| CPC H04W 36/0077 (2013.01) [H04W 36/00725 (2023.05); H04W 56/0045 (2013.01)] | 15 Claims |
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1. A user equipment (UE) comprising:
a receiver, which in operation, receives, from a source base station of a source radio cell, a common timing advance value for a target radio cell, the UE being connected to the source radio cell and being involved in a handover procedure to hand over the UE from the source radio cell to the target radio cell, wherein the common timing advance value is received from the source base station in a first message of the handover procedure, wherein the first message of the handover procedure further comprises a timing indication for transmitting a second message from the UE to the target base station,
a processor, which in operation,
determines a first uplink timing of uplink transmissions to the target base station with respect to downlink transmissions from the target base station, based on the received common timing advance value and the timing indication, and
a transmitter, which in operation, transmits a second message of the handover procedure to the target base station based on the determined first uplink timing,
the processor, when in operation, determines a UE-specific timing advance value, specific to the UE and the target radio cell, to be used by the UE for performing uplink transmissions in the target radio cell, wherein the UE-specific timing advance value for the UE and the target radio cell is determined as:
CTA source+ITA_source−CTA_target−2(T2−T1)+Off_target−Off source,
wherein CTA source is a common timing advance value of the source radio cell, ITA source is a UE-specific timing advance value for the UE and the source radio cell, CTA target is the received common timing advance value of the target radio cell, (T2-T1) is a downlink propagation time difference between the source base station and the target base station, Off target is a time offset between downlink and uplink delay in the target radio cell and is obtained by the UE from the first message and Off source is the time offset between the downlink and uplink delay in the source radio cell.
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