Low-Power Idle Listening Resolution to CID 144

1. Low-Power Idle Listening Resolution to CID 144 Date: 2014-5-18 Presenter: Bo Gao, Tsinghua University

2. 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. Bo Gao, Tsinghua University

3. 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. Bo Gao, Tsinghua University

4. 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. • 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

5. 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: • 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 IL 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. Fig. 1. Diagram of 1/M-bit-sampling receiver. Fig. 2. The proposed idle listening and receiving operation Bo Gao, Tsinghua University

6. 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. • 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. Fig.1. Detection performance evaluation Bo Gao, Tsinghua University

7. 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. SC/OFDM PHY: CNTRL PHY: Bo Gao, Tsinghua University

8. 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. • 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. 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 Bo Gao, Tsinghua University

9. 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: Bo Gao, Tsinghua University

10. 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. Bo Gao, Tsinghua University

11. Reference • 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. • 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 • K. Huang, Z. Wang, “Millimeter wave communication systems,” John Wiley & Sons Ltd., 2011 • 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 • 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. Bo Gao, Tsinghua University