Optical repeater device, communication control method, and communication control program

Abstract

This invention provides an optical repeater device, a communication control method, and a communication control program that improve the efficiency of frequency utilization in wireless communication. [Solution] The optical repeater device of this embodiment comprises an input unit, a calculation unit, a correction unit, and an output unit. The input unit receives a signal input. The calculation unit calculates the difference between the carrier frequency of the signal received by the input unit and a predetermined frequency. The correction unit corrects the carrier frequency of the signal if the difference calculated by the calculation unit is greater than or equal to a threshold. The output unit outputs the signal with the carrier frequency corrected by the correction unit.

Description

Technical Field

[0001] Embodiments of the present invention relate to an optical repeater device, a communication control method, and a communication control program.

Background Art

[0002] Conventionally, in mobile communication, the frequency band of wireless communication is allocated for each usage purpose and operator. An operator performs wireless communication in the frequency band allocated to itself using communication equipment installed independently.

[0003] When an error occurs in the frequency band of wireless communication, a communication device interferes with the frequency band of an adjacent operator. And when the communication device interferes with the frequency band of an adjacent operator, it may not be able to communicate normally. Therefore, in order to prevent interference with the frequency band of an adjacent operator, a frequency band not used for communication called a guard band is provided between the frequency bands of each operator.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, since the guard band is not used for communication, the utilization efficiency of the frequency of wireless communication is reduced.

[0006] Therefore, the present invention has been made in view of the above circumstances, and an object thereof is to improve the utilization efficiency of the frequency of wireless communication.

Means for Solving the Problems

[0007] The optical repeater device of this embodiment comprises an input unit, a calculation unit, a correction unit, and an output unit. The input unit receives a signal input. The calculation unit calculates the difference between the carrier frequency of the signal received by the input unit and a predetermined frequency. The correction unit corrects the carrier frequency of the signal if the difference calculated by the calculation unit is greater than or equal to a threshold. The output unit outputs the signal with the carrier frequency corrected by the correction unit. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 shows a schematic example of a distributed antenna system according to the first embodiment. [Figure 2] Figure 2 is an explanatory diagram illustrating the guard band bandwidth. [Figure 3] Figure 3 shows an example of the functional configuration of the master station device according to the first embodiment. [Figure 4] Figure 4 illustrates the carrier frequency correction in the OFDM scheme. [Figure 5] Figure 5 shows an example of a method for adjusting the signal transmission and reception timing in the TDD system. [Figure 6] Figure 6 is a flowchart showing an example of relay processing performed by the master station device according to the first embodiment. [Figure 7] Figure 7 shows an example of how to utilize the guard band bandwidth. [Figure 8] Figure 8 shows an example of the functional configuration of the master station device according to the second embodiment. [Figure 9] Figure 9 is a flowchart showing an example of relay processing performed by the master station device according to the second embodiment. [Modes for carrying out the invention]

[0009] The optical repeater device, communication control method, and communication control program will be described in detail below with reference to the attached drawings. In the following descriptions of each embodiment and modification, parts denoted by the same reference numerals have substantially the same function, and the explanation of overlapping parts will be omitted as appropriate.

[0010] (First Embodiment) Figure 1 shows a schematic example of a distributed antenna system 1 according to the first embodiment. The distributed antenna system 1 comprises a master station 10 and a plurality of slave station devices 20. The master station 10 and the plurality of slave station devices 20 are connected to each other via a transmission path so as to be communicative. The distributed antenna system 1 may also have devices not shown, such as relay devices.

[0011] The master station 10 is connected to multiple slave stations 20 within the distributed antenna system 1. The master station 10 may be connected to the multiple slave stations 20 via a relay device or the like, or it may be connected to the multiple slave stations 20 directly. The master station 10 is an example of an optical repeater device.

[0012] The master station device 10 is connected to the base station device 2 by a coaxial cable and transmits and receives radio signals with the base station device 2. Here, the radio signal is a signal in the radio communication band that is transmitted to the mobile terminal equipment 3. The master station device 10 transmits the radio signal received from the base station device 2 to the slave station device 20. The master station device 10 also transmits the radio signal received from the slave station device 20 to the base station device 2.

[0013] Base station device 2 is a device installed at a base station in, for example, a fifth-generation mobile communication network. For example, base station device 2 is a device that relays mobile terminals such as smartphones and tablet terminals between a network such as a fifth-generation mobile communication network.

[0014] The slave station device 20 is connected to an antenna for wireless communication with the mobile terminal equipment 3 via a wired cable, and transmits and receives wireless signals to and from the mobile terminal equipment 3 via this antenna. The slave station device 20 transmits the wireless signal received from the mobile terminal equipment 3 to the master station device 10. Also, the slave station device 20 transmits the wireless signal received from the master station device 10 to the mobile terminal equipment 3.

[0015] The mobile terminal equipment 3 is a portable terminal such as a smartphone or a tablet terminal.

[0016] According to the distributed antenna system 1 having such a configuration, it becomes possible to connect the mobile terminal equipment 3 to which radio waves cannot directly reach and the base station device 2, and the communicable range of the mobile communication network covered by the base station device 2 can be expanded. For example, the distributed antenna system 1 is applicable to the fifth-generation mobile communication network.

[0017] FIG. 2 is an explanatory diagram for explaining the guard band. A guard band is provided in the mobile communication network. For example, in the fifth-generation mobile communication system, frequencies from 3.6 GHz to 4.0 GHz are allocated as available frequencies. Each communication carrier installs communication equipment independently and constructs a communication area independently. And the communication carrier is performing communication using the carrier frequency band allocated to itself in the communication area constructed by each communication carrier.

[0018] The communication device may generate an error in the carrier frequency. In this case, if no countermeasure is taken against the error in the carrier frequency, communication using the carrier frequency with an error will interfere with the communication of the carrier frequency adjacent to the carrier frequency of the adjacent carrier. Therefore, for example, a mobile communication system such as the fifth-generation mobile communication system has a frequency band not used for communication called a guard band provided between the carrier frequency bands.

[0019] Even if an error occurs in the carrier frequency, as long as the error in the carrier frequency is within the guard band, the carrier frequency will not interfere with the communication of adjacent operators. Therefore, in the fifth-generation mobile communication system, a frequency band called the guard band that is not used for communication is provided between carrier frequency bands.

[0020] However, since the guard band is not used for communication, the frequency utilization efficiency is reduced. The distributed antenna system 1 corrects the error in the carrier frequency, so even if there is no guard band, the carrier frequency will not interfere with the communication of adjacent operators. And the distributed antenna system 1 can improve the frequency utilization efficiency because it uses the guard band for communication.

[0021] FIG. 3 is a diagram showing an example of the functional configuration of the master station apparatus 10 according to the first embodiment. The master station apparatus 10 includes a CPU (Central Processing Unit), a memory, an auxiliary storage device, etc. connected by a bus, and executes a program. The master station apparatus 10 includes a base station specific control unit 100 and a signal output unit 110 by executing the program. Further, the base station specific control unit 100 includes a signal input unit 101, a frequency detection unit 102, a frequency difference calculation unit 103, and a frequency correction unit 104. Note that all or part of each function of the master station apparatus 10 may be realized using hardware such as an ASIC (Application Specific Integrated Circuit), a PLD (Programmable Logic Device), or an FPGA (Field Programmable Gate Array). The program may be recorded on a computer-readable recording medium. A computer-readable recording medium is, for example, a portable medium such as a flexible disk, a magneto-optical disk, a ROM, a CD-ROM, or a storage device such as a hard disk built into a computer system. The program may be transmitted via a telecommunication line.

[0022] The base station control unit 100 corrects the frequency of the signals transmitted from each of the base station devices 2 according to the carrier frequency allocated to each telecommunications carrier. A base station control unit 100 is provided for each of the base station devices 2. The base station control unit 100 also includes a signal input unit 101, a frequency detection unit 102, a frequency difference calculation unit 103, and a frequency correction unit 104.

[0023] The signal input unit 101 receives signal input from the base station device 2. The signal input unit 101 is an example of an input unit. For example, the signal input unit 101 receives signal input from the base station device 2 connected by a coaxial cable.

[0024] The frequency detection unit 102 detects the carrier frequency of the signal received by the signal input unit 101. In other words, the frequency detection unit 102 detects the carrier frequency of the carrier wave that carries the signal.

[0025] The frequency difference calculation unit 103 calculates the difference between the carrier frequency of the signal received by the signal input unit 101 and a predetermined frequency. The frequency difference calculation unit 103 is an example of a calculation unit. More specifically, the frequency difference calculation unit 103 calculates the difference between the carrier frequency assigned to the operator of the base station equipment 2 corresponding to the base station control unit 100 and the carrier frequency detected by the frequency detection unit 102. In other words, the frequency difference calculation unit 103 determines whether there is an error between the carrier frequency assigned to the operator and the carrier frequency detected by the frequency detection unit 102. For example, the frequency difference calculation unit 103 determines that there is no error if the difference between any frequency included in the carrier frequency band assigned to the operator and the carrier frequency detected by the frequency detection unit 102 is less than a threshold. On the other hand, the frequency difference calculation unit 103 determines that there is an error if the difference between any frequency included in the carrier frequency band assigned to the operator and the carrier frequency detected by the frequency detection unit 102 is greater than or equal to a threshold.

[0026] The frequency correction unit 104 corrects the carrier frequency of the signal when the difference calculated by the frequency difference calculation unit 103 is greater than or equal to a threshold. The frequency correction unit 104 is an example of a correction unit. More specifically, the frequency correction unit 104 corrects the carrier frequency of the signal to the carrier frequency assigned to the operator when the frequency difference calculation unit 103 determines that there is an error in the carrier frequency of the signal. For example, the frequency correction unit 104 corrects the carrier frequency by any method such as frequency shift modulation.

[0027] More specifically, the frequency correction unit 104 performs a correction to adjust the signal's carrier frequency to a predetermined frequency. Here, the predetermined frequency is, for example, the carrier frequency allocated to the operator.

[0028] Furthermore, the frequency correction unit 104 corrects the carrier frequency of the signal so that the subcarriers in the orthogonal frequency division multiplexing (OFDM) scheme are orthogonal.

[0029] Figure 4 illustrates carrier frequency correction in the OFDM system. Figure 4(a) shows the state before carrier frequency correction. Figure 4(b) shows the state after carrier frequency correction. In the OFDM system, when small carrier waves called subcarriers are orthogonal, the master station 10 can communicate without mutual interference with adjacent carrier frequencies.

[0030] Figure 4(a) shows a state where the carrier frequency has not been corrected, but a guard band is provided between the first carrier and the second carrier. Because a guard band is provided, the first and second carriers, who are telecommunications carriers, can communicate without mutual interference with adjacent carrier frequencies.

[0031] Figure 4(b) shows a state in which the first operator and the second operator are communicating using the carrier frequency allocated to the third operator. The frequency correction unit 104 corrects the carrier frequency of the signal so that the subcarriers are orthogonal when there is an error in the carrier frequency. As a result, as shown in Figure 4(b), each subcarrier is orthogonal. Therefore, the master station device 10 can communicate without mutual interference with adjacent carrier frequencies.

[0032] The signal output unit 110 outputs a signal to each of the slave station devices 20. If the difference calculated by the frequency difference calculation unit 103 is greater than or equal to a threshold, the signal output unit 110 outputs a signal with a carrier frequency corrected by the frequency correction unit 104. The signal output unit 110 is an example of an output unit. The signal output unit 110 outputs a signal to each of the slave station devices 20, with the carrier frequency corrected by the frequency correction unit 104 of each of the multiple base station control units 100. More specifically, the signal output unit 110 outputs a signal to each of the slave station devices 20 using the TDD (Time Division Duplex) method, which synchronizes the timing of transmission and reception.

[0033] If the transmission and reception timings of signals from multiple carriers are out of sync, they can interfere with each other, potentially degrading communication quality. Therefore, the signal output unit 110 synchronizes the transmission and reception timings of signals from each of the multiple base station control units 100. More specifically, the signal output unit 110 performs communication by switching between transmitting and receiving signals at predetermined intervals.

[0034] Figure 5 shows an example of how to adjust the timing of signal transmission and reception in the TDD system. The signal output unit 110 transmits signals from the first carrier and the third carrier from timing T1. The signal output unit 110 also receives signals from the first carrier and the third carrier from timing T2. The signal output unit 110 adjusts to receive the signal from the second carrier from timing T2. This suppresses a decrease in communication quality in the signal output unit 110.

[0035] Next, we will describe the various processes performed by the master station device 10 according to the first embodiment.

[0036] Figure 6 is a flowchart showing an example of relay processing performed by the master station device 10 according to the first embodiment. Relay processing is the process of relaying data between the base station device 2 and the slave station device 20.

[0037] The signal input unit 101 receives the signal output from the base station device 2 (step S1).

[0038] The frequency detection unit 102 detects the frequency of the signal received by the signal input unit 101 (step S2).

[0039] The frequency difference calculation unit 103 determines whether the frequency of the signal detected by the frequency detection unit 102 matches the carrier frequency assigned to the relevant operator (step S3). That is, the frequency difference calculation unit 103 determines whether the difference between the frequency of the signal detected by the frequency detection unit 102 and the carrier frequency is less than a threshold.

[0040] If the frequency of the signal detected by the frequency difference calculation unit 103 matches the carrier frequency (step S3; Yes), the master station device 10 proceeds to step S5.

[0041] If the frequency of the signal detected by the frequency detection unit 102 does not match the carrier frequency (step S3; No), the frequency correction unit 104 corrects the frequency of the signal detected by the frequency detection unit 102 (step S4).

[0042] The signal output unit 110 outputs a signal to the slave station device 20 (step S5).

[0043] As a result, the master station device 10 terminates the relay process.

[0044] As described above, in the first embodiment, the master station 10 corrects the carrier frequency of the input signal if the carrier frequency does not match the carrier frequency allocated to the operator. The master station 10 then outputs the corrected signal to the slave station 20. As a result, the master station 10 can suppress interference between the carrier frequency and the communications of adjacent operators, even if a guard band is not provided. Therefore, the master station 10 can utilize the guard band for communication, thereby improving the frequency utilization efficiency of wireless communication.

[0045] In this way, the master station 10 can perform communication without mutual interference with adjacent carrier frequencies, even without a guard band bandwidth, by correcting the signal carrier frequency. Therefore, the master station 10 can utilize the guard band bandwidth for various purposes.

[0046] Figure 7 shows an example of how the guard band bandwidth is used. Figure 7(a) shows a state where the guard band bandwidth is not being used. Figure 7(b) shows a state where both telecommunications carriers on both sides are using the guard band bandwidth. Figure 7(c) shows a state where one of the telecommunications carriers is using the guard band bandwidth. Figure 7(d) shows a state where a new telecommunications carrier is using the guard band bandwidth.

[0047] As shown in Figure 7, there are four frequency bands: the first band B1, the second band B2, the third band B3, and the fourth band B4. The first band B1 is a frequency band lower than the carrier frequency allocated to the first operator. The second band B2 is a frequency band higher than the carrier frequency allocated to the first operator and lower than the third band B3. The third band B3 is a frequency band higher than the second band B2 and lower than the carrier frequency allocated to the second operator. The fourth band B4 is a frequency band higher than the carrier frequency allocated to the second operator.

[0048] For example, as shown in Figure 7(b), the first band B1 and the second band B2 are allocated to the first operator, and the third band B3 and the fourth band B4 are allocated to the second operator. In this way, guard band bandwidths may be used by operators of adjacent carrier frequencies.

[0049] For example, as shown in Figure 7(c), the first band B1, the second band B2, and the third band B3 are allocated to the first operator, and the fourth band B4 is allocated to the second operator. In this way, guard band bandwidths may be used by operators of adjacent carrier frequencies.

[0050] For example, as shown in Figure 7(d), the first band B1, the second band B2, the third band B3, and the fourth band B4 are allocated to new operators. In this way, guard band bandwidth may be used by new operators.

[0051] In this way, when the master station 10 receives an input signal with an error in the carrier frequency, it corrects the carrier frequency, thereby preventing interference with the frequency band allocated to adjacent operators even without a guard band. Therefore, the master station 10 can utilize the guard band for various purposes.

[0052] (Second embodiment) In the second embodiment, the master station device 10a does not output a signal if the difference between the frequency of the input signal and the carrier frequency is greater than or equal to a threshold when a signal using the guard band is input. This prevents the master station device 10a from interfering with the communications of adjacent carriers by transmitting or receiving signals with frequencies outside the guard band.

[0053] Figure 8 shows an example of the functional configuration of the master station device 10a according to the second embodiment. The master station device 10a includes a CPU, memory, and auxiliary storage device connected by a bus, and executes a program. The master station device 10a includes a base station-specific control unit 100a and a signal output unit 110 when the program is executed. The base station-specific control unit 100a also includes a signal input unit 101, a frequency detection unit 102a, a frequency difference calculation unit 103, and a signal output control unit 105. Note that all or part of the functions of the master station device 10a may be implemented using hardware such as ASICs, PLDs, or FPGAs. The program may be recorded on a computer-readable recording medium. Computer-readable recording media include, for example, portable media such as flexible disks, magneto-optical disks, ROMs, and CD-ROMs, and storage devices such as hard disks built into computer systems. The program may be transmitted via a telecommunications line.

[0054] The signal input unit 101 receives the input of a signal output from the base station device 2, similar to the first embodiment.

[0055] The frequency detection unit 102a determines whether or not to communicate using the guard band bandwidth based on the signal received by the signal input unit 101. The frequency detection unit 102a is an example of a second determination unit. For example, the frequency detection unit 102a determines whether or not to communicate using the guard band bandwidth based on flag information contained in the signal received by the signal input unit 101.

[0056] Furthermore, the frequency detection unit 102a detects the carrier frequency of the signal received by the signal input unit 101, similar to the first embodiment.

[0057] The frequency difference calculation unit 103 calculates the difference between the carrier frequency assigned to the operator of the base station equipment 2 corresponding to the base station control unit 100a and the carrier frequency detected by the frequency detection unit 102a, similar to the first embodiment.

[0058] The signal output control unit 105 determines whether or not to output a signal based on the calculation result of the frequency difference calculation unit 103. The signal output control unit 105 is an example of a first determination unit. More specifically, the signal output control unit 105 determines whether or not to output a signal when the frequency detection unit 102a determines that the communication uses the guard band bandwidth. For example, the signal output control unit 105 determines whether or not to output a signal based on the difference between the carrier frequency allocated to the carrier and the carrier frequency detected by the frequency detection unit 102a.

[0059] The signal output unit 110 outputs a signal based on the determination result of the signal output control unit 105. The signal output unit 110 is an example of an output unit. For example, the signal output unit 110 outputs a signal when the carrier frequency assigned to the operator matches the carrier frequency detected by the frequency detection unit 102a. Alternatively, the signal output unit 110 may output a signal when the difference between the carrier frequency assigned to the operator and the carrier frequency detected by the frequency detection unit 102a is less than a threshold.

[0060] For example, the signal output unit 110 does not output a signal if the carrier frequency assigned to the operator does not match the carrier frequency detected by the frequency detection unit 102a. Furthermore, the signal output unit 110 does not need to output a signal if the difference between the carrier frequency assigned to the operator and the carrier frequency detected by the frequency detection unit 102a is greater than or equal to a threshold.

[0061] Subsequently, the signal output unit 110 outputs a signal when the carrier frequency assigned to the operator matches the carrier frequency detected by the frequency detection unit 102a. This allows the master station device 10 to communicate while suppressing interference between the carrier frequency and the communications of adjacent operators.

[0062] Next, we will describe the various processes performed by the master station device 10a according to the second embodiment.

[0063] Figure 9 is a flowchart showing an example of relay processing performed by the master station device 10a according to the second embodiment.

[0064] The signal input unit 101 receives the signal output from the base station device 2 (step S11).

[0065] The frequency detection unit 102a determines whether or not to communicate the signal received by the signal input unit 101 using the guard band bandwidth (step S12). If the guard band bandwidth is not to be used (step S12; No), the master station device 10a proceeds to step S16.

[0066] If the guard band bandwidth is used (step S12; Yes), the frequency detection unit 102a detects the frequency of the signal received by the signal input unit 101 (step S13).

[0067] The frequency difference calculation unit 103 determines whether the frequency of the signal detected by the frequency detection unit 102a matches the carrier frequency assigned to the relevant operator (step S14). In other words, the frequency difference calculation unit 103 determines whether the difference between the frequency of the signal detected by the frequency detection unit 102a and the carrier frequency is less than a threshold.

[0068] If the frequency of the signal detected by the frequency detection unit 102a does not match the carrier frequency allocated to the operator (step S14; No), the signal output control unit 105 determines to stop outputting the signal (step S15). In other words, the signal output unit 110 does not output a signal. Then, proceeding to step S11, the signal input unit 101 accepts the signal input.

[0069] If the frequency of the signal detected by the frequency detection unit 102a matches the carrier frequency allocated to the operator (step S14; Yes), the signal output control unit 105 determines to output a signal (step S16). Then, the signal output unit 110 outputs a signal.

[0070] As a result, the master station device 10a terminates the relay process.

[0071] As described above, in the second embodiment, the master station 10a does not output a signal to the slave station 20 if the carrier frequency of the input signal does not match the carrier frequency allocated to the operator. The master station 10a outputs a signal to the slave station 20 when the carrier frequency of the input signal matches the carrier frequency allocated to the operator. As a result, the master station 10a can suppress interference between the carrier frequency and the communications of adjacent operators, even if a guard band is not provided. Therefore, the master station 10a can utilize the guard band for communication, thereby improving the frequency utilization efficiency of wireless communication.

[0072] Furthermore, the programs executed by the master station devices 10 and 10a of this embodiment are provided as installable or executable files recorded on a computer-readable recording medium such as a DVD (Digital Versatile Disk), USB (Universal Serial Bus) memory, or SSD (Solid State Drive).

[0073] Furthermore, the program may be configured to be stored on a computer connected to a network such as the Internet and provided by being downloaded via the network. Alternatively, the program may be configured to be provided or distributed via a network such as the Internet.

[0074] Alternatively, the program may be configured to be pre-installed in ROM or the like before being provided. [Explanation of Symbols]

[0075] 1…Distributed Antenna System, 2…Base station equipment, 3…Mobile terminal equipment, 10, 10a…Master station equipment, 20…Slave station equipment, 100, 100a…Base station-specific control unit, 101…Signal input unit, 102, 102a…Frequency detection unit, 103…Frequency difference calculation unit, 104…Frequency correction unit, 105…Signal output control unit, 110…Signal output unit, B1…First band, B2…Second band, B3…Third band, B4…Fourth band, T1, T2…Timing.

Claims

1. An input section that accepts signal inputs, A calculation unit calculates the difference between the carrier frequency of the signal received by the input unit and a predetermined frequency. If the difference calculated by the calculation unit is greater than or equal to a threshold, a correction unit corrects the carrier frequency of the signal. An output unit that outputs the signal with the carrier frequency corrected by the correction unit, An optical repeater device equipped with the following features.

2. The input unit receives the signal from the base station equipment in mobile communications. The optical repeater device according to claim 1.

3. The correction unit corrects the carrier frequency of the signal so that the subcarriers in the OFDM (Orthogonal Frequency Division Multiplexing) scheme are orthogonal. The optical repeater device according to claim 1.

4. The output unit outputs the signal using a TDD (Time Division Duplex) method to synchronize the timing of transmission and reception. The optical repeater device according to claim 1.

5. The correction unit adjusts the carrier frequency of the signal to the predetermined frequency. The optical repeater device according to claim 1.

6. An input section that accepts signal inputs, A calculation unit calculates the difference between the carrier frequency of the signal received by the input unit and a predetermined frequency. A first determination unit determines whether or not to output the signal based on the calculation result by the calculation unit, Based on the determination result of the first determination unit, an output unit outputs the signal, An optical repeater device equipped with the following features.

7. The system further includes a second determination unit that determines whether or not the communication uses the guard band frequency. The first determination unit determines whether or not to output the signal when the second determination unit determines that the communication uses the guard band bandwidth. The optical repeater device according to claim 6.

8. Accepts signal input, The difference between the carrier frequency of the received signal and a predetermined frequency is calculated. If the calculated difference is greater than or equal to a threshold, the carrier frequency of the signal is corrected. Outputting the signal with the corrected carrier frequency, A communication control method that includes the following.

9. Computers, An input section that accepts signal inputs, A calculation unit calculates the difference between the carrier frequency of the signal received by the input unit and a predetermined frequency. If the difference calculated by the calculation unit is greater than or equal to a threshold, a correction unit corrects the carrier frequency of the signal. An output unit that outputs the signal with the carrier frequency corrected by the correction unit, A communication control program to enable the function.

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