Application And Study Of Cynchonous Transmitting Technology With Same Frequency In350M Communication System For Public Secuirty

In order to protect the wireless communications’ coverage, improve theutilization of the police dedicated350MHz frequency, and solve the problem thatthe terminal machine automatically over the net when communicating wirelessly,the introduction of the consistent frequency and broadcast technology for the350MHz analog communication system is a better solution. Its working principle is:the method of dynamically allocating frequency is adopted in this system for allchannels of each base station besides the controlling channel. When a radio initiatesa call, the system will allocates signal from the frequency database according tothe pre-established allocation strategy, then the transmitting frequency of the voicechannel will be carried out in accordance with the newly assigned frequency, allfrequencies belongs to the police dedicated350MHz field. This technology uses thenode control center configuration strategy when allocating the frequency. When onevoice channel receives frequencies assigned by the node control center, the voicechannel is tuned to the corresponding frequency by the Phase-locked loop using thefrequency-synthesis-control technology.This research is mainly about the application of the consistent frequency andbroadcast technology in the police dedicated350MHz field, and also involves thetechnical characteristics and the differences between simulcast systems andconventional simulcast system, as well as the the latest application in Tianjin publicsecurity bureau. The analysis about the police350MHz analog communicationsystem, the research and design about the fequency-synthesis-control technologyare all completed. The research involves the feasibility and reliability of using thefequency-synthesis-control technology to solve such problems as system coverage,system nerworking, the capacity of base station, the use of frequency and rovingover the net. The research shows that can effectively solve some difficult problemsof traditional simulcast system, so intensive base station network can be adopted inthe simulcast system. At the same time, the expansion of the system will be freelyby means of increasing base stations to expand system coverage continuously.Also, the difficulties of network restructuring, overlapping coverage by base stationsand the network switch of controlling channels will all no longer exist.