Software and Hardware Implementation of an OFDM System

STUDENTS

ADVISORS

Adam Truelove

Surujlal Dasrath

Dr. In Soo Ahn

Dr. Thomas L. Stewart

Introduction

OFDM means Orthogonal Frequency Division Multiplexing. It is not new, but it is an emerging scheme in high-data-rate communications. Communication is limited not only by noise, but also by ISI Ė inter symbol interference, which is due to channel memory. Interactions among different transmitted symbols at the receiver result in the ISI of the channel. This in turn leads to an increase in errors.

The symbol rate of communication systems is practically limited by the channelís bandwidth. For higher symbol rates, the effects of ISI must be dealt with seriously. Several channel equalization techniques can be used to suppress the ISIs caused by the channel. However, to do this, the CIR Ė channel impulse response, must be estimated.

Recently, OFDM has been used to transmit data over a multi-path channel. Instead of trying to cancel the effects of the channelís ISIs, a set of sub-carriers can be used to transmit information symbols in parallel sub-channels over the channel, where the systemís output will be the sum of all the parallel channelís throughputs. The data rate per sub-channel is only a fraction of the data rate of a conventional single carrier system having the same output. Hence, a system can be designed to support high data rates while deferring the need for channel equalizations.