Doc.: IEEE 802.22-07/0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 1 Interleaving for 802.22 IEEE P802.22 Wireless RANs Date: 2007-03-12

March 2007

Carlos de Segovia, France Telecom

Slide 1

doc.: IEEE 802.22-07/0117r1

Submission

Interleaving for 802.22IEEE P802.22 Wireless RANs Date: 2007-03-12

Name Company Address Phone email

Carlos de Segovia France Telecom Rue du Clos Courtel 35510 Cesson-Sévigné France

+33299124111 [email protected]

Patrick Pirat France Telecom Rue du Clos Courtel 35510 Cesson-Sévigné France

[email protected]

Isabelle Siaud France Telecom Rue du Clos Courtel 35510 Cesson Sévigne France

+33 299 124 629 [email protected]

Anne-Marie Ulmer-Moll

France Telecom Rue du Clos Courtel 35510 Cesson Sévigne France

+33 299 124 593 [email protected]

John Benko France Telecom 801 Gateway Blvd. Suite 500 South San Francisco, CA 94080

+1 650 875-1593 [email protected]

Authors:

Notice: This document has been prepared to assist IEEE 802.22. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein.

Release: The contributor grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE 802.22.

Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures http://standards.ieee.org/guides/bylaws/sb-bylaws.pdf including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair Carl R. Stevenson as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE 802.22 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at [email protected].>

March 2007


Slide 2

doc.: IEEE 802.22-07/0117r1

Submission

Abstract

After the Channel encoding and the IFFT transformation, it is necessary to scramble (interleave) the data that will be placed on the sub-carriers of the OFDM symbol.

This interleaving operation is split into two phases:– A bit interleaving is applied on a FEC block.

– A frequency interleaving is applied on the data symbols before they are mapped on the sub-carriers.

This document presents a rationale for these two types of interleaving and the gain they bring to the system.

March 2007


Slide 3

doc.: IEEE 802.22-07/0117r1

Submission

Content

• Definitions

• Modulator block diagram

• Frequency interleaving

• Bit interleaving

• Interleaving Proposal principles

• Simulations

March 2007


Slide 4

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Submission

Definitions

• FEC Block = Set of bits delivered by the channel coding devices.

• Data symbol = Set of bits that is mapped on a sub-carrier (2 in QPSK, 4 in 16 QAM, 6 in 64 QAM).

March 2007


Slide 5

doc.: IEEE 802.22-07/0117r1

Submission

Modulator Block Diagram

Encoder Puncturer BitInterleaver

BitInterleaver

QAMMapper

iFFTWindow

& GIRF

Pil

ots

& n

ull

FrequencyInterleaver

FrequencyInterleaver

March 2007


Slide 6

doc.: IEEE 802.22-07/0117r1

Submission

Frequency interleaving• Problem: Multi-path creates deep fades in spectrum

– Damages consecutive sub-carriers– Impairs data symbols carried by these sub-carriers

• Solution: Frequency diversity via interleaving– Spreading consecutive data symbols uniformly over spectrum– We describe a distributed carrier interleaving permutation

• Band-type and Scatter-type adjacent subcarrier permutation also possible

Spectrum of 802.22 Channel B

March 2007


Slide 7

doc.: IEEE 802.22-07/0117r1

Submission

802.16 PUSC Permutation0 1 22 23Subchannel

iLogical cluster24 among 120

i+1 i+22 i+23

xPhysical cluster120 per symbol

zy t

Logical to physical allocation

Distribution of data symbols of a sub-channel not uniform!

Frequency Interleaving for Subchannel 0

0

200

400

600

800

1000

1200

1400

0 5 10 15 20 25# Data Symbol

Fre

qu

en

cy

March 2007


Slide 8

doc.: IEEE 802.22-07/0117r1

Submission

Block interleaving proposal [1][2][3]

Structure• A unique mathematical algorithm

– Generate block interleaving with a size K

• Permutation based on:– 2 integer parameters {p,q}

– Iterative structure with j iterations

Procedure• Divide block into sub-blocks of length p, K=pm

( )

, ( )j

p qI k(2), ( )p qI k

I I Ik I

, ( )p qI k

( )

, ( )j

p qI k

x0 x1 x2.. …xp-1 xp xp+1 … x2p-1 xp(m-1) x1+p(m-1)x2+p(m-1) … xpm-1

March 2007


Slide 9

doc.: IEEE 802.22-07/0117r1

Submission

Block interleaving proposal (2)

Conservation of a sample interleaving pattern p p is a parameter of the interleaver (submultiple of K)

Maximize interleaving spreading I(s) - Between adjacent sub-carriers and sub-channels

x0 x1 x2.. …xp-1 xp xp+1 … x2p-1xp(m-1) x1+p(m-1) … xpm-1

x'0 x'1 x'2 x'3 …x'p-1 x'p x'p+1 ….x'2p-1 x'p(m-1) x'1+p(m-1) … x'pm-1

S=1 S=1S=p ( j ) ( j )

p ,q p ,qI( s ) Min I ( k s ) I ( k )

March 2007


Slide 10

doc.: IEEE 802.22-07/0117r1

Submission

Frequency permutation proposal• Interleaving spreading maximisation between sub-channels (s=24) and between sub-carriers close {p,q,j} values•Optimized permutation rule :K=1440 p=32,q=2, j=3

Distance(s)

FTR&DproposalI(s)

802.16e PUSC

I(s)

1 577 92

2 286 82

4 572 127

24 552 207

Subchannel 0

0

200

400

600

800

1000

1200

1400

1600

0 5 10 15 20 25# Data Symbol

Fre

qu

ency

March 2007


Slide 11

doc.: IEEE 802.22-07/0117r1

Submission

Bit interleaving

• Rationale – If data symbol corrupted, a set of 2, 4, or 6 contiguous bits is corrupted.

• Purpose– To spread the bits of a data symbol onto several data symbols.

– When bursts spread over several OFDM symbols, the bit interleaver also performs time interleaving.

March 2007


Slide 12

doc.: IEEE 802.22-07/0117r1

Submission

Bit interleavingSame algorithm as frequency interleaver Optimum values: {p,q,j}={36,2,1} Provides high interleaving spreading: 217

Binary interleaving patternX'k)=X(L(k))

-100

0

100

200

300

400

500

600

700

0 10 20 30 40 50 60 70 80 90 100

k

L(k

) :

ipo

siti

on

in

dex

aft

er i

nte

rlea

vin

g

Distance(s)

FTR&DproposalI(s)

802.16e I(s)

1 217 37

2 142 72

2 75 109

3 284 144

March 2007


Slide 13

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Submission

Simulation results

March 2007


Slide 14

doc.: IEEE 802.22-07/0117r1

Submission

Simulation environment• Downlink

• FFT size : 2048

• Guard sub-carriers: 184 on the left side, 183 on the right side

• DC sub-carrier: 1

• Pilots: 240

• Data sub-carriers: 1440

• Sub-channel size: 24 data symbols

• Block size: 576

• Channel coding: Convolutional as in draft 0.1

• Channel model: Profile B

March 2007


Slide 15

doc.: IEEE 802.22-07/0117r1

Submission

Block in a single OFDM symbol

The 576 bits of a block are allocated to 12, 6, or 4 sub-channels when QPSK, 16 QAM, 64 QAM

12 sub-channels

t

f

QPSK

6 sub-channels

t

f

16 QAM

4 sub-channels

t

f

64 QAM

March 2007


Slide 16

doc.: IEEE 802.22-07/0117r1

Submission

Conv_OFDM - QPSK - 1/2 - BER

-7.00

-6.00

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

2 3 4 5 6 7 8 9

C/N

Lo

g B

ER

802.16 Proposed_interleaver

March 2007


Slide 17

doc.: IEEE 802.22-07/0117r1

Submission

Conv_OFDM - 16 QAM - 1/2 - Profile B- BER

-7.00

-6.00

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

8 9 10 11 12 13 14 15

C/N

Lo

g B

ER

802.16_PUSC Proposed_interleaver

March 2007


Slide 18

doc.: IEEE 802.22-07/0117r1

Submission

Conv_OFDM - 64 QAM - 1/2 - BER

-7.00

-6.00

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

14 15 16 17 18 19 20

C/N

Lo

g B

ER

802.16 Proposed_interleaver

March 2007


Slide 19

doc.: IEEE 802.22-07/0117r1

Submission

Block in a single Sub-channelThe 576 bits of a block are allocated to 12, 6, or 4 OFDM

symbols when QPSK, 16 QAM, 64 QAM

12 OFDM symbols

t

f

QPSK

6 OFDM symbols

t

f

16 QAM

6 OFDM symbols

4 OFDM symbols

t

f

64 QAM

March 2007


Slide 20

doc.: IEEE 802.22-07/0117r1

Submission

Conv_OFDM - QPSK - 1/2 - BER

-7.00

-6.00

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

2 3 4 5 6 7 8 9 10 11 12 13

C/N

Lo

g B

ER

802.16 Proposed_Interleaver

March 2007


Slide 21

doc.: IEEE 802.22-07/0117r1

Submission

Conv_OFDM - 64 QAM - 1/2 - BER

-7.00

-6.00

-5.00

-4.00

-3.00

-2.00

-1.00

0.00

12 13 14 15 16 17 18 19 20 21

C/N

Lo

g B

ER

802.16 Proposed_Interleaver

March 2007


Slide 22

doc.: IEEE 802.22-07/0117r1

Submission

Conclusions

• An unique mathematical algorithm for both binary and frequency interleaving for OFDM/OFDMA schemes

• Increases the distance between adjacent bits and adjacent carriers to enhance performance

• Proposed interleaver performs better on all WRAN channel models

• There is no additional complexity to system– Only the interleaving matrix required

March 2007


Slide 23

doc.: IEEE 802.22-07/0117r1

Submission

References[1] Siaud.I, Ulmer-Moll A.M, "A Novel Adaptive sub-carrier Interleaving : application to millimeter-wave

WPAN OFDM Systems (IST MAGNET project)", IEEE portable 2007 conf, 25-29 March 2007, Orlando (USA).

[2] Siaud.I, Ulmer-Moll, "Advanced Interleaving algorithms for OFDM based millimeter wave WPAN transmissions", SCEE Seminar, 8 February 2007, France.

[3] Siaud.I, Ulmer-Moll A.M, P. Desmoulin, "A novel HiperMAN OFDM/OFDMA PHY dynamic sub-carrier mapping algorithm based on a dynamic turbo-structure interleaving (Version V.2) ", ETSI BRAN #44, document d032, February 2006.

Documents

Doc.: IEEE 802.22-07/0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 1 Interleaving for 802.22 IEEE P802.22 Wireless RANs Date: 2007-03-12