Just Plug It In: Networking Via Power Circuits
HomePlug makes it easy to use existing in-wall wiring for fast home
networks.
Yardena Arar -
From the April 2002 issue of PC World magazine
 No new wires. That's the mantra of almost everyone
contemplating a home or small-office network, which is why wireless
networks have become so popular. But a new standard that uses existing
electrical wiring, HomePlug, could offer users a real alternative to
wireless.
We tried out the first HomePlug networking products
and found them easy to install, robust, and fast. They're especially
suitable for hooking up desktop systems in larger homes and in small
offices where wireless options may not be practical because of signal
attenuation (related to distance from an access point).
HomePlug isn't the first technology to use existing
wiring: The HomePNA standard for networks using telephone circuits was
first published more than three years ago, and other power-line products
have launched in the past. But previous power-line efforts were hampered
by a combination of poor performance and a lack of standards, and HomePNA
networks using telephone wires are hampered by the relative scarcity of
telephone jacks in most homes. HomePlug, which lets you network devices by
plugging an external adapter into a standard wall outlet, delivers
performance superior to that of 802.11b wireless networks at only a small
price premium--no more than $25 to $50 per computer.
For our tests, we tried out three paperback
book-size, preproduction Linksys Instant Powerline products: two EtherFast
10/100 Bridges and one USB adapter (each at a street price of $149).
Making Connections
To network two PCs, we hooked one of the EtherFast
10/100 Bridges to the first system's standard ethernet port, and the USB
adapter to the second PC's USB port. To add Internet access, we plugged
the second EtherFast 10/100 Bridge into a conventional network router,
which in turn was connected to a broadband modem (see diagram).
Alternatively, if you have static IP addresses for your computers, you can
substitute a hub for a router. By the time you read this, Linksys expects
to release a $179 router with HomePlug technology built in, eliminating a
box. Other vendors that expect to ship HomePlug components in the next few
months include GigaFast, Netgear, Phonex Broadband, and SMC Networks.
We tested the adapters in a single-family home and
in a condominium in a 29-unit building, using them to transfer files and
surf the Web. The network ran flawlessly everywhere we plugged in, except
for one outlet in the single-family home (HomePlug engineers say wiring
quirks will occasionally cause this, but typically a nearby outlet will
work just fine).
In these informal tests, the network appeared
largely unaffected by our use of power strips and household electrical
appliances, a problem that had plagued previous power-line networking
systems. However, audiophiles who use special power conditioners to "clean
up" electrical signals could run into problems if they plug a
HomePlug unit into the conditioner, as the filtering system might perceive
the network traffic as noise and filter it out.
The HomePlug specification protects your data from
the prying eyes of others on your power grid by using DES encryption--as
opposed to the RC4 algorithm, whose implementation in 802.11b has known
security flaws--that works at the MAC address level (the unique identifier
for each piece of hardware). Officials at Intellon, the chip maker that
developed the HomePlug spec, say that hacking into a HomePlug network
would require cracking the government's DES encryption standard.
Faster Than 802.11b
HomePlug's theoretical maximum speed of 14 megabits
per second is slightly faster than 802.11b's 11-mbps top speed, as well as
the 10-mbps speed of older ethernet networks. Because typical broadband
Internet access tops out at 1.5 mbps, neither network type gives you an
advantage for Web surfing. But we were surprised at how much faster
HomePlug was than 802.11b for file transfers. Transferring an 11MB file
between our two HomePlug-equipped notebooks took only about 30 seconds,
compared with 1 minute, 15 seconds when we substituted 802.11b PC Cards.
Intellon engineers say this probably happened because HomePlug allowed
data to flow directly between the two side-by-side notebooks (even with
the router installed), while the 802.11b traffic had to move via the more
distant router and back.
Additionally, HomePlug is not subject to other
wireless traffic or to interference from walls and doors, all of which can
significantly slow down 802.11b signals, especially if larger distances
are involved.
Drawbacks? HomePlug is not supercheap--you can
purchase 802.11b USB adapters for slightly less. It's also not ideal for
notebooks, especially if you're often on the move: No HomePlug PC Cards
have been announced, and having the paperback-size adapter as well as a
standard AC adapter hanging off the back of your notebook is definitely
cumbersome. In fact, people who wish to network both notebooks and desktop
systems should consider creating their own hybrid 802.11b/HomePlug
network, built around an 802.11b router with at least one extra ethernet
port. Plug a HomePlug ethernet bridge into the router, slip an 802.11b PC
Card into the notebook, plug your desktops into the wall outlet, and you
have the best of both worlds.
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