Code division multiple access (CDMA) schemes allow a number of asynchronous users to share a transmission medium with minimum cooperation among them. However sophisticated signal processing algorithms are needed at the receiver to combat interference from other users and multipath effects. In this paper a discrete-time multirate formulation is introduced for asynchronous CDMA systems which can incorporate multipath effects. This formulation reveals interesting links between CDMA receivers and array processing problems. In this framework linear receivers are derived that can completely suppress multiuser interference (decorrelating receivers). A criterion is introduced which guarantees the decorrelating property while providing optimal solutions in the presence of noise. Parametric FIR designs as well as nonparametric solutions are delineated and their performance is analyzed. The proposed receivers are resistant to near-far effects and do not require the estimation of the users' and noise powers.
Bibliographical noteFunding Information:
Manuscript received May 1, 1995, revised March 25, 1996. This work was supported by the National Science Foundation Grant NSF-MIP 9424305 Part of the results of this paper was presented at the Conference on Information Sciences and Systems, Johns Hopkm University, Baltimore, MD, USA, March 22-24, 1995. The associate editor coordinating the review of this paper and approving it for publication was Dr Yingbo Hua M K Tsatsanis is with the Electncal Enginenng and Computer Science Department, Stevens Institute of Technology,Castle-Point on Hudson, Hobo-ken, NJ 07030 USA. G B Giaunalus is with the Department of Electncal Engineenng, University of Virginia, Charlottesville, VA 22903-2442 USA Publisher Item Identifier S 1053-587X(96)09044 7