| Communications Toolbox | |
The procedure below describes how you would typically implement the semianalytic technique using the semianalytic function:
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.
Invoke the semianalytic function using the txsig and rxsig data from earlier steps. Specify a receive filter as a pair of input arguments, unless you want to use the function's default filter. The function filters rxsig and then determines the error probability of each received signal point by analytically applying the Gaussian noise distribution to each point. The function 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 the function converts it to a bit error rate, typically by assuming Gray coding. The function returns the bit error rate (or, in the case of DQPSK modulation, an upper bound on the bit error rate).
| | When to Use the Semianalytic Technique | Example: Using the Semianalytic Technique | |
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