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HO Averaging / BSIC measurements

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  • #58145 Reply
    Askari
    Guest

    Hi eveyone I have a three questions.

    1. Imitiately after HO if the new serving cell has some common neighbours with the old serving cell ( which it usually does), does the MS keep previous measurements (including FCH and SCH) info of those common neis measured before HO, or discard all previous measurements and start afresh.

    2. for the Measurements of neighbours it has two times one withen a frame when its done with the UL And DL TS, (4 TS used to measure neighbour) and the Idle TS every SAACH Multiframe ( used to sync with FCH and SCH of nei). What does the MS do first
    A) measure the level of neighbour BCCH, and then tune to the top Neighbours in SAACH MF for FCH and then measure BSIC. or
    B)Measure FCH And SCH And use this information to periodically measure the levels of these neighbours.

    3. How does the MS khow as to which of its SAACH MF Idle TS to use to measure which neighbour, as they need to be synchronized i.e neighbours FCH and SCH should come in the time MS is listening.
    Are neighbours synchronied in such way and BA list keeps track of this information

    #58146 Reply
    Pix
    Guest

    Hello Askari,

    I could tell you what i think, but that wouldn’t be very “correct”. The only way to get proper answers is to dig into 3GPP documents, or wait for Pan to do so ๐Ÿ™‚

    #58147 Reply
    Pan
    Guest

    Thank you for recommendations Pix. But who will give such recommendations to my chief:) I want to say also that I don’t know the answers on 99,9% (or may be 99.99%) of questions on which I am answering:)
    To Askari: I Want to notice, you are digging very deeply:) I think that some things that you are rising are implementation dependent. The rest – see 45.008 for the Radio link measurements issues and may be 45.010 for the sinchronisation ussue.
    B.R.

    #58148 Reply
    Pix
    Guest

    Pan,

    if you’re not appreciated in your work, then change company ๐Ÿ™‚ you do have a *little* knowledge (:o)) of telecom networks, I’m sure that would interest some other companies…

    #58149 Reply
    Pan
    Guest

    Askari, concerning your 3 item: Idle frame in 26-multiframe (even number of frames) is sliding respective to FCH and SCH in TS0 wich have 51-multiframe structure. The maximum search time is about 8 frame. Try to count itself.
    B.R.

    #58150 Reply
    Pan
    Guest

    I am sorry for mistake, i was in hurry:). The maximum search time is about 8 26-multiframes or 4 51-multiframes (approximately 1 s)

    #58151 Reply
    Askari
    Guest

    Well Actually I am digging in to investigate how useful it is to have a shorter rather optimal Neighbour list and how it reports etc.

    #58152 Reply
    AliAsgher
    Guest

    Dear Askari, based on some observation on Drive Test logs I guess that

    1) Even if the new cell has got same neighbors as previous the MS will start AFRESH measuring the ARFCNs in the BA list.

    2) Also I have seen that MS actually first measures BCCH RxLevel and then will try to decode the BSIC of the cell. [MS reports Rxlevel of BCCH first in TEMS and then will try to decode BSIC against ARFCNs]

    3) To answer your third question, I might have to develop my own MS first ๐Ÿ™‚

    And BTW, a short neighbor list might add a very little benefit from MS perspective, but it may lead to increased drops in case of overshooting cells etc.

    #58153 Reply
    Askari
    Guest

    Dear Pan,
    For your point in reply to item 3. it is true that the 51 frame Idle is sliding against 24 frome SACCH MF. but how does the site synchronize with its neighbours. As the synchronization should be such that the MS knows which neighbour to measure to decode its FCH / SCH. As far as the standard says a neighbour’s info is measured in 10 secs.
    As far as synchronization is concerned it is beleavable for PCM / GPS synchronized network that the sites might be synchronized with each other and know where in 51 MF which neighbour is. but what would be the case in free running network where BTSs are opperating on internal clocks.

    #58154 Reply
    Pan
    Guest

    Dear, Askari!
    I am supposing the following synchronization scenario when MS search Neighbouring BCCH for the first time (if I am wrong you may to correct me):
    MS gets neighbour’s ARFCHN, BSIC, and RTD (Real Time Difference) from the system info on SACCH.
    By means of RTD it find out TS0 of neighbouring cell.
    Then during each Idle frame in 26-multiframe MS peeks in Neighbour BCCH TS0 and looking for FCCH and SCH.
    As Idle frame is shifting ahead on 1 frame per 1 51-multiframe in TS0 of a Neighbouring BCCH, then at one time the MS will find out the FCCH and SCH (and will check out the BSIC value) of the neighbouring BCCH.
    All subsequential searchings for measurements are based on this result.
    B.R.

    #58155 Reply
    Pix
    Guest

    What is RTD ? I mean… where can I find info about it ?

    #58156 Reply
    Pan
    Guest

    Hello, Pix!
    You may see about RTD in 45.010 and 44.018.

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