Study of multicarrier CDMA as enhancement of 1xEV-DV system

Abstract

cdma2000 1x EV-DV (1x Evolution for high-speed integrated Data and Voice) is a high-speed wireless data packet transmission system application designed for wideband systems. In general, the system requires some form of equalization at the receiver. This is because the ISI (Inter-symbol Interference) caused by multipath greatly prohibits utilization of higher order modulation scheme such as 16-QAM, which is operated in a relatively high SNR range. Simulations demonstrate that high-speed data transmission, without equalization, is completely impossible in multipath fading channels with large delay spread. A few equalization techniques at the receiver side, including parallel interference cancellation scheme, to reduce the effect of channel frequency selectivity are previously investigated in [4] and [5]. Even though with the LMMSE (Linear Minimum Mean Square Error) equalization technique or hybrid scheme of various interference cancellation techniques applied, the performance of fully loaded data rate setting is still not satisfactory, unacceptable in terms of packet error rate performance. Furthermore, the complexity of conventional equalization techniques is a important consideration for designing resource limited application such as a mobile handset. Thus, we aim to simultaneously resolve frequency selectivity of dispersive channels and to reduce the complexity of a system. In this thesis, we propose a multi-carrier CDMA (MC-CDMA) approach for forward link PDCH (Forward Packet Data Channel) of cdma2000 1x EV-DV which successfully alleviates the effect of ISI. The proposed MC-CDMA system can provide the same data rates with significantly better performance. Meanwhile, the proposed MC-CDMA system is comparable to the conventional system in the sense that same channel coding, modulation slot structure and CDMA chip duration time as defined for 1xEV-DV system are used. This can be achieved by exploiting the RISIC (Residual ISI Cancellation) algorithm which req...