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

概要

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We describe a DS-CDMA adaptive modulation system in which high-rate-datu 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-chainnel environment. For f_dT_<slot> ≤ 0.08, which is fading maximum Doppler frequency f_d normalized by slot time T_<Slot>, the following results are obtained. The average bit error rate (BER) of RER ≤ 1 × 10^<-3> necessary to ensure quality of high-rate-data transmission for moving pictures and LAN's without error correction is attainable at low symbol-to-noise power ratio of E_s/N_o ≤ 14dB and channel-use rate lower than 65%. The cell capacityof 17.2% is about 1.4 times that of the conventional system. Also. F_dT_<slot> = 0.08 corresponds to the traveling speed of about 250km/h at a carrier frequency of 8GHz. 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 100km/h at high carrier frequencies of the microwave band.
2003-02-01