Wireless networking is
one of several ways to connect the computers in your home. It creates a
network by sending radio-frequency signals between your computers to share
Please be sure to read the companion article
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
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 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
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!
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
There are four types of wireless networks, ranging from slow and
inexpensive to fast and expensive:
- 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
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.
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
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
- It's difficult to integrate into existing wired networks.
This wireless PCI card is inserted inside your
computer to build a wireless network.
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
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.
Photo courtesy Nexland
The ISB Wavebase by Nexland allows you to connect
wireless devices to your fast Internet connection.
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
This is the base unit of a wireless system used to
connect workers with laptops.
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