comm.CCDF

Measure complementary cumulative distribution function

Description

The comm.CCDF object measures the probability that the instantaneous power of the input signal being a specified level above its average power.

To measure complementary cumulative distribution of a signal:

1. Define and set up your CCDF object. See Construction .

2. Call step to measure complementary cumulative distribution according to the properties of comm.CCDF. The behavior of step is specific to each object in the toolbox.

Note

Starting in R2016b, instead of using the step method to perform the operation defined by the System object™, you can call the object with arguments, as if it were a function. For example, y = step(obj,x) and y = obj(x) perform equivalent operations.

Construction

ccdf = comm.CCDF creates a complementary cumulative distribution function measurement (CCDF) System object, ccdf, that measures the probability of a signal's instantaneous power to be a specified level above its average power.

ccdf = comm.CCDF(Name,Value) creates a CCDF object, ccdf, with each specified property set to the specified value. You can specify additional name-value pair arguments in any order as (Name1,Value1,...,NameN,ValueN).

Properties

NumPoints	Number of CCDF points Specify the number of CCDF points that the object calculates. This property requires a numeric, positive, integer scalar. The default is 1000. Use this property with the MaximumPowerLimit property to control the size of the histogram bins. The object uses these bins to estimate CCDF curves. This controls the resolution of the curves. All input channels must have the same number of CCDF points.
MaximumPowerLimit	Maximum expected input signal power Maximum expected input signal power limit for each input channel, specified as a scalar or row vector with length equal to the number of input channels. The default is 50. This property is expected to have the same units as the PowerUnits property. When you set this property to a scalar, the object assumes that the signals in all input channels have the same expected maximum power. When you set this property to a row vector, the object assumes that the i-th element of the vector is the maximum expected power for the signal at the i-th input channel. For each input channel, the object obtains CCDF results by integrating a histogram of instantaneous input signal powers. The object sets the bins of the histogram so that the last bin collects all power occurrences that are equal to, or greater than the power that you specify in this property. The object issues a warning if any input signal exceeds its specified maximum power limit. Use this property with the NumPoints property to control the size of the histogram bins that the object uses to estimate CCDF curves (such as control the resolution of the curves).
PowerUnits	Power units Specify the power measurement units as one of dBm | dBW | Watts. The default is dBm. The step method outputs power measurements in the units specified in the PowerUnits property. When you set this property to dBm or dBW, the step method outputs relative power values in a dB scale. When you set this property to Watts, the step method outputs relative power values in a linear scale. When you call the step method, the object assumes that the units of MaximumPowerLimit have the same value you specified in the PowerUnits property.
AveragePowerOutputPort	Enable average power measurement output When you set this property to true, running the object returns the running average power measurements. The default is false.
PeakPowerOutputPort	Enable peak power measurement output When you set this property to true, running the object returns the peak power measurements. The default is false.
PAPROutputPort	Enable PAPR measurement output When you set this property to true, running the object returns the peak-to-average-power measurements. The default is false.

Methods

getPercentileRelativePower	Get relative power value for given percentile
getProbability	Get the probability for a given relative power value
plot	Plot CCDF curves
step	Measure complementary cumulative distribution function

Common to All System Objects
release	Allow System object property value changes
reset	Reset internal states of System object

Examples

Obtain CCDF curves for 16-QAM and QPSK signals

Create a CCDF System object and specify that it output average power and peak power measurements.

ccdf = comm.CCDF('AveragePowerOutputPort',true, ...
    'PeakPowerOutputPort',true);

Generate 16-QAM and QPSK modulated signals.

qamTxSig = qammod(randi([0 15],20e3,1),16,'UnitAveragePower',true);
qpskTxSig = pskmod(randi([0 3],20e3,1),4,pi/4);

Pass the signals through an AWGN channel.

qamRxSig = awgn(qamTxSig,15);
qpskRxSig = awgn(qpskTxSig,15);

Measure the CCDF of the two waveforms. Plot the CCDF using the plot method of comm.CCDF.

[CCDFy,CCDFx,AvgPwr,PeakPwr] = ccdf([qamRxSig qpskRxSig]);

plot(ccdf)
legend('16-QAM','QPSK')

Extended Capabilities

C/C++ Code Generation

Generate C and C++ code using MATLAB® Coder™.

Usage notes and limitations:

See System Objects in MATLAB Code Generation (MATLAB Coder).