1. Multi-channel, multi-radio
COSC 6590
Fall 2007

2. Single Channel: Capacity
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)

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

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

6. Solution 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, GHz, GHz, GHz, GHz, GHz, GHz, GHz, GHz, GHz, GHz, GHz
Use multiple antennas to transmit and receive at the same time
wireless routers

7. Multi-channel Multi-radio Networks

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

9. Design Issues

10. Design Issues (2)

11. Design Issues (3)

12. Protocols

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

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