JP7764338B2 - wireless communication system - Google Patents

Description

The present invention relates to a wireless communication device, and more particularly to a wireless communication system that can improve data transmission efficiency within the system.

Description of the Prior Art
In a general wireless communication system used in a commercial wireless system or the like, a plurality of base station devices have an inter-base station synchronization function and communicate using the same operating wave.
In such a case, if the transmission timings of the multiple base station devices are misaligned, mutual interference may occur in an overreach area where the incoming waves from the multiple base station devices overlap, resulting in a blind zone.

Therefore, in a wireless communication system, it is necessary to synchronize the transmission start timings from a plurality of base station devices.
For example, a line control device transmits a downlink transmission start instruction to each base station device, and each base station device starts transmission in accordance with the transmission timing included in the downlink transmission start instruction, thereby aligning the transmission timing of multiple base stations.

Furthermore, some conventional wireless communication systems perform data transmission by periodically notifying location information in addition to a general voice communication function.
Specifically, when a mobile station periodically notifies its location information using uplink data transmission, a data server connected to the line control device stores the location information and transmits a response to the mobile station that sent the notification. The response is transmitted as downlink data transmission from the base station device to the mobile station via the line control device. At this time, as described above, all base station devices transmit downlink data at the same timing.

That is, base station devices that do not have the coverage area of the target mobile station that is the destination of the response to the uplink transmission also simultaneously perform downlink transmission operations.
Therefore, even if a new mobile station enters the area while the base station device is transmitting downlink data, the mobile station cannot transmit uplink data.
This is because, particularly, a mobile station in a system using the SCPC (Single Channel Per Carrier) radio method cannot transmit while receiving, and cannot receive while transmitting.

As such, in a system using inter-base station synchronization, all base station devices in the system transmit downlink data at the same time, meaning that uplink data cannot be transmitted from mobile stations during that time.

In general, data transmission is used frequently and for short periods of time, while voice calls are used less frequently and for longer periods of time than data transmission. Therefore, it is necessary to process frequently used data transmissions efficiently without letting them accumulate within the system.

[Related Technology]
Incidentally, conventional technologies relating to wireless communication systems include Japanese Patent Laid-Open No. 2020-022029 "Wireless communication system and wireless communication method" (Patent Document 1) and Japanese Patent Laid-Open No. 2015-144408 "Wireless communication system" (Patent Document 2).

Patent document 1 describes how a control device determines the direction of movement from the mobile station's location information, determines the base station to which the mobile station should move, and a line control device grants transmission rights to the base station to which the mobile station should move, causing it to send a signal to the mobile station.

Patent document 2 also describes that the line control device sets, as the downlink transmission start timing frame number, a frame number that is spaced apart from the transmission timing of the downlink transmission start instruction by an interval equal to the maximum transmission time between the line control device and multiple base stations.

Japanese Patent Application Laid-Open No. 2020-022029 JP 2015-144408 A

However, in conventional wireless communication systems, when transmitting downlink data in response to an uplink data transmission, downlink transmission is performed at the same time even by base station devices that are not in the coverage area of the mobile station to which the response is to be sent. This means that even if another mobile station enters the coverage area, uplink data transmission is not possible, resulting in a problem of reduced data transmission efficiency.

Note that Patent Documents 1 and 2 do not mention that the line control device stores the base station device used when transmitting uplink data from a mobile station, and then selects the stored base station device to transmit downlink data in response.

The present invention was made in consideration of the above-mentioned circumstances, and aims to provide a wireless communication system that transmits downlink data in response to an uplink data transmission only to the base station device that transmitted the uplink data, and does not transmit downlink data to other base station devices, thereby enabling uplink data transmission from mobile stations in the areas of other base station devices, thereby improving data transmission efficiency within the system.

The present invention, which solves the problems of the above-mentioned conventional examples, is a wireless communication system having a plurality of base station devices that perform downlink transmission using the same frequency, and a line control device that controls the plurality of base station devices, wherein the line control device stores, for each of the plurality of base station devices, adjacent base stations whose communication areas partially overlap with those of the base station devices, and when it receives uplink data from a base station device, it stores the line used by that base station device, and when it transmits downlink data in response to the uplink data on the line used by the stored base station device, if there is no adjacent base station that corresponds to the stored base station device, it transmits the downlink data only to the stored base station device.

Furthermore, the present invention is characterized in that when transmitting downlink data in response to uplink data to a line used by a stored base station device, if there is an adjacent base station corresponding to the stored base station device, the line control device transmits the downlink data to the line used by the adjacent base station in addition to the stored base station device .

Furthermore, in the above-mentioned wireless communication system, the present invention is characterized in that, when transmitting downlink data, the line control device designates, to each destination base station device, the timing at which each base station device will start transmitting the downlink data, the timing that is the maximum transmission time between the line control device and the multiple base station devices from the transmission timing of the downlink data, and transmits the designated timing.

Furthermore, the present invention is characterized in that in the above-mentioned wireless communication system, the areas of the multiple base station devices are arranged in a line or a plane.

According to the present invention, there is provided a wireless communication system having a plurality of base station devices that perform downlink transmissions using the same frequency, and a line control device that controls the plurality of base station devices. The line control device stores, for each of the plurality of base station devices, adjacent base stations whose communication areas partially overlap with those of the base station devices. When uplink data is received from a base station device, it stores the line used by the base station device. When downlink data is transmitted in response to the uplink data on the line used by the stored base station device, if there is no adjacent base station corresponding to the stored base station device, the wireless communication system transmits the downlink data only to the stored base station device. Therefore, base station devices other than the base station device transmitting the downlink data do not transmit downlink data, and uplink data can be transmitted. This has the effect of transmitting uplink data, such as location information from a mobile station device that has newly entered the area of another base station device, thereby improving the data transmission efficiency of the entire system.

Furthermore, according to the present invention, when the line control device transmits downlink data in response to uplink data to the line used by the stored base station device, if there is an adjacent base station corresponding to the stored base station device, the line control device transmits the downlink data to the line used by the adjacent base station in addition to the stored base station device in the wireless communication system. Therefore, by transmitting the same downlink data in an area where the areas of the stored base station device and the adjacent base station device overlap, it is possible to prevent the occurrence of blind spots and ensure the reliability of communication services.

Furthermore, according to the present invention, in the wireless communication system described above, when transmitting downlink data, the line control device specifies the timing at which each base station device will start transmitting the downlink data, which is the maximum transmission time between the line control device and the multiple base station devices from the transmission timing of the downlink data, and transmits the data to each base station device. Therefore, the base station device transmitting the downlink data can start downlink transmission at the same transmission timing regardless of the distance from the line control device, which has the effect of suppressing mutual interference between base stations and preventing the occurrence of blind zones.

FIG. 1 is an explanatory diagram showing an example of the configuration of a wireless communication system. 2 is an explanatory diagram showing the configuration of a line control device 2 of the present wireless communication system. 10 is an explanatory diagram showing frame generation in the line control device 2 of the wireless communication system. FIG. 10 is an explanatory diagram showing the setting of the downlink transmission start timing in the wireless communication system. FIG. FIG. 2 is a sequence diagram showing control of downlink transmission timing in the wireless communication system. 1 is a sequence diagram showing downlink data transmission (1) relative to uplink data transmission in the wireless communication system. FIG. FIG. 1 is an explanatory diagram showing the occurrence of a blind spot in the wireless communication system. FIG. 10 is a sequence diagram showing downlink data transmission (2) in relation to uplink data transmission in the wireless communication system. 1 is an explanatory diagram showing the operation state when the number of adjacent base stations in the wireless communication system is set to 2. FIG.

An embodiment of the present invention will be described with reference to the drawings.
[Outline of the embodiment]
A wireless communication system according to an embodiment of the present invention (this wireless communication system) is a wireless communication system having a plurality of base station devices that perform downlink transmission using the same frequency, and a line control device that controls the base station devices. When the line control device receives uplink data from a base station device, it stores the line used by that base station device and transmits downlink data in response to the uplink data to the line used by the stored base station device. Downlink data is not transmitted to base station devices that do not require a response, and uplink data transmission from new mobile stations within the area of that base station device is possible, thereby improving the data transmission efficiency of the entire system.

In addition, in this wireless communication system, when the line control device sends downlink data in response to uplink data, it transmits the downlink data to lines used by base station devices in areas adjacent to the area of the stored base station device, in addition to the lines used by the stored base station device. This prevents blind spots caused by interference between uplink and downlink data in areas where the areas of base station devices overlap, and ensures that downlink data can be received normally throughout the area of the stored base station device, ensuring the reliability of communication services.

[Configuration of this wireless communication system: Figure 1]
The configuration of this wireless communication system will be described with reference to Fig. 1. Fig. 1 is an explanatory diagram showing an example of the configuration of this wireless communication system.
As shown in FIG. 1, this wireless communication system is used, for example, as a business wireless system, and comprises command desks 1-1 to 1-n (sometimes referred to as command desk 1 when the individual command desks are not distinguished), a line control device 2, a plurality of base station devices 3-1 to 3-n (sometimes simply referred to as base station devices 3), and a data server 6, and a plurality of mobile station devices 4-1 to 4-n (sometimes simply referred to as mobile station devices 4) communicate with the command desk 1, the data server 6, and other mobile station devices 4 within the communication area of the base station device 3.

The line control device 2 and each base station device 3 are equipped with a GPS antenna that receives GPS signals from GPS (Global Positioning System) satellites 7, and the line control device 2 and each base station device 3, as well as the base station devices 3 themselves, are time-synchronized.

Each mobile station device 4 is connected to a location information collection device 5-1 to 5-n (sometimes simply referred to as location information collection device 5) by wire.
The location information collection device 5 receives GPS signals from GPS satellites 5 to acquire location information, and outputs the location information to the mobile station device 4 periodically or at the timing of a preset event (such as a change in the internal state). The location information collection device 5 may be provided inside the mobile station device 4.

Each part of this wireless communication system will now be described.
The command desk 1 is connected to the line control device 2 and controls the wireless system. The command desk 1 may also monitor and control multiple systems in an integrated manner. The command desk 1 also communicates with the mobile station devices 4 to give instructions and manage the services.

The line control device 2 is connected to the command desk 1 and a plurality of base station devices 3 via wired lines, and performs line control and call control in this wireless communication system.
Furthermore, by capturing GPS data from the GPS satellites 7, the timing of wireless transmission in this system is adjusted.

Furthermore, as will be described later, when the line control device 2 of this wireless communication system receives uplink data from a base station device 3, it stores the base station device 3 in question, and when transmitting downlink data in response, it controls the transmission to occur only over the line used by the stored base station device 3.
The operation of the line control device 3 will be described later.
The base station device 3 is connected to the line control device 2 by wire and to the mobile station device 4 by wireless. As described above, the base station device 3 also receives GPS data and adjusts the timing of wireless transmission.

The mobile station device 4 is a vehicle-mounted or portable wireless communication terminal, and can be operated in a mobile state or in a fixedly installed state.
The mobile station device 4 performs wireless communication with the base station device 3 within the service area (communication area) of the base station device 3 .
Furthermore, the mobile station device 4 transmits the location information received from the location information collection device 5 to the data server 6 via the base station device 3 and the line control device 3 .

GPS satellite 7 is a satellite based on the general GNSS (Global Navigation Satellite System), which transmits signals with time information from multiple positioning satellites and enables measurement of current position on Earth, etc.

[Configuration of the line control device 2: Figure 2]
Next, the configuration of the line control device 2 of this wireless communication system will be described with reference to Fig. 2. Fig. 2 is an explanatory diagram showing the configuration of the line control device 2.
As shown in FIG. 2, the line control device 2 includes a frame generating unit 21, a control unit 22, a base station interface unit 23, and a GPS antenna 24.
The line control device 2 is connected to a plurality of base station devices 3 (only one is shown here) and a data server 6. Furthermore, the line control device 2 is connected to a higher-level command desk 1, which is not shown here.

The frame generation unit 21 includes a GPS module 211, a PLL (Phase Locked Loop) unit 212, and a superframe counter 213, and generates a radio frame.
The generation of radio frames and superframes will be described later.

The control unit 22 includes a CPU 221 and controls the entire line control device 2 .
In particular, in the operation of this wireless communication system, when an uplink transmission message including the location information of a mobile station 4 is input from a base station 3, the control unit 22 stores the line used by the base station 3. The base station 3 that performs the uplink transmission has a mobile station 4 within its area. On the other hand, there is no mobile station 4 within the area of a base station 3 that has not performed the uplink transmission at that time.
When a downstream transmission is made in response to the upstream transmission, the downstream transmission message is output to the stored line used by the base station device 3 .

As a result, in this wireless communication system, downlink transmission is performed only by base station devices 3 that have a mobile station device 4 in their coverage area that is the destination of the response. Base station devices 3 that do not have a mobile station device 4 in their coverage area and do not require a response do not perform downlink transmission, so that uplink transmission is possible for such base station devices 3.
When a new mobile station device 4 enters the area of a base station device 3 that is not performing downlink transmission, location information can be immediately reported by uplink transmission, thereby improving the efficiency of data transmission.

In addition, the control unit 22 of the line control device 2 of this wireless communication system stores the arrangement of base station devices 3 within the system, and for each base station device 3, also stores information on other base station devices 3 that are adjacent to the base station device 3 and whose communication areas partially overlap.
As will be described later, the information on the adjacent base station device 3 is used when performing downstream transmission in response to upstream transmission.

Furthermore, as in the past, when a downstream transmission message is input from the command desk 1 or the like, the control unit 22 of the line control device 2 sends a downstream transmission start instruction to multiple base station devices 3, along with information instructing them on the timing to start downstream transmission. The downstream transmission start instruction will be described later.

The base station interface unit 23 is an interface that connects to the base station device 3 .
The GPS antenna 24 receives signals from a plurality of GPS satellites and outputs the GPS received signals to the GPS module 211 .
The GPS module 211 outputs a 10 MHz clock signal and a 1 PPS (Pulse Per Second) signal based on the signal received by the GPS antenna 24. The 1 PPS signal is a square wave signal with a 1-second cycle that indicates the timing of the seconds.

[Frame generation in the line control device 2: Figure 3]
Next, frame generation in the frame generation section 21 of the line control device 2 will be described with reference to Fig. 3. Fig. 3 is an explanatory diagram showing frame generation in the line control device 2.
As shown in FIG. 3, the GPS module 211 of the frame generating unit 21 outputs a 10 MHz clock signal and a 1 PPS signal.
The PLL unit 212 outputs a 40 ms signal indicating frame timing every 40 ms based on the 10 MHz clock signal.

The superframe counter 213 assigns a frame number that identifies a radio frame having a frame length of 40 ms for each frame timing (40 ms period) based on the 40 ms signal output from the PLL unit 212 and the 1 PPS signal output from the GPS module 211, and notifies the CPU 221 of the control unit 22 of the frame number.
Here, one superframe (720 ms) is made up of 18 radio frames (40 ms x 18).

At this time, the superframe counter 213 assigns each radio frame a frame number from "1" to "18" that indicates its position (order) within the superframe. The frame numbers are assigned using a frame counter that is incremented (+1) every 40 ms signal period. This frame counter synchronizes with one PPS signal every three minutes (180 seconds: 250 superframes) (the figure states "one superframe is generated based on one PPS signal").
The frame number generated by the superframe counter 213 is notified to the CPU 221 of the control unit 22 at each frame timing of a 40 ms cycle.

[Setting the downstream transmission start timing: Figure 4]
Next, the setting of downlink transmission start timing for a plurality of base station devices 3 by the control unit 22 of the line control device 2 will be described with reference to Fig. 4. Fig. 4 is an explanatory diagram showing the setting of downlink transmission start timing in this wireless communication system.
FIG. 4 also shows the relationship between the timing signal generated from the GPS received signal and the frame generation.

As shown in Fig. 4(a), the GPS module 211 of the line control device 2 acquires and outputs a 1PPS signal from a GPS reception signal. Fig. 4(b) shows an enlarged view of one period (one second) of the 1PPS signal.
As shown in FIG. 4(c), one superframe is made up of 18 40 ms radio frames, and one period of one PPS signal includes the first to seventh radio frames of the next superframe.

Then, when the control unit 22 of the line control device 2 receives a downstream transmission instruction, for example, from the command desk 1, it sends a downstream transmission start instruction (downstream transmission start message) to multiple base station devices 3, specifying the timing to start downstream transmission.
At this time, the control unit 22 specifies the timing for transmitting the downlink transmission start instruction by adding at least the maximum transmission time between the line control device 2 and the base station device 3. Here, the frame number for transmitting the downlink transmission start instruction is referred to as the transmission timing definition frame number.

Specifically, the control unit 22 sets a frame number that is spaced apart from the transmission timing definition frame number by the number of frames corresponding to the maximum transmission time as the transmission timing frame number at which multiple base station devices 3 simultaneously start downlink transmission in the downlink transmission start instruction, and transmits the set frame number.

In the examples of Figures 4(d) and (e), the maximum transmission time between the line control device 2 and multiple base station devices 3 is at most one frame time (40 ms), and when the control unit 22 of the line control device 2 transmits a downlink transmission start instruction at frame number 1 (when the transmission timing specification frame number is "1"), the transmission timing frame number set for the downlink transmission start instruction is "3".
As a result, when the plurality of base station devices 3 receive the downlink transmission start instruction, they will simultaneously start downlink transmission at frame number "3".
As a result, the transmission timings of the plurality of base station devices 3 are synchronized regardless of differences in distance from the line control device 2 .

In this wireless communication system, the targets of downlink transmission are limited to base station devices 3 within the area of the mobile station device 4, so the downlink transmission start instruction is also sent only to the base station device 3 that is the target of the downlink transmission.

[Downstream transmission timing control: Figure 5]
Next, the control of the downlink transmission timing will be described with reference to Fig. 5. Fig. 5 is a sequence diagram showing the control of the downlink transmission timing.
As shown in Figure 5, when an instruction to start transmission is sent from the command desk 1 or the data server 6 (S11), the line control device 2 receives it, assigns a transmission frame timing number to the data from the command desk 1 or the data server 6, and generates a telegram instructing the start of downstream transmission (S12).
As described above, the transmission frame timing number is a number that specifies the timing at which each base station device 3 starts downlink transmission.

The line control device 2 then transmits the generated downlink transmission start instruction to the plurality of base station devices 3 that perform downlink transmission. Here, since the transmission start instruction from the data server 6 is a response to the uplink data transmission, the downlink transmission start instruction is transmitted to the stored base station device 3.
The base station device 3 that has received the downlink transmission start instruction starts downlink transmission when the frame number counted within the device itself matches the transmission frame timing number included in the received downlink transmission start instruction.

[Downstream data transmission relative to upstream data transmission (1): Figure 6]
Next, downstream data transmission (1) in this wireless communication system will be described with reference to Fig. 6. Fig. 6 is a sequence diagram showing downstream data transmission (1) in response to upstream data transmission (hereinafter referred to as downstream data transmission (1)).
FIG. 6 shows the operations of the data server 6, the line control device 2, and the base station devices 3-n-1, 3-n, and 3-n+1.

Here, the base station devices 3 are arranged in a line, and the base station device 3-n is adjacent to the base station devices 3-n-1 and 3-n+1, with their areas partially overlapping.
The base station devices 3 may be arranged in a planar manner, in which case the number of adjacent base station devices 3 will be greater.

6, when uplink data transmission is performed from the base station device 3-n (S21), the line control device 2 stores the line used by the base station device 3-n (line used by the base station) (S22). The uplink data transmission is, for example, periodic location information notification from the mobile station device 4.
Then, the line control device 2 transmits the received upstream data to the data server 6 (S23).

When the data server 6 receives the upstream data, it checks the consistency of the data and transmits a downstream data transmission (response) in response to the upstream data (S24).
When the line control device 2 receives the downlink data transmission (response), it reads out the stored base station use line, sets it as the destination of the downlink data transmission (response), and transmits the downlink data transmission (response) only to the base station device 3-n that is the destination of the downlink data transmission (response) (S26).

If a plurality of base station use lines are stored, downlink data transmission (response) is also transmitted to the base station devices 3 corresponding to each use line.
At this time, as described above, the line control device 2 transmits the downstream transmission start timing of the base station device 3 in the downstream data transmission (response).
In this way, downstream data transmission (1) is carried out.

As a result, if a mobile station device 4 is present within the area, downlink data can be transmitted in response only to the base station device 3 that has transmitted uplink data. The base station device 3 in question transmits downlink data, but other base station devices 3 do not transmit downlink data. Therefore, if a new mobile station device 4 enters the area, it can immediately notify the mobile station device 4 of its location information, thereby improving the efficiency of data transmission throughout the system.
When the next uplink data transmission starts, the line control device 2 resets the stored base station used line, and when it receives uplink data transmission from the mobile station device 4, it overwrites and updates it.

[Occurrence of blind zones: Figure 7]
When the base station devices 3 are located far enough apart, data transmission can be performed efficiently using the sequence shown in Fig. 6. However, when the base station devices 3 are located adjacent to each other and their communication areas partially overlap, blind zones occur.
The occurrence of a dead zone will be explained with reference to Fig. 7. Fig. 7 is an explanatory diagram showing the occurrence of a dead zone.
As shown in Figure 7, if downlink data (response) is sent only to base station device 3-n that is stored as a line used by the base station, even if that base station device 3-n starts downlink data transmission, adjacent base station devices 3-n-1 and 3-n+1 will not transmit downlink data and will be able to transmit uplink data.

As a result, in overreach area 71, where the areas of base station device 3-n-1 and base station device 3-n overlap, and overreach area 72, where the areas of base station device 3-n and base station device 3-n+1 overlap, downlink data from both base stations can become congested, resulting in dead zones.

[Neighboring base station]
Therefore, in this wireless communication system, as another downlink data transmission method (downlink data transmission (2) in response to uplink data transmission, hereinafter referred to as downlink data transmission (2)), downlink data (response) is transmitted not only to the base station device 3 stored as the line used by the base station, but also to the adjacent base station device 3 (adjacent base station).
The adjacent base stations are stored in the line control device 2 in association with each base station device 3, and are base station devices 3 whose communication areas partially overlap with those of the base station device 3 in question.

When transmitting downlink data, the number of adjacent base stations to which the same downlink data is transmitted (the number of adjacent base stations) is preset depending on the environment in which the system is installed, etc.
In the downstream data transmission (1) shown in FIGS. 6 and 7, downstream data is transmitted only to the base station device 3 corresponding to the line used by the base station, and the number of adjacent base stations is set to "0".

On the other hand, in downlink data transmission (2), when transmitting downlink data (response), the line control device 2 transmits the same downlink data not only to the base station device 3 stored as a line used by the base station, but also to the adjacent base station stored in correspondence with that base station device 3.

[Downstream data transmission relative to upstream data transmission (2): Figure 8]
Here, a description will be given of downlink data transmission (2) relative to uplink data transmission when the number of adjacent base stations is set to "2" with reference to Fig. 8. Fig. 8 is a sequence diagram showing downlink data transmission (2) relative to uplink data transmission.
In FIG. 8, steps S31 to S34 are the same as steps S21 to S24 shown in FIG. 6, and therefore a description thereof will be omitted.

When a downstream data transmission (response) is received from the data server 6 in process S34, the line control device 2 reads out the stored base station line and sets it as the destination of the downstream data transmission (response), and also reads out the adjacent base station stored in association with the base station device 3 and sets the line used by the adjacent base station as the destination (S35).

Then, the line control device 2 sends a downstream data transmission (response) to the base station device 3-n (S36), and sends the same downstream data transmission (response) to the adjacent base station device 3-n-1 and base station device 3-n+1 (S37, S38).
In this way, downstream data transmission (2) for upstream data transmission is performed.

[Operation status when the number of adjacent base stations is 2: Figure 9]
The operation state when the number of adjacent base stations is set to two will be described with reference to Fig. 9. Fig. 9 is an explanatory diagram showing the operation state when the number of adjacent base stations is set to two.
In FIG. 9, similarly to FIG. 7, base station device 3-n-1, base station device 3-n, and base station device 3-n+1 are arranged in a line.

Then, as shown in the sequence in Figure 8, if the same downlink data transmission (response) is sent to base station device 3-n as well as base station device 3-n-1 and base station device 3-n+1, all three base stations will perform downlink transmission at the same time.

As a result, data congestion does not occur in overreach area 71 and overreach area 72, and downlink transmission is carried out normally. In other words, downlink transmission is carried out normally anywhere within the area of base station device 3-n in which the mobile station device 4 that performed uplink data transmission is located, and no blind spots occur.

In this way, when base station devices 3 are arranged in a line, by setting the number of adjacent base stations to "2", downlink data can be transmitted to both adjacent base station devices 3, preventing the occurrence of blind spots and maintaining the reliability of the service.
In addition, overreach areas 73 and 74 are formed with adjacent base station devices 3 at the left end of the area of base station device 3-n-1 and the right end of the area of base station device 3-n+1, and these become dead zones. However, since mobile station device 4 is not present in the areas of base station device 3-n-1 and base station device 3-n+1, the impact is limited.

The arrangement of the base station devices 3 is not limited to series, but may be parallel, or may be in a planar form such as a honeycomb or random pattern.
The control unit 22 of the line control device 2 stores the number of base station devices 3 adjacent to each base station device 3 according to the arrangement of the base station devices 3 .

[Effects of the embodiment]
According to this wireless communication system, the system has a plurality of base station devices 3 that perform downlink transmission using the same frequency, and a line control device 2 that controls the base station devices 3. When the line control device 2 receives uplink data from a base station device 2, it stores the line used by that base station device 3 and transmits downlink data in response to the uplink data to the stored line used by the base station device 3. This means that downlink data is not transmitted to base station devices 3 that do not require a response, and uplink data transmission from new mobile station devices 4 is possible, thereby improving the data transmission efficiency of the entire system.

Furthermore, according to this wireless communication system, when the line control device 2 transmits downlink data in response to uplink data, it transmits the downlink data to the lines used by base station devices 3 in areas adjacent to the area of the base station device 3 in addition to the lines used by the stored base station device 3. This prevents blind spots in areas where the areas of base station devices 3 overlap, where downlink data from both base stations interferes with each other, and ensures normal reception of downlink data throughout the area of the stored base station device 3, thereby ensuring the reliability of communication services.

The present invention is suitable for wireless communication systems that can improve data transmission efficiency within the system.

1...Command desk, 2...Line control device, 3...Base station device, 4...Mobile station device, 5...Location information collection device, 6...Data server, 7...GPS satellite, 21...Frame generation unit, 22...Control unit, 23...Base station interface unit, 24...GPS antenna, 71, 72, 73, 74...Overreach area, 211...GPS module, 212...PLL unit, 213...Superframe counter, 221...CPU

Claims (4)

A wireless communication system having a plurality of base station devices that perform downlink transmission using the same frequency, and a line control device that controls the plurality of base station devices,
The line control device stores adjacent base stations corresponding to the plurality of base station devices whose communication areas partially overlap with those of the base station devices, and when it receives uplink data from a base station device, it stores the line used by the base station device, and when it transmits downlink data in response to the uplink data to the line used by the stored base station device, if there is no adjacent base station corresponding to the stored base station device, it transmits the downlink data only to the stored base station device. The wireless communication system according to claim 1, characterized in that when the line control device transmits downlink data in response to the uplink data to the line used by the stored base station device, if there is an adjacent base station corresponding to the stored base station device, the line control device transmits the downlink data to the line used by the adjacent base station in addition to the stored base station device . A wireless communication system according to claim 1 or 2, characterized in that, when transmitting the downlink data, the line control device specifies to each base station device to which the data is to be transmitted the timing at which each base station device will start transmitting the downlink data, the timing being the maximum transmission time between the line control device and the plurality of base stations from the transmission timing of the downlink data. A wireless communication system according to claim 1 or 2, characterized in that the areas of the multiple base station devices are arranged linearly or planarly.