Secure, Full-duplex multi-domain communication network for Marine Robots

Abstract

The underwater channel is a difficult communications medium as its link quality depends on the highly variable seabed and water column characteristics that vary on hourly, weekly, monthly and seasonal scales. One of the thesis objectives is to understand the channel characteristics for data transmission/reception towards development and evaluation of existing or new communication (MAC and routing level) protocols that could better utilize the limited resources within this harsh and unpredictable communications channel. orthogonal frequency-division multiplexing (OFDM) and CDMA are promising physical layer and multiple access techniques for underwater-acoustic sensor networks UW-ASNs as they are: (i) robust to frequency selective fading; (ii) compensate for multi-path effects at the receiver, and (iii) allow receivers to distinguish between signals simultaneously transmitted by multiple devices through a unique code for each transmitting node. Therefore, CDMA increases channel re-use and reduces packet re-transmissions, which results in decreased energy consumption and increased network throughput. This Ph.D. thesis proposes a communications framework for autonomous co-ordination and networking of marine robot teams from extended (over-the-horizon) ranges to transmit images/information from underwater to above water using OFDM-based CDMA. This creates a stack of communication protocols for marine robots that span multiple domains —that is under, on and above the water. Currently, there is no complete protocol stack which spans multiple domains in this way. This thesis proposes an innovative OFDM-based CDMA topology and also presents preliminary results attesting to its effectiveness.