Doc.:IEEE 802.11-10/0359r1 Submission xx. xx, 2010 Il-Gu Lee et al.Slide 1 802.11ac preamble for VHT auto-detection Date: 2010-05-18 Authors:

doc.:IEEE 802.11-10/0359r1

Submission

xx. xx, 2010

Il-Gu Lee et al.Slide 1

802.11ac preamble for VHT auto-detection

Date: 2010-05-18Authors:

Name Affiliations Address Phone email Il-Gu Lee ETRI Daejeon, Korea +82 42 860 1633 [email protected]

In-Kyeong Choi ETRI Daejeon, Korea +82 42 860 5242 [email protected]

YuRo Lee ETRI Daejeon, Korea +82 42 860 5693 [email protected]

Jong-Ee Oh ETRI Daejeon, Korea +82 42 860 1758 [email protected]

Eun-Young Choi ETRI Daejeon, Korea +82 42 860 1633 [email protected]

Sok-Kyu Lee ETRI Daejeon, Korea +82 42 860 5919 [email protected]

Minho Cheong ETRI Daejeon, Korea +82 42 860 5635 [email protected]

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Slide 2

Overview

• Preamble design considerations for VHT auto-detection– Fairness / safety for 11a/n and 11ac devices– Reliability for 11a/n and 11ac devices

• Proposals in TGac on preamble– Proposal (1) 10/070r0 (Zhang, et al)

• VHT-SIGA1: BPSK• VHT-SIGA2: Q-BPSK

– Proposal (2) 10/039r0 (Lee, et al)• VHT-SIGA1: BPSK• VHT-SIGA2: Alternative Q-BPSK/BPSK

• Evaluation results– 11ac preamble design evaluation for 11n receivers

– 11ac/11a detection performance for 11ac receivers

Il-Gu Lee et al.

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Slide 3

Proposal (1) in 10/0070r0

Il-Gu Lee et al.

VHT-STF VHT-LTFsL-STF L-LTF L-SIG VHTSIGA VHTSIGB VHTData

2 symbols 1 symbol

T

VHT auto-detection

Rate=6MbpsLength determined by T

• For two symbols of VHT-SIGA, I energy equals to Q energy.

• Q-BPSK 2nd symbol of VHTSIGA: Need to consider about 11n devices which use 2nd symbol of HT-SIG for HT auto-detection.

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Slide 4

Issues with proposal (1)

• Backward compatibility issue– 802.11n standard defines Q-BPSK in two symbols of HT-SIG.– Given various existing implementations of 11n auto-detection.– Not fair to pre-assume any 11n auto-detect method.– Proposal (1) assumes that all 11n receivers do not use 2nd symbol

of HT-SIG for HT auto-detection. – It is unfair and risky to use Q-BPSK in 2nd symbol of VHT-SIG.

Il-Gu Lee et al.

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

HT-SIG in IEEE 802.11n Standard


[1] IEEE 802.11n, “Part 11: Wireless LAN Media Access Control (MAC) and Physical Layer (PHY) Specifications: Enhancements for Higher Throughput,” IEEE Std. 802.11n, Oct. 2009.

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Backward Compatibility with 802.11nin TGac Functional Requirements


[2] Peter Loc, et. al., TGac Functional Requirements and Evaluation Methodology Rev. 12, IEEE 802.11-09/00451r13, Mar. 18, 2010

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Slide 7

Our Proposal (2)

Il-Gu Lee et al.

L-STF L-LTF VHT-LTFsVHT-SIGB

VHT-DATAVHT-STF

L-SIGVHT-

SIGA1VHT-

SIGA2

• 11n auto-detection in 11n devices with alternative Q-BPSK/BPSK– VHT-SIGA1 gives certainty to 11a/n devices as I energy of full subcarriers.– VHT-SIGA2 gives uncertainty to 11n devices which use 2nd symbol of HT-SIG for

HT auto-detection.– For two symbols, VHT-SIGA1 is only meaningful for 11n receiver.– 11n devices detect the proposal (2) type 11ac packet as legacy packet.

VHT-SIGA2(Alternative Q-BPSK/BPSK)

Q

I

Q

I

Q

I

L-SIG(BPSK)

VHT-SIGA1(BPSK)

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Simulation Results

1) 11ac Preamble Design Evaluation for 11n Receivers 2) 11ac/11a Auto-detection Performance for 11ac Receivers


Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

1) 11ac Preamble Design Evaluation for 11n Receivers


Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Simulation Conditions

• 1x1 802.11n configuration.

• 1 spatial stream 20MHz bandwidth mode.

• Transmitted packets (N : number of Q-BPSK tones);– Proposal (1)

• N=48; Full Q-BPSK

– Proposal (2)• N=24 : Alternative Q-BPSK(2n+1)/BPSK(2n)

• N=36 : Alternative Q-BPSK(4n+1,4n+2 and 4n+3)/BPSK(4n)

• AWGN added.

• HT auto-detection w/ 2 symbols of HT-SIG.

Slide 10 Il-Gu Lee et al.

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Proposal 1

Figure 1. High SNR (25dB) Figure 2. Low SNR (5dB)

High SNR Low SNR

VHT-SIGA1

VHT-SIGA2

Total EnergyEquality

VHT-SIGA1

VHT-SIGA2

Total EnergyEquality

I-phase 0.38 0.01 0.39 100% 0.39 0.11 0.50 96%

Q-phase 0.01 0.38 0.39 0.10 0.38 0.48

- Regardless the signal to noise ratio, I energy equals to Q energy over 2 symbols of HT-SIG.- 11n receivers which use 2 symbols of HT-SIG may have severe performance degradation

Blue: In-phaseRed: Quadrature-phase

Slide 11

-1 0 1

-1

0

1

Constellation of VHT-SIGA1

In-Phase

Qua

drat

ure-

Pha

se

-1 0 1

-1

0

1


In-Phase

Qua

drat

ure-

Pha

se

0 20 40 60

-1

0

1

sample index

nom

aliz

ed a

mpl

itude

Equalized Output of VHT-SIGA1

0 20 40 60

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-1 0 1

-1

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1


In-Phase

Qua

drat

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-1 0 1

-1

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In-PhaseQ

uadr

atur

e-P

hase

0 20 40 60

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0 20 40 60

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Il-Gu Lee et al.

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Proposal 2 (N=24)

- Regardless the signal to noise ratio, I energy is larger than Q energy over 2 symbols of HT-SIG.- 11n receivers which use 2 symbols of HT-SIG can detect (2) type packet as a legacy mode



Slide 12

High SNR Low SNR

VHT-SIGA1

VHT-SIGA2

Total Energyequality

VHT-SIGA1

VHT-SIGA2


I-phase 0.38 0.18 0.56 39% 0.39 0.21 0.60 56%

Q-phase 0.01 0.21 0.22 0.10 0.24 0.34

-1 0 1

-1

0

1


In-Phase

Qua

drat

ure-

Pha

se

-1 0 1

-1

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1


In-PhaseQ

uadr

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e-P

hase

0 20 40 60

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mpl

itude


0 20 40 60

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-1 0 1

-1

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In-Phase

Qua

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In-Phase

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nom

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Il-Gu Lee et al.

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Proposal 2 (N=36)

- Regardless the signal to noise ratio, I energy is larger than Q energy over 2 symbols of HT-SIG.- 11n receivers which use 2 symbols of HT-SIG can detect (2) type packet as a legacy mode



Slide 13

High SNR Low SNR

VHT-SIGA1

VHT-SIGA2


VHT-SIGA1

VHT-SIGA2


I-phase 0.38 0.09 0.47 64% 0.40 0.17 0.57 66%

Q-phase 0.01 0.29 0.30 0.10 0.28 0.38

-1 0 1

-1

0

1


In-Phase

Qua

drat

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In-Phase

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-1 0 1

-1

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In-PhaseQ

uadr

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0 20 40 60

-1

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nom

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0 20 40 60

-1

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nom

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Il-Gu Lee et al.

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

11n Auto-detection Error Rate in 11n DeviceSNR [dB] Proposal 1

(N=48)Proposal 2

(N=24)Proposal 2

(N=36)

14 0.56 0 0

12 0.55 0 0

10 0.54 0 0

8 0.56 0 0

6 0.52 0 0

4 0.54 0 0.009

2 0.49 0.004 0.054

- Proposal (1) has about 50% 11n auto-detection error rate regardless signal-to-noise ratio.

- On the other hand, proposal (2) doesn’t have auto-detection error in this simulation.

- Tradeoff relationship between 11n safety and 11ac/11a auto-detection.

• Depend on the number of Q-BPSK tones.

• The larger number of Q-BPSK tones allow 11ac receivers to auto-detect 11ac/11a better, but worse 11n safety for 11n standard.

• The smaller number of Q-BPSK tones give safety to 11n standard, but worse 11ac/11a auto-detection for 11ac receivers.


Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

2) 11ac/11a Auto-detection Performance for 11ac Receivers


Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

11ac Miss Detection Simulation Conditions

• 1x1 802.11ac configuration.


• Transmitted packets;– Proposal (1)

– Proposal (2)

• Channel D

• 11ac/11a auto-detection comparison;– Proposal(1)

– Proposal(2)


Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

11ac Miss Detection for 11ac Packet

When 11ac packet sent to 11ac receiver, miss detection of 11ac packet as 11a packet

8.5dB


Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

11ac False Detection Simulation Conditions

• 1x1 802.11ac configuration


• Transmitted packets;– 11a packet

• Channel D

• 11ac/11a auto-detection comparison;– Proposal (1)

– Proposal (2)


Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

11ac False Detection for 11a Packet

When11a packet sent to 11ac receiver, false detection of 11a packet as 11ac packet

Slide 19

8.7dB

Il-Gu Lee et al.

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

11ac/11a auto-detection performance

- Proposal 2 (N=24)- Even/odd alternative Q-BPSK/BPSK.

- 24 Q-BPSK tones and 24 BPSK tones.

- 11ac auto-detection performance degradation due to the reduced Q-BPSK tones is ~1.5dB at 10-2 error rate.

- Proposal 2 (N=36)- Modulo 4 alternative Q-BPSK/BPSK.

- For example, Q-BPSK for 4n+1, 4n+2, 4n+3, and BPSK for 4n (n=0,1,2..11)

- 36 Q-BPSK tones and 12 BPSK tones.

- 11ac auto-detection performance has only ~0.2dB loss at 10-2 error rate.

- For SNR range of interest for packet demodulation (> 10 dB) both proposals provide sufficient performance.

- Tradeoff relationship between 11n safety and 11ac/11a auto-detection performance.


Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Comparisons

Criterions Proposal 1

Proposal 2

1st VHT-SIG BPSK BPSK

2nd VHT-SIG Q-BPSK Alternative Q-BPSK/BPSK

11n fairness & safety Bad Good

11ac/11a reliability Sufficient Sufficient


- 11ac standard should be backward-compatible with 11n standard.- Proposal (1) needs safety mechanism for concerns on the standard issue.- Proposal (2) is a possible solution.

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Slide 22

Summary

• Existing proposal in TGac for VHT auto-detection– Proposal (1) 10/070r0 (Zhang, et al)– Unfair and risky to pre-assume any HT auto-detection of 11n devices.

• A possible method proposed:– (2A) uses alternative Q-BPSK/BPSK on 2nd VHT-SIG symbol.

• Guarantee more reliable auto-detection for existing 11n devices.

• Conclusion– Proposal(1) has concerns about 11n auto-detection for 11n receivers.– Our proposal guarantees more reliable auto-detection for existing 11n devices by simple

modification, and at the same time, maintain sufficient 11a/11ac detection performance.– Considering the fairness, safety, and reliability for HT/VHT auto-detection, our proposed

method can be a good compromised solution for VHT preamble structure.

Il-Gu Lee et al.

Submission

doc.:IEEE 802.11-10/0359r1xx. xx, 2010

Slide 23

References

• [1] IEEE 802.11n, “Part 11: Wireless LAN Media Access Control (MAC) and Physical Layer (PHY) Specifications: Enhancements for Higher Throughput,” IEEE Std. 802.11n, Oct. 2009.

• [2] Peter Loc, et. al., TGac Functional Requirements and Evaluation Methodology Rev. 12, IEEE 802.11-09/00451r13, Mar. 18, 2010

• [3] Hongyuan Zhang , et. al., 802.11ac Preamble, IEEE 802.11-10/0070r1, Feb. 10, 2010

• [4] Yung-Szu Tu, et. al., Proposed TGac Preamble, IEEE 802.11-10/0130r0, Jan. 20, 2010

• [5] Il-Gu Lee, et. al., 802.11ac preamble for VHT auto-detection, Mar. 16, 2010

Il-Gu Lee et al.

Documents

Doc.:IEEE 802.11-10/0359r1 Submission xx. xx, 2010 Il-Gu Lee et al.Slide 1 802.11ac preamble for VHT auto-detection Date: 2010-05-18 Authors: