Low-cost Turbo receiver for coded asynchronous DS-CDMA in frequency selective channels

When channel coding is used on a CDMA transmission, the most appropriate approach for reception is joint Multiuser detection and decoding. This joint problem can be successfully processed by the Turbo-techniques. Therefore, we consider a low-complexity iterative receiver for the CDMA uplink transmission, called Turbo-CDMA, and we propose to further improve it. First, we derive a new DFE to be used at the first iteration. Then, we propose to fully use the decoded information in a new structure called Full Turbo-CDMA. Finally, we derive a new demodulation order that is well suited to the Turbo-CDMA receiver. This improved receiver, called Full Turbo-CDMA, aims to eliminate MUI and ISI almost completely in the presence of frequency selective channels. Improved performance is illustrated by simulations.