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Interview questions and answers on WiFi 6 | 802.11ax

This page covers top WiFi 6 interview questions and answers will help interviewee pass the job interview for WiFi 6 engineer job position. This WiFi 6 (i.e. 802.11ax WLAN ) questions are written by specialists in WiFi 6 domain.

Question -1: What is WiFi 6 ?
Answer -1: WiFi 6 is the 6th generation of wifi. It is successor ro wifi 5 which is based on IEEE 802.11ac. WiFi-6 follows IEEE 802.11 ax specifications. It supports MU-MIMO, 1024-QAM, longer OFDM symbol duration, higher spatial streams and so on. The concepts such as BSS coloring are unique to wifi-6. Data rates of 600.4 Mbits/sec (with 80 MHz, 1 SS) and 9.6078 Gbits/sec (with 160 MHz, 8 SS) are supported by wifi 6.

Question -2: What is the difference between wifi 5 and wifi 6 ?
Answer -2: As mentioned wifi 5 follows IEEE 802.11 ac specifications and wifi 6 follows IEEE 802.11 ax specifications. Follow table below to know difference between wifi 5 and wifi 6 technologies.
Refer WiFi 5 versus WiFi 6 >>.

Difference between wifi 5 and wifi 6

Question -3: What are the advantages and disadvantages of wifi 6 ?
Answer -3: Advantages : High peak data rate, higher network efficiency, longer battery life, Less co-channel interference, Robust high efficiency signaling and so on.
Disadvantages : less OFDM subcarrier spacing, tight EVM requirements, stringent frequency synchronization requirement and so on. Refer Pros and Cons of WiFi 6 >>.

802.11ax features and advantages
Image Courtesy: Ruckus Networks

Question -4: Mention popular wifi 6 router manufacturers ?
Answer -4: The popular manufacturers of wifi 6 include Aerohive networks, Asus, D-link, TP-link and so on.
Refer WiFi 6 Routers >>.

Question -5: Which are the MCS (Modulation Coding Schemes ) rates supported by wifi 6 ?
Answer -5: Following table mentions various MCS rates for short guard interval (i.e. 800 ns). SS refers to Number of Spatial Streams. 8 xSS refers to eight number of spatial streams. Data rates are specified in units of Mbps.

MCS Rate Modulation and Code Rate 20 MHz, 1 xSS 20 MHz, 2 xSS 20 MHz, 4 xSS 20 MHz, 8 xSS 40 MHz, 1 xSS 40 MHz, 2 xSS 40 MHz, 4 xSS 40 MHz, 8 xSS 80 MHz, 1 xSS 80 MHz, 2 xSS 80 MHz, 4 xSS 80 MHz, 8 xSS 160 MHz, 8 xSS
MCS0 BPSK 1/2 8.6 17.2 34.4 68.8 17.2 34.4 68.8 137.6 36.0 72.1 144.1 288.2
MCS1 QPSK-1/2 17.2 34.4 68.8 137.6 34.4 68.8 137.6 275.3 72.1 144.1 288.2 576.5
MCS2 QPSK-3/4 25.8 51.6 103.2 206.5 51.6 103.2 206.5 412.9 108.1 216.2 432.4 864.7
MCS3 16QAM 1/2 34.4 68.8 137.6 275.3 68.8 137.6 275.3 550.6 144.1 288.2 576.5 1152.9
MCS4 16QAM 3/4 51.6 103.2 206.5 412.9 103.2 206.5 412.9 825.9 216.2 432.4 864.7 1729.4
MCS5 64QAM 2/3 68.8 137.6 275.3 550.6 137.6 275.3 550.6 1101.2 288.2 576.5 1152.9 2305.9
MCS6 64QAM 3/4 77.4 154.9 309.7 619.4 154.9 309.7 619.4 1238.8 324.3 648.5 1297.1 2594.1
MCS7 64QAM 5/6 86.0 172.1 344.1 688.2 172.1 344.1 688.2 1376.5 360.3 720.6 1441.2 2882.4
MCS8 256QAM 3/4 103.2 206.5 412.9 825.9 206.5 412.9 825.9 1651.8 432.4 864.7 1729.4 3458.8
MCS9 256QAM 5/6 114.7 229.4 458.8 917.6 229.4 458.8 917.6 1835.3 480.4 960.8 1921.6 3843.1
MCS10 1024QAM 3/4 129.0 258.1 516.2 1032.4 258.1 516.2 1032.4 2064.7 540.4 1080.9 2161.8 4323.5
MCS11 1024QAM 5/6 143.4 286.8 573.5 1147.1 286.8 573.5 1147.1 2294.1 600.5 1201.0 2402.0 4803.9 9607.8

Question -6: What is RU in wifi 6 (IEEE 802.11ax) ?
Answer -6: In WiFi-6 channel consisting of 256 subcarriers are grouped into smaller subchannels using OFDMA. This subchannels are known as RUs (Resource Units).The figure depicts the same.
Refer RU >>.

RUs in WLAN 802.11ax
Image Courtesy: Aerohive Networks

Question -7: What is MU-OFDMA in wifi 6 ?
Answer -7: It is the short form of Multi-User OFDMA. MU-OFDMA in which channel bandwidth is divided into number of channels. Each of these channels can be used by multiple clients at different time instants unlike previous wifi standards.
Refer MU-OFDMA >>.

MU-OFDMA 802.11ax

Question -8: What is BSS Coloring in Wifi 6 ?
Answer -8: Using this feature, stations identify transmissions from another network and take right action accordingly. The figure-2 depicts BSS coloring concept. Here same channel BSSs are only blocked on color match. In BSS coloring concept, each BSS (i.e. AP) uses a different unique color which is 6 bits in size and carried by signal preamble or SIG field. Each STA (i.e. client) learns its own BSS upon association and other BSSs or OBSSs.
Refer BSS coloring >>.

802.11ax BSS coloring

Question -9: What is TWT in wifi 6 ?
Answer -9: TWT stands for Target Wake Time. It reduces power consumption by adopting sleep time. Hence battery life is increased. It minimizes contention among stations by adopting scheduled uplink access.
Refer TWT >>.

TWT in 802.11ax wifi 6 frame

Question -10: Explain wifi 6 i.e. 802.11ax frame structure.
Answer -10: Its structure is similar to 802.11n and 802.11ac. It consists of preamble, header and data. The figure depicts both single user and multi user frame structures.
Refer WiFi 6 Frame >>.


This set of WiFi 6 interview questions and answers are useful for freshers and experienced level of job positions. Refer following links on WiFi 6 for more information.

WiFi 6 related links

The 802.11ax WiFi 6 tutorial covers following sub topics:
802.11n versus 802.11ax
802.11ac versus 802.11ax
802.11ax wave1 vs wave2
Advantages and disadvantages of 802.11ax
BSS coloring in 11ax
RU in 802.11ax
MU-OFDMA in 802.11ax
MU-MIMO in 802.11ax
TWT power save mode in 802.11ax
EVM specification in 802.11ax
802.11ax Speed calculator

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