Performance study on high data rate modulation technique of W-CDMA in multipath fading channel

Abstract

Downlink transmission (base station to mobile terminal) using high data rate Mary Quadrature Amplitude Modulation (QAM) and Quadrature Phase Shift Keying (QPSK) modulation schemes are considered in a Wideband-Code Division Multiple Access (W-CDMA) system. The performances of these modulation techniques are evaluated when the system is subjected to a number of users as well as noise and interference in the channel. Additive White Noise Gaussian (AWGN) and multipath Rayleigh fading are considered in the channel. Computer simulation tool, MATLAB, will be used throughout the research to evaluate Bit-Error-Rate (BER) for W-CDMA system models. Two approaches are used in this simulation. They are simulations using Simulink and simulations using M files. A study of different modulation techniques is needed so that a W-CDMA system can choose suitable modulation technique to suit the channel quality, thus delivering optimum and efficient data rate to mobile terminal. It is discovered that the performance of 16-QAM is significantly degraded in AWGN and multipath Rayleigh fading channel compared to that of QPSK. Error correction coding is needed to be used in this system particularly with 16-QAM to ensure better performance of WCDMA system