Analytical models for understanding misbehavior and MAC friendliness in CSMA networks

Nodes using contention-based CSMA protocols are susceptible to the misbehavior of other nodes and also have little flexibility in controlling quality of service. To address the misbehavior problem, continuous-time protocols are proposed. The effects of “misbehavior” on the QoS of all nodes in the system caused by changing the cheater’s arrival rate and backoff rate are studied. The problem of flexibility in controlling QoS is addressed by introducing the concept of “MAC friendliness” where nodes can adjust arrival rates and backoff rates while maintaining a fixed share of the channel. The continuous-time system is modeled using an iterative method and matrix exponential distributions. Collision probabilities are determined both by the channel utilization of the entire system, as well as the actual stage within the backoff process. The model itself is a key contribution because it is accurate over all ranges of traffic loads and models both queueing within nodes and contention for the channel.