mmWave Cell Search Beam Selection and Scanning Order
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Solution Overview
Problem
The conventional mmWave based communication systems face high latency and complexity during cell search due to the lack of directional information, leading to a performance versus latency tradeoff when using either wider or narrower receive beams.
Innovation Solution
A method where the User Equipment (UE) monitors signals on multiple receive beams, determines power metrics, selects a subset of beams based on these metrics, and performs a cell search by scanning the selected beams in a predetermined order to detect the cell identifier of the Base Station.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the UE scans all possible receive beam directions exhaustively during cell search, then the cell detection reliability is improved, but the cell search latency increases
Solution Approach 1:
The base station performs preliminary action by transmitting synchronization signal blocks (SSBs) in specific directions with associated directional information before the UE needs to search for cells. This pre-positioning of signal and metadata allows the UE to efficiently locate cells without exhaustive scanning, resolving the contradiction between detection reliability and search latency.
Solution Approach 2:
Directional information acts as an intermediary that bridges the base station's transmitted signals and the UE's cell detection process. This metadata enables the UE to interpret received signals in the context of specific directions, allowing selective scanning of promising beams rather than exhaustive searching, thus reducing latency while maintaining reliability.
2Loss of time
If the UE uses wider receive beams for cell search, then the cell search latency is reduced, but the measurement precision deteriorates
Solution Approach 1:
The system dynamically adjusts the receive beam width based on operational requirements. During cell search, wider beams are used to reduce latency by covering more directions simultaneously. Once cell detection is complete, the system can switch to narrower beams for precise signal measurements and communication, thus resolving the contradiction between search speed and measurement accuracy.
Solution Approach 2:
The cell search process is segmented into distinct phases: initial detection using wider beams to quickly identify candidate cells, followed by refined measurement using narrower beams on selected directions. This segmentation allows the system to optimize for speed during search and for precision during measurement, eliminating the need to compromise either objective.
3Measurement precision
If the UE uses narrower receive beams for cell search, then the measurement precision is improved, but the cell search latency increases
Solution Approach 1:
The base station performs preliminary action by transmitting synchronization signal blocks (SSBs) in specific directions with associated directional information before the UE needs to search for cells. This pre-positioning of signal and metadata allows the UE to efficiently locate cells without exhaustive scanning, resolving the contradiction between detection reliability and search latency.
Solution Approach 2:
The system dynamically adjusts the receive beam width based on operational requirements. During cell search, wider beams are used to reduce latency by covering more directions simultaneously. Once cell detection is complete, the system can switch to narrower beams for precise signal measurements and communication, thus resolving the contradiction between search speed and measurement accuracy.
4Reliability
If the UE performs exhaustive beam scanning without directional information, then the cell detection reliability is improved, but the system complexity increases
Solution Approach 1:
Directional information acts as an intermediary that bridges the base station's transmitted signals and the UE's cell detection process. This metadata enables the UE to interpret received signals in the context of specific directions, allowing selective scanning of promising beams rather than exhaustive searching, thus reducing latency while maintaining reliability.
Solution Approach 2:
The base station performs preliminary action by transmitting synchronization signal blocks (SSBs) in specific directions with associated directional information before the UE needs to search for cells. This pre-positioning of signal and metadata allows the UE to efficiently locate cells without exhaustive scanning, resolving the contradiction between detection reliability and search latency.
Data Source
AI summary
Presented herein is a pre-5th-Generation (5G) or 5G communication system that supports higher data rates beyond 4th-Generation (4G) communication systems. In particular, methods and systems for performing cell search in a millimeter wave (mmWave) based communication network are presented. A method disclosed herein includes selecting a subset of receive (Rx) beams from a plurality of Rx beams and scheduling a scan order for the selected subset of Rx beams, upon receiving a plurality of signals from a Base Station. The method also includes performing a cell search using the selected subset of Rx beams individually in the determined scan order. The method further includes combining two or more of the selected Rx beams, upon failing the cell search using the selected subset of Rx beams individually. The method further includes performing the cell search using the combined Rx beams.