doc.: IEEE yy/0847r0 Submission Slide 1Leonardo Lanante, Ochi Lab, KIT July 2009 IEEE802.11ac Preamble with Legacy a/n Backward Compatibility Date: Authors:

doc.: IEEE yy/0847r0 Submission Slide 2Leonardo Lanante, Ochi Lab, KIT July 2009 Outline I.Introduction II. Proposed Preamble Format III. Preamble Waveform IV.PAPR V.Preamble Efficiency

doc.: IEEE yy/0847r0 Submission Slide 3Leonardo Lanante, Ochi Lab, KIT July 2009 I. Introduction Functional requirements for TGac. A)System Performance 1.Shall operate in 5GHz frequency band 2.At least 1Gbps at MAC SAPs utilizing 80MHz 3.At least 500Mbps for Single STA 4.Spectral efficiency at least 7.5 bps/Hz B)Shall ensure backward compatibility with IEEE a/n. C)Enable coexistence and spectrum sharing with IEEE a/n. D)Compliance to PAR Doc.IEEE /0304r0 March 2009

doc.: IEEE yy/0847r0 Submission Slide 4Leonardo Lanante, Ochi Lab, KIT July 2009 II. Proposed Preamble Main Features –Uses 80MHz channel and meets all functional requirements for a VHT preamble –Three preamble modes to minimize overhead –Seamless upgrade from n preamble –Almost identical PAPR characteristics with n –Comparable Preamble Efficiency to n

doc.: IEEE yy/0847r0 Submission Slide 5Leonardo Lanante, Ochi Lab, KIT July 2009 Proposed Preamble Modes A)Mixed 11a/n Mode 1.56us duration 2.Backward compatible with a/n B)Mixed 11n Mode 1.44us duration 2.Backward compatible with n C)VHT Greenfield Mode 1.36us duration 2.VHT only mode

doc.: IEEE yy/0847r0 Submission Slide 6Leonardo Lanante, Ochi Lab, KIT July 2009 A) Mixed 11a/n Mode Frame Format Proposed Mixed 11a/n mode: Backward compatible with IEEE802.11a/n Duration=56μs * L-STF L-LTF L-SIG HT-SIG VHT-SIG VHT STF VHT LTF1 VHT LTF4 VHT LTF4 Data 8μs8μs8μs8μs4μs4μs8μs8μs8μs8μs4μs4μs4μs per LTF4/3.6μs per Data * 4 spatial streams L-STF L-LTF L-SIG HT-SIG HT STF HT LTF1 HT LTF4 HT LTF4 Data 8μs8μs8μs8μs4μs4μs8μs8μs4μs4μs4μs per LTF4/3.6μs per Data Duration=48μs * n Mixed Mode Preamble A New SIG field is defined to accommodate changes in VHT while maintaining compatibility

doc.: IEEE yy/0847r0 Submission Slide 7Leonardo Lanante, Ochi Lab, KIT July 2009 Proposed Phase Rotation for 80 MHz Channel to Maintain Low PAPR n 40Mhz case Proposed scheme for 80Mhz S = subcarrier pattern for a system -This phase rotation scheme is used for all preamble symbols -The phases were chosen to give lowest PAPR

doc.: IEEE yy/0847r0 Submission Slide 8Leonardo Lanante, Ochi Lab, KIT July 2009 Legacy – Short Training Field L-STF L-LTFL-SIGHT-SIGVHT-SIG VHT STF VHT LTF1 VHT LTF4 Data Subcarriers # L-STF 20MHz

doc.: IEEE yy/0847r0 Submission Slide 9Leonardo Lanante, Ochi Lab, KIT July 2009 Legacy - Long Training Field Subcarriers # L-STFL-LTFL-SIGHT-SIGVHT-SIG VHT STF VHT LTF1 VHT LTF4 Data L-LTF 20MHz

doc.: IEEE yy/0847r0 Submission Slide 10Leonardo Lanante, Ochi Lab, KIT July 2009 Legacy - SIGNAL Field Subcarriers # L-SIG 20MHz L-SIGGI s 3.2 s s 0.8 s L-STFL-LTFL-SIGHT-SIGVHT-SIG VHT STF VHT LTF1 VHT LTF4 Data

doc.: IEEE yy/0847r0 Submission Slide 11Leonardo Lanante, Ochi Lab, KIT July 2009 VHT – SIGNAL Field 64 options of MCS octet of data LENGTH = 2 X n. CRC protected. STBCShort GIReserved one STBC BW LSB BW MSB LENGTH should be increased by one bit to maintain preamble efficiency lost with the use of 80MHz channel

doc.: IEEE yy/0847r0 Submission Slide 12Leonardo Lanante, Ochi Lab, KIT July 2009 B) Mixed 11n Mode Frame Format HT mode: Backward compatibility with IEEE802.11n Duration=44μs * HT-STF HT-LTF HT-SIG VHT-SIG VHT LTF2 VHT LTF4 VHT LTF4 Data 8μs8μs8μs8μs8μs8μs8μs8μs4μs per LTF4/3.6μs per Data The difference with n greenfield preamble is the additional SIG symbol n Greenfield Preamble Duration=36μs * HT-STF HT-LTF1 HT-SIG HT LTF2 HT LTF4 HT LTF4 Data 8μs8μs8μs8μs8μs8μs4μs per LTF4/3.6μs per Data * 4 spatial streams

doc.: IEEE yy/0847r0 Submission Slide 13Leonardo Lanante, Ochi Lab, KIT July 2009 C) VHT Greenfield Mode Frame Format Greenfield mode: No backward compatibility with IEEE802.11a/n Duration=36μs* VHT-STF VHT-LTF1 VHT-SIG VHT LTF2 VHT LTF4 VHT LTF4 Data 8μs8μs8μs8μs8μs8μs4μs per LTF4/3.6μs per Data -Same purpose as the n greenfield format preamble

doc.: IEEE yy/0847r0 Submission Slide 14Leonardo Lanante, Ochi Lab, KIT July 2009 III. Preamble Waveform s Time ( ) L-STFL-LTF VHT- STF VHT- LTF1 VHT- LTF2 VHT- LTF3 VHT- LTF4 L- SIG HT- SIG1 HT- SIG2 VHT- SIG1 VHT- SIG2

doc.: IEEE yy/0847r0 Submission Slide 15Leonardo Lanante, Ochi Lab, KIT July 2009 V. Preamble Efficiency The preamble efficiency is defined as

doc.: IEEE yy/0847r0 Submission Slide 16Leonardo Lanante, Ochi Lab, KIT July 2009 IV. PAPR

doc.: IEEE yy/0847r0 Submission Slide 17Leonardo Lanante, Ochi Lab, KIT July 2009 Conclusion We have been developing an 80MHz BW WLAN preamble which has backward compatibility with IEEE802.11a/n system. The proposed preamble has comparable efficiency compared to IEEE802.11ns preamble. The proposed preamble has comparable PAPR with IEEE802.11ns preamble.

doc.: IEEE yy/0847r0 Submission Slide 18Leonardo Lanante, Ochi Lab, KIT July 2009 References 1.E. Perahia, IEEE P Wireless LANs: VHT below 6GHz PAR Plus 5Cs, doc.:IEEE /0807r4. 2.Supplement to IEEE STANDARD for Information Technology – Telecommunications and Information Exchange between Systems - Local and Metropolitan Area Networks - Specific Requirements, IEEE Std a- 1999(R2003), June Draft STANDARD for Information Technology – Telecommunications and Information Exchange between Systems - Local and Metropolitan Area Networks - Specific Requirements, IEEE P802.11n./D9.0, March Peter L and Minho C, TGac Functional Requirements Rev.0, doc.:IEEE /0304r0. 5.Rolf de V, ac Usage Models Document, doc.:IEEE /0161r2. 6.Minho C and Peter L, Proposal for TGac Evaluation Methodology, doc.:IEEE /0376r1.