Linear multiuser transmission for CDMA with reduced computational complexity

CDMA system capacity is interference limited. Whereas for the uplink multiuser detection can be applied, for the downlink multiuser transmission (MUT) is required. Using channel knowledge, the transmit signal is jointly preprocessed in such a way that the performance in the receivers is optimized. Linear MUT methods like joint transmission (JT) or the transmit Wiener filter are computational intensive due to the inversion of the system matrix. Efficient algorithms are proposed and compared, such as the block tridiagonal algorithm or the band Cholesky algorithm. Approximations of the former and frequency-domain processing are also considered. The MUT complexity and performance is compared for TD-SCDMA.