Method and apparatus for determining an optimum timeout under varying data rates in an RLC wireless system which uses a PDU counter

• US 6,473,399 B1
• Filed: 11/30/1998
• Issued: 10/29/2002
• Est. Priority Date: 11/30/1998
• Status: Expired due to Term

• Current Assignee: Blackberry Limited
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Roobol, Christian, Larsson, Johan, Johansson, Mathias
• Primary Examiner(s): VINCENT, DAVID ROBERT
• Application Number:
  US09/201,389
• Time in Patent Office: 1,429 Days
• Field of Search: 370/229, 370/235, 370/242, 370/248, 370/252, 370/469-473, 370/310, 370/328, 370/329, 714/748-751, 455/466
• US Class Current: 370/229
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/1809 Selective-repeat protocols
• CPC Class Codes: H04L 1/1848 Time-out mechanisms

Abstract

A data communications unit determines both efficiently and accurately when one or more data units should be received under a variety of conditions. In particular, the present invention compensates for transmission delays and for varying transmission rates over the communications channel. During a communication between first and second communications nodes, the first node receives a sequence of data units transmitted from the second node. The first communications node determines that one or more of the transmitted data units was either not received at all or was erroneously received (i.e., corrupted). The first node then sends a request to the second node to retransmit the one or more data units not received or erroneously received. A retransmit timer is started when the retransmission request is sent. The retransmit timer accounts for the delay time period required for the retransmit request to reach the second node, for the second node to retransmit the requested data units, and for the retransmitted data units to reach the first node. When the timer indicates that the delay time period has occurred/expired, a counter is started. Based on the counter'"'"'s value, a determination is made whether all of the data units requested to be retransmitted have been properly received. If the determination indicates that the requested one or more data units has been retransmitted and properly received, no further action is taken. On the other hand, if the requested one or more data units to be retransmitted is not received or is erroneously received, the above-described procedure is repeated.

Claims

1. A first communications node capable of communicating with a second communications node, comprising the steps of:

sending a request to the second node requesting transmission of one or more data units;

starting a counter after a time period associated with the transmission request; and

determining, based on a value output by the counter, whether the requested one or more data units has been received.

2. The method in claim 1, wherein before the sending step the method further comprises:

receiving data units transmitted from the second communications node, and

determining that one or more of the transmitted data units was not received or was improperly received,

wherein the sending step includes requesting retransmission of one or more data units not received or improperly received, and

wherein the counter is started after a time period associated with the retransmission request.

3. The method in claim 2, wherein if the requested one or more data units is not received or is improperly received, repeating the sending, starting, and determining steps.

4. The method in claim 1, further comprising:

providing a counter controller to establish the time period.

5. The method in claim 4, wherein the counter controller is a timer, the method further comprising:

starting the timer when the request is sent, and

setting the counter with an initial value at or before the ending of the timer.

6. The method in claim 5, wherein when the timer reaches the time period, the counter counts to provide an estimate of a number of data units that should have been received from the second node.

7. The method in claim 5, wherein if a requested PDU is received before the time period expires, the counter then begins counting from the requested PDU.

8. The method in claim 4, wherein the counter controller is another counter counting time intervals in order to estimate the time period.

9. The method in claim 1, further comprising:

changing the count value after a time interval expires during which a number of data units may be transmitted.

10. The method in claim 9, wherein the count value is incremented after each time interval until the count value equals the number of data units that should have been received from the second node.

11. The method in claim 10, wherein if the one or more data units is not received or is improperly received when the count value equals the number of data units that should have been received from the second node, the method further comprises:

setting the time period again;

requesting that the one or more data units not received or improperly received be retransmitted;

resetting the counter; and

starting the counter after the set time period expires.

12. The method in claim 9, wherein the time interval corresponds to a frame on a communications channel between the first and second communications nodes.

13. The method in claim 12, wherein the time interval corresponds to plural frames.

14. The method in claim 12, wherein the communications channel is a radio channel and the time interval is a radio frame on the order of 10 milliseconds.

15. The method in claim 9, wherein an integral number of data units is transmitted during the time interval.

16. The method in claim 9, wherein the count value is changed each time interval with a number of data units that should have been transmitted during that time interval.

17. In a radio communications system where protocol data units (PDUs) are communicated between a transmitter and a receiver over a radio communications channel, where data units are sent during specified channel time intervals, a method of monitoring a communication between the transmitter and the receiver, comprising the steps of:

(a) detecting that a PDU transmitted by the transmitter to the receiver was not properly received by the receiver;

(b) sending a message from the receiver to the transmitter requesting that the PDU be retransmitted;

(c) starting a time monitor in cooperation with sending the message;

(d) after the time monitor indicates that a predetermined time period has elapsed, starting a PDU counter;

(e) changing a value in the PDU counter after a next specified radio time interval expires; and

(f) determining, based on a value output by the PDU counter, whether the requested PDU has been properly received.

18. The method in claim 17, wherein after the next specified radio time interval, the value in the PDU counter is changed based on a number of PDUs that should have been delivered to the receiver during that next specified radio time interval.

19. The method in claim 17, wherein if the PDU counter reaches a count value indicating that the requested PDU should have been properly received by the receiver, and if the requested PDU has not been properly received at the receiver, repeating steps (b)-(f).

20. The method in claim 17, wherein in response to a change in a transmission rate, different numbers of PDUs may be transmitted during one of the specified radio time intervals.

21. The method in claim 17, wherein the message is a selective acknowledgment message transmitted on a radio link control (RLC) communications protocol layer.

22. The method in claim 17, wherein if the requested PDU is received before the time period expires, the counter then begins counting from the requested PDU.

23. The method in claim 17, wherein the timer monitor is another counter counting time intervals in order to estimate the predetermined time period.

24. For use in a communications system, a communications unit comprising:

a receiver configured to receive data units over a communications channel from another communications unit;

a transmitter configured to transmit a request to the other communications unit to transmit a number of data units to the communications unit;

a counter for storing a count value indicating the number of data units to be transmitted; and

a time monitor configured to cause the counter to begin counting after a time interval associated with the transmit request expires,

wherein the communications unit is configured to use the count value to determine whether number of data units have been transmitted and then properly received.

25. The communications unit in claim 24, wherein data units are communicated over a communications channel in channel frames and the counter is incremented after a channel frame.

26. The communications unit in claim 24, wherein during a channel frame, an integer number of data units may be transmitted and wherein the integer number of data units per channel frame may differ for different channel frames.

27. The communications unit in claim 26, wherein the number of data units transmitted during a channel frame varies depending on a size of the data unit and a data unit transmission rate.

28. The communications unit in claim 24, wherein the communication unit is a mobile station having a radio link control (RLC) protocol layer that includes the time monitor and the counter.

29. The communications unit in claim 24, wherein the communication unit is a radio network controller in a radio access network having a radio link control (RLC) protocol layer that includes the timer and the counter.

30. The communications unit in claim 24, wherein the communications system is a radio communications system and the communications unit is a mobile station.

31. The communications unit in claim 24, wherein the communications system is a radio communications system and the communications unit is a radio network node.

32. The method in claim 24, wherein if a requested PDU is received before the time period expires, the PDU counter then begins counting from the requested PDU.

33. The method in claim 24, wherein the timer monitor is another counter counting time intervals in order to estimate the time interval.

34. A method for operating a first communications unit, comprising the steps of:

receiving at the first communications unit data units transmitted by a second communications unit over a communications channel;

requesting the second communications unit to transmit one or more data units to the first communications unit; and

determining at the first communications unit when the requested one or more data units should be received including compensating for a delay corresponding to the transmit request and for a current transmission rate over the communications channel.

35. The method in claim 34, wherein the delay is compensated for using a timer and the current transmission rate is compensated for using a counter.

36. The method in claim 35, wherein when the timer indicates that a predetermined time period corresponding to the delay has expired, the counter begins counting to determine when the requested one or more data units should be received by the first communications unit.

37. The method in claim 36, wherein if the requested one or more data units are not received when the counter reaches a particular count value, the method further comprises:

sending a retransmit request to the second communications unit.

38. The method in claim 37, wherein the particular count value corresponds to a number of data units that should have been received by the first communications unit.

39. The method in claim 34, wherein the second communications unit is requested to retransmit one or more data units to the first communications unit.