JP2018088578A - Terminal device, communication method, communication system, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a terminal device capable of simultaneous transmission even when carrier sense is executed.SOLUTION: A terminal device includes: a carrier sense unit for executing carrier sense for a frequency band used by the terminal device; a radio communication unit for starting radio communication if the carrier sense unit does not detect other communication competing against each other at the frequency band; a communication termination detection unit for detecting termination of radio communication at the frequency band by another terminal device; and a waiting time setting unit for setting, to a waiting time, a time from prescribed transmission timing to detection of the termination of the radio communication by the other terminal device. The carrier sense unit starts carrier sense at timing when the waiting time has passed from the prescribed transmission timing.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a terminal device, a communication method, a communication system, and a program.

  When performing wireless communication, checking whether there is another communication using the same frequency band as that of itself is called carrier sense. In some countries, laws regarding the use of radio waves may require that carrier sense be performed before transmission of communication radio waves. For example, when the terminal device A detects other communication by carrier sense, the terminal device A does not perform communication in order to prevent interference. Then, after a predetermined time has elapsed, the terminal device A performs carrier sense again and confirms that there is no other communication, and then starts communication.

  By the way, Patent Document 1 describes a technique in which a usable frequency band is finely divided, a different frequency band after division is assigned to each of a plurality of terminal devices, and a plurality of terminal devices communicate simultaneously. .

Japanese Patent No. 5736450

  According to the method of Patent Document 1, a plurality of terminal devices can communicate simultaneously using divided frequency bands. However, when it is mandatory to carry out carrier sense, carrier sense is not performed for the fine frequency band after division, but for the full width of the usable frequency band before division, so the frequency band after division is used. When the terminal device A that intends to start communication performs carrier sense, it also detects communication using another frequency band after division. In this case, the terminal device A cannot start communication. Thus, when carrier sense is obliged, there is a problem that it is actually difficult for a plurality of terminal devices to communicate simultaneously.

  Therefore, an object of the present invention is to provide a terminal device, a communication method, a communication system, and a program that can solve the above-described problems.

According to the first aspect of the present invention, when the terminal device does not detect a carrier sense unit that performs carrier sense for the frequency band used by the terminal device and other communication in which the carrier sense unit competes in the frequency band. A wireless communication unit that starts wireless communication, a communication end detection unit that detects the end of wireless communication in the frequency band by another terminal device, and the end of wireless communication by the other terminal device from a predetermined transmission timing A standby time setting unit that sets a time until detection as a standby time, and the carrier sense unit starts carrier sense at a timing when the standby time has elapsed from the predetermined transmission timing.
The terminal device according to this aspect waits until communication by another terminal device is completed, and then performs carrier sense and wireless communication. Therefore, even when there are a plurality of terminal devices that use the same frequency band and carrier sense is required before communication, the possibility of communication is increased. Also, after setting the waiting time, there is no need to perform carrier sense during the waiting time.

According to the second aspect of the present invention, the carrier sense by the carrier sense unit includes a carrier sense for detecting the end of the other wireless communication and a carrier sense based on a standard, and the carrier sense unit The carrier sense based on the standard may be started at the timing when the carrier sense for detecting the end of the other wireless communication is completed.
In addition to the carrier sense based on the standard, the possibility of detecting competing communications in the carrier sense based on the standard can be reduced by performing carrier sense that detects the end of another wireless communication. In addition, the possibility that the terminal device can transmit after carrier sense based on the standard increases.

According to the third aspect of the present invention, the carrier sense unit may start carrier sense for detecting the end of the other radio communication at a timing when the standby time has elapsed from the predetermined transmission timing.
Since carrier sense for detecting the end of another wireless communication is executed after the standby time has elapsed, for example, when another communication is being executed after the standby time has elapsed, the end of the communication can be detected. Accordingly, it is possible to reduce the possibility of detecting a conflicting communication in the carrier sense based on the standard executed following the carrier sense for detecting the end of another wireless communication. In addition, the possibility that the terminal device can transmit after carrier sense based on the standard increases.

According to the fourth aspect of the present invention, the radio communication unit may determine whether communication is possible after the completion of carrier sense by the carrier sense unit.
By starting wireless communication after execution of these two carrier senses, the wireless communication unit can start wireless communication more reliably.

According to the fifth aspect of the present invention, the standby time setting unit adds the time when the carrier sense for detecting the end of the other wireless communication is performed to the set standby time, and the carrier sense unit When the own device reaches the next transmission timing, the carrier sense may be started at the timing when the waiting time after the addition has elapsed from the transmission timing.
By adding the execution time of carrier sense for detecting the end of another wireless communication to the standby time, the execution time of carrier sense at the next transmission timing can be shortened.

According to the sixth aspect of the present invention, the standby time setting unit may set a value obtained by subtracting a predetermined time from the calculated standby time as the standby time.
By setting the standby time shorter by a predetermined time, it is possible to more reliably detect the end timing of wireless communication by another terminal device at the next transmission timing.

According to the seventh aspect of the present invention, when the difference between the standby time and a predetermined upper limit value is within a predetermined range, the standby time setting unit may not add to the standby time. .
By comprising in this way, it can prevent that a terminal device loses a transmission timing because standby time becomes too long.

According to an eighth aspect of the present invention, the standby time setting unit may set an initial value for the standby time when a difference between the standby time and a predetermined upper limit value is within a predetermined range. Good.
By comprising in this way, it can prevent that a terminal device loses a transmission timing because standby time becomes too long.

According to a ninth aspect of the present invention, the communication system is a wireless communication system assigned a predetermined frequency band as a frequency band of radio waves for wireless communication, and the terminal according to any one of the above The communication system may include a plurality of devices, and any one of the divided frequency bands may be assigned to each of the plurality of terminal devices.
Even when carrier sense for the allocated frequency band is required, a plurality of terminal devices can perform simultaneous communication.

  According to the tenth aspect of the present invention, the communication method includes a step of performing carrier sense for the frequency band used by the own device, and when no other communication competing in the frequency band is detected in the carrier sense, A step of starting communication, a step of detecting the end of wireless communication in the frequency band by another terminal device, and a time from a predetermined transmission timing to the detection of the end of wireless communication by the other terminal device. In the step of performing carrier sense, carrier sense is started at the timing when the standby time has elapsed from the predetermined transmission timing.

  According to the eleventh aspect of the present invention, the program detects the communication of the terminal device computer for means of performing carrier sense for the frequency band used by the own device, and other communication competing in the frequency band in the carrier sense. If not, means for starting wireless communication, means for detecting the end of wireless communication in the frequency band by another terminal device, time from the predetermined transmission timing until detection of the end of wireless communication by the other terminal device The means for functioning as a means for setting the standby time and performing the carrier sense starts the carrier sense at a timing when the standby time has elapsed from the predetermined transmission timing.

  According to the present invention, even when carrier sense is required before the start of communication, simultaneous communication using different frequency bands among a plurality of frequency bands obtained by dividing available frequency bands is possible. Become.

It is a functional block diagram of the terminal device in a first embodiment according to the present invention. It is a figure which shows the outline | summary of the communication system in 1st embodiment which concerns on this invention. It is a 1st figure explaining the control method of career sense in a first embodiment concerning the present invention. It is a 2nd figure explaining the control method of the carrier sense in 1st embodiment which concerns on this invention. It is a flowchart which shows an example of the carrier sense execution control process in 1st embodiment which concerns on this invention. It is a figure which shows an example of the hardware constitutions of the terminal device in 1st embodiment which concerns on this invention.

<First embodiment>
Hereinafter, a terminal device according to a first embodiment of the present invention will be described with reference to FIGS.
FIG. 1 is a functional block diagram of a terminal device according to the first embodiment of the present invention.
As illustrated, the terminal device 10 includes a carrier sense unit 11, a communication end detection unit 12, a wireless communication unit 13, a standby time setting unit 14, a timer unit 15, and a storage unit 16.

  The carrier sense part 11 performs the carrier sense which detects whether the other radio | wireless communication using the frequency band which an own apparatus uses is performed. The time for performing carrier sense is determined for each frequency band in the standard (for example, ARIB-STD-T108). The carrier sense unit 11 detects the radio wave intensity of a communication radio wave in a target frequency band, and determines that another radio communication is being performed when the detected radio wave intensity is higher than a predetermined threshold. When other communication is detected by carrier sense according to a law or the like, the terminal device 10 cannot perform communication. Carrier sense is performed for the entire width of the frequency band used by the device itself.

The communication end detection unit 12 detects the end timing of other wireless communication based on the radio wave intensity detected by the carrier sense unit 11.
The wireless communication unit 13 performs wireless communication with other devices via the base station. The wireless communication unit 13 determines whether communication is possible based on the result of carrier sense. For example, the wireless communication unit 13 starts wireless communication when the carrier sense unit 11 determines that other wireless communication is not performed as a result of carrier sense (in carrier sense).
The standby time setting unit 14 sets a standby time from the predetermined transmission timing until the carrier sense unit 11 starts carrier sense.
The timer unit 15 measures time.
The storage unit 16 stores various information such as the standby time calculated by the standby time setting unit 14.

FIG. 2 is a diagram showing an outline of the communication system in the first embodiment according to the present invention.
In FIG. 2, the communication system 1 includes a base station 20 and terminal devices 10A, 10B, 10C, 10D, and 10E. The terminal devices 10A, 10B, 10C, 10D, and 10E are collectively referred to as the terminal device 10. Further, for example, the carrier sense unit 11 included in the terminal device 10A is described as a carrier sense unit 11A, and the carrier sense unit 11 included in the terminal device 10B is described as a carrier sense unit 11B. Further, the carrier sense units 11A, 11B and the like are collectively referred to as a carrier sense unit 11. For example, one occupied frequency band is assigned to the communication system 1, and the base station 20 performs radio communication with the terminal devices 10A, 10B, 10C, 10D, and 10E using this frequency band. The wireless communication in the present embodiment is, for example, communication using a 920 Mhz band radio wave performed between the terminal device 10 and the base station 20 that is a specific low power wireless station, for example. Communication using radio waves in this band is used in fields such as IoT (Internet of Things), M2M (Machine to Machine), etc., in situations where information on measured values from each sensor is transmitted from a telemeter, smart meter, etc. Yes. Note that the telemeter and smart meter in the above example correspond to the terminal device 10. For example, ARIB-STD-T108 is a standard related to communication using this frequency band. According to this standard, there is an upper limit of transmission time per transmission and a pause time that must be inserted between transmissions. Length etc. are defined. Also, the standard stipulates that carrier sense must be performed before transmission to confirm that there is no interfering communication. For example, when the terminal device 10A is performing wireless communication with the base station 20, even if the terminal device 10B attempts to perform wireless communication, the carrier sense unit 11B included in the terminal device 10B causes the terminal device 10A and the base station 20 to Since the wireless communication is detected, the terminal device 10B cannot start the wireless communication. Moreover, if the allocated frequency band is frequency-divided and a different frequency band after division (referred to as sub-frequency band) is allocated to each of the terminal devices 10A to 10E, the frequencies used by the terminal devices 10A to 10E do not overlap. Therefore, the terminal devices 10A to 10E should be able to perform wireless communication with the base station 20 at the same time. However, according to the carrier sense standard, for example, when the terminal device 10B starts wireless communication, the carrier sense unit 11B must detect that there is no communication radio wave competing for the full width of the frequency band before the division. . Then, for example, when the terminal device 10A is already communicating with the base station 20, the carrier sense unit 11B detects wireless communication by the terminal device 10A, and thus the terminal device 10B cannot start communication. When carrier sense is required in this way, in a situation where one of the sub-frequency bands after division is used, wireless communication using other sub-frequency bands cannot be performed and resources are wasted. In particular, the data size of the measurement value transmitted by a telemeter or the like is often relatively small, and the bandwidth is often sufficient to transmit the measurement value even in the divided frequency band. That is, technically, a plurality of telemeters (terminal devices 10) can simultaneously transmit measurement values to the base station 20 using different frequency bands after division. However, when carrier sense is required, simultaneous transmission is hindered by the restriction due to the carrier sense described above.

Therefore, in the present embodiment, simultaneous communication by a plurality of terminal devices 10A to 10E and the like is enabled by appropriately controlling the execution time of carrier sense.
Note that the communication method of the present embodiment described below is not limited to wireless communication using the 920 Mhz band. The present invention can be applied to various communication methods that perform carrier sense.

(Example of periodic transmission)
FIG. 3 is a first diagram illustrating a carrier sense control method according to the first embodiment of the present invention.
FIG. 3 shows a state in which each of the terminal devices 10A, 10B, and 10C communicates with the base station 20 at a fixed period. As an example, sensors are connected to the terminal devices 10 </ b> A, 10 </ b> B, and 10 </ b> C, and each terminal device 10 collects measured data of the connected sensors via the base station 20. Suppose you send to. Therefore, the terminal devices 10A, 10B, and 10C are fixedly installed near the sensor. Further, it is assumed that the terminal devices 10A, 10B, and 10C have a maximum number of transmissions per day and have the same transmission cycle (for example, T minutes). Note that the terminal apparatuses 10A, 10B, and 10C perform communication using sub-frequency bands having different frequencies from each other, which are obtained by dividing the bandwidth of 200 kHz. Further, it is assumed that the transmission cycle of the terminal devices 10A, 10B, and 10C is T minutes. That is, the terminal device 10A reaches the transmission timing for transmitting data to the base station 20 at time “SA1”, and reaches the next transmission timing at time “SA2” after the transmission cycle “T minutes”. Thereafter, the terminal apparatus 10A reaches the transmission timing to the base station 20 every T minutes. Similarly, the terminal device 10B reaches the transmission timing for transmitting data to the base station 20 at time “SB1”, and reaches the next transmission timing at time “SB2” T minutes later. Thereafter, the terminal device 10B reaches the transmission timing every T minutes. In addition, the terminal device 10C reaches the transmission timing for transmitting data to the base station 20 at time “SC1”, and reaches the next transmission timing at time “SC2” T minutes later. Thereafter, the terminal device 10C reaches the transmission timing every T minutes. Next, the difference between the carrier sense in this embodiment and the conventional carrier sense will be described.

  For example, in the case of the terminal device 10A, when the transmission timing comes at time “SA1,” the carrier sense unit 11 performs other wireless communication before performing carrier sense based on the standard (“CS (5 ms)” in the figure). Carrier sense (communication end detection carrier sense) for confirming the end of the communication is performed ("communication end detection CS" in the figure). The carrier sense based on the standard corresponds to the carrier sense required by law. In the case of the conventional method, in the case of the terminal device 10A, when the transmission timing comes at time “SA1,” the carrier sense unit 11 performs carrier sense based on the standard (“CS (5 ms)” in the figure). When other communication is detected, the transmission is temporarily given up, and carrier sense based on the standard is performed again after a predetermined time. On the other hand, in this embodiment, communication end detection carrier sense is performed before carrier sense based on the standard. With this method, since the carrier sense based on the standard is performed after confirming the end of other communication, the possibility of detecting other communication during the carrier sense based on the standard can be reduced. The transmission can be performed more reliably after the execution of the carrier sense based on it. Further, it is possible to increase the possibility that the delay from the predetermined transmission timing to the actual transmission can be shortened.

  Next, according to the present embodiment, it will be described that simultaneous communication using a sub-frequency band by a plurality of terminal devices 10B and 10C is possible even when carrier sense is required. As described above, the terminal apparatuses 10B and 10C perform transmission for each transmission period T at independent transmission timings. First, in the terminal device 10B, when the transmission timing “SB1” is reached, the carrier sense unit 11B performs communication end detection carrier sense. The communication end detection unit 12B acquires the detection result of the radio wave intensity from the carrier sense unit 11B. Before the time T1, since the terminal device 10A is communicating, the carrier sense unit 11B detects the radio wave intensity exceeding a predetermined threshold. The communication end detection unit 12B determines that other communication is continued based on the detection result. The carrier sense unit 11B continues the communication end detection carrier sense. Next, when the time T1 is reached, the communication of the terminal device 10A is completed, so that the radio wave intensity detected by the carrier sense unit 11B is equal to or less than a predetermined threshold. The communication end detection unit 12B determines that the other communication has ended based on the radio wave intensity being equal to or less than a predetermined threshold, and notifies the carrier sense unit 11B of the end of the other communication. In addition, the standby time setting unit 14B records in the storage unit 16 the time (Xms) from the start of carrier sense until the end of other communication is detected.

  The same applies to the terminal device 10C. That is, in the terminal device 10C, when the transmission timing “SC1” is reached, the carrier sense unit 11C starts carrier sense. Prior to time T1, the communication end detection unit 12C determines that another communication is continuing, and continues the carrier end detection carrier sense by the carrier sense unit 11C. When the time T1 is reached, the communication of the terminal device 10A ends, so the communication end detection unit 12C determines that the other communication has ended, and outputs the end of the other communication to the carrier sense unit 11C. The standby time setting unit 14C records the time (Yms) from the start of carrier sense until the end of other communication is detected in the storage unit 16.

  After time T1, the carrier sense unit 11B of the terminal device 10B performs carrier sense based on the standard for, for example, 5 ms. Similarly, the carrier sense unit 11C of the terminal device 10C performs carrier sense based on the standard for 5 ms, for example. As shown in the figure, the terminal device 10A does not perform communication for a predetermined time after the time T1 (for example, 50 ms) because it is defined by the downtime and the standard. Therefore, the carrier sense unit 11B and the carrier sense unit 11C do not detect the radio wave intensity that suggests the presence of another communication for 5 ms of the carrier sense based on the standard. Accordingly, the wireless communication unit 13B and the wireless communication unit 13C start transmission at time T2 after carrier sense based on the standard. In this way, when each of the terminal devices 10B and 10C reaches the transmission timing during communication of the other terminal device A, the terminal device 10B and the terminal device 10C perform the communication end detection carrier sense, Synchronization can be achieved using the end timing of communication of the terminal device A. Then, even if the terminal device 10B and the terminal device 10C perform carrier sense based on the standard at the same timing so as to determine the standard, communication is started at time T2 without detecting other communication in the carrier sense. can do. That is, the terminal device 10B and the terminal device 10C can simultaneously communicate using the sub-bandwidth obtained by dividing the bandwidth 200 kHz.

  Further, processing when the terminal device 10B reaches the next transmission timing “SB2” will be described. When the transmission timing “SB2” is reached, the carrier sense unit 11B reads “Xms” recorded by the standby time setting unit 14B from the storage unit 16B. Then, the carrier sense unit 11B stands by without performing carrier sense for Xms. When the standby time Xms has elapsed from the transmission timing “SB2”, the carrier sense unit 11B performs communication end detection carrier sense (time T3). As shown in the figure, when the carrier sense unit 11B performs carrier end detection carrier sense, there is no other communication, so the communication end detection unit 12B immediately determines the end of other communication. In addition, the standby time setting unit 14B is a time (X1 ms) from the start time of communication end detection carrier sense (time T3) to the time when the end of other communication (communication of the terminal device 10A in the example of FIG. 3) is detected. Is stored in the storage unit 16. That is, the time “X1” is the time from when it is detected that other communication has been completed to when it is detected again that other communication has already been completed.

  The same applies to the terminal device 10C. That is, at the terminal device 10C, when the transmission timing “SC2” is reached, the carrier sense unit 11C reads “Yms” recorded by the standby time setting unit 14C from the storage unit 16C. Then, the carrier sense unit 11C waits for Yms. When the standby time Yms elapses from the transmission timing “SC2”, the carrier sense unit 11C performs communication end detection carrier sense (time T3). The communication end detection unit 12C immediately determines the end of another communication, and the standby time setting unit 14C records in the storage unit 16 the time (Y1ms) from the start of the communication end detection carrier sense to the detection of the end of other communication. To do.

  Thereafter, the carrier sense unit 11B and the carrier sense unit 11C perform carrier sense based on the standard for 5 ms. The terminal device 10A does not communicate for 50 ms after the time T3 due to a pause. The carrier sense unit 11B and the carrier sense unit 11C do not detect other communications in performing the carrier sense based on the standard. Accordingly, the wireless communication unit 13B and the wireless communication unit 13C start communication at time T4 after carrier sense based on the standard. Thus, when terminal device 10A-10C performs regular transmission, the relative time relationship of the transmission timing which each terminal device 10A-10C reaches is constant. In the present embodiment, the standby time setting unit 14 records the time (standby time) from the predetermined transmission timing measured in the first communication end detection carrier sense to the communication end detection in the storage unit 16 as the standby time. Set. In the second and subsequent transmission timings, the carrier sense unit 11 first waits for the standby time set by the standby time setting unit 14 without immediately starting the communication end detection carrier sense. Then, the carrier sense unit 11 then performs communication end detection carrier sense. Thereby, execution of carrier sense can be omitted for the standby time, and excess power consumption can be suppressed. The reason for executing the carrier end detection carrier sense after the standby time is that, for example, when a terminal device 10D other than the terminal devices 10A to 10C is newly added when the transmission timing is reached, the terminal device 10D. This is because it is necessary to detect the presence or absence of communication (end of communication if there is communication). If only the terminal devices 10A to 10C continue, the communication end detection carrier sense performed at the second and subsequent transmission timings is considered to end immediately.

  Next, processing when the third and subsequent communication timings (not shown) are reached will be described. The standby time setting unit 14B adds the time (X1ms) from the start of the second communication end detection carrier sense to the detection of the end of other communication to the second standby time (Xms), and sets the next standby time. To do. When the third transmission timing is reached, the carrier sense unit 11A waits for (X + X1) ms. When the standby time (X + X1) has elapsed, the carrier sense unit 11A then starts communication end detection carrier sense.

  The same applies to the terminal device 10C. The standby time setting unit 14C adds the time (Y1ms) from the start of the second communication end detection carrier sense to the detection of the end of other communication to the second standby time (Yms), and sets the next standby time. To do. When the third transmission timing is reached, the carrier sense unit 11C waits for (Y + Y1) ms. Then, the carrier sense unit 11C starts communication end detection carrier sense.

  As in the case of the second transmission, the terminal device 10B and the terminal device 10C that have reached the third transmission timing at their respective timings end the waiting time at the same time. Then, the terminal device 10B and the terminal device 10C simultaneously start communication end detection carrier sense and end simultaneously. Subsequently, the terminal device 10B and the terminal device 10C simultaneously start carrier sense based on the standard, and end simultaneously. When only terminal devices 10A, 10B, and 10C exist as shown in FIG. 3 and transmission is performed at regular intervals, the terminal devices 10B and 10C detect other communications in the carrier sense based on the communication end detection carrier sense and the standard. It is thought that there is nothing. In that case, the wireless communication units 13A and 13B start communication at the same time after the completion of the carrier sense based on the standard. Accordingly, the terminal devices 10B and 10C can perform simultaneous communication even in the third transmission. The same is true when the fourth and subsequent transmission timings are reached. As described above, according to the present embodiment, a plurality of terminal devices can communicate simultaneously while minimizing the time required for carrier sense.

  Here, the case where the time required for the carrier sense for communication completion detection is added to the previous standby time as an example of the method for calculating the standby time has been described, but the present invention is not limited to this. For example, a value obtained by subtracting a predetermined time from a value obtained by adding the time required for carrier sense for communication completion detection to the previous standby time or a value obtained by subtracting the predetermined time from the previous standby time is set as the next standby time. May be. The predetermined time may be set to, for example, the minimum unit time or a length of several units according to the minimum unit (resolution) by which the terminal device 10A or the like can detect other communication by carrier sense. Alternatively, it may be set to several ms. If the standby time is set a little shorter, the communication end timing of the terminal device 10A can be reliably captured, and the standby time can be prevented from gradually increasing each time the communication timing is reached. .

  Also, here, the start and end of communication end detection carrier sense and the start and end of carrier sense based on the standard are separated, but the carrier sense unit 11 is from the start of communication end detection carrier sense to the end of carrier sense based on the standard. Is executed as a group of carrier senses, and from the start of carrier sense to the end of detection of other communications in the group of carrier senses, the carrier end detection carrier sense is performed for the time determined by the standard. A method of executing carrier sense as carrier sense based on a standard may be used. Alternatively, a method may be used in which the carrier sense unit 11 sequentially and independently performs carrier end detection carrier sense and carrier sense based on a standard.

  Further, in FIG. 3, the case where the transmission timing of the terminal devices 10B and 10C is in communication with the terminal device 10A is taken as an example. However, for example, the transmission timing of the terminal devices 10D and 10E is the idle time of the terminal device 10A. For example, when the communication end detection carrier sense is provided longer, simultaneous transmission by the terminal devices 10B, 10C, 10D, and 10E can be enabled. Note that the terminal device 10A may not be a terminal device belonging to the communication system 1 for the simultaneous transmission of the terminal devices 10B and 10C in FIG. For example, the terminal device 10B or the like may be a terminal device belonging to another communication system that can detect communication radio waves by carrier sense.

(Example of scheduled transmission)
FIG. 4 is a first diagram illustrating a method for adjusting the transmission timing of the terminal device according to the first embodiment of the present invention.
FIG. 4 shows a state in which each of the terminal devices 10A, 10B, and 30 communicates with the base station 20 at a fixed time. As an example, it is assumed that the terminal devices 10A and 10B are connected to sensors and fixedly installed. Further, the terminal devices 10A and 10B have a prescribed maximum number of transmissions per day, and all the terminals are transmitted at a regular timing (for example, every hour U). Note that the terminal apparatuses 10A and 10B perform communication using sub-frequency bands having different frequencies from each other, which are obtained by dividing a bandwidth of 200 khz. In addition, it is assumed that the terminal devices 10A and 10B reach the start timing of communication with the base station 20 at “H1: 00” and “H2: 00”. The terminal device 30 is a communication terminal belonging to an arbitrary communication system other than the communication system 1, and uses a frequency band detected as an interference radio wave when the terminal device 10A or the like performs carrier sense based on the standard. Thus, it is assumed that the terminal device is an arbitrary terminal device belonging to another communication system that performs communication at a distance at which an interference radio wave is detected. It is assumed that the terminal device 30 belonging to another system is transmitted at a regular timing (for example, every hour Y minutes). Further, it is assumed that the terminal device 30 is communicating at “H1: 00” and “H2: 00”.

  In the terminal device 10A, when the time “H1: 00” is reached, the carrier sense unit 11A executes carrier end detection carrier sense. When the communication of the terminal device 30 is completed, the communication end detection unit 12B determines that the other communication has been completed, and the standby time setting unit 14B determines the other from the start of carrier sense (time “H10: 00”). The time (Zms) until the end of communication is detected is recorded in the storage unit 16. Thereafter, the carrier sense unit 11B performs carrier sense based on the standard for 5 ms, for example.

  The terminal device 10B performs the same processing as the terminal device 10A. In the example of FIG. 4, the terminal device 30 does not perform communication while the carrier sense unit 11A or the like is performing carrier sense based on the standard. Therefore, the wireless communication unit 13A and the wireless communication unit 13B can start communication at time T5 after carrier sense based on the standard. Thereby, even if carrier sense based on the standard is obliged, the terminal devices 10A and 10B can perform simultaneous communication.

  Further, a process when the second transmission timing “H2: 00” is reached will be described. When “H2: 00” is reached, the carrier sense unit 11A reads “Zms” recorded by the standby time setting unit 14A from the storage unit 16A. Then, the carrier sense unit 11A waits for Zms. When the standby time Zms elapses from the transmission timing “H2: 00”, the carrier sense unit 11A performs communication end detection carrier sense (time T6). As shown in the figure, when the carrier sense unit 11A performs the communication end detection carrier sense, since there is no other communication, the communication end detection unit 12A immediately determines the end of the other communication. Further, the standby time setting unit 14A records the time (Z1 ms) from the start of communication end detection carrier sense to the detection of the end of other communication in the storage unit 16. The terminal device 10B performs the same processing as the terminal device 10A. The standby time setting unit 14B records the standby time (Z1 ms) in the storage unit 16.

  Thereafter, the carrier sense unit 11A and the carrier sense unit 11B perform carrier sense based on the standard for 5 ms. In the example of FIG. 4, the terminal device 30 does not perform communication while the carrier sense unit 11A and the like are performing carrier sense based on the standard. Accordingly, the wireless communication unit 13A and the wireless communication unit 13B can start communication at time T7 after carrier sense based on the standard. Accordingly, the terminal devices 10A and 10B can perform simultaneous communication. In addition, since the time for executing the carrier sense can be shortened in order to detect the timing when the communication of the terminal device 30 ends, the power consumption required for the carrier sense can be reduced.

  Next, processing when the third and subsequent communication timings (not shown) are reached will be described. The standby time setting unit 14A adds the time (Z1ms) from the start of the second communication end detection carrier sense to the detection of the end of other communication to the second standby time (Zms), and sets it as the next standby time. To do. When the third transmission timing is reached, the carrier sense unit 11A stands by for (Z + Z1) ms. Then, the carrier sense unit 11A starts communication end detection carrier sense. When the communication end detection carrier sense is completed, the carrier sense unit 11A next executes carrier sense based on the standard. If no competing communication is detected during the carrier sense based on the standard, the wireless communication unit 13A starts communication.

  The same applies to the terminal device 10B. In the case of scheduled transmission as shown in FIG. 4, since the transmission timings of the terminal device 10A and the terminal device 10B are the same timing, the standby time has the same length. That is, the standby time setting unit 14B adds the time (Z1 ms) from the start of the second communication end detection carrier sense to the detection of the end of other communication to the second standby time (Zms), and the next standby time Set to. When the third transmission timing is reached, the carrier sense unit 11B waits for (Z + Z1) ms. The carrier sense unit 11B then starts communication end detection carrier sense at the same timing as the carrier sense unit 11A. When the communication end detection carrier sense is completed, the carrier sense unit 11A starts carrier sense based on the standard at the same timing as the carrier sense unit 11A. When no competing communication is detected during the carrier sense based on the standard, the wireless communication unit 13B starts communication. Thus, even when the third communication timing is reached, the terminal devices 10A and 10B can perform simultaneous transmission. The same is true when the fourth and subsequent transmission timings are reached. Each time the standby time setting unit 14A and the standby time setting unit 14B reach the transmission timing, the standby time at the previous transmission timing is added to the time required for carrier sense for detecting the completion of communication at the previous transmission timing. Set this time as standby time. Then, in the example of FIG. 4, a plurality of terminal devices 10 (for example, the terminal devices 10 </ b> A and 10 </ b> B) that reach the transmission timing during communication of the terminal device 30 synchronize the carrier sense start timing based on the standard. be able to. Then, in the carrier sense based on the standard, the communication after the carrier sense based on the standard becomes possible without mutually detecting the communication by the other terminal devices 10. Thereby, the some terminal device 10 becomes possible for simultaneous communication.

  In addition, as mentioned in the example of the fixed cycle, the communication end detection carrier sense is performed after the standby time because, for example, a new terminal device that has not existed before may perform communication. It is. Further, by executing the communication end detection carrier sense for a longer time, it is possible that simultaneous transmission can be performed by more terminal devices including other terminal devices 10D.

Here, the case where the time required for the carrier sense for communication completion detection is added to the previous standby time as an example of the method for calculating the standby time has been described, but the present invention is not limited to this. For example, a value obtained by subtracting a predetermined time (for example, 10 ms) from the previous standby time may be set as the next standby time. Alternatively, a value obtained by subtracting a predetermined time (for example, 10 ms) from a value obtained by adding the time required for communication completion detection carrier sense to the previous standby time may be set as the next standby time. If the standby time is set a little shorter, the communication end timing of the terminal device 30 can be reliably captured, and the standby time can be prevented from gradually increasing each time the communication timing is reached. .
Note that the values such as 5 ms of the carrier sense time and 50 ms of the pause time shown in FIGS. 3 and 4 are values determined by the standard for a certain usage channel, and are not limited thereto.

Next, the flow of the carrier sense execution process of this embodiment will be described with reference to FIG.
FIG. 5 is a flowchart showing an example of the carrier sense execution control process in the first embodiment according to the present invention.
As a premise, setting information regarding transmission timing is recorded in the storage unit 16, and the wireless communication unit 13 reads out the setting information and performs communication at a predetermined transmission timing. Further, it is assumed that different sub-frequency bands are assigned to the terminal devices 10A to 10E.
First, the wireless communication unit 13 determines whether or not the transmission timing set in the setting information has been reached (step S11). When it is not a transmission timing (step S11; No), the radio | wireless communication part 13 repeats determination of step S11 at a predetermined time interval, for example. When the transmission timing is reached (step S11; Yes), the wireless communication unit 13 instructs the carrier sense unit 11 to perform carrier sense. The carrier sense unit 11 inquires of the standby time setting unit 14 about the standby time. The standby time setting unit 14 reads the standby time from the storage unit 16. When the first communication timing is reached, the standby time setting unit 14 has not calculated the standby time, so an initial value (for example, 0) of the standby time is set in the storage unit 16. The standby time setting unit 14 responds to the carrier sense unit 11 with the read standby time. The carrier sense unit 11 determines whether or not the standby time acquired from the standby time setting unit 14 is an initial value (step S12).

(First time communication)
When an initial value is set for the standby time (step S12; Yes), the carrier sense unit 11 performs communication end detection carrier sense (step S16). Specifically, the carrier sense unit 11 starts detection of the radio wave intensity of a communication radio wave that performs communication at a frequency included in the frequency band for the entire width of the frequency band assigned as an available band. The carrier sense unit 11 outputs the detected radio wave intensity to the communication end detection unit 12. The communication end detection unit 12 determines whether another communication is performed based on the acquired radio wave intensity (step S17). Specifically, if the radio field intensity exceeds a predetermined threshold, the communication end detection unit 12 determines that another communication is being performed. If the radio wave intensity is equal to or less than the predetermined threshold, the communication end detection unit 12 It is determined that no other communication is performed. If it is determined that another communication is being performed (step S17; Yes), the communication end detection unit 12 repeatedly performs the determination in step S17.

  When it is determined that no other communication is performed (step S <b> 17; No), the communication end detection unit 12 outputs the determination result to the carrier sense unit 11. Further, the communication end detection unit 12 uses the timer unit 15 to measure the time from when the carrier sense unit 11 starts carrier sense until it is determined that no other communication is performed, and the measured time is Output to the standby time setting unit 14.

  The carrier sense unit 11 that has acquired the determination result that no other communication is being performed subsequently performs carrier sense based on the standard (step S18). Specifically, the carrier sense unit 11 continues the carrier sense for a time (for example, 5 ms) determined by the standard from the time when the communication end detection unit 12 determines that no other communication is performed, for example. . The carrier sense unit 11 determines whether another communication has been performed during this period based on the radio wave intensity detected within the time determined by the standard. The determination method may be the same as the determination method by the communication end detection unit 12 in step S17, for example. The carrier sense unit 11 outputs this determination result to the wireless communication unit 13.

Next, the standby time setting unit 14 that has acquired from the communication end detection unit 12 the time from the start of carrier sense to the determination of the non-detection of other communication sets the standby time (step S19). For example, when the initial value “0” is set as the standby time, the standby time setting unit 14 records the acquired time in the storage unit 16 as the standby time.
Next, the wireless communication part 13 which acquired the determination result from the carrier sense part 11 determines whether communication is possible according to a determination result (step S20). For example, when a determination result indicating that no other communication is detected is acquired at a time determined by the standard, the wireless communication unit 13 starts transmission.

(At the second and subsequent communication)
On the other hand, when the initial value is not set for the standby time (step S12; No), the carrier sense unit 11 waits for the standby time to elapse from a predetermined transmission timing (step S15). When the standby time elapses from the transmission timing, the carrier sense unit 11 performs communication end detection carrier sense (step S16). When the communication end detection carrier sense is executed, the communication end detection unit 12 determines whether another communication is being performed based on the radio wave intensity detected by the communication end detection carrier sense (step S17). When it is determined that no other communication is performed (step S17; No), the communication end detection unit 12 outputs to the carrier sense unit 11 that the end of communication has been determined. Further, the communication end detection unit 12 outputs the time from the start of carrier sense to the communication end determination to the standby time setting unit 14.

Next, the carrier sense unit 11 performs carrier sense based on the standard (step S18). The standby time setting unit 14 sets the standby time (step S19). For example, when a value other than the initial value has already been set for the standby time, the standby time setting unit 14 has already recorded the time for performing the communication end detection carrier sense acquired from the communication end detection unit 12 in the storage unit 16. Add to the waiting time. Then, the standby time setting unit 14 records the added standby time in the storage unit 16 as a new standby time. Note that the standby time setting unit 14 may record the time obtained by subtracting a predetermined value from the added standby time in the storage unit 16 as a new standby time. Alternatively, the standby time setting unit 14 may record a time obtained by subtracting a predetermined value from the standby time before addition in the storage unit 16 as a new standby time. Next, the wireless communication unit 13 determines whether or not communication is possible according to the detection result of other communication in the carrier sense based on the standard (step S20).
By controlling the transmission timing according to the above flowchart, the possibility that the terminal devices 10A to 10E can transmit simultaneously increases.

  For example, when data is collected from the terminal devices 10A to 10E every hour in a certain system, if the standby time exceeds the transmission cycle T, data for the number of times assumed per day is collected. It will be impossible. As a countermeasure in such a case, when the difference between the standby time and a predetermined upper limit value (for example, transmission cycle T) falls within a predetermined range, the standby time setting unit 14 once sets the standby time as an initial value. You may perform the process which returns to. Alternatively, when the difference between the standby time and the predetermined upper limit value is within a predetermined range, the standby time setting unit 14 does not add the time required for the communication end detection carrier sense to the standby time, and the current standby time May be maintained.

  According to the terminal device 10 of the present embodiment, a variable carrier sense time (communication end detection carrier) for monitoring the surrounding communication status and determining the transmission timing for the carrier sense for checking the surrounding communication status before transmission. Sense) is newly introduced, and transmission is started when it is confirmed that there is no other communication. This increases the possibility of simultaneous transmission by a plurality of terminal devices even when the carrier sense based on the standard is required by law or the like. In order to increase the number of simultaneous transmissions, it is effective to increase the carrier sense time, but increasing the carrier sense time increases the power consumption of the terminal, and the number of simultaneous transmissions and the power consumption are a trade-off. Are in a relationship. In this embodiment, the standby time setting unit 14 calculates the standby time, and the carrier sense unit 11 stands by without performing carrier sense during the standby time. Thereby, the time of carrier sense can be shortened and power saving can be realized.

FIG. 6 is a diagram illustrating an example of a hardware configuration of the terminal device according to the first embodiment of the present invention.
The computer 900 includes a CPU 901, a main storage device 902, an auxiliary storage device 903, an input / output interface 904, and a communication interface 905.
The terminal device 10 described above is mounted on a computer 900. The operation of each processing unit described above is stored in the auxiliary storage device 903 in the form of a program. The CPU 901 reads a program from the auxiliary storage device 903, develops it in the main storage device 902, and executes the above processing according to the program. In addition, the CPU 901 ensures a storage area corresponding to the storage unit 113 in the main storage device 902 according to the program. In addition, the CPU 901 ensures a storage area for storing data being processed in the auxiliary storage device 903 according to the program.

  In at least one embodiment, the auxiliary storage device 903 is an example of a tangible medium that is not temporary. Other examples of the tangible medium that is not temporary include a magnetic disk, a magneto-optical disk, a CD-ROM, a DVD-ROM, and a semiconductor memory connected via the input / output interface 904. When this program is distributed to the computer 900 via a communication line, the computer 900 that has received the distribution may develop the program in the main storage device 902 and execute the above processing.

  The program may be for realizing a part of the functions described above. Further, the program may be a so-called difference file (difference program) that realizes the above-described function in combination with another program already stored in the auxiliary storage device 903.

  All or some of the functions of the terminal device 10 described above are realized by using hardware such as an application specific integrated circuit (ASIC), a programmable logic device (PLD), and a field-programmable gate array (FPGA). Also good.

  In addition, it is possible to appropriately replace the components in the above-described embodiments with known components without departing from the spirit of the present invention. The technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Communication system 10, 10A, 10B, 10C, 10D, 10E ... Terminal device 20 ... Base station 11 ... Carrier sense part 12 ... Communication end detection part 13 ... Wireless communication part 14 ... Standby time setting unit 15 ... Timer unit 16 ... Storage unit 900 ... Computer 901 ... CPU
902 ... Main storage device 903 ... Auxiliary storage device 904 ... Input / output interface 905 ... Communication interface

Claims (11)

A carrier sense unit that performs carrier sense for the frequency band used by the device;
If the carrier sense unit does not detect other communication competing in the frequency band, a wireless communication unit to start wireless communication;
A communication end detection unit for detecting the end of wireless communication in the frequency band by another terminal device;
A standby time setting unit for setting a time from a predetermined transmission timing to detection of the end of wireless communication by the other terminal device as a standby time;
With
The carrier sense unit starts carrier sense at a timing when the standby time has elapsed from the predetermined transmission timing.
Terminal device. Carrier sense by the carrier sense unit includes carrier sense for detecting the end of the other wireless communication, and carrier sense based on the standard,
The carrier sense unit starts carrier sense based on the standard at a timing when carrier sense for detecting the end of the other wireless communication is completed.
The terminal device according to claim 1. The carrier sense unit starts carrier sense for detecting the end of the other wireless communication at a timing when the standby time has elapsed from the predetermined transmission timing.
The terminal device according to claim 2. The wireless communication unit determines whether communication is possible after completion of carrier sense by the carrier sense unit.
The terminal device according to any one of claims 2 and 3. The standby time setting unit adds the time for performing carrier sense to detect the end of the other wireless communication to the set standby time,
The carrier sense unit starts the carrier sense at the timing when the standby time after the addition has elapsed from the transmission timing when the own device reaches the next transmission timing,
The terminal device according to any one of claims 2 to 4. The waiting time setting unit sets a value obtained by subtracting a predetermined time from the calculated waiting time as the waiting time.
The terminal device according to any one of claims 1 to 5. When the difference between the standby time and a predetermined upper limit value is within a predetermined range, the standby time setting unit does not add to the standby time,
The terminal device according to claim 5 or 6. The waiting time setting unit sets an initial value for the waiting time when a difference between the waiting time and a predetermined upper limit value falls within a predetermined range.
The terminal device according to claim 5 or 6. A radio communication system assigned a predetermined frequency band as a frequency band of radio waves for performing radio communication,
A plurality of terminal devices according to any one of claims 1 to 8,
A communication system in which any one of the divided frequency bands obtained by dividing the frequency band is assigned to each of the plurality of terminal devices. Performing carrier sense for the frequency band used by the device;
In the carrier sense, when no other communication competing in the frequency band is detected, starting wireless communication;
Detecting the end of wireless communication in the frequency band by another terminal device;
Setting a time from a predetermined transmission timing to the detection of the end of wireless communication by the other terminal device as a standby time;
With
In the step of performing carrier sense, carrier sense is started at a timing when the standby time has elapsed from the predetermined transmission timing.
Communication method. The terminal computer,
Means for performing carrier sense on the frequency band used by the own device;
In the carrier sense, when other communication competing in the frequency band is not detected, means for starting wireless communication,
Means for detecting the end of wireless communication in the frequency band by another terminal device;
Means for setting a waiting time from a predetermined transmission timing to detection of the end of wireless communication by the other terminal device;
Function as
The means for performing carrier sense starts carrier sense at a timing when the standby time has elapsed from the predetermined transmission timing.
program.

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