Improving Non-Coherent Grant-Free Massive Access With Dual-Mode Index Modulation

In this paper, a dual-mode index modulation aided non-coherent (DMIM-NC) scheme is proposed to improve the transmission efficiency of non-coherent grant-free systems. In DMIM-NC, a transmitted frame is partitioned into multiple groups, each of which contains multiple channel blocks. Driven by the transmitted bits, different groups employ distinct index modulation modes, choosing activated channel blocks for each group. At the receiver, a low-complexity pruning aided block coordinate descend (PBCD) detector is conceived for the proposed DMIM-NC grant-free systems. Simulation results show that DMIM-NC utilizing the designed PBCD detector is able to outperform conventional detectors in terms of transmission rate, active user detection performance, and bit recovery accuracy.