Full duplex random access for multi-user OFDMA communication systems

Random medium access control (MAC) plays a critical role in OFDMA wireless networks to support services with bursty traffic. However, the existing OFDMA random access protocols suffer from low efficiency due to the constraints in half-duplex communications. In this paper, the capability of full-duplex communications is leveraged to propose novel mechanisms such as full duplex carrier sensing, collision detection, and collision jamming. With these mechanisms, a full-duplex carrier sense multiple access with collision detection (FD-CSMA/CD) protocol is developed for OFDMA wireless networks. It is based on a hierarchical design: (1) with full-duplex communications, operation of subchannels is decoupled, and a CSMA/CD-like protocol is implemented in each subchannel as a random access scheme; (2) on top of random access per-subchannel, a simple but effective subchannel selection scheme is executed locally on each client to harvest multi-user diversity. Both theoretical analysis and simulations are carried out to validate the effectiveness and efficiency of our protocol.