MeshLinx MWI-5000 User Guide
MESHLINX CONFIDENTIAL
8
7.1.2 Mode
Each wireless interface may be set to operate in one of four 802.11 modes, 11A, 11B,
11BG and 11G. Switching modes may have side-effects that must be anticipated. For
example, switching from 11A to 11B causes the selection of a new default channel
appropriate to that mode. More on this under each mode discussed below.11A Mode
11A mode selects the 5 GHz band (channels 36, 40, 44, 48 etc). The 5 GHz band has the
advantages of less interference than the 2.4 GHz band, more channels to choose from and
data rates up to 54 Mbps. Setting the mode of a wireless interface to 11A restricts
associations on that interface to stations operating in 11A mode.
One disadvantage of 11A mode is the regulatory domain specific restrictions on operating
in the presence of radar signaling. In the US, Europe and Australia, it is a requirement to
immediately vacate certain channels where known radar signatures are detected. The sets
of channels to be concerned about are 52 – 64 (US and Europe) and 100 – 140 (Australia,
parts of Europe and soon to be US).
The MWI-5000 will automatically monitor for known radar signatures when Spectrum
Management is enabled (see discussion of this parameter below). If radar signatures are
detected, the MWI-5000 will switch to a radar-free channel. The process of switching
channels may disrupt the quality of time-sensitive services like voice. Since radar
avoidance is required by law (see the 802.11h standard and associated FCC and ETSI
documents), this potential disruption is unavoidable when operating in affected channels.
7.1.2.1
11B Mode
11B mode selects the 2.4 GHz band (channels 1 through 11). The 2.4 GHz band is
considerably more congested than the 5 GHz band and is limited to data rates up to 11
Mbps. Setting the mode of a wireless interface to 11B restricts associations on that
interface to stations operating in 11B mode.
Select 11B mode when the BSS needs to support only 11B stations and not 11G stations.
7.1.2.2
11BG Mode
11BG mode selects the 2.4 GHz band (channels 1 through 11) in “mixed” mode. The 2.4
GHz band is considerably more congested than the 5 GHz band and is limited to data
rates up to 11 Mbps for 11B stations and 54 Mbps for 11G stations.
Note that the overall throughput for a station operating in mixed mode may be
significantly lower, due to 11G protection mode (self-CTS). 11G protection mode adds
some overhead to 11G transmissions to prevent them from impacting legacy 11B traffic.
The MWI-5000 (and participating 11G stations) automatically engage this mode when