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Chapter 2: Channel Widths

Once you have selected a base frequency range, you need to pick a “channel width.” Typically for Ubiquiti and Mikrotik equipment, these are available as 5mhz, 10mhz, 20mhz, 30mhz and 40mhz. With the advent of 802.11ac based equipment, even larger channel widths (up to 80 mhz) are becoming available. Channel width is a trade-off, and should be carefully considered.

Once you have selected a base frequency range, you need to pick a “channel width.” Typically for Ubiquiti and Mikrotik equipment, these are available as 5mhz, 10mhz, 20mhz, 30mhz and 40mhz. With the advent of 802.11ac based equipment, even larger channel widths (up to 80 mhz) are becoming available.

Channel width is a trade-off, and should be carefully considered. Factors to consider include:

A good rule of thumb for channel-width selection is to always: use the smallest channel-width that provides the bandwidth you require.

The following table summarizes throughput for 802.11N devices (assuming a 2x2 antenna array):

Channel Width Air-Encoding Max Actual Throughput Comment
5 Mhz 32.5 mbit/s 10-15 mbit/s Strongest signal
10 Mhz 65 mbit/s 20-30 mbit/s Strong signal.
20 Mhz 130 mbit/s 45-60 mbit/s Default.
30 Mhz* 200 mbit/s 65-90 mbit/s Requires good link.
40 Mhz 300 mbit/s 75-90 mbit/s Requires near-perfect link.

* - Ubiquiti equipment often handles 30 Mhz as a single, over-sized channel rather than the two channels utilized for 40 Mhz widths. As a result, some users find 30 Mhz channels to out-perform than 40 Mhz channel widths.

The following table summarizes available performance for the newly available 802.11AC range of devices (assuming a 2x2 antenna array):

Channel Width Air-Encoding Max Actual Throughput Comment
20 Mhz 346.7 mbit/s 150 mbit/s Strongest signal.
40 Mhz 800 mbit/s 200 mbit/s Requires good link.
80 Mhz 1.73 gbit/s 560 mbit/s Requires near-perfect link. Very few WISPs can spare 80mhz of spectrum!

Note that is very rare to see actual 80 mhz links in use – that is a lot of spectrum to dedicate to a single link!

« Chapter 2: Proprietary Cellular Protocols (WiMAX and LTE) Up To Contents Chapter 2: Polarity and MIMO »

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