ORTHOGONAL CHIRP DIVISION MULTIPLEXING TO IMPROVE RELIABILITY OF UNDERWATER ACOUSTIC COMMUNICATION

Abstract

Covert underwater communication methods are constantly evolving, and there is a need for more robust techniques. In this thesis, the benefits and detriments of a number of currently in-use single-carrier covert underwater wireless acoustic commu- nication techniques are described, with special attention paid to the chirp method for its robustness underwater. Multiple-carrier orthogonal frequency division mul- tiplexing (OFDM) is then described as a way to improve bandwidth of underwater communications, and orthogonal chirp division multiplexing (OCDM) is investigated to determine if it can take advantage of the robustness of chirps and the throughput of OFDM. A comparison in simulation is made between OFDM and OCDM using chan- nel data from St. Margaret’s Bay in Halifax, Nova Scotia. The impact of the front end transmitter on the signal is investigated. An experiment is then performed in the Dalhousie Aquatron comparing OFDM and OCDM, and the results are discussed.