Protocol context transfer in a mobile communication system

• US 7,508,792 B2
• Filed: 04/23/2004
• Issued: 03/24/2009
• Est. Priority Date: 09/23/2003
• Status: Active Grant

• Current Assignee: Panasonic Intellectual Property Corporation of America (Panasonic Holdings Corporation)
• Original Assignee: Panasonic Corporation (Panasonic Holdings Corporation)
• Inventors: Lohr, Joachim, Seidel, Eiko, Petrovic, Dragan
• Primary Examiner(s): Kincaid; Lester
• Assistant Examiner(s): DOAN, PHUOC HUU
• Application Number:
  US10/572,277
• Publication Number:
  US 20070081492A1
• Time in Patent Office: 1,796 Days
• Field of Search: None
• US Class Current: 370/331
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]
• CPC Class Codes: H04W 36/0033 with transfer of context information
• CPC Class Codes: H04W 36/02 Buffering or recovering information during reselection ; Modification of the traffic flow during hand-off
• CPC Class Codes: H04W 92/20 between access points

Abstract

The present invention relates to a method for controlling a radio cell change of a communication terminal from a first radio cell to a second radio cell, wherein the first and the second radio cell is controlled by at least one base station of a mobile communication system. The present invention further provides a base station and a communication system comprising a plurality of base stations and a communication terminal adapted to execute the control method. To overcome negative impacts of data loss and delay during a cell change procedure the protocol context of a retransmission protocols are transferred from a source base station to a target base station upon an cell change of a communication terminal in issue.

Claims

1. A method for forwarding retransmission protocol related data upon a radio cell change of a communication terminal from a source radio cell to a target radio cell, wherein each of the source and the target radio cells is controlled by a base station of a mobile communication system, the method comprising:

forwarding, by the base station controlling the source radio cell, data packets of a retransmission protocol that have not been successfully transmitted to the communication terminal by the base station controlling the source radio cell to the base station controlling said target radio cell, and

assigning the communication terminal from the source radio cell to the target radio cell,

wherein the data packets of the retransmission protocol are forwarded to the base station controlling the target radio cell via a direct interface between the base station controlling the source radio cell and the base station controlling the target radio cell using a data packet of a frame protocol, and

wherein a header of a frame protocol data packet indicates whether the respective forwarded data packets comprised in a payload section of said frame protocol data packet are waiting for initial transmission.

2. The method according to claim 1, wherein the data packets of a retransmission protocol that have not been successfully transmitted to the communication terminal are data packets of the retransmission protocol pending for initial transmission and for retransmission at the base station controlling the source radio cell.

3. The method according to claim 1, further comprising:

determining an activation time, at which the base station controlling the target radio cell starts transmitting data to the communication terminal, and

transmitting the determined activation time from the base station controlling the source radio cell to the base station controlling the target radio cell controlling said target radio cell.

4. The method according to claim 3, wherein the activation time is transmitted to the base station controlling the target radio cell using a radio link setup message of a Radio Network Subsystem Application Part (RNSAP+) protocol.

5. The method according to claim 4, wherein the radio link setup message comprises parameters of retransmission protocol transmitting entities used for setting-up a radio bearer between the communication terminal and the base station controlling the target radio cell after cell change.

6. The method according to claim 3, further comprising transmitting the determined activation time to the communication terminal.

7. The method according to claim 1, further comprising transmitting information relating to the set up of a radio link between the base station controlling the source radio cell and the base station controlling the target radio cell, from the base station controlling the source radio cell to base station controlling the target radio cell prior to activation time.

8. The method according to claim 6, wherein at least one of the activation time and the information relating to the set up of a radio bearer is transmitted to the communication terminal in a radio bearer setup message of a radio resource control protocol.

9. The method according to claim 3, further comprising the base station controlling the target radio cell and the communication terminal starting data transmissions via the target radio cell upon reaching the determined activation time.

10. The method according to claim 1, wherein a shared channel is employed for downlink data transmission.

11. The method according to claim 9, wherein the shared channel is a High-Speed Downlink Shared Channel (HS-DSCH).

12. The method according to claim 1, wherein the data retransmission protocol is a Hybrid Automatic Repeat Request (HARQ) protocol.

13. The method according to claim 1, wherein the data retransmission protocol is a Radio Link Control (RLC) protocol.

14. The method according to claim 1, wherein the data retransmission protocol employs a Hybrid Automatic Repeat Request (HARQ) protocol and a Radio Link Control (RLC) protocol.

15. The method according to claim 12, wherein the data packets waiting for initial transmission and the data packets pending for retransmission are transmitted to the target base station as part of a protocol context further comprising HARQ process state variables, the state of timers of HARQ transmission entities, and physical layer related information.

16. The method according to claim 15, wherein the physical channel related information is a redundancy version used for data transmissions of a HARQ process, a constellation used for data transmissions of a HARQ process, a HARQ process number, and a New Data Indicator.

17. The method according to claim 15, wherein the HARQ process state variable comprises the reached number of transmissions for a particular transmission data packet of a HARQ process.

18. The method according to claim 15, wherein the protocol context further comprises parameters of the HARQ transmitting entities, in case the parameters have not been transmitted to the base station controlling the target radio cell in a radio link setup message.

19. The method according to claim 18, wherein the parameters of the HARQ transmitting entities comprise at least one of a value of a discard timer and the maximum number of allowed transmissions for data packets.

20. The method according to claim 15, wherein the state of timers comprises the current values of discard timers for transmission of data packets of different HARQ processes.

21. The method according to claim 13, wherein the data packets waiting for initial transmission and the data packets pending for retransmission are transmitted to the target base station as part of a protocol context further comprising control packets pending for transmission, RLC state variables, and the state of timers of the RLC transmission entities.

22. The method according to claim 21, wherein the RLC state variables are at least one of variables VT (DAT) indicating the number of times transmission data packets have been scheduled for transmission and an acknowledge state variable VT(A) indicating the sequence number of the transmission data packet acknowledged last by the communication terminal and the state of timers of the RLC transmission entities comprise the state of the Timer Discard.

23. The method according to claim 21, wherein the protocol context further comprises parameters of the RLC transmission entities, in case the parameters have not been transmitted to the base station controlling the target radio cell in a radio link setup message.

24. The method according to claim 23, wherein the parameters of the RLC transmission entities comprise at least one of the maximum number of times a data packet is transmitted MaxDat and a Timer Discard value.

25. The method according to claim 1, wherein the protocol context comprises parameters specifying a quality of service of the data transmissions or parameters for the configuration of entities of Hybrid Automatic Repeat Request/Radio Link Control (HARQ/RLC) retransmission protocols.

26. The method according to claim 1, wherein the frame protocol is the High Speed Downlink Shared Channel (HS-DSCH) Frame Protocol.

27. The method according to claim 1, wherein when forwarding the data packets that are not waiting for initial transmission from the base station controlling the source radio cell to the base station controlling the target radio cell, a payload section of a frame protocol data packet comprises at least one forwarded data packet and information corresponding to at least one forwarded data packet indicating the transmitting entity'"'"'s state.

28. The method according to claim 27, wherein said information corresponding to the at least one transmission data packet comprises a redundancy version used for data transmissions of a Hybrid Automatic Repeat Request (HARQ) process, a constellation used for data transmissions of a HARQ process, a HARQ process number, a New Data Indicator, and the number of retransmissions of the corresponding transmission data packet.

29. The method according to one of claims 1 to 9, wherein an Enhanced Dedicated Channel (E-DCH) is employed for uplink data transmission.

30. A base station for forwarding retransmission protocol related data upon a radio cell change of a communication terminal from a source radio cell to a target radio cell, wherein each of the first and the target radio cells is controlled by a base station of a mobile communication system, the base station of the source radio cell comprising:

a transmission unit configured to forward data packets of a retransmission protocol that have not been successfully transmitted to the communication terminal to the base station controlling said target radio cell and for transmitting data to the communication terminal and the base station controlling the target radio cell related to the assignment of the communication terminal to the target radio cell,

wherein the transmission unit is further configured to forward the data packets of the retransmission protocol to the base station controlling the target radio cell via a direct interface between the base station controlling the source radio cell and the base station controlling the target radio cell using a data packet of a frame protocol, and

wherein the base station is configured to include an indication to the header of a frame protocol data packet indicating whether the respective forwarded data packets comprised in a payload section of said frame protocol data packet are waiting for initial transmission.

31. A communication system comprising the base station according to claim 30 and a communication terminal.