802.11 WLAN Standards

Question 1

What are the key characteristics of 802.11b?

Answer 1

Frequency: 2.4 GHz
Max Speed: 11 Mbps
Channel Width: 20 MHz
Modulation: DSSS (Direct-Sequence Spread Spectrum)
Range: Long but susceptible to interference
Notes: First mainstream Wi-Fi standard for homes/small businesses.

Question 2

What are the key characteristics of 802.11a?

Answer 2

Frequency: 5 GHz
Max Speed: 54 Mbps
Channel Width: 20 MHz
Modulation: OFDM (Orthogonal Frequency-Division Multiplexing)
Range: Shorter than 2.4 GHz but less interference
Notes: Higher speed for commercial use; more costly.

Question 3

What are the key characteristics of 802.11g?

Answer 3

Frequency: 2.4 GHz
Max Speed: 54 Mbps
Channel Width: 20 MHz
Modulation: OFDM (replaces DSSS in 802.11b)
Range: Longer range, but more interference than 5 GHz
Notes: Backwards compatible with 802.11b; common for home use.

Question 4

What are the key characteristics of 802.11n (Wi-Fi 4)?

Answer 4

Frequency: 2.4 GHz and 5 GHz (Dual-band)
Max Speed: Up to 600 Mbps
Channel Width: 40 MHz (first to support channel bonding)
Features: MIMO (Multi-in, Multi-out) for multiple spatial streams
Notes: Introduces channel bonding and dual-band support.

Question 5

What are the key characteristics of 802.11ac (Wi-Fi 5)?

Answer 5

Frequency: 5 GHz
Max Speed: Up to 3.6 Gbps (1 Gbps typical)
Channel Width: 80 MHz, supports up to 160 MHz
Features: MU-MIMO (Multi-user MIMO), Beamforming
Notes: Improves MIMO to support multiple users and introduces beamforming for stronger connections.

Question 6

What are the key characteristics of 802.11ax (Wi-Fi 6)?

Answer 6

Frequency: 2.4 GHz and 5 GHz
Max Speed: Up to 9.6 Gbps
Channel Width: 160 MHz
Features: OFDMA (Orthogonal Frequency-Division Multiple Access), Improved MU-MIMO (8 spatial streams), Target Wake Time (TWT)
Notes: Optimized for high-density environments and IoT support.

Question 7

What are the key characteristics of 802.11ax (Wi-Fi 6E)?

Answer 7

Frequency: 2.4 GHz, 5 GHz, and 6 GHz
Max Speed: Up to 9.6 Gbps
Channel Width: 160 MHz
Features: Access to 59 non-overlapping channels on 6 GHz; no DFS requirement for 6 GHz
Notes: Adds 6 GHz band, increasing capacity and reducing congestion.

Question 8

Which Wi-Fi standards can operate on the 2.4 GHz band?

Answer 8

802.11b, 802.11g, 802.11n, and 802.11ax.

Question 9

Which Wi-Fi standards support dual-band (2.4 GHz and 5 GHz)?

Answer 9

802.11n (Wi-Fi 4) and 802.11ax (Wi-Fi 6).

Question 10

What are the maximum theoretical speeds for each Wi-Fi standard from 802.11b to 802.11ax?

Answer 10

802.11b: 11 Mbps
802.11a: 54 Mbps
802.11g: 54 Mbps
802.11n: 600 Mbps
802.11ac: 3.6 Gbps
802.11ax: 9.6 Gbps

Question 11

Which standards support channel bonding, and what is its purpose?

Answer 11

802.11n, 802.11ac, and 802.11ax support channel bonding, which combines two or more 20 MHz channels to increase data throughput.

Question 12

Which 802.11 standards introduced MIMO and MU-MIMO, and what are their benefits?

Answer 12

MIMO was introduced in 802.11n (Wi-Fi 4), allowing multiple data streams for higher speed and reliability.
MU-MIMO was introduced in 802.11ac (Wi-Fi 5) and expanded in 802.11ax (Wi-Fi 6), allowing simultaneous data streams for multiple users, improving efficiency in high-density environments.

Question 13

What is Target Wake Time (TWT), and which Wi-Fi standard introduced it? What is it best suitable for?

Answer 13

Target Wake Time (TWT) is a feature introduced in 802.11ax (Wi-Fi 6) that schedules when devices wake up to send/receive data, conserving power—making it best suitable for IoT devices.

Question 14

What are the non-overlapping channels for 2.4 GHz and 5 GHz?

Answer 14

2.4 GHz: Channels 1, 6, and 11 are non-overlapping.
5 GHz: All channels are non-overlapping, though DFS channels (52-144) may be temporarily unavailable if radar is detected.

Question 15

For 5 GHz channels, what is DFS, and why is it necessary?

Answer 15

DFS (Dynamic Frequency Selection) prevents interference with radar by temporarily blocking certain channels (52-144) if radar signals are detected. It’s required for some 5 GHz channels to ensure compliance and reduce interference.

Question 16

Which Wi-Fi standard has the longest range, and why?

Answer 16

802.11b has the longest range due to its use of the 2.4 GHz band and DSSS (Direct-Sequence Spread Spectrum). DSSS transmits data by spreading it over a wider frequency range, allowing stronger, more reliable signals over long distances. However, 2.4 GHz is more susceptible to interference from other devices using the same frequency.

Question 17

Why is 5 GHz generally preferred for high-speed applications despite a shorter range than 2.4 GHz?

Answer 17

5 GHz offers less interference and more non-overlapping channels, allowing for higher data throughput with fewer network conflicts—ideal for high-speed and bandwidth-heavy applications.

Question 18

What is beamforming, and which Wi-Fi standard first introduced it?

Answer 18

802.11ac (Wi-Fi 5) introduced beamforming, a technology that directs the Wi-Fi signal toward specific devices for stronger, more reliable connections rather than broadcasting it in all directions.

Question 19

How does OFDMA differ from OFDM, and which standard uses OFDMA?

Answer 19

OFDMA (Orthogonal Frequency-Division Multiple Access), introduced in 802.11ax (Wi-Fi 6), allows channels to be divided into smaller “resource units” for more efficient data distribution, especially in high-density environments. OFDM sends data in larger blocks without splitting.

Question 20

What does channel bonding do, and which Wi-Fi standards allow it?

Answer 20

Channel bonding combines multiple 20 MHz channels for higher throughput. 802.11n (Wi-Fi 4), 802.11ac (Wi-Fi 5), and 802.11ax (Wi-Fi 6) allow channel bonding, up to 40 MHz, 80 MHz, and 160 MHz respectively.

Question 21

What benefit does 6 GHz provide in Wi-Fi 6E, and how does it affect channel availability?

Answer 21

The 6 GHz band in Wi-Fi 6E adds 59 non-overlapping channels, reducing congestion and allowing for higher throughput. It also doesn’t require DFS, giving access to all channels without radar interference concerns.