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where is the wrong on my idea?

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  • #48101 Reply

    Hi guys,

    Any body tell me what is incorrect in my idea regarding the half rate traffic (NAMR)


    There is 10 time slots
    with 70% Half rate, we will get the following:

    3 full rate time slots
    14 half rate time slots

    in NAMR, the 3 full rate time slots will be assigned to the users untill being all dedicated. Then the other 14 time slots will start being loaded.

    that means for the above example, and when the capacity is fully utilized, I should see half rate traffic (14 time slots) more than the full rate traffic (3 time slots) but this is not the fact. In statistic, I see full rate traffic always more !

    Note: ericcsson

    #48102 Reply

    Are you sure it works this way ? I think the 70% corresponds to the load limit at which the calls are being established in HR.

    For instance, if this threshold is set to 70% :
    from 0% to 70% of TCH load (number of busy TCH / total number of TCH), calls are setup in FR.
    If the load is greater, then the new calls are established in HR.
    When the TCH load goes below another threshold (usually 30% or 40%), the calls are established in FR again.

    Maybe i’m wrong for ericsson, though…? They implemented it in a special way ?

    You can try to decrease 70% to 40%; and see what is the effect on the ration HR/FR.

    #48103 Reply

    Hi Pix how are you?

    HR=70%, this is the percentage of the idle tch. Once this percentage become less, the half rate time slots will work.

    We can avoid the confusion by saying that we have 10 rooms (time slots) in a hotel (TRU). The first three subscribers will be given a whole room for each. Any additional subscribers will be given 1/2 room (two people in one room).

    The capacity of the Hotel, therefore is 14 subscribers
    3 living alone
    14 living in pairs

    therefore, the HR traffic should be more !

    Half rate traffic = people living in sharing rooms.

    But in the statistic, the full is always more ! even if there is congestion (whole capacity is utilized)

    #48104 Reply

    Hi Akefa,

    Thx for the great explanation ๐Ÿ˜€ So who’s paying the hotel bill in the end ?

    So if your threshold definition is correct, then let’s see at it differently : you can check your traffic load calculation speed. By the time the system detects more than 30% of FR utilization (3 ts used for FR, in your example), the actual cell load is already more than 70% … ?

    So have a look to the traffic load averaging windows… who knows ?

    Other than that, there must be a problem somewhere. You’re probably missing out something : BSC capacity is enough ? other thresholds somewhere ?
    what about the limit threshold to stop the usage of HR, and setup the new calls in FR ?

    good luck,

    #48105 Reply

    I was also thinking about incoming HO : is it possible that incoming HO remain in FR ? That would explain…

    #48106 Reply
    Da Architect

    I haven’t faced FR traffic more than HR in case DTHNAMR = 70% (E//) or in case THR_FR_LOAD_L_SV1 = 30%THR_FR_LOAD_L_SV3 = 30% (alcatel). But i have few cells with DTHNAMR = 100% and still carry FR Traffic. Therefore I thought of PIX last suggestion that is Incoming HO remains FR. I would really appreciate if someone can explain why incoming HO doesn’t change to HR in case target cell has DTHNAMR = 100% (Ericsson)or THR_FR_LOAD_L_SV = 0% (alcatel).

    many thanks,

    #48107 Reply

    well, in alcatel system, it is related to the cell parameter “KEEP CODEC”… i don’t know for ericsson.

    #48108 Reply


    We should understand one thing, in Ericsson system there is two parameters work as trigger point when the cell will start carrying HR traffic.
    – DTHNAMR ..for NON AMR calls.
    – DTHAMR..for AMR calls only.

    So, if you set DTHNAMR to 70% for example, this means that when the load on the cell reach more than 70%, the HR traffic will start, mean any new call will be on HR not FR. As sson as the percenatge of IDLE TCH time slots is less than or equal 70% all the traffic on the cell will be on FR not HR.

    I suggest to you check the busy hour traffic for the cell and check the traffic hourly on the cell, you will see sure the peak hour is not much so the majority of the traffic will be on FR.
    Hope this can help all.

    #48109 Reply

    Jehad, your definition of the NAMRHR is reversed. Plz look at my second answere in this topic :). Furthermore, I said the cell is congested which means i am talking about the peak traffic hour.

    Pix & Da Architect,

    I am suspecting that the capacity limit of the BSC is the reason. thanx pix to remind me what i should remember all the time ! I will check this issue.
    In fact I am interested in the case of 100% HR in which FR traffic survive. if we want to be sure that the incoming HOs are the source of the full rate traffic, Da Architect I suggested for you to make a table of two coloms: incoming handover and full-rate traffic to see if thier values increase and decrease togather ๐Ÿ™‚ let us know

    #48110 Reply
    Da Architect

    Dear Akefa

    Accompanied to your value suggesiton, i will conduct a drive test scenario in E// cells to realize reason behind this FR traffic.

    #48111 Reply
    Da Architect

    Dear Pix,

    in Alcatel, if parameter [KEEP_CODEC_HO = free choice of the codec]; what would be the BSC desicsion for incoming HO to a target cell that has THR_FR_LOAD_L_SV1 = THR_FR_LOAD_L_SV3 = 0%

    Dear Akefa,

    Is there a similar parameter in Ericsson?

    #48112 Reply

    da architect,

    you need to set the THR_FR_LOAD_U_SVi as well.
    If they’re all at 0%, the cell will only carry HR calls, at any time of the day, and incoming HO with KEEP CODEC HO FREE will be allocated as HR.
    Well, that’s what’s written in the doc, i never tried it on the field.

    I’m sorry if my question is too personal, but in which country are you working in ?

    #48113 Reply
    Da Architect

    Hello pix,

    ofcourse, I know that i have to modify the upper threshold too. but i didn’t know about the keep_ho_codec action in case it was set to free.

    Recently I work in Africa in the systems(3G/EDGE/GPRS/2G) for the two platforms (Alcatel + Ericsson)

    #48114 Reply

    can you please tell me if BCCH, SDCCH , Dynamic SDCCH and reserved data Time Slots are taken into account in the calculation of the cell load : [load = NB_BUSY_TS / NB_TS ]
    I’m speaking about Alcatel BSS
    Thanks ๐Ÿ™‚

    #48115 Reply

    Ericsson document tell us:
    In general the following cases occur:

    If the MS and the cell support AMR HR and the number of idle FR TCH:s divided by the total number of de-blocked FR TCH:s is equal or above DTHAMR FR TCH:s will have precedence over HR TCH:s. If the number of idle FR TCH:s divided by the total number of de-blocked FR TCH:s is less than DTHAMR HR TCH:s will have precedence over FR TCH:s
    If the MS or the cell do not support AMR HR and the number of idle FR TCH:s divided by the total number of de-blocked FR TCH:s is equal or above DTHNAMR FR TCH:s will have precedence over HR TCH:s. If the number of idle FR TCH:s divided by the total number of de-blocked FR TCH:s is less than DTHNAMR HR TCH:s will have precedence over FR TCH:s

    so if your threshold for DTHNAMR be 70% so the traffic will start with FR channel.
    4 TRXs (1 BCCH & 2 SDCCHs & 29 TCHs)
    %70 * 29 = 21
    the BSC assigns FR channel in the begining until 8th channel assignment, for 9th MS assigning HR channel will be start.
    1- some MSs can not support HR, so BSC assigns FR channel to them.
    2- sometimes incoming HO parameters forces BSC to assign FR channel to MS.

    Hi pix, Ericsson has only 1 threshold for Half Rate. Nokia has 2 threshold (FRL and FRU) for Half Rate (Hysteresis).

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