| Wireless sensor networks (WSNs) have become one of the important research fields in the world, which integrate the technologies of sensors, embedded computation, modern networks, distributed processing, etc. WSNs are composed of low cost sensor nodes that can communicate with each other in a wireless manner, have limited computing capability and memory and operate with limited battery power.The main goal of such networks is to perform distributed sensing tasks, particularly for applications like military affairs, climate precision, smart spaces. In civil fields, such as medical systems, environmental monitoring, smart traffic control, industry control and family residence intelligence, WSNs have become one of the most active encouraging measures.Generally, WPAN and LR-WPAN is best for WSNs. At present, ZigBee is the new technology to deploy WSNs. Its technical characteristic determines that it is the better choice of short-distance and low-rate WSNs.Integrated with the crosswise project "Embedded Wireless Auto Meter Reading System Based on ZigBee", this paper mainly researches on the energy efficiency and security of WSNs. Energy efficiency is the basis of WSNs and security is a kernel issues. On the basis of analyzing network architecture of WSNs, this paper mainly makes the following researched around these two aspects:①To the energy limitation of WSNs, a combination weight energy balance clustering and routing algorithm (CW-EBCR) is proposed. This algorithm takes into consideration the following elements: the node degree and energy level, the average distance between node and its neighbors, the accumulative time of node being cluster head, the distance to sink and the optimal cluster number. Then a regulating rule of cluster communication radius and a method of selecting redundancy substitute of cluster head are developed. At the same time, the self-maintenance tactics of cluster is put forward. Simulation and analysis show that this algorithm can make energy balanced both in inner-cluster and in inter-clusters, can postpone the network life time.②A key pre-deployment scheme based on matrix QR decomposition (QR-KM) is proposed. In this scheme, what the node broadcasts are its ID and the row vector of Q orthogonal matrix, not the key itself. After receiving the row vector, node can confirm the identity by orthogonality validation. Therefore, the attacker can not access the key itself and can not decrypt the cryptography text. Analysis result shows that this scheme strengthens the WSNs security.③Aiming to the data characteristic of WSNs, grey prediction method is introduced to WSNs data stream predictions. On the basis of modifying G(1,1) model, a CO-GA algorithm for WSNs is proposed. And a combination optimization tactic is used to system parameters identification. The results of analysis and simulation show that this algorithm can predict data stream real-timely only by small-sample, meeting with the WSNs requirements for low resource occupation and for quick response. This algorithm can be used in both sensing node and sink node.④According to the security threats of WSNs, a distributed intrusion detection algorithm (DP-EFKM) is put forward. Based on modifying fuzzy K-means, this algorithm uses particle swarm optimization (PSO) method to find the optimal parameters values. The results of analysis and simulation show that this method is feasible, and it is characterized by its simple structure, small calculating amount and fast speed. Moreover, its distributing character makes integration of local detection and global detection, reducing the energy spending, improving the detection rate and decreasing the false positive rate.⑤A proto type system of WSN base on ZigBee and IEEE802.15.4 is designed which aims to realize"wireless auto gas-meter reading system based on ZigBee". Using PIC18F4620 and CC2420 to make up the wireless gas-meter node, this proto system realized correct communication between two nodes. This project has been checked and accepted.
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