Full-Duplex-Based Rate/Mode Adaptation Strategies for Wi-Fi/LTE-U Coexistence: A POMDP Approach

The rapid increase in wireless demand prompted the FCC to open up parts of the 5-GHz band for unlicensed access. This caught the interest of 4G/LTE providers, who wish to extend their LTE-A services to the unlicensed spectrum (LTE-U). In LTE-U, small-cell base stations aggregate unlicensed and licensed bands to increase the throughput. Wi-Fi/LTE-U coexistence is a challenging issue due to the different access mechanisms of these two systems, which may cause high collision rates and delays. By leveraging self-interference-suppression techniques, we propose joint mode/rate adaptation strategies for Wi-Fi/LTE-U coexistence. Specifically, a full-duplex enabled Wi-Fi station can transmit and receive data simultaneously to increase the throughput, or transmit and sense (TS mode) simultaneously to monitor the LTE-U activity. We model the LTE-U interference as a hidden Markov process, and solve the problem of jointly adapting Wi-Fi rates/modes using a framework of partially observable Markov decision process. A detection approach based on the sliding window correlator is analyzed for the TS mode, which can differentiate between Wi-Fi and LTE-U signals. Our results indicate that our scheme provides 1.5x (1.9x) average throughput gain for Wi-Fi system in the low (high) signal-to-interference-and-noise regime relative to a half-duplex-based scheme.