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# PSTN GOS and leased lines

Viewing 3 posts - 1 through 3 (of 3 total)
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• #32370
B. Green
Guest

I have two questions. The first one is….Does anyone know what the probabilty of blocking is for the PSTN? I come from a mobile background where the goal is usually 2%.

Second. I have a design problem where I am allocating a fixed number of lines between two sites based on the amount of traffic between them. I need to determine what percentage of traffic is handled by lines 1 and 2 out of 5 total lines if it is assumed that if a call comes into an empty system it’s given to line 1 and if it comes into a non-empty system, it’s given to the lowest numbered link that is not busy. This involves using a Markov chain and the call arrival rate (.2) and call departure rate (n/5).

#32371
Gilbert de Bree
Guest

I have to answer your first answer quickly for the moment, the GOS for PSTN is 0,01% so 1 out 100 calls blocked.

Regards.

#32372
Peter Turner
Guest

With usual assumptions we can calculate your answers with Erlang B as follows with E being the erlang b function and a the offered traffic:

Traffic carried on first circuit = a(1 – E(1,a)) Traffic carried on second cct= a(E(1,a) – E(2,a)) Traffic carried on third cct = a(E(2,a) – E(3,a)) Traffic carried on fourth cct= a(E(3,a) – E(4,a)) Traffic carried on fifth cct = a(E(4,a) – E(5,a))

The pattern continues.

Viewing 3 posts - 1 through 3 (of 3 total)
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