Efficient implementation of pilot-aided 32 QAM for fixed wireless and mobile ISDN applications

Abstract

This paper presents the design and performance of a pilot tone-aided 32 QAM modem developed for wireless ISDN applications. The modem is capable of transmitting a gross data rate of 70 kbit/s in a 20 kHz channel spacing. A low complexity receiver has been designed that allows the effects of fading and frequency offset to be removed digitally at a low IF using information extracted from the pilot tone. The design has been fully evaluated in narrowband Rayleigh and Rician fading channels. Computer simulations show that extreme Doppler shifts and frequency offsets have little effect on system performance. The design is suitable for mobile radio as well as fixed applications such as wireless in the local loop (WLL).