JP3167122B2 - Broadcast communication control method and broadcast communication control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broadcast communication control method and a broadcast communication control apparatus, and more particularly to a broadcast communication control method in a cellular mobile communication system capable of maintaining communication quality at a predetermined value or more even during broadcast communication. The present invention relates to a method and a simultaneous communication control device.

[0002]

2. Description of the Related Art FIG. 1 is a block diagram showing a configuration of a general cellular mobile communication system. Since a mobile communication system accommodates a large number of mobile stations moving in a wide area, it is general to use a cellular system in which a service area is covered by a plurality of cells (wireless zones) formed by a plurality of base stations. It is. Each mobile station (□, ○
) Is wirelessly connected to the nearest base station 13 and each base station 1
Reference numeral 3 is connected to the central control station 12 via a ground wire line 17.

Here, when the base station 13 wirelessly connects to the mobile station, an unused channel which is not currently used is allocated from the channels of the base station 13 and used. The channel assignment is based on a centralized control system in which one centralized control station 12 centrally manages channel assignments in all base stations. Further, the central control station 12 is provided with the simultaneous command station 11, and the simultaneous command station 11 performs simultaneous communication with a specific group of plural mobile stations.

[0004] Incidentally, as a communication form of general mobile communication, for example, one communication from a mobile station to a base station (or mobile station) is performed.
There are one-to-one individual communication and one-to-N simultaneous communication from the broadcast command station 11 to a plurality of mobile stations. Simultaneous communication transmits the same communication contents to a plurality of other parties at once. When viewed within one cell (wireless zone), the number of channels used by the cell base station is 1 even if there are a plurality of other mobile stations. Channel only. FIG.
In the individual communication of the mobile station marked with ○, one channel of the cell is always required for each mobile station. In the cell 4, for example, the fifth channel CH4-5 (15) of the base station of the cell 4 is required, and in the cell 6, the seventh channel CH6-7 of the base station of the cell 6 is required.

[0005] On the other hand, in the simultaneous communication to the □ -marked mobile station, only one channel is required for one simultaneous communication in the cell where the mobile station is located. In cell 4, for example, there are two target mobile stations for broadcast a, but the second channel C of the base station in cell 4
Only one channel of H4-2 (14) is used. The target mobile station of the broadcast a also exists in the cell 7, and one channel of the second channel CH7-2 of the base station of the cell 7 is used. When another simultaneous communication b (16 in the figure) is performed, the target mobile station of the simultaneous communication b is located in the cell 5 and the cell 5
One channel of the first channel CH5-1 (16) of the base station is used.

[0006]

However, the number of stations to be broadcasted is generally large in business and private mobile communication systems such as electric power, gas, and municipalities where simultaneous communication is frequently used, and the number of broadcast target mobile stations is limited to the service area. If it is widely distributed throughout, almost all of the wireless zones in which it is located require a channel for simultaneous communication. If a large number of simultaneous broadcasts occur at the same time, multiple broadcast channels are required in most of the wireless zones. It becomes a heavy load.

[0007] Therefore, due to the increase in the traffic volume of the simultaneous communication, call loss including not only the simultaneous communication but also the individual communication (a situation where the base station attempts to allocate a channel and cannot be wirelessly connected to the mobile station because there is no empty channel) increases. However, there has been a problem that the serviceability of the entire system is reduced.

For this reason, it is conceivable to disperse the traffic volume of the simultaneous communication temporally or quantitatively to prevent a decrease in system performance and serviceability. However,
Even if the traffic is distributed, if the distribution is performed without quantitatively grasping the change in the system performance,
Despite the distribution, the system performance drops below the permissible value. Conversely, it takes time for the simultaneous communication to end even though there is room in the system performance due to unnecessary traffic distribution. There was a point. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems of the prior art and to provide a broadcast communication control method and a broadcast communication control device in a cellular mobile communication system capable of performing optimal distribution for broadcast communication. It is in.

[0009]

To achieve the above object, the present invention relates to a cellular mobile communication system in which a service area for communicating with a mobile station is formed by a plurality of radio zones formed by a plurality of base stations. ,
The current channel allocation information of each cell base station, the mobile station location information, and a predetermined model value are used as initial values, and the maximum limit value of the simultaneous call volume is set so that the call loss rate falls within an allowable range of deterioration. Simulation means or a first step for determining a threshold call volume by a simulation calculation;
If the requested traffic volume of the broadcast exceeds the allowable threshold traffic volume, the traffic volume below the allowable threshold is divided from the broadcast traffic volume, and the channel allocation of the broadcast call is performed by the divided traffic volume. Repeating the sending means or the second step for performing and sending, and the simulation means and the sending means or the first step and the second step until the remaining divided simultaneous traffic volume falls below the allowable threshold traffic volume. A feature is a simultaneous communication control device or a simultaneous communication control method including control means or steps for operating.

In the simulation means or the first step, the current channel allocation information, the mobile station location information, and each call information in each cell base station during a predetermined period are provided as initial values given in the allowable threshold call volume simulation calculation. The broadcast communication control apparatus or broadcast control method uses at least a part of the hold time of each call, the time interval of occurrence of each call, and the statistical average value of the number of allocated channels.

According to the present invention, with regard to the simultaneous communication, the contents of the simultaneous communication are first recorded in a memory, and then, for example, at every simultaneous communication hold time interval, a traffic volume equal to or less than an allowable threshold value calculated by simulation is cut out, thereby obtaining the simultaneous communication. The traffic is divided into several times, channels are allocated, and transmitted. Accordingly, each of the divided call volumes is an optimal amount that quantitatively evaluates the system performance such as a loss probability at each time point and appropriately maintains the system performance within an allowable range.
Despite the division of the traffic volume, effective and appropriate traffic distribution is ensured so that the system performance does not drop below the allowable value, and conversely, the system performance does not take too much room due to unnecessary traffic distribution. realizable.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a cellular mobile communication system to which the present invention is applied. A cell serving as a plurality of wireless zones formed by the plurality of base stations 13 forms a service area for performing communication with the mobile station. Each mobile station (□, ○
) Is wirelessly connected to the nearest base station 13 and each base station 1
Reference numeral 3 is connected to the central control station 12 via a ground wire line 17.

FIG. 2 is a block diagram showing the configuration of the central control station 12 according to the present invention. The central control station 12 includes a line control device 20 and a transmission device 27. The line controller 20 includes two line interface circuits 21 and 2
3, an exchange unit 22, an exchange control unit 24, a wireless control unit 25, and a storage device 26.

The line interface circuits 21 and 23
Command console 2 for a plurality of users constituting the simultaneous command station 11
8. A circuit for interfacing transmission with a general switching network or a wired line from a terminal and the transmission device 27. The switching unit 22 includes a communication path switch for exchanging a line from the broadcast command station, a general switching network or a line from a terminal with a line from a base station. The switching control unit 24 is a control device that monitors and controls the line interface circuits 21 and 23 and the switching unit 22.

The radio control unit 25 communicates with the base station through the line interface circuit 23, manages the movement of the mobile station, and sends the broadcast command station 1 given through the exchange control unit 24.
This is a control device that performs wireless management in accordance with a general call from the first, a switching network, and a general call connection request from a terminal. Storage device 2
Reference numeral 6 denotes a storage device accessible from the exchange control unit 24 and the wireless control unit 25, and stores information on the location of the mobile station in each cell, channel assignment information, and the like.

Next, a procedure for processing a general call according to the present invention will be described. According to the present invention, the simultaneous communication traffic is controlled and dispersed in the following procedure. (1) The central control station 12 periodically collects and stores current channel assignment information (assigned channels), mobile station location information, and other traffic information of each cell base station. (2) With respect to the generated general call, the call volume E is obtained. (3) Using the above-mentioned channel allocation and mobile station location information as initial values, a simulation is used to estimate a call loss rate when simultaneous communication and individual communication are added to the traffic of the entire system (the number of simultaneous mobile stations and communication hold time). calculate. Further, by changing the simultaneous call volume, the maximum limit value “allowable threshold call amount Et” of the general call amount such that the estimated call loss rate falls within an allowable range of deterioration is obtained by simulation calculation.

(4) Simultaneous call traffic E and allowable threshold traffic Et
Is compared. (5) In the above comparison, the traffic volume E falls below the allowable threshold traffic volume Et,
That is, if the estimated call loss rate falls within an allowable range of deterioration even when the traffic E is allocated and transmitted, the channel is allocated and transmitted for the traffic E as it is, and the call control for the broadcast is ended. However, the traffic volume E is equal to the allowable threshold traffic volume E.
t, that is, when the traffic volume E is assigned and transmitted,
If the estimated call loss rate exceeds the allowable range, the content of the simultaneous communication is first recorded in a memory, and then the channel is allocated to a traffic volume Et 'equal to or less than the allowable threshold value, and transmitted. Next, the traffic volume E and the traffic volume Et 'below the permissible threshold value
(The traffic volume E-the traffic volume Et 'below the permissible threshold) is newly replaced with the traffic volume E, and after the delay of the simultaneous hold time, the processing after the simulation (3) is repeated again. This repetition is performed as long as the traffic volume E updated temporarily exceeds the allowable threshold traffic volume Et. If the traffic E after several repetitions falls below the allowable threshold traffic Et, a channel is allocated and transmitted for the updated traffic E, and the call control for the broadcast is ended.

FIGS. 3 to 6 are flowcharts showing the contents of the simultaneous communication control processing in the central control station 12 in the cellular mobile communication system embodying the present invention. FIG.
5 is a flowchart showing the contents of an information collection process according to the present invention. This process is started at a predetermined cycle. S
In step 30, information on allocated channels for simultaneous and individual communication, information on the serving cell of the target mobile station, hold time of each call, occurrence interval information, and the like are collected. Since such information is stored in the storage device 26 of the line control device 20, the information can be read from a predetermined area. In S31, statistical averages of the current call holding time and call occurrence time intervals obtained by recording past simultaneous calls, the number of simultaneous and individual allocated channels, and the distribution of cells in each mobile station are shown. Calculate and save the value.

FIG. 3 is a flowchart showing the contents of the broadcast call receiving process in the present invention. This processing is performed by command console 2.
8 is activated each time a general call occurs. In S10, the information is put in a first-in first-out queue (FIFO queue). This means that the simultaneous calls are generated and input one after another, so that the subsequent processes are queued in the order of occurrence so that the subsequent processing is not congested, and the divided call processing is performed for one general call input.
The next general call is output by a signal CTS (Clear To Send) indicating that the processing has been completed. In S11, if the simultaneous call transmission processing shown in FIG. 4 has not been activated, the simultaneous call transmission processing is activated.

FIG. 4 is a flowchart showing the contents of the broadcast call sending process in the present invention. In S20,
Read one call from the FIFO queue. In S21, the read call hold time value (communication time length) is obtained. S22
In, the simulation of the traffic of the entire cellular mobile communication system shown in FIG. 6 is performed by setting various parameters, and the call loss rate becomes equal to the allowable deterioration threshold when the simultaneous traffic volume is added in the current state. The simultaneous traffic volume Et is output.

FIG. 6 is a flowchart showing the contents of the simulation processing in the present invention. In S40, the hold time obtained in S21 is read as one of the simultaneous traffic parameters used in the simulation. Here, the traffic volume for one simultaneous communication is represented by (total number of channels occupied by each cell) × (hold time) as described above. The total number of channels occupied by each cell is determined by the number of target stations for simultaneous communication and its spatial (distance) distribution. Therefore, the simultaneous traffic volume parameter is S4
Hold time obtained from 0, number of target stations S obtained from S47 described later
The spatial distribution obtained from the location information of 30 or S31 may be mentioned, but since the spatial distribution is input as an initial value from the information collection processing unit, the former two are particularly referred to as the general traffic parameters here. In S40, the information collected in S30 is also read as an initial value parameter.

In S41, it is determined whether or not to use the statistical value obtained in the information collection process as a part of the initial value parameter used for the simulation. If the determination result is affirmative, the process proceeds to S43. Is negative, S
Move to 42. In S42, a preset model value stored in advance is read. In S43, the statistical value calculated in S31 is read. The determination in S41 is performed, for example, based on whether the statistic value use flag is on. The statistic value use flag may be configured to be turned on / off manually, for example, or the initial state is off, and the quality of the statistic value is predetermined. May be configured to be turned on when the condition is satisfied. By using the statistics, it is possible to further improve the accuracy of the simulation calculation in the system.

In S44, the latest state information of the entire system such as channel assignment information and mobile station location information collected by the central control station, and other predetermined system model information (in the case of S42) Then, a simulation parameter in which the information on the number of target stations is added to the hold time information as one of the broadcast traffic parameters is set.

In S45, the simulation initial value and the parameter values of the simultaneous call volume (holding time and the number of target stations) are given, and the entire system loss probability simulation is executed. Here, generally, various statistical properties of the spatial distribution and the temporal distribution of occurrence of telephone calls have been actually measured and verified in the past. For example, each model value as shown in the specifications of FIG. It is widely known in the art that it closely approximates the actual phenomenon. Since these can be adopted as general characteristics of telephone calls without actually measuring in the cellular system, the latest channel assignment and mobile station location information which are always measured as "predetermined system model information" Along with
Apply to simulation.

Next, a general method of simulating a loss rate of a cellular mobile communication system will be described. Typical measures for evaluating system performance include call blocking rate,
The forced disconnection rate, the handover frequency, and the like can be cited. Here, as described above, the call loss rate (the ratio of calls that cannot be wirelessly connected to the mobile station because there is no free channel even if the base station attempts to allocate a channel to all generated calls) Is an evaluation scale. In a cellular mobile communication system, a large number of mobiles as wireless connection targets with a base station are distributed throughout the coverage area according to various spatial or temporal densities, and each of them moves independently and every moment. ,
It is generally extremely difficult to mathematically calculate the call loss rate from general system specifications.

For this reason, in the technical field, after modeling a real system as faithfully as possible, the space or time distribution of the mobile station and its motion are virtually generated on the model, and the resulting call loss count It is a general practice to analytically obtain such values by computer simulation and evaluate them. General-purpose software for this simulation calculation includes BONeS (reference internet homepage: http://www.cadence.co.jp/index.html), O
PNET (reference internet homepage: http: //www.johoko
bo.co.jp/opnet_top.html), Visual SLAM
(References: Structural Planning Institute, Morito et al., “System Simulation by VisualSLAM”), etc., and the above modeling and setting of each parameter as shown in the specifications of FIG. 8 can be easily performed. Moreover, this computer simulation is based on the recent increase in speed and performance of electronic computers.
It can be performed in a very short time with a small facility.

At S46, the total system call loss rate obtained by the call loss rate simulation is compared with a predetermined allowable deterioration threshold value of the system. The permissible deterioration threshold varies depending on the characteristics of the system, but in a general system, the call blocking rate is 1 to 10%. Then, if the total system call loss rate is substantially equal to the allowable deterioration threshold, the processing is terminated. However, when it is determined that the total system call loss rate calculated by the simulation is not substantially equal to the allowable deterioration threshold, the process proceeds to S47.

In S47, the number of target stations, which is one of the general traffic parameters, is reduced (for example, the number of target stations is -1) when the calculated call loss rate> permissible deterioration threshold, and the calculated call loss rate <
If it is the allowable deterioration threshold, it is increased (for example, the number of target stations is increased by +1), and the process returns to S44 to repeat the simulation again. Therefore, this processing loop is repeated until the total system blocking rate becomes substantially equal to the allowable deterioration threshold. And
Eventually, the total system call loss rate becomes substantially equal to the allowable deterioration threshold, and the “allowable threshold call volume Et” at that time can be obtained by expressing the number of target stations, which is one of the simultaneous traffic parameters.

Returning to FIG. 4, in step S23, the "allowable threshold traffic volume Et" is compared with the simultaneous traffic volume E, and when the traffic volume E falls below the allowable threshold traffic volume Et, that is, the simultaneous traffic volume E is allocated to the channel. If the estimated call loss rate falls within an allowable range of deterioration even after transmission, the process proceeds to S24. However, if the traffic E exceeds the allowable threshold traffic Et, that is, it is estimated that the traffic E is allocated and transmitted. If the deterioration of the call blocking rate exceeds the allowable range, the process proceeds to S26.

In S26, first, the contents of the simultaneous communication are recorded in a storage device. In S27, the allowable threshold E
Channel allocation / transmission is performed for a traffic volume Et 'equal to or less than t. In S28, the system waits for the simultaneous communication hold time, and in S29, subtracts the transmitted traffic volume Et 'that is equal to or less than the transmitted threshold value from the traffic volume E, and replaces the result with a new traffic volume E. The process proceeds to S22 to repeat the simulation and the transmission.

This repetition is repeated as long as the traffic volume E temporarily updated exceeds the allowable threshold traffic volume Et, that is, if the estimated traffic loss rate exceeds the allowable range when the updated traffic volume E is assigned to the channel and transmitted. After several repetitions, if the updated traffic volume E falls below the permissible threshold traffic volume Et, the estimated traffic loss rate falls within an allowable deterioration range even if the updated traffic volume E is assigned and transmitted. The threshold value Et is reached, and the flow shifts to S24.

In S24, a channel is allocated and transmitted for the updated traffic volume E. In S25, if the next simultaneous communication is in the queue FIFO queue, the process proceeds to S20, where the call processing of the next simultaneous communication is performed, and if not in the FIFO queue, the call control for the simultaneous communication is ended.

FIG. 7 is a time chart showing an example of simultaneous communication control. In this example, as shown in the figure, the first simultaneous call A (the number of simultaneously targeted stations: 80) occurs at time t0,
Thereafter, general call B and general call C have occurred. These calls are sequentially stored in a FIFO queue. At time t0, the simultaneous call A is first read from the FIFO queue, and an allowable threshold call volume calculation (simulation) is started (a), and an allowable threshold call volume Et as a calculation result is obtained (b). Assuming that the permissible threshold traffic volume Et is 35 stations in the simultaneous target station number expression, a traffic volume Et 'equal to or less than the permissible threshold value (here, 35 stations equal to the threshold value) is assigned as A1 (35) and the channel is allocated. Send out (c).

Next, after a delay of the simultaneous communication hold time τ, the allowable threshold traffic volume calculation is started again and the results are obtained (d, e, f) for the remaining 45 stations of A, and the allowable threshold traffic volume is obtained. Assuming that Et is 38 stations, the channel allocation / transmission is performed as A2 (38) for the traffic volume Et '(here, 38 stations) equal to or smaller than the allowable threshold (time t0 + τ: g).

Further, after the delay of the simultaneous communication hold time τ, the activation of the allowable threshold traffic volume calculation and the result acquisition (h, i, j) are performed again for the remaining seven stations of A, and the allowable threshold traffic volume is obtained. Assuming that Et is 31 stations, the remaining 7 stations are less than the allowable threshold traffic volume Et31 station, so that all remaining traffic is channel-assigned and transmitted as A3 (7) (time t0 + 2).
τ: k). As a result, the traffic of the simultaneous communication A is divided into A1 to A3 at time τ intervals from the time t0, and all of them are transmitted. If the FIFO queue is not empty in S25, the end signal of the process of the general call A is returned to S20 as a Clear To Send signal, and the next general call B (40) stored in the FIFO queue (l in FIG. 7). Starts, and is repeated in the same manner.

Although the embodiment has been disclosed above, the present invention may be modified as described below. The signal transmitted in the cellular system to which the present invention is applied may be an analog signal such as a voice signal, or a digital signal of voice or data. For example, FDMA, CDMA, TDM, etc.
Any method combining A or a combination thereof can be used.

In the embodiment, when a simulation is executed, for example, in which cell a general call is to be executed (transmitted) is randomly selected, but the number of vacant channels at the time of the general call differs depending on the cell. I have. Therefore, when selecting a cell for sending a general call, for example, by selecting cells in descending order of the number of available channels, the allowable threshold call volume Et increases as compared with the case of selecting randomly. Therefore, the number of broadcast target stations that can be transmitted simultaneously increases.

[0038]

As described above, according to the present invention,
With regard to the simultaneous communication, while extracting a traffic volume equal to or less than the allowable threshold value estimated and calculated at each time point of the simultaneous communication suspension time interval, the broadcast traffic volume is divided into several times and the channel is allocated and transmitted. Each of the divided call volumes is an optimal call volume that quantitatively evaluates a call loss rate, which is a main index of system performance, at each time point, and appropriately maintains the value within an allowable range. Therefore, it is possible to realize an effective and appropriate distribution of the simultaneous traffic volume without excess or shortage. As a result, there is an effect that it is possible to perform a simultaneous communication service required in the cellular mobile communication system while maintaining the system performance within an appropriate range.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a general cellular mobile communication system.

FIG. 2 is a block diagram illustrating a configuration of a central control station according to the present invention.

FIG. 3 is a flowchart showing the contents of a broadcast call receiving process in the present invention.

FIG. 4 is a flowchart showing the contents of a broadcast call transmission process in the present invention.

FIG. 5 is a flowchart showing the contents of an information collection process according to the present invention.

FIG. 6 is a flowchart showing the contents of a simulation process according to the present invention.

FIG. 7 is an explanatory diagram illustrating a control example of simultaneous communication.

FIG. 8 is a table showing examples of distributions and values of specifications that are actually measured and verified in a general mobile communication system model.

[Explanation of symbols]

11: Simultaneous command station, 12: Central control station, 13: Base station,
14 simultaneous communication a, 15 ... individual communication, 16 ... simultaneous communication b,
17: ground wire line, 20: line controller, 21, 23
... Line interface circuit, 22 ... Exchange unit, 24 ... Exchange control unit, 25 ... Wireless control unit, 26 ... Storage device, 27 ...
Transmission device, 28 ... Command console

Claims (4)

(57) [Claims] In a cellular mobile communication system in which a service area for communicating with a mobile station is formed by a plurality of radio zones formed by a plurality of base stations, current channel allocation information of each cell base station, A first step in which the area information and a predetermined model value are set as initial values, and a permissible threshold call volume which is a maximum limit value of the simultaneous traffic volume such that the call loss rate falls within an allowable deterioration range is obtained by a simulation calculation; If the requested traffic volume of the broadcast exceeds the allowable threshold traffic volume, the traffic volume below the allowable threshold is divided from the broadcast traffic volume, and the channel allocation of the broadcast call is performed by the divided traffic volume. Performing a second step of transmitting and sending, and repeating the first step and the second step until the remaining divided simultaneous traffic volume falls below an allowable threshold traffic volume. Simultaneous communication control method. 2. In the first step, as initial values given in an allowable threshold traffic volume simulation calculation, current channel assignment information, mobile station location information in each cell base station during a predetermined period, and hold time of each call. 2. The broadcast communication control method according to claim 1, wherein at least a part of an occurrence time interval of each call and a statistical average value of the number of allocated channels is used. 3. A cellular mobile communication system in which a service area for communicating with a mobile station is formed by a plurality of radio zones formed by a plurality of base stations, wherein current channel allocation information of each cell base station, Simulation means for determining, by simulation, an allowable threshold call volume, which is a maximum limit value of the simultaneous traffic volume such that the call blocking rate falls within an allowable range of deterioration, with the area information and a predetermined model value as initial values, If the traffic volume of the simultaneous communication exceeds the allowable threshold traffic volume, the traffic volume equal to or smaller than the allowable threshold is divided from the broadcast traffic volume, and a channel allocation of the broadcast call is performed by the divided traffic volume, Sending means for sending, and repeatedly operating the simulation means and sending means until the remaining divided simultaneous traffic volume falls below the allowable threshold traffic volume. Communication control apparatus all together, characterized in that a control means for. 4. The simulation means as an initial value given in an allowable threshold call volume simulation calculation,
At least a part of the current channel assignment information, mobile station location information, each call holding time, each call occurrence time interval, and the statistical average value of the number of assigned channels in each cell base station during a predetermined period. 4. The simultaneous communication control device according to claim 3, wherein the communication control device uses a communication device.