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    WCDMA Radio Interface PhysicalLayer

    Confidential Information of Huawei. No Spreading Without Permission

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    www.huawei.com

    Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.

    WCDMA Radio InterfacePhysical Layer

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    WCDMA Radio Interface PhysicalLayer

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    Page1Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.

    Foreword

    The physical layer offers data transport services to higher layers.

    The physical layer is expected to perform the following functions in

    order to provide the data transport service, for example: spreading,

    modulation and demodulation, despreading, Inner-loop power

    control and etc.

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    WCDMA Radio Interface PhysicalLayer

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    Page2Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.

    Objectives

    Upon completion of this course, you will be able to:

    Outline radio interface protocol Architecture

    Describe structure and functions of different physical channels

    Describe UMTS physical layer procedures

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    WCDMA Radio Interface PhysicalLayer

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    Page3Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.

    Contents

    1. Physical Layer Overview

    2. Physical Channels

    3. Physical Layer Procedure

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    Page4Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.

    UTRAN Network Structure

    RNS

    RNC

    RNS

    RNC

    Core Network

    NodeB NodeB NodeB NodeB

    Iu-CS Iu-PS

    Iur

    Iub IubIub Iub

    CN

    UTRAN

    UEUu

    CS PS

    Iu-CSIu-PS

    CSPS

    UTRAN: UMTS Terrestrial Radio Access Network.

    The UTRAN consists of a set of Radio Network Subsystems connected to the Core Network

    through the Iu interface.

    A RNS consists of a Radio Network Controller and one or more NodeBs. A NodeB is

    connected to the RNC through the Iub interface.

    Inside the UTRAN, the RNCs of the RNS can be interconnected together through the Iur.

    Iu(s) and Iur are logical interfaces. Iur can be conveyed over direct physical connection

    between RNCs or virtual networks using any suitable transport network.

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    WCDMA Radio Interface PhysicalLayer

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    Page5Copyright 2008 Huawei Technologies Co., Ltd. All rights reserved.

    Uu Interface Protocol Structure

    L3

    control

    control

    control

    control

    C-plane signaling U-plane information

    PHY

    L2/MAC

    L1

    RLC

    DCNtGC

    L2/RLC

    MAC

    RLCRLC

    RLC

    Duplication avoidance

    UuS boundary

    L2/BMC

    control

    PDCPPDCP L2/PDCP

    DCNtGC

    RRC

    RLCRLC

    RLCRLC

    BMC

    radio bearer

    logical channel

    transport channel

    The layer 1 supports all functions required for the transmission of bit streams on the

    physical medium. It is also in charge of measurements function consisting in indicating to

    higher layers, for example, Frame Error Rate (FER), Signal to Interference Ratio (SIR),interference power, transmit power, It is basically composed of a layer 1 management

    entity, a transport channel entity, and a physical channel entity.

    The layer 2 protocol is responsible for providing functions such as mapping, ciphering,

    retransmission and segmentation. It is made of four sub-layers: MAC (Medium Access

    Control), RLC (Radio Link Control), PDCP (Packet Data Convergence Protocol) and BMC

    (Broadcast/Multicast Control).

    The layer 3 is split into 2 parts: the access stratum and the non access stratum. The access

    stratum part is made of RRC (Radio Resource Control) entity and duplication avoidance

    entity. duplication avoidance terminates in the CN but is part of the Access Stratum. Thehigher layer signalling such as Mobility Management (MM) and Call Control (CC) is

    assumed to belong to the non-access stratum, and therefore not in the scope of 3GPP TSG

    RAN. In the C-plane, the interface between 'Duplication avoidance' and higher L3 sub-

    layers (CC, MM) is defined by the General Control (GC), Notification (Nt) and Dedicated

    Control (DC) SAPs.

    Not shown on the figure are connections between RRC and all the other protocol layers

    (RLC, MAC, PDCP, BMC and L1), which provide local inter-layer control services.

    The protocol layers are located in the UE and the peer entities are in the NodeB or the RNC.

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    Many functions are managed by the RRC layer. Here is the list of the most important:

    Establishment, re-establishment, maintenance and release of an RRC

    connection between the UE and UTRAN: it includes an optional cell re-selection,

    an admission control, and a layer 2 signaling link establishment. When a RNC is in

    charge of a specific connection towards a UE, it acts as the Serving RNC.

    Establishment, reconfiguration and release of Radio Bearers: a number of

    Radio Bearers can be established for a UE at the same time. These bearers are

    configured depending on the requested QoS. The RNC is also in charge of ensuring

    that the requested QoS can be met.

    Assignment, reconfiguration and release of radio resources for the RRC

    connection: it handles the assignment of radio resources (e.g. codes, shared

    channels). RRC communicates with the UE to indicate new resources allocation

    when handovers are managed.

    Paging/Notification: it broadcasts paging information from network to UEs.

    Broadcasting of information provided by the non-access stratum (Core Network)

    or access Stratum. This corresponds to system information regularly repeated.

    UE measurement reporting and control of the reporting: RRC indicates what

    to measure, when and how to report.

    Outer loop power control: controls setting of the target values.

    Control of ciphering: provides procedures for setting of ciphering.

    The RRC layer is defined in the 25.331 specification from 3GPP.

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    The RLCs main function is the transfer of data from either the user or the control plane

    over the Radio interface. Two different transfer modes are used: transparent and non-

    transparent. In non-transparent mode, 2 sub-modes are used: acknowledged or

    unacknowledged.

    RLC provides services to upper layers:

    data transfer (transparent, acknowledged and unacknowledged modes).

    QoS setting: the retransmission protocol (for AM only) shall be configurable by

    layer 3 to provide different QoS.

    notification of unrecoverable errors: RLC notifies the upper layers of errors that

    cannot be resolved by RLC.

    The RLC functions are:

    mapping between higher layer PDUs and logical channels.

    ciphering: prevents unauthorized acquisition of data; performed in RLC layer for

    non-transparent RLC mode.

    segmentation/reassembly: this function performs segmentation/reassembly of

    variable-length higher layer PDUs into/from smaller RLC Payload Units. The RLC size

    is adjustable to the actual set of transport formats (decided when service is

    established). Concatenation and padding may also be used.

    error correction: done by retransmission (acknowledged data transfer mode only).

    flow control: allows the RLC receiver to control the rate at which the peer RLC

    transmitting entity may send information.

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    MAC services include:

    Data transfer: service providing unacknowledged transfer of MAC SDUs between

    peer MAC entities.

    Reallocation of radio resources and MAC parameters: reconfiguration of MACfunctions such as change of identity of UE. Requested by the RRC layer.

    Reporting of measurements: local measurements such as traffic volume and

    quality indication are reported to the RRC layer.

    The functions accomplished by the MAC sub-layer are listed above. Heres a quick

    explanation for some of them:

    Priority handling between the data flows of one UE: since UMTS is multimedia,

    a user may activate several services at the same time, having possibly different

    profiles (priority, QoS parameters...). Priority handling consists in setting the right

    transport format for a high bit rate service and for a low bit rate