Performance analysis of Sc fdma idma scheme in acoustic environment

Abstract

The various applications of underwater communication have motivated the research community for the development of more advanced and sophisticated communication techniques. The main problem associated with underwater communication is related to the carrier of information signal. Radio frequency waves are greatly attenuated in conductive medium like ocean and optical communication is highly scattering sensitive. Acoustic waves are the only carriers that can be applied with the conductive underwater applications. Bandwidth limitations due to ambient noise at low frequency and attenuation at high frequency, slow propagation speed of acoustic waves, multipath fading and limited power back-ups also poses various limitations for underwater acoustic (UWA) communication systems. newlineThe situation gets more complicated if simultaneous multiple users are present in a system. In the development of multiple access system for underwater environment, code-division multiple-access (CDMA) scheme has been the leading technique to combat multiple access interference (MAI) among users. However, in CDMA scheme, for large user count, multi-user detection (MUD) gets more complicated at receiver. Interleave-division multiple-access (IDMA) scheme is another multiple access approach researched thoroughly for underwater communication environment. In IDMA scheme unique patterns of interleaving are applied to differentiate multiple users in a system, while CDMA scheme applies unique spreading sequences for distinguishing the users. Conventionally, interleaving is applied to de-correlate the data-bits, so that noise bursts through the channel can be handled efficiently at the receiver. For IDMA systems interleaved chips after coding and spreading are transmitted which are almost un-correlated and CDMA systems transmit the spreaded chips of the same bit after coding, which are correlated up to some extent. After transmission through the multipath channel, adjacent chips interfere with each other at the receiver. At receiver, MUD works under the as