Biblio

The harsh environment in the water has imposed challenges for underwater sensor networks (USNs), which collect the sensed data from the underwater sensors to the sink on land. The time-varying underwater acoustic channel has low band-width and high bit error rate, which leads to low data collection efficiency. Furthermore, the heterogeneous model of USNs that uses acoustic communications under the water and wireless communication above the water makes it difficult in efficient routing and forwarding for data collection. To this end, we propose a novel on-surface wireless-assisted opportunistic routing (SurOpp) for USNs. SurOpp deploys multiple buoy nodes on surface and includes all of them in the forwarding candidates to form a receive diversity. The opportunities of reception and forwarding in buoy nodes are exploited to improve the end-to-end transmissions. SurOpp also adopts rateless codes in the source to achieve opportunistic reception in the sink. The cooperation of both opportunistic reception in the buoys and the sink further decreases the messages of control overhead. The wireless interface in the buoy undertakes all the message exchanges in forwarding coordination to compensate the bandwidth limit of the acoustic channel. Simulations in NS3 show that SurOpp outperforms the traditional routing and existing opportunistic routing in terms of packet delivery ratio, end-to-end delay and energy consumption.

We consider 3-dimensional(3D) underwater random network (UAN) where the nodes are uniformly distributed in a cuboid region. Then we derive the closed-form probability of finding a receiver in an ellipsoid neighborhood of an arbitrary sender. Computer simulation shows that the analytical result is generally consistent with the simulated result.