
90 Keysight WLAN Measurement Guide
Concepts
WLAN Standards
802.11a
802.11a operates in the 5 GHz band and uses orthogonal frequency division
multiplexing (OFDM) as its transmission scheme.
Division Multiplexing (OFDM) Concepts” on page 104.
The 802.11a offers 6, 12 and 24 Mbps and optionally 9, 18, 36, 48 and 54 Mbps
bit-rates. The OFDM physical layer uses 52 sub-carriers with 0.3125 MHz
spacing, of which 48 are used to carry data and 4 are used as pilots. The
occupied bandwidth is 16.6 MHz. Forward error correction coding
(convolutional coding) is used with a coding rate of 1/2, 2/3, or 3/4.
The modulation of the individual carriers in the OFDM depends on the data
rates. For 6 and 9 Mbps BPSK is used, 12 and 18 Mbps uses QPSK, 24 and 36
Mbps uses 16 QAM, and 48 and 54 Mbps operation uses 64 QAM.
provides a summary of the different modulation formats used in OFDM
systems and their associated rate-dependent parameters.
Number of
carriers per
channel
48 data &
4 pilot
1 (DSSS)
48 data &
4 pilot
- 52 data &
4 pilot
(20 MHz)
- 108 data &
6 pilot
(40 MHz)
- 52 data &
4 pilot
(20 MHz)
- 108 data &
6 pilot
(40 MHz)
- 234 data &
8 pilot
(80 MHz)
- 468 data &
16 pilot
(160 MHz)
MIMO
1
1
1
4 x 4
8 x 8,
Multi-user MIMO
Table 3-1
IEEE 802.11 Standards Family
Wireless LAN Standards
802.11a
802.11b
802.11g
802.11n
802.11ac
Table 3-2
802.11a Rate-dependent parameters
Data rate
(Mbps)
Modulation
Coding
rate (R)
Coded bits per
subcarrier
(NBPSC)
Coded bits
per OFDM
symbol
(NCBPS)
Data bits
per OFDM
symbol
(NDBPS)
6
BPSK
1/2
1
48
24
9
BPSK
3/4
1
48
36
12
QPSK
1/2
2
96
48