Notification system and notification method

Abstract

To provide a broadcasting system and a broadcasting method for transmitting broadcast information.SOLUTION: A broadcasting system according to an embodiment includes a master station, a plurality of relay stations that relay broadcast information transmitted from the master station, and a plurality of slave stations that receive the broadcast information transmitted from the plurality of relay stations. The plurality of relay stations are time-synchronized with other relay stations, and transmit radio signals each containing the same carrier frequency with synchronized transmission timing. If a faulty relay station that cannot synchronize time with other relay stations occurs among the plurality of relay stations, one or more relay stations are selected from the plurality of relay stations, and the radio signals are transmitted by shifting the transmission timing of the selected relay stations.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] Embodiments of the present invention relate to a notification system and a notification method.

Background Art

[0002] A disaster prevention administrative radio system used in, for example, municipal disaster prevention radio, is a system in which a master station (control station) transmits disaster information and notices from a local government to slave stations (outdoor slave stations) installed outdoors in parks, etc., and slave stations (door-to-door receivers) arranged indoors via relay stations (retransmitting slave stations), etc. In this system, conventionally, in order to prevent an interference area where a plurality of radio signals output from a plurality of relay stations reach overlappingly, relay stations in adjacent areas have been broadcasting to the slave stations in the area at different frequencies.

[0003] However, there is a shortage of allocated frequencies for disaster prevention radio, and it has become necessary to effectively utilize frequencies also in the frequency band of the disaster prevention administrative radio system. For this reason, it has been considered to transmit notification information to door-to-door receivers installed in the interference area by having each relay station transmit radio signals of the same frequency simultaneously with synchronization of transmission timings to adjacent areas.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in a system that synchronizes transmission timing, if synchronization between relay stations cannot be achieved due to a failure of the GPS receiver or a failure of the synchronization unit, a deviation in transmission timing will occur, resulting in interference of radio signals in the interference area and the possibility that the slave stations cannot receive the broadcast information. In particular, when the GPS receiver fails, the relay station operates with its internal self-running clock, and the desired D / U (desired signal-to-interference ratio) cannot be achieved in the interference area, and the slave stations in the interference area are highly likely to fail to receive the broadcast information.

[0006] The problem to be solved by the present invention is to provide a broadcast system and a broadcast method for transmitting broadcast information.

Means for Solving the Problem

[0007] The broadcast system according to the embodiment has a master station, a plurality of relay stations that relay the broadcast information transmitted from the master station, and a plurality of slave stations that receive the broadcast information transmitted from the plurality of relay stations. In the broadcast system, the plurality of relay stations synchronize their time with other relay stations and transmit radio signals each including the same carrier frequency with synchronized transmission timing. When a failed relay station occurs where the plurality of relay stations cannot synchronize their time with other relay stations, one or more relay stations are selected from the plurality of relay stations, and the transmission timing of the selected relay station is shifted to transmit a radio signal. The selected one or more relay stations include adjacent failed relay stations that share an interference area with the failed relay station.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

[0009] Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0010] In the present embodiment, an example is shown in which information of slave stations installed in the interference area and the like are registered in advance in the master station (control station), and rebroadcasting is performed only to a group of slave stations installed in the interference area (hereinafter referred to as the interference area group). (Embodiment) In the dissemination system of the disaster prevention administrative radio, it is necessary to allocate frequencies to municipalities nationwide, and the frequencies are insufficient. Therefore, in order to effectively utilize the frequency band, each relay station 2 within the same municipality performs transmission of radio signals of the same radio frequency.

[0011] FIG. 1 is a conceptual diagram of the dissemination system of the disaster prevention administrative radio system according to the embodiment.

[0012] The dissemination system of the disaster prevention administrative radio system according to the embodiment is a communication system by digital radio including a master station (control station) 1 (hereinafter referred to as the master station 1), and a plurality of slave stations 3 (slave stations 3-1 to 3-7, 3-11 to 3-17 in FIG. 1) via relay stations 2-1 and 2-2 (referred to as relay station 2 when not particularly distinguished) as necessary. Also, let the radio frequency assigned to the local government for disaster prevention administration radio shown in FIG. 1 be f1 (MHz) (hereinafter referred to as radio frequency f1). Also, let the radio signal transmitted from the master station 1 to the relay station 2 or the slave stations 3 around the master station 1 not shown in the figure be r1, and the radio signal transmitted from the relay station 2 to the surrounding slave stations be r2. Note that the relay station 2 and the slave stations 3 shown in FIG. 1 are installation examples, and there is no limitation on the number of installations.

[0013] In FIG. 1, the installation areas GA and GB respectively show groups of a plurality of slave stations 3 (hereinafter referred to as installation areas) that receive the same information transmitted by the relay stations 2-1 and 2-2. For example, the same information transmitted by the relay station 2-1 is received by the slave stations 3-1 to 3-7, and the same information transmitted by the relay station 2-2 is received by the slave stations 3-11 to 3-17. Also, the relay station 2 and the slave stations 3 within the same installation area may be referred to as an installation group. For example, in the example of FIG. 1, the relay station 2-1 and the slave stations 3-1 to 3-7 are referred to as an installation group. Also, the relay station 2-1 may be referred to as a group relay station when viewed from the slave stations 3-1 to 3-7.

[0014] The master station 1 is a control station that broadcasts the same information for local residents such as disaster prevention information by radio signal r1 of radio frequency f1. The control station is installed, for example, in a municipal office (government office), etc.

[0015] The relay station 2 has a relay function between the master station 1 and the slave stations 3. The relay station 2 receives the radio signal r1 of radio frequency f1 transmitted by the master station 1, acquires the same information from the received radio signal r1, and broadcasts the acquired same information to the slave stations 3 by radio signal r2 of radio frequency f1.

[0016] The slave station 3 includes outdoor slave stations installed outdoors such as in parks, and a plurality of door receivers arranged indoors, etc. The door receiver is distributed, for example, to a household in a mountainous area or the like where it is difficult to hear the broadcast from the outdoor slave station.

[0017] In the interference area A1, the transmission radio waves from the relay station 2-1 and the relay station 2-2 overlap and interference occurs. In this same-report system, although each relay station 2 transmits a radio signal r2 of the same radio frequency f1 at the same transmission timing, there is a difference in the reception level due to differences such as the distance from the relay station to each slave station. Therefore, the slave station 3 installed in the interference area A1 can also receive the same-report information based on D / U (the ratio of the desired wave to the interference wave). This will be shown in more detail below.

[0018] The radio signal arrival area (the reception level of the slave station 3) remains the same whether the transmission timing is synchronized or not. When the transmission timing is synchronized, the required D / U (D: the level of the desired wave radio signal from the relay station 2-2, U: the level of the interfering wave radio signal from the relay station 2-1) is less than when the transmission timing is not synchronized. Also, when the transmission timing is synchronized, the radio signal of frequency f1 from the relay station 2-1 did not affect the slave station 3-17 in terms of the D / U relationship, but it will have an impact when the synchronization is lost. More specifically, it is shown below.

[0019] Assume that the required D / U when the transmission timing is synchronized is 10 dB, and the required D / U when the transmission timing is not synchronized is 17 dB. Also, assume that the reception level of the D wave (desired wave) from the relay station 2-2 of the slave station 3-17 is 40 dBμV, and the reception level of the U wave (interfering wave) from the relay station 2-1 is 30 dBμV. In this case, if the transmission timing is synchronized, since the required D / U is 10 dB, there is no problem as long as the reception level of the U wave (interfering wave) from the relay station 2-1 is up to 30 dBμV. On the other hand, when the transmission timing is not synchronized, since a required D / U of 17 dB is needed, if the U wave is 30 dBμV, it will interfere with the D wave (desired wave).

[0020] In this reporting system, each relay station performs time synchronization so that each relay station can transmit at the same transmission timing. As a method for time synchronization of each relay station, for example, time synchronization between a plurality of relay stations 2 may be performed by a GPS system or the like. For example, a GPS receiver is installed in each relay station 2, and each relay station 2 uses a transmission frequency (carrier frequency) and a transmission timing signal (sometimes referred to as a frame signal) generated based on a reference clock, a timing signal, etc. generated by the GPS receiver to transmit reporting information.

[0021] However, in such a system, when synchronization between each relay station 2 cannot be achieved due to a failure of the GPS receiver or a failure of the synchronization unit, etc., radio signal interference occurs in the interference area A1, and there is a possibility that the slave station 3 cannot receive the reporting information. Hereinafter, a relay station 2 in which a failure such as a failure of the GPS receiver or a failure of the synchronization unit has occurred is particularly referred to as a failed relay station. Also, a relay station 2 that is not faulty but is affected by a failed relay station, such as radio signals from the failed relay station causing interference, is referred to as an adjacent failed relay station.

[0022] FIG. 2 is a functional block diagram showing a configuration example of the master station according to the embodiment. The master station 1 includes a GPS antenna 100, a GPS synchronization unit section 101, an antenna for relay stations 10, a radio section 11, and a radio control section 12, and may be provided with computer functions such as a CPU and a memory.

[0023] The GPS antenna 100 receives radio waves transmitted by GPS satellites or the like.

[0024] The GPS synchronization unit section 101 extracts and outputs a reference clock, a timing signal (1PPS), etc. from the GPS signal obtained by processing the radio waves received from the GPS antenna 100.

[0025] The antenna for relay stations 10 transmits and receives radio signals of radio frequency f1.

[0026] The radio unit 11 performs demodulation processing and decoding processing on the radio signal received by the relay station antenna 10, using the reference clock and timing signal input from the GPS synchronization unit 101, or outputs a radio signal of radio frequency r1 to the relay station antenna 10 by encoding processing and modulation processing of digital data, etc.

[0027] The radio control unit 12 generates digital data such as the same information to be output to the radio unit 11, or processes the digital data input from the radio unit 11. The radio control unit 12 may include an interference group table 121 and an interference group retransmission unit 122.

[0028] Also, the radio control unit 12 can also specify the slave station that is the transmission destination of the same information. The method for specifying the slave station that is the transmission destination of the same information enables selection for all slave stations, for a specific group, or for a specific slave station by including a flag indicating the transmission destination in the digital data and transmitting it. Here. The specific group is not necessarily limited to the relay station unit, and may be the same group for each area preset within the municipality. For example, when the same information is to be transmitted to all slave stations, the radio control unit 12 includes a flag indicating "for all slave stations" in the digital data output to the radio unit 11 and transmits it, so that the slave station 3 recognizes that the same information is "for all slave stations".

[0029] Also, in the case of a specific group, by including a group number or the like predetermined for the group of the slave station 3 to be transmitted in the digital data output to the radio unit 11 and transmitting it, the slave station 3 stores its own group number in the storage unit or the like, acquires the group number from the radio signal transmitted from the relay station 2, and recognizes that the same information is for its own group when it matches its own group number.

[0030] Also, when the same information is for a specific slave station, the radio control unit 12 includes the identification number (slave station ID) of the slave station assigned in advance for each slave station in the digital data output to the radio unit 11. Thereby, the slave station 3 can recognize that the same information is addressed to itself.

[0031] The interference group table 121 may be data stored in a memory or the like, and includes data regarding the relay station 2 to which the master station 1 transmits the broadcast information.

[0032] FIG. 3 is an example of data of the interference group table of the master station according to the embodiment. The data for the relay station 2 shown in the data column 1211 is shown for each row.

[0033] The data column 1211 indicates the identification number of the relay station 2. For example, the relay station IDs "2-1" and "2-2" in the data column 1211 correspond to the relay stations 2-1 and 2-2 in FIG. 1. The data column 1212 is data indicating whether there is a failure in the relay station 2. Specifically, it indicates the presence or absence of a failure related to the reference signal or transmission timing when the relay station 2 transmits the radio signal r2 of the radio frequency f1, such as a failure of the GPS receiver or a failure of the synchronization unit. The data column 1213 indicates the number of the relay station 2 in which interference may occur with the radio signal output by the relay station 2 shown in the data column 1211. The data column 1214 indicates the presence or absence of an interference area in the installation area of the relay station 2. The data column 1215 indicates the ID (identification number) of the slave station 3 installed in the interference area in the installation area of the relay station 2.

[0034] In the example of FIG. 3, since the relay station 2-2 is the interfering relay station for the relay station 2-1, the interference area in the data column 1214 is "Yes". Also, it is shown that the IDs of the slave stations installed in the interference area (interference area A1 in FIG. 1) of the relay station 2-1 are "3-5", "3-6", and "3-7". The relay station 2-3 in FIG. 3 (not shown in FIG. 1) is an example where there is no interfering relay station, the interference area is "No", and the ID of the relay station 2 is "No".

[0035] Note that the data shown in FIG. 3 is an example, and it is not necessarily required to provide a database for all the data shown in FIG. 3.

[0036] Returning to FIG. 2, the interference group retransmission unit 122 determines whether retransmission of the notification information is necessary based on the interference group table 121, and performs retransmission of the notification information based on the determination result.

[0037] FIG. 4 is a functional block diagram showing a configuration example of a relay station according to an embodiment. The relay station 2 includes a relay unit (for parent station) 21 and a relay unit (for child station) 22, and may have computer functions such as a CPU and a memory.

[0038] The relay unit (for parent station) 21 includes a radio unit 211 and a radio control unit 212, and mainly performs wireless communication with the parent station 1.

[0039] The radio unit 211 includes encoding / decoding processing such as modulation / demodulation processing and error correction. More specifically, the radio unit 211 acquires digital data through demodulation processing and decoding processing of the radio signal r1 of the radio frequency f1 received by the antenna 210 for the parent station, or outputs the radio signal r1 of the radio frequency f1 to the antenna 210 for the parent station through encoding processing and modulation processing of digital data.

[0040] The radio control unit 212 generates digital data such as a failure notification to be output to the radio unit 211, or processes digital data such as notification information input from the radio unit 211.

[0041] The relay unit (for child station) 22 includes a radio control unit 23, a radio unit 24, and a GPS synchronization unit 25.

[0042] The radio control unit 23 outputs digital data including, for example, notification information input from the radio control unit 212 to the radio unit 24, or outputs failure information such as the GPS synchronization unit 25 to the relay unit (for parent station) 21. The radio control unit 23 has a slave timing generation function of making the timing signal subordinate to the frame signal output by the parent station 1 when the GPS synchronization unit 25 fails, and a function of monitoring the failure of the GPS synchronization unit and the like.

[0043] The fault monitoring unit 231 monitors faults related to the transmission frequency, transmission timing, etc. when the relay unit (for slave stations) 22 transmits the synchronization information. The fault monitoring unit 231 collects fault information such as from the GPS receiver 252 of the GPS synchronization unit 25, for example, and when a fault is detected, outputs the fault information to the master station 1.

[0044] The slave timing generation unit 232 generates a timing signal (frame signal) from digital data including the synchronization information transmitted by the master station 1.

[0045] The wireless unit 24 includes a modulation unit 241, a transmission frequency generation unit 242, a self-running clock unit 243 that runs autonomously when the GPS synchronization unit 25 fails, etc., a demodulation unit 244, and a transceiver unit 245. The wireless unit 24 outputs a wireless signal including the synchronization information to the slave station antenna 240 based on the data including the synchronization information input from the wireless control unit 23, the reference clock, timing signal, etc. input from the GPS synchronization unit 25, the slave timing generation unit 232, etc.

[0046] The slave station antenna 240 outputs a wireless signal r2 of the wireless frequency f1.

[0047] The modulation unit 241 performs modulation processing to wirelessly transmit the data including the synchronization information input from the wireless control unit 23 from the slave station antenna 240.

[0048] The transmission frequency generation unit 242 generates the transmission frequency input to the modulation unit 241 based on the reference signal input from the GPS synchronization unit 25 or the self-running clock unit 243.

[0049] The self-running clock unit 243 is an internal clock that outputs a reference clock (also referred to as a self-running clock) when the GPS synchronization unit 25 fails.

[0050] The demodulation unit 244 performs demodulation processing of the wireless signal received from the slave station antenna 240.

[0051] The transmission / reception unit 245 performs a process of switching between the input from the slave station antenna 240 and the output to the slave station antenna 240.

[0052] The timing signal switching unit 246 has a switching function such as a switch that switches the timing signal (frame signal) input to the modulation unit 241 to either the output of the slave timing generation unit 232 or the output of the timing output unit 251, triggered by a failure of the GPS synchronization unit 25 or the like.

[0053] The reference signal switching unit 247 has a function such as a switch that switches the reference signal input to the transmission frequency generation unit 242 to either the reference clock output by the GPS receiver 252 or the free-running clock output by the free-running clock unit 25, triggered by a failure of the GPS synchronization unit 25 or the like.

[0054] The GPS synchronization unit 25 outputs a reference clock synchronized with the high-precision reference clock generated by the GPS receiver 252. Further, it includes a timing generation unit 251 that generates and transmits a timing signal (frame signal) synchronized with the GPS signal output by the GPS receiver 252.

[0055] In the relay station 2 in this embodiment, when the GPS synchronization unit 25 fails and becomes a failed relay station, it can no longer generate and transmit a frame signal and a reference signal synchronized with the received GPS signal. At this time, it switches to the frame signal generated by the slave timing generation unit 232 and the reference signal based on the free-running clock output by the free-running clock unit 243, respectively. As a result, it becomes impossible to achieve the desired transmission timing synchronization with the relay station 2 (referred to as an adjacent failed relay station) adjacent to the failed relay station. Consequently, the slave station 3 installed in the interference area shared by the failed relay station and the adjacent failed relay station cannot satisfy the desired D / U and cannot receive the broadcast information.

[0056] The relay station 2 with the failed GPS synchronization unit 25 uses the fault monitoring unit 231 to send a fault notification to the master station 1. After receiving the fault notification, the master station 1 performs normal feedback broadcasting to the relay station 2 with the failed GPS synchronization unit 25, and then refers to the interference group table 121 pre-registered in the master station 1, and uses the interference group retransmission unit 122 to sequentially rebroadcast the feedback information to the slave stations 3 (interference groups) within the interference areas of the faulty relay station and adjacent faulty relay stations.

[0057] Figure 5 is a functional block diagram showing a configuration example of a slave station according to an embodiment.

[0058] The slave station 3 is a wireless receiver for feedback information and may be equipped with computer functions such as a CPU and a memory. At the slave station 3, the antenna 30 receives the radio signal r2 of the radio frequency f1 transmitted by the relay station 2, and acquires the feedback information transmitted by the master station 1.

[0059] The radio unit 31 performs processing such as demodulation and decoding on the radio signal r2 of the radio frequency f1 received by the antenna 30, and acquires digital data.

[0060] The reception processing unit 32 acquires the feedback information transmitted by the master station 1 from the digital data. The acquired feedback information may be provided as voice from the speaker 34 of the slave station 3 to people in the vicinity.

[0061] The storage unit 33 is a memory or the like, and may store the identification number of the receiver assigned to the slave station 3 (which may also be referred to as the receiver ID).

[0062] Based on the feedback information acquired by the reception processing unit 32, the speaker 34 outputs the broadcast content as voice or outputs alarm information such as a siren as sound.

[0063] Figure 6 is a flowchart showing an operation example during mode change processing of the feedback system according to the embodiment.

[0064] Figure 6(a) shows the processing operation of the master station 1. Here, when the master station 1 has not received a fault notification from the relay station 2 or when no fault has occurred in all the relay stations 2, it shall be referred to as the normal mode with the normal operation state. On the other hand, when the master station 1 has received a fault notification or the like from the relay station 2 or when a fault has occurred in at least one relay station 2, it shall be referred to as the fault mode with the fault operation state. In FIG. 6(a), in step S101, the master station 1 is operating in the normal mode.

[0065] In step S102, when the master station 1 has received a fault notification from one or more relay stations 2 in the normal mode state (Yes case), it proceeds to step S103, and the master station 1 shifts to the fault mode.

[0066] FIG. 6(b) shows the processing operations of each relay station 2. Regarding the relay station 2 as well, the state of the relay station 2 where no fault has occurred shall be referred to as the normal mode. On the other hand, the state of the relay station 2 when the relay station 2 has detected its own fault and the self-running clock unit 243 has activated the self-running clock shall be referred to as the fault mode.

[0067] In FIG. 6(b), in step S201, the relay station 2 is in the normal mode where no fault has occurred. In step S202, when the relay station 2 has detected a fault in the GPS synchronization unit 25 by its own fault monitoring unit 231 in the normal mode state (Yes case), it proceeds to step S203. In step S203, the switch of the reference signal switching unit 247 is switched to the self-running clock unit 243. The clock signal (self-running clock signal) output by the self-running clock unit 243 is input to the transmission frequency generation unit 242 as a reference signal, and the transmission frequency generation unit 242 generates a transmission frequency signal based on the self-running clock signal. Note that in the normal mode, the switch of the reference signal switching unit 247 is connected to the GPS synchronization unit 25. Next, in step S204, when the relay station 2 has detected its own fault, it transmits a fault notification to the master station 1 of the installation group to which it belongs. Then, in step S205, the relay station 2 shifts to the "fault mode". Next, in step S206, the relay station 2 switches the switch to the slave timing generation unit 232 at the timing signal switching unit 246.

[0068] FIG. 7 is a flowchart showing an operation example at the time of broadcast transmission of the master station according to the embodiment.

[0069] FIG. 7(a) shows the overall flow. In FIG. 7(a), in step S121, when a broadcast transmission request occurs at the master station 1 (in the case of Yes), the process proceeds to step S122. Here, the trigger for broadcast transmission at the master station 1 may be a request from outside the broadcast system or any trigger such as a spontaneous trigger generated inside the master station 1. In step S122, the broadcast information is transmitted as a radio signal r1 of radio frequency f1. Next, in step S123, the master station 1 checks whether it is currently in the fault mode. The master station 1 may determine whether it is in the fault mode from information such as the data sequence 1212 in FIG. 3 stored in a storage unit (not shown). When the master station 1 confirms that it is in the fault mode (Yes in step S123), the process proceeds to step S124 to perform the retransmission process of the broadcast information to the interference group. Also, when there is no broadcast information transmission or when the master station 1 is not in the fault mode, the master station 1 may return to step S121 and wait until a broadcast transmission trigger occurs (No in step S121, No in step S123). The process of step S124 will be shown in more detail below.

[0070] FIG. 7(b) shows the detailed flow of the interference group retransmission process in step S124. In FIG. 7(b), in step S125, the master station 1 refers to the data in, for example, the interference group table of FIG. 3 that it holds, and selects a relay station in which there is a "yes" for a fault in data column 1212. In the case of FIG. 3, relay station 2-1 is selected. Next, the relay stations included in the interfering relay stations in data column 1213 of the selected relay station are selected. For example, in FIG. 3, relay station 2-2 is selected. Here, in step S125, relay station 2-2 is selected because although there is no fault in itself, it is affected by the faulty relay station 2-1. Next, in step S126, the master station 1 checks whether there is an interference area with the relay stations 2-1 and 2-2 selected by the above procedure. The master station 1 selects both relay stations 2-1 and 2-2 having an interference area as relay stations to retransmit the same information by referring to data column 1214 in the case of the data in the interference group table of FIG. 3, for example. In step S127, the master station 1 retransmits the same information to the relay station 2-1 selected in step S126. That is, the master station 1 transmits the same information only to the relay station 2-1 with a time shift from the same information transmission performed in step S122. Furthermore, in step S128, the master station 1 retransmits the same information to the relay station 2-2 selected in step S126. That is, the master station 1 transmits the same information only to the relay station 2-2 with a time shift from the same information transmission performed in step S122 and the retransmission to the relay station 2-1 in step S127. In this way, the master station 1 can insert data unique to each relay station 2 into the transmitted data by retransmitting the same information to the two relay stations 2 with a time shift. Step S127 is shown in more detail.

[0071] In step S127, the master station 1 retransmits the same information to the relay station 2-1 selected in step S126 with a radio signal r1 of radio frequency f1. At this time, the master station 1 may also attach the relay station ID and interference information of FIG. 3 to the same information. When the master station 1 transmits the same information to a specific relay station 2, it attaches the relay station ID of the transmission target to the same information.

[0072] Also, when there is an interference area in the installation area where the relay station 2 with the relay station ID to be transmitted is included among the relay stations to be transmitted by the master station 1, the master station 1 sets the interference information to, for example, "1", and when there is no interference area, the master station 1 sets the interference information to "0". Therefore, the master station 1 sets "1" in the interference information when performing steps S127 and S128.

[0073] The relay station 2 that has received the radio signal r1 from the master station 1 determines whether the received information is addressed to itself based on the relay station ID given to the received information.

[0074] FIG. 8 is a flowchart showing an operation example at the time of broadcast transmission of a relay station according to an embodiment.

[0075] In step S221, the relay station 2 receives the radio signal r1 transmitted from the master station 1 at the radio frequency f1 in step S127 of FIG. 7 (in the case of Yes), and in step S222, the relay station 2 acquires data by demodulation processing or the like and confirms the relay station ID of the data. Here, when the received data is addressed to itself (in the case of YES), the relay station 2 transmits the received data as a radio signal r2 of the radio frequency f1 toward the slave station 3 in the same manner as the operation in the normal mode in step S223.

[0076] On the other hand, in step S222, when the received data is not addressed to the relay station 2 (in the case of No), the relay station 2 discards the received data in step S224.

[0077] FIG. 9 is a flowchart showing an operation example at the time of broadcast transmission of a slave station according to an embodiment.

[0078] In step S301, when the slave station 3 acquires data by demodulating the radio signal r2 of the radio frequency f1 or the like (in the case of Yes), the slave station 3 proceeds to step S302. In step S302, it is determined whether the data is addressed to itself. The slave station 3 determines whether the data is addressed to itself based on, for example, the relay station ID and interference information of the received data. Note that the relay station ID and interference information are preset in the storage unit 33 of the slave station 3 or the like. The relay station ID set for the slave station 3 is the relay station ID of the relay station 2 (group relay station) installed in the same installation area as shown in FIG. 1. For example, "2-1" is set as the relay station ID for the slave stations 3-5, 3-6, and 3-7.

[0079] When the slave station 3 is installed in the interference area A1 shown in FIG. 1, "1" may be set as the interference information in the storage unit 33 of the slave station 3, and "0" may be set when it is installed in other areas.

[0080] In step S302, the slave station 3 compares the relay station ID and interference information of the received data with the relay station ID and interference information stored in its own storage unit 33, and determines that the received data is addressed to itself when, for example, both match (in the case of Yes).

[0081] In step S303, when the slave station 3 determines that the received data is addressed to itself, it performs reception processing.

[0082] On the other hand, when the slave station 3 determines that the received data is not addressed to itself (in the case of No in step S302), in step S304, it discards the received data.

[0083] Through the above steps, only the slave station 3 installed in the interference area A1 can receive the warning information. In step S303, the slave station 3 may use the warning information in various ways, such as outputting the warning information obtained from the received data as sound from the speaker 34 or sounding an alarm.

[0084] In step S128, the same processing as in step S127 is performed, but the time is shifted from step S127, and only the relay station 2-2 transmits the radio signal r2, so that only the slave stations 3 installed in the interference area A1 of the installation group of the relay station 2-2 can receive the same information. Note that the above relay station ID and interference information may be used as the receiver ID, or the receiver ID may be stored in the storage unit 33 when each slave station 3 is installed.

[0085] As described above, by transmitting the same information in a time-division manner with a time shift between the relay stations 2-1 and 2-2, the relay station 2-1 can transmit the same information only to the slave stations 3-5, 3-6, and 3-7 included in the interference group within the interference area A1, and the relay station 2-2 can transmit the same information only to the slave stations 3-15, 3-16, and 3-17 included in the interference group within the interference area A1.

[0086] By the above procedure, it is possible to transmit the same information to the slave stations 3 that have not received the same information. According to the present embodiment, although the slave stations 3 in some interference areas are subject to time-difference broadcasting, the same information can be received even when a failure occurs in the GPS receiver or the synchronization unit.

[0087] (Modification example) In the embodiment, the case where there are two relay stations 2 is shown, but it is also applicable to the case where there are three or more relay stations 2.

[0088] FIG. 10 is a conceptual diagram of a same-information system according to a modification example.

[0089] In FIG. 10(a), the radio signal arrival areas 2A-1, 2A-2, and 2A-3 indicate the radio signal arrival areas of the radio frequency r0 transmitted by the relay stations 2-1, 2-2, and 2-3, respectively. The slave stations 3 are installed in the areas where the radio signal arrival areas 2A-1, 2A-2, and 2A-3 overlap. In this case, only the relay station 2, which is the group relay station of the slave station 3, shifts the time and performs the processing of step S127 (or S128) in FIG. 7(b), so that the same effect as in the embodiment can be obtained.

[0090] In FIG. 10(b), the wireless signal coverage areas 2A-1, 2A-2, and 2A-3 indicate the coverage areas of the radio signals r2 of the radio frequency f1 transmitted by the relay stations 2-1, 2-2, and 2-3, respectively. In the coverage area 2A-2 of the radio signal r2, two interference areas are formed, and slave stations 3-1 and 3-2 are installed in each interference area. Also in this case, only the relay station 2, which is the group relay station of each of the slave stations 3-1 and 3-2, shifts the time and performs the process of step S127 (or S128) in FIG. 7(b), so that the same effect as in the embodiment can be obtained.

[0091] Note that the scenarios applicable to the embodiment are not limited to the forms shown in this modification example, and any form can be considered, and the embodiment is similarly applicable. Also, in the embodiment and the modification example, an example in which each relay station 3 is time-synchronized by a GPS system is shown, but the time synchronization method may be any method. Also, even when time synchronization is not taken among the relay stations 3, a part of this embodiment or a modification method can be applied.

[0092] According to at least one of the above-described embodiments and modification examples, it is possible to provide an information dissemination system and an information dissemination method for transmitting the same information.

[0093] Note that the present invention is not limited to the above-described embodiments as they are, and at the implementation stage, the components can be modified and embodied without departing from the gist thereof. Also, various inventions can be formed by appropriately combining a plurality of components disclosed in the above-described embodiments. For example, some components may be deleted from all the components shown in the embodiment. Further, components from different embodiments may be appropriately combined. In addition, the processes shown in flowcharts, sequence charts, etc. may be realized by software (such as programs) that operates on a computer including hardware such as an IC chip, a digital signal processor (Digital Signal Processor or DSP), or a microcomputer, or a combination of hardware and software. Also, when the claims are expressed as control logic, when expressed as a program including instructions for causing a computer to execute, and when expressed as a computer-readable recording medium storing the instructions, the device of the present invention is applied. Furthermore, the names and terms used are not limited, and other expressions that are substantially the same in content and meaning are included in the present invention.

Explanation of Reference Numerals

[0094] 1... master station, 2... relay station, 3... slave station, 10... receiving antenna, 11... radio section, 12... radio control section, 21... relay section (for master station), 22... relay section (for slave station), 23... radio control section, 24... radio section, 25... GPS antenna synchronization unit section, 100... GPS antenna, 101... GPS antenna synchronization unit section, 121... interference group table, 122... interference group retransmission section, 121... interference group table, 122... interference group retransmission section, 210... antenna for master station, 211... radio section, 212... radio control section, 232... subordinate timing generation section, 231... fault monitoring section, 241... modulation section, 242... transmission frequency generation section, 243... self-running clock section, 244... demodulation section, 245... transceiver section, 246... timing signal switching section, 247... reference signal switching section, 251... timing generation section, 252... GPS receiver.

Claims

1. In a reporting system having a master station, a plurality of relay stations that relay the reporting information transmitted from the master station, and a plurality of slave stations that receive the reporting information transmitted from the plurality of relay stations, the plurality of relay stations perform time synchronization with other relay stations and transmit radio signals each including the same carrier frequency in synchronization with the transmission timing, when a failed relay station that cannot perform time synchronization with other relay stations occurs among the plurality of relay stations, one or more relay stations are selected from the plurality of relay stations, and the transmission timing of the selected relay stations is shifted to transmit radio signals, the one or more selected relay stations include adjacent failed relay stations that share an interference area with the failed relay station, a reporting system.

2. when the slave station is installed in the interference area, including, in the one or more selected relay stations, a failed relay station or an adjacent failed relay station that includes the interference area in the radio signal reach area, the reporting system according to claim 1.

3. including, in the one or more selected relay stations, a group relay station that is a relay station for which it is predetermined to transmit a radio signal including the reporting information to the slave station, the reporting system according to claim 2.

4. the master station has relay station information regarding the presence or absence of the interference area for each of the plurality of relay stations, the reporting system according to any one of claims 1 to 3.

5. the relay station information includes information about relay stations that share the interference area for a relay station having the interference area, the reporting system according to claim 4.

6. when the master station receives a failure notification from the failed relay station, the master station selects the one or more relay stations based on the relay station information and outputs a transmission command to cause the one or more relay stations to transmit the radio signal, The notification system according to claim 5.

7. In a notification method of a notification system having a master station, a plurality of relay stations that relay the notification information transmitted from the master station, and a plurality of slave stations that receive the notification information transmitted from the plurality of relay stations, a procedure in which the plurality of relay stations perform time synchronization with other relay stations and transmit radio signals each including the same carrier frequency with synchronized transmission timings; when a failed relay station that cannot perform time synchronization with other relay stations occurs among the plurality of relay stations, a procedure of selecting one or more relay stations from the plurality of relay stations; a procedure in which the one or more selected relay stations each shift the transmission timing and transmit radio signals; comprising the one or more selected relay stations include adjacent failed relay stations that share an interference area with the failed relay station, notification method.

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