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Viewing 15 posts - 1 through 15 (of 20 total)
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  • #33043

    How can I know the traffic
    handling capacity of my switch
    if I know that it can handle
    20000 BHCA;

    Ou Danyang

    I am a wireless neywork plan engineer.I want to know how to calculate a wireless cell’s traffic.I am from China.

    Oscar Reyes

    all depends on your Average Call Holding Time(usually in seconds)… after knowing that you just multiply times the 20,000 BHCAs and that would be the total traffic (in seconds). If you want that on Erlangs you just divide by 3600 (60 times 60, first to convert to minutes then to erlangs)….

    Rodney Anthony


    What is the definition of ACHT mentioned in your answer above, how do we calculate it

    Oscar Reyes

    The ACHT is the average time (usaully in seconds) or duration of a call, for example, if the average of the calls is 2 minutes, that means your ACHT is 120 seconds, you could measure it by dividing the total traffic by the total number of call attempts or calls. If the traffic is in Erlangs then your ACHT would be in erlangs (i.e. if the ACHT is 0.1 Erlangs that would represent that the lenght of each call in average is 0.1 Er or 6 minutes or 360 seconds, rememebr that 1 Er equals 60 minutes).
    The total traffic can be obtained from the statistics of your switch as well as the call attempts.
    Be sure that the traffic and the call attempts were obtained during the same period of time (for example a 24 hour period or specific day).




    Supposed that I gonna purchase a system. Apart from specifying the BHCA, do I need to specify also the ACHT for something meaningful?

    Oscr Reyes

    Usually you only specify BHCAs, but if you already know ACHT, is OK…


    Hi Oscr,

    Refering to the equation in your previous reply to Babis, if we’re requiring a system that has a capacity to deal with a certain amount of traffic, it appears that we should specify both BHCA and ACHT. I really don’t understand why in most cases, only BHCA is specified and it is meaningful enough?!

    oscar reyes

    that’s because the ACHT is almost always considered to be 3 minutes (0.05 Erl)… I know this may not be true most of the time, but it simplifies the calculation… at least that is what I have seen most of the time, and it has worked for me…



    v k sharma

    I want to know the relation between BHCA & per line traffic in erlang

    Sunil Kumar

    How we can calculate AHT ?




    i want to know that in order to design the cyclic traffic control system what should be used in order to sense the weight of the vehicle, so that the system will procced further according to the density of the traffic]


    my fix network is APZ 212 30, I want to know Total number of call attempts during the busy hour(BHCA) and formula to do it.


    adding to the discussion about ACHT. 3 mins always used to be the safe but dumb figure – but there are three factors, nowadays which will undermine that assumption.
    Are these connections carring dial up to ISPs. If the answer is yes 3 mins may be too short.
    Do the terminating numbers have voicemail. If yes the number of calls answered will obviously be higher but the call durations will be lower. I have done real measurements on 60 trunk systems and found the ACHT to be less than 40 seconds when Vmail is in place.

    The last factor is mobiles – which nearly always have Vmail. Vmails as origin or destination will also depress the ACHT.
    Hope this helps.

    (NB a tip in dimensioning systems) – always model them as slightly under capacity. Traffic very rarely rises in a steep curve. Then look at your growth to see when you are likely to run out and plan to meet it. If you over provide its very difficult to know how much to cut back as its very difficult to measure headroom.


    Hi Reyes, As you are telling

    ACHT = Total Traffic/BHCA

    i think it is not true coz not all call gets thru’ so what i feel is
    ACHT = Total Traffic/ Answered Calls
    What u say?

Viewing 15 posts - 1 through 15 (of 20 total)
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