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Adaptive Beaconing

Adaptive Beaconing. Pekko Orava, Henry Haverinen, Simon Black (Nokia) TGk July 2003. Background. The Beacon protocol is a principle mechanism by which a STA can discover the presence of a BSS TGk already defines the Beacon Report to allow STAs to report received beacons

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Adaptive Beaconing

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  1. Adaptive Beaconing Pekko Orava, Henry Haverinen,Simon Black (Nokia) TGk July 2003 Black/Orava/Haverinen, Nokia

  2. Background • The Beacon protocol is a principle mechanism by which a STA can discover the presence of a BSS • TGk already defines the Beacon Report to allow STAs to report received beacons • May be the only mechanism available when joining due to the lack of regulatory domain knowledge Black/Orava/Haverinen, Nokia

  3. Beacons are useful! • Beacon frames contain most useful information about the BSS • Capabilities, supported rates, possibly load information • In an infrastructure BSS they come from the AP and thus give an indication of the signal quality from that AP • BSS timing • TGk proposal to add neighbourhood BSS/site information to Beacon frame further increases efficiency Black/Orava/Haverinen, Nokia

  4. Beacon overhead • Beacon overhead is quite low • Typically <0.5% of capacity, worst case about 1.5% (IEEE802.11b, 100TU beacon interval, 2Mbps beacons) • Active scanning can be quite costly in terms of overhead for non-directed probe request • Wait Probe Delay, transmit probe request and wait for either MinChannelTime (no response) or MaxChannelTime • Lack of a channel number in probe request may lead to adjacent channel responses with certain PHYs • Transmissions cost power Black/Orava/Haverinen, Nokia

  5. Short Beacon intervals best for RRM • The efficiency by which BSSs are discovered passively through beacons is improved by shortening the beacon interval • Shorter beacon interval leads to shorter scan times, faster discovery and lower power consumption • This increases overhead, but that may be acceptable at low load • Currently beacon interval is fixed and a core part of the IEEE802.11 protocol Black/Orava/Haverinen, Nokia

  6. Adaptive Beaconing • Not a new IEEE802.11 Beacon protocol!! • Propose to define a new ‘RRM beacon’ • A new RRM frame distinct from the existing beacon, but containing the same fields (with the exception of the TIM) • New frame ensures that there are not issues with legacy STAs • Signal quality, capabilities, timing information and possibly load provides complete information for a roaming decision. • RRM Beacon scheduled for transmission between existing beacons if BSS load is low • Frequency depends on BSS load • Add an element to the beacon to announce the presence of ‘RRM beacons’ and frequency in the next Beacon Interval Black/Orava/Haverinen, Nokia

  7. Proposal Summary • The objective is to enhance passive STA BSS discovery • Four elements: • Define a new RRM information frame containing the Beacon Information elements (with the exception of the TIM) • Access points send the information frame at low BSS loads only • Information frame is sent at regular intervals within a Beacon Period with interval dependent on BSS load • The presence of the frame is announced through a new information element within the Beacon Black/Orava/Haverinen, Nokia

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