As most readers of this magazine know, LTE (News - Alert) network speeds are comparable to wired connections. The resulting insatiable desire to be connected at all times, everywhere has been a huge growth driver for the wireless industry. The GSA estimates that there was more than 130 percent growth in subscriptions in 2014 compared to 2013, and Statistica estimates that the number of subscribers will grow from more than 300 million in December 2014 to more than 1.3 billion in December 2018. Data and video usage, and smartphones that support the mobile on-ramp to the Internet, is what LTE has been justifiably all about to date.
Voice, however, is starting to play a part in LTE and will continue to play a larger role going forward. While 3G fallback for voice might work for some operators, at least for a period of time, having a single network for voice and data as soon as possible will be the way forward for some. The predominant type of voice with LTE will be HD Voice, and the latest GSA figures show 11 LTE operators have launched with HD Voice. Phones are also now capable of handling HD Voice. Apple’s inclusion of HD Voice support in the iPhone 6 is a clear indication of the coming importance of HD Voice on the LTE networks.
According to the GSMA (News - Alert), “HD Voice provides customers with high-quality, crystal clear, more natural voice calls on mobile and fixed terminal networks. Using wideband technology and further acoustical enhancements on phones, users experience greater clarity and intelligently reduced background noise.” For those familiar with HD Voice, that comes as no surprise. Many vendors supporting HD Voice, including Dialogic (News - Alert), have websites that include non-HD Voice and HD Voice demonstrations. But those are demonstrations.
There is now research coming out that supports these claims and also points to other VoLTE benefits. Signals Research Group has published a paper about VoLTE performance. The study tells a very good story, such as call quality as measured by MOS score (3.8) “greatly exceeding” 3G voice and being “measurably higher” than Skype (News - Alert) (3.4). This is not surprising given use of HD Voice with VoLTE. However, other information is just as important to VoLTE such as call setup times being “nearly twice as fast” as 3G and from a network resource perspective, there being “substantially fewer” resources required than Skype which results in longer battery life.
Ericsson has also released a study of VoLTE compared to three over the top voice services. The MOS scores and speech delay were markedly better with VoLTE. The Ericsson (News - Alert) reports goes on to say: “In summary, VoLTE is a real-time telephony service managed over the operator network end to end (IMS, EPC, LTE with policy control), and the service is always prioritized over all other services. OTT VoIP services run as best-effort data services over the LTE network and are thus mixed with all other data traffic. The OTT services can thus sometimes have high quality, and sometimes very poor quality, while VoLTE offers a high and stable quality throughout the calls.”
This is important information given that on a data network, many voice services will operate as OTT services. The kind of voice service you get on a wired Internet network is the type of voice service you’ll get on a wireless Internet network – that is, any OTT service is subject to the vagaries of the network. That is common sense as well, but often forgotten. The Ericsson document also points out improved battery life.
All of these factors point to VoLTE coming of age. There are more VoLTE hurdles to overcome, such as getting ubiquitous VoLTE roaming (like we do with 3G) and proving out call handover via Single Radio Voice Call Continuity. These are technical hurdles which undoubtedly will be overcome and point to a rich future for VoLTE.
Jim Machi is vice president of product management at Dialogic Inc. (www.dialogic.com).
Edited by Maurice Nagle