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US-12621188-B2 - Method and network node configured for selection of transmission layers

US12621188B2US 12621188 B2US12621188 B2US 12621188B2US-12621188-B2

Abstract

A method performed by a network node is provided. The network node calculates a first Information Carrying Capacity (ICC) associated with a first layer. The first ICC is calculated based on beam weights calculated for the first layer, and an established channel estimate of the first layer. The first layer is selected to a set of layers. The network node performs actions iteratively at least one time for layer selection, adds a subsequent layer, adapts the calculated beam weights to be used as subsequent beam weights for a subsequent layer, calculates a subsequent ICC for the subsequent layer, decides whether to select the added subsequent layer to the set of layers and rejecting the subsequent layer when the sum of the ICCs of the layers in the set of layers and the subsequent ICC is lower than the sum of ICCs of the layers in the set of layers.

Inventors

  • Mats Åhlander
  • Kevin Luo

Assignees

  • TELEFONAKTIEBOLAGET LM ERICSSON (PUBL)

Dates

Publication Date
20260505
Application Date
20210526

Claims (13)

  1. 1 . A method performed by a network node for selecting a layer for a set of layers for transmissions between the network node and at least one User Equipment, UE, in a wireless communications network, which set of layers are to be spatial multiplexed for the transmissions, the method comprising: calculating a first Information Carrying Capacity, ICC, associated with a first layer, which first ICC is calculated based on beam weights calculated for the first layer and an established channel estimate of the first layer; selecting the first layer to the set of layers; and performing the following actions iteratively at least one time for layer selection: adding a subsequent layer, adapting the calculated beam weights used for the layers in the set of layers to be used as subsequent beam weights for the subsequent layer, based on an established channel estimate of the subsequent layer, and the established channel estimates of the layers in the set of layers, calculating a subsequent ICC for the subsequent layer, based on the subsequent beam weights and the channel estimate of the subsequent layer, and deciding whether or not to select the added subsequent layer to the set of layers based on the ICCs of the layers in the set of layers and the subsequent ICC, by selecting the subsequent layer when the sum of the ICCs of the layers in the set of layers and the subsequent ICC is equal or larger than the sum of ICCs of the layers in the set of layers, and rejecting the subsequent layer when the sum of the ICCs of the layers in the set of layers and the subsequent ICC is lower than the sum of ICCs of the layers in the set of layers.
  2. 2 . The method according to claim 1 , wherein the actions for layer selection are performed iteratively until any one out of: there are no more available layers to add, or the number of selected layers exceed a first threshold, or the allowed number of repeating the actions for layer selection exceeds a second threshold.
  3. 3 . The method according to claim 1 , wherein the adapting of the calculated beam weights, further is based on updating any one or more out of: a calculation of a channel covariance matrix, a regularization of a channel covariance matrix, and an inversion of a regularized channel covariance matrix.
  4. 4 . The method according to claim 1 , wherein a first UE is associated with the selected first layer, and one or more additional UE is associated with a respective selected subsequent layer, and wherein the method further comprises: based on the channel estimate of the first layer, scheduling a first transmission for the first UE to be spatial multiplexed for the transmissions, and for each subsequent layer that has been selected: based on the channel estimate of the subsequent layer co-scheduling an additional transmission for the additional UE to be spatial multiplexed for the transmissions.
  5. 5 . The method according to claim 1 , wherein a Signal to Interference and Noise Ratio, SINR, of a layer the set of layers is a function of the channel estimate the first layer, and a subsequent SINR is a function of the channel estimate of the subsequent layer.
  6. 6 . The method according to claim 1 , further comprising: establishing a channel estimate of the first layer; and calculating the beam weights for the first layer based on the established channel estimate.
  7. 7 . A computer program comprising instructions stored on a non-transitory computer-readable storage medium, which when executed by a processor, causes the processor to perform actions comprising: calculating a first Information Carrying Capacity, ICC, associated with a first layer, which first ICC is calculated based on beam weights calculated for the first layer and an established channel estimate of the first layer; selecting the first layer to the set of layers; and performing the following actions iteratively at least one time for layer selection: adding a subsequent layer, adapting the calculated beam weights used for the layers in the set of layers to be used as subsequent beam weights for the subsequent layer, based on an established channel estimate of the subsequent layer, and the established channel estimates of the layers in the set of layers, calculating a subsequent ICC for the subsequent layer, based on the subsequent beam weights and the channel estimate of the subsequent layer, and deciding whether or not to select the added subsequent layer to the set of layers based on the ICCs of the layers in the set of layers and the subsequent ICC, by selecting the subsequent layer when the sum of the ICCs of the layers in the set of layers and the subsequent ICC is equal or larger than the sum of ICCs of the layers in the set of layers, and rejecting the subsequent layer when the sum of the ICCs of the layers in the set of layers and the subsequent ICC is lower than the sum of ICCs of the layers in the set of layers.
  8. 8 . A network node configured to select a layer for a set of layers for transmissions between the network node and at least one UE in a wireless communications network, which layers in the set of layers are to be spatial multiplexed for the transmissions, the network node further being configured to: calculate a first Information Carrying Capacity, ICC, associated with a first layer, which first ICC is adapted to be calculated based on beam weights calculated for the first layer, and an established channel estimate of the first layer; select the first layer to the set of layers; and perform the following actions iteratively at least one time for layer selection: add a subsequent layer for the transmissions, adapt the calculated beam weights used for the layers in the set of layers to be used as subsequent beam weights for the subsequent layer, based on an established channel estimate of the subsequent layer, and the established channel estimates of the layers in the set of layers, calculate a subsequent ICC for the subsequent layer, based on the subsequent beam weights and the channel estimate of the subsequent layer, and decide whether or not to select the added subsequent layer to the set of layers based on the ICCs of the layers in the set of layers and the subsequent ICC, by selecting the subsequent layer when the sum of first ICC and the subsequent ICC is equal or larger than the first ICC, and rejecting the subsequent layer when the sum of the ICCs of the layers in the set of layers and the subsequent ICC is lower than the sum of ICCs of the layers in the set of layers.
  9. 9 . The network node according to claim 8 , wherein the network node further is configured to perform the actions for layer selection iteratively until any one out of: there are no more available layers add, or the number of selected layers exceed a first threshold, or the allowed number of repeating the actions for the layer selection exceeds a second threshold.
  10. 10 . The network node according to claim 8 , wherein the network node further is configured to adapt the calculated beam weights, further based on updating any one or more out of a calculation of a channel covariance matrix, a regularization of a channel covariance matrix, and an inversion of a regularized channel covariance matrix.
  11. 11 . The network node according to claim 8 , wherein a first UE is associated with the first layer, and one or more additional UE is associated with a respective selected subsequent layer, and wherein the network node further is configured to: based on the channel estimate of the first layer, schedule a first transmission for the first UE to be spatial multiplexed for the transmissions, and for each subsequent layer that has been selected: based on the channel estimate of the subsequent layer co-schedule an additional transmission for the additional UE ( 122 ) to be spatial multiplexed for the transmissions.
  12. 12 . The network node according to claim 8 , wherein a Signal to Interference and Noise Ratio, SINR, of a layer of the set of layers is adapted to be a function of the channel estimate the first layer, and a subsequent SINR is adapted to be a function of the channel estimate of the subsequent layer.
  13. 13 . The network node according to claim 8 , further the being configured to: establish a channel estimate of the first layer for the transmissions; and calculate the beam weights for the first layer based on the established channel estimate.

Description

CROSS REFERENCE TO RELATED APPLICATIONS This application is a 35 U.S.C. § 371 national stage application of PCT International Application No. PCT/SE2021/050493 filed on May 26, 2021, the disclosure and content of which is incorporated by reference herein in its entirety. TECHNICAL FIELD Embodiments herein relate to a network node and methods therein. In some aspects, they relate to selecting a layer for a set of layers for transmissions between the network node and at least one UE in a wireless communications network. BACKGROUND In a typical wireless communication network, wireless devices, also known as wireless communication devices, mobile stations, stations (STA) and/or User Equipment (UE), communicate via a Wide Area Network or a Local Area Network such as a Wi-Fi network or a cellular network comprising a Radio Access Network (RAN) part and a Core Network (CN) part. The RAN covers a geographical area which is divided into service areas or cell areas, which may also be referred to as a beam or a beam group, with each service area or cell area being served by a radio network node such as a radio access node e.g., a Wi-Fi access point or a radio base station (RBS), which in some networks may also be denoted, for example, a NodeB, eNodeB (eNB), or gNB as denoted in Fifth Generation (5G) telecommunications. A service area or cell area is a geographical area where radio coverage is provided by the radio network node. The radio network node communicates over an air interface operating on radio frequencies with the wireless device within range of the radio network node. 3GPP is the standardization body for specify the standards for the cellular system evolution, e.g., including 3G, 4G, 5G and the future evolutions. Specifications for the Evolved Packet System (EPS), also called a Fourth Generation (4G) network, have been completed within the 3rd Generation Partnership Project (3GPP). As a continued network evolution, the new releases of 3GPP specifies a 5G network also referred to as 5G New Radio (NR). Frequency bands for 5G NR are being separated into two different frequency ranges, Frequency Range 1 (FR1) and Frequency Range 2 (FR2). FR1 comprises sub-6 GHz frequency bands. Some of these bands are bands traditionally used by legacy standards but have been extended to cover potential new spectrum offerings from 410 MHz to 7125 MHz. FR2 comprises frequency bands from 24.25 GHz to 52.6 GHZ. Bands in this millimeter wave range have shorter range but higher available bandwidth than bands in the FR1. Multi-antenna techniques may significantly increase the data rates and reliability of a wireless communication system. For a wireless connection between a single user, such as UE, and a base station, the performance is in particular improved if both the transmitter and the receiver are equipped with multiple antennas, which results in a Multiple-Input Multiple-Output (MIMO) communication channel. This may be referred to as Single-User (SU)-MIMO. In the scenario where MIMO techniques is used for the wireless connection between multiple users and the base station, MIMO enables the users to communicate with the base station simultaneously using the same time-frequency resources by spatially separating the users, which increases further the cell capacity. This may be referred to as Multi-User (MU)-MIMO. Note that MU-MIMO may benefit when each UE only has one antenna. Such systems and/or related techniques are commonly referred to as MIMO. In 4G and 5G, the introduction of Advanced Antenna Systems (AAS) on base stations has allowed for the possibility to perform beamforming and spatial multiplexing schemes with many more transmission layers than was previously possible in legacy antenna systems which uses only 2 or 4 antennas. The wording transmission layer when used herein e.g. means a statistically independent stream of modulation symbols whose complete mapping onto an antenna array can be described by a beamforming vector, a corresponding mathematical definition is available in 3GPP specification 38.211 The wording user-layer when used herein e.g. means a transmission layer of the UE of interest. In spatial multiplexing several data streams, also referred to as layers, are transmitted over independent channels that are spatially separated, e.g. by means of beamforming. The more parallel layers that can be sent at the same time, the more data can be passed over the air. Beamforming when used herein e.g. means a technique which multiplexes a signal with different weights in frequency-domain at multiple antennas. The beamforming causes the signal energy to be sent to space according to a wanted beam pattern to form a directional beam to concentrate to certain direction or to form nulling to a certain direction, or the combination of two beamforming and spatial multiplexing. For each resource element, a beam weight, e.g. an amplitude and phase shift is added to each base station antenna element with the effect of creating