SSB Beam Grouping for Faster PRACH Initial Access

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Solution Overview

Problem

In future radio communication systems, the use of multiple beams for synchronization signal blocks (SSBs) leads to a prolonged time for SSB measurement and determination of the best beam, which degrades communication throughput during initial access.

Innovation Solution

A terminal that measures synchronization signal blocks corresponding to a set of beams and determines the index of the best beam based on measurement results, then transmits a Physical Random Access Channel (PRACH) corresponding to this index.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a terminal uses a plurality of beams to receive a plurality of respective synchronization signals (SSBs) in each SSB transmission period, then the coverage and reliability of initial access are improved, but the time for SSB measurement and determination of the best beam increases, which degrades communication throughput

Engineering Contradiction:
Improveinitial access reliabilityVSAvoidSSB measurement time
Core Design Contradiction:
ReliabilityVSLoss of time

Solution Approach 1:

The patent divides the plurality of beams into multiple groups, where each group is associated with a specific SSB index. Instead of measuring all beams individually, the terminal measures SSBs corresponding to different beam groups and determines the best beam group first, then selects the best beam within that group. This segmentation reduces the total measurement time while maintaining reliable initial access.

Inventive Principle:
Principle #1Segmentation

2Area of stationary object

If the number of beams is increased to improve coverage, then the coverage area is expanded, but the number of SSBs to be transmitted increases, causing longer initial access time

Engineering Contradiction:
Improvecoverage areaVSAvoidinitial access speed
Core Design Contradiction:
Area of stationary objectVSProductivity

Solution Approach 1:

The patent segments the large number of beams into multiple groups, each represented by a specific SSB index. The terminal performs measurements on a reduced set of SSBs corresponding to different beam groups, identifies the best beam group, and then determines the specific best beam within that group. This approach maintains comprehensive coverage while significantly reducing the time required for initial access.

Inventive Principle:
Principle #1Segmentation

Data Source

PatentEP4657764A1Terminal, wireless communication method, and base station
Publication Date: 2025.12.03 NTT DOCOMO INC
  • EP4657764A1 patent drawingFigure 1A~1C
  • EP4657764A1 patent drawingFigure 2
  • EP4657764A1 patent drawingFigure 3

AI summary

A terminal according to one aspect of the present disclosure includes: a control section that measures a synchronization signal block (SSB) corresponding to a set of a plurality of beams of each layer, and determines an index of a best beam, based on a measurement result; and a transmitting section that transmits a Physical Random Access Channel (PRACH) corresponding to the index of the best beam. According to one aspect of the present disclosure, it is possible to perform determination of the best beam at high speed.