Unsourced Sparse Multiple Access: A Promising Transmission Scheme for 6G Massive Communication

Massive communication is a key scenario of 6G, which requires a hundred times higher connection density than 5G. As a promising direction, unsourced multiple access has a capacity bound much higher than those of orthogonal multiple access or slotted-ALOHA. In this article, we describe a framework of unsourced sparse multiple access (USMA) realization that consists of two key modules: compressed sensing for preamble generation and sparse interleaver division multiple access for main packet transmission. By the proper combination of various components such as compressed sensing matrix, channel codes, interleaver, and receiver algorithms, USMA offers a more feasible engineering design that can support a larger number of users than the state-of-the-art scheme. To illustrate the scalability of USMA, a customized implementation is proposed for ambient Internet of Things to further reduce the memory and computation complexities. Simulation results of Rayleigh fading and realistic channel estimation show that the solution can deliver nearly four times the resource efficiency of traditional slotted-ALOHA systems.