How to save object in .mat file when object has private or protected properties
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john karli on 16 Sep 2021
I want to save the dataset but its not saving the exect file and giving me the following warning.
Warning: The helperModClassTestChannel System object has private or protected properties, but does not implement both the
saveObjectImpl and loadObjectImpl methods. The save, load, and clone methods may not copy the object exactly when it is
classdef helperModClassTestChannel < matlab.System
%helperModClassTestChannel Test channel for modulation classification
% CH = helperModClassTestChannel creates an channel System object, CH.
% This object adds multipath fading, clock offset effects, and white
% Gaussian noise to a framed signal.
% CH = helperModClassTestChannel(Name,Value) creates a channel object,
% CH, with the specified property Name set to the specified Value. You
% can specify additional name-value pair arguments in any order as
% The channel object uses the default MATLAB random stream. Reset the
% default stream for repeatable simulations. Type 'help RandStream' for
% more information.
% Step method syntax:
% Y = step(CH,X) adds multipath fading, clock offset effects, and white
% Gaussian noise to input X and returns the result in Y. The input X must
% be a double or single precision data type column vector. Each frame is
% impaired with an independent channel. The channel applies following
% impairments in the given order:
% 1) Add Rician multipath fading to input, X, based on PathDelays,
% AveragePathGains, KFactor, and MaximumDopplerShift settings. Channel
% path gains are regenerated for each frame, which provides independent
% path gain values for each frame.
% 2) Add clock offset effects.
% a) Frequency offset, which is determined by the clock offset (ppm)
% and the center frequency, as fOffset = -(C-1)*fc, where fc is the
% center frequency in Hz and C is the clock offset factor. clock offset
% factor, C, is calculated as C = (1+offset/1e6), where offset is the
% clock offset in ppm.
% b) Sampling offset, which is determined by the clock offset (ppm) and
% sampling rate, fs. This method first generates a clock offset value,
% offset, in ppm, based on the specified maximum clock offset and
% calculates the offset factor, C, as C = (1+offset/1e6), where offset
% is the clock offset in ppm. The signal is resampled using interp1
% function at a new sampling rate of C*fs.
% 3) Add Gaussian noise based on the specified SNR value. Channel object,
% CH, assumes that the input signal is normalized to unity power.
% System objects may be called directly like a function instead of using
% the step method. For example, y = step(obj, x) and y = obj(x) are
% helperModClassTestChannel methods:
% step - Add channel impairments to input signal (see above)
% release - Allow property value and input characteristics changes
% clone - Create a channel object with same property values
% isLocked - Locked status (logical)
% reset - Reset channel object
% helperModClassTestChannel properties:
% SNR - SNR (dB)
% CenterFrequency - Center frequency (Hz)
% SampleRate - Input signal sample rate (Hz)
% PathDelays - Discrete path delay vector (s)
% AveragePathGains - Average path gain vector (dB)
% KFactor - Rician K-factor (linear scale)
% MaximumDopplerShift - Maximum Doppler shift (Hz)
% MaximumClockOffset - Maximum clock offset (ppm)
% See also ModulationClassificationWithDeepLearningExample.
% Copyright 2018 The MathWorks, Inc.
%SNR SNR (dB)
% Specify the SNR value in decibels. Set this property to a numeric,
% real scalar. The default is 20 dB. This property is tunable.
SNR = 15
%CenterFrequency Center frequency (Hz)
% Specify the center frequency as a double precision nonnegative
% scalar. The default is 2.4 GHz. Center frequency value is used to
% calculate expected frequency offset in the received signal based on
% the maximum clock offset value. This property is tunable.
CenterFrequency = 2.4e9
%SampleRate Sample rate (Hz)
% Specify the sample rate of the input signal in Hz as a double
% precision, real, positive scalar. The default is 1 Hz.
SampleRate = 1
%PathDelays Discrete path delays (s)
% Specify the delays of the discrete paths in seconds as a double
% precision, real, scalar or row vector. When PathDelays is a scalar,
% the channel is frequency-flat; When PathDelays is a vector, the
% channel is frequency-selective. The default is 0.
PathDelays = 0
%AveragePathGains Average path gains (dB)
% Specify the average gains of the discrete paths in dB as a double
% precision, real, scalar or row vector. AveragePathGains must have
% the same size as PathDelays. The default is 0.
AveragePathGains = 0
% Specify the K factor of a Rician fading channel as a double
% precision, real, positive scalar. The first discrete path is a
% Rician fading process with a Rician K-factor of KFactor and the
% remaining discrete paths are independent Rayleigh fading processes.
% The default is 3.
KFactor = 3
%MaximumDopplerShift Maximum Doppler shift (Hz)
% Specify the maximum Doppler shift for the path(s) of the channel in
% Hz as a double precision, real, nonnegative scalar. It applies to
% all the paths of the channel. When MaximumDopplerShift is 0, the
% channel is static for the entire input and you can use the reset
% method to generate a new channel realization. The
% MaximumDopplerShift must be smaller than SampleRate/10 for each
% path. The default is 0.
MaximumDopplerShift = 0
%MaximumClockOffset Maximum clock offset (ppm)
% Specify the maximum clock offset in ppm as a double precision,
% real, non-negative scalar. Channel generates a uniformly
% distributed random clock offset value between -MaximumClockOffset
% and MaximumClockOffset for each frame. This clock offset value is
% used to calculate frequency and timing offset for the current
% frame. The default is 0.
MaximumClockOffset = 0
properties(Access = private)
C % 1+(ppm/1e6)
function obj = helperModClassTestChannel(varargin)
% Support name-value pair arguments when constructing object
methods(Access = protected)
obj.MultipathChannel = comm.RicianChannel(...
'SampleRate', obj.SampleRate, ...
'PathDelays', obj.PathDelays, ...
'AveragePathGains', obj.AveragePathGains, ...
'KFactor', obj.KFactor, ...
obj.FrequencyShifter = comm.PhaseFrequencyOffset(...
function y = stepImpl(obj,x)
% Add channel impairments
yInt1 = addMultipathFading(obj,x);
yInt2 = addClockOffset(obj, yInt1);
y = addNoise(obj, yInt2);
function out = addMultipathFading(obj, in)
%addMultipathFading Add Rician multipath fading
% Y=addMultipathFading(CH,X) adds Rician multipath fading effects
% to input, X, based on PathDelays, AveragePathGains, KFactor, and
% MaximumDopplerShift settings. Channel path gains are regenerated
% for each frame, which provides independent path gain values for
% each frame.
% Get new path gains
% Pass input through the new channel
out = obj.MultipathChannel(in);
function out = addClockOffset(obj, in)
%addClockOffset Add effects of clock offset
% Y=addClockOffset(CH,X) adds effects of clock offset. Clock offset
% has two effects on the received signal: 1) Frequency offset,
% which is determined by the clock offset (ppm) and the carrier
% frequency; 2) Sampling time drift, which is determined by the
% clock offset (ppm) and sampling rate. This method first generates
% a clock offset value in ppm, based on the specified maximum clock
% offset and calculates the offset factor, C, as
% C = (1+offset/1e6), where offset is the clock offset in ppm.
% applyFrequencyOffset and applyTimingDrift add frequency offset
% and sampling time drift to the signal, respectively.
% Determine clock offset factor
maxOffset = obj.MaximumClockOffset;
clockOffset = (rand() * 2*maxOffset) - maxOffset;
obj.C = 1 + clockOffset / 1e6;
% Add frequency offset
outInt1 = applyFrequencyOffset(obj, in);
% Add sampling time drift
out = applyTimingDrift(obj, outInt1);
function out = applyFrequencyOffset(obj, in)
%applyFrequencyOffset Apply frequency offset
% Y=applyFrequencyOffset(CH,X) applies frequency offset to input,
% X, based on the clock offset for the current frame and center
% fOffset = -(C-1)*fc, where fc is center frequency in Hz
% y = x .* exp(1i*2*pi*fOffset*t)
obj.FrequencyShifter.FrequencyOffset = ...
out = obj.FrequencyShifter(in);
function out = applyTimingDrift(obj, in)
%applyTimingDrift Apply sampling time drift
% Y=applyTimingDrift(CH,X) applies sampling time drift to
% input, X, based on the clock offset for the current frame and
% specified sampling rate, Fs. X is resampled at C*Fs Hz using
% linear interpolation.
originalFs = obj.SampleRate;
x = (0:length(in)-1)' / originalFs;
newFs = originalFs * obj.C;
xp = (0:length(in)-1)' / newFs;
out = interp1(x, in, xp);
function out = addNoise(obj, in)
%addNoise Add Gaussian noise
% Y=addNoise(CH,X) adds Gaussian noise to input, X, based on the
% specified SNR value. Channel object, CH, assumes that the input
% signal is normalized to unity power.
out = awgn(in,obj.SNR);
function s = infoImpl(obj)
% Get channel delay from fading channel object delay
mpInfo = info(obj.MultipathChannel);
% Calculate maximum frequency offset
maxClockOffset = obj.MaximumClockOffset;
maxFreqOffset = (maxClockOffset / 1e6) * obj.CenterFrequency;
% Calculate maximum timing offset
maxClockOffset = obj.MaximumClockOffset;
maxSampleRateOffset = (maxClockOffset / 1e6) * obj.SampleRate;
s = struct('ChannelDelay', ...
'MaximumFrequencyOffset', maxFreqOffset, ...
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