 Wires, it seems, are every-where. The good news is that wire-weary digital enthusiasts have many wireless alter-natives. Thanks to savvy product engineers, many hardware products, from cell phones to PDAs to digital cam-eras to PCs, have integrated wireless capabilities. And although wireless technology isn’t new, not everyone understands how wireless devices conjure their communications wizardry.
 Radio Heads
Some products, such as your DVD player’s remote control, use infrared light to transfer quick flashes of data. Infrared works great for many similar purposes, but you usually need to have a line-of-sight view from one device to another; in this case you must point your remote directly at the DVD player. Also, this kind of infrared technology generally lets only two devices communicate. To combat these problems, most digital products use radio signals to transfer data instead.
Radio signals vary greatly in characteristics. For some purposes, such as a station that broadcasts football games, radio signals are incredibly strong and carry for hundreds of miles. In other instances radio signals travel only shorts distances. In the end, though, these signals are related because a transmitter produces the electromagnetic waves.
A transmitter is a device that takes data, such as the words you speak into your cell phone, and converts that data into a radio wave subsequently projected via an antenna. To capture and use that radio wave, you need another antenna--one that connects to a receiver. The receiver helps decode the radio wave so that the other device, in this case a cell phone, can reconstitute the data as a voice that the recipient hears through a speaker.
You can add Bluetooth capability to some devices just by adding a Bluetooth adapter. This Canon adapter lets you add Bluetooth to a portable inkjet printer.
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Digital devices most often use FM (frequency modulation) frequencies, which is more resistant to interference than the old AM (amplitude modulation) radio standard. Keep reading, and you’ll see how different FM frequencies come into play with a variety of digital hardware.
Wi-Fi Fine Points
Some of the most popular wireless devices on the market fall into the Wi-Fi category. Wi-Fi is a general term for devices that conform to the 802.11b wireless networking standard. Actually, Wi-Fi is just about everywhere, letting you use your notebook to connect to the Web at a coffee shop or helping you create a LAN (local-area network) between the computers in your home, all without wires.
Many notebook PCs come with built-in Wi-Fi radio antennas. If yours didn’t, you can simply slip a Wi-Fi adapter into your notebook’s PC Card slot. Thus equipped, your computer can communicate with a wireless access point that’s as far as 300 feet away. An access point is basi-cally a radio device you can use to connect to the Internet or other computers that make up the LAN in your area.
Bluetooth technology has an entire Web site (www.bluetooth.com) devoted to propagating information about this wireless standard. Bluetooth is best suited for short-range networks.
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Wi-Fi lets you transfer data at a maximum rate of 11Mbps (megabits per second) and works at a 2.4GHz signaling frequency. Because devices such as cordless phones, microwaves, and other wireless networks can emit transmissions at this frequency, the potential exists for interference with Wi-Fi communications.
Wi-Fi can overcome interference, though, because it uses DSSS (Direct Sequence Spread Spectrum) to divide the 2.4GHz frequency into overlapping channels that are each 22MHz wide. It spreads redundant data through these channels, so if one channel experiences interference, a receiver can still piece together the entire transmission using data from the other channels. This kind of error prevention creates high-fidelity transmissions that degrade very little until you move out of range or some significant interference occurs.
Of course, 802.11b isn’t the only wireless standard that is available, but it’s the most common. Other standards (including 802.11a, 802.11g, and 802.11i) provide faster trans-fer speeds, and in some cases longer range. As wireless standards continue to evolve, a speedier and more secure standard will naturally replace Wi-Fi--but it’s a sure thing that high-speed wireless networking is here to stay.
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If your notebook PC doesn’t have a built-in Wi-Fi adapter, don’t worry. You can buy a PC Card, such as this D-Link model, and slip it into your computer to gain wireless communications capabilities.
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Blue In The Teeth
Bluetooth is a wireless communications standard that’s common in PDAs, notebook PCs, inkjet printers, and other devices. Bluetooth is designed for close quarters networking purposes; some pundits call Bluetooth a cable replacement technology that is best-suited for creating a short-range PAN (personal-area network).
With Bluetooth radio signals, you can transfer files from your PDA to a co-worker’s, transmit a document to a Bluetooth-enabled printer, or move a file to the hard drive of a nearby PC that has a Bluetooth adapter. In fact, there are so many possible uses for Bluetooth that there’s no way for us to list them all here. The transmitters and receivers are relatively inexpensive, and they’re so small that manufacturers can integrate Bluetooth capability into just about any gizmo that has just a bit of extra internal space.
One of the coolest aspects of Blue-tooth is that you don’t have to engage it manually to make it work. If you try to use a notebook PC with a built-in 802.11b adapter within a network you haven’t used before, you’ll often have to designate the wireless signal you want to use, and in many cases you’re required to provide authentication information.
In stark contrast, to make two Blue-tooth devices find each other, all you have to do is make sure they’re within range of one another. The devices communicate automatically to determine whether one piece of equipment should control the other. For instance, if you place a Bluetooth PDA near a Bluetooth printer, the PDA establishes control over the printer, and togeth-er these two devices create a PAN.
Cell phones are really just radios. Each phone contains a receiver and transmitter to help it communicate with base stations distributed throughout cities.
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Bluetooth has a maximum data trans-fer rate of about 1Mbps, works at a frequency of 2.45GHz, and has a range of about 30 feet. To avoid interference with other products that access similar frequencies, Bluetooth uses FHSS (frequency hopping spread spectrum), which is basically a fancy way of saying that the transmitter quickly cycles through frequencies in a specified range, greatly reducing the chances of any lasting interference.
Cell Phones
Bluetooth and Wi-Fi are very different, but they have one thing in common: Although they’re wireless, they have limited range and mobility. Cell phones use radio waves, too, but radio waves work across a much larger geographical range than, say, your PC’s Wi-Fi connection.
In short, cell phones are sophisticated radios, and they include a transmitter and a receiver that use different frequencies to prevent interference. But they aren’t just radios because these phones work via an intricate wireless networking system many of us never stop to consider.
Cell phone companies provide signals through the use of large antennas distributed throughout cities and often in rural areas, as well. Of course, one of the immediate problems of setting up a wireless phone system in a large city is that there are a limited number of frequencies and millions of people who want to make phone calls. If you’ve ever been in an area where there are too many people trying to make calls, you’ll know it. Your phone will refuse to make the call and it might display a message such as “Network Busy.”
Cell service providers combat this problem by dividing cities into cells that have a diameter of a few miles. Each cell uses a different range of frequencies to prevent frequency interference with adjacent cells. As you move about a city on your phone, you’ll leave one cell and enter another; the services provider’s antennas seamlessly pass your signal from one tower to another.
Those are the basic details that help your phone function anywhere in your city. It’s not magic; rather, it’s just a lot of invisible radio waves working to keep you in touch with friends and family.
Wireless World
Wireless digital devices really aren’t as mysterious as they might first seem. They use proven radio technologies that are fast and secure, and the radio components inside are so affordable that manufacturers can add some form of wireless communications to almost any newfangled digital toy.
So the next time you head out to buy digital devices for home or business use, be sure to do some research and find out if a wireless version is available. With some persistence you’ll find a lot of ways to untangle your too-wired world. 
by Nathan Chandler
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