1. Key Features Summary and Results Update
November 2004
Key Features Summary and Results Update
Institute for Infocomm Research (I2R)
Sumei SUN, WU Yan, LI Yuan,
Patrick FUNG, Ying-Chang LIANG,
Zhongding LEI
( to:
16 November 2004
Institute for Infocomm Research (I2R)

2. Outline Summary of Key Features Results Update
November 2004
Outline
Summary of Key Features
Results Update
Performance comparison of CDD, SM and GSTBC
Performance comparison of Unequal Error Protection (UEP) mapping and direct mapping in LDPC
Institute for Infocomm Research (I2R)

3. November 2004
Summary of Key Points - 1
For 4x2 MIMO, the GSTBC open loop structure has the following advantages:
Excellent performance – Up to 6 dB gain over 2x2 SM, and up to 5dB gain over 4x2 CDD;
Simple implementation;
No CSI.
Institute for Infocomm Research (I2R)

4. November 2004
Summary of Key Points - 2
For 4x2 MIMO, Fixed beamforming has the following advantages:
No requirement for instantaneous CSI, but only 2nd order channel statistics;
No requirement for dedicated PPDU;
Simple implementation – time domain beamforming reduced the per user complexity;
Slower tracking requirement.
Institute for Infocomm Research (I2R)

5. Summary of Key Points - 3 Long preamble design:
November 2004
Summary of Key Points - 3
Long preamble design:
Can be readily integrated into the training field;
Reduced overhead – better efficiency;
Enabling simple channel estimation;
Enabling more accurate residual frequency offset estimation.
Institute for Infocomm Research (I2R)

6. November 2004
Summary of Key Points - 4
Unequal Error Protection (UEP) mapping in LDPC
Simple implementation;
Performance gains at no additional cost.
Institute for Infocomm Research (I2R)

7. Summary of Key Points - 5 2-D Linear transform Reduced PAPR;
November 2004
Summary of Key Points - 5
2-D Linear transform
Reduced PAPR;
Further SNR gains;
Can be seamlessly integrated with Spatial Spreading and CDD.
Institute for Infocomm Research (I2R)

8. Performance comparison of CDD, SM and GSTBC
November 2004
Results Update – Part 1
Performance comparison of CDD, SM and GSTBC
Institute for Infocomm Research (I2R)

9. November 2004
PER Comparison of 2-rx MRC, CDD and STBC, Conv Code (chan B perfect CE and FOE ) -5 5 10 15 20 25 30 -4 -3 -2 -1
SNR per receive antenna (dB)
PER
0.65dB
0.71dB
1.4dB 1
2 SIMO 2
2 CDD delay=32
2 STBC
108 Mbps
48 Mbps
24 Mbps
Diversity order of 2-rx MRC
Diversity order of STBC
Diversity order of CDD
STBC gives the lower bound of CDD!
Institute for Infocomm Research (I2R)

10. November 2004
PER Comparison of 2x2 SM, 4x2 CDD and 4x2 GSTBC, Conv Code (chan B with practical CE and FOE ) 5 10 15 20 25 30 35 -3 -2 -1
SNR per receive antenna (dB)
PER
0.98dB
2.1dB
4.8dB 2
24Mbps SM
48Mbps SM
108Mbps SM
24Mbps GSTBC
48Mbps GSTBC
108Mbps GSTBC
24Mbps CDD
48Mbps CDD
108Mbps CDD
40MHz BW,
1000B packet, Channel Model B Convolutional coded with CE, FOE and PC
At PER=10-1, CDD does not have much of gain over SM;
GSTBC outperforms CDD and SM, and the higher the modulation order, the more the gain.
Institute for Infocomm Research (I2R)

11. November 2004
PER Comparison of 2x2 SM, 4x2 CDD and 4x2 GSTBC, LDPC (chan B with practical CE and FOE ) 5 10 15 20 25 30 35 -4 -3 -2 -1
40 MHz BW 4
2 two group CDD Channel B DC11 LDPC coded with CE FOE delay=32
SNR per receive antenna (dB)
per
0.24dB
0.94dB
1.7dB 2
24Mbps SM
48Mbps SM
108Mbps SM
24Mbps GSTBC
48Mbps GSTBC
108Mbps GSTBC
24Mbps CDD
48Mbps CDD
108Mbps CDD
A more powerful code can better exploit the advantage of CDD.
CDD outperforms SM, but still inferior to GSTBC.
Institute for Infocomm Research (I2R)

12. November 2004
PER Comparison of 2x2 SM, 4x2 CDD and 4x2 GSTBC, LDPC (chan E with practical CE and FOE ) 5 10 15 20 25 30 -4 -3 -2 -1
40 MHz BW 4
2 two group CDD Channel E DC11 LDPC coded with CE FOE delay=32
SNR per receive antenna (dB)
per
0.97dB
1.6dB
2.6dB 2
24Mbps SM
48Mbps SM
108Mbps SM
24Mbps GSTBC
48Mbps GSTBC
108Mbps GSTBC
24Mbps CDD
48Mbps CDD
108Mbps CDD
Even with a more powerful code, the diversity gain from CDD can not be very well exploited.
Institute for Infocomm Research (I2R)

13. Diversity Order of 2x2 SM, 4x2 CDD, and 4x2 GSTBC, Linear Detection
November 2004
Diversity Order of 2x2 SM, 4x2 CDD, and 4x2 GSTBC, Linear Detection
Assume linear detection : i.e. no diversity gain from detection.
SM: dsys  min(dpath, dfree);
CDD : dsys  min(2×dpath, dfree);
GSTBC: dsys  2×min(dpath, dfree);
dSM  dCDD  dGSTBC
Institute for Infocomm Research (I2R)

14. Performance Comparison of UEP and Direct Mapping in LDPC
November 2004
Results Update – Part 2
Performance Comparison of UEP and Direct Mapping in LDPC
Institute for Infocomm Research (I2R)

15. The Scheme Conventional scheme—direct mapping
November 2004
The Scheme
Conventional scheme—direct mapping
Pre-designed UEP permutation embedded in LDPC encoder
Systematic bits in LDPC require more protection than parity check bits
Different from bit-interleaver: no latency, no additional complexity
Write coded sequence (systematic + parity) into a rectangular block of put systematic bits into MSB positions.
Institute for Infocomm Research (I2R)

16. Simulation Setup for LDPC Coded QAM with 2x2 SM
November 2004
Simulation Setup for LDPC Coded QAM with 2x2 SM
PD-LDPC (2304, 1152) of R=1/2;
UEP vs Direct mapping
H1 designed using progressive edge growth (PEG);
Three kinds of H1 column weights: 4, 6, 8.
64QAM with Gray mapping;
Single encoder for two spatial streams in 2x2 SM
Practical Receiver
FOE, PC, CE and SNR estimation
Channel model B and E
Institute for Infocomm Research (I2R)

17. 2x2 SM in Channel B UEP vs Direct mapping Weight, w Gain,dB 4 0.28 6
November 2004
2x2 SM in Channel B
UEP vs Direct mapping
Weight, w
Gain,dB 4
0.28 6
0.46 8
1.2
w=6 vs w=4
UEP: gain=0.18dB
Direct: gain=0dB
PD-LDPC of w=8 does not introduce performance gain at PER=10-2, although it shows higher diversity order.
Institute for Infocomm Research (I2R)

18. 2x2 SM in Channel E UEP vs Direct mapping Weight, w Gain,dB 4 0.29 6
November 2004
2x2 SM in Channel E
UEP vs Direct mapping
Weight, w
Gain,dB 4
0.29 6
0.67 8
1.6
Gain from w=6 to w=4
UEP: gain=0.15dB
Direct: gain=-0.25dB
PD-LDPC of w=8 does not perform better than w=4 and 6 at PER=10-2.
Institute for Infocomm Research (I2R)

19. UEP permutation is superior to direct mapping
November 2004
Summary
UEP permutation is superior to direct mapping
Performance gain at target PER
gain increases with column weight of PD-LDPC
At best choice of w=6, gains are 0.46dB and 0.67dB for Channel Model B and E
Performance gain achieved at no extra cost
not extra redundancy;
no extra latency (embedded in LDPC encoder);
no extra encoder/decoder complexity (pre-designed).
Institute for Infocomm Research (I2R)