AirCard: A Reasonably Good Way to Stay in Touch

FRAMINGHAM (02/07/2000) - Gearhead was delighted when an old friend, Tony Miranda, gave us a cool trinket: A radio frequency bug. This small device (just under an inch in diameter) detects RF signals. Put it near a cell phone and a sequence of flashing LEDs indicate when it has detected a transmission. Way cool.

One interesting thing the bug reveals is that digital cell phones "talk" to the cell they're in about once every 10 minutes, even when the phones are not in use. Much more often than Gearhead had expected, and frequently enough for governmental busybodies to get information on where you are . . .

But enough paranoia! This bug also detects the Sierra Technologies Inc.

Wireless AirCard 300 we just started to check out.

The AirCard is a PC Card (the new name for PCMCIA) that provides a Cellular Digital Packet Data (CDPD) connection. CDPD is a neat hack that carries packet data over the analog cellular network.

The card has a stubby antenna that can be easily removed when you wish to stay streamlined, although the way it plugs into the card is a little kludgey. It uses a miniature coaxial connector that can become stretched so the antenna keeps falling over - nothing a quick pinch with your fingers can't fix, but less than satisfactory.

The nominal data rate is 19.2K bit/sec (more on this later), which means you're not going to be downloading your mail or moving video files around. But you can access things such as stock tickers and corporate Web pages optimized for low bandwidth.

The card is compatible with Windows 95/98/NT, and Sierra offers cards for Windows CE as well as a multimode version that includes a cellular modem. And for the power mongers among you, Sierra also offers a version that plugs into a booster that increases the RF output from 600 milliwatts to 3 watts.

Installation was pretty easy once we removed all other network connections - and that is the first gotcha: Once installed, AirCard won't allow other network cards to work. Gearhead is speechless over this deficiency.

Be that as it may, once working, the AirCard is way cool. We used the AT&T wireless network, but there are several other carriers offering CDPD service.

We ran a Web browser to check the massive Gearhead securities holdings and also managed to pick up some e-mail, but neither operation seemed reliable. Indeed, in New York last week (where it was -20 degrees, for heaven's sake!) the packet loss rate was around 30 percent.

Here in the Ventura office that Gearhead shares with that reprobate Mark Gibbs, there is no packet loss, at least at the odd hours (usually post-midnight) when Gearhead is in the office. The packet-loss rate seems to be directly related to network loading (we observed a low but still significant packet-loss rate when we were in our Los Angeles office).

Now about that nominal data rate of 19.2K bit/sec. Our research department reports that other reviewers rate the real throughput at something around 16K bit/sec. That wouldn't be too bad if it were true (are those guys overmedicated?). Our tests found a rate of around 8.33K bit/sec when pinging an Internet host with 716-byte packets, and an average of 6.32K bit/sec over the range of packet sizes from 56 bytes to 756 bytes.

In fact, the transmissions seemed reliable up to around packets of 426 bytes, after which timeouts occurred. This indicates that optimizing your applications under CDPD is highly desirable if you want to avoid reducing your data rate even further due to retries.

The AirCard 300 is a nice device and at $442 not too badly priced. Definitely worth checking out if you can make your mobile applications fit the bandwidth.

You can get the cards direct from Sierra (www.sierrawireless.com) but sorry, we have no idea where to get the RF bugs.

Transmissions to gh@gibbs.com.

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