REDUCED-BANDWIDTH 16 QAM:A POWER AND BANDWIDTH EFFICIENT MODULATION TECHNIQUE FOR DIGITAL MICROWAVE RADIO SYSTEMS

摘要

A reduced-bandwidth 16 QAM scheme is presented which oFFers substantial power economy over 64 QAM while achieving similar spectral eFFiciency.Bandwidth reduction is performed by narrow-band raised-cosine filtering equally split between the transmitter and the receiver.The intersymbol interference due to the narrow-band filtering is compensated for at the receiver using a decisionfeedback equalizer (DFE).In a 140 Mbit/s-30 MHz digital radio system,the presented modulation technique with a 4-coeFficient DFE at the receiver achieves a 2 dB improvement over 64 QAM in transmitted energy per bit to noise spectral density ratio.With a 5-coeFFicient DFE at the receiver,this improvement is as high as 2.8 dB.Main results of an extensive computer simulation study are reported to show the performance oF the presented modulation technique as compared to 64 QAM.