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Thread: What is best Frequency plan with 20 frequencies.

  1. #1
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    Default What is best Frequency plan with 20 frequencies.

    Dears

    I need your help if some one did frequency plan for GSM only Have 20 Frequencies for cells configured with Two TRXs(BCCH+TCH).

    BR
    RF engineer

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  3. #2
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    Default Re: What is best Frequency plan with 20 frequencies.

    Hi, long time ago i heard about following setup, where 7 ARFCN are dedicated to BCCHs, remaining for Synthesized hopping. All the traffic is forced onto synthesized hopping. BCCH plan is very tight, so it is only used for neighbor detection.

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    Default Re: What is best Frequency plan with 20 frequencies.

    Quote Originally Posted by RF engineer View Post
    Dears

    I need your help if some one did frequency plan for GSM only Have 20 Frequencies for cells configured with Two TRXs(BCCH+TCH).

    BR
    Hello!
    It depends on antenna planning. If you did well (optimized for UMTS/LTE) then you can do with 11 or 12 BCCHs. Assign border BCCH to cells with low load amd use 8/7 TCH frequencies, other cells can use 9/8 ARFCHs. 1:1 reuse, of course (all cosited cells same MA list, same HSN, and MAIO in step of 2 shall be different for every hopping TRX).

    In one project I did BCCH 7 on 1800 in order to get LTE 1800 up and running. Works fine, but GSM 900 layer is compensating for interference.

    And if you do not take care of antennas: sorry. Drop call rate above 0.5 % and some bad interference areas.
    Buy another MHz or two.

    If you have good interfrence matrixes based on real network data (say: you want to put LTE 900 on 9 MHz of GSM 900) then run simmulations with different BCCH bands. FInd smallest one where you have reasonable number of same BCCH neighbors, then add one more and go to live network.
    This can point to areas where antenna optimization is needed.

    I got different results on different networks: it is all based on how network is designed initially. With UMTS/LTE on the mind or not.

    BR
    s52d

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    Default Re: What is best Frequency plan with 20 frequencies.

    Quote Originally Posted by s52d View Post
    Hello!
    It depends on antenna planning. If you did well (optimized for UMTS/LTE) then you can do with 11 or 12 BCCHs. Assign border BCCH to cells with low load amd use 8/7 TCH frequencies, other cells can use 9/8 ARFCHs. 1:1 reuse, of course (all cosited cells same MA list, same HSN, and MAIO in step of 2 shall be different for every hopping TRX).

    In one project I did BCCH 7 on 1800 in order to get LTE 1800 up and running. Works fine, but GSM 900 layer is compensating for interference.

    And if you do not take care of antennas: sorry. Drop call rate above 0.5 % and some bad interference areas.
    Buy another MHz or two.

    If you have good interfrence matrixes based on real network data (say: you want to put LTE 900 on 9 MHz of GSM 900) then run simmulations with different BCCH bands. FInd smallest one where you have reasonable number of same BCCH neighbors, then add one more and go to live network.
    This can point to areas where antenna optimization is needed.

    I got different results on different networks: it is all based on how network is designed initially. With UMTS/LTE on the mind or not.

    BR
    s52d
    Dear

    Thanks for your input , what about to have 1:1 SFH with only 7 frequencies in MA list .


    BR
    RF engineer

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    Default Re: What is best Frequency plan with 20 frequencies.

    Quote Originally Posted by RF engineer View Post
    Dear

    Thanks for your input , what about to have 1:1 SFH with only 7 frequencies in MA list .


    BR
    it works for 2+2+2 cells. Use MAIO 0,2,4 so no two TRXes receive in the same time on same or adjacent frequencies.
    You have hopping gain: remeber, 20 ms is spread over 8 TS, so from pure hoppong there is no gain above 8 frequencies.
    Try to push traffic to BCCH frequency to unload TCH band.
    Remember: MAIO problems are observed on uplink (near-far effect) more as in downlink.

    In general, for decent 1:1 reuse you need twice as much ARFCNs in MA list as you have hopping TRXes on site.
    There are a bit more complicated ways around: make sure not to have two terminals with 20 dB difference on TRX RX on adjacent frequency.
    Of course, BCCH and TCH shall not be adjacent as well.

    BR
    s52d

    br
    s52d

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    Default Re: What is best Frequency plan with 20 frequencies.

    Baseband hopping with Bach 60 : tch 40%

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