| The establishment of China Tower in 2014 coincided with the beginning of large-scale construction of China’s fourth generation mobile communication network(4G)and fifth generation mobile communication network(5G),and the explosive growth of data services gradually dominated.According to statistics,75% of 4G services occur in indoor scenarios,and the industry predicts that more than 80% of 5G services will occur in indoor scenarios.The proportion of indoor services is increasing,and the importance of indoor coverage is increasing.Distributed antenna system is more sensitive to system interference than macro base stations.Distributed antenna system coordinated and shared by China Tower,the frequencies of China Mobile,China Unicom and China Telecom will coexist in the same system.Interference has become a key issue affecting the coverage quality of the sharing and joint-success communication project.At the beginning of the establishment of China Tower,the industry lacked systematic research achievements on distributed antenna system sharing and joint-success and did not formulate corresponding technical standards.The same set of compartment needs to meet the sharing of up to 9 to 12 systems at the same time.Passive intermodulation is the main interference problem shared by multi frequency and multi system.Passive intermodulation related to product quality,source power,construction technology,connection stability and other factors;As a result,it is very difficult to avoid the Passive intermodulation between systems.Based on the analysis of the sharing needs of the three operators,this paper forms key technical points,calculates and analyzes the best electrical performance that can be supported by components and leaky cables one by one,and verifies it through the deployment of sample points through laboratory testing.Through systematic product design,laboratory performance testing,and deployment of products and solutions at sample points in the laboratory,the product standards and prevention system improved to achieve the purpose of reducing the impact of passive intermodulation.From theoretical analysis to experimental verification,the main work is as follow.1.Systematic research on multi system sharing.Passive intermodulation of multi system shared is studied,and a method to avoid passive intermodulation interference of multi system shared proposed.It makes it possible to deploy distributed antenna system with stable and reliable performance in a shared way.2.Solve the problem of shared frequency interference.The generation of interference signal related to the quality of components and their connection stability.The connection stability is enhanced the use of enhanced connectors to connect with feeders.The passive intermodulation interference index of distributed antenna system has greatly improved.3.The railway tunnel scene is special,and the train runs fast.The leaky cable scheme used to achieve wireless signal coverage.After the 5G signal added,the leaky cable high-frequency index optimized through an innovative scheme,and the 5G source equipment deployed in common with other sources.The signal coverage ensured and Passive Inter Modulation interference suppressed to the greatest extent.In this paper,the causes of passive intermodulation and the suppression scheme combined with specific engineering practice.Through tests and sample point tests,it concluded that using equipment that meets the requirements of intermodulation index,strengthening the stability of components and formulating a reasonable construction scheme provides a specific solution f or passive intermodulation suppression when mobile communication systems sharing and joint-success. |
PDF Full Text Request