1. COSC 6590 Fall 2009 1 Multi-channel, multi-radio wireless networks

2. Single Channel: Capacity 2 Theoretical upper limit of the per node throughput capacity : Theoretically achievable capacity of every node in a random static wireless ad hoc network with ideal global routing and scheduling …

3. Single Channel: Capacity (2) 3

4. Single Channel: Capacity (3) 4 Experimental results from CSMA/CA MAC on a string topology. Throughput ≈ 1 / n

5. Reasons 5 Exposed terminal problem (main factor!) Hidden terminal problem High error rate on wireless channel MAC characteristics etc.

6. Solution 6 Multi-channel, multi-radio Use multiple frequencies to transmit on. 802.11a has 12 non overlapping channels in the 5GHz range. each channel is 20MHz wide 5.200 GHz, 5.180 GHz, 5.220 GHz, 5.240 GHz, 5.260 GHz, 5.280 GHz, 5.300 GHz, 5.320 GHz, 5.745 GHz, 5.765 GHz, 5.785 GHz, 5.805 GHz Use multiple antennas to transmit and receive at the same time wireless routers

7. Multi-channel Multi-radio Networks 7

8. Why use multi-channel, multi-radio? 8

9. Design Issues 9

10. Design Issues (2) 10

11. Design Issues (3) 11

12. Protocols 12

13. Summary 13 Multiple channels and multiple antennas will increase throughput. Any solution should support distribution of load across channels maintaining node connectivity broadcast abilities

14. References 14 10) “Wireless Mesh Networking” book, chapters 1 and 2