A Joint TA and CFO Estimation Method Using Random Access Preambles in Non-Terrestrial Networks

Non-terrestrial networks (NTNs) are poised to play a critical role in 6G and future communication technologies for providing reliable, wide-reaching, cost-effective connectivity. In NTNs, random access is fundamental for establishing reliable and efficient communication between user equipment (UE) and satellite. Since NTNs are subject to challenges such as high dynamics, long-range propagation, and variable Doppler effects, both timing advanced (TA) and carrier frequency offset estimation (CFO) must be accurate to enhance the performance, reliability, and efficiency of random access. Based on conjugate symmetric Zadoff-Chu (CSZC) sequences, we propose a novel joint TA and CFO estimation method in this paper. In the proposed method, the fractional frequency offset is iteratively estimated and compensated to eliminate its adverse impact on the ZC sequence in the correlation. Accurate TA and integer CFO estimations are achieved by leveraging the excellent zeroautocorrelation and symmetry properties of CSZC sequences. Simulations show that the proposed method outperforms the existing methods in terms of both TA and CFO estimation performance in NTN environments with low Signal-to-Noise Ratio and large Doppler shifts.