Performance of DS-CDMA Adaptive Modulation System in a Multipath-Channel Environment

Kazuaki TSUKAKOSHI  Toshiya KOBASHI  Yukiyoshi KAMIO  

IEICE TRANSACTIONS on Communications   Vol.E86-B   No.2   pp.743-756
Publication Date: 2003/02/01
Online ISSN: 
Print ISSN: 0916-8516
Type of Manuscript: PAPER
Category: Wireless Communication Technology
DS-CDMA,  adaptive modulation,  SNIR,  RAKE,  multipath,  

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We describe a DS-CDMA adaptive modulation system in which high-rate-data for moving pictures and LANs is transmitted to a high-speed traveling mobile terminal in the down-link. The transmission data rate is constant by changing the data-modulation level and the number of multiplex channels. We use computer simulation to evaluate the performance of the system using a RAKE receiver in a multipath-channel environment. For fdTslot 0.08, which is fading maximum Doppler frequency fd normalized by slot time Tslot, the following results are obtained. The average bit error rate (BER) of BER 1 10-3 necessary to ensure quality of high-rate-data transmission for moving pictures and LANs without error correction is attainable at low symbol-to-noise power ratio of ES/N0 14 dB and channel-use rate lower than 65%. The cell capacity of 17.2% is about 1.4 times that of the conventional system. Also, fdTslot=0.08 corresponds to the traveling speed of about 250 km/h at a carrier frequency of 8 GHz. Thus, the system enables high-rate-data and high-quality transmission needed for the moving pictures and LANs at mobile terminals with a traveling speed higher than 100 km/h at high carrier frequencies of the microwave band.