JP4660686B2 - Mobile radio communication system - Google Patents

Description

The present invention relates to a mobile radio communication system including a plurality of base stations that perform transmission / reception operations on carriers of the same frequency.

In mobile radio communication systems, in order to expand a communicable area by a mobile station, a method in which base stations that perform transmission / reception operations using carriers of the same frequency are arranged at different points has been used. Therefore, for an example of a mobile radio communication system provided with such a plurality of base stations,
This will be described with reference to FIG. Here, in this example, there are two base stations, that is, base station 7 and base station 7 ′.
Is provided.

In FIG. 2, first, reference numeral 1 denotes a central device, which includes a signal generator 2. The central device 1 is further provided with a plurality of buffers 3, 3 ′ and a plurality of network interfaces 4, 4 ′. Here, the buffers 3, 3 ′ synchronize signals with the network. The network interfaces 4 and 4 ′ are provided for transmitting signals from the buffer 3 or the buffer 3 ′ at a network timing and transmitting the signals to the network.

Each network interface 4, 4 ′ is connected to a network terminal 5, 5 ′ on the central device side, and these network terminals 5, 5 ′ on the central device side are respectively connected to network terminals 6, 6 ′ on the base station side. As a result, the network interfaces 4 and 4 ′ of the central apparatus 1 are connected to the base stations 7 and 7 ′ via the network terminals 5 and 5 ′ and the network terminals 6 and 6 ′ via the networks NW and NW ′, respectively. Will be connected to.

Each base station 7, 7 ′ is provided with a network interface 8, 8 ′, buffers 9, 9 ′, and radios 10, 10 ′.
8 'operates to acquire a required signal from the network in synchronization with the network and transmit it to the buffers 9, 9'. Next, the buffers 9, 9 'temporarily store the input signal at this time. It works to hold on. Then, the radios 10 and 10 'are connected to the buffer 9 at a predetermined timing.
A signal is extracted from 9 ', placed on a carrier having a predetermined frequency, transmitted as a radio wave, and received by the mobile station 11 as a signal receiving source.

Next, the operation of this prior art will be described in more detail. First, the signal generator 2 periodically outputs signal data. Therefore, the buffers 3 and 3 ′ store the signals and temporarily store them. At this time, the network interfaces 4 and 4 ′ are always synchronized with the network terminals 6 and 6 ′. Therefore, at this time, a signal is acquired from the buffers 3 and 3 ′ at the network timing and notified to the network.

At this time, the network interfaces 8 and 8 ′ of the base stations 7 and 7 ′ are also synchronized with the network timing. Therefore, the base station side also has buffers 3, 3 on the central device side.
The signal is acquired from the network including the network terminals 5, 6, 5 ′ and 6 ′ at the network timing, stored in the buffers 9 and 9 ′ on the base station side, and temporarily stored therein. deep. After this, the radios 10 and 10 ′ access the buffers 9 and 9 ′ at the timing on the radio side after the timing when the data is accumulated in the buffers 9 and 9 ′, take out the signals, and transmit them. It is received by the mobile station 11.

As a result, both a communication area by one base station, for example, the base station 7, and a communication area by the other base station, that is, the base station 7 ′, are established. Can be extended to the transmission range.

Here, according to this prior art, since a network interface is provided between each device in the system and the network, each device can operate at a timing different from the network timing, and the system fluctuations. There is an advantage that communication can be performed according to the convenience of the processing source and processing destination.

For example, Patent Document 1 can be cited as an example of disclosure related to the related art of the present invention.
JP 2002-325270 A

The above prior art does not take into account radio wave interference (also called collision) when radio waves from the same frequency carrier are transmitted from multiple base stations, making it difficult to communicate in specific areas between base stations There was a problem that an area appeared.

Referring to FIG. 2, since the base station 7 and the base station 7 ′ are installed at different locations apart from the central apparatus 1, respectively, the network between them has different signal delays. Will occur. At this time, since each device also moves at an independent timing, a difference due to the timing also occurs.

On the other hand, the mobile station 1 that is a signal receiving destination is a radio device mounted on a train, for example, and moves along a track, so that it moves to an area where radio waves from the base station 7 and the base station 7 'interfere with each other. Although it is unavoidable that the data is transmitted at this time, even if the transmitted data is the same, the timing is different, and therefore the mobile station 11 cannot receive the data.

Here, even if it is going to compensate for this delay, this delay is not necessarily fixed in the case of a general-purpose multiplex transmission device (SDH: Synchronous Digital Hierachy) used in the network, and the delay amount is changed. Sometimes. For this reason, even if the timing is adjusted by the network interface of the base station, if it is changed by SDH or the like, it cannot be received.

On the other hand, if a non-general-purpose multiplex transmission apparatus is used, it is necessary to use a unique network apparatus capable of providing equivalent services, and problems such as an increase in development cost and a decrease in service quality become apparent.

The present invention has been made in response to the problems of the prior art, and an object of the present invention is to provide a mobile radio communication system capable of reception even in an area where radio wave interference occurs.

The above-mentioned object is connected to a central device via independent networks , each comprising a plurality of base stations each having a radio and a buffer, and the plurality of base stations acquired from the central device via the network The signal is stored in the buffer at the timing of the network, and the signal extracted from the buffer at a timing on the radio side different from the timing of the network is transmitted from the radio unit, so that the same from the plurality of base stations In a mobile radio communication system configured to transmit the same data using a frequency carrier, a timing signal is transmitted from the central unit to each of the plurality of base stations via a timing signal transmission line different from the network. a timing signal transmitting means for transmitting, provided to each of said plurality of base stations, the timing The timing signal transmitted by the transmission signal transmission means is given a larger delay time among the data transmission delay times from the central device to each of the plurality of base stations, and the radio device side timing is given by A plurality of delay means for supplying to each of the plurality of base stations, the timing synchronization of the data transmitted from each of the plurality of base stations is transmitted by the timing signal transmission means, and by a timing signal given a delay time by the delay means Achieved as taken.

Similarly, the above object is connected to the central device through independent networks, each having a radio and a buffer, and comprising a plurality of base stations installed in the vicinity of the railway line, the plurality of base stations, The signal acquired from the central apparatus via the network is stored in the buffer at the timing of the network, and the signal extracted from the buffer is transmitted from the radio at a timing on the radio side different from the timing of the network Thus, the mobile radio communication system for trains transmits the same data from the plurality of base stations using carriers of the same frequency, and performs radio communication with the plurality of mobile stations moving on the railroad track. in, from the central unit, via another timing signal transmission line and the network, data in each of the plurality of base stations A timing signal transmission means for transmitting a timing signal, and a data transmission from the central apparatus to each of the plurality of base stations to the timing signal transmitted by the timing signal transmission means. A delay time which is larger among the delay times is provided, and a plurality of delay means for supplying the radio as timing on the radio side are provided, and timing synchronization of data transmitted from each of the plurality of base stations is performed. This is achieved by being taken by a timing signal transmitted by the timing signal transmission means and given a delay time by the delay means.

According to the present invention, it is possible to enable reception in a radio wave interference area simply by adding a simple transmission path, and to provide a mobile radio communication system with little increase in development cost and low service quality.

Further, according to the present invention, since the transmission timing of the base station is adjusted based on the timing of the signal transmission source, no matter what delay characteristics exist in the transmission system between the central apparatus and the base station, Communication can be performed without being influenced.

According to the present invention, since only a single signal needs to be transmitted, the addition of a necessary configuration can be reduced.

Hereinafter, a mobile radio system according to the present invention will be described in detail with reference to embodiments shown in the drawings.

FIG. 1 shows an embodiment of the present invention, which is also an embodiment in which there are two base stations. In the central apparatus 1 including the signal source 2, a plurality of buffers 3, 3 ′ and a plurality of network interfaces 4 are provided. 4 ′, whereby signals are acquired from the buffers 3 and 3 ′ at the timing of the network and transmitted to the network, which is the same as in the case of the prior art described with reference to FIG.

At this time, each network interface 4, 4 ′ is connected to the network terminal 5, 5 ′ on the central device side, and the network terminal 5, 5 ′ on the central device side is connected to the network terminal 6, 6 ′ on the base station side, respectively. As a result, the network interface 4, 4 ′ of the central device 1 is connected to each base station 7, 7 ′ via each network terminal 5, 5 ′ and network terminal 6, 6 ′. This is also the same as the prior art.

Furthermore, the base stations 7, 7 ′ have network interfaces 8, 8 ′ and buffers 9, respectively.
9 'and radios 10 and 10' are provided. First, the network interface 8, 8 'acquires a required signal from the network in synchronization with the network and transmits it to the buffers 9, 9'. The buffers 9 and 9 'are also provided for temporarily holding the signal input at this time, and are also the same as the prior art. Therefore, in this embodiment, the radio 10 is also provided. 10 ′ takes out a signal from the buffers 9, 9 ′ at a predetermined timing, puts it on a carrier of a predetermined frequency, transmits it as a radio wave, and receives the signal from the mobile station 11
Will be received.

Therefore, also in this embodiment, when a signal is output from the signal generation source 2, the signal is temporarily stored in the buffers 3 and 3, and the signal is acquired from the buffers 3 and 3 'at the timing of the network interfaces 4 and 4'. The network interfaces 8, 8 'of the base stations 7, 7' are also notified at the network timing through the network including the network terminals 5, 6, 5 ', 6' at the central device side buffers 3, 3 '. Signal, and temporarily store it in the base station side buffer 9, 9 ', and after this accumulated timing, the radios 10, 10'
The buffers 9 and 9 'are accessed at the timing on the radio side, the signal is extracted and transmitted, and is received by the mobile station 11.

Therefore, also in this embodiment, both the communication area by one base station, for example, the base station 7, and the communication area by the other base station, that is, the base station 7 ′ are established, and the communication range of the mobile station 11 The range of transmission by both base stations can be expanded. At this time, since each network device is provided with a network interface, each device can operate at a timing different from the network timing. As a result, there is the same merit as the conventional technique that communication can be performed according to the fluctuation of the system, the convenience of the processing source, and the processing destination.

However, in this embodiment, in addition to the above-described configuration, the following configuration is further added as a timing signal transmission unit, and this brings about an effect that cannot be obtained by the above-described conventional technology. This will be described in detail.

First, in FIG. 1, 12 is a timing transmission device, which is provided on the central device 1 side, functions to transmit the synchronization timing from the central device 1 side to the base stations 7 and 7 ′, and confirm the transmission result. Therefore, a synchronization timing generation unit 13, a synchronization timing transmission unit 14, a return timing reception unit 18, and an alarm detection unit 19 are provided.

Next, 15 and 15 ′ are timing receivers, which are provided on the base stations 7 and 7 ′ side, respectively, and receive the synchronization timing transmitted from the central device 1 side on the base stations 7 and 7 ′ side. The radios 10 and 10 'are timed according to the synchronized timing, and when the synchronization timing is received, the wireless devices 10 and 10' function to send them back as return timings. And return timing transmission units 17 and 17 ′, and timing delay units 20 and 20 ′.

Here, L1, L2, and L3 are timing signal transmission lines for transmitting timing signals. First, the timing signal transmission line L1 is a synchronization timing transmission unit 14 of the timing transmission device 12 and a synchronization timing reception unit of the timing reception device 15. 16 is connected between the return timing transmitter 17 of the timing receiver 15 and the synchronous timing receiver 16 ′ of the timing receiver 15 ′, and the timing signal transmission line L3. Are connected between the return timing transmitter 17 ′ of the timing receiver 15 ′ and the return timing receiver 18 of the timing transmitter 12.

The timing signal transmitted at this time only needs to have only the timing as information. For this reason, for example, a simple voltage pulse may be used as the signal. Therefore, the synchronization timing transmission unit 14 and the return timing transmission units 17 and 17 ′, and the synchronization timing reception unit 16,
Unlike a general transmission apparatus, 16 'and the return timing receiver 18 do not require a configuration for complicated processing such as multiplexing, and may be a simple pulse transmission / reception apparatus, and the timing signal transmission line L1, L2 and L3 are similarly simple lines.

Here, as an embodiment of the present invention, an optical transmission method may be applied to the transmission of this timing information. In this case, the synchronization timing transmission unit 14 and the return timing transmission units 17, 17 ′,
And the synchronization timing receivers 16 and 16 ′ and the return timing receiver 18 for optical transmission,
Each of the timing signal transmission lines L1, L has a configuration including an electrical-optical conversion unit and an optical-electrical conversion unit.
2 and L3 are optical fiber cables.

Next, the operation of this embodiment will be described. Assuming that a signal is output from the signal generation source 2, first, in the timing transmission device 12, the synchronization timing generation unit 13 takes in the timing of the original signal from the signal generation source 2, and generates a synchronization timing signal based on this. To do. Therefore, the synchronization timing transmitter 14 transmits this synchronization timing signal to the synchronization timing receiver 16 of the timing receiver 15 via the timing signal transmission line L1. At this time, as described above, since it is only necessary to know the timing, complicated processing such as multiplexing is unnecessary, and for example, a voltage pulse signal may be transmitted.

Then, this synchronization timing signal is the synchronization timing receiver 1 of the timing receiver 15.
6 is input to the delay unit 20, receives a time delay set in advance here, and a delay-corrected timing signal is supplied to the radio device 10. Therefore, the radio device 10 accesses the buffer 9 at the timing of the delay-corrected timing signal, extracts the signal, transmits it, and receives it at the mobile station 11.

On the other hand, the timing signal received by the synchronization timing receiver 16 at this time is also supplied to the return timing transmitter 17 as it is. Then, the return timing transmitter 17 relays and transmits the signal to the synchronous timing receiver 16 ′ of the timing receiver 15 ′ via the timing signal transmission line L2.

Here, when the synchronization timing signal is received by the synchronization timing receiver 16 ′ of the timing receiver 15 ′, it is also input to the delay unit 20 ′ and receives a preset time delay. The corrected timing signal is supplied to the edgeless machine 10 ′.
Therefore, the radio device 10 ′ also accesses the buffer 9 ′ at the timing of the delay-corrected timing signal, extracts the signal, transmits it, and receives it at the mobile station 11.

On the other hand, the timing signal received by the synchronization timing receiver 16 ′ is also supplied to the return timing transmitter 17 ′ as it is, but this time the timing receiver on the central device 1 side is now sent via the timing signal transmission line L3. 12 is relayed to 12 and received by the return timing receiver 18.

Therefore, the return timing receiving unit 18 supplies the received signal to the alarm detecting unit 19. At this time, the alarm detecting unit 19 supplies the signal from the return timing receiving unit 18 based on the timing signal fetched from the timing generating unit 12. The received signal is sampled and a timing signal is detected from the received signal. When a timing signal is not detected, a predetermined alarm notification is activated.

Next, the delay times of the delay units 20 and 20 ′ in this embodiment will be described. First, in the case of this embodiment, the transmission timings of the radio devices 10 and 10 ′ are the same as those of the timing receivers 15 and 15 ′. Based on the timing signals received by the synchronization timing receivers 16 and 16 ′, the timing is determined by adding the delay times of the delay units 20 and 20 ′ thereto.

At this time, the transmission time of the signal by the timing signal transmission line L1 and the transmission time of the signal by the timing signal transmission line L2 are almost negligible compared with the transmission cycle of the signal data of the signal source 2, so that the base station 7 side The timing signal received by the timing receiving device 15 and the timing signal received by the timing receiving device 15 ′ on the base station 7 ′ side can be regarded as having the same timing and being synchronized.

Therefore, the network terminal 5 and the network NW on the base station 7 side, and the data transmission delay time by the network terminal 6 is τ, and the network terminal 5 ′ and the network NW ′ on the base station 7 ′ side and the network terminal 6 ′. Let τ ′ be the data transmission delay time due to. Then, the transmission delay times τ and τ ′ are compared, and the one with the larger transmission delay time is selected. Then, this larger time is set as a delay time in each of the delay units 20 and 20 ′.

More specifically, when the transmission delay time is τ> τ ′, the delay unit 20
, 20 ′ and the delay time τ ′ is set in both of the delay units 20 and 20 ′, the delay time τ ′ is set in both the delay units 20 and 20 ′. , Delay units 20, 20
Assuming that the delay time set for both of T is T, the following is obtained.

τ> τ '⇒ T = τ
τ <τ '⇒ T = τ'
As a result, the transmission timing of the base station 7-side radio 10 and the base station 7'-side radio 10 '
The transmission timings of the two are delayed by the time T from the timing at which the signal data is generated from the signal generation source 2, but are matched to ensure transmission of synchronized data from a plurality of base stations. Will be able to.

Therefore, according to this embodiment, even when the mobile station 11 moves to an area where radio waves of the base station 7 and the base station 7 'interfere, the timing of the transmitted data is synchronized. As a result, according to this embodiment, expansion of the communicable range due to an increase in the number of installed base stations can be achieved without problems.

By the way, at this time, as described above, the alarm detection unit 19 constantly monitors the signal supplied from the return timing reception unit 18 so that when a timing signal is not detected, a predetermined alarm notification is made. It is configured.

Therefore, according to this embodiment, whether or not the mobile station 11 can receive data without any problem when the mobile station 11 moves to an area where the radio waves of the base station 7 and the base station 7 ′ interfere with each other is always determined. Thus, the reliability of the mobile radio system can be ensured and the soundness of the system can be maintained.

As described above, according to the embodiment of the present invention, it is effective for a train radio communication system based on the digital LCX radio system used for railways. Specifically, the LCX radio system has the advantage that the same frequency can be used by adjacent base stations, but at the base station boundary, the downlink direction
This embodiment can solve the problem that radio wave interference occurs in the direction from the base station to the mobile station and a section (dead zone) in which communication cannot be performed partially occurs.

In particular, when the digital wireless system is adopted, the data transmission speed is significantly faster than the analog wireless system, so the presence of the dead section significantly deteriorates the transmission quality seen from the entire train wireless communication section. In order to ensure stable transmission quality regardless of the position of the mobile station, this embodiment is effective in eliminating this dead zone.

Specifically, the cause of the radio wave interference is the intersymbol interference, but the occurrence of this intersymbol interference is caused by the difference in arrival time of each data sent from the central device to the plurality of base stations ( Due to delay difference). When this delay difference is viewed from the mobile station, it has been found that the dead zone can be eliminated if the delay difference is set to the same value, and the present embodiment is configured by inserting a timing circuit for equalizing the delay difference at the time of buffer reading of the base station.

More specifically, the timing for reading data to each radio is determined by a timing circuit installed independently from the data information transmission path from the central unit to the base station.

The delay difference is equivalent to the maximum delay time in the base station to which the timing circuit is connected, and this delay time is determined by the timing circuit.

Accordingly, stable communication can be performed over the entire section in which the mobile radio communication system is configured regardless of the type, state, and position of the mobile station of the information transmission path connected to the train mobile radio communication system.

1 is a block diagram showing an embodiment of a mobile radio communication system according to the present invention. It is a block diagram which shows an example of the mobile radio | wireless communications system by a prior art.

Explanation of symbols

1: Central device 2: Signal generation source 3, 3 ': Buffer (central device side)
4, 4 ': Network interface (central device side)
5, 5 ': Network terminal (central device side)
6, 6 ': Network terminal (base station side)
7, 7 ': Base station 8, 8': Network interface (base station side)
9, 9 ': Buffer (base station side)
10, 10 ': Radio 11: Mobile station (signal receiving destination)
12: Timing transmitter 13: Synchronization timing generator 14: Synchronization timing transmitter 15, 15 ': Timing receiver 16, 16': Synchronization timing receiver 17, 17 ': Return timing transmitter 18, 18': Return timing Receiver 19: Alarm detector 20, 20 ′: Delay unit NW, NW ′: Network L1, L2, L3: Timing signal transmission line

Claims (2)

Each of the plurality of base stations is connected to a central device via an independent network and each has a radio and a buffer, and the plurality of base stations acquire signals acquired from the central device via the network. The signal is stored in the buffer at the timing of the network, and the signal extracted from the buffer is transmitted from the radio at a timing on the radio side different from the timing of the network. In the mobile radio communication system used to transmit the same data,
Timing signal transmission means for transmitting a timing signal to each of the plurality of base stations from the central device via a timing signal transmission line different from the network,
Each of the plurality of base stations is provided with a larger delay time among the data transmission delay times from the central apparatus to each of the plurality of base stations in the timing signal transmitted by the timing signal transmission means. A plurality of delay means for supplying to the radio as timing on the radio side ,
Timing synchronization of data transmitted from each of the plurality of base stations is configured to be taken by a timing signal transmitted by the timing signal transmission unit and given a delay time by the delay unit. Mobile radio communication system. Each connected to a central device via an independent network, each having a radio and a buffer, comprising a plurality of base stations installed in the vicinity of a railway track, wherein the plurality of base stations are connected to the central device from the central device By storing the signal acquired through the network in the buffer at the timing of the network, and transmitting the signal extracted from the buffer at the timing on the radio side different from the timing of the network, In a mobile radio communication system for trains that transmits the same data using carriers of the same frequency from a plurality of base stations, and performs radio communication with a plurality of mobile stations that move on the railroad track ,
Timing signal transmission means for transmitting a timing signal to each of the plurality of base stations from the central device via a timing signal transmission line different from the network,
Each of the plurality of base stations is provided with a larger delay time among the data transmission delay times from the central apparatus to each of the plurality of base stations in the timing signal transmitted by the timing signal transmission means. A plurality of delay means for supplying to the radio as timing on the radio side,
Timing synchronization of data transmitted from each of the plurality of base stations is configured to be taken by a timing signal transmitted by the timing signal transmission unit and given a delay time by the delay unit. A mobile radio communication system for trains.

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