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Calculating BHCA from traffic carried?

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  • #40801 Reply
    Frank
    Guest

    Hi there,

    I’m confused about the following:
    where ever you read about traffic engineering (even in some earlier postings here) you find the following formula:

    BHCA=(Traffic in Erlang)*3600/MHT

    with
    BHCA = Busy Hour Call Attempts
    MHT = Mean Holding Time.

    As far as I understand ITU-T E.600 says that “Traffic offered” is the superset of all traffic that arrives at a resource, including “Traffic Carried” by the resource and “Overflow traffic”.

    What is confusing me now is the exact meaning of “Traffic in Erlang” in the context of the above formula. As far as I understand, it can only be “Traffic Offered” because this is the superset of “Traffic” including both successful and unsuccessful seizures, just like BHCA is defined (BHCA is related to ALL call attempts, no matter whether they are successful or not). If I wanted to take a look at successful seizures, I wouldn’t calculate BHCA but BHCC (Busy Hour Call Completions).

    So if I use the Formula at the top of this posting for calculating BHCA, I have to enter “Traffic Offered” as a value for “Traffic in Erlangs”.

    Usually, network operators calculate with an average traffic value per subscriber (e.g 0.1 Erl is a typical value for one PSTN subscriber to calculate with) when they do network engineering. But as far as I understand, this per-subscriber-value relates to “Traffic Carried” (because it’s calculated by active connection hours) and includes both outbound AND inbound traffic of a subscriber. So this would not be a value that could be used to calculate BHCA if you don’t divide it by 2 (to separate between incoming and outgoing traffic) and multiply it with a blocking factor.

    So how do I calculate a true BHCA if I only have “Traffic Carried”?

    Thanks in advance

    Frank

    #40802 Reply
    dmck
    Guest

    I agree with your logic. I dont believe you can calculate BHCA from carried traffic. You must either measure it or estimate it. You can estimate it by ‘knowing’ the GOS for the route and dividing into the BHCC. This assumes your GOS figure is accurate!

    #40803 Reply
    mayank
    Guest

    ya you are rite
    Traffic in Er is calculated by call occupied not by call attampet

    #40804 Reply
    Jingtao Liu
    Guest

    About BHCA Formal, If we want put ASR in denominator. it is right on not. if it is not true. how can prove or find some doc to prove it is mistake.

    #40805 Reply
    jitendra
    Guest

    Estimated Busy Hours Traffic Erl=BHCA*Call Duration/3600
    Where Call Duration=60 sec
    So u can find the
    BHCA=Traffic in Busy Houre*60 @ 2%
    this are only estimation of BHCA

    OR it can be found using million Lines , no of user & their avg erl used to estimate busy Houre traffic & thus BHCA.

    #40806 Reply
    Efren
    Guest

    How do we compute the traffic if you have several calls of different durations? For example, in one BH i have 10 calls at 5-min then 20 calls at 2.5 min… what is my traffic then in Erlangs?

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