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Erlang Formula

Viewing 15 posts - 91 through 105 (of 181 total)
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  • #32952

    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?


    Hi Erik,

    I am taliking from Switch point of View.

    I think this will be giving clear Picture.For a call….

    Actual Holding Time :- Time between ISUP-IAM message and ISUP-RLC Message.

    Act. Call Time:- Time duration between ISUP-ANM and REL Messages.

    What do you think guys ?

    What abt in AIR Iterface ?



    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 Davidt, If i’m not wrong then the capacity planning always consider Busy hour traffic. If yes then your example does not fit here.



    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…


    Mobile users in a certain GSM cell generate 700 calls per hour. Furthermore users
    in this cell’s coverage area receive 1000 calls per hour while calls are handed over
    from neighbouring cells in to this cell at a rate, 300 calls per hour. Assuming that all
    calls (handover and new) have an average call length of 3 minutes, what is the
    bandwidth required in this cell to support all calls at a GoS blocking probability of
    1%. (Assume that the handover traffic from this cell to any of the neighbouring cells
    is negligible.)

    Vijay Sharma

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


    Thank you Vijay Sharma

    but could you inform me how can i find the realtion between the channel whicj i have and the bandwidth which i have to find ?


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


    When dimensioning trunks using erlang-B formula, should the “maximum busy hour” during the observation period be used or a “busy hour averaged for the individual busy hours of each day” ?

    Abhishek Ranjan

    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 ???


    “Wireless: Principles and Practices” by Rappaport is a good one.


    [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 all
    Why don’t have Erlang A?
    can you explain me?



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

Viewing 15 posts - 91 through 105 (of 181 total)
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