Cooperating timer and retransmission counter for buffer management in a HARQ wireless network

• US 20090168920A1
• Filed: 02/28/2009
• Published: 07/02/2009
• Est. Priority Date: 03/07/2008
• Status: Active Grant

• Current Assignee: HFI Innovation, Inc. (MediaTek, Inc.)
• Original Assignee: MediaTek, Inc.
• Inventors: Chen, Yih-Shen
• Granted Patent: US 9,203,562 B2
• Time in Patent Office: Days
• US Class Current: 375/295
• CPC Class Codes: H04L 1/1835 Buffer management
• CPC Class Codes: H04L 1/1851 using multiple timers

Abstract

In a Hybrid Automatic Repeat ReQuest (HARQ) communication system, a receiver receives from a transmitter a HARQ sub-burst. A retransmission counter (RE_TX_CNT) in the receiver is incremented if either: (i) the receiver cannot decode the sub-burst, or (ii) no retransmission of the sub-burst is received within a Predetermined Retransmission Delay (PRD) interval. If RE_TX_CNT reaches a Maximal Retransmission Count (MAX_RE_CNT), then information for the sub-burst that was previously stored for HARQ purposes in a soft combining buffer in the receiver is flushed. Parameters that set the PRD interval and the MAX_RE_CNT value are pre-negotiated between the transmitter and the receiver. In another embodiment, if a novel timer in the receiver indicates that a first threshold time has elapsed after receipt of an undecodable HARQ transmission then buffered information is marked, whereas if the timer indicates that a second threshold time has elapsed then the marked information is flushed.

Claims

1. A method comprising:

(a) using a wait transmission counter (WAIT_TX_CNT) to determine whether a retransmission of a Hybrid Automatic Repeat ReQuest (HARQ) sub-burst has not been received within a Predetermined Retransmission Delay (PRD) interval after receipt of a last transmission of the HARQ sub-burst;

(b) incrementing a retransmission counter (RE_TX_CNT) in response to a determination in (a) that a retransmission of the HARQ sub-burst has not been received within a PRD interval; and

(c) flushing a soft combining buffer if the RE_TX_CNT reaches a maximal retransmission count (MAX_RE_CNT), wherein the WAIT_TX_CNT, the RE_TX_CNT, and the soft combining buffer are maintained on a mobile station, and wherein steps (a) thru (c) occur on the mobile station.

2. The method of claim 1, wherein (b) also includes incrementing the RE_TX_CNT in response to a receiving of an undecodable retransmission of the HARQ sub-burst onto the mobile station.

3. The method of claim 1, wherein the incrementing the RE_TX_CNT comprises a timing mechanism to track the timing of the PRD interval and the timing mechanism restarts the timing for tracking the timing of the PRD interval if the timing mechanism determines the timing reaches an end of the PRD interval.

4. The method of claim 1, wherein the PRD interval is the maximal retransmission delay interval that the WAIT_TX_CNT allows to determine whether a retransmission of a Hybrid Automatic Repeat ReQuest (HARQ) sub-burst has been received.

5. The method of claim 1, wherein the PRD interval in (a) is an interval of time starting at approximately the receipt by the mobile station of the last transmission of the HARQ sub-burst.

6. The method of claim 1, wherein the PRD interval in (a) is an interval of time starting at approximately a time of transmission by the mobile station of a Negative ACKnowledgement (NACK).

7. The method of claim 1, wherein the WAIT_TX_CNT starts timing a PRD interval in response to the receipt of the last transmission of the HARQ sub-burst but begins incrementing approximately at the time the mobile station transmits a Negative ACKnowledgement (NACK) of the retransmission.

8. The method of claim 1, further comprising:

(d) resetting the RE_TX_CNT in response to receiving onto the mobile station a transmission of another HARQ sub-burst.

9. The method of claim 1, further comprising:

(d) resetting the RE_TX_CNT in response to receiving onto the mobile station a decodable retransmission of the HARQ sub-burst.

10. The method of claim 1, wherein the flushing of (c) is a flushing of HARQ sub-burst information pertaining to the HARQ sub-burst, and wherein other HARQ sub-burst information for other HARQ sub-bursts remains stored in the soft combining buffer and is not flushed.

11. The method of claim 1, wherein the PRD interval is a time interval that is a fixed amount of time from increment to increment of the WAIT_TX_CNT.

12. The method of claim 1, wherein the PRD interval has a duration that is substantially equal to a time duration of a number of frames.

13. The method of claim 1, wherein it is determined in (a) that a retransmission of the HARQ sub-burst was not received within a PRD interval if the WAIT_TX_CNT reaches a Maximal Retransmission Count (MAX_RE_CNT).

14. A method comprising:

receiving a Hybrid Automatic Repeat ReQuest (HARQ) burst and attempting to decode the HARQ burst;

increasing a retransmission counter (RE_TX_CNT) if either;

(i) the HARQ burst is not capable of being decoded, or (ii) no retransmission of the HARQ burst is received within a Predetermined Retransmission Delay (PRD) interval; and

discarding the HARQ burst from a soft combining buffer if the RE_TX_CNT reaches a maximal retransmission count (MAX_RE_CNT).

15. The method of claim 14, wherein a retransmission interval (RI) between two successive retransmissions of the HARQ burst is less than the PRD time interval.

16. The method of claim 14, further comprising:

resetting the RE_TX_CNT if the HARQ burst is decodable.

17. The method of claim 14, further comprising:

resetting the RE_TX_CNT if a second HARQ burst is received.

18. An apparatus comprising:

a retransmission counter (RE_TX_CNT) mechanism that increments after receiving of a HARQ burst if;

(i) the HARQ burst is undecodable, or (ii) no retransmission of the HARQ burst is received on the apparatus within a Predetermined Retransmission Delay (PRD) interval;

a wait transmission timer (WAIT_TX_CNT) mechanism that determines whether the PRD interval has expired without a retransmission of the HARQ burst being received onto the apparatus; and

a soft combining buffer from which HARQ burst information pertaining to the HARQ burst is flushed if RE_TX_CNT reaches a maximal retransmission count (MAX_RE_CNT).

19. The apparatus of claim 18, further comprising:

a processor operatively coupled to the retransmission counter mechanism and to the wait transmission timer mechanism, wherein the processor determines when to flush the soft combining buffer.

20. The apparatus of claim 18, wherein the apparatus is a mobile station.

21. The apparatus of claim 18, wherein the RE_TX_CNT mechanism includes a hardware counter, and wherein the WAIT_TX_CNT mechanism includes a hardware timer.

22. The apparatus of claim 18, wherein the RE_TX_CNT mechanism is a software-implemented counter, and wherein the WAIT_TX_CNT mechanism is a software-implemented timer.

23. A method comprising:

transmitting a value from a Base Station (BS) to a Mobile Station (MS), wherein the MS is configured to use the value to set a Predetermined Retransmission Delay (PRD) interval time at which a wait transmission timer mechanism (WAIT_TX_CNT) in the MS will expire if a retransmission of a Hybrid Automatic Repeat ReQuest (HARQ) sub-burst has not been received onto the MS from the BS within the PRD interval after receipt of a last transmission of the HARQ sub-burst.

24. The method of claim 23, wherein the value is communicated from the BS in a DSA-RSP message.

25. The method of claim 23, wherein value is transmitted from the BS in an IEEE 802.16 compliant transmission.

26. A method comprising:

(a) using a timer to track an amount of time that has elapsed after receipt onto a mobile station of an undecodable HARQ sub-burst;

(b) marking information in a soft combining buffer if the amount of elapsed time reaches a first threshold time, wherein the information marked is information of the undecodable HARQ sub-burst; and

(c) flushing the marked information from the soft combining buffer if the amount of elapsed time reaches a second threshold time, wherein steps (a) thru (c) occur on the mobile station and wherein the timer and the soft combining buffer are parts of the mobile station.

27. The method of claim 26, further comprising:

(d) maintaining a retransmission counter (RE_TX_CNT) on the mobile station;

(e) determining on the mobile station a first timer count value that corresponds to the first threshold time, wherein the determining of (e) is based at least in part on a frame time parameter (MIN_INTVL) and on a retransmission count as indicated by RE_TX_CNT; and

(f) determining on the mobile station a second timer count value that corresponds to the second threshold time.

28. An apparatus comprising:

a timer mechanism (LOST_MAP_CNT) that tracks an amount of time that has elapsed after receipt onto the apparatus of an undecodable HARQ sub-burst;

a soft combining buffer that stores HARQ information of the undecodable HARQ sub-burst; and

a mechanism that marks the HARQ information if the elasped time as indicated by the timer reaches a first threshold time (THR1), and that controls the soft combining buffer to flush the HARQ information if the elapsed time as indicated by the timer reaches a second threshold time (THR2).

29. The apparatus of claim 28, wherein the apparatus is a mobile station, wherein the mobile station includes an integrated circuit, and wherein the timer mechanism, the soft combining buffer, and the mechanism that marks the HARQ information are parts of the integrated circuit.

30. The apparatus of claim 29, wherein the integrated circuit includes a processor that executes instructions, wherein timer mechanism is a software-implemented timer that involves a first set of the instructions, and wherein the mechanism that marks the HARQ information is a software-implemented mechanism that involves a second set of the instructions.

31. A method comprising:

(a) using a timer to track an amount of time that has elapsed after receipt onto a mobile station of an undecodable HARQ sub-burst;

(b) marking information in a soft combining buffer if the amount of elapsed time reaches a first threshold time, wherein the information marked is information of the undecodable HARQ sub-burst; and

(c) flushing the marked information from the soft combining buffer if MS determines the soft combining buffer is about to be overflowed, wherein steps (a) thru (c) occur on the mobile station and wherein the timer and the soft combining buffer are parts of the mobile station.

32. The method of claim 31, further comprising:

(d) flushing the marked information from the soft combining buffer if the amount of elapsed time reaches a second threshold time.