SRS transmission. In Fig. 4 can be seen that for the 20 MB case, having SRS allocated in 4 RBs brings similar performance as having SRS allocated in 272 RBs. However, for the 1 MB case, having SRS allocated in a higher number of RBs yields better performance.

[0087] Fig. 5 schematically illustrates, in terms of a number of structural units, the components of a network node 500 according to an embodiment. Processing circuitry 510 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 710 (as in Fig. 7), e.g. in the form of a storage medium 530. The processing circuitry 510 may further be provided as at least one application specific integrated circuit (ASIC), or field programmable gate array (FPGA).

[0088] Particularly, the processing circuitry 510 is configured to cause the network node 500 to perform a set of operations, or steps, as disclosed above. For example, the storage medium 530 may store the set of operations, and the processing circuitry 510 may be configured to retrieve the set of operations from the storage medium 530 to cause the network node 500 to perform the set of operations. The set of operations may be provided as a set of executable instructions.

[0089] Thus the processing circuitry 510 is thereby arranged to execute methods as herein disclosed. The storage medium 530 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 500 may further comprise a communications (comm.) interface 520 at least configured for communications with other entities, functions, nodes, and devices, as in the communication network 100. As such the communications interface 520 may comprise one or more transmitters and receivers, comprising analogue and digital components. The processing circuitry 510 controls the general operation of the network node 500 e.g. by sending data and control signals to the communications interface 520 and the storage medium 530, by receiving data and reports from the communications interface 520, and by retrieving data and instructions from the storage medium 530. Other components, as well as the related functionality, of the network node 500 are omitted in order not to obscure the concepts presented herein.

[0090] Fig. 6 schematically illustrates, in terms of a number of functional modules, the components of a network node 600 according to an embodiment. The network node 600 of Fig. 6 comprises a number of functional modules; an allocate module 630 configured to perform step S106, and a configure module 640 configured to perform step S108. The network node 600 of Fig. 6 may further comprise a number of optional functional modules, such as any of an obtain module 610 configured to perform step S102, a verify module 620 configured to perform step S104, a monitor module 650 configured to perform step S110, and a check module 660 configured to perform step S112. In general terms, each functional module 6io:66omay 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 530 which when run on the processing circuitry makes the network node 500 perform the corresponding steps mentioned above in conjunction with Fig 6. 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 6io:66omay be implemented by the processing circuitry 510, possibly in cooperation with the communications interface 520 and / or the storage medium 530. The processing circuitry 510 may thus be configured to from the storage medium 530 fetch instructions as provided by a functional module 610:660 and to execute these instructions, thereby performing any steps as disclosed herein.

[0091] The network node 110, 500, 600 may be provided as a standalone device or as a part of at least one further device. For example, the network node 110, 500, 600 maybe provided in a node of the radio access network or in a node of the core network. Alternatively, functionality of the network node 110, 500, 600 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 110, 500, 600 may be executed in a first device, and a second portion of the of the instructions performed by the network node 110, 500, 600 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 110, 500, 600 may be executed. Hence, the methods according to the herein disclosed embodiments are suitable to be performed by a network node 110, 500, 600 residing in a cloud computational environment. Therefore, although a single processing circuitry 510 is illustrated in Fig. 5 the processing circuitry 510 may be distributed among a plurality of devices, or nodes. The same applies to the functional modules 610:660 of Fig. 6 and the computer program 720 of Fig. 7.

[0092] 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 110, 500, 600 in the downlink (i.e., from the CU to the RU) or received by the network node 110, 500, 600 in the uplink (i.e., from the RU to the CU). Fig. 7 shows one example of a computer program product 710 comprising computer readable storage medium 730. On this computer readable storage medium 730, a computer program 720 can be stored, which computer program 720 can cause the processing circuitry 510 and thereto operatively coupled entities and devices, such as the communications interface 520 and the storage medium 530, to execute methods according to embodiments described herein. The computer program 720 and / or computer program product 710 may thus provide means for performing any steps as herein disclosed.

[0093] In the example of Fig. 7, the computer program product 710 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 710 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 720 is here schematically shown as a track on the depicted optical disk, the computer program 720 can be stored in any way which is suitable for the computer program product 710.

[0094] 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 configuring a user equipment, UE (130a), with uplink reference signal resources, where the UE (130a) is qualified for reciprocity assisted transmission, wherein the method is performed by a network node (110, 500, 600), and wherein the method comprises: allocating (S106) a bandwidth for the uplink reference signal resources to the UE (130a), wherein the bandwidth is allocated to the UE (130a) based on which one of at least two bandwidth groups the UE (130a) belongs to, as based on amount of buffered data of the UE (130a), wherein each of the bandwidth groups is associated with its own allocation of bandwidth for the uplink reference signal resources, and wherein, according to the bandwidth groups, the higher the amount of buffered data of the UE (130a) is, the smaller the bandwidth for the uplink reference signal resources the UE (130a) is allocated; and configuring (S108) the UE (130a) with the uplink reference signal resources in accordance with the allocated bandwidth.

2. The method according to claim 1, wherein the method further comprises: verifying (S104) that the UE (130a) is qualified for reciprocity assisted transmission before allocating the bandwidth for the uplink reference signal resources to the UE (130a).

3. The method according to claim 2, wherein verifying that the UE (130a) is qualified for reciprocity assisted transmission comprises verifying at least one of:- the amount of buffered data is larger than a threshold data amount,- a channel quality of a wireless link to the UE (130a) is better than a channel quality threshold value,- a time domain channel variability of the UE (130a) is smaller than a variability threshold.

4. The method according to any preceding claim, wherein the amount of buffered data of the UE (130a) is either an actual amount of buffered data or a predicted amount of buffered data, and wherein the method further comprises: obtaining (S102) the actual amount of buffered data or the predicted amount of buffered data.

5. The method according to any preceding claim, wherein the UE (130a) is configured with a transmission time interval of the uplink reference signal resources that is independent of the amount of buffered data of the UE (130a).

6. The method according to claim 5, wherein, according to the bandwidth groups, the longer the transmission time interval is, the larger the bandwidth for the uplink reference signal resources the UE (130a) is allocated.

7. The method according to claim 6, wherein there are k =1, 2, ..., K different bandwidth groups with larger and larger bandwidth for the uplink reference signal resources, where bandwidth group k is associated with bandwidth k for the uplink reference signal resources, and wherein the UE (130a) belongs to bandwidth group k when the transmission time interval is larger or equal to transmission time interval threshold value k-1 and smaller than transmission time interval threshold value k, where transmission time interval threshold value k > transmission time interval threshold value k-i.

8. The method according to any preceding claim, wherein there are k =1, 2, ..., K different bandwidth groups with larger and larger bandwidth for the uplink reference signal resources, where bandwidth group k is associated with bandwidth k for the uplink reference signal resources, and wherein the UE (130a) belongs to bandwidth group k when the amount of buffered data of the UE (130a) is lower than buffer threshold value k-i and higher or equal to buffer threshold value k, where buffer threshold value k-i > buffer threshold value k.

9. The method according to any preceding claim, wherein the UE (130a) is configured to transmit the uplink reference signal resources in accordance with the allocated bandwidth either periodically, a-periodically, or semi-persistently.

10. The method according to any preceding claim, wherein the method further comprises: monitoring (S110) the amount of buffered data of the UE (130a); and updating (S112) the bandwidth for the uplink reference signal resources to the UE (130a) and configuring the UE (130a) with the thus updated bandwidth for the uplink reference signal resources, responsive to a change of the amount of buffered data of the UE (130a) fulfilling an updating condition.

11. The method according to claims 9 and 10, wherein whether the UE (130a) is configured to transmit the uplink reference signal resources in accordance with the allocated bandwidth periodically or a-periodically depends on a monitoring interval at which the amount of buffered data of the UE (130a) is monitored.

12. The method according to claim 11, wherein the UE (130a) is configured to transmit the uplink reference signal resources in accordance with the allocated bandwidth periodically in case the monitoring interval is longer than a monitoring length threshold value.

13. The method according to claim 11, wherein the UE (130a) is configured to transmit the uplink reference signal resources in accordance with the allocated bandwidth a-periodically in case the monitoring interval is shorter than a monitoring length threshold value.

14. A network node (110, 500) for configuring a user equipment, UE (130a), with uplink reference signal resources, where the UE (130a) is qualified for reciprocity assisted transmission, the network node (110, 500) comprising processing circuitry (510), the processing circuitry being configured to cause the network node (110, 500) to: allocate a bandwidth for the uplink reference signal resources to the UE (130a), wherein the bandwidth is allocated to the UE (130a) based on which one of at least two bandwidth groups the UE (130a) belongs to, as based on amount of buffered data of the UE (130a),wherein each of the bandwidth groups is associated with its own allocation of bandwidth for the uplink reference signal resources, and wherein, according to the bandwidth groups, the higher the amount of buffered data of the UE (130a) is, the smaller the bandwidth for the uplink reference signal resources the UE (130a) is allocated; and configure the UE (130a) with the uplink reference signal resources in accordance with the allocated bandwidth.

15. The network node (110, 500, 600) according to claim 14, further being configured to perform the method according to any of claims 2 to 13.

16. A computer program (720) for configuring a user equipment, UE (130a), with uplink reference signal resources, where the UE (130a) is qualified for reciprocity assisted transmission, the computer program comprising computer code which, when run on processing circuitry (510) of a network node (110, 500, 600), causes the network node (110, 500, 600) to: allocate (S106) a bandwidth for the uplink reference signal resources to the UE (130a), wherein the bandwidth is allocated to the UE (130a) based on which one of at least two bandwidth groups the UE (130a) belongs to, as based on amount of buffered data of the UE (130a), wherein each of the bandwidth groups is associated with its own allocation of bandwidth for the uplink reference signal resources, and wherein, according to the bandwidth groups, the higher the amount of buffered data of the UE (130a) is, the smaller the bandwidth for the uplink reference signal resources the UE (130a) is allocated; and configure (S108) the UE (130a) with the uplink reference signal resources in accordance with the allocated bandwidth.17- A computer program product (710) comprising a computer program (720) according to claim 16, and a computer readable storage medium (730) on which the computer program is stored.

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