Uplink MC-DS-CDMA using ZCZ sequences for frequency-selective block-fading channels

In this paper, a time and frequency (TF) domain spreading multicarrier direct sequence code division multiple access (MC-DS-CDMA) scheme employing zero correlation zone (ZCZ) sequences, designed specifically for quasi-synchronous uplink transmissions, is proposed to exploit frequency and temporal diversity in frequency-selective block-fading channels. This is in contrast to previously proposed schemes designed only to exploit frequency diversity in frequency-selective slow fading channels. Almost optimal quadriphase ZCZ sequences are employed to minimize multi-user interference (MUI) in the uplink channel. Joint detection is employed at the receiver using the optimal maximum likelihood (ML) detector and sub-optimal minimum mean square error (MMSE) detector. When using the ML detector, the proposed system showed a performance improvement of 2.7 dB at a BER of 10
^-4
over a previously proposed scheme designed only to exploit frequency diversity.