A Random Access Protocol Based on Idle Pilot Reallocation for Crowded Massive MIMO Systems

As the occurrence of massive machine type communication (mMTC), the requirements for the performance of random access in crowded massive multiple-input multiple-output (MIMO) systems are increasing. To improve the access performance, a novel random access protocol called strongest-user collision resolution combined idle pilot reallocation (SUCR-IPRA) scheme is proposed. Through the idle pilot reallocation strategy, the utilization of idle pilots can be significantly improved, and its expression is derived in this letter. Numerical results show that the proposed scheme observably outperform the existing strongest-user collision resolution (SUCRe) and SUCR combined idle pilot access (SUCR-IPA) schemes in terms of increasing the efficiency and success rate during the random access process.