VoLTE (Voice over LTE) is a technology that carries voice calls over the 4G LTE data network. Compared to traditional 3G circuit-switched calls, it offers three key benefits: HD Voice for higher audio quality, faster call setup (from about 2 seconds down to about 1 second), and the ability to use data while on a call.
Before VoLTE, a method called CSFB (Circuit Switched Fallback) was used, which dropped the connection to 3G for voice calls. This approach took several seconds to connect and limited data to 3G speeds during calls. VoLTE eliminated these issues by keeping calls on 4G. NTT Docomo launched the first VoLTE service in Japan in 2014.
For 5G networks the equivalent technology is VoNR (Voice over New Radio), the successor to VoLTE. VoNR offers even lower latency than VoLTE and allows simultaneous use of 5G ultra-high-speed data and voice calls. The difference from VoIP and Wi-Fi Calling is that VoLTE runs natively on the carrier's mobile network.
The spread of VoLTE is closely tied to 3G network shutdowns (3G sunset). KDDI and Okinawa Cellular ended au 3G service on March 31, 2022. SoftBank ended its own on April 15, 2024 everywhere except Ishikawa Prefecture, where it ran until July 31 of the same year. NTT Docomo followed on March 31, 2026, closing FOMA and i-mode, so as of August 2026 all three major Japanese carriers have shut down their 3G networks. After the 3G shutdown, devices that do not support VoLTE are unable to make voice calls, so users with older handsets need to upgrade to VoLTE-compatible devices. See VoIP Basics for an overview of voice call technologies.