Cross-layer Design in Wireless Mesh Networks Hu Wenjie Computer Network and Protocol Testing...
-
Upload
sofia-figueroa -
Category
Documents
-
view
226 -
download
4
Transcript of Cross-layer Design in Wireless Mesh Networks Hu Wenjie Computer Network and Protocol Testing...
Cross-layer Design in
Wireless Mesh Networks
Hu Wenjie
Computer Network and Protocol Testing Laboratory,
Dept. of Computer Science & Technology, Tsinghua Univ.
Saturday, February 16, 2008
Outline
Introduction to the Wireless Mesh Networks
Motivation of Cross-layer design
Recent Cross-layer design schemes
Negative consequences of Cross-layer design
Conclusions
Saturday, February 16, 2008
Introduction to the Wireless Mesh Networks
Centralized Wireless Networks
Distributed Wireless Networks
mesh router
mesh client
mesh router
mesh router
mesh router
mesh router
mesh client
mesh client
mesh client
mesh client
mesh client+
Wireless Mesh
Networks
Traditional •Easy
management
•Easy update
•Unbalanced load
•Small coverage area
•Large Coverage area
•Balanced load
•Dynamic topology
•Hard management
Saturday, February 16, 2008
Introduction to the Wireless Mesh Networks
mesh router
mesh client
mesh router
mesh router
mesh router
mesh router
mesh client
mesh client
mesh client
mesh client
mesh client
Mesh Routers:•Infrastructure•Almost stable•No power limitation•Multiple Wireless Interface•Routing/Bridge/Gateway
Mesh Clients:•Mobile•Battery powered•One Wireless Interface•Routing
Saturday, February 16, 2008
Motivation of Cross-layer design
Unreliable of physical layer:• Various wireless technology
IEEE 802.11,802.16,3G various capacity, bit error rate• Advanced physical technology
Multiradio/multichannel, directional antenna, MIMO
Conclusion1: MAC, routing, and transport protocols have to work together with the physical layer.
A B
Saturday, February 16, 2008
Motivation of Cross-layer design
Multi-hop:• Accumulated effect
Performance degradation
• Local vs. Global optimization
MAC layer vs. Routing, Transport layer
A
B
C
D
E
Conclusion2: MAC, routing, and transport protocols need to work collaboratively among themselves.
Saturday, February 16, 2008
Cross-layer Design Schemes
According to the relationship of different layers:
1. Loosely-coupled
Use parameters in other protocol layers
• Don’t totally abandon the transparency between layers
• Limited improvement
2. Tightly-coupled
Different layers are optimized together
Extreme: merge different protocol layers into one layer
• Better performance
• Lose protocol layer abstraction
Saturday, February 16, 2008
MAC/PHY Cross-layer Design
PHY
MAC
Routing
Transport
Application
TCP/IP protocol
stackphysical layer can provide: OFDM, UWB, multiradio/multichannel, MIMO, etcMAC layer can provide: The function to tune the parameters to achieve optimal performance
Saturday, February 16, 2008
Routing/MAC Cross-layer Design
PHY
MAC
Routing
Transport
Application
TCP/IP protocol
stack
The routing performance is poor if the MAC layer doesn’t provide satisfying performance. The information in MAC layer, such as link quality, interference level, traffic load information and channel allocation, is also important to determine the best routing path.
Saturday, February 16, 2008
Transport/PHY Cross-layer Design
PHY
MAC
Routing
Transport
Application
TCP/IP protocol
stack
TCP has to use physical information to determine real congestion or poor quality in a link. When the link is congested, the physical layer can turn down the transmit power to avoid congestion. If the link quality is low, the physical layer can adjust coding rate or transmit power to enhance the quality.
Saturday, February 16, 2008
Negative Consequences of Cross-layer Design
Reason: destroy the protocol layer abstraction
Spaghetti design
Incompatibility with existing protocols
Difficulty in maintenance and management
Saturday, February 16, 2008
Conclusion
Cross-layer design:
•Optimal performance
•Loss of good architecture
TCP/IP protocol:•Good architecture
•Low performance
A New Protocol Stack!
Saturday, February 16, 2008
Thank you!