Wireless communication system, wireless communication method, base station, and central control device

Abstract

To provide a technology that allows a plurality of base stations to transmit wireless signals simultaneously with a simple configuration.SOLUTION: A wireless communication system includes a central control device that transmits a data signal with a first timing signal attached thereto, a plurality of first base stations that transmits wireless signals on the basis of the data signals, and a second base station that transmits a wireless signal on the basis of the data signal. The second base station controls the timing at which the second base station and the plurality of first base stations transmit a wireless signal on the basis of the first timing signal.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a wireless communication system and a wireless communication method. [Background technology]

[0002] Various technologies have been proposed for wireless communication systems that apply a method in which multiple base stations simultaneously transmit wireless signals, i.e., a multi-station simultaneous transmission method. For example, in the wireless communication system disclosed in Patent Document 1, multiple base stations, which are subordinate stations, are configured to be subordinate to a switching station, which is a higher-level station. Each base station has a control circuit that generates and individually controls transmission timing so that multiple base stations in one zone can transmit the same data at the same frequency and timing based on a reference timing signal from the switching station. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2766894 Summary of the Invention [Problem to be solved by the invention]

[0004] In a conventional wireless communication system that employs a multi-station simultaneous transmission method, the above control circuit must be provided in each base station, which causes problems such as a complicated system configuration and increased costs.

[0005] Therefore, the present disclosure has been made in consideration of the above-mentioned problems, and aims to provide a technology that enables multiple base stations to simultaneously transmit radio signals with a simple configuration. [Means for solving the problem]

[0006] The wireless communication system of the present disclosure comprises a central control device that transmits a data signal to which a first timing signal is added, a plurality of first base stations that transmit radio signals based on the data signal, and a second base station connected between the central control device and the plurality of first base stations and that transmits the radio signals based on the data signal, wherein the second base station controls the timing at which the second base station and the plurality of first base stations transmit the radio signals based on the first timing signal. [Effects of the Invention]

[0007] According to the present disclosure, the second base station controls the timing at which the second base station and the plurality of first base stations transmit radio signals based on the first timing signal added to the data signal. This configuration allows the plurality of base stations to simultaneously transmit radio signals with a simple configuration. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a block diagram showing a configuration of a wireless communication system according to a first embodiment. [Figure 2] 1 is a block diagram showing a configuration of a central control device according to a first embodiment. [Figure 3] FIG. 2 is a block diagram showing a configuration of a zone parent base station according to the first embodiment. [Figure 4] 5 is a timing chart showing the operation of a zone parent base station according to the first embodiment. [Figure 5] 5 is a timing chart showing the operation of a zone parent base station according to the first embodiment. [Figure 6] 10 is a flowchart showing processing by a zone parent base station according to the first embodiment. [Figure 7] 10 is a flowchart showing processing by a zone parent base station according to the first embodiment. [Figure 8] FIG. 10 is a block diagram showing a configuration of a wireless communication system according to a second embodiment. [Figure 9] FIG. 10 is a block diagram showing the configuration of a central control device according to a second embodiment. [Figure 10] FIG. 10 is a block diagram showing the configuration of a zone parent base station according to a second embodiment. [Figure 11] 10 is a flowchart showing processing of a zone parent base station according to the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] <First Embodiment> 1 is a block diagram showing the configuration of a wireless communication system according to the present embodiment 1. The wireless communication system according to the present embodiment 1 is applied to, for example, a digital train radio system using a method in which a plurality of base stations simultaneously transmit wireless signals, that is, a multi-station simultaneous transmission method.

[0010] The wireless communication system of FIG. 1 includes a central control device 100, base stations 101-1a, 101-1b, and 101-1c which are a plurality of first base stations, a zone parent base station 101-2 which is a second base station, and a carrier device 102.

[0011] The central control device 100, base stations 101-1a to 101-1c, and zone parent base station 101-2 constitute a network. The network configuration of the central control device 100, base stations 101-1a to 101-1c, and zone parent base station 101-2 may be, for example, a ring-shaped loop configuration as shown in Fig. 1. In the ring-shaped loop configuration, a signal transmitted from the central control device 100 passes through the zone parent base station 101-2 and base stations 101-1a to 101-1c and then returns to the central control device 100.

[0012] Zone parent base station 101-2 transmits a radio signal based on a data signal transmitted from central control device 100 over the network. Base stations 101-1a to 101-1c transmit a radio signal based on a data signal transmitted from central control device 100 over the network via zone parent base station 101-2. As will be described below, zone parent base station 101-2 and base stations 101-1a to 101-1c perform simultaneous multi-station transmission, transmitting radio signals of the same data at the same frequency and at the same timing, for example. The area covered by simultaneous multi-station transmission is called zone 101, and the radio signals simultaneously transmitted from zone parent base station 101-2 and base stations 101-1a to 101-1c are received by on-board station 103 within zone 101.

[0013] 1, a first zone 101a, a second zone 101b, and a third zone 101c are illustrated as zones 101. A transport device 102 that buffers or amplifies data signals is provided between the central control device 100 and the first zone 101a and the third zone 101c, which are located at a relatively large distance from the central control device 100. On the other hand, no transport device 102 is provided between the central control device 100 and the second zone 101b, which is located at a relatively small distance from the central control device 100.

[0014] In a typical wireless communication system, simultaneous transmission from multiple stations is difficult because transmission delays and variations in transmission delays occur in the network due to the influence of the carrier device 102. In contrast, the wireless communication system according to the first embodiment is able to suppress network delays and variations in network delays, as will be described below.

[0015] Zone parent base station 101-2 is connected between central control device 100 and base stations 101-1a to 101-1c, and a data signal transmitted from central control device 100 and arriving at zone 101 is received by zone parent base station 101-2. A timing signal, which is a first timing signal, is added to the data signal transmitted from central control device 100, and zone parent base station 101-2 controls the timing of transmitting radio signals for all base stations in zone 101 based on this timing signal.

[0016] For example, zone parent base station 101-2 determines whether zone parent base station 101-2 and base stations 101-1a to 101-1c, a total of four base stations, are capable of multi-station simultaneous transmission, i.e., whether they are capable of transmission at the same time. If zone parent base station 101-2 determines that multi-station simultaneous transmission is possible, it transmits the data signals to base stations 101-1a to 101-1c without actually controlling the timing of transmitting the data signals. On the other hand, if zone parent base station 101-2 determines that multi-station simultaneous transmission is not possible, it controls the timing of transmitting the data signals and transmits the data signals to base stations 101-1a to 101-1c. As described above, zone parent base station 101-2 and base stations 101-1a to 101-1c are capable of multi-station simultaneous transmission toward on-board station 103.

[0017] Next, the configurations and operations of the central control unit 100 and the zone parent base station 101-2 will be described in detail.

[0018] <Central control unit> Fig. 2 is a block diagram showing the configuration of central control device 100 according to embodiment 1. Central control device 100 in Fig. 2 includes a data processing unit 200, a zone control unit 201, and a transmission timing control unit 202. Transmission timing control unit 202 includes a transmission timing correction unit 202-1 and a timing signal addition unit 202-2.

[0019] Data processing unit 200 generates transmission information and processes reception information output from zone control unit 201. Zone control unit 201 determines zone 101 to which the transmission information generated by data processing unit 200 should be transmitted, and based on the determination result, distributes the transmission information to transmission timing control unit 202. Zone control unit 201 also outputs reception information from transmission timing control unit 202 to data processing unit 200.

[0020] Transmission timing correction section 202-1 of transmission timing control section 202 generates a data signal based on the transmission information from zone control section 201, and outputs the signal to timing signal addition section 202-2.

[0021] Furthermore, transmission timing correction section 202-1 acquires a central control correction signal that is added to a received signal transmitted from zone parent base station 101-2 via base stations 101-1a to 101-1c and received by transmission timing control section 202. Based on the central control correction signal, transmission timing correction section 202-1 appropriately corrects the timing at which the data signal is output to timing signal addition section 202-2. This appropriately corrects the timing at which central control device 100 transmits a data signal to zone parent base station 101-2. Note that reception information indicated by the portion of the received signal received by transmission timing control section 202 other than the central control correction signal is output to zone control section 201.

[0022] Timing signal adding section 202-2 adds a timing signal to the data signal from transmission timing correcting section 202-1 and transmits the signal to zone parent base stations 101-2 of first to third zones 101a to 101c. The timing signal includes time information such as the transmission time and frame time of the data signal, for example.

[0023] <Zone parent base station> Fig. 3 is a block diagram showing the configuration of zone parent base station 101-2 according to the first embodiment. Zone parent base station 101-2 in Fig. 3 includes radio processing section 300, timing determination section 301, buffer section 302, buffer control section 303, selector 304, and central control correction signal adding section 305. Radio processing section 300 includes transmitting / receiving section 300-1, radio frequency section 300-2, antenna 300-3, and GPS synchronization section 300-4.

[0024] 1 includes a radio processing unit similar to radio processing unit 300, which includes GPS synchronization unit 300-4. Zone parent base station 101-2 is synchronized with base stations 101-1a to 101-1c in one zone 101 by GPS synchronization unit 300-4, which performs GPS (Global Positioning System) synchronization.

[0025] Timing determination unit 301 acquires a timing signal added to a data signal that is transmitted from central control device 100 and input (arrives) at zone parent base station 101-2 via carrier device 102. Based on the timing signal, timing determination unit 301 determines whether zone parent base station 101-2 and base stations 101-1a to 101-1c are capable of multi-station simultaneous transmission. For example, based on the timing at which the data signal is input to zone parent base station 101-2 and the time information indicated by the timing signal, timing determination unit 301 determines whether zone parent base station 101-2 and base stations 101-1a to 101-1c are capable of multi-station simultaneous transmission. Hereinafter, the timing at which the data signal is input to zone parent base station 101-2, that is, the timing at which the data signal arrives at zone parent base station 101-2, may be referred to as the "input timing."

[0026] If the timing determination unit 301 determines that simultaneous multi-station transmission is possible, it controls the selector 304 so that the data signal that does not pass through the buffer unit 302 is output to the central control correction signal addition unit 305 .

[0027] On the other hand, if the timing determination unit 301 determines that simultaneous multi-station transmission is not possible, it controls the selector 304 so that the data signal that has passed through the buffer unit 302 is output to the central control correction signal addition unit 305. Then, the timing determination unit 301 calculates the timing at which simultaneous multi-station transmission is possible based on the timing signal and synchronization information from the GPS synchronization unit 300-4, and controls the buffer control unit 303 based on this timing, thereby controlling the read processing of the buffer unit 302. In this way, the timing at which the data signal that has passed through the buffer unit 302 is output to the central control correction signal addition unit 305 is controlled.

[0028] Furthermore, the timing determination unit 301 calculates a correction value to be used in the transmission timing correction unit 202-1 of the central control unit 100 based on the timing signal, and generates a central control correction signal corresponding to the calculated correction value.

[0029] The central control correction signal adding unit 305 outputs the data signal output from the selector 304 to the radio processing unit 300. The radio processing unit 300 performs signal processing such as modulation on the data signal from the central control correction signal adding unit 305 in the transceiver unit 300-1, and performs RF processing in the high frequency unit 300-2 to generate a radio signal, and transmits the radio signal to the on-board station 103 from the antenna 300-3.

[0030] Furthermore, central control correction signal adding section 305 adds the central control correction signal generated by timing determining section 301 to the data signal output from selector 304, and transmits the signal to base stations 101-1a to 101-1c. Base stations 101-1a to 101-1c receive the data signals in this order, and radio processing section 300 of each of base stations 101-1a to 101-1c transmits a radio signal based on the data signal.

[0031] Zone parent base station 101-2 configured as above controls the timing at which zone parent base station 101-2 and base stations 101-1a to 101-1c transmit radio signals based on the timing signal.

[0032] The base station 101-1c transmits the data signal received from the base station 101-1b to the central control device 100 via the network. The transmission timing correction unit 202-1 of the central control device 100 appropriately corrects the timing at which the central control device 100 transmits the data signal, based on the central control correction signal added to the data signal from the base station 101-1c.

[0033] <Zone parent base station operation> 4 and 5, the operation of zone parent base station 101-2 according to the first embodiment will be mainly described. When base stations 101-1a, 101-1b, and 101-1c are not to be distinguished from one another, they may be referred to as "each base station" below.

[0034] FIG. 4 is a timing chart showing control when the delay time of the data signal transmitted from the central control device 100 increases due to delay variations in the transport device 102 or the network.

[0035] 4 shows frames 400-1 to 400-5 arranged in chronological order, each frame boundary 401, transmission enable end timings 402-1 to 402-5, and data signals DATA0, DATA1, and DATA2. Transmission enable end timings 402-1 to 402-5 are timings at which zone parent base station 101-2 determines whether simultaneous transmission from multiple stations is possible.

[0036] 4, the left edge of DATA0 of zone parent base station 101-2 is to the left of transmittable end timing 402-1, which means that the input timing of DATA0 to zone parent base station 101-2 is earlier than transmittable end timing 402-1. Because the input timing of DATA0 to zone parent base station 101-2 is earlier than transmittable end timing 402-1, zone parent base station 101-2 determines in frame 400-2 that zone parent base station 101-2 and each base station are capable of simultaneous multi-station transmission.

[0037] If such a determination result is obtained, zone parent base station 101-2 outputs DATA0 to base stations 101-1a to 101-1c without passing through buffer unit 302. Thereafter, in frame 400-2, zone parent base station 101-2 and each base station transmit a radio signal based on DATA0.

[0038] 4, the left edge of DATA1 (data signal 403-1) from zone parent base station 101-2 is to the right of transmission enable end timing 402-2, which means that the input timing of DATA1 to zone parent base station 101-2 is later than transmission enable end timing 402-2. If the input timing of DATA1 to zone parent base station 101-2 is later than transmission enable end timing 402-2, base station 101-1c will not be able to prepare for transmission of DATA1 (data signal 403-2) in time for the start of frame 400-3. Therefore, zone parent base station 101-2 determines in frame 400-3 that zone parent base station 101-2 and each base station are not capable of multi-station simultaneous transmission.

[0039] If such a determination result is obtained, zone parent base station 101-2 stores DATA1 in buffer unit 302. Then, at or around transmission enable end timing 402-3, zone parent base station 101-2 outputs DATA1 stored in buffer unit 302 to base stations 101-1a to 101-1c. Thereafter, in frame 400-4, zone parent base station 101-2 and each base station transmit radio signals based on DATA1.

[0040] 4, DATA2 from central control device 100 is input to zone parent base station 101-2 at a timing earlier than transmission enable end timing 402-3. Because the previous radio signal of DATA1 (data signal 403-1) is transmitted in frame 400-4 as described above, zone parent base station 101-2 stores DATA2 in buffer unit 302. Then, zone parent base station 101-2 performs the same processing as above, and in frame 400-5, zone parent base station 101-2 and each base station transmit radio signals based on DATA2.

[0041] During this time, the central control device 100 corrects the timing of transmitting the data signal based on the central control correction signal, so that the data signal from the central control device 100 is not input to the zone parent base station 101-2 in frame 400-4. In view of this, the zone parent base station 101-2 may be configured to only perform processing to read out the data signal from the buffer unit 302 at transmission enable end timing 402-4.

[0042] In the first embodiment, zone parent base station 101-2 and each base station are synchronized with GPS. Therefore, timings shifted by a predetermined delay amount from each frame boundary 401 may be used for transmission enable end timings 402-1 to 402-5. The predetermined delay amount may be, for example, at least one of the delay amount between zone parent base station 101-2 and base station 101-1c, which is farthest from zone parent base station 101-2 in one zone 101, and the processing delay amount of radio processing unit 300 in each base station.

[0043] FIG. 5 is a timing chart showing control when the input timing of the data signal transmitted from the central control device 100 is earlier than expected due to delay variations in the transport device 102 or the network.

[0044] 5 shows frames 400-1 to 400-4 arranged in chronological order, each frame boundary 401, transmission enable end timings 402-1 to 402-3, transmission enable start timings 502-1 to 502-3, and data signals DATA0, DATA1, and DATA2. Transmission enable start timings 502-1 to 502-3 are timings at which zone parent base station 101-2 determines whether or not simultaneous multi-station transmission is possible, and are timings that precede the corresponding transmission enable end timings 402-1 to 402-3.

[0045] 5, the left edge of DATA0 of zone parent base station 101-2 is to the right of transmission enable start timing 502-1, which means that the input timing of DATA0 to zone parent base station 101-2 is later than transmission enable start timing 502-1. Because the input timing of DATA0 to zone parent base station 101-2 is later than transmission enable start timing 502-1, zone parent base station 101-2 determines in frame 400-2 that zone parent base station 101-2 and each base station are capable of multi-station simultaneous transmission.

[0046] If such a determination result is obtained, zone parent base station 101-2 outputs DATA0 to base stations 101-1a to 101-1c without passing through buffer unit 302. Thereafter, in frame 400-2, zone parent base station 101-2 and each base station transmit a radio signal based on DATA0.

[0047] In FIG. 5, the left edge of DATA1 (data signal 503-1) from zone parent base station 101-2 is to the left of transmission enable start timing 502-2, which means that the input timing of DATA1 to zone parent base station 101-2 is earlier than transmission enable start timing 502-2. If the input timing of DATA1 to zone parent base station 101-2 is earlier than transmission enable start timing 502-2, preparation for transmission of DATA1 (data signal 503-2) at base station 101-1a will be completed by the start of frame 400-2. In this case, the wireless signal will be transmitted unintentionally. For this reason, zone parent base station 101-2 determines in frame 400-3 that zone parent base station 101-2 and each base station are not capable of multi-station simultaneous transmission.

[0048] If such a determination result is obtained, zone parent base station 101-2 stores DATA1 in buffer unit 302. Then, at or around transmission enable end timing 402-2, zone parent base station 101-2 outputs DATA1 stored in buffer unit 302 to base stations 101-1a to 101-1c. Thereafter, in frame 400-3, zone parent base station 101-2 and each base station transmit radio signals based on DATA1.

[0049] During this time, central control device 100 corrects the timing of transmitting the data signal based on the central control correction signal, so that in frame 400-3, DATA2 is input to zone parent base station 101-2 at a timing later than transmission enable start timing 502-3. As a result, zone parent base station 101-2 outputs DATA2 to base stations 101-1a to 101-1c without passing through buffer unit 302, and in frame 400-4, zone parent base station 101-2 and each base station transmits a radio signal based on DATA2.

[0050] The transmittable start timings 502-1 to 502-3 may be shifted by a predetermined delay amount from each frame boundary 401. The predetermined delay amount may be, for example, the delay amount between the zone parent base station 101-2 and the base station 101-1a that is closest to the zone parent base station 101-2 in one zone 101, or the processing delay amount of the radio processing unit 300 of the zone parent base station 101-2 that completes preparation for transmission earliest.

[0051] <Generation of correction signals for central control> Next, we will explain an example of generating a central control correction signal in timing determination section 301. Cases in which buffering processing occurs in buffer section 302 in zone parent base station 101-2 are divided into the cases shown in Fig. 4 and Fig. 5 above.

[0052] The case in Figure 4 is when the timing at which the data signal is input to zone parent base station 101-2 is later than the timing at which transmission is possible and ends. In other words, this is a case where, due to a large transmission delay in the network, some base stations are unable to prepare for transmission in time for the start of the target frame in which the wireless signal should be transmitted. The case in Figure 5 is when the timing at which the data signal is input to zone parent base station 101-2 is earlier than the timing at which transmission is possible and begins. In other words, this is a case where, due to an excessively large margin being allowed for transmission delay in the network, some base stations are able to complete preparation for transmission in a frame prior to the target frame. Early timing is preferable for transmitting the data signal from central control device 100 to zone parent base station 101-2 in order to allow for a sufficient delay margin, but too early timing is undesirable because it requires buffering, which increases the amount of delay.

[0053] Therefore, the timing determination unit 301 according to the first embodiment determines whether the input timing of each frame is earlier than the transmittable start timing, based on the timing signal added by the central control device 100. If it is determined that the input timing is earlier than the transmittable start timing, the timing determination unit 301 generates a central control correction signal for delaying the transmission timing of the data signal in the central control device 100. With this configuration, the input timing can be made later than the transmittable start timing, thereby suppressing communication delays due to buffering in the buffer unit 302.

[0054] Note that a similar correction may be performed when the input timing of each frame continues to be later than the end timing of enabled transmission based on the timing signal added by the central control device 100. For example, when it is determined that the input timing is later than the end timing of enabled transmission, the timing determination unit 301 may generate a central control correction signal for causing the central control device 100 to advance the timing of transmitting the data signal. With this configuration, the input timing can be made earlier than the end timing of enabled transmission, thereby suppressing communication delays due to buffering in the buffer unit 302.

[0055] <Flowchart> 6 is a flowchart showing the processing performed by the zone parent base station 101-2 when it receives data from the central control device 100. The processing in FIG. 6 is started when the zone parent base station 101-2 receives a data signal from the central control device 100.

[0056] In step S1, zone parent base station 101-2 determines whether or not a data signal is stored in buffer unit 302. If it is determined that a data signal is stored, the process proceeds to step S5, and if it is not determined that a data signal is stored, the process proceeds to step S2.

[0057] In step S2, timing determination unit 301 determines whether the input timing is later than the transmission enable start timing based on the timing signal added by central control device 100. That is, timing determination unit 301 determines whether or not zone parent base station 101-2 and base stations 101-1a to 101-1c have completed transmission preparations in a frame earlier than the frame in which multi-station simultaneous transmission without buffering is assumed. If it is determined that the input timing is later than the transmission enable start timing, the process proceeds to step S3; if it is not determined that the input timing is later than the transmission enable start timing, the process proceeds to step S5.

[0058] In step S3, timing determination unit 301 determines whether the input timing is earlier than the end timing of enabled transmission based on the timing signal added by central control device 100. That is, timing determination unit 301 determines whether zone parent base station 101-2 and base stations 101-1a to 101-1c will be ready to transmit by the time of the frame in which simultaneous multi-station transmission without buffering is expected. If it is determined that the input timing is earlier than the end timing of enabled transmission, the process proceeds to step S4, and if it is not determined that the input timing is earlier than the end timing of enabled transmission, the process proceeds to step S5.

[0059] If the process proceeds to step S4, simultaneous transmission to multiple stations is possible using a data signal that does not pass through buffer unit 302. Therefore, in step S4, zone parent base station 101-2 transmits to base stations 101-1a to 101-1c a data signal that does not pass through buffer unit 302. Thereafter, the process in FIG. 6 ends.

[0060] If the process proceeds to step S5, simultaneous multi-station transmission is not possible using a data signal that does not pass through the buffer unit 302. Therefore, in step S5, the buffer unit 302 stores the data signal.

[0061] In step S6, timing determination unit 301 determines whether the current timing is the end timing of transmission. If it is determined that the current timing is the end timing of transmission, the process proceeds to step S7, and if it is not determined that the current timing is the end timing of transmission, the process of step S6 is performed again.

[0062] In step S7, buffer control unit 303 reads the data signal from buffer unit 302, and zone parent base station 101-2 transmits the data signal read by buffer control unit 303 to base stations 101-1a to 101-1c. After that, the processing in FIG. 6 ends.

[0063] 7 is a flowchart showing the process of generating a central control correction signal in zone parent base station 101-2. The process in FIG.

[0064] In step S11, the timing determination unit 301 acquires the timing signal added to the data signal received by the zone parent base station 101-2 from the central control device 100. Thereafter, the processes of steps S12 and S17 are carried out.

[0065] In step S12, timing determination section 301 determines whether the input timing is earlier than the transmission enable start timing by X counts or more. Note that the parameters of the transmission enable start timing and X counts are set in advance in, for example, zone parent base station 101-2. If it is determined that the input timing is earlier than the transmission enable start timing by X counts or more, the process proceeds to step S14, and if it is not determined that the input timing is earlier than the transmission enable start timing by X counts or more, the process proceeds to step S13.

[0066] In step S13, the timing determination unit 301 resets the frame counter N to initialize it to 0. After that, the process returns to step S11.

[0067] In step S14, the timing determination unit 301 increments the frame counter N by one.

[0068] In step S15, the timing determination unit 301 determines whether the frame counter N is 10 or more. That is, the timing determination unit 301 determines whether the determination that the input timing is earlier than the transmittable start timing by X counts or more has occurred for 10 or more consecutive frames. Note that the threshold value used in this example is 10, but is not limited to this. If it is determined that the frame counter N is 10 or more, the process proceeds to step S16, and if it is not determined that the frame counter N is 10 or more, the process returns to step S11.

[0069] In step S16, the timing determination unit 301 generates a central control correction signal for delaying the timing at which the central control device 100 transmits a data signal, based on the average value of the input timings of 10 frames. The central control correction signal adding unit 305 adds the central control correction signal to the data signal, and the zone parent base station 101-2 transmits the data signal to the base stations 101-1a to 101-1c. Thereafter, the processing in FIG. 7 ends. Although not shown, the data signals transmitted to the base stations 101-1a to 101-1c are transmitted to the central control device 100, and the central control device 100 delays the timing at which the data signal is transmitted, based on the central control correction signal added to the data signal.

[0070] In step S17, timing determination section 301 determines whether the input timing is later than the transmission enable end timing by Y counts or more. Note that the parameters of the transmission enable end timing and the Y count are set in advance in, for example, zone parent base station 101-2. If it is determined that the input timing is later than the transmission enable end timing by Y counts or more, the process proceeds to step S19, and if it is not determined that the input timing is later than the transmission enable end timing by Y counts or more, the process proceeds to step S18.

[0071] In step S18, the timing determination unit 301 resets the frame counter M to initialize it to 0. After that, the process returns to step S11.

[0072] In step S19, the timing determination unit 301 increments the frame counter M by one.

[0073] In step S20, timing determination unit 301 determines whether frame counter M is 10 or greater. That is, timing determination unit 301 determines whether the input timing is determined to be later than the transmittable end timing by Y counts or more for 10 or more consecutive frames. Note that the threshold value used in this example is 10, but is not limited to this. If it is determined that frame counter M is 10 or greater, the process proceeds to step S21, and if it is not determined that frame counter M is 10 or greater, the process returns to step S11.

[0074] In step S21, the timing determination unit 301 generates a central control correction signal for advancing the timing at which the central control device 100 transmits a data signal, based on the average value of the input timings of 10 frames. The central control correction signal adding unit 305 adds the central control correction signal to the data signal, and the zone parent base station 101-2 transmits the data signal to the base stations 101-1a to 101-1c. Thereafter, the processing in FIG. 7 ends. Although not shown, the data signals transmitted to the base stations 101-1a to 101-1c are transmitted to the central control device 100, and the central control device 100 advances the timing at which it transmits the data signal based on the central control correction signal added to the data signal.

[0075] <Summary of the First Embodiment> According to the above-described first embodiment, zone parent base station 101-2 centrally controls the timings at which zone parent base station 101-2 and base stations 101-1a to 101-1c transmit radio signals, based on a timing signal. With such a configuration, base stations 101-1a to 101-1c do not need circuits for timing control, and therefore simultaneous transmission from multiple stations can be achieved with a simple configuration. Furthermore, since only the input timing of zone parent base station 101-2 needs to be considered, the timings at which zone parent base station 101-2 and base stations 101-1a to 101-1c transmit radio signals can be easily controlled.

[0076] Furthermore, according to the first embodiment, the central control device 100 controls the timing of transmitting a data signal based on a central control correction signal corresponding to a correction value generated by the zone parent base station 101-2. With this configuration, it is possible to suppress communication delays caused by buffering processing in the zone parent base station 101-2.

[0077] <Embodiment 2> 8 is a block diagram showing the configuration of a wireless communication system according to the present embodiment 2. Below, among the components according to the present embodiment 2, components that are the same as or similar to the components described above are given the same or similar reference numerals, and different components will be mainly described.

[0078] In the wireless communication system according to the first embodiment shown in Fig. 1, the network configuration of the central control device 100 and the zones 101 is a single ring-shaped loop. In contrast to this, in the wireless communication system according to the second embodiment shown in Fig. 8, the network configuration of the central control device 100 and the zones 101 is a double ring-shaped loop. Furthermore, the wireless communication system according to the second embodiment includes a zone parent base station 101-2a which is a first parent base station and a zone parent base station 101-2b which is a second parent base station, instead of the zone parent base station 101-2 in Fig. 1. Note that each of the zone parent base stations 101-2a and 101-2b is included in the concept of the zone parent base station 101-2 in Fig. 1.

[0079] Zone parent base stations 101-2a and 101-2b are provided on either side of base stations 101-1a to 101-1c, sandwiching base stations 101-1a to 101-1c between them. This enables zone parent base stations 101-2a and 101-2b to perform dual network routing in which data signals are transmitted in different directions.

[0080] As will be described later, at least one of zone parent base stations 101-2a and 101-2b controls the timing at which zone parent base stations 101-2a and 101-2b and base stations 101-1a to 101-1c transmit radio signals. This makes it possible to realize a radio communication system that is independent of the direction of network routing and that provides the same effects as those of the first embodiment, thereby enabling redundant route selection processing in transmission and reception processing.

[0081] <Central control unit> Fig. 9 is a block diagram showing the configuration of central control device 100 according to the second embodiment. Transmission timing control section 202 in Fig. 9 includes first transmission timing correction section 202-1a and second transmission timing correction section 202-1b, each of which is included in the concept of transmission timing correction section 202-1, instead of transmission timing correction section 202-1 in Fig. 2. Furthermore, transmission timing control section 202 in Fig. 9 includes first timing signal addition section 202-2a and second timing signal addition section 202-2b, each of which is included in the concept of timing signal addition section 202-2, instead of timing signal addition section 202-2 in Fig. 2.

[0082] Data processing unit 200 generates transmission information and processes reception information output from zone control unit 201. Zone control unit 201 determines zone 101 to which the transmission information generated by data processing unit 200 should be transmitted, and based on the determination result, distributes the transmission information to transmission timing control unit 202. Zone control unit 201 also outputs reception information from transmission timing control unit 202 to data processing unit 200.

[0083] The first transmission timing corrector 202-1a of the transmission timing controller 202 generates a data signal based on the transmission information from the zone controller 201, and outputs the signal to the timing signal adder 202-2.

[0084] Furthermore, the first transmission timing corrector 202-1a acquires the central control correction signal that is transmitted from the zone parent base station 101-2a and added to the received signal received by the transmission timing controller 202. The first transmission timing corrector 202-1a appropriately corrects the timing at which the data signal is output to the first timing signal adder 202-2a based on the central control correction signal. This appropriately corrects the timing at which the central controller 100 transmits the data signal to the zone parent base station 101-2a. Note that reception information indicated by the portion of the received signal received by the transmission timing controller 202 other than the central control correction signal is output to the zone controller 201.

[0085] First timing signal adding section 202-2a adds a timing signal to the data signal from first transmission timing correcting section 202-1a and transmits the signal to zone parent base station 101-2a of first to third zones 101a to 101c. The timing signal includes time information such as the transmission time of the data signal and the frame time.

[0086] The second transmission timing correction unit 202-1b and the second timing signal addition unit 202-2b perform the same processing as that performed by the first transmission timing correction unit 202-1a and the first timing signal addition unit 202-2a, but for the zone parent base station 101-2b, not for the zone parent base station 101-2a.

[0087] <Zone parent base station> 10 is a block diagram showing the configuration of zone parent base station 101-2a according to Embodiment 2. The configuration of zone parent base station 101-2b is similar to the configuration of zone parent base station 101-2a.

[0088] Zone parent base station 101-2a in Fig. 10 has the same configuration as the corresponding components in Fig. 3, with zone delay timing signal adding section 306 added. Also, radio processing section 300 in Fig. 10 has the same configuration as radio processing section 300 in Fig. 3, with redundancy processing section 300-5 added, resulting in a duplicated network.

[0089] The redundancy processing unit 300-5 of the wireless processing unit 300 selects which of the two networks' data signals to use to transmit a wireless signal, and selects which of the two networks to transmit a signal received by the wireless processing unit 300.

[0090] Although not shown, base stations 101-1a to 101-1c in Fig. 8 each include a radio processing unit similar to radio processing unit 300. As a result, zone parent base stations 101-2a and 101-2b are synchronized with base stations 101-1a to 101-1c in one zone 101 by GPS synchronization unit 300-4 that performs GPS synchronization. Also, the above selection is performed by redundancy processing unit 300-5 of zone parent base stations 101-2a and 101-2b.

[0091] Zone parent base station 101-2a has the same components as zone parent base station 101-2 in Fig. 3. This enables zone parent base station 101-2a to control the timing of transmitting data signals to zone parent base station 101-2b and base stations 101-1a to 101-1c, based on a timing signal added to a data signal from central control device 100. This control may be performed by zone parent base station 101-2a or 101-2b alone, or may be performed by zone parent base station 101-2a and 101-2b in cooperation with each other.

[0092] Zone delay timing signal adding section 306 adds a zone delay timing signal, which is a second timing signal, to the data signal. The zone delay timing signal includes time information such as the time when zone parent base station 101-2a transmits the data signal.

[0093] The data signal to which the zone delay timing signal has been added by zone parent base station 101-2a is transmitted from zone parent base station 101-2a via each base station and received by zone parent base station 101-2b. Similarly, the data signal to which the zone delay timing signal has been added by zone parent base station 101-2b is transmitted from zone parent base station 101-2b via each base station and received by zone parent base station 101-2a.

[0094] Timing determination section 301 of zone parent base station 101-2a acquires the zone delay timing signal added to the data signal from zone parent base station 101-2b. Based on the zone delay timing signal, timing determination section 301 then calculates in real time the amount of delay in the section between zone parent base stations 101-2a and 101-2b, including base stations 101-1a to 101-1c, as the intra-zone delay amount. For example, timing determination section 301 calculates the intra-zone delay amount based on the zone delay timing signal from zone parent base station 101-2b and the set timing known to zone parent base station 101-2a.

[0095] Zone parent base station 101-2a controls the timings at which zone parent base stations 101-2a and 101-2b and base stations 101-1a to 101-1c transmit radio signals, based on a timing signal from central control device 100 and the amount of intra-zone delay. For example, zone parent base station 101-2a may be configured to correct at least one of the transmission enable end timing and the set timing known to zone parent base station 101-2a, based on the amount of intra-zone delay. Zone parent base station 101-2a may also be configured to control the timings at which zone parent base stations 101-2a and 101-2b and base stations 101-1a to 101-1c transmit radio signals, based on the timing signal, the transmission enable end timing, and the set timing.

[0096] Furthermore, the zone parent base station 101-2a transmits the amount of intra-zone delay to the central control device 100. Then, the central control device 100 controls the timing of transmitting data signals to the zone parent base stations 101-2a and 101-2b based on the central control correction signal and the amount of intra-zone delay.

[0097] With the above configuration, it is possible to optimize and shorten the timing control for transmitting radio signals from zone parent base stations 101-2a and 101-2b and base stations 101-1a to 101-1c. Furthermore, when the system configuration is changed, for example, when the number of base stations in zone 101 or the network path length is changed, it is possible to easily calculate the amount of delay within the zone that changes with the change. Furthermore, even after the system configuration is changed, it is possible to optimize and shorten the timing control in the same way as above.

[0098] 10, the central control correction signal adding unit 305 of the zone parent base station 101-2a is configured to add a central control correction signal to the data signal from the zone parent base station 101-2b. However, the central control correction signal adding unit 305 may be configured to add a central control correction signal to the data signal to the base stations 101-1a to 101-1c, as in the case of FIG.

[0099] <Flowchart> Fig. 11 is a flowchart showing the processing of zone parent base station 101-2a according to the second embodiment. The processing of Fig. 11 starts when zone parent base station 101-2a receives a zone delay timing signal transmitted from zone parent base station 101-2b via base stations 101-1a to 101-1c. The processing of zone parent base station 101-2b according to the second embodiment is also substantially the same as the following processing.

[0100] In step S31, the timing determination unit 301 acquires a timing signal for zone delay.

[0101] In step S32, timing determination section 301 calculates the difference between the time indicated by the zone delay timing signal and the time of the set timing known by zone parent base station 101-2a as the intra-zone delay amount. Timing determination section 301 then determines whether the intra-zone delay amount is equal to or greater than Z counts. Z count is, for example, the offset tolerance set in zone parent base station 101-2a. If it is determined that the intra-zone delay amount is equal to or greater than Z counts, the process proceeds to step S34; if it is not determined that the intra-zone delay amount is equal to or greater than Z counts, the process proceeds to step S33.

[0102] In step S33, the timing determination unit 301 resets the frame counter L to initialize it to 0. After that, the process returns to step S31.

[0103] In step S34, the timing determination unit 301 increments the frame counter L by one.

[0104] In step S35, the timing determination unit 301 determines whether the frame counter L is 10 or more. That is, the timing determination unit 301 determines whether the determination that the intra-zone delay amount is equal to or greater than the Z count has occurred for 10 or more consecutive frames. Note that the threshold value used in this example is 10, but is not limited to this. If it is determined that the frame counter L is 10 or more, the process proceeds to step S36, and if it is not determined that the frame counter L is 10 or more, the process returns to step S31.

[0105] In step S36, timing determination section 301 corrects the set timing of zone parent base station 101-2a and corrects the transmittable end timing based on the average value of the intra-zone delay amounts for 10 frames. Zone parent base station 101-2a also transmits the intra-zone delay amount to central control device 100. Thereafter, the processing of FIG. 11 ends.

[0106] <Summary of the second embodiment> According to the second embodiment described above, zone parent base stations 101-2a and 101-2b in a double-loop redundant configuration control the timings at which zone parent base stations 101-2a and 101-2b and base stations 101-1a to 101-1c transmit radio signals based on the timing signal. This configuration eliminates the need for timing control circuits in base stations 101-1a to 101-1c, making it possible to achieve simultaneous transmission from multiple stations with a simple configuration. Furthermore, since only the input timing of zone parent base stations 101-2a and 101-2b needs to be considered, the timings at which zone parent base stations 101-2a and 101-2b and base stations 101-1a to 101-1c transmit radio signals can be easily controlled.

[0107] Furthermore, according to the second embodiment, zone parent base stations 101-2a and 101-2b sandwiching base stations 101-1a to 101-1c transmit timing signals for zone delay, thereby enabling calculation of the amount of intra-zone delay. This allows for more appropriate and shorter timing control of radio signal transmission by zone parent base stations 101-2a and 101-2b and base stations 101-1a to 101-1c.

[0108] <Modification> In the above example, zone 101 is made up of three zones (first to third zones 101a to 101c), and each base station other than the zone parent base station in zone 101 is made up of three base stations (base stations 101-1a to 101-1c). However, the number of zones and the number of base stations in a zone are not limited to this.

[0109] In the above example, the network configuration is a ring-shaped loop configuration, but it is not limited to this. Any network configuration is possible as long as the base station within a zone that first receives a data signal transmitted from central control device 100 is the zone parent base station. For example, the network may be configured such that the base stations within the same zone are subordinate to the zone parent base station in a tree structure.

[0110] In the above example, the signals added by timing signal adding unit 202-2, first timing signal adding unit 202-2a, second timing signal adding unit 202-2b, and zone delay timing signal adding unit 306 include time information, but are not limited to this. For example, if GPS synchronization is configured to be performed between the zone parent base station, each base station, and central control device 100, the signals may include counter values ​​that are counted within the same system.

[0111] In the above example, when a timing deviation greater than the allowable amount occurs for 10 or more consecutive frames, a central control correction signal is generated (see FIG. 7) and timing control based on a zone delay timing signal (see FIG. 11) is performed, but this is not limited to this. For example, when the average value of the timing deviations for each frame exceeds a threshold, a central control correction signal may be generated and timing control based on a zone delay timing signal may be performed.

[0112] In the above example, the central control correction signal is generated and various corrections are made based on the average value of the input timing and the average value of the intra-zone delay amount for 10 frames in which a timing deviation exceeding the allowable amount is detected, but this is not limiting. For example, the central control correction signal may be generated and various corrections may be made based on the input timing and intra-zone delay amount in which a deviation exceeding the allowable amount is greatest among a certain number of past frames.

[0113] It should be noted that the embodiments and modifications may be freely combined, and the embodiments and modifications may be modified or omitted as appropriate. [Explanation of symbols]

[0114] 100 central control unit, 101-1a,101-1b,101-1c base station, 101-2,101-2a,101-2b zone parent base station.

Claims

1. a central control unit for transmitting a data signal having a first timing signal added thereto; a plurality of first base stations connected in series to each other and configured to transmit radio signals based on the data signals; a second base station connected between the central control device and one end of the first base stations and configured to transmit a radio signal based on the data signal; Equipped with A wireless communication system, wherein the second base station controls timings at which the second base station and the plurality of first base stations transmit the wireless signals based on the first timing signal.

2. 2. The wireless communication system according to claim 1, the second base station calculates a correction value used in the central control device based on the first timing signal; The central control device controls a timing for transmitting the data signal based on the correction value.

3. 3. The wireless communication system according to claim 1, The second base station, a first parent base station connected to one end of the plurality of first base stations, and a second parent base station connected to the other end of the plurality of first base stations, A wireless communication system in which at least one of the first parent base station and the second parent base station controls timing at which the first parent base station, the second parent base station and the plurality of first base stations transmit the wireless signals.

4. 4. The wireless communication system according to claim 3, one of the first parent base station and the second parent base station transmits a second timing signal; A wireless communication system in which the other of the first parent base station and the second parent base station calculates a delay amount of a section between the first parent base station and the second parent base station, the section including the multiple first base stations, based on the second timing signal transmitted from the one of the first parent base station and the second parent base station via the multiple first base stations.

5. 5. The wireless communication system according to claim 4, A wireless communication system in which at least one of the first parent base station and the second parent base station controls the timing at which the first parent base station, the second parent base station, and the multiple first base stations transmit the wireless signals based on the first timing signal and the delay amount.

6. 3. The wireless communication system according to claim 2, The second base station, a first parent base station connected to one end of the plurality of first base stations, and a second parent base station connected to the other end of the plurality of first base stations, At least one of the first parent base station and the second parent base station controls timings at which the first parent base station, the second parent base station and the plurality of first base stations transmit the radio signals; one of the first parent base station and the second parent base station transmits a second timing signal; the other of the first parent base station and the second parent base station calculates an amount of delay between the first parent base station and the second parent base station based on the second timing signal transmitted from the one of the first parent base station and the second parent base station via the plurality of first base stations; The central control device controls a timing for transmitting the data signal based on the correction value and the amount of delay.

7. 1. A wireless communication method using a central control device, a plurality of first base stations, and a second base station, comprising: the central control unit transmits a data signal having a first timing signal added thereto; the plurality of first base stations are connected in series to each other and transmit radio signals based on the data signal; the second base station is connected between the central control device and one end of the plurality of first base stations, and transmits a radio signal based on the data signal; The second base station controls timings at which the second base station and the plurality of first base stations transmit the radio signals based on the first timing signal.

8. A base station connected between a central control device that transmits a data signal and one end of a plurality of first base stations that are connected in series with each other and transmit radio signals based on the data signal, the base station transmitting the radio signals based on the data signal, A base station that controls timings at which the base station and the plurality of first base stations transmit the radio signals based on a first timing signal added to the data signal.

9. A base station according to claim 8, A base station that calculates, based on the first timing signal, a correction value used for controlling, by the central control device, the timing of transmitting the data signal.

10. A base station according to claim 8 or claim 9, The base station, a first parent base station connected to one end of the plurality of first base stations, and a second parent base station connected to the other end of the plurality of first base stations, A base station, wherein at least one of the first parent base station and the second parent base station controls timing at which the first parent base station, the second parent base station and the plurality of first base stations transmit the radio signals.

11. The base station according to claim 10, one of the first parent base station and the second parent base station transmits a second timing signal; A base station in which the other of the first parent base station and the second parent base station calculates the amount of delay of a section between the first parent base station and the second parent base station, the section including the multiple first base stations, based on the second timing signal transmitted from the one of the first parent base station and the second parent base station via the multiple first base stations.

12. The base station according to claim 11, A base station in which at least one of the first parent base station and the second parent base station controls the timing at which the first parent base station, the second parent base station, and the multiple first base stations transmit the radio signals based on the first timing signal and the delay amount.

13. A base station among a plurality of base stations connected in series with each other, the base station being connected between a central control device that transmits a data signal and a second base station that transmits a radio signal based on the data signal, the base station transmitting the radio signal based on the data signal, a base station that transmits the radio signal, the transmission timing of which is controlled by the second base station based on a first timing signal added to the data signal;

14. A central control device in a wireless communication system comprising: a central control device that transmits a data signal; a plurality of first base stations connected in series to each other and transmitting radio signals based on the data signal; and a second base station connected between the central control device and one end of the plurality of first base stations and transmitting radio signals based on the data signal, a central control device that adds to the data signal a first timing signal used by the second base station to control the timing at which the second base station and the plurality of first base stations transmit their radio signals; 15. The central control device according to claim 14, a central control device that controls a timing of transmitting the data signal based on a correction value calculated by the second base station based on the first timing signal; 16. The central control device according to claim 15, The second base station, a first parent base station connected to one end of the plurality of first base stations, and a second parent base station connected to the other end of the plurality of first base stations, one of the first parent base station and the second parent base station transmits a second timing signal; the other of the first parent base station and the second parent base station calculates an amount of delay between the first parent base station and the second parent base station based on the second timing signal transmitted from the one of the first parent base station and the second parent base station via the plurality of first base stations; A central control device controls a timing for transmitting the data signal based on the correction value and the amount of delay.

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