Abstract :
Performance of a code-division multiple-access (CDMA) system is studied. The frame-error rate (FER) and bit-error rate (BER) of the forward traffic channel are obtained by using a simulation system based on TIA/EIA/IS-95. A diversity receiver structure with an adaptive search engine is developed and analyzed. The adaptive rate of the search engine is optimized to achieve high diversity gain. The diversity gain factor is derived based on a cluster of wide-band tapped delay-line multipath fading models. The relationships between receiver diversity gain, multipath channel characteristics, and the number of distributed antennas are derived. The multipath channel characteristics have a major impact on the system performance. Simulation shows that when channel mean delay spread is less than the chip interval, a distributed antenna system is essential for improving the system capacity. When more users are served in the system, FER is more sensitive to the channel characteristics. Uncaptured energy acts as self-interference, which can increase the BER by an order of magnitude and reduce system capacities, FER could also be improved by reducing the resolution of the diversity receiver branches to one half of the chip interval. The system performance for the indoor and outdoor environments are evaluated by utilizing the proposed diversity receiver over typical personal communications services channel models specified by the Joint Technical Committee (JTC)
Keywords :
antennas; cellular radio; code division multiple access; delays; diversity reception; error statistics; fading channels; multipath channels; radio receivers; radiofrequency interference; search engines; spread spectrum communication; telecommunication traffic; BER; CDMA system; DS-SS; Joint Technical Committee; TIA/EIA/IS-95; adaptive rate; adaptive search engine; bit-error rate; chip interval; code-division multiple-access; distributed antennas; diversity receiver; forward traffic channel; frame-error rate; high diversity gain; indoor environment; mean delay spread; multipath channel characteristics; outdoor environment; personal communications services; self-interference; simulation system; system capacity; system performance evaluation; tapped delay-line; wide-band multipath fading models; Bit error rate; Delay; Diversity methods; Fading; Multiaccess communication; Multipath channels; Search engines; System performance; Traffic control; Wideband;
