Please use this identifier to cite or link to this item: http://scholarbank.nus.edu.sg/handle/10635/134672
Title: TRANSMISSION SCHEDULING STRATEGIES FOR UNDERWATER ACOUSTIC NETWORKS WITH LARGE PROPAGATION DELAYS
Authors: V PRASAD ANJANGI
Keywords: Scheduling, Large propagation delays, Underwater acoustic networks, TDMA, Super-TDMA, MILP Scheduling
Issue Date: 10-Aug-2016
Source: V PRASAD ANJANGI (2016-08-10). TRANSMISSION SCHEDULING STRATEGIES FOR UNDERWATER ACOUSTIC NETWORKS WITH LARGE PROPAGATION DELAYS. ScholarBank@NUS Repository.
Abstract: Propagation delays in underwater acoustic (UWA) networks are large when compared to those in radio-frequency based terrestrial wireless networks due to the slower speed of sound. Several Medium Access Control (MAC) protocol designs for UWA networks have attempted to mitigate its ill-effects. However, studies on the fundamental understanding of large propagation delays have highlighted the advantages of its exploitation rather than mitigation in the design of throughput-maximizing MAC strategies. A review of the state-of-the-art in the development of MAC protocols utilizing the propagation delay information reveals open problems such as (a) how to compute throughput-maximizing transmission schedules for arbitrarily deployed practical UWA networks with packet traffic demands; (b) how to design transmission strategies that better exploit large propagation delays; (c) how to extend such techniques to much larger multi-hop networks; (d) how to compute transmission schedules robust to the uncertainties in the propagation delay information; and (e) whether such techniques are implementable in practice on underwater acoustic modems. This thesis contributes toward answering these problems and facilitates the advancement of such novel techniques one step closer to reality through experimental demonstration. This research presents strategies to improve the network throughput in arbitrary networks by better utilization of propagation delay information leading to a network throughput much closer to the upper bound. The first strategy to improve throughput in arbitrary network geometries adopts time-slotted schedules. By controlling the transmission power, the interference range can be limited, thereby increasing the network throughput significantly. The second strategy considers unslotted schedules with variable packet lengths. Given the propagation delay between nodes in the network and packet traffic demands, an optimization problem is formulated for minimizing the fractional idle time in a frame (or period) of the schedule as a Mixed-Integer Linear Fractional Problem (MILFP). The research is also extended to much larger multi-hop grid networks and to deal with uncertainties in propagation delays. Finally, this research also studies the practical modem constraints and implements such schedules on the underwater acoustic modem. The inclusion of modem constraints results in the design which can be realized in practice. The optimal packet and time slot lengths are computed, resulting in the maximum utilization of time slots while minimizing the guard times. Through experiments in Singapore waters, the research validates the key concepts involved in the proposed protocols.
URI: http://scholarbank.nus.edu.sg/handle/10635/134672
Appears in Collections:Ph.D Theses (Open)

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