User's Manual

17
DragonWave Inc. Features
3.5 Dynamic Frequency Selection (DFS)
Radar detection is required when Lite operates on channels that have a nominal band-
width falling partly, or completely, within the frequency range from 5250 MHz to 5350
MHz, or 5470 MHz to 5725 MHz.
Furthermore, Lite does not share the channel with other device, so beside radar signal,
once Lite detected other equipment operating on the same channel, it will automatically
switch to another channel.
Lite implements DFS according to EN 301 893, EN 302 502, FCC 47CFR part 15 oper-
ating as a master.
Accordingly, the operational behavior and individual DFS requirement that are associ-
ated with Lite are as follows:
• At installation (or re-installation), it is assumed to have no available channels within
the 5250 MHz to 5350 MHz band and/or the 5470 MHz and 5725 MHz band. In such
a case, before starting operations on one of those channels, the equipment performs
a channel availability check (CAC) to ensure that there is no radar operating on the
channel. If no radar has been detected, the channel becomes an available channel
and remains as is until a radar signal is detected during the in-service monitoring.
There will be no transmissions by Lite within the channel being checked during this
process.
• Once Lite has started operations on an available channel, that channel becomes the
operating channel. During normal operation, the operating channel will be monitored
(in-service monitoring) to ensure that there is no radar operating on the channel.
• If a radar signal or signal from other device is detected during in-service monitoring,
Lite devices in the link will stop transmitting on this channel which becomes an
unavailable channel.
• An unavailable channel becomes a usable channel after the non-occupancy period.
A new CAC is required to verify that there is no radar operating on the channel,
before it may be used again. If no radar is detected, the channel becomes an avail-
able channel once again.
3.6 Dynamic Channel Selection (DCS)
Besides DFS required by regulation, Lite also implements DCS to dynamically select the
working channel according to the interference level, because the interference from co-
channel and adjacent channels may affect the performance of Lite.
• Spectrum scan
Before occupying a channel, Lite must scan the current band and select the best
channel as the operation channel.
After the spectrum scan, Lite will give a graphic report of the interference level of
each 20 MHz channel.
• In-service monitoring
After occupying a channel, Lite executes in-service monitoring to detect if there is
interference from co-channel or adjacent channel.
By monitoring the errors on the physical layer, Lite can count the PHY error, channel
utilization ratio and packet error rate to determine whether to change to another
channel.