This model shows symbol timing phase recovery for an 8-PSK modulated and filtered signal that is transmitted over a channel whose delay varies.
The example models an 8-PSK transmitted signal, including these components:
An M-PSK Modulator BasebandM-PSK Modulator Baseband block followed by a Raised Cosine Transmit FilterRaised Cosine Transmit Filter block. The first block modulates the random signal, while the second block upsamples and applies pulse shaping to the modulated signal for transmission.
When you run the simulation, the Display blocks show how closely the Gardner method tracks the introduced delay in the link. The block labeled SER Display shows the error performance via three numbers: the calculated SER, the number of errors observed, and the number of symbols processed.
At the end of the simulation, a plot shows the actual delay and the estimated delay for sets of 100 symbols. The piecewise constant curve is the actual delay, while the less regular curve is the estimated delay. From this plot, you can see the tracking behavior of the method.
The Model Parameters block makes it easy for you to vary certain parameters in the model. Here are some ways that you can modify the model to learn more about its components or about timing recovery:
Vary the transmit and receive filter characteristics, such as Rolloff factor or Group delay.
Vary the step size of the timing recovery method (that is, the Error update gain parameter of the Gardner Timing Recovery block).
Vary the noise level in the AWGN.
Vary the simulation frame size.
You can also try using a different modulation scheme, such as QPSK or 16-QAM. To switch from PSK to another modulation type, you would not only replace the modulator and demodulator blocks, but also change the Alphabet size parameter in the Model Parameters block.