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

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

Month 2002 doc.: IEEE 802.11-02/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

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

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

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

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

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

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

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

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