Abstract
IEEE 802.11 consists of one of the most used wireless access technologies, which can be found in almost all consumer electronics devices available. Recently, Wake-up Radio (WuR) systems have emerged as a solution for energy-efficient communications. WuR mechanisms rely on using a secondary low-power radio interface that is always in the active operation mode and is in charge of switching the primary interface, used for main data exchange, from the power-saving state to the active mode. In this paper, we present a WuR solution based on IEEE 802.11 technology employing transmissions of legacy frames by an IEEE 802.11 standard-compliant transmitter during a Transmission Opportunity (TXOP) period. Unlike other proposals available in the literature, the WuR system presented in this paper exploits the PHY characteristics of modern IEEE 802.11 radios, where different signal bandwidths can be used on a per-packet basis. The proposal is validated through the Matlab software tool, and extensive simulation results are presented in a wide variety of scenario configurations. Moreover, insights are provided on the feasibility of the WuR proposal for its implementation in real hardware. Our approach allows the transmission of complex Wake-up Radio signals (i.e., including address field and other binary data) from legacy Wi-Fi devices (from IEEE 802.11n-2009 on), avoiding hardware or even firmware modifications intended to alter standard MAC/PHY behavior, and achieving a bit rate of up to 33 kbps.
Highlights
More than two decades after the first IEEE 802.11 specification saw the light of day, the devices using that technology are counted in billions, and it continues to gain momentum [1]
Our goal is to offer an IEEE 802.11-based Wake-up Radio (WuR) solution that is compatible with the existing ecosystem of Wi-Fi devices at the cost of a minimum software update
We have proposed a WuR system based on the transmission of legacy frames by an IEEE 802.11 standard-compliant transmitter during a TXOP period
Summary
More than two decades after the first IEEE 802.11 specification saw the light of day, the devices using that technology are counted in billions, and it continues to gain momentum [1]. The WuC is generated, activating/deactivating the central 13 subcarriers of a 20 MHz IEEE 802.11’s OFDM symbol, reducing the effective bandwidth to 4 MHz. The WuC contains a synchronization sequence intended to allow frame detection and synchronization by the WuRx, and the WuC data, which is Manchester encoded. The proposal exploits the PHY characteristics of specifications from IEEE 802.11n on, where different signal bandwidths can be employed for frame transmission, making use of the so-called channel bonding mechanism In this way, IEEE 802.11n allows operation for 20 and 40 MHz of signal bandwidth, while IEEE 802.11ac and 11ax can use 20, 40, 80, and 160 MHz. If transmitted frames inside a TXOP employ MCSs using different signal bandwidths, and these signals of different bandwidths can be distinguished at the receiver, the bandwidth of such transmitted frames can be used to encode different symbols composing a WuC. For longer WuC length and in order to avoid synchronization issues, we can force different IEEE 802.11n/ac symbols to have the same duration, applying an extension of 4 μs to signals larger than 20 MHz by the usage of bit padding in the MAC payload
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