Cross-Layer Wireless Multimedia Transmission: Challenges, Principles, and New Paradigms

1. Cross-Layer Wireless Multimedia Transmission: Challenges, Principles, and New Paradigms IEEE Wireless Commun., Aug. 2005 Mihaela Van Der Schaar, UC Davis Sai Shankar N, Qualcomm Inc., USA

2. Outline • Introduction • The Cross-Layer Design Problem • Classification of Cross-Layer Solutions • More Problems • New Paradigm

3. Introduction • Existing wireless networks provide only limited, time-varying quality of service (QoS) for delay-sensitive, bandwidth-intense, and loss-tolerant multimedia applications. • Real-time multimedia applications need that the application layer cooperatewith the lower layers to select the optimal wireless transmission strategy that maximizes multimedia performance.

4. Introduction (cont.) • Layered optimization leads to a simple independent implementation, but results in suboptimal multimedia (objective and/or perceptual quality) performance.

5. The Cross-Layer Design Problem • The cross-layer design problem is formulated as an optimization with the objective to select a joint strategy across multiple OSI layers.

6. The Cross-Layer Design Problem (cont.) • Let NP, NM, and NAdenote the number of adaptation and protection strategies available at the PHY, MAC, and APP layers, respectively.

7. The Cross-Layer Design Problem (cont.)

8. The Cross-Layer Design Problem (cont.)

9. The conceptual framework

10. Challenging • The functions of Q, Delay, and Power are non-deterministic and non-linear, and there are dependencies between some of the strategies. • The traditional algorithms and protocols at the various layers are often designed to optimize each layer independently and often have different objectives.

11. Challenging (cont.) • Formal procedures are required to establish optimal initialization, groupingof strategies at different stages and ordering. [那幾層可合併, 調整效能時由那一層控制為主] [Buffer size vs Delay vs re-try] • Different practical considerations for the deployed wireless standard.

12. Classification Of Cross-Layer Solutions • Top-down approach • Bottom-up approach • Application-centric approach • MAC-centric approach • Integrated approach

13. Top-down approach • The higher-layer protocols optimize their parameters and the strategies at the next lower layer. • This solution has been deployed in most existing systems.

14. Bottom-up approach • The lower layers try to insulate the higher layers from losses and bandwidth variations. • Not optimal for multimedia transmission. (unnecessary delays and throughput reductions)

15. Application-centric approach • The APP layer optimizes the lower layer parameters one at a time in a bottom-up or top-down manner, based on its requirements. • Not always efficient.

16. MAC-centric approach • The APP layer passes its traffic information and requirements to the MAC, which decides which APP layer packets/flows should be transmitted and at what QoS level. • The MAC decides the PHY layer parameters based on the available channel information.

17. Integrated approach • Exhaustively trying all the possible strategies and their parameters is impractical. • A possible solution to solve this complex cross-layer optimization problem in an integrated manner is to use learning and classification techniques

18. More problems • Fairness • Time • Air • MULTIMEDIA QUALITY

19. New Paradigm • Wireless stations can exchange information and distribute resources. • Mixture of competition and cooperation. • D. Krishnaswamy and M. van der Schaar, “Adaptive Modulated Scalable Video Transmission over Wireless Networks with a Game Theoretic Approach,” Proc. IEEE MMSP. Wksp., Sept. 2004. • A Larcher et al., “Decentralized Transmission Strategy for Delay-Sensitive Applications over Spectrum Agile Network,” Packet Video 2004.

20. VoIP Video RTP/RTCP SCTP/UDP/TCP IPv4/IPv6 MIP/HMIP Mobile Management