Low-Complexity Grant-Free Random Access Based on Chirp Signals in Asynchronous Scenarios

Abstract

Grant-free random access, as a crucial access mechanism in current massive machine-type communication (mMTC) scenarios, can significantly reduce signaling overhead. Base station(BS) achieve joint device activity detection and channel estimation (JADCE) through received pilot sequences. However, time delays severely degrade detection performance and increase computational complexity. In this letter, we first design a novel pilot sequence composed of chirp signals with distinct parity index values. Then, we construct a reduced candidate pilot set by leveraging the invariant parity property of index value sums under time delays. Finally, exploiting the favorable correlation characteristics of the pilot sequences, we propose a low-complexity orthogonal matching pursuit with successive interference cancellation (OMP-SIC) algorithm for solving the JADCE problem in asynchronous multiple access scenarios.