PLAYOUT BASED DELAY SCHEDULER

• US 20080095198A1
• Filed: 03/13/2007
• Published: 04/24/2008
• Est. Priority Date: 10/18/2006
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Sagfors, Mats, Synnergren, Per, Torsner, Johan, Wager, Stefan, Peisa, Janne
• Granted Patent: US 7,733,773 B2
• Time in Patent Office: Days
• US Class Current: 370/519
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/2416 Real-time traffic
• 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 47/50 Queue scheduling
• CPC Class Codes: H04L 47/56 implementing delay-aware scheduling
• CPC Class Codes: H04W 28/02 Traffic management, e.g. flow control or congestion control
• 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 72/12 Wireless traffic scheduling
• CPC Class Codes: H04W 8/04 Registration at HLR or HSS [Home Subscriber Server]

Abstract

A node (22) of a telecommunications network (2) receives, over a transmission chain (24) subject to packet jitter, packets of a connection involving a client device (26). The node (22) comprises a packet buffer (38) configured to store the packets received over the transmission chain prior to transmission of the packets to the client device (26). The node (22) further comprises a client-conscious scheduler (40) which is configured to schedule the transmission of the packets from the packet buffer (38) over a channel (32) to the client device (26) in accordance with a timing consideration of the client device (26). In an example embodiment, the timing consideration of the client device (26) which is taken into account by the scheduler (40) is avoidance of drain of a playout buffer of the client device.

Claims

1. A node of a telecommunications network which receives, over a transmission chain subject to packet jitter, packets of a connection involving a client device, the node comprising:

a packet buffer configured to store the packets received over the transmission chain prior to transmission of the packets to the client device;

a scheduler configured to schedule the transmission of the packets from the packet buffer over a channel to the client device in accordance with a timing consideration of the client device.

2. The apparatus of claim 1, wherein the scheduler is configured to prebuffer an amount of data that corresponds to a maximum jitter allowed for a connection.

3. The apparatus of claim 1, wherein the timing consideration of the client device is avoidance of drain of a playout buffer of the client device.

4. The apparatus of claim 3, wherein the scheduler comprises a process configured to execute a software program comprising instructions stored on a tangible media, and wherein when executed the instructions result in performance of the following acts:

maintaining a transmission deadline variable indicative of a time at which transmission of a packet(s) should occur from the scheduling buffer to prevent the playout buffer of client device from draining;

for each transmission time interval (TTI) of the connection, decreasing the transmission deadline variable by an amount comparable to the transmission time interval (TTI);

for each transmission of a frame(s), increasing the transmission deadline variable by an amount comparable to a product of a number of frame(s) transmitted and a frame inter-arrival time.

5. The apparatus of claim 4, wherein the frame inter-arrival time is a constant.

6. The apparatus of claim 4, wherein the frame inter-arrival time is variable, and wherein when executed the instructions result in determining the frame-interarrival time with reference to information carried in the packets.

7. The apparatus of claim 6, wherein the information carried in the packets is a time stamp.

8. The apparatus of claim 4, wherein when executed the instructions result in performance of the following further acts:

detecting a lost packet;

increasing the transmission deadline variable by the frame inter-arrival time when the lost packet is detected.

9. A method of operating a node of a communications network, the method comprising:

receiving, over a transmission chain subject to packet jitter, packets of a connection involving a client device;

storing the packets received over the transmission chain in a packet buffer;

scheduling transmission of the packets from the packet buffer over a channel to the client device in accordance with a timing consideration of the client device.

10. The method of claim 9, further comprising prebuffering in the packet buffer an amount of data that corresponds to a maximum jitter allowed for a connection.

11. The method of claim 9, wherein the timing consideration of the client device is avoidance of drain of a playout buffer of the client device.

12. The method of claim 11, further comprising:

maintaining a transmission deadline variable indicative of a time at which transmission of a packet(s) should occur from the scheduling buffer to prevent the playout buffer of client device from draining;

for each transmission time interval (TTI) of the connection, decreasing the transmission deadline variable by an amount comparable to the transmission time interval (TTI);

for each transmission of a frame(s), increasing the transmission deadline variable by an amount comparable to a product of a number of frame(s) transmitted and a frame inter-arrival time.

13. The method of claim 12, wherein the frame inter-arrival time is a constant.

14. The method of claim 12, wherein the frame inter-arrival time is variable, and further comprising determining the frame-interarrival time with reference to information carried in the packets.

15. The method of claim 14, wherein the information carried in the packets is a time stamp.

16. The method of claim 12, further comprising:

detecting a lost packet;

increasing the transmission deadline variable by the frame inter-arrival time when the lost packet is detected.