NSF Workshop on Bridging the Gap between Networking and Physical Layer Research

1. NSF Workshop on Bridging the Gap between Networking and Physical Layer Research Breakout Group #2 Reston, VAAug 27-28, 2007

2. The PHY-NET “Gap” Technology Theory V2V Networks Mesh Networks Queueing Theory Network Models Cross Layer Routing Relay Nodes Economic Models Cross Layer Designs Generalized MAC New Models & Tools Decentralized RRM Algorithms The Gap! Network Optimization Network IT PHY Layer Abstractions Security Algorithms Radio Resource Algorithms Network Coding MIMO Spectrum Algorithms Information Theory Collaborative PHY Cognitive Radio Modern Codes (LDPC, etc.) PHY-NET gap more pronounced as wireless networks migrate from single hop/centralized control to multi-hop/decentralized control  Timely for the community to try and close the gap through collaboration and increased awareness across sub-disciplines

3. Physical Layer Perspective • New generation of codes (LDPC, turbo, etc.) • MIMO now in the technology mainstream • Cognitive radio and dynamic spectrum emerging • Recent progress on collaborative PHY and network coding, particularly on the theory side • Near-future PHY advances may have a significant impact on network design: • Potential for major performance gains • Involve a new kind of radio API (abstraction) • Need to re-evaluate conventional PHY/MAC/net layers • Require protocol support for distributed control

4. Network Layer Perspective • Wireless network research at a particularly active stage due to: • Increasing availability of commodity radios • Moore’s law improvements in bit-rate • Economic viability of new applications • Development of future networking systems challenged by unique wireless medium • Still using old wired “link” model for radios • Existing (broadcast) and future (MIMO, network coding) yet to be exploited • Serious MAC layer issues in multi-hop networks • Need for generic radio API’s and software control • Performance of layered designs considered inadequate • Decentralized control protocols yet to be defined

5. Ideas for Bridging the Gap • Theory topics include: • New tools for PHY analysis (harmonizing combinatorial network models with continuous PHY models) • Tractable PHY models for improved realism/net technology • System models with source/session burstiness • Accounting for control protocol overheads • Improved interference models for multi-hop nets • Integrating mobility into theoretical models • Multi-hop network optimization • Impact of collaborative PHY & network coding on network performance • Delay as a key metric

6. Ideas for Bridging the Gap • Technology topics include: • Generalized PHY abstractions for use by network designers – describing MIMO, directional antennas, interference,… • Trade-offs between modulation, synchronization, soft error recovery, etc. • Location as a basic PHY parameter? • New concepts for multi-hop MAC – should this be a PHY+ issue? • Distributed radio resource management algorithms • Control protocol design and implementation • Cross-layer network protocols for discovery, routing, … • Decentralized monitoring and dissemination (..fault tolerance) • Practical protocols for network coding and collaborative PHY • New transport layer protocols (beyond TCP) and impact on applications

7. Recommendations to NSF • Focus on “PHY-NET gap” is timely  potential for large performance gains particularly in multi-hop networks • Collaborative team projects likely to be needed • Educational aspects (e.g. comm theory for CS majors and systems exposure for EE’s) should be considered • Establish a joint conference to encourage joint PHY/net research, improve mutual understanding • New PHY-NET research program on major challenges: • Unified IT/comm theory for wireless networks • Optimization of cross-layer systems • Decentralized control in multi-hop wireless • “open systems” protocols for cross-layer, collaborative PHY (….project ideas for each topic above given in earlier slides)

8. Participants • Dharma Agrawal • Michael Fang • Mingyan Liu • Rockey Luo • Urbashi Mitra • David Tse • Jie Wu • Edmund Yeh • Junshan Zhang • Kang Shin • D. Raychaudhuri