Research On Event Driven Application MAC Protocol And The Design Of The Application System

With the rapid development of microelectronics technology, computer technology and wireless communication technology, the wireless sensor network (WSN) is used more and more widely. And it is gradually applied in the fields of the military, environmental monitoring, traffic control, and so on. But the data transmission delay and the energy consumption seriously restrict the application of WSN.In the architecture of wireless sensor networks, MAC (medium access control) protocol decides the usage mode of wireless channel and assigns the wireless resources to nodes. The MAC protocol ensures the effective communication, which directly influences the overall performance of the network. And the MAC protocol is widely researched in the field of WSN; however, the existing MAC protocols are less designed for the specific application. Aiming at the event-driven application-aware multimodality WSN application, an event-driven application WSN MAC protocol is proposed in this paper. And combining with specific difficulty of traffic, we research the key problems of traffic control system based on WSN. The main contributions of my paper include:(1) Based on the idea of IEEE802.15.4 MAC protocol, an event driven application WSN MAC protocol (Event Driven Application MAC, EDA-MAC) is proposed. In this protocol, a new time slots assignment algorithm and time slots adjustment algorithm are presented. In the time slots assignment algorithm, the event with the highest priority is selected as a standard to prevent the competition of lower priority event. This algorithm can effectively reduce the collisions and confirm integrity and real time of the data transmission. Furthermore, a time slots adjustment algorithm is proposed to adjust the time slot number between contention free period and inactive period, which can reduce the idle listening period, prolong the sleep period, and effectively reduce energy consumption.(2) Adopting TOSSIM simulator based on TinyOS platform and nesC and combing with real-time and low power consumption of traffic control system and inherent characters of WSN: multimodality, event-oriented, prioritized significant events transmitted first and so on, we analysis and evaluate the performance of EDA-MAC protocol from four aspects: event delivery latency, event fairness, sensor fairness and energy consumption. And we do the performance comparisons with the typical WSN MAC protocols.(3) In order to reduce the cost of system deployment and improve system operating efficiency, combing with the knowledge reduction method based on Rough set theory, the design method of the application system is proposed from the necessity and independence of the relation. Do the reduction to the remainder sets using the knowledge reduction to get the minimal and independent reminder sets. Doing this not only reduces the amount of deployment hardware, but also reduces the amount of the system states sets and simplifies the design of circuit. Besides, the intelligent control circuit is designed adopting the state diagram based on the finite-state machines. The cost of hardware is reduced further and the reaction speed of the system is improved.(4) Based on the design method of WSN application system, the traffic control prototype system is proposed. This prototype system includes data-aware subsystem and traffic control subsystem. The data-aware subsystem adopts wireless sensor network to gather data in real time, which has the advantages of ease of deployment, gather data in real-time and on-site processing. The traffic control subsystem adopts the state diagram based on the finite-state machines to complete the design of intelligent control circuits. The cost of hardware is reduced further and the reaction speed of the system is improved.