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Amount of GPRSusers per sector in alcate

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  • #65256 Reply
    Pawa
    Guest

    Hi dear experts,

    please enlighten me in one question: how many GPRS users can be on one sector simultaneously? i have info that 15. is it true? is there a parameter that supervise tat? where can i find it? edit cell? or edit bsc?

    thank you very much
    i really need your help

    Pawa

    #65257 Reply
    Pawa
    Guest

    Please help if you can

    #65258 Reply
    pix
    Guest

    hi pawa,

    the number of gprs users in one cell is theoretically very high.
    what you can do is limit the number of TBF per PDCH (= number of gprs users per timeslot)
    and also the number of PDCH per cell.

    If I set 10 PDCH and 5 DL TBF / PDCH (case a)
    And then later I go for 8 PDCH and 2 DL TBF / PDCH (case b)

    that will limit the total amount of gprs users

    (note: 1 user should get 3 or 4 PDCH per TBF)

    but there is no “static” limit.
    in case (a) you could expect about 15 users simultaneously, or more. (peak = 50)
    in case (b, expect 3 to 5 users simultaneously. (peak = 16)
    but that’s really not how you should start your gprs dimensioning. You should think in terms of throughput rather than the number of users.

    regards
    pix

    #65259 Reply
    Pawa
    Guest

    hi Pix

    thank you very much yuor explanation is very good you should be a tutor!
    you helped me a lot already but i still have some questions
    1/ what is the commonly used value for amount TBF per PDCH? is 5 good one?

    2/not about GPRS
    we activated hopping (NH_RH) in one area and i want to estimate result because kpis changed much. some cells became better other feels worse. as i know in case of hopping we shouldn’t take into account RxQual but use FER. i want to find indicators related toFER in NPO but saw that there ones only for UL. maybe i was looking for them in wrong folder? or there are no indicators for FER in DL inNPO at all?

    sorry if my questions are too stupid but i new in gsm

    thank you for help

    best regards, Pawa

    #65260 Reply
    pix
    Guest

    pawa,

    there are no stupid questions ! (and your guesses are all good…)

    1/ yes, 5 is a good value. Just for an exeample, if you choose 3, it means you limit the number of users, but want to provide more throughput per user (less sharing)

    2/ NH_RH : refer to other older threads in this forum to find some valuable info.
    Regarding DL FER : it is not available in NPO, because to be so, it should be reported by the MS… and it is not πŸ™‚ You can use a rxqual threshold = 5, instead of 4, and that would be close enough to reality.
    to assess dl fer, only one solution : the drive-test.

    Cheers
    pix

    #65261 Reply
    Pawa
    Guest

    Hello Pix
    thank you
    i try to do my best

    still have questions, this time about specific parameters
    1/ in edit cell in OMC-r i can see the following parametrs:
    MAX_PDCH_PER_TBF = 5 – it means (as i understand) that one user theoretically can occupy 5 time-slot. is it correct? but as far as i know there are no MS that can do that – max numb 4?
    will some change if we set MAX_PDCH_PER_TBF = 4 instead of 5?

    i found out 2 parameters in OMC_R related (possibly) to supervising amount TBF per PDCH – seprate for UL and DL. am i on the right path?

    MAX_UL_TBF_SPDCH = 5 – it means that in UL we can share one PDCH (as i heard in B10 we have only SPDCH, no MPDCH) between 5 users. is it correct?

    MAX_DL_TBF_SPDCH = 8 and this means that in DL we can share one PDCH between 8 users. is it correct?

    what do you think about such values?

    thanks for help, Pix

    best regards, Pawa

    #65262 Reply
    pix
    Guest

    hi pawa,

    —–
    1/ in edit cell in OMC-r i can see the following parametrs:
    MAX_PDCH_PER_TBF = 5 – it means (as i understand) that one user theoretically can occupy 5 time-slot. is it correct? but as far as i know there are no MS that can do that – max numb 4?
    will some change if we set MAX_PDCH_PER_TBF = 4 instead of 5?
    —–

    some MS (class 30 to 34) can support up to 5 timeslots in DL. Your interpretation of this parameter is correct.

    —–
    i found out 2 parameters in OMC_R related (possibly) to supervising amount TBF per PDCH – seprate for UL and DL. am i on the right path?
    —–

    yes

    —–
    MAX_UL_TBF_SPDCH = 5 – it means that in UL we can share one PDCH (as i heard in B10 we have only SPDCH, no MPDCH) between 5 users. is it correct?
    —–

    yes

    —–
    MAX_DL_TBF_SPDCH = 8 and this means that in DL we can share one PDCH between 8 users. is it correct?
    —–

    yes

    —–
    what do you think about such values?
    —–

    those values tend to maximize the number of users per cell, but at the expense of the throughpupt per user. It is a safe choice.
    Reduce this value to provide more throughput per user, but then you might see a higher TBF congestion.
    you could try to perform such optimization, step by step, to find the best compromise :
    MAX_DL_TBF_SPDCH = 8 –> 6 –> -> 4

    Major parameters in GPRS are:
    max pdch
    max pdch high load
    min pdch

    They must be chosen carefully depending on the number of TRX in your cell.

    Cheers
    pix

    #65263 Reply
    Pawa
    Guest

    hi Pix

    thanks for quick answer i appreciate it very much

    i will try to apply parameters you recommended and will write about result here

    another question – just can’t understand the difference between MIN_PDCH and MAX_PDCH_HIGH_LOAD – i set
    MIN_PDCH = 3 and saw in statistic that 3 time-slots are always busy
    then set MIN_PDCH = 0 but MAX_PDCH_HIGH_LOAD = 3 – and got the same 3 time-slots which are always busy … h-mmmm

    another question about FER and RxQual:
    I exported RxQualAverage for my test area for 10 days and was surprised with coloration NPO did. RxQual > 0.8 has RED color…. i saw the formula – very unusual way to get average value – am i right if i say that is a “weighted” value?
    but back to my original issue – i need a way to estimate the result of hopping activation citywide, because main kpis changed specifically and drive test i ll do maybe next week. moreover i thought that the same method could aplied for estimation other mass changes – new frequency plan for example.
    i am looking for something as descriptive as logs from drive-test are and as easy-to-get as daily statistic data (RMS i mean…)

    best regards, Pawa

    #65264 Reply
    pix
    Guest

    pawa,


    MIN_PDCH = 0 but MAX_PDCH_HIGH_LOAD = 3 – and got the same 3 time-slots which are always busy … h-mmmm

    that’s normal, it is the way it works now. the max_pdch_high_load timeslots are “cleared” only when there is no more GPRS traffic in the cell. In which case they can be used by TCH.
    Min_pdch are always booked by PDCH, even when there is no PS traffic.


    fh activation and follow-up

    i’m not sure that the RMS can help you. you should rely on more standard indicators, such as call drop rate, CSSR, sdcch assign unsuccess rate, outgoing handover execution rate, handover quality, handover interference, etc.


    rxqual average

    it’s not weighted. It is a pure arithmetic average, no worries.
    0*samples(rxqual0) +
    1*samples(rxqual1) +
    2*samples(rxqual2) +
    3*samples(rxqual3) +

    all divided by the total number of samples.

    regards
    pix

    #65265 Reply
    Pawa
    Guest

    Hi Pix!

    Thanks a lot for detailed answer. I see i should be very careful with MAX_PDCH_HIGH_LOAD in the future πŸ™‚

    but i still have questions…
    this one is theoretical, but still – very curious to me.

    we use for speech normal burst, don’t we? which contains 114 “useful” bits and 26 – TSC and 8 – tail bits and flags. What kind of burst we use for PS? Still – normal burst (i.e. 114 bits as payload)? or we use all 148(140) bits for “user’s” data? i’m asking this question because as i know MS doesn’t send measurement reports while in PS mode – maybe because 26 bit for TSC are also used for “user’s” data? and MS just can’t calculate BER (RxQual)….
    i’m sure that MS “is silent” while in PS – i saw it in NPO – all trxs carring PS data are empty and have no RMS data at all – no RxLev, nor RxQual, nor TA data….

    oh, about RxQual, FER and other stuff:
    i exported FER_UL for my test area for 10 days and saw an amazing picture – sometimes it is enormous (permanently, without spalashes) even while everything elseis OK: RxLev and RxQuall for example.
    What could be reason for such abnormal behavioure – bad UL FER?

    Many thanks in advance !!!

    Best regards, Pawa

    #65266 Reply
    Pawa
    Guest

    Hi Pix!
    Sorry for my molestation but i don’t know other person who can help us πŸ™‚ please πŸ™‚

    New question:
    – Is it a SUB value for UL FER that we can see in NPO?

    I can’t find a precise information about this in the description of the indicator “RMS_UL_ConsecutiveFrameErasure” – just common info…
    i think it should be a SUB value but i’m not confident in my assumptions.

    and the second question:
    I read one pretty thing:
    “Rel’99 specification includes the enhanced measurement report,
    which together with other enhancements brings the DL FER reporting. With this enhancement,
    terminals will report DL FER, thus permitting the network to generate DL FER
    statistics based on these reports. The FER performance data presented in this section have
    been collected through drive tests”

    I saw parameter EN_EXT_MEAS_REP in OMC-R… we use B10 – so… if i set it to ENABLE – will i get desired data? :)))

    Best regerds, Pawa

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