The global Voice over LTE (VoLTE) market is forecast to grow at a CAGR of more than 47% by 2021, according to a new study by market research firm Technavio.

Chetan Mohan, lead analyst at Technavio for M2M and connected devices research, described VoLTE technology as a "highly efficient spectrum" that improves data service capabilities.

"VoLTE enables mobile operators to integrate voice and data to one network technology while simultaneously evolving voice services that are above and beyond the benchmark set by the OTT players," said Mohan.

20170811_EETI_Technavio_VoLTE_Market (cr) Figure 1: Global VoLTE market by technology. (Source: Technavio)

One of VoLTE market's major product segments is the Voice over IP Multimedia Subsystem (VoIM) technology, which deals with the transmission of voice data over an architectural framework to deliver IP multimedia services.

According to Technavio analysts, the VoLTE market in VoIMs will grow significantly during the forecast period. However, as VoIP takes over the fixed-line voice subscriber base and VoLTE begins to rise, vendors must continuously formulate and modify their strategies to capitalise on the evolution of legacy core network technologies and invest in advanced technologies to allow their customers to compete in an all-IP voice market.

In the frame of next generation networks, many telecommunication companies have created their own solution with its own understanding of the SIP protocol. In turn, the operators had to purchase comprehensive end-to-end equipment from one vendor as such equipment was not compatible with the equipment of the other vendors. This led to interoperability problems among different telecommunication devices as well as interoperability problems between communicated messages from one solution to another. To solve these problems, VoIMS standards were created.

“VoIM base evolution on voice network in LTE will expand over time with the advent of 5G networks. In addition, the virtualisation and cloudification of IMS network functions and related elements will add to the growth of this technology,” said Mohan.

Service handover procedure circuit-switched fallback (CSFB) is another major VoLTE segment. The technology, by which SMS and voice services are delivered to LTE devices via GSM or other circuit-switched networks, is required since the LTE is a packet-based all-IP network that cannot support circuit-switched calls. The device falls back to the 3G or 2G network to complete the call or to deliver the SMS text message when an LTE device is used to make or receive a voice call or SMS. CSFB is mostly used as a temporary solution for LTE operators. VoLTE is the long-term goal for the delivery of voice services on LTE networks.

In November, Ericsson predicted that VoLTE would not be an overnight success in India as popular mobile carriers are expected to continue depending on the traditional CSFB technology for voice services. In VoLTE voice, the speech is broken and transferred as small packets using the IMS technology. Circuit-switched voice calling needs a particular circuit to be set up and reserved for the duration of a voice call.

The others segment includes dual radio or simultaneous voice LTE (SVLTE), single radio voice call continuity (SRVCC) and voice over LTE via a generic access (VOLGA) network. VOLGA offers short-term service acceleration and long-term investment protection, which are designed to provide profitable telephony services. VOLGA is likely to witness a rapid growth during the forecast period because all the operators are dealing with approaches for VoLTE and also attributed to faster call setup times as compared to other technologies, according to Technavio.

Meanwhile, SRVCC offers seamless voice call continuity when user equipment deliveries from LTE to 2G or 3G access networks are disrupted. Enhanced SRVCC (eSRVCC) offers support for advanced features like mid-call and alerting. It also supports access transfer control function (ATCF) and access transfer gateway (ATGW), which anchor the media in the IMS network to considerably decrease handover setup time from 1 second to less than 300 milliseconds.