31519066 WCDMA Air Interface Fundamentals

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Transcript of 31519066 WCDMA Air Interface Fundamentals

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    Lucent Technologies Proprietary 2

    OBJECTIVES

    Describe the requirements and drivers behinds the W-CDMA Air Interface.

    List the layers UMTS radio Air Interface protocol stackand the responsibility of each layer

    UMTS Channel Types and their purpose Gain understanding of UMTS Modes: FDD and TDD

    Protection in UMTS:Describe the forward error correctionemployed by UMTS Air interface

    Channelizations in UMTS Source Identification: Scrambling codes/Gold Codes

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    UTRAN FUNCTIONS

    Node B

    Termination of Iub Interface from RNC Conduct Radio Environment Survey (BER estimate, Rx signal strength

    etc..)

    Inner Loop Power Control

    Open loop power control

    Radio Channel Coding/decoding Mapping of coded composite transport channels on physical channel

    modulation and spreading/dispreading of physical channels

    Frequency and time Synchronization

    Error detection on transport channels and indication to higher layers

    Termination of Uu interface from the UE etc..

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    Lucent Technologies Proprietary 6

    3G SERVICES

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    3G CHARACTERISTICS - Asymmetric

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    3G CHARACTERISTICS Concurrent Services

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    3G CHARACTERISTICS ALWAYS ON

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    W-CDMA INTERFACE

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    SPECTRUM FOR UMTS

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    UMTS MODES

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    UMTS RADIO PROTOCOL STACK

    Layer-1

    Layer-2L

    Layer-2U

    Layer-3

    OSI

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    RADIO PROTOCOL STACK FUNCTIONS

    Physical Layer Functions (Layer-1)

    Forward error correction, coding,interleaving Measurements

    Soft handover execution

    Multiplexing/mapping of services on dedicated physical code channels

    Modulation, spreading, demodulation, dispreading of physical channels

    Frequency and time synchronization

    Fast closed-loop power control RF processing

    MAC Layer Function (Layer-2L)

    Selection of appropriate transport format

    Service multiplexing on RACH, FACH and dedicated channels

    Scheduling

    Access resolution on RACH Contention resolution on RACH etc..

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    RADIO PROTOCOL STACK FUNCTIONS

    RLC Functions (Layer-2U): Segmentation and assembly

    Transfer of user data

    Error correction through retransmission optimized for physicallayer

    Sequence integrity

    Flow control

    PDCP Function (Layer-2U) Service specific. Exists only in the User Plane and only for

    services from PS domain. Contains compression methods neededfor better spectral efficiency

    RRC Functions: Broadcast of system information Radio Resource handling

    Control of requested QOS

    UE measurements reporting and control of the reporting

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    W-CDMA Channel Architecture

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    OBJECTIVE

    UMTS W-CDMA Channels Structure

    Map channels to radio interface protocol

    stack

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    CHANNELS OVERVIEW

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    Gift ANALOGY

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    Channel Overview Cont

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    UMTS RADIO INTERFACE CHANNELS

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    LOGICAL CHANNELS

    Traffic Channels - Dedicated Traffic Channel (DTCH)

    - Common Traffic Channel (CTCH)

    Control Channels - Dedicated Control Channel (DCCH)

    - Common Control Channel (CCCH)

    - Broadcast Control Channel (BCCH)

    - Paging Control Channel (PCCH)

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    TRANSPORT CHANNELS

    Dedicated Channels - Dedicated Channel (DCH)

    Common Channels - Random Access Channel (RACH)

    - Forward Access Channel (FACH)

    - Broadcast Channel (BCH)- Paging Channel (PCH)

    - Common Packet Channel (CPCH)

    - Downlink Shared Channel (DSCH)

    (CPCH & DSCH are optional channels and

    are not supported in Lucents initial release)

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    PHYSICAL CHANNELS

    Uplink Dedicated Channels

    Dedicated Physical Data Channel (DPDCH) Dedicated Physical Control Channel (DPCCH)

    Common Channels Physical Random Access Channel (PRACH) Physical Common Packet Channel (PCPCH)

    Downlink

    Dedicated Channel Dedicated Physical Channel (DPCH) Common Channels

    Common Pilot Channel (CPICH) Primary Common Control Physical Channel (P-CCPCH) Secondary Common Control Physical Channel(S-CCPCH) Synchronization Channel (SCH) Physical Downlink Shared Channel (PDSCH) Acquisition Indication Channel (AICH) Page Indication Channel (PICH)

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    UMTS RADIO CHANNEL MAPPING

    BCCH

    PCCH

    CCCH

    DCCH

    DTCH

    CTCH

    BCH

    CPCH

    DSCH

    DCH

    RACH

    FACH

    PCH

    P-CCPCH

    S-CCPCH

    P-CPICH

    PRACH

    DPDCH

    DPCCH

    PDSCH

    PICH

    P-SCH

    S-SCH

    AICH

    S-CPICH

    PCPCH

    Logical Channels Transport Channels Physical Channels

    DPCHKey: Uplink

    Downlink

    Bidirectional

    Data Transfer

    Association

    Control Ch

    Traffic Ch

    Common Ch (no FPC)

    Common Ch (FPC)

    Dedicated Ch (FPC)

    Info Channels

    Assoc Channels

    Fixed Channels

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    W-CDMA PHYSICAL LAYER PROCESSING

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    W-CDMA PHYSICAL LAYER PROCESSING

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    W-CDMA PHYSICAL LAYER PROCESSING

    Protecting Data/User Information:

    Forward error correction mechanism are applied to allow addinginformation to the data streams enabling receiver to correct the errorsduring decoding process.

    Achieved by digital coding techniques such as:

    Convolution coding:

    Can use or 1/3 rating coders.

    Used for services 19.2Kbps or less e.g. Voice

    Turbo Coding:

    Uses two convolution coder working in parallel.

    Turbo coder defined as 1/3 rate.

    Additional processing relative to convolution coder.

    Added delay due to additional processing makes it perfect fornon real-time services such as WEB browsing.

    Used for services data rate 19.2Kbps or higher.

    Interleaving:

    Reorder original coded data streams to help error correction

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    W-CDMA PHYSICAL LAYER PROCESSING

    Channel Separation

    Uses OVSF codes OVSF is applied to achieve 3.84Mcps

    fixed channel rate

    Source Identification

    Scrambling codes are used for

    Node-B and UE identification

    The set of scrambling codes are

    known as Gold codes

    2-24 Gold codes for UL (UE)

    512 are assigned for DL(Node-B)