The Dsign Of ZigBee Node Based On CC2430 And The Improvement Of The MAC Protocol

Since the majority of medical drugs and biological agents contain unstable protein and sensitive to environmental factors such as temperature, it is easy to make drugs and vaccines deteriorated. Therefore, it is necessary to monitor some environmental factors such as temperature during biopharmac- eutical or bio-fermentation. And we can guarantee the quality of medical products in this way. Wireless sensor networks,which consists of large number of sensor nodes, can apperceive, sample and monitor some important real-time environmental parameters. It has many advantages, such as fast deployment, unattended operation, low power consumption and high cost performance. Therefore, wireless sensor networks are ideal for biological information monitoring system, which wired network is difficult to build in.On the basis of ZigBee protocol, the dissertation designs wireless sensor network nodes for biological monitoring system. These nodes uses RF chip CC2430 which has integrated 8051 core. They can sample real-time environmental information. This dissertation first describes the system design of the node and then introduces the data collection modules, processor and wireless communication modules, power supply modules and the external circuit in detail. By transplanting Z-Stack 1.4.3 developed by TEXAS INSTRUMENTS to nodes after discussing the ZigBee protocol and the Z-Stack, wireless communication between two nodes has been realized.Furthermore, in order to solve the problems of large delay time and low throughput brought by a large number of nodes and improve the system's real-time and high efficiency, this dissertation proposes an improved CSMA/CA bckoff algorithm based on Markov model after analyzing IEEE802.15.4 CSMA/CA algorithm. The algorithm sets the maximum CSMA backoff unrestricted in backoff mechanism. In order to solve the problems of large delay time and low throughput brought by a large number of nodes and improve the system's real-time and high efficiency, this dissertation propose an improved CSMA/CA bckoff algorithm based on Markov model after analyzing IEEE802.15.4 CSMA/CA algorithm. The algorithm sets the maximum CSMA backoff unrestricted in backoff mechanism.In other words, it cancels the limit of the backoff counter.The backoff counter will increase from 23 to 23+5 after m steps and then it reduces the collision rate espically in large-scale nodes.In this way, It can improve the throughput and real-time of the system. At last, we conclude that the throughput increased 5% to 10% and transmission delay reduced 8% to 15% in a large amount of nodes from several experiments, which indicated the superiority of improved MAC protocol.