Study On The Co-existing Interference Between Gsm And Td-scdma

This article is based on the special fund of Tianjin science and technology innovation projects and it is a sub-project of the next-generation mobile communication network research and applied demonstration for the coverage key technology. The purpose of the study is to provide guidance to protect GSM and TD-SCDMA interference between systems of the recommendations, and to give the corresponding anti-jamming solutions for the coexistence of the two systems.Presently, in the condition of 2G and 3G mobile communications coexistence, GSM system will exsit for a long time because it has improved its own technology and the existing network infrastructures. TD-SCDMA is the first self-innovation standard of the third-generation mobile communication of China. With the growing of data services, the demands for frequencies are very urgent. Different operators with different network configuration and network coverage are used more and more widely. Addtionaly, less antenna isolation in base stations of the system and other radio frequency devices may also cause interference.If we do not receive proper isolation and filtering for adjacent channel coexistence of two systems, it may cause the users who stay in base station coverage area many problems, such as dropped calls, poor call quality and so on.According to China's 3G system frequency planning of the program, TD-SCDMA system's uplink frequency band (1880MHz～1920MHz) and GSM's downlink frequency band (DCS 1800:1805 MHz～1880MHz) coexist in the 1880MHz frequency point. Due to the imperfection of the transmitter and receiver, the coexistence of two systems will continue to produce mutual interference, resulting in decreased link quality and system capacity reduction.The main researches of this thesis are as follows:1. The article contexts of the current foreign and domestic development of mobile communication systems, meanwhile, also it describes the status of co-existence interference study about the domestic TD-SCDMA system and the GSM system. By analyzing the key TD-SCDMA technology, GSM frequency bands, as well as interfering with the composition of the type, the article proposes anti-interference measures between systems.2. Based on a deterministic analysis method and Monte Carlo method, it is likely to analysis the co-existence interference at 1880MHz frequency of the DCS1800 and TD-SCDMA system, so it can give values of adjacent channel interference power ratio ACIR and the impact on the capacity situation.3. Shielding and isolation program designed——One coexistent filter for DCS1800 and TD-SCDMA system to suppression the interference. This filter can cut off its work frequency of the two systems, so useful frequency can get through and unwanted frequencies which resulting in interference can be filtered out. As a result, dual system adjacent frequency bands can not disturb each other. The filter can be used either in the system or a total station when they co-exist, and it is flexible and easy to operate. In addition, it can be installed according to the interfere cases. By comparison with MATLAB simulation, the digital filter can filter out the interference of adjacent frequency bands and make a reasonable coexistence of adjacent systems, after all, it improve the interference problem between the DCS 1800 and the TD-SCDMA system.