Communication device, method for predicting interruption, control circuit, and program recording medium

A communication device includes a signal determiner determining whether there is a reception signal, and a period estimator estimating an interruption period of interruption of a signal transmitted from a device as a source of the reception signal, using a determination result from the signal determiner. The period estimator includes a differential operator calculating a differential value of the determination result, a masking operator calculating a provisional period of the interruption period using the differential value, controlling use of the differential value and provisional period based on internal state, and outputting the provisional period to be used, a period calculator calculating the interruption period using the provisional period, a signal existing section calculator calculating a signal existing section using the provisional period, a periodic timing estimator estimating periodic timing using the provisional period and signal existing section, and a state determiner determining the internal state using the interruption period.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The disclosure relates to a communication device that communicates in an environment in which a communication channel is expected to be interrupted periodically, to a method for predicting interruption, to a control circuit, and to a program recording medium.

2. Description of the Related Art

In an environment in which a signal is interrupted periodically, a communication device undergoes a reduction in communication efficiency as compared to when the signal is not interrupted. An example of situation of communication in such environment occurs in a helicopter satellite communication system. A helicopter satellite communication system is a system in which a helicopter and a terrestrial station communicate with each other via a communication satellite. A signal transmitted from the helicopter to the communication satellite is interrupted periodically by the rotary wing of the helicopter. In addition, a signal transmitted from the communication satellite to the helicopter is also interrupted periodically by the rotary wing of the helicopter. This reduces efficiency of communication performed by a communication device provided in a helicopter as compared to usual communication.

Japanese Patent No. 2503883 discloses a technology in which a flying station installed in a flying object includes a receiver that detects a reception level of a signal received from a stationary station via a communication satellite, and detects, from the reception level at the receiver, radio wave interruption timing on a propagation channel. Upon transmission of a signal to the stationary station via the communication satellite, the flying station transmits the signal when there is no interruption of radio wave, and stops transmission of the signal when there is interruption of radio wave, on the basis of the reception level. In addition, the flying station detects reception timing from the detected reception level, and detects the phase difference between the reception timing and the interruption timing. The flying station informs the stationary station of the phase difference via the communication satellite, and the stationary station transmits a signal only when there is no interruption on the basis of the phase difference. The flying station can communicate at timing when there is no interruption of radio wave due to the rotary wing, and can thus provide efficient communication.

However, in the foregoing conventional technology, the flying station detects interruption timing, reception timing, and a phase difference based on the reception level of a signal received. This causes detection accuracy to be susceptible to an instantaneous change in the reception level, which presents a problem of being incapable of providing highly accurate and stable detection.

The disclosure has been made in view of the foregoing, and it is an object of the disclosure to provide a communication device capable of improving accuracy of estimation of the period, or cycle period, of interruption of a communication channel.

SUMMARY OF THE INVENTION

To solve the problem and achieve the object described above, a communication device according to the disclosure includes a signal determination unit to determine whether there is a reception signal or not; and a period estimation unit to estimate an interruption period of interruption of a signal transmitted from a device that is a source of the reception signal, using a determination result from the signal determination unit. The period estimation unit includes a differential operation unit to calculate a differential value of the determination result, and a masking operation unit to calculate a provisional period of the interruption period using the differential value, to control use of the differential value and of the provisional period based on an internal state representing an operational state of the period estimation unit, and to output the provisional period to be used. The period estimation unit further includes a period calculation unit to calculate the interruption period using the provisional period output from the masking operation unit, and a signal existing section calculation unit to calculate a signal existing section referring to a section in which the reception signal exists, using the provisional period output from the masking operation unit. The period estimation unit further includes a periodic timing estimation unit to estimate periodic timing representing timing of a change, in the determination result, from a section in which the reception signal does not exist to the signal existing section, using the provisional period output from the masking operation unit and using the signal existing section, and a state determination unit to determine the internal state using the interruption period.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A communication device, a method for predicting interruption, a control circuit, and a program recording medium according to embodiments will be described in detail below with reference to the drawings.

First Embodiment

FIG. 1is a diagram illustrating an example configuration of a communication system110according to a first embodiment. The communication system110includes a helicopter103, a communication satellite104, and a terrestrial station105. The communication system110is a helicopter satellite communication system in which the helicopter103and the terrestrial station105communicate with each other via the communication satellite104. The helicopter103includes a communication device100including a receiving device200and a transmission device300. The helicopter103also includes a rotary wing102provided on the top of an airframe101to provide buoyancy and propelling force. In the communication system110, rotation of the rotary wing102causes the communication channel between the communication device100of the helicopter103and the communication satellite104to be interrupted periodically. Possible examples of communication whose communication channel is interrupted periodically also include communication using a drone, a windmill, or the like, but are not limited thereto. In the present embodiment, the communication device100estimates the period, or cycle period, of interruption of the communication channel caused by rotation of the rotary wing102, and performs communication taking into consideration the period of interruption of the communication channel.

First, a configuration and an operation of the receiving device200included in the communication device100will be described.FIG. 2is a block diagram illustrating an example configuration of the receiving device200included in the communication device100according to the first embodiment. In addition,FIG. 3is a flowchart illustrating an operation of the receiving device200according to the first embodiment. The receiving device200includes an antenna210, a signal determination unit220, and a period estimation unit230. The antenna210receives a signal transmitted from the communication satellite104and periodically interrupted by the rotary wing102(step S1).

The signal determination unit220determines whether there is a reception signal or not based on a signal reception state in the antenna210(step S2). Specifically, the signal determination unit220compares the signal level of a reception signal that is a signal received by the antenna210with a determination threshold predetermined to determine whether there is a signal or not, and determines whether the situation is “signal existing” or “signal non-existing” based on the comparison result. The phrase “signal existing” herein refers to a situation in which there is a reception signal, and the phrase “signal non-existing” herein refers to a situation in which there is no reception signal. There is no limitation on the method for determining whether there is a reception signal or not, but one example will now be described. The signal determination unit220converts the reception signal input from the antenna210into, for example, a reception IQ signal formed of two orthogonal signals, through digital signal processing, and calculates signal power for a certain time period (this certain time period hereinafter referred to as one block) for multiple reception IQ signals in one block. The signal determination unit220performs an averaging operation on the calculated signal power, using infinite impulse response (IIR) averaging, a simple average, or the like, to calculate an average signal power value. The signal determination unit220compares the calculated average signal power value with the determination threshold. If the average signal power value is greater than or equal to the determination threshold, the signal determination unit220determines that there is a reception signal, that is, the situation is “signal existing”, and thus outputs a determination result of “1” indicating “signal existing” as for whether there is a reception signal or not for one block. If the average signal power value is less than the determination threshold, the signal determination unit220determines that there is no reception signal, that is, the situation is “signal non-existing”, and thus outputs a determination result of “0” indicating “signal non-existing” as for whether there is a reception signal or not for one block.

The period estimation unit230estimates an interruption period, or interruption cycle period, of interruption of the signal transmitted from the source device, e.g., the communication satellite104in the example ofFIG. 1, to the communication device100using the determination result from the signal determination unit220(step S3). Specifically, the period estimation unit230generates, in a set of operations to estimate the interruption period, the interruption period representing the period of interruption of the signal, periodic timing representing timing of a change from “0” to “1” in terms of the determination result from the signal determination unit220, a signal existing section referring to a section in which the reception signal exists in one interruption period, and an internal state representing an operational state of the period estimation unit230. Among these, the interruption period, the periodic timing, and the signal existing section are given in units of blocks, and each have an integer value. The period estimation unit230includes, as illustrated inFIG. 2, a differential operation unit231, a masking operation unit232, a period calculation unit233, a state determination unit234, a periodic timing estimation unit235, and a signal existing section calculation unit236. The differential operation unit231calculates a differential value with respect to the determination result from the signal determination unit220. The masking operation unit232calculates a provisional period, or provisional cycle period, based on the differential value calculated by the differential operation unit231, and masks the differential value and the provisional period based on an internal state, more specifically, based on a condition that has been set depending on the internal state. The period calculation unit233calculates the interruption period based on the provisional period output from the masking operation unit232. The state determination unit234determines the internal state of the period estimation unit230using the interruption period calculated by the period calculation unit233. The periodic timing estimation unit235estimates the periodic timing using the provisional period output from the masking operation unit232and using a signal existing section calculated by the signal existing section calculation unit236. The signal existing section calculation unit236calculates the signal existing section based on the provisional period calculated by the masking operation unit232.

A detailed operation of the period estimation unit230will now be described.FIG. 4is a flowchart illustrating an operation to estimate the interruption period in the period estimation unit230according to the first embodiment.

The differential operation unit231calculates a differential value with respect to the determination result output from the signal determination unit220, that is, detects a rising edge and a falling edge of the determination result (step S11). Specifically, when the determination result of the immediately previous block is “0” (signal non-existing) and the determination result of the current block is “1” (signal existing), the differential operation unit231detects a rising edge, and outputs a differential value of “1”. When the determination result of the immediately previous block is “1” (signal existing) and the determination result of the current block is “0” (signal non-existing), the differential operation unit231detects a falling edge, and outputs a differential value of “−1”. Otherwise, the differential operation unit231outputs a differential value of “0”.

The masking operation unit232calculates a provisional period with respect to the differential value calculated by the differential operation unit231(step S12). The masking operation unit232calculates a provisional period when the differential value is “1” or “−1”, and does not calculate a provisional period when the differential value is “0”. When a differential value of “1” or “−1” is input from the differential operation unit231, the masking operation unit232calculates a provisional period based on the difference between the current time and the previous time when the same differential value was input.FIGS. 5A and 5Bare a set of charts illustrating an example of the determination result from the signal determination unit220and of the differential value calculated by the differential operation unit231, of the receiving device200according to the first embodiment.FIG. 5Aillustrates the determination result from the signal determination unit220; and the horizontal axis represents the time, and the vertical axis represents the value of the determination result.FIG. 5Billustrates the differential value calculated by the differential operation unit231; and the horizontal axis represents the time, and the vertical axis represents the differential value. As illustrated inFIGS. 5A and 5B, the differential operation unit231calculates the differential value as “−1” at the timing of falling edge of the determination result from the signal determination unit220, and the differential operation unit231calculates the differential value as “1” at the timing of rising edge of the determination result from the signal determination unit220. For example, the differential value at time t3is “−1”, and the previous time when the same differential value of “−1” was input is time t1inFIGS. 5A and 5B, and therefore, the masking operation unit232calculates a provisional period of “t3−t1” at time t3. Similarly, the differential value at time t4is “1”, and the previous time when the same differential value of “1” was input is time t2inFIGS. 5A and 5B, and therefore, the masking operation unit232calculates a provisional period of “t4−t2” at time t4. As used herein, the provisional period calculated in association with the differential value of “−1” is referred to as falling edge period, and the provisional period calculated in association with the differential value of “1” is referred to as rising edge period.

The masking operation unit232controls use of the differential value and of the provisional period that has been calculated, based on the internal state. Specifically, the masking operation unit232performs masking operation to mask the differential value and the provisional period when a condition dependent on the internal state is met (step S13). As used herein, the term “internal state” refers to an operational state of the period estimation unit230determined by the state determination unit234, and has two states: period seeking state and period-identified state. A period seeking state is a state in which the period estimation unit230has not yet identified the interruption period. A period-identified state is a state in which the period estimation unit230has identified the interruption period. The method for determining the internal state in the state determination unit234will be described later herein.

When the internal state is the period seeking state, the masking operation unit232compares the provisional period with a maximum period, which is a predetermined parameter. The masking operation unit232performs no operation when the provisional period is less than or equal to the maximum period, and when the provisional period exceeds the maximum period, divides the provisional period by D0(where D0is an integer greater than or equal to 2) to reduce the provisional period to less than the maximum period. In this operation, the masking operation unit232selects the minimum value of D0that will reduce the division result to less than or equal to the maximum period. The provisional period greater than the maximum period may be twice or more the actual value of the provisional period because of masking of the differential value. Accordingly, the masking operation unit232divides the provisional period greater than the maximum period by an integer to calculate a correct provisional period. Next, the masking operation unit232compares the provisional period with a minimum period, which is another predetermined parameter. The masking operation unit232masks the differential value input to the masking operation unit232and the provisional period that has been calculated, when the provisional period is less than the minimum period. That is, when the internal state is the period seeking state, the masking operation unit232does not use the differential value input to the masking operation unit232or the provisional period that has been calculated, when the provisional period is out of the range from the predetermined minimum period to the predetermined maximum period. The masking operation unit232outputs the provisional period calculated, when the provisional period is greater than or equal to the minimum period.

When the internal state is the period-identified state, the masking operation unit232compares the provisional period with an identified period calculated by the period calculation unit233. The term “identified period” refers to the interruption period calculated by the period calculation unit233in the period-identified state. The interruption period calculated by the period calculation unit233, i.e., the identified period, is what has been calculated in the previous operation in the period calculation unit233. The masking operation unit232performs no operation when the provisional period is less than or equal to “identified period+WMS” (where WMSis a tolerance in masking operation), and when the provisional period exceeds “identified period+WMS”, subtracts “identified period×D1” from the provisional period to reduce the provisional period to less than or equal to “identified period+WMS×D1” (where D1is an integer greater than or equal to 2). In this operation, the masking operation unit232selects the minimum value of D1that will reduce the subtraction result to less than or equal to “identified period+WMS×D1”. Similarly to the case in the period seeking state, when a provisional period greater than “identified period+WMS” is input, masking of the differential value may cause the provisional period to be twice or more the actual value, and thus, the masking operation unit232subtracts “identified period×D1” from the provisional period greater than “identified period+Wms” to calculate a correct provisional period. Next, the masking operation unit232determines whether the provisional period falls within a range from a lower limit Mminto an upper limit Mmaxcalculated from Formula (1) below. When the provisional period is out of the range from the lower limit Mminto the upper limit Mmax, the masking operation unit232masks the differential value input to the masking operation unit232and the provisional period calculated. That is, when the internal state is the period-identified state and the provisional period is out of a predetermined range including the identified period, the masking operation unit232does not use the differential value input to the masking operation unit232or the provisional period calculated.
Mmax=min(Cmax,C1+WMS×D1)
Mmin=max(Cmin,C1−WMS×D1)  (1)

In Formula (1), Cmaxrepresents the maximum period, Cminrepresents the minimum period, and C1represents the identified period. In addition, in Formula (1), max(a, b) is a function that outputs a when a≥b, and outputs b when a<b; and min(a, b) is a function that outputs a when a≤b, and outputs b when a>b.

As described above, the masking operation unit232masks the differential value and the provisional period when a condition dependent on the internal state of the period estimation unit230is met. A detailed operation dependent on whether to perform the masking operation is as follows. When the differential value is not to be masked, the masking operation unit232stores the time when the differential value is “−1” or “1” to calculate the provisional period. When the differential value is to be masked, the masking operation unit232does not store the time when the differential value is “−1” or “1”. In addition, when the provisional period is not to be masked, the masking operation unit232generates and outputs an enable signal together with the provisional period to specify the provisional period calculated, as a valid value. When the provisional period is to be masked, the masking operation unit232outputs neither the provisional period nor the enable signal. Note that, upon outputting of the provisional period, the masking operation unit232outputs the provisional period to allow distinction between the provisional period of a rising edge period and the provisional period of a falling edge period.

Upon reception of the provisional period together with the enable signal, the period calculation unit233calculates the interruption period using the provisional period output from the masking operation unit232(step S14).FIG. 6is a chart illustrating an example of the determination result from the signal determination unit220and of the interruption period calculated by the period calculation unit233, of the receiving device200according to the first embodiment. InFIG. 6, the horizontal axis represents the time, and the vertical axis represents the value of the determination result. As illustrated inFIG. 6, assuming an ideal determination result from the signal determination unit220, the interruption period corresponds to a section from the rising edge of the determination result to the rising edge of the next determination result or to a section from the falling edge of the determination result to the falling edge of the next determination result. When the provisional period has been input in order from a falling edge period to a rising edge period or when the provisional period has been input in order from a rising edge period to a falling edge period, from the masking operation unit232, the period calculation unit233calculates the interruption period using Formula (2) below.
C=(Cr+Cf)/2  (2)

In Formula (2), C represents the interruption period, Crrepresents the rising edge period, and Cfrepresents the falling edge period. Since the interruption period has an integer value as described above, the period calculation unit233rounds the value C to the nearest integer value in a case in which the calculation result of Formula (2) is a decimal fraction.FIG. 7is a chart illustrating an example of time points of inputting of a falling edge period or a rising edge period from the masking operation unit232in the period calculation unit233according to the first embodiment. InFIG. 7, the horizontal axis represents the time, and the vertical axis represents the differential value after the masking operation performed by the masking operation unit232. In a case in which, for example, a falling edge period, or a falling edge cycle period, is input at time t5, and a rising edge period, or a rising edge cycle period, is input at time t6illustrated inFIG. 7, the period calculation unit233calculates the interruption period using Formula (2) using the falling edge period at time t5and the rising edge period at time t6, and outputs the interruption period at time t6. As illustrated inFIG. 7, in a case in which the indication of a falling edge, i.e., the differential value of “−1”, is masked between time t8and time t9, the period calculation unit233does not calculate the interruption period at time t9because two values of the rising edge period are input consecutively. Note that, due to input of the falling edge period at time t10, the period calculation unit233calculates an interruption period using Formula (2) using the rising edge period at time t9and the falling edge period at time t10, and outputs the interruption period at time t10.

The state determination unit234determines the internal state of the period estimation unit230using the interruption period calculated by the period calculation unit233(step S15). As described above, the internal state has two states defined: period seeking state and period-identified state. It is assumed here that the period estimation unit230has an initial state of the period seeking state. The state determination unit234determines, in the period seeking state, whether the transition condition from the period seeking state to the period-identified state is met, and determines, in the period-identified state, whether the transition condition from the period-identified state to the period seeking state is met. The transition condition from the period seeking state to the period-identified state is that, for example, the interruption periods for previous NBKcycles fall within a range from “reference period−WBK” to “reference period+WBK” in the state determination unit234, where the reference period refers to the interruption period input at the current time, i.e., the latest interruption period calculated by the period calculation unit233. In this regard, NBKrepresents the number of backward protection zones, and is set to an integer greater than or equal to 1. In addition, WBKrepresents a tolerance of backward protection, and is set to an integer greater than or equal to 0. The reference period is given in units of blocks, and has an integer value. Moreover, the transition condition from the period-identified state to the period seeking state is that, for example, when monitoring is performed on the update time of the identified period, which is an interruption period calculated in the period-identified state, the identified period is not updated even after a time period of “identified period×NFR” has elapsed since the previous update time in the state determination unit234. In this regard, NFRrepresents the number of forward protection zones, and is set to an integer greater than or equal to 1.

The signal existing section calculation unit236calculates the signal existing section using the provisional period output from the masking operation unit232(step S16). The term “signal existing section” refers to a section from a rising edge to a falling edge of the determination result as illustrated inFIG. 6for an ideal determination result from the signal determination unit220. When the provisional period is input in order from the rising edge period to the falling edge period, the signal existing section calculation unit236calculates the signal existing section using Formula (3) below.
A=tf−tr(3)

In Formula (3), A represents the signal existing section, tfrepresents the time when the falling edge period was input, and trrepresents the time when the rising edge period was input.

The periodic timing estimation unit235estimates the periodic timing using the provisional period output from the masking operation unit232and the signal existing section calculated by the signal existing section calculation unit236(step S17). The periodic timing is, for example, the timing of a rising edge of the determination result as illustrated inFIG. 6for an ideal determination result from the signal determination unit220. That is, the periodic timing is timing of a change from a section in which the reception signal does not exist to a section in which the reception signal exists in terms of the determination result from the signal determination unit220. Thus, when the provisional period input from the masking operation unit232is a rising edge period, the periodic timing estimation unit235determines that the time when the rising edge period was input is the periodic timing. Otherwise, when the provisional period input from the masking operation unit232is a falling edge period, the periodic timing estimation unit235calculates the time that is one signal existing section back from the time when the falling edge period was input, and estimates that time to be the periodic timing.

In the receiving device200, the period estimation unit230outputs the internal state, the interruption period, the periodic timing, and the signal existing section to the transmission device300. The transmission device300controls transmission of a transmission signal using the internal state, the interruption period, the periodic timing, and the signal existing section obtained from the receiving device200. A configuration and an operation of the transmission device300will now be described.FIG. 8is a block diagram illustrating an example configuration of the transmission device300according to the first embodiment. In addition,FIG. 9is a flowchart illustrating an operation of the transmission device300according to the first embodiment. The transmission device300includes a transmission control unit310, a transmission signal generation unit320, and an antenna330.

The transmission control unit310determines transmission start timing when a transmission signal is to be generated and transmission thereof is to be started, and the length of the transmission signal to be generated, using the internal state, the interruption period, the periodic timing, and the signal existing section that have been input from the receiving device200(step S21). The transmission control unit310determines the transmission start timing based on, for example, the periodic timing when the internal state is the period-identified state. The transmission control unit310predicts the periodic timing for the next or later cycle based on the interruption period when the internal state is the period-identified state, and if no update of the periodic timing occurs before the predicted next periodic timing, determines that the periodic timing predicted is the transmission start timing. In addition, the transmission control unit310determines the length of the transmission signal based on the signal existing section when the internal state is the period-identified state. The transmission control unit310generates a control signal including the transmission start timing and the length of the transmission signal that have been determined, and outputs the control signal generated, to the transmission signal generation unit320.

The transmission signal generation unit320generates a transmission signal based on the transmission start timing and the length of the transmission signal included in the control signal obtained (step S22). The transmission signal generation unit320then transmits the transmission signal via the antenna330(step S23).

A hardware configuration of the receiving device200included in the communication device100will next be described. In the receiving device200, the antenna210is an antenna device. The signal determination unit220and the period estimation unit230are implemented in a processing circuit. The processing circuit may be a combination of a processor that executes a program stored in a memory and the memory, or may be a dedicated hardware element.

FIG. 10is a diagram illustrating an example of a case in which a processing circuit included in the receiving device200according to the first embodiment is configured using a processor and a memory. In a case in which the processing circuit is configured using a processor91and a memory92, the functionality of the processing circuit of the receiving device200is implemented in software, firmware, or a combination of software and firmware. The software or firmware is described as a program or programs, and is stored in the memory92. In the processing circuit, the functionality is implemented by the processor91by reading and executing a program stored in the memory92. That is, the processing circuit includes the memory92for storing programs that cause the processing of the signal determination unit220and of the period estimation unit230to be performed. It can also be said that these programs cause a computer to execute the procedures and methods of the signal determination unit220and of the period estimation unit230.

In this regard, the processor91may be a central processing unit (CPU), a processing unit, a computing unit, a microprocessor, a microcomputer, a digital signal processor (DSP), or the like. In addition, the memory92is, for example, a non-volatile 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 erasable programmable ROM (EEPROM) (registered trademark); a magnetic disk, a flexible disk, an optical disk, a compact disc, a MiniDisc, a digital versatile disc (DVD), or the like.

FIG. 11is a diagram illustrating an example of a case in which the processing circuit included in the receiving device200according to the first embodiment is configured using a dedicated hardware element. In a case in which the processing circuit is configured using a dedicated hardware element, a processing circuit93illustrated inFIG. 11is, for example, a single circuit, a set of multiple circuits, a programmed processor, a set of programmed processors, an application specific integrated circuit (ASIC), a field programmable gate array (FPGA), or a combination thereof. The functionality of the signal determination unit220and of the period estimation unit230may be implemented in the processing circuit93on a function-by-function basis, or implemented in the processing circuit93collectively as a whole.

Note that the functionality of the signal determination unit220and of the period estimation unit230may be implemented partly in a dedicated hardware element, and partly in software or firmware. Thus, the processing circuit can provide the foregoing functionality by a dedicated hardware element, software, firmware, or a combination thereof.

A hardware configuration of the transmission device300included in the communication device100will next be described. In the transmission device300, the antenna330is an antenna device. The transmission control unit310and the transmission signal generation unit320are implemented in a processing circuit. The processing circuit is, similarly to the processing circuit included in the receiving device200, configured as illustrated inFIG. 10 or 11.

As described above, according to the present embodiment, the communication device100is configured such that the receiving device200performs signal determination based on the signal level of a reception signal, and obtains, from the determination result, the internal state representing an operational state, the interruption period of interruption of the signal transmitted to the communication device100, the periodic timing representing timing of a change from a section in which the reception signal does not exist to a section in which the reception signal exists in terms of the determination result, and the signal existing section representing the section in which the reception signal exists. The transmission device300is configured to determine the timing of generation of a transmission signal and the length of the transmission signal using the internal state, the interruption period, the periodic timing, and the signal existing section, and to transmit the transmission signal. This enables the communication device100to improve accuracy of estimation of the interruption period of interruption of a communication channel by masking an internal state including the number of protection zones and unexpected interruption detection in an environment in which the communication channel is expected to be interrupted periodically. In addition, utilization of periodicity of the interruption period enables the communication device100to predict next transmission start timing even when detection of signal interruption has been unsuccessful, and thus to provide more efficient communication.

Second Embodiment

In a second embodiment, an averaging unit and a smoothing unit are added to the period estimation unit230to estimate the interruption period, the periodic timing, and the signal existing section with higher accuracy than in the first embodiment. Differences from the first embodiment will be described below.

FIG. 12is a block diagram illustrating an example configuration of a receiving device200aincluded in the communication device100according to the second embodiment. The receiving device200aof the second embodiment illustrated inFIG. 12includes a period estimation unit230ain place of the period estimation unit230as compared to the receiving device200of the first embodiment illustrated inFIG. 2. The period estimation unit230aadditionally includes an averaging unit401and a smoothing unit402relative to the period estimation unit230. The example ofFIG. 12is illustrated such that processing is performed in order from the averaging unit401to the smoothing unit402, but processing may also be performed in order from the smoothing unit402to the averaging unit401. The present embodiment will be described in terms of the case in which processing is performed in order from the averaging unit401to the smoothing unit402as illustrated inFIG. 12. The receiving device200aoperates similarly to the receiving device200of the first embodiment illustrated in the flowchart ofFIG. 3, but the operation at step S3to estimate the interruption period is different.FIG. 13is a flowchart illustrating an operation to estimate the interruption period in the period estimation unit230aaccording to the second embodiment.

The averaging unit401performs an averaging operation on the determination result output from the signal determination unit220depending on the internal state (step S31). Specifically, the averaging unit401does not perform the averaging operation when the internal state is the period seeking state, but performs the averaging operation when the internal state is the period-identified state. When the internal state is the period-identified state, the averaging unit401performs the averaging operation using the identified period using, for example, Formula (4) below in the case of averaging using a simple average.
[Formula 1]
S1(t)=Σk=0Naved(t−C1×k)  (4)

In Formula (4), d(t) represents the determination result input from the signal determination unit220to the averaging unit401at time t, Naverepresents the number of cycles to be used in averaging in the simple average, C1represents the identified period, and s1(t) represents the sum at time t. The interruption period calculated by the period calculation unit233, i.e., the identified period, is one that has been calculated in the previous operation in the period calculation unit233. The averaging unit401outputs “1” when “s1(t)≥Nave/2”, and outputs “0” when “s1(t)<Nave/2” based on the sum s1(t) obtained using Formula (4). Note that, in the case of use of averaging based on IIR averaging, the averaging unit401performs the averaging operation using Formula (5) below.
s2(t)=d(t)×(1−α)+s2(t−C1)×α  (5)

In Formula (5), a represents the forgetting coefficient, and a has a value ranging from 0 to 1. The averaging unit401outputs “1” when “s2(t)≥0.5”, and outputs “0” when “s2(t)<0.5” based on an IIR average value s2(t) obtained using Formula (5). Thus, the averaging unit401averages periodically input values of the determination result using the identified period, and can thus improve accuracy of the determination result. Note that, in a case in which processing is performed in order from the smoothing unit402to the averaging unit401in the period estimation unit230a, the averaging unit401performs the averaging operation on a value input from the smoothing unit402.

The smoothing unit402performs a smoothing operation on the value input from the averaging unit401(step S32). Specifically, the smoothing unit402performs a smoothing operation by executing a smoothing loop L times (where L is an integer greater than or equal to 1), which is a predetermined number of times of smoothing. By way of example, in processing of an n-th smoothing loop (where n is an integer ranging from 1 to L, inclusive), the smoothing unit402corrects the value input at time t from “0” to “1” if the values input from the averaging unit401at time t-n, time t, and time t+1 are respectively “1”, “0”, and “1”. Similarly, the smoothing unit402corrects the value input at time t from “1” to “0” if the values input from the averaging unit401at time t−n, time t, and time t+1 are respectively “0”, “1”, and “0”. Note that time t has a discretized value of the time when a determination result is output from the signal determination unit220, and time t is assumed to be in a range that keeps the value of t−n a positive value.

FIGS. 14A to 14Eare diagrams illustrating an example of operation of smoothing in the smoothing unit402according to the second embodiment. InFIGS. 14A to 14E, the graph ofFIG. 14Aillustrates the ideal value of the determination result from the signal determination unit220, and the graph ofFIG. 14Billustrates the value input from the averaging unit401to the smoothing unit402when the determination result includes an error. InFIGS. 14A to 14E, the horizontal axis represents the time. In addition,FIG. 14Cillustrates the values illustrated in the graph ofFIG. 14Bon a per-block basis. The smoothing unit402performs the smoothing operation according to the predetermined number of times L of the smoothing loop. Referring toFIGS. 14A to 14E, an operation of smoothing for L=2 will be described by way of example. The smoothing unit402checks the values input at time t−1, time t, and time t+1 in the operation of the first smoothing loop. The example ofFIGS. 14A to 14Eis illustrated such that the values input at time t12−1, time t12, and time t12+1 are “1”, “0”, and “1”, and the smoothing unit402therefore corrects the value input at time t12from “0” to “1”. This situation is illustrated inFIG. 14D. The smoothing unit402checks the values input at time t−2, time t, and time t+1 in the operation of the second smoothing loop. The example ofFIGS. 14A to 14Eis illustrated such that the values input at time t13−2, time t13, and time t13+1 are “1”, “0”, and “1”, and the smoothing unit402therefore corrects the value input at time t13from “0” to “1”. This situation is illustrated inFIG. 14E. Thus, even when wrong values are consecutively input over two blocks, the smoothing unit402can correct the wrong values in the operation of the second smoothing loop. Note that, in a case in which processing is performed in order from the smoothing unit402to the averaging unit401in the period estimation unit230a, the smoothing unit402performs the smoothing operation on the determination result output from the signal determination unit220.

The differential operation unit231and the elements downstream thereof in the period estimation unit230aoperate similarly to the first embodiment as illustrated in the flowchart ofFIG. 4. In addition, in the second embodiment, the receiving device200ahas a hardware configuration similar to the hardware configuration of the receiving device200of the first embodiment.

As described above, according to the present embodiment, the period estimation unit230ais configured such that the averaging unit401performs an averaging operation on the determination result from the signal determination unit220, and the smoothing unit402then performs a smoothing operation. This enables the period estimation unit230ato improve accuracy of the determination result of the signal determination unit220, and thus to improve, due to the improvement in the accuracy of the determination result used, accuracy of estimation of the interruption period, of the periodic timing, and of the signal existing section.

Third Embodiment

In a third embodiment, a period averaging unit, a periodic timing averaging unit, and a signal existing section averaging unit are added to the period estimation unit230ato estimate the interruption period, the periodic timing, and the signal existing section with higher accuracy than in the second embodiment. Differences from the second embodiment will be described below.

FIG. 15is a block diagram illustrating an example configuration of a receiving device200bincluded in the communication device100according to the third embodiment. The receiving device200bof the third embodiment illustrated inFIG. 15includes a period estimation unit230bin place of the period estimation unit230aas compared to the receiving device200aof the second embodiment illustrated inFIG. 12. The period estimation unit230badditionally includes a period averaging unit501, a periodic timing averaging unit502, and a signal existing section averaging unit503relative to the period estimation unit230a. The receiving device200boperates similarly to the receiving device200of the first embodiment illustrated in the flowchart ofFIG. 3, but the operation at step S3to estimate the interruption period is different.FIG. 16is a flowchart illustrating an operation to estimate the interruption period in the period estimation unit230baccording to the third embodiment. The operations of steps S31to S17in the flowchart illustrated inFIG. 16are similar to the corresponding operations in the second embodiment illustrated in the flowchart ofFIG. 13, except that the operations of the period averaging unit501, of the periodic timing averaging unit502, and of the signal existing section averaging unit503are added.

After the operation at step S15, the period averaging unit501performs an averaging operation on the interruption period calculated by the period calculation unit233depending on the internal state (step S41). Specifically, the period averaging unit501does not perform the averaging operation when the internal state is the period seeking state, and performs the averaging operation when the internal state is the period-identified state. That is, the period averaging unit501calculates an average interruption period, which is the average value of the identified period. The period averaging unit501is capable of performing the averaging operation using a simple average, IIR averaging, or the like, and there is no particular limitation on the averaging technique. In the case of averaging using a simple average, for example, the period averaging unit501sums up the interruption periods for previous Ncyclecycles updated in the period calculation unit233, and divides the sum by Ncycleto calculate an average interruption period Cave, where Ncyclerepresents the number of cycles to be used in averaging of the interruption period. The period averaging unit501outputs the average interruption period to the transmission device300. Note that the masking operation unit232and the averaging unit401use an average interruption period calculated in the previous operation in the period averaging unit501as the interruption period, i.e., the identified period.

After the operation at step S16, the signal existing section averaging unit503performs an averaging operation on the signal existing section calculated by the signal existing section calculation unit236depending on the internal state (step S42). Specifically, similarly to the period averaging unit501and to the periodic timing averaging unit502, the signal existing section averaging unit503does not perform the averaging operation when the internal state is the period seeking state, and performs the averaging operation when the internal state is the period-identified state. Similarly to the period averaging unit501and to the periodic timing averaging unit502, the signal existing section averaging unit503is capable of performing the averaging operation using a simple average, IIR averaging, or the like, and there is no limitation on the averaging technique. An operation in the case of using a simple average will now be described by way of example. In the case of averaging using a simple average, the signal existing section averaging unit503sums up the signal existing sections for previous Navailcycles updated in the signal existing section calculation unit236, and divides the sum by Navailto calculate an average signal existing section Aave, where Navailrepresents the number of cycles to be used in averaging of the signal existing section. The signal existing section averaging unit503outputs the average signal existing section to the transmission device300.

After the operation at step S17, the periodic timing averaging unit502performs an averaging operation on the periodic timing calculated by the periodic timing estimation unit235depending on the internal state (step S43). Specifically, similarly to the period averaging unit501, the periodic timing averaging unit502does not perform the averaging operation when the internal state is the period seeking state, and performs the averaging operation when the internal state is the period-identified state. The periodic timing averaging unit502is capable of performing the averaging operation using a simple average, IIR averaging, or the like, and there is no particular limitation on the averaging technique. An operation using a simple average will now be described by way of example.

The periodic timing averaging unit502performs an averaging operation when the provisional period is input from the masking operation unit232. When the provisional period is input to the periodic timing averaging unit502, the provisional period is also input to the periodic timing estimation unit235, and the periodic timing is therein calculated. Accordingly, when the provisional period is input from the masking operation unit232to the periodic timing averaging unit502, the periodic timing is input from the periodic timing estimation unit235to the periodic timing averaging unit502. The periodic timing averaging unit502stores the input periodic timing in a memory. In addition, the periodic timing averaging unit502calculates the falling edge time from the input provisional period. Specifically, the periodic timing averaging unit502calculates the falling edge time by adding the average signal existing section calculated by the signal existing section averaging unit503to the time when the rising edge period was input in a case in which the provisional period is a rising edge period, and determines that the time when the falling edge period was input is the falling edge time in a case in which the provisional period is a falling edge period. The periodic timing averaging unit502calculates a periodic timing adjustment value tadjusing Formula (6) below using the periodic timing stored in a memory and the falling edge time calculated.
[Formula 2]
tadj=Aare−(1/Ntim)×Σx=1Ntimmod(tf−tr(x),Cave)  (6)

In Formula (6), Aaverepresents the average signal existing section calculated by the signal existing section averaging unit503, tfrepresents the falling edge time calculated, tr(x) represents the periodic timing input in an x-th cycle in the past, Caverepresents the average interruption period calculated by the period averaging unit501, Ntimrepresents the number of cycles to be used in averaging of the periodic timing, and mod(a, b) represents the remainder of division of a by b. The periodic timing averaging unit502calculates an average periodic timing Tavebased on the periodic timing adjustment value tadjcalculated using Formula (6). In a case in which the provisional period input is a falling edge period, the periodic timing averaging unit502calculates the average periodic timing Taveusing Formula (7) below.
Tave=t+Cave−Aave+tadj(7)

In Formula (7), t is the current time, and in this case, represents the time when the falling edge period was input. In addition, in a case in which the provisional period that is input to the periodic timing averaging unit502is a rising edge period, the periodic timing averaging unit502calculates the average periodic timing Taveusing Formula (8) below.
Tave=t+tadj(8)

In Formula (8), t is the current time, and represents the time when the rising edge period was input. The periodic timing averaging unit502outputs the average periodic timing to the transmission device300.

In the third embodiment, the period averaging unit501and the signal existing section averaging unit503are added to the period estimation unit230aof the second embodiment. Thus, the averaging unit401and the masking operation unit232change the identified period to be used, to the average interruption period calculated by the period averaging unit501. In addition, in the period-identified state, the periodic timing estimation unit235changes the signal existing section to be used, to the average signal existing section calculated by the signal existing section averaging unit503.

The averaging unit401performs the averaging operation using the average interruption period Caveas the identified period C1in Formula (1). In addition, in the period-identified state, the masking operation unit232performs the masking operation using the average interruption period Caveas the identified period. Moreover, the periodic timing estimation unit235uses, as the periodic timing, a time that is one signal existing section back from the input falling edge period as in the above case when the internal state is the period seeking state, and uses, as the periodic timing, a time that is one average signal existing section back from the input falling edge period when the internal state is the period-identified state.

Note that the period estimation unit230bhas been described as performing the operation of step S41after the operation of step S15, the operation of step S42after the operation of step S16, and the operation of step S43after the operation of step S17, but the order of the operations is not limited thereto. For example, the period estimation unit230bmay perform the operations of steps S41, S42, and S43after step S17.

In the third embodiment, the receiving device200bhas a hardware configuration similar to the hardware configuration of the receiving device200of the first embodiment.

As described above, according to the present embodiment, the period estimation unit230bfurther includes the period averaging unit501, the periodic timing averaging unit502, and the signal existing section averaging unit503to average the interruption period, the periodic timing, and the signal existing section. This enables the period estimation unit230bto improve accuracy of estimation of the interruption period, the periodic timing, and the signal existing section.

Fourth Embodiment

In a fourth embodiment, the receiving device determines non-periodicity of interruption, and the transmission device provides transmission control dependent on the non-periodicity of interruption. Thus, a situation of no signal interruption is detected to provide efficient communication, and a situation of complete interruption of a signal is detected to prevent useless transmission. This is applicable to any one of the first through third embodiments, but, by way of example, a case of application to the first embodiment will be described below focusing on differences from the first embodiment.

FIG. 17is a block diagram illustrating an example configuration of a receiving device200cincluded in the communication device100according to the fourth embodiment. The receiving device200cof the fourth embodiment illustrated inFIG. 17includes a period estimation unit230cin place of the period estimation unit230as compared to the receiving device200of the first embodiment illustrated inFIG. 2. The period estimation unit230cadditionally includes a non-periodicity determination unit601relative to the period estimation unit230. The receiving device200coperates similarly to the receiving device200of the first embodiment illustrated in the flowchart ofFIG. 3, but the operation at step S3to estimate the interruption period is different.FIG. 18is a flowchart illustrating an operation to estimate the interruption period in the period estimation unit230caccording to the fourth embodiment. The operations of steps S11to S17in the flowchart illustrated inFIG. 18are similar to the corresponding operations in the first embodiment illustrated in the flowchart ofFIG. 4.

The non-periodicity determination unit601determines non-periodicity of interruption, that is, determines whether the situation is “signal constantly existing” or “signal constantly non-existing” based on the determination result input from the signal determination unit220(step S51). The phrase “signal constantly existing” refers to a situation in which the signal is being continuously received, and the phrase “signal constantly non-existing” refers to a situation in which the signal is being continuously unreceived. Specifically, the non-periodicity determination unit601generates a signal constantly existing flag that indicates whether the signal is being continuously received, and a signal constantly non-existing flag that indicates whether the signal is being continuously unreceived, based on the determination result input from the signal determination unit220. An operation of the non-periodicity determination unit601will now be described in detail.FIG. 19is a flowchart illustrating an operation to determine non-periodicity of interruption in the non-periodicity determination unit601according to the fourth embodiment.

The non-periodicity determination unit601counts the determination result input from the signal determination unit220(step S61). The non-periodicity determination unit601counts the number of inputs of the determination result that is input, and sets an inputting count value as Min. The non-periodicity determination unit601also counts the number of inputs of the determination result that is input and has a value of “1”, and sets a determination result “1” count value as M. The non-periodicity determination unit601further counts the number of inputs of the determination result that is input and has a value of “0”, and sets a determination result “0” count value as M0.

The non-periodicity determination unit601determines whether the inputting count value Minmatches a determination section E (step S62). Specifically, the non-periodicity determination unit601determines whether the number of inputs has reached the determination section E, where the determination section E represents the number of inputs of the determination result for counting the number of the determination results each having a value of “1” and “0”. If a relationship of [inputting count value Min]<[determination section E] holds (step S62: No), the non-periodicity determination unit601does not change a signal constantly existing flag Favailand a signal constantly non-existing flag Fmaskfrom the values at the time of inputting of the determination result, and outputs, without change, a signal constantly existing flag Favail_oldand a signal constantly non-existing flag Fmask_oldat the time of inputting of the same value as at a previous time (step S63). If a relationship of [inputting count value Min]=[determination section E] holds (step S62: Yes), the non-periodicity determination unit601counts the number of times of reaching the determination section, and counts up a determination section count value ML(step S64).

The non-periodicity determination unit601makes a threshold determination on the determination result “1” count value M1and on the determination result “0” count value M0(step S65). The non-periodicity determination unit601counts up an interruption count value Kmaskif a relation of [determination result “1” count value M1]≤[threshold H1] holds, and counts up a non-interruption count value Kavailif a relation of [determination result “0” count value M0]≤[threshold H0] holds. In this regard, the threshold H1is a threshold of the determination result “1” count value M1, and the threshold H0is a threshold of the determination result “0” count value M0.

The non-periodicity determination unit601determines whether the determination section count value MLmatches the number of protection zones NSfor non-periodicity determination (step S66). Specifically, the non-periodicity determination unit601determines whether the determination section count value MLcounted using the number of inputs has reached the number of protection zones NSfor non-periodicity determination. In this regard, the number of protection zones NSfor non-periodicity determination represents the number of the determination sections required for non-periodicity determination. If a relationship of [determination section count value ML]<[number of protection zones NSfor non-periodicity determination] holds (step S66: No), the non-periodicity determination unit601does not change the signal constantly existing flag Favailand the signal constantly non-existing flag Fmaskfrom the values at the time of inputting of the determination result, and outputs, without change, the signal constantly existing flag Favail_oldand the signal constantly non-existing flag Fmask_oldat the time of inputting of the same value as at a previous time (step S63). If a relationship of [determination section count value ML]=[number of protection zones NSfor non-periodicity determination] holds (step S66: Yes), the non-periodicity determination unit601determines whether the non-interruption count value Kavailmatches the number of protection zones NSfor non-periodicity determination (step S67).

If a relationship of [non-interruption count value Kavail]=[number of protection zones NSfor non-periodicity determination] holds (step S67: Yes), the non-periodicity determination unit601outputs the signal constantly existing flag Favailafter the determination having a value of “1” and the signal constantly non-existing flag Fmaskafter the determination having a value of “0” (step S68). Note that the signal constantly existing flag Favailafter the determination may also be hereinafter referred to simply as signal constantly existing flag Favail, and the signal constantly non-existing flag Fmaskafter the determination may also be hereinafter referred to simply as signal constantly non-existing flag Fmask. The signal constantly existing flag Favailhaving a value of “1” is a signal constantly existing flag indicating that the signal is being continuously received, while the signal constantly non-existing flag Fmaskhaving a value of “0” is a signal constantly non-existing flag indicating that it is not in a situation in which the signal is being continuously unreceived. The phrase “it is not in a situation in which the signal is being continuously unreceived” refers to either a situation in which the signal is being continuously received or a situation in which the signal is interrupted and being periodically received. If a relationship of [non-interruption count value Kavail]<[number of protection zones NSfor non-periodicity determination] holds (step S67: No), the non-periodicity determination unit601determines whether the interruption count value Kmaskmatches the number of protection zones NSfor non-periodicity determination (step S69). If a relationship of [interruption count value Kmask]=[number of protection zones NSfor non-periodicity determination] holds (step S69: Yes), the non-periodicity determination unit601outputs the signal constantly existing flag Favailhaving a value of “0” and the signal constantly non-existing flag Fmaskhaving a value of “1” (step S70). The signal constantly existing flag Favailhaving a value of “0” is a signal constantly existing flag indicating that it is not in a situation in which the signal is being continuously received. In addition, the signal constantly non-existing flag Fmaskhaving a value of “1” is a signal constantly non-existing flag indicating that the signal is being continuously unreceived. The phrase “it is not in a situation in which the signal is being continuously received” refers to either a situation in which the signal is being continuously unreceived or a situation in which the signal is interrupted and being periodically received. If a relationship of [interruption count value Kmask]<[number of protection zones NSfor non-periodicity determination] holds (step S69: No), the non-periodicity determination unit601outputs the signal constantly existing flag Favailhaving a value of “0” and the signal constantly non-existing flag Fmaskhaving a value of “0” (step S71). The non-periodicity determination unit601is capable of generating and outputting the signal constantly existing flag Favailand the signal constantly non-existing flag Fmaskin the operation of the flowchart illustrated inFIG. 19.

Note that the foregoing description assumes that, in the period estimation unit230c, the operation of the non-periodicity determination unit601is performed after the operations of the elements from the differential operation unit231to the signal existing section calculation unit236. However, there is no limitation on when to perform the operation of the non-periodicity determination unit601. In the period estimation unit230c, the operation of the non-periodicity determination unit601may be performed prior to the operations of the elements from the differential operation unit231to the signal existing section calculation unit236, or the operation of the non-periodicity determination unit601may be performed in parallel with the operations of the elements from the differential operation unit231to the signal existing section calculation unit236.

In the fourth embodiment, the receiving device200chas a hardware configuration similar to the hardware configuration of the receiving device200of the first embodiment.

An operation of the transmission device300that has received the signal constantly existing flag Favailand the signal constantly non-existing flag Fmaskwill next be described. The transmission device300of the fourth embodiment is configured similarly to the transmission device300of the first embodiment illustrated inFIG. 8. However, the transmission device300is configured such that the transmission control unit310further receives the signal constantly existing flag Favailand the signal constantly non-existing flag Fmaskfrom the receiving device200c.

FIG. 20is a flowchart illustrating a transmission control operation in a transmission control unit310of the transmission device300according to the fourth embodiment. In a case of reception of the signal constantly existing flag Favailhaving a value of “1” (step S81: Yes), the transmission control unit310determines that no signal interruption is occurring, and thus determines to continuously transmit a signal from the communication device100(step S82). The transmission control unit310generates a control signal that indicates continuous transmission, and outputs the control signal to the transmission signal generation unit320. In a case of reception of the signal constantly existing flag Favailhaving a value of “0” (step S81: No) and of reception of the signal constantly non-existing flag Fmaskhaving a value of “1” (step S83: Yes), the transmission control unit310determines that the signal is completely interrupted, and determines to stop transmission of the signal from the communication device100(step S84). The transmission control unit310generates a control signal that indicates stop of transmission, and outputs the control signal to the transmission signal generation unit320. In a case of reception of the signal constantly existing flag Favailhaving a value of “0” (step S81: No) and of reception of the signal constantly non-existing flag Fmaskhaving a value of “0” (step S83: No), the transmission control unit310determines that the signal is periodically interrupted, and determines to transmit a burst signal (step S85). In this case, the transmission control unit310performs the operation of step S21illustrated in the flowchart ofFIG. 9described in the first embodiment to determine the transmission start timing and the length of the transmission signal. Specifically, the transmission control unit310provides control to transmit a burst signal that is a transmission signal having a burst signal length less than the length of the signal existing section. The transmission control unit310generates a control signal including the transmission start timing and the length of the transmission signal that have been determined, and outputs the control signal to the transmission signal generation unit320.

As described above, according to the present embodiment, the period estimation unit230cis configured such that the non-periodicity determination unit601determines periodicity of signal interruption, and generates the signal constantly existing flag and the signal constantly non-existing flag, and the transmission control unit310provides transmission control using the signal constantly existing flag and the signal constantly non-existing flag. Specifically, the transmission control unit310performs continuous transmission when no signal interruption is occurring, stops transmission when the signal is completely interrupted, and when the signal is periodically interrupted, determines the transmission start timing and the length of the transmission signal for transmitting a burst signal, using the interruption period, the periodic timing, and the signal existing section, and then transmits a burst signal. This enables the transmission control unit310to provide more efficient signal transmission than when non-periodicity of signal interruption is unused.

Fifth Embodiment

In a fifth embodiment, the receiving device applies a weight to the reception signal to improve demodulation performance. This is applicable to any one of the first through fourth embodiments, but, by way of example, a case of application to the first embodiment will be described below focusing on differences from the first embodiment.

FIG. 21is a block diagram illustrating an example configuration of a receiving device200dincluded in the communication device100according to the fifth embodiment. The receiving device200dof the fifth embodiment illustrated inFIG. 21additionally includes a period signal generation unit701and a no-signal weighting unit702relative to the receiving device200of the first embodiment illustrated inFIG. 2.FIG. 22is a flowchart illustrating an operation of the receiving device200daccording to the fifth embodiment. The operations of steps S1to S3in the flowchart illustrated inFIG. 22are similar to the corresponding operations in the first embodiment illustrated in the flowchart ofFIG. 3.

The period signal generation unit701generates a period signal that indicates the period of interruption of a signal from the communication satellite104in the receiving device200d, using the internal state, the interruption period, the periodic timing, and the signal existing section obtained from the period estimation unit230(step S91). Specifically, when the internal state is the period seeking state, the period signal generation unit701does not use the interruption period, the periodic timing, or the signal existing section, and generates a signal having a fixed value of “1” as the period signal. When the internal state is the period-identified state, the period signal generation unit701generates the period signal using the interruption period, the periodic timing, and the signal existing section.FIG. 23is a chart illustrating an example of the period signal generated by the period signal generation unit701in the receiving device200daccording to the fifth embodiment when the internal state is the period-identified state. InFIG. 23, the horizontal axis represents the time, and the vertical axis represents the value of the period signal. Reception, as the interruption period, of the interruption period based on the falling edge period and of the interruption period based on the rising edge period from the period calculation unit233of the period estimation unit230enables the period signal generation unit701to generate a period signal as illustrated inFIG. 23using the interruption period, the periodic timing, and the signal existing section. An ideal waveform of the period signal illustrated inFIG. 23is practically similar to the ideal waveform of the determination result in the signal determination unit220illustrated inFIG. 6.

The no-signal weighting unit702applies a weight to the reception signal using the period signal generated by the period signal generation unit701(step S92). Specifically, the no-signal weighting unit702determines to apply a weight to a reception signal in a time period in which the period signal has a value of “0” (no signal), and multiplies the reception signal to be weighted, by a weighting factor W, thus to provide weighting. In this regard, the weighting factor W is a parameter, and the weighting factor may have different values when the reception signal is data and when the reception signal is a pilot signal. For example, when the reception signal to be weighted is a pilot signal, setting the weighting factor W as W=0 can mask, to “0”, the value in a noise portion in the pilot signal received during a signal non-existing section meaning a section in which the reception signal does not exist. This enables the receiving device200dto improve accuracy of estimation of transmission channel estimation and/or frequency deviation estimated during demodulation using the pilot signal.

In the fifth embodiment, the receiving device200dhas a hardware configuration similar to the hardware configuration of the receiving device200of the first embodiment.

As described above, according to the present embodiment, the receiving device200dis configured such that the period signal generation unit701generates a period signal indicating the period of interruption of the signal, and the no-signal weighting unit702applies a weight to a signal that has been received during a time period determined to be “signal non-existing” in the period signal. This enables the receiving device200dto prioritize the signal received during a signal non-existing section and a signal received during a signal existing section, and to improve demodulation performance as compared to the cases of the first through fourth embodiments.

Sixth Embodiment

In a sixth embodiment, the transmission control unit310in the transmission device300described in the fourth embodiment performs time diversity transmission when the burst signal length obtained from the signal existing section is less than a minimum burst signal length determined based on the transmission frame format. Differences from the fourth embodiment will be described below.

The transmission device300of the sixth embodiment is configured similarly to the transmission device300of the fourth embodiment, i.e., the transmission device300of the first embodiment illustrated inFIG. 8. However, the transmission device300is configured, similarly to the case of the fourth embodiment, such that the transmission control unit310further receives the signal constantly existing flag Favailand the signal constantly non-existing flag Fmaskfrom the receiving device200c.

FIG. 24is a flowchart illustrating a transmission control operation in the transmission control unit310of the transmission device300according to the sixth embodiment. The operations of steps S81to S84in the flowchart illustrated inFIG. 24are similar to the corresponding operations in the fourth embodiment illustrated in the flowchart ofFIG. 20. In a case of reception of the signal constantly existing flag Favailhaving a value of “0” (step S81: No) and of reception of the signal constantly non-existing flag Fmaskhaving a value of “0” (step S83: No), the transmission control unit310determines that the signal is periodically interrupted, and thus firstly determines the transmission start timing (step S101). The transmission control unit310determines the transmission start timing, as described above, in a similar manner to the determination method at step S21illustrated in the flowchart ofFIG. 9described in the first embodiment, or to the determination method at step S85illustrated in the flowchart ofFIG. 20described in the fourth embodiment.

The transmission control unit310determines the length of the transmission signal, i.e., the burst signal length (step S102). The transmission control unit310determines the burst signal length using, for example, the method illustrated inFIGS. 25A and 25B.FIGS. 25A and 25Bare a set of charts illustrating a method for determining a burst signal length in the transmission control unit310according to the sixth embodiment.FIG. 25Ais a chart illustrating the determination result; and the horizontal axis represents the time, and the vertical axis represents the value of the determination result.FIG. 25Bis a chart illustrating the burst signal; and the horizontal axis represents the time, and the vertical axis represents the transmission level of the burst signal. In the transmission control unit310, the relationship illustrated inFIG. 25Acan be obtained from the interruption period, the periodic timing, and the signal existing section that have been obtained. The transmission control unit310determines the burst signal length using a signal existing section A illustrated inFIG. 25A. For example, as illustrated inFIG. 25Bin the lower portion ofFIGS. 25A and 25B, the transmission control unit310sets a transmission margin of a time period T1before the signal existing section A and a transmission margin of a time period T2after the signal existing section A, with respect to the signal existing section A, and then calculates the burst signal length of Bc=A−T1−T2to determine the burst signal length. The transmission margin of a time period T1provided before the signal existing section A is a first time margin, and the transmission margin of a time period T2provided after the signal existing section A is a second time margin. Note that the transmission control unit310may control the transmission level of the burst signal illustrated inFIG. 25Bto output the burst signal at a predetermined transmission level, or change the transmission level depending on the burst signal length and output the resultant burst signal.

The transmission control unit310compares the burst signal length Bcdetermined, with a minimum burst signal length Bmin(step S103), where the minimum burst signal length Bminrepresents the minimum transmittable burst signal length. If a relationship of [burst signal length Bc]≥[minimum burst signal length Bmin] holds (step S103: Yes), the transmission control unit310determines to perform burst transmission operation using a transmission signal having the burst signal length Bc, i.e., a burst signal (step S104). The transmission control unit310generates a control signal including the transmission start timing and the burst signal length Bcthat have been determined, and indicating burst transmission, and outputs the control signal to the transmission signal generation unit320. If a relationship of [burst signal length Bc]<[minimum burst signal length Bmin] holds (step S103: No), the transmission control unit310determines to sequentially transmit a burst signal through time diversity transmission (step S105). The transmission control unit310generates a control signal including the transmission start timing and the burst signal length Bcthat have been determined, and indicating time diversity transmission, and outputs the control signal to the transmission signal generation unit320. The time diversity transmission can be implemented by, for example, the transmission device300by repeatedly transmitting a signal in units of transmission signals having a length less than or equal to the signal existing section A. This may enable the reception-side device, e.g., the communication satellite104in the example ofFIG. 1, to receive a signal through diversity combining even when the signal is interrupted.

As described above, according to the present embodiment, the transmission control unit310provides control to perform continuous transmission by time diversity transmission when the burst signal length obtained is less than the minimum burst signal length. This enables the communication device100to provide efficient signal transmission when burst transmission cannot be provided to avoid interruption.

Seventh Embodiment

In a seventh embodiment, the transmission control unit310controls signal transmission by allocating a symbol having a higher required received power, i.e., higher required signal-to-noise ratio (SNR) in a center of the burst signal, and allocating a symbol having a lower required SNR in a front half portion and in a rear half portion of the burst signal with respect to the length of the transmission signal determined, i.e., the burst signal length of the burst signal. This is applicable to any one of the first through sixth embodiments, but, by way of example, a case of application to the first embodiment will be described below focusing on differences from the first embodiment.

The transmission device300of the seventh embodiment is configured similarly to the transmission device300of the first embodiment illustrated inFIG. 8. In the transmission device300, when, for example, a signal has symbols Q1, Q2, and Q3having different required SNR values, and the required SNR values satisfy a relationship Q1<Q2<Q3, the transmission control unit310allocates the symbol Q3in the center of the burst signal, the symbol Q2before and after the symbol Q3, and the symbol Q1at the head and tail of the burst signal as illustrated inFIG. 26. That is, the transmission control unit310allocates a symbol having a higher required SNR in the center of the burst signal, and allocates a symbol having a lower required SNR in the front half and in the rear half of the burst signal. The transmission control unit310generates a control signal indicating the symbol allocation determined, and outputs the control signal to the transmission signal generation unit320.

FIG. 26is a diagram illustrating an example of symbol allocation by transmission control of the transmission control unit310in the transmission device300according to the seventh embodiment. InFIG. 26, the horizontal axis represents the time, and the vertical axis represents the transmission level of the burst signal. The transmission device300determines the symbol allocation in a burst signal to be in order of Q1, Q2, Q3, Q2, and Q1. This causes the receive-side device, e.g., the communication satellite104in the example ofFIG. 1, to have the signal affected by interruption with a probability of Q1>Q2>Q3, and thus the average SNR values satisfy a relationship of Q1<Q2<Q3. The transmission control unit310allocates a symbol having a lower required SNR in the front half and in the rear half of a burst signal where interruption is more likely to occur, and allocates a symbol having a higher required SNR in the center of the burst signal where interruption is less likely to occur, thereby enabling an effect of interruption to be reduced, and efficient communication to be provided even when, for example, the interruption period, the periodic timing, and the signal existing section estimated in the period estimation unit230have an error.

As described above, according to the present embodiment, the transmission control unit310allocates a symbol having a higher required SNR in the center of a burst signal, and allocates a symbol having a lower required SNR in the front half and in the rear half of the burst signal. This enables the communication device100to allocate symbols depending on required SNR values thereof thus to provide efficient transmission.

A communication device according to the disclosure provides an advantage in being capable of improving accuracy of estimation of the period, or cycle period, of interruption of a communication channel.

The configurations described in the foregoing embodiments are merely examples. These configurations may be combined with a known other technology, and moreover, a part of such configurations may be omitted and/or modified without departing from the spirit.