Unsourced Random Access With Tensor-Based and Coherent Modulations

Unsourced random access (URA) is a particular form of grant-free uncoordinated multiple access wherein the users’ identities are not associated to specific waveforms at the physical layer. Tensor-based modulation (TBM) has been recently advocated as a promising technique for URA due to its ability to support a large number of active users transmitting simultaneously by exploiting tensor decomposition for user separation. In the present paper, we introduce a novel URA scheme that builds upon TBM by splitting the transmit message into two sub-messages. This first part is modulated according to a TBM scheme, while the second is encoded using a coherent non-orthogonal multiple access (NOMA) modulation. At the receiver side, we exploit the advantages of forward error correction (FEC) coding and interference cancellation techniques. The performance of the introduced scheme is compared with state-of-the-art URA schemes under a quasi-static Rayleigh fading model, proving the energy efficiency and robustness to large-scale fading of the proposed solution.