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245U-E Wireless Ethernet Modem User Manual
Rev Version 2.24
3.1 Selecting a Channel
802.11b/g (2.4 GHz)
The 245U-E-G conforms to the IEEE 802.11b/g Wireless LAN specification. The 245U-E-G supports 13 x 20
MHz, 12 x 10 MHz and 13 x 5 MHz radio channels in the 2412 MHz to 2482 MHz frequency range. Channels
are country or region specific. Please check your local regulatory body for compliance and channel
selection.
Figure 20 shows that there are a limited number of channels available in the 2.4 GHz frequency range.
Care must be taken when selecting an operating channel, as some of the channels overlap. The 20-MHz
channels have a separation of 5 MHz, which means there is some overlap into the next channel. Channel
1 will overlap into channel 2, 3, and 4, channel 6 will overlap into channels 3, 4, 5, 7, 8 and 9. If complete
separation is required, you can use channels 1, 6 and 11 without any interference between the channels.
The 10 MHz channels are also separated by 5 MHz and overlap the adjacent channels by 5 MHz forward
and backward. Channel 41 will overlap with channel 42, channel 46 will overlap with channel 45 and 47.
The 5 MHz channels are separated by 5 MHz and do not overlap at all, so you can operate all 13 channels
at the same time with minimal interference from the adjacent channel.
Figure 19 Channel Separation
Only one of these channels is used at a time and is configured at the access point, The access point then
uses this channel to send out beacon transmissions and connections. Clients scan all channels for a suitable
access point and then adopt the same channel as the access point when a connection is established. Figure
20 shows the RF energy distribution for the 802.11b/g transmission.
Figure 20 2.4-GHz Frequencies
