Abstract
In underwater acoustic sensor networks (UASNs), the propagation delay of acoustic signals is much longer than Radio Frequency (RF). There is spatial unfairness problem caused by space-time uncertainty. Hence, the design of Medium Access Control (MAC) is a challenging issue. In underwater, it not only considers transmission time but also takes location into account. In this paper, we propose Response to the Earliest Transmitter of RTS MAC (RET-MAC) protocol to solve the problem. RET-MAC adopts adaptive RTS Contention Phase (RTS CP) to determine the earliest transmitter of RTS. And CTS Delay Phase (CTS DP) is added to postpone sending CTS in order to avoid collision. In addition, we propose CTS back-off mechanism to adjust the length of CTS DP as needed. Contention back-off mechanism is used to reduce network congestion and increase fairness further. The simulation results show that our scheme can achieve higher fairness and throughput; at the same time it also guarantees lower energy consumption and delay.
Highlights
With the development of the computer technology, microelectronics technology, and communication technology, underwater acoustic sensor networks (UASNs) have got great progress
A Media Access Control (MAC) protocol is used to coordinate the access to the shared acoustic channel among multiple nodes, which is very critical to the network performance [2]
Underwater acoustic communications are characterized by three major differences with respect to terrestrial radio: the very low propagation speed; the strongly anisotropic nature, whereby horizontal channels are usually harsher than vertical channels; the significant difference between the power required to operate acoustic transducers and the power required to receive or listen to an acoustic signal [4]
Summary
With the development of the computer technology, microelectronics technology, and communication technology, underwater acoustic sensor networks (UASNs) have got great progress. A Media Access Control (MAC) protocol is used to coordinate the access to the shared acoustic channel among multiple nodes, which is very critical to the network performance [2]. There is an important significance to design the fairness and low energy consumption of UASN MAC protocol. MAC protocols decide how multiple nodes share the underlying acoustic channel, which is critical to the overall network performance [9]. To the Earliest Transmitter of RTS MAC (RET-MAC) protocol, which can ensure node to contend the channel fairness.
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