1. RRM and Roaming Support
January, 2003
RRM and Roaming Support
Zhun Zhong
Philips
01/14/2003
Zhun Zhong, Philips

2. Outline What is the problem?
January, 2003
Outline
What is the problem?
Long handoff interruption due to time consuming channel scanning.
What need to be done to solve the problem?
Provide STAs with neighboring AP channel information prior to handoff.
How to do it?
AP collects neighboring AP channel information and forwards it to STAs via special management frame.
Zhun Zhong, Philips

3. Month 2002
doc.: IEEE /xxxr0
January, 2003
Background
To reduce interference, neighbor BSSs often operate on different channels
Typically a station can NOT simulaneously listen on more than one channels
To scan another channel, a station needs stop communication in its current channel
 Handoff interruption.
Zhun Zhong, Philips
John Doe, His Company

4. Handoff interruption January, 2003
Numbers are for illustration purpose
Zhun Zhong, Philips

5. January, 2003
Observations
Typical handoff processes we observed take up to hundreds of milliseconds.
Blindly channel scanning contributes most to the handoff service disruption.
Knowledge of neighbor APs’ operation channels helps to reduce the searching set thus accelerates the handoff process.
Zhun Zhong, Philips

6. January, 2003
Recommendations
To provide STAs with, at least, the information of immediate neighbor AP’s channel of operation to accelerate scanning process.
Extra information, if available, may be helpful for STAs to make optimal handoff decisions.
Zhun Zhong, Philips

7. Requirements Collection of neighboring AP channel information
January, 2003
Requirements
Collection of neighboring AP channel information
AP in the best position to collect neighboring APs’ channel information
Pre-configured by administrator
Via backbone
Other
A topic for subsequent submissions
Mechanism to transfer this knowledge to all the STAs in the service set
Zhun Zhong, Philips

8. Neighbor AP (BSS?) Information
January, 2003
Neighbor AP (BSS?) Information
Neighbor AP (BSS?) Information
Neighbor AP (BSS?) #1
Neighbor AP (BSS?) #2
Neighbor AP (BSS?) #N
Length
Other Information
BSSID
Channel
Zhun Zhong, Philips

9. Carrier Beacon? Probe Response? Special Management Frame
January, 2003
Carrier
Beacon?
Overhead (sent periodically)
Probe Response?
Lack of flexibility (only issued upon request)
Special Management Frame
Flexibility and low overhead
Seems to be a good choice
Zhun Zhong, Philips

10. Assistance, NOT Control
January, 2003
Assistance, NOT Control
How the STAs use this information should not be specified.
No mandatory change of STAs’ handoff behavior.
STA is the one that chooses how to scan the channels and makes its handoff decision.
Zhun Zhong, Philips

11. Conclusions What is the problem?
January, 2003
Conclusions
What is the problem?
Long handoff interruption due to time consuming channel scanning.
What need to be done to solve the problem?
Provide STAs with neighboring AP channel information prior to handoff.
How to do it?
AP collects neighboring AP channel information and forwards it to STAs via special management frame.
Zhun Zhong, Philips