LAYER 2 TUNNELING OF DATA DURING HANDOVER IN A WIRELESS COMMUNICATION SYSTEM

• US 20090124259A1
• Filed: 08/07/2008
• Published: 05/14/2009
• Est. Priority Date: 08/08/2007
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Duncan Ho, Sai Yiu, Tenny, Nathan Edward, Attar, Rashid Ahmed Akbar, Meylan, Arnaud, Grilli, Francesco, Barany, Peter Anthony
• Granted Patent: US 8,437,306 B2
• Time in Patent Office: Days
• US Class Current: 455/436
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/34 ensuring sequence integrity, e.g. using sequence numbers
• CPC Class Codes: H04W 28/02 Traffic management, e.g. flow control or congestion control
• CPC Class Codes: H04W 36/02 Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
• CPC Class Codes: H04W 36/08 Reselecting an access point
• CPC Class Codes: H04W 8/04 Registration at HLR or HSS [Home Subscriber Server]
• CPC Class Codes: H04W 92/20 between access points

Abstract

Techniques for sending data during handover with Layer 2 tunneling are described. In one design, a user equipment (UE) sends first Layer 2 packets to a source base station prior to handover to a target base station. The UE sends at least one second Layer 2 packet to the target base station, which identifies the second Layer 2 packet(s) as being intended for the source base station and thus forwards the second Layer 2 packet(s) to the source base station via a Layer 2 tunnel. The UE sends third Layer 2 packets to the target base station after the handover. The target base station processes the third Layer 2 packets to obtain IP packets and sends the IP packets to a serving gateway after a trigger condition, which may be defined to achieve in-order delivery of IP packets from the source and target base stations to the serving gateway.

Claims

1. A method of sending data in a wireless communication system, comprising:

sending first Layer 2 packets to a source base station prior to handover of a user equipment (UE) from the source base station to a target base station, the first Layer 2 packets being intended for the source base station;

sending at least one second Layer 2 packet to the target base station, the at least one second Layer 2 packet being intended for the source base station and forwarded from the target base station to the source base station via a Layer 2 tunnel; and

sending third Layer 2 packets to the target base station after the handover, the third Layer 2 packets being intended for the target base station.

2. The method of claim 1, further comprising:

setting a destination indicator of each first Layer 2 packet and each second Layer 2 packet to a first value for the source base station; and

setting a destination indicator of each third Layer 2 packet to a second value for the target base station.

3. The method of claim 1, further comprising:

processing first Internet Protocol (IP) packets in accordance with a first Layer 2 configuration for the source base station to obtain the first and second Layer 2 packets; and

processing second IP packets in accordance with a second Layer 2 configuration for the target base station to obtain the third Layer 2 packets.

4. The method of claim 3, further comprising:

receiving from the target base station a message indicating a connection between the target base station and a serving gateway is set up;

using the first Layer 2 configuration prior to receiving the message; and

using the first or second Layer 2 configuration after receiving the message.

5. The method of claim 1, further comprising:

receiving from the target base station a message indicating a connection between the target base station and a serving gateway is set up; and

switching to the connection in response to receiving the message.

6. The method of claim 1, further comprising:

sending a flush message to indicate that no more Layer 2 packets are intended for the source base station, the flush message being received by the target base station and forwarded to the source base station.

7. The method of claim 1, wherein the first, second, and third Layer 2 packets comprise Radio Link Control (RLC) protocol data units (PDUs).

8. An apparatus for wireless communication, comprising:

at least one processor configured to send first Layer 2 packets to a source base station prior to handover of a user equipment (UE) from the source base station to a target base station, the first Layer 2 packets being intended for the source base station, to send at least one second Layer 2 packet to the target base station, the at least one second Layer 2 packet being intended for the source base station and forwarded from the target base station to the source base station via a Layer 2 tunnel, and to send third Layer 2 packets to the target base station after the handover, the third Layer 2 packets being intended for the target base station.

9. The apparatus of claim 8, wherein the at least one processor is configured to set a destination indicator of each first Layer 2 packet and each second Layer 2 packet to a first value for the source base station, and to set a destination indicator of each third Layer 2 packet to a second value for the target base station.

10. The apparatus of claim 8, wherein the at least one processor is configured to process first Internet Protocol (IP) packets in accordance with a first Layer 2 configuration for the source base station to obtain the first and second Layer 2 packets, and to process second IP packets in accordance with a second Layer 2 configuration for the target base station to obtain the third Layer 2 packets.

11. An apparatus for wireless communication, comprising:

means for sending first Layer 2 packets to a source base station prior to handover of a user equipment (UE) from the source base station to a target base station, the first Layer 2 packets being intended for the source base station;

means for sending at least one second Layer 2 packet to the target base station, the at least one second Layer 2 packet being intended for the source base station and forwarded from the target base station to the source base station via a Layer 2 tunnel; and

means for sending third Layer 2 packets to the target base station after the handover, the third Layer 2 packets being intended for the target base station.

12. The apparatus of claim 11, further comprising:

means for setting a destination indicator of each first Layer 2 packet and each second Layer 2 packet to a first value for the source base station; and

means for setting a destination indicator of each third Layer 2 packet to a second value for the target base station.

13. The apparatus of claim 11, further comprising:

means for processing first Internet Protocol (IP) packets in accordance with a first Layer 2 configuration for the source base station to obtain the first and second Layer 2 packets; and

means for processing second IP packets in accordance with a second Layer 2 configuration for the target base station to obtain the third Layer 2 packets.

14. A computer program product, comprising:

a computer-readable medium comprising;

code for causing at least one computer to send first Layer 2 packets to a source base station prior to handover of a user equipment (UE) from the source base station to a target base station, the first Layer 2 packets being intended for the source base station,

code for causing the at least one computer to send at least one second Layer 2 packet to the target base station, the at least one second Layer 2 packet being intended for the source base station and forwarded from the target base station to the source base station via a Layer 2 tunnel, and

code for causing the at least one computer to send third Layer 2 packets to the target base station after the handover, the third Layer 2 packets being intended for the target base station.

15. A method of receiving data in a wireless communication system, comprising:

receiving Layer 2 packets from a user equipment (UE) performing handover from a source base station to a target base station;

identifying Layer 2 packets intended for the source base station among the Layer 2 packets received from the UE; and

forwarding the Layer 2 packets intended for the source base station via a Layer 2 tunnel from the target base station to the source base station.

16. The method of claim 15, wherein the identifying the Layer 2 packets intended for the source base station comprises determining whether each Layer 2 packet received from the UE is intended for the source base station based on a destination indicator of the Layer 2 packet.

17. The method of claim 16, wherein the destination indicator is set to a first value for the source base station or to a second value for the target base station.

18. The method of claim 15, further comprising:

receiving a flush message from the UE to flush Layer 2 packets at the source base station; and

forwarding the flush message from the target base station to the source base station.

19. The method of claim 15, further comprising:

processing Layer 2 packets intended for the target base station to obtain Internet Protocol (IP) packets;

receiving a handover complete message from the source base station; and

sending the IP packets to a serving gateway after receiving the handover complete message.

20. The method of claim 19, further comprising:

starting a timer after receiving a message confirming completion of handover tasks by the UE;

processing Layer 2 packets intended for the target base station to obtain Internet Protocol (IP) packets; and

sending the IP packets to a serving gateway after expiration of the timer.

21. The method of claim 20, further comprising:

restarting the timer whenever a Layer 2 packet intended for the source base station is received from the UE at the target base station.

22. The method of claim 15, further comprising:

processing Layer 2 packets intended for the target base station to obtain Internet Protocol (IP) packets;

forwarding the IP packets via an IP tunnel from the target base station to the source base station if a connection from the target base station to a serving gateway is not set up; and

sending the IP packets to the serving gateway if the connection is set up.

23. The method of claim 15, wherein the Layer 2 packets forwarded to the source base station comprise Layer 2 packets for Internet Protocol (IP) fragments sent by the UE and received in error by the source base station and Layer 2 packets for IP fragments not yet sent to the source base station by the UE.

24. An apparatus for wireless communication, comprising:

at least one processor configured to receive Layer 2 packets from a user equipment (UE) performing handover from a source base station to a target base station, to identify Layer 2 packets intended for the source base station among the Layer 2 packets received from the UE, and to forward the Layer 2 packets intended for the source base station via a Layer 2 tunnel from the target base station to the source base station.

25. The apparatus of claim 24, wherein the at least one processor is configured to determine whether each Layer 2 packet received from the UE is intended for the source base station based on a destination indicator of the Layer 2 packet.

26. The apparatus of claim 24, wherein the at least one processor is configured to process Layer 2 packets intended for the target base station to obtain Internet Protocol (IP) packets, to receive a handover complete message from the source base station, and to send the IP packets to a serving gateway after receiving the handover complete message.

27. The apparatus of claim 24, wherein the at least one processor is configured to set a timer after receiving a message confirming completion of handover tasks by the UE, to process Layer 2 packets intended for the target base station to obtain Internet Protocol (IP) packets, and to send the IP packets to a serving gateway after expiration of the timer.

28. The apparatus of claim 24, wherein the at least one processor is configured to process Layer 2 packets intended for the target base station to obtain Internet Protocol (IP) packets, to forward the IP packets via an IP tunnel from the target base station to the source base station if a connection from the target base station to a serving gateway is not set up, and to send the IP packets to the serving gateway if the connection is set up.

29. A method of receiving data in a wireless communication system, comprising:

receiving first Layer 2 packets from a user equipment (UE) prior to handover of the UE from a source base station to a target base station;

receiving at least one second Layer 2 packet sent by the UE to the target base station and forwarded to the source base station via a Layer 2 tunnel; and

processing the first Layer 2 packets and the at least one second Layer 2 packet to obtain at least one Internet Protocol (IP) packet.

30. The method of claim 29, further comprising:

receiving a flush message sent by the UE to the target base station and forwarded to the source base station; and

flushing Layer 2 packets to upper layer at the source base station in response to receiving the flush message.

31. The method of claim 30, further comprising:

sending a handover complete message after receiving the flush message or if no more Layer 2 packets are expected from the UE at the source base station.

32. A method of sending data in a wireless communication system, comprising:

receiving at least one first Layer 2 packet forwarded by a source base station to a target base station via a Layer 2 tunnel;

sending the at least one first Layer 2 packet to a user equipment (UE) performing handover from the source base station to the target base station;

generating second Layer 2 packets for the UE at the target base station; and

sending the second Layer 2 packets to the UE.

33. The method of claim 32, wherein each first Layer 2 packet includes a source indicator set to a first value for the source base station, the method further comprising:

setting a source indicator of each second Layer 2 packet to a second value for the target base station.

34. The method of claim 32, further comprising:

maintaining a first buffer for the at least one first Layer 2 packet received from the source base station;

maintaining a second buffer for the second Layer 2 packets generated by the target base station; and

sending the at least one first Layer 2 packet in the first buffer to the UE before sending the second Layer 2 packets in the second buffer to the UE.

35. The method of claim 32, further comprising:

receiving from the source base station a message indicating no more first Layer 2 packets to forward to the target base station; and

sending the second Layer 2 packets to the UE after receiving the message.

36. The method of claim 32, further comprising:

sending a handover complete message to the UE;

starting a timer in response to sending the handover complete message; and

sending the second Layer 2 packets to UE after expiration of the timer.

37. The method of claim 32, further comprising:

receiving first Internet Protocol (IP) packets forwarded by the source base station to the target base station via an IP tunnel;

receiving second IP packets from a serving gateway; and

processing the first IP packets followed by the second IP packets to generate the second Layer 2 packets.

38. An apparatus for wireless communication, comprising:

at least one processor configured to receive at least one first Layer 2 packet forwarded by a source base station to a target base station via a Layer 2 tunnel, to send the at least one first Layer 2 packet to a user equipment (UE) performing handover from the source base station to the target base station, to generate second Layer 2 packets for the UE at the target base station, and to send the second Layer 2 packets to the UE.

39. The apparatus of claim 38, wherein the at least one processor is configured to receive from the source base station a message indicating no more first Layer 2 packets to forward to the target base station, and to send the second Layer 2 packets to the UE after receiving the message.

40. The apparatus of claim 38, wherein the at least one processor is configured to send a handover complete message to the UE, to start a timer in response to sending the handover complete message, and to send the second Layer 2 packets to UE after expiration of the timer.

41. A method of receiving data in a wireless communication system, comprising:

receiving first Layer 2 packets from a source base station prior to handover of a user equipment (UE) from the source base station to a target base station, the first Layer 2 packets being generated by the source base station;

receiving at least one second Layer 2 packet from the target base station, the at least one second Layer 2 packet being generated by the source base station and forwarded to the target base station via a Layer 2 tunnel; and

receiving third Layer 2 packets from the target base station after the handover, the third Layer 2 packets being generated by the target base station.

42. The method of claim 41, further comprising:

determining whether each Layer 2 packet is generated by the source base station or the target base station based on a source indicator of the Layer 2 packet.

43. The method of claim 42, wherein the source indicator is set to a first value for the source base station or a second value for the target base station.

44. The method of claim 41, further comprising:

receiving a message indicating no more first Layer 2 packets, the message being originated by the source base station and forwarded by the target base station to the UE; and

passing the first Layer 2 packets and the at least one second Layer 2 packet up to a next higher protocol in a protocol stack in response to receiving the message.

45. An apparatus for wireless communication, comprising:

at least one processor configured to receive first Layer 2 packets from a source base station prior to handover of a user equipment (UE) from the source base station to a target base station, the first Layer 2 packets being generated by the source base station, to receive at least one second Layer 2 packet from the target base station, the at least one second Layer 2 packet being generated by the source base station and forwarded to the target base station via a Layer 2 tunnel, and to receive third Layer 2 packets from the target base station after the handover, the third Layer 2 packets being generated by the target base station.

46. The apparatus of claim 45, wherein the at least one processor is configured to determine whether each Layer 2 packet is generated by the source base station or the target base station based on a source indicator of the Layer 2 packet.

47. The apparatus of claim 45, wherein the at least one processor is configured to receive a message indicating no more first Layer 2 packets, the message being originated by the source base station and forwarded by the target base station to the UE, and to pass the first Layer 2 packets and the at least one second Layer 2 packet up to a next higher protocol in a protocol stack in response to receiving the message.