Two-Stage Beam Selection for 5G Initial Access Latency
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Solution Overview
Problem
Current wireless communication systems face challenges in efficiently managing beams for 5G mobile communication systems, particularly in selecting the optimal reference signals for channel state information and data transmission, which affects spectral efficiency and latency in massive MIMO systems.
Innovation Solution
The proposed solution involves a nested reference signal design where wide beam synchronization signals and channel state information-reference signals are used for coarse and fine beam selection, respectively, with the UE reporting reference signal receive power and channel state information to the base station for beam configuration, enabling efficient beam management and data channel transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If beam sweep with multiple beams is performed for beam selection, then beam selection accuracy is improved, but initial access latency increases
Solution Approach 1:
The beam selection process is segmented into two stages: first, a coarse beam selection is performed using a limited set of wide beams to quickly identify candidate directions; second, a fine beam selection is performed using narrow beams only in the identified candidate directions. This segmentation reduces the total number of beams that need to be swept while maintaining accurate beam selection.
Solution Approach 2:
The coarse beam selection is performed as a preliminary action before the fine beam selection. By first identifying candidate beam directions using wide beams, the system prepares the groundwork for subsequent narrow beam measurements, avoiding the need to perform exhaustive beam sweeps and reducing overall access latency.
2Measurement precision
If comprehensive beam measurement and reporting is performed, then beam selection accuracy is improved, but signaling overhead increases
Solution Approach 1:
The system extracts only the essential information needed for beam selection from the comprehensive beam measurements. Instead of reporting all beam measurement results, the UE reports only the identified candidate beams and their metrics, filtering out redundant information and reducing signaling overhead while maintaining beam selection accuracy.
Solution Approach 2:
The system performs partial measurement and reporting by focusing computational and reporting resources only on the top candidate beams identified during coarse selection, rather than comprehensively measuring and reporting all possible beams. This partial action approach achieves sufficient beam selection accuracy with reduced signaling overhead.
3Measurement precision
If UE computes CSI for multiple beams, then channel state information accuracy is improved, but computation complexity increases
Solution Approach 1:
The UE applies different computation efforts to different beams based on their importance. High computation effort (full CSI computation) is applied only to the top candidate beams that are most likely to be selected, while lower computation effort is applied to other beams. This local quality approach ensures high CSI accuracy for critical beams while reducing overall computation complexity.
Solution Approach 2:
The UE performs partial CSI computation by calculating channel state information only for the subset of candidate beams that are most promising, rather than computing CSI for all beams. This partial action provides sufficient channel state information accuracy for beam selection while significantly reducing the computational burden on the UE.
Data Source
AI summary
A base station receives a report of channel state information (CSI) computation capability from a UE, configures the UE with X and Y values based on the reported computation capability, performs a beam sweep by transmitting direction-unique beams, and receives a beam measurement report from the UE comprising a reference signal receive power (RSRP) of Y strongest beams of the transmitted beams and at least a portion of the CSI of X strongest beams of the Y beams. Based on the beam measurement report, one of the X beams is selected to configure the UE for subsequent data and control channel transmissions. X and Y are positive integers, Y is greater than or equal to X, and Y is at least 1.