Effect of constellation design, pulse shaping and BCH codes on performance of M-ary QAM transmitted over gaussian bandlimited channels

Abstract

Computer simulation is used to study several issues relevant to the design of quadrature amplitude modulation (QAM) with M-ary alphabet. The QAM signals are transmitted over gaussian bandlimited channels. Signal constellations, pulse shaping, and error correcting codes are optimized for power and bandwidth efficiency. For each QAM channel, there exists an optimal transmission rate which depends on filtering, constellation design, pulse shaping, and equalization. Optimizing both the signal constellation and pulse shaping offer an appreciable gain, especially for higher signal alphabet and bandwidth efficiency. Finally, properly chosen BCH error-correcting code provides substantial coding gain especially at a high -ary and a high transmission rate.