Wireless LAN Primer, part 1
May 07, 2001
The intrinsic allure of understanding wire-free local area networks is two-fold: The systems are relatively simple to build and inexpensive to operate. Cheap and easytwo fundamental features required to build a potentially profitable service venture.
Residential users, businesses, and service providers can benefit from understanding wireless LANs (WLANs). Compared to wired LANs, wireless systems can be faster to deploy and cheaper to operate. As throughput and interoperability increase and equipment costs decrease, WLANs have become a realistic alternative to wired counterparts.
In small- and home-office markets, residential gateways are leveraging wireless technologies to eliminate costly inside wiring fees, while simplifying shared Internet access deployment in single-family homes and multi-unit dwellings.
In the enterprise market segment, wireless systems are being used to provide untethered LANs in shared spaces -- like conference rooms, and hard-to-wire locations -- like warehouses. While the gear required to setup these networks becomes increasingly cost-effective and our understanding of the technology deepens, WLANs are a viable alternative to wire-bound office LANs.
Big bucks, no whammies
Increasingly, WLAN technology is being used to offer fixed wireless Internet access. By connecting customer premise radios to ISP-owned Access Points (APs), "wireless local loops" can be a lucrative broadband service venture.
Potential revenues represented by these services are staggering. According to Frost & Sullivan, the WLAN market grew 43 percent in 1999, and is estimated to reach $1.8 billion by 2006. Although products differ for each application, the underlying technology remains the same -- IEEE 802.11. In this primer, we explain the nuts and bolts of 802.11 Wireless LANs.
In the beginning
In your basic 802.3 Ethernet LAN, Cat5 cable connects LAN stations to a hub. In a wireless LAN, Cat5 cable is replaced by a radio channel, connecting stations to wireless Access Points (APs). Each wireless station -- laptop, desktop, or server -- has a radio Network Interface Card (NIC). APs are essentially hubs, outfitted with a radio transceiver, Ethernet uplink, and 802.1d bridging software. Wireless stations transmit to an AP over a shared channel, carved out of the unlicensed 2.4 GHz band.
Approved in 1997, the original IEEE 802.11 standard uses the 2.4 GHz band to provide shared bandwidth at a maximum rate of 1 to 2 Mbps. In 1999, the IEEE approved the 802.11b High Rate (Wi-Fi) amendment, increasing the rate to 11 Mbps. Together, these standards specify WLAN Physical (PHY), Media Access Control (MAC), and Logical Link Control (LLC) layers for fixed wireless broadband access and WLANs.