1. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 1 Proposed TGac Preamble Date: 2010-01-20 Authors:

2. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 2 Outline PPDU format VHT-SIG Legacy Rx state machine for VHT-SIG VHT-LTF –2 options Conclusion and future work

3. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 3 PPDU Format

4. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 4 VHT PPDU Format Design Considerations Immediate (no symbol delay) detection Reliable Backward compatibility with 11a/n Low PAPR

5. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 5 Possible VHT PPDU Formats All packet types present in MM-VHT network –Support for VHT-GF is optional

6. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 6 Phase Rotation 09/1174r0 [2] mentioned phase rotation over 4 sub- bands is required for low PAPR Our simulation result on phase rotation agrees with 09/0847r1 [3] by Leonardo et al., i.e. 1 j 1 -j We also found other sets of rotation that yield low PAPR

7. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 7 VHT-SIG

8. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 8 VHT Signal Field Challenges for VHT-SIG design Immediate and Reliable detection on first symbol after L-SIG –Minimize false detection Backward compatibility –With 11a/n Efficiency –Support enhanced features of TGac with no unnecessary fields

9. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 9 Previously Proposed VHT Preamble Format Proposed Signaling scheme allows MM/GF structure identical to 11n Alternating subcarriers get 90-degree shift –“Orthogonal shift” compared to 0-degree and 90-degree

10. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 10 11n HT-SIG Field detection using 90 degree BPSK 90 degree detector –Operate on 1 st symbol following L-SIG –Detection: Measure FEQ output Compare I vs Q energy levels: High Q energy  HT packet Legacy data symbols: low Q, or equal I and Q components

11. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 11 Previously Proposed VHT-SIG modified 90 degree BPSK Alternate 0/90 degree BPSK symbols on odd/even subcarriers Will not be detected as 11n HT-SIG field

12. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 12 Previously Proposed VHT-SIG MM Detection Scheme MetricData Symbol11a L-SIG11n HT-SIG11ac VHT- SIG 11n0S-S0 11ac000-S

13. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 13 Newly Proposed VHT-SIG with +45/+135 degree BPSK Rotate VHT BPSK symbols +45 degrees –Alternate +45/-45 (+135) degree BPSK symbols on odd/even subcarriers –Will not be detected as 11n HT-SIG field Even just a few subcarriers would detect equal I/Q energy

14. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 14 Newly Proposed VHT-SIG MM Detection with Rotation Detection metrics unchanged More robust 11n spoofing All subcarriers appear as QPSK to 11n detector (i.e., data symbol) VHT detection on de-rotated symbols –Recovers original orthogonal 90-degree BPSK shift

15. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 15 Orthogonal shift provides better backward compatibility Both VHT-SIG1, 2 appear as QPSK data to 11n detector –All subcarriers contain both I/Q energy –Both VHT-SIG fields appear as data symbols under 11n detection Delayed-90 shift could result in “false positive” 11n detection –Certain 11n implementations could trigger off either HT-SIG field to declare 11n packet More efficient SIG field design –Open possibility to QPSK VHT-SIG2 –No need for VHT-SIG3 –Or, pack twice as much VHT descriptor info. by employing higher- order Modulation and Code Rate

16. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 16 Detection Timeline with and without Rotation of VHT-SIG1 With VHT-SIG1 rotation, 11ac devices can recognize 11ac packets at FEQ output immediately after VHT-SIG1

17. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 17 Straightforward Extension to Greenfield Allows highly efficient all-GF operation –Eventual phase-out of 11a devices: all 11n/ac network

18. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 18 Rx State Machine

19. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 19 11a PLCP Rx State Machine

20. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 20 11n PLCP Rx State Machine

21. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 21 Legacy Rx State Machine 11a devices can recognize L-SIG but not the following VHT-SIG, so it will wait LENGTH indicated in L-SIG 11n devices cannot recognize VHT-SIG, so three ways at “RX HT-SIG” are all possible 1.Carrier lost 2.HT-SIG, but CRC will fail 3.Claimed as 11a/g, but can’t be decoded  wait LENGTH –1 and 2 will return to IDLE state when the PPDU is over, just as invalid and corrupted 11n PPDU All legacy devices are not affected

22. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 22 Summary Use “orthogonal shift” to signal new VHT packet format –Take advantage of OFDM property to expand signaling space –More robust detection VHT-SIG1,2 appear as QPSK to 11n detector More efficient SIG field design –Open possibility to QPSK VHT-SIG2 No need for VHT-SIG3 Additional user data GF compatibility –Extends gracefully to VHT-GF operation

23. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 23 VHT-LTF

24. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 24 Channel Estimation by P Matrix CSDQIFFT

25. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 25 Generation of the New P matrix for More Tx Antenna Requirement of generating P –P must be a unitary matrix ( ) –The element of P must be +1 or -1 Ensures the Tx and Rx power the same as payload. –The 2x2 P must be a sub-matrix of 3x3 P

26. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 26 Compatible with 11n P Matrix The size of the P matrix must be even. There exists no 6x6 P matrix which is also compatible with the 11n P matrix(4x4) 88 87 86 85 44 43 22 11 N DLTF N STS

27. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 27 MIMO Channel Estimation by FDM LTF (1)

28. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 28 MIMO Channel Estimation by FDM LTF (2)

29. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 29 Mean Square Error for 6x6 Channel BChannel D

30. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 30 Mean Square Error for 6x8 Channel BChannel D

31. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 31 Mean Square Error for 8x8 Channel BChannel D

32. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 32 Comparison FDM is more efficiency –For FDM, No. of symbols = No. of streams –For P matrix, No. of symbols = 8 for 5~7 streams –At the expense of worse MSE P matrix method is compatible with 11n and has lower MSE

33. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 33 Conclusion and Future Work VHT-SIG is refined with extra 45 degree rotation, compared with 09/1258r0 VHT-SIG is backward compatible with legacy Rx state machine Two options of VHT-LTF are proposed Future work: –Simulation of VHT-SIG –More PHY designs

34. doc.: IEEE 802.11-10/0130r0 Submission January 2010 Yung-Szu Tu, et al., Ralink Tech.Slide 34 References [1] Yug-Szu Tu, et. al., Proposal for TGac VHT Format, IEEE 802.11-09/1258r0, Nov. 19, 2009 [2] Hongyuan Zhang, et. al., 802.11ac Preamble, IEEE 802.11-10/0070r0, Jan. 19, 2010 [3] Leonardo Lanante, et. al., IEEE802.11ac Preamble with Legacy 802.11a/n Backward Compatibility, IEEE 802.11-09/0847r1, Nov. 16, 2009