This model shows how to process complex data in transmission signals of a communication system.

**What Is Frame Synchronization?**

In communication systems, frame synchronization is a method
of finding valid data in a transmission that consists of *data
frames*. To aid frame synchronization, the transmitter inserts
a fixed data pattern at the start of each data frame to mark the start
of valid data. The receiver searches for the fixed pattern in each
data frame and achieves frame synchronization when the correlation
between the input data and the fixed pattern is high.

**Model Structure**

The model contains the following components.

The C chart contains the following states, transitions, and MATLAB^{®} functions.

Key characteristics of the C chart include:

Complex input and output signals

The chart accepts a complex input signal

`I/Q`

. After synchronizing the data frame, the chart stores the valid data in a complex output signal`frame`

.Complex multiplication

The output signal

`frame`

is a vector of complex products between each valid data point and the phase angle of the carrier wave.Indexing into a complex vector

The chart uses the

`temporalCount`

operator to index into the complex vector`frame`

.MATLAB functions with complex arguments

The MATLAB functions

`correlate`

and`get_carrier_phase`

have complex input and output arguments.

**Simulation Results**

The `sf_frame_sync_controller`

model does not
produce simulation results. The purpose of this example is to explain
how to process complex data in a chart.

**How the C Chart Works**

The chart calculates the correlation between the input signal `I/Q`

and
the fixed data pattern `trainSig`

. You define `trainSig`

by
writing and running a MATLAB script before you simulate the model.

If the correlation exceeds 50 percent, frame synchronization occurs. The chart stores 220 valid data points in the complex vector

`frame`

.If the correlation stays below 50 percent after the chart has evaluated 300 data points, the frame synchronization algorithm resets.

Stage | Summary | Details |
---|---|---|

1 | Activation of the frame synchronization algorithm | When the chart wakes up, the state |

2 | Calculation of correlation between the input signal and the fixed pattern | The MATLAB function |

3 | Calculation of absolute value of the complex correlation | The MATLAB function |

4 | Identification of valid data in a frame | If If |

5 | Storage of valid data in a complex vector | When the correlation is high, the state The MATLAB function |

6 | Output of valid frame data | After collecting 220 data points, the chart outputs the
vector |

7 | Restart of the frame synchronization algorithm | The state |

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