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Synchronisation


Different UTRAN synchronisation required in a 3G network:
  • Network synchronisation
  • Node synchronisation
  • Transport channel synchronisation
  • Radio interface cynchronisation
  • Time alignment handling


    25402 Synchronisation Issues Model

    Synchronisation Issues Model


    Network Synchronisation relates to the distribution of synchronisation references to the UTRAN Nodes and the stability of the clocks in the UTRAN (and performance requirements on UTRAN internal interfaces). The distribution of an accurate frequency reference to the network elements in the UTRAN is related to several aspects. One main issue is the possibility to provide a synchronisation reference with a frequency accuracy better than 0.05 ppm at the Node B in order to properly generate signals on the radio interface.

    Node Synchronisation relates to the estimation and compensation of timing differences among UTRAN nodes. FDD and TDD modes have different requirements on the accuracy of the timing difference estimation and on the necessity to compensate for these differences. Positioning / Localisation functions may also set requirements on Node Synchronisation.

    The Transport Channel Synchronisation mechanism defines synchronisation of the frame transport between RNC and Node B, considering radio interface timing.

    The Radio Interface Synchronisation relates to the timing of the radio frame transmission (either in downlink [FDD] or in both directions [TDD]). FDD and TDD have different mechanisms to determine the exact timing of the radio frame transmission and also different requirements on the accuracy of this timing. In FDD Radio Interface Synchronisation is necessary to assure that the UE receives radio frames synchronously from different cells, in order to minimise UE buffers.

    The Time Alignment Handling procedure over Iu relates to the control of DL transmission timing in the CN nodes in order to minimise the buffer delay in SRNC. This procedure is controlled by SRNC.



    Further reading: 3GPP TS 25.402


      UMTS Overview UMTS Network UMTS Frequencies UMTS Coding UMTS Link Budget
    UMTS Security UMTS Codes Synchronisation Co-location
    3G Data Speeds UTRA Time Slots UTRA Channels WCDMA Spreading
    UMTS QoS Channel Coding Media Formats Compressed Mode
    UMTS HSDPA UMTS Handovers Location Services UMTS Power Control
    UMTS Overview Cell Search Random Access RCC States Iui Frame Structure
    CDMA Overview Call Setup UTRAN Interfaces Paging Virtual Home Environment

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