Last year was the year of LTE. Following significant global LTE deployments (318 operators in 111 countries, according to Frost and Sullivan), Voice-over-LTE (VoLTE) is now finding traction. As with many technology firsts in mobile networks, Asia Pacific is leading the way. In fact, of the ten VoLTE launches that have taken place across the world, as many as eight are in Asia, in markets such as Singapore, Hong Kong, and South Korea.
VoLTE will determine the timetable for all-IP mobile networks
Mobile traffic today is dominated by data. However, until recently, voice / SMS represented as much as 70% of operator revenues in the region and are still the most used mobile services on a global scale. It is the addition of voice to LTE services – Voice over LTE, or VoLTE – that will allow mobile operators to start removing their legacy 2G/3G network overlays that currently provide voice services and migrate to all-IP packet-based networks. It is well accepted among the operator community that the higher quality of user experience offered by VoLTE will make it a key differentiator against new entrants and Over-the-top (OTT) players, since VoLTE will use dedicated bandwidth unlike OTT solutions.
In 3G networks and first generation LTE networks, operators are relying on circuit-switched technology to provide voice services. This is inefficient and expensive. VoLTE will allow mobile operators to simplify their networks by having voice services carried over the same LTE network that carries data today, which will allow for significant savings. It will make mobile networks more efficient as voice over IP improves wireless spectral utilization while taking up less bandwidth than circuit switched voice on the backhaul network. Mobile operators could offer HD voice, or wide-band voice, which is hotly anticipated as providing far better audio quality and easily integrated into applications such as speech recognition, interactive voice response systems, and even high fidelity music.
One of the key issues affecting VoLTE deployment timescales will be the time taken by legacy 2G/3G subscribers to migrate to 4G/LTE handsets, which in turn will be driven by affordability and mobile handset subsidies. More affordable 4G handsets have started to appear in the market. Until VoLTE uptake achieves critical mass, there will be a transitional period when networks will operate 2G/3G and LTE technologies side by side.
Underlying packet-based networks need to be optimized for VoLTE delivery
OTT VoIP applications (ex. Skype) run over an LTE best effort data network, and thus cannot guarantee quality of service, as they share bandwidth with web browsing, gaming, and audio/video streaming. VoLTE will use dedicated bandwidth that enables better voice (and video) call quality compared to OTT VoIP-based solutions. As a result VoLTE will place greater demands than ever before on mobile network performance and end-to-end quality of service.
The VoLTE quality of experience for the end-user is dependent upon the underlying end-to-end network with respect to packet loss, inter-packet delay, and inter-packet jitter. To enable high quality voice with low latency and a realistic experience, alongside value added services such as video calling, mobile operators must invest strategically in VoLTE hardware and software.
To handle the traffic loads a new class of metro Ethernet platforms is needed that combine carrier-grade Ethernet with coherent 100G+ transmission technology. Of particular importance will be an end-to-end packet-based network that offers very low latency, jitter, and loss to ensure a competitive quality of experience; attributes that legacy router based-networks are not able to deliver. These investments will become even more important as operators remove the legacy TDM networks used for synchronization of 2G/3G based voice services.
Additionally, the core network supporting VoLTE services will need to be agile to respond to traffic patterns, small-cell deployments, and the evolution towards cloud RANs. It should also easily scale to meet capacity requirements. As VoLTE gets established, we can expect to see fully SDN-enabled mobile network infrastructure that then serves as a “platform” for new kinds of application and services delivery.
As they plan for the launch of VoLTE services, mobile operators must invest now in an underlying network architecture that delivers high quality, and enables flexibility, programmability, and scalability, all while keeping transport costs to a minimum.
Karl Horne, Chief Technology Officer, Asia Pacific, Ciena