As if the variety of OSs weren't confusing enough, a host of expansion options is available. The most popular standards are MMCs (multimedia cards), SD (secure digital) cards and Compact Flash cards. MMCs are nonvolatile (data is not lost when power is cut) cards used to store data. Capacity ranges from 16 MB to 64 MB, and transfer rates go up to 2.5 MBps.
The successor to MMCs, SD cards, has capacity from 16 MB to 512 MB and a transfer rate of up to 10 MBps. SD also supports content encryption to ensure copy protection and can be used for I/O expansion, as demonstrated by the Palm/ Toshiba SD Bluetooth card. With prices of SD and MMC similar, the SD cards are a better investment.
Compact Flash cards have a capacity ranging from 16 MB to 1 GB and a transfer rate up to 3.5 MBps. They are also used for I/O expansion, as with Symbol's Spectrum24. Compact Flash has the most versatility for I/O applications and offers more storage, so if you are concerned with expansion, go with Compact Flash.
Networking Options
Once you have chosen a PDA platform, how do you connect it to the network? Among the options are infrared, Ethernet, 802.11b, Bluetooth, wireless WANs and modems. These are all supported by Palm and Pocket PC. Many Linux devices have support for some or all of these networking standards.
Which networking solution is right for your enterprise? That depends on your requirements. Ethernet has great speed but leaves users tethered to cables. Infrared operates at relatively slow speed and requires line of sight, but it allows for more mobility. 802.11b and Bluetooth allow for mobility but are vulnerable to RF interference (a big issue for manufacturing environments). Wireless WAN access may not be available in all areas, can be expensive and is slow.
For the security conscious, VPNs can be implemented for use with PDAs. In addition to Microsoft's integrated VPN client, third-party solutions, such as Certicom's movianVPN, are available for Pocket PC and Palm. From a performance standpoint, Pocket PC 2002 tends to have better network I/O performance than Palm. This may be because the Palm OS was not designed with high-speed networking performance in mind. Performance may increase with Palm OS 5, though there are now no clear performance tests for Palm OS 5 or the various Linux OSs.
What The Future Holds
Mobile computing will grow beyond PDAs in the next few years. Intel's X-Scale architecture promises to increase the speed of mobile devices. Already we are seeing PDAs and other devices like cellular phones converge into all-in-one mobile devices (see buyer's guide, "It's a PDA! It's a Phone! It's a Data-Enable Cell Phone"). Microsoft's tablet PC may offer even more versatility for mobile devices as it blurs the line between PDAs and laptops. Only time will tell how much the role of mobile devices in the enterprise will increase.
Sean Ginevan is a research associate with the Center for Emerging Network Technologies at Syracuse University. He has conducted research in convergent multimedia and electronic books, and has spoken at Dickinson College and the National Archives College Park on oral history and the Web. Send your comments on this article to him at sean@ginevan.com.
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