Simulation of Third Generation CDMA Systems - Virginia Tech

The pass-band of the pulse shaping filter is the band of interest in the simulator. The channelcoefficients are normalized so thatN2Ê h kk = 1= 1, where we have N channel coefficients. Thisnormalization ensures that the average signal energy at both end of the channel remains thesame. This allows us to take the energy of the signal at the transmitter as the received signalenergy (E b ) during the estimation of receiver front end E b /N 0 value.The channels used in the simulator are linear time variant filters. We have a number ofindependently Rayleigh faded components on the sampling instants. Figure 3.5 shows theblock diagram of the time varying channelRayleighWaveformRayleighWaveformTransmittedFrameDelay of the2nd pathRayleighWaveformDelay of theNth pathFigure 3.5: Time Varying ChannelThe delays are implemented by treating each the transmitted data block (a frame of 10ms for the simulator) in a circular fashion. To implement a delay of τ samples, the last τsamples of a transmitted frame are taken out. This block of τ samples is then added to thebeginning of the truncated transmitted data block. This is shown in the Figure 3.6.The Rayleigh waveform is generated using Clarke’s model [9]. Complex Normalnoise samples, which are uncorrelated in the time domain, are passed through a Doppler35