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Adding 1800 in 900

Viewing 14 posts - 1 through 14 (of 14 total)
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  • #54303 Reply


    If you have to add two TRX of 1800 band in every cell of your network which are presently working in 900 band with 444 configurations…

    With the addition of 1800 the new configuration per cell will be 6 (4+2) and per site will be 6 +6 + 6.

    How will you go…

    Condition is that 1800 band is to be used for TCH only(no BCCH).

    Any precuations……


    #54304 Reply

    So, I think you must used two bts

    #54305 Reply

    adding a new BTS is very expensive !!
    these 3×2 1800 TRX will be put into existing 900 BTS, if they can support it. I think they can, can’t they ??

    Then, it’s up to you:
    1/ you create 3 new cells “1800”, which will be considered as neighbors to the collocated 900 cells. It’s quite complex to manage.

    2/ you include these TRX in the existing 900 cells, meaning that you’re going to create a site with 3 “multiband” cells. This is the cleanest solution, if you master it properly and know its limitations (depending on vendor).
    The TRX1800 are located in the inner zones of each cell, while the TRX900 will be located in the outer zones.

    #54306 Reply

    Inner Zone/Outer Zone?

    Do we say the “region” nearer to BTS as the inner or farther from the BTS as outer


    The 1800 is termed as inner always and 900 as outer?


    At any point any one out of 1800 or 900 whichever is having low Rxlevel will become the “inner” and the other will become the “outer”

    #54307 Reply

    Hi Pix,

    You said…
    “The TRX1800 are located in the inner zones of each cell, while the TRX900 will be located in the outer zones. ”

    How do we make 1800 TRX to serve the “inner ” zone and the 900 to “outer”?

    Is it by default?
    It has to done by some parameter?


    #54308 Reply

    in OMCR, you define which TRX will be set in inner zone, and which will serve the outer zone.
    One TRX can’t serve the two zones.

    In case of multiband cells, the inner is one band (usually DCS1800) and the outer zone is another band (GSM900)

    The distinction is based on the UL and DL RXLEV, not the distance. There is also a condition about the load, optionally.

    If RXLEV UL AND DL > threshold + Hyst –> TCH is allocated in inner, or if there is already an ongoing call there is a HO outer > inner (cause 13).

    If RXLEV UL OR DL < threshold --> TCH allocated in outer zone, or there is HO from inner to outer (cause 10 for low UL, cause 11 for low DL).


    #54309 Reply

    Thanks Pix,

    As you said the inner or outer zone classification is based on Rxlevel.

    So, can we say that by virtue of propogation phenonmenon 1800 Mhz will have low Rxlevel as compared to 900 at all the points in a cell.
    1800 is the inner zone AND 900 is the outer zone.


    #54310 Reply

    Let us say..

    In OMCR I define the TRX of 900 as inner and 1800 as outer.

    Will it work in same way??

    I mean…the Rxlevel of 1800 will be lower to 900 always(isn’t it)


    By virtue of Rxlevel classification the 1800 TRX is supposed to be inner…and it will be if Rxlevel concept holds good.


    what is the need to define in OMCR as inner or outer.???


    1) which will have the FIRST PREFERENCE in the allocation of a TCH…1800 or 900? + WHY?

    2) If it is 1800 TCH…and Rxlevel is LESS then 900 (likely to be)…then will it take the Intracell HO 900 immediatly by virtue of Rxlevel HO algorithm trigerring in BSC??


    Is there any way to stop “this” type of intracell handovers.


    #54311 Reply


    1/ 1800 = outer, 900 = inner
    possible, but weird.

    2/ Preference goes to inner zone. If TCH can be allocated in inner (good radio conditions) then it is allocated in inner.
    If not, then outer.

    3/ Rxlev(1800) < Rxlev(900), TCh is allcoated in inner zone --> no intracell HO back to outer zone.

    I’m afraid you didn’t look at the algorithms I gave you in my previous post.

    If the TCH is allocated in inner zone, it means the radio condition are GOOD, so the MS will stay in inner zone.
    The intracell HO inner>outer is triggered only if radio conditions are BAD. Which was not the case at TCH allocation !


    #54312 Reply

    OK agreed..

    1800 is INNER
    900 is OUTER


    Lets take a look at following cases:

    How do BSC came to know that at this moment the Rxlevel of 1800 is so and so? I mean who is going to report this to BSC? Unless BSC knows the Rxlevel of 1800, i think it will not be possible for the BSC to decide whether it is > threshold or not. So, how do the case 1 : Alloting a TCH on INNER zone will be done.


    The call is on OUTER. ie 900.
    Again the same situation as with the case-1.

    * BCCH is on 900…OUTER ZONE
    * 1800…INNER ZONE is having only TCH.

    Who is going to perform the measurements on the TCH of 1800, as the TCH is yet to be allocated.

    Pl discuss


    #54313 Reply


    Sorry, I thought I said it before:
    the decision is based on RXLEV(900) only.
    For instance, if DL RXLEV(900) > -70dBm and UL RXLEV(900) > -80dBm, then the TCH is allocated in INNER zone.
    Once the MS is in inner zone, the DL RXLEV(1800) will probably be equal to -70 – 10dB = -80dBm. The UL RXLEV(1800) will probably be = -90dBm.

    Now it’s your job to fine tune the thresholds, so that the MS doesn’t enter the inner zone if the “expected” 1800 level is going to be too low.
    RXLEV DL ZONE = -80dBm
    RXLEV UL ZONE = -90dBm
    ZONE HO HYST DL = 15dBm
    ZONE HO HYST UL = 12dBm

    With this parameters:
    if DL RXLEV(900) > -65dBm (-80 +15) and UL RXLEV(900) > -75dBm (-90 +12 +3), then the TCH is allocated in INNER zone.

    For the -75dBm in UL, the additional 3dB comes from the difference in the MS TXPWR MAX and MS TXPWR MAX INNER.

    You should also set EN_LOAD_BALANCE = DISABLE, in order to load the inner zone as much as possible.

    Finally, set EN_LOAD_OUTER = ENABLE, this works better with GPRS.

    Ok, I gave you all settings to get a great multiband cell…

    #54314 Reply

    Thanks Pix..

    #54315 Reply

    hi everybody
    who can help me?
    i have a problem,during the drive test handover occured in my network between two cells from cell 900 band to cell 1800 band but they are non neighbors in the system and not co-site.the BCCH and BSIC also difference between two cells.any Parameter have to solve this problem?
    our network Ericsson,we have two bands 900MHz and 1800MHz.
    my software for drive test is TEMS investigation (v6.1.3).

    #54316 Reply


    You mean your MS is doing a HO from cell A to cell B, but cell B is not a neighbour defined in the OMCR ?

    That’s impossible, unless another neighbor of cell A is using same BCCH/BSIC as the cell B.
    Or unless I forgot something…

    Perhaps the TEMS MS is behaving differently ? Did you force a HO to this cell B ?

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