Distributed Clustering-Based Data Gathering Protocol For Mobile Wireless Sensor Networks

Wireless sensor networks are regarded as a new information accessing method and information processing mode, which have linked the logic information world with the objective physical world, changed the way of interaction between human, nature and eventually achieved connectivity among the physical world, the computing world and human society. Data collection, the most basic application of wireless sensor networks, is the basis for a variety of complex applications and also the focus of current research on sensor network. The former study on data collection protocols is mainly based on the static wireless sensor networks, but for the current two years, mobile wireless sensor networks has became the hotspot in academic circle. The original data collection protocol which is aimed at static wireless sensor networks, once it is applied to mobile wireless sensor networks, will greatly reduce its performance.This paper is primarily to design an energy-efficient data collection protocol in mobile wireless sensor networks. Based on these several aspects---the mobile wireless sensor network layout, distributed clustering technology, the node sleep scheduling mechanism, TDMA time slot splitting strategy and sink mobility strategy, it considers the node mobility to the impact of the protocol and follows the design criteria of reducing network energy consumption to achieve the purpose of an energy-efficient data collection protocol.The major work and innovative achievements can be divided into the following four chapters: (1)A hybrid mode of mobile wireless sensor networks deployed a mobile node and a fixed node is proposed.Specific deployment program is:first it covers the entire monitoring area Q with a grid deployed m fixed nodes, then fixes the distance between nodes as 1(slightly less than the free space model d0), finally a large number of mobile sensor nodes (n-m) randomly uniform deployed in the whole monitoring area.(2) A new energy-efficient clustering algorithm (ECBF) is proposed.In the algorithm, a mobile node can choose the closest fixed node to form clusters and the fixed node chooses mobile nodes within the high value of the nearest node in cluster as the cluster head. Therefore, this cluster head node selection strategy not only saves energy as much as possible, but also avoids the cluster head to leave the cluster. The cluster head node is responsible for collecting datum and fusing them. Routing backbone is constructed by the fixed node which is responsible for forwarding data and eventually submitted to the sink node. This clustering strategy makes all the sub-cluster with the same size and distributed evenly, avoiding the potential failure caused by backbone routing. This kind of routing, which can be achieved simply, has high reliability. ECBF clustering algorithm makes up for some drawbacks in LEACH-M protocol, which are not taken into consideration of the energy of the node, cluster head and mobility, the inconsistent number of clusters and uneven distribution. Through implementation of the ECBF algorithm, the amount of broadcast messages throughout the network complexity is O (n) and the entire network time complexity is O (1). Simulation result shows that ECBF data collection protocol, which is better than LEACH-M protocol, has a longer network lifetime and more successful data transmission.(3)A cross-layer scheduling algorithm (EDG) which can avoid the impact on the location of mobile nodes and meet the coverage of user expectations and energy-efficient cluster nodes is proposed.The algorithm, based on the coverage analysis theory, deduces the minimum number of nodes in cluster k by meeting coverageφof the user expectations. In the cluster, it only opts the higher energy and k nodes close to a fixed distance (avoiding the cluster nodes to leave the cluster as much as possible) so that most of the other nodes can be dormant and energy-efficient sleep scheduling rotation in the cluster node can eventually be achieved. Then it takes the whole network into a unified slot by adopting TDMA time-division multiplexing technology, in which slots in cluster are applied to a parallel mode and slots between clusters are applied to a serial mode. Therefore, this kind of slot division can deduce system delay, save the energy and achieve cross-layer design. Finally simulation results show that the adoption of cross-layer scheduling algorithm achieves a data collection protocol EDG, which leads to reduction of data latency and obvious energy-saving effect.(4)An algorithm MSBDG, which does not depend on the location of nodes, is based on mobile sink data collection is proposed.It solves the "hot spot" problem---multi-hop routing in sensor networks brings to energy hole. It also proves that when any square of side length of L is in the monitoring area and sink nodes move along the(?)L/2 trajectories, the energy consumption used by data collection can reach the minimum. Sink node builds the routing tree along the nearest fixed node as root node. At the same time, the sensed data in cluster node carries on data fusion calculation through the cluster head, thus the data fusion is flanked by trees to send to sink node in reverse-by-jump. As a result, simulation shows that in the aspect of average energy consumption and network lifetime, the performance of MSBDG surpasses data collection protocols of ECBF, EDG.