1. Wireless Network Management Issues: Current 802.11 Limitations
July 2004
IEEE /0000r0
September 2004
Wireless Network Management Issues: Current Limitations
Joe Kwak, Marian Rudolf / InterDigital
Kwak, Rudolf
<include authors here>

2. July 2004
IEEE /0000r0
September 2004
Today
802.11a,b,g
Association/Re-association always initiated by non-AP STA
But Disassociation initiated by any STA (AP or not)
Minimal signaling to help STAs set their parameters
Supported rates, capability info
No spectrum or transmit power management
802.11h
Applies to 5 GHz band
Spectrum management (e.g. channel switch)
Transmission power constraint
802.11k in ballot
Measurement reports
Several new measurements
Kwak, Rudolf
<include authors here>

3. Need for Managed Frequency Relocation
July 2004
IEEE /0000r0
September 2004
Need for Managed Frequency Relocation
Kwak, Rudolf
<include authors here>

4. July 2004
IEEE /0000r0
September 2004
What we cannot do today
Interference in the 2.4 GHz band can be a problem
E.g. microwave oven, another WLAN system, etc.
Could be mitigated by switching to a less affected channel
Channel switch
Channel 11 – severe interference
Channel 1 – less interference
The AP can’t switch channel without disruption for STAs
Channel switch notification not available in 2.4 GHz band, limited in 5 GHz.
STAs have to re-associate to AP (or other AP) following the channel change
“Hard” service interruption not acceptable for voice or streaming users
Kwak, Rudolf
<include authors here>

5. July 2004
IEEE /0000r0
September 2004
What can we do?
DFS service of h applied to 2.4 GHz could be a starting point.
Some of the limitations of h should be addressed:
Fact that channel switch announcements are broadcasted means AP has no way of knowing if the associated STA(s) heard the announcement.
Even if the STA heard the announcement, the AP does not know if the STA can/will change channel or when it did.
This leads to the AP repeatedly transmitting buffered packets to STA that have not followed on the new channel.
Some sort of hand-shaking mechanism is desirable
Kwak, Rudolf
<include authors here>

6. Need for Managed Load Balancing
July 2004
IEEE /0000r0
September 2004
Need for Managed Load Balancing
Kwak, Rudolf
<include authors here>

7. Motives for Load Balancing
July 2004
IEEE /0000r0
September 2004
Motives for Load Balancing
Traffic in WLAN environments is characterized as being particularly non-uniform and bursty
Dynamic load balancing allows for a better distribution and more efficient use of the radio resources
The load balancing can be driven by:
The STA
The AP
Optimal performance achieved when load balancing is performed in a coherent and cohesive manner
Kwak, Rudolf
<include authors here>

8. Current situation STA-driven load balancing: AP-driven load balancing:
July 2004
IEEE /0000r0
September 2004
Current situation
STA-driven load balancing:
Some STAs have it, others don’t
Each manufacturer uses its own algorithms
No cohesion behind the decision-making
Hard to execute without compromising QoS (e.g. real-time services)
Optimal performance require new signaling  proprietary solutions
AP-driven load balancing:
Allows for a more coherent decision-making
AP can only disassociate STA, STA must initiate reassociation
Hard to satisfy QoS of real-time users
Optimal performance requires new signaling  proprietary solutions
Need for standardization - explicitly outside of r
WNM can envisage various levels of control that AP could have in load balancing
Kwak, Rudolf
<include authors here>

9. Various levels of control of AP for Load Balancing
July 2004
IEEE /0000r0
September 2004
Various levels of control of AP for Load Balancing
Low
AP sending special beacons on other channels to advertise itself when adjacent BSSs are more loaded
Medium
Lightly-loaded AP sending association requests to STAs served by highly loaded APs
High
Serving AP instructing STA to associate to another AP (may involve prior hand-shaking between APs)
Kwak, Rudolf
<include authors here>

10. September 2004
CONCLUSIONS
As work begins in WNM, scenarios describing current limitations and desired future functions will emerge.
WNM needs to address management of seamless BSS Frequency Relocation to mitigate against transient sources of interference.
WNM needs to address management of seamless Load Balancing to adapt to dynamic traffic loads.
Kwak, Rudolf