Abstract
Internet of things (IoT) presupposes a massive number of low-complexity wireless devices, placed in hardly accessible locations and often powered by batteries with limited size and capacity. To extend the lifetime of these devices, wake-up radio (WuR) techniques were proposed. In the literature, WuR solutions have been evaluated with single-antenna base stations (BSs). In this paper, we evaluate the benefits of adding multiple antennas at BSs to transmit precoded WuR signals. The considered precoded schemes provide better spatial selectivity by focusing the power of the transmitted WuR signal on the targeted devices. Monte-Carlo simulations are used to assess the performance of the system in terms of successful wake-up probability of the WuR receiver. Numerical results show that, unlike data transmission scenarios, complex precoders as multicell minimum mean-squared error (M-MMSE), are surpassed by the simpler maximum ratio (MR) precoder for WuR.