Performance analysis of CDMA under Rayleigh Rician and Nakagami fading channels

Abstract

CDMA uses unique spreading codes to spread the baseband data before transmission. The signal is transmitted in a channel, which is below noise level. The receiver then uses a correlate to dispread the wanted signal, which is passed through a narrow band pass filter. Unwanted signals will not be dispread and will not pass through the filter. Codes take the form of a carefully designed one/zero sequence produced at a much higher rate than that of the baseband data. The rate of a spreading code is referred to as chip rate rather than bit rate Channel fading is characterized by the fl uctuations of channel coefficient ck for each user k. Despite the fact that channel fading was traditionally viewed as a source of error and unreliability that is undesirable, the fading is employed as a requirement for throughput maximization in multi-user diversity. This is accomplished by tracking the instantaneous channel quality of the users in the system and schedule transmissions to the user who has the best channel quality at any given time.