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900/1800 cell selection

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  • #54827

    Hi all,

    The case is 900 & 1800 are co-site. Which cell (900 or 1800) the mobile will camp on when he turns first time ?

    Please specify the procedure in details if you can ? Which parameters to control this.

    Thank you very much.


    the CELL BAR QUALIFY, the cell with CBQ = 0 will be selected first.

    If both cells have CBQ = 0, then the cell with highest C1 will be selected.

    C1 depends on RXLEV ACCESS MIN and MS TW POWER CCH

    MS TX PWR MAX CCH = 33dBm for GSM900
    = 30dBm for DCS1800

    C1 = (rxlev(cell) – RXLEV ACCESS MIN) – max(0, MS TX PWR MAX CCH – P)

    P is physical power of mobile in the cell frequency band.

    To increase MS chances to camp on 1800 at first selection, use the CBQ. The other parameters have less impact, and you’d need to change them too much in order to achieve what you want to do.

    However, keep in mind that after 5 seconds, the cell which was selected in the frst place will be replaced by the “better cell”, based on C2 criterion.

    It’s a little pointless to work so hard on the selection (C1), the reselection (C2) is much more important. I’m afraid it will not change much things on your network to put CBQ = 0 on DCS cells and CBQ = 1 in GSM cells. But you can give it a try.

    Note: a cell with CBQ = 1 cannot be barred. (3GPP restriction)

    Note 2: a phase 1 MS will not understand the CBQ parameter.


    Thanks pix,
    I would give a try

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