function s = PAM (M,N_s,sigma,sd)% ==================================================================% function s = PAM (M,N_s,sigma,sd)%% creates a sequence of N_s samples of M-PAM with variance sigma^2,% where M is an even integer.%% ---- Downloaded from the SPIB (Rice University) ----% ================================================================== % check if valid M  if M/2 ~= floor(M/2),   error('M must be an even integer');  end % generate M-PAM with constellation points at +/-{1,3,5,7,etc.} rand('seed',sd);  s = 2*(floor(M*rand(1,N_s))-M/2+0.5);  % adjust variance  var_cur = 2/M*sum((1+2*[0:M/2-1]).^2);		% current variance s = s*(sigma/sqrt(var_cur));