Performance of cooperative diversity assisted IDMA system for downlink transmission with transmitter pre-processing

In this paper, we investigate the performance of co-operative diversity aided downlink communications using multi-user transmitter preprocessing (MUTP) technique for interleave division multiple access(IDMA) scheme. The MUTP is realized by singular value decomposition (SVD) which exploits null space of all the users channel state information (CSI) at the base station (BS) and at the relays. We consider fixed infrastructure-based decode and forward relays that are capable of performing signal processing such as formulating pre-processing matrix in order to mitigate the effects of multi-user interference (MUI) and inter-relay interference (IRI). Particularly, we investigate the performance of MUTP assisted co-operative diversity aided IDMA DL transmission to mitigate the effects of multi-user interference (MUI) both at the BS and relays for the case in which all users supported by L relays where MUI is dominant at the relays and MUI and IRI are dominant at the MSs. It is shown through the simulations that, relay aided co-operative DL transmission with MUTP provides better performance in terms of achievable bit error rate (BER) by mitigating the effects of MUI at the relays and MUI and IRI at the MSs. Further it is observed that BER performance can be enhanced by considering more number of relays between BS and MS for MUTP assisted IDMA system in the context of downlink communication.