On the Feasibility of Collision Detection in Full-Duplex 802.11 Radio

Full-duplex radios are becoming a feasible reality thanks to recent advances in self-interference cancellation. Switching from half-to full-duplex requires a major re-design of many network features and characteristics, including the MAC layer. The literature provides several new proposals or improvements that are applicable in different topologies: centralized, distributed, and multi-hop Wireless LANs (WLANs). These proposals, however, mostly focus on directional, unicast communication. While the main goal of unicast-focused approaches is to get as close as possible to doubling the throughput, it is still unclear how to exploit full-duplex radios in broadcast-like environments such as the vehicular one or in general in WiFi-like scenarios where interference is the dominating impairment. In this work we analyze the possible benefits and drawbacks of exploiting self-interference cancellation in full-duplex radios to implement collision detection. We show that, if proved feasible, the required changes to the MAC layer of an 802.11-based transceiver would be minimal, and could largely improve the performance with respect to a standard collision avoidance mechanism. In addition, the paper discusses the tricky aspects and the parameters required to identify a collision in a wireless network and discusses the many differences between managing collisions in a wired and in a wireless environment.