Beam Refinement During Random Access Channel Procedure
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Solution Overview
Problem
In millimeter-wave wireless communication systems, the high path-loss and susceptibility to blockages pose challenges during the random access channel (RACH) procedure, leading to potential beam selection failures due to the use of wider beams with lower gain and non-optimal beam alignment, which affects signal-to-noise ratio (SNR) and communication efficiency.
Innovation Solution
The implementation of hybrid beamforming techniques, including the transmission of additional measurement reference signals (MRS) or beam refinement reference signals (BRRS) by the base station (NB) to refine the initial beam selection made by the user equipment (UE) during the RACH procedure, allowing for more precise directional beam alignment and enhanced signal energy delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If wider beams are used during RACH procedure, then beam coverage area is improved, but beam gain and signal-to-noise ratio deteriorate
Solution Approach 1:
The patent segments the beamforming process into two stages: initial beam selection using wider beams for coverage, and subsequent beam refinement using narrower beams for higher gain. This segmentation allows the system to first establish coverage area and then optimize signal quality within that coverage region.
Solution Approach 2:
The patent implements dynamic beam adjustment where the beam width and direction are modified based on feedback signals received during the RACH procedure. The base station adjusts beam parameters dynamically to transition from wide coverage beams to focused refinement beams, optimizing both coverage and signal quality at different stages.
2Device complexity
If initial beam selection is performed without refinement, then RACH procedure complexity is reduced, but beam alignment precision deteriorates
Solution Approach 1:
The patent performs preliminary beam selection using wider beams and simpler measurement procedures before conducting more complex beam refinement measurements. This preliminary action establishes an initial beam direction quickly, and subsequent refinement measurements are performed only in the narrowed-down directional range, achieving high precision without excessive overall complexity.
Solution Approach 2:
The patent employs feedback mechanisms where the base station receives signals from the UE and uses this feedback to adjust beam parameters. The feedback loop enables iterative refinement of beam alignment, where each iteration uses the results of the previous iteration to guide the next measurement and adjustment cycle, improving precision while managing complexity through feedback-driven optimization.
3Measurement precision
If beam refinement signals are transmitted, then beam selection accuracy is improved, but transmission time and procedure duration increase
Solution Approach 1:
The patent applies partial beam refinement by transmitting refinement signals only in specific directional sectors where the UE is likely to be located, rather than performing exhaustive beam measurements across all possible directions. This partial action achieves sufficient beam selection accuracy for the given scenario while significantly reducing the time required compared to complete beam sweeping.
Solution Approach 2:
The patent implements periodic beam refinement where refinement signals are transmitted at specific intervals rather than continuously. The base station transmits refinement signals periodically to allow the UE to measure and report back, enabling beam alignment to be updated at optimal moments without requiring continuous transmission, thus reducing overall procedure duration while maintaining accuracy.
Data Source
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AI summary
Aspects of the present disclosure relate to wireless communications and, more particularly, to beam refinement during a RACH procedure. A NB may receive a message via a first beam from a UE as part of a RACH procedure and may transmit at least one signal for beam refinement during the RACH procedure. A UE may transmit, to a NB, a message via a first beam as part of a RACH procedure and may receive, from the NB, at least one signal for beam refinement during the RACH procedure. Any directional signal beam may be used for beam refinement as described herein.