Wireless LANs (WLANs) utilizes electromagnetic waves, particularly spread-spectrum technology based on radio waves, to transfer information between devices in a limited area. There are two types of WLANs, infrastructure WLANs and independent WLANs. Infrastructure WLANs, where the wireless network is linked to a wired network, is more commonly deployed today. In an infrastructure WLAN, the wireless network is connected to a wired network such as Ethernet, via access points, which possesses both Ethernet links and antennas to send signals. These signals span microcells, or circular coverage areas (depending on walls and other physical obstructions), in which devices can communicate with the access points, and through these, with the wired network (see picture below). In a wireless LAN, devices can move within and between coverage areas without experiencing disruption in connectivity as long as they stay within range of an access point or extension point (similar to an access point) at all times.
How Wireless LANs Work:
In an (infrastructure) wireless LAN, devices communicate wirelessly with access points, which are connected to the wired network. Devices can maintain network connectivity while roaming in the shaded region.
Source: WR Hambrecht + CoThis model can be compared to those of wired LANs where devices connect via cables to hubs, or common wiring points, and from these to a central server. However, in wired networks, each hub has a finite number of jacks, and thus, can only connect a preset number of devices. Wireline networks are also confined by the existence of fixed cables, which limit connection to specified locations (see picture below).
Wired LANs
In a wired LAN, devices are connected to the network via cables. Devices are generally anchored to a set location depending on the placement of the network lines.
Source: WR Hambrecht + CoWhile WLANs provide some key benefits, including security, mobility, and scalability, they are currently much slower than wired LANs. For example, a wired LAN using 10BaseT Ethernet ranges from 10 – 100 Mbps. Other pros and cons of wireless LANs (in comparison with wired LANs) are listed in the table below:
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Wireless LAN Glosssary
access point—a device that connects the wireless network to the wired network. As a transceiver, it sports an antenna to send and receive signals from the various devices, providing coverage areas in which devices can roam freely.
extension point—a device that acts like an access point and connects the wireless network. Unlike access points, extension points do not connect the wireless network to the wireline but rather extend coverage areas between and beyond access points.
infrastructure network—the more common form of a wireless LAN. Infrastructure networks are comprised of WLANs connected to wired LANs and contain access points to channel network traffic.
independent network—a peer-to-peer network containing devices (with network adapters) connected to one another, independent of a managing server or other form of administration.
LAN adapter—generally a PC card in the portable device with an integrated antenna to receive signals from the access point/extension point. Can also be integrated into handhelds.
microcell—a coverage area in which devices can roam freely with a wireless connection. Microcells are generally circular (depending on the existence of interfering objects such as walls) and overlap to enable seamless connection as a user wanders through the wireless network.spread spectrum-a radio frequency technology most commonly used in WLANs. Frequency Hopping Spread Spectrum (FHSS) and Direct Sequence Spread Spectrum (DSSS) are two examples of the spread-spectrum technique.transceiver-a device, such as a LAN adapter, used to receive signals sent by the transmitter.transmitter-a device that sends signals to the transceiver (typically an access point or an extension point in WLANs). Source: WR Hambrecht + Co
Introduction to Networks
Overview of Wireless Networks
Wireless Local Area Networks (WLANs)
Wireless Wide Area Networks (WWANs)
Emerging Technologies
Josh Fisher worked in equity research at Volpe Brown Whelan & Co. and Montgomery Securities (now Banc of America Securities), focusing on the eHealth, pharmaceutical services, and managed care industries. Josh also worked at Columbia/HCA in the managed care division. Josh graduated with a BS in Economics and Pre-Med from the University of California at Berkeley.