1. Management in mobile wireless networks: The case for client-assistance
Suman Banerjee

2. Management in wired networks
Mostly performed through central entities
Firewalls
Nameservers
DHCP servers
A logical approach for many basic networking tasks
But needs some re-thinking in the wireless domain
Many properties in wireless domain are location-specific
Can only be observed at the clients and by the clients
The observation and experience of clients continuously change with their mobility

3. Impact of location Recvd: 1, 2, 4 AP-1 Client-A AP-2 Recvd: 1, 3, 4, 5
Sent: 1, 2, 3, 4, 5
Experience is property of location and cannot be always replicated

4. Client-assisted management
AP-1
Mgmt. module
Controller
AP-2

5. Client-assisted management
AP-1 B C ?
Controller
AP-2
Controller: Is there interference between clients B and C?

6. Client-assisted management
AP-1 B
Tx at time t C
Rx at time t
and report
Controller
AP-2
Controller: Is there interference between clients B and C?
- Interference test

7. Client-assisted management
AP-1 B C
Yes
Controller
AP-2
Client C: Yes, interference exists

8. Client-assisted management
AP-1 B No C
Controller
AP-2
At a later time (due to mobility):
Client C: No, interference does not exist

9. Applications of client-assisted management
Any RF management in a wireless network
Capacity and coverage planning
Interference mitigation
Hole detection
Network-wide transceiver parameter tuning
Power control
Channel assignment
User association, etc.
Policy provisioning
Wireless security

10. Example I: Channel assignment
AP-2
AP-3
AP-1
What channels to assign to APs?

11. Example I: Channel Assignment
AP-2
AP-3
AP-1
What channels to assign to APs? LCCS may assign same to all APs

12. Example I: Channel Assignment
AP-2
Interference
AP-3
AP-1
Correct answer depends on client distribution and association

13. Example I: Channel Assignment
AP-2
AP-3
AP-1
Correct answer should also adapt with client distributions

14. Example I: Channel Assignment
AP-2
AP-3
AP-1
Correct answer should also adapt with client distributions

15. Example I: Channel assignment
[Infocom 2006]
50 APs and 200 clients
Client-assisted
Throughput
Infrastructure-only

16. Example II: Performance characterization
Madison WiFi mesh
200+ APs
A few thousand clients
Performance on the
network is highly variable
Kind of information obtainable by instrumenting 1-2 clients over a few days
Exploits client mobility
Understand cause of variability, isolate performance problems, and automate remedial measures remains part of next steps

17. Example III: Hole detection

18. How do we implement a task?
A client-assisted management task would need to answer the following questions:
What tasklet should which clients perform and when?
What information to aggregate back from different clients (possibility of data fusion)?
How should an outcome be decided based on this aggregated data?
Of course, many more open issues …

19. Research agenda What functions do we need from clients?
Access to firmware? Driver? Application-layer?
How can we be minimally intrusive to clients?
Can we trust all client data equally?
How do we normalize across client feedback?
How can we preserve privacy of clients and networks?