JP2006245827A - Radio communication system and method for forming cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a cell constitution having an excellent efficiency while improving the degree of freedom of the place of an antenna installed when a cell is divided with the increase of a traffic, in a radio communication system capable of repeatedly using the same frequency in an adjacent cell and an adjacent sector in a DS-CDMA system or the like. <P>SOLUTION: Four sector antennas 2a to 2d in the different directionality at every 90° in a horizontal plane are fitted to each base station 1. Each cell 1 is divided into four centering around the base stations 1 by approximately square-shaped sectors (sectors 1 to 4) formed by the sector antennas 2a to 2d. The sector antennas 2a to 2d are optimized so that received powers in the vicinity of cell ends A to C are equalized approximately. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention divides a certain communication area into a plurality of cells, arranges a base station in each cell, and performs wireless communication between the terminal station located in the cell and the base station And a cell configuration method in this system.

  Conventionally, in wide area mobile communications such as mobile phones and PHS, a communication area is divided into a plurality of cells, a base station is arranged in each cell, and one base station corresponds to one cell. In such a cell system, the same frequency band is repeatedly used in base stations that are not close to each other in order to solve a shortage of frequency bands accompanying an increase in users. As a result, the frequency can be used efficiently and the number of subscribers can be increased. In addition, since one base station supports only a predetermined area called a cell, the radio field intensity can be minimized and communication can be performed. The output of the machine can also be suppressed.

  As described above, in order to use this cell system, it is necessary to prepare several types of frequency bands and arrange cells or sectors that do not suffer from the frequency band adjacent to each other. As a configuration method of the cells and the like, there are a regular triangle cell configuration, a regular square cell configuration, and a regular hexagonal cell configuration as shown in Patent Document 1 and FIGS.

  Comparing the configuration methods of these cells, as shown in the figure, the cell area covered by one base station, the SCPC (Single Channel Per Carrier) method such as PDC (Personal Digital Cellular) which is a Japanese standard method A regular hexagonal cell configuration is most efficient with respect to the shortest repetition distance of the same frequency. In this regular hexagonal cell configuration, as shown in Figs. 11 (a) to (c), a three-sector configuration (Fig. 11 (a)) that forms a diamond-shaped sector with a 120 ° directional antenna, 60 ° directional There are a 6-sector configuration (b) in which an equilateral triangle sector is formed by an antenna, and an omni configuration by an omnidirectional antenna.

  On the other hand, in recent years, a DS-CDMA (Direct Spread Code Division Multiple Access) system has attracted attention as a wireless communication system. This DS-CDMA system is one of the IMT-2000 standards, and sets the bandwidth of the channel for spreading data to 5 MHz or more for each of the uplink and downlink, and spreads the data transmitted by each terminal over the entire band. Therefore, it is possible to disperse noise during transmission to low level signals in a wide band, and to reduce the influence of noise on communication quality. Therefore, if each terminal uses a different spreading code, there is an advantage that communication can be performed without interference even if the same frequency is used.

  Therefore, in the cell configuration in the DS-CDMA system, the frequency can be arranged without depending on the shape of the cell and the sector, so that the same frequency can be used in common for each cell.

In addition, since each cell uses the same frequency, it is possible to flexibly cope with the subsequent increase in the number of users by dividing the cell into sectors or microcells without considering frequency repetition and the like. There is an advantage.
JP2001-268631

  However, in the regular hexagonal cell configuration described above, for example, to form a three-sector configuration, as shown in FIG. 12, a 120 ° directional antenna 20 is installed in three directions on the roof of the building (base station 1). However, since the horizontal section of the building is often rectangular, there are many restrictions on the installation location for maintaining the 120 ° range, and it is often difficult to ensure flexibility.

  Also, when the cells are further divided into microcells in response to the increase in the number of users (increase in traffic) as in the DS-CDMA system, as shown in FIG. In addition, if the shape of the micro cell or cell formed by further division is made a regular hexagon, it will protrude from the original cell range, resulting in an overlap with adjacent cells, making efficient cell division difficult Can occur.

  Furthermore, when three sectors are formed in a regular hexagonal cell, a 120 ° directional antenna (for example, a printed dipole antenna 30) is used. As shown in FIG. 14, a 120 ° directional antenna is formed. For this reason, the reflector 32 of the antenna element 31 is required, the antenna becomes larger, the restriction on the installation location increases, and it is difficult to secure the installation location.

  Therefore, the present invention has been made in view of the above points, and in a wireless communication system capable of repeating the same frequency in adjacent cells and adjacent sectors as in the DS-CDMA system, as traffic increases, It is an object of the present invention to provide a radio communication system and a cell configuration method capable of realizing an efficient cell configuration and improving the degree of freedom of an antenna installation place when performing division.

  In order to solve the above-mentioned problem, the present invention divides a certain area into a plurality of cells, places a base station in each cell, and connects between a terminal station located in the cell and the base station. A wireless communication system, the base station is equipped with four sector antennas whose directing directions differ every 90 ° in the horizontal plane, and each cell has a substantially square shape in the horizontal plane and is formed by the sector antenna. Each of the cells divided by the sector antenna is divided into four by a substantially square sector, and the same radio frequency is commonly used.

  Another invention is a system in which a certain area is divided into a plurality of cells, a base station is arranged in each cell, and wireless communication is performed between a terminal station located in the cell and the base station. In the cell configuration method, a base station is provided with four sector antennas whose directing directions are different every 90 ° in a horizontal plane, and each sector antenna forms a substantially square sector in the horizontal plane. The cell is divided by four sectors at the center and has a substantially square shape as a whole, and all the cells divided by the sector antenna use the same radio frequency in common.

  According to the present invention, since the shape of the sector is substantially square, when the cell is further divided, that is, into a microcell, the shape of the microcell is approximately the same as the original cell. Therefore, for example, cell division can be realized very easily by arranging a base station at the center of each sector to form four sectors. At this time, since the shape of the micro cell is a substantially square shape that is the same shape as the original cell, the micro cell is included in the cell before the division, and the micro cell does not overlap with the adjacent cell. Efficient cell division can be realized.

  In addition, when installing a sector antenna in a building, etc., the shape of the building is generally rectangular, so by installing antennas at the four corners of the building, a substantially square sector can be formed, and the antenna installation The degree of freedom can be improved.

  Furthermore, since the four corners of the building can be used, for example, a small antenna that can be installed on the wall of the building, such as a planar microstrip antenna, can be used, and the antenna installation location can be diversified. .

  Further, in the present invention, since each cell divided by the sector antennas uses the same radio frequency in common, the same frequency band can be repeatedly used in base stations that are not close to each other. Insufficient frequency band due to an increase in the frequency can be resolved.

  In the above invention, it is preferable that the sector antenna is optimized so that the received power in the vicinity of each vertex of the square sector separated from the base station is equal in each of the substantially square sectors.

  In this case, in the substantially square four-sector configuration, the directivity of the antenna covering each sector can be sharpened, and the cell radius can be increased as much as the gain of the antenna can be increased. The number of base stations can be reduced. In addition, by sharpening the antenna directivity, interference with adjacent sectors can be reduced, thereby improving the frequency utilization rate.

  The sector antenna preferably has a half width of about 60 °. In this case, it is possible to appropriately optimize the antenna so that the reception power in the vicinity of each vertex of the square sector separated from the base station becomes equal in each of the substantially square sectors.

  As described above, according to the present invention, a certain area is divided into a plurality of cells, a base station is arranged in each cell, and a terminal station located in the cell is connected between the base station and the base station. In a system that performs wireless communication, when a cell is divided along with an increase in traffic, an efficient cell configuration can be realized and the degree of freedom of an antenna installation location can be improved.

(Wireless communication system configuration)
Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of a radio communication system according to the present embodiment. In the present embodiment, a case where the present invention is applied to a wireless communication system capable of repeating the same frequency in adjacent cells and adjacent sectors as in the DS-CDMA system will be described as an example.

  As shown in the figure, in this embodiment, a predetermined communication area is divided by a number of substantially square cells arranged in a lattice pattern, and a base station 1 is arranged in each cell. Radio communication is performed between a terminal (not shown) located in the cell and the base station 1.

  Each base station 1 is provided with four sector antennas 2a to 2d whose directing directions are different every 90 ° in a horizontal plane, and each cell 1 is a substantially square formed by the sector antennas 2a to 2d, respectively. The base station 1 is divided into four by a sector (sector1 to 4).

  That is, as shown in FIGS. 2 (a) to 2 (c), the sector antennas 2a to 2d of the present embodiment are planar micros installed in parallel to the rooftop or wall surface of a square (here, square) building. It is a strip antenna, and is set so that the antenna directing direction faces the normal direction of the building wall surface. In addition, the directivity of the sector antennas 2a to 2d is 90 °, and the boundary line between adjacent sectors coincides with the diagonal line of the building. This planar microstrip antenna is a thin planar patch antenna capable of forming a 90 ° directivity as shown in FIGS. 3 (a) to 3 (c). A large number of the radiating elements 21 are attached to a plate-like main body.

  Furthermore, the sector antennas 2a to 2d support the DS-CDMA system, and the same radio frequency can be repeatedly used for each cell or each sector (the same radio frequency is commonly used for each cell or each sector). ing. And the terminal located in each sector communicates using the same frequency as each sector antenna 2a-2d, and communicates by changing the spreading code used in each sector.

  Further, as shown in FIG. 4, the sector antennas 2a to 2d have the same reception power in the vicinity of cell edges (vertical vertices of sectors separated from the base station 1) A to C in each of the substantially square sectors. Optimized for.

In detail, the received power of the terminals located in the sector is
The received power at cell edge A is
The received power at cell edges B and C is
It becomes. here,
Antenna pointing direction: OA
Antenna directivity gain G: (θ)
Transmit power: Pow
Propagation loss: Loss (r)
Distance between base station and mobile station: r
θ: Terminal direction.

In the present embodiment, the sector antennas 2a to 2d are optimized so that the received power is at the same level at the cell edges A to C.
The antenna directivity satisfies the conditions obtained in the above. Specifically, the half width of the antenna is about 60 °.

(Operations and effects of the cell configuration method of this embodiment)
By operating the radio communication system having the above configuration, the cell configuration method of the present invention can be implemented.

  That is, the sector antenna provided in the base station 1 forms four substantially square-shaped sectors in the horizontal plane, and the substantially square-shaped cell is divided by the four sectors centered on the base station 1.

  According to the present embodiment, since the sector shape is a substantially square shape, as shown in FIG. 5, when traffic is further increased and the cell is further divided, that is, into a microcell, the shape of the microcell Can have a substantially square shape that is the same shape as the original cell.

  As a result, for example, cell division can be realized very easily by arranging a base station at the center of each sector to form four sectors. At this time, since the shape of the micro cell is a substantially square shape that is the same shape as the original cell, the micro cell is included in the cell before the division, and the micro cell does not overlap with the adjacent cell. Efficient cell division can be realized.

  In particular, in this embodiment, since a planar microstrip antenna is used as the sector antenna, the antenna configuration can be reduced in size, and the antennas can be installed at the four corners of the building. The degree can be improved.

  Further, in the present embodiment, the sector antennas 2a to 2d are optimized so that the received power in the vicinity of the cell edges A to C is equal, so that the directivity of the antenna covering each sector is sharpened. As a result, the cell radius can be increased as much as the gain of the antenna can be increased. As a result, the number of base stations can be reduced. In addition, by sharpening the antenna directivity, interference with adjacent sectors can be reduced, thereby improving the frequency utilization rate.

More specifically, as shown in FIG. 4, since the distances OB and OC are shorter than the distance OA, the propagation loss Loss of the distances OB and OC is that of the distance OA as shown in the following equation. Smaller than.
Therefore, the antenna directivity gain at cell edges A and B, C is
Thus, the directional gain G (45 °) in the OB and OC directions can be made smaller than the directional gain G (0 °) in the OA direction. Thereby, the half width of the antenna can be set to about 60 °, and the antenna directivity can be narrowed (sharpened).

  Therefore, according to the cell configuration method according to the present embodiment, as shown in FIG. 6, compared to the conventional square cell / 4-sector method in which the half width of the antenna is 90 °, which is the sector angle, The width can be narrowed and the antenna gain can be increased. As a result, according to the present embodiment, the cell radius can be expanded and the number of base stations can be reduced.

  In addition, according to the present embodiment, the beam width can be made narrower than in the conventional method. Therefore, as shown in FIG. 7, the power leaking to the adjacent sector can be reduced, and the frequency utilization rate can be improved.

  Although the present embodiment has been described for the DS-CDMA system, the present invention is not limited to this, for example, MC-CDMA (Multi Carrier-CDMA) based on DS-CDMA or OFDM. It can be applied to a cell configuration of a radio communication system that can repeatedly use the same frequency in adjacent cells and adjacent sectors as in the method.

It is explanatory drawing which shows schematic structure of the radio | wireless communications system which concerns on embodiment. It is explanatory drawing which shows the example of installation of the sector antenna in the radio | wireless communications system which concerns on embodiment. It is explanatory drawing which shows the structure of the sector antenna in the radio | wireless communications system which concerns on embodiment. It is explanatory drawing which shows the optimization of the sector antenna which concerns on embodiment. It is explanatory drawing which shows the division | segmentation of the cell which concerns on embodiment. It is a graph which compares the half value width of the antenna which concerns on embodiment, and the half value width of the antenna by a conventional method. It is a graph which compares the interference power between the adjacent sectors by the antenna which concerns on embodiment, and the interference power between the adjacent sectors by the conventional antenna. It is explanatory drawing which compares the cell structure which concerns on a prior art example. It is explanatory drawing which compares the area area of the cell structure which concerns on a prior art example. It is explanatory drawing which compares the repetition distance of the cell structure which concerns on a prior art example. It is explanatory drawing which shows the sector formation of the regular hexagon cell structure which concerns on a prior art example. It is explanatory drawing which shows the antenna installation condition of the 3 sector structure which concerns on a prior art example. It is explanatory drawing which shows the cell division in the regular hexagonal cell structure which concerns on a prior art example. It is explanatory drawing which shows the structure of the printed dipole antenna in the regular hexagon cell / 3 sector structure which concerns on a prior art example.

Explanation of symbols

A to C ... cell edge
1 ... Base station
2a ~ 2d ... Sector antenna
sector1 ~ 4 ... sector
20 ... Directional antenna
21 ... Radiating element
22 Derivatives
23 ... Ground plate

Claims (6)

A system in which a certain area is divided into a plurality of cells, a base station is arranged in each cell, and wireless communication is performed between the base station located in the cell and the base station,
The base station includes four sector antennas whose directing directions are different every 90 ° in a horizontal plane,
Each of the cells has a substantially square shape in a horizontal plane and is divided into four around the base station by a substantially square sector formed by the sector antenna,
A wireless communication system, wherein each cell divided by the sector antenna uses the same radio frequency in common.   The sector antenna is optimized so that the reception powers in the vicinity of each vertex of each square-shaped sector spaced from the base station are substantially equal in each square-shaped sector. The wireless communication system according to 1.   2. The wireless communication system according to claim 1, wherein the sector antenna has a half width of about 60 degrees. A configuration method of the cell in a system in which a certain area is divided into a plurality of cells, a base station is arranged in each cell, and wireless communication is performed between a terminal station located in the cell and the base station Because
The base station is provided with four sector antennas whose directing directions are different every 90 ° in a horizontal plane,
Each sector antenna forms a substantially square sector in a horizontal plane, is divided by four sectors centered on the base station, and constitutes a generally square cell as a whole,
A cell configuration method, wherein each cell divided by the sector antenna uses the same radio frequency in common.   The sector antenna is optimized so that the reception power in the vicinity of each vertex of the square sector separated from the base station is substantially equal in each sector of the substantially square shape. 5. The cell configuration method according to claim 4, wherein   5. The cell configuration method according to claim 4, wherein the sector antenna has a half width of about 60 °.