Joint Frequency-domain Differential Detection and Equalization for 2-dimensional Spread/chip-interleaved DS-CDMA Uplink Transmissions

The multiple-access interference (MAI) limits the performance of the DS-CDMA uplink transmission. 2 dimensional (2D) spread/chip-interleaved DS-CDMA is an MAI-free system, where single-user coherent frequency-domain equalization (FDE) can be used instead of complicated multiuser detection (MUD). However, coherent FDE needs channel estimation. Pilot-assisted channel estimation is not reliable in a fast fading environment. In this paper, we apply joint frequency-domain differential detection and equalization (FDDDE) that requires no channel estimation to 2D spread/chip-interleaved DS-CDMA in a multiuser/multipath environment. The filter coefficient used in FDDDE is updated by estimating the normalized Doppler frequency. Computer simulation results show that 2D spread/chip-interleaved DS-CDMA using FDDDE is robust against fast fading.