Event-Driven Data Gathering in Pure Asynchronous Multi-Hop Underwater Acoustic Sensor Networks.

Sara Blanc

doi:10.3390/s20051407

Abstract

In underwater acoustic modem design, pure asynchrony can contribute to improved wake-up coordination, thus avoiding energy-inefficient synchronization mechanisms. Nodes are designed with a pre-receptor and an acoustically adapted Radio Frequency Identification system, which wakes up the node when it receives an external tone. The facts that no synchronism protocol is necessary and that the time between waking up and packet reception is narrow make pure asynchronism highly efficient for energy saving. However, handshaking in the Medium Control Access layer must be adapted to maintain the premise of pure asynchronism. This paper explores different models to carry out this type of adaptation, comparing them via simulation in ns-3. Moreover, because energy saving is highly important to data gathering driven by underwater vehicles, where nodes can spend long periods without connection, this paper is focused on multi-hop topologies. When a vehicle appears in a 3D scenario, it is expected to gather as much information as possible in the minimum amount of time. Vehicle appearance is the event that triggers the gathering process, not only from the nearest nodes but from every node in the 3D volume. Therefore, this paper assumes, as a requirement, a topology of at least three hops. The results show that classic handshaking will perform better than tone reservation because hidden nodes annulate the positive effect of channel reservation. However, in highly dense networks, a combination model with polling will shorten the gathering time.

Highlights

Our seas and oceans need us to take care of them
Because energy saving is highly important to data gathering driven by underwater vehicles, where nodes can spend long periods without connection, this paper is focused on multi-hop topologies
RTS/CTS/Data Sending (DS) and ACK packets are broadcast transmissions, while both PB and ACK include the residual energy value of the relay. Select their relays depending on the minimum hop number and residual energies

Summary

Introduction

The observation and control of our blue spaces is very important if we want to achieve a balance between maritime exploitation and the preservation of natural spaces and water quality. In the last two decades, great efforts have been made to develop more effective and robust technology, for both measurement instruments and autonomous underwater vehicles. In addition to the known difficulties for the transmission of signals in water, it is important to remember that humans live on land. A valid information system for water observation and control must include a means of transferring information out of the water. Sea–land data transference seeks to explore both suitable underwater protocols and land access, taking into account water channel problems [1] and propagation delays [2]

Methods

Results

Conclusion