Patent ID: 8787945

Claim:
A method for synchronizing a user equipment clock in a cellular telecommunications user equipment, the method comprising: periodically waking up the user equipment to receive signals transmitted on a cellular telecommunications network; selecting a synchronization mode to synchronize the user equipment clock to a network clock, based at least on one or more signals received by the user equipment while the user equipment is awake to receive signals in a first instance, wherein a first synchronization mode uses a first type of signals and a second synchronization mode uses at least a second type of signals that is different from the first type of signals; in response to selecting the first synchronization mode to synchronize the user equipment clock to the network clock, in a second instance that is subsequent to the first instance, waking up the user equipment for a first period of time to receive signals; and in response to selecting the second synchronization mode to synchronize the user equipment clock to the network clock, in the second instance that is subsequent to the first instance, waking up the user equipment for a second period of time to receive signals, such that the second period of time is different from the first period of time.