Research On Co-construction Of Indoor Distribution System

In recent years, the construction and investment of indoor distribution system has increased rapidly. Since seventy percent of communication occur indoor according to the business characteristics of subscribers, high-speed data services must have a guarantee of good signal for 3G and 4G market while this network uses high band and its propagation characteristics is not as good as traditional GSM900 or CDMA800. Hence the construction of indoor distribution system appears very important and will be the priority of network construction in the future. According to the Ministry of Information Industry’s requirement of co-construction and sharing of telecom infrastructure in 2015, since January 1, 2015, the three telecom enterprises do not construct the indoor distribution system any more in public transport sites such as subway, railway, expressway, airport and bus station. China Tower Company contracts to build the facilities above, making overall plans and take all the requests into consideration, taking the priority of co-construction. Co-construction and sharing of the construction of indoor distribution system can not only reduce a good number of laying of materials such as cables and components to save project investment but also decrease the difficulty of coordination with community property management.The passive distribution technology is widely used in the indoor system construction among three telephone service providers, which takes each road’s own standard system, respectively independent, avoiding interference by means of consulting avoidance of frequency. At present stage, the best way of co-construction of indoor contribution system is to access platform POI road through the multiple system, but now POI product performance is not as good as expected, which not only interferes with the network, and it can hardly support LTE MIMO, thus unable to give full play to the advantages of 4G. The analysis of the main three types of interference among operator’s indoor contribution system---spurious emission, blocking, intermodulation can determine that the most effective measure to avoid interference is to enhance the index requirements of POI, passive components’ isolation degree and intermodulation suppression, restraining the interference from the device capabilities. At the beginning of 2015, after detailed analysis and demonstration, the China Tower Company determined two POI products of standardization, and took the PIM≤-150 dBc high index for solving the problem of interference; standardize the POI with double cable routing scheme to support LTE MIMO technology; meet the three operators’ 9 or 12 frequency access requirements. Through confirmatory test, 9 POI frequency can well support China Mobile, China Unicom, China telecom’s co-construction and sharing, meeting the requirements of the room points LTE2×2MIMO double cable deployment.At the end of 2014, the Tower Company undertook the construction of indoor distribution system of Lanzhou west railway station. This project is the national first systemic ground cover project in which three operators’ nine systems of 2G, 3G and 4G construct and go into operation at the same time. 800-2700 MHZ wide frequency band and high-quality passive components and antenna got used in the project; The design of distribution system meets the functional requirements of implementing MIMO; POI + passive distribution system is adopted; standardized POI products are used by the Tower Company. After the completion of the project, the three operators’ network coverage, voice, data business met the qualification in the field tests. The design project of co-construction of indoor distribution system proved that by using the Tower Company’s standardized POI products, multi-band frequency and multisystem sharing can be realized in the same system, thus meeting the three operators’ coverage and capacity requirements in different scenarios.