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SDCCH dimensioning for HR environment

Viewing 15 posts - 76 through 90 (of 155 total)
  • Author
  • #35538
    Gurvinder Singh

    I am working in a GSM operating at 1800 using Nokia BTS/BSC, we are having high call drop on the border cell i mean on circle boundry ,as these are open cells so their call drop and handover failure is high.So there is a parameter known as DISB which is used to relase the call after Timing advance has exceded the threshold.So can any body tell me any thing about this or any other way by which KPI regarding the border sites can be improved


    So instead of naturally dropping the call because it’s too far, you want to drop it when it exceeds a certain distance MS-BTS.. By doing this, you wil increase the overall quality in the KPI, but in reality you will limit the number of people that can use the cell. You will loose voice traffic… so in the end, you loose subscribers and money 🙂

    One thing you can try : set your Radio Link Counter (MS and BTS) to the max. Effect : the subscriber can still make a call, but when the quality is bad, the BTS will wait 25 seconds before considering the call is “dropped”. Most of the time, the subsciber will hang up by himself before 25 seconds. And the BTS won’t consider it as a call drop.

    Good luck,



    Pix – this is a dirty trick you know.
    But nevertheless if someone desides to go for it do not forget that usually the subscriber will try again to make the call. And if RACH BT is -111 then you could have a SDCCH drop.



    I’ve got a handful of dirty tricks 🙂

    Yet, in such cases, i would say that the subscriber might want to keep the call for as long as possible, to give him time to move around and find a better spot.


    hello all
    can any body pleas tell me the reason why there are some cells with out sdcch ch ? Ifound it not logical to dedicate a whole cell for handover & gain 1 or 2 tch instead Am I missing something her


    hi summer,

    are you sure the sdcch is not combined with the bcch ?

    i’ve never encountered such cell…


    Its possible to use TCH for call set up in ericsson BSC by having a parameter CHAP set to 2.


    Hi as I seid in another posting it is not a problem to have call setup without SDCCH (direct TCH assignment in Siemens). But you need the SDCCH for the LU and SMS. But if in idle mode you never camp on this cell then there is no problem. We don’t use such thing but the idea is the following: In some countries the operators bid for 1800 the same way as for 900 so the have to have for example 97% coverage territory and 98% population on 1800. This meens that they have to have BCCH on 1800 to show coverage to the regulator. But actually they tune the cells as dualband. One site with colocated 900 and 1800.


    why is it that most GSM antennas are vertically polarized if not cross polarized? can anyone provide some reading materials or links on BSS radio parameters for Nokia and Ericsson? or any tutorial/paper related to GSM/3G radio system parameters.. I want to further enhance my knowledge in telecomm.


    hi dxt,

    in antenna catalogs, you find as much vertical polarized as cross polarized. They both have different advantages and drawbacks.

    good luck in finding your working materials.. i suggest you buy “paper” books to have a good and solid overview of the basics, and then ask for operators or vendors you’re working with to provide you wih their own docs.


    thanks pix, but i want to know the reason why we used vertical polarized antenna for most communication links. okay, horizontal polarization is possible but why do they gave preference to vertical polarization?


    Hi DXT,

    Ok, you didn’t mention about horizontal polarized in your first post. Cross-polar and Horizontal-polar are different.

    A horizontal polarized antenna would be exactly like a vertical polarized antenna, but spinned by 90°. Like a V-pol antenna laying on its side… It can be used, but the consequences of such a setup are obviously not useful in most situations :
    …. horizontal lobe would only be 7° to 14°, while the vertical lobe would be about 65° to 90°. As you understood, the lobes are inverted, compared to a vertical polarized antenna. Not very practical. Square antennas have about the same H-lobe than V-lobe (30° or 65°… depends).

    I wonder if you’re actually talking about space diversity, achived by horizontal separation or vertical separation. Let me know…


    Hi All

    I Have a problem with SDSR..if use link transmission with IDR (VSAT) and microwave, which one will have good SDSR ?.
    I have link transmission like below :
    BSC—link IDR–>BTS 1—link ericsson—>BTS 2.

    link IDR record in BTS 1 was often transmission error but in BTS 1 had good sdsr compare with BTS 2, from BER TEST result link ericsson had good result so why it can be happened?
    can u help me…

    Ramajayam cyr

    Hi Vanderley,

    In such case Trafic is more as compare normal the operator can use Dualband BTS in one cell having both frequency bands 900&1800 Mhz . The 1800 mhz band
    Lobe small as compare 900 Mhz band
    the 1800 coverd near by the cell and 900 coverd such distance more than 1800 the both bands are having same BCCH . The BCCH in 900 Band only . yout Block the all trx(900) in one cell you con’t able to make a call in 1800 Band . This methode are adopted in highly populated areas.


    hi Jembut,

    I know it might not help, but it might give hints :

    can you compare the radio QoS of those 2 BTS ? especially the call drop rate due to transmissions problems (or TC problems, whichever you call it in your system) and the TCH assignment failure rate due to BSS/hardware/TC.

    It will tell you which BTS is affected in reality by the faulty link. If only BTS 2, then link 2 is faulty. If BTS1 and BTS2 than link 1 (and possibly link 2 also) is faulty.

Viewing 15 posts - 76 through 90 (of 155 total)
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