31519066 WCDMA Air Interface Fundamentals

7/28/2019 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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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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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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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)

31519066 WCDMA Air Interface Fundamentals

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