802.11ec: Collision Avoidance Without Control Messages

In this paper, we design, implement, and evaluate 802.11ec (Encoded Control), an 802.11-based protocol without control messages: Instead, 802.11ec employs correlatable symbol sequences that, together with the timing the codes are transmitted, encode all control information and change the fundamental design properties of the MAC. The use of correlatable symbol sequences provides two key advantages: 1) efficiency, as it permits a near order of magnitude reduction of the control time; 2) robustness, because codes are short and easily detectable even at low signal-to-interference-plus-noise ratio (SINR) and even while a neighbor is transmitting data. We implement 802.11ec on a field programmable gate array (FPGA)-based software defined radio. We perform a large number of experiments and show that, compared to 802.11 (with and without RTS/CTS), 802.11ec achieves a vast efficiency gain in conveying control information and resolves key throughput and fairness problems in the presence of hidden terminals, asymmetric topologies, and general multihop topologies.