Voice over LTE (VoLTE)
In the mobile business, the telephony service has been the major source of revenue for most mobile operators. Even with the proliferation of smartphones, the voice service is still considered important by users. For the success of LTE, it is of crucial importance to maintain support for the voice service over the LTE network.
8.1 Voice Solutions for LTE
8.1.1 Ultimate Voice Solution
The open architecture of the Internet Protocol (IP) created the flexibility that has enabled a thriving multitude of multimedia services to be available over the Internet. To integrate mobile access with the IP multimedia services, 3GPP has defined an architectural framework, called the IP Multimedia Subsystem (IMS), to deliver IP multimedia services over 3GPP systems. The success of the IMS in 3GPP motivated other organizations in the same industry, such as 3GPP2, to adopt the IMS as the architectural framework for IP multimedia services. The IMS also supports integration with the wired network, creating the potential for fixed–mobile convergence.
The mobile industry has been motivated by the success of the IMS standard, and the richness and flexibility of the IMS architecture provides a reliable framework to enable fruitful multimedia services including a voice service with guaranteed quality of service. The IMS is considered by most operators to be the ultimate architecture to provide a voice service over the LTE network. Figure 8.1 illustrates the concept of a voice ...