Interview Questions

Difference between 11n,11ac and 11ad

WLAN testing FAQ


(Continued from previous question...)

Difference between 11n,11ac and 11ad

802.11n
It is a 802.11 family of standard which is developed to deliver high data rate and it extends capability of 11a/b/g standards. It is referred as HT(High Throughput) specification.
Frequency range : 2.4 GHz and 5 GHz
Backward compatibility: It supports legacy fallbacks of 11a,11b,11g systems
Modulation Scheme OFDM and DSSS/CCK
Data modulation:Supports BPSK,QPSK,16QAM,64 QAM
Channel Bandwidth: 20MHz and 40MHz
OFDM data subcarriers/pilots : 52/4 ,160/6
OFDM coding rate: 5/6
Short guard interval : 400 ns
Spatial streams : 4
Max. Data rate: 600 Mbps with 40 MHz bandwidth and 4 streams
Distance covered(appox.)- 70m (indoor),250m(outdoor)
MIMO configuration -Most of the devices uses 2T3R(2 antennas in transmit and 3 antennas in receive),
Maximum configuration goes upto 4T4R.
Supports many type of explicit beamforming
Supports single user transmission
PHY layer frame(in HT mixed mode) consists of L-STF,L-LTF,L-SIG,HT-STF,HT-LTFs and Data


802.11ac
It is also falls under 802.11 family and it extends capability of 11n standard. It is referred as VHT(Very High Throughput) specification and it is maintained and developed by TGac working group. It is referred as 5G WIFI by Broadcom.
Frequency range : 5 GHz
Modulation Scheme: OFDM and DSSS/CCK
Backward compatibility: It supports legacy 11n systems
Data modulation:Supports BPSK,QPSK,16QAM,64 QAM,256QAM
Channel Bandwidth: 20MHz,40MHz,80MHz,160MHz
OFDM data subcarriers/pilots : 52/4 ,108/6, 234/8, 468/16
OFDM coding rate: 5/6
Short guard interval : 400 ns
Spatial streams : 8
Max. Data rate: 6.93Gbps using 160MHz bandwidth,8 spatial streams,MCS9,256QAM,with short guard interval
Distance: About 80 m with 3 antenna(about 10 meter more than 11n) MIMO configuration : 4 X 4 Supports Only NDP(Null Data Packet) explicit beamforming
Supports single user transmission as well as multi-user transmission
PHY layer frame(VHT mode) consists of L-STF,L-LTF,L-SIG,VHT-SIG-A,VHT-STF,VHT-LTF,VHT-SIG-B and Data part.


802.11ad
Working Group TGad and Wireless Gigabit Alliance jointly developed this standard. It is referred as WiGig. The applications are digital camera and 3D video streaming
Frequency range : unlicensed frequency allocations around 60 GHz (58.32 GHz,60.48 GHz,62.64 GHz, 64.80 GHz), check below country wide allocations.
Backward compatibility: It is not backward compatible to 11ac and 11n but It is a completely new standard developed to cater extremely high data rate and to provide short range wireless connectivity.
No. of channels/Channel bandwidth : 4/each 2.16 GHz wide
Data rate:throughput of 7 Gbps
Distance : More than about 10 meters with beamforming enabled. 802.11ad country wide frequency allocations


U.S and cannada - 57.05 GHz - 64.0 GHz
European Union - 57.0 GHz - 66.0 GHz
South Korea - 57.0 GHz - 64.0 GHz
Japan - 59.00 GHz - 66.00 GHz
Australia - 59.4 GHz - 62.90 GHz
China - 59.0 GHz - 64.0 GHz

(Continued on next question...)

Other Interview Questions