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

Abstract

In the downlink of a wireless LAN, power-save mode is a typical method to reduce power consumption. However, it usually causes large delay. Recently, remote wake-up control via a low-power wake-up radio (WuR) has been introduced to activate a node to instantly receive packets from an access point (AP). But link quality is not taken into account and protocol overhead of wake-up per node is relatively large. To solve these problems, in this paper, a broadcast-based wake-up control framework is proposed, and a low-power WuR is used to receive traffic indication map from an AP, monitor link quality, and perform carrier sense. Among the nodes which have packets buffered at the AP, only those whose SNR is above a threshold will be activated, contending via a proper contention window to receive packets from the AP. Optimal SNR threshold, deduced by theoretical analysis, helps to reduce transmission collisions and false wake-ups (caused by wake-up latency) and improve transmission rate. Extensive simulations confirm that the proposed method (i) effectively reduces power consumption of nodes compared with other methods, (ii) has less delay than power-save mode in times of light traffic, and (iii) achieves higher throughput than other methods in the saturation state.

On the Joint Usage of Target Wake Time and 802.11ba Wake-Up Radio

“…The papers [28], [29] propose the answer to the first question by changing the addressing procedure in the network to reduce the ID field in the MAC header and also suggest using special address detectors based on the Bloom filter [28] and on the pulse width [29]. The authors of [30] address the second question by studying the data transmission delay, including the WUR frame transmissions, and propose periodically broadcasting wake-up frames to switch all WUR STAs to the awake state at once. This approach reduces the number of WUR frame transmissions but increases competition for the channel and, as a result, the sensor's energy consumption.…”

IEEE 802.11ba — Extremely Low Power Wi-Fi for Massive Internet of Things — Challenges, Open Issues, Performance Evaluation

“…A Wake-up frame can be unicast or groupcast. For example, [10] evaluates delays induced by WUR and proposes to periodically broadcast Wake-Up frames to wake up all WUR STAs. Such an approach decreases the number of WUR frames, but increases contention and, thus, energy consumption.…”

Hardware Mechanism for Energy Saving in WiFi Access Points

“…The reduction of idle pending combining the monitoring of WiFi downlink and low-power wake-up radio is simulated in [25] achieving considerable reduction of energy consumption. We implemented a hardware mechanism but not considering those techniques.…”