Spectrum efficient support of wake-up receivers by using (O)FDMA

The use of a wake-up receiver (WUR) is an attractive means to reduce power consumption. However, when the wake-up signal (WUS) is sent in-band, the use of a WUR may potentially reduce the spectrum efficiency of the system. In this paper, we propose to multiplex the WUS, based on ON-OFF keying, with the user data using FDMA or OFDMA to allow for spectrum efficient use of WURs. The proposed WUR architecture is based on an envelope detector and an uncertain intermediate frequency (IF), which means that the user data will act as interference for the WUS. In spite of its low complexity, it is shown by means of simulations that good sensitivity performance can still be obtained. In addition, the multiplexing allows for great flexibility and the power allocated to the WUS and the user data, respectively, can be selected based on actual requirements.