Grant-Free Multiple Access Scheme

In this chapter, the grant-free multiple access scheme is introduced for a transmission without dynamic scheduling. A few key technical components have been addressed, including the grant-free resource configuration, user equipment activity identification with contention transmission, HARQ procedure and soft-combining, contention resolutions. Numerical and simulation evaluation results have also been provided to demonstrate the performance of the grant-free scheme operating with OFDMA and NOMA. The grant-free multiple access scheme is able to achieve transmission latency and control signaling reduction, and the device energy saving; thus, it provides a promising solution to small data transmissions, massive connectivity, and low-latency applications such as mMTC and URLLC services.