Voice over long term evolution (VoLTE) is the new technology that is gaining momentum. As data consumption continues to grow by leaps and bounds, VoLTE is expected to be the future of voice traffic. The Indian telecom industry, however, is still awaiting the full implementation of LTE technology. With 3G services struggling to reach the masses in the country, leveraging the distinct advantages of VoLTE could be some time away for the Indian market.

VoLTE allows calls to be made and received using an LTE data network rather than through a traditional cellular voice connection. VoLTE is a popular concept in telecommunication circles because LTE does not natively support voice calls as it is a data-only network. This is one of the main reasons why LTE is a simpler network to set up for carriers and why it has significantly higher capacity, faster transmission speeds and reduced latency. VoLTE systems convert a voice call into data, which is then transmitted using the data connection. For the first time, voice and data will coexist in harmony on the same radio layer, implying that smartphones will not need to switch back to 3G or a different spectrum frequency to handle both capabilities. If operators fail to develop solutions that will allow voice calls to be made over LTE networks, they will have to maintain legacy networks for voice communications. This will leave them unable to benefit from the superior spectrum utilisation and cost efficiency that LTE offers over legacy technologies.

VoIP versus VoLTE

One of the major advantages of LTE would definitely be its faster data connectivity. Consumers will be able to experience the full potential of data services such as gaming and surfing on mobile phones. This will also mean more revenue streams for operators and the content industry.

VoIP using internet-based 2G and 3G applications (for instance, Skype and Gtalk) have been available since 2010. The data path used by over-the-top (OTT) voice applications is not differentiated from other IP data traffic; as a result, the quality of service for voice calls is severely compromised.

VoLTE, on the other hand, uses the IP Multimedia Subsystem (IMS) and new radio access network features to ensure low latency, improved error correction in fringe areas, and other features that guarantee voice services that match or surpass the quality of anything we have experienced so far. The fundamental difference between simple VoIP and VoLTE is that VoLTE has the ability to deliver quality of service.

Benefits of VoLTE

VoLTE supports the wideband advanced multirate codecs that enable the next level of evolution of the phone call, that is, high-definition (HD) voice. It also provides call continuity across different networks such as 2G and 3G, which is not available with OTT VoIP.

• Faster call set-up: One of the benefits of VoLTE is its one-two-second call set-up time, while on circuit switch, the UMTS/GSM layer typically takes 5-10 seconds.
• Sound quality: The highest possible bit rate can be defined in VoLTE. Currently, the global voice standard supports AMR-WB codec at 23.85 kbps, which is HD voice.
• Longer battery life:

1. Compared to OTT services like Skype and Gtalk over LTE, VoLTE sessions require significantly less power, since the processing happens on the baseband processor or modem rather than on the application processor.
2. As the call set-up time is less with VoLTE, the battery life of the user device is increased by 15-20 per cent.

• Sessions: Simultaneous voice and data connections are achieved through the shift to VoLTE. It also has the potential to be combined with rich media services.
• Multimedia services: VoLTE enables multimedia content sharing during voice calls, video calls and video sharing.

For network operators, VoLTE offers a host of marketing and operating advantages, including:

• Reduced cost and complexity of network since it is a single IP network for voice, video and other data services.
• Enhanced user experience, which could lead to ARPU augmentation.
• Capability to support rich multimedia applications like HD voice.
• Given its efficient spectrum utilisation, it provides opportunities for opex savings from consolidation and optimisation.
• The rich communication suite, which is supported in VoLTE, enables operators to compete with OTT providers with the ultimate combination of rich voice and messaging services including SMS, instant messaging, group chat, live video sharing and file transfer.

Roadblocks and challenges

The major challenge in the implementation of VoLTE will be to set up the infrastructure necessary for enabling seamless service. Some of the requirements are:

• Testing of end-to-end IMS signalling over the LTE radio access network.
• Mobility between packet switched and legacy circuit switched networks in order for voice calls to operate with no discernible effect on the user’s experience when moving from one network to another.
• Complying with standards to ensure global interoperability.
• Adherence to regulatory requirements such as emergency calls.
• Rapid evolution of the device ecosystem to support VoLTE functions seamlessly.

VoLTE deployment in India

When it comes to the post-deployment phase in India, a VoLTE operator could be faced with lack of network continuity, both intra- and inter-operator. Therefore, until an operator has deployed VoLTE across all its licensed service areas, subscribers’ VoLTE experience would remain limited within the coverage areas of select cities. Similarly, when subscribers move to service areas where the operator does not have service licences, there could be a disruption of service if the operators in that service area have not adopted VoLTE.

The lack of pan-Indian broadband wireless access spectrum is a significant challenge for enabling seamless roaming across India. IMS provides the framework to support VoLTE. However, the lack of this infrastructure is the single biggest challenge facing most Indian operators, and preventing them from leveraging their LTE assets fully. Due to this limitation, operators need to rely on circuit switched fallback technology to support voice calls. Currently, the Indian market is in the trial phase for both LTE and VoLTE. Experts predict that LTE adoption will take at least two more years. However, the LTE and VoLTE adoption curve is predicted to be faster than that of 3G.