Multiuser Transmitter Preprocessing Aided Downlink Communications in Correlated Frequency-Selective Channels

Abstract

In this treatise, we investigate and present the performance of zero- forcing multiuser transmitter preprocessing (ZF-MUTP) in the context of multiuser multiple-input multiple-output (MIMO) systems based on space division multiple access (SDMA) in correlated frequency-selective channel, as well as in downlink (DL) direct sequence code division multiple access (DS CDMA) systems. The ZF-MUTP approach adopted in this treatise creates an orthogonal subspace to the interfering subspace in contrast to the conventional approach of pseudo inverting the channel state information (CSI) matrix. This approach completely removes the multiuser interference in downlink (DL) communications. Further, we investigate two power allocation policies based on maximum signal to noise ratio (MSNR) and equal power in the context of achievable capacity and symbol error rate (SER) in the DL system. It is shown through simulation that the achievable capacity in SDMA systems in terms of the number of bits per second per channel use is better in the case of MSNR power allocation policy than equal power allocation scheme. Also, simulation results demonstrate that MSNR results in better achievable SER than equal power allocation policy. Further, this ZF-MUTP based on creating orthogonal subspace to interfering subspace results in the same performance as that of the conventional ZF-MUTP.