Uplink grant-free pattern division multiple access (GF-PDMA) for 5G radio access

Massive machine type communication (mMTC) is one of the key application scenarios for the fifth generation mobile communication (5G). Grant-free (GF) transmission can reduce the high signaling overhead in mMTC. Non-orthogonal multiple access (NMA) can support more users for mMTC than orthogonal frequency division multiple access (OFDMA). Applying GF transmission in NMA system becomes an active topic recently. The in-depth study on applying GF transmission in pattern division multiple access (PDMA), a competitive candidate scheme of NMA, is investigated in this paper. The definition, latency and allocation of resource and transmission mechanism for GF-PDMA are discussed in detail. The link-level and system-level evaluations are provided to verify the analysis. The analysis and simulation results demonstrate that the proposed GF-PDMA has lower latency than grant based PDMA (GB-PDMA), possesses strong scalability to confront collision and provides almost 2.15 times gain over GF-OFDMA in terms of supporting the number of active users in the system.