Research And Design Of Medium Access Control In Wireless Sensor Network

Wireless Sensor Network (WSN) combines some advanced technologies such as microelectronics, embedded computing, modern network, wireless communication and distributed information processing. It can real-timely monitor and collect various environmental information data that are processed and then sent through wireless communication. The transmission is in multi-hop and Ad hoc mode. WSN has broad application prospect. It can be applied to military affairs, industry, agriculture, environment monitoring, health care, emergency and disaster relief, remote control, smart home, et al. WSN has been highly emphasized by academic circles and industrial community in many countries.802.15.4/ZigBee is a low rate, low energy consumption Wireless Pan Area Network (WPAN) protocol defined by ZigBee Alliance. At present, 802.15.4/ZigBee is the most widely protocol architecture used in WSN. Characteristics of WSN determine that its wireless applications do not need high transfer bandwidth, but low latency and energy consumption. IEEE 802.15.4/ZigBee provides international communication standard to WSN and vast applications based on Micro Control Unit (MCU。Based on 802.15.4/ZigBee, this paper researches and designs a dynamic and on-demand MAC scheme called ZTF-MAC for application of Smart Building in WSN. ZTF-MAC combines Time Division Multiple Access and multi-channel scheduling. ZTF-MAC is discussed in detail for Star and Cluster-tree topology network respectively. In Star network, nodes are on-demand grouped and scheduled by time slots. In Cluster-tree network, in addition to grouping scheme, multi-channel scheduling is added for subnet. The on-demand grouping and dynamic multi-channel scheduling can reduce collision and interference induced by high node density, then increase network throughput. Furthermore, there are some real-time emergent data to transmit in WSN, and ZTF-MAC specially concerns and designs respond scheme for emergent events. In this way, ZTF-MAC can quickly responds for emergency with high throughput in the whole network.Throughput, energy Consumption and latency in response of emergency in ZTF-MAC is simulated. The results indicate that ZTF-MAC can improve performance of them in 802.15.4. At the same time, ZTF-MAC can quickly response for emergency in WSN. Service primitive and command frame are prototypes and reference specifications for design of protocol stack. At last, this paper studies and analyzes primitives and command frames in 802.15.4/ZigBee, and realizes relevant primitives and command frames of ZTF-MAC.