Packetizing media for a time slotted communication system

• US 7,778,169 B2
• Filed: 09/02/2005
• Issued: 08/17/2010
• Est. Priority Date: 09/02/2005
• Status: Active Grant

• Current Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Original Assignee: Cisco Technology, Inc. (Cisco Systems, Inc.)
• Inventors: Robison, Helen Marguerite, FitzGerald, Cary W.
• Primary Examiner(s): HSU, ALPUS
• Application Number:
  US11/218,978
• Publication Number:
  US 20070053373A1
• Time in Patent Office: 1,810 Days
• Field of Search: 370/230, 370/250, 370/252, 370/412, 370/458, 370/474
• US Class Current: 370/230
• CPC Class Codes: H04L 12/43 with synchronous transmission, e.g. time division multiplex [TDM], slotted rings
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/283 in response to processing delays, e.g. caused by jitter or round trip time [RTT]
• CPC Class Codes: H04L 49/90 Buffering arrangements
• CPC Class Codes: H04L 49/9023 for implementing a jitter-buffer
• CPC Class Codes: H04L 49/9094 Arrangements for simultaneous transmit and receive, e.g. simultaneous reading/writing from/to the storage element
• CPC Class Codes: H04W 28/06 Optimizing the usage of the radio link, e.g. header compression, information sizing , discarding information system modifying transmission characteristic according to link quality by modifying frame length H04L1/0007; dynamic adaptation of the packet size for flow control or congestion control H04L47/365
• CPC Class Codes: H04W 28/14 using intermediate storage
• CPC Class Codes: H04W 74/04 Scheduled access hybrid access H04W74/02

Abstract

Media that is normally packetized into many separate individual packets and then queued for individual transmission during a transmit window is combined together into one, or a few, packets. The larger packets more efficiently carry media over a time slotted communication media since only one, or a few, packet headers are used for carrying a larger amount of media. Since packets cannot be transmitted until the start of a new transmit window, the larger packets do not substantially add to the overall packet delay that normally occurs when larger packets are formatted and transmitted in non-time slotted networks.

In another aspect of the system, probe packets are used to identify the start of the transmit window. The transmit window start time is inferred from the round trip times for the probe packets and media packetization is then synchronized with the identified transmit windows.

Claims

1. A method of transmitting packet data, comprising:

receiving a packetized media stream;

identifying a portion of the packetized media stream that is queued while waiting for a transmit window, wherein the identified portion comprises a first number of packet payloads;

queuing probe packets during both a transmit cycle and a receive cycle;

comparing round trip times for the probe packets;

identifying the transmit window according to the round trip time comparisons;

utilizing a processor to re-packetize the identified portion of the packetized media stream, wherein said re-packetizing combines media from the first number of packet payloads into a second different number of packet payloads, wherein the second number is less than the first number; and

sending the re-packetized portion of the media stream during the transmit window.

2. The method according to claim 1, including combining a portion of the packetized media stream that is queued from an end of a previous transmit window up to at least a beginning of a next transmit window into a single packet.

3. The method according to claim 2 including combining at least a portion of the packetized media stream that is received during the previous transmit window into the same packet or combining at least a portion of the packetized media stream that is received during the next transmit window into the same packet.

4. The method according to claim 1, including sending a packet having a payload that contains media received in the stream while waiting for the transmit window and media received in the stream during the transmit window.

5. The method according to claim 1, including identifying when the round trip times for the probe packets spike from a relatively short round trip time to a relatively large round trip time as an end of the transmit window and using the identified end of the transmit window to determine what media to combine into a same packet.

6. The method according to claim 1, including receiving the re-packetized portion of the media stream during a receive window.

7. A media packetizer, comprising:

a processor configured to combine media into a same packet according to an amount of media received while waiting for a next transmit window;

wherein the processor queues individual probe packets during an entire transmit and receive cycle for a slotted communication system and then identifies the transmit window by comparing the round trip times for the received probe packets.

8. The media packetizer according to claim 7, wherein the processor identifies an end of the transmit window by detecting a sharp increase in the probe packet round trip times and uses the identified end of the transmit window to infer the start time for the transmit window.

9. A system for transmitting packets over a slotted communication system, comprising:

means for combining all media queued while waiting for a transmit window into at least one packet;

means for queuing probe packets during both the transmit window and a receive window;

means for comparing round trip times for the probe packets;

means for identifying the transmit window according to the round trip time comparisons; and

means for sending the at least one packet during the identified transmit window.

10. The system according to claim 9, including means for combining at least all the media queued from an end of a previous transmit window up to at least a beginning of a next transmit window into the at least one packet.

11. The system according to claim 10, including means for combining at least a portion of the media received during the previous transmit window or at least a portion of the media received during the next transmit window into the at least one packet.

12. The system according to claim 9, including means for sending at least one additional packet that contains additional media received during the transmit window.

13. A memory device storing code that, if executed, results in:

queuing probe packets during both transmit windows and receive windows;

identifying when the probe packets are queued;

identifying when the probe packets are received back;

identifying round trip times from when the probe packets are queued to when the probe packets are received back;

identifying the transmit or receive windows by comparing the round trip times for the probe packets; and

transmitting or receiving packet data during the identified window.

14. The memory device of claim 13 wherein the code, if executed, further results in:

transferring the probe packets to a satellite access device;

identifying output times when the probe packets are transferred to the satellite access device;

identifying receive times when the probe packets are received back from the satellite access device;

determining round trip times for the probe packets according to the identified output times and receive times; and

inferring when the transmit windows are open according to the determined round trip times.

15. The memory device of claim 14 wherein the code, if executed, further results in:

inferring when one of the transmit windows ends by identifying when the determined round trip times for the probe packets spike from having a shortest round trip time to a longest round trip time.

16. The memory device of claim 13 wherein the code, if executed, further results in:

combining media queued for transmission during a next transmit window into a same media packet and sending the media packet during the next transmit window.

17. A memory device containing code that, if executed, results in:

receiving a packetized media stream;

queuing probe packets during both a transmit cycle and a receive cycle;

comparing round trip times for the probe packets;

identifying a transmit window according to the round trip time comparisons;

identifying a portion of the packetized media stream that is queued while waiting for the transmit window, wherein the identified portion comprises a first number of packet payloads;

utilizing a processor to re-packetize the identified portion of the packetized media stream, wherein said re-packetizing combines media from the first number of packet payloads into a second different number of packet payloads, wherein the second different number is less than the first number; and

sending the re-packetized portion of the media stream during the transmit window.

18. The memory device according to claim 17, wherein the code, if executed, results in combining queued media from at least an end of a last transmit window to at least a beginning of the next transmit window into the same packet.

19. The memory device according to claim 18, wherein the code, if executed, results in combining additional media received during the last transmit window or additional media received during the next transmit window into the same packet.

20. The memory device according to claim 18, wherein the code, if executed, results in combining other media received during the last transmit window or during the next transmit window into another packet.

21. The memory device according to claim 17, wherein the code, if executed, results in sending the packets to a satellite access device during the transmit window.

22. The memory device according to claim 21, wherein the code, if executed, results in synchronizing according to a transmit window time in response to the satellite access device identifying the transmit window time.

23. The memory device according to claim 17, wherein the memory device is located in a media source device, network processing device, or satellite access device.

24. The memory device according to claim 17, wherein the code, if executed, results in causing a satellite receiver to synchronize media packetization according to a satellite-transmitted global time clock.