METHODS AND SYSTEMS FOR BANDWIDTH PROTECTION

• US 20090175191A1
• Filed: 12/02/2008
• Published: 07/09/2009
• Est. Priority Date: 12/31/2007
• Status: Active Grant

• Current Assignee: Industrial Technology Research Institute
• Original Assignee: Industrial Technology Research Institute
• Inventors: HUANG, Chung-Ming, LIN, Chung-Wei, LIN, Xin-Ying
• Granted Patent: US 7,894,367 B2
• Time in Patent Office: Days
• US Class Current: 370/253
• CPC Class Codes: H04L 43/0829 Packet loss
• CPC Class Codes: H04L 43/0864 Round trip delays
• CPC Class Codes: H04L 43/0894 Packet rate

Abstract

Presented are methods and systems for providing bandwidth estimation and correction in a communications network. Bandwidth estimation and correction can include calculating a round trip time (RTT) value and a packet loss rate (PLR) value for each packet of a set of packets transmitted at different points in time from a server to a client terminal over the communications network; determining a bandwidth estimate based on the RTT and PLR values for the set of packets transmitted; determining a bandwidth measurement based on the RTT and PLR values for the set of packets; and determining a corrected bandwidth estimate based on the bandwidth estimate and the bandwidth measurement.

Claims

1. A method for bandwidth estimation and correction in a communications network, the method comprising:

calculating a round trip time (RTT) value and a packet loss rate (PLR) value for each packet of a set of packets transmitted at different points in time from a server to a client terminal over the communications network;

determining a bandwidth estimate based on the RTT and PLR values for the set of packets;

determining a bandwidth measurement based on the RTT and PLR values for the set of packets; and

determining a corrected bandwidth estimate based on the bandwidth estimate and the bandwidth measurement.

2. The method of claim 1, further comprising determining a transmission rate based on the bandwidth estimate and an available buffer size of the client terminal, wherein the transmission rate is used by the server to adjust packet transmissions.

3. The method of claim 1, wherein determining the bandwidth estimate includes using an a posteriori bandwidth estimate based on calculations averaging the RTT values and a sliding time-window.

4. The method of claim 3, wherein the sliding time-window is greater than 30 seconds when there are handoffs exceeding a predetermined frequency.

5. The method of claim 1, wherein determining the corrected bandwidth estimate comprises:

determining an estimate error covariance Q′

based on the bandwidth estimate;

determining an a priori-error covariance p⁻

(t) based on Q′

;

determining a measurement error covariance R′

;

determining a correction gain based on Q′

, p⁻

(t), and R′

; and

correcting the bandwidth estimate based on the correction gain.

6. The method of claim 5, wherein if a network handoff or handover occurs, then determining the corrected bandwidth estimate further includes assigning Q′

a first predetermined value and assigning R′

a second predetermined value.

7. The method of claim 6, further including setting the first predetermined value to be greater than the second predetermined value.

8. The method of claim 5, wherein if a response packet is lost, then determining the corrected bandwidth estimate further includes assigning Q′

a third predetermined value and assigning R′

a fourth predetermined value.

9. The method of claim 8, further including setting the third predetermined value to be greater than the fourth predetermined value.

10. The method of claim 5, further including calculating R′

based on the bandwidth measurement.

11. The method of claim 5, wherein if Q′

, R′

, and p⁻

(t) are all equal to zero, then determining the corrected bandwidth estimate includes assigning the bandwidth estimate value.

12. The method of claim 1, wherein determining the corrected bandwidth estimate further includes using a correction gain.

13. The method of claim 12, wherein using the correction gain includes using a Kalman gain.

14. The method of claim 5, wherein determining the correction gain further includes using a Kalman gain.

15. The method of claim 11, wherein determining the corrected bandwidth estimate further comprises:

determining an a posteriori error covariance p⁺(t) based on the a priori-error covariance p⁻

(t) and the correction gain; and

using the a posteriori error covariance p⁺(t) to calculate the a priori-error covariance p⁻

(t) for a subsequent packet.

16. The method of claim 2, further including repeating the method for a next set of packets.

17. A system for bandwidth estimation and correction in a communications network, the system comprising:

a network analysis module configured to calculate a round trip time (RTT) and a packet loss rate (PLR) for each packet of a set of packets transmitted at different times from a server to a client terminal over the communications network;

a bandwidth estimation module configured to determine a bandwidth estimate based on the RTT and PLR values for the set of packets;

a bandwidth measurement module configured to determine a bandwidth measurement based on the values of RTT and PLR for the set of packets; and

an estimation-error correction module configured to determine a corrected bandwidth estimate based on the bandwidth estimate and the bandwidth measurement.

18. The system of claim 17, further comprising a rate-decision module configured to determine a transmission rate based on the bandwidth estimate and an available buffer size of the client terminal, wherein the transmission rate is used by the server to adjust packet transmissions.

19. The system of claim 18, wherein the estimation-error correction module is further configured to use a correction gain.

20. The system of claim 19, wherein the correction gain is a Kalman gain.