Rate-Compatible LDPC Based IDMA Scheme Supporting Grant-Free Transmission in eMBB

Enhanced mobile broadband (eMBB) supports not only sustained high-data-rate transmission but also contention based grant-free transmission. For efficient radio resource utilization, interleave-division multiple access (IDMA) which is a promising instantiation of non-orthogonal multiple access is adopted for grant-free transmission in this paper. Conventional IDMA schemes mainly focus on low rate channel code which results in limited total spectral efficiency and limited choices of code rates. Moreover, IDMA schemes suffer from performance degradation under severe multi-user interference, since conventional coding scheme in IDMA is mainly optimized for point-to-point transmission. In this work, we propose a rate-compatible LDPC based IDMA solution to support grant-free transmission in eMBB. The raptor-like quasi-cyclic low-density parity-check (RL-QC-LDPC) codes contained in this solution are similar to the channel codes for 5G eMBB data channel in code rate and length, and optimized towards severe multi-user interference with the aid of multi-edge type density evolution based extrinsic information transfer chart tool. According to block error rate simulation results, the proposed rate-compatible LDPC based IDMA scheme is able to provide high throughput with near capacity performance and be robust to flexible number of access users.