%0 Journal Article
%T Design of Multiuser CDMA Systems in Fading Channels
%A J. RAJESH
%A Prof. K ASHOK BABU
%J International Journal of Computer Technology and Applications
%D 2011
%I Technopark Publications
%X In this paper, we examine the effect of channel estimation errors on the performance of multiple-input¨Cmultiple-output (MIMO) systems that employ code-division multiple-access (CDMA) transmission. Channel estimation based on training techniques has widely been considered throughout the literature. However, employing these training techniques in MIMO-CDMA systems degrades system performance due to multiuser interference. This degradation is clear as the diversity advantage of the MIMO system diminishes with the increased level of interference. As a remedy to this problem, we propose a channel-estimation and data-detection scheme based on the superimposed training technique for space-time spreading systems. The proposed scheme enhances the performance of the space-time system by eliminating the interference effect from both the channel and data estimates using two decorrelators: channel and data decorrelators. We investigate the performance of the proposed estimation technique considering an asynchronous CDMA uplink transmission over frequency-selective slow-fading channels. In particular, we analyze the bit-error-rate (BER) performance of the multiuser system with two-transmit-antenna and V -receive-antenna configuration over Rayleigh fading channels. Compared with other conventional estimation techniques, our results show that the proposed estimation technique is more robust to channel-estimation errors. Furthermore, both simulations and analytical results indicate that full system diversity is achieved
%K Channel estimation
%K code-division multiple access(CDMA )
%K multiple-input¨Cmultiple-output (MIMO)
%K super imposed training
%U http://ijcta.com/documents/volumes/vol2issue5/ijcta2011020563.pdf