matlab_通信系统的信道的仿真

function y = buffer_update(h, x); %BUFFER_UPDATE Buffer update. % h - Buffer object % x - Input signal (length x numchannels) % y - Output signal (when buffer flushed; otherwise []) % Copyright 1996-2007 The MathWorks, Inc. % $Revision: 1.1.6.2 $ $Date: 2007/09/14 15:58:04 $ % This update method will flush the buffer when it becomes full. % Check number of arguments. error(nargchk(2, 2, nargin,'struct')); % Check input signal is numeric. if ~isnumeric(x) error('comm:channel:buffer:buffer_update:inputNumeric', ... 'Input signal must be numeric.'); end % Input signal dimensions. [Lx, nChans] = size(x); % Begin assuming no output. y = zeros(0, nChans); % If buffer disabled or have no input signal, no operation required. if ~h.Enable || Lx==0, return; end % Buffer size, downsampling, and indices. LB = h.BufferSize; KR = h.DownsampleFactor; % Downsampling not yet supported. idxCurrent = h.IdxNext; idxNext = idxCurrent + Lx; nOverLength = idxNext - LB; % Flush buffer only when it becomes full or will overflow. if nOverLength>0 % Reset next buffer index if buffer full or will overflow. % Check that input is not too long for buffer (else would lose samples). idxNext = nOverLength; if idxNext>LB error('comm:channel:buffer:buffer_update:BufferOverflow','Input signal too long for buffer.'); end % Fill up buffer. idx = idxCurrent:LB; L1 = length(idx); h.Buffer(idx, :) = x(1:L1, :); % Flush and reset buffer. y = flush(h); % Fill buffer with remaining input samples. idx = 1:idxNext-1; h.Buffer(idx, :) = x(L1+1:end, :); else % Continue to fill buffer. idx = idxCurrent-1+(1:Lx); h.Buffer(idx, :) = x; end h.IdxNext = idxNext; h.NumNewSamples = Lx; h.NumSamplesProcessed = h.NumSamplesProcessed + h.NumNewSamples;