Handover Optimisation in a Wlan Radio Access Network

• US 20080192696A1
• Filed: 07/25/2005
• Published: 08/14/2008
• Est. Priority Date: 07/25/2005
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Herwono, Ian, Sachs, Joachim
• Granted Patent: US 8,050,232 B2
• Time in Patent Office: Days
• US Class Current: 370/331
• CPC Class Codes: H04W 36/02 Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off

Abstract

The invention provides a method for assisting handover of a communication session associated with a UT from a first radio access point, AP1, to a second radio access point, AP2, in a radio access network, said method to be carried out by said AP1 and comprising the steps of:—receiving a handover intention notify message comprising a session identifier identifying said session and indicating that said UT intends to perform a session handover,—assigning said session a buffer memory space in a memory of said AP1,—buffering downlink data packets addressed to said UT in said buffer memory as a response on receiving said handover intention notify message. The invention further provides a UT, an AP1, AP2, an AR, and software program/s co-operating and/or realizing the method according to the invention. The invention provides a smoother handover.

Claims

1. A method for assisting handover of a user terminal'"'"'s, UT'"'"'s, communication session from a first radio access point, AP1, to a second radio access point, AP2, in a radio access network, said method to be carried out by said AP1 comprising the following steps:

receiving a handover intention notify message comprising a session identifier identifying said session and indicating that said UT intends to perform a session handover,

assigning said session a buffer memory space in a memory of said AP1,

buffering downlink data packets addressed to said UT in said buffer memory as a response on receiving said handover intention notify message.

2. The method according to claim 1 wherein said radio access network is a wireless data network according to an IEEE 802 standard and wherein said network is arranged to authenticate UTs requesting network access, and wherein said session identifier is a MAC address of said UT as defined by said IEEE 802 standard.

3. The method according to claim 1 further comprising the step of:

blocking the transmission of downlink session packets to said UT as a response on receiving said handover intention notify message.

4. The method according to claim 1, wherein said handover intention notify message further comprises an AP-identifier identifying said second AP, indicating a handover of said session to said AP2, said method further comprising the step of:

sending said buffered downlink packets to said AP2 as a response on receiving said handover intention notify message.

5. The method according to claim 1, further comprising the steps of:

receiving an association update message identifying said AP2 and indicating that said UT is associated with said AP2,

sending said buffered downlink packets to said AP2 as a response on receiving said association update message.

6. The method according to claim 1, further comprising the step of:

sending a handover intention notify message to an access router, AR, in said radio access network, said message indicating a handover of said session and comprising a session identifier of said communications session instructing said AR to buffer downlink data packets addressed to said UT.

7. The method according to claim 6 wherein said handover notify message further comprises an AP-identifier identifying said AP2.

21. A radio access point AP1 allowing a user terminal, UT, access to a radio access network by means of a radio link connection comprising means realizing the method according to any of claims 1-7 when said AP1 is installed in a radio access network comprising a second access point AP2 and an access router AR.

22. The access point AP1 according to claim 21 wherein said means comprises a data memory having a first memory space with a first entrance forming a buffer memory for storing downlink packets addressed to said UT, said data memory further having a second memory space with stored program code means which, when loaded in a processing means of said AP1, make said processing means execute at least one procedure realizing said method.

23. The AP1 according to claim 22 realized as an access point according to the IEEE 802 standard wherein said AP1 is further arranged to authenticate user terminals requesting access to said wireless data network.

24. A computer program product comprising program code means which, when loaded into a processing means of a first access point AP1, being installed in a radio access network, make said processing means execute at least one procedure realizing the method according to claim 1.

25. A computer program product according to claim 24 including a computer readable medium having said program code means stored thereon.

8. A method for assisting a handover of a user terminal'"'"'s, UT'"'"'s, communication session from a first access point, AP1, to a second access point, AP2, in a radio access network, said method to be carried out by said AP2 comprising the following steps:

establishing that said communication session is to be handed over from said AP1 to said AP2,

sending a handover intention notify message to said AP1 indicating a handover of said session and comprising a session identifier identifying said session.

9. The method according to claim 8 further comprising the step of:

sending said handover notify message to an access router, instructing said AR to buffer downlink data packets of said session addressed to said UT.

10. The method according to claim 8 wherein said handover notify message further comprises an AP-identifier identifying said AP2.

11. The method according to claim 8, wherein said radio access network is a wireless data network according to an IEEE 802 arranged to authenticate UTs requesting network access, said method further comprising the step of:

authenticating said UT by sending and receiving authentication credentials to/from UT.

26. A radio access point AP2 allowing a user terminal, UT, access to a radio access network by means of a radio link comprising means realizing the method according to claim 8 when said AP2 is installed in a radio access network comprising a first access point AP1 and an access router AR.

27. The access point AP2 according to claim 26 wherein said means comprises a data memory having a first memory space with a first entrance forming a buffer memory for storing downlink packets addressed to said UT, said data memory further having a second memory space with stored program code means which, when loaded in a processing means of said AP2, make said processing means execute at least one procedure realizing said method.

28. The AP2 according to claim 26 realized as an access point according to the IEEE 802 standard, arranged to realize said method when said AP2 is installed in a wireless data network according to the IEEE 802 standard, and wherein said AP2 is further arranged to authenticate user terminals requesting access to said wireless data network.

29. A computer program product comprising program code means which, when loaded into a processing means of a second access point AP2, being installed in a radio access network, make said processing means execute at least one procedure realizing the method according to claim 8.

30. A computer program product according to claim 29 including a computer readable medium having said program code means stored thereon.

12. A method for assisting a handover of a user terminal'"'"'s, DT'"'"'s, communication session from a first access point, AP1, to a second access point, AP2, in a radio access network comprising an access router, AR, for routing data packets to/from said UT via said AP1 and/or AP2, said method to be carried out by said AR comprising the following steps:

receiving a handover intention notify message indicating a handover of said communication session,

buffering downlink data packets of said session in a buffer memory, as a response to said handover intention notify message.

13. The method according to claim 12 further comprising the steps of:

receiving an AP-update-message comprising a session identifier identifying said session and an AP-identifier identifying said AP2, said message indicating a handover to said AP2,

forwarding said buffered downlink data packets of said session to said AP2.

14. The method according to claim 12 wherein said radio access network is a wireless data network according to an IEEE 802 being arranged to authenticate UTs requesting access to said network.

31. An access router, AR, arranged to route a user terminal'"'"'s, UT'"'"'s, communication session via a first access point, AP1, and/or via a second access point, AP2, comprising means realizing the method according to claim 12 when said AR is installed in a radio access network comprising said AP1 and AP2.

32. The AR according to claim 31 wherein said means comprises a data memory having a first memory space with a first entrance forming a buffer memory for storing downlink packets addressed to said UT, said data memory further having a second memory space with stored program code means which, when loaded in a processing means of said AR, make said processing means execute at least one procedure realizing said method.

33. The AR according to claim 31 realized as an AR according to the IEEE 802 standard, being arranged to realize said method when said AR is installed in a wireless data network according to the IEEE 802 standard, and wherein said AR is further arranged to authenticate user terminals requesting access to said wireless data network.

34. A computer program product comprising program code means which, when loaded into a processing means of an AR being installed in a radio access network, make said processing means execute at least one procedure realizing the method according to claim 12.

35. A computer program product according to claim 34 including a computer readable medium having said program code means stored thereon.

15. A method for assisting a handover of a user terminal'"'"'s, UT'"'"'s, communication session from a first radio access point, AP1, to a second radio access point, AP2, in a radio access network, said method to be carried out by said UT characterised in that it comprises comprising the following steps:

a) establishing that said communication session is to be handed over from said AP1 to said AP2,

b) fetching a first packet from a first buffer memory of said UT,

c) extracting a frame sequence number, FSN, from said first packet and storing said FSN in a first memory space of a second buffer memory of said UT,

d) forwarding said first packet to an application running on said UT or to a higher level protocol of said UT,

e) fetching a next packet from said first buffer memory, said next packet being the next packet received by said UT after said first packet,

f) extracting a frame sequence number from said next packet, FSNNEXT,

g) establishing whether said next packet is a consecutive packet of said first packet by comparing said FSNNEXT with said FSN, and,

h) storing said FSNNEXT in said first memory space of said second buffer memory and forwarding said “

next packet”

to a higher level protocol or a final application if it was established in step g) that said “

next packet”

is a consecutive packet of said first packet, and otherwise buffering said “

next packet”

in a second memory space of said second buffer memory.

16. The method according to claim 15 wherein the step a) of establishing that said communication session is to be handed over from AP1 to AP2, comprises any of the following steps:

a de-association of AP1, or,

an association of AP2, or,

a handover decision taken by UT according to a certain handover criterion, or,

a handover decision according to a certain handover criterion taken by a network node and signaled to said UT.

17. The method according to claim 15 further comprising the step of:

limiting the size of said second memory space of said second buffer memory 243 by defining a maximum threshold number of stored packets/bytes for said second memory space or defining a maximum allowable storage time for a packet being stored in said second memory space.

18. The method according to claim 15, wherein data packets received from AP1 and/or AP2 are stored in received chronological order in said first buffer memory, said memory being of a FIFO type, wherein said steps a) and e) of fetching a first and second data packet comprise the step of:

reading a data packet from said FIFO memory.

19. The method according to claim 15 further comprising the steps of:

reading a third data packet from said FIFO and establishing that said third data packet is a consecutive data packet of the data packet being the last packet forwarded to said application,

forwarding said third data packet to said application and updating the first memory space of said buffer memory with the frame sequence number of said third data packet,

establishing that there is at least one stored data packet in said second memory space of said second buffer memory,

searching said second memory space of said buffer memory for a consecutive data packet of said third data packet.

20. The method according to claim 15 wherein said radio access network is a wireless data network according to the IEEE 802 standard and wherein said method further comprising the step of:

sending and receiving authentication credentials to/from AP2, for instance according to the EAP standard.

36. A UT for assisting a handover of a communication session from a first radio access point, AP1, to a second radio access point, AP2, in a radio access network, said UT comprising means realizing the method according to claim 15.

37. The UT according to claim 36 wherein said means comprises a data memory having a first memory space with a first entrance forming a buffer memory for storing downlink packets addressed to said UT and a second entrance for storing a frame sequence number associated with at least one downlink packet, said data memory further having a second memory space with stored program code means which, when loaded in a processing means of said UT, make said processing means execute at least one procedure realizing said method.

38. The UT according to claim 36 realized as a UT according to the IEEE 802 standard, being arranged to realize said method when said session is routed through a wireless data network according to the IEEE 802 standard and wherein said UT is further arranged to be authenticated by said wireless data network.

39. A computer program product comprising program code means which, when loaded into a processing means of a UT communicating with a radio access network, make said processing means execute at least one procedure realizing the method according to claim 15.

40. A computer program product according to claim 39 including a computer readable medium having said program code means stored thereon.