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No New Wires.: It’s time for wireless networking

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DQW Bureau
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Home networks, according to the Aug. 15 Stavance R&D

Newsflash, have recently reached the 10.5 million mark worldwide, and are

expected to grow to 16.6 million by 2006.

Many of you have been on the leading edge of this trend,

first pulling cable for 10 megabits/second Ethernet (often called 10bT). Or you

may have dabbled with HomePNA networking (see below). Or more recently, you may

have climbed on the 10 megabits/second wireless networking bandwagon under the

moniker of WiFi or 802.11b. But you probably haven't yet experimented with

networking that uses the existing electricity wires in the wall (the power line)

to carry data. Because power line networking is a relatively new home and small

office option, in this issue we'll see how it works, and try to put it in

perspective alongside other, more familiar networking contenders.

Let's begin by reviewing the common home and small office

networking technologies so that we have a sense of their strengths and

weaknesses: 

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l10bT (Ethernet, or

Category 5) wire is, for all reasonable purposes, very secure and delivers a

pretty error-free 10 megabits/second of raw data (or ten-times greater, if your

network cards support 100bT). But you have to pull a wire to every spot you want

a PC.If you use an "Ethernet switch" at the central point where all

the wires come together, then the full media speed will be available to each

device (a "hub," instead of a "switch," shares the media's

bandwidth among all PCs).

Each PC requires an Ethernet card (if one isn't built-in),

or something like a USB-Ethernet adapter. Most cable/DSL "modems"

provide an Ethernet jack. (Note that for all of the network configurations we'll

be discussing in this article, not only do you need a network adapter on each

PC, but you also need one more "box" if you want to share your cable/DSL

connection -- a "router." It could be a standalone box, a part of the

cable/DSL modem, or even a PC running the appropriate software.

For this discussion though, we'll assume that the router is

a part of the cable/DSL modem.) 

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l HomePNA (http://www.homepna.org

) piggybacks data onto your existing home telephone wiring (without interfering

with phone calls). Until recently, it ran at only one to two megabits/second,

but its V2 devices are now rated at 10 megabits/second. You plug a HomePNA

"modem" between each PC and a phone jack in the wall, and the PCs are

then networked together. If you have a cable/DSL modem/router, then another

HomePNA modem goes between the cable/DSL modem/router and a phone jack. 

l However, according

to Intel technical support (Intel is one of the manufacturers of HomePNA

devices), encryption is not a part of the current HomePNA products. Because the

signals degrade over distance, this may not be a huge security risk in a rural

area, but in high density apartment buildings most phone lines show up on a

common "punch block" where unencrypted signals could be siphoned

off. 

l HomePNA devices

are available as PCI cards, USB adapters, and Ethernet to phoneline

"bridges." 

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l WiFi, or 802.11b,

offers 10 megabits/second of data and the ultimate in flexibility, especially

where wandering notebooks are concerned. You connect a "wireless access

point" to your cable/DSL modem/router via an Ethernet cable, and then

"wirelessly-enable" each PC or notebook with a built-in PCI card, a

PCMCIA card for notebooks, or a USB adapter. But depending on the building

layout and construction, its coverage can be spotty, and documented flaws in the

current WEP encryption make it susceptible to hacking.

Power Line Networking.



Under the standardizing influence of the HomePlug Powerline Alliance,

several companies now offer products that use the existing electricity wires

within our walls to carry data at a maximum raw data rate of 14 megabits/second,

without affecting the power.

(One company, Phoenix, explains that the overhead

associated with networking over the very data-unfriendly power lines reduces

that "raw" 14 megabits/second to an effective data throughput of 8

megabits/second, but more on the speed issue in a moment.) The recommendation

for maximum distance between powerline modems seems to be about 150 feet,

although HomePlug indicates that they have yet to run into a house where it

didn't work. And a practical (if not an absolute) limit of 16 powerline modems

seems to be what's claimed for home or small office powerline networks.

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Similar to the other technologies, you need a "powerline

modem" between your cable/DSL modem/router and the wall, and another

powerline modem between each PC and the wall; various companies make versions

that connect to an existing Ethernet jack, to a PC's USB connector, or that can

be installed into a PCI slot.

Behind the tests.



Unlike the carefully controlled benchmark-driven tests conducted by many

"testing laboratories" (which are also valuable), I focus on pragmatic

real-world testing that uses the same type of equipment you probably have,

configured in similar ways. For example, I don't use PCs stripped of all of

their background tasks to keep normal CPU activity from affecting test results

(although I do make an effort to see that no unusual activity takes place during

the tests.) And for these file transfer speed tests, I didn't configure an FTP

or other specialized server. Instead, I used Window's File Sharing and

Explorer's "drag and drop" to copy a large 338 megabyte (aprox.) test

file between the two systems in the same way you'd likely transfer a file. Tests

were conducted in both directions and repeated twice, with the results averaged.

So while absolute test numbers might be better in optimized environments, these

results reflect how I would expect the technology to actually work for you.

For most tests I used powerline modems from the same

vendor, one attached to my cable/DSL modem/router and the other to the test PC

running Windows XP; each powerline modem was plugged into a different electrical

circuit (meaning that the signals had to travel down to the circuit breaker box

and back up.) The second PC in the file transfer tests was connected by wired

Ethernet directly to the router, and used Network Neighborhood to gain access to

the test PC.

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Installation.



Powerline modems that connect directly to an Ethernet jack, either on a

cable/DSL modem/router or to an existing Ethernet jack on a PC, didn't require

any setup or software install at all -- they were transparent to the machines.

Installing a USB version did require a typical software installation, which

proved flawless on a Windows XP machine. However, when I originally attempted to

install the ST&T USB software on a "well-used" Windows Millennium

system, the installation process repeatedly failed and eventually corrupted the

system. This may have been more an indictment of the state of this old Windows

Me machine than of the powerline modem software, and I didn't pursue it since

this seemed a good time to upgrade the machine to Windows XP. J But all of the

powerline modems did work fine under XP.

The Results.



To begin, I ran a benchmark file transfer between the two systems using only

standard wired 10bT Ethernet (no powerline modem), resulting in an end-user

throughput of 7.2 megabits/second. (Don't be surprised that wired Ethernet

doesn't live up to its "raw data rate" promise of 10 megabits/second

-- protocol and operating system overhead always take a toll on the

"end-user data rate," which is why we're going to be comparing actual

end-user file transfer performance.) For comparison, a previous similar test of

802.11b wireless Ethernet (high signal strength and only one wireless PC active)

yielded an end-user throughput of 7.0 megabits/second.

I then installed pairs of powerline modems and tested the

file transfer throughput as described above, yielding the following end-user

data rates: Asoka PL9610-ETH / PL9710-USB 4.0 megabits/second Phoenix Broadband

NeverWire 14 4.6 megabits/second ST&T M51 / U21 4.9 megabits/second 10bT

wired Ethernet only 7.2 megabits/second 802.11b 10 megabits/second wireless 7.0

megabits/second (You may well experience faster or slower speeds, depending on

your electrical system.)

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Analysis.



The most important result of this experiment, to me, is that these powerline

modems provided exactly what they promised -- simple, no-new-wires networking.

You might be concerned that the end-user data throughput of the powerline modems

(in my tests) was slower than wired or wireless Ethernet, but let's put that in

perspective -- if you do intend to transfer large files or expect to stream lots

of multimedia at speeds faster than your cable/DSL connection, the increased

speed of wired Ethernet might well justify the hassle of pulling cable. But for

most typical small network activities, such as sharing a cable or DSL

connection, remote-printing, and typical file transfers, the slower speeds of

the powerline modems may be unnoticeable compared to the flexibility of being

able to compute anywhere you can plug-in to an electrical socket.

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