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Design and Analysis of MMSE DFE forWideband Code Division Multiple Access (WCDMA)
Sanjay Kumar Sharma and S. Naseem Ahmad

The paper presents design and analysis of Minimum mean square error (MMSE) Decision Feedback Equalizer (DFE) for wideband code division multiple access (WCDMA). The most important third generation (3G) cellular communications standard is based upon wideband CDMA (WCDMA). We investigate a MMSE decision-feedback equalizer. The feed forward and feedback filters in a DFE have been optimized in accordance with the MMSE criterion to reduce the effects of noise, intersymbol interference (ISI), and multiple access interference (MAI) while maintaining reasonable system complexity at the same time. In the system model, the spreading codes of various interfering users have been modeled in the form of random sequences. The system performance has been evaluated using the Gaussian approximation. Numerical and simulation results show that the MMSE DFE exhibits significant performance improvement over the standard space-time coded RAKE, especially in interference limited conditions.

Keywords: Decision-feedback equalization, multiple access interference (MAI), RAKE, transmit diversity, wideband code-division multiple-access (WCDMA), bit error rate (BER).

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