% make_qam(M,N_s,sigma)% makes a sequence of N_s samples of M-QAM with variance sigma^2,% where M is of the form 4*N^2 (for integer N). % Copyright 1997-1998 Phil Schniterfunction s = make_qam(M,N_s,sigma) % a convenient quantity N = sqrt(M/4);					% M = 4N^2 % check if valid M (via checking if N is an integer) if N ~= floor(N),   error('M must be of the form 4*N^2 for integer N');  end % generate M-QAM with constellation points at +/-{1,3,5,7,etc.} s = 2*(floor(2*N*rand(1,N_s))-N+0.5) +...   j*2*(floor(2*N*rand(1,N_s))-N+0.5); % adjust variance  var_cur = 2/N*sum((1+2*[0:N-1]).^2);		% current variance s = s*(sigma/sqrt(var_cur));