Index Modulation Multiple Access for Unsourced Random Access

In this letter, a novel index modulation multiple access (IMMA) scheme is proposed in the quasi-static MIMO channel. In the proposed scheme, the transmit information bits are divided into two parts, IMMA bits and coded bits. The IMMA bits are employed to select the active compressed sensing codeword transmitted in the first phase, and determine the IMMA pattern. The encoding bits are LDPC encoded, modulated, and transmitted in the second phase through IMMA. In the multiuser detection, the IMMA patterns and active channels are first estimated by approximate message passing (MP) algorithm. Then, the encoding bits are decoded by MP algorithm based on the joint LDPC and IMMA factor graph. Finally, computer simulations are given to demonstrate the performance of the proposed scheme.