Wireless communication system, wireless communication method, base station, central control unit

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] This disclosure relates to a wireless communication system 、 and a wireless communication method , base station, central control unit .

Background Art

[0002] Regarding a wireless communication system that applies a method in which a plurality of base stations transmit wireless signals simultaneously, that is, a multi-station simultaneous transmission method, various technologies have been proposed. For example, in the wireless communication system of Patent Document 1, a plurality of base stations as subordinate stations are configured to be subordinate to an exchange station as a superior station. Each base station has a control circuit that individually controls the generation of transmission timing and the transmission timing so that a plurality of base stations within one zone can transmit the same data at the same frequency and the same timing based on a reference timing signal from the exchange station or the like.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a conventional wireless communication system that applies a multi-station simultaneous transmission method, since it is necessary to provide the above control circuit in each base station, there are problems such as the system configuration becoming complicated and the cost increasing.

[0005] Therefore, in view of the above problems, this disclosure has been made, and an object thereof is to provide a technology that enables a plurality of base stations to transmit wireless signals simultaneously with a simple configuration.

Means for Solving the Problems

[0006] The wireless communication system relating to this disclosure includes a central control unit that transmits a data signal to which a first timing signal has been added, They are connected in series with each other, A plurality of first base stations that transmit wireless signals based on the data signals, and the central control unit and the plurality of first base stations one part The system comprises a second base station connected between the first base station and the data signal, the second base station controlling the timing at which the second base station and the plurality of first base stations transmit the radio signal based on the first timing signal. [Effects of the Invention]

[0007] According to this disclosure, the second base station controls the timing at which the second base station and multiple first base stations transmit radio signals based on a first timing signal added to the data signal. With this configuration, multiple base stations can transmit radio signals simultaneously in a simple configuration. [Brief explanation of the drawing]

[0008] [Figure 1] This is a block diagram showing the configuration of the wireless communication system according to Embodiment 1. [Figure 2] This is a block diagram showing the configuration of the central control unit according to Embodiment 1. [Figure 3] This is a block diagram showing the configuration of the zone parent base station according to Embodiment 1. [Figure 4] This is a timing chart showing the operation of the zone master base station according to Embodiment 1. [Figure 5] This is a timing chart showing the operation of the zone master base station according to Embodiment 1. [Figure 6] This is a flowchart showing the processing of a zone parent base station according to Embodiment 1. [Figure 7] This is a flowchart showing the processing of a zone parent base station according to Embodiment 1. [Figure 8] This is a block diagram showing the configuration of the wireless communication system according to Embodiment 2. [Figure 9] This is a block diagram showing the configuration of the central control unit according to Embodiment 2. [Figure 10] This is a block diagram showing the configuration of the zone parent base station according to Embodiment 2. [Figure 11] This is a flowchart showing the processing of the zone parent base station according to Embodiment 2. [Modes for carrying out the invention]

[0009] <Embodiment 1> Figure 1 is a block diagram showing the configuration of the wireless communication system according to this embodiment 1. The wireless communication system according to this embodiment 1 is applicable, for example, to a digital train radio system that uses a method in which multiple base stations transmit radio signals simultaneously, that is, a dual-station simultaneous transmission method.

[0010] The wireless communication system shown in Figure 1 comprises a central control unit 100, multiple first base stations 101-1a, 101-1b, 101-1c, a second base station zone master base station 101-2, and a carrier device 102.

[0011] The central control unit 100, base stations 101-1a to 101-1c, and zone master base station 101-2 constitute a network. A possible network configuration for the central control unit 100, base stations 101-1a to 101-1c, and zone master base station 101-2 is a ring-shaped loop configuration, as shown in Figure 1. In a ring-shaped loop configuration, signals transmitted from the central control unit 100 pass through zone master base station 101-2 and base stations 101-1a to 101-1c before returning to the central control unit 100.

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

[0013] In the example of FIG. 1, as zone 101, a first zone 101a, a second zone 101b, and a third zone 101c are illustrated. A carrier device 102 for buffering or amplifying a data signal is provided between the central control device 100 and the first zone 101a and the third zone 101c having a relatively large distance from the central control device 100. On the other hand, the carrier device 102 is not provided between the central control device 100 and the second zone 101b having a relatively small distance from the central control device 100.

[0014] In a general wireless communication system, due to the influence of the carrier device 102 or the like, transmission delay in the network occurs or variation in the transmission delay occurs, making multi-station simultaneous transmission difficult. On the other hand, in the wireless communication system according to the first embodiment, as will be described below, it is possible to suppress network delay and variation in network delay.

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

[0016] For example, the zone parent base station 101-2 determines whether a total of four base stations, namely the zone parent base station 101-2 and the base stations 101-1a to 101-1c, can perform multi-station simultaneous transmission, that is, whether they can transmit at the same timing. When the zone parent base station 101-2 determines that multi-station simultaneous transmission is possible, it transmits the data signal to the base stations 101-1a to 101-1c without substantially controlling the timing for transmitting the data signal. On the other hand, when the zone parent base station 101-2 determines that multi-station simultaneous transmission is not possible, it controls the timing for transmitting the data signal and transmits the data signal to the base stations 101-1a to 101-1c. As described above, the zone parent base station 101-2 and the base stations 101-1a to 101-1c can perform multi-station simultaneous transmission toward the on-vehicle unit 103.

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

[0018] <Central Control Device> FIG. 2 is a block diagram showing the configuration of the central control device 100 according to Embodiment 1. The 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. The transmission timing control unit 202 includes a transmission timing correction unit 202-1 and a timing signal addition unit 202-2.

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

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

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

[0022] The timing signal addition unit 202-2 adds a timing signal to the data signal from the transmission timing correction unit 202-1 and transmits it to the zone master base stations 101-2 of the 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.

[0023] <Zone Parent Base Station> Figure 3 is a block diagram showing the configuration of a zone master base station 101-2 according to this embodiment 1. The zone master base station 101-2 in Figure 3 comprises a wireless processing unit 300, a timing determination unit 301, a buffer unit 302, a buffer control unit 303, a selector 304, and a central control correction signal addition unit 305. The wireless processing unit 300 comprises a transmitting / receiving unit 300-1, a high-frequency unit 300-2, an antenna 300-3, and a GPS synchronization unit 300-4.

[0024] Although not shown in the diagram, base stations 101-1a to 101-1c in Figure 1 are equipped with a radio processing unit similar to the radio processing unit 300, which includes a GPS synchronization unit 300-4. The zone parent base station 101-2 is synchronized with base stations 101-1a to 101-1c within a single zone 101 by the GPS synchronization unit 300-4, which performs GPS (Global Positioning System) synchronization.

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

[0026] If the timing determination unit 301 determines that simultaneous transmission from multiple stations is possible, it controls the selector 304 so that data signals that do not pass through the buffer unit 302 are output to the central control correction signal addition unit 305.

[0027] On the other hand, if the timing determination unit 301 determines that simultaneous transmission from multiple stations 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. The timing determination unit 301 then calculates the timing at which simultaneous transmission from multiple stations is possible based on the timing signal and the synchronization information of the GPS synchronization unit 300-4, and controls the buffer control unit 303 based on that timing to control the readout process of the buffer unit 302. This controls 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.

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

[0029] The central control correction signal addition unit 305 outputs the data signal output from the selector 304 to the wireless processing unit 300. The wireless processing unit 300 generates a wireless signal by performing signal processing such as modulation on the data signal from the central control correction signal addition unit 305 in the transmitting / receiving unit 300-1 and RF processing in the high-frequency unit 300-2, and transmits the wireless signal to the on-board station 103 from the antenna 300-3.

[0030] Furthermore, the central control correction signal addition unit 305 adds the central control correction signal generated by the timing determination unit 301 to the data signal output from the selector 304 and transmits it to the base stations 101-1a to 101-1c. The base stations 101-1a to 101-1c receive the data signals in this order, and each of the wireless processing units 300 of the base stations 101-1a to 101-1c transmits a wireless signal based on the data signal.

[0031] As configured above, the zone master base station 101-2 controls the timing at which the zone master 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 base station 101-1b to the central control unit 100 via the network. The transmission timing correction unit 202-1 of the central control unit 100 appropriately corrects the timing at which the central control unit 100 transmits the data signal based on the central control correction signal added to the data signal from base station 101-1c.

[0033] <Operation of the Zone Parent Base Station> The operation of the zone master base station 101-2 according to this embodiment 1 will be mainly explained below with reference to Figures 4 and 5. Note that when base stations 101-1a, 101-1b, and 101-1c are not distinguished, they may be referred to as "each base station" below.

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

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

[0036] In Figure 4, the fact that the leftmost edge of DATA0 at zone parent base station 101-2 is to the left of the transmit-ready end timing 402-1 means that the input timing of DATA0 to zone parent base station 101-2 is earlier than the transmit-ready end timing 402-1. Since the input timing of DATA0 to zone parent base station 101-2 is earlier than the transmit-ready 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 transmission.

[0037] If such a determination result is obtained, the zone parent base station 101-2 outputs DATA0, which does not pass through the buffer unit 302, to base stations 101-1a to 101-1c. Subsequently, in frame 400-2, the zone parent base station 101-2 and each base station transmit radio signals based on DATA0.

[0038] In Figure 4, the fact that the left end of DATA1 (data signal 403-1) from the zone parent base station 101-2 is to the right of the transmit-ready end timing 402-2 means that the input timing of DATA1 to the zone parent base station 101-2 is later than the transmit-ready end timing 402-2. If the input timing of DATA1 to the zone parent base station 101-2 is later than the transmit-ready end timing 402-2, the preparation for transmission of DATA1 (data signal 403-2) at base station 101-1c will not be completed in time for the start of frame 400-3. For this reason, the zone parent base station 101-2 determines in frame 400-3 that the zone parent base station 101-2 and each base station are not capable of simultaneous transmission across multiple stations.

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

[0040] In Figure 4, DATA2 from the central control unit 100 is input to the zone master base station 101-2 earlier than the transmission termination timing 402-3. The preceding radio signal DATA1 (data signal 403-1) is transmitted in frame 400-4 as described above, so the zone master base station 101-2 stores DATA2 in the buffer unit 302. Then, the zone master base station 101-2 performs the same processing as above, and in frame 400-5, the zone master base station 101-2 and each base station transmit radio signals based on DATA2.

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

[0042] In this embodiment 1, the zone parent base station 101-2 and each base station are GPS synchronized. Therefore, for the transmittable termination timings 402-1 to 402-5, timings shifted from each frame boundary 401 by a predetermined delay amount may be used. The predetermined delay amount may be, for example, at least one of the following: the delay amount between the base station 101-1c furthest from the zone parent base station 101-2 within a single zone 101 and the zone parent base station 101-2, and the processing delay amount of the radio processing unit 300 at each base station.

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

[0044] Figure 5 illustrates frames 400-1 to 400-4 arranged in chronological order, each frame boundary 401, the end of transmission time 402-1 to 402-3, the start of transmission time 502-1 to 502-3, and the data signals DATA0, DATA1, and DATA2. The start of transmission time 502-1 to 502-3 are the timings at which the zone parent base station 101-2 determines whether simultaneous transmission by multiple stations is possible, and these timings are earlier than the corresponding end of transmission time 402-1 to 402-3.

[0045] In Figure 5, the fact that the leftmost edge of DATA0 at zone parent base station 101-2 is to the right of the transmit-ready start timing 502-1 means that the input timing of DATA0 to zone parent base station 101-2 is later than the transmit-ready start timing 502-1. Because the input timing of DATA0 to zone parent base station 101-2 is later than the transmit-ready 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 simultaneous transmission.

[0046] If such a determination result is obtained, the zone parent base station 101-2 outputs DATA0, which does not pass through the buffer unit 302, to base stations 101-1a to 101-1c. Subsequently, in frame 400-2, the zone parent base station 101-2 and each base station transmit radio signals based on DATA0.

[0047] In Figure 5, the fact that the leftmost end of DATA1 (data signal 503-1) from the zone master base station 101-2 is to the left of the transmit-ready start timing 502-2 means that the input timing of DATA1 to the zone master base station 101-2 is earlier than the transmit-ready start timing 502-2. If the input timing of DATA1 to the zone master base station 101-2 is earlier than the transmit-ready start timing 502-2, the preparation for transmitting DATA1 (data signal 503-2) at base station 101-1a will be completed by the start of frame 400-2. In this case, the radio signal will be transmitted unintentionally. For this reason, the zone master base station 101-2 determines in frame 400-3 that the zone master base station 101-2 and each base station are not capable of simultaneous transmission by multiple stations.

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

[0049] During this time, the central control unit 100 corrects the timing of transmitting the data signal based on the central control correction signal, so in frame 400-3, DATA2 is input to the zone master base station 101-2 at a later timing than the transmission start timing 502-3. As a result, the zone master base station 101-2 outputs DATA2, which does not pass through the buffer unit 302, to base stations 101-1a to 101-1c, and in frame 400-4, the zone master base station 101-2 and each base station transmit radio signals based on DATA2.

[0050] Furthermore, for the transmission start timings 502-1 to 502-3, timings shifted from each frame boundary 401 by a predetermined delay amount may be used. The predetermined delay amount may be, for example, the delay amount between the base station 101-1a closest to the zone parent base station 101-2 within a single zone 101 and the zone parent base station 101-2, or the processing delay amount of the radio processing unit 300 of the zone parent base station 101-2, which completes transmission preparation as quickly as possible.

[0051] <Generation of correction signals for central control> Next, an example of generating a correction signal for central control in the timing determination unit 301 will be described. Cases in which buffer processing occurs in the buffer unit 302 at the zone parent base station 101-2 can be divided into the cases shown in Figure 4 and Figure 5 above.

[0052] In the case of Figure 4, the input timing of the data signal to the zone master base station 101-2 is later than the transmission-ready end timing. In other words, due to large transmission delays in the network, some base stations are unable to complete their transmission preparations in time for the start of the target frame in which they should transmit the radio signal. In the case of Figure 5, the input timing of the data signal to the zone master base station 101-2 is earlier than the transmission-ready start timing. In other words, because too much margin is provided for the transmission delays in the network, some base stations complete their transmission preparations within the frame before the target frame. As for the timing of transmitting the data signal from the central control unit 100 to the zone master base station 101-2, an early timing is preferable to allow for sufficient delay margins, but a timing that is too early is undesirable because it requires buffering and causes an increase in the amount of delay.

[0053] Therefore, the timing determination unit 301 in this embodiment 1 determines whether the input timing of each frame is earlier than the transmission start timing based on the timing signal added by the central control unit 100. If it is determined that the input timing is earlier than the transmission start timing, the timing determination unit 301 generates a central control correction signal to delay the transmission timing of the data signal in the central control unit 100. With this configuration, the input timing can be made later than the transmission start timing, thereby suppressing communication delays caused by buffer processing in the buffer unit 302.

[0054] Furthermore, based on the timing signals added by the central control unit 100, the same correction may be performed if the input timing for each frame continues to be slower than the transmission-ready end timing. For example, if the input timing is determined to be slower than the transmission-ready end timing, the timing determination unit 301 may generate a central control correction signal to speed up the transmission timing of the data signal in the central control unit 100. With such a configuration, the input timing can be made faster than the transmission-ready end timing, thereby suppressing communication delays caused by buffer processing in the buffer unit 302.

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

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

[0057] In step S2, the timing determination unit 301 determines, based on the timing signal added by the central control unit 100, whether the input timing is later than the transmission start timing. That is, the timing determination unit 301 determines whether the transmission preparation is not complete in a frame prior to the frame in which the zone parent base station 101-2 and base stations 101-1a to 101-1c are expected to transmit simultaneously without buffer processing. If it is determined that the input timing is later than the transmission start timing, the process proceeds to step S3; otherwise, the process proceeds to step S5.

[0058] In step S3, the timing determination unit 301 determines, based on the timing signal added by the central control device 100, whether the input timing is earlier than the transmission-ready end timing. That is, the timing determination unit 301 determines whether the transmission preparation is complete by the frame in which the zone parent base station 101-2 and base stations 101-1a to 101-1c are expected to transmit simultaneously without buffer processing. If it is determined that the input timing is earlier than the transmission-ready end timing, the process proceeds to step S4; otherwise, the process proceeds to step S5.

[0059] If the process proceeds to step S4, simultaneous transmission to multiple stations is possible using data signals that do not pass through the buffer unit 302. Therefore, in step S4, the zone master base station 101-2 transmits data signals that do not pass through the buffer unit 302 to base stations 101-1a to 101-1c. After that, the process shown in Figure 6 is completed.

[0060] If the process proceeds to step S5, simultaneous transmission to multiple stations is not possible with data signals that do not pass through the buffer unit 302. For this reason, in step S5, the buffer unit 302 stores the data signals.

[0061] In step S6, the timing determination unit 301 determines whether the current timing is the end timing for transmission. If it is determined that the current timing is the end timing for transmission, the process proceeds to step S7. If it is not determined that the current timing is the end timing for transmission, the process in step S6 is repeated.

[0062] In step S7, the buffer control unit 303 reads the data signal from the buffer unit 302, and the zone master base station 101-2 transmits the data signal read by the buffer control unit 303 to base stations 101-1a to 101-1c. After that, the process shown in Figure 6 is completed.

[0063] Figure 7 is a flowchart showing the process for generating a correction signal for central control at the zone master base station 101-2. The process in Figure 7 starts when the zone master base station 101-2 receives a data signal from the central control unit 100.

[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 unit 100. Subsequently, the processes in steps S12 and S17 are carried out.

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

[0066] In step S13, the timing determination unit 301 performs a reset, initializing the frame counter N 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 greater. That is, the timing determination unit 301 determines whether the determination that the input timing is X counts or more earlier than the transmission start timing has occurred for 10 frames or more consecutively. Note that the threshold used in this example is 10, but it is not limited to this value. If it is determined that the frame counter N is 10 or greater, the process proceeds to step S16; if it is not determined that the frame counter N is 10 or greater, the process returns to step S11.

[0069] In step S16, the timing determination unit 301 generates a central control correction signal based on the average value of the input timings of 10 frames to delay the timing at which the central control unit 100 transmits the data signal. The central control correction signal addition 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 base stations 101-1a to 101-1c. After that, the process shown in Figure 7 is completed. Although not shown, the data signals transmitted to base stations 101-1a to 101-1c are transmitted to the central control unit 100, and the central control unit 100 delays the timing at which it transmits the data signal based on the central control correction signal added to the data signal.

[0070] In step S17, the timing determination unit 301 determines whether the input timing is delayed by Y count or more compared to the transmission-ready end timing. The parameters for the transmission-ready end timing and Y count are set in advance, for example, by the zone parent base station 101-2. If it is determined that the input timing is delayed by Y count or more compared to the transmission-ready end timing, the process proceeds to step S19. If it is not determined that the input timing is delayed by Y count or more compared to the transmission-ready end timing, the process proceeds to step S18.

[0071] In step S18, the timing determination unit 301 performs a reset, initializing the frame counter M 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, the timing determination unit 301 determines whether the frame counter M is 10 or greater. That is, the timing determination unit 301 determines whether the determination that the input timing is Y count or more later than the transmission end timing has occurred for 10 frames or more consecutively. Note that the threshold used in this example is 10, but it is not limited to this value. If it is determined that the frame counter M is 10 or greater, the process proceeds to step S21; if it is not determined that the 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 based on the average value of the input timings of 10 frames to advance the timing at which the central control unit 100 transmits the data signal. The central control correction signal addition 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 base stations 101-1a to 101-1c. After that, the process shown in Figure 7 is completed. Although not shown, the data signals transmitted to base stations 101-1a to 101-1c are transmitted to the central control unit 100, and the central control unit 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 Embodiment 1> According to this embodiment 1 described above, the zone master base station 101-2 centrally controls the timing at which the zone master base station 101-2 and base stations 101-1a to 101-1c transmit radio signals based on timing signals. With this configuration, there is no need for timing control circuits in base stations 101-1a to 101-1c, so simultaneous transmission from multiple stations can be achieved with a simple configuration. Furthermore, since only the input timing of the zone master base station 101-2 needs to be considered, the timing at which the zone master base station 101-2 and base stations 101-1a to 101-1c transmit radio signals can be easily controlled.

[0076] Furthermore, according to this embodiment 1, the central control unit 100 controls the timing of transmitting data signals based on a central control correction signal corresponding to a correction value generated by the zone parent base station 101-2. With this configuration, communication delays caused by buffer processing in the zone parent base station 101-2 can be suppressed.

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

[0078] In the wireless communication system according to Embodiment 1 shown in Figure 1, the network configuration of the central control unit 100 and zone 101 was a single ring-shaped loop. In contrast, in the wireless communication system according to Embodiment 2 shown in Figure 8, the network configuration of the central control unit 100 and zone 101 is a double ring-shaped loop. Furthermore, the wireless communication system according to Embodiment 2 includes a first parent base station, zone parent base station 101-2a, and a second parent base station, zone parent base station 101-2b, instead of the zone parent base station 101-2 in Figure 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 Figure 1.

[0079] Zone parent base stations 101-2a and 101-2b are located at both ends of base stations 101-1a to 101-1c, flanking base stations 101-1a to 101-1c. This allows zone parent base stations 101-2a and 101-2b to perform dual network routing, where the direction of data signal transmission is different for each other.

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

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

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

[0083] The first transmission timing correction unit 202-1a of the transmission timing control unit 202 generates a data signal based on the transmission information from the zone control unit 201 and outputs it to the timing signal addition unit 202-2.

[0084] Furthermore, the first transmission timing correction unit 202-1a acquires the central control correction signal that is attached to the received signal transmitted from the zone master base station 101-2a and received by the transmission timing control unit 202. Based on the central control correction signal, the first transmission timing correction unit 202-1a appropriately corrects the timing at which the data signal is output to the first timing signal attachment unit 202-2a. This appropriately corrects the timing at which the central control device 100 transmits the data signal to the zone master base station 101-2a. The received information, which is the part of the received signal received by the transmission timing control unit 202 other than the central control correction signal, is output to the zone control unit 201.

[0085] The first timing signal addition unit 202-2a adds a timing signal to the data signal from the first transmission timing correction unit 202-1a and transmits it to the zone master base stations 101-2a of the 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 the first transmission timing correction unit 202-1a and the first timing signal addition unit 202-2a, but with respect to the zone parent base station 101-2b, not to the zone parent base station 101-2a.

[0087] <Zone Parent Base Station> Figure 10 is a block diagram showing the configuration of zone parent base station 101-2a according to this second embodiment. Note that the configuration of zone parent base station 101-2b is the same as the configuration of zone parent base station 101-2a.

[0088] The zone master base station 101-2a in Figure 10 is similar to the configuration in Figure 3, with the addition of a zone delay timing signal addition unit 306 to the corresponding components. Furthermore, the wireless processing unit 300 in Figure 10 is similar to the wireless processing unit 300 in Figure 3, with the addition of a redundant processing unit 300-5, resulting in a redundant network.

[0089] The redundant 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 also selects which of the two networks to transmit a received signal received by the wireless processing unit 300 to.

[0090] Although not shown in the diagram, base stations 101-1a to 101-1c in Figure 8 are equipped with a wireless processing unit similar to the wireless processing unit 300. As a result, the GPS synchronization unit 300-4, which performs GPS synchronization, synchronizes the zone parent base stations 101-2a and 101-2b with the base stations 101-1a to 101-1c within a single zone 101. Furthermore, the redundancy processing unit 300-5 of the zone parent base stations 101-2a and 101-2b makes the above selection.

[0091] Zone base station 101-2a has the same components as zone base station 101-2 in Figure 3. This allows zone base station 101-2a to control the timing of transmitting data signals to zone base station 101-2b and base stations 101-1a to 101-1c based on timing signals added to the data signals from the central control unit 100. This control may be performed by either zone base station 101-2a or 101-2b, or it may be performed jointly by zone base stations 101-2a and 101-2b.

[0092] The zone delay timing signal addition unit 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 the zone parent base station 101-2a transmits the data signal.

[0093] Data signals with a zone delay timing signal added at zone master base station 101-2a are transmitted from zone master base station 101-2a via each base station and received at zone master base station 101-2b. Similarly, data signals with a zone delay timing signal added at zone master base station 101-2b are transmitted from zone master base station 101-2b via each base station and received at zone master base station 101-2a.

[0094] The timing determination unit 301 of the zone parent base station 101-2a acquires a zone delay timing signal attached to the data signal from the zone parent base station 101-2b. Based on the zone delay timing signal, the timing determination unit 301 calculates 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, in real time as the in-zone delay amount. For example, the timing determination unit 301 calculates the in-zone delay amount based on the zone delay timing signal from the zone parent base station 101-2b and the set timing known to the zone parent base station 101-2a.

[0095] The zone master base station 101-2a controls the timing at which zone master base stations 101-2a, 101-2b and base stations 101-1a to 101-1c transmit radio signals based on timing signals from the central control unit 100 and the amount of intra-zone delay. For example, the zone master base station 101-2a may be configured to correct at least one of the transmit-ready end timing and a set timing known to the zone master base station 101-2a based on the amount of intra-zone delay. The zone master base station 101-2a may then be configured to control the timing at which zone master base stations 101-2a, 101-2b and base stations 101-1a to 101-1c transmit radio signals based on timing signals, the transmit-ready end timing, and the set timing.

[0096] Furthermore, the zone master base station 101-2a transmits the in-zone delay amount to the central control unit 100. The central control unit 100 then controls the timing for transmitting data signals to the zone master base stations 101-2a and 101-2b based on the central control correction signal and the in-zone delay amount.

[0097] With the above configuration, the timing control for transmitting radio signals by the zone parent base stations 101-2a, 101-2b and base stations 101-1a to 101-1c can be optimized and shortened. 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, the amount of in-zone delay that changes as a result of the change can be easily calculated. In addition, even after the system configuration has been changed, the timing control can be optimized and shortened in the same way as described above.

[0098] In the example shown in Figure 10, the central control correction signal addition 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 addition unit 305 may also be configured to add a central control correction signal to the data signals to base stations 101-1a to 101-1c, as in Figure 3.

[0099] <Flowchart> Figure 11 is a flowchart showing the processing of zone parent base station 101-2a according to this second embodiment. The processing in Figure 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 this second embodiment is generally the same as the processing described below.

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

[0101] In step S32, the timing determination unit 301 calculates the difference between the time indicated by the zone delay timing signal and the time of the set timing known by the zone parent base station 101-2a as the zone delay amount. The timing determination unit 301 then determines whether the zone delay amount is greater than or equal to Z count. Z count is, for example, the offset tolerance set within the zone parent base station 101-2a. If it is determined that the zone delay amount is greater than or equal to Z count, the process proceeds to step S34; otherwise, the process proceeds to step S33.

[0102] In step S33, the timing determination unit 301 performs a reset, initializing the frame counter L 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 greater. That is, the timing determination unit 301 determines whether the determination that the zone delay amount is 10 or greater has occurred for 10 consecutive frames or more. Note that the threshold used in this example is 10, but it is not limited to this. If it is determined that the frame counter L is 10 or greater, the process proceeds to step S36; if it is not determined that the frame counter L is 10 or greater, the process returns to step S31.

[0105] In step S36, the timing determination unit 301 corrects the timing set by the zone parent base station 101-2a and the transmission termination timing based on the average value of the zone delay amount over 10 frames. The zone parent base station 101-2a also transmits the zone delay amount to the central control unit 100. After that, the process shown in Figure 11 is completed.

[0106] <Summary of Embodiment 2> According to this embodiment 2 described above, in a redundant configuration with a double loop, the zone parent base stations 101-2a and 101-2b control the timing at which the zone parent base stations 101-2a and 101-2b and base stations 101-1a to 101-1c transmit radio signals based on timing signals. With this configuration, a circuit for timing control is not required in base stations 101-1a to 101-1c, so simultaneous transmission from multiple stations can be achieved with a simple configuration. Furthermore, since only the input timing of the zone parent base stations 101-2a and 101-2b needs to be considered, the timing at which the 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 this second embodiment, the zone parent base stations 101-2a and 101-2b, which sandwich base stations 101-1a to 101-1c, transmit zone delay timing signals, making it possible to calculate the in-zone delay amount. This makes it possible to optimize and shorten the timing control for transmitting radio signals by the zone parent base stations 101-2a and 101-2b and base stations 101-1a to 101-1c.

[0108] <Variation> In the example above, Zone 101 consisted of three zones (Zones 101a to 101c), and each base station within Zone 101, excluding the zone parent base station, consisted of three base stations (Base stations 101-1a to 101-1c). However, the number of zones and the number of base stations within each zone are not limited to this example.

[0109] Furthermore, while the network configuration in the above example was a ring-shaped loop configuration, it is not limited to this. Any network configuration is acceptable as long as the base station that first receives the data signal transmitted from the central control unit 100 among the base stations within the zone is the zone parent base station. For example, a network configuration in which base stations within the same zone are subordinate to the zone parent base station in a tree-like structure is also possible.

[0110] Furthermore, in the above examples, the signals added by the timing signal addition unit 202-2, the first timing signal addition unit 202-2a, the second timing signal addition unit 202-2b, and the zone delay timing signal addition unit 306 included time information, but are not limited to this. For example, if GPS synchronization is performed between the zone master base station, each base station, and the central control unit 100, the above signals may include counter values ​​that are marked within the same system.

[0111] Furthermore, in the above example, when a timing deviation exceeding the allowable limit occurred for 10 or more consecutive frames, a central control correction signal was generated (see Figure 7) and timing control based on a zone delay timing signal was performed (see Figure 11). However, this is not the only example. For instance, when the average value of the timing deviation of 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] Furthermore, in the above example, the generation of a central control correction signal and various corrections were performed based on the average value of the input timing and the average value of the zone delay amount for 10 frames in which a timing deviation exceeding the tolerance limit occurred, but this is not the only way. For example, the generation of a central control correction signal and various corrections may be performed based on the input timing and zone delay amount in which the largest deviation exceeding the tolerance limit occurred over a certain number of past frames.

[0113] Furthermore, it is possible to freely combine each embodiment and each variation, and to modify or omit each embodiment and each variation 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 that transmits a data signal to which a first timing signal has been added, A plurality of first base stations connected in series with each other and transmitting wireless signals based on the data signals, A second base station is connected between the central control unit and one end of the plurality of first base stations, and transmits a wireless signal based on the data signal. Equipped with, A wireless communication system in which the second base station controls the timing at which the second base station and the plurality of first base stations transmit the radio signal based on the first timing signal.

2. A wireless communication system according to claim 1, The second base station calculates a correction value used in the central control unit based on the first timing signal, A wireless communication system in which the central control unit controls the timing of transmitting the data signal based on the correction value transmitted from the second base station to the central control unit.

3. A wireless communication system according to claim 1 or claim 2, The second base station is, This includes a first master base station connected to one end of the plurality of first base stations, and a second master 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 base station and the second base station controls the timing at which the first base station, the second base station and the plurality of first base stations transmit the radio signal.

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

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

6. A wireless communication system according to claim 2, The second base station is, This includes a first master base station connected to one end of the plurality of first base stations, and a second master 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 the timing at which the first parent base station, the second parent base station and the plurality of first base stations transmit the radio signal. One of the first and second parent base stations transmits a second timing signal. The other of the first and second base stations calculates the delay amount between the first and second base stations based on the second timing signal transmitted from one of them via the plurality of first base stations. A wireless communication system in which the central control unit controls the timing of transmitting the data signal based on the correction value transmitted from the second base station to the central control unit and the delay amount transmitted from the other of the first and second base stations to the central control unit.

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

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

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

10. A base station according to claim 8 or claim 9, The aforementioned base station is This includes a first master base station connected to one end of the plurality of first base stations, and a second master base station connected to the other end of the plurality of first base stations, A base station in which at least one of the first base station and the second base station controls the timing at which the first base station, the second base station and the plurality of first base stations transmit the radio signal.

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

12. A 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 plurality of first base stations transmit the radio signal, based on the first timing signal and the delay amount.

13. A base station is connected to a central control unit that transmits a data signal, with a second base station that transmits a radio signal based on the data signal in between, and is one of a plurality of base stations connected in series to each other that transmit a radio signal based on the data signal, A base station that transmits a radio signal whose transmission timing is controlled by the second base station based on a first timing signal added to the data signal.

14. A central control unit in a wireless communication system comprising: a central control unit that transmits data signals; a plurality of first base stations connected in series with each other and transmitting wireless signals based on the data signals; and a second base station connected between the central control unit and one end of the plurality of first base stations and transmitting wireless signals based on the data signals, wherein A central control device that adds a first timing signal to the data signal, which is used by the second base station to control the timing at which the second base station and the plurality of first base stations transmit the radio signal.

15. A central control device according to claim 14, A central control unit that controls the timing for transmitting the data signal based on a correction value calculated by the second base station based on the first timing signal and transmitted from the second base station to the central control unit.

16. A central control device according to claim 15, The second base station is, This includes a first master base station connected to one end of the plurality of first base stations, and a second master base station connected to the other end of the plurality of first base stations, One of the first and second parent base stations transmits a second timing signal. The other of the first and second base stations calculates the delay amount between the first and second base stations based on the second timing signal transmitted from one of them via the plurality of first base stations. A central control unit that controls the timing for transmitting the data signal based on the correction value transmitted from the second base station to the central control unit and the delay amount transmitted from the other of the first and second base stations to the central control unit.

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