This model shows the modeling of channel impairments such as timing phase offset, carrier frequency, and phase offsets for a minimum shift keying (MSK) signal. The model also shows the use of blocks from the Synchronization library to recover the signal.
The example models an MSK transmitted signal undergoing channel impairments, including these components:
1. An MSK signal source that uses the Bernoulli Binary GeneratorBernoulli Binary Generator block to output equiprobable symbols and modulates the symbols using an MSK Modulator BasebandMSK Modulator Baseband block.
3. Signal recovery, consisting of
Carrier frequency recovery using the delay and multiply methods
5. Blocks that compute and display the system's bit error rate (BER).
When you load the model, it also initializes some parameters that several blocks share.
When you run the simulation, the displays show the estimated values for the impairments as well as the BER metrics. In particular, the display labeled BER Metrics shows a three-element vector containing the calculated bit error rate (BER), the number of errors observed, and the number of bits processed.
You can view the MSK signal via the Discrete-Time Scatter Plot ScopeDiscrete-Time Scatter Plot Scope blocks at the different stages. This provides a compelling visual rendition of the recovery algorithms in action, especially as you turn the algorithms on and off.
Scatter plot of received signal:
Scatter plot of signal after timing and carrier frequency recovery:
Scatter plot of signal after carrier phase recovery:
You can also reset the BER computation after the signal has reached a steady state.
The example is designed so that you can vary the impairments independently while the simulation is running. You can also use the toggle switches to turn the recovery schemes on and off while the simulation is running, and then see the effects on the scatter plots.