Optimal Preamble Design in Spatial Group-Based Random Access for Satellite-M2M Communications

Satellite communication is expected to play a pivotal role in supporting the ubiquitous machine-to-machine (M2M) connection. Due to its wide beam coverage, however, one of the major challenges is to accommodate massive and concurrent M2M random access (RA) requests with the guarantee of human-to-human communications. To tackle this challenge, an enhanced spatial group-based RA scheme is presented from the viewpoint of preamble design. By leveraging a large-capacity RA preamble set configured with only a single root Zadoff-Chu sequence and strictly constrained cyclic shift offset set, it can effectively eliminate non-orthogonal interference and achieve the robustness to location estimation error in preamble detection procedure. Simulation results demonstrate that the proposed scheme offers an outstanding detection performance improvement, and can accommodate a significantly larger number of M2M devices while having a notably reduced collision probability and access delay, in comparison with the conventional one.