Research On Key Issues Of Wireless Sensor Network In Networked Test And Control Systems

Wireless sensor-networks(WSN), as the base of networked measurement and control system, consists of a large number of distributed sensor nodes equipped with radio devices that organize themselves into a multi-hop wireless networks, which can break monitor and transmission limitations of single sensor and improve the precision and range of monitoring significantly. Wireless Sensor Network will be one of the most important new technologies in the future. Its development and extensive applications will have great impact on and get tremendous promotion of human social life and industrial renovation. Compared with familiar wireless networks such as Mobile Communication Network,Wireless Local Area Network,Bluetooth Network,Ad hoc Network etc, WSN has a lot new properties and many research hotspots. Based on a review and analysis of its current condition and development home and abroad, this dissertation expounds some research results in theory and methodology of several basic but important issues on WNS.(1) Low pass filters are widely used in sensor nodes of WSNs for extraction of micro signals and also for noise rejection purposes. Conventionally, active filters are used but the operational amplifiers would cause drift problems because of their nonideal properties. In this dissertation, an all pole active no-drift RC low pass filter is proposed, which does not cause any drift at the output despite the types of operational amplifier used and can be used to implemented a universal transfer function.The performance of the proposed filters have been compared to that of typical low pass filters with emphasis on their attenuation and drift characteristics. The result reveals that the two kind filters have similar attenuation characteristics, but the proposed filter has a much better drift performance than the conventional one. It is concluded that such configuration of low pass filter will be optimal for processing micro signals without causing any interference at the output.Through analyzing the Schoeffler multiparameter sensitivity of the proposed low pass filters, the dissertation proves that there is no relationship between the multiparameter sensitivity and the free variables used for designing. As the results, the simplest design formulas of the system are provided and the number of the kinds of the needed elements has been reduced to the half. The design problems of proposed Low-pass Filters based on non ideal operational amplifiers with limited gain and bandwidth are also investigated through mathematical method and experimental test. The result indicate that ideal model of operation amplifier is accurate enough for the design of Non-drift all-pole Active Low-pass Filters. The design formulas are also given and have been proved correct by Pspice simulations in this dissertation.(2) Wireless Sensor Network consists of energy-limited nodes, which use wireless communication to collect and process useful data from a particular area. So, it is a important research topic to collect and process data in an energy-efficient manner to guarantee the maximum life-time of WSN, which is named as energy problems. In the dissertation, we combine energy problems with communication protocols which are another research hotspot of WSN. Our research lays emphases on energy-efficient communication protocols. Based on the extensive analyzing of LEACH protocol, a new clustering hierarchy protocol named Lowest Energy Protective (LEP) clustering protocol is presented in this dissertation.LEACH protocol is one of classical wireless communication protocols for WSN. It is a self-organized,adaptive,energy-efficient,clustering network protocol, Which accounts for properties of WSN and prolongs the life-time of WSN efficiently.But the mechanism of stochastic Cluster-Heads (CHs) selection in LEACH protocol isn't optimal, which can't guarantee the proper position of CHs and doesn't account for energy of CHs left. So it would lead to the energy of CHs exhausted and reduce the life-time of network wholly. On the other hand, single-hop communication is taken when CHs send data to the base station, which aggravates the energy consummation of the CHs. So, in the dissertation, we present some modifications of LEACH protocol as follows.When we choose CHs, we take the energy of CHs left into consideration and propose a new clustering hierarchy algorithm named Lowest Energy Protective clustering algorithm. In LEP algorithm, the main idea is to make CHs close to nodes with the lowest residual energy so that energy dissipation of these nodes is least. The simulations prove that the metrics of First Node Dies (FND) improve a lot and the most nodes in the network have the nearly equal residual energy, so the life-time of the whole network is prolonged as much as possible.In this dissertation, catenulate communication between CHs is taken instead of single-hop communication when CHs send data to the base station, which results in the reduction of energy consumption of CHs and the balance of residual energy of CHs, so it is avoided that CHs away from the base station exhaust. Compared with LEACH protocol, our modifications have some improvement on the life-time of WSN and the data to the base station.To sum up, the LEP protocol in this paper can reduce the energy consummation of the codes and make the most nodes in the network have the nearly equal residual energy, so the life-time of the whole WSN is prolonged. In the same time, the data to the base station is improved a lot and the scope of applications of the protocol is enlarged.(3) The game theory is introduced to the power controlling of WSNs in the dissertation. We develop a power control algorithm on the reverse link of clustering wireless sensor network based TDMA-CDMA with Stackelberg strategy and bargain theory. Based on the theory of Nash equilibrium, Stackelberg pricing and bargain game, we can draw some useful conclusion by the aid of theoretical analysis and simulations.In the first place, we formulate a model of TDMA-CDMA based on Nash equilibrium, giving a characterization of clustering wireless sensor network. Secondly, we expound the power control model, putting the emphasis on applying Stackelberg theory and improving the utility function. Founded on above analysis, simulations under Matlab environment are constructed to evaluate performances of the power control model.Thirdly, we carry out two-person bargaining theory in power control model in which clustering nodes finds Pareto improving power solution by bargaining. The numerical results show that the bargaining theory provides two nodes a good method which benefits each other.At last, we review the entire work and suggest the direction for future research.