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Proposal for advanced interleaving in IEEE 802.16m
Document Number: IEEE C802.16m-11/317Date Submitted: 2007-11-11Source:
Venue: IEEE 802.16 Session #52 Atlanta, United StatesBase Contribution: NonePurpose: Response to SDD Call for Proposal of IEEE 802.16m Notice:
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Name Company Address Phone email Carlos de Segovia
France Telecom
Rue du Clos Courtel France
+33-299124395 [email protected]
Isabelle Siaud France Telecom
Rue du clos Courtel-France-
+33-299-124-629 [email protected]
Djamal-Eddine Meddour
France Telecom
Lannion, France [email protected]
Anne Marie Ulmer-Moll
France Telecom
Rue du Clos Courtel France
+33-299-124-593 [email protected]
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.
Modulator Block Diagram
Encoder Puncturer BitInterleaver
BitInterleaver
QAMMapper
iFFTWindow
& GIRF
Pil
ots
& n
ull
FrequencyInterleaver
FrequencyInterleaver
802.16 PUSC Permutation
Distribution of data symbols of a sub-channel not uniform!
DL PUSC Interleaving
0
100
200
300
400
500
600
700
0 5 10 15 20#Data Symbol
Fre
qu
ency
Subchannel 0
Subchannel 1
Subchannel 2
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
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 )
Frequency permutation proposal
• Interleaving spreading maximisation between sub-channels (s=24) and between sub-carriers close {p,q,j} values•Optimized permutation rule :K=720 p=12,q=2, j=1
Distance(s)
FTR&Dproposal
I(s)
802.16e PUSC
I(s)
1 311 46
2 98 46
4 213 47
24 264 210
K = 720 {12,2,2}
0
100
200
300
400
500
600
700
0 5 10 15 20 25
Subcarrier Index
Fre
qu
ency
Subchannel 0
Subchannel 1
Subchannel 2
Bit interleaving
Same algorithm as frequency interleaver Optimum values: {p,q,j}={36,2,1} for coded size = 576 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&Dproposal
I(s)802.16e
I(s)
1 217 37
2 142 72
2 75 109
3 284 144
Simulation results
Simulation environment
• Downlink
• FFT size : 1024
• Guard sub-carriers: 93 on the left side, 82 on the right side
• DC sub-carrier: 1
• Pilots: 120
• Data sub-carriers: 720
• Sub-channel size: 24 data symbols
• Block size: 576
• Channel coding: CTC
• Channel model: 3GPP Macro Urban
PER - 3km/h - DL PUSC - TC - SISO - 3GPP Urban macro- 1 sub-channel - QPSK
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
4 6 8 10 12
SNR, dB
Pac
kag
e E
rro
r R
ate
4PSK - FTR&D
4PSK - 802.16
PER - 3km/h - DL PUSC - TC - SISO - 3GPP Urban macro- 1 sub-channel - 16QAM
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
10 12 14 16 18
SNR, dB
Pac
kag
e E
rro
r R
ate
16QAM -FTR&D
16QAM - 802.16
PER - 3km/h - DL PUSC - TC - SISO - 3GPP urban macro - 1 sub-channel 64QAM
1.0E-04
1.0E-03
1.0E-02
1.0E-01
1.0E+00
10 12 14 16 18 20 22 24
SNR, dB
Pac
kag
e E
rro
r R
ate
64QAM_FTR&D
64QAM - 802.16
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
• There is no additional complexity to system– Only the interleaving matrix required
• Interleaving in 802.16 can be improvedneed to define a selection process for advanced interleavers
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.
[4] I. Siaud, J. Benko, full band diversity interleaving, IEEE 802.22 0242-00-0000
[5] P. Pagani, M. Piz, I. Siaud, E. Grass, et al., "France Telecom - IHP Joint Physical Layer Proposal for IEEE 802.15 Task Group 3c", IEEE 802.15 Working Group for WPAN, no. IEEE 802.15-07/689r0, May 2007.
[6] 3GPP TR 25-996 v6.1.0 Spatial channel model for Multiple Input Multiple Output (MIMO) simulations
