In-sequence delivery of upstream user traffic during handover
View Patent ↗The present invention relates to a donor radio access node (DeNB 1 ) configured to wirelessly connect to, and to proxy operation of a source relay node (RN 1 ), and further configured to forward upstream user traffic towards a serving gateway (S-GW 1 ) during a handover of a particular mobile device (UE 1 ) from a source cell (A) operated by the source relay node to a target cell (C) operated by a target radio access node (eNB 2 ). In accordance with an embodiment of the invention, the donor radio access node comprises: —first forwarding means (FW 1 ) for forwarding a sequence of upstream data packets (P 1 , P 2 , P 3 ) from the source relay node to the serving gateway, which sequence of upstream data packets comprising upstream data packets up to a particular packet sequence number (Y−1), —second forwarding means (FW 2 ) for forwarding a data transfer status message (SN STATUS TRANSFER) for the particular mobile device from the source relay node to the target radio access node, which data transfer status message comprising an information element (Y) indicative of the particular packet sequence number, wherein the donor radio access node comprises a forwarding controller (CTRL) coupled to the first and second forwarding means, and configured to interdependently control forwarding of the data transfer status message and of any pending upstream data packet (P 2 , P 3 ) out of the sequence of upstream data packets that has not been yet validly forwarded to the serving gateway. The present invention also relates to a method for forwarding upstream user traffic towards a serving gateway during a handover.
1. A donor radio access node configured to wirelessly connect to, and to proxy operation of, a source relay node, and further configured to forward upstream user traffic towards a serving gateway during a handover of a particular mobile device from a source cell operated by said source relay node to a target cell operated by a target radio access node, said donor radio access node comprising:
a first transmitter configured to forward a sequence of upstream data packets from said source relay node to said serving gateway, the sequence of upstream data packets comprising upstream data packets up to a particular packet sequence number;
a second transmitter configured to forward a data transfer status message for said particular mobile device from said source relay node to said target radio access node, the data transfer status message comprising an information element indicative of said particular packet sequence number,
wherein said donor radio access node comprises a forwarding controller coupled to said first and second transmitters, and configured to interdependently control forwarding of said data transfer status message and of at least one pending upstream data packet out of said sequence of upstream data packets that has not been yet validly forwarded to said serving gateway upon receipt of said data transfer status message and wherein said forwarding controller is further configured to delay forwarding of said data transfer status message to said target radio access node till said pending upstream data packet has been validly forwarded to said serving gateway or till a predetermined period of time has expired.
2. A donor radio access node according to claim 1 , wherein said forwarding controller is further configured to stop forwarding at least one still pending upstream data packet to said serving gateway after said pre-determined period of time has expired.
3. A donor radio access node according to claim 1 , wherein said forwarding controller is further configured to redirect at least one still pending upstream data packet to said target radio access node after said data transfer status message has been validly forwarded to said target radio access node.
4. A method for forwarding upstream user traffic towards a serving gateway during a handover of a particular mobile device from a source cell operated by a source relay node to a target cell operated by a target radio access node, said method comprising, by a donor radio access node configured to wirelessly connect to, and to proxy operation of, said source relay node:
forwarding a sequence of upstream data packets from said source relay node to said serving gateway, the sequence of upstream data packets comprising upstream data packets up to a particular packet sequence number;
forwarding a data transfer status message for said particular mobile device from said source relay node to said target radio access node, the data transfer status message comprising an information element indicative of said particular packet sequence number,
wherein said method further comprises, by said donor radio access node, interdependently controlling forwarding of said data transfer status message and of at least one pending upstream data packet out of said sequence of upstream data packets that has not been yet validly forwarded to said serving gateway upon receipt of said data transfer status message,
and wherein said interdependently controlling comprise delaying forwarding of said data transfer status message to said target radio access node till said at least one pending upstream data packet has been validly forwarded to said serving gateway or till a predetermined period of time has expired.
5. A method according to claim 4 , wherein said method further comprises, by said donor radio access node,
stopping forwarding at least one still pending upstream data packet to said serving gateway after said pre-determined period of time has expired.
6. A method according to claim 4 , wherein said method further comprises, by said donor radio access node, redirecting at least one still pending upstream data packet to said target radio access node after said data transfer status message has been validly forwarded to said target radio access node.