IEEE 802.11 Standard
The Institute of Electrical and Electronics Engineers developed the 802.11
standard to improve compatibility of products for Wireless Local Area Networks
(WLANs). The standard has similarities with
the 802.3 standard for ethernet wired LANs. The 802.11 series are the most well-known
Wireless LAN standards.
- 802.11a is based on OFDM and provides data rates of 6 to 54 Mbit/s in the
5GHz band. ·
- 802.11b is based on direct sequence CDMA with user data rates of 5.5 to
11 Mbit/s. It is interoperable with an older 802.11 DSSS standard. 802.11g
further extends the bit rates.
802.11 Media Access Control
The access algorithm is based on Carrier Sense
Multiple Access (CSMA) with collision avoidance, or CSMA/CA.
The MAC supports a variety of physical layers,
data rates and propagation characteristics, including infrared
and 2.4 GHz ISM radio communication.
Much attention has been paid to spectrum "etiquette".
Physical Layer
direct sequence or frequency hopping can be used.
- IEEE 802.11 provides data rates of 1 Mbit/s with BPSK modulation or 2 Mbit/s
with QPSK modulation at 2 Mbit/s, for DS-CDMA. To mitigate interference and
selective fading, five overlapping
sub-bands are defined of 26 MHz width each. Center frequencies are 2.412,
2.427, 2.442, 2.457, and 2.470 GHz,
- For frequency hopping, data rates of 1 Mbit/s and 2 Mbit/s are defined.
The band is divided into 79 sub-bands each with a bandwidth of 1 MHz. Each
sub-band hops at a rate of 2.5 hops/s.
- Recently bit rates of up to 11 Mbit/s have been standardized for 2.4 GHz
and OFDM schemes are chosen for 5.2 GHz, supporting up to 54 Mbit/s.
An N = 64 FFT is used. 48 subcarriers carry data, 4 pilots are used for phase tracking and 12 zeros
allow simple RF filtering.
