LTE is a long-term evolution plan based on the UMTS technology standard specified by 3GPP. It features high-speed, low-latency, and multi-bandwidth flexible networking. Can bring users a good data service experience.

The LTE network adopts a flat IP network interface and has no CS domain. It can only implement voice call through VOLTE. However, in the case that the previous LTE coverage is not perfect, in order to meet the needs of the user’s voice service, a transition solution, that is, a CSFB solution, is needed to enhance the user experience, and at the same time, the existing 3/2G network investment can be protected.

Currently, there are three main types of LTE voice service solutions: CS Fall Back architecture, SRVCC architecture, and VOLTE architecture. The three architectures evolved according to the scale of LTE coverage.

When LTE coverage is not perfect, the CSFB architecture is mainly adopted. When LTE coverage starts to take shape, but some areas are not continuously covered, the SRVCC architecture is adopted to implement VOLTE and 3/2G network handover. When the LTE network has reached continuous coverage conditions, The VOLTE architecture is adopted to implement voice service functions through the IMS on the EPC side.

 VoLTE (voice over LTE)

VoLTE, Voice over LTE, is an IMS-based voice service. It is an IP data transmission technology that does not require a 2G/3G network. All services are carried on a 4G network, which enables data and voice services to be unified under the same network. In other words, the 4G network not only provides high-speed data services, but also provides high-quality audio and video calls, which requires VoLTE technology.

CS Fall Back scheme introduction (Circuit Switched Fallback in Evolved Packet System)

Background: With the growing demand for wireless data services and the mature commercial conditions of LTE, operators will gradually introduce LTE networks to meet the rapidly growing demand for wireless data services based on existing GERAN/UTRAN networks, but how to simultaneously serve users. Providing voice services has also become a problem that operators have to face before introducing LTE. 3GPP TS23.272 V8.5.0 provides a mechanism for circuit domain fallback to ensure that users are simultaneously registered in the EPS network and the traditional circuit domain network. When the user initiates voice service, the EPS network indicates that the user falls back to the target circuit domain network. , then initiate a voice call. . The short message of the user is realized by passing between the EPS network and the traditional circuit domain network, and does not have to fall back to the target circuit domain network. The short message solution is SMS over SGs.

 SRVCC (Single Radio Voice Call Continuity)single voice call continues

Principle: When a user conducts voice services on an LTE network and needs to switch to a GSM/UMTS network,

To ensure that the user’s voice service is not interrupted, the product provides an SRVCC solution, which solves the seamless handover of the voice service based on the LTE network to the voice service of the GSM/UMTS network.

Application Scenario: The SRVCC service is mainly applied to the network of the hybrid network. In the initial stage of LTE network deployment, only the network exists in some areas. When the user roams from the LTE network to only the GSM/UMTS network area, the original LTE network Voice access needs to be switched to the GSM/UMTS network. The SRVCC ensures that the user’s voice service is not interrupted during the handover process, improving the service quality of the operator.

Dobry 4G fixed wireless phones use VoLTE solution. For details please click here