Adaptive selective retransmission of packets

• US 6,810,488 B2
• Filed: 05/22/2001
• Issued: 10/26/2004
• Est. Priority Date: 05/22/2001
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: WebEx Communications Incorporated (Cisco Systems, Inc.)
• Inventors: Teng, Chia-Yuan
• Primary Examiner(s): Iqbal, Nadeem
• Application Number:
  US09/863,218
• Publication Number:
  US 20030046601A1
• Time in Patent Office: 1,253 Days
• Field of Search: 714/4, 714/18, 714/20, 714/21, 714/27, 714/37, 714/47, 714/752, 714/786, 714/821, 370/216, 370/229, 370/432, 375/99, 375/102
• US Class Current: 714/4.1
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/163 In-band adaptation of TCP data exchange; In-band control procedures
• CPC Class Codes: H04L 9/40 Network security protocols

Abstract

A method for selectively retransmitting packets is disclosed. The method includes categorizing groups of packets in an order of importance. The order of importance is based on a scope of adverse impact that a loss of a particular group has on a quality of reconstructed original information. The method also includes selecting a subset of the groups of packets to be retransmitted. The selection is based on network condition parameters. The method further includes requesting retransmission of the subset of the groups of packets when a buffer occupancy condition is met.

Claims

1. A method for selectively retransmitting packets, comprising:

categorizing groups of packets in an order of importance, where the order of importance is based on a scope of adverse impact that a loss of a particular group has on a quality of reconstructed original information;

selecting a subset of said groups of packets to be retransmitted, said selecting based on network condition parameters; and

requesting retransmission of the subset of said groups of packets.

2. The method of claim 1, wherein said network condition parameters include ideal and actual data rates.

3. The method of claim 1, wherein said network condition parameters include a packet error rate.

4. The method of claim 1, wherein said network condition parameters include a total number of groups of packets.

5. The method of claim 1, wherein a lower group number indicates higher order of importance.

6. The method of claim 5, wherein said network condition parameters include ideal (R) and actual data rates (R′

), a packet error rate (P_e(t)), and a total number of groups of packets (m).

7. The method of claim 6, wherein the subset of said groups of packets include groups of packets sufficiently important to be given a privilege to request retransmission.

8. The method of claim 7 wherein said selecting the subset of said groups of packets includes computing n_max,

where $n_{\max }=\frac{m}{P_e\; <li></li>\left(t\right)}<br><br>\left(\frac{R}{R^{\mathrm{\prime <br><br>}}}-1\right),$

 

and including the particular group in the subset if a group number of the particular group is less than or equal to n_max.

9. The method of claim 1, wherein retransmission of the subset of said groups of packets is requested when a buffer occupancy condition is met.

10. The method of claim 9, wherein said buffer occupancy condition is met when buffer occupancy is greater than a threshold value.

11. The method of claim 10, wherein said threshold value is approximately equal to a round-trip delay plus a guard time.

12. The method of claim 11, wherein said round-trip delay is two times one-way delay.

13. A system for selectively retransmitting packets, comprising:

means for categorizing groups of packets in an order of importance, where the order of importance is based on a scope of adverse impact that a loss of a particular group has on a quality of reconstructed original information;

means for selecting a subset of said groups of packets to be retransmitted, said selecting based on network condition parameters; and

means for requesting retransmission of the subset of said groups of packets when a buffer occupancy condition is met.

14. The system of claim 13, wherein said means for selecting the subset of said groups of packets includes:

a computation element for computing $n_{\max }=\frac{m}{P_e<br><br>\left(t\right)}<br><br>\left(\frac{R}{R^{\mathrm{\prime <br><br>}}}-1\right),$

 

where R is an ideal data rate, R′

is an actual data rate, P_e(t) is a packet error rate, and m is a total number of groups of packets, and

a sorting element for including the particular group in the subset if a group number of the particular group is less than or equal to n_max, where a lower group number indicates higher order of importance.

15. A system for selectively retransmitting packets, comprising:

a categorizer to receive groups of packets, said categorizer to sort the groups of packets in an order of importance, where the order of importance is based on a scope of adverse impact that a loss of a particular group may have on a quality of reconstructed original information; and

a subset selector to receive each group of packets sorted in the order of importance, said selector to determine whether a particular group is sufficiently important to be retransmitted.

16. The system of claim 15, further comprising:

a buffer occupancy determining element to generate a request to retransmit the particular group determined to be sufficiently important when buffer occupancy is greater than a threshold value.

17. The system of claim 16, further comprising:

a requester to send the request to retransmit the particular group of packets.

18. The system of claim 15, wherein said subset selector determines whether a particular group is sufficiently important to be retransmitted by computing $n_{\max }=\frac{m}{P_e}$

(t)

(RR′

-1),

where R is an ideal data rate, R′

is an actual data rate, P_e(t) is a packet error rate, and m is a total number of groups of packets, and including the particular group in a sufficiently important subset if a group number of the particular group is less than or equal to n_max, where a lower group number indicates higher order of importance.

19. A system for selectively retransmitting packets, comprising:

a subset selector receiving each group of packets sorted in an order of importance, said selector operating to determine whether a particular group is sufficiently important to be retransmitted; and

a buffer occupancy determining element sending a request to retransmit the particular group determined to be sufficiently important when buffer occupancy is greater than a threshold value.

20. The system of claim 19, further comprising:

a categorizer receiving groups of packets, said categorizer to categorize the groups of packets in the order of importance, where the order of importance is based on a scope of adverse impact that a loss of a particular group may have on a quality of reconstructed original information.