Primitives that are specific to digital communications functions, such as pulse shapers, speech coders, and QAM encoders.
The limited set of communication primitives that have been developed are summarized below. Many of these are modules, and should be viewed as examples of systems that a user can create.
Sources and pulse shapers
- Produce "0" with probability ProbOfZero, else produce "1".
- Produce a cosine waveform whose energy is normalized with respect to Amplitude. It is used in simulations for binary frequency shift keying (BFSK) demonstrations. This module differs from the cosine primitive which computes the cosine of the input signal (see Nonlinear primitives for more information on the cosine primitive).
- This module uses the RaisedCosine primitive to implement an FIR filter for complex inputs with a raised cosine or square-root raised cosine transfer function.
- Binary to non-return-to-zero signaling converter
- Encode an input bit stream into a 4-QAM (or 4-PSK) complex symbol sequence.
- Encode an input bit stream into a 16-QAM complex symbol sequence.
- Scramble the input bit sequence using a feedback shift register. The taps of the feedback shift register are given by the polynomial parameter, which should be a positive integer. The n-th bit of this integer indicates whether the n-th tap of the delay line is fed back. The low-order bit is called the 0-th bit, and should always be set. The next low-order bit indicates whether the output of the first delay should be fed back, etc. The default polynomial is an octal number defining the V.22bis scrambler.
- Frame synchronized direct-sequence spreader.
- Binary frequency shift keying (BFSK) transmitter.
- Simple 2-level pulse amplitude modulation (PAM) transmitter.
- Simple 4-level pulse amplitude modulation (PAM) transmitter.
- Binary 2-level phase shift keying (BPSK) Modulator.
- Direct-sequence spreader (that is, spread-spectrum transmitter).
- Descramble the input bit sequence using a feedback shift register. The taps of the feedback shift register are given by the polynomial parameter. This is a self-synchronizing descrambler that will exactly reverse the operation of the Scrambler primitive if the polynomials are the same. The low-order bit of the polynomial should always be set.
- This module implements a phase splitter, in which the real-valued input signal is converted to an (approximate) analytic signal. The signal is filtered by the HilbertTransform primitive to generate the imaginary part of the output, while the real part is obtained by creating a matching delay.
- This module implements a slicer (decision device) for a 4-QAM (or equivalently, 4-PSK) signal. The output decision is a complex number with +1 or -1 for each of the real or imaginary parts.
- This module implements a slicer (decision device) for a 16-QAM complex signal. The output decision is a complex number with +1, -1, +3, or -3 for each of the real or imaginary parts.
- Shifts the phase of the input signal on the in input by the shift value on the shift input. The phase shifting is implemented by filtering the input signal with a complex FIR filter to convert it into an analytic signal and the complex result is modulated by a complex exponential. If the shift value is time varying, then its slope determines the instantaneous frequency shift.
- Binary frequency shift keying (BFSK) Receiver.
- Simple 2-level pulse amplitude modulation (PAM) receiver.
- Simple 4-level pulse amplitude modulation (PAM) receiver.
- Binary pulse shift keying (BPSK) demodulator.
- Direct sequence receiver.
- Model an additive Gaussian white noise channel with optional linear distortion.
Baseband equivalent channel.
- Impose frequency offset and/or phase jitter on a signal in order to model channels, such as telephone channels, that suffer these impairments.
- A simple channel model with additive Gaussian white noise.
Generate second and third harmonic distortion by squaring and cubing the signal, and adding the results in controlled proportion to the original signal.
- Simulate impairments commonly found on a telephone channel, including additive Gaussian noise, linear and nonlinear distortion, frequency offset, and phase jitter.