Research On Clustering Algorithm Based On Local Energy And Distance In Free Space Optical Sensor Network

With the wide application of Wireless Sensor Network(WSN) and the advantages of Free Space Optical Communication(FSO) such as high bandwidth, large capacity, high security and so on, Free Space Optical Sensor Network(FSOSN) which combines the advantages of WSN and FSO, has attracted more and more attentions.Similar to WSN, the energy, processing capacity and memory ability of the optical wireless sensor nodes in FSOSN are limited, thus how to effectively use energy and prolong the network lifetime becomes one of most important research fields in FSOSN. Clustering algorithm is a key energy-saving technology. Cluster head receives and aggregates the data sent by cluster members, and then sends them to the base station through single-hop or multihop to save energy. LEACH protocol is a typical clustering algorithm, which can effectively reduce energy consumption, but it still has some shortcomings, such as the random selection of cluster head, without considering the influence of node energy and distance, and so on.Aimed at the defect in LEACH protocol, based on the research of WSN, the omnidirectional antenna and energy consumption model for FSO are introduced in this thesis. On this basis, the works for single hop and multi-hop FSOSN are studied in detail.In single hop FSOSN, cluster heads transmit the aggregation data to the base station directly, but long distance transmission will consume more energy. Under this communication pattern, the cluster heads far away from the base station exhaust their energy early because of long distance communication, thus the network can’t be connected, and the monitored area fails to be covered. In multi-hop FSOSN, in cooperation way cluster heads complete the communication with the base station, which leads to the cluster heads near the base station to die earlier owing to their overmuch load. In this thesis, combined with LEACH protocol, Local energy and distance based clustering algorithms(LEDBCA) are proposed for single hop and multi-hop FSOSN topology respectively. In the LEDBCA, local energy of the node and its distance to the base station are considered in the threshold formula when selecting the cluster heads. In addition, the radius of the cluster is calculated based on the energy model and the distance from the node head to the base station, which can minimize the average energy consumption in the FSOSN.Through MATLAB, the corresponding LEDBCA simulations in different topology of FSOSN are carried out. Compared with LEACH protocol, simulation results show that LEDBCA reduces the energy consumption,increases the number of packets received and prolongs the lifetime of the FSOSN.