function y = wgn(varargin)
%WGN Generate white Gaussian noise.
% Y = WGN(M,N,P) generates an M-by-N matrix of white Gaussian noise. P
% specifies the power of the output noise in dBW. The unit of measure for
% the output of the wgn function is Volts. For power calculations, it is
% assumed that there is a load of 1 Ohm.
%
% Y = WGN(M,N,P,IMP) specifies the load impedance in Ohms.
%
% Y = WGN(M,N,P,IMP,S) uses S, which is a random stream handle, to
% generate random noise samples with RANDN. This syntax is useful to
% generate repeatable outputs. Type 'help RandStream' for more
% information.
%
% Y = WGN(M,N,P,IMP,STATE) resets the state of RANDN to STATE. This usage
% is deprecated and may be removed in a future release.
%
% Additional flags that can follow the numeric arguments are:
%
% Y = WGN(..., POWERTYPE) specifies the units of P. POWERTYPE can be
% 'dBW', 'dBm' or 'linear'. Linear power is in Watts.
%
% Y = WGN(..., OUTPUTTYPE); Specifies the output type. OUTPUTTYPE can be
% 'real' or 'complex'. If the output type is complex, then P is divided
% equally between the real and imaginary components.
%
% Example 1:
% % To generate a 1024-by-1 vector of complex noise with power
% % of 5 dBm across a 50 Ohm load, use:
% Y = wgn(1024, 1, 5, 50, 'dBm', 'complex')
%
% Example 2:
% % To generate a 256-by-5 matrix of real noise with power
% % of 10 dBW across a 1 Ohm load, use:
% Y = wgn(256, 5, 10, 'real')
%
% Example 3:
% % To generate a 1-by-10 vector of complex noise with power
% % of 3 Watts across a 75 Ohm load, use:
% Y = wgn(1, 10, 3, 75, 'linear', 'complex')
%
% See also RANDN, AWGN.
% Copyright 1996-2011 The MathWorks, Inc.
% --- Initial checks
error(nargchk(3,7,nargin,'struct'));
% --- Value set indicators (used for the strings)
pModeSet = 0;
cplxModeSet = 0;
% --- Set default values
pMode = 'dbw';
imp = 1;
cplxMode = 'real';
seed = [];
% --- Placeholders for the numeric and string index values
numArg = [];
strArg = [];
% --- Identify string and numeric arguments
% An empty in position 4 (Impedance) or 5 (Seed) are considered numeric
isStream = false;
for n=1:nargin
if(isempty(varargin{n}))
switch n
case 4
if(ischar(varargin{n}))
error(message('comm:wgn:InvalidDefaultImp'));
end;
varargin{n} = imp; % Impedance has a default value
case 5
if(ischar(varargin{n}))
error(message('comm:wgn:InvalidNumericInput'));
end;
varargin{n} = []; % Seed has no default
otherwise
varargin{n} = '';
end;
end;
% --- Assign the string and numeric vectors
if(ischar(varargin{n}))
strArg(size(strArg,2)+1) = n; %#ok<AGROW>
elseif(isnumeric(varargin{n}))
numArg(size(numArg,2)+1) = n; %#ok<AGROW>
elseif(isa(varargin{n},'RandStream'))
numArg(size(numArg,2)+1) = n; %#ok<AGROW>
isStream = true;
else
error(message('comm:wgn:InvalidArg'));
end;
end;
% --- Build the numeric argument set
switch(length(numArg))
case 3
% --- row is first (element 1), col (element 2), p (element 3)
if(all(numArg == [1 2 3]))
row = varargin{numArg(1)};
col = varargin{numArg(2)};
p = varargin{numArg(3)};
else
error(message('comm:wgn:InvalidSyntax'))
end;
case 4
% --- row is first (element 1), col (element 2), p (element 3), imp (element 4)
%
if(all(numArg(1:3) == [1 2 3]))
row = varargin{numArg(1)};
col = varargin{numArg(2)};
p = varargin{numArg(3)};
imp = varargin{numArg(4)};
else
error(message('comm:wgn:InvalidSyntax'))
end;
case 5
% --- row is first (element 1), col (element 2), p (element 3), imp (element 4), seed (element 5)
if(all(numArg(1:3) == [1 2 3]))
row = varargin{numArg(1)};
col = varargin{numArg(2)};
p = varargin{numArg(3)};
imp = varargin{numArg(4)};
seed = varargin{numArg(5)};
else
error(message('comm:wgn:InvalidSyntax'));
end;
otherwise
error(message('comm:wgn:InvalidSyntax'));
end;
% --- Build the string argument set
for n=1:length(strArg)
switch lower(varargin{strArg(n)})
case {'dbw' 'dbm' 'linear'}
if(~pModeSet)
pModeSet = 1;
pMode = lower(varargin{strArg(n)});
else
error(message('comm:wgn:TooManyPowerTypes'));
end;
case {'db'}
error(message('comm:wgn:InvalidPowerType'));
case {'real' 'complex'}
if(~cplxModeSet)
cplxModeSet = 1;
cplxMode = lower(varargin{strArg(n)});
else
error(message('comm:wgn:TooManyOutputTypes'));
end;
otherwise
error(message('comm:wgn:InvalidArgOption'));
end;
end;
% --- Arguments and defaults have all been set, either to their defaults or by the values passed in
% so, perform range and type checks
% --- p
if(isempty(p))
error(message('comm:wgn:InvalidPowerVal'));
end;
if(any([~isreal(p) (length(p)>1) (isempty(p))]))
error(message('comm:wgn:InvalidPowerVal'));
end;
if(strcmp(pMode,'linear'))
if(p<0)
error(message('comm:wgn:NegativePower'));
end;
end;
% --- Dimensions
if(any([isempty(row) isempty(col) ~isscalar(row) ~isscalar(col)]))
error(message('comm:wgn:InvalidDims'));
end;
if(any([(row<=0) (col<=0) ~isreal(row) ~isreal(col) ((row-floor(row))~=0) ((col-floor(col))~=0)]))
error(message('comm:wgn:InvalidDims'));
end;
% --- Impedance
if(any([~isreal(imp) (length(imp)>1) (isempty(imp)) any(imp<=0)]))
error(message('comm:wgn:InvalidImp'));
end;
% --- Seed
if(~isempty(seed))
if ~isStream
validateattributes(seed, {'double', 'RandStream'}, ...
{'real', 'scalar', 'integer'}, 'WGN', 'S');
end
end;
% --- All parameters are valid, so no extra checking is required
switch lower(pMode)
case 'linear'
noisePower = p;
case 'dbw'
noisePower = 10^(p/10);
case 'dbm'
noisePower = 10^((p-30)/10);
end;
% --- Generate the noise
if(~isempty(seed))
if isStream
hStream = seed;
else
hStream = RandStream('shr3cong', 'Seed', seed);
end
func = @(a,b)randn(hStream,a,b);
else
func = @(a,b)randn(a,b);
end;
if(strcmp(cplxMode,'complex'))
y = (sqrt(imp*noisePower/2))*(func(row, col)+1i*func(row, col));
else
y = (sqrt(imp*noisePower))*func(row, col);
end;
