IEEE 802.11 WIRELESS LAN

The Internet has started to penetrate the wireless world with the result that the emphasis on wireless communications will be TCP/IP-based applications.  Wireless Internet access may be considered just another path in communications.  Over the past several  years, the IEEE 802.11 wireless local area networks (LANs) have gained popularity and acceptance and have quickly become a significant niche in the LAN market.   It is envisioned that wireless LANs will become one of the most common wireless Internet access technologies in the near future.

802.1b using 2.4GHz ISM band can provide 11Mbps data rate and 802.11a operating on the 5GHz radio frequency with the OFDM modulation scheme can offer up to 54Mbps data rate.  Although the 802.11 standard has been around since 1997, research continues to make it more adaptable to the demand for higher data rates and true wireless flexibility.

The basic building block of an 802.11 wireless LAN is called basic service set (BSS), which is a set of wireless stations controlled by coordination functions.  The 802.11 wireless LAN can be configured as an ad-hoc network, an independent BSS,  or an infrastructure network composed of access points (APs) and wireless stations.

The basic 802.11 medium access mechanism is called Distributed Coordination Function (DCF) and is based on the Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA).  Another optional medium access mechanism is called Point Coordination Function (PCF) which is intended to support real-time services by using central polling mechanism.  PCF is not currently supported by most APs and wireless cards.

Because 802.11 wireless LANs have limited physical security to prevent unauthorized access.  802.11 defines two authentication services, open system authentication and shared key authentication,  to control LAN access to a level equal to a wired link.  Every wireless station, whether part of an independent BSS or an infrastructure network, must use the authentication service prior to establishing a connection with another wireless station with which it will communicate.

With the maturity of 3G cellular technologies, 4G is increasingly popular in telecommunications research.  A common view of 4G will be characterized by the integration of a multitude of existing and new wireless access technologies in a manner that, at any given time, a user may select the best suited of all access technologies that are available at his/her current location.  These technologies could include wireless LANs as well as various types of cellular technologies and even satellite networks.  Since 802.11 wireless LANs have been widely deployed in university campuses, hotels, and airports, wireless LANs would play an important role in future 4G cellular communications.