"Designing GSM segment of a network for the national operator of mobile communication Tunisie Telecom "

The rates of development of cellular communication in our country are so high, that only for a few years this service grew into a necessity for people with middle profits. Cellular communication becomes that, than she and must be - communication mean, competing already in separate regions with wire networks.

Development of segment of the GSM network for the national operator of the Tunisie Telecom communication is the purpose of this master's work.

Tasks of development:

- development of model of the GSM segment of network;

- research of descriptions of segment of network;

- design of the state of network at different fluctuations of traffic;

- choice of method of optimization of network structure and adaptation of her under a concrete prognosis;

- development of recommendations on the choice of equipment of the base stations, aerial highway, commutation equipment.

1. Principles of the GSM construction

Zoning the served territory is possible by two methods: statistical, based on measuring of statistical parameters of distribution of signals in communication networks, or determined, based on measuring or calculation of parameters of distribution of signal for a concrete district.

At a statistical method all served territory divides into identical on a form an area and by the statistical laws of distribution of radio waves is determined their possible sizes and distances to other areas.

Optimum to divide territory on zone, I.e. without ceiling or admissions of areas, three geometrical figures can be used only is triangle, square and hexagon. A hexagon is the most suitable figure, because if to set aerial in his center, the circular form of diagram of orientation will cover all his area almost.

Usually distributing of subscribers on all served territory is uneven (diminishes from a center to periphery), it is therefore expedient so to change cells, that was multiplied their sizes to periphery. It allows to decrease a cost on the whole due to diminishment of the necessary number BS. However in this case powers of transmitters of the central and mobile wireless stations will depend on the sizes of cells, it is therefore expedient to use the power of transmitter automatically managed on the signal of correspondent. In addition, for territories with the areas of a different size it is necessary more carefully to determine that of them, in which it is possible repeatedly to use working channels. At a static method the in most cases got interval between areas, identical working channels are used in which, turns out more of necessity from point of maintenance of mutual hindrances at possible level.

The determined method of division on areas is more optimum. At him carefully measure or expect the parameters of the system for determination of minimum number of the central stations providing satisfactory maintenance of subscribers on all territory, relief of locality for determination of optimum place of the TSRS location is taken into account, is present possibility to use the directed aerials, contiguous central stations in the moment of the spades loading and etc However difficult this method is and requires in a number of cases the design with the use of COMPUTER. It is necessary to define in the cellular systems, what TSRS to connect for communication with a subscriber SOFTWARE, I.e. to define the site of subscriber SOFTWARE on territory of service. High exactness of determination of site of mobile object is not thus required. At incoming communication, I.e. from TSS to the subscriber SOFTWARE, the signal of call can be passed either on the special calls or on free channels, to which wireless stations SOFTWARE tune in automatically. It is determined the location on the level of signal acting from the wireless station SOFTWARE on the nearest BS. which is included for the conduct of negotiations with subscribers SOFTWARE. At a move in the area of action of other BS the wireless station automatically passes SOFTWARE to the channel of new BS. Thus constantly the control after the wireless station must be provided SOFTWARE, for what in the process of conduct of talk with a subscriber SOFTWARE on BS and further in TSS jointly with speech control signals are passed.

2 Necessary basic data

The principles of planning resulted below are based on experience of planning of cellular communication networks in many countries of world and, foremost, on experience of the NOKIA firm.

The purpose of planning of network is: providing of scope of the required area of service with high quality of vocal communication; providing of capacity for maintenance of the subscriber loading with low intensity of losses. By the effective planning of network (for example, by the division of area of action of the base station on sector cellular cells), and also use of present buildings (buildings, masts, lines of transmissions and etc), it is possible to attain the minimum cost of infrastructure of cellular network. At planning of cellular networks every project is executed taking into account the desires and possibilities of customer.

For drafting of final project of network clear information about the following basic parameters is required: amount of present free channels; planned areas of service (cities and main roads); topography and types of localities in the areas of service (cards); existent buildings, etc. (list of the offered points of location of the base stations); estimation of distributing and increase of subscribers and loading; other parameters of planning (loading on a subscriber, possible intensity of losses, minimum acceptable tension of the field and etc) .

Because actually we do not know all afore-mentioned parameters, we produce here only the preliminary calculation of maximal capacity. He contains estimation of the required materials (base stations and channels). Two different aims stand before planning of network, dependency upon the served locality. In rural localities a main task is to produce large areas of scope with high power of transmission and high aerials (ordinary by nondirectional aerial). In towns, where loading is an intensive, main task is providing of maximal capacity and compact sizes of cells with small power and low aerials (often by the directed aerial and sector cells). The problem of planning of networks of city districts is that the same frequencies with a minimum hindrance are used. In city districts it is expedient to use the "umbellate" base stations, as they engulf such districts which are not enough well overcame by small cells.