ISP Wireless - Guide to Channel Width Selection
This article discusses advantages/disadvantages to using different channel widths in various deployment scenarios.
Introduction
For users that are new to the wireless ISP world, it is highly recommended that they first read our airMAX - Guide to airView Channel Scanning article that explains how to select the best frequency and channel width for outdoor links.
airMAX AC & LTU products follow the same basic rules, but there are some details that should be taken into account to get the very best out of the wireless link. In the following sections, we will describe the characteristics of different channel channel widths, and which is best for each scenario.
Narrow Channels
Narrow channels are those equal or narrower than 20MHz. They offer better radio sensitivity and better Signal-to-noise ratio (SNR), making them less susceptibility to noise, thus having better reliability, but "lower theoretical throughput". I emphasize "lower theoretical throughput", because even though they have less bandwidth available, which in theory would reduce the maximum throughput, in most cases the highest SNR level helps to achieve higher data rates and a more stable performance than wider channels.
However, in 802.11ac these channels will only be able to negotiate up to 11ac MCS8 (2 spatial streams) data rates, which could be an important factor if you need the highest throughput and your link has a very high signal strength. Narrow channels are ideal for video surveillance, VOIP and WISPs offering medium-speed plans using PtMP systems.
Medium Channels
Medium channels (between 30MHz and 50MHz) are probably the best choice for most cases where very high throughput is needed and the area's interference level is low. It's usually a good alternative for PtP networks and offer a balanced option between narrow and wide channels.
It is important to note that 30MHz channels only support 11ac MCS8 (2 spatial streams) rates. On the other hand 40MHz and 50MHz channels support up to 11ac MCS9 (2 spatial streams) data rates. Medium channels are ideal for high-performance PtP links and high-speed PtMP networks.
Wide Channels
Wide channels (60MHz and 80MHz) offer the ultimate throughput experience. They will support up to 11ac MCS9 data rates and throughput over 450Mbps. Unfortunately, these channels are very susceptible to interference because of the bandwidth used. They are only recommended when you have a very high signal strength and low interference (you can view how clean the RF spectrum is in your area using airView). Wide channels are ideal for highest-performance PtP links. Not recommended for PtMP networks.
Responsible Use of Spectrum
Ubiquiti ISP wireless devices use an unlicensed band, which is shared by all users (ex. 2.4GHz, 5GHz). Your interference could affect other users. In order to reduce the impact (and increase your own network reliability), we highly recommend that you use narrow channels in situations where you don't need the highest throughput. A good example of this would be video surveillance systems where a 10MHz channel is more than enough to stream full 1080p video.
Note: Please check your local regulations, different countries may have specific EIRP limits for certain frequencies and channel widths.