When people refer to wireless, or wireless telecommunications, they are really talking about a range of communications services and technologies that have one thing in common-the use of electromagnetic radio waves to transmit information between two places.
Some common examples include remote controls, garage-door openers, AM/FM radios and televisions. More recent examples would include cellular phones, wireless local-area networks (LANs), direct-to-home satellite and public wireless data services. Whether it is the wireless LAN or cellular phone, all wireless technologies offer freedom from wires. This means freedom to move, either within a building as in the case of relocating computers on a wireless LAN, or nationally as in the case of accessing the Internet.
Wireless LANs A wireless LAN (WLAN) is a flexible data-communications system implemented as an extension to, or as an alternative for, a wired LAN within a building or campus. Using radio frequency (RF) technology, WLANs transmit and receive data over the air, minimizing the need for wired connections. Thus, WLANs combine data connectivity with user mobility and, through simplified configuration, enable movable LANs. With wireless LANs, users can access shared information without looking for a place to plug in, and technology directors can set up or augment networks without installing or moving wires.
Almost all wireless LAN gear available uses either infrared or spread-spectrum transmission technology. For sheer speed, infrared is the best because it delivers throughput at or near Ethernet or Token Ring wire speed. However, infrared requires a clear line of sight between devices that are no more than 30 to 60 feet apart. These restrictions mean that infrared transmission is not an option when mobility is important.
Spread-spectrum technology Spread-spectrum technology includes provisions to protect against radio's two greatest potential dangers-interception and interference. Getting its name from how it works, spread-spectrum technology distributes, or spreads, a data signal's content over a wider frequency range (spectrum) than is really needed, then reassembles it at the RF receiver end. Results include improvements in security, performance, reliability and range.
Spread spectrum refers to the transmission of a signal using a wider bandwidth than normally would be required. It is harder for a person to eavesdrop on a wireless LAN because of spread spectrum. With the frequency hopping, an eavesdropper does not know how long a message will be on a particular frequency and which frequency it will hop to next. Therefore, wireless LANs based on spread-spectrum radio technology inherently are secure.
Over the past several years, WLANs have gained strong popularity in a number of vertical markets, including academic, health-care and retail arenas. These venues have profited from the productivity gains of using handheld terminals and notebook computers to transmit real-time information to centralized hosts for processing. Today, WLANs are becoming more recognized as a general-purpose connectivity alternative for a range of users, especially to handle basic tasks like text-based e-mail exchanges, Internet access and database queries.
Pros and cons Wireless LANs are easy to install. It is said that a wireless LAN can be set up in a couple of hours. This is a significant decrease from wired LANs because of the time and cost of having to drop cables for all of the computers, printers and other equipment.
Today, most wireless LANs are based on spread-spectrum technology, which increases the channel bandwidth of the signal to make it less vulnerable to interference. Wireless LANs can be used with existing wired LANs. If a school or college is trying to extend existing LANs, a wireless LAN can be used to connect wired LANs.
Wireless LANs offer the following advantages: -Mobility. Wireless LAN systems can provide LAN users with access to real-time information anywhere in the building. Consider an older building with a limited budget where staff can place several computers on a cart to move them from room to room.
-Installation speed and simplicity. Installing a wireless LAN system can be fast and easy, and can eliminate the need to pull cable through walls and ceilings.
-Installation flexibility. Wireless technology allows the network to go where wires cannot.
-Long-term cost benefits. Benefits are greatest in dynamic environments requiring frequent moves, adds and changes.
-Scalability. Wireless LAN systems can be configured in a variety of topologies to meet the needs of specific applications and installations.
Today's wireless LAN products give notebook computer users the throughput needed to perform basic tasks, like e-mail exchanges and database queries, while moving throughout the building or campus.
With a wireless LAN, the biggest drawback is that the throughput is about 2 Mbits/sec. With an Ethernet and Token Ring LAN, the throughput is between 10 to 16 Mbits/sec.
Obviously, a wireless LAN is much slower compared to a hardwired system. A wireless LAN is good when dealing with text files or e-mail files. However, when dealing with graphics and charts, it will seem like an eternity for information to arrive at the computer.
The initial cost for wireless LANs is quite expensive. For 25 wireless LAN adapters and five access points, the price will probably be between $25,000 and $30,000. Tests have shown that the money paid for a wireless LAN can be recouped in about two years, if several moves are made in that time.
The next step At present, the IEEE 802.11 standard defines LAN communications in the 2.4 GHz radio spectrum at a maximum data-communications rate of 2 Mbps. This new standard will do for wireless local-area networks what similar standards did for wired Ethernet. Some IEEE committee members believe the standards will quickly be defined at 10 Mbps.
Wireless networks have been examined. The upfront costs are expensive, but the investment could be profitable over time. Setting up a wireless network is less time-consuming and currently presents no health risks. Although there are problems with interference from various items, a wireless network may be a viable option in older buildings. At the same time, wireless LANs represent a market and a technology that have not reached maturity.
-Voice communications and paging.
-To network computers.
-Remote data acquisition.
-To provide access control and security.
-For environments where wires are not possible.
-Temperature control systems. -TV remotes.
Wireless networks are ideal for portable computers. Using wireless connections allows for portable computers to still be portable without sacrificing the advantages of being connected to a hard-wired network. The machines can be set up virtually anywhere within the school.
Going wireless may be a better choice where the physical makeup of the building makes it difficult or impossible to run wire in the building.
The wireless LAN serves the same purpose as that of a wired or optical LAN: to convey information among the devices attached to the LAN. But with the lack of physical cabling to tie down the location of a node on a network, the network can be much more flexible.
If portables, desktop PCs, computer peripherals and telephones could all function without a hardwire, it would increase mobility and productivity. This is the promise of wireless communications.