Efficient Collision Detection Based on Zadoff-Chu Sequences for Satellite-Enabled M2M Random Access

Due to concurrent access attempts from massive machine-type devices (MTDs) within the wide beam coverage, the existing contention-based random access (RA) scheme suffers from severe physical random access channel (PRACH) over-load when applied to the emerging satellite-enabled machine-to-machine (M2M) communications. In this paper, we propose an efficient collision detection scheme based on cyclically shifted Zadoff-Chu (ZC) sequences, which are generated by the minimum number of required root indexes and a fixed cyclic shift offset independent of the beam radius. The proposed scheme enables rapid collision detection at the first step of RA procedure by capturing correlation peaks at the timing positions corresponding to the multiples of the cyclic shift offset, thus can reduce the access delay and resource consumptions for the collided MTDs. Simulations are carried out to validate the correctness of mathematical analysis, and to demonstrate the significant detection performance improvement of our scheme with effective non-orthogonal interference (NOI) mitigation by compared to the conventional one.