Patent ID: 8284777

Claim:
A method implemented by a user equipment (UE) wirelessly connectable to a cellular mobile communication network adapted to perform uplink cell change of the UE from a first radio base station to a second radio base station, the method comprising the steps of: transmitting multiple Internet Protocol (IP) packets each comprising one or more protocol data units (PDUs) to the first radio base station; receiving one or more feedback indications from the first radio base station, each feedback indication indicating whether a corresponding PDU was successfully received by the first radio base station; transmitting one or more retransmissions of at least one of the PDUs based on the received feedback indications; coordinating a time point for performing a cell change with controlling ongoing retransmissions of outstanding PDUs, where before performing the cell change, finalizing outstanding retransmissions of PDUs for all IP-packets where a complete IP-packet has been transmitted by continuing to make the retransmissions until either acknowledgments are received for the outstanding PDUs or a maximum number of retransmissions is reached for the outstanding PDUs, wherein for any of the IP packets where only parts of the PDUs have been transmitted then retransmissions are not performed for those IP packets; and after the controlled ongoing retransmissions are performed, performing the cell change to the second radio base station and transmitting PDUs to the second radio base station starting from the first IP packet that was not delivered to the first radio base station, wherein the PDUs that were still outstanding after retransmissions at time of the cell change due to that the maximum number of retransmissions was reached are not transmitted to the second radio base station.