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Point of interconnect (POI)

  • This topic has 16 replies, 1 voice, and was last updated 13 years ago by navdeep kaur.
Viewing 15 posts - 1 through 15 (of 17 total)
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  • #37237
    Raghava Rao

    Can some body help me to guide the source / website to know guidelines to dimesnion POI E1s for Wireline / Wireless switch network to interconnect with other service providers.


    You do not need any specific books for that. All you need is, know what is the traffic that you are expecting. calculate the erlangs and based on erlangs and using Erlang B calculator, comeup with teh number of ckts and that will provide you teh number of E1s. IF these E1s are R2 (then no issue) if these are SS7 based put one pair of SS7 signaling likns for every 30-35 E1s

    Vijay SHarma

    Hello Pankaj,

    Lets say we have a GSM-MSC.

    It can serve 100K Roamers (Home +Vistiors ).Mostly there will be 5o K Usesr always.

    Average Call Hold Time – 120 Seconds.Minimum they make one call per day.

    Then How wecan calculate the No of Circuits ?



    Vijay, that calculations are always done based on the busy hour traffic. You haven’t mentioned that. I take that in the busy hour every subscriber makes one call on average (the number may be more or less). Having 120 seconds of call hold time and 50k subscribers, it will give you a total of 1667 erlangs. Considering a normal distribution of 20% m-M calls and 80% M-L + L-M calls, you get 80% of 1667, 1334 Erlangs for POI Traffic. 0.01% GoS (That is what one is supposed to take for PoI calculations and 1334 erlangs you get 1447 Circuits (using erlang B) or 49 E1s. One to bear in mind is that generally you will not have all teh E1s going to same PoI. In that case you should either take the rule of thumb i.e. 22 Er per E1 or calculate the E1s seperatly for each PoI.

    Vijay Sharma

    Hello Pankaj Thanks for your Info.

    Busy hour as usual.

    5 Pm to 7PM.

    As per Traffic Modelling:-

    20 % M-M Calls

    40 % Each for M-P/P-M Calls.

    Then How to calculate the A-Interface Link Capacity ?

    We have AXE10-BSC.




    Someone pls explain to me what is Point of Interconnect (POI) and how does this function? I am novice 🙂


    POI – Point of interconnect traffic
    When you want to calculate the traffic what you should have first is
    1.Total no of subscribes in MSC (Max at any given time in VLR)
    2. Expected BHCA/sub -Busy hour call attempts per subsriber
    3. Expected ACHT – Average call holding time
    4. % of calls being routed to each POI .

    Example:- Suppose one wants to serve 100K subs with BHCA of 3.5 and ACHT is 120 Secs.
    Which means each subcriber at Busy Hour is going to make 3&1/2 call and each call on average is of 120 secs

    So the traffic is
    11666.67 Erlang

    Now 8% of your Traffic goes to one POI then that traffic is 11666.67*(8/100)=933.33 Erlangs
    Now cahnnels required to carry Traffic of 933.33 Erlnag, As per Erlang B table is with Blocking of 2% is 994
    993/30(in case you are using only 30 Channels/E1)is around 33 E1s are required towards that POI.

    I think this will clarify the query. Please mail me on if any query on traffic. Its my pleasure to sort that out.


    Hello Pankaj and Srinivas,

    Thanks for your valuble infos.

    I have some questions for you.

    I am getting a Peak Hour Traffic Report from My OSS System.From there how can I determine the BHCA ?

    Because that report contains all the Traffic Infos from Software ( IN+Roaming ) Routes to Voice Routes ( BSS+POI+ VMS+Data Modem Routes ).

    Which are the things I have consider for calculating BHCA ?



    Vijay, while calculating BHCA we consider to factors
    Originated calls and Incoming calls.
    Originated calls are those originated by your subcscibers in your switch. and Incoming calls are those coming to your switch from other switchs.
    so BHCA = Originated + Incoming calls.
    Is it clear?


    Vijay Sharma

    Hello Vijay …

    Shall I say like :-

    INCOMING CALLS = POI Incoming + BSC Incoiming

    OUTGOING CALLS = POI Outgoing + BSC Outgoing.

    Nothing else to be considered like VMS/IN/Other IVR System Traffic…?

    I think we have to consider.And we are using AXE 10 R9 System.



    Vijay, there is some difference in terminating calls and incoming calls.
    Terminating calls are those which terminate to your subscriber, the origination could be from your bsc , poi, vms etc. and
    Incoming calls = Terminating calls – calls originated from your subscribers.
    SO originating calls are those which originates from your BSS part only.
    and Incoming calls = POI incoming + VMS incoming + any other outside source + transit calls.

    Vijay Sharma

    Hi Vijay,

    What about the Transit calls like Romaing , Call Forwarding.

    I beleve they also Originated calls if I am Correct.


    OG CALLS = BSC Outoing + Others like Roaming,CF,etc…


    How can we calculate switch capacity thru erlang or BHCA ?

    sunil saldhi

    what is ideal GOS?
    what is difference between CCR and CSR?


    How do we caluclate switching Capacity of a Particular E1?

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