doc.: IEEE 802.11-14/0713r1

Submission

May 2014

Bo Gao, Tsinghua University

Low-Power Idle Listening Resolution to CID 144

Date: 2014-5-20

Slide 1

Name Company Address Phone email Bo Gao

Tsinghua University

Luomu Building 10-202, Tsinghua University, Hai-

Dian District,Beijing, China

+86-10-62772387-312

bgao_cug@126.com

Changming Zhang

Wei Feng

Depeng Jin

doc.: IEEE 802.11-14/0713r1

Submission

Abstract

• This is a submission for comment resolution on D0.01 for comment #144. This submission provides a low power 1-bit-sampling idle listening mechanism for 11aj to reduce the power consumption. The low power idle listening mechanism keeps backward compatibility with DMG devices.

Slide 2

May 2014

Bo Gao, Tsinghua University

doc.: IEEE 802.11-14/0713r1

Submission

Comment #144

• In 60-GHz systems, the power consumption of idle listening is considerable, due to power-hungery multi-Gbps ADC. The packet detection with low-power lower-sampling-precision ADC is useful method to remedy the power of idle listening. Thus, the preamble settings (e.g., the number of Ga128/Gb128) need to consider the performance loss due to the reduction of sampling precision.

• Resolution ： This submission provides a low power idle listening mechanism using 1-bit sampling to reduce the power consumption. The length of preamble is added based on the performance requirements.

Slide 3

May 2014

Bo Gao, Tsinghua University

doc.: IEEE 802.11-14/0713r1

Submission

Power Consumption in Idle Listening

• Power consumption of idle listening is up to hundreds of milliwatts (mW) due to power-hungry ultra-high-speed ADC and analog RF chain. This problem may block 60-GHz WLAN (11aj) from being extensively used in battery-supply devices, such as smart phones, ipads.

Slide 4

− A natural way to reduce the power consumption is sleeping schedule. By exploiting the power-saving mode (PSM) in 802.11 standard, wireless stations (STAs) hibernate standby unless they expect to receive or intend to transmit packets.

− However, the PSM mechanism only reduce energy dissipation of STAs instead of a AP/PCP, which may be a power-sensitive portable device in 60-GHz WLAN.

Bo Gao, Tsinghua University

May 2014

doc.: IEEE 802.11-14/0713r1

Submission

Idle Listening Using 1-Bit Sampling

• Since the power consumption of an ADC is exponential to its bit depth, we propose a low power idle listening mechanism using 1-bit ADC, which is summarized as follows:

Slide 5

− A 1/M-bit-sampling receiver is proposed in Fig. 1.

− The receiver uses an ultra-low-power 1-bit ADC to detect packets during idle listening period. Once the arrival of a packet is successfully detected, the receiver switches to the original multi-bit, i.e., M-bit, ADC to demodulate information data normally.

− By using this receiver, the energy dissipation of IL is efficiently reduced, while the demodulation performance is maintained.

Bo Gao, Tsinghua University

1-bit ADC

M-bit ADC

Datato MAC

Packet detectorReceive RF

chainDigital

baseband

Preamble DataIdle Listening

…… ……

Detect a packet with 1-bit ADC

Switch to M-bit ADC sampling

Switch to 1-bit ADC sampling

Packet demodulationClock ticks

Fig. 1. Diagram of 1/M-bit-sampling receiver.

Fig. 2. The proposed idle listening and receiving operation

May 2014

doc.: IEEE 802.11-14/0713r1

Submission

Detection Performance Evaluation Using 1-Bit Sampling

• Since the sampling quantization of ADC is reduced from full-precision to 1-bit, the receiver is confronted with the degradation of packet detection. In 60-GHz LOS channel, we evaluate the detection performance of the receiver with 4×4 phase arrays.

Slide 6

− The performance evaluation is illustrated in Fig. 1, where the probability of false-alarm is 10-6 and the received SNR is -8 dB.

− In order to remedy the degradation induced by the reduction of the sampling precision, the lower power mechanism needs about 120 assisted symbols more than the conventional mechanism in the basically same detection performance. That is, one Ga128/Gb128 sequence more.

Bo Gao, Tsinghua University

Fig.1. Detection performance evaluation

0 50 100 150 200 250 300 350 400 450 50010

-4

10-3

10-2

10-1

100

The length of the assisted sequenceM

iss-

dete

ctio

n pr

obab

ility

Full-precision sampling

1-bit sampling

120-bit

May 2014

doc.: IEEE 802.11-14/0713r1

Submission

Preamble Modification in 802.11aj

• Two Ga128/Gb128 is added in the beginning of preamble. One Ga128 is used to remedy the performance degradation; the other Ga128 is used to occupy the ADC switch time, which can be limited to less than 100 ns.

Slide 7 Bo Gao, Tsinghua University

SC/OFDM PHY: …

Added sequences 802.11aj preamble 802.11aj data

Ga128 Ga128 Ga128 Ga128 -Ga128 CESFS

CNTRL PHY: …

Added sequences 802.11aj preamble 802.11aj data

Gb128 Gb128 Gb128 Gb128 -Gb128 CE

May 2014

doc.: IEEE 802.11-14/0713r1

Submission

Preamble Modification in 802.11aj

• One Ga128/Gb128 is used to remedy the performance degradation induced by the reduction of sampling precision. In 60-GHz Los channel, we evaluate the detection performance of the receiver with 4×4 phase arrays.

Slide 8

− The performance evaluation is illustrated in Fig. 1, where the conventional idle listening with full sampling precision uses two Ga128/Gb128 sequences, and the idle listening with 1-bit sampling uses three Ga128/Gb128.

− The stimulated curves for the two situation are basically the same, which means that the degradation has been remedied by appending one Ga128/Gb128 sequence.

Bo Gao, Tsinghua University

Fig.1. Detection performance where the assisted sequences for schemes with full-precision and 1-bit sampling are two and threeGa128/Gb 128 sequences, respectively

10-15

10-10

10-5

100

10-5

10-4

10-3

10-2

10-1

100

False-alarm probabilityM

iss-

dete

ctio

n pr

obab

ility

Full-precision sampling1-bit sampling

SNR = -12 dB

SNR = -10 dB

SNR = -8 dB

SNR = -6 dB

May 2014

doc.: IEEE 802.11-14/0713r1

Submission

Power Saving

• The power consumption of idle listening with 1-bit sampling is compared with that of conventional idle listening. Based on Refs [3, 4, 5], suppose that the overall power consumption of a receive RF chain with a 4 × 4 planner phased array is 0.3 W. Besides, the sampling frequency fs = 1.5 Gsps, and the conversion efficiency Cadc = 0.47 pJ/conv. The comparisons are as follows:

Slide 9 Bo Gao, Tsinghua University

BPSK/QPSK-SC 16QAM-SC 16QAM-OFDM 64QAM-OFDMADC bit-depth 6-bit 7-bit 8-bit 10-bitConventional（ W）

0.390 0.481 0.661 1.743

1-bit sampling（ W）

0.303 0.303 0.303 0.303

Power saving 22.3% 37.0% 54.2% 82.6%

May 2014

doc.: IEEE 802.11-14/0713r1

Submission

Summary

• This submission provides a lower power idle listening solution for comment #144 on the comment resolution for D0.01.

• Modifications to 802.11aj PHY packet:– Two Ga128/Gb128 is added in the beginning of preamble.

Slide 10 Bo Gao, Tsinghua University

May 2014

doc.: IEEE 802.11-14/0713r1

Submission

Reference

1. IEEE P802.11ad, “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) Specifications – Amendment 3: Enhancements for Very High Throughput in the 60 GHz band,” December 2012.

2. IEEE P802.11aj, “Part 11: Wireless LAN Medium Access Control (MAC) and Physical Layer (PHY) specifications Amendment X: Enhancements for Very High Throughput to Support Chinese Millimeter Wave Frequency Bands(60GHz) ,” January 2014

3. K. Huang, Z. Wang, “Millimeter wave communication systems,” John Wiley & Sons Ltd., 2011

4. K. Okada, et al. “A 60-GHz 16QAM/8PSK/QPSK/BPSK direct-conversion transceiver for IEEE 802.15.3c’, IEEE J. Solid-State Circ., vol. 46, no. 12, pp. 2988–3004, 2011

5. Y. Nakajima, et al. “ A Background Self-Calibrated 6b 2.7 GS/s ADC With Cascade-Calibrated Folding-Interpolating Architecture,” IEEE J. Solid-State Circuits, 2010, pp. 707–718.

Slide 11 Bo Gao, Tsinghua University

May 2014