Abstract
In underwater acoustic wireless sensor networks (UAWSNs), designing media access control (MAC) protocols is highly challenging because of their significant influence on network performance. It is a great challenge to design suitable MAC protocols for UAWSNs because of the specific characteristics of underwater acoustic channels, such as low communication rates, large propagation delays, and limited available bandwidth. Orthogonal frequency division multiple access (OFDMA) is a special case of OFDM-based multicarrier modulation in which multiple user symbols are transmitted simultaneously using different subcarriers with overlapping orthogonal frequency bands. In this paper, we propose an OFDMA-based subcarrier pregrouping MAC protocol for UAWSNs, termed OSPG-MAC. To make it easier to allocate subcarriers and avoid conflict, we group all the subcarriers into fixed subchannels in advance and allocate them in terms of these subchannels. To maximize the total throughput on each subchannel, a bit and power allocation algorithm for the protocol is proposed, termed the OSPG-MAC algorithm. Simulation results show that the performance of OSPG-MAC is better than that of classic underwater MAC protocols, including SFAMA and T-Lohi.
Highlights
Underwater acoustic wireless sensor networks (UAWSNs) have received tremendous attention in recent years since they can bring about significant benefits in many applications, such as tsunami warning, environment monitoring, disaster prevention, assisted navigation, and resource exploration [1]
We propose an Orthogonal frequency division multiple access (OFDMA)-based Subcarriers Pregrouping media access control (MAC) protocol called OSPG-MAC for underwater acoustic wireless sensor networks
In [19], the authors propose two medium access control (MAC) protocols, namely, Transmit Delay Allocation MAC (TDA-MAC) and Accelerated TDA-MAC, that are capable of providing time division multiple access (TDMA) to sensor nodes without the need for centralized clock synchronization
Summary
Underwater acoustic wireless sensor networks (UAWSNs) have received tremendous attention in recent years since they can bring about significant benefits in many applications, such as tsunami warning, environment monitoring, disaster prevention, assisted navigation, and resource exploration [1]. In UAWSNs, a media access control (MAC) protocol is used to allocate limited acoustic wireless channel resources among network nodes. Most existing terrestrial MAC protocols do not consider the characteristics of underwater channels and cannot be applied to underwater acoustic wireless sensor networks directly [2]. We propose an OFDMA-based Subcarriers Pregrouping MAC protocol called OSPG-MAC for underwater acoustic wireless sensor networks. The main feature of OSPG-MAC is the assignment of subcarriers to neighboring nodes in the form of subchannels containing sets of fixed subcarriers This allows simultaneous transmission between neighboring nodes while avoiding collisions. To maximize the total throughput on the corresponding subchannels, a bit and power allocation algorithm for the protocol, termed OSPG-MAC, which combines the advantages of the water-filling and greedy algorithms, is proposed.
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