Research On Several Key Technologies Of Wireless Sensor Networks

Wireless sensor networks are not only a new network technology, but also a muti-technology integration of mutual penetration of scientific products which including sensor technology, embedded computing technology and distributed information processing and communication technology. Wireless sensor networks have their own characteristics from node architecture to network architecture which make them a very broad application prospects such as military, environmental science, intelligent home, medical health, space exploration and other commercial areas. At present, the topology management of wireless sensor networks, network protocols, network security, positioning technology, data fusion technology and so on becomes the key technologies and research hot spots in wireless sensor networks. On the based of concluding the existing technology and research, this thesis has research and exploration for a number of key technical problems. Some major research and contributions are as follows:Based on the self-similarity statistical properties of wireless sensor networks, this thesis put forward a heterogeneous traffic statistical model of wireless sensor networks. Based on the ON/OFF structure, to point out that the aggregation traffic of heterogeneous traffic streams does not always show the long-rang dependence characteristics; to analyze the statistical property of different traffic streams which model by ON/OFF structure in the different situations, and theory proves that the statistical properties of aggregate traffic of heterogeneous traffic is still long-range dependence even if some of them are shot-range dependence. Finally, propose the structural modeling of heterogeneous traffic of wireless sensor networks. This model point out that the aggregated cumulative heterogeneous traffic is not the simple superposition of those different traffics and degree of its'fractal'is dependent on the biggest fractional contribution of those heterogeneous streams. Simulations are performed to illustrate the effectiveness of our model.Analyzing SMAC protocol, a typical MAC protocol of wireless sensor network, according to the limit energy of wireless sensor networks, this thesis put forward a new MAC protocol named AMPMAC protocol. In the real wireless sensor networks, the traffic will change as the wireless channels change. So the design of MAC protocol must take into account the changes in the network traffics. AMPMAC protocol modifies the message passing mechanism of SMAC protocol. It can adjust the data sub-size adaptively according to the change of network traffic and save the network energy. Simulation shows that regardless of network traffic is large or small the AMPMAC protocol can save energy. From antenna energy efficiency point of view, MODMAC protocol is proposed to save energy of wireless sensor networks. A large number of MAC protocols are using omni-directional antenna to send and receive data while the omni-directional antenna generats the same energy in all directions. However, the directional antenna can achieve a certain direction transmission. So the use of omni-directional antenna for wireless sensor networks is a clear waste of more energy. Therefore, this thesis introduces the directional antenna to the wireless sensor network MAC protocol and designs the MODMAC protocol. This protocol not only makes the network node send and transmit data toward the established direction, thus avoiding the energy waste from the other directions, but also can simplify the routing and further improve the energy efficiency.Baesd on bilinear pairings, a threshold signature scheme suitable for wireless sensor networks is proposed in the thesis. Assuming the abstrusity of computational Diffie-Hellman problem, we gave the secure proof in the model of random oracles using the reduction to the contravention. Compared with traditional networks, the nodes will be out of function at any moment, frequently join and leave the group. Furthermore, the nodes are limited in the storage, mobility, computation, energy and so on. So the proposed threshold scheme is a more suitable method for authentication, signature, and access control in the wireless sensor network. Our scheme also has other characteristics: robustness, multi-signature and parallel computation. The robustness prevents all nodes participated the signature from wrong behavior and computation. The multi-signature ensures to publish multi-message from different nodes in one signature generation step. The parallel computation accelerates the generating speed of the signature.Based on an ID-based signature scheme proposed in the thesis, we also propose an ID-based ring signature scheme. Two proposed signature schemes can resist to the key escrow problem, which is the inherent disadvantage for traditional ID-based cryptosystem. The conclusion of our analysis on security is that our scheme is secure against existential forgery on adaptively chosen message and ID attacks assuming the complexity of Computational Diffie-Hellman (CDH) problem. In traditional public-key cryptography, we need to verify, transport and store the public key certificates, which is not suitable for the limited-resource network. In ID-based cryptography, any two users securely communication without exchanging the public key certificate, without saving list of public key certificate, without using on-line third party, only require that a trusted private key generator (PKG) generates a private key for the user when the user had access to the cryptographic system in his/her first time. The convenience of key management makes ID-based cryptographic system widely used. But key escrow is an inherent disadvantage for traditional ID-based cryptosystem, i.e., the dishonest PKG can forge the signature of any user so that the user can deny the signature even if signed by him/herself actually. In the proposed signature schemes, the PKG is no longer treated as a trusted party, so we must present the exact secure proof in two cases: forgery with no participation of PKG and forgery with participation of PKG. Compared with previous signature schemes, we think proposed scheme is more efficient.At last, the main work and innovation are summarized, as well as the future research work are prospected.