A reconfigurable routing protocol for free space optical sensor network

Recently, there is a growing interest in free space optical sensor network (FSOSN) for wireless applications due to the advantages of lower energy consumption, lower cost, and larger capacity. However, the unidirectional communication of FSOSN suffers from a dramatic decrease of connectivity if certain nodes die of the depletion of energy, which further results in huge loss of packets in data transmission. Thus, this paper proposes a reconfigurable routing protocol for FSOSN to overcome this problem by reconfiguring the network virtual topology. The protocol is operated in four steps: (1) virtual topology construction, (2) routing establishment, (3) routing table update, (4) reconfigurable routing. During data transmission, the data is firstly routed through the shortest hop path. Then the reconfiguration is initiated by the node whose residual energy is bellow a threshold. The nodes affected by this dying node are classified into two types: maintenance nodes and adjustment nodes. They are reconfigured according to their types. An energy model is set up and the performance of the protocol is evaluated and compared with simple-link, a modified secure integrated routing and localization scheme and a direct reconfiguration scheme in terms of connectivity, the number of living node and packet delivery ratio by OPNET simulation.