1. TRUNKING AND GOS

8. Trunking Theory Each user generates a traffic intensity of Au Erlangs. Au= H, where H is the average duration of a call and is the average number of call requests per unit time for each user Total offered traffic intensity A for a system containing U users A=U*Au, where U number of users and A is the total offered traffic intensity In a C channel trunked system, the traffic intensity per channel is Ac=U*Au/C, where C is the number of channels Offered traffic >= the traffic carried by the trunked system

10. no queuing for call requests, no setup time user is given immediate access to a channel if channels are available. If no channels are available, the requesting user is blocked without access. Gos: The probability that a call is blocked Erlang B formula Erlang-B : Blocked calls cleared system

11. Erlang c : Blocked Calls Delayed system Queue is used to hold blocked calls Blocked calls are delayed until channels are available, Gos: The probability that a call is blocked after waiting a specific time in the queue Erlang C formula Pr[delay>t] = Pr[delay>0]* Pr[delay>t|delay>0] = GoS = Pr[delay>0] * exp(-(C-A)t/H) Pr[delay>0] is probability that a call is initially denied access to the system The average delay D for all calls in a queued system is given by D=Pr[delay>0] *H/(C-A)