% calculate the upper bound () of the minimal distance for a given number of points.
% Note: for N antipodal symmetric samples, use CoveringRadiusUpperBound(2*N).
%
% USAGE:
% ub = CoveringRadiusUpperBound(N)
%
% INPUT
% N : an integer number.
%
%
% OUTPUT
% up : an upper bound (spherical distance in radian)
%
% References:
% 1. http://mathworld.wolfram.com/SphericalCode.html
% 2. "Single- and Multiple-Shell Uniform Sampling Schemes for Diffusion MRI Using Spherical Codes",
% Jian Cheng, Dinggang Shen, Pew-Thian Yap, Peter J. Basser, IEEE Transactions on Medical Imaging, 2017.
% 3. "Designing Single- and Multiple-Shell Sampling Schemes for Diffusion MRI Using Spherical Code",
% Jian Cheng, Dinggang Shen, Pew-Thian Yap, MICCAI 2014.
%
%
% Copyright (c) 2014, Jian Cheng <jian.cheng.1983@gmail.com>
%
