Specifications

Scanning Phase
Summit WM Series WLAN Switch and Altitude Access Point Software Version 4.1 Technical Reference Guide
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● Compliant to all 802.11 standards
● Requires no connections between APs (i.e. only the APs that can hear each other participate in the
process)
The channel selection process has several phases:
● Scanning (localized site survey)
● Selection (pick the best channel)
● Negotiate (request to operate on the selected channel)
● Operate (begin operation on the channel selected)
Scanning Phase
During the scanning phase, each AP scans all of the channels available in the regulatory domain. The
APs search for other APs already operating on the channel, determine their signal strength, and locate
other sources of non-802.11 interference. This information is used to determine the best channel for this
AP to operate on.
In addition to listening for existing devices operating on the channel, the DRM APs notify other DRM
APs that they are in the process of selecting a channel. This serves the following purpose:
● Synchronize all DRM APs during the channel selection process (only applies to situations where all
APs are booting at the same time such as after a power failure).
Once the data is collected about existing APs operating on all channels in the environment and other
DRM APs that are booting, DRM APs move onto the Selection phase.
Selection Phase
This phase determines the best channel to operate on. In DRM Version 1.0, the algorithm scans the
information obtained in the scanning phase looking for the loudest transmitting device on each channel.
The result is a list similar to the following:
Each channels loudest signal is captured. These signals are scanned and the channel with the quietest
signal is selected. In the example above, Channel 6 would be selected because -50dSummit is the
weakest signal.
The selection process for DRM Version 1.2 is quite a bit more sophisticated. The information obtained in
the scanning phase is fed into an algorithm to create a Channel Quality Index (CQI). The channel with
the lowest CQI is then selected as the best channel. The CQI is computed using the following
information:
● Loudest transmitting device operating on a channel
● Noise floor of the channel
Channel 1: -32dSummit
Channel 6: -50dSummit
Channel 11: -29dSummit