| Communications Toolbox | |
The procedure below describes how you would typically implement the semianalytic technique using BERTool:
Generate a message signal containing at least ML symbols, where M is the alphabet size of the modulation and L is the length of the impulse response of the channel, in symbols. A common approach is to start with an augmented binary pseudonoise (PN) sequence of total length (log2M)ML. An augmented PN sequence is a PN sequence with an extra zero appended, which makes the distribution of ones and zeros equal.
Modulate a carrier with the message signal using baseband modulation. Supported modulation types are listed on the reference page for semianalytic.
Filter the modulated signal with a transmit filter. This filter is often a square-root raised cosine filter, but you can also use a Butterworth, Bessel, Chebyshev type 1 or 2, elliptic, or more general FIR or IIR filter. Store the result of this step as txsig for later use.
Run the filtered signal through a noiseless channel. This channel can include multipath fading effects, phase shifts, amplifier nonlinearities, quantization, and additional filtering, but it must not include noise. Store the result of this step as rxsig for later use.
On the Semianalytic panel of BERTool, enter parameters as in the table below.
| Parameter Name | Meaning |
|---|---|
| Eb/No range | A vector that lists the values of Eb/N0 for which you want to collect BER data. The value in this field can be a MATLAB expression or the name of a variable in the MATLAB workspace. |
| Modulation type | These parameters describe the modulation scheme that you used earlier in this procedure. |
| Modulation order | |
| Differential encoding | This check box, which is visible and active for MSK and PSK modulation, enables you to choose between differential and nondifferential encoding. |
| Samples per symbol | The number of samples per symbol in the transmitted signal. This value is also the sampling rate of the transmitted and received signals, in Hz. |
| Transmitted signal | The txsig signal that you generated earlier in this procedure |
| Received signal | The rxsig signal that you generated earlier in this procedure |
| Numerator | Coefficients of the receiver filter that BERTool applies to the received signal |
| Denominator |
Note Consistency among the values in the GUI is important. For example, if the signal referenced in the Transmitted signal field was generated using DPSK and you set Modulation type to MSK then the results might not be meaningful. |
Click Plot.
After you click Plot, BERTool performs these tasks:
Filters rxsig and then determines the error probability of each received signal point by analytically applying the Gaussian noise distribution to each point. BERTool averages the error probabilities over the entire received signal to determine the overall error probability. If the error probability calculated in this way is a symbol error probability, then BERTool converts it to a bit error rate, typically by assuming Gray coding. (If the modulation type is DQPSK or cross QAM, the result is an upper bound on the bit error rate rather than the bit error rate itself.)
Enters the resulting BER data in the data viewer of the BERTool window.
Plots the resulting BER data in the BER Figure window.
| | Example: Using the Semianalytic Panel in BERTool | Running MATLAB Simulations | |
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