Real time packet transforms to avoid re-transmission

• US 8,514,852 B2
• Filed: 11/24/2009
• Issued: 08/20/2013
• Est. Priority Date: 11/24/2008
• Status: Active Grant

• Current Assignee: Dynamic MESH Networks Incorporated
• Original Assignee: Mesh Dynamics Incorporated
• Inventors: daCosta, Francis, Dayanandan, Sriram
• Primary Examiner(s): Hamza, Faruk
• Assistant Examiner(s): TRAN, THINH D
• Application Number:
  US12/625,365
• Publication Number:
  US 20100128725A1
• Time in Patent Office: 1,365 Days
• Field of Search: None
• US Class Current: 370/389
• CPC Class Codes: H03M 13/09 Error detection only, e.g. using cyclic redundancy check [CRC] codes or single parity bit
• CPC Class Codes: H03M 13/093 CRC update after modification of the information word
• CPC Class Codes: H03M 13/19 Single error correction without using particular properties of the cyclic codes, e.g. Hamming codes, extended or generalised Hamming codes
• CPC Class Codes: H03M 13/2906 using block codes H03M13/2957 takes precedence
• CPC Class Codes: H03M 13/2927 Decoding strategies
• CPC Class Codes: H03M 13/6527 IEEE 802.11 [WLAN]
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/0072 Error control for data other than payload data, e.g. control data
• CPC Class Codes: H04L 1/0083 Formatting with frames or packets; Protocol or part of protocol for error control
• CPC Class Codes: H04L 1/1812 Hybrid protocols; Hybrid automatic repeat request [HARQ]
• CPC Class Codes: H04L 2001/0097 Relays
• CPC Class Codes: H04N 21/2383 Channel coding or modulation of digital bit-stream, e.g. QPSK modulation arrangements for detecting or preventing errors in the information received by adapting the channel coding H04L1/0009; analogue front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/4382 Demodulation or channel decoding, e.g. QPSK demodulation analog front ends or means for connecting modulators, demodulators or transceivers to a transmission line H04L27/0002
• CPC Class Codes: H04N 21/6437 Real-time Transport Protocol [RTP]

Abstract

There exists a need to reduce re-transmission delays in real time feeds (such as video) by sending the packet with sufficient repair/recovery information inside the packet container so the relaying stations and/or the receiving devices can fix errors in transmission by perusing the contents of the packet and the repair information, and modify the packet and then relay it. By providing the relaying station the ability to fix the error, retransmission of the packet is avoided along each relay station along the network path from source to destination and also by receiving devices that would otherwise request a re-transmission. This application teaches a method so real time streams (e.g. video) may be more efficiently transported over a CSMA based network.

Claims

1. A method for transmitting a standard format network packet containing real time information, comprising the steps of:

modifying said packet by adding redundant information to the packet;

modifying at least one packet header to add a position offset reference number that points to redundant information;

revising all checksums within the packet as modified to agree with the packet contents as modified;

transmitting the packet through a network;

modifying the packet, including modifying all checksums, to return the packet'"'"'s format to that of the standard packet format;

if the modified packet, having been transmitted through a network, is determined to have a checksum mismatch as received, modifying the packet by retrieving the redundant information pointed to by said position offset reference number and replacing a portion of the packet with said redundant information; and

revising all checksums within the packet as modified to agree with the contents of the modified packet.

2. The method of claim 1 wherein the redundant information is exclusively header information.

3. The method of claim 2 wherein the redundant header information contains a checksum that specifically determines the validity of said redundant header information.

4. The method of claim 3 wherein the IP header and the RTP header of a packet containing real time information are both modified to add position offset references that point to redundant header information for each header respectively.

5. The method of claim 1 wherein a number indicating a specific position offset reference number is repeated multiple times as a means to later determine the validity of the position offset reference number after transmission.

6. The method of claim 2, wherein only redundant header information is included within the modified packet and no redundant information is included to provide for repair of RTP data.

7. The method of claim 1, wherein revising all checksums within the packet as modified to agree with the contents of the modified packet includes creating at least one checksum that matches real time video content containing errors.

8. A method for transmitting a standard format network packet containing real time information through a multi-hop network, comprising the steps of:

modifying said packet by adding redundant header information to the packet;

modifying at least one packet header within said packet to add a position offset reference number that points to redundant header information;

revising all checksums within the packet as modified to agree with the packet contents as modified;

transmitting the packet to a first relay node in the multi-hop network;

if the modified packet as received by the first relay node is determined to have a checksum mismatch relative to header information, modifying the packet by retrieving the redundant header information pointed to by said position offset reference number and replacing a portion of the header information for the packet with said redundant header information;

recalculating checksums as required within the packet to agree with the packet contents as modified;

transmitting the modified packet to a second network node within the multi-hop network; and

when the packet is received by an end point node within the multi-hop network, modifying the packet including recalculating all checksums to return the packet'"'"'s format to that of the standard packet format.

9. The method of claim 8, wherein only redundant header information is included within the modified packet and no redundant information is included to provide for repair of real time information data.

10. The method of claim 8, wherein recalculating checksums as required within the packet to agree with the packet contents as modified includes creating at least one checksum that matches real time video content containing errors.

11. The method of claim 8 wherein the redundant header information contains a checksum that specifically determines the validity of said redundant header information.

12. The method of claim 8 wherein the IP header and the RTP header of a packet containing real time information are both modified to add position offset references that point to redundant header information for each header respectively.

13. The method of claim 8 wherein a number indicating a specific position offset reference number is repeated multiple times as a means to later determine the validity of the position offset reference number after transmission.

14. A method of transforming of an IP packet for transmission on an 802.11 network comprising:

transforming the IP packet by adding redundant header information and position offset reference numbers that point to said redundant header information to the IP packet; and

whereupon being received by a network node, said transformed IP packet is processed by the method comprising the steps of;

examining the transformed packet to determine if a level 2 cyclic redundancy check data for the packet'"'"'s Layer 2 header matches;

if the level 2 cyclic redundancy check data for the Layer 2 header does not match, retrieving first redundant header information located within said transformed packet according to a first position offset reference number and repairing the Layer 2 header utilizing said first redundant header information;

examining the transformed packet to determine if a level 3 cyclic redundancy check data for the packet'"'"'s header related to Layer 3 and above matches;

if the level 3 cyclic redundancy check data related to Layer 3 and above does not match, retrieving second redundant header information located within said transformed packet according to a second position offset reference number and repairing the header related to Layer 3 and above utilizing said second redundant header information; and

if it is determined that the network node is not an end point node, recalculating all cyclic redundancy check data sets within the transformed packet as required to agree with the contents of the transformed packet thus repaired, and transmitting the transformed packet to another network node;

converting the transformed packet to the standard 802.11 format if it is determined that the network node processing the transformed packet is an end point node, including recalculating cyclic redundancy check data sets within the transformed packet as required to agree with the contents of the transformed packet thus converted; and

wherein a number indicating a specific position offset reference number is repeated multiple times as a means to later determine the validity of the position offset reference number after transmission.

15. The method of claim 14, wherein recalculating all CRCs within the transformed packet as required to agree with the transformed packet contents thus converted includes creating at least one checksum that matches real time video content containing errors.

16. The method of claim 14, wherein the redundant header information contains a CRC that specifically determines the validity of said redundant header information.