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Abis structure question

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  • #49615 Reply
    Keith
    Guest

    All,

    I’ve been reading up on A-bis interface structure and have ended up a bit confused. I hope you can help

    The standards and books tend to discuss the E1 method with a number of structures for differing numbers of TRX etc. Which of these structures tends to get deployed?

    I also see a lot of attempts to make the Abis interface more efficient, using ATM or IP backhaul ( usually over the same E1 bearers ) how widespread are these solutions?

    best regards,

    Keith

    #49616 Reply
    pix
    Guest

    hello keith,

    E1 is divided in 32 TS. Each TS = 64 kbps.
    TS 0 is reserved for synchro or adressing (??? to be verified ???).

    Then each TRX occupies 2 TS for its traffic, and need few kilobits for its signalling (the RSL)..

    There are many possibilities regarding the RSL : mostly it can be carried on one quarter, one half, or on full TS.

    Sometimes it can even be carried within the 2 TS reserved for the TRX traffic (that’s a special configuration, with restrictions on TRX configuration)

    Most common configurations : 4 RSL within one TS, or 2 RSL within one TS (depending on how much signalling & SMS the cell is carrying)

    FYI, the OML (link with OMCR, for supervision) is multiplexed with the RSLs, because it doesn’t require much bandwidth.

    About Abis over IP, it is spreading. I believe some vendors already have this solution available in their portfolio. For alcatel, it will be available end of next year (release B11).

    #49617 Reply
    Ted
    Guest

    Hi PIX,

    If Alcatel makes available A.bis over IP, will it be on totally new BTS and BSC models or existing BTS can be used? Or using external boxes? Thanks

    #49618 Reply
    Keith
    Guest

    Pix, Many Thanks, that helps a lot.

    I also notice the A-bis protocol includes cyphering commands to protect the air interface. Is the cyphering done on the BSC or the BTS nodes? That is , is the speech within the TRAU frames in clear channels on the A-bis interface and then cyphered/decyphered on the BTS?

    #49619 Reply
    RK
    Guest

    Just wonder how the Abis over IP will work – will it be Abis over IP over TDM (E1) ? or somekind of ethernet cable running from BTS using ADSL or something ?
    I would also think the IP network will have to be private since QoS (bandwidth) necessary otherwise cannot be maintained.

    I believe Ericsson and Nokia already offer this feature but wonder how they’ve implemented this on their BSS- any significant changes to BTS or BSC design ?

    PLease extend your comments.

    RK

    #49620 Reply
    pix
    Guest

    Ted …..
    regarding ABIS IP : i don’t know for sure, but it seems impossible for alcatel to design a new feature that would force customer to change their BTS’s.

    For the BSC, it might be needed to use the latest BSC/MFS EVOLUTION (MX) (i’m 80% sure about this info). so the BSC G2 will not support Abis IP.

    Keith….
    The ciphering is performed inside the BTS and the MS(encryption/decoding)? The TRAU frames are not ciphered.

    RK…
    The Abis over IP uses the same physical link as before (2 Mb/s link or more, over microwave, sattelite, or cable). The benefit of IP-protocol is to have some kind of flexibility in the usage of this link. I don’t think the BTS-BSC link will ever be carried on the Internet 🙂

    Sorry about the late answers, i missed out this thread..

    #49621 Reply
    RK
    Guest

    But Femto BTSs (the home base stations thats catching-up) are using the public internet for backhauling. But maybe since you’re talking about 1-2 users only the public IP network is OK (?)

    I fully agree though, that for a macro BTS with say 12 radios per sector an IP backhaul and using public IP doesn’t sound logical.

    Another solution that vendors are using to save on the backhaul is the Abis compression technique in case their IP backhaul solution is not ready.

    RK

    #49622 Reply
    Keith
    Guest

    All,

    Is the structure on an A-bis T1 trunk anything like the E1? I.e how are the TRX/signalling channels organised compared to an E1?

    #49623 Reply
    Keith
    Guest

    Hi All,

    I’m still trying to figure out the differences in A-bis on T1 from E1. Can anyone help? Much Appreciated

    #49624 Reply
    pix
    Guest

    keith,

    i think this can be found easily on wikipedia, doesn’t it ?

    #49625 Reply
    bert
    Guest

    ericsson
    has a full ip solution implementing a extra node between the bts and the bsc from bsc to the siu ip connection from
    siu to bts lapd e1 or t1 up to 64 trx’s.
    total ip towards a micro or a pico is also possible

    #49626 Reply
    Joeee
    Guest

    Hi,

    What is the meaning of interface ?

    #49627 Reply
    pix
    Guest

    interface is the link between two equipments. i.e. between BTS and BSC, it is a abis link, a.k.a. an abis interface.

    check wikipedia for more details 😉

    #49628 Reply
    inder
    Guest

    Is ciphering done on bts side,whn VLR sends a command to MSC.about Ciphering of a particular MS.

    Wht is the parameter that BTS has(if it does the Ciphering)

    #49629 Reply
    inder
    Guest

    why do we use transcoder for Packet Control unit to link with SGSN.
    As SGSN has its own parametrs,still we have to link it with Transcoder for Gb link.(For data Transmission)

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