Wireless LAN CF Card Showdown (by Dave Ruske)
Review By James McCarthy | July 04, 2002
Category: not categorized
If you want to access the internet from your handheld, 802.11b or "Wi-Fi" compact flash cards offer a fast, reliable wireless connection at a reasonable price. I tried three of the most popular cards with Sharp's Zaurus SL-5500, testing each for range, battery life, and features. Our contestants? The Linksys WCF11 (US$145), the SMC SMC2642W (US$155), and the Socket Communications Wireless LAN CF Card (US$189).
Physical Differences
Both the Linksys and SMC cards are based on the Prism 2 chipset. Fitting this chipset into a compact flash card requires some components to be placed in the antenna housing that protrudes from the handheld. This makes the Linksys and SMC cards somewhat larger than the Socket Communications card, which uses the newer Prism 2.5 chipset. The Linksys and SMC cards are both Type II cards, the Socket card is Type I (translation: the Socket card is thinner and will fit in any compact flash slot).
If your handheld can handle Type II compact flash cards, then there's no real advantage to the Socket card's thin profile. But size does matter in some PDAs. In this evaluation, I found that the Linksys card's antenna housing was so wide that it actually blocked the stylus silo, preventing the stylus from being inserted or removed while using the card. I've heard tales on the ZaurusZone forum about users who machined the antenna housing with a Dremel-like motor tool, but if you void your warranty and destroy your card, you didn't hear it from me!
Zaurus Configuration Issues
Getting the cards running on the Zaurus required patience in some instances. The SMC card worked right away with no surprises or additional software, but the Linksys and Socket cards took some effort.
In the case of the Linksys, once I added it to the wlan-ng.conf file, the Zaurus would recognize the card (run lsmod in Terminal and you should see that prism2_cs has been loaded). But the card wouldn't actually run, and when I'd check for system errors by running dmesg (also in Terminal), I'd see a "Vcc mismatch" error. At that point I thought perhaps I could write a CIS override file and stuff it into /etc/pcmcia/cis, and I still think that might've worked --- but I couldn't figure out what I needed to put in the file. Part of my problem was that when I'd try to dump the tuple information (using dump_cis -v), the Zaurus would spit out a bus error and refuse to provide further information on the card. Hmm; I don't know what that's about.
The trouble with the Linksys card turned out to be the ROM containing the CIS, or Card Information Structure. And since I was having difficulty overriding it, there was but one thing to do: get an updated card from Linksys. Calling Linksys technical support was less than satisfying. They told me, quite simply, that the Zaurus wasn't a supported device. Fortunately, my press contact, Diana, came to the rescue and replaced the card. Now the Linksys worked as well as the SMC. That just left the Socket card.
Like Linksys, Socket took the position that they were not yet supporting the Zaurus. But hey, this is Linux, right? Who needs the manufacturer? Well...
It turns out that a fellow on the ZaurusZone's forums, a man I know only by his nickname of albertr, built a driver that would supposedly work for the Socket and Symbol cards. I followed Albert's instructions and gave it a whirl. Actually, I gave several versions a whirl, and the last version I tried (1.1) was still locking up the Zaurus if you'd insert the card but would fail to connect (out of the wireless access point's range, for instance).
The real gotcha with the Socket card --- and it's a biggie, in my opinion --- is that WEP won't work with it, at least not on the Zaurus. For those new to 802.11b, WEP is a lightweight encryption scheme to keep your wireless communication secure. While WEP can be broken, it's still a first line of defense that can keep out casual eavesdroppers. The trouble is that Sharp built Linux without the wireless extensions enabled, and the driver Albert ported happens to need them. The current solutions are to either make do without WEP (as I did for the remainder of the testing), or hack the driver to hardcode the WEP settings (have fun).
All hope is not lost, however: I have spoken with the product manager for the Socket card, and he assures me that an officially supported driver for the Zaurus is in the works.
It needs to be emphasized, I think, that the Zaurus is a new platform that manufacturers are just beginning to warm up to. Had I tested with a Pocket PC, all three cards might've worked without a hitch. But since I don't happen to have a Pocket PC, we'll lay the configuration issues aside and press on.
Battery Life
I started by testing battery life. Wireless cards are radio tranceivers and need power to generate and process signals. First, I did a baseline test on the Zaurus without a wireless card inserted. Then I tried an idle test with each card, where the card was inserted, but not being used for communication. Finally, I ran a VNC client on the Zaurus, firing up a KDE desktop on a remote Linux box and letting its screensaver kick in so that the display on the Zaurus would continuously need to update over the network. For all tests, the backlight on the Zaurus was on continuously at 50% power. The results, in hours and minutes:
No card . . . . . . . 3:51
Linksys (idle). . . . 2:33
SMC (idle). . . . . . 2:36
Socket (idle) . . . . 3:19
Linksys (busy). . . . 1:30
SMC (busy). . . . . . 1:23
Socket (busy) . . . . 1:25
(And, just in case you were wondering, once the Zaurus battery is drained it takes 1 hour, 50 minutes to recharge).
The Socket card clearly has an advantage for battery life when idling, with the SMC and Linksys cards more or less tied for second place. Under heavy load, however, all three cards kill the Zaurus in about an hour and a half. For typical use the Socket card should outlast the other two.
Range Test
Range is another consideration when choosing a wireless network card. My test for this was very informal, and your results may vary depending on how many walls the signal needs to penetrate and how the building is constructed. My wireless router is located near the center of a three bedroom ranch style home, and I found I could ping my main Linux box from anywhere in the house. So I ventured outside, watching the Zaurus as I walked across my back yard, hoping that the neighbors weren't watching.
The Linksys and SMC cards both kept pinging most of the way to the corner of my small yard, and both dropped out at about the same spot. The larger antenna casing of the Linksys card does not appear to offer any advantage over the SMC card. The Socket card didn't fare as well in this test, dropping out roughly thirty feet sooner than the other cards. Whether this is a natural tradeoff for lower power consumption or the consequence of using a half-baked driver, I can't say.
Conclusion
Despite the bumps caused by my early adoption of Sharp's Zaurus, all three cards tested proved to be usable. The Linksys has a bulky housing that blocks the stylus silo, and some versions also have a ROM problem which keeps them from working with the Zaurus. The SMC card has equivalent battery life and range without those drawbacks. Socket's big advantage is battery life, but it takes blows in range, stability of the current driver, and lack of WEP support.
Manufacturer Links
Linksys
SMC Networks
Socket Communications, Inc.
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