Unsourced random access (URA) is a particular form of grant-free uncoordinated random 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. We propose 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. We compare the performances of the introduced scheme with state-of-the-art URA schemes under a quasi-static Rayleigh fading model, proving the energy efficiency and the fading robustness of the proposed solution.

翻译：无源随机接入（URA）是一种特殊的免授权非协调随机接入方式，其中用户身份在物理层不与特定波形相关联。张量调制（TBM）近期被提出作为URA的一种有前景技术，因其能够通过利用张量分解进行用户分离，支持大量活跃用户同时传输。我们提出了一种新颖的URA方案，该方案基于TBM，将传输消息分为两个子消息：第一部分采用TBM方案进行调制，而第二部分则使用相干非正交多址（NOMA）调制进行编码。在接收端，我们利用了前向纠错（FEC）编码和干扰消除技术的优势。我们在准静态瑞利衰落模型下，将所提方案的性能与现有URA方案进行了比较，证明了该方案的能量效率和抗衰落鲁棒性。