The Research On Energy-efficient Communication Technology In Wireless Sensor Networks

Wireless sensor networks (WSNs) comprising a microprocessor, sensor and a wireless communication interface, using new data acquisition and processing technologies have gained attention in military, environment and medical fields. Since sensor nodes are usually deployed in unattended or harsh environments, where the power supply cannot be replaced easily, therefore the protocol must be energy-efficient. The inherent characteristics of WSNs such as large-scale network deployment, management self-organisation, resilience to node failure and dynamic wireless channel changes will also affect the overall network performance. How to design specialised algorithms and protocols to better reduce energy consumption and improve network performance has become an important issue. This thesis discusses the theme of WSN energy-efficiency,studies the algorithms and protocols closely related to the improvement of network performance and energy efficient clustering of WSNs.Firstly, analysis and research on MAC protocols and energy consumption has been performed. MAC protocol is likely to cause numerous conflicts in local communication and increase the amount of idle listening, leading to a waste of the nodes energy. TDMA based MAC protocol reduces the energy consumption of the node, but with poor scalability and low channel utilisation. To solve these problems, this thesis presents a cluster-based energy-efficient hybrid MAC algorithm based on Clustering(CEEH-MAC), using TDMA-based mechanism to dynamically adjust the slot size of the nodes in the cluster to reduce data transmission delay. To save energy, the cluster nodes that do not need data transmission do not allocate time slots, extending the sleep time of nodes and reducing the energy consumption of the state transition according to time slots formed by the node residual energy factor. Using a CSMA/CA mechanism to achieve neighbour cluster heads communication reduces energy consumption by reducing crosstalk and idle listening and decreasing the time delay and improves channel utilisation by dynamically allocating time slots. Simulation results indicate that the CEEH-MAC algorithm is energy efficient in the case of greater network load, with a smaller average network delay and longer lifetime.Secondly,we study existing clustering algorithms, in order to overcome the problem of energy consumption in role switching in the cluster formation process, energy consumption of the periodic cluster head conversion, determination of the time to sub-cluster head conversion on the next round, etc. This thesis proposes an energy balance dynamic clustering algorithm based on the probability(EBDCP). This divides the cluster into a number of grids using a virtual grid, in which each grid has only one active node and the remaining nodes are in a sleep state. Then the probability of the active node going into the next round cluster head is calculated according to its residual energy and the number of packets that are sent, reducing the computational and communication energy consumption. A dynamic threshold is used to achieve the dynamic generation of cluster heads in the network. The simulation demonstrates the algorithm improves the energy efficiency of WSNs effectively, balancing the energy consumption of nodes and extending the network lifetime.Then, we study the WSN routing protocol. According to the problems existing in the routing protocol like unbalanced energy consumption, transmission delay, optimal route selection; this thesis gives the energy balanced approximate minimum spanning routing (EBAMST). This algorithm is based on clustering structure, calculating the probability of being next hop by taking into consideration the surplus energy of the cluster head, the number of neighbouring nodes, the transmission distance and other factors, and constructs the lowest cost routing tree dynamically by the Prim. The simulation shows that this scheme has a good performance in energy consumption, average delay, network life cycle, etc.Finally, we study the key management of the WSN security infrastructure, which has some problems such as computation overhead, poor survivability and poor scalability. This thesis presents an energy efficient and secure dynamic key management based on cluster ( EESDKMC),adopting dynamic cluster-based key management and a one-way hash function to achieve the communication between the cluster head and the active nodes within the cluster. Using a modified version of the Blom matrix communication between cluster heads is accomplished. Based on dynamically changing the network topology, the algorithm can update the keys and one-way key instantly. Experimental results show that the algorithm has good performance in security, scalability, communication and computation overhead.