RU2475965C2 - Method to assign radio data in cellular network - Google Patents

Abstract

FIELD: radio engineering, communication.

SUBSTANCE: in a cellular network comprising base stations they are arranged in units of communication lines crossing between base stations, providing for full coverage of a service area. Crossing of mutually perpendicular lines breaks the service area into squares, in angles of which they install the first base stations, and inside squares they install two additional base stations at equal distance both from the first base stations and from each other, besides, in adjacent squares communication lines between additional base stations are mutually perpendicular. Assignment of radio data is carried out in the following order: base stations in angles of squares formed by crossing of mutually perpendicular lines serially with identical shift by a module of cluster size bottom-up and from left to right. Two basic stations inside squares are marked with the same frequency shift by a module of a cluster from right to left or top-down depending on their installation inside the square.

EFFECT: provision of optimal use of a frequency resource by placement of basic stations on the specified territory with full coverage of an area for provision of continuity of radio exchange during transition from one cell into another.

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Description

The method of assigning radio data relates to the field of radio communications, in particular to communication systems and information exchange.

The organization of cellular communication systems is based on the division of the served territory into microzones - cells. In the cell allocate a base station (BS) located in the center of the circle, called the communication zone of the BS. To ensure continuous communication in a given territory, it is necessary that the communication zones from adjacent BSs completely, without gaps, cover the service area. This achieves the condition under which the area irradiated by the BS radio station was as large as possible while maintaining the conditions for ensuring the necessary level of the received signal. The following basic geometries of placement of base stations are known, which provide full coverage of the served territory (see the book “Communication with Mobile Objects in the Microwave Range” / Edited by W.K. Dzheyksa. - M .: Communication, 1979. - 520 pp.): a) equilateral triangles, b) rectangles (squares), c) hexagons. Cases a) and c) are the same, since hexagonal honeycombs can be constructed from equilateral triangles. Therefore, only the first two structures will be considered as analogues. The optimal location of the BS stations is achieved when the distance between the BS is approximately equal to the doubled radius of the BS communication zone (See the book by Lee W. Technique of mobile communication systems: Transl. From English M: Radio and communication. 1985, P.121-123). In the service area, channel switching between radio zones is controlled so that when a mobile station moves from one zone to another, radio exchange can continue without interruption.

To organize communication on a cellular network, a certain portion of the frequency spectrum is allocated, which is divided into several channels with a given carrier frequency spacing. In a cellular network, reuse of fixed frequencies is usually used, which can dramatically increase the number of network subscribers. The principle of building cellular networks makes it possible to reduce the deficit of radio channels due to their reuse, however, this leads to a relative excess of the number of BSs (see the book Babakov V.Yu., Voznyuk MA, Nikitin AN, Sivers MA Communication systems with code division of channels / SPbGUT, SPb, 1999. 120 p.).

To assess the effectiveness of the use of radio data, a value called the spectral efficiency of frequency assignment is used. The spectral efficiency of the assignment of channel frequencies determines the probability of erroneous reception of information in cellular networks.

The spectral efficiency E _{S of the} frequency assignment is determined by the formula:

where a _c - load intensity (Earl); ΔF _k is the difference of the channel frequencies; S _c - the average area of the service area of one BS; C is a cluster factor.

The closest in technical essence to the proposed solution is the method of building a cellular network, described in the book Land mobile communication: Book 1. Fundamentals of the theory / I.M. Pyshkin et al .; Ed. V.S.Semenikhin and I.M. Pyshkin. M .: Radio and communications, 1990. S. 110, Fig. 3.22, presented in figure 1.

The prototype method consists in the fact that in a prototype cellular network consisting of BS located at the intersections of communication lines (FIG. 1), BSs are controlled with the condition that, when a mobile station moves from one zone to another, the radio exchange of mobile objects could continue without break, radio data is assigned according to the allocated cluster size (7) with the condition that the radio data is repeated after two flights.

The power of the BS transmitters is taken equal, the antennas used have a circular radiation pattern, and the radii of the communication zones of each BS are the same. In figure 1, the circles of large size display the radius of the communication zone, in the center of which there are BS. The number indicates the number of the frequency channel assigned by the BS located in the center of the circle. BS are located at an equal distance from each other, forming regular triangles. To ensure the effectiveness of radio communications by expanding the service area while maintaining the number of BSs, the prototype offers circular scanning using phased array antennas mounted on a BS, where signals from moving objects are received, estimation of parameters of received signals, based on which the BS on which the received signal is selected maximum. The use of phased antenna arrays requires storing the azimuthal angle of the moving object relative to the BS and making a connection with the moving object only during the intersection of the main lobe of the phased antenna array of the BS of the moving object. For the normal loading of the communication system, a uniform distribution of moving objects along the azimuthal angle of the radiation pattern is required.

The disadvantage of the prototype method is not the optimal use of the frequency resource.

The objective of the proposed method is to ensure optimal use of the frequency resource by placing the BS in a given territory, provided that the territory is fully covered to ensure the continuity of radio communication when moving from one cell to another.

To solve the problem in the method of assigning radio data in a cellular network, consisting of base stations located at the intersections of communication lines, controlled with the condition that when a mobile station moves from one zone to another, the radio exchange of mobile objects could continue without interruption, the radio data are assigned according to the selected cluster size with the condition that the repetition of radio data is carried out through two spans, according to the invention,

By intersecting mutually perpendicular lines, the service area is divided into squares, in the corners of which the first base stations are located, and inside the squares are two additional base stations at an equal distance both from the first base stations and among themselves, and in adjacent squares of the communication line between the additional base stations are mutually perpendicular;

radio data is assigned in the following order: base stations in the corners of squares formed by the intersection of mutually perpendicular lines, sequentially with the same shift modulo cluster size from bottom to top and from left to right;

two base stations inside the squares are marked with the same frequency shift modulo the cluster from right to left or from top to bottom, depending on their placement inside the square.

The inventive method of assigning radio data in a cellular network is as follows.

Base stations are located at the intersection of communication lines between base stations, providing full coverage of the service area. As the initial topology, you can use the placement of base stations in the nodes of the square grid. A separate square of such a grid is shown in FIG. In addition to the 4 base stations located at the nodes of such a grid, two additional base stations are located inside the square, located at the same distance from the two side stations and between themselves. In this case, 4 BSs (1, 2, 3,) are located at the intersection of mutually perpendicular lines forming a structure with minimum distances between the DC equal to d, of which four BS form squares with a side of 1,823 d, where d is the minimum distance between the BS, and other base stations (5 and 6) are located inside the formed square at a distance d from each other and from the side base stations. Then from 4 sides add the squares shown in figure 3, but with a rotation of 90 °. Moreover, the base stations located at the tops of the square are combined. The result is a continuous surface coating, shown in figure 4, which will be called "pentagonal".

. Полупериметр треугольника будет

. Площадь треугольника 1-3-5 найдем по формуле Герона

. Отсюда найдем высоту h=0,4115d. Расстояние между базовыми станциями 5 и 6 находится как разность l₅₆=1,823d-2·h=d. Следовательно, минимальное расстояние между БС пентагональной структуры составляет d.The vertices of the square form a BS, indicated by the numbers 1-2-3-4. The minimum distance between the BS located at the vertices of the square is 1.823 d. The minimum distance between the BS of the new pentagonal architecture is d. This can be proved. Consider a triangle 1-3-5, in which two sides are equal to d, and side 1-3 is equal to 1.823 d. We find the height h of this triangle based on its area S by the formula

. The perimeter of the triangle will be

. The area of a triangle 1-3-5 we find by the Heron formula

. From here we find the height h = 0.4115d. The distance between base stations 5 and 6 is found as the difference l ₅₆ = 1,823d-2 · h = d. Therefore, the minimum distance between the BS of the pentagonal structure is d.

Adjacent squares with a distance between the corner base stations of 1.823d are formed by rotating the square cell (FIG. 3) 90 °. The result is a topological structure covering a certain surface (figure 4), which serves as the basis for the appointment of radio data.

Radio data is assigned in the following order. Base stations at nodes at the intersection of horizontal and vertical lines formed by square cells (Fig. 3) are numbered sequentially with the same shift modulo the size of the cluster (5) from the bottom up and from left to right. Two base stations inside the cell are marked with the same frequency shift modulo the cluster from right to left or from top to bottom. The result is a network in which pentagons can be distinguished from base stations having different numbers of frequencies used (Fig. 4) and covering a continuously allocated territory.

To evaluate the frequency assignment efficiency, we introduce a characteristic that is derived from the spectral frequency assignment efficiency E _S. To do this, connect the base stations with repeating frequency numbers in straight lines. We choose the frequency of channel number 3. Next, we find the ratio of the area of the entire triangle to the area of the irradiation sectors with the same radio data. Given that the sum of the internal angles of a triangle is π (180 °), this ratio will be π times smaller than the calculated area of the triangles.

Compare the methods of assigning radio data for well-known cellular networks - hexagonal and rectangular.

, где l - расстояние между базовыми станциями.Assuming that the BS power of all frequencies have the same power, we get that the area of the irradiation sectors inside any triangles of the cellular network will be the same and equal

where l is the distance between base stations.

The area of the triangles highlighted by dashed lines in figure 1, equal to S ₃ = 2,132l ² . For a cellular network consisting of squares, a similar area would be S ₄ = 2.5l ² (FIG. 2). For pentagonal geometry, the area of the triangle connecting the BS with the same communication channels (frequency number 3) will be S ₅ = 2.87l ² (Fig. 5).

The calculation results are summarized in the table.

Table Parameter Squares Hexagonal honeycombs Pentagonal honeycombs S _Δ 2,5l ² 2,5l ² 2.84l ²

1,59 1,376 1.8

As can be seen from the table, the smallest ratio of the area of the triangle to the area of sectors with the same radio data has a prototype, and the largest is the claimed cellular network based on pentagonal geometry.

This achieves the condition under which the area irradiated by the BS radio station was as large as possible while maintaining the conditions for ensuring the necessary quality of the received signal.

The proposed method can be implemented by devices described in the book "UMTS Networks. Architecture, mobility, services. ” M .: Technosphere, 2007.P.77, Fig.4.1.

Claims (1)

The method of assigning radio data in a cellular network consisting of base stations located at the intersection of communication lines controlled with the condition that, when a mobile station moves from one zone to another, the radio exchange of moving objects can continue without interruption, radio data is assigned according to the allocated cluster size with the condition that the radio data is repeated through two adjacent zones, characterized in that the intersection of mutually perpendicular communication lines partition the service area into vadrats, in the corners of which the first base stations are located, and inside the squares there are two additional base stations at an equal distance both from each other and from the first neighboring base stations for each additional base station; Radio data is assigned in the following order: the base stations in the corners of the squares formed by the intersection of mutually perpendicular lines are numbered sequentially from bottom to top and left to right, and the two base stations inside the squares are numbered from right to left or from top to bottom, depending on their location inside the square.

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