How Wireless Internet Cards Work

To understand the mechanism behind wireless Internet cards, you first have to grasp how the wireless Internet itself works. Rather than transmitting data through a phone line, digital subscriber line (DSL) or high-speed cable, a wireless Internet network transmits data the same way that radios and cell phones do: radio waves.

A WiFi hot spot, usually a wireless router or access point, first receives information from the Internet the old-fashioned way: through wires. It then translates that data from the binary form (the computer code of 1s and 0s) into radio waves. Next it broadcasts those radio waves into the surrounding area. Wireless signals typically travel between 75 feet and 150 feet (23 meters and 46 meters). In a wide open area with no obstacles, however, they have been known to transmit up to 1,000 feet (305 meters) and, with optimal conditions, even a mile (1.6 kilometers) [source: Wi-Fi Alliance]. More on those optimal conditions in a little bit.

Wireless Internet cards within the range of the radio signal pick it up using a tiny antenna and translate it back into binary code for your computer to read. The process also works in the opposite direction, with the card translating your computer's information into radio waves to send to the router, where it is put back into binary form and sent to the Internet over the wires.

The radio communication used by wireless networks is slightly different from that of radios and cell phones. For instance, wireless Internet cards are designed to work at higher frequencies to handle more data -- typically either 2.4 gigahertz or 5 gigahertz. In addition, the cards and the routers can communicate on one of three different frequency channels. In cases where many people are using the wireless signal, like an airport crowded with business travelers, the cards and the routers can also jump between channels to reduce interference.

Wireless cards operate under networking standards that are a variation of the basic 802.11 standard. These standards were developed by the Institute of Electrical and Electronics Engineers to differentiate between the various technologies. The 802.11b and 802.11g standards are the most common, while the faster 802.11n, which was recently released, is not as widespread.

Although WiFi radio signals have some benefits over regular radio signals, they are still subject to interference by physical obstacles. Interference happens when a signal is hampered by distance or a physical obstacle. For instance, microwaves and many cordless phones operate in the same frequency used by some WiFi networks, so you might notice a slowdown in your service if you're trying to warm your latte while you sign on. Likewise, if you move to another room or if an elephant comes to stand between you and the hot spot, the signal could be lost.

Don't worry if you don't have your own wireless network at home or at work. You can purchase prepaid wireless Internet cards in the U.S. from companies such as T-Mobile, which allow you access to all the T-Mobile hot spots. This can get kind of pricey, though, so you may want to kick in the cash to set up your own network or find a local spot that advertises a free Wi-Fi connection.

If you're overwhelmed by computer acronyms, brace yourself. On the next page, you'll learn the difference between PCI, PCMCIA (PC) and WCF cards.

If you've ever gone into a computer store and looked in the section devoted to adapter cards, you're aware of how many different kinds await you. Cards labeled as PCI refer to the specific language the card uses to communicate with the computer's central processor. PCI stands for Peripheral Component Interconnect, which is an industry standard that refers to the way an attached device talks to the computer through a central pathway called the bus.

PCI network adapters come in many different shapes and sizes called form factors. Two common form factors are the mini PCI, which is a wireless network card that comes embedded inside a laptop computer, and the PCI wireless adapter card for desktops. Since a desktop computer's bus is located inside the computer, wireless Internet cards for desktops have to be installed inside the unit, and most computers come with one preinstalled. If you want an external Internet adapter, you need to look for one that connects through the USB.

Other labels you might see are the PC Card or ExpressCard designations. Whereas PCI wireless network adapters communicate through a computer's bus, PC Card adapters just fit into a slot on the side and are used mainly in laptops because of their thin design. The newer ExpressCard technology has gradually been replacing PC Card adapters.

The PC Card and ExpressCard designations come from PCMCIA, the Personal Computer Memory Card International Association, which is the organization that developed a standard network adapter using the PC form factor. You'll sometimes see these cards labeled as PCMCIA cards. Regardless of the name, they all insert into a slot on the laptop's side, and typically stick out a little bit to better transmit and receive signals with their built-in WiFi antennas.

You also can buy USB keys that plug in to use as wireless adapters. These devices, which resemble the memory sticks or flash drives you stick into an available USB port on the side of your computer, seem to be an increasingly popular choice.

Yet another type of wireless Internet card exists for PDAs. For people who haven't yet jumped on the BlackBerry bandwagon, there is WCF. Wireless CompactFlash cards, like PC Cards, fit into a slot on the side or back of a PDA and enable it to communicate with the Internet.

The variations in wireless Internet cards don't stop there. Learn about some of the other differences next.

You'll need to pay attention to several things when purchasing a wireless Internet card, such as the networking standard that the card uses. For example, 802.11b, which used to be the dominant WiFi standard, is meant for wireless networks operating in the 2.4-gigahertz range. It supports a bandwidth of 11 megabits of data per second. The bandwidth refers to how much data can be transferred in a set amount of time. The higher the number, the faster the rate of transfer. So 802.11g and 802.11n, which send data over the Internet at speeds of 54 and 140 megabits per second, respectively, are going to stream your video faster than the clunkier 802.11b standard.

Paying attention to the network standard on the card you purchase is important because you need it to be able to communicate with the other wireless products you'll be using. For instance, if your home network uses the 2.4-gigahertz frequency, and you buy a card that just works in the 5-gigahertz range, you'll be out of luck. However, if you buy a card that is WiFi-certified for the same frequency band and with the same features (such as encryption codes) of the other products you'll be using, you're good to go. If you want a card that works on different frequencies, you can get a dual-band one, which will be compatible with all WiFi-certified products.

In addition, don't forget to look at the card's transfer rate, range and the operating system it requires. Also, consider whether you want a card with an external or internal antenna. Last but not least is security. Wireless networks are notoriously easier to hack into than wired ones, which means you have to take extra measures to protect yourself. The Wi-Fi Alliance suggests always connecting through a trusted provider that uses encryption technologies, enabling security if you have your own network and buying products that are WiFi-certified for WiFi Protected Access (WPA).

Wireless technology shows no signs of stopping its quest to allow you to check your e-mail anytime, anywhere. Soon you may even be able to surf the net while flying at 30,000 feet (9,144 meters). For more on wireless technology, including where to find the nearest hot spot, try some of the links on the next page.