JP7012601B2 - Wireless communication system - Google Patents

Description

The present invention relates to a wireless communication system.

A time division multiplexing method is adopted as a communication method when the wireless communication system is applied to a train radio communication system. This is a method in which a plurality of signals are divided into fixed time (time slots), each signal is arranged for each division, and the signals are sequentially transmitted. When the mobile station moves from the coverage area of the base station being communicated to the coverage area of the adjacent base station, the mobile station continues communication while switching the frequency and the transmission order (time slot number) assigned to itself. Let me.

In the conventional train radio communication system, if the base station to be moved does not have an empty slot, it is not possible to newly enter the mobile station into the cover area of the base station. In order to increase the number of mobile stations that can be controlled by one base station, it is necessary to increase the transmission speed and shorten the transmission time for each mobile station.

Patent Document 1 discloses a method of thinning out unique words included in a transmission signal for each time slot to increase the transmission time. Since the unique word is important data for performing the synchronization accurately, the thinning number of the unique word is determined by the synchronization error measurement each time. The time slot with the unique words thinned out makes it possible to increase the transmission time for control data and communication data.

From the above, even in a train radio communication system, it is possible to increase the number of time slots per frame and increase the number of mobile stations that can be controlled by one base station by increasing the transmission time by thinning out data.

Japanese Unexamined Patent Publication No. 9-8782

In a train radio communication system using a time division multiplexing system, one frame of a transmission signal from a base station is divided into two or more broadcast communication time slots and two or more mobile station control time slots. ing. One mobile station is assigned to one mobile station control time slot, and mobile stations exceeding the number of mobile station control time slots in one frame cannot enter the coverage area of the base station. ..

When a new mobile station enters the coverage area beyond the upper limit of the number of mobile stations that can be controlled by the base station, the transmission time allocated for each mobile station is shortened, and the new mobile station is used. It is necessary to secure a control time slot. However, depending on the data that is reduced due to the reduction in transmission time, it may interfere with train operation.

In a wireless communication system using a conventional time division multiplexing method as described in Patent Document 1, it is possible to reduce the frequency of inserting unique words in each time slot and increase the data that can be transmitted in each time slot. However, since the number of time slots per frame does not change, it is not possible to secure a time slot for a new mobile station.

Therefore, according to the present invention, in a wireless communication system, even after the upper limit of the number of mobile stations that can be controlled by a base station is reached, the time for a mobile station that newly needs to be controlled without reducing the required data. The purpose is to provide technology that can secure slots.

The wireless communication system according to the present invention includes a base station and a plurality of mobile stations capable of performing wireless communication between the base stations, and is transmitted from the base station to each mobile station. Each frame of the transmission signal of the above includes a plurality of broadcast communication time slots and a plurality of mobile station control time slots, and the base station reaches the upper limit of the number of controllable mobile stations, and then the first. By using a part of the plurality of broadcast communication time slots included in each of the transmission signals of the above as the mobile station control time slot, radio communication with the mobile station that requires new control is performed. It is possible to communicate.

According to the present invention, each frame of the first transmission signal transmitted from the base station to each mobile station includes a plurality of broadcast communication time slots and a plurality of mobile station control time slots. After reaching the upper limit of the number of controllable mobile stations, a part of the plurality of broadcast communication time slots included in each frame of the first transmission signal can be used as the mobile station control time slot. It is possible to perform wireless communication with mobile stations that require new control. Therefore, even after the base station reaches the upper limit of the number of mobile stations that can be controlled, it is possible to secure a time slot for a mobile station that newly needs to be controlled without reducing the required data.

It is an overall block diagram of the train radio communication system which is one of the radio communication systems which concerns on Embodiment 1. FIG. It is a figure which shows the data frame format of the transmission signal transmitted from the base station to the mobile station provided in the wireless communication system which concerns on Embodiment 1. FIG. It is a figure which shows the data frame format of the transmission signal transmitted from the mobile station to the base station provided in the wireless communication system which concerns on Embodiment 1. FIG. Indicates the data frame format of the transmitted signal transmitted from the base station to the mobile station when an uncontrolled mobile station enters the coverage area of the base station after the base station has reached the upper limit of the number of mobile stations that can be controlled. It is a figure. After the base station has reached the upper limit of the number of mobile stations that can be controlled, when an uncontrolled mobile station enters the coverage area of the base station, the data frame format of the transmission signal transmitted from each mobile station to the base station It is a figure which shows. In the wireless communication system according to the second embodiment, when an uncontrolled mobile station enters the cover area of the base station after the upper limit of the number of mobile stations that can be controlled by the base station is reached, the base station is sent from each mobile station. It is a figure which shows the data frame format of the transmission signal transmitted to.

<Embodiment 1>
Embodiment 1 of the present invention will be described below with reference to the drawings. FIG. 1 is an overall configuration diagram of a wireless communication system according to the first embodiment.

FIG. 1 is an example of applying a wireless communication system to a train radio communication system. As shown in FIG. 1, the wireless communication system includes a base device (not shown), base stations 11 and 12, and mobile stations 2a, 21 to 26. Note that in FIG. 1, the mobile stations 22 to 26 (see FIG. 3) are not shown.

First, the operation of the premise technology will be described, and then the operation of the wireless communication system according to the first embodiment will be described. The mobile station 2a is approaching the handover zone with the cover area 31 of the base station 11 while traveling in the cover area 32 of the base station 12. In the cover area 31, the mobile station 21 is running and is communicating with the base station 11.

The mobile station 2a attempts to communicate with the base station 11 in order to enter the cover area 31. At this time, if there is an empty slot in the transmission signal of the base station 11, the time slot is used as a mobile station control time slot which is a communication time slot between the base station 11 and the mobile station 2a. If there is no empty slot in the base station 11, the mobile station 2a cannot enter the cover area 31.

The base stations 11 and 12 are connected to the base device by an optical line, and the position information of the current positions of the mobile stations 2a and 21 is transmitted to the base device. When the mobile station 2a approaches the cover area 31 of the base station 11, the base device confirms the presence or absence of an empty slot in the base station 11.

If there is an empty slot, the base device allocates the empty slot for communication with the mobile station 2a. The base device transmits the communication time slot number in the cover area 31 to the mobile station 2a through the base station 12. If there is no empty slot, the base device issues a stop instruction to the mobile station 2a and makes the mobile station stand by until an empty slot is created. An empty slot occurs when one or more mobile stations in the cover area 31 move to another cover area or disconnect communication with the base station 11 and enter a non-operating state.

In a wireless communication system, a TDM (time division multiplexing) method is adopted for communication from base stations 11 and 12 to mobile stations 2a and 21 to 26 (hereinafter referred to as "A → B"), and mobile stations 2a and 21 to A TDMA (time division multiple access) method is adopted for communication from 26 to base stations 11 and 12 (hereinafter referred to as “B → A”).

FIG. 2 is a diagram showing a data frame format of a transmission signal transmitted from base stations 11 and 12 to mobile stations 2a and 21 to 26.

As shown in FIG. 2, one frame of the transmission signal from A to B consists of two types of time slots, that is, a plurality of mobile station control time slots (# 0 to # 5) and a plurality of broadcast communication time slots. It is composed of an array. The mobile station control time slot stores data unique to each mobile station 2a, 21 to 26 such as SW, CRC, and FEC, and communication data. The broadcast communication time slot stores data common to all mobile stations. The number of mobile stations that can be controlled by one communication depends on the number of mobile station control time slots in one frame. The transmission signal from A to B corresponds to the first transmission signal.

FIG. 3 is a diagram showing a data frame format of a transmission signal transmitted from mobile stations 2a, 21 to 26 to base stations 11 and 12.

As shown in FIG. 3, each mobile station 2a, 21 to 26 divides the transmission signal for each time and transmits the transmission signal to the base station 11 in order. This order is determined by the mobile station control time slot shown in FIG.

In B → A, the mobile stations 2a, 21 to 26 differ in the moving speed, the distance from the base station 11, the surrounding environment, and the like. Therefore, there is a delay in the time when the transmission signal arrives at the receiver included in the base station 11, and even if the mobile stations 2a, 21 to 26 transmit the transmission signals in the correct order, the signals are transmitted in the adjacent transmission lines. Collisions between each other may occur. In order to avoid this collision, it is necessary to provide G (guard time) in one frame of the transmission signal from B to A, as shown in FIG. The transmission signal from B to A corresponds to the second transmission signal.

FIG. 4 shows transmission from the base station 11 to the mobile station 2a when the uncontrolled mobile station 2a enters the cover area 31 of the base station 11 after the base station 11 reaches the upper limit of the number of controllable mobile stations. It is a figure which shows the data frame format of the transmitted signal which is made.

As shown in FIG. 4, the base station 11 reaches each frame of the transmission signal when the uncontrolled mobile station 2a enters the cover area 31 of the base station 11 after reaching the upper limit of the number of controllable mobile stations. By rewriting a part of the plurality of broadcast communication time slots included in the above and using it as a mobile station control time slot for controlling the mobile station 2a, the mobile station 2a requires new control. Perform wireless communication.

After reaching the upper limit of the number of controllable mobile stations, the base station 11 is assigned to each frame of the transmission signal regardless of whether or not the uncontrolled mobile station 2a enters the cover area 31 of the base station 11. A part of the plurality of included broadcast communication time slots may be rewritten and prepared in advance as a mobile station control time slot for controlling the mobile station 2a. That is, the base station 11 may secure the time required for wireless communication with the mobile station 2a that newly needs to be controlled.

FIG. 5 shows from the mobile stations 2a, 21 to 26 when the uncontrolled mobile station 2a enters the cover area 31 of the base station 11 after the base station 11 reaches the upper limit of the number of controllable mobile stations. It is a figure which shows the data frame format of the transmission signal transmitted to a base station 11.

As shown in FIG. 5, when the uncontrolled mobile station 2a enters the cover area 31 of the base station 11 after the base station 11 reaches the upper limit of the number of controllable mobile stations, the mobile stations 2a, 21 respectively. ~ 26 can shorten the transmission time of the transmission signal from each mobile station 2a, 21 to 2 to the base station 11 by reducing a part of the PR (preamble) included in each frame of the transmission signal. Is. That is, each mobile station 2a, 21 to 26 can shorten the time slot used for wireless communication with the base station 11. Thereby, it is possible to allocate to the transmission time at the time of wireless communication between the mobile station 2a and the base station 11 which newly needs to be controlled.

After the base station 11 reaches the upper limit of the number of controllable mobile stations, the uncontrolled mobile stations 2a enter the cover area 31 of the base station 11, and the mobile stations 2a, 21 to 21 26 may be prepared by reducing a part of PR included in each frame of the transmission signal in advance. As a result, each mobile station 2a, 21 to 26 can secure the time required for wireless communication between the mobile station 2a and the base station 11, which newly needs to be controlled.

PR is used for timing synchronization at the time of reception. In order to prevent synchronization deviation, we will not reduce PR completely. The amount of PR reduction differs depending on each mobile station 2a, 21 to 26. The base stations 11 and 12 transmit the position information and the traveling speed of the current positions of the mobile stations 2a and 21 to 26 that are being controlled to the base device.

The change of the frame format is carried out according to the instruction from the base device. When the base device obtains information that the mobile station 2a is approaching the cover area 31 of the base station 11 through the base station 12, the base devices are approaching the mobile stations 21 to 26 in the cover area 31 and the cover area 31. The amount of PR reduction that can be reduced is determined based on the position information or movement speed of the mobile station 2a. When the transmission time required for the mobile station 2a can be secured from this PR reduction amount, the base device issues an instruction to accept the mobile station 2a to the base station 11.

As shown in FIG. 4, the base station 11 to which the acceptance instruction is issued allocates a part of the broadcast communication time slot for the mobile station 2a, and transmits the assigned time slot number (#a) to the base device. .. The transmission signal to each mobile station 2a, 21 to 26 includes an instruction of the reduction amount of PR. Each mobile station 2a, 21 to 26 reduces the PR transmitted by itself by the instructed amount. The base device notifies the mobile station 2a of the time slot number for the mobile station 2a acquired from the base station 11 through the base station 12. After invading the cover area 31, the mobile station 2a that has received the notification starts communication with the base station 11 using the assigned time slot number.

After securing the time slot of the mobile station 2a, when the mobile station 21 in the cover area 31 of the base station 11 tries to enter the cover area of the adjacent base station, the frames A → B and B → A again. The format is changed. The base device that has acquired the position information of the mobile station 21 issues an instruction to the base station 11 to return the frame format as shown in FIG. 2 after the handover processing of the mobile station 21 is completed. At this time, the time slot number used by the mobile station 21 is assigned to the mobile station 2a.

As described above, in the wireless communication system according to the first embodiment, the base station 11 has a plurality of broadcast communication time slots included in each frame of the transmission signal after reaching the upper limit of the number of controllable mobile stations. By using a part of the above as a time slot for controlling a mobile station, wireless communication with a mobile station 2a that newly needs to be controlled is performed.

Therefore, even after the base station 11 reaches the upper limit of the number of mobile stations that can be controlled, it is possible to secure a time slot for the mobile station 2a that newly needs to be controlled without reducing the required data. .. This makes it possible for the mobile station 2a to enter the cover area 31.

After reaching the upper limit of the number of mobile stations that can be controlled, the base station 11 uses a part of the plurality of broadcast communication time slots included in each frame of the transmission signal as the mobile station control time slot. It is possible to secure the time required for wireless communication with the mobile station 2a, which newly needs to be controlled. Therefore, the uncontrolled mobile station 2a can be prepared in advance before entering the cover area 31 of the base station 11.

Each frame of the transmission signal transmitted from each mobile station 2a, 21 to 26 to the base station 11 includes communication data and PR, and each mobile station 2a, 21 to 26 includes PR included in each frame of the transmission signal. By reducing a part of the above, it is possible to shorten the time slot used for wireless communication with the base station 11. Therefore, without reducing the amount of data unique to each mobile station 2a, 21 transmitted to the base station 11, the shortened time slot can be used as a base station with another mobile station 2a that desires communication with the base station 11. It can be assigned as a time slot for communication with 11.

The wireless communication system further includes a base device connected to the base station 11, and the base device determines the amount of PR reduction based on the position information or the traveling speed of each mobile station 2a, 21 to 26, so that each movement PR can be effectively reduced for each station 2a, 21 to 26.

Each mobile station 2a, 21 to 26 can allocate the time generated by shortening the time slot used for wireless communication with the base station 11 to the mobile station 2a that needs to be newly controlled. Therefore, it is possible to allow the mobile station 2a to enter the cover area 31.

<Embodiment 2>
Next, the wireless communication system according to the second embodiment will be described. FIG. 6 shows that in the wireless communication system according to the second embodiment, after the base station 11 reaches the upper limit of the number of controllable mobile stations, the uncontrolled mobile station 2a enters the cover area 31 of the base station 11. At this time, it is a figure which shows the data frame format of the transmission signal transmitted from each mobile station 2a, 21-26 to a base station 11. In the second embodiment, the same components as those described in the first embodiment are designated by the same reference numerals, and the description thereof will be omitted.

In the first embodiment, the PR is reduced in B → A, but in the second embodiment, a method of securing the transmission time when the G is reduced will be described. Regarding A → B, the broadcast communication time slot is used as the mobile station control time slot as in the case of the first embodiment.

As shown in FIG. 6, by reducing a part of G in the frame, it is possible to shorten the transmission time of the transmission signal from each mobile station 2a, 21 to 2 to the base station 11. That is, each mobile station 2a, 21 to 26 can shorten the time slot used for wireless communication with the base station 11. Thereby, it is possible to allocate to the transmission time at the time of wireless communication between the mobile station 2a and the base station 11 which newly needs to be controlled.

After the base station 11 reaches the upper limit of the number of controllable mobile stations, the uncontrolled mobile stations 2a enter the cover area 31 of the base station 11, and the mobile stations 2a, 21 to 21 26 may be prepared by reducing a part of G included in each frame of the transmission signal in advance. As a result, each mobile station 2a, 21 to 26 can secure the time required for wireless communication between the mobile station 2a and the base station 11, which newly needs to be controlled.

G is provided to prevent collisions between transmission signals of the mobile stations 2a, 21 to 26. Each mobile station 2a, 21 to 26 transmits information from the base station 11 in order so that the transmission signals do not collide with each other. However, the timing at which the transmission signal arrives at the base station 11 is inaccurate due to reflections due to the surrounding environment of the mobile stations 2a, 21 to 26. If the transmission signal is delayed, it may interfere with the transmission signal from another mobile station and may not be received correctly. Therefore, G is provided to prevent collisions between transmitted signals.

As described above, a large reduction in G is unacceptable in a situation where interference is likely to occur, such as during high-speed driving in which the surrounding environment of mobile stations 2a, 21 to 26 fluctuates rapidly. Therefore, the reduction of G is implemented only when there is a mobile station traveling at low speed in an emergency or the like. That is, when the uncontrolled mobile station 2a enters the cover area 31 of the base station 11, each mobile station 2a, 21 to 26 has a predetermined low-speed reference based on the transmission signal received from the base station 11. When it is recognized that there are other mobile stations traveling below the value, a part of G contained in each frame of the transmission signal is reduced. The change of the frame format is the same as the PR reduction method of the first embodiment.

As described above, in the wireless communication system according to the second embodiment, each frame of the transmission signal transmitted from each mobile station 2a, 21 to 26 to the base station 11 includes communication data and G, and each mobile station. In 2a, 21 to 26, it is possible to shorten the time slot used for wireless communication with the base station 11 by reducing a part of G included in each frame of the transmission signal.

Therefore, without reducing the amount of data unique to each mobile station 2a, 21 transmitted to the base station 11, the shortened time slot can be used as a base station with another mobile station 2a that desires communication with the base station 11. It can be assigned as a time slot for communication with 11.

Each mobile station 2a, 21 to 26 is included in each frame of the transmission signal when it recognizes that there is another mobile station traveling below a predetermined low-speed reference value based on the received transmission signal. In order to reduce a part of the G, it is possible to secure a time slot for the mobile station 2a that needs to be newly controlled and to prevent collisions between the transmission signals of the mobile stations 2a, 21 to 26. can do.

Here, in a situation where the base station 11 and the mobile station are in a line-of-sight environment and there is no obstruction in the surroundings, G is considered unnecessary. Therefore, unlike PR, G can be reduced altogether depending on the situation of the mobile station. There is a possibility.

Each mobile station 2a, 21 to 26 can allocate the time generated by shortening the time slot used for wireless communication with the base station 11 to the mobile station 2a that needs to be newly controlled. Therefore, it is possible to allow the mobile station 2a to enter the cover area 31.

In the present invention, each embodiment can be freely combined, and each embodiment can be appropriately modified or omitted within the scope of the invention.

2a Mobile station, 11,12 base station, 21-26 mobile station.

Claims (7)

With the base station
A plurality of mobile stations capable of wireless communication with the base station,
Equipped with
Each frame of the first transmission signal transmitted from the base station to each mobile station includes a plurality of broadcast communication time slots and a plurality of mobile station control time slots.
After the base station reaches the upper limit of the number of mobile stations that can be controlled, a part of the plurality of broadcast communication time slots included in each frame of the first transmission signal is used for controlling the mobile station. A wireless communication system that can be used as a time slot to perform wireless communication with the mobile station that requires new control. After the base station reaches the upper limit of the number of mobile stations that can be controlled, a part of the plurality of broadcast communication time slots included in each frame of the first transmission signal is used for controlling the mobile station. The wireless communication system according to claim 1, wherein by using it as a time slot, it is possible to secure the time required for wireless communication with the mobile station that newly needs to be controlled. Each frame of the second transmission signal transmitted from each mobile station to the base station includes communication data and a preamble.
Each mobile station can shorten the time slot used for wireless communication with the base station by reducing a part of the preamble included in each frame of the second transmission signal. , The wireless communication system according to claim 1. Further equipped with a base device connected to the base station,
The wireless communication system according to claim 3, wherein the base device determines the amount of reduction of the preamble based on the position information or the traveling speed of each mobile station. Each frame of the second transmission signal transmitted from each mobile station to the base station includes communication data and a guard time.
Each mobile station can shorten the time slot used for wireless communication with the base station by reducing a part of the guard time included in each frame of the second transmission signal. The wireless communication system according to claim 1. When each mobile station recognizes that there is another mobile station traveling below a predetermined low-speed reference value based on the received first transmission signal, the second transmission signal The wireless communication system according to claim 5, wherein a part of the guard time included in each of the frames is reduced. 3. The mobile station can allocate the time generated by shortening the time slot used for wireless communication with the base station to the mobile station that needs new control. The wireless communication system according to claim 5.

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