Frequency Planning Methods For GSM System

Since the seventies of the last century, mobile communication system has experienced different stages of development with the tide of information technology. AMPS (Advanced Mobile Phone System), NMT (Nordic Mobile Telephone) are the first generation of mobile communications systems. These systems had a weak anti-interference ability, low spectral efficiency, poor confidentiality, and customers could not roam. Different manufacturers’ equipment could not be interconnected. To overcome the disadvantages CEPT (Conference of European Posts and Telecommunications) set up GSM (Group Special Mobile) for a second-generation mobile communication system in 1982. In 1988 eighteen European countries reached a GSM MOU (Memorandum of Understanding). In 1989 GSM standards were released. In 1991 GSM system was officially launched in Europe. Since the birth of GSM systems it has been gradually adopted by operators of most countries and becomes the only one universal mobile communication system.Theory of cellular technology is to divide a large area into a number of hexagonal cells. Each cell has a BTS (Base Transreceiver station) transmitting wireless signals to achieve coverage. The carrier frequency within a cell can be reused in another cell after a distance, because the same frequency interference has been reduced to a reasonable range. How to allocate each carrier frequency to make the system have good voice quality and more users at the same time is an important problem that network designers consider. On the basis of the frequency resources operator owned, the equipment capacities, as well as the actual situation to determine the frequency planning was concerned also by operators and vendors. In this article we study some frequently used frequency planning methods in GSM900 mobile communication systems, and calculate the respective C/I for these planning methods. This article also provides the conclusions of simulation tests which are consistent with these calculations. In the case of high frequency reusing C/I reduces, and hopping Frequencies have to be adopted for anti-interference. The article also gives the analysis and the proofs of the gain of hopping frequencies.