SRVCC (Single Radio Voice Call Continuity)

SRVCC stands for Single Radio Voice Call Continuity. It is a mechanism that allows a mobile device to continue a voice call from an VOLTE network to another 2G/3G network.

When a mobile device is making a voice call over LTE, it is connected to the LTE network using a PS connection. A PS connection is a connection that is used to carry data, such as voice calls, text messages, and data transfers.

When the mobile device moves out of range of the current LTE network, it will be handed over to another LTE network. This is because LTE networks are designed to seamlessly hand over mobile devices from one network to another.

During an SRVCC handover, the mobile device will not be disconnected from the LTE network. Instead, the voice call will be transferred to the new LTE network. Once the mobile device has connected to the new LTE network, the voice call will be resumed.

·         SRVCC is a mechanism introduced in LTE networks to provide uninterrupted voice services when transitioning between LTE and legacy circuit-switched networks.

·         SRVCC enables the handover of an ongoing voice call from the LTE network (VoLTE) to the legacy circuit-switched network (2G or 3G) without interrupting the call.

·         When an LTE device initiates a voice call over VoLTE, the call remains on the LTE network as long as possible. However, if the LTE signal weakens or the device moves out of LTE coverage, SRVCC is triggered.

·         During SRVCC, the LTE device performs a seamless handover from VoLTE to the circuit-switched network, ensuring that the voice call continues without interruption. The handover is coordinated between the LTE and circuit-switched networks to maintain call quality and reliability.

·         When the LTE device returns to LTE coverage, it can switch back to VoLTE, and the ongoing call is handed back to the LTE network, ensuring a smooth transition between the networks.

Both CSFB and SRVCC mechanisms are important for providing voice services in LTE networks, especially in scenarios where VoLTE coverage is limited, or the device lacks VoLTE support. CSFB allows devices to fallback to legacy circuit-switched networks for voice calls, while SRVCC enables seamless handover between VoLTE and circuit-switched networks during ongoing voice calls, ensuring uninterrupted communication for LTE users.

SRVCC Evolution: