Engineers at Qualcomm and Ericsson have managed to achieve the world's first mid-call switch between Voice over LTE (VoLTE) and a WCDMA 3G network. The ability to switch between networks seamlessly during a call is a requirement of standards regulator 3GPP, making this an important milestone on the way to making VoLTE available to consumers. The use of VoLTE could significantly lighten the load on 3G networks, and enable carriers to begin using the system even where their LTE coverage isn't widespread — something we heard that Verizon may already be trialing.

The in-call switching relies on two advances, single radio voice call continuity (SRVCC) and circuit-switched fallback technology (CSFB). CSFB is currently already in use in handsets, and is responsible for switching to the 3G modem when a user needs to make a call. The combination of SRVCC and CSFB mean that one radio is capable of handling both 3G and LTE connections, which could also be a major step in overcoming the battery life issues that currently plague many LTE handsets.

Qualcomm will demo the technology — based on its Snapdragon S4 MSM8960 chipset — at Mobile World Congress later this month.