Open Access

An Improved Overloading Scheme for Downlink CDMA

EURASIP Journal on Advances in Signal Processing20052005:387618

Received: 24 July 2003

Published: 20 April 2005


An improved overloading scheme is presented for single-user detection in the downlink of multiple-access systems based on OCDMA/OCDMA (O/O). By displacing in time the orthogonal signatures of the two user sets that make up the overloaded system, the cross-correlation between the users of the two sets is reduced. For random O/O with square-root cosine rolloff chip pulses, the multiuser interference can be decreased by up to 50% (depending on the chip pulse bandwidth) as compared to quasiorthogonal sequences (QOS) that are presently part of the downlink standard of Cdma2000. This reduction of the multiuser interference gives rise to an increase of the achievable signal-to-interference-plus-noise ratio for a particular channel load.

Keywords and phrases

CDMAquasiorthogonal sequencesdownlink transmissionoversaturated channelspower control

Authors’ Affiliations

Telecommunications and Information Processing (TELIN) Department, Ghent University


© Vanhaverbeke and Moeneclaey 2005