Multiple Pre-Rake Filtering Based on the Predicted Channel Impulse Response in the Transmitter and a Rake Combiner in the Receiver for TDD/DS-CDMA Mobile Communication Systems

Chang-Jun AHN  Iwao SASASE  

IEICE TRANSACTIONS on Communications   Vol.E85-B   No.10   pp.2282-2291
Publication Date: 2002/10/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technology
CDMA,  Rake receiver,  pre-Rake system,  time division duplex (TDD),  

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The pre-Rake system is known as a technique in TDD DS/CDMA system to reduce the mobile complexity and achieve the same BER performance like Rake receiver. The pre-Rake system itself is not optimum, since the channel impulse responses of uplink and downlink are slightly different in TDD system, so the signal- to-noise ratio (SNR) can be maximized with a matched filter based Rake receiver, which has not been considered in the conventional pre-Rake system. Furthermore pre-Rake system is sensitive to the Doppler frequency. Even though the pre-Rake system has the ability to suppress other user interference, it is not efficient to maximize the received signal in high Doppler frequency. However, Rake combiner is utilized for the detection method in our proposed system. So the maximized signal can keep the orthogonality better than the pre-Rake system and our proposed system can compensate the Doppler frequency effect. From these reasons, our system achieves better BER performance than that of the pre-Rake system with increasing the number of users in high Doppler frequency.