Which standard allowed mobile phones to provide international roaming and conferencing calling in the 1990s?

The standard that enabled mobile phones to provide international roaming and conferencing calling in the 1990s is 2G (second generation). This technology marked a significant advancement over the previous 1G analog systems, which primarily supported voice calls without any data services.

2G introduced digital transmission, which allowed for encrypted communication and improved sound quality, along with the ability to send text messages (SMS) and multimedia messages (MMS). Importantly, 2G networks established the groundwork for additional services like international roaming, allowing users to use their mobile devices in different countries seamlessly. This capability was essential for travelers and contributed to the global expansion of mobile communications at that time.

Furthermore, with the implementation of digital signals, conferencing calling became more viable, enabling multiple callers to join the same conversation. The standards associated with 2G, such as GSM (Global System for Mobile Communications), facilitated these advancements, making it a critical milestone in the evolution of mobile technology.

In contrast, while 1G was limited to voice communication, and 3G and HSPA+ came later, bringing higher data rates and more complex services, they were not the standards primarily responsible for the introduction of international roaming and conferencing during the 1990s.