In the first three parts of this series we have wandered widely over the whys, wherefores, and hows of voice over Wi-Fi. Today we're wrapping up our VoIP Wi-Fi phone overview with a look at multi-mode portable devices: combination cell phones/Wi-Fi phones/Web browsers/PDAs/kitchen sink devices that fit in a pocket. Sometimes a large pocket, but still a pocket.
Dual-mode phones: cellular + Wi-Fi
You don't have to make a choice between cellular or Wi-Fi, or carry around masses of gadgets, because now you can have all these different protocols stuffed into a single phone. There are two categories of dual-mode cellular+Wi-Fi phones: Smartphones, which are phone + PDA (Personal Digital Assistant) combos, and plain old dual-mode phones that just make and receive phone calls.
The Nokia E61 (Europe) and E61i (USA) is one of the elite multi-mode smartphones, possibly the elitest. It supports quad-band GSM (850-, 900-, 1800- and 1900-MHz) so it's capable of world roaming. All you do is swap in different SIMs for different service providers to take advantage of the best rates.
It supports 802.11a/b/g Wi-Fi with WEP/WPA/WPA2 security, and comes with a SIP client for wireless VoIP. (Remember, WEP is a fairly weak security systemalways use WPA or WPA2.) The E16/16i also comes with all of the usual goodies: Web browser, e-mail, instant messaging, texting, a nice keyboard, voice recorder, media player, camera, expandable storage, provisioning and management over your network, and gobs moreall crammed into this little gadget. The E61/61i is readily available unlocked, so you can use it with any cellular carrier, and hook up to any wireless network for VoIP. It has a neat little "Wireless Wizard" to help you connect when you're traveling.
Watch out when you're looking at these fancy smartphonesmany of them boast of being dual-mode cellular plus Wi-Fi, but most of them do not support voice over Wi-Fi, just wireless Internet. Which is a nice thing if you happen to be yakking and Web-surfing at the same time, but it's not VoIPyou need a SIP client for that. You can get add-on Skype client software for several models of the Blackberry; it's called WebMessenger Mobile. Jajah is a Web-based VoIP service that works via any Web browser, so it should work on all Wi-Fi-enabled PDAs and smartphones that have Web browsers. Unfortunately, Jajah's call quality usually leaves a lot to be desiredbut it's worth trying.
There seems to be a wider variety of not-smart dual-modes phones, but beware of terminology confusion. Dual-mode refers to cellular + wireless VoIP, and it is also used in connection with cordless VoIP phones. For example, Linksys and Netgear both have dual-mode cordless Skype phones (DECT or Wi-Fi plus PSTN). These won't do you much good on the road, but they're convenient as corded desk phone replacements.
The UTStarcom GF-210, Pirelli DualPhone DP-L10, and the D-Link V-Click Dual-Mode Phone are three examples of the booming dual-mode GSM/SIP phone market. The UTStarcom and the Pirelli have settings for wireless preferred or cellular preferred, and will switch automatically according to what is available. Or you may select wireless-only or cellular-only. The D-Link phone has a button for manual switching. All three accept SIMs for easy traveling.
If you're a world traveler you really want a quad-band phone, or one that supports the 850/900/1800/1900 frequency bands. Of course these cost more. You can save money on a tri-band phone, but you have to be careful what you get. Tri-band 850/1800/1900 is best for North America, and 900/1800/1900 for Europe and parts of Asia.
What many users dream of are cellular and Wi-Fi services that interoperate seamlessly, switching back and forth as conditions warrant and never missing a call or noticing anything amiss. But we're not quite there yet. The necessary switching-technology issues have been solved by several solution providers, but most of these solutions are service-provider centric (that is, the equipment is deployed in the service provider's network), and the carriers just haven't adopted them yet.
Voice-over-Wi-Fi roaming within a wireless network is possible, but unless the WLAN in question is one of a number of proprietary centrally managed systems, the experience is likely to be choppy at best. Wi-Fi roaming across networks is even farther in the future, since there is no universal standard for roaming between WiFi networks. This, too, will most likely depend on cooperation between service providers. So, don't expect to be able to drive and talk via Wi-Fi connectoins any time soon, as you can with cell networks today. (But then, you shouldn't drive and talk anyway.)
Locked and unlocked phones
Some phones are sold as "locked," which means it works only with a single carrier's network. Unlocked phones can change networks simply by changing SIM cards. This is slick for globetrotting, because taking advantage of local networks and rates is as easy as swapping SIMs. You can't do this with a locked phone. Usually you'll get a substantial discount (or subsidy) on a locked phone, so figuring out the best deal is just a question of mathdo you pay more now, or pay more later?
That wraps up our look at wireless VoIP. Executive summary: Right now we're in the early-adopter, bleeding-edge phase.
Bold prediction: Wireless VoIPespecially with the adoption of WiMAX, the long-range broadband wireless standardwill someday dominate over old-fashioned cellular networks. It offers the potential of better security, and it will penetrate into rural areas where cellular providers don't like to go, so we'll get better coverage. We'll finally start to see genuine video phones and high-quality streaming services, even to small devices like phones. If you need an excuse to justify purchasing some cool gear, it won't hurt to starting getting familiar with Wi-Fi VoIP.