function [snrlow, snrhigh] = capsnr(rate)
%CAPSNR - 
%  [SNRLOW, SNRHIGH] = CAPSNR(CAP) calculates upper (SNRHIGH) and lower 
%  (SNRLOW) bounds on the SNR required (in dB) to achieve the capacity
%  given by CAP for the binary input AWGN channel.
%
%  For example, to calculate the minimum SNR required to achieve capacity
%  for a binary rate R code (R<1), use [SNRLOW, SNRHIGH] = CAPSNR(R)
%

%  (C) Mark Shane (shane@ee.ucla.edu) and Richard Wesel (wesel@ee.ucla.edu)
%  University of California, Los Angeles

snrlow  = fzero('bincapup',0,optimset('disp','off'),rate);
snrhigh = fzero('bincaplo',0,optimset('disp','off'),rate);

function y = Q(x)
y = 0.5*erfc(x/sqrt(2));