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EP-4738746-A2 - POLARIZATION DIVERSITY IN TIME-DOMAIN BEAMFORMING

EP4738746A2EP 4738746 A2EP4738746 A2EP 4738746A2EP-4738746-A2

Abstract

A network node (600), computer program product, and a method by a network node to allocate at least two beams in a slot to schedule multiple user equipments, UEs, (500) are provided. Each UE is allocated (801) to a baseband port (0, 1) of a plurality of baseband ports such that there is more than one UE allocated to each baseband port. For each baseband port of the plurality of baseband ports: the baseband port is mapped (803) to a polarization of an antenna having multiple polarizations and to one beam of a plurality of beams. The polarization of a baseband port is switched (805) in a time domain to create time diversity of services towards the multiple UEs, wherein a UE is subject to a first polarization for a subset of time occasions and to a second polarization for other time occasions.

Inventors

  • YIN, Zhiming
  • HURD, MAGNUS
  • KARLSSON, JONAS
  • RAO, JING
  • BERGMAN, SVANTE
  • OVESJÖ, Fredrik

Assignees

  • Telefonaktiebolaget LM Ericsson (publ)

Dates

Publication Date
20260506
Application Date
20211019

Claims (9)

  1. A method by a user equipment, UE, (500, 1212A, 1212B, 1212C, 1212D, 1300, 1604, 1608A, 1608B, 1706) in a network where a network node (600, 1210A, 1210B, 1400, 1604, 1608A, 1608B) allocates at least two beams in a slot to schedule multiple user equipments, UEs, the method comprising: receiving (1001) from a network an allocation of the UE to a baseband port (0, 1) of a plurality of baseband ports (0, 1) where there is more than one UE allocated to each baseband port of the plurality of baseband ports, each baseband port mapped to a polarization of an antenna having multiple polarizations and to one beam of a plurality of beams, wherein a number of the plurality of beams matches a number of the multiple polarizations and wherein the UE is subject to a first polarization for a subset of time occasions and to a second polarization for other time occasions; receiving (1003) an indication of whether or not to disable demodulation reference signal, DM-RS, filtering when performing measurements on a DM-RS; and performing (1005) measurements on the DM-RS based on the indication.
  2. The method of Claim 1, wherein receiving the indication comprises obtaining a parameter in a control resource set information element, IE, to indicate whether the DM-RS can be subject to filtering by the UE.
  3. The method of Claim 2, wherein the parameter in the control resource set IE comprises a dmrs-NoFilteringWithinSlot parameter.
  4. The method of Claim 1, wherein receiving the indication comprises one of: obtaining a parameter in a DMRS-downlink configuration information element, IE, to indicate whether the DM-RS can be subject to filtering by the UE; receiving a DMRS No Filtering Within Slot Activation/Deactivation medium access control, MAC, control element, CE to indicate whether to activate or deactivate no filtering for DM-RS within a slot; and receiving a downlink control information, DCI, that indicates whether DM-RS no filtering is enabled.
  5. The method of Claim 1, further comprising dynamically receiving (1101) scheduling of a physical downlink shared channel for which DM-RS filtering is enabled or disabled by the UE based on the indication.
  6. A user equipment, UE, (500, 1212A, 1212B, 1212C, 1212D, 1300, 1604, 1608A, 1608B, 1706) comprising: processing circuitry (503, 1302, 1612); and memory (505, 1310) coupled with the processing circuitry, wherein the memory includes instructions that when executed by the processing circuitry causes the UE to perform operations comprising: receiving from a network an allocation of the UE to a baseband port (0, 1) of a plurality of baseband ports (0, 1) where there is more than one UE allocated to each baseband port of the plurality of baseband ports, each baseband port mapped to a polarization of an antenna having multiple polarizations and to one beam of a plurality of beams, wherein a number of the plurality of beams matches a number of the multiple polarizations and wherein the UE is subject to a first polarization for a subset of time occasions and to a second polarization for other time occasions; receiving an indication of whether or not to disable demodulation reference signal, DM-RS, filtering when performing measurements on a DM-RS; and performing measurements on the DM-RS based on the indication.
  7. The UE (500, 1212A, 1212B, 1212C, 1212D, 1300, 1604, 1608A, 1608B, 1706) of Claim 6, wherein the memory includes further instructions that when executed causes the UE (500, 1212A, 1212B, 1212C, 1212D, 1300, 1604, 1608A, 1608B, 1706) to perform according to any of Claims 2-5.
  8. A computer program product comprising a non-transitory storage medium including program code to be executed by processing circuitry (503, 1302, 1612) of a user equipment, UE (500, 1212A, 1212B, 1212C, 1212D, 1300, 1604, 1608A, 1608B, 1706), whereby execution of the program code causes the UE (500, 1212A, 1212B, 1212C, 1212D, 1300, 1604, 1608A, 1608B, 1706) to perform operations comprising: receiving from a network an allocation of the UE to a baseband port (0, 1) of a plurality of baseband ports (0, 1) where there is more than one UE allocated to each baseband port of the plurality of baseband ports, each baseband port mapped to a polarization of an antenna having multiple polarizations and to one beam of a plurality of beams, wherein a number of the plurality of beams matches a number of the multiple polarizations and wherein the UE is subject to a first polarization for a subset of time occasions and to a second polarization for other time occasions; receiving an indication of whether or not to disable demodulation reference signal, DM-RS, filtering when performing measurements on a DM-RS; and performing measurements on the DM-RS based on the indication.
  9. The computer program product of Claim 8, wherein the non-transitory storage medium includes further program code, whereby execution of the program code causes the UE (500, 1212A, 1212B, 1212C, 1212D, 1300, 1604, 1608A, 1608B, 1706) to perform operations according to any of Claims 2-5.

Description

TECHNICAL FIELD The present disclosure relates generally to communications, and more particularly to communication methods and related devices and nodes supporting wireless communications. BACKGROUND Time-domain beamforming means one beamform applies to all frequency resources part of a transmission in one time slot. Typically, a set of predefined beamforms are designed to cover a certain spatial area such as seen in Figure 1, where each beamform includes two orthogonal polarizations, such as horizontal and vertical polarization. The presence of two polarizations allows the option to transmit two data streams independent from the other. Based on user equipment (UE) feedback (either formulated as a report indicating a preferred beamform or simply based on a physical measurement of received power per predefined beamform), the base station would transmit on one of these beamforms accordingly to communicate a message to the UE. This means only users being associated to a beamform currently selected by the base station can be served at one point in time, the other users need to wait until the base station selects a beamform of their preference. This beamforming constraint is the essence of time-domain beamforming, as illustrated in Figure 2 where only one beamform happens at one particular time instant. One approach to improve latency for time-domain beamforming is to introduce MU-MIMO (Multi-User - Multiple-Input, Multiple-Output) transmissions. This means one frequency-time resource is used to carry two different data streams, each targeting a different user (in other words a different UE). This way the latency is potentially reduced by a half assuming two users can be found to engage in a MU-MIMO transmission. The benefit of MU-MIMO could be more than reduced latency. For example, if there are many small packet users or low-throughput video users, MU-MIMO transmissions can also improve cell throughput. Some AAS (Advanced Antenna Systems) systems intended for time-domain beamforming apply spatial beamforming per polarization. This means transmission on one polarization may be assigned a beamform covering a certain area whereas transmission on the other polarization is assigned another beamform covering some other area. Of course, the beamforms of the polarizations may be selected to be the same; in fact, this would be the typical operational mode to offer UEs two-layer single user-MIMO (SU-MIMO) transmissions. Then both polarizations in any transmission like reference signals for beam management and channel state information (CSI) estimation as well as data transmissions on shared channel (physical downlink shared channel (PDSCH)/physical uplink shared channel (PUSCH)) would be subject to the same analog beamform. SUMMARY For AAS systems intended for time-domain beamforming that applies spatial beamforming per polarization, there are opportunities to serve UEs associated to different beamforms (directions). For a SU-MIMO approach both polarizations are assigned the same predefined beam in each slot. If there are multiple users in the cell distributed in different areas (each covered by different beams), then users not scheduled in the slot will have to wait regardless of if there are still unused resources. This results in lower cell throughput and increased latency. Introducing the option of having UEs of several areas/directions/beamforms served at one point in time can be done in a couple of ways. First, regarding multi-directional time domain beamforming, there are two problems. One problem is that users' frequency domain resources cannot overlap with each other. The other problem is that because each directional beamform covers several directions for the full frequency range, a data allocation for a user in some part of the frequency spectrum would need also to radiate energy in a direction towards a user in another direction (however served by another part of the frequency spectrum). In other words, the power resource cannot be used efficiently. Second, for MU-MIMO solutions based on allocating different beamforms per polarization there is a mismatch between CSI measurements by the UE and upcoming transmissions. UEs measure on a channel state information-reference signal (CSI-RS) with 2 antenna ports whereas the base station is only capable of beamforming on a per-port basis. The reporting of RI/PMI/CQI (rank indicator/precoding matrix indicator /channel quality information) involves both of the antenna ports (of the CSI-RS) where each port represents one polarization. If the beamforming is only capable of operating on a per-port basis, a UE would receive a signal only over one of the ports at a MU-MIMO transmission (the other port is allocated to the other UE). It could happen that one of the UEs is allocated to a port (or polarization) not performing well. According to some embodiments of inventive concepts, a method by a network node to allocate two beams in a slot to schedule multiple user equipments