China Mobile, China Telecom, China Unicom, and China Radio and Television jointly announced the launch of commercial promotion of 5G cross network roaming, which is closely related to each mobile phone user. When the operator to which our phone number belongs does not have 5G network coverage in the region of use, it can automatically connect to the 5G network of other operators without changing the card or number. This is an important measure for 5G network sharing and a further deepening of telecommunications infrastructure co construction and sharing, which is conducive to reducing resource waste and improving user experience. The commercial use of 5G cross network roaming will effectively improve the coverage level of 5G networks and user 5G service experience in remote areas. The latest data shows that as of April this year, the number of 5G package users of three telecommunications operators, China Mobile, China Telecom, and China Unicom, has exceeded 1.4 billion. The 5G network has been complained by netizens from time to time about the poor signal, which is still in the construction period, and the 5G signal has not been covered in some areas, which is one of the important reasons. The commercial use of 5G cross network roaming will achieve fast coverage of 5G networks, reduce signal blind spots, improve user 5G network experience, especially allowing users in remote and rural areas to share 5G network services and narrow the digital divide. 5G network sharing helps empower various industries. 5G networks are an important component of new infrastructure, with significant integration and empowerment effects. If the coverage of 5G networks in remote and rural areas expands, the pace of digital transformation and upgrading of local industries will also accelerate. For example, 5G+agriculture can create a number of smart farms, smart ranches, and smart fishing grounds to improve agricultural production and operation efficiency; 5G+rural live streaming e-commerce can help farmers harvest and increase their income; 5G+healthcare and education can enhance public services in remote areas. For many years, China has spared no effort to comprehensively enhance the supply and service capabilities of broadband networks, precisely in order to connect the information arteries of high-quality development in various regions. There is a real market demand for promoting 5G cross network roaming for commercial use. On May 17th last year, China launched the world's first trial commercial trial of 5G cross network roaming in Xinjiang. The number of daily roaming users, roaming data volume, and roaming call duration exceeded 34000 people, 2000GB, and 200 hours, respectively. This not only verified the feasibility of 5G cross network roaming for commercial use on the current network, but also reflected the huge market demand. The commercial use of 5G cross network roaming can undoubtedly effectively reduce duplicate investment. If reasonable cross operator settlement can be done, comprehensive evaluation of 5G network coverage status and construction plan, network construction cost, user scale and other factors can be carried out, and 5G cross network roaming cooperation can be carried out as needed, the promotion pace will be faster and farther. The commercial use of 5G cross network roaming is essentially the co construction and sharing of telecommunications infrastructure. "Intensive utilization of existing resources, sharing without building new ones." Based on this principle, from China Tower Corporation, which emerged in response to the requirements of co construction and sharing in 2014, to the joint construction of 5G networks by telecommunications operators in recent years, co construction and sharing have always been the main theme of 5G network construction. Telecommunications infrastructure belongs to strategic, fundamental, and pioneering public infrastructure, and adopts the principle of moderate and advanced construction. Although 5G has high performance, the investment cost is also high, but achieving returns is not as fast. Therefore, telecom operators with competitive relationships are willing to join forces, indicating that co construction and sharing can reduce investment, achieve complementary advantages, and win more market opportunities. Further deepening co construction and sharing is the key to expanding the digital economy. Telecommunications infrastructure is the foundation for high-quality development of the digital economy, playing an important role in stabilizing investment, promoting consumption, assisting upgrading, and cultivating new driving forces. At present, 5G applications have been promoted in key fields such as industry, mining, power, medical care, etc., and the application of "5G+industrial Internet" has accelerated to expand to core control links; Integrating 5G with various technologies such as artificial intelligence, big data, and cloud computing to accelerate the evolution of 5G; Generative artificial intelligence is being promoted and popularized in applications such as chatbots, intelligent search, and text generation. Expanding the scope of co construction and sharing, innovating co construction and sharing measures, will inject strong momentum into industry transformation and digital transformation. Co construction and sharing do not necessarily mean a discount on network quality and service. Taking the commercial use of 5G cross network roaming as an example, this is a global initiative and will inevitably face many technical difficulties, including the launch of mobile phones and software that support 5G cross network roaming, effective network collaboration management between different operators, and cross operator settlement. With the increasing number of 5G users and applications, co construction and sharing also need to fully consider user scale and network carrying capacity, and solve technical problems caused by bandwidth doubling and multi frequency coexistence. More importantly, with network sharing, services cannot be reduced in dimensionality. Telecom operators should continue to optimize network quality, improve service levels, and enable users to truly share the benefits of information technology development. (Lai Xin She)