Interaction Engineering. Taming of the CSMA

Carrier Sense Multiple Access (CSMA) protocols are unable to effectively arbitrate the medium in multi-hop wireless networks; problems such as hidden and exposed terminals occur frequently leading to collisions, poor performance and unfairness. CSMA networks can be optimized by careful tuning of transceiver parameters, such as transmission power and carrier sensing threshold, to maximize transmission concurrency while minimizing collisions. Existing approaches optimize these parameters by considering only some aspects of CSMA operation (e.g., considering only PHY parameters such as SINR), thus leading to suboptimal solutions. We present a new approach that leverages recent insights into the behavior of CSMA networks. Specifically, this recent work identifies that links interfere only in a few discrete interaction modes at the MAC-layer. Each interaction mode determines how the interacting links interfere with each other and leads to different performance and fairness behavior. The proposed methodology controls the transciever parameters to convert the destructive interactions into constructive ones; we call this approach Interaction Engineering. The global optimization problem is computationally infeasible and requires central solution. Therefore, we first formulate an interaction engineering model that computes the parameters based on one-to-one interaction between the links. Second, we extend the model into a distributed interaction-aware MAC protocol (I-MAC). Testbed and simulation results show that collisions and retransmissions are almost completely eliminated, leading to large improvements in throughput and delay.