Effect of Wake-Up Signal Location and Guard RB on Interference Mitigation at Wake-Up Receiver in 5G

Low-power wake-up signal (LP-WUS) has been introduced in 3GPP NR Release 18 as a key feature for UE power saving. Optimal performance of a LP-WUS receiver (LR) requires suitable ways of mitigating the interference experienced by the simple LP-WUS due to adjacent channel interference (ACI) and in-channel interference (ICI). In this paper, we present a simulation study of the relative interference level (RIL), and bandwidth efficiency of LP-WUS at the LR taking into account the impact of guard resource blocks (RBs) on either side of LP-WUS, location of LP-WUS within 5G NR channel, carrier frequency offset (CFO) of the LR local oscillator, and the LR filter order. The simulation results show that for LR CFO of 200KHz (500KHz), when LP-WUS with 5MHz bandwidth is centrally placed within a 20MHz NR channel, upto two (four) guard RBs will be required to keep RIL < −10dBc. Whereas when the ACI is increased by placing the LP-WUS 5MHz away from edge of the channel, the required guard RBs increase to four (six) respectively thereby reducing the bandwidth efficiency by 14.3%. Interestingly, the results reveal that LP-WUS cannot be placed at the immediate edge of the channel, there needs to be an offset of 19 RBs for proper detection of LP-WUS.