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basic frequency questions

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  • #56518 Reply

    Hi everyone, i just have a basic basic question regarding frequencies.
    i wanted to know that for example if one rbs is radiating 800 Mhz , 2 W and there is anotehr taht is radiating at 1900 Mhz , 2 W also. I want to knwo which one will be stronger?

    like say we have two freuencies, one is 1800 Mhz and teh other is 2100 Mhz. so when we connect the mobile, the phone sees about 4 bars or RF signal and when we connect the 2100 the phone sees full signal ( 5 bars)

    why is that so?
    can you please explain to me the concept behind this?

    thank you.

    #56519 Reply

    please it is important

    #56520 Reply

    Hello AB,

    for the same TX Power (for example, 2W), the lowest frequency will have the strongest Rx signal.
    The reason is that the lower frequency propagates better. In Wikipedia, look for “free space loss”.

    Your second question is uncorrelated to the 1st one, I believe. The MS doesn’t display bars depending on the RxLevel, but rather depending on the criterion C1, which also depends on parameters such as RX LEV ACCESS MIN and MS TX PWR MAX CCH


    #56521 Reply

    Pix ,
    I miss understand for long time about display bars on Mobile .Please you help to explain more because I still so confuse How C1 is related .
    Thank you

    #56522 Reply

    In GSM system MS is always within the cell offering the best coverage. In dedicated mode this is handled by handovers, but in idle mode it is done by a process called “Cell Selection”, based on C1 and C2 comparison. Mobile compares field strength levels coming from different cells with each other and chooses the best one.

    where A=average recieved level-p1
    & B=p2-Max RF power of MS

    p1=Rxlevel access min
    p2=MSTX powqer max CCH

    more over

    Rxlevel access min is broadcast on the BCCH, and is related to the minimum signal that the operator wants the network to receive when being initially accessed by an MS.

    msTxPwrMaxCCH, which is also broadcast on the BCCH, and is the maximum power that an MS may use when initially accessing the network

    #56523 Reply

    hope the point is clear to u now Phantom

    #56524 Reply

    Hi, all
    Manu wrote:
    “…In GSM system MS is always within the cell offering the best coverage. …”

    What in fact is” best coverage”…?


    #56525 Reply

    better signal strength

    #56526 Reply


    so the MS is NOT “always camping within the cell offering the best coverage”.


    #56527 Reply

    I mean “the best cell” but not this one with “best coverage”.

    @ AB (your original question ):

    I’m not sure that it’s correct to compare the number of signal indicator bars
    in DCS and UMTS…


    #56528 Reply

    Problem with saying ‘best coverage’ is that might not be the dominant coverage at the point which mobile is located.

    Dominant coverage determined from rxlev does not always mean mobile will using that coverage due to ‘interference’ or other quality issues.

    I have test results where the cell the MS is camped has lower rxlev C1 but really good C2, yet next best serving cell has better C1 but not so good C2, so how define ‘best coverage’. I think what ever is provided at particular location. Beside even if MS starts on camped cells with low rxlev network handover occur to better server when it can, maybe?

    MS may detect dominant coverage (rxlev) but BTS might be overloaded with tarffic etc

    I think both these are right depending where MS is located:

    Manu wrote:
    “…In GSM system MS is always within the cell offering the best coverage. …”

    TNS wrote: “so the MS is NOT “always camping within the cell offering the best coverage”.

    #56529 Reply

    Basically MS camps on the best serving cell on the basis of C1 and C2. C1 is cell selection criteria which is already mentioned by manu. if “enabled” C2 criteria decides which cell to preferably camp on. C2 is defined as

    C2 = C1 + CRO – TO * H ( PT – T )

    CRO = Cell Reselect Offset
    TO = Temporary Offset
    PT = Penality time

    T is initiated from
    zero when the MS places the neighbouring cell on the list of the six
    strongest carriers.

    In this manner we can camp the MS on the cell which may not be the best server. This practise is often used for traffic balancing.

    So we may say that MS is NOT “always camping within the cell offering the best coverage”.

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