Study Of Routing Protocol Based On LEACH For Wireless Sensor Networks

Ⅰ. IntroductionIn the wireless sensor network the node energy resources, computation ability and the band width are all limited extremely, moreover the wireless sensor network usually by the massive crowded sensing hybrid structure, this decided the wireless sensor network protocol stack of each layer design all to have consider the energy validity as the most important design essential factor. In this paper, we considered for a factor of energy valid, makes the improvement to LEACH routing protocol of wireless sensor network, after improved LEACH can save more energy and maximum prolong the life cycle of the entire wireless sensor network.Ⅱ. Improved LEACH Routing Protocol Because the original LEACH algorithm has following several shortcomings:(1) Node become cluster-head is the strict equal probability, the energy is 1 and the energy is 10 nodes makes a cluster of head the probability to be completely same, once the energy low node elects to make a cluster of head, very easy to exhaust the energy to expire. On the one hand this does not favor the network life cycle the extension, on the other hand cluster-head of expires, the entire cluster is unable to communication, does not favor the network the toughness. (2)LEACH routing protocol the cluster of head selection is stochastic, this very possibly appears some bad cluster of plan (cluster-head in the entire cluster of edge, such cluster-head node and member sensor node will all waste energy), sometimes will be able to cause the mumber of each cluster-head node seriously imbalanced, will not favor the entire network communications.In view of a LEACH algorithm the election of cluster-head is the random, we improved the original algorithm. After the improvement of the LEACH algorithm is composed of three stages: the optimal cluster-head probability decision phase, the set-up phase and the data collection and transmission phase.2.1 The Optimal Cluster-Head Probability Decision Phase In LEACH the selection of cluster-head is stochastic, sometimes this will be able to cause serious imbalance about the number of sensor node in cluster. In view of this point, the improved LEACH algorithm had considered fully the sensor node position information and the node residual energy, at last we found the optimized P value, this prolong the entire network life cycle.Regarding there are N wireless sensor node in square region, this paper uses mathematical instruments and so on the theory of probability and mathematical statistic infers has caused this kind of wireless sensor network total energy consumption smallest and optimized the number of cluster. With the expression the total energy which consumes in the entire network, then it mainly includes two parts of energies:one is the cluster-head transmission fusioned data the energy which to the base station, another is the energy which internal sensor node transmission data to cluster-head respectively. Namely the total energy may be represented as: The sensor node produces the number between 0 and 1 randomly, if this value is smaller than the threshold value, then this sensor node is elected as cluster-head. When a node is selected as a cluster-head, it generates a cluster-head token. Then, every selected cluster-head advertises its token by the CSMA/CA MAC protocol to all its neighbors. The non-cluster-head nodes receive these advertisements and compare their signal strength. It keeps only the token with the strongest signal and randomly chooses a one when a tie occurs. After the advertisements, every non-cluster-head node recognizes the source of token as its cluster-head and broadcasts the topology answer packet by the CSMA/CA MAC protocol back to the cluster-head. In the answer packet, the node's position and remaining energy level are included. When the cluster-head receive the answer packets, they set up a schedule for its local cluster.Base on the number of nodes in the cluster, the cluster-head creates a TDMA schedule telling when each node can transmit the packets. The schedule is broadcast back to the nodes in the cluster.2.3 The Data Collection and Transmission PhaseAfter the set-up phase, the data collection and transmission phase starts.Every node collects local data, and sends the packet to the cluster-head in its allocated transmission time.Based on the strength of the received cluster-head advertisement signal and the assumption of symmetrical radio channel, the transmission can use a minimum amount of energy. The radio of other nodes are turned off until their allocated transmission time to save the energy. Each cluster-head keeps its receiver on to collect data from its member nodes and continuously updates the energy table in the schedule base on the received packet. When the data from all non-cluster-head nodes have been received, the cluster-head process data fusion to aggregate all received data into one signal. The data fusion can be a simple averaging or complex data processing. After data fusion, the cluster-head send the information of the cluster to the base station.Ⅲ. ConclusionIn this paper we had considered the node residual energy and the cluster-head's position correlation information found which has caused the entire network energy consumption smallest and most optimized cluster number, simultaneously we have given this algorithm use mathematics inferential reasoning and the computer simulation experiment, has confirmed this algorithm validity and the feasibility. Thus realized the improvement of LEACH algorithm to be able the effective reduction node energy consumption and maximum prolong the life cycle of the entire wireless sensor network.