Improved Preamble Detection and Round-Trip Delay Estimation for Random Access in High-Mobility Airborne Communication Systems

摘要

In this paper, an improved preamble detection and round-trip delay (RTD) estimation algorithm is proposed for random access, particularly in the context of airborne wireless communication systems. The proposed algorithm is capable of both combating large Doppler shifts occurring in high-mobility scenarios and dealing with the energy leakage problem caused by sampling misalignment at the receiver. Specifically, we use the so-called paired Zadoff-Chu (PZC) sequences as preambles, which are detected by a simple correlator. Then the RTD of the user equipment (UE) is estimated based on the relation between the peak values’ indices (PVI) of the squared absolute values (SAV) of two cross-correlation functions (CCF), helping to combat the severe Doppler shift effect. While the conventional symmetric Zadoff-Chu (SZC) scheme determines the two PVIs independently, the proposed PZC scheme jointly calculates both PVIs, which successfully mitigates the PVI ambiguity problem. As a result, the performance of RTD estimation can be significantly improved. Simulation results validate the proposed scheme under a very high UE mobility of 1020ms, which eliminates the timing error floor observed in conventional SZC-aided systems.