ieee802 11ac preamble with legacy 802 11a n backward compatibility l.
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Date: 2009-07-14. IEEE802.11ac Preamble with Legacy 802.11a/n Backward Compatibility . Authors:. Introduction Proposed Preamble Format Preamble Waveform PAPR Preamble Efficiency. Outline. Functional requirements for TGac. System Performance Shall operate in 5GHz frequency band

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IEEE802.11ac Preamble with Legacy 802.11a/n Backward Compatibility


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Presentation Transcript
outline

Introduction

  • Proposed Preamble Format
  • Preamble Waveform
  • PAPR
  • Preamble Efficiency
Outline
i introduction

Functional requirements for TGac.

  • System Performance
    • Shall operate in 5GHz frequency band
    • At least 1Gbps at MAC SAPs utilizing 80MHz
    • At least 500Mbps for Single STA
    • Spectral efficiency at least 7.5 bps/Hz
  • Shall ensure backward compatibility with IEEE 802.11a/n.
  • Enable coexistence and spectrum sharing with IEEE 802.11a/n.
  • Compliance to PAR
I. Introduction

Doc.IEEE802.11-09/0304r0 March 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 802.11n preamble
    • Almost identical PAPR characteristics with 802.11n
    • Comparable Preamble Efficiency to 802.11n
II. Proposed Preamble
proposed preamble modes

Mixed 11a/n Mode

    • 56us duration
    • Backward compatible with 802.11a/n
  • Mixed 11n Mode
    • 44us duration
    • Backward compatible with 802.11n
  • VHT Greenfield Mode
    • 36us duration
    • VHT only mode
Proposed Preamble Modes
a mixed 11a n mode frame format
A) Mixed 11a/n Mode Frame Format

Proposed Mixed 11a/n mode: Backward compatible with IEEE802.11a/n

8μs

8μs

4μs

8μs

8μs

4μs

4μs per LTF

4/3.6μs per Data

L-STF

L-LTF

L-SIG

HT-SIG

VHT-SIG

VHT STF

VHT LTF1

VHT

LTF4

Data

Data

Duration=56μs *

A New SIG field is defined to accommodate changes in VHT while maintaining compatibility

802.11n Mixed Mode Preamble

8μs

8μs

4μs

8μs

4μs

4μs per LTF

4/3.6μs per Data

L-STF

L-LTF

L-SIG

HT-SIG

HT STF

HT LTF1

HT

LTF4

Data

Data

Duration=48μs *

* 4 spatial streams

proposed phase rotation for 80 mhz channel to maintain low papr
Proposed Phase Rotation for 80 MHz Channel to Maintain Low PAPR

-128

-64

0

64

127

Proposed scheme for 80Mhz

S = subcarrier pattern for 802.11a system

-64

0

63

802.11n 40Mhz case

-This phase rotation scheme is used for all preamble symbols

-The phases were chosen to give lowest PAPR

slide8

L-STF

L-LTF

L-SIG

HT-SIG

VHT-SIG

VHT STF

VHT LTF1

VHT

LTF4

Data

Data

Legacy – Short Training Field

L-STF 20MHz

-128

127

-64

0

64

Subcarriers #

legacy long training field

L-STF

L-LTF

L-SIG

HT-SIG

VHT-SIG

VHT STF

VHT LTF1

VHT

LTF4

Data

Data

Legacy - Long Training Field

L-LTF 20MHz

-128

127

-64

0

64

Subcarriers #

legacy signal field

L-STF

L-LTF

L-SIG

HT-SIG

VHT-SIG

VHT STF

VHT LTF1

VHT

LTF4

Data

Data

Legacy - SIGNAL Field

L-SIG 20MHz

-128

127

-64

0

64

Subcarriers #

GI

L-SIG

0.8

m

m

3.2

m

m

s

s

s

s

vht signal field
VHT – SIGNAL Field

BW

BW

MSB

LSB

STBC

LENGTH should be increased by one bit to maintain preamble efficiency lost with the use of 80MHz channel

Reserved one

STBC

Short GI

  • 64 options of MCS.
  • 131072 octet of data LENGTH = 2 X 802.11n.
  • CRC protected.
b mixed 11n mode frame format
B) Mixed 11n Mode Frame Format

HT mode: Backward compatibility with IEEE802.11n

8μs

8μs

8μs

8μs

4μs per LTF

4/3.6μs per Data

HT-STF

HT-LTF

HT-SIG

VHT-SIG

VHT LTF2

VHT

LTF4

Data

Data

Duration=44μs *

The difference with 802.11n greenfield preamble is the additional SIG symbol

802.11n Greenfield Preamble

8μs

8μs

8μs

4μs per LTF

4/3.6μs per Data

HT-STF

HT-LTF1

HT-SIG

HT LTF2

HT

LTF4

Data

Data

Duration=36μs *

* 4 spatial streams

c vht greenfield mode frame format
C) VHT Greenfield Mode Frame Format

Greenfield mode: No backward compatibility with IEEE802.11a/n

8μs

8μs

8μs

4μs per LTF

4/3.6μs per Data

VHT-STF

VHT-LTF1

VHT-SIG

VHT LTF2

VHT

LTF4

Data

Data

Duration=36μs*

-Same purpose as the 802.11n greenfield format preamble

iii preamble waveform
III. Preamble Waveform

VHT-

LTF2

VHT-

LTF4

L-

SIG

HT-

SIG1

HT-

SIG2

VHT-

SIG1

VHT-

SIG2

VHT-

STF

VHT-

LTF1

VHT-

LTF3

L-STF

L-LTF

Time ( )

m

s

v preamble efficiency
V. Preamble Efficiency

The preamble efficiency is defined as

95.29

48

96.43

36

131072

94.26

230

56

131072

44

95.43

230

131072

230

96.23

36

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 IEEE802.11n’s preamble.

The proposed preamble has comparable PAPR with IEEE802.11n’s preamble.

Conclusion
references

E. Perahia, ”IEEE P802.11 Wireless LANs: VHT below 6GHz PAR Plus 5C’s”, doc.:IEEE 802.11-08/0807r4.

  • ”Supplement to IEEE STANDARD for Information Technology – Telecommunications and Information Exchange between Systems - Local and Metropolitan Area Networks - Specific Requirements”, IEEE Std 802.11a- 1999(R2003), June 2003.
  • ”Draft STANDARD for Information Technology – Telecommunications and Information Exchange between Systems - Local and Metropolitan Area Networks - Specific Requirements”, IEEE P802.11n./D9.0, March 2009.
  • Peter L and Minho C, ”TGac Functional Requirements Rev.0”, doc.:IEEE 802.11-09/0304r0.
  • Rolf de V, ”802.11ac Usage Models Document”, doc.:IEEE802.11- 09/0161r2.
  • Minho C and Peter L, ”Proposal for TGac Evaluation Methodology”, doc.:IEEE802.11-09/0376r1.
References