DESIGN AND IMPLEMENTATION OF 16-QAM MODEM

Abstract

Spectrum congestion and increase in data and voice traffic suggests the use of high-level modulation techniques. Among the amplitude and phase shift keying -schemes, Quadrature Amplitude Modulation (GAM) represents the best tradeoff between theoretical performance and implementation complexity. To avoid the intersymbol interference during data transmission through bandlimited channel, proper pulse shaping is required prior to modulation. Customary methods for implementating the pulse function use filters which have their own limitations. A number of digital techniques for pulse shaping have been suggested in the literature. A digital approach has been chosen for development of a QAM modem in this dissertation. An experimental 16-QAM modem for a data rate of 12,000 bits/sec has been developed. The theoretical performance evaluation of the 16-QAM signalling in the presence of additive white Gaussian noise has also been carried out. The results of our investigation are reported in this dissertation.