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RRM and Roaming Support

RRM and Roaming Support. Zhun Zhong Philips 01/14/2003. 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?

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RRM and Roaming Support

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

  2. 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. 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

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

  5. 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. 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 • 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 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? • 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 • 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? • 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

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