1. Adaptive Video Streaming in Vertical Handoff: A Case Study Ling-Jyh Chen, Guang Yang, Tony Sun, M. Y. Sanadidi, Mario Gerla Computer Science Department, University of California at Los Angeles

2. MobiQuitous 20042 Aug. 24, 2004 Outline of the Talk The problem: the performance of video streaming may degrade due to wireless channel errors and vertical handoffs. Key idea:  Adaptive video delivery can improve the end user’s perceived quality.  Seamless handoff can provide uninterrupted services even with the presence of mobility. The results: we show that the combination of adaptive video streaming and seamless handoff can go a long way in providing better video streaming in mobile computing scenarios. Adaptive Video Streaming in Vertical Handoff: A Case Study

3. MobiQuitous 20043 Aug. 24, 2004 Introduction Mobile Computing Scenarios Adaptive Video Streaming in Vertical Handoff: A Case Study Mobility

4. MobiQuitous 20044 Aug. 24, 2004 Introduction (cont.) Three issues: 1. Seamless mobility across heterogeneous networks. 2. Adaptation to network dynamics such as wireless channel errors and congestion. 3. Application adaptation to maximize the end user’s perceived quality. Adaptive Video Streaming in Vertical Handoff: A Case Study

5. MobiQuitous 20045 Aug. 24, 2004 Background – Seamless Handoff Adaptive Video Streaming in Vertical Handoff: A Case Study A seamless handoff is defined as a handoff scheme that maintains the connectivity of all applications on the mobile device when the handoff occurs.

6. MobiQuitous 20046 Aug. 24, 2004 Background – Seamless Handoff Two goals: low latencies and few packet losses Related Work  Network Layer Approaches  MIPv4, IPv6  Upper Layer Approaches  End-to-End Approaches (e.g. Dynamic DNS)  New Session Layer Protocols (e.g. MSOCKS)  Transport Layer Protocols (e.g. TCP-MH and SCTP)  Middleware Approach (e.g. USHA) Q: Which seamless handoff solution are you using? Adaptive Video Streaming in Vertical Handoff: A Case Study

7. MobiQuitous 20047 Aug. 24, 2004 Proposed Approach: USHA NAT Server All packets are encapsulated and transmitted using UDP NAT server Applications are bound to the tunnel and transparent to the handoff. Universal Seamless Handoff Architecture Adaptive Video Streaming in Vertical Handoff: A Case Study

8. MobiQuitous 20048 Aug. 24, 2004 Real-time streaming adapt sending rate and stream quality Best-effort streaming adapt sending rate Background – Video Streaming SCP RAP TEAR TFRC VTP Helix Microsoft Adaptive Video Streaming in Vertical Handoff: A Case Study

9. MobiQuitous 20049 Aug. 24, 2004 Proposed Approach: VTP Video Transport Protocol 1. Bandwidth Estimation Achieved Rate Measurement: Available Bandwidth Estimation: Assume we use packet trains of length k to measure the achieved rate. Denote d i as the number of bytes in packet i, t i as the time when packet i arrives at the client. Adaptive Video Streaming in Vertical Handoff: A Case Study

10. MobiQuitous 200410 Aug. 24, 2004 Proposed Approach: VTP (cont.) 2. Rate Adaptation: Multiple streams of the same content are encoded at different rates. DR: Decreasing Rate State IR: Increasing Rate State Q0: Lowest Quality Video (56Kbps) Q1: Normal Quality Video (150Kbps) Q2: Highest Quality Video (500Kbps) Adaptive Video Streaming in Vertical Handoff: A Case Study

11. MobiQuitous 200411 Aug. 24, 2004 Proposed Approach: VTP (cont.) 3. Variable Bit Rate (VBR) Video  VTP divides a video clip into a number of segments.  For each segment, VTP computes a target rate, at which neither buffer overrun or underrun should occur.  Since video streams are pre-stored, instantaneous sending rates are available beforehand, and so are the target rates of the segments.  VTP applies these target rates to the finite state machine for rate adaptation. Adaptive Video Streaming in Vertical Handoff: A Case Study

12. MobiQuitous 200412 Aug. 24, 2004 Experiments VTP server/client are implemented on Linux. USHA system is set up on Linux, with custom configured NAT and IP tunneling. VTP client is connected to the Internet via 802.11b and 1xRTT, which is provided by Verizon Wireless. Two vertical handoff scenarios are tested: 1. From 1xRTT to 802.11b 2. From 802.11b to 1xRTT Adaptive Video Streaming in Vertical Handoff: A Case Study

13. MobiQuitous 200413 Aug. 24, 2004 Experiments: 1xRTT to 802.11b Non-adaptive Video Streaming Frame Rate received at the Mobile HostSending Rate at the Video Server Adaptive Video Streaming in Vertical Handoff: A Case Study

14. MobiQuitous 200414 Aug. 24, 2004 Frame Rate received at the Mobile Host Experiments: 1xRTT to 802.11b Adaptive Video Streaming Sending Rate at the Video Server Video Quality sent at the Video Server Adaptive Video Streaming in Vertical Handoff: A Case Study

15. MobiQuitous 200415 Aug. 24, 2004 Experiments: 802.11b to 1xRTT Non-adaptive Video Streaming Frame Rate received at the Mobile HostSending Rate at the Video Server Adaptive Video Streaming in Vertical Handoff: A Case Study

16. MobiQuitous 200416 Aug. 24, 2004 Frame Rate received at the Mobile HostVideo Quality sent at the Video Server Experiments: 802.11b to 1xRTT Adaptive Video Streaming Sending Rate at the Video Server Adaptive Video Streaming in Vertical Handoff: A Case Study

17. MobiQuitous 200417 Aug. 24, 2004 Discussion Drastic changes in the link capacity are often associated with vertical handoffs. Most traditional streaming algorithms incorporate the well-known slowly-responsive congestion control (SlowCC) and thus cannot take aggressive advantage of the rapid change of resources in emerging vertical handoff scenarios. Adaptive Video Streaming in Vertical Handoff: A Case Study

18. MobiQuitous 200418 Aug. 24, 2004 Discussion (cont.) For a handoff from LOW to HIGH, VTP can properly and rapidly adapt its sending rate and video quality to available bandwidth, and hence is successful in handling vertical handoffs. For a handoff from HIGH to LOW, application performance would benefit if the server could predict the handoff and thus adapt its sending rate in advance. Adaptive Video Streaming in Vertical Handoff: A Case Study

19. MobiQuitous 200419 Aug. 24, 2004 Conclusion We studied the need and evaluated the performance of adaptive video streaming in vertical handoff scenarios. Experiments with handoffs from 1xRTT to 802.11b and vice versa have been carried out to evaluate the performance of our proposed solution. Such a combination of adaptive video streaming and seamless vertical handoff will become desirable in the emerging ubiquitous mobile computing environment. Adaptive Video Streaming in Vertical Handoff: A Case Study

20. MobiQuitous 200420 Aug. 24, 2004 T h a n k s ! Adaptive Video Streaming in Vertical Handoff: A Case Study