% Erlang B plotting routine
%
% based on Ted Rappaport's Wireless text ... page 560 (equation A.28)
%
% by Dr. Thad B. Welch, PE {t.b.welch@ieee.org}
%
% 6 September 2001

N = 500;                % number of points calculated
A = logspace(-3,3,N);   % x-axis vector (0.001 to 10)
C = [1:10 15:5:50 60:10:100];

for index = 1:23 % 10        % number of channels.  Each "channel" creates a new curve on the graph
    denom = zeros(1, N);
    
    for n = 0:C(index)
        denom = denom + (A.^n)/factorial(n);
    end

    Pblock = ((A.^C(index))/factorial(C(index)))./denom;
    if (C(index) == 1)
        loglog(A,Pblock,'r')
        hold on
    elseif (C(index) == 15)
        loglog(A,Pblock,'r')
    elseif (C(index) == 60)
        loglog(A,Pblock,'r')
    else
        loglog(A,Pblock,'b')
    end
end    

grid
axis([A(1) A(N) 0.001 1])
title('Plot of the Erlang B Distribution')
xlabel('A, traffic intensity in Erlangs')
ylabel('P_{block}, probability of blocking')
hold off