Uplink Beam Refinement Using Low-Overhead xSRS Tracking
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Solution Overview
Problem
Existing 5G wireless communication systems face challenges in refining and tracking uplink receiving beams efficiently, which affects channel knowledge and performance in MIMO systems.
Innovation Solution
The implementation of a lower overhead Sounding Reference Signal (xSRS) structure, utilizing Quadrature Phase Shift Keying or Zadoff-Chu sequences, allows for refined uplink receiving beam tracking and estimation of modulation and coding schemes, power control, and Doppler frequency offset, through techniques like Interleaved Frequency Division Multiplexing Access (IFDMA) and extended cyclic prefixes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional reference signals (CSI-RS and SRS) are used for beamforming measurements, then downlink channel quality and uplink channel status can be measured, but the overhead is high and beam refinement efficiency is insufficient
Solution Approach 1:
The patent extracts the essential function of beam refinement from traditional reference signals by introducing a dedicated beam refinement reference signal (BR-RS) that is specifically designed for this purpose. This separates the beam refinement function from general channel measurement functions, allowing optimized signal design with lower overhead while maintaining measurement precision.
Solution Approach 2:
The beam refinement reference signal is designed to serve multiple functions simultaneously: it enables both downlink beam refinement and uplink beam refinement, supports channel quality measurement, and facilitates beam tracking. This multi-functionality reduces the need for separate dedicated signals for each function, thereby reducing overall overhead.
2Reliability
If two-dimensional active antenna array is used to exploit elevation and azimuth dimensions, then system performance is improved, but device complexity and measurement complexity increase
Solution Approach 1:
The patent segments the beam refinement process into distinct phases: initial beam acquisition using traditional reference signals, followed by beam refinement using the new BR-RS. This segmentation allows the system to use simpler procedures for initial connection while employing more sophisticated two-dimensional beamforming only when needed for performance optimization.
Solution Approach 2:
The patent implements preliminary beam acquisition using conventional reference signals before deploying the more complex two-dimensional beam refinement process. This preliminary action establishes a baseline connection, allowing the system to then apply advanced beamforming techniques only when performance improvements are needed, rather than using complex procedures from the start.
3Loss of information
If beam sweeping is performed to select the best beam, then channel knowledge is improved, but time consumption and overhead increase
Solution Approach 1:
The patent implements periodic beam refinement using the BR-RS, where beam sweeping and refinement are performed at optimized intervals rather than continuously. This periodic approach maintains up-to-date channel knowledge while minimizing the time and overhead associated with frequent beam sweeping operations.
Solution Approach 2:
Instead of performing exhaustive beam sweeping across all possible beams, the patent applies beam refinement only to the most promising beam directions identified during initial acquisition. This partial action approach maintains sufficient channel knowledge while significantly reducing the time and overhead compared to complete beam sweeping.
Data Source
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AI summary
Techniques related to uplink beam refinement are described. Briefly, in accordance with one embodiment, a Fifth Generation (5G) Sounding Reference Signal (xSRS) is used to refine and/or track an uplink Receiving (Rx) beam. In an embodiment, the xSRS is mapped to a plurality of Orthogonal Frequency Division Multiplexing (OFDM) symbols in a subframe. Other embodiments are also disclosed and claimed.