Abstract
Current standardization process for Wake-up Radio (WuR) within the IEEE 802.11 Working Group, known as the IEEE 802.11ba, has brought interest to the IEEE 802.11-related technologies for the implementation of WuR systems. This paper proposes a new WuR system, where the Wake-up Transmitter (WuTx) is based on the legacy IEEE 802.11 Orthogonal Frequency Division Modulation (OFDM) Physical Layer (PHY) specification. Using the IEEE 802.11, OFDM PHY makes it possible for an IEEE 802.11a/g/n/ac transmitter to operate as WuTx for this WuR system. The WuTx generates a Wake-up Signal (WuS) coded with an amplitude-based digital modulation, achieving a bit rate of 250 kbps. This modulation, which we call Peak-Flat modulation, can be received using low-power receivers. A simulated proof of concept of the WuTx based on the IEEE 802.11g is presented and evaluated using MATLAB WLAN Toolbox. A method to generate the Peak-Flat modulated WuS from an IEEE 802.11a/g standard-compliant transmitter, using only software-level access, is explained. In addition, two possible low-power Wake-up Receiver (WuRx) architectures capable of decoding the presented modulation are proposed. The design of those receivers is generic enough to be used as a reference to compare the performance of the Peak-Flat Modulation with the other state-of-the-art approaches. The evaluation results conclude that the Peak-Flat modulation has similar performance compared to the other IEEE 802.11 WuR solutions on the reference receivers. Moreover, this solution provides a notorious advantage: legacy OFDM-based IEEE 802.11 transmitters can generate the Peak-Flat modulated WuS.
Highlights
Devices compliant with the IEEE 802.11 family of specifications are pervasive, with over 9.5 billion installed devices, as of 2018 [1]
WORK We devised a complete Wake-up Radio (WuR) system, as an alternative to IEEE 802.11ba, that is compatible with legacy IEEE 802.11 transmitters
The WuTx for this system is based on a standard compliant IEEE 802.11 Orthogonal Frequency Division Modulation (OFDM) Physical Layer (PHY), for which a Proof of Concept (PoC) has been presented using IEEE 802.11g
Summary
Devices compliant with the IEEE 802.11 family of specifications are pervasive, with over 9.5 billion installed devices, as of 2018 [1]. Our solution uses the legacy IEEE 802.11 OFDM PHY transmitter as WuTx. In order to maintain backward compatibility, it uses an amplitude-based modulation that differs from OOK, which we will call Peak-Flat modulation. These systems are more complex to implement since they need to manipulate the waveforms generated by the OFDM symbols in order to create a signal recoverable by relatively simple WuRx. IEEE 802.11 PHY specifications describe a complex transceiver architecture that incorporates: scrambling, coding, interleaving, pilot tone addition, guard intervals and other mechanisms added to increase performance and reliability. This Peak-Flat modulation deviates greatly from the usual OFDM symbols used in IEEE 802.11 OFDM PHY, which are constructed with mechanisms devised to limit their PAPR This deviation can introduce problems related to clipping that can affect both the transmitter and the receiver.
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