Bands and channels
It is well known that a wifi network uses radio waves that are transmitted in the 2.4 and 5 GHz bands. Each of these bands contains a number of nearby frequencies that we call channels. There are differences per region, but there are also sufficient matching parts that certified equipment must work worldwide. For the Netherlands and most European countries, the 5 GHz frequency contains 19 channels, each 20 MHz wide, that do not overlap, while the 2.4 GHz band consists of 13 channels, also 20 MHz wide, that do overlap - with the exception of channels 1, 6 and 11.
When you create a wireless network, your router chooses a channel for all data transmissions between your router, access point(s) and clients. Each channel has a limited bandwidth, which determines how much data can be sent at the same time. The minimum channel width is 20 MHz, which usually allows the most stable connection, with the downside that the amount of data that can be transported is limited.
Since the 802.11n standard it is possible to combine channels, also called channel bonding. This way the bandwidth and the amount of data per time unit can increase. In short, the wider your composite channel is, the fewer evasive options there are in the event of a failure or congestion. After all, the 5 GHz band offers 19 channels of 20 MHz, 9 channels of 40 MHz, 5 channels of 80 MHz or 2 channels of 160 MHz. Moreover, almost every router automatically searches for a channel where it finds as little interference as possible from other devices, and this naturally becomes more complicated as the available space, i.e. the bundling of frequencies, consists of fewer separate parts, i.e. wider channels.
In addition, some of the frequency areas where the 19 channels mentioned above can be found are in a non-exclusive part of the spectrum. This area is also used, for example, by radar systems, which have priority over home users' Wi-Fi networks. These so-called dynamic frequency selection (dfs) channels may be used as long as they are not used for other purposes. If your router detects otherwise, it must immediately leave the channel in question. This means that if you need a reliable network in the first place, without the Dfs channels you will only have 4 channels of 20 MHz, 2 of 40 MHz or only 1 of 80 MHz left.
160 MHz because it can be done
This makes the support for 160 MHz wide channels in the 802.11ac wave 2 standard mainly a theoretical matter. As you can see from the diagram, the chance of a interference-free channel with this width is nil, unless you live in the middle of nowhere. For that reason 802.11ac routers are usually set to a maximum of 80 MHz. Under the motto 'because it can be done' we will soon see if and if so how much extra throughput the Killer Wireless-AC 1550 in combination with the R9000 manages to realize at 160 MHz, compared to a 'regular' channel width of 80 MHz.