A Wake-Up Signal Design with Flat Frequency Spectrum for Low-Power Wake-Up Receiver

The low-power wake-up receiver (LP-WUR) has been proposed recently to reduce the power consumption and meet the low latency requirement. The design of the wake-up signal (WUS) is especially important for LP-WUR. To integrate it into orthogonal frequency division multiplexing (OFDM) based system, e.g., New Radio (NR), without incurring extra cost, the WUS should both achieve the low detection complexity and avoid interfering with other signals in the existing OFDM systems. Current WUS designs mainly focus on optimizing waveform in the time domain to approximate the on-off keying (OOK) modulation while neglecting characteristic in the frequency domain which results in poor performance under fading channels. In this paper, we present a novel WUS design with flat frequency spectrum for integration into the NR system. An alternating optimization with the gradient projection algorithm which has a low complexity and acceptable convergence is proposed. Simulation results show that the proposed WUS design outperforms the existing schemes by achieving a higher frequency diversity gain under various fading channels.