1. Defining Cross-Layer Design for Wireless Networking ICC 2003 Panel Discussion Organizer: Junshan Zhang Arizona State University

2. Challenges and Opportunities  A central problem: How to efficiently transmit heterogeneous traffic over wireless links?  Physical-layer limits of wireless channel: otime-varying fading, multipath, … oco-channel interference, hostile jamming, … omobility, dynamic network topology, …  Wireless networking: oApplications: wireless Internet access, (tactical) ad hoc networks, sensor networks oDiverse requirements: high-bandwidth video and data, low- bandwidth voice and data oGoal: reliable communication-on-the-move in highly dynamic environments, QoS provisioning

3. Why and How to do Cross-Layer Design  Why: o There exists direct coupling between physical layer and upper protocol layers o Is cross-layer design the only approach to meeting the fast-growing demands?  How: Adaptive protocol design oWhich layers should respond to channel variations? oWhat layers should be jointly optimized/designed? oComplexity and scalability: cross-layer versus layered module –- conflicting paradigms ?

4. Wireless Network Architecture  Do we need unified or different methodologies for different networks? oAd hoc networks oWireless LAN oCellular networks oNew drivers: (dense) sensor networks?  Existing paradigms: opportunistic scheduling, energy- efficient MAC and routing, channel –aware data compression, …  A fundament issue: Would the advantages of cross- layer design lead to new network architecture ?

5. Academic Research on Cross-Layer Design  Is cross-layer design short-term or long-term?  Research focus: theory, algorithm and/or simulation?  Funding sources: government? industry?  What advice would you give to new graduate students looking for thesis topics?

6. Our Panelists  Prof. Anthony Ephremides, U. Maryland  Prof. Lang Tong, Cornell U.  Prof. Andrea Goldsmith, Stanford U.  Prof. P.R. Kumar, UIUC Moderator: Junshan Zhang, Arizona State U.

7. Panel Format  Panelist presentations (12-15 min each)  Panelist observations/questions  Open discussion with the audience Enjoy the panel discussion!

8. Appended Remarks (from Moderator)  Misconceptions: o Cross-layer design means to get rid of protocol layers. oCross-layer design requires to integrate all protocol layers.  Key to cross-layer design: A holistic view of wireless networking.