JP2017143481A - Communication device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a communication device capable of reducing a probability of occurrence of a communication error due to failure to receive a preamble.SOLUTION: While a communication unit 12 is operating in a standby mode, a selection unit 11 periodically switches a use channel among plural channels so that the use channel is switched each time a specified time elapses. When the communication unit 12 receives a signal while the communication unit 12 is operating in the standby mode and the signal satisfies a predetermined stop condition, a stop unit 13 stops the switching of the use channel by the selection unit 11 during a retransmission period for which the communication unit 12 receives a retransmission signal. The stop unit 13 stops the switching of the use channel by the selection unit 11 so that the use channel is fixed to the same channel as the use channel when the communicating unit 12 has received the signal.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a communication device.

  2. Description of the Related Art Conventionally, a dual mode wireless communication system has been proposed that includes a communication device (parent device) that can communicate with two system wireless devices using one wireless device (see, for example, Patent Document 1).

  In this type of system, the communication device repeatedly waits for reception of a plurality of channels two or more times by sequentially switching the reception channels. As a result, the communication device receives the signal from the wireless device that is the communication partner during reception waiting for the second and subsequent rounds even if it fails to receive the signal during reception waiting for the first round.

JP 2001-16663 A

  However, a communication apparatus that repeatedly waits for reception of a plurality of channels as described above has a high probability of causing a communication error because, for example, a preamble of a signal transmitted from a wireless device that is a communication partner cannot be received for a sufficient length. There is a possibility.

  The present invention has been made in view of the above reasons, and an object of the present invention is to provide a communication device that can reduce the probability of occurrence of a communication error due to the inability to receive a preamble.

  A communication apparatus according to an aspect of the present invention includes a selection unit that selects one channel as a use channel from a plurality of channels, and a communication unit that performs communication using the use channel, and the communication unit includes: When the preamble is received during operation in the standby mode, the reception unit is configured to switch to the reception mode for receiving a packet. The selection unit is configured to operate for a specified time while the communication unit is operating in the standby mode. The used channel is periodically switched in the plurality of channels so that the used channel is switched every time elapses, and the used channel is switched to the plurality of channels while the communication unit is operating in the reception mode. The communication unit receives a signal while the communication unit is operating in the standby mode. When the signal satisfies a predetermined stop condition, the use channel is fixed to the same channel as the use channel when the communication unit receives the signal in the retransmission period in which the communication unit receives the retransmission signal. As described above, the information processing apparatus further includes a stop unit that stops the switching of the used channel by the selection unit.

  The present invention has an advantage that a communication apparatus capable of reducing the probability of occurrence of a communication error due to failure to receive a preamble can be obtained.

It is a block diagram of the communication system using the communication apparatus which concerns on one Embodiment of this invention. 6 is a timing chart illustrating an operation when switching of a use channel is stopped in a retransmission period, with respect to a communication apparatus according to an embodiment of the present invention. It is a timing chart which shows operation at the time of receiving a signal from the 1st terminal about a communication device concerning one embodiment of the present invention. It is a timing chart which shows operation | movement in case a signal is transmitted from a 1st terminal at various timings regarding the communication apparatus which concerns on one Embodiment of this invention.

  The following embodiments relate to a communication apparatus, and more particularly, to a communication apparatus that performs communication using one channel selected from a plurality of channels.

(1) Overview The communication device 1 according to the present embodiment includes a selection unit 11, a communication unit 12, and a stop unit 13, as illustrated in FIG. The selection unit 11 selects one channel as a use channel from among a plurality of channels. The communication unit 12 performs communication using the used channel.

  The communication unit 12 is configured to switch to a reception mode in which a packet is received when a preamble is received during operation in the standby mode.

  While the communication unit 12 is operating in the standby mode, the selection unit 11 periodically switches the use channel within the plurality of channels so that the use channel is switched every time the specified time elapses. The selection unit 11 is configured to fix the used channel to one channel among the plurality of channels while the communication unit 12 operates in the reception mode.

  The stopping unit 13 is a retransmission period in which the communication unit 12 receives a signal while the communication unit 12 operates in the standby mode, and the communication unit 12 receives a retransmission signal when the signal satisfies a predetermined stop condition. , The switching of the used channel by the selection unit 11 is stopped. The stop unit 13 stops the use channel switching by the selection unit 11 so that the use channel is fixed to the same channel as the use channel when the communication unit 12 receives the signal.

  The “channel” here is, for example, a frequency band in frequency division multiple access communication. In the present embodiment, a plurality of frequency bands are used as a plurality of channels. The “preamble” here is a bit string that is added to the head of a packet received by the communication unit 12 and that allows the communication unit 12 to synchronize. Therefore, the communication unit 12 can receive the bit string of the packet in synchronization with the received signal by receiving the preamble. Further, the “retransmission signal” here is a signal having the same content as the previously transmitted signal and is retransmitted when the previously transmitted signal is not normally received. A retransmission interval, which is a time interval from when a signal is transmitted to when a retransmission signal having the same content as this signal is transmitted, is determined by a communication standard (protocol). For example, the retransmission interval is determined in the MAC (Media Access Control) layer in the data link layer of the OSI (Open Systems Interconnection) reference model. If the device that transmits the signal and the device that receives the signal conform to the same communication standard, predict the timing at which the retransmission signal is transmitted in the device that receives the signal (communication device 1). Can do. Therefore, in the communication apparatus 1, when the communication unit 12 receives a signal, a retransmission period during which the communication unit 12 receives a retransmission signal can be predicted.

  In short, as shown in FIG. 2, while the communication unit 12 is operating in the standby mode (a period indicated by “Tm1” in FIG. 2), the selection unit 11 performs the specified time T1 or T2 every time. The used channels are periodically switched in a plurality of channels so that the used channels are switched at the same time. That is, the communication unit 12 repeatedly waits for reception of a plurality of channels in the standby mode. In addition, while the communication unit 12 is operating in the reception mode (a period indicated by “Tm2” in FIG. 2), the selection unit 11 fixes the used channel to one of the plurality of channels. In FIG. 2, the horizontal axis is the time axis, the channel used is “CH”, and the signal is “Sig”. In the example of FIG. 2, one channel is selected as a use channel by the selection unit 11 from the two channels CH1 and CH2 of the (first) channel CH1 and the (second) channel CH2.

  When the communication unit 12 receives a signal during the period Tm1 during which the communication unit 12 operates in the standby mode, and this signal satisfies the stop condition, the stop unit 13 uses the channel used by the selection unit 11 during the retransmission period Tr1. Stop switching. In this case, in the retransmission period Tr1, the use channel is fixed to the same channel as the use channel when the communication unit 12 receives the signal. In the example of FIG. 2, since the communication unit 12 receives a signal when the use channel is the channel CH1 in the standby mode, the stop unit 13 stops switching the use channel in the retransmission period Tr1 and uses the channel. Is fixed to channel CH1. In other words, when the communication unit 12 receives a signal that satisfies the stop condition, the stopping unit 13 sets the channel to be used in accordance with the retransmission period Tr1 that the communication unit 12 is expected to receive the retransmission signal of this signal. Secure to.

  As described above, in the communication apparatus 1, when the signal received while the communication unit 12 is operating in the standby mode satisfies the stop condition, the used channel is the same as the used channel at the time of receiving the signal in the retransmission period Tr1. Fixed to the channel. Therefore, when a signal including a preamble is transmitted while the communication unit 12 is operating in the standby mode, the preamble can be received in the retransmission period Tr1 even if the preamble cannot be received once, and a preamble reception error occurs. It becomes difficult to occur. As a result, the communication apparatus 1 has an advantage that it is possible to reduce the probability of occurrence of a communication error due to the inability to receive a preamble despite repeatedly waiting for reception of a plurality of channels.

  Moreover, even if the communication unit 12 receives a signal while operating in the standby mode, the stop unit 13 does not immediately stop switching the used channel, but in accordance with the retransmission period Tr1 in which the retransmission signal is transmitted, Stop switching the used channel. That is, even if the communication unit 12 receives a signal while operating in the standby mode, the used channel is not fixed immediately, but the used channel is fixed in accordance with the retransmission period Tr1. Therefore, until the retransmission period Tr1 starts, the selection unit 11 can continue to switch the use channel, and the original operation of the communication unit 12 in the standby mode of waiting while switching between the plurality of channels CH1 and CH2 is hardly hindered. .

  In addition, when the signal received while the communication unit 12 is operating in the standby mode does not satisfy the stop condition, the stop unit 13 does not stop the switching of the channel to be used. For example, a signal that does not satisfy the stop condition, such as noise, Not easily affected. Therefore, in the communication apparatus 1, it is possible to suppress the switching of the used channel from being stopped more than necessary due to the influence of noise or the like.

(2) Details Hereinafter, the communication device 1 of the present embodiment will be described in detail.

  Below, the case where the communication apparatus 1 is used for a HEMS (Home Energy Management System) controller is demonstrated to an example. The HEMS controller is installed in a customer facility that receives power supply from a power supply company. The communication device 1 used as a HEMS controller communicates with each of a smart meter installed in a customer facility and a home device installed in the customer facility (compatible with HEMS). Hereinafter, the smart meter is referred to as the first terminal 101 (see FIG. 1), and the home device is referred to as the second terminal 102 (see FIG. 1). The HEMS controller displays the meter reading information (measured value) of the first terminal 101 on the monitor in the customer facility, or controls the second terminal 102 based on the meter reading information. In the following, it is assumed that the customer facility is a detached house, but the consumer facility is not limited to a detached house, and may be, for example, each dwelling unit, office, or store of an apartment house.

(2.1) Communication System First, the overall configuration of the communication system 100 including the communication device 1 will be described with reference to FIG. The communication system 100 includes a communication device 1, a first terminal 101, and a second terminal 102.

  The first terminal 101 and the second terminal 102 are communication partners of the communication device 1, respectively. The communication device 1 and the first terminal 101 perform wireless communication using radio waves as a medium on the (first) channel CH1. The communication device 1 and the second terminal 102 perform wireless communication using radio waves as a medium in the (second) channel CH2. Channel CH1 and channel CH2 are different frequency bands. Therefore, the communication device 1 communicates with each of the first terminal 101 and the second terminal 102 by switching the channel (used channel) used for communication between a plurality of (two in this embodiment) channels CH1 and CH2. It becomes possible.

  The first terminal 101 (smart meter) has a measuring unit that functions as a power meter that measures the amount of power used at a customer facility, and a first wireless interface. For example, the first terminal 101 periodically transmits a signal including at least a measurement value (meter reading information) of the measurement unit from the first wireless interface to the communication device 1. Furthermore, the first terminal 101 receives a signal from the communication device 1 through the first wireless interface. That is, the first terminal 101 can communicate bidirectionally with the communication device 1.

  The second terminal 102 (in-home device) is, for example, an electric device such as an air conditioner or a television receiver. The second terminal 102 has a second wireless interface. The second terminal 102 transmits a signal to the communication device 1 from the second wireless interface, for example, periodically. Further, the second terminal 102 receives a signal from the communication device 1 through the second wireless interface. That is, the second terminal 102 can communicate bidirectionally with the communication device 1.

  The communication method used by the communication device 1 for communication with the first terminal 101 or the second terminal 102 is, for example, a low power radio (specific low power radio) that does not require a license. For this type of low-power radio, specifications such as the frequency band to be used and the antenna power are defined in each country depending on the application. In Japan, low-power radio that uses radio waves in the 920 MHz band or 420 MHz band is defined. As a specific example, communication between the communication device 1 and the first terminal 101 or the second terminal 102 is based on Wi-SUN (registered trademark). The communication path between the communication device 1 and the first terminal 101 or the second terminal 102 is included in a communication route (so-called B route) inside the house from the smart meter.

  Note that the communication device 1 may be connected to the Internet via a network device such as a router.

(2.2) Communication Device As shown in FIG. 1, the communication device 1 includes a control unit 10 and a communication unit 12. The control unit 10 includes a selection unit 11, a stop unit 13, and a memory 14.

  The control unit 10 controls the communication unit 12. Here, the control unit 10 is mainly composed of a microcomputer having a processor and a memory 14. The control unit 10 causes the microcomputer to function as the selection unit 11 and the stop unit 13 by executing a program stored in the memory 14 by the processor of the microcomputer.

  The communication unit 12 is a wireless communication module that performs communication with the first terminal 101 and the second terminal 102. The communication unit 12 performs communication with the first terminal 101 and communication with the second terminal 102 with one wireless chip. The communication unit 12 has a function of modulation and demodulation, and is capable of bi-directional data transmission with each of the first terminal 101 and the second terminal 102. The communication unit 12 includes a PLL (Phase Locked Loop) frequency synthesizer. Thereby, the communication part 12 can switch the channel (this embodiment frequency band) used for communication.

  The communication unit 12 and the first terminal 101 conform to the same communication standard. Therefore, for example, when a signal is transmitted from the first terminal 101 to the communication device 1, the device that receives the signal (communication device 1) can predict the timing at which the retransmission signal is transmitted. Therefore, in the communication device 1, when the communication unit 12 receives a signal from the first terminal 101, the communication unit 12 may predict a retransmission period Tr <b> 1 (see FIG. 2) for receiving a retransmission signal from the first terminal 101. it can. Similarly, the communication unit 12 and the second terminal 102 conform to the same communication standard. Therefore, in the communication device 1, when the communication unit 12 receives a signal from the second terminal 102, the retransmission period Tr <b> 1 in which the communication unit 12 receives a retransmission signal from the second terminal 102 can be predicted. However, the retransmission period Tr1 may not be fixed. For example, when a signal is transmitted from the first terminal 101 to the communication apparatus 1, the retransmission period Tr1 varies within a certain range, such as when the first terminal 101 transmits a retransmission signal after waiting for a random time (backoff). There is. Even in such a case, the retransmission period Tr1 can be predicted by the communication apparatus 1 by widening the retransmission period Tr1 by a certain width.

  Further, the operation mode of the communication unit 12 includes two modes, a standby mode and a reception mode. The standby mode is a mode for achieving synchronization between the communication unit 12 and the first terminal 101 or the second terminal 102, and the communication unit 12 receives a preamble from the first terminal 101 or the second terminal 102. Wait (standby). The reception mode is a mode for the communication unit 12 to receive a packet from the first terminal 101 or the second terminal 102, and the communication unit 12 communicates with either the first terminal 101 or the second terminal 102. Do. The communication unit 12 is configured to switch to the reception mode when receiving the preamble while operating in the standby mode.

  The memory 14 stores various parameters including parameters related to a plurality of channels and a specified time.

  The selection unit 11 selects one channel as a use channel from among a plurality (two in the present embodiment) of channels CH1 and CH2. The “used channel” here is a channel used for communication in the communication unit 12. Specifically, the selection unit 11 controls the frequency synthesizer of the communication unit 12 according to the parameters stored in the memory 14. Thereby, the channel (use channel) which the communication part 12 uses is determined in the selection part 11 (control part 10).

  The selection status of the channel used by the selection unit 11 varies depending on the operation mode of the communication unit 12. That is, while the communication unit 12 is operating in the standby mode, the selection unit 11 periodically switches the use channel within the plurality of channels CH1 and CH2 so that the use channel is switched every time the specified time elapses. . On the other hand, while the communication unit 12 operates in the reception mode, the selection unit 11 is configured to fix the used channel to one channel among the plurality of channels CH1 and CH2.

  Specifically, as shown in FIG. 3, during the period Tm1 during which the communication unit 12 is operating in the standby mode, the selection unit 11 alternately selects the channel CH1 and the channel CH2 as the use channels. In this case, the switching timing at which the selection unit 11 switches the used channel is defined by a specified time. In FIG. 3, the horizontal axis is the time axis, the channel used is “CH”, and the signal transmitted from the first terminal 101 is “Sig”.

  Here, a plurality (two in this embodiment) of predetermined times are set corresponding to the plurality of channels CH1 and CH2 on a one-to-one basis. The specified time corresponding to the channel CH1 is the (first) specified time T1, and the specified time corresponding to the channel CH2 is the (second) specified time T2. In the present embodiment, the specified time T1 and the specified time T2 are the same length. Each of the prescribed times T1 and T2 is the total time of the time required for the channel switching process and the time for waiting for the preamble. The time required for the channel switching process includes, for example, a register setting time and a PLL convergence time.

  While the channel CH1 is selected as the use channel, the selection unit 11 counts the specified time T1. When the specified time T1 has elapsed since the channel CH1 was selected, that is, when the specified time T1 has been counted, the selection unit 11 switches the channel to be used to the channel CH2. Similarly, while the channel CH2 is selected as the use channel, the selection unit 11 counts the specified time T2. When the specified time T2 has elapsed since the channel CH2 was selected, that is, when the specified time T2 has been counted, the selection unit 11 switches the channel to be used to the channel CH1. In this way, in the period Tm1 during which the communication unit 12 is operating in the standby mode, the use channel is switched every time the specified time T1 or T2 elapses. Therefore, the use channel is periodically switched among the plurality of channels CH1 and CH2 with the sum of the specified times T1 and T2 as one cycle.

  In the example of FIG. 3, the communication unit 12 receives a signal from the first terminal 101 during the period Tm1 during which the communication unit 12 is operating in the standby mode, while the channel used is the channel CH1. Here, the signal transmitted from the first terminal 101 includes a preamble 21, an SFD (Start Frame Delimiter) 22, and data (DATA) 23 in order from the top. Therefore, the communication unit 12 receives the preamble 21 in the standby mode, and the operation mode of the communication unit 12 is switched to the reception mode. Here, “SFD” is a bit string immediately after the preamble 21 and indicating the start of a packet (frame). “Data” is data transmitted from the first terminal 101 to the communication apparatus 1.

  In the period Tm2 during which the communication unit 12 is operating in the reception mode, the selection unit 11 selects the channel CH1 when the communication unit 12 is switched to the reception mode, that is, the channel CH1 when the communication unit 12 receives the preamble 21 as the use channel. After that, the selection unit 11 fixes the channel to be used without switching the used channel until the end of the period Tm2 during which the communication unit 12 is operating in the reception mode. When the communication unit 12 completes reception of the data 23, the communication unit 12 ends the reception mode and starts the standby mode.

  When the communication unit 12 resumes the operation in the standby mode, the selection unit 11 alternately selects the channel CH1 and the channel CH2 as use channels. Therefore, thereafter, in the period Tm1 during which the communication unit 12 is operating in the standby mode, the use channel is switched each time the specified time T1 or T2 elapses.

  By the way, since the communication device 1 includes the stop unit 13, even when the communication unit 12 is operating in the standby mode, even if the selection unit 11 switches the use channel at the time when the specified time T <b> 1 or T <b> 2 elapses. Is not limited. That is, while the communication unit 12 is operating in the standby mode, in principle, the selection unit 11 periodically switches the use channel, but the stop unit 13 may stop the use channel switching by the selection unit 11. is there. In short, when the communication unit 12 receives a signal while the communication unit 12 operates in the standby mode and the signal satisfies a predetermined stop condition, the stop unit 13 is in the retransmission period Tr1 (see FIG. 2). Then, switching of the used channel by the selection unit 11 is stopped. The retransmission period Tr1 is a period during which the communication unit 12 receives a retransmission signal. Here, the stop unit 13 stops the use channel switching by the selection unit 11 so that the use channel is fixed to the same channel as the use channel when the communication unit 12 receives the signal.

  The stop condition may include various conditions. In the present embodiment, the stop condition includes at least one of the following first condition to fourth condition.

  The first condition is that the signal reception intensity is equal to or greater than a threshold value. The threshold value is stored in the memory 14. When the stop condition is only the first condition, the stop unit 13 enters the retransmission period Tr1 if the reception strength of the signal received by the communication unit 12 while the communication unit 12 operates in the standby mode is equal to or greater than the threshold. Then, switching of the used channel by the selection unit 11 is stopped. That is, when the communication unit 12 receives a signal while operating in the standby mode, the stop unit 13 compares the received strength (RSSI) of this signal with a threshold value. For example, the stopping unit 13 compares the received signal strength with the threshold value at the time when the specified time T1 or T2 has elapsed, that is, when the communication unit 12 switches the first used channel after receiving the signal. If the reception strength is equal to or greater than the threshold, the switching unit 13 stops the switching of the used channel in the retransmission period Tr1 during which a retransmission signal having the same content as this signal is transmitted. If the reception intensity of the signal received while the communication unit 12 is operating in the standby mode is less than the threshold value, the stop unit 13 does not stop the switching of the used channel by the selection unit 11.

  Here, a plurality (two in this embodiment) of threshold values are set in a one-to-one correspondence with the plurality of channels CH1 and CH2. The threshold corresponding to the channel CH1 is the (first) threshold Ith1, and the threshold corresponding to the channel CH2 is the (second) threshold Ith2. In the present embodiment, the threshold value Ith1 and the threshold value Ith2 are the same value.

  The second condition is a condition that the signal length of the signal is not less than a predetermined value. The predetermined value is stored in the memory 14. When the stop condition is only the second condition, the stop unit 13 determines the retransmission period Tr1 if the signal length of the signal received by the communication unit 12 while the communication unit 12 operates in the standby mode is equal to or greater than a predetermined value. The switching of the used channel by the selection unit 11 is stopped. If the signal length of the signal received while the communication unit 12 is operating in the standby mode is less than the predetermined value, the stop unit 13 does not stop the switching of the used channel by the selection unit 11.

  The third condition is that the signal length of the signal is within a predetermined range with reference to the specified value. The specified value and the predetermined range are stored in the memory 14. When the stop condition is only the third condition, the stop unit 13 determines the retransmission period Tr1 if the signal length of the signal received by the communication unit 12 while the communication unit 12 operates in the standby mode is within a predetermined range. The switching of the used channel by the selection unit 11 is stopped. If the signal length of the signal received while the communication unit 12 is operating in the standby mode is outside the predetermined range, the stop unit 13 does not stop the switching of the used channel by the selection unit 11. Here, the “predetermined range” is a range in which an upper limit value and a lower limit value are set by giving a margin for an allowable error to the specified value. When the signal length of the signal is the same value as the upper limit value or the lower limit value of the predetermined range, the signal length of the signal is within the predetermined range. The “specified value” is, for example, a packet length transmitted from the first terminal 101 or the second terminal 102 to the communication apparatus 1, and “allowable error” includes, for example, a preamble length.

  In the second condition or the third condition, the “signal length of the signal” is, for example, the length of time that the communication unit 12 receives the signal. When the communication unit 12 receives a signal a plurality of times over a plurality of switching periods of the used channels, the “signal length of the signal” is the number of times the communication unit 12 has received the signal. For example, when the signal length of the signal is longer than one cycle (T1 + T2) of the used channel switching cycle, one signal is received by the communication unit 12 over a plurality of used channel switching cycles. In this case, if the signal is a signal transmitted from the first terminal 101, the communication unit 12 receives the signal only while the use channel is the channel CH1, and transmits the signal while the use channel is the channel CH2. Since it is not received, the signal is received intermittently. In such a case, the communication unit 12 receives the signal n times if the signal is over n cycles (n is an integer equal to or greater than 2) of the used channel switching cycle. Therefore, the “signal length of the signal” is represented by the product of the number of times the communication unit 12 receives the signal and the channel switching cycle (T1 + T2). Therefore, the stopping unit 13 uses the number of times the communication unit 12 has received a signal as the “signal length of the signal”. Further, the “predetermined value” in the second condition and the “specified value” in the third condition are assumed to be the same value in the present embodiment, but may be different from each other.

  The fourth condition is a condition that the correlation value between the signal and the reference signal is greater than or equal to the reference value. The “reference signal” here is a bit string included in a signal transmitted from the first terminal 101 or the second terminal 102 and is stored in the memory 14. When the stop condition is only the fourth condition, the stop unit 13 determines that the correlation value between the signal received by the communication unit 12 and the reference signal while the communication unit 12 operates in the standby mode is greater than or equal to the reference value. If there is, switching of the channel used by the selection unit 11 is stopped in the retransmission period Tr1. If the correlation value between the signal received while the communication unit 12 is operating in the standby mode and the reference signal is less than the reference value, the stop unit 13 does not stop the switching of the channel used by the selection unit 11. The “correlation value” here is a value representing the similarity between the waveform of the received signal and the reference signal, and the correlation value increases as the similarity between the signal and the reference signal increases. The correlation value is obtained by, for example, cross correlation analysis.

  When the communication unit 12 receives a signal while the communication unit 12 operates in the standby mode, the stop unit 13 uses a stop condition including at least one of the first to fourth conditions described above. Then, it is determined whether or not the use channel switching by the selection unit 11 is stopped. Hereinafter, as an example, a case where the stop condition includes only the first condition will be described. However, the stop condition is, for example, a combination of the first condition and the second condition or the third condition, a combination of the first condition and the fourth condition, a combination of the third condition and the fourth condition, or the first condition. A combination of the second condition and the fourth condition may be used.

  With the above configuration, if the reception strength of the signal received by the communication unit 12 when the use channel is the channel CH1 in the standby mode is greater than or equal to the threshold value Ith1, the stop unit 13 is controlled by the selection unit 11 during the retransmission period Tr1. Stop switching the used channel. In this case, the stopping unit 13 stops the switching of the used channel by the selecting unit 11 immediately before the start of the retransmission period Tr1 so that the used channel is fixed to the channel CH1 in the retransmission period Tr1. Specifically, in the monitoring period set immediately before the start of the retransmission period Tr1, when the use channel becomes the channel CH1, the stop unit 13 sets the selection unit 11 so that the use channel is fixed to the channel CH1 thereafter. Stops switching the channel used by. The “monitoring period” here is a period of a predetermined time with the end point of the retransmission period Tr1 as the end point.

  The stop unit 13 stops the use channel switching by the selection unit 11 when the communication unit 12 receives the preamble 21 or stops a certain time (timeout) after stopping the use channel switching by the selection unit 11. To release. The “certain time” here is, for example, a time longer than the signal length (time length) of the preamble 21 and shorter than the signal length of the entire signal. That is, there is a limit to the time during which the use channel is fixed to the channel CH1 by the stop unit 13. However, when the communication unit 12 receives the preamble 21, since the operation mode of the communication unit 12 is switched from the standby mode to the reception mode, the channel used is the channel CH1. When the predetermined time has elapsed, the stop by the stop unit 13 is released, and the selection unit 11 switches the use channel to the channel CH2. The certain time may be a time longer than the signal length of the entire signal, for example.

  Similarly, if the reception strength of the signal received by the communication unit 12 in the standby mode and the use channel is the channel CH2 is greater than or equal to the threshold Ith2, the stop unit 13 uses the selection unit 11 in the retransmission period Tr1. Stop channel switching. In this case, the stopping unit 13 stops the switching of the used channel by the selecting unit 11 immediately before the start of the retransmission period Tr1 so that the used channel is fixed to the channel CH2 in the retransmission period Tr1. Then, after a certain period of time has elapsed after the stop unit 13 stops switching the use channel by the selection unit 11, the stop by the stop unit 13 is released, and the selection unit 11 switches the use channel to the channel CH1.

  By the way, in the communication apparatus 1 according to the present embodiment, when the communication unit 12 receives a signal while operating in the standby mode, regardless of the content of the signal, if the signal reception strength is equal to or higher than the threshold, the retransmission period Tr1 Then, the stop unit 13 stops the switching of the used channel. Therefore, even if the signal received by the communication unit 12 does not include the preamble 21, the stop unit 13 may stop switching the used channel. In this case, a reception error of the preamble 21 occurs in the retransmission period Tr1. Arise. Therefore, if the stopping unit 13 stops switching the used channel without any change, there is a possibility that the reception error rate of the preamble 21 in the retransmission period Tr1 when the stopping unit 13 stops the switching of the used channel becomes high. Hereinafter, the reception error rate of the preamble 21 in the retransmission period Tr1 when the stop unit 13 stops switching the used channel is simply referred to as “reception error rate”.

  Therefore, it is preferable that the stopping unit 13 counts the number of times switching of the used channel is stopped as the number of stops. The stop unit 13 preferably obtains, as a reception error rate, a ratio of the number of times that the communication unit 12 has not received the preamble 21 to the number of stops when switching of the used channel is stopped. Specifically, when the switching of the use channel is stopped, the stop unit 13 receives the number of times the communication unit 12 has received the preamble 21 and the number of times the preamble 21 has not been received (hereinafter referred to as “number of errors”). Is counted. And the stop part 13 calculates | requires the ratio with respect to the frequency | count of a stop of an error frequency as a reception error rate. As a result, the stopping unit 13 can determine, as a reception error rate, a rate at which the preamble 21 cannot be received in the retransmission period Tr1 even though switching of the used channel is stopped.

  The stopping unit 13 increases the threshold value Ith1 or Ith2 when the reception error rate exceeds a predetermined upper limit value. When the threshold value Ith1 or Ith2 increases, the frequency at which the switching of the used channel is stopped by the stopping unit 13 decreases, and the reception error rate decreases.

  Conversely, when the reception error rate is equal to or lower than the predetermined lower limit value, the stopping unit 13 may decrease the threshold value Ith1 or Ith2. When the threshold value Ith1 or Ith2 is decreased, the frequency of stopping the switching of the used channel by the stopping unit 13 is increased, so that the reception error rate is increased.

  As described above, the stopping unit 13 can optimize the reception error rate by adjusting the threshold value Ith1 or Ith2 according to the reception error rate. That is, the stopping unit 13 can optimize the reception error rate so that the reception error rate falls within the range from the lower limit value to the upper limit value.

  However, since a low reception error rate is not a problem, a lower limit value may not be set for the reception error rate. In short, the stop unit 13 only needs to reduce the threshold value Ith1 or Ith2 when a predetermined determination condition is satisfied, and the determination condition here is not limited to the reception error rate being equal to or lower than the lower limit value.

  For example, the determination condition may be that a certain time has elapsed. In this case, the stopping unit 13 periodically decreases the threshold value Ith1 or Ith2. This periodically increases the reception error rate.

  Further, the lengths of the specified times T1 and T2 can be set as appropriate. However, if each of the specified times T1 and T2 is too short, the communication unit 12 may not be able to receive the preamble 21 within the specified time. Therefore, it is preferable that the lengths of the specified times T1 and T2 are set according to the preamble length so that the communication unit 12 can receive the preamble. When the preamble length varies, it is preferable that each of the prescribed times T1 and T2 is set to such a length that the communication unit 12 can receive the preamble 21 with a certain probability.

  However, if it is assumed that the switching of the channel to be used is stopped in the retransmission period Tr1 by the stopping unit 13, the specified time T1, T2 until the lower limit value of the range in which the reception intensity of the signal received by the communication unit 12 can be detected. Each of these can be set short. Here, the lower limit value of the range in which the reception intensity can be detected is the minimum time required for the stop unit 13 to determine that the reception intensity of the signal is equal to or greater than the threshold, and is hereinafter referred to as “strength determination time”. .

(2.3) Operation Hereinafter, the operation of the communication device 1 of the present embodiment will be described in comparison with the communication device of the comparative example. In the communication device of the comparative example here, the stop unit 13 is omitted from the communication device 1 of the present embodiment. As for the configuration other than the stopping unit 13, it is assumed that the communication device of the comparative example has the same configuration as the communication device 1 of the present embodiment. Hereinafter, the operation of the communication apparatus 1 when receiving a signal transmitted from the first terminal 101, that is, when receiving a signal of the channel CH1 will be described.

  In FIG. 4, the horizontal axis is the time axis, the channel used is “CH”, and the signals transmitted from the first terminal 101 are represented by “Sig1”, “Sig2”, “Sig3”, and “Sig4”. Here, it is assumed that the specified times T1 and T2 are both 600 μs, the transmission time of the preamble 21 is 1200 μs, and the minimum time required for receiving the preamble 21 is 500 μs. A time interval from when a signal is transmitted until a retransmission signal having the same content as this signal is transmitted (retransmission interval), that is, a time interval from when the communication unit 12 finishes receiving a signal until the retransmission period starts. Is assumed to be 1 s. Furthermore, the intensity determination time is assumed to be 20 μs. However, these values are merely examples, and can be changed as appropriate.

  In the communication apparatus of the comparative example, the period in which the preamble 21 can be normally received includes a period Tx1 of 100 μs in the first half of the period in which the used channel is the channel CH1 and a period in which the used channel is the channel CH2, as shown in FIG. Including the section Tx2 of 700 μs. The section Tx2 is a total section of a 100 μs section in the latter half of the period in which the used channel is the channel CH1 and all sections in the period in which the used channel is the channel CH2. Therefore, the signal “Sig1” that starts transmission of the preamble 21 in the section Tx1 and the signal “Sig4” that starts transmission of the preamble 21 in the section Tx2 can be normally received by the communication unit 12. Further, in the communication device of the comparative example, the signal “Sig2” and the signal “Sig3” that start transmission of the preamble 21 in the section Ty1 cause a reception error in the communication unit 12.

  That is, in the communication device of the comparative example, in order for the communication unit 12 to normally receive the preamble 21, the preamble over the entire period Tz1 or Tz2 of the first half or the second half in the period in which the used channel is the channel CH1. 21 needs to be transmitted. If the signal starts transmission of the preamble 21 in the section Tx1, the preamble 21 is transmitted over the entire section Tz1, so that the communication unit 12 can normally receive the preamble 21. If the signal starts transmission of the preamble 21 in the section Tx2, the preamble 21 is transmitted over the entire section Tz2, so that the communication unit 12 can normally receive the preamble 21.

  On the other hand, if the signal starts transmission of the preamble 21 in the section Ty1, only a part of the preamble 21 is transmitted in any of the sections Tz1 and Tz2, and thus the communication unit 12 may cause a reception error of the preamble 21. There is. If the preamble length is sufficiently long, the communication unit 12 can normally receive the preamble 21 in the second and subsequent periods in which the used channel is the channel CH1 even if the preamble 21 transmission starts in the section Ty1. . However, when the preamble length is relatively short as in the example of FIG. 4 (for example, 15 bytes (100 kbps)), with respect to a signal that starts transmission of the preamble 21 in the section Ty1, the communication unit 12 receives a reception error of the preamble 21. Prone to occur.

  Therefore, in the communication apparatus of the comparative example, the ratio of the section (Tx1 + Tx2 = 800 μs) in which the communication unit 12 can normally receive the preamble 21 in one cycle (T1 + T2 = 1200 μs) in which the used channel is switched is, that is, the reception success rate is It becomes approximately 67%.

  On the other hand, in the communication apparatus 1 according to the present embodiment, the period in which the preamble 21 can be normally received is the entire period in which the used channel is the channel CH1 and the entire period in which the used channel is the channel CH2. . Therefore, the signal “Sig1” that starts transmission of the preamble 21 in the section Tx1 and the signal “Sig4” that starts transmission of the preamble 21 in the section Tx2 can be normally received by the communication unit 12. Further, in the communication apparatus 1, the signals “Sig2” and “Sig3” for which transmission of the preamble 21 starts in the section Ty1 are also normally performed in the communication unit 12 by stopping the switching of the used channel in the retransmission period Tr1. It can be received.

  Here, the operation of the communication apparatus 1 when the communication unit 12 receives the signal “Sig2” that starts transmission of the preamble 21 in the section Ty1 will be described in detail with reference to FIG.

  In the example of FIG. 2, the communication unit 12 receives a signal when the standby mode is set and the channel used is the channel CH1. For this reason, the stopping unit 13 stops switching the used channel in accordance with the start time (time t1) of the retransmission period Tr1 of this signal, and fixes the used channel to the channel CH1. Specifically, in the monitoring period set immediately before time t1, when the used channel becomes channel CH1 (time t0), the stop unit 13 selects the channel so that the used channel is fixed to channel CH1 thereafter. The use channel switching by the unit 11 is stopped.

  In the example of FIG. 2, after the stop unit 13 stops the use channel switching by the selection unit 11, the use channel is not switched even after a predetermined time has elapsed, and the use channel is the channel CH 1 over the entire retransmission period Tr 1. It is. This is because the communication unit 12 has already received the preamble 21 at time t2 before a certain time has elapsed from time t0, and the operation mode of the communication unit 12 is switched to the reception mode at time t2. That is, in the period Tm2 during which the communication unit 12 is operating in the reception mode, as described above, the selection unit 11 selects the channel CH1 at the time of switching to the reception mode as the use channel.

  As a result, the communication unit 12 can normally receive the preamble 21 within the retransmission period Tr1 even for the signal “Sig2” that could not be normally received by the communication device of the comparative example. That is, in the communication apparatus 1, when the communication unit 12 receives a signal while operating in the standby mode, the selection unit 11 in the retransmission period Tr1 if the reception strength of the signal is equal to or greater than the threshold regardless of the content of the signal. Switching of the used channel is stopped by the stop unit 13. That is, even if a reception error of the preamble 21 occurs once in the communication unit 12, the communication unit 12 can normally receive the preamble 21 in the retransmission period Tr1. The case where the preamble 21 is normally received in the retransmission period Tr1 is also included in the case where the preamble 21 is normally received. Therefore, in the communication apparatus 1 of the present embodiment, the ratio of the section in which the communication unit 12 can normally receive the preamble 21 in one cycle (T1 + T2 = 1200 μs) when the used channel is switched, that is, the reception success rate is approximately 100%. Become. As described above, the communication device 1 includes the stop unit 13, thereby improving the success rate of receiving the preamble 21 in the communication unit 12.

(3) Advantages According to the communication device 1, the stop unit 13 receives a signal while the communication unit 12 is operating in the standby mode, and when the signal satisfies the stop condition, the stop unit 13 uses the selection unit 11 in the retransmission period Tr1. Stop channel switching. In this case, in the retransmission period Tr1, the use channel is fixed to the same channel as the use channel when the communication unit 12 receives the signal. Therefore, when a signal including the preamble 21 is transmitted while the communication unit 12 is operating in the standby mode, the preamble 21 can be received in the retransmission period Tr1 even if the preamble cannot be received once. Reception errors are less likely to occur. As a result, the communication apparatus 1 has an advantage that it is possible to reduce the probability of occurrence of a communication error due to the inability to receive a preamble despite repeatedly waiting for reception of a plurality of channels.

  Further, as in the present embodiment, the stop condition preferably includes that the signal reception intensity is equal to or greater than a threshold value. That is, it is preferable that the stop condition includes the first condition described above. According to this configuration, if the signal is received over a period equal to or greater than the strength determination time while the communication unit 12 is operating in the standby mode, the stop unit 13 can determine whether the signal satisfies the stop condition. . Therefore, even if the signal received while the communication unit 12 is operating in the standby mode is a relatively short signal, the stop unit 13 can stop the switching of the channel used by the selection unit 11 in the retransmission period Tr1.

  Further, as in the present embodiment, the stop condition preferably includes that the signal length of the signal is a predetermined value or more. That is, the stop condition preferably includes the second condition described above. According to this configuration, there is an advantage that the stop unit 13 is less susceptible to noise and the reception error rate is reduced.

  Further, as in the present embodiment, the stop condition preferably includes that the signal length of the signal is within a predetermined range with reference to the specified value. That is, it is preferable that the stop condition includes the third condition described above. According to this configuration, there is an advantage that the stop unit 13 is less susceptible to noise and the reception error rate is reduced.

  Further, when the stop condition includes the second condition or the third condition described above, when the communication unit 12 receives a signal a plurality of times over a plurality of cycles of the use channel switching period, the signal length of the signal is determined by the communication unit 12. Preferably, the number of times the signal has been received. According to this configuration, the signal length of the signal can be easily estimated by the stop unit 13 even when the signal extends over a plurality of switching periods of the used channels.

  Further, as in the present embodiment, the stop condition preferably includes that the correlation value between the signal and the reference signal is greater than or equal to the reference value. That is, it is preferable that the stop condition includes the fourth condition described above. According to this configuration, there is an advantage that the stop unit 13 is less susceptible to noise and the reception error rate is reduced.

(4) Modifications The above embodiment can be variously modified according to design or the like as long as it does not depart from the technical idea of the present invention. That is, the present invention is not limited to the above embodiment.

  In the communication device 1 according to the first modification, the stopping unit 13 stops the switching of the used channel by the selecting unit 11 only when the used channel is a specific channel among the plurality of channels CH1 and CH2. It is configured as follows. The specific channel may be any of a plurality of channels CH1 and CH2. For example, when the preamble length differs between channel CH1 and channel CH2, it is preferable that the channel with a short preamble length is the specific channel. For example, if the preamble length of the channel CH1 is shorter than that of the channel CH2, the stopping unit 13 stops the switching of the used channel only when the used channel is the channel CH1. According to the first modified example, there is an advantage that the frequency at which the switching of the use channel is stopped by the stopping unit 13 is suppressed low, and the probability of occurrence of erroneous synchronization is suppressed low.

  In the communication device 1 according to the second modification, the length of the specified time differs depending on which of the plurality of channels CH1 and CH2 is used. That is, in the above embodiment, the specified time T1 corresponding to the channel CH1 and the specified time T2 corresponding to the channel CH2 are the same length, but in this modified example, the specified time T1 and the specified time T2 are different. Length. For example, when the preamble length differs between channel CH1 and channel CH2, it is preferable that the prescribed time corresponding to a channel with a short preamble length becomes long. For example, if the preamble length of the channel CH1 is shorter than that of the channel CH2, the specified time T1 when the used channel is the channel CH1 is longer than the specified time T2. According to the second modification, there is an advantage that the reception success rate of the preamble 21 is improved.

  In the communication device 1 according to the third modification, the stopping unit 13 does not completely stop the switching of the used channel in the retransmission period Tr1, but changes the ratio between the specified time T1 and the specified time T2. It may be configured to. That is, when one cycle (T1 + T2) of the used channel switching cycle is defined as “unit time”, the stopping unit 13 instead of stopping the switching of the used channel in the retransmission period Tr1, the specified time T1 occupying the unit time Alternatively, the ratio of T2 may be changed. In other words, when the communication unit 12 receives a signal while the communication unit 12 is operating in the standby mode and this signal satisfies the stop condition, the stop unit 13 changes the timing of switching the used channel by the selection unit 11 in the retransmission period Tr1. To do. In this case, in the retransmission period Tr1, the proportion of the used channel is increased so that the proportion of the unit time in which the same channel as the used channel when the communication unit 12 receives the signal is selected as the used channel becomes large. The switching timing is changed.

  In this modification, if the proportion of the time (specified time T1 or T2) in which the same channel as the channel used when the communication unit 12 receives the signal is selected as the channel used is 100% The use channel switching is stopped. For example, as illustrated in FIG. 2, it is assumed that the communication unit 12 receives a signal when the standby mode is set and the use channel is the channel CH1. In this case, the stopping unit 13 changes the used channel switching timing so that the proportion of the time during which the used channel is the channel CH1 (that is, the specified time T1) in the unit time increases in the retransmission period Tr1. At this time, if the stopping unit 13 sets the ratio of the specified time T1 to the unit time in the retransmission period Tr1 to 100%, switching of the used channel is stopped and the used channel is fixed to the channel CH1.

  Below, other modifications of the above embodiment will be listed.

  The communication device 1 is not limited to the HEMS controller but can be used in various communication systems.

  Further, the communication method used by the communication apparatus 1 for communication with the first terminal 101 or the second terminal 102 is not limited to Wi-SUN (registered trademark), for example, Wi-Fi (registered trademark) or Bluetooth (registered trademark). Or the like. Further, the communication method used by the communication device 1 for communication with the first terminal 101 or the second terminal 102 is not limited to wireless communication, and is, for example, wired communication such as power line communication (PLC). Also good.

  The communication device 1 is not limited to two terminals (the first terminal 101 and the second terminal 102), and may be configured to communicate with three or more terminals. In this case, it is preferable that the use channel is selected from three or more channels that are one-to-one associated with three or more terminals that are communication partners of the communication device 1. In this case, while the communication unit 12 is operating in the standby mode, the selection unit 11 periodically sets the use channel within three or more channels so that the use channel is switched every time the specified time elapses. It is preferable to switch. For example, when the selection unit 11 periodically switches the use channel among the three channels CH1, CH2, and CH3, the use channel is switched in the order of CH1, CH2, CH3, CH1, CH2, CH3, CH1, CH2,.

  The synchronization method between the communication device 1 and the first terminal 101 and the second terminal 102 may be a character synchronization method or a flag synchronization method. In the case of the character synchronization method, the character code (SYN) added to the head of the message (data) becomes the preamble, and in the case of the flag synchronization method, the flag attached to the head of the data becomes the preamble.

  The communication method of the communication unit 12 is not limited to frequency division multiple access. For example, in code division multiple access communication, a plurality of spreading codes are used as a plurality of channels. In time division multiple access communication, a plurality of time slots are used as a plurality of channels.

  Further, in the above embodiment, in the comparison between two values such as the reception intensity and the threshold, “more than” is both when the two values are equal and when one of the two values exceeds the other. Is meant to include. However, the present invention is not limited thereto, and “more than” may be synonymous with “greater than” including only when one of the two values exceeds the other. That is, whether or not the case where the two values are equal can be arbitrarily changed depending on the setting of the threshold value or the like, so there is no technical difference between “more than” and “greater than”. Similarly, “below” may be synonymous with “less than”.

  Note that various configurations (including modifications) described in the above embodiments can be applied in appropriate combination.

DESCRIPTION OF SYMBOLS 1 Communication apparatus 11 Selection part 12 Communication part 13 Stop part 21 Preamble CH1, CH2 Channel T1, T2 Specified time Tr1 Retransmission period

Claims (7)

A selection unit that selects one channel as a use channel from a plurality of channels;
A communication unit that performs communication using the use channel,
The communication unit is
When receiving the preamble while operating in standby mode, it is configured to switch to reception mode to receive packets,
The selection unit includes:
While the communication unit is operating in the standby mode, the use channel is periodically switched in the plurality of channels so that the use channel is switched each time a specified time elapses.
While the communication unit is operating in the reception mode, the use channel is configured to be fixed to one of the plurality of channels,
When the communication unit receives a signal while the communication unit is operating in the standby mode, and the signal satisfies a predetermined stop condition, the communication unit receives the retransmission signal in a retransmission period. A communication unit further comprising: a stopping unit that stops switching of the used channel by the selection unit so that the used channel is fixed to the same channel as the used channel when the unit receives the signal. apparatus. The stop condition is
The communication apparatus according to claim 1, wherein the reception intensity of the signal includes a threshold value or more. The stop condition is
The communication apparatus according to claim 1, wherein a signal length of the signal is greater than or equal to a predetermined value. The stop condition is
The communication apparatus according to claim 1, wherein the signal length of the signal is within a predetermined range with reference to a specified value. When the communication unit receives the signal a plurality of times over a plurality of cycles of the switching cycle of the used channel,
The communication apparatus according to claim 3 or 4, wherein the signal length of the signal is the number of times the communication unit has received the signal. The stop condition is
The communication apparatus according to claim 1, wherein a correlation value between the signal and a reference signal includes a reference value or more. The stop part is
The configuration is such that the switching of the used channel by the selection unit is stopped only when the used channel is a specific channel among the plurality of channels. The communication apparatus according to claim 1.

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