Analysis of large MIMO DS-CDMA systems with imperfect CSI and spatial correlation

The large system analysis of randomly spread MIMO DS-CDMA systems is provided. Correlated Rayleigh fading MIMO channels are assumed for all users. Linear multiuser detection with separate decoding and pilot-aided channel estimation are used. The results imply that with channel estimation, the performance can improve significantly as the correlation between the transmit antennas increases. No channel information at the transmitter is required, but the channel estimator needs knowlegde of the long term transmit correlation in advance. The numerical results demonstrate that in a 4 × 4 MIMO DS-CDMA system with two users per chip, high antenna correlation at the transmitter can double the ergodic spectral efficiency compared to the case of uncorrelated transmit antennas.