Flag Vector Assisted Multi-user Semantic Communications for Downlink Text Transmission

Semantic communication has become a promising paradigm tailored for multi-user intelligent communications. Existing semantic methods for multi-user schemes assume that the receiver sends channel state information (CSI) feedback to the transmitter, which is not always realistic. In this work, we design a feedback-free scheme called Multi-user Efficient Transmission DeepSC (MET_DeepSC) for multi-user semantic communication. The idea is to utilize dedicated flag vectors for the identification of different users. We embed these flag vectors on both the transmitter and receiver sides, and thus the feedback of CSI is no longer needed. We also propose a fusion mechanism that compresses the semantic messages of all the users into a single signal. In this way, all the users' messages can be simultaneously sent, and thus the transmission workload is greatly relieved. Simulation results show that the MET_DeepSC transmits multi-user messages without additional resources at the cost of only slight performance degradation and outperforms the baselines.