Some comments : in a Radio Mobile Network (ex: GSM), you are dealing with a very low quantity of radio channels. Typical example : n = 7 (case of a microcell). Usually the design GoS is 2%. In that case you can only carry an offered traffic of 2,9 erlang !
This is due to the fact incoming trafic is coming by burst (Poisson Law is behind erlang law), and even if you have enough channels to carry the average trafic, you need extra channels to grant burst without extra blocking.
And if you want a very low blocking rate (GoS), you need to pay that by having a lot of extra channels.