Transport Channel Processing

Introduction

Introduction

Transport Channel Processing

› Encoding

› Modulation techniques

› Scrambling?

eNBeNB

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?) ?Radio Channel

Transport Block

Scope and objectives

› Error correction and error protection

› Scrambling codes in LTE

› Modulation

› Describe LTE physical layer processing

› Explain the principle of error correction

› Describe CRC and FEC coding

› Explain the problem of multipath propagation

› Describe the use of scrambling in LTE

› Describe the use of modulation

Objectives

Scope

> Pre-testPre-test

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> OverviewOverview

Transport Channel Processing

› CRC– Error Detection

› FEC– Error Correction

› Modulation

MUX

D

P1

P2

Turbo Encoder

Encoder #1

Encoder #2

Interleaver

Data

Checksum 24 bitsOriginal Data

x bits

CRC Generator

Original Data x bits

Transport Channel Processing

Physical layer processing

Coding

Scrambling

Modulation

CRC

Decoding

Descrambling

Demodulation

CRC check

OFDM(IFFT) OFDM(FFT)

Radio Channel

Tx Rx

Transport Block

Cellular Error Correction

Digital Cellular

Analog Cellular

Transmitted Signal Received Signal + Noise

Transmitted Signal Received Signal + Noise

EM

5 Main Street

Littletown

Eddie McConnell

5 Main Street

Littletown LT1701

Digital Cellular Error Correction

With minimal data...Errors are uncorrectable

With redundant data...Errors are correctable

CRC Coding

Checksum 24 bits110010…110011

Original Data

x bits

CRC Generator

Original Data 1001011010…

CRC Generator

Re-Generated Checksum 110010…110001

Transmitter

Receiver

If Checksums do not match, there exists at least one error

Received Data 1001010010…

Received Checksum

110010…110011

RF Transmission Path

PROPERTIES

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FEC Coding

Coding

Scrambling

Modulation

CRC

Decoding

Descrambling

Demodulation

CRC check

OFDM(IFFT) OFDM(FFT)

Radio Channel

Tx Rx

Transport Block

FEC Coding Approaches

Block Codes Ex. transmit “New York City” to represent ‘NYC’

Continuous Codes Data processed continuously through FEC Built-in redundancy correct bit errors LTE uses Turbo codes

PROPERTIES

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Continous Codes

Original Data 00011011...

FEC Generator

FEC Encoded data 1010011100110110...

Original Data 00011011

Decoder

Transmitter

Receiver

RF Transmission Path

Multipath Propagation

Time-delayed replicas

Varying signal power Burst errors

PROPERTIES

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Turbo Coding

Data

MUX

D

P1

P2

Turbo Encoder

Encoder #1

Encoder #2Interleaver

Turbo Decoder

DecodedData

DE-MUX

D

P1

P2

D

Interleaver

Inte

rleav

er

De-

Inte

rleav

er

Decoder #2

Decoder #1

Parallel, recursive & systematic Detect/correct errors - digital data, different channels

PROPERTIES

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Scrambling in LTE

› Inter cell interference› Cell specific bit-level scrambling› ICIC

Coding

Scrambling

Modulation

CRC

Decoding

Descrambling

Demodulation

CRC check

OFDM(IFFT) OFDM(FFT)

Radio Channel

Tx Rx

Modulation

Coding

Scrambling

Modulation

CRC

Decoding

Descrambling

Demodulation

CRC check

OFDM(IFFT) OFDM(FFT)

Radio Channel

Tx Rx

Modulation schemes

2 bits/symbol

QPSK

00

11

10

01

4 bits/symbol

16-QAM

1111

6 bits/symbol

64-QAM

111111

OFDM

Coding

Scrambling

Modulation

CRC

Decoding

Descrambling

Demodulation

CRC check

OFDM(IFFT) OFDM(FFT)

Radio Channel

Tx Rx

Summary

Summary

Summary

› Cyclic Redundancy Check› Channel coding› Cell specific bit-level

scrambling› Data modulation› OFDM

Coding

Scrambling

Modulation

CRC

Decoding

Descrambling

Demodulation

CRC check

OFDM(IFFT) OFDM(FFT)

Radio Channel

Tx Rx

QUIZ

Quiz

PROPERTIES

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