JP2526503B2 - Channel allocation method for wireless communication system - Google Patents

Abstract

PURPOSE:To increase an accommodated traffic per a base station by reducing the frequency of occurrence of interference and disturbance when radio communication is made between plural base stations and radio terminal equipments having a service area divided by sector cells. CONSTITUTION:Base stations 11, 12, 13, 14 forming a service area with plural sector cells 31a-31d and sector cells 34a-34d are respectively provided with sector antennas 21a-21d and sector antennas 24a-24d covering each sector cell one to one. The selection order of channels is decided in advance so that the selection order is the same as to sector cells having the same direction in sectors cells of different base stations. When a call takes place for communication, a channel according to the selection order provided in advance is allocated according to the occurrence of calls sequentially as to the sector cell covering the radio terminal equipment from which the call takes place.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a channel allocating method for a wireless communication system, and more particularly to a channel allocating method for a cellular type wireless communication system for mobiles.

[0002]

2. Description of the Related Art In a wireless communication system for wirelessly communicating between a moving wireless terminal and a base station such as a car telephone system, the same channel is repeatedly used between zones where interference between them does not occur. It is carried out.

The omni structure and the sector structure are known as the above-mentioned zone structures.

In the omni-structured zone, a base station is provided with an omnidirectional antenna in the horizontal plane to cover one zone centered on the base station and is a wireless terminal existing in this zone. This is a configuration for performing wireless communication between the mobile station and the above-mentioned base station.

On the other hand, in a sector zone, a plurality of antennas (hereinafter referred to as sector antennas) having a fan-shaped directivity in a horizontal plane are installed in the base station, and the plurality of sector antennas are used to operate the above-mentioned base. The sector antennas are arranged so that their directional center directions are different from each other so as to cover the entire horizontal plane centered on the station, and sector cells are formed by these sector antennas. A plurality of sector cells thus formed form one zone covering the entire periphery of the base station.

In such a sector structure, a sector antenna having a fan-shaped directivity for covering a moving body existing in a certain direction within a horizontal plane is used.

A sector-shaped area covered by the directivity of one sector antenna is hereinafter referred to as a sector cell.

In a wireless communication system such as a car telephone system utilizing the zone structure having such a sector structure, for example, "Nippon Telegraph and Telephone Public Corporation, Research Practical Report, Vol. 23, 1974, No. 8". As described in "Wireless Zone Construction Method for Car Phones", due to the directivity of the sector antenna, there is less interference in the same channel,
Compared with the wireless communication system using the zone structure, which is the omni structure, the repetition distance of the same channel can be shortened, so that the frequency utilization efficiency is high.

Channel allocation methods include a fixed channel allocation method and a dynamic channel allocation method.

The fixed channel allocation method is a method of preliminarily fixedly allocating channels to be used in each zone in consideration of interference conditions between the zones.

On the other hand, the dynamic channel allocation method is
Instead of fixedly assigning channels to zones, the base station selects a specific channel from all available channels for each communication, measures the level of incoming waves for the selected channel, and determines the desired channel This is a method of allocating a channel if the value of the wave-to-interference power ratio (hereinafter, referred to as CIR) value is equal to or greater than a predetermined threshold value (hereinafter, referred to as CIR threshold value) or the like. .

[0012] In this method, the channels can be effectively used due to the large grouping effect by all channels being shared and allocated by all the base stations constituting the radio communication system. Further, if the CIR threshold is satisfied, the channel can be repeatedly used, so that the channel can be effectively used by repeatedly using the same channel for different mobile stations at a short distance as compared with the fixed channel allocation method. .

Therefore, by using the dynamic channel allocation method, it is possible to obtain higher frequency utilization efficiency than when using the fixed channel allocation method.

In the above-mentioned dynamic channel allocation method, when a communication request is made, channels are generally allocated in the following procedure. The base station measures the desired wave level from the wireless terminal (mobile station such as a car) and the interference level of each channel, and based on the result, at the base station,
A channel that satisfies the allocation condition is selected and notified to the wireless terminal.

The wireless terminal measures the interference wave level of the designated channel, and if the wireless terminal also satisfies the allocation condition, it starts communication using that channel. If the allocation condition is not satisfied in the wireless terminal, the base station selects another channel that satisfies the allocation condition, measures the level of the selected channel and the interference wave level, obtains a CIR threshold value, and performs a predetermined CIR. If the threshold value is satisfied, communication is performed using the selected channel. Hereafter, the specified C
Similar processing is repeated until the IR threshold is satisfied.

In such a dynamic channel allocation method, the frequency utilization efficiency greatly differs depending on the method of determining the channel selection order.

As one of the methods of selecting a channel with high frequency utilization efficiency, for example, Proceedings of IEEE Society is established.
Vehicular Technology Soci
ety), 42nd, VTS Conference, 1992, 5
Mon, p. 782-785, Autonomous Reuse Partitioning in Cellular Systems (Aut
onomouse Reuse Partitionin
As described in a paper published under the title of “g in Cellular Systems”, a method of selecting channels in the same order in all base stations (hereinafter referred to as ARP method) has been proposed.

According to this ARP method, the channel selected first, that is, the channel having a higher selection order, is used more by the terminal closer to the base station and can be reused at a shorter distance interval. It has been shown that frequency utilization efficiency can be increased.

The dynamic channel allocation method described so far can be expected to improve frequency utilization efficiency when combined with a sector configuration. When the sector configuration is used in combination with the already-described ARP method, a method is conceivable in which channels are selected in the same order in all sectors of all base stations.

In the sector configuration, it is considered that by using the same channel between sectors in which the direction in which the directional gain of the antenna is large is the same, the repetition distance of the same channel in that direction can be shortened.

The fluctuations in the reception levels of the desired wave and the interference wave are affected by the topography and features of the arrival direction. However, if the same channel is used between sectors having the same direction, the reception levels of the desired wave and the interference wave will be changed. This is because the correlation becomes high and the CIR easily satisfies the required value.

Further, at the same time, since interference interference exerted in a direction perpendicular to the direction in which the directional gain of the antenna is large becomes small, the repetition distance of the same channel in the vertical direction can be shortened and the frequency utilization efficiency is improved. It is thought to be possible.

In the sector configuration, a method of combining the ARP schemes while using the same channel between the same sectors of base stations whose antenna directivity gains are different is different from each other. A method of selecting channels in the same selection order for each sector having the same direction can be considered.

For example, the number of channels is 40 and 4
When one sector covers the horizontal plane, the selection order is as follows. In the sector having the maximum directional gain in the 0 degree direction, the channels with channel numbers 1, 2, 3, ..., 40 are selected in this order. For the sector used and having the maximum directional gain in the direction of 180 degrees, the channel number is 11,1.
Channels 21, 2, ..., 40, 1, ..., 10 are selected and used in this order of description, and channel numbers 21 and 2 are assigned to the sector having the maximum directional gain in the direction of 90 degrees.
Channels 2, 23, ..., 40, 1, ..., 20 are selected and used in this order, and for sectors having the maximum directional gain in the direction of 270 degrees, 21, 32, 33 ,.
A method of selecting and using each channel of 40, 1, ..., 30 can be considered in this order of description.

[0025]

When the dynamic channel allocation method is used, if the CIR of the allocation candidate channel is greater than or equal to the CIR threshold value, the channel is allocated, but the same channel is allocated in the surroundings by the allocation. There is a possibility of causing interference to a wireless terminal or a base station with which it is communicating.

The conventional method of this kind has a problem that such interference is highly likely to occur when the same channel is allocated between sectors having different antenna directivity gains.

A first object of the present invention is to solve this problem in the case where the ARP system is combined while the same channel is used in the sectors in which the direction of the antenna has a large directional gain and the sector is used. It is an object of the present invention to provide a channel allocation method for a wireless communication system capable of reducing the frequency of occurrence of interference and increasing the traffic accommodation capacity per base station in the configured wireless communication system.

Further, in the channel allocation method using the conventional dynamic channel allocation method, the effect of using the same channel between the sectors having the same antenna directional gain is not sufficiently obtained. There is a point.

A second object of the present invention is to solve this problem and to improve the frequency utilization efficiency and increase the traffic capacity per base station in a sector-configured wireless communication system. It is to provide a channel allocation method.

[0030]

According to a first aspect of the present invention, there is provided a channel allocation method for a wireless communication system, wherein a cell serving as a service area of each of a plurality of base stations is divided into a plurality of sector-shaped sector cells of the same number. Radiation for arranging the sector cells so that the centers of the individual sector cells of the base stations are parallel to each other, and corresponding one-to-one to the sector cells of the base stations to cover the corresponding sector cells. An antenna having characteristics is provided in each of the base stations, and when a communication request with a wireless terminal in the sector cell is generated, a sector cell that covers the wireless terminal that has generated the communication request and covers the wireless terminal , Assigning channels according to a predetermined selection order for communication, and the selection order is such that the direction of the center of the sector cell is the same. In a channel allocation method for a wireless communication system in which the same sector cell is used in any of the base stations, N usable channels are assigned channel numbers from 1 to N, and the channels are arranged in this order. The channel number 1 and the channel number N of the channel arrangement are connected to each other, and the interval between the channels having the first selection order assigned to the sector cells in different directions on the channel arrangement is set by the base station. The number of sector cells is selected to be close to a value obtained by dividing the number of channels, and for a channel having the selection order of 1, the selection order of the channels in the order of moving away from the adjacent channels on the channel array to both sides. Stipulates to choose.

A channel allocation method for a wireless communication system according to a second aspect of the present invention is the same as the channel allocation method for a wireless communication system according to the first aspect, in which the sector cell among the sector cells of the base stations is It is determined that the smaller the angle formed between the center directions, the smaller the interval on the channel array of the channels having the first selection order.

[0032]

In general, when a channel is assigned with a high desired wave level, there is a relatively high possibility of causing interference in surrounding zones using the same channel. This is because even if the interference wave level is relatively high, the CIR is large and allocation is often possible, but if the same channel is used at a low desired wave level in the surrounding zones, This is because the allocation increases the interference wave level and does not satisfy the required CIR value.

Further, when the transmission power control is performed so that the desired wave level becomes constant, the same channel is similarly set.
It is highly possible that interference will occur when one zone is used with a high transmission power and is used in another surrounding zone with a low transmission power.

This is because in both zones using the same channel, the desired wave levels are almost equal due to the transmission power control, but the interference wave levels exerting on each other differ depending on the transmission power. On the other hand, even if one looks at it, on the other hand, it often does not satisfy.

In the ARP system, a channel having a higher selection order is often used in a state where the desired wave level and the interference wave level are higher. This is because a channel with a higher selection order is used by a larger number of different zones at the same time, so that the interference wave level is often high, and accordingly, it is assigned to a wireless terminal having a relatively high desired wave level. Because there are many.

Further, when the transmission power is controlled so that the desired wave level is constant, the higher the selection order, the larger the desired wave level before controlling the transmission power, and thus the smaller the transmission power. Often used in the state.

From the above, in the ARP system, when the same channel is used between sectors in different directions, that channel is a channel with a high selection priority in one sector and a selection priority in the other sector. In the case of a low channel, the desired wave level and the transmission power often differ from each other, and it is considered that there is a high possibility that interference will occur.

On the contrary, if the same channel is used with the same desired wave level and the same transmission power, it is possible to reduce the possibility of causing interference.

In the first invention, when channels are arbitrarily numbered, mutually different channels are selected first among the sectors having different directions of high antenna directional gain, and sequentially,
Channels are selected in order from the closest one.

However, the channel numbers are 1, 2, 3,
, N, the channel numbers are i and i + 1 (i =
1 to N-1) and channel numbers N and 1 are channel numbers having frequencies adjacent to each other.

At this time, since the channels having a high selection order are different between the sectors having different directions, they are rarely used at the same time and are less likely to interfere with each other.

Channels having numbers near the middle of the number of the channel first selected by a certain sector and the number of the channel first selected by the sector having a different direction have substantially the same selection order in any sector. Becomes

Although these channels are relatively often used simultaneously between sectors having different directions, they are used in a state in which the desired wave level and the transmission power are almost the same because the selection orders are almost the same. Due to the increased opportunities, it is unlikely that they will interfere with each other for the reasons explained earlier.

A channel with a lower selection order than this is a channel with a high selection order in sectors in different directions, and if used at the same time, it is relatively likely to cause interference and interference, but it is used less frequently, so it is not so often used. It doesn't matter.

By allocating the channels as described above, the frequency of occurrence of interference is reduced, and the traffic accommodating capacity per base station can be increased.

In the second invention, as in the first invention, when the channels are arbitrarily numbered, the channel selected first among the sectors in which the directions in which the antenna directivity gains are high are close to each other. The order of channel selection is determined so that the numbers of the channels are close to each other.

Therefore, a channel having an intermediate selection order with respect to the channel number first selected by the sectors whose directivities are close to each other is a channel which is frequently used simultaneously among sectors having different directions. .

However, since the direction in which the antenna directional gain is high in the sectors using these channels is relatively close, as described above, the direction in which the antenna directional gain is large is the same in the same sector. The effect of using the channel is obtained, the frequency utilization efficiency is improved, and the traffic capacity per base station is increased.

[0049]

Embodiments of the present invention will now be described with reference to the drawings.

FIG. 1 is an explanatory diagram showing an example of the configuration of a wireless communication system to which the channel allocation method of the wireless communication system of the present invention is applied, and FIG. 2A is a channel allocation method of the wireless communication system of the present invention. FIG. 2B is an explanatory diagram showing an example of a selection order of channels to be applied and assigned.
FIG. 3 is an explanatory diagram showing the concept of how to give the selection order to be assigned, and FIG. 3 shows the selection order of the channels to be assigned to which the channel assignment method of the wireless communication system of the present invention different from that of FIG. 2 is applied. It is explanatory drawing which shows an example.

In the radio communication system shown in FIG. 1, cells are formed by base stations 11, 12, 13 and 14 which are arranged at different positions and cover different areas. A terminal (a mobile station such as an automobile) wirelessly communicates with a base station whose service range is the cell.

The base station 11 divides the horizontal plane into four fan-shaped areas of 90 degrees each, and is equipped with sector antennas 21a, 21b, 21c and 21d having the maximum directional gain in the respective central directions. Sector antenna 21
a to 21d cover the angular range of the service area of the base station 11 with sector-shaped sector cells 31a, 31b, 31c and 31d.

Similarly, the base station 12 uses the sector antenna 22.
a, 22b, 22c and 22d, which are sector cells 32a, 32b, 32c and 3 which are fan-shaped in the horizontal plane.
2d are covered respectively.

The base station 13 has sector antennas 23a, 2
Sector cells 33a, 33b, 33c and 33d having a sector shape in the horizontal plane.
Respectively, and further, the base station 14
Sector antennas 24a, 24b, 24c and 24d are provided to cover the sector cells 34a, 34b, 34c and 34d, respectively.

The center directions of the sector cells 31a, 32a, 33a and 34a in the horizontal plane are parallel to each other, and
They are arranged in the same direction.

The center directions of the other sector cells 31b, 32b, 33b and 34b in the horizontal plane are parallel to each other,
In addition, the directions are the same.

Here, the sector cells 31a, 32a, 33
a and 34a are sector cells in the direction A, sector cells 31
b, 32b, 33b and 34b are sector cells in the direction B, sector cells 31c, 32c, 33c and 34c are sector cells in the direction C and sector cells 31d, 32d and 33.
Let d and 34d be called sector cells in direction D,
For sector cells having the same direction, channel numbers are selected in the same selection order.

In the channel allocation method shown in FIG. 2A, a channel to be selected first, that is, a channel having a selection order of 1 is determined for each sector cell.

In FIG. 2A, each of the base stations 11, 12, 13 and 14 shown in FIG. 1 has channels with channel numbers 1 to 28, and the arrangement thereof is shown in FIG.
The order written in the top line of (A), namely 1, 2, 3,
It is assumed that the order is ...

When a channel having a selection order of 1 is assigned to each sector cell, the channel array shown in the uppermost row of FIG. 2 (A) has a value close to a value obtained by dividing the total number of channels by the number of sector cells. , Channel number intervals (hereinafter referred to as channel distances).

For example, as shown in FIG. 2A, for the sector cell in the direction A, the channel having the channel number 4 and for the sector cell in the direction B, the channel having the channel number 18 are used. For the sector cell in the direction C, the channel having the channel number 11 is determined, and for the sector cell in the direction D, the channel having the channel number 25 is determined as the channel number to be assigned first.

Selection order 1 for sector cells in direction A
Of channel number 4 which is the channel of B and direction B
The channel distance to the channel having the channel number 18 which is the channel having the selection order 1 of the sector cell is 17.

As shown in the uppermost row of FIG. 2A, the channel with the smaller number is set to the left and the channel numbers are sequentially increased from the channels arranged to the right as the channel numbers are sequentially increased. For each sector cell in the direction (direction A to direction C), the channel adjacent to the left of the channel determined to be selected first as described above is the channel to be selected second, and the channel selected third. As a channel to be selected, a channel adjacent to the right of the channel to be selected first is defined as the channel to be selected third.

Similarly, the fourth channel to be selected is the channel to the left of the first channel to be selected, and the channel adjacent to the left of the second channel to be selected. The channel to be selected is a channel adjacent to the right of the above-mentioned third channel to be selected. Similarly, the channels to the left and right of the channels that are located closer to the channel that is selected to be selected first, and the channels that are located farther from the channel that is defined to be selected first, in that order. Channel selection order (alternately to the left and then to the right). However, when the channel selection order is determined in this way,
Array number of the channel shown in the top row of (A) Channel number 1
On the left side of the channel, it is considered that channels having channel numbers 28, 27, ... Are arranged in this order from right to left, and on the right side of the channel of channel number 28, the channel number 1 , 2, ... are arranged in this order from left to right.

If each base station 1 shown in FIG.
1, 12, 13 and 14 respectively use the channel number N from channel number 1 to N, and when the channels are arranged in the order of this number, when determining the channel selection order as described above, the channel number 1 On the left side of the channel, it is considered that the channel numbers N, N-1, ... Are arranged in this order from right to left, and on the right side of the channel number N, channel numbers 1, 2, 3 , ... can be regarded as arranged in this order from left to right.

FIG. 2 (B) is shown in FIG. 2 (A),
6 illustrates a method of determining a channel selection order for a sector cell in direction A. That is, the channel number 4 is the selection order 1 (indicated by in the figure),
The channel with the selection order 2 is the channel with the channel number 4 adjacent to the left of the channel number 4 (indicated by the selection order in the figure) 3 and the channel number with the channel adjacent to the right of the channel number 4 (selection order in the figure. 5) is a channel of selection order 3, which is shown in FIG. 2B below.
The order of channel selection is determined in the order of ,, ....

With respect to the sector cells in the direction B, the sector cells in the direction C, and the sector cells in the direction D, if the selection order of the channels whose selection order is 2 or later is determined by the same method as the selection order of the sector cells in the direction A. Good. In the second to fifth rows from the top of FIG. 2A, the channel selection order for the sector cells in each direction thus determined is from the highest selection order to the lowest selection order, from left to right. It is indicated by the channel number.

One of the base stations having such a selection order,
For example, if there is a communication request from a wireless terminal existing in the sector cell 31a, which is the service area of the base station 11,
The base station 11 checks the CIR of the channel number 4 from the channel number 4 whose channel selection order is 1 for the sector cell 31a in the direction A in the order already described, and the CIR is the CIR. If the threshold value is satisfied, the channel with the channel number 4 is used. If the CIR does not satisfy the CIR threshold value, the base station 11 determines the CIR for the channel with the channel number 3 which is the next selection order. Check whether the CIR threshold is satisfied, and if the CIR threshold is satisfied, the channel of channel number 3 is used.

In this way, communication is performed by sequentially allocating channels in order from the channel having a predetermined channel number having a higher selection order.

Channels used for communication with the wireless terminals are assigned to the other base stations 12, 13 and 14 in a similar manner.

In the above-described embodiment, the sector cells in the direction A select channels having channel numbers 4, 3, 5, ... In this order for communication, but channels having these channel numbers are used in other directions. Since the selection order when used in the sector cell is the 13th or higher, the frequency of use is low. Further, after selecting the channel numbers 4, 3, and 5 in the sector cell in the direction A, the selected channel numbers are 2, 6, 1, 7, 28, 8, 27 and 9
Channels having a selection order of 4 to 11 are highly likely to be selected and used at the same time as sector cells in other directions, but these channels are used in sector cells in other directions, for example, sector cells in the C direction. The selection order in the sector cells in the and D directions is also from 4th to 11th, and the selection order is almost the same as the selection order in the sector cells in the A direction.

The channels having these channel numbers have a selection order of 13 in the sector cell in the direction B.
After the second, the frequency of use is low.

In the above embodiment, the number of channels is 28,
Although the case where the number of sector cells is 4 has been described, in general, the number of channels is N and the number of sector cells is M (M
When <N> is set, the above-mentioned channel of selection order 1 may be determined so that the channel spacing between channels of selection order 1 for each sector cell is as close to N / M as possible.

In the channel allocation embodiment shown in FIG. 3, each of the base stations 11, 12, 13 and 14 has the same four-direction sector cells (sector cells in the A direction and B direction) as in the above-described embodiments. Sector cell, C-direction sector cell, and D-direction sector cell). Channels from channel number 1 to channel number 28 are arranged in this order, and these channels are used by each base station 11, 12, 13 and 14.

In the channel allocation method shown in FIG. 3, when a channel to be selected first (a channel whose selection order is 1) is determined for each sector cell in each direction, it is created between straight lines in the center direction of each sector cell. A channel having a selection order of 1 is determined so that a channel in a relatively close position in the above-mentioned channel arrangement is selected as the angle between sector cells becomes smaller.

That is, when the channel number of the channel having the selection order of 1 for the sector cell in the direction A is 4,
Since the sector cell in the direction B and the sector cell in the direction D are the sector cells closest to the sector cell in the direction A, the channel having the channel number 11 is determined as the channel having the selection order 1 for the sector cell in the direction B.

At this time, the channel distance between channel number 4 and channel number 11 is 7.

For the sector cell in the direction D, the channel having the channel number 25 is defined as the channel having the selection order 1.

As described above, the method of allocating the channels having the second or lower selection order after the channels having the selection order of 1 are set in the sector cells in each direction is the same as the method shown in the embodiment of FIG. .

In the channel allocation method of FIG. 3,
Although the case where the number of channels is 28 and the number of sector cells is 4 has been described, when the number of channels is N and the number of sector cells is M, which is less than the number of channels N, adjacent sector cells in each sector cell are adjacent. For the channel distance of the selection order 1 of each sector cell between them, a value close to N / M is selected, and the channel number adjacent to the channel number defined as the selection order 1 is selected for each sector cell as a channel with a lower selection order. Allocate it.

In the above embodiment, with respect to the channel number defined as the selection order 1, as the channel of the second selection order, the channel located to the left of the predetermined channel array is selected second. The channel next to the channel having the selection order 1 is located next to the right of the channel having the selection order 1, and the channel next to the channel having the selection order 1 is the left side of the channel having the selection order 1 to the left of the already selected channel. To the channel of the fourth selection order, then to the right of the channel of selection order 1 and to the right of the already selected channel, the channel of the fifth selection order, and so on. Channels are allocated, but the channel located to the right of the channel with selection order 1 is the channel next to the channel with the second selection order, and the channel located to the left of it. Channel of the third selection order Le,
Similarly, with respect to the channel having the selection order 1, it is clear that the channels located on the both sides of the selection order may be alternately selected from the channels located on the right side and the left side, which are away from the channel having the selection order 1. Is.

[0082]

As described above, when performing communication,
When allocating channels to be used according to a predetermined selection order as the number of channels used at the same time increases, regarding a sector cell that a sector antenna having the maximum gain characteristic in the same direction with each other among a plurality of base stations, By sequentially allocating channels having the same selection order, it is possible to reduce the frequency of occurrence of interference and interference between the channels.

Further, among the sector cells having the directions adjacent to each other among the sector cells, the channels having relatively short channel distances are set as the channels having the first selection order, thereby further reducing the frequency of occurrence of interference. By doing so, there is an effect that it is possible to further increase the frequency utilization efficiency and increase the traffic accommodation capacity for each base station.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an example of a wireless communication system to which a channel allocation method of a wireless communication system of the present invention is applied.

FIG. 2A is an explanatory diagram showing an example of a selection order of channels to be allocated by the channel allocation method of the wireless communication system of the present invention. FIG. 2B is an explanatory diagram illustrating a method of setting the channel selection order for the sector cells in the A direction shown in FIG.

FIG. 3 is an explanatory view showing a selection order of channels to be allocated by a channel allocation method of the present invention different from that shown in FIG.

[Explanation of symbols]

 11-14 Base station 21a-21d Sector antenna 22a-22d Sector antenna 23a-23d Sector antenna 24a-24d Sector antenna 31a-31d Sector cell 32a-32d Sector cell 33a-33d Sector cell 34a-34d Sector cell

Claims (2)

(57) [Claims] 1. For each of a plurality of base stations, a cell serving as its service area is divided into a plurality of sector cells having the same number of sectors, and the respective sector cells of the respective base stations have their centers parallel to each other. The sector cells are arranged in such a manner that each of the base stations is provided with an antenna having a radiation characteristic that covers the corresponding sector cell in a one-to-one correspondence with the sector cell of each of the base stations. When a communication request with the wireless terminal is generated, a sector cell that covers the wireless terminal that has generated the communication request and covers the wireless terminal is assigned a channel in accordance with a predetermined selection order, and communication is performed. The order of radio communication is the same in any of the base stations in a sector cell in which the direction of the center of the sector cell is the same. In the channel allocation method of the communication system, N usable channels are assigned channel numbers from 1 to N, the channels are arranged in this order, and the channel number 1 and the channel number N in the channel arrangement are further assigned. The interval on the channel arrangement between the channels having the first selection order that are connected and assigned to the sector cells in different directions is close to a value obtained by dividing the number of channels by the number of sector cells of the base station. Of the channel having the selection order of 1, the channel selection order is selected in the order of moving away from the adjacent channels on the channel arrangement on both sides of the channel arrangement. Channel allocation method. 2. The channel allocation method for a wireless communication system according to claim 1, wherein the smaller the angle formed between the center directions of the sector cells among the sector cells of each of the base stations is, the first selection order is set. A channel allocation method for a wireless communication system, characterized in that the intervals of the channels to be possessed are set to be small.