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WO-2026093898-A1 - UL MIMO CODEBOOK PROCEDURE

WO2026093898A1WO 2026093898 A1WO2026093898 A1WO 2026093898A1WO-2026093898-A1

Abstract

A UE receives a first index for TPMI and a second index for an AP vector and determines a TPMI to use by searching for the first index from multiple TPMIs comprising phase settings from one AP to a maximum number of supported APs. The UE determines an AP vector to use by searching for the second index from multiple AP vectors. The UE determines which elements in the determined AP vector to use based on a number of phase settings in the TPMI, and determines an AP configuration based on the determined elements and the TPMI. The UE transmits an uplink transmission by applying the TPMI and the antenna port configuration. The network element determines the first index and the second index, transmits, to the UE, the first index for the TPMI and the second index for the antenna port vector, and receives, from the UE, the uplink transmission.

Inventors

  • SVENDSEN, SIMON
  • ROM, CHRISTIAN
  • Fernandes, Filipa

Assignees

  • NOKIA TECHNOLOGIES OY

Dates

Publication Date
20260507
Application Date
20251027
Priority Date
20241030

Claims (20)

  1. 1. A method, comprising: receiving, by a user equipment from a network element, a first index for transmit precoding matrix identity (TPM I) and a second index for an antenna port vector for an uplink transmission by the user equipment; determining, by the user equipment, a TPMI to use by searching for the first index from multiple TPMIs comprising phase settings from one antenna port to a maximum number of supported antenna ports; determining, by the user equipment, an antenna port vector to use by searching for the second index from multiple antenna port vectors; determining, by the user equipment, which elements in the determined antenna port vector to use based on a number of phase settings in the determined TPMI; determining, by the user equipment, an antenna port configuration based at least on the determined elements for the determined antenna port vector and the determined TPMI; and transmitting, by the user equipment, an uplink transmission at least by applying the TPMI and the antenna port configuration.
  2. 2. An apparatus, comprising: one or more processors; and one or more memories storing instructions that, when executed by the one or more processors, cause the apparatus at least to perform: receiving, by a user equipment from a network element, a first index for transmit precoding matrix identity (TPMI) and a second index for an antenna port vector for an uplink transmission by the user equipment; determining, by the user equipment, a TPMI to use by searching for the first index from multiple TPMIs comprising phase settings from one antenna port to a maximum number of supported antenna ports; determining, by the user equipment, an antenna port vector to use by searching for the second index from multiple antenna port vectors; determining, by the user equipment, which elements in the determined antenna port vector to use based on a number of phase settings in the determined TPMI; determining, by the user equipment, an antenna port configuration based at least on the determined elements for the determined antenna port vector and the determined TP M I ; and transmitting, by the user equipment, an uplink transmission at least by applying the TPMI and the antenna port configuration.
  3. 3. The apparatus according to claim 2, wherein: the antenna port vectors indicate how the TPMI are to be or are not to be reordered.
  4. 4. The apparatus according to claim 3, wherein for a determined TPMI that contains fewer phase settings than the number of entries in the antenna port vectors, the user equipment will only use a number of entries in the determined antenna port vector equal to a number of phase settings in the determined TPMI for the transmitting.
  5. 5. The apparatus according to any of claims 2 to 4, wherein: the multiple TPMIs comprise phase settings for one of 2, 3, or 4 antenna ports or 1, 2, 3, or 4 antenna ports.
  6. 6. The apparatus according to any of claims 3 to 5, wherein: individual elements in the antenna port vectors refer to positions of individual phase settings in the TPMIs, and an order of the individual elements in the antenna port vectors describe how the phase settings in the TPMIs should or should not be reordered; and transmitting by the user equipment the uplink transmission at least by applying the determined TPMI and the antenna port configuration comprises applying ordering of the individual elements in the determined antenna port vector to the individual phase settings in the determined TPMI to form the antenna port configuration and applying the phase settings in the antenna port configuration to corresponding antenna ports..
  7. 7. The apparatus according to claim 6, wherein one of the antenna port vectors in the multiple antenna port vectors does not reorder the individual phase settings in the TPMI for the applying but the others of the multiple antenna port vectors reorder the individual phase settings in the TPMI for the applying.
  8. 8. The apparatus according to any of claims 2 to 7, wherein the multiple TPMIs are indicated via 4 bits and the multiple antenna port vectors are indicated via 3 bits.
  9. 9. The apparatus according to claim 8, wherein the multiple TPMIs are selected from a table with 16 indexes for 2, 3, or 4 antenna ports.
  10. 10. The apparatus according to claim 8, wherein the antenna port vector is determined from the multiple antenna port vectors using one of eight possible values.
  11. 11. The apparatus according to any of claims 2 to 10, wherein: the first index for the TPMI is received as a current first index for a current reception; the second index for the antenna port vector is received as a previous second index for a previous reception of the second index, but no second index is received in the current reception; and the transmitting comprises transmitting an uplink transmission at least by applying the determined TPMI based on the current first index and the antenna port configuration based on the previous second index.
  12. 12. The apparatus according to any of claims 2 to 10, wherein: wherein the multiple TPMIs are selected from a table with 16 indexes for 1, 2, 3, or 4 antenna ports. the first index for the TPMI is received as a previous first index for a previous reception, and no first index for the TPMI is received for a current reception; the second index for the antenna port vector is received as a current second index for a current reception of the second index; and the transmitting comprises transmitting an uplink transmission at least by applying the TPMI based on the previous first index and the antenna port configuration based on the current second index.
  13. 13. The apparatus according to claim 12, wherein the table comprises a TPMI in a first element of the table having a single non-zero phase setting corresponding to a single antenna port and having all other phase settings being zero for the other antenna ports.
  14. 14. The apparatus according to any of claims 2 to 13, wherein: the one or more memories further store instructions that, when executed by the one or more processors, cause the apparatus at least to perform indicating, by the user equipment to the network element, a capability to support uniform or non-uniform antenna array characteristics, the indicating performed prior to the receiving; and the determining the TPMI, determining the antenna port vector, determining, by the user equipment, determining the antenna port configuration, and the transmitting are performed based on the capability to support non-uniform antenna array characteristics.
  15. 15. The apparatus according to claim 14, wherein the capability is indicated via radio resource control signaling.
  16. 16. The apparatus according to any of claims 2 to 15, wherein the second index for the antenna port vector is indicated via a field in downlink control information from the network element to the user equipment.
  17. 17. The apparatus according to claim 16, wherein the downlink control information (DCI) is DCI format 0_1.
  18. 18. An apparatus comprising: one or more processors; and one or more memories storing instructions that, when executed by the one or more processors, cause the apparatus at least to perform: determining, by a network element, a first index for transmit precoding matrix identity (TPMI) and a second index for an antenna port vector of multiple antenna port vectors for an uplink transmission by a user equipment, wherein the first index for the TPMI is determined from multiple TPMIs comprising phase settings from one antenna port to a maximum number of supported antenna ports; transmitting, by the network element to the user equipment, the first index for the TPMI and the second index for the antenna port vector; and receiving, by the network element from the user equipment, the uplink transmission.
  19. 19. The apparatus according to claim 18, wherein: individual elements in the antenna port vectors refer to positions of individual phase settings in the TPMIs, and an order of the individual elements in the antenna port vectors describe how the phase settings in the TPMIs should or should not be reordered.
  20. 20. The apparatus according to claim 19, wherein one of the antenna port vectors in the multiple antenna port vectors does not reorder the individual phase settings in the TPM I but the others of the multiple antenna port vectors reorder the individual phase settings in the TPMI.

Description

UL MIMO Codebook Procedure TECHNICAL FIELD [0001] Examples of embodiments herein relate generally to wireless communications and, more specifically, relate to codebook use in the wireless communications. BACKGROUND [0002] Uplink Multiple Input Multiple Output (MIMO) using a codebook in 3GPP (3rd Generation Partnership Project) standards refers to a technique where multiple antennas at the transmitter (e.g., a user equipment, e.g., a mobile device) and receiver (e.g., a base station) are used to improve the communication performance. [0003] In uplink (UL) MIMO, the communication occurs from the mobile device (User Equipment, UE) to the base station (e.g., eNodeB or gNodeB, depending on the generation). Uplink MIMO enhances data rates, coverage, and reliability by exploiting spatial diversity and spatial multiplexing gains. Spatial diversity uses multiple antennas to combat fading, while spatial multiplexing allows the transmission of multiple data streams simultaneously to increase throughput. [0004] The use of a codebook in MIMO systems refers to the selection of predefined precoding matrices. These matrices dictate how signals are combined across different antennas before transmission, enabling better signal quality and spatial separation. The codebook is a set of fixed precoder matrices known to both the transmitter and the receiver. The codebook-based approach reduces the amount of channel state information (CSI) needed for feedback, simplifying the system design. [0005] Steps in Codebook-Based Precoding are as follows: [0006] 1 . The receiver (a network element such as a base station) measures the channel characteristics based on reference signals sent by the transmitter. [0007] 2. The base station determines the optimal precoding matrix from the predefined codebook based on channel measurements. [0008] 3. The base station sends feedback to the UE, indicating the selected codebook entry or index. [0009] 4. The UE uses the specified precoding matrix from the codebook to pre-process the transmitted signal across its antennas. [0010] In 4G LTE (fourth generation, long term evolution), LTE initially supported Single-User MIMO (SU-MIMO), with enhancements for Multi-User MIMO (MU-MIMO) in later releases. LTE used relatively simple codebooks for two-antenna and four-antenna configurations, primarily supporting openloop and closed-loop MIMO modes. Open-loop does not require feedback, while closed-loop relies on codebook feedback from the base station. The rank, e.g., the number of independent data streams, is dynamically adapted based on the channel conditions. [0011] 5G NR (fifth generation, new radio) improved upon this using more advanced MIMO. In particular, 5G NR significantly expands the MIMO capabilities with higher-order MIMO (up to 8 layers for UL), flexible numerology, and support for Massive MIMO. 5G employs a two-stage codebook approach, providing more refined beamforming and spatial domain optimization. The codebook includes the following: 1) a Type I codebook, which supports single-layer or multi-layer transmission with different levels of quantization for precoding matrices; and a type II codebook, which is used for advanced scenarios like higher-layer MIMO or Massive MIMO, where finer granularity in beam selection is needed. 5G also includes more sophisticated feedback mechanisms, which allow better adaptation of the transmission parameters based on the channel's spatial characteristics. [0012] In summary, uplink MIMO with a codebook in 3GPP standards provides a structured approach to using multiple antennas for performance gains, enabling adaptive spatial processing to optimize transmission. BRIEF SUMMARY [0013] This section is intended to include examples and is not intended to be limiting. [0014] In an exemplary embodiment, a method is disclosed that includes receiving, by a user equipment from a network element, a first index for transmit precoding matrix identity (TPMI) and a second index for an antenna port vector for an uplink transmission by the user equipment; determining, by the user equipment, a TPMI to use by searching for the first index from multiple TPMIs comprising phase settings from one antenna port to a maximum number of supported antenna ports; determining, by the user equipment, an antenna port vector to use by searching for the second index from multiple antenna port vectors; determining, by the user equipment, which elements in the determined antenna port vector to use based on a number of phase settings in the determined TPMI; determining, by the user equipment, an antenna port configuration based at least on the determined elements for the determined antenna port vector and the determined TPMI; and transmitting, by the user equipment, an uplink transmission at least by applying the TPMI and the antenna port configuration. [0015] An additional exemplary embodiment includes a computer program, comprising instructions for performing the method of the previous paragraph, w