As Mobile VoIP grows in the coming years, users will get on board via 3G networks provided by cellular handsets rather than over Wi-Fi.

That's the word from research firm Disruptive Analysis, which predicts 3G VoIP will draw more than 250 million users by 2021, as compared to less than 100 million voice users on Wi-Fi.

There will be technological and business hurdles to overcome, but the move to 3G VoIP ultimately is "inevitable," according to Disruptive Analysis's founder Dean Bubley.

In the first place, Wi-Fi simply is not up to the job, Bubley said. "It's fine in certain locations but has problems with continuous coverage indoor/outdoor," he noted. Moreover, "most Wi-Fi is not carrier-controlled—especially in enterprise—which means a whole raft of separate login procedures, or security configurations."

3G VoIP on the other hand will be given a big boost as carriers migrate their networks to all-IP radio in the next five to 10 years. Carriers are moving toward 3G-based LTE and UMB, and "if you want to run voice on these, it has to be VoIP-based," Bubley said.

Though it is early days yet, some companies already are moving in this direction. Bubley points to Skype, Truphone, Fring and Yeigo as VoIP players already supporting VoIPo3G.

In another technological evolution, "carriers are increasingly pushing EVDO or HSPA modems for consumer laptop users, competing versus DSL and cable broadband," Bubley noted, adding that such modems could easily prove a gateway to VoIP among willing users. "Some permit VoIP, and I expect many users ignore any prohibitions anyway."

Of course, the tide won't break all at once. Not all carriers will adopt 3G technologies straight out of the gate. Many will run different networks in parallel, supporting circuit voice for years to come. As a result, Bubley said, initial VoIPo3G will be tempered in some way. "There will be very few all-VoIPo3G users. Most will also have some usage of circuit voice, and some will use VoWLAN as well."

Nor will VoIPo3G muscle aside dual-mode (Wi-Fi/cellular) solutions in the immediate future.

"While there are some dual-mode enthusiast operators, they are few, notably Orange and T-Mobile US," Bubley said. "They will probably continue to push dual-mode, although they too will ultimately also look at wide-area wireless VoIP as they migrate their macro networks."

Dual-mode may persist in large part due to certain situation-specific advantages in Wi-Fi. For example, "Wi-Fi will continue to be more useful in some enterprise contexts, as businesses control it and can offload voice traffic onto their own networks."

Looking ahead, a number of variables could serve either to bolster or impede adoption of VoIPo3G, depending on how circumstances play out.

Bubley points in particular to the roll out of Long Term Evolution (LTE) and Ultra Mobile Broadband (UMB). On the plus side, both are all-IP and thus their speedy appearance in the marketplace could give a push to 3G-based VoIP. On the other hand, any number of factors could slow the appearance of LTE and UMB. An economic slowdown impacting carriers, standardization problems, or poor performance of handsets, all could prove problematic.

Likewise, it will take a while for HSPA (and the typical 3GPP carrier core networks) to be optimized for mass, scalable, efficient VoIP, Bubley predicted.

Carriers meanwhile could help move VoIPo3G forward by adjusting certain 3G terms-of-service policies that today are perceived as hostile to VoIP. Bubley points to Vodafone and Verizon,* which effectively restrict the user of VoIP on a cellular data plan. He points to policy changes already under way, including an offering by T-Mobile UK that specifically permits VoIP.

A further wildcard in the evolution of VoIPo3G has to do with the emerging role of third-party providers such as Truphone. Bubley says they might just play a role.

"To extend beyond the core 'enthusiast' base—i.e. people who know and care what a smartphone is, and who actually use its smartness if they get one—they will need to partner to get software preloaded and preconfigured on phones," he said. "This is starting to happen."

* Since this writing, Verizon stunned the world by announcing that, starting some time next year, it would open its network to all devices and applications—effectively reversing course and paving the way for widespread adoption of VoIPo3G.

Article courtesy of EnterpriseVoIPPlanet.com.