Network Implementation · Topic 6 of 8
Wireless Standards and Bands
Compare 802.11 Wi-Fi standards, the 2.4, 5 and 6 GHz bands, channels, channel width, MIMO and cellular options for wireless network design on Network+.
- 5 min
- 802.11b and g use 2.4 GHz. 802.11a uses 5 GHz. 802.11n uses both. 802.11ac uses 5 GHz. 802.11ax uses 2.4 and 5 GHz, plus 6 GHz in Wi-Fi 6E.
- Wi-Fi 4 is 802.11n, Wi-Fi 5 is 802.11ac, and Wi-Fi 6 is 802.11ax.
- 2.4 GHz has longer range and more interference. 5 and 6 GHz have higher speed and shorter range.
What it is
Wi-Fi is the common name for wireless local area networks built on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 family of standards. Each new standard offers more speed, uses different radio bands and adds features.
The exam asks you to match a standard to a band and a speed class, and to choose channel settings that avoid interference. It also covers other wireless links such as cellular.
How it works
The 802.11 standards
| Standard | Wi-Fi name | Band | Notes |
|---|---|---|---|
| 802.11b | none | 2.4 GHz | Up to 11 Mbps, old |
| 802.11a | none | 5 GHz | Up to 54 Mbps |
| 802.11g | none | 2.4 GHz | Up to 54 Mbps, works with b |
| 802.11n | Wi-Fi 4 | 2.4 and 5 GHz | Introduced multiple input multiple output (MIMO), up to 600 Mbps in theory |
| 802.11ac | Wi-Fi 5 | 5 GHz | Higher speeds, wider channels, multi user MIMO |
| 802.11ax | Wi-Fi 6 and 6E | 2.4 and 5 GHz, and 6 GHz for 6E | Better efficiency in crowded areas using orthogonal frequency division multiple access (OFDMA) |
The newer names, Wi-Fi 4, 5 and 6, are marketing labels for 802.11n, ac and ax. Newer standards are backward compatible with older ones, but older clients can slow a shared network.
Frequency bands
| Band | Range | Speed | Interference |
|---|---|---|---|
| 2.4 GHz | Longer, passes through walls better | Lower | High, shared with Bluetooth, microwaves and cordless phones |
| 5 GHz | Shorter | Higher | Lower, many more channels |
| 6 GHz | Shortest | Highest | Lowest, new band that needs newer devices |
Use 2.4 GHz for coverage and older devices. Use 5 or 6 GHz for speed and for dense areas.
Channels and channel width
A band is divided into channels. In the 2.4 GHz band, channels overlap, and the three non overlapping channels commonly used in North America are 1, 6 and 11.
Neighboring access points (APs) should use different non overlapping channels. Co channel interference happens when nearby access points use the same channel, and adjacent channel interference happens when they use overlapping ones.
Channel width is how much spectrum one channel uses, such as 20, 40, 80 or 160 megahertz (MHz). Joining adjacent channels into a wider one is called channel bonding. Wider channels give more speed but leave fewer channels and increase the chance of interference.
Band steering nudges dual band clients toward 5 GHz instead of 2.4 GHz. Regulations limit the channels and power allowed in each country, and the 802.11h amendment adds dynamic frequency selection so 5 GHz access points move off a channel when radar is detected.
MIMO and related features
MIMO uses several antennas to send more than one data stream at once. Multi user MIMO (MU-MIMO) serves several clients at the same time. Beamforming focuses the signal toward a client.
OFDMA in 802.11ax divides a channel into smaller parts so many clients with small packets can be served efficiently.
Other wireless technologies
| Technology | Use |
|---|---|
| Cellular (4G Long Term Evolution, 5G) | Wide area mobile data, often a backup link |
| Satellite | Remote areas, with high latency |
| Bluetooth | Personal area links such as headsets |
Wi-Fi uses unlicensed spectrum that anyone can use. Cellular uses licensed spectrum owned by carriers, so it is less open to random interference.
What to remember for the exam
- 802.11b and g use 2.4 GHz. 802.11a uses 5 GHz. 802.11n uses both. 802.11ac uses 5 GHz. 802.11ax uses 2.4 and 5 GHz, plus 6 GHz in Wi-Fi 6E.
- Wi-Fi 4 is 802.11n, Wi-Fi 5 is 802.11ac, and Wi-Fi 6 is 802.11ax.
- 2.4 GHz has longer range and more interference. 5 and 6 GHz have higher speed and shorter range.
- Non overlapping 2.4 GHz channels are 1, 6 and 11.
- Wider channels give more speed but fewer usable channels.
- MIMO uses multiple antennas. MU-MIMO serves multiple clients at once.
- Co channel interference comes from neighboring access points on the same channel.
- Wi-Fi uses unlicensed spectrum, and cellular uses licensed spectrum.
If a user far from an access point has a weak signal, switch to 2.4 GHz for range. If a crowded office has slow Wi-Fi, move devices to 5 or 6 GHz and plan channels.
Common mistakes
Assuming 5 GHz goes farther. Higher frequencies are absorbed more by walls and travel a shorter distance.
Using overlapping 2.4 GHz channels. Channels such as 2, 3 or 4 overlap with others. Stick to 1, 6 and 11.
Setting very wide channels everywhere. In dense deployments this causes interference and reduces overall performance.
Mixing up the standard and the Wi-Fi number. Wi-Fi 5 is 802.11ac, not 802.11a.
Forgetting that old clients slow a network. A legacy device on the same access point can reduce speed for others.
Quoted maximum speeds are theoretical and shared among all clients. Real throughput is much lower, so do not treat the headline number as the expected speed.
Check yourself
Answer these three.
Which three 2.4 GHz channels do not overlap in North America?
Channels 1, 6 and 11.
Which band offers the longest range but the most interference?
The 2.4 GHz band.
What is Wi-Fi 6E?
802.11ax extended to use the 6 GHz band in addition to 2.4 and 5 GHz.
Topic 6 of 8 in Network Implementation
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