Please be sure to read the companion article How Home Networking Works, which provides information about configuring your computers, routers and firewalls, Ethernet networking and sharing an Internet connection. There are also companion articles about power-line networking and phone-line networking. By the time you finish this series of articles, you will be able to choose a network technology that suits your needs and then configure the whole thing!

In this edition of HowStuffWorks, we'll talk about wireless networking and the technology used to make it happen. We'll also discuss the advantages and disadvantages of using a wireless network.

Wireless Networking
Wireless networking technologies take the concept of "no new wires" one step further. In a wireless network, all of the computers in your home broadcast their information to one another using radio signals. This can make networking extremely easy, especially if you have computers all over your house. It also makes it a whole lot simpler to move computers around. For example, a laptop with a wireless network card is completely portable throughout the house!

In How Power-line Networking Works, we discussed peer-to-peer and client/server networks. In wireless networking, a peer-to-peer (or point-to-point) wireless network means that each computer can communicate directly with every other computer on the network. But some wireless networks are client/server. They have an access point, which is a wired controller that receives and transmits data to the wireless adapters installed in each computer.

There are four types of wireless networks, ranging from slow and inexpensive to fast and expensive:

• Bluetooth
• IrDA
• HomeRF (SWAP)
• WECA (Wi-Fi)

Bluetooth is not widely available yet and is not expected to replace the need for high-speed data networks between computers. You can read more about this cutting-edge technology in How Bluetooth Short Range Radio Systems Works.

IrDA (Infrared Data Association) is a standard for devices to communicate using infrared light pulses. This is how remote controls operate, and the fact that all remotes use this standard allows a remote from one manufacturer to control a device from another manufacturer. Since IrDA devices use infrared light, they depend on being in direct line of sight with each other. Although you can purchase and install an IrDA-based network capable of transmitting data at speeds up to 4 megabits per second (Mbps), the requirement for line of sight means that you would need an access point in each room, limiting the usefulness of an IrDA network in a typical home layout.

Before we talk about SWAP and Wi-Fi, we need to understand the original standard that both of these new specifications are based on. The original Institute of Electrical and Electronics Engineers wireless-Ethernet specification, known as IEEE 802.11, designated two ways of communicating between devices and allowed for speeds up to 2 Mbps. Both communication methods, direct-sequence spread spectrum (DSSS) and frequency-hopping spread spectrum (FHSS), use the frequency-shift keying (FSK) technology we discussed in power-line networking. Also, both are based on spread-spectrum radio waves in the 2.4-gigahertz (GHz) range.

Spread spectrum simply means that data is sent in small pieces over a number of the discrete frequencies available for use at any time in the specified range. Devices using direct-sequence spread spectrum (DSSS) communicate by splitting each byte of data into several parts and sending them concurrently on different frequencies. DSSS uses a lot of the available bandwidth, about 22 megahertz (MHz). Devices using frequency-hopping spread spectrum (FHSS) send a short burst of data, shift frequencies (hop) and then send another short burst. Since the FHSS devices that are communicating agree on which frequencies to hop to, and use each frequency for a brief period of time (less than 400 milliseconds) before moving on, several independent FHSS networks can exist in the same physical area without interfering with each other. Also, due to FCC restrictions, as well as the fact that FHSS devices generally send data on just two to four frequencies simultaneously, they only use 1 MHz or less of the available bandwidth. Because they use any given frequency for such a short time, FHSS devices are less prone to interference than DSSS devices. But DSSS is capable of much greater speed than FHSS since these devices can send a lot more data at the same time. Currently, FHSS-based devices are easier and cheaper to produce, which has led the HomeRF group to adopt FHSS as the method of communication for their products.

HomeRF and SWAP
HomeRF (RF stands for radio frequency) is an alliance of businesses that have developed a standard called Shared Wireless Access Protocol (SWAP). A sort of hybrid standard, SWAP includes six voice channels based on the Digital Enhanced Cordless Telecommunications (DECT) standard and the 802.11 wireless-Ethernet specification for data. SWAP devices make 50 hops per second and transmit at 1 Mbps. Depending on the manufacturer, some of these can step up to 2 Mbps if there is very little interference in their operational area.

Here are the advantages of SWAP:

• It's inexpensive ($70 to $200 per device).
• It's easy to install.
• It requires no additional wires.
• It has no access point.
• It uses six full-duplex voice channels and one data channel.
• It allows up to 127 devices per network.
• It allows multiple networks in the same location.
• You can use encryption to make your data secure.

Here are the disadvantages of SWAP:

• It's not very fast (normally 1 Mbps).
• It has a limited range (75 to 125 ft / 23 to 38 m).
• It's not compatible with FHSS devices.
• Physical obstructions (walls, large metal objects) can interfere with communication.
• It's difficult to integrate into existing wired networks.

The actual wireless transceiver, with a small, integrated antenna, is built into an ISA, PCI or PCMCIA card. If you have a laptop computer, the PCMCIA card plugs directly into one of the PCMCIA slots. For desktop computers, you will either need a dedicated ISA or PCI HomeRF card, or a PCMCIA card with a special adapter. ISA and PCI adapters are inserted inside the computer and have a slot that is accessible from the back of your computer so you can plug in the PCMCIA card. USB adapters are external devices that you plug the PCMCIA card into and then connect to a USB port on the computer. Some of the HomeRF manufacturers sell kits that include the appropriate adapter along with the PCMCIA cards and installation software. Currently, because of the need to use dedicated cards, only computers can participate in a SWAP network. Printers and other peripheral devices need to be physically connected to a computer and shared as a resource by that computer.

In most cases, SWAP-based networks are point-to-point. Some manufacturers do offer access points as an option to increase the effective range of the wireless network, but they are not required equipment. Mainly because of this lack of an access point, HomeRF networks are significantly cheaper than the other viable wireless network, WECA's Wi-Fi. But the tradeoffs for cost are speed and distance. If you can set up a wired network using HomePNA or traditional Ethernet, you will get 10 to 100 times the speed for the same amount of money or less. However, unless you plan to send large amounts of data (like video) back and forth, SWAP speed is probably adequate for most home use, and the freedom of no wires can be quite appealing. Just remember that this is still a developing technology.

WECA and Wi-Fi
The Wireless Ethernet Compatibility Alliance (WECA) has gone in a completely different direction from HomeRF. Targeted more at office use than home networks, Wi-Fi (for "wireless fidelity", like Hi-Fi for "high fidelity" in audio equipment) is essentially a seal of approval that says the manufacturer's product is compliant with a variation of the IEEE 802.11 specification known as IEEE 802.11b. This specification drops FHSS and focuses on DSSS because of the higher data rate it can attain. Under 802.11b, devices communicate at a speed of 11 Mbps whenever possible. If signal strength or interference is disrupting data, the devices will drop back to 5.5 Mbps, then 2 Mbps and finally down to 1 Mbps. Though it may occasionally slow down, this keeps the network stable and very reliable.

Here are the advantages of Wi-Fi:

• It's fast (11 Mbps).
• It's reliable.
• It has a long range (1,000 ft / 305 m in open areas, 250 to 400 ft / 76 to 122 m in closed areas)
• It's easily integrated into existing wired-Ethernet networks.
• It's compatible with original 802.11 DSSS devices.

Here are the disadvantages:

• It's expensive.
• It can be difficult to set up.
• Speed can fluctuate significantly.

Wi-Fi offers Ethernet speeds without the wires, but you pay for it. There are Wi-Fi compatible PC cards that operate in peer-to-peer mode, but Wi-Fi usually requires access points, which range in cost from about $300 to $1,400. Most access points have an integrated Ethernet controller to connect to an existing wired-Ethernet network. It also has an omni-directional antenna to receive the data transmitted by the wireless transceivers. Apple sells an inexpensive ($299 list) and easy-to-configure access point called Airport. Airport has to be connected to an Apple computer (iMac, PowerMac, iBook), but it will accept signals from any 802.11b-compatible wireless-network card, whether it's PC or Mac-based.

Like HomeRF systems, the majority of Wi-Fi wireless transceivers available are in PCMCIA card form. But some manufacturers do offer PCI or ISA format cards, not just adapters. The cost per card ranges from $99 to more than $300. Because these products are not targeted at the home market, they are not typically sold in "do-it-yourself" kits. Instead, everything is a la carte, allowing customers to build a system that exactly meets their needs.

At the HowStuffWorks offices, we have installed the 3Com Airconnect wireless system with great results. Several of our staff members now freely roam about the workplace with their laptops constantly connected to the network. We invested about $1,400 for the access point and three PCMCIA cards. That's not a bad investment to foster a dynamic work environment, but is certainly on the expensive side for most home networks.

If you are a Mac owner, setting up a Wi-Fi-compatible network is easy, and reasonable in terms of cost. Otherwise, this is an expensive undertaking that requires careful consideration of your needs. In fact, you can buy an inexpensive Apple computer and an Airport access point for close to the amount of money you would invest in most other access points currently available.