A Strategy For Prolong The Lifetime Of Wireless Sensor Network Based On Mixed Transmission

As the rising of ocean economic and the deepgoing research of wireless sensor networks (WSN), underwater wireless sensor networks (UWSN) becomes hot spot recent years, which applies the technology of traditional terrestrial WSN into underwater environments. UWSN is a combination of underwater acoustic sensor nodes, autonomous underwater vehicles (AUV) and a above water base station which is connected to the terrestrial control center. UWSN has the great applying prospect such as data collection of ocean information, ocean monitoring, pollution and disaster early warning, salvage and martial applications. Data collected by sensor nodes and AUV is send to the base station by particular routing or navigation algorithms. There are significant differences between UWSN and traditional terrestrial WSN.The bandwidth, network throughput and channel quality of UWSN are seriously effected or decreased by the unique characteristics and rugged environment of underwater channel. Moreover, UWSN nodes are energy restricted and it is impractical for battery replacement in underwater applications, which brings a major challenge for the deployment of UWSN. Thus, the problem of energy saving and prolonging network lifetime becomes hot spot in UWSN researching. In this paper we introduced unique characteristics of UWSN, underwater channels and network architecture. We also analyzed energy consumption problem of UWSN and existing schemes for prolonging network lifetime. Then we proposed our new algorithm to prolong network lifetime based on current achievements in scientific research. The basic idea is to decrease and balance the nodes'energy consumption. In the algorithm we emphasized the underwater network model and routing protocol. In the routing protocol a combined transmission is advanced. A node transmits to its neighbors by probabilities; and nodes residual energy is also considered, if it is below a threshold, the node will refuse to be a relay and avoid a deadlock in the network, then we improved the network reliability. Besides,if some nodes dead advanced,other nodes could find the appropriate route when they send message to the sink,so can assure the network runs normal.We compared our energy efficient routing protocol and traditional routing protocol in a detailed simulation. In direct transmission dominant (where all nodes transmit to the base station directly) and multi-hop transmission dominant routing, the furthest or nearest node to the base station will die first, while in our routing protocol, energy consumption of nodes is balanced and network lifetime is prolonged at the same time.