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Mix Magazine

This installment of The Bitstream column appeared in the July 2002 issue of Mix Magazine.

The Bitstream

This column discusses new wireless data networking standards, including 802.11b and Bluetooth…

Sven, Where’s My Mead

Imagine having an Internet connection all the time, as you tote your computer hither and yon. Imagine the power of sharing files, directories and applications with your collaborators without plugging in to a wired network. Well, stop dreaming and get with it! The wireless paradigm is here and man, is it great!

Wireless networks provide portability, flexibility and scalability along with simplicity for the user. Modern wireless local area networks or WLANs use either of two protocols: 802.11x or Bluetooth. I’m going to start with 802.11b as Bluetooth is typically used for the quaintly named PAN or Personal Area Network.

Anyway, 802.11b (“eight oh two dot eleven”) or Wi-Fi is a subset of the larger 802.11 IEEE standard for WLANs. The standard includes several PHYs or physical layer choices including infrared and the 2.4 GHz frequency band with spread spectrum channel coding. Data rates are defined from 1 to 11 Mbit/s, about the same as 10BaseT. Also, no FCC license is needed for any of these WLAN/PAN technologies.

Let’s start with adapters & access points, the stuff of which Wi-Fi networks are made. Adapters are hardware, typically mobile, that bridge the host’s OS and 802.11 transceivers. Mobile implies small and adapters typically are PC (PCMCIA) Cards or USB blobules, a technical term for science wrapped in little bits of plastic.

Access points are base stations: fixed location hardware that buffers the transmissions and bridges 802.11 to wired LAN services. Access points can act as extension points when they are physically separated and/or tied to other wired networks. This effectively extends the reach for seamless coverage and roaming across “microcells,” where a wireless node maintains network connectivity as it moves from one wireless cell to another. For really large spaces such as a campus environment, office building or auditorium, external antennas can be deployed to reinforce the signal. Typical wireless LAN access points support up to 256 users within 100 meters while an add–on antenna will boost the range to 300 meters. By the way, mobile adapters can establish “ad–hoc” or peer–to–peer connections amongst themselves without the need for an access point.

I mentioned spread spectrum earlier (try saying that fast 5 times!). 802.11b specifies either of two distinctly different methods, Direct Sequence Spread Spectrum (DSSS) or Frequency Hopping Spread Spectrum. DSSS is the transmission method used in most 2.4 GHz-based wireless spread spectrum LANs such as Apple’s AirPort products and compatibles. The direct-sequence transmitter spreads its radiation by adding redundant data bits, called chips, to its transmissions. When transceivers begin negotiations prior to interoperation, they agree on a “chipping code” to decipher the bidirectional data. To an unintended receiver, DSSS appears as low-power, wideband noise and is completely ignored by most narrowband receivers.

This chipping or spreading code allows multiple DSSS transmitters to operate without interference. The wideband nature of their radiation means the likelihood of RFI is less than traditional AM or FM radio frequency technologies. One caveat bears emphasizing here. Because of different channel coding methods and frequency allocations, interoperability is an issue when building a WLAN. Stick with one vendor within any physical space to avoid interference and connection problems. (Another problem with 802.11b networks, which I didn’t realize was quite so severe when I wrote this, is interference from wireless phones, which operate in the same RF spectrum. See the “my Airport setup” link below - OMas)

Once a network admin builds, configures and tests a network, the whole thing can be moved to a new venue and be up and running in no time at all. Up–front costs are higher than wired networks, but long term admin costs should be lower and, of course, wired networks don’t travel well at all.

As far as security is concerned, first generation Wi-Fi products had weak, 40 bit encryption making it fairly easy for a motivated jerk to break in to your network. New versions provide 128 bit keys, making it much more difficult to crack. But, as with any scheme, it ain’t out of the question so take a moment to use the available security features offered by your vendor. In my Airport setup, I’ve enforced passwords, enabled WEP encryption and registered the AirPort ID (MAC address) of my TiBook with the base station.

My Teeth Are Blue

Wireless keeps getting smarter and one good example of that is the PAN technology mentioned above. Svend Forkbeard, king of Denmark from 986 to 1014 AD, gained the thrown by overthrowing his dad, King Harald Blåtand. Dad’s distinctive moniker translates as either Bluetooth or Blacktooth, take your pick. Early in his career, Sven Christianized his country but his evangelical zeal might not be appreciated today since Bluetooth technology is already suffering from massive media hype.

Bluetooth: wireless, 10 meter operating range, 1 Mbps throughput. Good for headphones, head–mounted displays, keyboards and traditional peripherals as well as bridges to wired networks. Slow & relatively cheap but no setup or administration makes it a great replacement for USB at short distances.

As 3Com says, “Share files with other Bluetooth PCs with point-and-click ease. Sync your PC and handheld with the push of a button. Or jump on the Internet or network through a Bluetooth access point, or using your Bluetooth phone.” Their products are typical, a choice of USB or PCMCIA adapter.

There are other wireless networking standards in the CE marketplace. The HomeRF standard, a.k.a. the Shared Wired Access Protocol or SWAP specification, is compatible with many cordless consumer electronic items such as telephones, audio, cameras and streaming-media products. Expect data transfer rates up to 10 Mbps, also over the 2.4 GHz frequency band, which could interfere with 802.11 in that band. There’s also the HomePNA standard, which goes “wireless” by using your premises’ AC wiring. Though I haven’t tested it, it should induce noise in some older audio gear or in a facility with dicey grounding. So, keep that gear in the house where it belongs.

Though the jury’s still out on Bluetooth, the future looks bright for 802.11. There’s a task group building the 802.11a standard, which operates in the 5 GHz frequency band and will provide rates up to 54 Mbps. The ongoing 802.11g effort strives to develop a higher speed, backward compatible extension to the 802.11b standard with a maximum data rate of at least 20 Mbit/s.

A Real World Tale of 802.11b

Growing Pains

OK, Wi–Fi’s great once you’ve actually got all your cyberducks in a row and therein lies a bit of a chafe. You see, installing a wireless LAN system can be fast and easy, if you have a Mac. “Apple was the first to build in Ethernet, one of the first to build in USB, the first to build in FireWire and the first to build in 802.11b wireless networking,” says Steve J., CEO of Apple. “Now we’re offering a Bluetooth solution that works and is simple to use.”

But Ken, one of my clients, just bought a new AP Two Cascade and wanted his new laptop to act as the front end. The portable, a Toshiba, came with an 802.11b adapter built in. So, foolish me went out and purchased a Netgear ME102 access point. After installation, I couldn’t get it to work completely and called tech support as it came with no user manual. Early on, the CS guy confessed that the manual was still being written. After determining that it wasn’t user error, he suggested I uninstall and reinstall. Great, I already wasted enough time on the thing but hey…well, the “wizard” uninstalled the management app and, gorsh golly, some part of W2k along with it. Tah–dah, dead computer. Moral of the story: never trust a wizard wearing a Windoze hat and never buy anything that doesn’t have complete documentation!