Data unit management in communications

• US 20060067238A1
• Filed: 09/24/2004
• Published: 03/30/2006
• Est. Priority Date: 09/24/2004
• Status: Active Grant

• Current Assignee: Malikie Innovations Limited (Key Patent Innovations Limited)
• Original Assignee: M-Stack Limited (Blackberry Limited)
• Inventors: de Jong, Gjalt, Olsson, Patrik
• Granted Patent: US 7,525,908 B2
• Time in Patent Office: Days
• US Class Current: 370/242
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control
• CPC Class Codes: H04L 1/1614 using bitmaps
• CPC Class Codes: H04L 1/1628 List acknowledgements, i.e. the acknowledgement message consisting of a list of identifiers, e.g. of sequence numbers H04L1/1614 takes precedence
• CPC Class Codes: H04L 1/1664 the supervisory signal being transmitted together with payload signals; piggybacking
• CPC Class Codes: H04L 1/1685 the supervisory signal being transmitted in response to a specific request, e.g. to a polling signal
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 1/1848 Time-out mechanisms
• CPC Class Codes: H04L 1/1858 Transmission or retransmission of more than one copy of acknowledgement message
• CPC Class Codes: H04L 1/187 Details of sliding window management

Abstract

In Radio Link Control (RLC) apparatus, a mechanism is provided for detecting missing or corrupted data units at the receiving end of a transmission link, requesting retransmission and then monitoring the response to the retransmission request. Distinctively, a receiving communications entity 300 is equipped to act on a nil response. If no data unit is retransmitted, the receiving entity triggers at least one repeat retransmission request. This is the case even if no further data unit is received after the retransmission request is triggered. Retransmission requests are repeated up to a preset number, whereafter a different recovery mechanism is triggered.

Claims

1. Data unit management apparatus for use in communications receiving equipment in receiving data units over a transmission link, the apparatus comprising:

i) a data unit reception monitor for monitoring receipt of data units;

ii) a retransmission request sender for triggering the sending of at least one retransmission request in respect of one or more missing or corrupted data units; and

iii) a retransmitted data unit monitor for monitoring receipt of one or more retransmitted data units,

wherein the retransmitted data unit monitor comprises a timer for timing a predetermined period, and is adapted to monitor receipt within the predetermined period of retransmitted data units.

2. Data unit management apparatus according to claim 1, wherein the timer is adapted to be triggered to start timing by the sending of a retransmission request.

3. Data unit management apparatus according to claim 1, wherein a sent retransmission request comprises a status report indicating a reception status for at least one data unit.

4. Data unit management apparatus according to claim 1 wherein a sent retransmission request comprises a status report indicating a reception status for each of more than one data unit.

5. Data unit management apparatus according to claim 1, wherein each received data unit is identifiably distinct, the receiving equipment is adapted to assemble said identifiably distinct data units in an ordered sequence of data units, and the retransmitted data unit monitor is adapted to identify a retransmitted data unit by reference to its position in a sequence of data units received by the receiving equipment relative to its position in said ordered sequence.

6. Data unit management apparatus according to claim 5 wherein the apparatus further comprises a sequence reception state monitor for monitoring the reception state of said ordered sequence by reference to the position in the ordered sequence of received data units, the sequence reception state monitor being adapted to maintain updatable values for at least two variables representing said reception state, and wherein the retransmitted data unit monitor is adapted to identify a retransmitted data unit by comparing its position in the ordered sequence with current values for said at least two variables.

7. Data unit management apparatus according to claim 6 wherein a current value for one of said variables is set by the most recently received data unit whose position in the ordered sequence is in-sequence.

8. Data unit management apparatus according to claim 6 wherein a current value for one of said variables is set by the received data unit whose position is latest in the ordered sequence.

9. Data unit management apparatus according to claim 1, wherein the retransmitted data unit monitor is adapted to terminate timing by the timer on receipt of at least one retransmitted data unit within the predetermined period associated with a retransmission request in respect of that data unit.

10. Data unit management apparatus according to claim 1, wherein the retransmitted data unit monitor is adapted to trigger at least one repeat retransmission request in the event that no data units subject to an earlier retransmission request are received within the associated predetermined period.

11. Data unit management apparatus according to claim 10 wherein the retransmitted data unit monitor is adapted to trigger at least one repeat retransmission request in the event that no data units are received within the associated predetermined period.

12. Data unit management apparatus according to claim 10 wherein the retransmitted data unit monitor is adapted to trigger up to a predetermined number of such repeat retransmission requests in respect of said earlier retransmission request, and to initiate a different recovery mechanism thereafter in the event that no data units subject to the earlier retransmission request are received within the associated predetermined periods.

13. Data unit management apparatus according to claim 12 wherein the retransmitted data unit monitor is adapted to trigger up to a predetermined number of such repeat retransmission requests in respect of said earlier retransmission request, and to initiate a different recovery mechanism thereafter in the event that no data units are received within the associated predetermined periods.

14. Data unit management apparatus according to claim 1 wherein the predetermined period is at least partially dependent on the number of data units for which a retransmission request is made.

15. Data unit management apparatus according to claim 14 wherein the predetermined period is at least partially directly dependent on the number of data units.

16. Data unit management apparatus according to claim 14 wherein the predetermined period is at least partially inversely dependent on the number of data units.

17. Data unit management apparatus according to claim 1, for use in receiving identifiably distinct data units over a transmission path that comprises an air interface.

18. Data unit management apparatus according to claim 17 wherein said air interface comprises a radio link.

19. Receiving apparatus for use in communications, comprising data unit management apparatus according to claim 1.

20. Receiving apparatus for use in receiving a plurality of data units and ordering them into a predetermined sequence, the receiving apparatus comprising a missing data unit detector for detecting data units which are corrupted or missing from the sequence, a retransmission request sender for requesting retransmission of such data units and a retransmission failure detector for detecting no response to a retransmission request.

21. A method of receiving identifiably distinct data units at a receiving entity from a transmitting entity, which method comprises the steps of:

a) detecting at the receiving entity one or more lost or damaged data units;

b) sending to the transmitting entity a retransmission request identifying at least one of said lost or damaged unit(s) for retransmission; and

c) monitoring data units received at the receiving entity for receipt of at least one data unit so identified within a predetermined time period after sending the retransmission request.

22. A method according to claim 21 wherein said predetermined time period starts on sending the retransmission request.

23. A method according to claim 21 wherein said retransmission request comprises a status report indicating a reception status for each of more than one data unit.

24. A method according to claim 21, further comprising the steps of:

d) on receipt at the receiving entity within the time period of at least one unit identified in step b), terminating step c); and

e) in the event that no data units subject to an earlier retransmission request are received within the time period, repeating steps b) and c).

25. A method according to claim 24 wherein, in the event that no data units are received within the time period, steps b) and c) are repeated.

26. A method according to claim 24 wherein step e) is repeated a predetermined number of times whereafter a different recovery mechanism is initiated.

27. A method according to claim 21 wherein the method is a method of receiving identifiably distinct data units over a transmission link that comprises an air interface.

28. A method according to claim 27 wherein said transmission link comprises a radio link.