802.11n Channels
What are channels in 802.11n?
Channels in 802.11n refer to specific frequency ranges in the 2.4 GHz and 5 GHz bands, supporting both 20 MHz and optional 40 MHz widths.
How many channels are available in 802.11n?
In 2.4 GHz, up to 14 channels exist globally; in 5 GHz, dozens of channels are available depending on region and DFS rules.
What is a frequency band in wireless communication?
A frequency band is a defined portion of the radio spectrum, such as 2.4 GHz or 5 GHz, used for wireless transmission.
Which frequency band does 802.11n operate in?
802.11n operates in both the 2.4 GHz and 5 GHz frequency bands, offering improved performance and flexibility.
What are UNII bands in 802.11n?
UNII (Unlicensed National Information Infrastructure) bands are 5 GHz spectrum segments used for unlicensed wireless communication.
What are UNII-1, UNII-2, and UNII-3 bands?
These are subdivisions of the 5 GHz spectrum, each with specific rules for power, DFS, and allowed usage.
What is channel width in 802.11n?
Channel width defines the size of the frequency band used for data. 802.11n supports 20 MHz and 40 MHz channels.
Why does 802.11n use 20 MHz and 40 MHz channels?
20 MHz channels are more compatible and less prone to interference; 40 MHz offers higher speeds but may overlap with adjacent channels.
Are 802.11n channels overlapping?
In 2.4 GHz, yes — especially with 40 MHz mode. In 5 GHz, channels are typically non-overlapping due to greater spacing.
What determines the number of usable channels?
Regulatory domain, band (2.4 or 5 GHz), DFS/TPC requirements, and interference determine usable channels.
What is Dynamic Frequency Selection (DFS)?
DFS enables 802.11n devices to detect radar and automatically switch channels to avoid interference in 5 GHz UNII-2 bands.
What is Transmit Power Control (TPC)?
TPC dynamically adjusts transmission power to reduce interference and stay within regulatory limits.
Can 802.11n use 40 MHz or 80 MHz channels?
802.11n supports up to 40 MHz channels. 80 MHz and wider are supported in later standards like 802.11ac and 802.11ax.
Why is channel planning important in 802.11n?
Effective planning minimizes co-channel interference and ensures optimal performance, especially with 40 MHz usage.
Are all 5 GHz channels available globally?
No, availability depends on country-specific regulations and enforcement of DFS/TPC requirements.
Can devices auto-select 802.11n channels?
Yes, modern devices often auto-select based on interference, regulatory limits, and signal strength.
How do clients know which channel to use?
Clients scan available channels and select an access point based on beacon signals and quality metrics.
What is the channel center frequency?
The center frequency is the midpoint of a channel’s frequency range (e.g., Channel 36 = 5.180 GHz).
How are 802.11n channels numbered?
In 2.4 GHz, channels are numbered 1–14; in 5 GHz, common numbers include 36, 40, 44, 48, 149, 153, etc.
What are the typical channel numbers for 802.11n?
In 2.4 GHz: 1, 6, 11; in 5 GHz: 36–64, 100–144, and 149–165, depending on region.
How far apart are 802.11n channels spaced?
In 2.4 GHz, channels are 5 MHz apart; in 5 GHz, 20 MHz apart. 40 MHz bonds two adjacent channels.
What is co-channel interference?
It occurs when multiple devices use the same channel, causing packet collisions and reduced throughput.
How can co-channel interference be avoided in 802.11n?
By using non-overlapping channels and proper AP spacing, especially in 2.4 GHz.
Does weather affect 5 GHz channel performance?
Indoors, minimal effect. Outdoors, 5 GHz is more affected by rain and obstructions than 2.4 GHz.
Why is 5 GHz considered less congested than 2.4 GHz?
More available channels and fewer legacy devices reduce interference in 5 GHz.
What is the typical range of 802.11n channels?
Indoors: ~30–70 meters depending on frequency, antenna setup, and obstacles. 2.4 GHz has longer range than 5 GHz.
Can 802.11n channels be used outdoors?
Yes, but only with adherence to DFS, TPC, and local regulations, especially in the 5 GHz band.
What happens if two APs use the same channel?
They compete for airtime, causing contention and reducing efficiency and performance.
What tools help with 802.11n channel planning?
Tools like Wi-Fi analyzers, heatmapping software, and spectrum scanners help optimize channel usage and placement.
Topics in this section,
Channel Number (MHz) |
Center Frequency (MHz) |
Frequency Range |
DFS Required |
|---|---|---|---|
1 |
2412 |
2401 – 2423 |
No |
2 |
2417 |
2406 – 2428 |
No |
3 |
2422 |
2411 – 2433 |
No |
4 |
2427 |
2416 – 2438 |
No |
5 |
2432 |
2421 – 2443 |
No |
6 |
2437 |
2426 – 2448 |
No |
7 |
2442 |
2431 – 2453 |
No |
8 |
2447 |
2436 – 2458 |
No |
9 |
2452 |
2441 – 2463 |
No |
10 |
2457 |
2446 – 2468 |
No |
11 |
2462 |
2451 – 2473 |
No |
12 |
2467 |
2456 – 2478 |
No (region dependent) |
13 |
2472 |
2461 – 2483 |
No (region dependent) |
14 |
2484 |
2473 – 2495 |
No (Japan only) |
Channel Number (MHz) |
Center Frequency (MHz) |
Frequency Range |
DFS Required |
|---|---|---|---|
36 |
5180 |
5170 – 5190 |
No |
40 |
5200 |
5190 – 5210 |
No |
44 |
5220 |
5210 – 5230 |
No |
48 |
5240 |
5230 – 5250 |
No |
52 |
5260 |
5250 – 5270 |
Yes |
56 |
5280 |
5270 – 5290 |
Yes |
60 |
5300 |
5290 – 5310 |
Yes |
64 |
5320 |
5310 – 5330 |
Yes |
100 |
5500 |
5490 – 5510 |
Yes |
104 |
5520 |
5510 – 5530 |
Yes |
108 |
5540 |
5530 – 5550 |
Yes |
112 |
5560 |
5550 – 5570 |
Yes |
116 |
5580 |
5570 – 5590 |
Yes |
120 |
5600 |
5590 – 5610 |
Yes |
124 |
5620 |
5610 – 5630 |
Yes |
128 |
5640 |
5630 – 5650 |
Yes |
132 |
5660 |
5650 – 5670 |
Yes |
136 |
5680 |
5670 – 5690 |
Yes |
140 |
5700 |
5690 – 5710 |
Yes |
144 |
5720 |
5710 – 5730 |
Yes |
149 |
5745 |
5735 – 5755 |
No |
153 |
5765 |
5755 – 5775 |
No |
157 |
5785 |
5775 – 5795 |
No |
161 |
5805 |
5795 – 5815 |
No |
165 |
5825 |
5815 – 5835 |
No |
channel widths
Band Name |
Frequency Range (GHz) |
Frequency Range (MHz) |
Channels |
|---|---|---|---|
2.4 GHz Band |
2.400 – 2.485 |
2400 – 2485 |
1 – 14 (region dependent) |
UNII-1 |
5.150 – 5.250 |
5150 – 5250 |
36, 40, 44, 48 |
UNII-2 (DFS) |
5.250 – 5.350 |
5250 – 5350 |
52, 56, 60, 64 |
UNII-2 Extended (DFS) |
5.470 – 5.725 |
5470 – 5725 |
100, 104, 108, 112, 116, 120, 124, 128, 132, 136, 140, 144 |
UNII-3 |
5.725 – 5.825 |
5725 – 5825 |
149, 153, 157, 161, 165 |
Reference links