Reality Check: Finding a voice for 4G wireless

Editor’s Note: Welcome to our weekly Reality Check column. We’ve gathered a group of visionaries and veterans in the mobile industry to give their insights into the marketplace.
Fourth-generation wireless mobile broadband technologies such as Worldwide Interoperability for Microwave Access (WiMAX) and Long Term Evolution (LTE) are known for their fast data transmission rates. While they deliver on this front, neither WiMAX nor LTE were designed to deliver voice. This begs an important question: When operators adopt these technologies as their next-generation data solutions, how will voice be delivered?
There are a number of different 4G-compatible voice technologies currently under consideration by operators. Before an implementation strategy can be devised, however, the following key aspects of the proposed voice technology must be weighed:
—Features. Can the voice technology meet all the requirements (emergency calls, roaming, text messaging, etc.) of a commercial voice network? Can quality of service be guaranteed?
—Compatibility. Is the voice technology compatible with legacy voice networks?
—Devices. Will mobile devices that can use this voice technology be readily available? How many original equipment manufacturers can supply them?
—Investment. What level of capital investment is required to deploy new infrastructure for the voice technology? Are alternative models such as managed services feasible?
Each of the potential 4G-compatible voice technologies being contemplated by operators comes with a different implementation model:
—Circuit switched fall back. With this technology, smartphones will use the all IP-based network for data and switch to the traditional 2G/3G network (circuit wwitched) for voice. This is the most straightforward solution for operators who have existing 2G/3G telephony infrastructure. Currently, Verizon Wireless is using CSFB with its IP-based LTE network; Sprint Nextel Corp. is using it with its WiMAX network; and AT&T Mobility’s LTE network will soon follow suit.
CSFB is far from a one-size-fits-all solution, however. Operators who don’t have 2G/3G infrastructure won’t be able to employ this solution unless they partner with other operators who do. Further, CSFB won’t support many of the enhanced features possible with IP-based technologies, such as high-definition voice. CSFB can only be an interim solution as operators obsolete their 2G/3G infrastructure and migrate to all-IP alternatives.
—Session Initiation Protocol (SIP)/Voice over IP (VoIP) Telephony. SIP is a signaling and call-setup protocol that connects IP-based networks with the public switched telephone network, the “traditional” telephone network. VoIP technology uses SIP to implement software applications (e.g., Skype) and IP-based telephones (e.g., Vonage) that can function like regular telephones. SIP/VoIP telephony can operate on any broadband network with minimal capital investment.
Though SIP/VoIP has been widely successful in the wireline world, it still faces many challenges as a mobile telephony technology. For instance, many SIP/VoIP applications can’t provide QoS, so the overall quality of their voice performance can’t be guaranteed. SIP/VoIP phones also currently lack the ability to roam between networks, an essential requirement for commercial wireless networks.
—Voice over LTE (VoLTE). Designed only for LTE, VoLTE is the most advanced voice solution for IP-based 4G technologies so far. It’s built on top of IP Multimedia Subsystem, a complex framework that controls multimedia applications on IP-based networks. VoLTE supports all the standard 2G/3G network features as well as advanced features such as high-definition voice, and guarantees QoS. Given these unparalleled capabilities, Verizon Wireless and AT&T Mobilty have both shown their commitment to VoLTE, with plans to start building infrastructure in 2012.
Still, many smaller operators may suffer roadblocks. The heavy capital investment required will force them to source IMS from legacy mobile network infrastructure wholesalers. It will take years to build out VoLTE infrastructure that covers most geographical areas in the United States. In other countries, the time frame is extended even further.
Which option will win out? In the near term, CSFB is emerging as the voice solution for both WiMAX and LTE, as it leverages existing 2G/3G networks and coverage. In the long term, however, we expect VoLTE to win out as LTE proliferates and operators seek to consolidate on the most efficient and best-performing network technology.