Double-equalization-algorithm for time and frequency selective multiuser channels

We describe a transmission scheme and a new low complexity equalization algorithm for a multiuser system to equalize time and frequency selective multiuser channels. Under appropriate assumptions the channels are asymptotically transformed into AWGN subchannels. The transmission scheme for each user is a block transmission scheme based on a Walsh-Hadamard transform. The receiver is a combination of a vector decision feedback equalizer to equalize the multiple access interference due to multipath propagation in a multiuser environment and an iterative block decision feedback equalizer to equalize the intra block interference caused by the time variance of the channel. The algorithm combining the two types of equalizers in a suitable way by means of an additional interleaver is called the double-equalization-algorithm. It is shown in simulations that the performance of the system with antipodal signalling in a time varying multipath environment is close to the performance of antipodal signalling in AWGN