| With the development of urban rail transit industry, to ensure the safe and efficient operation of urban tail train, we should enhance the ability to monitor the key parts of the driving equipment. However, in the actual environment of urban tail transit, we can not monitor the equipment in real time, therefore, the wireless sensor network which has the efficient monitoring ability, at the same time, has the advantages of low power consumption and low cost, suitable for the real-time monitoring environment of urban rail transit.In the environment of urban rail, battery has been used as energy in the nodes of the wireless sensor network, however it suffered with short life time and difficulty of changing, at the same time, the topology of wireless sensor network being ribbon also can bring out several problems such as the uneven energy consumption of network, data latency and redundancy. So the design of efficient routing protocol, which makes network connect better as well as reduces the energy consumption and prolongs the survival time of network, is the key to decide the viability of the wireless sensor network.In order to solve the problem, two classical routing protocols, LEACH and PEGASIS with low energy consumption, are introduced, analyzed and improved in detail in this thesis, besides chain based clustering routing protocol (LP)-a routing protocol which is suitable for urban rail transit environments has been proposed in combination with the two above kinds of improved algorithm. Chain based clustering routing protocol is executed according to the period. The unit of the execution is "round". And the communication cycle of each round is divided into two stages, the establishment of clusters and the data transmission with stability. According to two stages we mainly finish the following aspects of work:(1) We will use the fixed clustering strategy of improved LEACH algorithm, at the same time leading into the strategy that during cluster building phase the mechanism of tentative cluster head will be used. With this algorithm, different ranging scope of competition are produced based on the distance from candidates to the sink node and its residual energy. Also the cluster head relative energy levels of themselves and neighbor candidate are used as a proof for electing the "final nodes" in order to get a balance in consuming energy.(2) After the formation of the cluster the chain topology will be constituted in each cluster in the light of PEGASIS algorithm.In this way, the original long chain will be transformed into several short ones increasing parallel speed of information transmission.(3) The chain head node increases a link of the clusters again when the head node of each chain finishing fusing data in its own chain. In this way it is avoided that each chain head node send data to sink node consuming more energy.Therefore,this algorithm not only shows the advantages of PEGASIS algorithm in saving energy but also uses static clustering of the LEACH improved algorithm,making the energy consumption of the whole net more balanced.At the end of thesis, the LEACH, PEGASIS and LP algorithm have been carried on simulation separately from four aspects. They are the lifetime of the network, the total energy consumption of the network, the total time delay of the network and the total data amount received from sink nodes. Results show that chain clustering algorithm effectively prolong the lifetime of the network and save the network energy consumption, being suitable for urban rail transit environment as well as achieving the purpose of improving the algorithm. |
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