FREQUENCY PLANNING FOR CELLULAR MOBILE RADIO NETWORKS

Cellular mobile radio (CMR) networks with a high radio-frequency spectrum utilization efficiency began to be developed in many countries in 1980. In such systems, the number of subscribers for each assigned frequency spectrum is significantly greater than in traditional CMR networks. This efficiency is achieved by selecting the operating parameters of each of the base stations (BS) in the CMR system such that the base stations service small zones (cells) of radius R0 = 500-5000 meters. These cells provide coverage over the entire territory of population centers in which the base station network has been deployed as well as the roads connecting various population centers. In CMR networks, the distances between cells using the same frequency channels are not large [D = (3.5-5.5)R0] and hence a higher radio-frequency spectrum utilization efficiency is achieved due to the high degree of reuse of channels in these networks [1]. The set of nearby cells in which the same frequency channels cannot be used due to mutual interference is referred to as a cluster, while the number of cells comprising a cluster is referred to as its size. Antennas that are nondirectional in a horizontal plane as well as sector antennas (with a radiation pattern width of 60-degrees or 120-degrees) may be used at base stations. When sector antennas are used, each cell is divided into either 6 or 3 sectors with different frequency channels required for use in each sector [1]. Frequency bands have been assigned in the 450 and 900 MHz bands for CMR networks in Europe. The NMT-450 and NMT-900 Scandinavian narrowband analog systems operating in both frequency bands listed above are more commonly used. The European GSM system began to be introduced in 1992 in the 900 MHz band in a number of countries. NMT-450 systems are currently under development and construction in Moscow and St. Petersburg. The Ministry of Communications of Russia has decided to use the GSM standard to establish a nationwide CMR network. Deployment of the GSM networks in cooperation with foreign companies should begin in certain regions of Russia as early as this year. This paper describes a procedure for determining the fundamental parameters of the frequency plan for the CMR network which will make it possible to service a given number of subscribers at a prescribed level of quality.