Pekko Orava, Henry Haverinen, Simon Black (Nokia) Month 2002 doc.: IEEE 802.11-02/xxxr0 July 2003 Adaptive Beaconing Pekko Orava, Henry Haverinen, Simon Black (Nokia) TGk July 2003 Black/Orava/Haverinen, Nokia John Doe, His Company

Month 2002 doc.: IEEE 802.11-02/xxxr0 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 May be the only mechanism available when joining due to the lack of regulatory domain knowledge Black/Orava/Haverinen, Nokia John Doe, His Company

July 2003 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

Beacon overhead Beacon overhead is quite low July 2003 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

Short Beacon intervals best for RRM July 2003 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

Adaptive Beaconing Not a new IEEE802.11 Beacon protocol!! July 2003 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

Proposal Summary The objective is to enhance passive STA BSS discovery July 2003 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