JP2002262340A - Wireless channel assignment method in zone/cell coexisting mobile communication network and channel controller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless channel assignment method in a zone/cell coexistence mobile communication network that can enhance re-utilization efficiency of wireless channels. SOLUTION: Logical cells 31 -33 are a set of a plurality of physical cells located within interference distance with each other. As a set of a plurality of logical cells not interfered with each other, the logical cells 31 -33 are selected as a group 40 . A zone 1 and the group share a plurality of wireless channels assigned to a network in common. The number groups can be decreased by providing logical cells handling a combination of the physical cell as one cell in the groups.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio channel allocating method and a line controller in a zone / cell coexisting mobile communication network.

[0002]

2. Description of the Related Art Conventionally, there is known a digital communication system for public service of a large zone system in which a single base station covers a wide area with a radius of a wireless zone of about 30 km. Here, in order to cover one or a plurality of small areas where traffic is concentrated, arranging a cell base station in each area is being studied. Here, the wireless channel allocated to the entire network is shared (exclusive sharing that cannot be used simultaneously) between the cell of the cell base station and the zone of the original zone base station, so that the wireless channel is used efficiently. Can be.

Furthermore, since the area of such a cell is small, when a plurality of cells exist in a zone, a plurality of cells physically separated by a distance that does not cause frequency interference are collected into a group (wireless channel re-establishment). Use group). Each cell in the group can use the same radio channel simultaneously (geographic reuse). However, cells whose frequencies interfere with each other cannot be placed in the same group. Therefore, cells that form a plurality of groups and whose frequencies interfere with each other belong to different groups, and do not use the same radio channel simultaneously in zones and groups.

FIG. 8 is a network configuration diagram for explaining an outline of the above-described conventional technology and the examination method. FIG.
In (a), 1 is a zone (wireless zone), 1a is a zone base station (indicated by an antenna symbol). Assume that the call volume generated in the entire network is 5. In order to cope with an increase in traffic (generated traffic volume 10) as shown in FIG. 8B, a physical cell base station is installed in an area where traffic is concentrated as shown in FIG. A cell is provided.
2 _{1 to} 2 ₆ are physical cells, and 2a _{1 to} 2a ₆ are physical cell base stations (indicated by antenna symbols). Here, the “physical cell” refers to the “cell” described above and a “logical cell” described later.
This is the name used to distinguish it from Therefore, the “physical cell” means a wireless communication service area provided by a base station existing at a certain geographical position.

[0005] 4 is a group, 4 ₁ The first group is 4 ₂ is the second group. Physical cell 2 ₁ frequency is separated by a distance that does not interfere with each other, 2 _2, 2 ₃ attracted to the first group 4 _1, similar conditions, physical cell 2 _4, 2 _5, 2 ₆ collects second Group 4 ₂
Physical cells 2 ₁ , which are close in distance and have frequency interference,
2 _4, physical cell ₂ 2, 2 _5, physical cell 2 _3, 2 _6, to belong to different groups. That is, a group (radio channel reuse group) that can use different radio channels at the same time is configured, and physical cells that cannot use the same radio channel at the same time due to interference belong to different groups. Reuse. On the other hand, as the number of groups increases, different groups cannot use the same wireless channel at the same time, so that there is a problem that the reuse efficiency of the wireless channel deteriorates.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems of the conventional system or the study system. By changing a mobile communication network configuration method, the wireless channel reuse efficiency can be improved. It is an object of the present invention to provide a radio channel assignment method and a line control device in a zone / cell coexisting mobile communication network, which can improve the communication quality.

[0007]

According to a first aspect of the present invention, there is provided a base station for a plurality of physical cells each covering a plurality of specific areas in a zone, and the base station except for the specific area. Having a zone base station that covers the zone, at least one logical cell is set as a set of a plurality of the physical cells at least partially interfering with each other, and the logical cell and an independent logical cell that does not constitute the logical cell At least one group is set for the set of physical cells, the group is set such that the logical cells or the independent physical cells in the group do not interfere with each other, and at least one of the groups is The zone and the zone are set to include one logic cell and another logic cell or the independent physical cell. A method for allocating a radio channel in a zone / cell coexisting mobile communication network sharing a plurality of radio channels with said group, wherein the radio channel is allocated between each logical cell and each independent physical cell in the same group. The wireless channel is allocated so that it can be reused. Therefore, the wireless channel can be used efficiently by sharing and reusing the wireless channel. In addition, since the group for reusing the wireless channel is set in advance, the process of allocating the wireless channel is simplified. Even when there are physical cells that interfere with each other, the number of groups can be reduced by grouping them into logical cells and then making the same group that reuses the wireless channel. Efficiency can be increased.

[0008] In a second aspect of the present invention, in the wireless channel allocation method in the zone / cell coexisting mobile communication network according to the first aspect, it has been confirmed that a communication link is released in a base station of the physical cell. Sometimes, in the group to which the physical cell belongs,
If the number of radio channel lines is used more than necessary after releasing the communication link, a process of reducing the number of radio channel lines in use by reallocating the radio channel in use is performed. Is what you do. Therefore, wireless channels can be efficiently reused by switching wireless channels even during communication. On the other hand, when a base station of a physical cell issues a wireless channel allocation request, the wireless base station receives this allocation request and is in use by the group to which the physical cell belongs, but cannot be used by the logical cell to which the physical cell belongs. The radio channel to be used may be assigned with priority over radio channels not used in the zone and each group.

According to a third aspect of the present invention, in the wireless channel allocation method in the zone / cell coexisting mobile communication network according to the first or second aspect, the number of lines of the wireless channel shared by the zone and the group is set. Is defined as n (an integer of 2 or more), and the number of lines of the wireless channel implemented in each of the physical cell base stations is defined as n
To make it smaller. Therefore, network equipment can be reduced by only slightly deteriorating the call blocking rate characteristics.

[0010] In a fourth aspect of the present invention, there is provided a base station of a plurality of physical cells each covering a plurality of specific areas in a zone, and a base station of a zone covering the zone excluding the specific area. At least one logical cell is set as a set of a plurality of the physical cells at least partially interfering with each other, and at least one logical cell and a set of independent physical cells that do not constitute the logical cell are provided. One group is set, the group is set so that the logical cells or the independent physical cells in the group do not interfere with each other, and at least one group is formed by one logical cell and another logical cell. It is set to include a logical cell or the independent physical cell, and a plurality of non- A circuit controller for use in a zone / cell coexisting mobile communication network sharing a channel, wherein the radio channel is re-used between each logical cell and each independent physical cell in the same group. It has wireless channel allocating means for allocating channels. Therefore, the wireless channel allocation method in the zone / cell coexisting mobile communication network described in claim 1 can be easily realized.

According to a fifth aspect of the present invention, in the line control apparatus used in the zone / cell coexisting mobile communication network according to the fourth aspect, it is confirmed that a communication link is released at a base station of the physical cell. Means, the wireless channel allocating means, when confirming the release of the communication link, in the group to which the physical cell belongs, after releasing the communication link, the number of lines of the wireless channel is used more than necessary. If so, a process of reducing the number of lines of the used wireless channel is performed by re-assigning the used wireless channel. Therefore, the wireless channel allocation method in the zone / cell coexisting mobile communication network according to the second aspect can be easily realized.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is an explanatory diagram of a network configuration for explaining an embodiment of the present invention. Figure 1
(A) is a network configuration diagram. In the figure, the same parts as those in FIG. 8 are denoted by the same reference numerals. FIG. 1B is a table showing a hierarchical structure of a network including groups, logical cells, and physical cells. FIG. 1C is a table illustrating various hierarchical structures different from FIG. 1B. The network configuration illustrated in FIG.
This is a zone / cell coexistence network configuration in consideration of geographical reuse of a wireless channel, in which a zone and a group share a wireless channel between a base station and a mobile station assigned to an existing zone base station. 3 ₁ to 3 ₃ logic cells 4 ₀ is a single group to reuse radio channels. Logic cells 3 ₁ to 3 ₃ is a set of a plurality of physical cell, in the illustrated example, a set of physical cell 2 _1, 2 ₄ and logic cells 3 _1, a set of physical cell 2 _2, 2 ₅ A logical cell 3 ₂ and a set of physical cells 2 ₃ and 2 ₆ are a logical cell 3 ₃ . Typically, it is a set of a plurality of physical cells at distances that interfere with each other, but physical cells that do not interfere may be included.

Next, a physical cell included in each logical cell is
One group (wireless channel reuse group) is set as a set of a plurality of logical cells that do not interfere with each other between different logical cells. A plurality of such groups may be set. In the illustrated example, the logic cells 3 _{1 to} 3 ₃
There are set as a single group 4 _0. Therefore,
Between each logic cell 3 ₁ to 3 ₃ single Group 4 in _0, it is possible to reuse the same radio channel. Note that the zone 1 and each group share (exclusively share) a plurality of wireless channels allocated to the network.

[0014] As shown in FIG. 1 (b), in the example of the network configuration of FIG. 1 (a), the column of the group 0 is described, it illustrates the Group 4 _0. In the column of the logic cell corresponding to the group 40, ₁ to 3 are described.
Shows _{1-3 3.} In the physical cell row corresponding to the logical cell 31, ₁ and 4 are described, which indicate the physical cells 2 ₁ and 2 ₄ . 2 and 5 are described in the row of the physical cell corresponding to logic cells 3 _2, which shows physical cell 2 _2, 2 _5. 3 and 6 are described in the row of the physical cell corresponding to logic cells 3 _3, which shows the physical cell 2 _3, 2 _6. Thus, in this table, the hierarchical relationship between groups, logical cells, and physical cells is set based on the interference relationship between wireless channels in the network. Here, FIG.
So although there is only provided a single group 4 _0, in general, it is possible to provide a plurality of groups. However, even if the providing a plurality of groups, unlike the groups in study method described in the prior art section, the at least one group, such as the Group 4 _0, which groups a plurality of logic cells Therefore, the number of groups can be reduced as compared with the above-described study method.

The use status of the radio channel and the assignment of the radio channel will be described later with reference to FIG. 6, which is connected to the zone base station 1a and each of the physical cell base stations 2a _{1 to} 2a ₆ via a transmission line. It is managed by the line control device of the control station, and actual control is performed in each base station.

[0016] In reference to study scheme described with FIG. 8 (c), the interference physical cell together with interference, in the illustrated example, the physical cell 2 _1, 2 _4, firstly, the different groups (radio channel reuse group ). On the other hand, in the present invention, the idea is changed, and physical cells having interference are defined and put together as the same logical cell. Then, in a different logic cells 3 ₁ to 3 _3, so that even using the same radio channel do not interfere.

[0017] Thus, the logic cells 3 ₁ to 3 _3, interference-free physical cell with regards to the group (radio channel reuse group) can be of. Typically,
Physical cells in a certain interfering neighboring area are collectively referred to as a logical cell. By collecting these logic cells, a conventional group (radio channel reuse group) can be formed. However, even in the present invention, wireless channels cannot be reused between physical cells in the same logical cell. Therefore, the physical cell itself as an entity is not different from the conventional physical cell in the present invention.

However, the handling of the physical cell when reusing the frequency is different. It has been found that this difference in handling improves the call blocking rate characteristics, in other words, the number of radio channel lines required to realize the same call blocking rate can be reduced. That is, by treating a combination of physical cells as one logical cell, the number of groups to be reused is reduced, and the efficiency of wireless channel reuse is increased. First, a typical example in which a difference clearly appears will be described qualitatively.

FIG. 2 is an explanatory diagram of a reuse pattern for explaining the principle of the present invention. FIG. 2A shows FIG.
It is explanatory drawing of the reuse pattern similar to the examination method shown to (c). FIG. 2B is an explanatory diagram of a reuse pattern similar to the embodiment of the present invention shown in FIG. 1A.
In the figure, the same parts as those in FIGS. 8C and 1A are denoted by the same reference numerals. In each case, the physical cell base station is 2a ₁ ,
A case will be described in which only four stations 2a ₂ , 2a ₄ , and 2a ₅ are used, and two channels, ch1 and ch2, are allocated to all four stations as wireless channels, and all two channels are used. FIG.
(A) and the left side of FIG. 2 (b) are network configuration diagrams.
The right side is a diagram showing the wireless channels ch1 and ch2 used by each base station and the reuse relationship of the wireless channels.

In FIG. 2A, since the wireless channel cannot be reused between different groups, there are a total of three types of wireless channel reuse patterns. If this is discriminated up to the channel number (line number), it is twice as large. The details are as shown below. In certain one physical cell base station 2a _2, when the number of calls is 2 1 pattern (physical cell base station 2a _2, 2a ₁ each ch
1 and 2 simultaneously). One physical cell base station 2a
₂ , when the number of calls is 1, one pattern (the physical cell base stations 2a ₂ and 2a _1
5 and 2a ₄ simultaneously use ch2). In certain one physical cell base station 2a _2, (simultaneous use of physical cell base station 2a _5, 2a ₄ respectively ch1, ch2) 1 pattern when the number of calls is zero.

On the other hand, in FIG. 2B, the concept of a logic cell is introduced to form one group. The radio channel cannot be reused in a logical cell, but can be reused between diagonal directions in the figure. As a result, there are a total of ten types of wireless channel reuse patterns. If this is discriminated up to the channel number (line number), it is twice as large.
The details are as shown below. In certain one physical cell base station 2a _2, 3 pattern when the number of call 2 (physical cell base station 2a _2, 2a ₁ each ch
1 and 2 simultaneously, physical cell base stations 2a ₂ and 2a ₁ each use ch 1 and physical cell base stations 2a ₂ and 2a ₄ each simultaneously use ch 2 and physical cell base stations 2a ₂ and 2a 2
a ₄ simultaneous use each ch1, ch2). In certain one physical cell base station 2a _2, the four patterns (physical cell base station 2a _2, 2a ₁ each ch1 when the number of calls is 1,
Also, the physical cell base stations 2a ₅ and 2a ₁ simultaneously use ch2, and the physical cell base stations 2a ₂ and 2a ₁ each use ch1.
And the physical cell base stations 2a ₅ and 2a ₄
, And the physical cell base stations 2a ₂ and 2a ₄
ch1 and physical cell base stations 2a ₅ and 2a ₁
ch2 is used simultaneously, physical cell base stations 2a ₂ and 2a ₄ each use ch 1 and physical cell base stations 2a ₅ and 2a ₄ simultaneously use ch 2), and one physical cell base station 2a
_{In 2} , when the number of calls is 0, three patterns (physical cell base stations 2a ₅ and 2a ₁ simultaneously use ch1 and ch2 respectively,
Each of the physical cell base stations 2a ₅ and 2a ₁ is ch1 and
The physical cell base stations 2a ₅ and 2a ₄ use ch2 simultaneously, and the physical cell base stations 2a ₅ and 2a ₄ use ch1 and ch, respectively.
2 at the same time).

In the case of FIG. 2B, the number of reuse patterns of the radio channel increases by an amount corresponding to the decrease in the number of groups. As a result, when a request for a radio channel is made in a certain physical cell, The probability that another wireless channel in use can be reused increases. Therefore, it can be seen that even if there is a physical cell having interference, by grouping such physical cells as logical cells and then grouping them, the reuse efficiency of the wireless channel is improved. However, since the wireless channel cannot be reused in one large logical cell including a plurality of cells, the point lies in the difference in the contents of the traffic. Therefore, in general, when a relatively small number of physical cells are arranged non-uniformly according to the traffic distribution, such as the zone / cell coexisting mobile communication network described above, which is not always advantageous, the arrangement of It is easy to effectively introduce a logic cell according to the situation, and an improvement in call blocking rate characteristics can be expected.
Therefore, a theoretical calculation was performed as described later, and a specific example of the improvement was shown.

On the other hand, each time a wireless channel assignment is requested, the interference between cells can be determined by examining the distance between cells or measuring the CIR (desired frequency-to-interference power ratio). Radio channel assignment can be performed. However, there is a disadvantage that complicated processing is required. In the present invention, if a logical cell is set in advance, it can be treated as if it were a physical cell, a group for reusing the wireless channel can be formed, and the wireless channel can be allocated. In the above-described zone / cell coexisting mobile communication network, a physical cell is installed only in an area with a lot of traffic. Therefore,
The number of physical cells to be installed is relatively small and is often arranged unevenly. Such an arrangement is advantageous for setting a logic cell and forming a group, and setting a logic cell and forming a group can be performed relatively easily.

On the other hand, one logical cell may be considered as one physical cell and covered by one base station. However, in this case, if one base station is used, the distance to the mobile station becomes longer, so that it is necessary to increase the power. Then, the cell area is isotropic from the base station, and the cell area is wider than the collection of small cells, so that interference with other physical cells also increases. As a result, the geographical reusable distance of the wireless channel increases. Therefore, the logical cell integration is advantageous because the service area can be narrowed down to a necessary area.

The above description is based on FIGS. 1 (a) and 1 (b).
This is an explanation of the specific example shown in FIG. However, the present invention is applicable to other than such a network configuration. This will be described with reference to FIG. In FIG. 1 (c), the FIG. 1 (a), the network configuration shown in FIG. 1 (b), shows that by adding a physical cell base station 2a ₇ to 2A region ₁₄ for explanation. That is, in the zone 1, are new, provided the physical cell 2 _{7-2 1 4.} Numbers 7 to 14 representing the numbers of the added physical cells are shown in parentheses. In the column of the logic cells, the shaded row indicates a case where there is no logic cell and the physical cell directly belongs to the group. Some groups may be composed of one logical cell and one physical cell. For example,
Since it is assumed that the radio channel is exclusively shared between the zone and the group, there can be one logical cell or one physical cell that interferes with any other groups.

[0026] (1) physical cell 2a ₇ of logic cells 3 in _1,
Physical cell 2 _1, 2 ₄ and no problem there is that there is no radio channel interference. However, when viewed only from the viewpoint of recycling efficiency of the radio channels, such physical cell 2a ₇ is
It is better not put in the logic cell 3 _1. (2) Although the physical cells 2 ₈ and 2 ₉ do not constitute a logical cell,
Those belonging to the group 4 _0. That is, both
Not only does there be no radio channel interference with each other, but also there is no interference with the physical cells that make up the other logical cells 21 and 22. It is better that these physical cells 2 ₈ and 2 ₉ are formed as independent constituent units rather than being grouped as logical cells (this physical cell is not employed in this embodiment, Can be adopted as a logic cell one by one, and a method of assigning a logic cell number is also possible). Even if such an independent physical cell is included in a group, at least one logical cell is included in this group.
It only has to be included separately. The presence of other logic cells improves the efficiency of wireless channel reuse due to the reduced number of groups.

[0027] (3) as in the physical cell 2 _10, 2 _11, Group 4 ₁ also comprise only physical cell. The group 4 ₁ is unchanged and groups in Study system shown in Figure 8 (c). However, if the group 4 ₀ contributing to the recycling efficiency of a radio channel to the other, when viewed as a whole communication network, re-use efficiency of the radio channel is improved than the proposed method. (4) As in the logic cells 3 _4, which may constitute one group 4 ₂ in one logic cell. However, if the group 4 ₀ contributing to the recycling efficiency of a radio channel to the other, when viewed as a whole communication network, re-use efficiency of the radio channel is improved than the proposed method. (5) as in the physical cell 2 _14, 1 in one physical cell 2 ₁₄
Which may constitute One of the group 4 _3. Within this group, wireless channels cannot be reused. However, Group 4 has contributed to the improvement of wireless channel reuse efficiency.
If there is ₀ elsewhere, looking at the communication network as a whole,
The reuse efficiency of the wireless channel is higher than that of the proposed method.

Referring to FIG. 1C, various network configurations were examined. However, in order to improve the reuse efficiency of the radio channel as much as possible, the logical cells are constituted only by physical cell base stations which interfere with each other, and at least one group is composed of one logical cell and another logical cell or independent logical cells. The network configuration is designed so that the number of groups, including physical cells, is as small as possible, preferably one.

Next, a method of allocating a wireless channel in the communication network shown in FIGS. 1A and 1B will be described. When there is a call request by Zone base station 1a is in zone 1 and Group 4 ₀ allocates the unused radio channel (vacant channel) to establish a communication link. In contrast, in the group, for example, when there is a call request with the physical cell base station 2a _1, first, a radio channel in use in Group 4 _0, and the base station for which the call request 2a preferentially assign unused radio channel ₁ of a logic cell 3 ₁ belonging. When this is no condition is satisfied radio channels such, for the first time, in the zone 1 and Group 4 ₀ allocates the unused radio channel (vacant channel) to establish a communication link. On the other hand, when the call is terminated at the base station, the communication link is released. At this time, the time the call is terminated at the physical cell base station, after releasing the communication link, in group 4 within _0, is reusable radio channel is not reused, so that the use of excessive radio channels There are cases. At this time, the wireless channel under communication is switched.

FIG. 3 is an explanatory diagram exemplifying a case in which a radio channel under communication is switched at the end of a call. In the figure, the mobile station A _1, A _2, for example, to a mobile station located in the physical cell 2 ₁ in FIG. 1 (a). On the other hand, the mobile station B ₂ is assumed to be a mobile station located in the physical cell 2 _2. Physical cell 2 _1, 2 _2, which belongs to a different logical cell, belong to the same group. First, the mobile station A ₁ is communicating on a radio channel ch1, the mobile station B _2, communicate using the same radio channel ch1. Next, the mobile station A on the same physical cell 2 ₁ and the mobile station A _{1
When 2} communicates, it must use radio channel ch2. After this, the mobile station A ₁ finishes communication, in the figure, in the period in which hatched, although the actual number lines of the radio channels required good one, to be using the two lines Become. Accordingly, when the mobile station A ₁ releases the communication link to terminate communication, the mobile station A _2, in any of the mobile station B _2, switches the radio channel to the other.

FIG. 4 is a flow chart for explaining the operation of processing for switching the radio channel under communication at the end of a call. In S11, it is confirmed whether or not there is a group that releases a communication link between the base station and the mobile station in the group upon termination of the call. With this confirmation, it is confirmed whether wireless channel switching is necessary. In S12, when the communication link is released, the process proceeds to S13,
If not, the process returns to S11. In S13, a wireless channel switching process is started. First, in S14, the number of simultaneous connections in each logic cell in the group is checked. In S15, the maximum value in the investigation in S14 is set as the required minimum number of lines in the group. In S16, the number of lines actually used in the group is checked. In S17, it is determined whether the number of lines actually used is larger than the required minimum number of lines,
If the number is large, the process proceeds to S18, and if not, the process ends.

In S18, the wireless channel used in the group is re-assigned. The wireless channel is reassigned so that the number of actually used lines is reduced to the required minimum number of lines. The method of reassignment may be any of the following methods. (A) Select arbitrarily from radio channels allocated to the network but not used by zones and groups. (B) Within the group, select the wireless channels in the order of the number of used wireless channels. (C) Selection is made in the group in order of the use start time. (D) Within the group, select the communication links in which the number of communication links requiring switching of the radio channel is small. The above-described reassignment is executed by the base station of the physical cell belonging to this group by performing a process of switching the radio channel in use while at least some of the communication links in communication continue communication.

The above-described radio channel reassignment processing at the end of a call is a relatively complicated control. Therefore,
Although the re-use efficiency of the radio channel is slightly deteriorated, the re-allocation is performed only when the effect is large and the processing is not complicated, and the re-allocation process of the radio channel at the end of the call is not performed uniformly. Alternatively, only the process of assigning a wireless channel at the time of calling may be performed.

FIG. 5 is a diagram showing theoretical calculation results according to an embodiment of the present invention. In the figure, the horizontal axis is the number of radio channel lines provided to the entire network, and the vertical axis is the call loss rate of the entire network. In the figure, the black square points are
This corresponds to the case of FIG. 8A and is a characteristic in the case where the traffic volume generated in the entire network is 5 [erl] (erlang).
The black dots correspond to the case of FIG. 8B and are the characteristics when the traffic volume generated in the entire network is 10 [erl]. The upward black triangle point corresponds to the case of FIG.
This is a characteristic when two groups are formed without providing a logic cell. The traffic volume generated in the entire network is 10 [er
l], the first and second groups each include three physical cells, each of which is about 8.4 of the entire network.
% When the call volume is generated. This is a characteristic when a traffic volume of 50% of the entire network is generated from an area excluding the area of all the logic cells from the zone 1.

On the other hand, the downward white triangle points in FIG.
In this case, the call volume generated in the entire network is 10 [er
l], a single group is provided, and this group includes three logic cells, each of which is a characteristic when a traffic volume of about 16.7% of the entire network occurs. From the area obtained by removing all of the physical cell 2 ₁ to 2 _6-cell from zone 1, which is characteristic of the case where 50% of the traffic intensity of the entire network is generated. In FIG. 1, the white diamond points indicate that the traffic generated in the entire network is 10 [erl], a single group is provided, and this group includes three logical cells. %, 16.7
% And 13.4% when the call volume is non-uniform.

The conclusions derived from the diagram shown in FIG. 5 are as follows. (1) It is more effective to reduce the number of groups by logically integrating physical cells and to reduce the number of groups than to separate groups for reusing wireless channels while keeping the total call volume constant. (2) When a single wireless channel reuse group is formed with the total call volume kept constant, if the number of logical cells constituting this group is equal, it is better to equalize the traffic volume of each group. High reduction effect. FIG. 5 shows a case where traffic is made uniform and a case where traffic is made non-uniform for a logical cell. However, even in the case of a physical cell, the same conclusion is drawn because the method of theoretical calculation is the same.

The above-mentioned theoretical calculation formula evaluates the blocking rate by theoretical calculation. Therefore, it is previously refused that a method that does not exactly match the actually performed wireless channel assignment is used. First, the basic traffic calculation formula will be described. The “cell” described below means both the “physical cell” and “logical cell” described above, and can be applied in any case. In the target network, a zone and one or more groups coexist, the zone is a service area of one zone base station, and each cell serves a part of the zone by the base station of the cell. Area. A group is defined as a set of cells that can reuse the same radio channel. Zones and cells exclusively share radio channels assigned to the entire network.

In response to the call request, as long as the wireless channel has a vacancy (there is an unused wireless channel), the call request is sequentially performed without distinguishing between the zone and the cell. , Assign a wireless channel. However, as long as a reusable radio channel exists for a call from a cell, that is, when there is a channel being used by another cell in the group to which the cell belongs, this is given priority. And assign. The origination of the call is a Poisson process, and the calling process of the zone and each cell is independent. At this time,
The number of intra-system calls (the number of simultaneous connections) of a zone and a cell is given by Erlang distribution when the number of terminals is sufficiently large.

The total number of lines assigned to the network is
n, there are two groups U (u = 1, 2,..., p) and V (v = 1, 2,..., q), and p and q cells respectively of the radio channel Taking the case of reuse as an example, a theoretical calculation formula of a call blocking rate for evaluating network characteristics is obtained. At a certain time, m is the number of simultaneous connections of the zone (the number of simultaneous connections of the radio channel between the mobile station and the zone base station in the zone excluding the cell area), and i is the number of cells x (u = x) of group U. The number of simultaneous connections (the number of simultaneous connections of the radio channel between the mobile station and the cell base station in cell x), j is the cell y of group V (v
= Y) (the number of simultaneous connections of the radio channel between the mobile station and the base station in the cell y), this can be regarded as an equilibrium state of the three-dimensional immediate exchange, and the simultaneous connection probability P _{x, y} (m, i, j) can be obtained. The simultaneous connection probability is a probability that communication between the mobile station and the base station for m lines in the zone, i lines in the cell x, and j lines in the cell y will be performed simultaneously.

At this time, the probability that i and j in the simultaneous connection probability P _{x, y} (m, i, j) are the maximum number of simultaneous connections (the maximum number of occupied channels) in each group U, V is Q _{x, y} (m, i,
j). On the other hand, cell u = 1, 2, ..., the number of simultaneous connections the radio channel between the mobile station and a base station in a p a k _u, for the simultaneous connection probability and P _u (k _u). Also, the number of simultaneous connections of the radio channel between the mobile station and the base station in the cell v = 1, 2 _,.
And the simultaneous connection probability is P _v (l _v ).

Q _{x, y} (m, i, j) is given by the following equation.

(Equation 1) Here, sigma _{is, k u ≦ i, l v} ≦ j becomes P _u (k _u) and P _v (l _v)
For all combinations of

(Equation 2)

(Equation 3)

(Equation 4) a _z , a _x , a _y , a _u and a _v are the zone, cell x,
traffic volume of y, u and v

The traffic volume A _{x, y} (m, i, j) carried in this state is given by the following equation.

(Equation 5) Therefore, the traffic volume Ac carried from the whole network is
It is obtained from the following equation.

(Equation 6) here,

(Equation 7) It is. If the total call volume is a, the call loss rate B is

(Equation 8) From.

The following is a supplementary explanation of the above formula. In Equations (3) and (4), the maximum number of outgoing lines is set to nm and nmi because, in Equation (3), m channels are used in the zone, nm is the upper limit of the number of available lines, Similarly, in equation (4), since m lines are used in the zone and i lines are used in the group u, nmi is the upper limit of the number of usable lines.

Although the above-mentioned theoretical calculation formula is a complete definition of the probability, the highest priority is given to the line assignment to the zone.
Then, the group U is prioritized, and does not match the actual wireless channel assignment procedure. Therefore, an error occurs between the theoretical calculation of the blocking rate and the actual calculation, but the difference is small. In particular, when there is one group (the traffic volume of the group V is zero in each of the above equations), the error can be almost ignored.

Next, for reference, in the case of P = 3, q = 3, x = 1, y = 1, that is, the cell u = 1 uses the maximum number of lines i among the cells belonging to the group U. And v = 1 uses the maximum number of lines j in the cells belonging to group V, (5)
A specific expression of the traffic volume carried from the network shown in the equation is shown.

(Equation 9) The call volume carried from the network is a calculation for calculating the average value of the number of simultaneous connections. Basically, ｛(the number of simultaneous connections) ×
(Probability at that time) The sum of｝ is calculated.

The probability that cell u = 1 uses the maximum number of lines i in group U and v = 1 uses the maximum number j of lines in group V is P _{x, y} ( m, i, j). At this time, the probability for each of the possible combinations of the other cells of the group U (u ≠ 1) and the other cells v ≠ 1 of the group V is as follows:

(Equation 10) It is. In each combination, the number of simultaneous connections in the zone is m lines, the number of simultaneous connections in cell u = 1 is i lines, and the number of simultaneous connections in cell v = 1 is j. Further, in all other cells (u ≠ 1) of group U and all other cells v の 1 of group V,
Radio channel and cell used by cell u = 1, respectively
The wireless channel used by v = 1 is reused, and the total number of simultaneous connections is as follows.

[Equation 11] It is. From the above, the above equation (8) is derived.

Next, when P = 3, q = 3, x = 1, y = 2, a specific expression of the expression (5) will be shown.

(Equation 12) Referring to equations (8) and (9), matters to be considered when actually calculating equation (6) theoretically will be described. L ₂ = j in equation (8), l _{1 in} equation (9)
When = j, the number of simultaneous connections of the zone and each cell is the same. Therefore, in the equation (6), the same state may appear repeatedly, and it is necessary to exclude the overlapping term from the theoretical calculation. In the above example, these overlapping terms do not coincide with each other except in the case where the traffic volumes of the cells corresponding to l ₁ and l ₂ are equal, so that the expression (6) is not stochastically complete. But,
The difference is small, and the error given to the entire call blocking rate is negligible.

FIG. 6 is another diagram showing a theoretical calculation result according to the embodiment of the present invention. This figure is a diagram similar to FIG. 3B, but forms a single group, sets the generated traffic volume a of the network to 10 [erl], and the generated traffic volume is equal (9% of the entire network). ), Three logical cells are installed, and the number of radio channels installed in each logical cell is limited to T (<n) (T = 3, 4, 5, 6,
n). T = n gives the upper limit n of the number of lines and corresponds to the case of FIG. In each of the above-described theoretical calculation formulas, if nm> T, nm is replaced with T, and if nmi> T, nmi is replaced with T, so that the call blocking rate shown in FIG. 6 can be obtained. If T = 6 or more, the call loss rate hardly changes.

While the diagram shown in FIG. 6 shows the results of one embodiment, the following conclusions are generally drawn. In each of the theoretical calculation formulas described above, the probability including the case where each logical cell uses all the number of wireless channel lines allocated to the network is theoretically calculated. However, even if the number of installed lines of the wireless channel is limited to T (<n), it is understood that the call loss rate does not deteriorate so much if a certain number of lines is secured. Since the above-mentioned logical cell is actually realized by a physical cell base station, the number of lines installed in each physical cell base station equipment is changed according to the predicted maximum traffic of each physical cell, by the number of radio channels allocated to the entire network. By making the number smaller than the number, the network equipment can be reduced with a slight deterioration of the call loss rate characteristics.

FIG. 7 is a block diagram for explaining the line controller of the present invention. In the figure, 21 is a command center, 2
2 is a control station, 23 is a line controller, 24 is a memory, 25
Is a transmission device, 26 is a transmission device, 27 is a transmission device, 28 is an antenna duplexer, 29 is a transmission antenna, 30 is a reception antenna, 31 is a reception amplifier, 32 is a reception device, and 33 is a base station control device. The command center 21 has a command table and performs communication work. Control station 22, control center 21 and,, zone base station 1a, be in between the physical cell base station 2a ₁ to 2A region _6, and controls the mobile radio channel. It also controls connection with other networks not shown.

In the control station 22, the line controller 23
Performs registration management of mobile stations and location registration management of mobile stations. In addition, together with the base station control device 33 in each base station, the base station performs call processing control in each base station and wireless channel allocation processing in each base station described above. In addition, voice and non-voice communication data is transmitted to and received from the command center 21 or a terrestrial subscriber telephone network (not shown).

The memory 24 stores a registration table for mobile stations,
Mobile station location registration table, examples in FIGS. 1 (b) and 1 (c)
Store the network structure table etc. as shown
ing. In addition, radio channel assignment in each base station
A table indicating the situation is stored. These tables
Is read and written by the line controller 23.
Is A mobile station located in a physical cell is located in a physical cell.
Location is registered so that
Mobile stations that are not in the zone know that they are in the zone
It is registered as follows. The transmission device 25 is a transmission path
Through the zone base station 1a and the physical cell base station 2a ₁
~ 2a₆Control signal and communication with the transmission device 26
Performs data transmission.

[0053] The base station is representative for the base station 2a ₁ will be described. The transmission device 27 transfers data of the control channel and the communication channel (the wireless channel described above is a communication channel) from the transmission antenna 29 through the antenna sharing device 28 to the mobile station 2a in the physical cell 2a. Send to the station. A reception signal from a mobile station is received by a reception antenna 30 and passed through a reception amplifier 31 to a reception device 3.
2 is received. The base station control device 33 controls the transmission device 27 and the reception device 33 according to the control of the control station 22 to execute call setting and radio channel assignment.
Mobile stations not shown include on-board mobile stations, portable mobile stations,
There are portable mobile stations.

When making a call from the mobile station, the mobile station transmits a connection request on the control channel. Upon receiving this connection request, the base station controller 33 of the physical cell base station 2a ₁ performs centralized control by the control station 22 to select _one of the radio channels allocated to the network according to the radio channel allocation method described above. A radio channel is set, and this is notified to the mobile station through a control channel to switch the radio channel. Physical cell base station 2a
When calling from _1, the base station controller 33 of the physical cell base station 2a ₁ is a centralized control by the control station 22, and determines a radio channel in the same manner, the control channel from the physical cell base station 2a ₁ Then, a paging signal is transmitted to the target mobile station, and then the determined radio channel is set as the communication channel.

Further, as described with reference to FIGS. 3 and 4, the line control device 23 and the base station control device 33 of each base station perform a predetermined condition when one call ends even during communication. Is satisfied, processing for switching the wireless channel being used is performed while continuing the communication. It should be noted that two-way simultaneous communication may be performed in addition to the communication using only the uplink wireless channel and the downlink wireless channel. When performing two-way simultaneous communication, a pair of uplink and downlink radio channels is used. In this case, in the wireless channel assignment according to the present invention, a pair of uplink and downlink wireless channels are collectively assigned.

[0056] The mobile station, zone 1, the mutual physical cell base station 2a ₁ to 2A region _6, in the case to be able to move while continuing communication, the handover process. In this case, the reassignment and assignment of the wireless channels may be performed by combining the above-described wireless channel switching processing at the end of a call and the wireless channel assignment processing at the time of calling. In this case, the switching timing is considered so that the communication is not interrupted before and after the handover, and the assignment that does not need to switch the radio channel before and after the handover is considered as much as possible.

As described above, according to the present invention, physical cells for which interference of radio channels is known in advance, such as the distance between physical cells, are grouped together as one logical cell. When actually designing a network, the locations where physical cell base stations are installed are determined by terrain,
Since the determination is started based on the traffic prediction or the like, the logical cell is also determined in conjunction with the installation of the physical cell base station.

In the above description, it is assumed that frequency channels are allocated on the premise of FDMA (frequency division multiple access), and the above-mentioned radio channels are frequency channels. However, when time-division channels are allocated on the premise of TDMA (time-division multiple access), if the same time-division channel is used in base stations of different cells, interference may similarly occur in adjacent cells. become. Therefore, the present invention is also applicable to a case where a time division channel is allocated on the premise of TDMA (time division multiple access).

[0059]

As described above, according to the present invention,
Even in a situation where groups of physical cells interfere with each other, these physical cells are used as logical cells, and a radio channel reuse group is formed to improve frequency use efficiency and improve the overall network. This has the effect of increasing the communication capacity.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a network configuration for explaining an embodiment of the present invention. FIG. 1A is a network configuration diagram. FIG. 1B is a table showing a hierarchical structure of a network including groups, logical cells, and physical cells. FIG. 1C is a table illustrating various hierarchical structures different from FIG. 1B.

FIG. 2 is an explanatory diagram of a reuse pattern for explaining the principle of the present invention.

FIG. 3 is an explanatory diagram of a case where wireless channel switching is performed during communication in one embodiment of the present invention.

FIG. 4 is a flowchart illustrating an operation of processing for switching a wireless channel during communication at the end of a call according to an embodiment of the present invention.

FIG. 5 is a diagram showing theoretical calculation results according to the embodiment of the present invention.

FIG. 6 is another diagram showing a theoretical calculation result according to the embodiment of the present invention.

FIG. 7 is a block diagram for explaining an embodiment of the present invention.

FIG. 8 is a network configuration diagram illustrating an outline of a conventional technique and a study method.

[Explanation of symbols]

1 zone, 1a zone base station, 2 ₁ to 2 ₆ physical cell, 2a ₁ to 2A region ₆ physical cell base station, 3 ₁ to 3 ₃ logic cell, four groups, 4 ₀ single group, 4 ₁ a first group , 4 ₂ Second group

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Minoru Yamamoto 3-2 Hikarinooka, Yokosuka-shi, Kanagawa FRP term FK-term (reference) 5K067 AA11 BB02 BB21 CC02 CC04 EE02 EE10 EE16 HH23 JJ12 JJ74

Claims (5)

[Claims] 1. A base station of a plurality of physical cells each covering a plurality of specific areas in a zone, and a base station of a zone covering the zone except for the specific area, at least some of which interfere with each other. At least one logical cell is set as a set of the plurality of physical cells,
And, at least one group is set for the set of the logical cells and the independent physical cells that do not constitute the logical cell, and the group is such that the logical cells or the independent physical cells in the group interfere with each other. Not to be set, and at least one of the groups is set to include one of the logical cells and another of the logical cells or the independent physical cells. A method of allocating a radio channel in a zone / cell coexisting mobile communication network sharing a channel, wherein the radio channel is reused between each logical cell and each independent physical cell in the same group. Allocating channels, zone / cell coexisting mobile communication network Radio channel assignment method in a chromatography click. 2. When it is confirmed that a communication link is released in a base station of the physical cell, in the group to which the physical cell belongs, after releasing the communication link, the number of radio channel lines becomes more than necessary. The zone / cell according to claim 1, wherein when used, a process of reducing the number of lines of the used wireless channel is performed by re-assigning the used wireless channel. A wireless channel allocation method in a coexisting mobile communication network. 3. The number of lines of the radio channel shared by the zone and the group is n (an integer of 2 or more), and the number of lines of the radio channel implemented in each of the physical cell base stations is n The radio channel assignment method in a zone / cell coexisting mobile communication network according to claim 1 or 2, wherein the radio channel assignment method is used. 4. A base station of a plurality of physical cells each covering a plurality of specific areas in a zone, and a base station of a zone covering the zone except for the specific area, at least some of which interfere with each other. At least one logical cell is set as a set of the plurality of physical cells,
And, at least one group is set for the set of the logical cells and the independent physical cells that do not constitute the logical cell, and the group is such that the logical cells or the independent physical cells in the group interfere with each other. Not to be set, and at least one of the groups is set to include one of the logical cells and another of the logical cells or the independent physical cells. A circuit controller for use in a zone / cell coexisting mobile communication network sharing a channel, wherein the radio channel is reusable between each logical cell and each independent physical cell in the same group. Wireless channel allocating means for allocating a channel. Line control device used in the co mobile communications network. 5. A communication system comprising: means for confirming that a communication link has been released in a base station of the physical cell, wherein the radio channel allocating means, when confirming that the communication link has been released, In the group, if the number of radio channels is used more than necessary after releasing the communication link, the number of radio channels in use is reduced by re-assigning the radio channels in use. 5. The line control device used in a zone / cell coexisting mobile communication network according to claim 4, wherein the line control device performs a process for causing the line / cell to coexist.