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Promising Techniques to Enhance Radio Link Performance of Wideband Wireless Access Based on DS-CDMA
Fumiyuki ADACHI Mamoru SAWAHASHI Hirohito SUDA
IEICE TRANSACTIONS on Fundamentals of Electronics, Communications and Computer Sciences
Publication Date: 1998/11/25
Print ISSN: 0916-8508
Type of Manuscript: INVITED PAPER (Special Section on Spread Spectrum Techniques and Applications)
DS-CDMA, wireless access, mobile communications,
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Wideband wireless access based on DS-CDMA (W-CDMA) is a promising access technique for the 3rd generation mobile communication systems using 2 GHz carrier frequencies. In this paper, several promising techniques to enhance significantly the link performance or capacity are identified. They are (a) interference reduction techniques: interference cancellation and adaptive antenna array (b) required E b/I0 reduction techniques: channel coding and adaptive transmit power control (TPC). For the last decade, many theoretical studies have been done on interference cancellation and adaptive antenna array techniques. Now, it is time to implement real hardware to demonstrate their capabilities under real mobile radio propagation channels. In mobile radio, because of the well-known near/far problem and the adverse effect of fading, fast TPC is indispensable. Currently, a simple closed-loop fast TPC is adopted. The use of a more sophisticated adaptive fast TPC algorithm, which can adapt its power up/down step size according to the variations in channel conditions, may reduce the power control error, resulting in reduced interference to other users. Fast TPC and channel coding work complementarily against fading. Channel coding is another interesting area of research. Turbo coding is the most promising technique. In this paper, the above mentioned techniques are introduced. Preliminary experimental results of interference cancellation and adaptive antenna array techniques are also presented.