Uppsala universitet

Designing Equalizers Based on Linear Baseband Models of Direct-Sequence Code-Division Multiple Access Systems

Claes Tidestav,

Internal Report UPTEC 96025R, Dept. of Technology, Uppsala University.

Over the years, many detectors have been proposed for systems employing Code-Division Multiple Access (CDMA). Here we develop a framework for the design of such detectors, (especially multiuser detectors). We also derive such a detector, the fractionally spaced multivariable DFE.

In this report, we show how the entire process of transmission and reception in a DS-CDMA system, including the spreading, can be described as a tapped delay line with multiple inputs and a single output.

We then demonstrate how this model can be used to design a fractionally spaced decision feedback equalizer with a single input and multiple outputs. In the proposed approach, long codes can be used and channel estimation can be performed in an efficient way. The suggested detector is near-far resistant and the capacity of the system is not limited by intracell interference.

Monte Carlo simulations are conducted to demonstrate the superiority of the proposed approach as compared to the conventional detector. The simulation scenario constitutes a heavily loaded system with multipath. Situations with and without power control are considered.

Related publications:
Conference paper in IEEE ICUPC'96.
Conference paper at the Swedish Radio Conference 1996.

Pdf 788K

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