METHOD FOR RETRANSMISSION USING CHECKSUMS FOR IDENTIFYING LOST DATA PACKETS

• US 20130007823A1
• Filed: 10/02/2009
• Published: 01/03/2013
• Est. Priority Date: 10/02/2009
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Mangs, Jan-Erik, Halen, Joacim, Kolhi, Johan, Souza, Victor
• Granted Patent: US 9,065,980 B2
• Time in Patent Office: Days
• US Class Current: 725/109
• CPC Class Codes: H04L 1/0061 Error detection codes
• CPC Class Codes: H04L 1/1832 Details of sliding window management
• CPC Class Codes: H04L 1/1838 for semi-reliable protocols, e.g. for less sensitive applications such as streaming video buffer level management for video bitstream receiver H04N21/44004
• CPC Class Codes: H04L 65/611 for multicast or broadcast systems for broadcast or conference H04L12/18; arrangements for broadcast or distribution combined with broadcast H04H20/00; arrangements for broadcast applications with a direct linkage to broadcast information or to broadcast space-time H04H60/00; selective distribution of broadcast services, e.g. multimedia broadcast multicast service [MBMS], H04W4/06
• CPC Class Codes: H04N 21/6375 for requesting retransmission , e.g. of data packets lost or corrupted during transmission from serverARQ protocols H04L1/18; implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP] H04L69/16
• CPC Class Codes: H04N 21/6377 directed to server one-way streaming services wherein the source is controlled by the destination H04L65/613
• CPC Class Codes: H04N 21/658 Transmission by the client directed to the server
• CPC Class Codes: H04N 7/17318 Direct or substantially direct transmission and handling of requests

Abstract

The present invention relates to a method for retransmission of lost data, a receiving device operating according to the invented method and a retransmission server. In the absence of a unique identifier per data packet or data frame, there is obviously a problem to directly identify a specific data packet, data block or data frame in the stream and retransmission can'"'"'t take place with current technologies. The object of the present invention is to offer a retransmission method and means for making said retransmission of missing data packets possible in the absence of a unique identifier.

Claims

1. A method for retransmission of data packets in the absence of sequence numbers, wherein the data packets are sent in data frames, each frame comprising a checksum, during a data transmission of a session between a data transmitter and a receiving device, the method comprising the steps of:

detecting data loss in the data stream transmission;

determining checksums of at least the received adjacent data frames enclosing the detected data loss;

sending an identification key comprising said determined checksums to a retransmission server, whereby the sent checksums constitute arc constituting a checksum sequence and said identification key is used by the server for identifying the data loss;

receiving the requested missing data comprising at least one data frame, from the retransmission server;

interleaving the received at least one data frame in the correct place in the received data transmission before rendering the data information of the data transmission.

2. The method according to claim 1, wherein more checksums than the two checksums of the two received adjacent data frames enclosing the detected data loss are detected and sent to the retransmission server as an identification key thereby facilitating the identification of the correct data loss.

3. The method according to claim 1, wherein the identification key comprises time stamps of said checksums, each time stamp corresponding to a data frame and its checksum recorded at the reception of the data frame.

4. The method according to claim 1, wherein the sending of the identification key is performed by including said identification key in a Request message which is sent to the retransmission server.

5. The method according to claim 1, wherein the data transmission is a User Datagram Protocol stream.

6. The method according to claim 1, wherein the session is an IPTV transmission utilizing Moving Picture Expert Group 2—

Transport stream (MPEG-TS) and the data transmitter is a Media server.

7. The method according to claim 1, wherein each data packet is a Moving Picture Expert Group 2—

Transport stream (MPEG-TS) unit having a continuity number which is used for detecting data loss in the data transmission in the detecting step.

8. A receiving device for retransmission of data packets in the absence of sequence numbers, wherein the data packets are sent in frames, each frame comprising a checksum, during a data transmission of a session from a data transmitter to the receiving device the receiving device comprising:

detecting means for detecting data loss in the data stream transmission;

determining means for determining the checksums of at least the received adjacent data frames enclosing the detected data loss;

sending means for sending adapted to send an identification key comprising said determined checksums to a retransmission server, whereby the sent checksums constitute a checksum sequence and said identification key is used by the server for identifying the data loss;

receiving means for receiving the requested missing data comprising at least one data frame from the retransmission server;

interleaving means for interleaving said received at least one data frame in the correct place in the received data transmission before rendering the data information of the data transmission.

9. The receiving device according to claim 8, wherein more checksums than the two checksums of the two received adjacent data frames enclosing the detected data loss are detected and sent to the retransmission server as an identification key thereby facilitating the identification of the correct data loss.

10. The receiving device according to claim 8, wherein the identification key is also comprising the time stamps of said checksums, each time stamp corresponding to a data frame and its checksum recorded at the reception of the data frame.

11. The receiving device according to claim 8, wherein the sending means being adapted to include said identification key in a Request message which is sent to the retransmission server.

12. The receiving device according to claim 8, wherein the data transmission is a User Datagram Protocol stream.

13. The receiving device according to claim 8, wherein the session is an IPTV transmission utilizing Moving Picture Expert Group 2—

Transport stream (MPEG-TS) and the data transmitter is a Media server.

14. The receiving device according to claim 13, wherein each data packet is a Moving Picture Expert Group 2—

Transport stream (MPEG-TS) unit having a continuity number which is used for detecting data loss in the data transmission by the detecting means.

15. A retransmission server for retransmission of data packets in the absence of sequence numbers, wherein the data packets are sent in frames, each frame comprising a checksum, during a data transmission of a session from a data transmitter to at least one receiving device, the retransmission server comprising a buffer storage and means for storing the sent data frames in the buffer storage the retransmission server for receiving an identification key from a retransmission requesting receiving device, said identification key comprising checksums of the sent data frames, whereby the received checksums constitute a checksum sequence, and said identification key is used by the retransmission server for identifying stored data frames and data packets, for which the retransmission server is adapted for sending to the requesting receiving device.

16. The retransmission server according to claim 15, said server further comprising a buffer storage reader for identifying the stored data frames by means of said identification key and copy said data frames for retransmission to the requesting receiving device.

17. The retransmission server according to claim 15, comprising a transceiver block for handling the reception of request messages that comprise the identification key and for sending response messages comprising the requested data frames, which are detected by the requesting unit as missing data.

18. The retransmission server according to claim 15, 17, wherein the identification key comprises more checksums than the two checksums of the two received adjacent data frames enclosing a detected data loss thereby facilitating the identification of the correct data loss.

19. The retransmission server according to claim 15, wherein the identification key further comprises the time stamps of said checksums, each time stamp corresponding to a data frame and the data frame'"'"'s checksum recorded at the reception of the data frame.

20. The retransmission server according to claim 15, wherein the buffer storage is a ring buffer, keeping the stored frames only for a predetermined length of time, denoted by a sliding time window.