7. Problems of design and monitoring in cellular mobile communication systems. 7.1. Goals and objectives of design

The aim of the design is the optimal construction of a cellular mobile communication network according to the main criterion: high efficiency - minimal cost [7.1–7.3]. In this regard, the tasks of designing such a network include:

- determination of installation sites for base stations (BTS),

- distribution of frequency channels between cells, that is, drawing up a scheme of repeated cluster allocation of frequencies in a cellular network,

- determining the number of users for the calculated traffic,

- optimization of the cellular network for the minimum number of cells (minimum cost of network deployment) and high reliability of communication.

Naturally, the requirements of high efficiency and minimum cost are contradictory: if the number of cells is excessively increased (that is, cell sizes are reduced by creating micro or pico cells), this will increase communication reliability (that is, increase communication quality — a specified error probability value per bit) will increase the possible the number of users will reduce the maximum values ​​of the output power of mobile stations at the edges of the cells (that is, reduce the level of electromagnetic exposure of users), but all this will lead to an increase in cost times turning the cellular network and to a certain extent its operation. In the case of a rare location of cells (a small number of them) with large maximum radii of cells, “dead zones” may appear in which user service is impossible, and the radiation power of mobile phones at the edges of the cells will increase (the level of electromagnetic exposure of users will increase). Since the technology and parameters of the cellular network substantially depend on the terrain conditions (terrain, forest areas, buildings, etc.), the design of a cellular network requires the presence of:

- topographic maps of the area with all parameters and characteristics (irregularities, forests, building density);

- characteristics of the equipment to be used and the results of an approximate assessment of the energy balance, as well as the results of the preliminary design of the network hundreds and locations of base stations (radio coverage of the territory);

- the obtained scheme of radio coverage of the territory using appropriate models of radio wave propagation and terrain characteristics; it is also necessary to more accurately calculate the parameters of the electromagnetic field within the service area, allowing to assess the quality of radio coverage;

- drawn up a territorial-frequency plan (distribution of frequency channels by cells in accordance with the principle of frequency reuse) for the developed cellular network, as well as traffic and capacity estimates for specific sections, cells and the network as a whole.

If for any indicators (quality of radio coverage, traffic, capacity), the compiled scheme does not meet the requirements imposed on it, a repeated adjustment is made, and the calculations are repeated for the refined cellular network scheme.

Thus, the cellular network design process is iterative. In addition to the design procedure considered above, it is necessary to add experimental measurements of the electromagnetic field levels (usually the power flux or electric field density at various points from the base stations) and, based on the measurement results, correct the cellular network scheme again. The final quality of the project is assessed at the stage of network operation, where adjustments and refinement of the network are also needed. This especially applies to the initial stage of operation of a cellular network operator, when setting up the equipment and optimizing the cellular network is implemented. This stage is the most time consuming.

Below, we consider the first estimated design stage of a cellular mobile communication network, which implements approximate estimates of the radio coverage of the service area, frequency distribution (by clusters and cells), traffic and the number of possible subscribers (which are served in cells and in the entire cellular network).