JPH09275584A - Mobile communication network - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the mobile communication network in which interference with adjacent cells is reduced even when traffic density is different from positions. SOLUTION: A communication area is formed by cells 10-30 each having plural sectors. Each cell has a base station (1-3) and a mean transmission power to each sector of each base station is decided depending on the traffic density of the cell of the base station. The base station has a means sending power smaller than the average transmission power to each sector in the 2nd cell with respect to sectors adjacent to the 1st cell in the 2nd cell adjacent to the 1st cell whose traffic density is higher. The base station of the 2nd cell is arranged at a position closer to the base station of the 1st cell than the distance to the other base stations. The center angle of sectors adjacent to the 1st cell may be narrower than the mean center angle of sectors of the 2nd cell. As the traffic density, e.g. the mean traffic or a prediction value of the maximum traffic is used.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sector-structured mobile communication network, and more particularly to a mobile communication network capable of efficiently communicating when traffic densities are spatially different.

[0002]

2. Description of the Related Art FIG. 4 shows a cell configuration when traffic densities are spatially different. FIG. 4A shows a spatial change in traffic density. The position of the distance 0 corresponds to the center of the city, and the traffic density is maximum. Traffic decreases exponentially with distance from the city center. FIG. 4B shows the structure of the cell. In areas with high traffic density, the distance between base stations was shortened to form small cells, and in areas with low traffic density, the distance between base stations was increased to form large cells.

[0003]

In FIG. 4, each base station has six
It has cells of sectors. Here, since the sector of the cell 20 is larger than the sector of the cell 10, the sectors 21 to 21 of the cell 20 are
It is necessary to increase the transmission power of the mobile station at the end of 26. Therefore, the interference from the mobile station in the sector 21 to the base station 1 becomes particularly large. In conventional FDMA or TDMA, adjacent cells use different frequencies to prevent interference. However, in CDMA, increased interference causes deterioration of communication quality or reduction of subscriber capacity.

Further, in FDMA or TDMA, distant cells use the same frequency. For example, since the sector 31 is larger than the sector 14, the transmission power of the mobile station at the edge of the sector 31 is large. Therefore, if the sector 31 and the sector 14 use the same frequency, interference from the mobile station located in the sector 31 to the base station 1 of the sector 14 increases. Conventionally, since a narrow band system is used, the frequency allocation can be adjusted in units of narrow band carriers. Therefore, interference is avoided by allocating different frequency bands to cells having greatly different sizes. Then, a small frequency band is allocated to the area with low traffic density, and different frequency bands are used in the sectors where there is a risk of interference.

However, a wide band system such as CDMA requires a wide band even in an area where the traffic density is low. When different frequency bands are assigned to cells, frequency utilization efficiency cannot be improved. Therefore, an object of the present invention is to provide a mobile communication network that can solve such problems.

[0006]

In order to achieve such an object, in the structure according to claim 1, in a mobile communication network in which a communication area is composed of a plurality of cells,
Each of the cells has a plurality of sectors, and a base station that transmits radio waves to the plurality of sectors, the plurality of cells,
A second cell having a first cell and a second cell adjacent to the first cell and having a traffic density smaller than that of the first cell, wherein the second base station in the second cell is the second cell; Power that is smaller than the average value of the transmission power of the second cell is transmitted to a sector adjacent to the first cell in the cell.

In the mobile communication network according to the first aspect, the central angle of the sector adjacent to the first cell is the average center of the sectors of the second cell. Characterized by being narrower than a corner.

According to the third aspect of the invention, in a mobile communication network in which a communication area is composed of a plurality of cells, each of the cells transmits a plurality of sectors and radio waves to the plurality of sectors. A plurality of cells adjacent to the first cell and the first cell.
Second cell having a smaller traffic density than that of the second cell, and the central angle of the sector adjacent to the first cell in the second cell is smaller than the average central angle of each sector of the second cell. It is characterized by being enlarged.

According to the structure of claim 4, in a mobile communication network in which a communication area is composed of a plurality of cells, each of the cells transmits a radio wave to a plurality of sectors and the plurality of sectors. A plurality of cells adjacent to the first cell and the first cell.
Second cell having a traffic density smaller than that of the second cell, the tilt angle of a sector adjacent to the first cell in the second cell is calculated from an average tilt angle of each sector of the second cell. It is characterized by being enlarged.

Further, in the configuration according to claim 5, in the mobile communication network according to any one of claims 1 to 4,
The traffic density is a predicted value of average traffic or maximum traffic.

[0011]

An embodiment of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 shows a cell structure of a first embodiment of the present invention. Spatial distribution of traffic density (Fig. 1
(A)) is the same as FIG. 4 (A). Among the sectors of the cell 20, the transmission power of the sector 21 adjacent to the cell 10 having a high traffic density is minimized. The transmission power of the sectors 22 and 26 near the cell 10 is set lower than the average transmission power of the base station 2. Here, as traffic density,
It is possible to use the average value or the maximum value of the daily or weekly traffic density of each area. This traffic density can be predicted from statistics or population density, for example.

According to this embodiment, the sectors 21, 22, and 26 near the cell 10 have a smaller sector size than the conventional configuration shown in FIG. 4, and the interference with the cell 10 is reduced.
The base station 2 is brought closer to the base station 1 than in FIG. 4, and the size of the cell 10 is kept the same as in FIG. On the other hand, the transmission power of the sectors 23 to 25 is set higher than the average value, and the sector size of the sectors 23 to 25 having low traffic density is increased. Similarly to the base station 2, the cell of the base station 3 also minimizes the sector in contact with the cell 20 having a higher traffic density and increases the sector as the distance from the cell 30 increases. According to this embodiment, it is possible to reduce interference with a cell having large traffic and improve communication quality. In particular, when CDMA communication is performed using the same frequency in adjacent cells, the communication capacity can be increased.

(Second Embodiment) FIG. 2 shows a cell configuration of a second embodiment of the present invention. In this embodiment, the transmission power of the sector 21 is made smaller than that of the first embodiment, and the central angle of the sector 21 is made smaller than the average angle (60 °). The base station antenna gain is increased, and the transmission power from the mobile station in sector 21 can be further reduced. Therefore, the interference from the mobile station to the base station 1 can be further reduced as compared with the first embodiment.

(Embodiment 3) FIG. 3 shows a cell configuration of a third embodiment of the present invention. In this embodiment, the transmission power of each sector is made equal for each base station. On the other hand, the central angle of the sector 21 is made wider than 60 ° and the central angle of the sector 24 is made narrower than 60 °. Since the base station antenna gain of the sector 21 is reduced, the radius of the sector is similar to that when the transmission power is reduced as shown in FIG.
Shorter. Therefore, as in the first embodiment, the sectors 21,
The interference from 22, 26 to the cell 10 is reduced.

By reducing the central angle, the sector 24
Since the base station antenna gain is increased, the radius of the sector 24 is increased as in the case of the first embodiment. The radius of the sector 21 may be shortened by increasing the tilt angle of the sector 21. In this case, the tilt angle of the sector 24 can be reduced and the radius of the sector 24 can be increased. The cell configuration at this time is the same as in FIG. According to this embodiment, it is possible to reduce the interference from the base station of the cell with low traffic to the sector of the cell with high traffic.

Although the embodiments of the invention have been described above, the technical scope of the invention according to the present application is not limited to the above embodiments. The invention described in the claims can be implemented by adding various changes to the above embodiment. It is obvious from the description of the claims that such an invention belongs to the technical scope of the invention according to the present application.

[0017]

As is apparent from the above description, according to the present invention, it is possible to reduce the interference of adjacent cells even when the traffic densities are locally different.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a cell configuration according to a first embodiment.

FIG. 2 is an explanatory diagram showing a cell configuration according to a second embodiment.

FIG. 3 is an explanatory diagram showing a cell configuration according to a third embodiment.

FIG. 4 is an explanatory diagram showing a conventional cell configuration when the traffic density varies depending on the location.

[Explanation of symbols]

 1 Base Station 10 Cell 11-16 Sector 2 Base Station 20 Cell 21-26 Sector 3 Base Station 30 Cell 31-36 Sector

Claims (5)

[Claims] 1. In a mobile communication network in which a communication area is composed of a plurality of cells, each of the cells has a plurality of sectors and a base station transmitting radio waves to the plurality of sectors, The cell includes a first cell and a second cell adjacent to the first cell and having a traffic density smaller than that of the first cell.
And a second base station in the second cell has an average of transmission power of the second cell with respect to a sector adjacent to the first cell in the second cell. A mobile communication network characterized by transmitting electric power smaller than a value. 2. The mobile communication network according to claim 1, wherein a central angle of a sector adjacent to the first cell is narrower than an average central angle of a sector of the second cell. 3. In a mobile communication network in which a communication area is composed of a plurality of cells, each of the cells has a plurality of sectors and a base station transmitting radio waves to the plurality of sectors, The cell includes a first cell and a second cell adjacent to the first cell and having a traffic density smaller than that of the first cell.
And a center angle of a sector adjacent to the first cell in the second cell is larger than an average center angle of each sector of the second cell. network. 4. In a mobile communication network in which a communication area is composed of a plurality of cells, each of the cells has a plurality of sectors and a base station transmitting radio waves to the plurality of sectors, The cell includes a first cell and a second cell adjacent to the first cell and having a traffic density smaller than that of the first cell.
And a tilt angle of a sector adjacent to the first cell in the second cell is larger than an average tilt angle of each sector of the second cell. network. 5. The mobile communication network according to claim 1, wherein the traffic density is a predicted value of average traffic or maximum traffic.