Keysight WLAN Measurement Guide 95
Concepts
WLAN Standards
802.11n
The emerging 802.11n standard was ratified in 2009 based on several draft
versions. The major evolution of the 802.11n technology includes MIMO
(Multi-Input Multiple-Output), 40 MHz channels in the PHY layer, and frame
aggregation in the MAC layer. In addition, 802.11n is backward compatible
with legacy 802.11 standards. High Throughput (Greenfield) mode, Non-HT
(legacy) mode and HT Mixed mode are three operating modes of 802.11n.
Technically, 802.11n will deliver a higher speed, up to 600 Mbps, which is more
than 10 times the throughput of 802.11a/g. This increased speed also
addresses the need for wireless networks to provide data transfer rates similar
to those of Fast Ethernet.
There two other amendments to IEEE 802.11 which are not listed in Table 1.
They are 802.11j for Japan and 802.11p for vehicular applications. Both use
the half clock rate as defined in the standard.
Because 802.11n defines 77 possible permutations of the factors that
determine data rate, a new concept has been defined for 802.11n, called MCS
(Modulation and Coding Scheme). MCS assigns a simple integer to every
permutation of modulation, coding rate, guard interval, channel width, and
number of spatial streams.
Table below (Part 1) lists MCS values (index 0-9) currently supported by
N9077A & W9077A WLAN measurement application.
MCS
index
Type
Coding
rate
Spatial
streams
Data rate (Mbps) with 20
MHz BW
Data rate (Mbps) with 40
MHz BW
800 ns
400 ns (SGI)
800 ns
400 ns
(SGI)
0
BPSK
1/2
1
6.50
7.20
13.50
15.00
1
QPSK
1/2
1
13.00
14.40
27.00
30.00
2
QPSK
3/4
1
19.50
21.70
40.50
45.00
3
16QAM
1/2
1
26.00
28.90
54.00
60.00
4
16QAM
3/4
1
39.00
43.30
81.00
90.00
5
64QAM
2/3
1
52.00
57.80
108.00
120.00
6
64QAM
3/4
1
58.50
65.00
121.50
135.00
7
64QAM
5/6
1
65.00
72.20
135.00
150.00
8
256QAM
3/4
1
78
86.7
162
180
9
256QAM
5/6
1
N/A
N/A
180
200