JPS6069923A - Method for constituting base station zone in mobile communication - Google Patents

Abstract

PURPOSE:To increase talking traffic by dividing a communication zone in the form of a hexagonal cell into unit cells, forming cell clusters in the unit of three cells and directing the directivity of an antenna provided at the center of each cell toward each vertex of the hexagon. CONSTITUTION:The service area consisting of hexagons of equal area of a base station zone is divided to each sector and the zone is constituted by distributing all talkings usable to each sector and control channels to it. Three adjacent hexagonal cells are formed as a three-leaf where one side of a cell is in contact with that of the other two and used as one set of the cell cluster, which is used as one unit, and the clusters are stacked in the directions of east and west, 30 deg. to northeast and 30 deg. to northwest so as to cause no clearance to each other. The base station is provided to the center of each sector, the six directive antennas are installed so that the main beam of the antennas is directed toward each vertex of the hexagonal cells thereby forming independent talking areas respectively. The east sector of each cell is named as A1, B1 and C1 and the radio channel is allocated while the sector number is made correspond clockwise.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a base station zone configuration method in mobile communications such as car telephones.

Conventional configuration and its problems Traditionally, in the wireless zone configuration of the car telephone system, a channel arrangement using omnidirectional antennas was used.
The shape of the wireless (wireless) cells is a geometric figure, such as a regular triangle, a regular quadrangle, or a regular hexagon, with an antenna at the center of each cell. Other complex shapes are possible, but among these, the communication service area is divided into hexagonal cells that are closest to a circle, and adjacent wireless cells are assigned different wireless channels to perform individual communications. There are many.

The number of wireless cells when providing surface service like a car phone is 3 cells, 4 cells, 7 cells, or 9 cells.

There are zone configuration methods such as 12 cells...23 cells, but in order to make effective use of limited wireless channels, create a group of infinite cells (cell cluster) as small as possible, and assign as many cells as possible to each wireless cell. It is necessary to increase call traffic by repeatedly allocating radio channels to each cell cluster.

The minimum for area service is a three-cell cluster, but in order to ensure a constant value for the interference/disturbance ratio of the same frequency used for different communications between adjacent wireless cells using an omnidirectional antenna, a minimum of seven cells or more is required. It is necessary to do so. However, in areas where telephone traffic congestion is concentrated, such as large cities,
It is necessary to further subdivide the rectangular (wireless) cells to increase communication traffic. On the other hand, subdividing a (wireless) cell requires an increase in the number of base stations, which requires an increase in base station buildings, grounds, and communication equipment that connects the base stations. In addition, the maintenance work required to keep these communication facilities in good condition is extremely expensive.
The problem was how to carry out subdivision economically.

To achieve this economically, one base station is equipped with multiple directional antennas, and the wireless zone is subdivided into multiple small zones (sectors) to increase call traffic. Attempts to achieve this goal have been proposed and implemented since around 1968. An example of this is the train telephone system of the Japan Railway Corporation (NR). This is widely known as the Shinkansen wireless telephone system. Since railway communication is a linear service, one base station divides its service area using multiple uplink and downlink directional antennas, and communicates using different frequencies. Since railways are linear services, the division is for communication in two or three directions, but it was well known in Japan in the 1960s that at least one base station handles communication in multiple radio zones using a directional antenna. Met.

In addition, for car telephone systems that require area service, a method of installing multiple directional antennas in one base station and dividing it into wireless zones of different frequencies (channels) is known, for example, from Japanese Patent Publication No. 14122/1983. ing.

Judging the merits and demerits of a wireless cell configuration is related to how it can cope with the increase in call traffic concentrated in large cities, and how economically a zone configuration can be realized. In cases where land is extremely expensive, such as in Japan, it is economically advantageous to have one base station handle communications for multiple wireless zones.

Further, it is free to use the hexagonal cell as one wireless zone, or to divide it into two, three, . . . n. In that case, whether the interference ratio from adjacent interlayer wavenumber channels can be kept above the desired value by division, and whether it is possible to increase the call traffic (amount), the magnitude of the interference ratio, the amount of interference waves, and the call traffic The amount of increase will be subject to evaluation.

Conventionally, a channel arrangement using hexagonal cells using omnidirectional antennas requires a seven-cell configuration or more to ensure an acceptable interference ratio.

On the other hand, a configuration method using a directional antenna and four hexagonal wireless cells is disclosed in, for example, US Pat.
According to No. 28740, it is as shown in Figure 1. In the same figure, 4
Each cell (w, x, y, z) is divided into 6 triangular sectors. The six triangular sectors each consist of six directional antenna beams located at a common center position, with the maximum direction of the directional antenna beams pointing toward the center of adjacent cells. Furthermore, among the six cells, the sector numbers increase clockwise for W, X, and Y, but for Z, the sector numbers increase clockwise starting from Z3, z2
．． zl, z5. z4. They are arranged in the order of z6.

In the conventional configuration described above, an improvement effect of only 14 channels with a call loss rate of 0.5 was obtained compared to the call traffic of a 7-cell configuration using omnidirectional antennas.

In addition, in the method of dividing each cell into 6 in the 4-cell configuration described above, the channel (sector) arrangement of one cell Z among the 4 cells must be different from the channels (sectors) of the other three cells. There was a drawback that regularity could not be applied.

In addition, since the main beam of the directional antenna used in the 4-cell configuration extends into the communication range of adjacent cells, there is a large overlap with the adjacent cells, making it possible to effectively utilize the gain of the directional antenna. There wasn't. Therefore, when the effective radiated power (ERP) is limited due to regulations regarding the use of radio waves, the radius of the communication area inevitably becomes smaller.

Purpose of the Invention The present invention eliminates the drawbacks of the conventional example, and has the following advantages over the conventional communication system using four cells and directional antennas.
It is an object of the present invention to provide an economical method for configuring a base station zone, which allows the number of cells to be configured as small as possible, thereby increasing traffic.

Structure of the Invention In order to achieve the above object, the present invention divides a communication area in which communication services are provided into units of hexagonal cells, and forms a trilobal cell cluster using three hexagonal cells as a unit. In addition, the six diamond mark-shaped sectors constituting the hexagonal cell are formed by six sets of directional antenna beams provided at the center position of the hexagonal cell, and the center (maximum) direction of the directional antenna beam is is arranged in the direction of each apex of the hexagonal cell to avoid the center of adjacent cells, and by giving a certain regularity to the total number of channels between each sector, even in a 3-cell configuration, it is possible to avoid the center of adjacent cells. The structure is such that the above characteristics can be obtained.

DESCRIPTION OF EMBODIMENTS The configuration of an embodiment of the present invention will be described below with reference to the drawings.

Figure 2 is a diagram showing the configuration of a service area that provides mobile communication services.For convenience of explanation below, the upper part of Figure 2 is north (N), the lower part is south (S), the right is east (E), and the left is to the west (W
), the service area is divided into sectors by regular hexagons of equal area, and all available communication and control channels (wireless channels) are distributed to these sectors. Next, three adjacent hexagonal cells are formed in a trilobal shape so that one side touches the other two cells, forming a set of cell clusters (clumps), and this cell cluster is considered as a unit with a gap between each other. They are stacked in the east-west (EW) direction, the northeast (NE) 300 direction, and the northwest (NW) so° direction so as not to cause

Next, with reference to the center point (first center point) of each of the regular hexagonal cells, proceed in the north-south (NS) direction, northwest (NW) e○0
A dividing line is drawn in the northeast (NE) direction, and the regular hexagonal cell is shaped like a diamond mark (Diamon).
d) Divide into six sectors.

In this method, a base station is installed at the center of each sector, and the main beams of six directional antennas are aligned with the six apex angles of each of the hexagonal cells. It forms a communication area.

Next, as shown in Figure 2, each cell in a set of three regular hexagonal cell clusters is cell A (first cell), cell B on the south side (second cell),
cell), the east side C cell (the third self, and the sector in the east position of each cell is A1.B1.C1,
A2. A3...A6, B2. B3. ,,,
, , B6, C2, C3-C6, the sector numbers of each cell correspond to each other, and radio channels are assigned to these as shown in FIG.

In the figure, A1 to C6 represent the names of each sector, and the numbers represent channels (numbers). Said channel is a call channel (
CH) and control CH.

Therefore, sector A1 has 22...328 18
1 communication channel and 1 control channel (1CH) are allocated. The same is true for the others, but the shaded areas represent areas where no allocation is made due to the limit on the total number of channels.

Next, FIG. 4 is a diagram showing a method of configuring each sector, and is shown in comparison with the conventional example shown in FIG. 1 for reference. In the figure, the base station antenna position is 01, and the hexagonal cells shown in FIG. 2 are represented by N1 to N6, and the hexagonal cells shown in FIG. 1 are represented by M1 to M6.

Furthermore, the diamond in Fig. 2 that constitutes one of the hexagonal cells
(mark) type sector with 082N1s1, and the first
The triangular sector in the figure is 0M6M1.

At this time, the beam of the directional antenna in the diamond-shaped sector is 3. The beam of the directional antenna in the triangular sector is 2.
, and the beam of the omnidirectional antenna used in the following explanation is represented by 1. What is characteristic in this figure is that the center direction (and thus the maximum direction) of the directional antenna beam 3 is along the axis x1.
In contrast, the center direction of the directional antenna beam 2 is in the direction of the axis Y1, and both are at an angle of 30 degrees to each other. Furthermore, in the same figure, point 81 (B2) and Ml
The antenna gain at point (M2) is defined to be half (half width - ±3Q0) of the maximum value.

Next, the respective reach distances of the directional antenna beams 2 and 3 and the omnidirectional antenna beam 1 will be explained. For example, using the propagation curve for land mobile radio specified in 0CTH, the effective radiated power (ERP) is 100W, and the antenna height is 1.
The electric field strength of omnidirectional antenna 1 when set at 60m is 39
If we add the distance (cell radius) Ro that becomes dBμV/m, we get O
U1=R0-12km. On the other hand, if the cell radius RN corresponding to directional antenna beam 3 is 0N1-11Jan,
Further, the cell radius RM corresponding to directional antenna beam 2 is 0M.

(0M6) -9, 5Jan. That is, for directional antenna beam 3, the shaded area in the figure is smaller than the shaded area for directional antenna beam 2. In other words, in the direction of directional antenna beam 2, the area (I) to the adjacent area (n) Even if it moves to , the electric field strength does not decrease and the overlapping region becomes large.

Next, if we calculate the distance to the adjacent sector where the same frequency is repeated in triangular sector 2 and diamond mark sector 3, it will be between 4 and 5 in Figure 1, and 6 and 5 in Figure 2.
7, and when these are expressed as DM and DN, as is clear from Figures 1 and 2, DM = 2-, /TR.
M = 32.9 k7n.

DN=3RN=33kn, so DM and DN are almost equal, indicating that the distance intervals at which interference occurs between them are almost equal.

That is, in the above configuration, interference is reduced by configuring the antenna beams constituting each sector to avoid the center of adjacent cells, and as a result, compared to the conventional 4
Compared to the cell configuration, a 3-cell configuration can achieve interference reduction equivalent to that of a 4-cell configuration.

However, considering the direction of directivity of the directional antennas, even at the above distance, the two directional antennas 4 and 5
and 6 and 7 are facing in opposite directions, and if the front-back ratio (F/B) of the directivity is 25 dB, the back communication distance D is
a is Da=1.81 cm, and the distance from the interfering base station to the above point is B3-Da=31.9-1+8=
30.11 cIn, and the interference ratio (S/I) between the two is about 15 dB.

Furthermore, in the present invention, since the arrangement of each sector and cell is determined according to a fixed rule, the S/I ratio between all sectors can be maintained at the same value. That is, when allocating wireless channels using directional antennas, for example, each cell A,
The eastward sectors of B and C are A1. B1. 6 as C1
A1 at 00 intervals. There is no A2. Of course A1. B1 and C1
Even if the base point is placed in a different direction on the map, the same result can still be obtained even if the wireless channel allocation is performed so that the channel assignment is rotated in a counterclockwise direction.

Here, base station equipment for realizing the configuration of the embodiment will be explained with reference to FIG. 5. 51 is the antenna tower, 6
2 is a base station antenna, 66 is an antenna reflector,
Directional antennas 52A to s2 with a gain half width of 600 or more
F makes each sector a communication area. 53A~53
F is a transmitting/receiving duplexer, which is used for each antenna to share the transmitting/receiving frequency for each sector. 54A~54
F is a coaxial cable or waveguide (in the case of several GHz) that couples each of the antennas 52A to 52F and the transmission/reception duplexer, 65A to 65F is a transmission duplexer for each antenna, and 6
6a to 56n are multiple transmitters that transmit a plurality of channel frequencies for each antenna, 57A to 57F are reception duplexers provided for each antenna, and radio receivers 58a to 58
The received power of each antenna is distributed equally to n without loss.

Reference numeral 59 denotes a base station control unit (CSU), which performs various controls peculiar to wireless communication, such as sending and receiving various control signals for switching and connecting mobile radio telephones and wired telephone subscribers, tracking mobile radio telephones, and switching channels. It is a device that performs 6o is a telephone exchange (MTSO) that controls a plurality of C3Us, and connects telephone subscribers (telephones) via mobile radio telephones 62A...62N, a long-distance telephone network 63, and a local exchange 64 at the destination.
Figure 7 shows a 3-cell cluster (A, B, C) connected to 65.
) is a diagram showing a method of arranging (wireless) channels (group numbers) to each sector of
Assign a (wireless) channel to the lowest numbered sector, C6 to the highest numbered sector, and assign a (wireless) channel to the first sector, A1.B1.C1゜A2.
1.4, 7, 10, 13.16 are assigned to each sector A1 to 80 of cell A in order of (none, 1i) so that the channel group number increases in 3-channel increments. (Wireless)
For each sector B1 to B6 of cell B, slide the channel arrangement to the cell parallel to cell B so that sector A1 overlaps sector B1, and channel group numbers 1 to B6 of cell A are assigned.
Channel group number 2, 5, 8, which is 16 plus 1
11,14°17 are assigned to sectors B1 to B6. Next, for each sector of cell C, sector A1 is overlapped with sector 01 at the same time as cell B, and channel group numbers 3, 6, 9, 12, 15, . 18 is shown. Broken arrows and solid arrows indicate the direction in which the numbers increase.

Note that sector A1 of cell A is selected with the largest channel group number, and A1. Channels may be allocated in the order of A2, . . . A6 at three channel intervals.

For example, A1=18. A2=16. A3-12. A4=
9°A6:6, A6:3, each sector of cell B may be a number obtained by subtracting 1 from cell A, and each sector of cell B may be a number subtracted from cell A.

Figure 8 shows channel allocation within a cell in sector A of cell A.
This is an example of assigning from 1 to anti-time rotation.

For example, if the channel group number is A1-1. A6=4゜A
5=7. A4-10. A3=13, A2=16,
Cell B and cell A! =In, 1 is added to the channel group number of cell A, and cell C, like cell A, also assigns a channel whose number is obtained by adding 2 to the channel group number of cell A to sector B1. The channel group number increases from C1 as a base point, and the broken line arrow and solid line arrow indicate the increasing direction of the channel group number.

Incidentally, similarly to FIG. 7, the channel group in sector A1 may be selected as the largest number, and smaller numbers may be sequentially assigned to every three channels.

FIG. 9 shows the assignment of channel groups to cells A, B, and C in the opposite direction to the rotation direction of FIG. 8.

B, sector A1 is channel group number 1, B
In this example, 1 is set to 3, C1 is set to 2, and channel group numbers are increased clockwise within each cell.

Note that the highest channel group number is assigned to sector A, and A1. B1. C1 and A1-A6. B1-B
6. Small numbers may be assigned in the direction of C1 to C6.O Figure 10 shows the assignment of channel group numbers to each cell A,
C, B each sector A1. A6. A5. A4. A
3゜A2. B1. B6-B2. cl, c6 to c2, which are assigned in anti-chronological rotation, and sector A1 is the maximum number and 1 to 1 indicates that the channel group number is decreased in the opposite manner to the above.

In the cell cluster configuration of the present invention, the base point for allocating kJl and channel groups is any sector among cells 8, B, and C, and channel group numbers can be allocated in the manner described above.

Figure 11 shows that the base point for channel allocation is sector A of cell A.
Starting from 4, the state is /toshi. Dashed line arrows and solid line arrows indicate the direction of channel allocation to sectors and cells, indicating that the channel allocation increases or decreases in the direction of the arrow.

Next, 12 cell method, 7 cell method, 4 cell 6 division method,
When the call volume and call volume ratio of the 3-cell 6-division system are calculated assuming that the number of call channels is 312 (333 to 21) and the call loss rate is 0.5%, the results are as shown in FIG.

That is, according to the cell configuration of the present invention, it is possible to increase the roughness by about 1.74 times compared to the γ cell system using omnidirectional antennas, and by about 3.5 - [) rough times compared to the 12 cell system. . Even compared to the conventional 4-cell 6-division system, the traffic has increased by more than 1.5 times. This is particularly important in communication systems that use limited frequency bands. Further, according to the present invention, the number of interference waves can be reduced by 20% compared to the 3-cell system using omnidirectional antennas by using a directional antenna, so that advantages can also be obtained in terms of interference.

Effects of the Invention The present invention has the above-described configuration, and provides the following effects when improving cell traffic without increasing the number of base stations.

(a) By distributing 3 cells to 6, the number of communication channels distributed to each sector antenna can be increased,
It becomes possible to significantly increase call traffic in each cell. For example, for call traffic in a cell cluster with 7 cells using omnidirectional antennas, 4 cells,
In the 6-division system, the increase in call traffic is only 14 times, but with the cluster configuration of the present invention, an increase of 74 times can be obtained, so the effect of improving call traffic is significant.

(b) This method is particularly advantageous in terms of economy and characteristics as a method for increasing call traffic without increasing the number of base stations.

(C) Communication channels can be arranged regularly in each sector of each cell in a cluster in a clockwise or counterclockwise direction, and there is no need for irregular arrangement, so the system configuration can be improved. It has the advantage of being simple.

(d) Compared to the 3-cell omnidirectional antenna system, it is possible to reduce the number of interference waves by 1.9%, and the 3-cell repetition system, which has fewer cells than the 4-cell system, can be used. is extremely advantageous in terms of frequency utilization for mobile communications.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a cell arrangement in a conventional example, FIG. 2 is a diagram showing a cell arrangement and a channel arrangement in a base station zone configuration method according to an embodiment of the present invention, and FIG. 3 is a diagram showing a sub-array in the same method. Diagram showing the regularity of channels allocated to sectors, 4th
The figure is a diagram comparing the communication area of the same method and the conventional example, Figure 5 is a diagram showing the configuration of base station equipment implementing the method of the present invention, and Figure 6 is the traffic volume in various cell systems. FIGS. 7, 8, 9, 10, and 11 are diagrams for explaining channel allocation methods according to other embodiments of the present invention, respectively. A, B, C...Cell A-C-...Sector, 1
1 6 51...Antenna tower, 62A to 52F Base station antenna, 53A to 53F...Transmission/reception duplexer, 5
5A ~ 66F ・Transmission duplexer, 56 a ~ 56 n・
...Transmitter, 57A to 57F...Reception duplexer, 58a
~58n... Radio receiver, 59... Base station controller, 6o... Telephone exchange, 62A~62N... Mobile radio telephone, 64... Local exchange, 66...-
...Telephone subscriber (telephone), 66, mountain, antenna reflector - 8 Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 2 ■ Figure 4 ×l Figure 5 , 52D Figure 7 Figure 8 Figure 9 Figure 10

Claims (1)

[Claims] six directional antenna beams for each base station arranged around a first center point form hexagonal cells each having a diamond-shaped sector; The three hexagonal cells are made into one unit, and the second hexagonal cell is adjacent to the first cell, clockwise or counterclockwise. A third cell is provided to form a cell cluster, and the three cells make sectors in the same direction correspond to each other, and the cell cluster is moved in parallel so that cells with the same number of different cell clusters are not adjacent to each other. A plurality of channels are arranged in a communication zone, a plurality of channels are repeatedly used for each cell cluster, and the plurality of channels are sequentially and repeatedly assigned in the direction of increasing or decreasing channel numbers to give 18 channel group numbers, Channel group numbers are assigned to every three channels in the clockwise or counterclockwise direction with reference to an arbitrary sector in the first cell, and
For the cell, a communication zone is formed by allocating a channel group number obtained by adding 1 to the channel group number and 2 to the corresponding sector of the first cell. Base station zone configuration method in communications.