Erlang Formula

First of all, i am most probably younger in this field than a few other posters on this board, so excuse me -and please explain me- if i am wrong.

You are talking about holding time and call time.
holding time is about signalling (call setup) and should be around 1 or 2 seconds in a GSM network.
Call time is about the call in itself, the conversation between people and can last for a while (70 seconds in average for the same GSM network).
Are you doing (on purpose or not) some comparison between SDCCH and TCH traffic?

Bear in mind that Erlang B is theory.

For example a long term average 2% blocking in a cell can mean 0% for 4 days then 10% on Friday!

You will also find that blocking in low capacity cells doesn’t follow Erlang B (or Erlang C) – why? because it’s not random. An extreme example, say, in a conference hall, everone will try make a call at the end of the presentation. So you get blocking even though the average traffic is much lower than what Erlang B predicts.

So, be-aware of using Erlang B for capacity planning on small numbers of circuits.

Hi Vijay,
It depends what you mean by busy hour… Typically, you would average BH traffic over a few days to decide what ‘weekly’ BH traffic (for dimensioning & projecting purposes) is… Some enlightened operators even use ‘bouncing busy hour’ to dimension resources.

If you don’t average, then you end up building capacity for the peak-of-peaks and dimensioning for non-typical spikes in demand. Which means your congestion is unecessarily low, but more importantly, you’ve got excessive network capacity (transcievers, transmission links, line cards, switching capcity, trunks etc) that only get used for about 72 seconds a week (if you have 2% blocking for the BH).

In India, as I understand it, with the huge increases in subscribers/traffic, you’d be well advised to ignore Erlang tables and put a load of capacity in anyway – it’ll save you having to go back 2 weeks later and add new radios!

Erlang is still theory and nobody told the callers they have to call with a Poisson distribution and not retry if they don’t get through…

Hi Loulou, to cater 100 erlang with 1% GOS u need 118 TCH.

i m looking for a programm which look the number organ(n) in the erlang B

Hi! can u let me know abt design parameters. for example.-

mobile subscribers- 12650
fixed wireless – 8433
erlangs – 865 (How ?)
cell sites with 2C – 18
Erlangs built -2052 (how ?)
%ge buffer – 138 (wat does this mean?)
erlang/carrier – 48

tell me abt this design ???

[Quote]’bouncing busy hour'[/Quote]

Hi all. Davidt, what do you mean by “bouncing BH”? Is it some kind of averaging? for example, taking the 3 busiest hours in the week? or taking into account the weekly BH over a few weeks (in order to discard “special events” congestion?
Thanks in advance and good day

Hi,

Can you tell me the difference between LSR/QSR/TRD in traffic ?