Serial Search Based Initial Code Acquisition in the Multiple Transmit/Receive Antenna Aided Multi-Carrier DS-CDMA Downlink

Initial code acquisition schemes designed for the multiple transmit/receive antenna aided multi-carrier (MC)-DS-CDMA downlink are analysed, when communicating over uncorrelated Rayleigh channels. The achievable mean acquisition time (MAT) performance is characterised as a function of both the number of transmit/receive antennas and that of the number of subcarriers. It is demonstrated that in contrast to our expectations, the achievable MAT tends to degrade at low E_c/I _o values right across the signal-to-interference plus noise ratio (SINR) per chip (E_c/I_o) range considered, when the number of transmit antennas and/or that of the subcarriers are increased. An exception is constituted by single-carrier (SC)-DS-CDMA using P=2 and 4 transmit antennas and R=1 receive antenna. This increased MAT has a grave detrimental effect on the performance of Rake receiver based synchronisation schemes, when the perfectly synchronised idealised system is capable of attaining its target bit error rate performance at reduced SINR values, as a benefit of the diversity gain achieved by employing both multiple transmit antennas and multiple subcarriers. Therefore our future research will be aimed at specifically designing powerful iterative acquisition schemes for MIMO-aided multi-carrier transmission systems