Design And Simulation Of IEEE802.15.4MAC Protocol Based On Priority

Wireless sensor networks (WSNs) are self-organization and multi-hop wireless networks. Because of the advantages of low-power, low cost and flexibility, WSN is one of the most influential technologies of the21st century. Wireless sensor network has promising applications, such as home automation, environmental protection and monitoring, health care, and military detection. As one of the core technologies for wireless sensor networks, IEEE802.15.4is a network protocol standard with superiority in power and rate, aiming to provide low-speed interconnection for wireless personal area networks (WPAN).The existing Media Access Control (MAC) protocol in wireless sensor network and IEEE802.15.4standard almost use the Guaranteed Time Slot (GTS) reservation mechanism to give priority access to specific information, but have a few studies in priority access to the Competitive Access Period (CAP). The GTS mechanism has many deficiencies in specific areas such as smart home, there only a few of nodes being allocated the GTS in a beacon period, the GTS could not being made full use, and the performance could not meet the application requirements of high latency.Based on the above, a random access mechanism with priority level was proposed in this thesis. The mechanism has two main points:one is to achieve the priority assignment for different monitoring nodes, by adjusting the parameters of the backoff exponent and the backoff window of the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) algorithm; the other is to divide the CAP into different time slots for large load networks. The performance of the proposed scheme is tested by NS-2and compared with the original standard. The results have shown that the proposed scheme is better in performance of packet delivery ratio and delay for high-priority information.