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  • This topic has 7 replies, 1 voice, and was last updated 17 years ago by Ayat.
Viewing 8 posts - 1 through 8 (of 8 total)
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  • #47994

    Dear, All
    i need your help
    i need to know the dufference between TCH assignment and TCH allocate
    what is the meaning of TCH assign , is it the call reach to the MSC or BSC , it is the call start or not also for TCH allocate
    i our network the most time TCH allocated > TCH assign
    Could you explian the call phase from begning to end plz as soon as you can


    Hello Ayat,

    You’re asking the same question in three threads, but i’ll just answer here :

    you can divide the call phase in four sub-phases :
    1- sdcch assignment (MS asks the BTS to get a SDCCH, thanks to BCCH channel)
    2- sdcch phase (exchange of info between MS and NSS on the dedicated SDCCH)
    3- tch assignment (BTS requires a TCH and allocate it to the MS)
    4- tch phase (exchange of speech frames on the dedicated TCH)

    as far as i can see, you have 3 TCH counters :
    TCH allocated
    TCH assigned
    TCH seizure

    You must know that a counter is incremented in the BSC as soon as the BSC sends (or receives) a ABIS message. Check the description of those counters, and find the message to which they’re associated.

    Finally, get the 3GPP doc about the message flows for call setup (sorry don'(t have the ref…)


    Hi Ayat,

    The answer was useful ?


    Hello , Pix thx for you alot ,but i am still Confused , because i can not understand these Details.In our company , we claclate the call success (%) as a function on TCH asssign ,we note the result alawys big (99%) that means it is good but we have a problem in congestion ,we called it TCH ovrflow , and TCH allcoted faliure is very big for example (50%) , i need to connect between these problem , that means , how come it’s call succ. but TCH allocated is big and also TCH overflow , do you find that logic or i missed some thing . plz try to be Patience teacher , and help me by explain it step by step
    As you said we have three counter
    TCH allocated
    TCH assigned
    TCH seizure
    why we did not calculate the call success by TCH Seizure/TCH Call Attempt *100 . thanks alot for your support.
    i am waiting for your reply


    Hi Ayat,

    CSSR – Call Set-Up Success Rate ,

    To have big value like 99%, it is impossible to have TCH congestion or assignment fail 50%.

    The main things that affect the CSSR is the SDCCH drop and SDCCH congestion and TCH congestion.
    Some operator ignor the SDCCH congestion from there calculations when they calculate teh CSSR, so the TCH congestion will affect the TCH_ASS_SUCC rate, another thing could affect the assignment of the TCH is the bad quality.

    Hoppe this can help you…



    As Jehad said, your indicators are not correct. You need to check their formulas !

    The call success % (or rather, the call SETUP success %) should take into account the TCH overflow.

    I’m very patient, don’t worry 🙂 So what you have to do is to get the technical doc from your vendor. Ask exactly what is the formula of each indicator.

    After you get that, then only you can start working…

    You can also try to experiment with your counters directly : make some formulas based on counters, calculate the result, and match it to an existing indicator (if the result is the same, it must mean the formula is the same…).

    Good luck 🙂

    Da Architect

    Dear Ayat,

    Letting us know your platform(Ericsson, Alcatel, Nokia, etc…) will make it easier to help you specially in calculating indicators. if it was ericsson, make sure that CSSR = [(CMSESTAB-CNDROP)x(TCH Assignment Success Rate)]/CCALLS


    Thanks for all
    i am really to glad for your best cor.
    i need to say we have two counters one we called it Call setup succ rate (radio switch) it is function TCH congestion , SDCCH Congestion
    but also we have also call succ. it is only function on TCH assign and in case we have TCH allocate Failure high , we find call succ high (good) , i hope understand me thanks

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