The Improvement And Implementation Of MAC Protocol Mechanism For Wireless Sensor Networks Based On IEEE 802.15.4

Wireless sensor networks (WSNs) extend sensor applications with limited range into rich variety of ubiquitous network applications. WSNs establish an effective communication way between people and the objective world, and have good prospects. Currently, WSNs have wide applications in the aspects of military reconnaissance, smart home, environment monitoring, health care and industrial control.In WSNs, medium access control (MAC) protocol as the underlying base protocol is responsible for the construction and maintenance of WSNs and the management of wireless channels. IEEE 802.15.4 standard has been one of the most suitable standards for the underlying protocol stack of WSNs because of low-rate, power-consumption, and short-distance. However, many mechanisms of IEEE 802.15.4 MAC protocol are not universal in specific applications with growing diversity to meet the increased demand on information for people, and need to be improved. The paper is supported by CNGI "Application of Next Generation Internet Technology in Energy-saving of Intelligent Building" program. We make several innovative improvements to IEEE 802.15.4 MAC protocol for the practical application of intelligent building monitoring.Firstly, we review and make a comparative analysis for MAC protocols widely used in WSNs especially for IEEE 802.15.4 MAC protocol. And then we design and implement an IEEE 802.15.4 MAC driver on the ARM9 S3C2440A platform with high performance, low power, low cost and rich features. Then, we propose an address configuration mechanism for WSNs based on IEEE 802.15.4 MAC short address. Based on this address configuration mechanism, we divide data types into normal data with low priority and critical data with high priority after studying the data transfer mode of WSNs. And then we introduce the RTS/CTS mechanism combining with the overhearing and the ACK mechanism based on priority to ensure the effectiveness of critical data and reduce its transmission delay. Finally, we implement the improved IEEE 802.15.4 MAC protocol and compare it with the original IEEE 802.15.4 MAC protocol. The results indicate that the improved IEEE 802.15.4 MAC protocol has a significant advantage in energy efficiency, packet loss rate and transmission delay.