REPEATER CONTROL DEVICE, WIRELESS COMMUNICATION SYSTEM, CONTROL CIRCUIT, STORAGE MEDIUM, AND CONTROL VALUE DETERMINATION METHOD

In a repeater control device for controlling a communication repeater that has a beamforming function and relays a wireless communication signal including communication data addressed from a transmission device to a reception device, the repeater control device includes: a parameter determination unit that determines a gain adjustment value for adjusting input power to an amplifier that amplifies the wireless communication signal relayed by the communication repeater, on the basis of an evaluation value indicating communication quality in the reception device and calculated on the basis of: state information indicating a state of the communication repeater; a beam pattern requested when the communication repeater transmits the wireless communication signal to the reception device; transmission path information indicating a state of a transmission path between the communication repeater and the reception device; and reception device information indicating a state of the reception device.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present disclosure relates to a repeater control device, a wireless communication system, a control circuit, a storage medium, and a control value determination method for controlling a communication repeater that relays a wireless communication signal including communication data addressed from a transmission device to a reception device.

2. Description of the Related Art

In a communication repeater that has a beamforming function and relays a wireless communication signal including communication data addressed from a transmission device to a reception device, the wireless communication signal to be relayed is amplified using an amplifier and then transmitted toward the reception device. Here, in a case where a non-linear amplifier with high power efficiency is used, a back-off margin is set for amplification in a linear region of the amplifier for the purpose of causing distortion in a communication signal. By setting the back-off margin, a usable dynamic range of the amplifier is reduced. In a case where the back-off margin is set only on the basis of electrical characteristics of the amplifier alone, communication quality is degraded with an excessive back-off margin.

International Publication No. 2020/158040 discloses a multi-beam type relay communication system that reduces a back-off margin, by calculating a weight for beam formation so as to reduce peak-to-average power and multiplying the weight by a relay signal.

However, according to the above-described conventional technique, there has been a problem that communication quality in a reception device that receives a relay signal is not necessarily improved.

SUMMARY OF THE INVENTION

In order to solve the above-described problems, a repeater control device according to the present disclosure is a repeater control device for controlling a communication repeater that relays a wireless communication signal including communication data addressed from a transmission device to a reception device, the communication repeater having a beamforming function, the repeater control device includes: a parameter determination unit to determine a gain adjustment value for adjusting input power to an amplifier, the amplifier amplifying the wireless communication signal relayed by the communication repeater, based on an evaluation value indicating communication quality in the reception device and calculated based on: state information indicating a state of the communication repeater; a beam pattern requested when the communication repeater transmits the wireless communication signal to the reception device; transmission path information indicating a state of a transmission path between the communication repeater and the reception device; and reception device information indicating a state of the reception device.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a repeater control device, a wireless communication system, a control circuit, a storage medium, and a control value determination method according to embodiments of the present disclosure will be described in detail with reference to the drawings.

First Embodiment

FIG.1is a diagram illustrating a configuration of a wireless communication system1according to a first embodiment. The wireless communication system1includes a communication repeater2, a transmission device3, a reception device4, a communication control device5, and a repeater control device6. For example, the wireless communication system1may be a satellite communication system in which the communication repeater2is a communication satellite, the transmission device3may be a gateway, the reception device4may be a communication terminal, the communication control device5may be a network operation center (NOC), and the repeater control device6may be a communication satellite control device.

The communication repeater2relays a wireless communication signal including communication data addressed from the transmission device3as a transmission device to the reception device4as a reception device. The transmission device3transmits a wireless communication signal including communication data addressed to the reception device4to the communication repeater2. The reception device4receives a wireless communication signal from the transmission device3via the communication repeater2. The communication control device5is a device provided to operate and manage the wireless communication system1, and has a function of monitoring a state of each device included in the wireless communication system1and controlling each device included in the wireless communication system1. For example, the communication control device5can change settings of the transmission device3and the reception device4, and can change settings of the communication repeater2via the repeater control device6.

FIG.2is a sequence diagram for explaining an operation of the wireless communication system1illustrated inFIG.1. The communication control device5transmits a control value calculation request to the repeater control device6(step S101). Upon receiving the control value calculation request from the communication control device5, the repeater control device6calculates a control value in response to the control value calculation request (step S102). The repeater control device6transmits a control value calculation response including a calculation result to the communication control device5(step S103).

Upon receiving the control value calculation response, the communication control device5transmits a control value setting request including the control value to be set in the communication repeater2, to the repeater control device6in response to the received control value calculation response (step S104). Upon receiving the control value setting request, the repeater control device6transmits a control value setting command, which is a command to set the control value of the communication repeater2, to the communication repeater2in response to the received control value setting request (step S105). Upon receiving the control value setting command, the communication repeater2sets the control value on the basis of the received control value setting command (step S106).

In addition, upon transmitting the control value setting request to the repeater control device6, the communication control device5sets a communication parameter in the transmission device3(step S107). By using the set communication parameter, the transmission device3transmits, to the communication repeater2, a wireless communication signal including communication data addressed to the reception device4(step S108). The communication repeater2transmits the relayed wireless communication signal to the reception device4(step S109).

As described above, in addition to the communication illustrated inFIG.2, between the communication repeater2and the repeater control device6, communication is performed such as telemetry to transmit state information including information obtained from various sensors installed on the communication repeater2to the repeater control device6, and a command to transmit information to be used for navigation of the communication repeater2from the repeater control device6to the communication repeater2.

FIG.3is a diagram illustrating a functional configuration of the communication repeater2illustrated inFIG.1. The communication repeater2includes a plurality of reception units21, a switch22, a plurality of transmission units23, and a control unit24. Each of the plurality of reception units21and each of the plurality of transmission units23have a beamforming function, and can control individual beam directions in different directions. The communication repeater2receives a wireless communication signal transmitted from the transmission device3by using the reception unit21, and outputs, to the switch22, a signal divided by a frequency as a result of demultiplexing. The switch22converts arrangement of the signals divided by the frequency, and outputs the signals to the transmission unit23. The transmission unit23outputs and transmits the multiplexed signal to the reception device4. The control unit24performs various settings of the reception unit21, the switch22, and the transmission unit23. For example, the control unit24can set an excitation coefficient and a gain adjustment value, which are control values, on the basis of the control value setting command from the repeater control device6.

FIG.4is a diagram illustrating an example of a functional configuration of the transmission unit23illustrated inFIG.3. The transmission unit23includes a plurality of excitation coefficient multiplication units231-1to231-n, a plurality of gain adjustment units232-1to232-n, a plurality of multiplexing units233-1to233-n, a plurality of digital analog converters (DACs)234-1to234-n, a plurality of amplifiers235-1to235-n, a plurality of antenna elements236-1to236-n, and a storage device237. Note that, in the following description, in a case where it is not particularly necessary to distinguish each of a plurality of constituent elements having similar functions, only common reference numerals are given for description. For example, each of the excitation coefficient multiplication units231-1to231-nis referred to as an excitation coefficient multiplication unit231when it is not necessary to distinguish from each other. The excitation coefficient multiplication unit231, the gain adjustment unit232, the multiplexing unit233, the DAC234, the amplifier235, and the antenna element236are provided in n pieces of systems, and components of the individual systems are distinguished from each other by adding an identical numeral after a hyphen. Note that the transmission unit23copies an input signal to generate a signal for each antenna element236, and inputs the generated signal to each of the excitation coefficient multiplication units231-1to231-n.

The excitation coefficient multiplication unit231multiplies the input signal by an excitation coefficient and outputs the multiplied signal to the gain adjustment unit232. The gain adjustment unit232adjusts input power to the amplifier235by multiplying the input signal by a gain adjustment value, and outputs the adjusted signal to the multiplexing unit233. The multiplexing unit233converts a signal divided in a frequency domain into a time waveform, and outputs the converted signal to the DAC234. The DAC234converts the input signal from a digital signal to an analog signal, and outputs the converted signal to the amplifier235. The amplifier235amplifies the analog signal output from the DAC234and outputs the amplified signal to the antenna element236. The antenna element236transmits the signal output from the amplifier235. The storage device237receives, from the control unit24, a gain adjustment value and an excitation coefficient, which are control values whose notification is provided from the repeater control device6to the communication repeater2, and stores the gain adjustment value and the excitation coefficient. The storage device237provides the excitation coefficient to each of the excitation coefficient multiplication units231-1to231-n, and provides the gain adjustment value to each of the gain adjustment units232-1to232-n.

Although the excitation coefficient multiplication unit231and the gain adjustment unit232are different functional blocks here, a function of the gain adjustment unit232may be performed by the excitation coefficient multiplication unit231, by including the adjustment of the input power by the gain adjustment value into the excitation coefficient.

FIG.5is a diagram illustrating an example of a functional configuration of the repeater control device6illustrated inFIG.1. The repeater control device6includes a repeater control value generation unit61and a repeater control value setting unit62. The repeater control value generation unit61calculates a control value for controlling the repeater in response to the control value calculation request from the communication control device5, and transmits the calculated control value as the control value calculation response to the communication control device5. In response to the control value setting request from the communication control device5, the repeater control value setting unit62transmits the control value setting command to instruct the communication repeater2to set the control value.

FIG.6is a view illustrating an example of information included in a control value calculation request T2received by the repeater control device6illustrated inFIG.5. The control value calculation request T2includes an evaluation frequency and regulation point information. The evaluation frequency is a center frequency of a relay signal for calculating communication quality, and the evaluation frequency is used as an evaluation value. The regulation point information includes, for K pieces of regulation points, coordinates indicating positions of the regulation points, and upper and lower limits of gains at the regulation points. K is an integer of 1 or more.

Here, a specific method in which the repeater control device6calculates a control value of the communication repeater2will be described.FIG.7is a diagram illustrating an example of a specific configuration of the repeater control value generation unit61illustrated inFIG.5. The repeater control value generation unit61includes a repeater state storage unit611, a repeater setting storage unit612, an environmental parameter setting unit613, a database (DB)614, a radio frequency (RF) characteristic calculation unit615, and a parameter determination unit616.

The repeater state storage unit611stores state information acquired by the repeater control device6from the communication repeater2, through communication called the telemetry described above. The repeater setting storage unit612stores information included in the control value calculation request transmitted from the communication control device5. The environmental parameter setting unit613stores: transmission path information including rainfall information for each point and indicating a state of a transmission path between the communication repeater2and the reception device4; and reception device information indicating a state of the reception device4. The DB614stores amplifier characteristic information indicating characteristics of the amplifier235included in the communication repeater2. The RF characteristic calculation unit615calculates an RF characteristic at the time point, on the basis of the amplifier characteristic information stored in the DB614and the state information stored in the repeater state storage unit611, and outputs the calculated RF characteristic to the parameter determination unit616. When the amplifier characteristic varies depending on the frequency, the RF characteristic calculation unit615acquires the amplifier characteristic information on the basis of the evaluation frequency stored in the repeater setting storage unit612. The RF characteristic calculation unit615calculates, for example, an AM/AM characteristic indicating a relationship between input power and output power of the amplifier, and an AM/PM characteristic indicating a relationship between input power and an output phase of the amplifier. In a non-linear amplifier, the output power becomes linear, and the output phase does not change until the input power reaches a certain value. However, when the input power exceeds the certain value, the output power becomes non-linear, and the phase also shifts. Since these characteristics change in accordance with a frequency and a temperature, the RF characteristic calculation unit615calculates the RF characteristic on the basis of the evaluation frequency and the temperature.

FIG.8is a view illustrating an example of amplifier characteristic information T1stored in the DB614illustrated inFIG.7. The amplifier characteristic information T1is created on the basis of, for example, a value measured in advance. In the amplifier characteristic information T1illustrated inFIG.8, the input power, the output power, and the output phase of the amplifier235are associated with the frequency and the temperature of the input signal.

The RF characteristic calculation unit615outputs, to the parameter determination unit616, the RF characteristic including the output power and the output phase with respect to the input power for each frequency associated with the temperature at the time point of the communication repeater2. In a case where the amplifier characteristic information T1does not include data corresponding to the temperature at the time point, the RF characteristic calculation unit615may output the output power and the output phase corresponding to the temperature at the time point by performing interpolation, on the basis of data close to the temperature at the time point. The parameter determination unit616generates a control value of the communication repeater2on the basis of the RF characteristic output from the RF characteristic calculation unit615, information included in the control value calculation request stored in the repeater setting storage unit612, and information stored in the environmental parameter setting unit613. In a case where the control value calculation request includes a position of the regulation point and an upper limit and a lower limit of the gain at the regulation point, the parameter determination unit616generates an excitation coefficient and a gain adjustment value, which are control values, such that the gain at the regulation point satisfies the upper limit and the lower limit of the gain included in the control value calculation request.

FIG.9is a flowchart for explaining an operation of the parameter determination unit616illustrated inFIG.7. First, the parameter determination unit616sets regulation point information, frequency information, a modulation method, a threshold Tq of an evaluation value, and a terminal type, which are parameters for determining the gain adjustment value and the excitation coefficient (step S201). The parameter determination unit616sets the gain adjustment value to 0 (step S202).

The parameter determination unit616sets an initial value of the excitation coefficient for forming a beam toward the regulation point so as to maximize total emission power in a state where the gain adjustment value is 0 (step S203). Thereafter, the parameter determination unit616calculates an evaluation value indicating communication quality in the reception device4(step S204). The parameter determination unit616determines whether or not the evaluation value exceeds the predetermined threshold Tq (step S205). Here, it is assumed that a larger evaluation value indicates higher communication quality. When the evaluation value is equal to or less than the threshold Tq (step S205: No), the parameter determination unit616adjusts the gain adjustment value by lowering the gain adjustment value by one step, and adjusts the excitation coefficient such that the total emission power is maximized when the adjusted gain adjustment value is used (step S206).

The parameter determination unit616repeats the processing of steps S204to S206. When the evaluation value exceeds the threshold Tq (step S205: Yes), the parameter determination unit616stores the gain adjustment value, the excitation coefficient, and the evaluation value at this time (step S207), and transmits the control value calculation response to the communication control device5.

When the control value calculation request includes a plurality of pieces of regulation point information, the parameter determination unit616calculates an evaluation value for each regulation point, and repeats the processing of steps S204to S206until all the evaluation values exceed the threshold Tqin step S205.

FIG.10is a flowchart for explaining a specific example of a method for calculating an evaluation value by the parameter determination unit616according to the first embodiment. The operation illustrated inFIG.10is a specific example of step S204inFIG.9, and illustrates a case where the evaluation value is a signal to interference and noise ratio (SINR).

Using the set excitation coefficient and gain adjustment value, the parameter determination unit616calculates transmission power Pti for a beam i in a direction of the regulation point, on the basis of a position of the communication repeater2, a position of the regulation point, and an antenna orientation direction of the communication repeater2(step S208). The position information and the antenna orientation direction of the communication repeater2are included in, for example, the state information stored in the repeater state storage unit611. The position of the regulation point is included in the control value calculation request, and the parameter determination unit616acquires the position information of the regulation point from the repeater setting storage unit612.

Subsequently, the parameter determination unit616calculates an atmospheric absorption loss La and a rainfall attenuation amount Lr, on the basis of the transmission path information stored in the environmental parameter setting unit613(step S209). The parameter determination unit616calculates a distance between the communication repeater2and the reception device4on the basis of the position information of each of the communication repeater2and the reception device4, and calculates a distance attenuation amount Ld on the basis of the calculated distance (step S210). The position information of the reception device4is included in, for example, the reception device information stored in the environmental parameter setting unit613. The atmospheric absorption loss La and the rainfall attenuation amount Lr are included in the transmission path information stored by the environmental parameter setting unit613, for example.

The parameter determination unit616calculates a reception antenna gain Gr and various losses LR including a tracking loss and a feeder loss that are set for each terminal type (step S211). The reception antenna gain Gr and the various losses LR including the tracking loss and the feeder loss are included in, for example, the reception device information stored in the environmental parameter setting unit613. It is conceivable that the reception antenna gain Gr and the various losses LR including the tracking loss and the feeder loss are stored as the reception device information for each terminal type, and the reception device information corresponding to a designated terminal type is used.

The parameter determination unit616calculates reception power Si=Pti+La+Lr+LR+Ld+Gr at the regulation point of each beam (step S212). When i main is a beam having the largest reception power Si at the regulation point, the parameter determination unit616calculates the SINR by using Si/(Ip+N) on the basis of the reception power Si (i=i main) calculated in step S212, total reception power Ip=ΣSi (i≠i_main) of beams other than i_main, and noise power N (step S213). The noise power N is included in, for example, the reception device information stored in the environmental parameter setting unit613.

The above processing is implemented by software that simulates each of the transmission unit23of the communication repeater2, the reception device4, and the transmission path between the communication repeater2and the reception device4.

Among the functional units described above, a functional unit performed by digital processing is configured by software having a configuration with a matched quantization bit rate. A functional unit performed in normal analog processing holds analog characteristics as a database. When the characteristics of the amplifier235are obtained in the RF characteristic calculation unit615, the output power and the output phase with respect to the input power are obtained from the evaluation frequency and the temperature acquired by communication called the telemetry.

The repeater control device6stores the excitation coefficient and the gain adjustment value obtained as described above, and transmits, as beam pattern information obtained when the excitation coefficient and the gain adjustment value are set, a position represented by latitude and longitude of the regulation point and the gain at the regulation point, as the control value calculation response, to the communication control device5. When the control value is transmitted as the control value setting request from the communication control device5, the repeater control device6transmits the stored excitation coefficient and gain adjustment value to the communication repeater2as the control value setting command. The communication repeater2stores the excitation coefficient and the gain adjustment value, which are the control values, into the storage device237via the control unit24, and sets the excitation coefficient in the excitation coefficient multiplication unit231and sets the gain adjustment value in the gain adjustment unit232.

FIG.11is a graph for explaining an effect obtained by the wireless communication system1illustrated inFIG.1. As the input power to the amplifier235increases, signal power for noise increases, so that the communication quality increases as the input power increases. However, in a case where the amplifier235is a non-linear amplifier, non-linear distortion occurs in proportion to the input power when the input power becomes equal to or more than a certain value, and the communication quality is deteriorated. By repeating a process of calculating the evaluation value of the communication quality of when a gain adjustment value ag is gradually decreased from a value that causes the input power to an extent that the non-linear distortion occurs, it is possible to obtain the gain adjustment value ag=A with which the evaluation value exceeds the threshold Tqof the communication quality. For example, when the evaluation value of the communication quality is calculated in a state of the gain adjustment value ag=0, the calculated evaluation value is equal to or less than the threshold Tq. Therefore, the gain adjustment value agis decreased and set to the gain adjustment value ag=−1. When the evaluation value is calculated again in this state, since the evaluation value is still equal to or less than the threshold Tq, the processing of calculating the evaluation value by further decreasing the gain adjustment value agis repeated, and the evaluation value exceeds the threshold Tqwhen the gain adjustment value ag=A.

The individual functions of the communication repeater2, the transmission device3, the reception device4, the communication control device5, and the repeater control device6illustrated inFIG.1may be implemented by a dedicated circuit, or may be implemented by a control circuit such as a central processing unit (CPU) that executes a program. In the case of being implemented by the dedicated circuit, the individual functions of the communication repeater2, the transmission device3, the reception device4, the communication control device5, and the repeater control device6are implemented as processing circuitry7as illustrated inFIG.12.FIG.12is a diagram illustrating dedicated hardware for implementing each function of the wireless communication system1illustrated inFIG.1. The processing circuitry7illustrated inFIG.12is a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or a combination of these.

FIG.13is a diagram illustrating a hardware configuration for implementing each function of the wireless communication system1illustrated inFIG.1by using a CPU. Each function of the wireless communication system1can be implemented by using a CPU8, a memory9, and a storage10. The CPU8is a control circuit, and is also called an arithmetic device, a microprocessor, a microcomputer, a digital signal processor (DSP), or the like. The memory9and the storage10are a nonvolatile or volatile semiconductor memory such as a random access memory (RAM), a read only memory (ROM), a flash memory, an erasable programmable ROM (EPROM), or an electrically EPROM (EEPROM, registered trademark), a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, a digital versatile disk (DVD), or the like.

The CPU8reads and executes a program stored in the memory9or the storage10to implement each function of the wireless communication system1. A part of the functions of the wireless communication system1may be implemented by using a dedicated circuit, and a part thereof may be implemented by using a program and a CPU. Further, a way of dividing the functional blocks illustrated inFIGS.3,4,5, and7is an example, processing performed by a plurality of functional blocks may be implemented by one piece of the processing circuitry7or one program, or processing performed by one functional block may be implemented by a plurality of pieces of the processing circuitry7or a plurality of programs. Note that the program executed by the CPU8may be provided in a state of being stored in a storage medium, and the program may be read from the storage medium and stored in the memory9or the storage10, or the program provided via a communication path such as the Internet may be downloaded to the memory9or the storage10.

As described above, the communication repeater2according to the first embodiment has a beamforming function and relays a wireless communication signal including communication data addressed from the transmission device3to the reception device4, and the repeater control device6controls the communication repeater2. The repeater control device6includes the parameter determination unit616that determines a gain adjustment value for adjusting input power to the amplifier235that amplifies the wireless communication signal relayed by the communication repeater2, on the basis of an evaluation value indicating communication quality in the reception device4. The evaluation value is calculated on the basis of: state information indicating a state of the communication repeater2; a beam pattern requested when the communication repeater2transmits the wireless communication signal to the reception device4; transmission path information indicating a state of a transmission path between the communication repeater2and the reception device4; and reception device information indicating a state of the reception device4. Therefore, the gain is adjusted such that the communication quality in the reception device4becomes a desired value, and a transmission power level can be adjusted on the basis of the communication quality of the entire wireless communication system1without excessively setting a back-off margin. In addition, by performing such setting at a design stage, wasteful use of the high-performance amplifier235becomes unnecessary, and the hardware cost can be reduced.

Note that, in the first embodiment, an example in which the evaluation value is a signal-to-noise ratio has been described. Further, in the first embodiment, the parameter determination unit616sequentially performs processing of calculating the evaluation value and determining the gain adjustment value in response to the control value calculation request. This parameter determination unit616calculates the evaluation value while changing the gain adjustment value, and obtains the gain adjustment value with which the calculated evaluation value satisfies a predetermined condition. In the first embodiment, the predetermined condition is to exceed a predetermined threshold, and the parameter determination unit616repeats changing the gain adjustment value and comparing the evaluation value with the threshold until the evaluation value exceeds the threshold. More specifically, the parameter determination unit616provisionally sets the gain adjustment value, calculates the excitation coefficient so as to maximize the total emission power when the set gain adjustment value is used, and repeats changing the gain adjustment value and calculating the excitation coefficient until the condition is satisfied by the evaluation value when the provisionally set gain adjustment value and the calculated excitation coefficient are used. Note that, in the first embodiment, the control value calculation request transmitted from the communication control device5includes, as a control condition, information indicating a position of the regulation point and an upper limit and a lower limit of the gain at the regulation point. The parameter determination unit616determines the gain adjustment value such that the gain at the position of the regulation point included in the received control value calculation request falls within a range of the upper limit and the lower limit included in the control value calculation request.

Further, according to the first embodiment, it is possible to provide the wireless communication system1including: the transmission device3that converts communication data addressed to the reception device4into a wireless communication signal and transmits the wireless communication signal; the communication repeater2that relays the wireless communication signal transmitted from the transmission device3and transmits the wireless communication signal to the reception device4; the reception device4that receives the wireless communication signal from the communication repeater2and converts the wireless communication signal into communication data; and the repeater control device6that controls the communication repeater2. Note that, in the first embodiment, the communication repeater2is a communication satellite.

Furthermore, according to the first embodiment, it is possible to provide a control value determination method for determining a control value for controlling the communication repeater2that has a beamforming function and relays a wireless communication signal including communication data addressed from the transmission device3to the reception device4. This control value determination method may include: a step of determining a gain adjustment value that is a control value for adjusting input power to the amplifier235that amplifies the wireless communication signal relayed by the communication repeater2, on the basis of an evaluation value indicating communication quality in the reception device4. The evaluation value is calculated on the basis of: state information indicating a state of the communication repeater2; a beam pattern requested when the communication repeater2transmits the wireless communication signal to the reception device4; transmission path information indicating a state of a transmission path between the communication repeater2and the reception device4; and reception device information indicating a state of the reception device4. Note that, in the first embodiment, the control value determination method further includes a step of calculating an evaluation value in response to the control value calculation request, and a step of determining a gain adjustment value on the basis of the calculated evaluation value, and these steps are performed by the repeater control device6.

Second Embodiment

In the first embodiment, the repeater control device6uses the SINR as the evaluation value of the communication quality. However, in a second embodiment, an example will be described in which error vector magnitude (EVM) is used as an evaluation value of communication quality.

In the second embodiment, a configuration of the wireless communication system1is as illustrated inFIG.1. The second embodiment is different from the first embodiment in an operation in which the parameter determination unit616of the repeater control value generation unit61of the repeater control device6calculates an evaluation value, and other parts are similar to those in the first embodiment, and thus a detailed description thereof is omitted here. Note that, constituent elements of the second embodiment will be described with reference numerals identical to those in the first embodiment.

FIG.14is a flowchart for explaining a specific example of a method for calculating an evaluation value by the parameter determination unit616according to the second embodiment. The operation illustrated inFIG.14is a specific example of step S204inFIG.9, and illustrates a case where the evaluation value is the EVM.

The parameter determination unit616generates a relay signal by using a function that simulates a transmission path from the transmission device3to the communication repeater2for a wireless communication signal transmitted from the transmission device3and simulates the reception unit21, the switch22, and the transmission unit23in the communication repeater2(step S214).

Subsequently, by executing processing similar to steps S209to S211inFIG.10, the parameter determination unit616calculates the atmospheric absorption loss La, the rainfall attenuation amount Lr, the distance attenuation amount Ld, the various losses LR for each terminal type, and the reception antenna gain Gr, and calculates a transmission path gain adjustment value C=La+Lr+LR+Ld+Gr by using these values. The gain adjustment of the relay signal is performed using the calculated transmission path gain adjustment value C, and a reception signal is calculated by adding noise of the noise power N (step S215). The parameter determination unit616extracts a symbol of the reception signal by performing frequency conversion which is reception processing (step S216), performing rate conversion (step S217), and performing waveform shaping and bit timing recovery (step S218). The parameter determination unit616calculates the EVM by comparing the extracted symbol of the reception signal with ideal signal point arrangement of a modulation scheme included in a parameter that is set in step S201ofFIG.9(step S219). The EVM is obtained by squaring a difference between the reception signal point position and the ideal signal point arrangement, and dividing the result by a square root. Since lower EVM indicates better communication quality, in a case where the EVM is used as the evaluation value, step S205may use “the evaluation value falls below the threshold”, or whether or not the evaluation value exceeds the threshold may be determined using the reciprocal of the EVM as the evaluation value.

As described above, in the wireless communication system1according to the second embodiment, the EVM is used as the evaluation value. Therefore, the communication quality can be calculated at a waveform level of the wireless communication signal, and more detailed optimization can be performed.

Third Embodiment

In the first and second embodiments, the control value is sequentially calculated in response to the control value calculation request transmitted in step S101ofFIG.2. In a third embodiment, the repeater control device6holds in advance a table in which calculated results are associated with a control condition. Further, in the control value calculation in step S102ofFIG.2, the repeater control device6extracts a control value corresponding to the control condition included in the control value calculation request from the table, and transmits the extracted control value as the control value calculation response in step S103.

FIG.15is a diagram illustrating a configuration of a repeater control value generation unit61-3according to the third embodiment. In the third embodiment, a configuration of the wireless communication system1is similar to that of the first embodiment, and a configuration of each device included in the wireless communication system1is similar to that of the first embodiment except that the repeater control device6includes the repeater control value generation unit61-3illustrated inFIG.15instead of the repeater control value generation unit61. Therefore, reference numerals identical to those in the first embodiment are used. Hereinafter, differences from the first embodiment will be mainly described.

In addition to the configuration of the repeater control value generation unit61, the repeater control value generation unit61-3further includes a control value table617in which a control condition and a gain adjustment value, which is a control value, are associated with each other. In addition, instead of the parameter determination unit616, the repeater control value generation unit61-3includes a parameter determination unit616-3that determines a gain adjustment value, which is a control value, by using the control value table617. In response to the control value calculation request, the parameter determination unit616-3extracts a gain adjustment value corresponding to the control condition included in the control value calculation request from the control value table617, and outputs the extracted gain adjustment value. Here, the control value table617includes, for example, an evaluation frequency and regulation point information which are the control condition, and an evaluation value, an excitation coefficient, and a gain adjustment value associated with the control condition.

As described above, according to the third embodiment, it is no longer necessary to sequentially calculate the evaluation value and the parameter, and thus, it is possible to improve a response speed to the control value calculation request.

Fourth Embodiment

In the first to the third embodiments described above, a condition used for determining the gain adjustment value is set to “the evaluation value exceeds the threshold”, and it is determined whether or not the desired communication quality is satisfied by comparing the evaluation value of the communication quality with the predetermined threshold. In a fourth embodiment, an example will be described in which this condition is set to “the evaluation value of the communication quality is maximized”.

In this case, the parameter determination unit616searches for a gain adjustment value with which the evaluation value is maximized while changing the gain adjustment value. For example, the parameter determination unit616can search for the gain adjustment value with which the evaluation value is maximized, by using an annealing method.

The parameter determination unit616uses the temperature and the gain adjustment value as variables, sets a sufficiently high value as an initial value of the temperature, and sets a value with which the evaluation value becomes sufficiently low as an initial value of the gain adjustment value. Then, the parameter determination unit616calculates the evaluation value of the communication quality by using the initial value of the temperature and the initial value of the gain adjustment value, and sets the calculated evaluation value as a variable to store the maximum value of the evaluation value. Thereafter, the parameter determination unit616decreases the gain adjustment value by 1 each time a processing step is advanced while decreasing the temperature, calculates the evaluation value each time, and compares the calculated evaluation value with the value set as the variable to store the maximum value of the evaluation value. When the calculated evaluation value is larger than the value set as the variable, the parameter determination unit616updates the maximum value of the evaluation value by setting the calculated evaluation value as the variable, and determines whether to stochastically adopt the maximum value as the maximum communication quality in the step, by using a probability based on the temperature. The parameter determination unit616repeats the above operation a predetermined number of times. Note that the operation described here is an example, and the search for the gain adjustment value can be implemented by using another global optimum algorithm.

As described above, since the parameter determination unit616searches for the maximum value of the evaluation value searchingly instead of using threshold determination, it is possible to obtain the gain adjustment value capable of further improving the communication quality without falling into the local optimum. In the fourth embodiment, it is not necessary to set a threshold provided for the evaluation value in advance.

The configurations illustrated in the above embodiments illustrate one example and can be combined with another known technique, and it is also possible to combine embodiments with each other and omit and change a part of the configuration without departing from the subject matter of the present disclosure.

A repeater control device according to the present disclosure has an effect of being able to improve communication quality in a reception device that receives a relay signal.

For example, in the above embodiments, a larger evaluation value indicates better communication quality, but it is possible to use an evaluation value indicating better communication quality as the evaluation value is smaller. In this case, in the above embodiments, “the evaluation value exceeds the threshold” may be read as “the evaluation value falls below the threshold”, and “the evaluation value is maximum” may be read as “the evaluation value is minimum”.