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.
