How do you handle the handover and roaming of VoLTE and IMS calls across different 4G networks and regions?

1 What is VoLTE and IMS?

VoLTE stands for Voice over LTE, which means using the LTE network to carry voice calls instead of the traditional circuit-switched networks. This allows for better voice quality, lower latency, and more efficient use of network resources. IMS stands for IP Multimedia Subsystem, which is a framework that enables the delivery of multimedia services over IP networks, such as video calls, instant messaging, and conferencing. IMS is based on the SIP protocol, which is a standard for initiating and managing sessions between different endpoints.

2 What are the handover and roaming issues?

A major challenge of VoLTE and IMS is maintaining a seamless and uninterrupted service when a user moves from one network to another or from one region to another. This can occur in two scenarios: handover and roaming. Handover is when a user switches from one base station to another within the same network operator, while roaming is when a user connects to a different network operator. However, there are several factors that can affect the quality and continuity of the VoLTE and IMS calls, such as network compatibility, network congestion, and network authentication. Network compatibility can cause issues or service degradation if different networks use different frequency bands, codecs, or features. Network congestion can lead to poor voice quality, dropped calls, or delayed messages due to high traffic or interference. Lastly, authentication and establishing a secure connection when roaming to a different network operator can take time and consume battery power, resulting in a negative user experience.

3 How are the handover and roaming issues solved?

To address the handover and roaming issues of VoLTE and IMS, the industry and regulators have developed several standards and solutions. SRVCC is a mechanism that allows users to switch from a VoLTE call to a circuit-switched call when they move to a network that does not support VoLTE, although this may result in lower voice quality or different features. VoLTE roaming enables users to make and receive VoLTE calls when they roam to a different network operator that supports VoLTE, as long as the network operators have an agreement and connection between their IMS cores, with a common set of features and QoS parameters. RCS is a set of features and applications that enhance the IMS services, such as chat, file sharing, group messaging, and video calling; it is designed to work across different networks and devices with a common platform and interface. This allows users to enjoy the benefits of IMS services even when they roam to another network.

4 What are the benefits of VoLTE and IMS?

VoLTE and IMS offer several benefits for both users and network operators, such as improved voice quality due to high-definition codecs and QoS mechanisms, enhanced multimedia services, and increased network efficiency. Users can access a variety of multimedia services over the LTE network, such as video calls, instant messaging, conferencing, and social media. All of these services are integrated with the user's contacts and phone number, offering a richer and more interactive experience. Additionally, VoLTE and IMS use the LTE network more efficiently than circuit-switched calls, allowing network operators to optimize their network resources and capacity while reducing operational costs.

5 What are the challenges of VoLTE and IMS?

Despite the advantages of VoLTE and IMS, there are also some challenges that need to be addressed. Network coverage can be inconsistent or unreliable in some areas, which can affect user experience, network performance and security. Additionally, not all devices are compatible with VoLTE and IMS, limiting user access and choice of services. Furthermore, user adoption may depend on factors such as user education, marketing, pricing, and incentives.