【正文】 isions. both are gated by the data burst randomizer signal. The Error Rate Calculation block pares the transmitted bits and the received decisions, and produces the raw (that is, without channel coding) bit error rate. This rate is displayed in the model window during the simulation. Visible Results of the Demo The demo shows the raw bit error rate (BER) for the reverse channel. The BER depends on the channel conditions and the number of rake receiver fingers active. As the signaltonoise ratio or the channel conditions are changed, the effect of these on the raw BER can be seen by running the model for these different conditions. Changing Demo Parameters This section suggests some ways that you can alter the parameters in the demo after you understand the model. The simulation duration in this demo is set to 2 seconds. Because the frame duration in IS95A is second, this model processes 100 frames. This gives a sufficient time for the BER measurements to converge at reasonable SNR settings. To run the simulation for a longer or shorter time, select Parameters from the Simulation menu and change the Stop time to times the number of frames you want to simulate. To change the data rate, doubleclick on the Data Source icon. Then doubleclick on the Mobile Station Transmitter Data Rate icon and change the Data Rate parameter. Choices are Full, Half, Quarter, and OneEighth rates. To change the long code mask, doubleclick on the Spreading and Modulation icon. Then doubleclick on the IS95A Rev Ch Walsh Modulation and Spreading icon, and enter a new value for the Long code mask parameter. This parameter can be any nonnegative integer less than 2421. The block uses the binary representation of this number to generate the code. The value for the Long code mask parameter is also required in the IS95A Rev Ch Detector library block. Experiment with using the same or different values in the two blocks. This illustrates why the receiver does not demodulate the signal not intended for it, although they are transmitted in the same frequency band. For more information, see the IS95A specification. To change the Doppler frequency, doubleclick on the Rayleigh Multipath and AWGN Channel icon. Then doubleclick on the Multipath Rayleigh Fading icon, and change the Doppler frequency parameter. Reasonable Doppler frequencies representative of the cellular mobile environment are in the 0 to 200 Hz range. Change the Es/No parameter in the AWGN Channel block in the channel subsystem. The detection performance improves with an increase in the signaltonoise ratio. To run the simulation with different seeds, change the Initial seed parameters in one or more of these: Random Data Frame Generator Multipath Rayleigh Fading AWGN Channel The first item is inside the Data Source subsystem and the last two blocks are inside the Rayleigh Multipath and AWGN Channel subsystem. Channel Paths and Rake Fingers. Changes in the number or delay of fading channel