Compressive sensing based signal design for multiple access in return channel

Recently, some orthogonal multiple access schemes are utilized in return channels. However, in the field of wireless communication, as the number of users increases, the orthogonal resources are difficult to meet the explosive demand of access. For this reason, some non-orthogonal multiple access (NOMA) schemes have been proposed to solve the key problem of massive connectivity. In this paper, we adopt the low-density spreading orthogonal frequency division multiplexing (LDS-OFDM) scheme, in which message passing algorithm (MPA) based multi-user detection (MUD) has been utilized to eliminate the interference between different subcarriers belong to different users. Then we propose an optimal reference signal design scheme based on compressive sensing methods for user activity detection. In simulation, we analyze the mean square error (MSE) and bit error rate (BER) performance of the proposed optimal reference signal and a random reference signal. The simulation results demonstrate that the proposed scheme performs better than the random one.