E-MiLi: Energy-Minimizing Idle Listening in Wireless Networks

Abstract

Abstract-WiFi interface is known to be a primary energy consumer in mobile devices, and idle listening (IL) is the dominant source of energy consumption in WiFi. Most existing protocols, such as the 802.11 power-saving mode (PSM), attempt to reduce the time spent in IL by sleep scheduling. However, through an extensive analysis of real-world traffic, we found more than 60 percent of energy is consumed in IL, even with PSM enabled. To remedy this problem, we propose Energy-Minimizing idle Listening (E-MiLi) that reduces the power consumption in IL, given that the time spent in IL has already been optimized by sleep scheduling. Observing that radio power consumption decreases proportionally to its clock rate, E-MiLi adaptively downclocks the radio during IL, and reverts to full clock rate when an incoming packet is detected or a packet has to be transmitted. E-MiLi incorporates sampling rate invariant detection, ensuring accurate packet detection and address filtering even when the receiver's sampling clock rate is much lower than the signal bandwidth. Further, it employs an opportunistic downclocking mechanism to optimize the efficiency of switching clock rate, based on a simple interface to existing MAC-layer scheduling protocols. We have implemented E-MiLi on the USRP software radio platform. Our experimental evaluation shows that E-MiLi can detect packets with close to 100 percent accuracy even with downclocking by a factor of 16. When integrated with 802.11, E-MiLi can reduce energy consumption by around 44 percent for 92 percent of users in real-world wireless networks.

Energy Efficient Downlink Transmission in Wireless LANs by Using Low-Power Wake-Up Radio

“…To this end, a WuR shares the same channel with WLAN modules and a WuM is transmitted from the WLAN module of an AP to a WuR. [24]. (iii) OOK modulation can be emulated to transmit a WuM by modulating the envelope of an OFDM signal [19].…”

“…In the case of Rayleigh fading, if instantaneous The length of wake-up period, WU , varies with devices and mainly depends on the performance of high frequency oscillator. According to [24], it takes 139 s to switch from 1/4 clock rate to full clock rate and takes about 200 s to generate a stable carrier frequency within 50 kHz of the desired value in MAX7032 (https://www.maximintegrated.com/en/ products/comms/wireless-rf/MAX7032.html/). In the analysis, the wake-up latency is assumed to be WU = 200 s, approximately WU = 22 slots with = 9 s. Out of these nodes, with a probability…”

Reducing false wake-up in contention-based wake-up control of wireless LANs

“…An example is illustrated in [8]. A WLAN module in its idle state reduces its clock rate to reduce power consumption.…”

“…In the remote wake-up control [5,[8][9][10][11][12], the wake-up latency of WLAN modules, although not clearly addressed, can be solved by letting the transmitter hold the channel via a long preamble [13]. But when using a WuR for carrier sensing at the transmitter side, the wake-up is contention-based and the wake-up latency leads to false wake-ups, which has not been studied before.…”

“…Recently, the standardization of wake-up control for WLAN module was started as well [7]. In this remote wake-up control [5,[8][9][10][11][12], usually a unique ID is used to identify a specific receiver.…”