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Efficient Handoff Optimization for Roaming Support in Wireless Networks

Addressing long handoff interruptions in wireless networks due to time-consuming channel scanning. Solution involves providing STAs with neighboring AP channel information prior to handoff. APs collect and forward this data to STAs through a special management frame. Observations, recommendations, requirements, and conclusions discussed in detail.

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Efficient Handoff Optimization for Roaming Support in Wireless Networks

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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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