JPH11266478A - Tdma mobile communication system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To extend a radio channel in a radio base station in the unit of time slots in response to traffic in a TDMA(time division multiple access) mobile communication system. SOLUTION: In this communication system, occupied frequencies without overlapping among adjacent cells are fixedly assigned to radio base stations 102-104. The radio base stations 102-104 calculate the availability of a time slot of the occupied frequency assigned to itself and send the calculated result to a base station controller 101, which supplements the time slot of the common use radio frequency shared among a plurality of cells based on each time slot availability received from a plurality of the radio base stations.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a TDMA (Time
The present invention relates to a mobile communication system using a vision multiple access (vision multiple access) method, and more particularly to traffic control when sharing radio frequencies between different radio communication areas.

[0002]

2. Description of the Related Art In cellular mobile communication, the same occupied radio frequency is repeatedly allocated between different cells in order to increase the frequency utilization efficiency of the entire system. This allocation is fixedly allocated to each base station when constructing a base station, and occupied radio frequencies fi (i = 1, 2, 3, ..., I) such that each base station does not interfere with each other. ) Is assigned in repeat units. Initially, it was common to assign one occupied radio frequency to one cell. FIG.
7 shows an example of a seven-cell repetition pattern in which seven waves on the occupied radio frequency are allocated in repetition units. In recent years, when the traffic of a cell has increased due to an increase in the number of subscribers, it has been dealt with by adding another occupied radio frequency to one cell. That is, two occupied radio frequencies are fixedly assigned to one cell. Also in this case, an occupied radio frequency that does not cause interference between the base stations is assigned. For example, f8 which does not interfere with f1 to f7 is assigned to the cell of f1 in FIG.

Incidentally, Japanese Patent Application Laid-Open No. 62-197844.
In Japanese Unexamined Patent Publication, in TDMA, the same radio frequency is assigned to all radio zones, and the TDMA of that frequency is assigned.
A method is described in which a channel in a frame is divided and assigned to each wireless zone, thereby shortening an instantaneous interruption caused by frequency switching at the time of handoff.

[0004]

[Problems to be solved by the invention]
Traffic may concentrate on a specific cell due to an event or the like. As described above, in the conventional digital car telephone system, the traffic capacity is increased by increasing the occupied radio frequency allocated to each cell in the service area. In the conventional TDMA system, one occupied frequency is allocated to several slots.

[0005] However, a TD that divides into a very large number of time slots such as 64 time slots per radio frequency wave.
In consideration of the MA system, in the conventional method of adding channels in units of frequency, 64 time slots are fixedly increased every time one radio frequency wave is added. For example, as shown in FIG. 12, if 64 time slots are fixedly added to one radio base station in spite of a traffic state in which only one slot needs to be increased, 63 time slots waste resources. There is the first problem of being useful.

Further, in the prior art in which the same radio frequency is allocated to all the radio zones, and the channel in the TDMA frame of that frequency is divided and allocated to each radio zone, time slots are allocated in accordance with an increase in traffic. There is a second issue that is not taken into account.

[0007] It is an object of the present invention to appropriately increase the time slot in each base station according to the increase in traffic even when traffic is concentrated on a specific cell due to a sudden increase in new subscribers or events. In this way, effective use of resources is achieved.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention divides a service area into a plurality of cells, and comprises at least one radio base station arranged in each of the cells, and a radio base station. TD comprising base station controller to control
In the MA mobile communication system, a radio frequency that does not overlap between adjacent cells is fixedly assigned to the radio base station, and the radio base station calculates a utilization rate of a time slot of an occupied frequency assigned to the radio base station, The calculated time slot utilization is transmitted to the base station controller, and the base station controller compares the time slot utilization received from each radio base station with a threshold value, and the time slot allocation is When it is determined that it is necessary, at least one of the time slots of the shared radio frequency shared by a plurality of cells is supplemented to the radio base station that is determined to need the time slot allocation.

[0009] In order to solve the above problems, the present invention provides
The TDMA mobile communication system according to claim 1,
The time slot utilization rate is calculated based on a ratio of time slots of the occupied frequency allocated to the radio base station used by mobile stations communicating with the radio base station.

According to the present invention, in order to solve the above-mentioned problem, the base station control device has a database for storing an identifier indicating the radio base station and a time slot utilization rate corresponding to the radio base station. Features.

Further, in order to solve the above-mentioned problem, the present invention fixedly assigns an occupied frequency that does not overlap between adjacent cells to the radio base station, and the radio base station determines the time of the occupied frequency assigned to itself. Calculate slot utilization,
The calculated time slot utilization is transmitted to the base station controller, and the base station controller transmits a plurality of timeslots to the radio base station based on the time slot utilizations received from the plurality of radio base stations. It is characterized in that a time slot of a shared radio frequency shared between cells is supplemented. Further, in order to solve the above problem, the present invention is characterized in that the base station control device replenishes the shared radio frequency time slots in proportion to the respective time slot utilization rates received from the plurality of radio base stations. Features.

According to another aspect of the present invention, a radio base station calculates a time slot utilization rate of a shared radio frequency allocated to itself, and calculates the calculated time slot utilization rate of the shared radio frequency. To the base station controller, the base station controller compares the time slot utilization of the shared radio frequency received from each radio base station with a threshold value, and allocates more time slots of the shared radio frequency. When it is determined that is necessary, at least one of the time slots of another shared radio frequency is supplemented to the radio base station.

[0013]

Embodiments of the present invention will be described with reference to the drawings. In the present invention, the radio frequency band allocated to the mobile communication service is used by dividing it into an occupied radio frequency band and a shared radio frequency band. FIG. 11 is a diagram showing an example of frequency allocation according to the present invention. In the figure, Fi indicates an occupied radio frequency band, and FXj indicates a shared radio frequency band. Here, the occupied radio frequency band refers to a group of occupied radio frequencies, most of which are a group of radio frequencies fixedly allocated at the time of installation of the base station. , Which does not change its allocation. On the other hand, the shared radio frequency band refers to a group of shared radio frequencies, and the shared radio frequency refers to a frequency commonly assigned to a plurality of cells, and may be fixedly assigned or dynamically assigned. In the present invention, this shared radio frequency is divided into, for example, 64 time slots and the like, and the time slots are shared between adjacent cells according to the traffic.

FIG. 1 is a diagram showing a network configuration according to the present invention. In this embodiment, cells 110, 111, and 112 indicate cells (wireless communication areas) formed by the base stations 102, 103, and 104, respectively. Each cell is assigned a frequency so as not to interfere with each other. For example, the occupied radio frequencies fi (i = 1, 2, 3,...) Are assigned to the cells 110, 111, 112 according to the frequency repetition shown in FIG. Mobile station 105-109
Communicates with a base station forming this cell through a time slot on the occupied radio frequency when present in any cell. If there is no time slot on the occupied radio frequency, communication is performed using the time slot on the shared radio frequency. That is, by allocating an empty time slot of the shared radio frequency to a base station where traffic is concentrated and there is no empty time slot on the occupied radio frequency, the traffic capacity is increased while minimizing the occurrence of the empty time slot. It becomes possible.

Here, the shared radio frequency fxj (j = 1, 2,
3, .., J) are the base stations 102, 103, 104 in the service area.
To share with. Although the shared radio frequency fxj is shared by three base stations in the embodiment shown in FIG. 1, it may be shared by more base stations. Alternatively, a plurality of shared radio frequencies may be prepared and used repeatedly in the service area by the system.

In the embodiment shown in FIG.
With respect to the above, the connection between the base stations 102 to 104 and the base station control device 101 is star-shaped, but it is obvious that the present invention can be applied to other connection forms such as a bus. The transmission clock between the base stations 102 to 104 and the base station controller 101 is synchronized with one of the digital transmission lines 114.

The base station controller 101 collectively manages several base stations, that is, cells 110 to 112 formed by the base stations 102 to 104. The cell unit managed by the base station controller 101 is referred to as a group cell 113 here. In each of the cells C1 to C3 managed by the base station control device 101, the occupied radio frequencies fi (i =
Wireless communication is performed using the time slots of 1, 2, 3) and the time slot of the shared radio frequency fxj (j = 1, 2, 3) according to the present invention as necessary. The number of cells managed as the group cell 113 is determined at the time of arranging the base station (at the time of designing the station) in consideration of the topography, population density, etc. of the area forming the cell. Specifically, in urban areas with high population density, the number of cells managed as group cells is increased and cells are densely arranged.
In rural areas where population density is low, measures are taken such as reducing the number of cells managed as group cells and arranging cells roughly.

Next, an example of the configuration of each device according to the present invention will be described. FIG. 2 is a diagram illustrating a configuration example of the base station control device 101. As illustrated, the base station control device 101 includes a communication processing unit 200 and a control unit 201. In FIG. 2, only base stations 102 and 103 are shown for explanation, and other base stations are omitted. The communication processing unit 200 includes a multiplex processing unit 201 that processes communication information from each of the base stations 102 to 104, and an interface unit 203 that transmits communication information to the mobile switching network via the digital transmission line 115. On the other hand, the control unit 201 occupies the occupied radio frequencies fi (i = 1, 2, 3, ...,
I), a shared radio frequency fxj (j = 1, 2, 3,..., J), and a resource management / allocation unit 204 that manages an allocation status with each time slot and allocates a time slot.
Resource management table (time slot management table 206, 2
07) is stored.

FIG. 3 is a diagram showing a configuration example of a mobile station.
As shown in the figure, the mobile stations 105 to 109 include a transmitting unit 305 and a receiving unit 3
06, a transmitting / receiving unit 301, an antenna 300 connected to the transmitting / receiving unit 301, and a switch unit 3 including switches 307 and 308.
02, and a control unit 304 that controls the transmission / reception unit 301 and the switch unit 302 so that communication is performed in a predetermined time slot,
A human interface unit 303 is provided.

FIG. 4 is a diagram showing a configuration example of the base stations 102 to 104. As shown, the base station includes a transmitting unit 410 and a receiving unit 4
11, a communication processing unit 402 having switches 412, 413, and an interface unit 405, and a transmission / reception unit 401 such that communication is performed in a predetermined time slot. And communication processing unit 4
02 control unit 403 and Global Positioning System GPS
(Global Positioning System) 406 and GPS antenna 40
7 is provided. Here, the control unit 403 includes a transmission quality detection unit 414 and a reception timing control unit 415 as illustrated.
In addition, the global positioning system GPS400 is provided to absorb the delay time difference of the transmission line caused by the difference in the transmission line length of the digital transmission line 114 connected to each base station, and to synchronize between the base stations. It is. The base station is G
By determining the clock in accordance with the time signal of the PS 400, synchronization between the base stations is obtained.

Next, the TDMA radio frame format used in this embodiment will be described. FIG. 5 shows each base station 10
Shared radio frequency fxj commonly used by 2 to 104 (j = 1, 2,
FIG. 3 is a diagram showing a time slot configuration of a TDMA radio frame format of 3, .., J). Numerals 1 to 64 shown in the figure indicate time slot numbers. Each of the 64 slots can be used as either a communication time slot assigned to each user or a control time slot commonly used by many users. In this embodiment, in order to simplify the description, all 64 slots are allocated to communication time slots. Here, the communication time slot refers to a time slot for transmitting user information such as voice, and is equivalent to a conventional communication channel. Once allocated to a mobile station, the communication time slot is occupied by that mobile station until the communication ends.

Next, the operation of this embodiment will be described.
The time slot allocation method according to the present invention is as follows.

(1) In the mobile station, a signal from the human interface unit 303 passes through a switch 307,
Modulated by transmitting section 305, and transmitted from antenna 300.

(2) In the base station, the signal received by antenna 400 is sent to receiving section 411, where it is demodulated and sent to switch 413.

(3) The transmission quality detecting section 415 calculates the time slot utilization rate of the occupied radio frequency based on the received signal from each mobile station processed by the communication processing section 402.

FIG. 6 is a flowchart for explaining a method of allocating time slots according to the present invention. The time slot utilization rate Ua (%) is obtained from the ratio of the total number of time slots within the occupied radio frequency allocated to each base station to the number of time slots used for communication as shown in the following equation (step 1).

(Time slot utilization rate Ua (%) 703) =
(Number of used time slots 704) / (total number of time slots in occupied radio frequency 705) × 100 That is, the transmission quality detecting section 415 of each base station regards a slot considered to be a low-power no-signal as an empty time slot. , The number of time slots used for communication, and the ratio to the total number of time slots in the occupied radio frequency registered in advance.

(4) In FIG. 6, the transmission quality detecting section 41
The time slot utilization rate Ua (%) calculated in step 5 is sent from the interface unit 405 to the base station controller 101 via the digital transmission path 114.

(5) In the base station controller 101 of FIG. 2, the time slot utilization Ua transmitted from each base station
(%) Is transmitted to the resource management / allocation unit 204 in the control unit 201. The time slot utilization rate Ua (%) is stored in the occupied radio frequency time slot management table 206 in the DB unit 205 (step 2).

The occupied radio frequency time slot management table 206 is configured, for example, as shown in FIG. The occupied radio frequency time slot management table 206 includes an occupied radio frequency 701, a base station number 702, a time slot utilization rate Ua (%) 7
03, the number of used time slots 704, the total number of time slots in occupied radio frequency 705, and the like are stored. FIG. 7 shows the calculation result of the time slot utilization rate Ua (%) as an example. The time slot utilization rate Ua (%) is stored by rounding up, for example, decimals.

(6) In FIG. 2, the resource management / allocation unit 204 stores, in the DB unit, a cell having a time slot utilization rate Ua of 90% or more, that is, a base station number having a large amount of traffic and an insufficient number of available slots. The base station number is searched by searching the time slot management table 206 of the occupied radio frequency in 205 and storing the base station number. If there is no base station with an insufficient number of empty slots, the process is shifted to the process (13) because the traffic is not enough to allocate the shared radio frequency (step 3).

(7) In the resource management / allocation unit 204,
The required number of time slots S to be added to each base station is determined based on the occupied radio frequency time slot management table 206, and the occupied radio frequency time slot management table 206 is added.
To memorize. In FIG. 7, the time slot utilization rate Ua (%) of the base station number 1 is 90% or more. For this reason, four time slots are allocated from the shared radio frequency, but the number of time slots to be allocated may be dynamically varied in consideration of the time variation of traffic in a cell. For example, it is well known that there is a time zone in which congestion is expected empirically, but it is conceivable to increase the number of assigned time slots in that time zone as compared with the normal time slot.

(8) The resource management / allocation unit 204 sets the total number of time slots S allocated to a cell unit (group cell) managed by the base station control apparatus 101 ΣS in the DB.
The occupied radio frequency is obtained from the time slot management table 206 in the unit 205 (step 4).

(9) Next, the resource management / allocation unit 204
Is the shared radio frequency fxj (j =
The total number of empty time slots 1Tb of (1, 2, 3,..., J) is obtained from the time slot management table 207 of the shared radio frequency in the DB unit 205 (step 5).

FIG. 8 shows an example of the configuration of the time slot management table 207 for the shared radio frequency. The shared radio frequency 80
1, the number of used time slots 802, the total number of time slots 803 in the shared radio frequency, the number of empty time slots 804, and the like are stored. The number of empty time slots is obtained from the following equation.

(Number of empty time slots 804) = (Total number of time slots in shared radio frequency 803) − (Number of used time slots 802) The number of used time slots is always determined by resource management / allocation section 204 for each base station. And stored in the time slot management table 207 of the shared radio frequency.

(10) Next, the resource management / allocation unit 204
Performs a comparison between ΣS and 、 Tb, and adds a new shared radio frequency fx (j + 1) to the group cell when there are not enough available slots of the shared radio frequency fxj allocated to the cell (ΣTb <ΣS). Specifically, the shared radio frequencies are sequentially allocated to the group cells starting from fxj (j = 1, 2, 3,..., J), and the next fx ( It is conceivable to newly add (j + 1) as a shared radio frequency (step 6).

(11) Note that all shared radio frequencies (fx1
If there is no empty time slot in (.about.fxJ), a call is lost. However, it is necessary to avoid a process in which all the calls are blocked while some time slots can be assigned. For this reason, a procedure for determining which call is to be blocked is determined as “blocking processing”. For example, the following can be considered as a method of determining the procedure.

(A) A call having a long communication duration is utilized while a short call is regarded as a call loss.

(B) A call from a base station having a high time slot utilization rate Ua is prioritized, and a call from a base station having a low time slot utilization rate Ua is determined as a call loss.

(12) In FIG. 2, the shared radio frequencies fxj (j = 1, 2, 3) are sequentially arranged from the base station having the highest time slot utilization rate Ua stored in the occupied radio frequency time slot management table 206 of the DB unit 205. , .., J) are allocated (step 7).

(13) Time slot management table 20
6. Update 207. The timer is started, and after a predetermined time elapses (for example, when 120 seconds elapse assuming a normal voice call time), the processing from (1) is repeated (step 8).

(14) The resource management / allocation unit 204 of the base station controller 101 sends a time slot allocation signal to each base station via the digital transmission line 114. The time slot assignment signal includes an identifier indicating one of the shared radio frequencies and an identifier indicating the time slot.

(15) Upon receiving the time slot assignment signal, the base station gives the mobile station a time slot assignment based on the shared radio frequency designated by the time slot assignment signal of the base station controller 101 and the time slot. Send an assignment signal.

(16) In FIG. 3, the signal from the base station received by the antenna 300 of the mobile station is sent to the receiving unit 306, where it is demodulated, passed through the switch 304, and sent to the human interface unit 303. Processing such as images or sounds is performed to exchange information with the user. here,
The control unit 304 controls the transmission / reception unit 301, the switch unit 302, and the human interface unit 303.

Although the present invention has been described in detail based on the embodiments, the present invention is not limited to only the embodiments. For example, in the embodiment, the time slot utilization rate is measured at each base station, but may be collectively measured at the base station control device side. Further, in this example, the number of TDMA multiplexes is 64, but it is not necessary to be 64. Further, the present invention can be applied to the TD-CDMA system in which code division multiplexing is performed in each time slot.

FIG. 9 shows the relationship between the number of time slots and the number of radio frequencies when the present invention is applied. Conventionally, radio resources were fixedly assigned to one cell,
Many empty time slots were occurring. For example, in the example of FIG. 12, 63 time slots have become empty time slots, and the frequency use efficiency has been reduced.

According to the present invention, since the radio resources of the shared radio frequency are shared by a plurality of base stations, the vacant time slots not used in the cell C1 are allocated to the other cells C2 and C3 in the service area, so that the vacant time is allocated. Slots can be reduced. This effect increases as the number of shared cells increases. For example, if the shared radio frequency is shared by 10 cells, the empty time slots can be reduced to 1/10. That is, in the example of FIG. 12, the number of empty time slots of 63 time slots can be suppressed to an average of 6 time slots. As a result, the problem can be solved, and as a result, it is possible to promote the effective use of radio resources and to increase the traffic capacity.

[0049]

As described above, according to the present invention,
By allocating time slots within one radio frequency to a plurality of cells as needed, empty time slots can be used effectively, and a mobile communication system that can flexibly cope with traffic fluctuations can be configured. Effective use of frequency can be promoted.

[Brief description of the drawings]

FIG. 1 is a diagram showing an embodiment of a network configuration according to the present invention.

FIG. 2 is a diagram showing a configuration example of a base station control device according to the present invention.

FIG. 3 is a diagram illustrating a configuration example of a mobile station according to the present invention.

FIG. 4 is a diagram illustrating a configuration example of a base station according to the present invention.

FIG. 5 shows a shared radio frequency fxj (j = 1, 2,
FIG. 3 is a diagram showing a time slot configuration of a TDMA radio frame format of 3, .., J).

FIG. 6 is a flowchart illustrating a time slot allocation method according to the present invention.

FIG. 7 is a diagram showing a time slot management table of occupied radio frequencies according to the present invention.

FIG. 8 is a diagram showing a time slot management table of a shared radio frequency according to the present invention.

FIG. 9 is a diagram showing a relationship between the number of time slots and the number of radio frequencies when the present invention is applied.

FIG. 10 is a diagram illustrating an example of a seven-cell repetition pattern in which seven waves on an occupied radio frequency are allocated in repetition units.

FIG. 11 is a diagram showing an example of frequency allocation according to the present invention.

FIG. 12 is a diagram illustrating a relationship between a traffic capacity and the number of occupied radio frequencies in the case of a 6-multiplex TDMA system.

[Explanation of symbols]

101… Base Station Control Equipment
t), 102-104 base station, 105-109 mobile station, 110-112 radio communication area (cell) to which occupied radio frequency is allocated, 113 radio communication area (cell) to which shared radio frequency is allocated, 114 ... Digital transmission line, 115 ... Digital transmission line.

Claims (9)

[Claims] 1. A radio base station, wherein a service area is divided into a plurality of cells, and at least one radio base station is arranged in each of the cells.
A base station controller for controlling the radio base station.
In the DMA mobile communication system, an occupied frequency that does not overlap between adjacent cells is fixedly assigned to the radio base station, and the radio base station calculates a utilization rate of a time slot of the occupied frequency assigned to itself. The calculated time slot utilization is transmitted to the base station controller, and the base station controller compares the time slot utilization received from each radio base station with a threshold value, and the time slot allocation is TDMA mobile communication characterized by replenishing at least one of the shared radio frequency time slots shared by a plurality of cells to a radio base station determined to require the time slot allocation when judged necessary. system. 2. The TDMA mobile communication system according to claim 1, wherein the time slot utilization rate is used for a mobile station in which a time slot of an occupied frequency allocated to the radio base station communicates with the radio base station. A TDMA mobile communication system, wherein the TDMA mobile communication system is calculated based on a ratio of the TDMA mobile communication system. 3. The TDMA mobile communication system according to claim 1, wherein the base station control device stores a database storing an identifier indicating the radio base station and a time slot utilization rate corresponding to the radio base station. A TDMA mobile communication system, comprising: 4. A radio base station, wherein a service area is divided into a plurality of cells, and at least one radio base station is arranged in each of the cells.
A base station controller for controlling the radio base station.
In the DMA mobile communication system, an occupied frequency that does not overlap between adjacent cells is fixedly assigned to the radio base station, and the radio base station calculates a utilization rate of a time slot of the occupied frequency assigned to itself. Transmitting the calculated time slot utilization rate to the base station control device, wherein the base station control device is shared among a plurality of cells based on the respective time slot utilization rates received from the plurality of radio base stations. A TDMA mobile communication system, wherein a time slot of a radio frequency is supplemented to the radio base station. 5. The TDMA mobile communication system according to claim 4, wherein the base station control device is configured to control a time slot of the shared radio frequency in proportion to a time slot utilization rate received from each of the plurality of radio base stations. A TDMA mobile communication system, comprising: 6. The TDMA mobile communication system according to claim 4, wherein the radio base station calculates a utilization rate of a time slot of a shared radio frequency allocated to the radio base station, and calculates the calculated time of the shared radio frequency. Transmitting a slot utilization to the base station controller, the base station controller comparing the time slot utilization of the shared radio frequency received from each radio base station with a threshold, and further comparing the time of the shared radio frequency. A TDMA mobile communication system, wherein when it is determined that slot allocation is necessary, at least one of time slots of another shared radio frequency is supplemented to the radio base station. 7. A radio base station in which a service area is divided into a plurality of cells and occupied frequencies that do not overlap between adjacent cells are fixedly allocated, and a base station control device that controls the plurality of radio base stations. In the TDMA mobile communication system, the radio base station calculates a utilization rate of a time slot of an occupied frequency allocated to the radio base station, and calculates the time slot utilization rate calculated by the calculation apparatus to the base station. The base station control device compares the time slot utilization rate received from each radio base station with a threshold value, and determines that the time slot needs to be supplemented. Allocate at least one of the time slots of the shared radio frequency shared by a plurality of cells to the radio base station determined to need to be allocated. TDMA mobile communication system, comprising a Teru allocation apparatus. 8. A radio base station in which a service area is divided into a plurality of cells and occupied frequencies that do not overlap between adjacent cells are fixedly allocated, and a base station control device that controls the plurality of radio base stations. In the TDMA mobile communication system, the radio base station calculates a utilization rate of a time slot of an occupied frequency assigned to the radio base station, and controls the base station to control the time slot utilization rate calculated by the calculation apparatus. A transmitting device for transmitting to the device, the base station control device transmits a time slot of a shared radio frequency shared by a plurality of cells based on a time slot utilization rate received from each of the plurality of radio base stations. T for controlling replenishment to the base station.
DMA mobile communication system. 9. The TDMA mobile communication system according to claim 8, wherein the calculating device calculates a utilization rate of a time slot of a shared radio frequency, and the transmitting device calculates a time slot of the shared radio frequency. Transmitting a utilization rate to the base station control apparatus, the base station control apparatus compares the time slot utilization rate of the shared radio frequency received from each radio base station with a threshold value, and further compares the time slot utilization time slot of the shared radio frequency. A TDMA mobile communication system, wherein when it is determined that allocation is necessary, at least one of time slots of another shared radio frequency is supplemented to the radio base station.