Documentation

comm.CCDF

Measure complementary cumulative distribution function

Description

The CCDF object measures the probability of a signal's instantaneous power to be 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

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

H = comm.CCDF(Name,Value) creates a CCDF object, H, 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 Specify the maximum expected input signal power limit for each input channel. The default is 50. Set this property to a numeric scalar or row vector length equal to the number of input channels. 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 length equal to the number of input channels, 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. When you call the step method, the object displays the value of this property is in the units that you specify in the PowerUnits property. 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, the step method outputs running average power measurements. The default is false. PeakPowerOutputPort Enable peak power measurement output When you set this property to true, the step method outputs running peak power measurements. The default is false. PAPROutputPort Enable PAPR measurement output When you set this property to true, the step method outputs running peak-to-average-power measurements. The default is false.

Methods

 getPercentileRelativePower Get relative power value for a given probability getProbability Get the probability for a given relative power value plot Plot CCDF curves reset Reset states of CCDF measurement object step Measure complementary cumulative distribution function
Common to All System Objects
release

Allow System object property value changes

Examples

expand all

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') 