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WCDMA Design using Simulink

Chanpreet Singh (10804131)Harpartap Singh (10801557)Jagraj Singh (10807772)Malkeet Singh (10804149)

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Agenda

• About WCDMA

• WCDMA Simulink Model– About the models– Physical Layer – parameters– Coding and Multiplexing– Modulation and Spreading – Channel Models

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About WCDMA …

• WCDMA stands for Wideband Code Division Multiple Access.

• WCDMA can support multiple and simultaneous communications such as voice, images, data, and video.

– Very high and variable bit rates:• 144 kbps: vehicle speed, rural environ.• 384 kbps: walking speed, urban outdoor.• 2048 kbps: fixed, indoor.

– Different QoS for different connections.– High spectrum efficient.– Coexistence with current systems.

• WCDMA is being specified by the 3GPP (Third Generation Partnership Project).

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About the models

• WCDMA has two basic modes of operation:– TDD (Time Division Duplex).

• Low Chip Rate TDD (TD-SCDMA)– FDD (Frequency Division Duplex).

• Duplex communications:– Downlink Channel

• From Node B (Base Station) to UE (User Equipment).– Uplink Channel

• From UE to Node B

• Model simulates transmission of information data (DCH – Dedicated Channel) during a connection.

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About the models

WCDMA Library

WCDMA Multiplexingand Coding

WCDMA Spreadingand Modulation

WCDMA PhysicalLayer

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Physical Layer Specifications

• Physical layer provides data transport support to higher layers via Transport Channels.

• Functions of the Physical Layer:– Error detection.– Encoding/decoding.– Rate Matching/Dematching.– Multiplexing/Demultiplexing different Transport Channels

into/from a Coded Composite Transport Channel (CCTrCH).– Mapping/Demapping of CCTrCH into/from Physical Channels.– Modulation and Spreading/Demodulation and Despreading.– Power Weighting and combining of physical channels.– RF Processing.

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WCDMA Physical Layer Transmitter

Channel Coding andMultiplexing

Layer 2MAC

TransportChannels

Layer 1

CCTrCh PhysicalChannelMapping

SpreadingAnd

Modulation

Channel

DPCH

Pilot BitsControl Channels

Interference (OCNS)Orthogonal

Codes

SlotDPCH

- Scrambling Code- Channelization Code- Transmit Density- Slot Format- Power Settings

- Transport Block Set Size- Transport Block Size- Transmission Time Interval- Size of CRC- Type of Error Correction- Coding Rate- Rate Matching Attribute

Transport Format

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Coding and Multiplexing Specifications

• Physical layer provides data transport support to higher layers via Transport Channels.

• There is a Transport Format associated to each Transport Channel that describes the processing ( Size, encoding scheme, coding rate, …) to be applied by the Physical Layer.

• Every transport block is generated every 10, 20, 40 or 80 ms (Time Transmission Interval – TTI).

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Coding and Multiplexing Overview

CRC Concat/Segment

ChannelEncoder

RateMatching

1st

InterleaverRadioFrame

Segment

CCTrCH

CRC Concat/Segment

ChannelEncoder

RateMatching

1st Interleaver

RadioFrame

Segment

Layer 1

Coding Schemes:- No coding- Convolutional Coding- Turbocoding

Accommodates data ratesto a fixed channel bit rate

Interleaves bits within each Transport Channel

Limits Max Sizeof Codewords

Multiplexes bits from different Transport Channels every 10 ms.

Attaches CRCSize={0,8,12,16,24}

Transmission Time Interval{10,20,40 and 80ms}

Radio Frame{10ms}

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Physical Channel Mapping Overview

PhysicalChannel

Segmentation

2ndInterleaver

One CCTrCH can be mapped onto one or

several PhCHs

SlotBuilder

CCTrCh DPCHDPCH DPCH

TFCI

Power Control Bits

Pilot Bits

Interleaves bits within a Radio Frame coming from

different Transport Channels

Transport Format Combination Index contains information of how the

different transport channel have been processed

Data 1 TPC TFCI Data 2 Pilot

Structure of slot is defined by the Higher Layers via

Slot Format

Data is sent to the Modulation and Spreading

block

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Modulation and Spreading Specifications

• Modulation:– QPSK.– Same gain for I and Q components.

• Spreading or Channelization Operation:– Transforms every bit into a given number of chips, hence

increasing the bandwidth.– Chip Rate = 3.84 Mcps.– By using an orthogonal code for each physical channel, receiver

can separate them.– Orthogonal codes are real-valued OVSF codes (Orthogonal

Variable Spreading Factor) of different length.

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Modulation and Spreading Specifications

• Physical channels required during a connection:– Dedicated Channel:

• DPCH Dedicated Physical Channel– Common Channels:

• P-CPICH Primary Common Pilot Channel– Could be used at the receiver end for channel estimation, tracking

• P-CCPCH Primary Common Control Physical Channel• SCH Synchronization Channel

– Not multiplied by orthogonal code.– Used mainly for cell search: slot and frame timing acquisition.

• PICH Paging Indicator Channel• OCNS Orthogonal Channel Noise Simulator

– Simulates interference caused by other users or signals.

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Modulation and Spreading Overview

DPCH

Spreading

I&QMapping

Common Channels

Scrambling PowerSettings + To

Channel

Orthogonal Codes OVSF

PN SequenceGold Codes

OCNS SCH

QPSK Modulation

Bit Rate Chip Rate{3.84Mcps}

Channelization

Common Channels are

introduced

Scrambling

Power Weighting

Physical Channels are added before being sent to

Pulse Shaping

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Thank you