Modeling And Energy-Efficiency Study Of IEEE 802.15.4 MAC In Wireless Sensor Networks

To meet the increasing demand for"ubiquitous computing", wireless sensor networks have enjoyed tremendous growth in the last decade. Recent advances in wireless sensor networks have led to many new protocols specifically designed for this burgeoning area of networking, where energy-efficiency is an essential consideration. Ever since the initial release of IEEE 802.15.4, it has been judged as one of the most important protocols well suited to low cost, low power, and low complexity applications, thus it has become a solid foundation for low rate wireless solutions.With regard to promoting energy-efficiency in IEEE 802.15.4 MAC, comprehensive simulation experiments have been conducted. The energy consumption per packet was introduced to study the impacts of duty cycle and packet interval on energy-efficiency of the IEEE 802.15.4 MAC.According to the IEEE 802.15.4, one of most straightforward yet effective ways to reduce the nodes'power consumption is to enable the optional sleep mode, which can be used to make each node enter the low power mode under some specific situations. To describe the IEEE 802.15.4 MAC with the sleep mode enabled effectively, a new Markov-based analytical model for IEEE 802.15.4 slotted CSMA/CA algorithm introduced with the sleep states was proposed. The impacts of protocol parameters, especially including duty cycle and unsaturated traffic, on throughput and power consumption were analyzed. Moreover, some discussion based on the numerical results of the model was carried out for further understanding. It is showed that the results given by the analytical model have an accurate match with the simulations, and the impact of the sleep mode on the performance of IEEE 802.15.4 can be studied by the model well.Furthermore, to improve the performance of IEEE 802.15.4 MAC in consideration of the trade-off between power consumption and end-to-end delay, an individual duty cycle adaptation algorithm was proposed, which can individually adapt the duty cycle and beacon interval of each node at the same time, according to traffic queue of the each node. Taking advantage of the assumptions of the previous modeling of IEEE 802.15.4 MAC, a simple and feasible early sleep mechanism for nodes was also introduced to achieve energy-efficiency in the proposed duty cycle adaptation algorithm. The simulations showed that, the proposed algorithm effectively handled the trade-off between power consumption and end-to-end delay according to different traffic load conditions in the IEEE 802.15.4 networks, and the throughput was also improved.