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NACC/PSI

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  • 16th January 2008 at 09:42 #50501
    slim
    Guest

    Hello everyone,
    Is it possible to activate NACC without PSI or the inverse?
    what is the predicted result of such tunning or what’s tke impact on general?

    Thanks in advance

    17th January 2008 at 10:29 #50502
    Pix
    Guest

    NACC and PSI are two independent features, that both leads to reducing the down-time of a cell reselection during transfer mode.

    Using just one of them will reduce the down-time.
    Using two of them will further reduce the down-time.

    29th February 2008 at 19:15 #50503
    Ater
    Guest

    Sorry but what is PSI?

    1st March 2008 at 12:37 #50504
    Pix
    Guest

    Packet System Information (PSI)
    these messages are sent asap to the MS after a cell reselection during packet transfer mode. They allow the MS to resume the transfer, this is the reason why they are provided to the MS earlier than their usual occurence in the PACCH.

    It is a special feature, of cours, which allows a shorter reselection outage.

    1st March 2008 at 12:41 #50505
    Pix
    Guest

    You have a good article here :
    mobilewireless.wordpress.com/2007/11/17/improving-gprs-data-experience-using-nacc/

    1st March 2008 at 15:27 #50506
    paraHO
    Guest

    The article seems to suggest that the MS selects the cell for re-selection and instructs the network the cell to reselect and the network just performs the processes to make that happen. If I understand right this put control of handover in the hands of MS and not the network as previous with e.g GSM or have I got that wrong?

    2nd March 2008 at 10:13 #50507
    Pix
    Guest

    ParaHO,

    In GPRS/EGPRS, there is no handover : indeed the MS is in charge of deciding to perform a cell reselection or not. This is the default “NC0” mode.

    A reselection is always a “bad” suprise for the BSS : the transfer is stopped until the MS eventually finished to reselect the new cell. Then only, after the MS gathered some sys-info messages, the transfer is resumed.

    NACC/PSI add 2 main features to this “stupid” reselection :
    1. the MS informs the BSS beforehand –> the BSS transmits the needed SI before the reselection
    2. after reselection, the needed SI are transmitted ASAP, in order for the MS to be ready for resume.

    I’m simplfying a lot because I don’t have all the details in memory. Do you need more info ?

    2nd March 2008 at 15:33 #50508
    paraHO
    Guest

    Pix you are right and I wrong about handover and GPRS. Reading the article I thinking about GPRS Classes (A, B, C) and thinking of Class A which has handover in dedicated-mode I blur the issues in my mind with all Classes….

    I send me back to school and write out 100 times I must not blur GPRS Classes :-))

    2nd March 2008 at 17:52 #50509
    Pix
    Guest

    ParaHO, it’s okay, we’re all allowed to blur some stuff, once in a while.

    Seeing how you helped people out on some questions, I personnaly don’t think you should not sit on a bench at school, but rather stand up behind the desk 😉

    2nd March 2008 at 19:42 #50510
    paraHO
    Guest

    thx Pix… maybe when I know as much as you 😉

    3rd March 2008 at 19:10 #50511
    Ater
    Guest

    thanks Pix for the info.

    Let me see if I understood well.

    For PSI you need to alocate a MPDCH in the cell?

    Our vendor dont recomend this because not many MS support it

    3rd March 2008 at 20:27 #50512
    Pix
    Guest

    No MPDCH needed : the PSI are transmitted on the PACCH of the MS.

    Your vendor is right : there is no MS that supports MPDCH, as far as i know.

    3rd June 2008 at 15:53 #50513
    NiceTelecom
    Guest

    Hello everybody,
    I thought that only ericsson used the abbrevation MPDCH (standing for master PDCH)

    Normally The MPDCH is a dedicated PDCH carrying the PBCCH (and a PCCCH and a PDTCH).
    So I don’t understand how a MS is not able to read a PBCCH?

    3rd June 2008 at 20:01 #50514
    pix
    Guest

    MPDCH is 3GPP-standard, not Ericsson’s. It does mean Master PDCH, in opposition to the Slave PDCH (or just called “PDCH”)

    As per today, a MS is not able to listen to a BCCH timeslot and a MPDCH timeslot at the same time.

    The reason why they’re not able to do it, i don’t know… that’s the way it is 🙂 Perhaps there are some inconsistencies in the 3GPP, that makes it too complicated to implement ?

    4th June 2008 at 08:18 #50515
    NiceTelecom
    Guest

    Hello pix, thanks to make it clear, for other.
    In fact I didn t say that it is an ericsson standard 😉 I just said that only ericsson use this abbreviation (In fact this this what ericsson claim in one of their equipment material).So Apparently I am wrong: Not only Ericsson use MPDCH, unless Ericsson use MPDCH for an other purpose

    In Ericsson it seems it is working like that:
    you have the information about the MPDCH inside the bcch.
    You listen first the bcch and you have info about where to find the MPDCH (a dedicated PDCH)
    But without MPDCH you don’t have PCCCH.

    According with what I understand
    If we have a MPDCH, we don’t have to use PCH, RACH,or AGCH, for a PS
    instead we use PPCH, PRACH, PAGCH which are in a dedicated PDCH (the MPDCH).
    And in the point of view equipment we use only the PCU.

    If we don’t have MPDCH, we don’t have PPCH, PRACH, PAGCH, we use the normal GSM logical channel, PCH, RACH, AGCH,
    and in point of view equipment we use both TRH(GSM signaling handler) and PCU.

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