Underwater acoustic local area networks (UA-LANs) can be used to improve the coverage of an underwater network by introducing a tier of local area communications. Media access control (MAC) is a crucial issue for UA-LANs. Existing MAC protocols for terrestrial WLANs cannot be directly applied to UA-LANs due to the acoustic channel features of limited bandwidth and high and variable propagation delay. In this paper, we propose a handshake based ordered scheduling MAC (HOSM) protocol for UA-LANs. The nodes with data packets to be transmitted first reserve the channel in a channel reservation phase. Then an order list is calculated, and the data packets of these nodes are transmitted according to this order list. We develop a control packets transmission adjustment mechanism to reduce collisions of control packets. The key idea of this mechanism is to utilize the information of propagation delay to adjust the time instant of control packets transmitting. To improve channel utilization, we present a variant Max-Min Ant System algorithm to calculate an optimal order for each data transmission round. Simulation results have confirmed that the proposed protocol can achieve high throughput with low delay and good spatial fairness. Media access control (MAC) is a crucial issue for UA-LANs. It is also a challenging task. One of the reasons is the acoustic channel features of limited bandwidth, high and variable propagation delay, and time-variability. Firstly, the available bandwidth of the acoustic channel is low and variable. The amount of available bandwidth depends on the communication range; a long-range system that operates over several tens of kilometers may have a bandwidth of only a few kilohertz, while a short-range system operating over several tens of meters may have more than a hundred kilohertz of bandwidth [1] . The low available bandwidth would lead to low data transmission rate. Secondly, as the propagation speed of sound is approximately 1500 m/s, the propagation delay of underwater acoustic communication is significant. Moreover, the propagation delay is variable because the propagation speed of sound depends on many factors including temperature, depth, and salinity [6] . Due to the high and variable propagation delay, precise synchronization is difficult to be realized in underwater environment. Thus the MAC protocols relying on precise synchronization are usually difficult to be applied in practical underwater networks. Thirdly, the acoustic channel is time varying. There are two sources of the
Liao et al. REF propose a handshake-based ordered scheduling MAC (HOSM) protocol for an underwater acoustic LAN.
A Handshake Based Ordered Scheduling MAC Protocol for Underwater Acoustic Local Area Networks
International Journal of Distributed Sensor Networks
Computer Science