We studied the article suggested by Nicolae Panait. But it does not consider data traffic. It is about voice, although it does discuss multi-service (eg. 64kbps voice and 384kbps video together).
It seems to me that Erlang B, which uses blocking to define it’s grade of service just won’t work for data. Delay should be the metric used for data. So, perhaps Erlang C would be more appropriate.