Abstract
Underwater acoustic sensor networks are an enabling technology for many applications. Long propagation delays and limited bandwidth of the acoustic channel place constraints on the trade-off between achievable end-to-end delay, channel utilization, and fairness. This paper provides new insights into the use of the combined free/demand assignment multiple access (CFDAMA) schemes. The CFDAMA can be classified as adaptive TDMA, where capacity is usually assigned on demand. The CFDAMA with round robin requests (CFDAMA-RRs) are shown to minimize end-to-end delay and maximize channel utilization underwater. It sustains fairness between nodes with minimum overhead and adapts to changes in the underwater channel and time-varying traffic requirements. However, its performance is heavily dependent on the network size. The major contribution of this paper is a new scheme employing the round robin request strategy in a systematic manner (CFDAMA-SRR). Comprehensive event-driven Riverbed simulations of a network deployed on the sea bed show that the CFDAMA-SRR outperforms its underlying scheme, CFDAMA-RR, especially when sensor nodes are widely spread. Considering node locations, the novel scheme has a bias against long delay demand assigned slots to enhance the performance of the CFDAMA-RR. The illustrative examples show good agreement between the analytical and simulation results.
Highlights
Underwater Acoustic Sensor Networks (UASNs) are an enabling technology for numerous underwater scientific, industrial and homeland security applications [1]
This paper has shown that the combined free/demand assignment multiple access (CFDAMA) protocol offers excellent performance in dealing with the trade-off between end-to-end packet delays and channel utilization with both Poisson and Pareto ON/OFF data traffic types through simulated underwater scenarios
The major advantage of the CFDAMA protocol is the fact that it exploits the contentionless nature of free assignment and the effectiveness of demand assignment in achieving high channel utilization efficiency
Summary
Underwater Acoustic Sensor Networks (UASNs) are an enabling technology for numerous underwater scientific, industrial and homeland security applications [1]. It has been proposed in [9] for satellite channels to enhance the delay/utilization performance of long delay geostationary satellite links It is capable of improving the overall performance of networks which suffer from long propagation delays and limited capacity such as UASNs. The presence of the free assignment strategy in CFDAMA works as a backup slot provider. Intermediate Scheduler, to significantly reduce the average round-trip time required for making capacity requests and receiving subsequent acknowledgements This enhances the overall delay/utilization performance of CFDAMA. Due to the long propagation delay underwater and the fact that sensor nodes can be widely spread, implementing CFDAMA with one of the conventional request strategies and without considering the location of nodes results in poorer efficiency than the level of which the scheme is capable. The rest of the paper is organized as follows: Section II introduces CFDAMA, Section III describes the new CFDAMA variant, Section IV presents the simulated underwater scenarios and parameters, Section V illustrates the outcomes of the detailed simulation study, and Section VI concludes the paper
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