Retransmission method with soft combining in a telecommunications system

• US 20040013105A1
• Filed: 12/13/2000
• Published: 01/22/2004
• Est. Priority Date: 04/13/1999
• Status: Active Grant

• Current Assignee: Nokia Technologies Oy (Nokia Corporation)
• Original Assignee: Nokia Networks (Nokia Corporation)
• Inventors: Malkamaki, Esa, Longoni, Fabio, Vialen, Jukka, Ahmavaara, Kalle
• Granted Patent: US 6,842,445 B2
• Time in Patent Office: Days
• US Class Current: 370/349
• CPC Class Codes: H04L 1/1819 with retransmission of additional or different redundancy
• CPC Class Codes: H04L 1/1845 Combining techniques, e.g. code combining

Abstract

An automatic repeat request mechanism (such as Type II/III hybrid ARQ) which includes (soft or hard) combining of initially transmitted and retransmitted versions of a packet, is provided for retransmission of erroneous packets. According to the present invention, in association with each retransmission, there is outband signaling from a transmitter to a receiver that unambiguously indicates when, e.g. the exact time or physical location, the first transmission of the packet was carried out, so that it is possible to combine the retransmitted version with the previous version(s) of the packet. Soft combining requires that the initial packet and the retransmitted packet be identical. In an embodiment of the invention, in order to overcome this problem, the information that needs to be changed between the initial transmission and the retransmission(s) of a packet is sent outband with other outband signaling information. Thus, the retransmitted packet can be maintained unchanged and the requirement for identical packets in soft combining is met.

Claims

1. A data transmission method in a communications system, comprising the steps of

transmitting data packets from a transmitter to a receiver,

using an automatic repeat request mechanism for retransmissions, said mechanism including combining initially transmitted and retransmitted versions of the data packet,

characterized by further steps of

sending, in association with each packet retransmission, outband signaling information which unambiguously indicates when the initial version of the data packet was transmitted,

combining the retransmitted version of the data packet with at least the initial version of the data packet indicated by said outband signaling information at the receiver.

2. The method according to claim 1, characterized by said outband signaling information indicating the exact time or physical location of the retransmission of the initial version of the data packet.

3. The method according to claim 1 or 2, characterized by transmitting said data packets by using frame number-based synchronizing, preferably connection frame number synchronization.

4. The claim according to claim 1, 2 or 3, characterized by further steps of

ciphering each data packet at the transmitter according to a frame number used for the respective data packet in frame synchronization,

deciphering each data packet at the receiver according to the same frame number as used for ciphering the respective data packet,

ciphering any retransmitted version of the data packet according to the same frame number as used for ciphering the initially transmitted version of the data packet,

deciphering the combined data packet according to the frame number included in said outband signaling information associated with the retransmitted version of the data packet.

5. The method according to claim 3 or 4, characterized by said outband signaling information including at least the frame number indicating a first data packet in a transmission frame in which the initial version of the data packet was transmitted, and the position of the initial version of the data packet within said transmission frame.

6. The method according to claim 3 or 4, characterized by said outband signaling information including the frame number indicating a first data packet in a transmission frame in which the initial version of the data packet was transmitted, and the position of the initial version of the data packet within said transmission frame, and the number of frame number cycles elapsed after the transmission of the initial version of the frame.

7. The method according to claim 4, characterized by said outband information including a data packet number of the initial version of the data packet and the frame number used for ciphering the initial version of the data packet.

8. The method according to claim 4, characterized by said outband information including a data packet number of the initial version of the data packet, and the frame number used for ciphering the initial version of the data packet, and the number of frame number cycles elapsed after the transmission of the initial version of the frame.

9. The method according to any one of claims 1 to 8, characterized by the data packet being a radio link control layer (RLC) protocol data unit (PDU) in a mobile communication system.

10. The method according to any one of claims 1 to 9, characterized by said information on the position of the data packet in the transmission frame indicating the position of the data packet in a transfer block set (TBS).

11. The method according to any one of claims 1 to 10, characterized by

sending the retransmitted version of the packet with an inband information content identical to that of the initial version of the packet,

sending with said outband information such inband information on the retransmitted version of the packet which needs to be changed in relation to the corresponding inband information of the initial version of the packet,

soft combing the identical initial and retransmitted versions of the packet,

replacing with the inband information received with the outband information the corresponding inband information received in the retransmitted version of the packet.

12. The method according to claim 11, characterized by

said inband information being inband header information, such as medium access control (MAC) header information or radio link access control (RLC) header information.

13. The method according to claim 12, characterized by said inband header information including a bit used to request an acknowledgement message, such as a polling bit.

14. A communications system, comprising

means for transmitting data packets from a transmitter to a receiver,

an automatic repeat request mechanism for retransmissions, said mechanism including combining initially transmitted and retransmitted versions of the data packet,

characterized by further comprising

means for sending, in association with each packet retransmission, outband signaling information which unambiguously indicates when the initial version of the data packet was transmitted,

means for combining the retransmitted version of the data packet with at least the initial version of the data packet indicated by said outband signaling information at the receiver.

15. The system according to claim 14, characterized by said outband signaling information indicating the exact time or physical location of the transmission of the initial version of the data packet.

16. The system according to claim 14 or 15, characterized by the transmission of said data packets being arranged to use frame number-based synchronization, preferably connection frame number-based synchronization.

17. The system according to claim 14, 15 or 16, characterized by further comprising

means for ciphering each data packet at the transmitter according to a frame number used for the respective data packet in frame synchronization,

means for deciphering each data packet at the receiver according to the same frame number as used for ciphering the respective data packet at the transmitter,

means for ciphering any retransmitted version of the data packet according to the same frame number as used for ciphering the initially transmitted version of the data packet,

means for deciphering the combined data packet according to the frame number included in said outband signaling information associated with the retransmitted version of the data packet.

18. The system according to claim 16 or 17, characterized by said outband signaling information including at least the frame number indicating a first data packet in a transmission frame in which the initial version of the data packet was transmitted, and the position of the initial version of the data packet within said transmission frame.

19. The system according to claim 16 or 17, characterized by said outband signaling information including the frame number indicating a first data packet in a transmission frame in which the initial version of the data packet was transmitted, and the position of the initial version of the data packet within said transmission frame, and the number of frame number cycles elapsed after the transmission of the initial version of the frame.

20. The system according to claim 17, characterized by said outband information including a data packet number of the initial version of the data packet and the connection frame number used for ciphering the initial version of the data packet.

21. The system according to claim 17, characterized by said outband information including a data packet number of the initial version of the data packet, and the frame number used for ciphering the initial version of the data packet, and the number of frame number cycles elapsed after the transmission of the initial version of the frame.

22. The system according to any one of claims 15 to 21, characterized by the data packet being a radio link control layer (RLC) protocol data unit (PDU) in a mobile communication system.

23. The system according to any one of claims 15 to 22, characterized by said information on the position of the data packet in the transmission frame indicating the position of the data packet in a transfer block set.

24. The system according to any one of claims 15 to 23, characterized by

the inband information content of the retransmitted version of the packet being identical to that of the initial version of the packet, in order to enable soft combining in the receiver,

said outband information including such inband information on the retransmitted version of the packet which needs to be changed in relation to the corresponding inband information on the initial version of the packet,

said inband information received with the outband information overriding the corresponding inband information received in the retransmitted version of the packet.

25. The system according to claim 24, characterized by

said inband information being inband header information, such as medium access control (MAC) header information or radio link access control (RLC) header information.

26. The system according to claim 25, characterized by said inband header information including a bit used as a request for an acknowledgement message, such as a polling bit.

27. A transmitter unit in a communications system, comprising

means for transmitting data packets to a receiver,

an automatic repeat request mechanism for retransmissions, characterized by further comprising

means for sending, in association with each packet retransmission, outband signaling information which unambiguously indicates when the initial version of the data packet was transmitted, in order to enable the receiver to combine the retransmitted version of the data packet with at least the initial version of the data packet indicated by said outband signaling information at the receiver.

28. The transmitter unit according to claim 27, characterized by said outband signaling information indicating the exact time or physical location of the transmission of the initial version of the data packet.

29. The transmitter unit according to claim 27 or 28, characterized by the unit being arranged to use frame number-based synchronization, preferably connection frame-based synchronization.

30. The transmitter unit according to claim 27, 28 or 29, characterized by the unit being arranged to use frame number-based ciphering for the data packets, the unit being arranged to cipher any retransmitted version of the data packet according to the same frame number as used for ciphering the initially transmitted version of the data packet, and to indicate the frame number to the receiver for deciphering.

31. The transmitter according to any one of claims 27 to 30, characterized by

the transmitter being arranged to send the retransmitted version of the packet with an inband information content identical to that of the initial version of the packet,

the transmitter being arranged to send with said outband information such inband information on the retransmitted version of the packet which needs to be changed in relation to the corresponding inband information on the initial version of the packet.

32. A receiver unit in a communications system, comprising

means for receiving data packets from a transmitter,

an automatic repeat request mechanism for retransmissions, said mechanism including combining initially transmitted and retransmitted versions of the data packet,

characterized by further comprising

means for receiving from the transmitter, in association with each packet retransmission, outband signaling information which unambiguously indicates when the initial version of the data packet was transmitted,

means for combining the retransmitted version of the data packet with at least the initial version of the data packet indicated by said outband signaling information.

33. The receiver unit according to claim 32, characterized by said outband signaling information indicating the exact time or physical location of the transmission of the initial version of the data packet.

34. The receiver unit according to claim 32 or 33, characterized by the unit being arranged to use frame number-based synchronization, preferably connection frame number-based synchronization.

35. The receiver unit according to claim 32, 33 or 34, characterized by the unit being arranged to use frame number-based ciphering for the data packets, the unit being arranged to decipher any retransmitted version of the data packet according to a frame number included in said outband signaling information.

36. The receiver unit according to any one of claims 32 to 35, characterized by

the inband information content of the retransmitted version of the packet being identical to that of the initial version of the packet, in order to enable a soft combining in the receiver,

said outband information including such inband information on the retransmitted version of the packet which needs to be changed in relation to the corresponding inband information on the initial version of the packet,

the receiver unit being arranged to use said inband information received with the outband information instead of the corresponding inband information received in the retransmitted version of the packet.