1. Purpose: To be discussed and adopted by TGm for the 802.16m AWD.
Tail-Biting Convolutional Codes for the Secondary Fast Feedback Channel: Fading Channel Results
Document Number: C802.16m-09/0910
Date Submitted:
Source: Ericsson AB, Tsao-Tsen (Jason) Chen
Kai Yu
Sten Sjöberg
Per-Erik Östling
Re: Category: AWD comments / Area: Chapter (UL-CTRL) “Comments on AWD UL-CTRL”
Venue:
Base Contribution:
Purpose: To be discussed and adopted by TGm for the m AWD.
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2. Tail-biting convolutional codes (TBCC) for Secondary Fast Feedback Channel (SFBCH)
Performances of 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~2.3dB PER=10-1 ~10-3
7 to 12 bits: about the same performances
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]

3. TBCC w 1 Encoding: one 18-bit payload Linear Code w 2 Encodings: two 9-bit payloads

4. TBCC gains over the best of 3 linear codes: payload >12 bits (0
TBCC gains over the best of 3 linear codes: payload >12 bits (0.4dB~2.3dB)
Channel
Model
Estimation
Target PER
Payload
14 bits
16 bits
18 bits
20 bits
22 bits
24 bits
PedB-3
pilot avg
10%
0.54
0.47
0.43
0.42
VehA-120
0.79
0.70
0.68
0.71
0.69
0.66
VehA-350
Perfect
1.35
1.47
1.31
1.22
1.27
1.18 1%
0.49
0.53
0.50
0.38
1.06
1.03
1.04
1.08
1.12
1.83
1.84
1.73
1.67
1.56
0.1%
0.57
0.45 NA
1.66
1.68
1.78
1.96
2.05
2.34
2.12
2.18
1.99
1.91
1.82
1.76

5. TBCC losses over the best of 3 linear codes: payload ≤ 12 bits (about the same performances)
Channel
Model
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%
0.09
0.08
0.06
0.05
0.07
VehA-120 1%
0.04
0.12
VehA-350
Perfect
-0.46
0.18
0.1%
0.10
0.16
0.33
0.22
0.13

6. Conclusion and References
We recommend that TBCC [1] be used to encode the SFBCH with payload sizes from 7 to 24 bits, with one encoding [1] for all payload cases.
[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”.

7. Backup Slides

8. 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 and pilot averaging
Tile Structure
3 distributed 2x6 tiles, 2 pilots per tile
Decoder
TBCC: Wrap-around Viterbi algorithm with simple termination condition and maximum 4 iterations
Linear codes: 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