The IEEE 802.11 is a Wireless Local are a Network standard capable of
providing data rates of 1 and 2 Mbps. The standard specifies Medium Access Control (MAC)
and Physical (PHY) layer characteristics for data transmission in the
unlicensed ISM band (2.4 GHz).
The IEEE in late
1999 released the 802.11b WLAN standard for a higher speed physical (PHY)
layer in the 2.4 GHz band to replace that specified in the 802.11
standard. This new PHY layer can support data speeds of upto 11Mbps,
although the actual experienced data rate may be around half of this speed. The Wireless Ethernet
Compatibility Alliance (WECA) certifies all products that are 802.11b
compliant as Wi-Fi.About the
The IEEE 802.11b
standard uses Direct Sequence Spread Spectrum (DSSS) technique to
achieve the 11 Mbps data rates. In noisy environments the
standard allows the data rates to be dropped to 5.5 or 2 or 1 Mbps.
802.11b uses Complementary Code Keying (CCK) as its coding technique
for its excellent performance in combating multipath.
The bandwidth of a single channel in DSSS is 20 MHz. The standard uses
the same MAC layer as specified by the 802.11 standard, i.e. Carrier
Sense Multiple Access/Collision Avoidance (CSMA/CA). For security,
802.11b uses Wired Equivalent Privacy (WEP). WEP is based on the RC4
stream cipher and uses a 40-bit shared key. WEP was intended as a
security measure, but has failed in its attempts. More on security is
explained in the security section.
An 802.11 WLAN consists of either only clients which constitutes an
'Ad-Hoc' network, or with multiple clients connected to a central
Access Point to form a 'Infrastructure' network.
In the Market
802.11b was the first standard to hit the market, and its products
started shipping in volume by 2000-2001. As a result 802.11b has found
wide acceptance in the industry and is almost the defacto WLAN
standard at this point of time. Current most wired LANs already
provides speeds of 100 Mbps, so the need for higher speeds in the
wireless will require an alternative to 802.11b.