Y. Wang, Y. Zeng, S. Sun and Y. Nan, "High Accuracy Uplink Timing Synchronization for 5G NR in Unlicensed Spectrum," in IEEE Wireless Communications Letters, vol. 10, no. 3, pp. 604-608, March 2021, doi: 10.1109/LWC.2020.3039501.
Sub-microsecond high accuracy clock synchronization is essential in time critical applications such as factory automation. In 3GPP, 5G New Radio in unlicensed spectrum (NR-U) is being discussed to support time critical applications. In 5G NR-U uplink, synchronization is achieved by using block interleaved frequency division multiple access (B-IFDMA) reference signals (RS). Based on the B-IFDMA-structured RS, conventional methods can only obtain the frequency domain channel at non-evenly spaced frequency points. When this channel is transformed from frequency domain to time domain, the resultant channel impulse response (CIR) will contain additional “pseudo” paths. In multipath channel, such “pseudo” paths may cause aliasing effects, affecting accuracy of CIR-based timing synchronization algorithms. In this letter, we propose two methods to address the above problem, namely, the frequency-domain subspace (FDS) based algorithm, and FDS-aided algorithm. Simulation result shows that our proposed methods counteract the aliasing effects effectively and significantly outperform the conventional algorithms.
This research / project is supported by the Agency for Science, Technology and Research - RIE2020 IAF-PP Grant Industrial Internet of Things Research Program
Grant Reference no. : A1788a0023