Methods of controlling data rate in wireless communications systems

• US 20040151122A1
• Filed: 01/31/2003
• Published: 08/05/2004
• Est. Priority Date: 01/31/2003
• Status: Active Grant

• Current Assignee: RPX Corporation
• Original Assignee: Alcatel-Lucent USA, Inc. (Nokia Corporation)
• Inventors: Lau, Kin Nang, Sanders, Susan Wu, Meyers, Martin H., Liu, Youjian
• Granted Patent: US 7,583,637 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04L 1/0002 by adapting the transmission rate
• CPC Class Codes: H04L 1/0007 by modifying the frame length
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/29 using a combination of thresholds
• CPC Class Codes: H04W 24/00 Supervisory, monitoring or testing arrangements
• CPC Class Codes: H04W 28/0236 radio quality, e.g. interference, losses or delay
• CPC Class Codes: H04W 28/22 Negotiating communication rate
• CPC Class Codes: H04W 8/04 Registration at HLR or HSS [Home Subscriber Server]

Abstract

In an aspect of the method, a received data packet is decoded in order to determine a packet error rate value, and an average package error value for N received data packets is updated based on the determined packet error rate value. The updated average packet error rate value is then compared against a threshold value and a data rate request is issued based on this comparison. In another aspect, a response to a transmitted data packet is received, the response being related to an average packet error rate value. The average packet error rate value is compared against a threshold and a data rate is modified based on the comparison. In each of the above aspects, a data rate control margin that is used to overcome channel estimate errors resulting from transmission delays may be dynamically adjusted, e.g., in real time, in order to optimize system resources.

Claims

1. A method of data rate control in a wireless system, comprising:

decoding a received data packet to determine a packet error rate value;

updating an average packet error rate value for N received data packets based on said determined packet error rate value;

comparing said updated average packet error rate value against at least one threshold value; and

issuing a data rate request based on said comparison.

2. The method of claim 1, further comprising measuring a signal to noise ratio value (SNR_MEAS) associated with the decoded data packet.

3. The method of claim 1, wherein said updating includes calculating an average encoded packet error rate (EPER_AVG) on a per-packet basis over a sliding window, said EPER_AVG changing with time.

4. The method of claim 2, further comprising:

adjusting a data rate control margin parameter (DRC_MARGIN) that is used to overcome channel estimate errors resulting from transmission delays based on said comparison, and

estimating a signal to noise ratio value (SNR_EST) that accounts for transmission delays based on said SNR_MEAS and said adjusted DRC_MARGIN,

wherein said issued data rate request is based on said SNR_EST.

5. The method of claim 4, wherein said adjusting is performed in real time.

6. The method of claim 4, wherein

said at least one threshold value is selected from one of a first threshold and a second threshold,

said adjusting further includes increasing DRC_MARGIN if the average packet error rate value is equal to or exceeds the first threshold, and

said SNR_EST being reduced as defined by an expression

SNR_EST=SNR_MEAS−

DRC_MARGIN.

7. The method of claim 4, wherein said issuing a data rate request further includes sending a date rate control (DRC) value that specifies a requested transmission rate based on said SNR_EST.

8. The method of claim 6, wherein said issuing a data rate request further includes:

determining a DRC value using said SNR_EST, and

sending said (DRC) value to specify a requested data rate.

9. The method of claim 4, wherein said comparing is defined by an expression

EPER_AVG(k)≧

TPER(k)+Hys1(k),

where k represents a data rate control (DRC) value specifying a requested transmission rate, EPER_AVG(k) is an average encoded packet error rate, TPER(k)+Hys1(k) representing said first threshold value, TPER(k) is the target packet error rate, and Hys1(k) is a specified constant rate.

10. The method of claim 9, said adjusting further defined by an expression:

DRC_MARGIN(new)=DRC_MARGIN+UpStep, if EPER_AVG(k)≧

TPER(k)+Hys1(k),

where UpStep is a specified increase adjustment to DRC_MARGIN.

11. The method of claim 4, wherein

said at least one threshold value is selected from one of a first threshold and a second threshold,

said adjusting further including decreasing DRC_MARGIN if the average packet error rate value is less than a second threshold value, and

said SNR_EST being increased as defined by an expression

SNR_EST=SNR_MEAS−

DRC_MARGIN.

12. The method of claim 11, wherein said issuing a data rate request further includes:

determining a DRC value using said SNR_EST, and

sending said (DRC) value to specify a requested data rate.

13. The method of claim 4, wherein said comparing is defined by an expression

EPER_AVG(k)<

TPER(k)−

Hys2(k),

where k represents a data rate control (DRC) value specifying a requested transmission rate, EPER_AVG(k) is an average encoded packet error rate, TPER(k) is the target packet error rate, and Hys(2) is a specified constant rate.

14. The method of claim 13, said adjusting further defined by an expression:

DRC_MARGIN(new)=DRC_MARGIN−

DownStep, if EPER_AVG(k)<

TPER(k)−

Hys2(k),

where DownStep is a specified decrease adjustment to DRC_MARGIN.

15. A method of data rate control in a wireless system, comprising:

receiving a response to a transmitted data packet, the response indicative of a change in calculated average packet error rate;

comparing an updated average packet error rate value against a threshold value; and

modifying a data rate based on said comparison.

16. The method of claim 15, further comprising:

adjusting a data rate control margin parameter (DRC_MARGIN) that is used to overcome channel estimate errors resulting from transmission delays based on said comparison.

17. The method of claim 15, wherein said adjusting is performed in real time.

18. The method of claim 15, wherein said receiving further includes receiving an acknowledgment (ACK) message, said ACK message indicating a decrease in calculated average packet error rate.

19. The method of claim 15, wherein said receiving further includes receiving a negative acknowledgment (NAK) message, said NAK message indicating a increase in calculated average packet error rate.

20. A method of determining a data rate control margin (DRC_MARGIN) for data rate control in a wireless system, the DRC_MARGIN used to overcome channel estimate errors resulting from transmission delay, comprising:

decoding a received data packet to determine a packet error rate value;

updating an average packet error rate value for N received data packets based on said determined packet error rate value;

comparing said updated packet error rate value against a threshold value; and

determining an adjustment to DRC_MARGIN based on said comparison.

21. The method of claim 20, further comprising issuing a data rate request based on said determined adjustment to DRC_MARGIN.

22. The method of claim 20, wherein said determining is performed in real time.

23. A method of determining a data rate control margin (DRC_MARGIN) for data rate control in a wireless system, the DRC_MARGIN used to overcome channel estimate errors resulting from transmission delay, comprising:

receiving a response to a transmitted data packet;

updating an average packet error rate value based on said received response;

comparing said updated packet error rate value against a threshold value; and

determining an adjustment to DRC_MARGIN based on said comparison.

24. The method of claim 23, further comprising adjusting a data rate based on said determined adjustment to DRC_MARGIN.

25. The method of claim 23, wherein said determining is performed in real time.