Tail-Biting Convolutional Codes for the Secondary Fast Feedback Channel: Fading Channel Results
Document Number: C802.16m-09/0910r1
Date Submitted: 2009-05-04
Source:
Ericsson AB, Tsao-Tsen (Jason) Chen (jason.t.chen@ericsson.com)
Kai Yu
Sten Sjöberg
Per-Erik Östling
Re:
Venue:
Category: AWD comments / Area: Chapter 15.3.9 (UL-CTRL) “Comments on AWD 15.3.9 UL-CTRL”
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Purpose: To be discussed and adopted by TGm for the 802.16m AWD.
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Tail-biting convolutional codes (TBCC) for
Secondary Fast Feedback Channel (SFBCH)
• Performances of Ericsson’s TBCC [1] over fading channels are
better than or about the same as other linear block codes [2]
for SFBCH for payload 7 to 24 bits
– 13 to 24 bits: 0.4dB~3.3dB gain @ PER=10-1 ~10-3
– 7 to 12 bits: 0.3dB or much less loss (about the same
performances) @ PER=10-1 ~10-3
• TBCC can be decoded efficiently by simple Wrap-Around
Viterbi Algorithm (WAVA), with complexity much less than
linear codes with MLD or trellis decoding for most payload
cases [1]
Ericsson’s TBCC vs Intel’s TBCC
• Ericsson [1]: 128 state, Intel [3]: 64 states
• Ericsson’s TBCC has larger minimum distances than
Intel’s TBCC for most of the payload cases
– for payload 12 bits: Ericsson d_min=24 > Intel d_min=20
– for payload 7 to 11 bits: Ericsson has much larger d_min
– For payload 13 to 24 bits: Ericsson d_min ≥ Intel d_min
Comparison of minimum distances (d_min)
lower bound on d_min
upper bound on d_min
Intel TBCC
Samsung 1st code
Samsung 2nd code
LGe 1st code
LGe 2nd code
Ericsson TBCC
d_min of (60,k) codes
30
25
d_min
20
15
10
5
6
8
10
12
14
16
18
k: number of payload bits
20
22
24
Ericsson’s TBCC vs Intel’s TBCC: payload 12 bits,
AWGN
(60,12) TBCC, AWGN
0
10
Intel TBCC
Ericsson TBCC
-1
10
-2
10
-3
PER
10
-4
10
-5
10
-6
10
-7
10
-6
-4
-2
0
2
EbN0 (dB)
4
6
8
Ericsson’s TBCC w 1 Encoding: one 20-bit payload
Linear Code w 2 Encodings: two 10-bit payloads
payload 20 bits, 1Tx2Rx, VehA 120Km/hr
0
10
Samsung (30,10)
LGe (30,10)
Ericsson TBCC (60,20)
-1
PER
10
-2
10
-3
10
-4
10
-6
-4
-2
0
2
4
6
EsN0 (dB)
8
10
12
14
Ericsson TBCC gain over the best of 2 proposed
linear codes: payload >12 bits (0.4dB~3.3dB)
Channel
Model
Channel
Estimation
Target
PER
Payload 14
bits
Payload 16
bitd
Payload 18
bits
Payload 20
bits
Payload 22
bits
Payload 24
bits
PedB-3
pilot avg
10%
0.61
0.61
0.60
0.61
0.56
0.47
VehA-120
pilot avg
10%
0.79
0.86
0.84
0.82
0.77
0.78
VehA-350
Perfect
10%
1.44
1.51
1.37
1.32
1.34
1.22
PedB-3
pilot avg
1%
0.71
0.69
0.62
0.61
0.60
0.53
VehA-120
pilot avg
1%
1.25
1.32
1.29
1.37
1.40
1.47
VehA-350
Perfect
1%
1.95
1.95
1.84
1.81
1.68
1.55
PedB-3
pilot avg
0.1%
0.54
0.62
0.62
0.59
0.45
NA
VehA-120
pilot avg
0.1%
2.21
2.65
2.86
3.29
NA
NA
VehA-350
Perfect
0.1%
2.32
2.31
2.17
2.13
2.00
1.85
Ericsson TBCC loss over the best of 2 proposed linear
codes: payload ≤ 12 bits (0.3dB or about the same
performances)
Channel
Model
Channel
Estimation
Target
PER
Payload 7
bits
Payload 8
bits
Payload 9
bits
Payload 10
bits
Payload 11
bits
Payload 12
bits
PedB-3
pilot avg
10%
0.17
0.13
0.09
0.07
0.06
0.06
VehA-120
pilot avg
10%
0.17
0.15
0.09
0.08
0.09
0.08
PedB-3
pilot avg
1%
0.17
0.14
0.11
0.08
0.07
0.07
VehA-120
pilot avg
1%
0.19
0.17
0.10
0.08
0.07
0.07
VehA-350
Perfect
1%
NA
0.19
0.12
0.09
0.10
0.08
PedB-3
pilot avg
0.1%
0.12
0.12
0.09
0.09
0.11
0.07
VehA-120
pilot avg
0.1%
0.21
0.22
0.15
0.11
0.10
0.10
VehA-350
Perfect
0.1%
0.36
0.22
0.14
0.10
0.09
0.08
Conclusions
• We recommend that Ericsson’s TBCC [1] be used to
encode the SFBCH with payload sizes from 7 to 24
bits, with one encoding [1] for all payload cases.
References
• [1] IEEE C80216m-09_0506r3, “Tail-Biting Convolutional
Codes with Expurgation and Rate-Compatible Puncturing for
the Secondary Fast Feedback Channel”.
• [2] IEEE C80216m-09_0387, “Proposed Text for the Draft
P802.16m Amendment on the PHY structure for UL control –
merged version”.
• [3] IEEE C80216m-09_0875, “Proposed Tailed Biting
Convolutional Codes for SFBCH”.
• [4] IEEE C80216m-09_1012, “Performance comparison on
SFBCH coding schemes”.
Backup Slides
Simulation Assumptions
Channel Bandwidth
10MHz
FFT Size
1024
Cyclic Prefix Ratio
1/8
Channel Model
PedB-3Km/hr, VehA-120Km/hr, VehA-350Km/hr
Antenna Scheme
1Tx2Rx
Modulation
QPSK
Channel Estimation
Perfect channel estimation, or pilot averaging with 3dB pilot power boosting
Tile Structure
3 distributed 2x6 tiles, 2 pilots per tile with pilot shifting
De-mapping
Log-MAP
Decoder
TBCC: Wrap-around Viterbi algorithm with simple termination condition and maximum 4
iterations
Linear codes: bit-level MLD
Error Statistics
For linear codes with 2 smaller encoded packets per payload (13 bits to 24 bits), the overall
packet is declared erroneous if either one of the 2 smaller encoded packets is in error