1. CS541 Advanced Networking 1 Wireless Mesh Networks Neil Tang 1/26/2009

2. CS541 Advanced Networking 2 Outline  Network Architecture  Characteristics  Applications  Major Concerns  MAC Layer Challenges  Network Layer Challenges  Cross-layer Optimization  Placement Problems

3. CS541 Advanced Networking 3 Wireless Mesh Network (WMN) Mesh Client Mesh Router Mesh Router/Gateway WLANWireless Sensor Network Cellular Network Internet Mesh Router/Gateway Mesh Router Wireless Mesh Backbone Mesh Router

4. CS541 Advanced Networking 4 Network Architecture  Infrastructure/Backbone WMNs  Client WMNs: MANET  Hybrid WMNs: MANET + Backbone WMN

5. CS541 Advanced Networking 5 Hybrid WMN

6. CS541 Advanced Networking 6 Characteristics  Multihop wireless network.  Stationary mesh routers, and stationary/mobile mesh clients.  Mesh routers are connected with AC power but mesh clients are usually powered by battery.  Multi-radio and multi-channel  Various physical layer techniques, e.g., OFDM/OFDMA, directional antenna, cognitive radio

7. CS541 Advanced Networking 7 Applications  Broadband Internet Access  Emergency Networking  Community and Neighborhood Networking  Transportation System  Surveillance Systems.

8. CS541 Advanced Networking 8 Major Concerns  Throughput  Fairness  QoS  Scalability  Compatibility and inter-operability.  Security

9. CS541 Advanced Networking 9 MAC Layer Challenges  Channel assignment: > Static > Dynamic  Scheduling-based MAC (TDMA) Design: Find a collision-free transmission schedule with the objective of improving throughput, fairness, QoS.  Scalability: distributed channel assignment and scheduling algorithms are needed.  Various physical layers: directional antenna, cognitive radio

10. CS541 Advanced Networking 10 Network Layer Challenges  Routing mechanism: on-demand vs. proactive  Routing metric design: load balancing and intra-flow interference must be addressed.  End-to-end QoS support: intra-flow interference must be addressed.  Multicast/Broadcast Routing

11. CS541 Advanced Networking 11 Cross-layer Optimization Under dynamic traffic model:  Static channel assignment + joint routing and scheduling  Joint routing, scheduling and channel assignment Under static traffic model:  Static channel assignment + joint congestion control, routing and scheduling  Joint congestion control, scheduling and channel assignment  Joint congestion control, scheduling, routing and channel assignment  Joint congestion control, scheduling, routing, power control and channel assignment If using 802.11MAC, no need to consider scheduling.

12. CS541 Advanced Networking 12 Placement Problems  Mesh router (access point placement): place minimum number of mesh router to cover a region or a set of points (houses) such as the traffic demands can be satisfied.  Gateway placement: select minimum number of mesh routers as gateway such as the traffic demands can be satisfied.