JP7270354B2 - Wireless communication systems, base stations, repeaters and terminating repeaters - Google Patents

Description

The present invention relates to a wireless communication system that corrects signal delay due to transmission path differences.

At present, optical fibers are applied to many wireless communication systems, making it possible to provide high-speed, large-capacity communications that are difficult to achieve with wireless communications alone, and to provide services in communication environments where radio waves are difficult to reach. Wireless communication systems that have conventionally performed wireless communication using leaky coaxial cables (LCX) are no exception, and flexible wireless communication systems are being developed by applying radio over fiber (RoF). have been constructed (see, for example, US Pat. Such systems mainly consist of base stations, relay stations, and mobile stations, and the base stations and mobile stations communicate through the relay stations.

As a wireless communication system for performing communication between a base station and a mobile station via LCX and an optical fiber, there are those disclosed in Patent Document 2 and Patent Document 3, for example. In this system, a base station has interfaces with LCX and optical fibers, and each interface is connected to a relay station. In addition, the repeater station has interfaces with upper LCX, lower LCX, and optical fiber, the optical fiber is connected to the base station, and the LCX is connected between the repeaters except for the initial repeater station. Since each relay station is installed at a different location, the length of the LCX and optical fiber from the base station to each relay station is different. Therefore, when a signal is transmitted from the base station to each relay station, the time required for each relay station to receive the signal and transmit it to the LCX differs. Further, the signal transmission path from the base station to the specific relay station includes a path for the specific relay station to receive from the LCX and transmit to the LCX and a path for the specific relay station to receive from the optical fiber and transmit to the LCX. When the transmission time differs between these transmission routes, the signal phase received from the LCX by the mobile station passing through the specific relay station differs depending on the transmission route, and the communication between the base station and the mobile station runs across the area boundary of the specific relay station. There is a possibility of momentary interruption.

Therefore, in the radio communication system of Patent Document 2, the phase of the signal received by the mobile station from the LCX is adjusted by adjusting the optical fiber length using the optical fiber bobbin in the delay correction device installed in the base station. The adjustment amount of the optical fiber length is calculated by converting the result of measuring the signal delay due to the transmission path difference on the mobile station into the optical fiber length. By connecting the base station and the repeater station with an optical fiber transmission line for single-fiber two-way communication, the adjustment amount of the optical fiber length is made common in the upstream direction and the downstream direction.

Further, in order to solve the problem of measurement accuracy in Patent Document 2, Patent Document 3 generates a delay adjustment signal different from the main signal, and from the result of detection by a delay correction signal reception unit mounted on the mobile station, , discloses calculating an adjustment amount for an optical fiber length.

JP-A-9-130322 JP 2004-236165 A JP 2011-223505 A

In conventional wireless communication systems that communicate between base stations and mobile stations via LCX and optical fiber, the mobile station calculates the amount of signal delay due to the difference in transmission paths, so the amount of correction for the length of the optical fiber is known. For this purpose, it was necessary to install a mobile station or a device with a signal delay amount detection function at the site and actually measure it. In other words, even if the delay correction device is installed in the base station, there is a problem that on-site measurement is required to know the amount of correction. SUMMARY OF THE INVENTION It is an object of the present invention to provide a wireless communication system capable of performing delay correction without the need for a measurement staff to go to the site and measure the signal.

A first wireless communication system of the present disclosure includes a base station, and a plurality of relay stations connected one-to-one with the base station by optical fiber and connected in a daisy chain by LCX. A relay station at one end is connected to a base station by LCX, and further includes a terminating relay station connected to a relay station at the other end of a daisy chain by LCX, and the base station is at least two relay stations among the plurality of relay stations. A signal is transmitted through an optical fiber to a target repeater station, and the terminating repeater station receives the signal from the target repeater station through the LCX and measures the phase difference of the signal received from the target repeater station. is transmitted to the base station, and the base station corrects the delay of the optical fiber connecting the target relay station and the base station so that the phase difference between the signals is less than a predetermined threshold.

A second wireless communication system of the present disclosure includes a base station, and a plurality of relay stations connected one-to-one with the base station by optical fiber and connected in a daisy chain by LCX. A relay station at one end is connected to a base station by LCX, and further includes a terminating relay station connected to a relay station at the other end by LCX, and the base station sends a first test signal to each relay station via an optical fiber. While transmitting the signal, acquire the reception time of the first test signal at each relay station via the relay station monitoring line, transmit the second test signal to each relay station via LCX, and connect the relay station monitoring line obtain the reception time of the second test signal at each relay station via the relay station, calculate the time difference between the transmission time of the first test signal and the reception time at each relay station as the first time difference, and calculate the transmission time of the second test signal and A time difference from the reception time at each relay station is calculated as a second time difference, and based on the difference between the first time difference and the second time difference, the delay of the transmission line through the optical fiber connected to each relay station is corrected.

In the first wireless communication system of the present invention, since the base station acquires the phase difference of the test signal from the terminating relay station, the delay correction can be performed without the need for measurement personnel to go to each relay station and measure the signal. be able to.

In the second wireless communication system of the present invention, since the base station acquires the reception times of the first test signal and the second test signal at each relay station, measurement personnel do not have to go to each relay station to measure the signals. delay correction can be performed.

1 is a configuration diagram of a radio communication system according to Embodiment 1; FIG. 4 is a flow chart showing delay correction processing of the wireless communication system according to the first embodiment; 1 is a configuration diagram of a radio communication system according to Embodiment 1; FIG. 9 is a flow chart showing delay correction processing of the wireless communication system according to the second embodiment; 1 is a configuration diagram of a radio communication system according to Embodiment 1; FIG. 1 is a configuration diagram of a radio communication system according to Embodiment 1; FIG. 11 is a flow chart showing delay correction processing of the wireless communication system of Embodiment 3;

<A. Embodiment 1>
<A-1. Configuration>
FIG. 1 is a configuration diagram of a wireless communication system 101 according to the first embodiment. The wireless communication system 101 detects the transmission path difference in each relay station 5 by arranging the demodulator for the main signal in the terminal relay station 6A and switching the transmission path.

A wireless communication system 101 includes a base station 1A, a mobile station (not shown), X relay stations 5 and a terminal relay station 6A. It should be noted that the X relay stations 5 are distinguished by assigning ids from 1 to X, respectively. X relay stations 5 are connected in a daisy chain by LCX2 in order of id. Also, the relay station 5 with id=X, which is one end of the daisy chain, is connected to the base station 1A and LCX2, and the relay station 5 of id=1, which is the other end of the daisy chain, is connected to the terminal relay station 6A and LCX2. there is The base station 1A and each relay station 5 are connected one-to-one by optical fibers 3. FIG. The base station 1A and the mobile station transmit and receive signals via LCX 2 and optical fiber 3, which are transmission lines.

The base station 1A includes a control section 11, a transmission/reception section 12 and a delay correction device 13. FIG. The control unit 11 controls the entire base station 1A. The transmitting/receiving unit 12 transmits/receives signals to/from the relay station 5 using the LCX 2 and the optical fiber 3 . The delay correction device 13 receives an instruction from the control unit 11 and corrects the delay of the optical fiber 3 connected to each relay station 5 .

The relay station 5 has two sets of changeover switches 51 and amplifiers 52 . In FIG. 1, the changeover switch 51U and the amplification section 52U are shown on the upper side in the relay station 5, and the changeover switch 51D and the amplification section 52D are shown on the lower side. However, when there is no particular need to distinguish them in the following description, they will be referred to as the switch 51 or the amplifier 52 . The changeover switch 51 selects a transmission path for the relay station 5 to receive. The amplifier 52 amplifies the signal passing through the relay station 5 . Which pair operates depends on the traveling direction of the mobile station. When the mobile station proceeds from left to right in FIG. 1, changeover switch 51U and amplifier 52U operate, and when the mobile station proceeds from right to left in FIG. 1, changeover switch 51D and amplifier 52D operate.

The changeover switch 51 switches between the LCX 2 as a transmission line and the optical fiber 3 . Since it is necessary to minimize the influence between the LCX 2 and the optical fiber 3, the isolation of these transmission lines is desirably set to 30 dB or more, but is not limited to this range. In addition, although a mechanical switch or a semiconductor switch is assumed for the changeover switch 51, it is not limited to these.

The amplifier 52 amplifies the signal that has passed through the changeover switch 51 . The signal amplified by the amplifier 52 is transmitted to the relay station 5 in the next stage via the LCX2.

In FIG. 1, the switch 51 and the amplifier 52 are shown as components of the relay station 5, but other components such as a monitor, a photoelectric conversion unit, a supervisory control unit, etc. are added to the relay station 5. Also good. 1 shows two selector switches 51U and 51D and two amplifiers 52U and 52D, the number of these can be increased or decreased in consideration of redundancy or commonality. is not limited to

The terminal repeater station 6A has two sets of a distributor 61, a demodulator 62 and a delay comparator 63. FIG. In FIG. 1, the distributor 61U, the demodulator 62U, and the delay comparator 63U are shown on the upper side in the terminal repeater station 6A, and the distributor 61D, the demodulator 62D, and the delay comparator 63U are shown on the lower side. This is the delay comparator 63D. However, in the following description, they are referred to as a distributor 61, a demodulator 62, or a delay comparator 63 when there is no particular need to distinguish them. Which pair operates depends on the traveling direction of the mobile station. When the mobile station proceeds from left to right in FIG. 1, distributor 61U, demodulator 62U and delay comparator 63U operate, and when the mobile station proceeds from right to left in FIG. 62D and delay comparator 63D operate.

Distributor 61 distributes the signal received from LCX2. Since the splitter 61 only needs to transmit signals of the same level to the subsequent demodulators 62U and 62D, the split ratio is usually set to 50%, but the range is not limited to this range.

Demodulator 62 demodulates the received signal distributed by distributor 61 . This signal is a signal that is modulated by an arbitrary modulation method in the transmitting/receiving section 12 of the base station 1A, is transmitted, and is received via the LCX 2 or the optical fiber 3. FIG. This signal basically consists of main data, a header portion, an error correction portion, a frame check sequence portion, a guard time portion, and the like. The demodulator 62 demodulates the received signal by an appropriate demodulation method based on the modulation method of the transmission signal. In general, the demodulator 62 detects a signal phase to be compared by detecting a specific bit pattern periodically arranged from the header of the received signal during demodulation. The demodulator 62 then transmits the detected signal phase to the delay comparator 63 in the subsequent stage.

When there are a plurality of demodulators 62, generally the received signal is often a frequency-multiplexed signal. The demodulator 62 incorporates a local oscillator (LO) and a low pass filter (LPF), and uses these to receive a desired frequency signal. However, since the demodulator 62 only needs to be able to detect the signal phase, the number of demodulators 62 installed, the internal frame structure of the received signal, and the demodulation method are not limited to the ranges described above.

The delay comparator 63 compares the phases of the signals detected by the demodulator 62 to calculate the signal phase difference, that is, the correction amount. The calculated correction amount is transmitted to the controller 11 of the base station 1A via the terminating relay station monitoring line 4. FIG.

Although FIG. 1 shows the distributor 61, the demodulator 62, and the delay comparator 63 as the configuration of the terminal repeater station 6A, other configurations such as a monitor unit and a supervisory control unit are added to the terminal repeater station 6A. It's okay to be. In addition, although two demodulators 62U and 62D are shown in FIG. 1, the number of these can be increased or decreased in consideration of redundancy or commonality, and is not limited to the above number.

The control unit 11 receives the correction amount from the terminal repeater station 6A via the terminal repeater station monitor line 4, and based on this, calculates the optical fiber length to be adjusted by the delay corrector 13. FIG. Since the delay correction device 13 only needs to be able to adjust the amount of delay in the base station 1A, it does not matter whether the means for correcting the delay is analog or digital. Here, an analog method for adjusting the optical fiber length is adopted, but digital processing such as adding a delay block in digital signal processing at the time of transmission signal generation may be adopted.

<A-2. Operation>
Next, the delay correction processing of the transmission path difference in the wireless communication system 101 will be described with reference to the flowchart of FIG. First, all the relay stations 5 connected to the base station 1A switch the selector switches 51 to the LCX2 side. Then, the transmitting/receiving section 12 of the base station 1A transmits the signal. This signal is received by the terminal relay station 6A via the X relay stations 5 by the LCX2. The terminal relay station 6A detects the phase of the signal by the demodulator 62 and stores it in the delay comparator 63 . The phase of this signal becomes the reference phase used in the delay correction process (step S101). Incidentally, here, the phase detected by the terminal relay station 6A when all the relay stations 5 connected to the base station 1A are switched to the LCX2 side is used as the reference phase. The detection path of the reference phase can be flexibly changed according to the laying condition of the optical fiber 3 to be connected. For example, the phase transmitted from the base station 1A to the relay station 5 (id=1) via the optical fiber 3 and then detected by the terminal relay station 6A via the LCX 2 may be used as the reference phase.

Next, the control unit 11 of the base station 1A sets a threshold used for determining completion of the delay correction process (step S102). This threshold value is set as a signal phase difference that does not cause an instantaneous communication interruption with the base station 1A even when a mobile station (not shown) runs. The value depends on the synchronization detection accuracy of the transmitting/receiving unit 12 installed in the base station 1A and the mobile station (not shown), and the value corresponding to the system configuration of the application destination such as the signal format or transmission speed can be obtained by numerical calculation. . The delay correction process continues until the signal phase difference falls below the threshold.

Next, the control unit 11 sets the number of relay stations connected to the base station 1A to the parameter n, and sets the initial value 0 to the loop counter i (step S103). Then, the control unit 11 adds α (α=1) to the loop counter i in order to perform the delay correction process from the relay station 5 (id=1) (step S104). Note that the value of α can be flexibly changed by setting the reference phase.

Next, the control unit 11 sets the parameter N for determining the relay station 5 to which the signal is to be transmitted to a value equal to the loop counter i (step S105). The relay station 5 (id=N) designated by the parameter N switches the switch 51 to the optical fiber 3 side. Then, the transmitting/receiving section 12 of the base station 1A transmits the test signal to the designated repeater station 5 (id=N) via the optical fiber 3 (step S106).

When the relay station 5 (id=N) receives the test signal from the transmitting/receiving unit 12 of the base station 1A via the optical fiber 3, it transmits the test signal to the next-stage relay station 5 via the LCX2, As a result, the terminal relay station 6A finally receives the test signal. In the terminal repeater station 6A, the demodulator 62 demodulates the test signal (step S107) and detects the signal phase at the time of reception from the obtained demodulation result. Then, the delay comparator 63 stores the signal phase detected by the step demodulator 62, that is, the signal reception timing (step S108).

Next, the control unit 11 compares the value of the loop counter i with the parameter N for determining the relay station 5 to which the signal is to be transmitted (step S109). Since the control unit 11 sets the value of the parameter N and the value of the loop counter i to be the same in step S105, the value of the parameter N does not become larger than the value of the loop counter i in the first determination process of step S109. In that case, the control unit 11 adds 1 to the parameter N (step S110) and transmits the test signal to the next relay station 5 (id=N) (step S106). In the second determination process in step S109, the parameter N is always larger than the loop counter i, so the answer is Yes and the process proceeds to step S111.

Next, the delay comparator 63 compares the phases of the plurality of test signals stored in step S108 and calculates the relative signal phase difference (step S111). As described above, when the loop counter i is 1, the signal is transmitted from the base station 1A to the repeater station 5 (id=1) through the optical fiber 3, and transmitted from the repeater station 5 (id=1) to the terminal repeater station 6A through the LCX2. The phase of the obtained test signal is stored in the delay comparator 63 . Also, when the loop counter i is 2, the signal is transmitted from the base station 1A to the relay station 5 (id=2) through the optical fiber 3, and the relay station 5 (id=1) is transmitted from the relay station 5 (id=2) to the relay station 5 (id=1) by the LCX2. The delay comparator 63 stores the phase of the test signal received by the terminal relay station 6A via the terminal relay station 6A. Thus, the relay station 5 (id=1) and the relay station 5 (id=2) to which the test signal is transmitted are also called target relay stations. The delay comparator 63 compares the phases of these two test signals to calculate the relative signal phase difference between the relay station 5 (id=1) and the relay station 5 (id=2), This is the correction amount for relay station 5 (id=2).

Next, the correction amount for the relay station 5 (id=2) calculated in step S111 is transmitted from the terminal relay station 6A to the control unit 11 of the base station 1A via the terminal relay station monitoring line 4. FIG. The control unit 11 compares the correction amount for the relay station 5 (id=2) with the threshold set in step S102 (step S112). If the correction amount for relay station 5 (id=2) is not less than the threshold set in step S102, control unit 11 determines that the transmission path length of relay station 5 (id=2) needs to be corrected. In the case of FIG. 1, the delay correction device 13 performs delay correction processing by adjusting the length of the optical fiber 3 connected between the base station 1A and the relay station 5 (id=2) (step S113). After that, the wireless communication system 101 repeats the processing from step S105 to step S113 until the correction amount for the relay station 5 (id=2) becomes less than the threshold set at step S102 at step S112.

In step S112, when the correction amount for relay station 5 (id=2) becomes less than the threshold value set in step S102, control unit 11 sets loop counter i to 1 from parameter n representing the number of relay stations connected to base station 1A. is equal to the subtracted value (step S114). If the loop counter i is not equal to the value obtained by subtracting 1 from the parameter n representing the number of relay stations connected to the base station 1A, the delay correction processing has been completed for all the relay stations 5 connected to the base station 1A. Therefore, the control unit 11 updates the loop counter i (step S104), and the wireless communication system 101 repeats the processing from step S105 to step S114. By this repetition, not only the delay correction process between the relay station 5 (id=1) and the relay station 5 (id=2) described above, but also the delay correction process between the relay station 5 (id=2) and the relay station 5 (id=3) ), delay correction processing between the relay station 5 (id=3) and the relay station 5 (id=4), and finally the relay station 5 (id=X−1) and the relay station 5 (id=X) delay correction processing is performed. In other words, the base station 1A selects the target relay stations from the relay station 5 (id=1) and the relay station 5 (id=2), the relay station 5 (id=2) and the relay station 5 (id=3), and furthermore, By repeating the transmission of the test signal to the target relay station while changing the relay station 5 (id=3) and the relay station 5 (id=4), delay correction processing is performed for all the relay stations 5. It can be carried out. When the delay correction process between the relay station 5 (id=X−1) and the relay station 5 (id=X) is completed, in step S114, the loop counter i is calculated from the parameter n representing the number of relay stations connected to the base station 1A. It becomes equal to the value obtained by subtracting 1, exits this loop, and the delay correction processing due to the transmission path difference of the wireless communication system 101 ends.

In the delay correction process described above, two relay stations 5 whose wireless communication areas are adjacent to each other, such as the relay station 5 (id=1) and the relay station 5 (id=2), are target relay stations. The signal phase difference between was successively corrected. However, if the terminal relay station 6A can acquire the relative signal phase difference between any two or more relay stations 5, the base station 1A can perform delay correction processing between the two or more relay stations 5. FIG. Therefore, any two or more relay stations 5 may be the target relay stations. For example, after acquiring signal phase differences between three or more relay stations 5 at the termination relay station 6A, the base station 1A may collectively perform delay correction processing for these three or more relay stations.

<A-3. Effect>
The wireless communication system 101 of Embodiment 1 includes a base station 1A, and a plurality of relay stations connected one-to-one to the base station 1A by optical fibers 3 and connected in a daisy chain by LCX 2, A relay station 5 (id=X) at one end of the daisy chain is connected to the base station 1A via LCX2, and a terminating relay station 6 is connected to the relay station 5 (id=1) at the other end of the daisy chain via LCX2. , the base station 1A transmits a test signal to target relay stations, which are at least two relay stations among the plurality of relay stations 5, via the optical fiber 3, and the terminal relay station 6A transmits the test signal from the target relay station via the LCX 2. A test signal is received, the phase difference of the test signal received from the target relay station is measured and transmitted to the base station 1A, and the base station 1A determines the target relay station and base station 1A based on the phase difference of the test signal. Delay correction of the optical fiber 3 to be connected is performed. Therefore, according to the wireless communication system 101, it is possible to perform delay correction so that the signal phase difference at the boundary of the relay station 5 is less than the threshold value, without the need for measurement staff to go to each relay station 5 and measure the signal. can. Therefore, it is possible to reduce the time and cost required for delay correction.

The transmitting/receiving section 12 and the delay correction device 13 may be a digital modulation/demodulation processing section and a digital delay correction block.

<B. Embodiment 2>
<B-1. Configuration>
FIG. 3 is a configuration diagram of the wireless communication system 102 according to the second embodiment. In FIG. 3, the same reference numerals are given to the same configurations as in FIG. Compared with the radio communication system 101 of the first embodiment, the radio communication system 102 has a configuration including a base station 1B instead of the base station 1A. The base station 1B has a time synchronization protocol 14 in addition to the configuration of the base station 1A. A relay station monitoring line 7 is connected between the base station 1B and the relay station 5 (id=X), between the adjacent relay station 5, and between the relay station 5 (id=1) and the terminal relay station 6A. .

The relay station monitoring line 7 is a line for transmitting a status notification request from the control unit 11 of the base station 1B to each relay station 5 and the terminal relay station 6A. Since the relay station monitor line 7 only needs to be able to connect the base station 1B, each relay station 5, and the terminal relay station 6A, the connection mode is not limited to the daisy chain connection as shown in FIG. 3, but may be a star connection. .

The time synchronization protocol 14 performs time synchronization between the host device (not shown) and the base station 1B via the interface between the host device and the base station 1B. For example, there is a network time protocol (NTP) server as the host device. The time synchronization protocol 14 can correct the time information ticked by the real time clock (Real Time Clock: RTC) installed in the base station 1B to synchronize with Coordinated Universal Time (UTC) by sending and receiving commands. As long as the base station 1B can receive the time information, the mechanism of time calibration by the time synchronization protocol 14 is not limited to the above contents.

The time information of the base station 1B whose time has been calibrated as described above is delivered to each relay station 5 via the relay station monitor line 7. FIG. This enables time synchronization in the entire wireless communication system 102 .

<B-2. Operation>
Next, the delay correction processing for the transmission path difference in the wireless communication system 102 will be described with reference to the flowchart of FIG. First, the control unit 11 of the base station 1B sets a threshold used for determining completion of the delay correction process (step S201). This threshold value is set using the inter-transmission-path time difference information received by the control unit 11 via the optical fiber 3 and the LCX 2 as a parameter.

Next, all relay stations 5 switch the changeover switch 51 to the optical fiber 3 side. Then, the transmitting/receiving section 12 of the base station 1B transmits a signal all at once to each relay station 5 via the optical fiber 3 (step S202). This signal will be referred to as the first test signal. At this time, the control section 11 stores the transmission time t0 of the first test signal from the transmission/reception section 12 . The first test signal is received at each relay station 5 (step S203).

Next, each relay station 5 detects reception times t1, t2, . . . tX of the first test signal from the base station 1B (step S204). This reception time is the time immediately before each relay station 5 receives the first test signal from the base station 1B and transmits the first test signal to the next-stage relay station 5 via the LCX2. Here, t1 is the reception time of relay station 5 (id=1), t2 is the reception time of relay station 5 (id=2), and tX is the reception time of relay station 5 (id=X). . Each relay station 5, upon receiving the status notification request from the base station 1B via the relay station monitoring line 7, transmits the reception time obtained in step S204 via the relay station monitoring line 7 (step S205). Specifically, the reception time tX of the relay station 5 (id=X) is transmitted from the relay station 5 (id=X) to the relay station 5 (id=X-1) via the relay station monitoring line 7. . Then, from the relay station 5 (id=X-1) to the relay station 5 (id=X-2) via the relay station monitoring line 7, the reception time tX of the relay station 5 (id=X) and the relay station 5 ( id=X-1) is transmitted. In this way, each relay station 5 transmits to the relay station 5 of the next stage including its own reception time in the reception time acquired from the relay station 5 of the preceding stage. Then, the relay station 5 (id=1) transmits the reception times t1, t2, . . . tX of all the relay stations 5 to the terminal relay station 6A, and It is transmitted from the terminal relay station 6A to the control unit 11 of the base station 1B via the terminal relay station monitoring line 4. FIG.

Next, all relay stations 5 switch the selector switch 51 to the LCX2 side. Then, the transmitting/receiving unit 12 of the base station 1B transmits a signal to the relay station 5 (id=X) via LCX2 (step S206). This signal is called the second test signal. At this time, the control unit 11 stores the transmission time t′0 of the second test signal from the transmission/reception unit 12 . The second test signal from the transmitting/receiving unit 12 is received in order from the relay station 5 with id=X to the relay station 5 with id=1 (step S207).

Next, each relay station 5 detects reception times t'1, t'2, . . . t'X of the second test signal from the base station 1B (step S208). This reception time is the time immediately before each relay station 5 receives the second test signal from the base station 1B and transmits the second test signal to the next-stage relay station 5 via the LCX2. Here, t'1 is the reception time of the relay station 5 (id=1), t'2 is the reception time of the relay station 5 (id=2), and t'X is the reception time of the relay station 5 (id=X ) is received. When each relay station 5 receives the status notification request from the base station 1B via the relay station monitoring line 7, each relay station 5 transmits the reception time obtained in step S208 via the relay station monitoring line 7 in the same manner as in step S205 ( step S209).

Since it is sufficient for the base station 1B to acquire the reception time in each relay station 5, the transmission of the reception time in steps S205 and S209 does not have to be triggered by the status notification request from the base station 1B.

Next, the control unit 11 of the base station 1B determines reception times t1, t2, . . . From t'X, the inter-route time difference is calculated as a correction amount (step S210). Specifically, the control unit 11 determines the transmission time of each relay station 5 from the difference between the transmission time t0 of the signal via the optical fiber 3 at the base station 1B and the reception time t1, t2, . Time differences R1, R2, . . . RX to the end are calculated. Further, the control unit 11, from the difference between the transmission time t'0 of the second test signal via the LCX2 at the base station 1B and the reception times t'1, t'2, . . . Time differences R'1, R'2, . . . R'X to the transmitting end of each relay station 5 are calculated. RX of the first test signal via the optical fiber 3 and time differences R'1, R'2, . . . Inter-path time differences T1, T2, . . . TX are calculated as correction amounts from the difference of R'X. Here, the inter-path time difference T1 at the relay station 5 (id=1) is (R1-R'1), and the inter-path time difference T2 at the relay station 5 (id=2) is (R2-R'2). and the inter-path time difference TX at the relay station 5 (id=X) is (RX-R'X).

Next, the control unit 11 compares the inter-path time differences T1, T2, . . . TX, which are correction amounts, with a threshold value (step S211). If any of the inter-path time differences T1, T2, . means that there is Therefore, the delay correction device 13 performs delay correction processing by adjusting the length of the optical fiber 3 connecting the base station 1B and the relay station 5 for the relay station 5 where the inter-path time difference exceeds the threshold ( step S212). After that, in step S211, the radio communication system 101 repeats the processing from step S202 to step S212 until the inter-path time differences T1, T2, .

In step S211, when the inter-path time differences T1, T2, .

<B-3. Effect>
The wireless communication system 102 of Embodiment 2 includes a base station 1B, and a plurality of repeater stations 5 that are connected to the base station 1B via optical fibers 3 on a one-to-one basis and that are connected in a daisy chain via LCX 2. , the relay station 5 (id=X) at one end of the daisy chain is connected to the base station 1B via LCX2, and the terminating relay station 6 is connected to the relay station 5 (id=1) at the other end of the daisy chain via LCX2. In preparation, the base station 1B transmits the first test signal to each relay station 5 via the optical fiber 3 and obtains the reception time of the first test signal at each relay station 5 via the relay station monitoring line 7. , LCX2 to each relay station 5, acquires the reception time of the second test signal at each relay station 5 via the relay station monitoring line 7, and obtains the transmission time of the first test signal. and the reception time at each relay station 5 is calculated as a first time difference, the time difference between the transmission time of the second test signal and the reception time at each relay station 5 is calculated as a second time difference, and the first time difference and the first Based on the two-time difference, the delay of the transmission line through the optical fiber 3 connected to each relay station 5 is corrected. As described above, in the wireless communication system 102, the base station 1B can simultaneously acquire the reception times of the first test signal and the second test signal at each relay station 5 through the relay station monitoring line 7, so delay correction can be performed. can be easily done. Further, according to the wireless communication system 102, measurement personnel do not have to go to each relay station 5 to measure the signal. , delay correction can be performed. Therefore, it is possible to reduce the time and cost required for delay correction.

<C. Embodiment 3>
<C-1. Configuration>
5 and 6 are configuration diagrams of the wireless communication system 103 according to the third embodiment. FIG. 5 is the left diagram and FIG. 6 is the right diagram of the configuration diagram of the wireless communication system 103 divided into two diagrams along the line BB. The radio communication system 103 has a configuration in which a plurality of the radio communication systems 101 of the first embodiment are connected using the terminating relay station 6B in common. 5 and 6, the same components as in FIGS. 1 and 3 are denoted by the same reference numerals. Here, the radio communication system 103 is described as a configuration in which a plurality of radio communication systems 101 are connected. However, the wireless communication system 103 may have a configuration in which a plurality of wireless communication systems 102 are connected, or may have a configuration in which at least one wireless communication system 101 and at least one wireless communication system 102 are connected. good.

A radio communication system 103 shown in FIGS. 5 and 6 has a configuration in which two radio communication systems 101 of the first embodiment are connected. Therefore, the wireless communication system 103 has a bilaterally symmetrical configuration centering on the terminal repeater station 6B. FIG. 5 shows the configuration of the left half of the radio communication system 103, that is, the base station 1A, a plurality of relay stations 5 connected thereto, and the terminal relay station 6B. These configurations are the same as those of the radio communication system 101 of Embodiment 1 shown in FIG. 1 except for the terminating relay station 6B, and are also referred to as a first radio communication system.

FIG. 6 shows the configuration of the right half of the radio communication system 103, which is also referred to as the second radio communication system. The second radio communication system is obtained by arranging the first radio communication system shown in FIG. 5 symmetrically. However, in FIG. 6, the base station is the base station 1A1, and the configuration of the first wireless communication system and the configuration of the second wireless communication system are shown by adding a to the reference numerals of the components such as the relay station 5a. are distinguished.

A first radio communication system centered on the base station 1A and a second radio communication system centered on the base station 1A1 share the terminal repeater station 6B and are connected at the terminal repeater station 6B. In the first wireless communication system, the terminal relay station 6B is connected to the base station 1A via the terminal relay station monitor line 4, and is connected to the relay station 5 (id=1) via the LCX2. In the second wireless communication system, the terminal relay station 6B is connected to the base station 1A1 via the terminal relay station monitoring line 4a, and is connected to the relay station 5a (id=1) via the LCX2a.

Therefore, the terminal relay station 6B has twice as many distributors 61, demodulators 62, and delay comparators 63 as the terminal relay station 6A in the wireless communication system 101 of the first embodiment. However, the number of components is not limited to the above, since these configurations can also aggregate functions.

In addition, the terminal relay station 6B has an inter-base-station delay comparator 64 . The inter-base station delay comparator 64 is connected to the demodulator 62D on the base station 1A side and the demodulator 62D on the base station 1A1 side, compares the phases of the signals demodulated by these demodulators 62D, and finds the phase difference. It is detected as a phase difference between base stations. The inter-base station phase difference is transmitted from the terminal relay station 6B to the base station 1A via the terminal relay station monitor line 4a.

<C-2. Operation>
Next, the delay correction processing for the transmission path difference in the radio communication system 103 will be described with reference to the flowchart of FIG. First, the radio communication system 103 performs delay correction processing on the first radio communication system, that is, the base station 1A side (step S301). This step is the same as steps S102 to S114 in FIG. This processing completes the delay correction processing from the relay station 5 (id=1) to the relay station 5 (id=X) in FIG.

Next, the transmitting/receiving section 12 of the base station 1A transmits the test signal to the relay station 5 (id=X) via the LCX2 (step S302). This test signal is called the third test signal. The third test signal is passed from the relay station 5 (id=X) to the subsequent relay station 5 in a daisy chain by the LCX2, and finally received by the terminal relay station 6B (step S303).

Also, the transmitting/receiving unit 12 of the base station 1A1 transmits the test signal to the relay station 5a (id=X) via the LCX2 (step S304). This test signal is called the fourth test signal. The fourth test signal is transferred from the relay station 5a (id=X) to the succeeding relay station 5a in a daisy chain by the LCX2, and finally received by the terminal relay station 6B (step S305).

In the terminal relay station 6B, the demodulator 62D demodulates the third test signal and the fourth test signal and outputs the phases of these signals to the inter-base station delay comparator 64. FIG. The inter-base station delay comparator 64 detects the phase difference between the third test signal and the fourth test signal as the inter-base station phase difference (step S306). After that, the terminal repeater station 6B transmits the inter-base-station phase difference to the base station 1A side via the terminal repeater station monitor line 4a (step S307).

The controller 11a of the base station 1A1 receives the inter-base station phase difference via the terminal relay station monitor line 4a. Then, the control unit 11a corrects the phase of the signal transmitted from the transmission/reception unit 12a so that the inter-base station phase difference is less than the threshold (step S308). The signal phase correction is performed by increasing or decreasing the post-bit length of one frame of the test signal (arbitrary signal including preamble + post-bit for phase adjustment) generated by the control section 11a of the base station 1A1. However, the frame structure of the test signal may be any other structure as long as the signal phase can be adjusted.

Thereafter, the radio communication system 103 performs delay correction processing on the second radio communication system, that is, the base station 1A1 side (step S309). This step is the same as steps S102 to S114 in FIG. This processing completes the delay correction processing from the relay station 5a (id=1) to the relay station 5a (id=X) in FIG.

In the above description, since the wireless communication system 103 is configured by connecting two wireless communication systems 101 of the first embodiment, the delay correction is performed by the method of the first embodiment in steps S301 and S309. However, if the radio communication system 103 includes the radio communication system 102 of the second embodiment, delay correction is performed for the radio communication system 102 by the method of the second embodiment in step S301 or step S309.

5 and 6, the radio communication system 103 has a configuration in which two radio communication systems 101 of Embodiment 1 are connected, but a configuration in which three or more radio communication systems are connected good. In this case, the phase correction between each base station is performed by sequentially performing the processing described with reference to FIG. 7 for the base stations subsequent to the base station 1A1.

<C-3. Effect>
In the radio communication system 103 of the third embodiment, the first radio communication system and the second radio communication system, which are the radio communication systems of the first embodiment or the second embodiment, are connected using the terminating repeater station 6B in common. It is a wireless communication system. In the radio communication system 103, the base station 1A of the first radio communication system transmits a third test signal to one relay station 5 via the optical fiber 3, and the base station 1A1 of the second radio communication system transmits the optical fiber 3a to one relay station 5a, the terminating relay station 6B receives the third and fourth test signals via LCX 2, 2a, and receives the third and fourth test signals. The phase difference of the test signal is measured as the inter-base-station phase difference, the inter-base-station phase difference is transmitted to the base station 1A1 of the second wireless communication system, and the base station 1A1 of the second wireless communication system transmits the inter-base-station phase difference , the phase of the signal to be transmitted to each relay station 5a is corrected. Therefore, according to the radio communication system 103, in addition to the effects of the first and second embodiments, by reducing the signal phase difference between the base station 1A and the base station 1A1, signal transmission/reception at the boundary of the communication areas of both base stations is possible. It is possible to suppress instantaneous interruption of

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

1A, 1A 1, 1B base station, 2, 2a LCX, 3, 3a optical fiber, 4, 4a terminal repeater station monitoring line, 5 repeater station, 6A, 6B terminal repeater station, 7 repeater station monitor line, 11, 11a control unit , 12, 12a transmission/reception unit, 13, 13a delay correction device, 14 time synchronization protocol, 51D, 51U changeover switch, 52D, 52U amplification unit, 61D, 61U distributor, 62D, 62U demodulation unit, 63D, 63U delay comparison unit, 64 Inter-base station delay comparison unit.

Claims (13)

a base station;
a plurality of relay stations connected one-to-one with the base station by optical fiber and connected in a daisy chain by LCX;
the relay station at one end of the daisy chain is connected to the base station by LCX;
further comprising a terminating relay station connected by LCX to the relay station at the other end of the daisy chain;
The base station transmits a signal via an optical fiber to target relay stations, which are at least two relay stations among the plurality of relay stations;
the terminating relay station receives the signal from the target relay station via LCX, measures a phase difference of the signal received from the target relay station, and transmits the phase difference to the base station;
the base station corrects the delay of the optical fiber connecting the target relay station and the base station so that the phase difference of the signals is less than a predetermined threshold ;
wireless communication system. the base station repeats transmission of the signal by changing the target relay station;
A wireless communication system according to claim 1 . The target relay station is a plurality of relay stations having adjacent wireless communication areas,
The radio communication system according to claim 1 or 2. a base station;
a plurality of relay stations connected one-to-one with the base station by optical fiber and connected in a daisy chain by LCX;
the relay station at one end of the daisy chain is connected to the base station by LCX;
further comprising a terminating relay station connected by LCX to the relay station at the other end of the daisy chain;
The base station
transmitting a first test signal to each of the relay stations via an optical fiber and acquiring the reception time of the first test signal at each of the relay stations via a relay station monitoring line;
transmitting a second test signal to each of the relay stations via the LCX, and acquiring the reception time of the second test signal at each of the relay stations via a relay station monitoring line;
calculating a time difference between the transmission time of the first test signal and the reception time at each relay station as a first time difference;
calculating the time difference between the transmission time of the second test signal and the reception time at each relay station as a second time difference;
Based on the difference between the first time difference and the second time difference, correcting the delay of the transmission line by the optical fiber connected to each of the relay stations;
wireless communication system. the base station synchronizes the time of the base station and each of the relay stations by transmitting time information to each of the relay stations;
A wireless communication system according to claim 4. A radio communication system in which the first radio communication system and the second radio communication system, which are the radio communication systems according to any one of claims 1 to 5, are connected using the terminal relay station in common. ,
the base station of the first wireless communication system transmitting a third test signal to one of the relay stations via an optical fiber;
the base station of the second wireless communication system transmitting a fourth test signal to one of the relay stations via an optical fiber;
The terminating relay station receives the third test signal and the fourth test signal via the LCX, measures the phase difference between the third test signal and the fourth test signal as a phase difference between base stations, and transmitting an inter-base station phase difference to the base station of the second wireless communication system;
The base station of the second wireless communication system corrects the phase of the signal to be transmitted to each of the relay stations based on the inter-base station phase difference.
wireless communication system. the base station performs the delay correction by adjusting the length of the optical fiber;
A radio communication system according to any one of claims 1 to 6. A base station connected one-to-one with a plurality of relay stations connected in a daisy chain by LCX and an optical fiber,
connected by LCX to the relay station at one end of the daisy chain;
transmitting a signal via an optical fiber to target relay stations, which are at least two relay stations among the plurality of relay stations;
The phase difference of the signal transmitted from the target relay station to the terminating relay station, measured at the terminating relay station connected by LCX to the relay station at the other end of the daisy chain , from the terminating relay station receive and
correcting the delay of the optical fiber connecting the target relay station and the base station so that the phase difference of the signal received from the terminal relay station is less than a predetermined threshold;
base station. repeating transmission of the signal by changing the target relay station;
A base station according to claim 8. A base station connected one-to-one with a plurality of relay stations connected in a daisy chain by LCX and an optical fiber,
connected by LCX to the relay station at one end of the daisy chain;
transmitting a first test signal to each of the relay stations via an optical fiber and acquiring the reception time of the first test signal at each of the relay stations via a relay station monitoring line;
transmitting a second test signal to each of the relay stations via the LCX, and acquiring the reception time of the second test signal at each of the relay stations via a relay station monitoring line;
calculating a time difference between the transmission time of the first test signal and the reception time at each relay station as a first time difference;
calculating the time difference between the transmission time of the second test signal and the reception time at each relay station as a second time difference;
Based on the difference between the first time difference and the second time difference, correcting the delay of the transmission line by the optical fiber connected to each of the relay stations;
base station. Synchronize with the time of each relay station by transmitting time information to each relay station;
11. A base station according to claim 10 . A relay station connected one-to-one with a base station by optical fiber and connected to other relay stations in a daisy chain by LCX,
A first test signal is received from the base station via an optical fiber, and the reception time of the first test signal is connected to the other relay station or the relay station at one end of the daisy chain via a relay station monitoring line. transmitted to the specified terminal repeater station,
receiving a second test signal from the base station via the LCX, and transmitting the reception time of the second test signal to the other relay station or the terminating relay station via a relay station monitoring line;
relay station. A terminating relay station connected by LCX to the relay station at one end of a plurality of relay stations connected in a daisy chain by LCX,
Each relay station transmits the reception time of the first test signal received from the base station via an optical fiber to the base station via a relay station monitoring line;
Each relay station transmits the reception time of the second test signal received from the base station via the LCX to the base station via a relay station monitoring line;
Terminating relay station.

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