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

2. Month 2002
doc.: IEEE /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

3. 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

4. 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

5. 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 IEEE protocol
Black/Orava/Haverinen, Nokia

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