Defining Cross-Layer Design
for
Wireless Networking
ICC 2003 Panel Discussion
Organizer: Junshan Zhang
Arizona State University
Challenges and Opportunities
 A central problem: How to efficiently transmit
heterogeneous traffic over wireless links?
 Physical-layer limits of wireless channel:
o time-varying fading, multipath, …
o co-channel interference, hostile jamming, …
o mobility, dynamic network topology, …
 Wireless networking:
o Applications: wireless Internet access, (tactical) ad hoc
networks, sensor networks
o Diverse requirements: high-bandwidth video and data, lowbandwidth voice and data
o Goal: reliable communication-on-the-move in highly dynamic
environments, QoS provisioning
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
o Which layers should respond to channel variations?
o What layers should be jointly optimized/designed?
o Complexity and scalability: cross-layer versus
layered module –- conflicting paradigms ?
Wireless Network Architecture
Do we need unified or different
methodologies for different networks?
o Ad hoc networks
o Wireless LAN
o Cellular networks
o New drivers: (dense) sensor networks?
 Existing paradigms: opportunistic scheduling, energyefficient MAC and routing, channel –aware data
compression, …
 A fundament issue: Would the advantages of crosslayer design lead to new network architecture?
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?
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.
Panel Format
 Panelist presentations (12-15 min each)
 Panelist observations/questions
 Open discussion with the audience
Enjoy the panel discussion!
Appended Remarks (from
Moderator)
Misconceptions:
o Cross-layer design means to get rid of
protocol layers.
o Cross-layer design requires to integrate all
protocol layers.
 Key to cross-layer design: A holistic
view of wireless networking.