doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 1 Interleaving for IEEE P Wireless RANs Date: Authors: Notice: This document has been prepared to assist IEEE 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 IEEEs name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEEs 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 Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures 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 Chairhttp://standards.ieee.org/guides/bylaws/sb-bylaws.pdf Carl R. StevensonCarl 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 Working Group. If you have questions, contact the IEEE Patent Committee Administrator at >

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 2 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.

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 3 Content Definitions Modulator block diagram Frequency interleaving Bit interleaving Interleaving Proposal principles Simulations

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 4 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).

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 5 Modulator Block Diagram Encoder Puncturer Bit Interleaver QAM Mapper iFFT Window & GI RF Pilots & null Frequency Interleaver

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 6 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 Channel B

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide PUSC Permutation Distribution of data symbols of a sub- channel not uniform!

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 8 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 x 0 x 1 x 2.. …x p-1 x p x p+1 … x 2p-1 x p(m-1) x 1+p(m-1) x 2+p(m-1) … x pm-1

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 9 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 x 0 x 1 x 2.. …x p-1 x p x p+1 … x 2p-1 x p(m-1) x 1+p(m-1) … x pm-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=p

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 10 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&D proposal I(s) e PUSC I(s)

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 11 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.

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 12 Bit interleaving Same algorithm as frequency interleaver Optimum values: {p,q,j}={36,2,1} Provides high interleaving spreading: 217 Distance (s) FTR&D proposal I(s) e I(s)

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 13 Simulation results

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 14 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

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 15 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

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 16

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 17

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 18

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 19 Block in a single Sub-channel The 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

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 20

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 21

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 22 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

doc.: IEEE /0117r1 Submission March 2007 Carlos de Segovia, France TelecomSlide 23 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, 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.