The Application Technology Research In The Wireless Sensor Network

Wireless Sensor network (WSN) is an advanced wireless network without infrastructure. It can be configured as a multi-hop ad hoc system consisting of a large number of networked sensor nodes designed to intercommunicate via wireless radio. It can also be used for real-time sensing, information collecting and processing on monitored objectives. Its great latent applied value in military affairs, industry and agriculture control, medical treatment, enviroment monitor and family nursing, etc, attracts many countyies and research institutions.Firstly, this thesis gives an overview of the hardware system of the WSN,then analyzes deep all modules'function characteristics and performance requirement of the wireless data gathering and transmitting, describes detailedly the general design scheme of the nodes'hardware system, circuit schematic diagram and the operational principles of every functional modules,and presents the block diagram of the system's software and programme design of nRF2401's receiving and transmitting mode.Secondly, sensor node's application environment and network's work characteristic determine that node must pay attention to low-power design. Considers such instance, the article has systems study on low-power theories and design methods, schemes out a low-power project of node. Then, it analyzes the project quantificationally.Moreover, the delay performance for IEEE 802.11 DCF in saturation situation is analyzed by introducing a two-dimensional Markov chain model. The evaluation of access delay by theoretical analysis is also presented. Simulation is done by using network simulating tool NS2, and the delay performance is compared both basic access mechanism and RTS/CTS access mechanism.Simulation results validated the effectiveness of theoretical analysis,which provids a research basis for real-time transmitting of packets in wireless local area networks.Finally, in order to make full use of WSN's energy sources,this thesis centres around the design of the WSN MAC protocol. Aiming at the poor performance of S-MAC protocol in the circumstance of high load and densely allocated nodes and the bad use of WSN's energy sources ,which is induced by the high collision probability, more retransmission times of packets and much more consumed energy, a new-style MAC protocol is proposed based on the improvement of the back-off algorithm of the S-MAC protocol. The basic idea of this improved MAC protocol is that the adaptive back-off algorithm adjust the sending probability based on the least consumed energy. Simulation results indicate that the improved MAC protocol has a better performance compared with S-MAC protocol.