A sequence number (sn) synchronization mechanism in rlc-based forwarding

A network node of a source cell configured to forward data packets during a handover of a User Equipment (UE) from the source cell to a target cell, the network node comprising:

• a communication interface;
• and
• a processing circuit communicatively connected to the communication interface, and configured to:
• determine a sequence number related to a data packet;
• forward a first set of one or more data packets to the target cell, the first set of one or more data packets being previously sent to the UE but unacknowledged by the UE and having respective sequence numbers inferior to the determined sequence number;
• forward to the target cell a second set of one or more data packets, from which a third set of one or more data packets are generated, the third set having respective sequence numbers equal or superior to the determined sequence number;
• and
• send the determined sequence number to the target cell.

A network node for forwarding data packets during a handover of a User Equipment (UE) from a source cell to a target cell, the network node comprising:

• a communication interface;
• and
• a processing circuit communicatively connected to the communication interface, and configured to:
• receive a sequence number related to a data packet from the source cell;
• receive a first set of one or more data packets from the source cell, the first set of one or more data packets being previously sent to the UE but unacknowledged by the UE and having respective sequence numbers inferior to the determined sequence number;
• receive from the source cell a second set of one or more data packets, from which a third set of one or more data packets are generated, the third set of one or more data packets having respective sequence numbers equal or superior to the determined sequence number.

A wireless device for synchronizing with a target cell, after a handover from a source cell to the target cell, the wireless device comprising:

• a communication interface;
• and
• a processing circuit communicatively connected to the communication interface, and configured to:
• receive a first data packet from the target cell, the first data packet having a first sequence number;
• send an acknowledgement for the receipt of the first data packet to the target cell;
• receive one or more data packets having respective sequence numbers inferior to the first sequence number;
• receive one or more data packets having respective sequence numbers superior to the first sequence number;
• decrypt the one or more packets having respective sequence numbers inferior to the first sequence number using an encryption key from the source cell;
• decrypt the first data packet and the one or more packets having respective sequence numbers superior to the first sequence number using an encryption key from the target cell.

A method in a communication network in which a handover of a wireless device occurs, the wireless device moving from a source cell to a target cell, the method comprising:

• at the source cell:
• determining a sequence number related to a data packet;
• forwarding a first set of one or more data packets to the target cell, the first set of one or more data packets being previously sent to the wireless device but unacknowledged by the wireless device, and having respective sequence numbers inferior to the determined sequence number;
• forwarding to the target cell a second set of one or more data packets, from which a third set of one or more data packets are generated, the third set of one or more data packets having respective sequence number equal or superior to the determined sequence number;
• and
• sending the determined sequence number to the target cell;
• at the target cell:
• sending a first data packet with the determined sequence number to the wireless device;
• receiving an acknowledgement associated with the sent first data packet from the wireless device;
• sending the first set of one or more data packets having respective sequence numbers inferior to the first sequence number;
• and
• sending the second set of one or more data packets having respective sequence numbers superior to the first sequence number;
• at the wireless device:
• decrypt the first set of one or more packets having respective sequence numbers inferior to the determined sequence number using an encryption key from the source cell;
• and
• decrypt the first data packet and the second set of one or more packets having respective sequence numbers superior to the determined sequence number using an encryption key from the target cell.