A novel scheme for linear multiuser detection in asynchronous DS-CDMA systems with frequency selective fading

A novel scheme for linear multiuser detection (MUD) based on sub-symbol diversity is presented that is applicable to asynchronous CDMA systems with frequency selective fading. Traditional solutions for asynchronous linear MUD result in a prohibitively large decorrelation matrix. The new scheme transforms the asynchronous problem into a synchronous one by creating sub-symbols that are, by design, time-aligned with all other users and their respective multipath signals. The resulting decorrelation matrix is dramatically reduced in size, thus offering a viable solution for implementation. We also present an optimal scheme for combining the sub-symbols that is based on the condition number of the decorrelation matrices