Cell-Free MIMO Beam Search Using Two-Stage Beam Refinement
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Solution Overview
Problem
The increased number of access points (APs) in cell-free MIMO techniques necessitates longer beam search processing times due to the need for identifying optimal beams for communication with user equipment (UEs).
Innovation Solution
A control apparatus that instructs the transmission of first reference signals using different parameters via multiple beams, obtains feedback information on signal strength, determines a reduced number of beams for further measurement, and reports narrower beams for use in subsequent measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the number of access points is increased to improve coverage and connectivity, then the system can serve more users and provide better redundancy, but the time required for beam search processing increases significantly
Solution Approach 1:
The beam search process is divided into two distinct stages: a first beam search that identifies candidate beams from multiple access points, and a second beam search that refines the selection using narrower beams. This segmentation allows the system to handle multiple access points efficiently by breaking down the complex search into manageable steps, reducing overall processing time while maintaining comprehensive coverage.
Solution Approach 2:
The first beam search performs preliminary identification of candidate beams and access points before the second beam search refines the selection. By pre-identifying promising candidates in the first stage, the system reduces the search space for the second stage, thereby reducing the total beam search processing time even when many access points are deployed.
2Reliability
If beam search processing is performed with all access points to ensure optimal beam selection, then communication quality is maximized, but the processing time becomes excessively long
Solution Approach 1:
The beam search is segmented into two stages where the first stage identifies candidate beams from all access points to ensure comprehensive evaluation, while the second stage refines the selection with narrower beams. This ensures optimal communication quality is not compromised while reducing redundant processing.
Solution Approach 2:
The first beam search performs a broader, less precise search to identify candidate beams, and the second beam search performs a more precise search on a reduced set of candidates. This partial action approach ensures that thorough evaluation is performed where necessary while avoiding excessive processing on all possible beams.
3Measurement precision
If the beam width is reduced to improve beam precision and signal focus, then the beam search becomes more accurate, but the time required to search through all possible beams increases
Solution Approach 1:
The beam search uses two different beam widths in sequence: wider beams in the first search to quickly identify candidate directions, and narrower beams in the second search to precisely determine the optimal beam. This segmentation allows the system to achieve high measurement precision without the time penalty of using narrow beams throughout the entire search process.
Solution Approach 2:
The first beam search with wider beams performs a preliminary exploration of the signal space to identify promising directions. This preliminary action with broader beams reduces the search space, allowing the second stage to use narrower beams more efficiently without having to search the entire space at high precision.
Data Source
AI summary
A control apparatus that controls beam search processing between dispersed communication apparatus and user equipment performs: instructing to transmit first reference signals using first beams; obtaining first feedback information including a combination of identification information of one or more first beams and received signal strength; if a predetermined number or greater of identification information of different first beams is included in the first feedback information obtained from the user equipment, determining first beams of a number fewer than the predetermined number to use in measuring second reference signals from among first beams of the predetermined number or greater; and reporting a parameter of the second reference signals transmitted using second beams that correspond to the first beam determined to use in measuring and that have a narrower beam width than the first beams.