JPH0247903B2 - - Google Patents

Description

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

Conventional configurations and their problems Conventionally, in the wireless zone configuration of a car telephone system, a channel arrangement using omnidirectional antennas has been used, and the (wireless) cell shape has been a geometric one with an antenna at the center of each cell. Use scientific figures such as regular triangles, regular quadrilaterals, and regular hexagons. Other complex shapes are possible, but among these, the communication service area is divided into hexagonal cells that are closest to a circle, and different wireless channels are assigned to adjacent wireless cells for individual communication. often.

There are zone configuration methods such as 3 cells, 4 cells, 7 cells, 9 cells, 12 cells...23 cells for the number of wireless cells when providing area service such as a car phone, but only a limited number of wireless channels can be used effectively. A group of infinite cells (cell cluster) that is as small as possible to use
It is necessary to increase the call traffic by repeatedly allocating as many radio channels as possible to each radio cell per cell cluster.

The minimum for area service is a 3-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 7 cells or more is required. It is necessary to do so. However, in areas where communication traffic is concentrated, such as in large cities, it is necessary to further subdivide the hexagonal (wireless) cells to increase communication traffic. On the other hand, subdividing (wireless) cells requires an increase in the number of base stations, and this increases the number of base station buildings and grounds as well as the communication equipment that connects the base stations. Furthermore, maintenance work to keep these communication facilities in good condition requires a very large amount of money, so there has been a problem in how to carry out subdivision economically.

An economical way to express this is to install multiple directional antennas on one base station and divide the wireless zone into multiple small zones (sectors) to subdivide the wireless zone and increase call traffic. Attempts to achieve this have been proposed and implemented since around 1968. For example, Japan Railway Corporation (JNR)
This is the train telephone system. 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. It was hot.

For car telephone systems that require area service, a method of installing multiple directional antennas in one base station and dividing it into radio zones of different frequencies (channels) is known, for example, from Japanese Patent Publication No. 52-14122. ing.

Judging the merits and demerits of wireless cell configurations is related to how well they can cope with the increase in call traffic concentrated in large cities, and how economically zone configurations 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 sections. In that case, whether the interference ratio from adjacent frequency channels can be kept above the desired value by dividing, 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 an omnidirectional antenna 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 as shown in FIG. 1, for example, according to US Pat. No. 4,128,740. In the figure, four cells W, X, Y, and Z are each divided into six triangular sectors. Each of the six triangular sectors is composed of six directional antenna beams located at a common central location, 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 _, , Z ₆ .

In the conventional configuration described above, the call loss rate is lower than the call traffic of a 7-cell configuration using omnidirectional antennas.
At 0.5%, an improvement effect of only 14% was obtained.

In addition, in the above-mentioned 4-cell configuration, in which each cell is divided into 6, 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. Nakatsuta. Therefore, when the effective radiated power (ERP) is limited by radio wave use regulations, etc., the radius of the communication area inevitably becomes smaller.

Purpose of the Invention The present invention eliminates the drawbacks of the conventional example, and enables a configuration with as few cells as possible compared to the conventional communication system using four cells and directional antennas, thereby reducing traffic. It is an object of the present invention to provide a method for configuring base station zones that can be increased and is economical.

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 By directing the hexagonal cells in the direction of each apex of the hexagonal cells, the centers of adjacent cells are avoided, and by giving a certain regularity to the channel arrangement between the sectors, even a 3-cell configuration can be used instead of a conventional 4-cell configuration. 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), and the right is east.
(E), with west (W) on the left, 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 an east-west (EW) direction, a 30° northeast (NE) direction, and a 30° northwest (NW) direction to prevent the occurrence of turbulence.

Next, the center point (first point) of each of the regular hexagonal cells is
With reference to the center point of into sectors. A base station is installed at the center of each sector, and the main beams of six directional antennas are directed to each of the six hexagonal cells.
The directional antennas are installed to match the two apex angles, and each of the directional antennas is used to form an independent 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 (second cell) on the south side, and cell C (third cell) on the east side. ), and the sectors in the east position of each cell are A ₁ , B ₁ , C ₁ , and clockwise A ₂ , A ₃ , etc.
The cells are named A ₆ , B _{2 ,} B ₃ . . . _B 6 , C ₂ , C ₃ .

In the figure, A ₁ to A ₆ represent each sector name, and the numbers represent channels (numbers). The channels are broadly classified into a communication channel (CH) and a control CH.
Therefore, 18 speech channels (22...328) and one control channel (1CH) are allocated to sector _A1 . The same is true for the others, but the shaded areas represent areas where there is no allocation 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 represented by O, 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 (mark) shaped sector in Fig. 2, which constitutes one of the hexagonal cells, is expressed as OS ₂ N ₁ S ₁ .
Also, the triangular sector in Figure 1 indicates OM ₆ M ₁ . At this time, the beam of the directional antenna of the diamond-shaped sector is represented by 3, the beam of the directional antenna of the triangular sector is represented by 2, and the beam of the omnidirectional antenna used in the following explanation is represented by 1. What is distinctive about this figure is that the center direction (therefore the maximum direction) of directional antenna beam 3 is oriented in the direction of axis _X1 , whereas the center direction of directional antenna beam 2 is oriented in the direction of axis _Y1 . , and both are 30 degrees apart from each other. Furthermore, in the same figure, point S ₁ (S ₂ ) and M ₁
The antenna gain at point (M ₂ ) is defined to be half of the maximum value (half width = ±30°).

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 elevated mobile radio specified in CCTR, the effective radiated power (ERP) is
When calculating the distance (cell radius) R ₀ at which the electric field strength of the omnidirectional antenna 1 is 39 dBμV/m when the power is 100 W and the antenna height is 150 m, OU ₁ = R ₀ = 12 Km. On the other hand, the cell radius R _N corresponding to directional antenna beam 3 is ON ₁ = 11 Km, and the cell radius R _M corresponding to directional antenna beam 2 is OM ₁ (OM ₆ ) =
It will be 9.5km. In other words, 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, the direction of directional antenna beam 2 is shifted from area () to adjacent area (). Even if the electric field strength is increased, the electric field strength will not decrease and the overlapping region will become large.

Next, if we calculate the distance to the adjacent sector where the same frequency is repeated in the triangular sector 2 and the diamond mark sector 3, we can see 4 and 5 in Figure 1.
and 6 and 7 in Figure 2, and when these are expressed as _DM and _DN , as is clear from Figures 1 and 2, _DM = 2√3R _M = 32.9 Km, D _N =
3R _N = 33Km, so D _M and D _N are almost equal,
It is shown that the distance intervals at which interference occurs between the two are approximately equal.

That is, in the above configuration, interference is reduced by configuring the antenna beams that make up each sector to avoid the center of adjacent cells, and as a result, the configuration is changed from the conventional 4-cell configuration to 3-cell configuration. Therefore, interference reduction equivalent to that of 4 cells can be achieved.

However, considering the direction of the directivity of the directional antenna, the two directional antennas 4 and 5 and 6 and 7 are facing in opposite directions even at the above distance, and the front-back ratio (F/B) of the directivity is If is 25dB, the back communication distance D _a is D _a = 1.8Km,
The distance from the interfering base station to the above point is D ₃ −D _a
=31.9−1.8=30.1Km, and the interference ratio (S/
I) is approximately 15dB.

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 assigning wireless channels using directional antennas, for example, the eastward sectors of each cell A, B, and C are designated A ₁ , B ₁ , C ₁ , and A ₁ , A ₂ , etc. are assigned at 60° intervals.
. . . A ₆ , B ₁ , _{B 2 .} . . B ₆ , C ₁ , C ₂ . Of course, A ₁ , B ₁ and C ₁ can be set in different directions from the map orientation, or the wireless channels can be arranged so that the channel assignments are rotated counterclockwise. Equivalent results are obtained.

Here, base station equipment for realizing the configuration of the embodiment will be explained with reference to FIG. 5. 51 is an antenna tower, 52 is a base station antenna, 66 is an antenna reflector, and each sector is made into a communication range by directional antennas 52A to 52F with a gain half width of 60 degrees or more. 53A to 53F are transmitting/receiving duplexers, which are used for each antenna to share the transmitting/receiving frequency for each sector. 54A-54F
is a coaxial cable or a waveguide (several G
Hz), 55A to 55F are transmission duplexers for each antenna, 56a to 56n are multiple transmitters that transmit multiple channel frequencies for each antenna, 5
7A to 57F are reception duplexers, which are provided for each antenna and equally distribute the received power of each antenna to the wireless receivers 58a to 58n without loss. Reference numeral 59 denotes a base station control unit (CSU), which performs various controls unique 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. 60 is a telephone exchange (MTSO) that controls multiple CSUs, and mobile radio telephones 62A...62N
It is connected to a telephone subscriber (telephone) 65 via a toll telephone network 63 and a local exchange 64 at the destination.

7 to 11 show other embodiments of the present invention, and FIG. 7 is a diagram showing a method of arranging (wireless) channels (group numbers) to each sector of three cell clusters A, B, and C. and any sector A ₁
is the lowest numbered sector, C ₆ is the highest numbered sector, and when assigning a (wireless) channel to each sector, the wireless channels are A ₁ , B ₁ ,
Each sector A ₁ to (wireless) cell A in the order of C ₁ and A ₂
Assign channel group numbers 1, 4, 7, 10, 13, and 16 to _A6 so that the channel group numbers increase in 3-channel increments. (Wireless) For each sector B ₁ to _{B 6} of cell B, slide the channel arrangement of cell A parallel to cell B so that sector A ₁ overlaps sector B ₁ , and add 1 to channel group number 1 to 16 of cell A. channel group numbers 2, 5, 8, 11, 14, and 17 are assigned to sectors _B1 to _B6 . Next, for each sector of cell C, overlap sector A ₁ with sector C ₁ at the same time as cell B, and add channel group number 1 of cell A.
Channel group number 3, which is ~16 plus 2,
This shows a state in which numbers 6, 9, 12, 15, and 18 are assigned. Dashed line arrows and solid line arrows indicate the direction in which the numbers increase.

Note that sector A ₁ of cell A may be selected with the largest channel group number, and channels may be allocated in the order of A ₁ , A ₂ . . . A ₆ at three-channel intervals.
For example, A ₁ = 18, A ₂ = 15, A ₃ = 12, A ₄ = 9, A ₅
=6, A ₆ =3, and each sector of cell B may have a number obtained by subtracting 1 from cell A, and each sector of cell B may have a number subtracted from cell A.

FIG. 8 is an example in which channels within a cell are allocated counterclockwise from sector _A1 of cell A.
For example, the channel group number is A ₁ = 1, A ₆ = 4,
A ₅ = 7, A ₄ = 10, A ₃ = 13, A ₂ = 16, cell B
Similarly to cell A, 1 is added to the channel group number of cell A, and like cell A, cell C is given a channel whose number is obtained by adding 2 to the channel group number of cell A, with sectors B ₁ and C ₁ as the base points. The broken line arrow and the solid line arrow indicate the increasing direction of the channel group number.

Note that, 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.

Figure 9 shows the assignment of channel groups to cells A, B, and C in the opposite direction to the rotation direction in Figure 8.
In this example, sector A ₁ is set to channel group number 1, B ₁ is set to 3, and C ₁ is set to 2, and the channel group numbers are increased clockwise within each cell.

Note that the highest channel group number is assigned to sector A ₁ , and A ₁ , B ₁ , C ₁ and A ₁ ~ A ₆ , B ₁ ~
Small numbers may be assigned in the B ₆ and C ₁ to C ₆ directions.

Figure 10 shows the assignment of channel group numbers to each cell A, C, B each sector A ₁ , A ₆ , A ₅ , A ₄ ,
They are assigned counterclockwise like A ₃ , A ₂ , B ₁ , B ₆ to _{B 2} , C ₁ , C ₆ to C ₂ , and if sector A ₁ is the maximum number, the channel group number is On the contrary, it shows a decline.

In the cell cluster configuration of the present invention, the base points for allocating channel groups are cells A, B, and C.
A channel group number can be assigned to any sector in the above-mentioned manner.

FIG. 11 shows a state in which the base point for channel assignment is sector _A4 of cell A. 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, when calculating the call volume and call volume ratio for the 12-cell system, 7-cell system, 4-cell 6-split system, and 3-cell 6-split system, assuming that the number of communication channels is 312 (333 to 21) and the call loss rate is 0.5%, the 6th It will look like the figure. That is, according to the cell configuration of the present invention, it is possible to increase traffic by about 1.74 times compared to a 7-cell system using omnidirectional antennas, and about 3.5 times compared to a 12-cell system.
Even compared to the conventional 4-cell 6-division system, this means that 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, by using a directional antenna, 3
Since the number of interference waves is reduced to 1/6 compared to the cell system, benefits 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 into 6, the number of communication channels distributed to each sector antenna can be increased, making it possible to significantly increase the communication traffic of each cell. For example, compared to the call traffic of a cell cluster with a seven-cell configuration using omnidirectional antennas, the increase in call traffic is only 14% in the four-cell, six-division system, whereas the increase in call traffic in the cluster configuration of the present invention is only 14%. According to the report, it is possible to obtain a 74% increase, so the effect of improving call traffic is significant.

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

(c) The communication channels can be placed regularly in each sector of each cell in the cluster in a clockwise or counterclockwise direction, and there is no need for irregular placement, which simplifies the system configuration. There are advantages that can be achieved.

(d) Compared to the omnidirectional antenna 3-cell system, it is possible to reduce the number of interference waves to 1/6,
The ability to use the 3-cell repetition system, which has fewer cells than the 4-cell system, is extremely advantageous in terms of frequency utilization for mobile communications.

[Brief explanation of drawings]

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. Figure 4 is a diagram showing the regularity of channels allocated to sectors, Figure 4 is a diagram for comparing the communication area of the same method and the conventional example, and Figure 5 is a diagram showing the regularity of channels assigned to sectors.
The figures are diagrams showing the configuration of base station equipment implementing the method of the present invention, Figure 6 is a diagram for comparing traffic volumes in various cell systems, Figures 7, 8, 9, and 1.
0 and 11 are diagrams for explaining channel allocation methods according to other embodiments of the present invention, respectively. A, B, C...Cell, _A1 ~ _C6 ...Sector,
51...Antenna tower, 52A to 52F...Base station antenna, 53A to 53F...Transmission/reception duplexer,
55A to 55F... Transmission duplexer, 56a to 56n
...Transmitter, 57A to 57F...Reception duplexer, 5
8a to 58n...Radio receiver, 59...Base station control device, 60...Telephone exchange, 62A to 62N...
...Mobile radio telephone, 64...Local exchange, 65...
...Telephone subscriber (telephone), 66...Antenna reflector.

Claims (1)

[Claims] 1 6 for each base station placed around the first center point
The directional antenna beams form hexagonal cells each having a diamond-shaped sector, and the directional antenna beams are connected to the six directional antenna beams.
A cell cluster is formed by aligning the apex angle direction of the rectangular cells, and forming a cell cluster by forming second and third cells adjacent to the first cell in the clockwise or counterclockwise direction, with the three hexagonal cells as one unit. At the same time, the three cells correspond to sectors in the same direction, and the cell clusters are moved in parallel to arrange a plurality of cells in a communication zone so that cells with the same number of different cell clusters are not adjacent to each other. , a plurality of channels are repeatedly used in the cell cluster unit, the plurality of channels are repeatedly assigned in the direction of increasing or decreasing channel numbers to give 18 channel group numbers; With the sector as a reference, channel group numbers are assigned in three-channel increments in a clockwise or counterclockwise direction, and for the second and third cells, one is assigned to the sector corresponding to the first cell. 1. A base station zone configuration method in mobile communication, characterized in that a channel group number is assigned by adding 1 to the channel group number and 2 to the other to form a communication zone.