Transmission and monitoring of low-power wake-up signals

1 . An apparatus, comprising:

at least one processor; and

at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform:

monitoring, in an inactive mode, low power wake-up signal (LP-WUS) occasions for detecting a transmission on a LP-WUS occasion, the transmission comprising:

a first signature indicating presence of at least one LP-WUS message in the transmission and the at least one LP-WUS message; or

a second signature indicating absence of a LP-WUS message in the transmission, wherein, in a case where the second signature is received, performing updating synchronization of the apparatus based on the second signature;

based on detecting, based on a metric for LP-WUS coverage estimation, that the apparatus is outside the LP-WUS coverage, the apparatus is caused to perform: switching to active mode;

triggering a LP-WUS mobility event; and

indicating to a network node that the apparatus has not received LP-WUS message(s) or either of the first signature and the second signature; and

wherein the transmission comprises the first signature, the apparatus is caused to perform:

detecting the first signature; and based on detecting the first signature;

monitoring the at least one LP-WUS message in a remaining portion of the LP-WUS occasion;

updating synchronization of the apparatus based on the first signature and the at least one LP-WUS message;

receiving the at least one LP-WUS message instructing to wake-up; and

switching to an active mode.