1. Qian Zhang and Christopher LIM Department of Computer Science and Engineering, Hong Kong University of Science and Technology IEEE ICC 2009

2. Outline Introduction Performance of existing channel assignment metrics Effective Channel Air Time (ECAT) Performance Evaluation Conclusion

3. Introduction To improve the system performance in wireless mesh network (WMN) Multiple channel Multiple radios The channel assignment for the APs with the access radio will affect the overall system City-wide WMN The mesh APs are densely deployed It will interfere with each other

4. Introduction To proposed a new channel assignment metric The Effective Channel Air Time (ECAT) The traffic in the adjacent channels has been explicitly taken into account The channel condition estimation can be provided

5. Performance of existing channel assignment metrics Existing channel assignment metrics Traffic volume based metric Packet delay based metric Channel time based metric

6. Traffic volume based metric The metric has two problem An 802.11 frame can transmit at various rates

7. Packet delay based metric

8. Channel time based metric It calculates the channel-time that used for frame transmission Channel busy time Channel idle time

9. Testbed configurations Each of mesh APs associated with 2 clients Clients continuously download tftp data

10. Experiments on the accuracy of CAT Traffic from different adjacent channel and how it affect the current channel bandwidth Access radio are set to channel 13

11. Experiments on the accuracy of CAT The effect of distance between the transmitting node and interfering node

12. Experiments on the accuracy of CAT The accuracy of CAT metric The RSSI of the interfering nodes is of 77-79

13. Experiments on the accuracy of CAT The accuracy of CAT metric The RSSI of the interfering nodes is of 59-62

14. Effective Channel Air Time (ECAT) The experiments demonstrated CAT channel metric tends to underestimate the channel’s utilization

15. Effective Channel Air Time (ECAT) It can have a effectiveness channel air time of channel N The CAT of that channel The busy period in its overlapping channel The neighboring channels and the neighbor’s neighboring channel Busy period

16. Effective Channel Air Time (ECAT) The maximum RSSI signal measured at the mesh AP The maximum transmitter’s power measured at transmitter’s channel

17. Effective Channel Air Time (ECAT) The maximum transmitter’s power measured at the channel i

18. Effective Channel Air Time (ECAT)

20. Performance Evaluation Lab environment testing

21. Performance Evaluation Real-world environment testing

22. Conclusion To discuss the performance of a hierarchical multi-radio mesh network To introduce a new metric to estimate the channel utilization Real experiments demonstrated that ECAT gives a more accurate measurement about the channel utilization