Two-Dimensional Residual Timing Offset Compensation for Enhanced 5 G SSB Identification in a 5 G Softwarized Modem

초록

The 5 G system employs multiple beams, and its initial cell selection procedure essentially involves identifying Synchronization Signal Blocks (SSBs) for beam detection. This SSB identification is significantly affected by Symbol Timing Offset (STO) due to its inherent nature of detection in the frequency domain. The performance of this process is likely to degrade in a softwarized modem that handles baseband signals within software environments. The softwarized modem relies on an STO estimation algorithm with low computational complexity, which may result in a larger STO. It can also encounter multi-path channels, which cause the additional effect of large STOs. In this paper, we propose a novel residual STO compensation scheme in both the time and frequency domains to improve the accuracy of SSB identification. A mathematical model is initially developed to observe the impact of STO on SSB identification. Based on the mathematical analysis, the proposed scheme is designed to adjust the estimated STO using the convex characteristics of auto-correlation for a 5 G synchronization signal. Additionally, the proposed scheme jointly considers multiple STO candidates for phase compensation in the frequency domain. For performance assessment, we conduct experiments using the testbed system of a softwarized modem that transmits and receives real signals through practical channels. The experimental results imply that the proposed scheme effectively addresses STO in practical multi-path channels and bring significant improvement to SSB identification.

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