How China’s First Cross‑Operator Traceable VoWiFi Call Is Changing Mobile Connectivity

Recently, the telecom industry marked a historic breakthrough: China Telecom and China Unicom successfully completed the industry's first cross‑operator traceable VoWiFi call in Shandong, offering a solution for indoor weak coverage that hampers voice and SMS services.

Even when callers belong to different operators, Wi‑Fi‑based calls display the real phone number, count toward the user's plan minutes, and support precise traceability to ensure security.

Back in May 2022, Shanghai Telecom achieved the world’s first end‑to‑end traceable VoWiFi call, laying the foundation for the new cross‑operator capability.

VoLTE (Voice over LTE) runs voice over 4G, while VoNR (Voice over New Radio) is its 5G evolution. VoWiFi (Voice over Wi‑Fi) shifts voice transport to Wi‑Fi, allowing users to make calls and send SMS without cellular signal, provided a Wi‑Fi network is available.

In China, VoWiFi has not been commercialized because emergency calls lack traceability. The new solution introduces a dual‑factor authentication scheme using the user and a home‑gateway, achieving reliable security and precise household‑level traceability, recognized by the Ministry of Industry and Information Technology and the China Academy of Information and Communications Technology.

Following the 2022 breakthrough, pilot VoWiFi services launched in Shanghai, Zhejiang, Guizhou, Sichuan, and Guangdong. Users in Guangzhou and Shenzhen can already experience the service if their phones support it.

When Wi‑Fi is stable, VoWiFi provides seamless signal switching, displays the real phone number, and is billed as regular voice traffic without extra fees or data consumption, often delivering clearer and more stable call quality than VoLTE or VoNR.

The core innovation is the "cross‑heterogeneous" broadband traceable interworking scheme, now adopted as a CCSA industry standard, filling a national standard gap and allowing other operators to follow the same technical specifications.

Field tests in Shandong and Hunan, using optimized DNS and ePDG discovery, achieved zero‑perception, zero‑wait handover, delivering a "one phone, all‑network" experience. The solution also extends to satellite communications, offering new paths for remote‑area connectivity.

Overall, VoWiFi is a highly practical technology that mitigates signal dead zones, provides stable calls, and, as it matures, will become widely available to enhance user experience.