Performance of Cooperative MC-DS-CDMA System in the Presence of Interference Using Transmitter Preprocessing Based on CSI Feedback

Abstract

The performance of a cooperative downlink (DL) time-frequency (TF) spread multi-carrier direct-sequence code-division multiple-access (MC-DS-CDMA) system in the presence of multi-user interference (MUI) and inter-relay interference (IRI) is considered in this paper. Transmitter preprocessing (TP) is employed at the base station (BS) to suppress the MUI at the relay stations (RSs). Similarly, we employ TP at the RSs to mitigate the effects of IRI at the DMSs. Specifically, the TP operated at the BS is based on the orthogonal subspace approach whilst, the TP op-erated at the RSs is based on the classical transmit zero-forcing (TZF) principle. Furthermore, the channel knowledge that is re-quired to formulate the preprocessing matrix especially at the BS is based on the quantized feedback of the channel state information (CSI), while that required at the relays is based on perfect CSI. Our simulation study shows that the TP efficiently suppresses the MUI and IRI at the RSs and DMSs, respectively, thus, greatly con-tributing to achieve the relay-diversity under perfect channel knowledge assumption both at the BS and the RSs in the context of TP construction. Also, it is inferred that, the TP based on quantized channel knowledge results in bit-error-rate (BER) performance that is close enough to that obtained with the perfect channel knowledge hypothesis.