Multicarrier communications for underwater wireless channels

Abstract

Orthogonal Frequency Division Multiplex (OFDM) is a multicarrier transmission technology which was first described by R. W. Chang in 1966 at Bell Labs. The first patent was granted in 1970. Later, M. Fattouche and H. Zaghloul described how the OFDM concept can be used to provide multiple access between different transceivers. This was the first description of Orthogonal Frequency Division Multiple Access (OFDMA).

The first OFDM based wireless standard was probably the Eureka Digital Audio Broadcast (DAB) standard for audio broadcasting which was released in 1995. Two years later, in 1997, the standard for terrestrial digital television, i.e. DVBT, was published.

OFDM and OFDMA is now becoming the major transmission and access technology for future mobile broadband systems. Mobile WiMAX is already available, and 3GPP has left WCDMA in favour of OFDMA for the next generation standard Evolved UTRA, often referred to as Long Term Evolution (LTE). While OFDM transmission over mobile communications channels can alleviate problem of multipath propagation, recent research efforts have focused on solving a set of inherent difficulties regarding OFDM, namely the peak-to-mean power ratio, time and frequency synchronization, and on mitigating the effects of the frequency selective fading channel.

In this Thesis, we study how multicarrier modulation techniques such as OFDM can help provide reliable underwater wireless communications. Furthermore, the main difficulties and challenges imposed by an underwater channel and OFDM’s application to it will also be discussed.