Multicast instant channel change in IPTV systems 1

Outline  Introduction  Instant Channel Change  Conclusion  Experimental Result 2

INTRODUCTION 3

Objective  Traditional Instant Channel Change (ICC)  Having a separate unicast for every user change channel.  We propose a multicast-based approach  Using a secondary “channel change stream” associated with each channel.  Carrying only I-frame and associated audio.  The drawback is the 50% additional capacity required. 4

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Network Architecture 6

 Content Source & D-Server  Content is buffered at Distribution Server (D-Server) in the Video Hub Office (VHO)  A separate D-Server could be used for every channel  All D-Server share the link to the VHO  Metro Network  Connects the VHO to a number of Central Offices (CO)  Is usually an optical network with significant capacity 7

INSTANT CHANNEL CHANGE 8

1. Join Current Approach (Unicast ICC) 9 D-Server Multicast Router TV Client

2. Unicast a stream with a higher bit rate 1. Join Current Approach (Unicast ICC) 10 D-Server Multicast Router TV Client

3. Start display 2. Unicast a stream with a higher bit rate 1. Join Current Approach (Unicast ICC) 11 D-Server Multicast Router TV Client

3. Start display 4. Join multicast 2. Unicast a stream with a higher bit rate 1. Join Current Approach (Unicast ICC) 12 D-Server Multicast Router TV Client

5a. Multicast stream 3. Start display 4. Join multicast 2. Unicast a stream with a higher bit rate 1. Join Current Approach (Unicast ICC) 13 D-Server Multicast Router TV Client

5b. Display full quality video 5a. Multicast stream 3. Start display 4. Join multicast 2. Unicast a stream with a higher bit rate 1. Join Current Approach (Unicast ICC) 14 D-Server Multicast Router TV Client

Drawback  The number of concurrent ICC requests is small.  When there are a number of concurrent ICC requests:  substantial load on the network.  service provider have to deploy additional servers. 15

Multicast ICC (Motivation)  Unicasting the same stream for a given channel is wasteful.  It is sufficient for the user to briefly (for 1-2 seconds) see a lower quality.  There are bandwidth constraint on the links from the DSLAM to CO.  To limit the number of concurrent streams delivered to a particular DSLAM. 16

Multicast ICC  Secondary lower-bandwidth channel change stream corresponding to each channel at the D-Server  This stream will consists of I-frame only  Each channel will add another IP multicast group called the “Secondary ICC Multicast Group” 17

Multicast ICC 18 Multicast Replicator TV Client 1. Join

2a. I-frame stream Multicast ICC 19 Multicast Replicator TV Client 1. Join

2a. I-frame stream 2b. Primary multicast stream Multicast ICC 20 Multicast Replicator TV Client 1. Join

2a. I-frame stream 2b. Primary multicast stream Multicast ICC 21 Multicast Replicator TV Client 1. Join 3. Display the frame from I-frame stream

2a. I-frame stream 2b. Primary multicast stream Multicast ICC 22 Multicast Replicator TV Client 1. Join 3. Display the frame from I-frame stream 4. Buffering the primary stream

2a. I-frame stream 2b. Primary multicast stream Multicast ICC 23 Multicast Replicator TV Client 1. Join 3. Display the frame from I-frame stream 4. Buffering the primary stream 5. Play the full quality video

CONCLUSION 24

 Requires approximately 50% additional capacity for each channel.  The requirement is relatively independent of, and does NOT grow with, the user population request.  Does not take into account the command processing delay time? 25

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EXPERIMENT 27

Tool & Objective  Build and NS-2 simulation of the metro/access network and the VHO servers.  The link between the CO and the DSLAM and the D-Server I/O were the bottlenecks.  To evaluate the unicast and multicast schemes in terms of:  Bandwidth consumption  Display latency  Channel switch latency  D-Server I/O 28

NS-2 Settings  With NS-2 simulation constraints, we set  The number of channels at the DSLAM to 10.  The link capacity of DSLAM →CO to 200 Mbps.  The simulation was run for 150 seconds. 29

Channel Change Requests  The empirical distribution of the channel change requests across all channels initiated from all users. 30

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Popular Channel & D-Server I/O  The channel change requests for the most popular channel at a D-Server collected.  The key bottleneck we examine here is the D-Server I/O.  The popularity of channel is defined by the largest number of users changes. 34

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Q & A Thanks 38