A 5G New Radio LDPC Coded NOMA Scheme Supporting High User Load for Massive MTC

Abstract

To provide massive connectivity of a large number of low-power devices in massive machine-type communications (mMTC), advanced physical layer multiple access technologies are imperative for next generation of cellular networks. In this paper, a physical layer non-orthogonal multiple access (NOMA) scheme, called resource-pattern-aided bit-interleave coded multiple access, BICMA for short, is proposed for mMTC to support high and flexible user load energy-efficiently with low complexity. The rate-compatible length-scalable low-density parity check (LDPC) codes, recommended for 5G new radio in 3GPP work item, are firstly incorporated into NOMA schemes to provide great flexibility and compatibility with other services, like enhanced mobile broadband. In BICMA, instead of spreading, the constellation symbols of users are directly mapped to chips according to resource patterns, of which the density can be adjusted to reduce multi-user interference at each chip. Thanks to the rate-compatible length-scalable LDPC codes and flexible resource pattern, the parameter optimization of BICMA is of low complexity. Simulation results show that the energy-efficiency of BICMA is higher than that of orthogonal multiple access schemes, especially with relatively high sum spectral efficiency. Various user loads, as high as 18 users with spectrum efficiency of 0.25 bits/chip/user, can be supported by BICMA, and the required signal-to-noise ratio of each user only increases slightly while much more users could access the same channel resources simultaneously.