An Uplink Grant-Free Access Solution Based on Sparse Resource Pattern for IoT

Abstract

With the rapid development of the Internet of things (IoT), simultaneous access of the massive devices to the network becomes essential. The current multiple access scheme in 4G is a traditional grant-based scheme which needs permission to access the system. It will suffer from congestion and overloading as the number of device increases. Therefore, grant-free random access, where users do not need to access channel resource through four step handshake process, recently gained wide interest in 5G new radio. Moreover, non-orthogonal technology is an effective way to deal with frequent collisions in the grant-free scheme. In this paper, we propose a grant-free non-orthogonal random access (GF-NORA) scheme based on sparse on-off resource pattern. The on-off pattern enables users to occupy resource blocks continuously or discontinuously. And the sparsity of resource pattern is helpful to change the distribution of non-collision part’s ratio of signals. A variety of operating modes are supported because of the flexible use of resource patterns. The simulation results indicate that the proposed method can effectively change the distribution of non-collision part’s ratio of signals when adopting the single user detection. By selecting the appropriate coded-modulation scheme to recover messages from the non-collision part, the outage probability will be reduced compared with slotted ALOHA.