PERFORMANCE ANALYSIS OF OFDM SYSTEM CONSIDERING QUANTIZATION EFFECTS

Abstract

This thesis presents the effects of fixed point implementation on the performance of a digital communication system. In recent times orthogonal frequency division multiplexing (OFDM) has emerged as a promising technology for wireless and mobile communication systems, since it eliminates the use of complex equalizers and utilizes the bandwidth efficiently. OFDM is a multi-carrier modulation scheme which can support high data rates without degradation induced by interference by exploiting orthogonality amongst the sub-carriers. Most DSP and Digital Communication algorithms are implemented using fixed-point hardware having finite precision. The reason for this is that the use of fixed-point hardware is cost effective in terns of silicon area and power consumption. However this reduction in precision introduces quantization noise which degrades the performance, thus giving rise to the classical trade-off of signal quality vs. cost effectiveness in DSP. A generic OFDM transceiver with frequency and timing synchronization was implemented and was converted to fixed point. This thesis shows that the performance of OFDM communication system measured in terms of the Bit Error Ratio (BER) remains within tolerable bounds even when the word-lengths are reduced to a certain limit provided the communication channel is clean enough. This analysis can be used to design a reconfigurable architecture, where we can adapt our OFDM transceiver according to our need in terms of the number of errors or the power consumption.