Dynamic reconfiguration of beaconless ieee 802.15.4 mac parameters to achieve lower packet loss rates

IEEE 802.15.4, a MAC/PHY protocol for low power and low data rate wireless networks, is emerging as the popular choice for various monitoring and control applications. Depending on the application, the traffic load on an IEEE 802.15.4 network may vary over a wide range. The performance of the protocol, measured in terms of the packet loss probability and the packet latency, depends upon the prevailing traffic load, interference, and the configuration of IEEE 802.15.4 MAC parameters. A stochastic model for beaconless operation of the IEEE 802.15.4 MAC protocol is developed as part of this dissertation. Assuming no interference from hidden nodes, the model predicts the packet loss probability as well as the packet latency given the number of nodes in a star topology network and their expected data rates. The model is then analyzed and some protocol modifications suggested. The impact of different configurable MAC parameters on the performance of beaconless IEEE 802.15.4 networks under different traffic loads and under different levels of interference from hidden nodes are then analyzed via ns2 simulations. Based on this analysis, static values of IEEE 802.15.4 MAC parameters (macMinBE/macMaxBE, macMaxCSMABackoffs, and macMaxFrameRetries) that result in a good tradeoff between the packet loss probability and the packet latency under different conditions are suggested. Static configuration of IEEE 802.15.4 MAC parameters, good for a particular traffic load range, may result in bad performance when the traffic load changes beyond that range. Thus a scheme that can be used by an IEEE 802.15.4 node to dynamically adjust its MAC configuration based on the observed packet loss rate and latency suffered by recent packets generated by the node is presented. The performance benefits of the proposed scheme are then illustrated via ns2 simulations.