Slotted ALOHA-based URA Scheme with Index Modulation for Short Block Length

Unsourced random access (URA) has become a promising technique to support massive connectivity scenarios. This work proposes a slotted ALOHA-based URA scheme with index modulation for short packet transmission under Multiple-Input Multiple-Output (MIMO) channel. In our scheme, the short data packet of each active user is divided into three parts, where the first two parts are encoded by compressed sensing (CS) and the low-density-parity-check (LDPC) code, respectively, while the third part is the index of the slot where the encoded packet is transmitted. The data decoding is implemented slot-by-slot at the base station (BS). To this end, a hard decision (HD)-based decoder, including the index modulation demodulation, CS decoding, and LDPC decoding, is developed. Simulation results reveal that our proposal outperforms the counterparts significantly.