Wireless communication system and delay correction method

Abstract

To provide a technique capable of adjusting signal propagation delay amount without using an optical fiber bobbin when signals propagated between a base station device and each relay device are analog signals.SOLUTION: A wireless communication system includes a base station device 1 and a plurality of relay devices 2. The base station device 1 transmits a main signal, which is an analog signal, to the plurality of relay devices 2 via an optical fiber 5, and also transmits the main signal, which is an analog signal, to the plurality of relay devices 2 via an LCX 4. Each of the relay devices 2 includes a timing comparison unit 22 that measures a timing difference by comparing the timing of the main signal received via the optical fiber 5 and the timing of the main signal received via the LCX 4, and delay adding units 24a and 24b that add the measured timing difference to the main signal transmitted and received via the optical fiber 5 as a delay amount.SELECTED DRAWING: Figure 3

Description

[Technical field]

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

[0002] Conventionally, there are wireless communication systems that employ both the Radio on Fiber (RoF) method, in which a base station device and multiple relay devices are connected one-to-one via optical fiber, and the direct amplification method, in which the devices are connected in a daisy chain via a leaky coaxial cable (LCX).

[0003] Since the signal propagation delay between the base station device and each relay device differs between the RoF system and the direct-multiplexing system, it is necessary to match them. Conventionally, an optical fiber bobbin is inserted between the base station device and each relay device, and the length of the optical fiber bobbin is adjusted for each relay device to match the signal propagation delay in the RoF system with the signal propagation delay in the direct-multiplexing system (see, for example, Patent Document 1).

[0004] In addition, a method for adjusting the amount of signal propagation delay that does not use an optical fiber bobbin includes measuring the distance between a base station device and each relay device by measuring the RTT (Round-Trip Time) between the base station device and each relay device, and adjusting the amount of signal propagation delay by adding a delay amount corresponding to the distance difference to the propagation signal (see, for example, Patent Document 2). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2020-53845 A [Patent Document 2] Patent No. 6362779 Summary of the Invention [Problem to be solved by the invention]

[0006] In the conventional method of adjusting the signal propagation delay amount without using an optical fiber bobbin, it is necessary to measure the RTT between the base station device and each relay device, and therefore it is necessary to transmit and receive digital signals between the base station device and each relay device. Therefore, when the propagation signal between the base station device and each relay device is an analog signal, it is difficult to adjust the signal propagation delay amount without using an optical fiber bobbin.

[0007] Therefore, an object of the present disclosure is to provide a technique capable of adjusting the amount of signal propagation delay without using an optical fiber bobbin when the propagation signal between a base station device and each relay device is an analog signal. [Means for solving the problem]

[0008] The wireless communication system according to the present disclosure includes a base station device, and a plurality of relay devices that are connected one-to-one to the base station device via optical fiber and are connected in a daisy chain via an LCX, wherein the base station device transmits a main signal, which is an analog signal, to the plurality of relay devices via the optical fiber and also transmits the main signal, which is an analog signal, to the plurality of relay devices via the LCX, and each of the relay devices includes a timing comparison unit that measures a timing difference by comparing the timing of the main signal received via the optical fiber with the timing of the main signal received via the LCX, and a delay addition unit that adds the measured timing difference as a delay amount to the main signal transmitted and received via the optical fiber. Effect of the Invention

[0009] According to the present disclosure, in each relay device, the measured timing difference is added as a delay to the main signal transmitted and received through the optical fiber, thereby matching the timing of the main signal received through the optical fiber with the timing of the main signal received through the LCX, thereby eliminating the need for an optical fiber bobbin connected between the base station device and each relay device. Furthermore, since there is no need to measure the RTT between the base station device and each relay device, there is also no need to transmit and receive a digital signal for measuring the RTT.

[0010] Therefore, when the signal propagating between the base station device and each relay device is an analog signal, the signal propagation delay amount can be adjusted without using an optical fiber bobbin. [Brief description of the drawings]

[0011] [Figure 1] 1 is a configuration diagram of a wireless communication system according to a first embodiment. [Diagram 2] 1 is a block diagram of a base station device included in a wireless communication system according to a first embodiment, and a configuration diagram of its surroundings. [Diagram 3] 2 is a block diagram of a relay device included in the wireless communication system according to the first embodiment. FIG. [Figure 4] FIG. 2 illustrates an example of a configuration of a processing circuit included in the relay device. [Diagram 5] 11 is a block diagram of a relay device included in a wireless communication system according to a second embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] <Embodiment 1> <Wireless communication system configuration> The first embodiment will be described below with reference to the drawings. Fig. 1 is a configuration diagram of a wireless communication system according to the first embodiment.

[0013] 1, the wireless communication system includes a base station device 1, a plurality of relay devices 2a to 2n, and a plurality of mobile station devices 3. In the following description, when there is no need to distinguish between the relay devices 2a to 2n, they will be described as a relay device 2.

[0014] The base station device 1 is connected one-to-one with multiple relay devices 2 via optical fiber 5, and is also connected in a daisy chain with the multiple relay devices 2 in the order of relay device 2a, relay device 2b, ..., relay device 2n via the LCX 4. This allows the base station device 1 to support both the RoF method and the direct increase method.

[0015] The main signal is transmitted and received between the base station device 1 and the multiple relay devices 2 via an optical fiber 5 or an LCX 4, and between the multiple relay devices 2 and the multiple mobile station devices 3, via a radio wave signal input / output from the LCX 4.

[0016] Next, the details of the base station device 1 and the relay device 2 will be described with reference to Fig. 2 and Fig. 3. Fig. 2 is a block diagram of the base station device 1 and a configuration diagram of its surroundings. Fig. 3 is a block diagram of the relay device 2.

[0017] First, a description will be given of the base station device 1. As shown in Fig. 2, the base station device 1 includes a multiplexing unit 11, a plurality of modulation units 12, a plurality of D / A units 13, high frequency units 14a and 14b, a plurality of E / O units 15, a plurality of A / D units 16, a plurality of demodulation units 17, and a plurality of O / E units 18.

[0018] The multiplexing unit 11 splits the signal into multiple signal paths and connects them to multiple modulation units 12. Each modulation unit 12 is connected to a respective D / A unit 13. Each D / A unit 13 is connected to a high frequency unit 14a and a respective E / O unit 15. The high frequency unit 14b and each O / E unit 18 are connected to a respective A / D unit 16. Each A / D unit 16 is connected to a respective demodulation unit 17. Each demodulation unit 17 is connected to the multiplexing unit 11.

[0019] The base station device 1 receives a main signal, which is a digital signal transmitted from a higher-level device, at a multiplexing unit 11, which separates the main signal into multiple signal paths and outputs the signals to multiple modulation units 12. Each modulation unit 12 modulates the main signal by an arbitrary modulation method, and then outputs the modulated signal to the respective D / A units 13.

[0020] Each D / A unit 13 converts the main signal from a digital signal to an analog signal, and outputs the main signal converted to an analog signal to the high frequency unit 14a as a path for the direct amplification method, and also outputs the main signal to each E / O unit 15 as a path for the RoF method. Hereinafter, converting the main signal from a digital signal to an analog signal is also referred to as "analog conversion".

[0021] The high frequency unit 14a multiplexes the main signals, which are analog signals, input from the multiple D / A units 13, and outputs the multiplexed signal to the LCX 4. Each E / O unit 15 converts the main signals, which are analog signals, from electrical signals to optical signals, and outputs the converted signals to the optical fibers 5.

[0022] The main signal, which is an analog signal input from the relay device 2a via the LCX 4 by the direct amplification method, is received by the high frequency unit 14b. The high frequency unit 14b branches the main signal into a plurality of signal paths and outputs the branched signal to a plurality of A / D units 16.

[0023] Meanwhile, the main signal, which is an analog signal input from the relay device 2 via the optical fiber 5 by the RoF system, is received by each O / E unit 18. Each O / E unit 18 converts the main signal, which is an analog signal, from an optical signal to an electrical signal and outputs it to the respective A / D unit 16. Each A / D unit 16 converts the main signal, which is an analog signal input from the high frequency unit 14b or the O / E unit 18, from an analog signal to a digital signal and outputs it to the respective demodulation unit 17. Hereinafter, converting the main signal from an analog signal to a digital signal will also be referred to as "digital conversion".

[0024] Each demodulator 17 demodulates the main signal using the same modulation method as the modulator 12, and outputs the demodulated main signal to the multiplexer 11. The multiplexer 11 multiplexes the main signals, which are digital signals input from the multiple demodulators 17, and outputs the multiplexed main signals to a higher-level device.

[0025] Next, a description will be given of the relay device 2. Note that the relay devices 2a, 2b, . . . , 2n have the same configuration and perform the same operations, so here, a description will be given of the relay device 2a.

[0026] As shown in FIG. 3, the relay device 2a includes A / D units 21a, 21b, and 21c, a timing comparison unit 22, an O / E unit 23, delay addition units 24a and 24b, D / A units 25a and 25b, amplifiers 26a and 26b, switching units 27a and 27b, and an E / O unit 28.

[0027] The A / D unit 21a receives the main signal, which is an analog signal input from the LCX 4 by the direct amplification method, converts the main signal from analog to digital, and outputs the main signal to the timing comparison unit 22. The O / E unit 23 receives the main signal, which is an analog signal input from the optical fiber 5 by the RoF method, converts the main signal from an optical signal to an electrical signal, and outputs the main signal to the A / D unit 21b. The A / D unit 21b converts the input main signal, which is an analog signal, from analog to digital, and outputs the main signal to the timing comparison unit 22 and the delay addition unit 24a. The A / D unit 21b corresponds to a first A / D unit.

[0028] The timing comparator 22 measures the timing difference by comparing the timing of the main signal input from the A / D unit 21a via the LCX 4 by the direct amplification method with the timing of the main signal input from the A / D unit 21b via the optical fiber 5 by the RoF method in a digital signal state. Specifically, the timing difference is measured using the arrival time of the main signal input via the LCX 4 by the direct amplification method and the arrival time of the main signal input via the optical fiber 5 by the RoF method. Furthermore, the timing comparator 22 outputs the measured timing difference as a delay amount to the delay adding units 24a and 24b. The delay amount is stored in the timing comparator 22 or the delay adding units 24a and 24b to be used for adjusting the signal propagation delay amount thereafter.

[0029] The delay adding unit 24a adds the delay amount input from the timing comparing unit 22 to the main signal input from the A / D unit 21b via the optical fiber 5 by the RoF system, and outputs the result to the D / A unit 25a. The D / A unit 25a converts the input main signal, which is a digital signal, from a digital signal to an analog signal, and outputs the result to the switching unit 27a. The delay adding unit 24a corresponds to a first delay adding unit.

[0030] The switching unit 27a selects either the main signal, which is an analog signal input from the LCX 4 by the direct amplification method, or the main signal, which is an analog signal input from the D / A unit 25a, and outputs the selected signal to the amplifier unit 26b. The amplifier unit 26b amplifies the main signal, which is an analog signal, and outputs the amplified signal to the adjacent relay device 2b via the LCX 4. The D / A unit 25a corresponds to the first D / A unit.

[0031] Here, the delay adding unit 24a adds a delay to the main signal by delaying the timing of outputting the main signal by the delay amount and outputting the main signal to the D / A unit 25a. As a result, the main signal is output to the adjacent repeater 2b with a delay of the delay amount.

[0032] On the other hand, the main signal, which is an analog signal received from the adjacent relay device 2b via the LCX 4, is input to the switching unit 27b. When communication is performed using the direct amplification method, the switching unit 27b outputs the main signal to the amplifier 26a, and when communication is performed using the RoF method, the switching unit 27b outputs the main signal to the A / D unit 21c.

[0033] The amplifier 26a amplifies the input analog main signal and outputs it to the base station device 1 via the LCX 4. The A / D unit 21c converts the input analog main signal from an analog signal to a digital signal and outputs it to the delay adding unit 24b. The A / D unit 21c corresponds to a second A / D unit.

[0034] The delay adding unit 24b adds the delay amount input from the timing comparing unit 22 to the main signal, which is a digital signal input from the A / D unit 21c, and outputs the result to the D / A unit 25b. The delay adding unit 24b corresponds to a second delay adding unit.

[0035] The D / A unit 25b converts the received digital main signal from a digital signal to an analog signal and outputs the signal to the E / O unit 28. The E / O unit 28 converts the analog main signal input from the D / A unit 25b from an electrical signal to an optical signal and outputs the optical signal to the base station device 1 via the optical fiber 5. The D / A unit 25b corresponds to a second D / A unit.

[0036] <Processing circuit> Next, a description will be given of the processing circuit 90 included in the relay device 2. Fig. 4 is a diagram showing an example of the configuration of the processing circuit 90 included in the relay device 2. The functions of the timing comparison unit 22 and the delay addition units 24a and 24b are realized by the processing circuit 90. That is, the processing circuit 90 includes the timing comparison unit 22 and the delay addition units 24a and 24b.

[0037] The processing circuit 90 is a dedicated hardware. The processing circuit 90 is, for example, a single circuit, a composite circuit, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a circuit that combines these. The functions of the timing comparison unit 22 and the delay adding units 24a and 24b may be realized individually by a plurality of processing circuits, or may be realized collectively by one processing circuit.

[0038] <Effects> As described above, the wireless communication system according to the first embodiment includes the base station device 1, and the multiple relay devices 2 that are connected to the base station device 1 on a one-to-one basis via the optical fiber 5 and are also connected in a daisy chain via the LCX 4. The base station device 1 transmits a main signal, which is an analog signal, to the multiple relay devices 2 via the optical fiber 5, and also transmits a main signal, which is an analog signal, to the multiple relay devices 2 via the LCX 4. Each relay device 2 includes a timing comparator 22 that measures a timing difference by comparing the timing of the main signal received via the optical fiber 5 with the timing of the main signal received via the LCX 4, and delay adders 24a, 24b that add the measured timing difference as a delay amount to the main signal transmitted and received via the optical fiber 5.

[0039] In each relay device 2, the measured timing difference is added as a delay amount to the main signal transmitted and received via the optical fiber 5, thereby matching the timing of the main signal received via the optical fiber 5 with the timing of the main signal received via the LCX 4, thereby eliminating the need for optical fiber bobbins connected between the base station device 1 and each relay device 2. Furthermore, since there is no need to measure the RTT between the base station device 1 and each relay device 2, there is also no need to transmit and receive digital signals for measuring the RTT.

[0040] Therefore, when the signal propagating between the base station device 1 and each relay device 2 is an analog signal, the signal propagation delay amount can be adjusted without using an optical fiber bobbin. As a result, the optical fiber bobbin is no longer necessary, and the wireless communication system can be made more compact.

[0041] Each relay device 2 further includes an A / D unit 21b that digitally converts a main signal received via the optical fiber 5. The delay adding unit 24a adds a delay to the main signal digitally converted by the A / D unit 21b. Each relay device 2 further includes a D / A unit 25a that converts the main signal to which the delay amount has been added by the delay adding unit 24a into an analog signal and transmits the analog-converted main signal to another relay device 2 via the LCX 4. Each relay device 2 further includes an A / D unit 21c that digitally converts a main signal received from another relay device 2 via the LCX 4. The delay adding unit 24b adds a delay to the main signal digitally converted by the A / D unit 21c. Each relay device 2 further includes a D / A unit 25b that converts the main signal to which the delay amount has been added by the delay adding unit 24b into an analog signal and transmits the analog-converted main signal to the base station device 1 via the optical fiber 5.

[0042] Therefore, the main signal between the base station device 1 and the relay device 2 remains an analog signal, so there is no need to change the configuration from the conventional base station device. In the relay device 2, the amplifier unit 26, the switching unit 27, the O / E unit 23, and the E / O unit 28 can be used from the conventional relay device, so there is no need to change the configuration significantly. This makes it possible to suppress an increase in manufacturing costs in the wireless communication system.

[0043] In addition, each relay device 2 further includes A / D units 21a, 21b that digitally convert the main signal received via the optical fiber 5 and the main signal received via the LCX 4, and a timing comparison unit 22 compares the timing of the main signal received via the optical fiber 5 with the timing of the main signal received via the LCX 4 in the state of digital signals.

[0044] Therefore, when the timing comparison unit 22 is realized by the processing circuit 90 (see FIG. 4), it is easier to design a digital circuit for comparing the phases of the two main signals than when comparing them in the form of analog signals.

[0045] <Embodiment 2> Next, a wireless communication system according to embodiment 2 will be described. Fig. 5 is a block diagram of a relay device 2a included in the wireless communication system according to embodiment 2. Note that in embodiment 2, the same components as those described in embodiment 1 are denoted by the same reference numerals and description thereof will be omitted.

[0046] <Configuration of relay device> As shown in Fig. 5, in the second embodiment, the configuration of the relay device 2 is different from that in the first embodiment. In the first embodiment, the timing comparator 22 compares the timing of the main signal received via the optical fiber 5 with the timing of the main signal received via the LCX 4 in a digital signal state. In contrast, in the second embodiment, the timing comparator 22 compares the timing of the main signal received via the optical fiber 5 with the timing of the main signal received via the LCX 4 in an analog signal state.

[0047] The repeater 2 of the second embodiment differs from the repeater 2 of the first embodiment in that it does not have an A / D unit 21a and that both signals input to the timing comparison unit 22 are analog signals.

[0048] The timing comparator 22 measures the timing difference by comparing the main signal input from the LCX 4 by the direct amplification method with the main signal input from the O / E unit 23 by the RoF method in an analog signal state, and outputs the timing difference as a delay amount to the delay adding units 24a and 24b. The other operations are the same as those in the first embodiment. Here, the timing difference between the two main signals is measured by, for example, adding a periodic pulse such as a frame pulse to the beginning of the main signal and measuring the time to detect this pulse.

[0049] <Effects> As described above, in the wireless communication system according to the second embodiment, the timing comparison unit 22 compares the timing of the main signal received via the optical fiber 5 with the timing of the main signal received via the LCX 4 in the form of analog signals.

[0050] Therefore, in each relay device 2, an A / D unit 21a that converts the main signal input via LCX 4 by the direct amplification method from an analog signal to a digital signal is not required, so that the relay device 2 can be made smaller than in embodiment 1.

[0051] It should be noted that the embodiments can be freely combined, and each embodiment can be modified or omitted as appropriate. [Explanation of symbols]

[0052] 1 base station equipment, 2 relay equipment, 21a, 21b, 21c A / D section, 22 timing comparison section, 24a, 24b delay adding sections, 25a, 25b D / A section.

Claims

1. A base station device, a plurality of relay devices connected to the base station device in a one-to-one relationship by optical fibers and connected in a daisy chain by an LCX; the base station device transmits a main signal, which is an analog signal, to the plurality of relay devices via the optical fiber, and transmits the main signal, which is an analog signal, to the plurality of relay devices via the LCX; Each of the relay devices is a timing comparison unit that measures a timing difference by comparing a timing of the main signal received via the optical fiber with a timing of the main signal received via the LCX; a delay adding unit that adds the measured timing difference as a delay amount to the main signal transmitted and received via the optical fiber.

2. Each of the relay devices further includes a first A / D unit that converts the main signal received via the optical fiber from an analog signal to a digital signal, the delay adding unit includes a first delay adding unit that adds the delay amount to the main signal digitally converted by the first A / D unit, Each of the relay devices further includes a first D / A unit that converts the main signal to which the delay amount is added by the first delay adding unit from a digital signal to an analog signal, and transmits the analog-converted main signal to another of the relay devices via the LCX; Each of the relay devices further includes a second A / D unit that converts the main signal received from another relay device via the LCX from an analog signal to a digital signal, the delay adding unit includes a second delay adding unit that adds the delay amount to the main signal digitally converted by the second A / D unit, 2. The wireless communication system according to claim 1, wherein each of the relay devices further comprises a second D / A unit that converts the main signal to which the delay amount has been added by the second delay adding unit from a digital signal to an analog signal, and transmits the analog-converted main signal to the base station device via the optical fiber.

3. Each of the relay devices further includes an A / D unit that converts the main signal received via the optical fiber and the main signal received via the LCX from an analog signal to a digital signal, 2. The wireless communication system according to claim 1, wherein the timing comparator compares the timing of the main signal received via the optical fiber with the timing of the main signal received via the LCX in a digital signal state.

4. 2. The wireless communication system according to claim 1, wherein the timing comparator compares the timing of the main signal received via the optical fiber with the timing of the main signal received via the LCX in an analog signal state.

5. The base station equipment and multiple relay devices are connected one-to-one by optical fiber, and are also connected in a daisy chain by LCX. the base station device transmits a main signal, which is an analog signal, to the plurality of relay devices via the optical fiber, and transmits the main signal, which is an analog signal, to the plurality of relay devices via the LCX; a delay correction method in which each of the relay devices measures a timing difference by comparing the timing of the main signal received via the optical fiber with the timing of the main signal received via the LCX, and adds the measured timing difference as a delay amount to the main signal transmitted and received via the optical fiber.

6. 6. The delay correction method according to claim 5, wherein each of the relay devices performs digital conversion of the main signal received via the optical fiber from an analog signal to a digital signal, adds the delay amount to the digitally converted main signal, performs analog conversion of the main signal with the delay amount added from a digital signal to an analog signal, and transmits the analog-converted main signal to another of the relay devices via the LCX, and also performs digital conversion of the main signal received from the other of the relay devices via the LCX from an analog signal to a digital signal, adds the delay amount to the digitally converted main signal, performs analog conversion of the main signal with the delay amount added from a digital signal to an analog signal, and transmits the analog-converted main signal to the base station device via the optical fiber.

7. 6. The delay correction method according to claim 5, wherein each of the relay devices digitally converts the main signal received via the optical fiber and the main signal received via the LCX from an analog signal to a digital signal, and compares the timing of the main signal received via the optical fiber with the timing of the main signal received via the LCX in a digital signal state.

8. 6. The delay correction method according to claim 5, wherein each of the repeater devices compares the timing of the main signal received via the optical fiber with the timing of the main signal received via the LCX in an analog signal state.

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