Only 8 out of 300 networks across the world currently provide VoLTE. As VoLTE is in its early days it will be complex, expensive and difficult, and as such, it may be more feasible to look at options via the circuit switch fall-back (CSFB) route. Reliance Jio can provide voice under the CSFB route. There have been limited deployments so far. Only the South Korean telecom market is an exception with VoLTE being widely used because of the availability of fibre across all towers, superior in-building coverage, and significantly higher consumer spending on telcos. Most operators are sticking to the Circuit Switched Fall back ( CSFB) option only as of now for VoLTE.
VoLTE Production in 2300MHz and 1800Mhz
VoLTE offers no obvious benefits except some minor benefits such High Definition (HD) voice by Integrating into the core network and special radio channels makes VoLTE expensive and incurs a production cost per minute compared with GSM.
- 2300 MHz Time Division Duplex (TDD) VoLTE – This option is full of challenges in the short term, particularly because this spectrum band suffers from poor indoor coverage.
- 1800 MHz Frequency Division Duplex (FDD) VoLTE & CSFB – Possible, but limited device range and high prices. Immature technology to use without a fall back to GSM/UMTS outside network coverage. It is possible to offer VoLTE as a primary solution and then fall back to 2G or 3G when, for example, you go out of coverage. Then it comes on SR-VCC (Single Radio Voice Call Continuity), however, it has led to significant operational issues and challenges.
- CSFB via Mobile Virtual Network Operator – Another alternative but MVNOs are not permitted in India and the regulations are still hazy.
- Using VoIP based application – No primary integrated voice service initially, however having a secondary voice service using a own VoIP based app which Reliance Jio has already developed licensing Codecs from a Russian innovator.
Challenges of TD and FD LTE services together
TD and FDD have a lot in common but in practice have a number of issues just not from the device side but also on the network side as it involves a switch from one to other, which usually means switching between bands at the same time, and notably band transitions are still relatively unusual in LTE, as most LTE network are single band. Hence the transition from one frequency band or one technology to another always has delays.