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Wireless options for PDAs and smartphones

Wireless PDA and smartphone sales are booming. Most of today's new handhelds have built-in wireless interfaces that can be used to reach other users, corporate servers, and the public Internet. Mobile connectivity has never been easier, but which wireless options should you look for in your new PDA or smartphone? In this tip, Lisa Phifer offers advice for selecting the right options for your mobile connectivity needs and discusses the pros and cons of Bluetooth, Wi-Fi and 3G.

Wireless PDA and smartphone sales are booming -- according to Gartner, more than 42 million units shipped during 1H06, up 57% from last year. Most of today's new handhelds have built-in wireless interfaces that can be used to reach other users, corporate servers, and the public Internet. Many also have expansion slots through which to add other wireless adapters. Mobile connectivity has never been easier, but which wireless options should you look for in your new PDA or smartphone? The right choice can be the difference between purchasing an indispensable sidekick and a stylish, expensive paperweight.

Wireless PANs
This year, the installed base of 802.15 Bluetooth devices topped one billion -- from cellular handsets and headsets to automobiles, media players and wireless keyboards. In particular, a significant number of new smartphones and PDAs ship with Bluetooth on board. Bluetooth is a "cable replacement" technology that uses short-range radio to interconnect portable personal devices, typically within 10 meters. Designed to minimize power consumption on small devices, basic-rate Bluetooth (v1) can deliver 780 Kbps, whereas the newer enhanced-rate Bluetooth (v2) can top 2 Mbps.

Bluetooth can be used to create Personal Area Networks (PANs). The vast majority of users rely on Bluetooth for connecting a wireless headset to a Bluetooth-enabled smartphone, PDA or MP3 player. You can also use Bluetooth to transfer files between your mobile handheld and a Bluetooth-capable PC or printer, or use Bluetooth to exchange small bits of data (e.g., business cards) with the smartphones and PDAs carried by your colleagues. As a peer-to-peer technology, Bluetooth requires no network and very limited configuration -- simply "pair" your mobile with another nearby Bluetooth device, then exchange data.

Bluetooth can be very handy, but it's also important to understand its limitations. Bluetooth functionality is divided into "profiles" -- for example, the Hands Free Profile is required for headset connection; the File Transfer Profile is needed to list, get, pull or delete files. Be sure to understand the profiles actually supported by any Bluetooth device before you buy. Some devices support the PAN profile used to create small Bluetooth networks, but don't expect Bluetooth to connect to or replace your wireless LAN (see below). Finally, many Bluetooth devices operate in an insecure, promiscuous fashion by default. To avoid unpleasant surprises, insist on security features in any Bluetooth handheld that you purchase -- then be sure to make good use of them.

Wireless LANs
Last year, almost every laptop shipped with embedded 802.11 Wi-Fi, as did many PDAs and a smaller but significant number of smartphones. Wi-Fi is a local area network (LAN) technology used to connect wireless stations to one another and to wired-network access points (APs). Designed as a wireless-world version of Ethernet, Wi-Fi typically reaches up to 300 feet indoors. Older laptops shipped with 11 Mbps 802.11b, but nearly every new laptop ships with 54 Mbps 802.11g. Mobile device support for 802.11g has lagged behind, but a PDA with "b" can connect to a LAN running "g" (unless the AP has been specifically configured for g-only operation).

Wireless LANs are big in home networks, linking PCs with broadband gateways that enable shared Internet access. WLAN hot spots are found in hotels, cafes and airports -- venues where customers will pay for Internet access but wires are impractical. As for business, Gartner estimates that two out of three companies have deployed Wi-Fi to some degree, ranging from common-area Internet access to campus-wide Ethernet replacement.

Wi-Fi is a good fit where network access is needed by devices within a few hundred feet of the nearest AP. This technology is a natural for computing devices (desktops, laptops and today's more powerful PDAs) that run applications requiring high-speed access (Web browsing, voice/video over IP, enterprise client/server applications.) Including Wi-Fi in your next PDA will make it relatively easy to connect that mobile device to any nearby office, home or hot-spot LAN -- for example, accessing a network file server from a conference room or checking email from an airport hot spot. Like Bluetooth, Wi-Fi can also be used for peer-to-peer "ad hoc" connections, but that is not really Wi-Fi's strong suit. In fact, many companies discourage Wi-Fi ad hocs, preferring to control wireless usage through IT-configured APs.

Wi-Fi is great for LAN connection, but there are important purchase considerations and caveats. For example, 802.11b/g support is common today, but many home WLANs are already migrating to pre-802.11n (the next generation of Wi-Fi). A Wi-Fi-capable PDA purchased today will work with most pre-N networks but at the slower speeds and shorter distances afforded by b/g. Although the number of metropolitan area Wi-Fi networks is growing, Wi-Fi isn't your best choice for connecting outdoors or when moving through a large area -- like checking email while taking the train to work (see WWAN below). Finally, Wi-Fi security features have improved substantially in the past few years. Mobile devices are still catching up, so make sure that any Wi-Fi handheld you buy today supports Wi-Fi Protected Access v2 (WPA2), preferably with 802.1X for enterprise-grade user authentication to access your corporate network.

Wireless WANs
All smartphones and many PDAs now include a built-in wireless Wide Area Network (WAN) interface. Many years ago, services like GSM and cdmaOne delivered data at a mere 10-20 Kbps. Post-second-generation (2.5G) services like CDMA2000 1XRTT and GPRS/EDGE promised data rates up to 144 Kbps, but typically achieve about 30-70 Kbps. Newer third generation (3G) services like CMDA2000 1xEV-DO and UMTS/HSDPA typically deliver data at 400-700 Kbps, with bursts up to 1 Mbps.

Unlike Bluetooth and Wi-Fi, these WWAN services operate in licensed spectrum owned by such carriers as Verizon Wireless, Cingular Wireless, T-Mobile and Sprint/Nextel. Today's smartphones are converged devices that use one of these carrier networks to support both cellular voice and data. Because the 2.5 or 3G interface must be compatible with (and provisioned for use with) a specific carrier's network, most users purchase WWAN-capable smartphones and PDAs along with a wireless data subscription.

3G is a great fit for interactive applications requiring true anytime/anywhere access. With 3G, you can use your smartphone or PDA to send text or multimedia messages, check email on the road, and query enterprise Web portals or mobile application servers. Industries with highly mobile workforces are drawn to 3G to support applications such as sales force automation, supply chain management and remote device monitoring.

But, here again, it's important to appreciate 3G constraints -- notably, coverage area vs. data rate. Best results are obtained outdoors, within major metropolitan areas. But expect lower (2.5G) data rates in rural areas, and less-than-stellar coverage when working indoors. WWAN is not the most direct way to connect to your home or office LAN, although it is often possible to do so by setting up a VPN gateway or mobility server. Finally, a WWAN connection always requires a data service subscription -- unlike Bluetooth or Wi-Fi, you cannot just create your own free 3G network.

What's next
Once you decide which kind(s) of wireless is right for you, the next step is selecting a platform. Do you want a smartphone with built-in wireless? Or do you want to add wireless adapter(s) to an existing PDA? In our next tip, we'll take a look at deployment alternatives for incorporating or adding wireless PAN, LAN and WAN services.

Continue to Part 2: Wireless adapters for PDAs and smartphones

About the author: Lisa Phifer is vice president of Core Competence Inc., a consulting firm specializing in network security and management technology. Phifer has been involved in the design, implementation, and evaluation of data communications, internetworking, security, and network management products for nearly 20 years. She teaches about wireless LANs and virtual private networking at industry conferences and has written extensively about network infrastructure and security technologies for numerous publications. She is also a site expert to and

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