A Low-Power OFDM-Based Wake-Up Mechanism for IoE Applications

This brief presents a wake-up mechanism for orthogonal frequency division multiplexing (OFDM) modulation-based systems by coding a low data-rate wake-up signal in transmitter without extra circuitry overhead. It is achieved by controlling data pattern for each OFDM subcarrier in one symbol of frame to produce an equivalent amplitude-modulated (AM) signal as a wake-up query without contaminating protocol integrity. A low-power wake-up receiver is used to demodulate this signal and interpret the wake-up query. A system using proposed wake-up mechanism has been built based on IEEE 802.11ah standard. Measurement results demonstrate that an AM-type wake-up signal with a data-rate of 31.25 Kb/s is generated through the proposed method. Moreover, an envelope detector with -35-dBm sensitivity at 900 MHz has been implemented in 0.13-μm CMOS technology for wake-up signal detection and consumes 120-nW power.