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No of neighbour cells

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  • #52864 Reply
    MKT
    Guest

    Hi all,

    For a cell you have neighbors.

    MS reads the list from SI2/SI5.

    MS performs measurements on neighbors and send them to BTS which in turn to BSC.

    Is there any logic for having the list in SI2 to be different from SI5?

    And if the list is same, then is there any logic for having two lists for conveying same info to MS?

    Do having a long list in SI2 or SI5 has some disadvantages? If yes then what?

    If no, then
    why don’t we make the list full at cell creation time only.Thereby reducing the work afterward.

    What is theoretical as per GSM for defining no of neighbours?

    Regards

    MKT

    #52865 Reply
    pix
    Guest

    I’ll give you answers that reflect my point of view. Not necessarily correct…

    1/ yes SI2 and SI5 can be different. No logic behind, except is you plan to prevent HO between two cells, but want to keep reselection available.

    2/ no logic behind having 2 different SI messages. But keep in mind that on SI is sent on BCCH, the other is sent on SACCH.

    3/ long list of neighbors lead to problems :

    – you can’t use co channel or adjacent channel BCCH between neighbor cells. It makes your FP more difficult.

    – the MS will spend a lot of time scanning the whole amount of neighbors. It will select the 6 strongest, ok, but it has to scan all of the neighbors to find the 6 strongest. Therefore it might miss measurements, and will not be able to update the RxLev(n1…n6) every 480ms.

    That’s it…

    #52866 Reply
    MKT
    Guest

    Pix,

    Thanks for reply

    But this is the height of complexity.

    Why telecommunications standards are made so complex.

    Regards.

    #52867 Reply
    pix
    Guest

    mkt,

    i don’t find it complex at all, they just decided to give possibility to have “idle” neighbours and “dedicated” neighbours, there will always be a case when this comes in handy.

    point of standard is to be as “evolutive” and non restrictive as possible. They give all possibilities. Up to the operator to use it or not.

    When you look at GPRS, then you see complexity at its highest 🙂

    #52868 Reply
    paraHO
    Guest

    I thought other reasons for SI2 and SI5 is that as SI2 collated cell inform at switch ON and the MS at early stage in idle mode the network may not know MS there, the MS is just identifying the best cell on which to camp.

    For SI5 the network has taken into account all cells within 35Km (?) boundary that could possibly be used by mobile but cell assigned for use is best on lots of factors taken into account eg:

    other cells at traffic capacity
    other cells with faults
    other cells may have high interference
    etc
    etc

    which the MS in idle mode, monitoring SI2, could not posibly know?

    #52869 Reply
    Peyo
    Guest

    SI2 has been designed for idle mode and SI5 for dedicated mode i think that’s all. As Pix mentionned it one is on bcch and the other on sacch. Consequently SI2 is for reselection and SI5 for HO

    #52870 Reply
    pix
    Guest

    paraho,

    the list sent in SI2 and SI5 are exactly the same. The BTS doesn’t choose to send only some cells in SI2, based on a filter, as you said.
    timing advance, traffic load, interference, all this is not measured, whether the MS is in idle or dedicated mode.

    #52871 Reply
    daban
    Guest

    Mr pix,please anser me,in the subject GOS and traffic assingment,iam one qustion toward you.

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