The role of a wireless LAN is to extend network coverage to allow for in-building or campus communication for mobile users; wireless LAN (WLAN) equipment can also be used to create ad hoc networks for temporary situations such as conference registrations.
WLANs use electromagnetic waves to transmit data without physical connection to the access points (APs). APs act as a bridge between the LAN and wireless clients (also referred to as end users or wireless adapters). APs can support a small group of users in a given range; the theoretical number of clients supported by an 802.11b AP is 256 within a 100-foot range (the theoretical number of clients for 802.11a is 1,024). Depending on usage patterns, 20–30 users are recommended for optimal performance. For example, e mails with attachments require more bandwidth than e mails with no attachments, and VoIP or video applications will require substantially more bandwidth.
The range of access points is related to speed. As the distance between AP and wireless client increases, the speeds decrease, and vice versa. Building materials, floor plans and environmental factors also affect the range. For example, Gartner estimates indoor and outdoor ranges to be 100 ft. (30 m.) and 200 ft. (60m.), respectively, for 802.11b. Using a site survey tool is recommended to measure signal strength at various locations throughout the site to determine the number of and positioning of APs.
There are four main physical-layer standards for WLANs: 802.11, 802.11b, 802.11a and 802.11g. The 802.11 is the first standard and is only found in legacy installations. It is discussed here for reference purposes and should not be purchased. The 802.11b reached dominance in late 2003 and has 11Mbps data rates in the 2.4GHz band. The 802.11a is the follow-up standard that is capable of reaching 54Mbps rates in the 5GHz range. The newest standard, 802.11g, increases data rates to 54Mbps in the 2.4GHz band and is backwards-compatible with 802.11b. The 802.11b, 802.11a and 802.11g can all operate in the same environment without causing interference with each other.
The Wireless LAN Brick shown below applies to both access points and Network Interface Cards (NICs). NIH aims to reduce the number of vendors in the wireless AP and NIC environment in order to achieve better cost discounts and to simplify patch distribution and network management.
