Analysis of Vrppic and Ppic for Siso and Simo Mc-cdma Uplink System

This paper presents an extended version of Partial Parallel Interference Cancellation (PPIC) called Variance reduced Partial Parallel Interference Cancellation (VRPPIC) for multicarrier code division multiple access uplink systems. The combination of PPIC receiver and new bit estimator is called VRPPIC detector. This realization is derived for the main PPIC operation and soft decision (SD) from PPIC, which are linear combination of the bit estimator using appropriate Weighting Factors (WF). These weighting factors are derived from Partial Parallel Interference Cancellation (PPIC) weighting factors. It is used to reduce the conditional variance of the final stage signal estimation. An Optimal Weighting Factor (OWF) selection algorithm has been derived for VRPPIC detector scheme, to minimize a monotonically increasing condition variance function. For all the interference cancellation stages the derived OWFs are equal and can easily be obtained from a linear function of active users. Simulation has been done in VRPPIC detector and PPIC detector using optimal weighting factors and randomly selected weighting factors. The result shows that the VRPPIC with OWFs outperforms both VRPPIC and PPIC with randomly selected weighting factors. Also it is shown in this paper that if there are multiple antennas at the receiving end, the performance of the detector is further improved. This leads to generalization that if data comes from single stream (single input) and there are multiple outputs (antennas) at the receiving end, the detector for multiple reception MC-CDMA strikingly outperforms the conventional systems with single antenna at the receiving end.