RTSS/CTSS: mitigation of exposed terminals in static 802.11-based mesh networks

Efficient usage of available capacity in wireless mesh networks is critical. Capacity is wasted due to the exposed terminal problem. In this paper, we propose a solution to mitigate the exposed terminal problem in static IEEE 802.11-based mesh networks, thereby improving the spatial reuse of the medium and increasing network throughput. Our solution is complementary to previously-proposed solutions that adjust the carrier-sense range for improved spatial reuse. The proposed solution consists of two phases. In the first phase, exposed links in the mesh topology are detected through an offline training process. Coordination of simultaneous transmissions over exposed links is then done in the second phase through the use of request-to-send- simultaneously (RTSS) and clear-to-send-simultaneously (CTSS) messages, which are added to the MAC protocol. Our solution preserves the distributed nature of the MAC protocol and does not require time synchronization between nodes. We present a simulation-based evaluation that demonstrates that the proposed solution effectively improves capacity usage and network throughput in representative topologies and traffic scenarios.