Wireless LANs

Wireless LANs Overview
Wireless LAN-based mobile computing solutions are becoming quite prevalent in many horizontal applications in the general office and vertical industries, such as health care (hospitals), manufacturing, goods distribution in a warehouse, stock-trading on the stock exchange floor, hospitality (restaurants), and retail.  Here are important but introductory facts about wireless LANs:

• Most wireless LANs operate in multiple frequency ranges - unlicensed 902-928 ISM (industrial, Scientific and Medical) band, unlicensed 2.4 GHz band and licensed 18-23 GHz band.
• There are two technologies used in wireless LANs - direct sequence (DS) coding or frequency hopping (FH).
• Key hardware components of a wireless LAN are a wireless LAN adapter along with an antenna that resides in the mobile computer device (notebook or PDA) and an "Access Point" which acts as the hub and connects multiple mobile devices to a server.  You can realistically support only 10-30 mobile devices per access point, depending on the network traffic.
• General distance range for coverage of wireless LANs is in 200 to 1000 feet depending on the type of walls, height of ceilings and existence of physical obstructions.  By having  multiple access points that span a building floor, you can support longer distances.  Physical design of a wireless LAN should be done by well-trained personnel who understand the technology and propagation of radio signals.
• First generation of wireless LANs supported 1-2 Mbps speed. However, during 2000, typical speed supported by IEEE 802.11 compatible wireless LAN adapters increased to 11 Mbps.  
• IEEE 802.11 is a recent (1998-99) standard for wireless LANs.  Many vendors (3COM, Lucent, Proxim) have started manufacturing products that meet this standard. However, interoperability across vendors is still problematic and spotty. A LAN Interoperability forum has been established to improve this. As of now, interoperability for 802.11 adapters is better with DS products than with FH products.
• There are two IEEE 802.11 standards - IEEE 802.11a and IEEE 802.11b. Oddly enough, the latter standard came before the former standard. IEEE 802.11a standard operates in less-crowded 5 GHz band. However equipment conforming to IEEE 802.11a standard  will start appearing in fall of 2001. European version of IEEE 802.11a, called HiperLAN2, will also ship in 2002.  For more info on HiperLAN2, go to www.hiperlan2.org.
• Vendors have been shipping 802.11b products since late 1999. 
• Both 802.11b Wireless LANs and Bluetooth operate on 2.4 GHz band. Therefore, there is potential for interference if you are using both technologies in close proximity.
• Prominent vendors in the wireless LAN arena are Proxim, Aironet (now part of Cisco), Symbol, Intermec , BreezeCOM, Xircom, Lucent, Ericsson and others.