Wireless Modems

Use carrier networks for wide-area wireless connectivity

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Wireless Modems
Wireless modems let mobile users wirelessly connect to the Internet and to private networks over a large geographical area. You might not be familiar with wireless WANs because this branch of the wireless market hasn't garnered a lot of attention lately. So, let me start by positioning wireless WANs in the marketplace. Three generally accepted types of wireless networks exist: Personal Area Networks (PANs), LANs, and WANs.

PANs rely on Bluetooth technology to provide short-range wireless connectivity between devices and peripherals. A PAN user can connect from a range as far as 100 meters and at speeds as fast as 1Mbps.

LANs rely on 802.11 specifications to provide short-range wireless connectivity as well as higher speeds, roaming capability, and access to wired networks. The specifications committees have attracted much attention by revising flavors of 802.11 to enable bandwidths as high as 53Mbps.

WANs are for users who need a wireless leash that's longer than 100 meters. Because wireless WANs use the wireless networks of commercial carriers (e.g., Sprint, Verizon, and AT&T), a wireless modem—equipped laptop or PDA can connect from anywhere that you have digital coverage.

The field of wireless-modem vendors is small and became even smaller after Metricom announced that it was shutting down its Ricochet wireless data network. The news was especially disappointing for Metricom's customers, who had become accustomed to 128Kbps Internet access, even though the coverage was spotty. At the time of this writing, the remaining alternatives are 19.2Kbps on Cellular Digital Packet Data (CDPD) networks and 14.4Kbps on Code Division Multiple Access (CDMA) networks. Two devices designed for Advanced Mobile Phone Service (AMPS) networks exist, but neither vendor chose to participate in this Buyer's Guide.

One future option will be General Packet Radio Service (GPRS), which has just begun its deployment in the United States. GPRS uses packet-based data transfer overlaid on circuit-switched networks. The big advantage of GPRS is a 53.6Kbps data rate and wide international availability. Cingular Wireless, Sprocket, and VoiceStream Wireless are testing GPRS, and Novatel Wireless is poised to release its Merlin G100 GPRS wireless modem.

Regardless of bandwidth, your primary consideration when you purchase a wireless modem should be security. Although CDMA technology is more resistant to eavesdropping than CDPD is, neither technology provides end-to-end security. To achieve such security, you need to consider a high-quality VPN solution.

Coverage is likely your next concern. In this regard, choosing a wireless modem is similar to choosing a cell phone. Examine coverage maps to ensure that you'll have connectivity where you need it. The Sierra Wireless AirCard 510, the only CDMA modem in this Buyer's Guide, gives you some of the best coverage in North American cities. However, the AirCard 510 works on only Sprint PCS and Bell Mobility digital networks and can't roam. Although roaming isn't as much of a concern on CDPD networks, you still need to see whether CDPD coverage meets your wireless connectivity needs. The http://www.wirelessdata.org/maps/maps/4q99us.gif Web site shows you CDPD coverage in the United States.

You'll probably choose a service and modem based on the portable device that you use. In this area, each vendor offers something unique. Novatel Wireless provides standard CDPD PC Cards and a range of CDPD modems designed for PDAs. Enfora provides a standard CDPD PC Card and the market's only CompactFlash (CF) wireless modem. Although Sierra Wireless's product line focuses on PC Cards, this company is the only vendor to offer modems for both CDPD and CDMA networks. Make sure that the wireless modem you choose has drivers for your portable device.

Final items for you to consider include technical support availability, the features of the included connectivity software, and the details that make your mobile computing needs unique. For example, if you need maximum battery life from your mobile device, scrutinize the power-saving features that the vendor offers. If you're frequently in areas that have weak signals, consider a power booster. Even with relatively few vendors in the wireless modem field, you have many options to meet your needs.

—Tom Iwanski