Brief introduction of Wireless Channel, Channel Width and DFS

1. What is channel?

In the 802.11 standard, the International Electro-Electronic Commission (IEEE) provides several radio frequency bands for Wi-Fi communications and divides these bands into smaller channels, some of which can be used by each networked system for wireless communications.

The 2.4GHz band has a frequency range of 2.4-2.4835 GHz, totaling about 83.5 MHz, and is divided into 14 channels (channel numbers 1-14). The range of channels that can be used varies from country to country, depending on regulations. The United States typically uses only channels 1 through 11, and most other countries can use channels 1 through 13.

For channels 1 through 13, the channel interval is 5 MHz, but the width of each channel is 22 MHz. Therefore, there is overlap between neighboring channels, which can lead to interference and degradation of the network.

Note:

If you want to minimize this interference, please let multiple networks choose channels with the widest possible interval. With the channel width selected as 20 MHz for three networks in the United States, you can select channels 1, 6, and 11, which are three channels that do not interfere with each other. In other countries, if the equipment permits, you can also select 1, 2, 7, 12 or 3, 8, 13, etc., which are three channels that do not interfere with each other at a channel width of 20 MHz.

The 5 GHz band has a wider frequency range (about 500+ MHz) and is divided into more channels, as well as providing more non-overlapping channels. The channels in the 5 GHz band are separated by a 20 MHz interval, and each channel is 20 MHz wide. The wider spacing between the channels makes it less likely that there will be interference and allows for more simultaneous connections, making it more suitable for high-speed data transmission.

The newest commercially available frequency band, 6 GHz, has a spectrum range of approximately 1200 MHz, which is more than twice as wide as 5 GHz. 6 GHz channels are also spaced 20 MHz apart, providing more channels that do not interfere with each other, and therefore offer faster speeds and less congestion. However, regulations regarding 6 GHz channels are also stricter, and many countries and regions cannot use the entire 6 GHz channel.

2. What is channel width?

Channel width refers to the frequency range occupied by the Wi-Fi channel. A wider channel width allows more data to be transmitted at the same time, resulting in higher data rates. However, wider channels consume more of the available spectrum, and wireless transmissions are more susceptible to interference.

20 MHz is the standard channel width for most Wi-Fi networks, including the 2.4 GHz and 5 GHz bands. 20 MHz channel width provides a balance between data rate and stability.

In the 802.11n protocol, the High Throughput (HT) Channel is defined. HT40 allows two 20 MHz channels to be bound to a single 40 MHz channel to increase wireless throughput. For example, a channel is like a one-way street that allows only one car to travel on it at a time. If we bundle two roads together and view them as a new road, this new road will allow two cars to travel on it at the same time. As a result, the total throughput doubles.

In the 802.11ac protocol, the Very High Throughput (VHT) Channel is defined. Just like the HT channel, VHT80 allows the binding of two 40MHz channels into one 80MHz channel. As for VHT160, it even allows two VHT80 channels to be bound to one 160MHz channel. In 802.11be, a maximum bandwidth of 320MHz is supported.

3. What is DFS?

Dynamic Frequency Selection (DFS) is an extension of the 802.11 standard protocol that specifies a mechanism for allowing Wi-Fi devices to use the 5 GHz channel shared with radar systems. The mechanism is designed to ensure that Wi-Fi networks and other devices operating in the unlicensed 5 GHz band do not interfere with radar systems.

The Unlicensed National Information Infrastructure (U-NII) radio band, defined by the FCC, is part of the radio spectrum used by wireless local area network (LAN) devices and many wireless Internet service providers. Channels that are typically in U-NII-2A and U-NII-2C require the utilization of DFS.

The following is a table of channel information commonly used in the 5 GHz band.

U-NII bands	Channel Number	Center Frequency (MHz)	Center Frequency Index Number			Regional regulatory requirements
	20MHz		HT40	VHT80	VHT160	US	EU
U-NII-1	36	5180	38	42	50	YES	Indoors
	40	5200				YES	Indoors
	44	5220	46			YES	Indoors
	48	5240				YES	Indoors
U-NII-2A	52	5260	54	58		DFS	Indoors/DFS
	56	5280				DFS	Indoors/DFS
	60	5300	62			DFS	Indoors/DFS
	64	5320				DFS	Indoors/DFS
U-NII-2C	100	5500	102	106	114	DFS	DFS
	104	5520				DFS	DFS
	108	5540	110			DFS	DFS
	112	5560				DFS	DFS
	116	5580	118	122		DFS	DFS
	120	5600				DFS	DFS
	124	5620	126			DFS	DFS
	128	5640				DFS	DFS
	132	5660	134	138		DFS	DFS
	136	5680				DFS	DFS
	140	5700	142			DFS	DFS
	144	5720				DFS	NO
U-NII-3	149	5745	151	155		YES	NO
	153	5765				YES	NO
	157	5785	159			YES	NO
	161	5805				YES	NO
	165	5825				YES	NO

Note:

1. In the Regional regulatory requirements column, “YES” means it can be used normally, “Indoors” means it can only be used indoors, “DFS” means the DFS feature is required, and “NO” means it cannot be used.

2. Some channels will be not be selectable when the channel width is selected to 40MHz, 80MHz, or 160MHz. Channel 165 is a special channel. To use channel 165, you must select a channel width of 20MHz.

To learn more about DFS, you can refer to Brief introduction of DFS function | TP-Link