Performance of MUTP assisted IDMA system for downlink communications

In this paper, we evaluate the performance of multi-user transmitter pre-processing (MUTP) assisted interleaved division multiple access (IDMA) over frequency-selective channel in the context of downlink (DL) communications. The MUTP is realized by singular value decomposition (SVD) which exploits imperfect channel state information (CSI) of all the users estimated at the mobile stations (MSs). In this considered work, the CSI is estimated using minimum mean square error (MMSE) algorithm and it is vector quantized at the MS and the bits representing the quantized magnitudes and phases are feedback to the base station (BS) through the dedicated low rate noisy channel. The quantized bits are recovered at the BSs to evaluate the transmitter pre-processing (TP) matrix. Further, we consider the turbo coded MUTP assisted IDMA system to mitigate the effects of multiple access interference (MAI) and multi stream interference (MSI) and we compare the performance of such coded system with uncoded system. It is discerned from the simulation results that the MUTP assisted IDMA system provides the better performance in terms of bit error rate (BER) with low signal to noise ratio (SNR).