Performance of QS-CDMA over frequency selective time non-selective multipath generalized gamma fading channels

Direct Sequence (DS) Code Division Multiple Access (CDMA) systems are considered for a variety of wireless applications and services because DS-CDMA enables the transmission of multimedia messages such as voice, data and video. The performance of Quasisynchronous DS-CDMA (QS-CDMA) communication system with a maximal ratio combiner (MRC) over a frequency selective time non-selective multipath Generalized Gamma fading channel is derived for not only any random / deterministic spreading sequences but also any chip-limited chip waveforms. Numerical and simulation results show that the performance of QS-CDMA is as good as or slightly better than synchronous CDMA (S-CDMA) when the maximum quasisynchronous delays do not need to be less than some specific values depending on the path power scattering. With this flexibility of quasisynchronous delays for the better performance, both the transmitter and receiver complexity is reduced as quasisynchronous communication is a challenging task for researchers. Lastly, a measure, Partial Power Ratio (PPR), is defined based on the partial autocorrelation functions, to select or design a chip waveform for quasisynchronous communication. Results show that QS-CDMA using the chip waveform whose PPR is greater, has better performance.