A Study And Simulation Of IS-95 CDMA Forward Link

Following the progress of the society, consumers' demands to communication become more and more high. Accordingly, mobile communications technology is continuously developing. Since the mid of 1980's, cellular mobile communications have developed from the first generation analog cellular mobile communications systems to the second generation digital cellular mobile communications systems. Now they have been evolved into the third generation cellular mobile communications systems. IS-95 CDMA system of North America is the first mature CDMA cellular mobile communications system, of which the underlying technology is including spread spectrum and code division multiple access(CDMA). In this thesis, a MATLAB simulation of forward traffic channel was implemented according to the physical layer specification of the IS-95 CDMA system. Firstly the basic transmitter, including convolutional encoding, interleaving, scrambling, Walsh modulation, quadrature spreading and baseband filtering was studied. Subsequently the channel was modeled for three types namely additive white Gaussian noise, flat fading and frequency selective fading. Lastly, the receiver was studied. This part laid emphasis on introducing Viterbi decoding. For different channel condition, the simulation analysis presented the time domain waveform, power spectral estimate and error rate plot. Moreover, multiple access interference due to the existence of other users was analyzed.