Core Viewpoint - The communication industry in China has achieved a historic breakthrough with the successful launch of the first cross-operator traceable VoWiFi call between China Telecom and China Unicom in Shandong, addressing issues related to weak cellular network coverage indoors [1][18]. Summary by Sections VoWiFi Technology - VoWiFi (Voice over WiFi) allows users to make voice calls over WiFi networks, solving issues in areas with poor cellular coverage [8][9]. - Unlike VoLTE (Voice over LTE) and VoNR (Voice over New Radio), which rely on 4G and 5G networks respectively, VoWiFi operates independently of cellular signals, requiring only a WiFi connection [8][9]. Historical Context - The first end-to-end traceable VoWiFi call was successfully made by Shanghai Telecom on May 20, 2022 [4]. - VoWiFi services had not been officially launched in China due to regulatory challenges regarding traceability [9]. Technical Innovations - A dual-factor authentication system was developed to ensure reliable traceability and security for VoWiFi calls, achieving higher precision than VoLTE [10]. - The cross-operator traceable VoWiFi solution has been recognized by experts from the Ministry of Industry and Information Technology and the China Academy of Information and Communications Technology [10]. Market Implementation - Following the announcement of VoWiFi by China Telecom in 2022, pilot programs were initiated in five provinces in 2023 [11]. - Users in cities like Guangzhou and Shenzhen can now experience this service, provided their devices support it [14]. User Experience and Benefits - VoWiFi can enhance call quality in areas with weak cellular signals, providing clearer and more stable communication compared to traditional voice calls [17]. - The service is automatically activated when mobile signals are poor, ensuring seamless connectivity [18]. Industry Impact - The technology has been adopted by both major operators and is set to become an industry standard under the China Communications Standards Association (CCSA), promoting collaborative development across the sector [19]. - The implementation of this technology not only expands the user base for VoWiFi but also opens new communication pathways in remote areas and special scenarios [19][20].

Group 1 - The article discusses the evolution and significance of dual SIM card functionality in mobile phones, highlighting its origins and the role of Chinese manufacturers in popularizing this feature globally [1][3][5] - The introduction of low-cost chip solutions by companies like MediaTek significantly reduced manufacturing costs, enabling the rapid proliferation of dual SIM phones [3][6] - The demand for dual SIM functionality in China is driven by factors such as varying telecom package costs, the need for separating work and personal numbers, and differences in network coverage among operators [8][10] Group 2 - The article explains the technical aspects of dual SIM technology, including the two main modes: DSDS (Dual SIM Dual Standby) and DSDA (Dual SIM Dual Active), detailing their operational differences [15][17][19] - DSDS allows both SIM cards to be on standby but only one can be active for calls or data at a time, while DSDA enables simultaneous use of both cards for calls and data [19][21] - The advancements in VoLTE and VoNR technologies have enhanced the quality of voice and video calls over 4G and 5G networks, respectively, improving the dual SIM user experience [23][25] Group 3 - The evolution of SIM card sizes from Mini-SIM to Nano-SIM has facilitated the physical implementation of dual SIM functionality in smartphones [29][30] - The design of SIM card slots has transitioned from fixed internal slots to more user-friendly removable trays, allowing for better space management within devices [30][33] - The emergence of eSIM technology represents a significant shift, eliminating the need for physical SIM slots and enhancing device waterproofing and user convenience [37][40][41]