JP5993320B2 - Communication terminal - Google Patents

Description

  The present invention relates to a communication terminal that is arranged in plural for one transmission target device and transmits acquired data to the transmission target device.

  As this type of communication terminal, a communication terminal (child device) disclosed as background art in Patent Document 1 below is known.

  This communication terminal performs carrier sense at the time of calling to confirm the presence or absence of carriers from other slave units, as described with an example applied to a local security system using an ad hoc network system, When there is no other carrier, a collision between a plurality of waiting communication terminals (transmitted from a plurality of communication terminals) is performed by executing transmission to a relay device (transmission target device) after a random waiting time generated by a random number. Occurrence of carrier collision).

  In this case, “when there is no other carrier” means that all the other communication terminals transmit data in a state where the communication terminals are exposed to each other (a relation in which both carriers can detect the carriers of the other communication terminals). The communication terminal is in a hidden relationship (a relationship in which both the carriers of other communication terminals cannot be detected).

  Therefore, if communication terminals are in an exposed relationship, the occurrence of carrier collision can be substantially avoided. However, when communication terminals are in a hidden relationship, each communication terminal determines that there is no other carrier. Execute transmission to the repeater over time. As a result, carrier collisions occur randomly between communication terminals in a hidden relationship.

Japanese Patent No. 4976258 (page 2)

  In this way, in this communication terminal, when the relationship with other communication terminals is hidden, a carrier collision state and a carrier non-collision state occur randomly, and thus a carrier collision occurs. It is desirable to reliably reduce the frequency of operation.

  The present invention has been made to improve such a problem, and has as its main object to provide a communication terminal that can reduce the occurrence of carrier collision among a plurality of communication terminals.

  In order to achieve the above object, the communication terminal according to claim 1 includes a transmission time required for wireless data transmission to the transmission target device and a reception time required for reception of a wireless response from the transmission target device for the data transmission. The data transmission is performed in the transmission slot with one slot selected from a plurality of slots obtained by dividing the transmission cycle defined in advance by a predetermined reference time equal to or greater than the total time as a transmission slot. Execute the data transmission in the same transmission slot until the state where the predetermined prescribed number of times cannot be continuously received even when the response is received and when the response cannot be received. When continuously executing the transmission cycle and reaching the state where the response cannot be received continuously for the specified number of times, A slot selection process for selecting one slot at random and determining the new transmission slot is executed according to a predetermined probability, and when the slot selection process is executed, the slot selection process is performed within the selected new transmission slot. When the data transmission is executed and the slot selection process is not executed, the data transmission in the same transmission slot is continued in the transmission cycle.

  The communication terminal according to claim 2 is the communication terminal according to claim 1, wherein when the response is not received in response to execution of the data transmission in the transmission slot immediately after activation, the slot selection processing is performed. Is executed according to the probability of value 1 to determine the new transmission slot.

  In the communication terminal according to claim 1, when the communication with the transmission target device is good (when a response is received) and when the response cannot be received, the prescribed number of times cannot be received continuously. Until the transmission slot is reached, the same transmission slot as the transmission slot in the immediately preceding transmission cycle is selected, and data transmission in the selected transmission slot is continuously executed in the transmission cycle.

  Therefore, according to this communication terminal, a carrier collision has occurred between the communication terminal that has already selected an appropriate transmission slot that can normally communicate with the transmission target device and the newly installed communication terminal. In this case, in the communication terminal that has already selected an appropriate transmission slot that can normally communicate with the transmission target device, transmission in the previous transmission cycle until a carrier collision occurs continuously more than the specified number of times. It is possible to continue to select the same transmission slot as the slot. Therefore, according to this communication terminal, it is newly installed while avoiding the occurrence of carrier collision between communication terminals that have already selected an appropriate transmission slot that can normally communicate with the transmission target device. The communication terminal can be made to select an appropriate transmission slot.

  Also, in this communication terminal, even when a state in which a response cannot be continuously received more than the specified number of times has been reached, the slot selection process for selecting a new transmission slot is not always performed, but a predetermined probability The slot selection process is executed according to

  Therefore, according to this communication terminal, due to minute variations in the time length of the transmission cycle at each communication terminal, which is a representative example when a carrier collision occurs continuously more than a specified number of times in the communication terminal, When a carrier collision occurs between communication terminals that have already selected an appropriate transmission slot that can normally communicate with the transmission target device, it is always applied to all communication terminals that have a carrier collision. Instead of executing selection of a new transmission slot, by leaving a room for selecting the same transmission slot as that of the immediately previous transmission slot (that is, allowing the same transmission slot to be used continuously), the transmission target device has already been selected. Among the communication terminals that have successfully selected an appropriate transmission slot that can communicate normally and a communication terminal in which no carrier collision has occurred. It is possible to lower the probability that a collision will occur. Thereby, according to this communication terminal, even when the number of communication terminals that communicate with one transmission target device increases, an appropriate transmission slot that can normally communicate with the transmission target device is selected. Each communication terminal can be shifted to a state where it has been completed in a short time.

  The communication terminal according to claim 2 executes the slot selection process according to the probability of value 1 when no response is received from the transmission target device in response to execution of data transmission in the transmission slot of the transmission cycle immediately after activation. (Always executing) to determine a new transmission slot.

  Therefore, according to this communication terminal, when there is a communication terminal that has already selected an appropriate transmission slot that can normally communicate with the transmission target device, when a new communication terminal is already installed, For communication terminals that have selected an appropriate transmission slot that can normally communicate with the transmission target device, select the same transmission slot as the transmission slot in the previous transmission cycle (already communicating with the transmission target device normally). While avoiding the occurrence of carrier collisions between communication terminals that have already selected an appropriate transmission slot capable of performing communication), by selecting a new transmission slot for a newly installed communication terminal, It is possible to select a proper transmission slot at an early stage.

1 is a configuration diagram of a data collection system 1. FIG. 2 is a configuration diagram of a slave unit (communication terminal) 2. FIG. It is a flowchart for demonstrating operation | movement in the transmission slot determination process 50 of the subunit | mobile_unit 2. FIG. It is a flowchart for demonstrating operation | movement in the transmission process 60 of the subunit | mobile_unit 2. FIG. 6 is a timing chart for explaining the operation of the handset 2; 6 is a timing chart for explaining the operation of the handset 2; 6 is a timing chart for explaining the operation of the handset 2; 6 is a timing chart for explaining the operation of the handset 2;

  Hereinafter, embodiments of a data collection system including a communication terminal will be described with reference to the accompanying drawings.

  First, the configuration of the data collection system 1 will be described with reference to the drawings.

  As shown in FIG. 1, the data collection system 1 includes a plurality of communication terminals (hereinafter also referred to as “slave units”) 2, one transmission target unit (hereinafter also referred to as “master unit”) 3, and a server computer ( (Hereinafter also referred to as “server”) 4, and is configured to be able to collect measurement data detected by the sensor 5 connected to each slave unit 2 in the server 4.

  As shown in FIG. 2 as an example, the plurality of slave units 2 (n: n is an integer of 2 or more) 2 includes a CPU 11, a storage unit 12, a wireless communication unit 13, an antenna 14, and a battery 15. The CPU 11 operates upon receiving an operating voltage supplied from the battery 15 and, based on an operation program stored in the storage unit 12 in advance, a data measurement process, a transmission slot determination process 50 (see FIG. 3), and a transmission process. 60 (see FIG. 4), the measurement data is acquired from the sensor 5 at the transmission cycle T defined in advance, and the acquired measurement data is wirelessly transmitted to the base unit 3 via the wireless communication unit 13. Send data. The storage unit 12 is configured by, for example, a non-volatile memory and operates by receiving an operation voltage supplied from the battery 15 and stores an operation program and measurement data for the CPU 11.

  As an example, the wireless communication unit 13 is configured as a specific low-power wireless station, operates by receiving an operating voltage supplied from the battery 15, and communicates with the base unit 3 via the antenna 14 in the CSMA / CA with Ack method. Data communication between the two. In this case, the CSMA / CA with Ack method is a method in which each wireless terminal transmits data after confirming by detecting the carrier that the communication path is continuously available for a certain time or more. Whether the data has been correctly transmitted is determined by the arrival of an ACK signal (acknowledgment, hereinafter simply referred to as “response”) from the receiving side. The battery 15 is comprised with a dry cell as an example, and supplies the constant voltage (operation voltage) for an operation | movement with respect to each component of the subunit | mobile_unit 2. As shown in FIG.

  The plurality of slave units 2 configured as described above are installed one by one together with the sensor 5 at a plurality of locations where measurement data is to be acquired. In this case, each slave unit 2 has a hidden relationship in which carriers from some other slave units 2 cannot be received (carrier sense) due to the topography of the installation location or the distance between other slave units 2. Or an exposure relationship in which carriers from some other handset 2 can be received.

  The base unit 3 performs data communication with each slave unit 2 via the transmission path 6 (for example, a public network) with a wireless communication function for performing data communication with each slave unit 2 using the CSMA / CA with Ack method. It has a communication function. Further, as shown in FIG. 1, the parent device 3 is installed in advance at a position where communication can be made with all the child devices 2, and is transmitted from each child device 2 periodically (with a transmission cycle T). When the measurement data is received, the measurement data is transmitted to the server 4 via the transmission path 6 every time or in units of the fixed period while being accumulated. The server 4 receives the measurement data measured by the sensor 5 connected to each slave unit 2 via the master unit 3 and stores it in a storage unit (not shown).

  As an example, the sensor 5 includes a debris flow sensor composed of a well-known wire sensor, vibration sensor, acoustic sensor, laser sensor, and the like, and a water level sensor. In the case of a water level sensor, the water level at the installation location is detected, and the detection result is output as measurement data to the corresponding slave unit 2. Note that the sensor 5 is configured by using a sensor other than the above-described sensor, and outputs detection results such as temperature, humidity, precipitation, sunshine duration, or the appearance state of birds and beasts at the installation location as measurement data. You may do it.

  Next, the operation of the data collection system 1 will be described with reference to the drawings, focusing on the operation of each slave unit 2.

  In each handset 2, when activated, the CPU 11 starts measuring a certain transmission cycle T (for example, 60 minutes). In this case, although the transmission cycle T repeatedly measured by the CPU 11 of each slave unit 2 is defined to be the same time, each slave unit 2 is individually provided when installed at each installation location, for example. It is activated. For this reason, the transmission cycle T measured by the CPU 11 of each slave unit 2 is in an asynchronous state.

  In addition, the CPU 11 of each slave unit 2 executes data measurement processing and transmission slot determination processing 50 at the beginning of the transmission cycle T. In this data measurement process, the CPU 11 acquires new measurement data to be transmitted from the corresponding sensor 5 to the parent device 3 in the transmission cycle T and stores the new measurement data in the storage unit 12. Further, in the transmission slot determination process 50, a transmission slot that defines the timing (timing) for transmitting the measurement data acquired in this transmission cycle T to the parent device 3 in this transmission cycle T is determined. .

  Here, the transmission slot is, for example, a time required for data transmission / reception between the slave unit 2 and the master unit 3 (a transmission time required for data transmission and a reception time required for receiving a response from the master unit 3). A predetermined reference time T1 (preferably, a total time (for example, 60 seconds)) or more, which is an arbitrary time more than twice this total time, and a time close to twice or twice. As a slot, each period obtained by dividing the transmission cycle T by twice the time (120 seconds) is one slot selected from all of the slots, and is used for data transmission / reception with the base unit 3 Refers to the slot used. In this example, since the reference time T1 (that is, the time length of one slot) is 120 seconds (2 minutes) as described above, one transmission cycle T has 30 (= 60/2) slots. It is divided into. Further, the number of slots is defined so as to be equal to or more than the number of slave units 2 installed for one master unit 3, and preferably twice or more that of the slave units 2 installed.

  Specifically, in the transmission slot determination process 50, as shown in FIG. 3, the CPU 11 first determines whether or not the transmission slot determination process 50 is executed for the first time (step 51). As a result of the determination in step 51, when the CPU 11 determines that it is the first time, the CPU 11 selects one new slot randomly (randomly) from all the slots defined within the transmission period T. The selection process is executed, the selected transmission slot is stored in the storage unit 12 as the current transmission slot (step 55), and the transmission slot determination process is terminated.

  In the slot selection process executed in step 55, the CPU 11 also has a probability of (1 / slot number) even when the same slot as the transmission slot used in the immediately preceding transmission cycle T is selected as a new transmission slot. Get different, but choose different slots with higher probability ((slots minus 1) / slots).

  On the other hand, when the CPU 11 determines that it is not the first time as a result of the determination in step 51, the communication with the parent device 3 in the transmission slot in the immediately preceding transmission cycle T is the carrier of the other child devices 2. It is determined whether or not a failure has occurred due to a collision (whether or not a response from the parent device 3 has not been received), and a transmission slot that has failed to communicate with the parent device 3 is transmitted in the immediately preceding transmission cycle T. It is a new transmission slot randomly selected by the CPU 11 by executing step 55, or the CPU 11 executes step 56 to be described later in the transmission cycle T immediately before this, so that one more immediately before this transmission cycle T (one) It is also determined whether or not the transmission slot in the previous transmission cycle T is the transmission slot determined as the current transmission slot (step 52).

  As a result of the determination in step 52, the CPU 11 has failed in communication with the parent device 3 in the transmission slot in the immediately preceding transmission cycle T, and this transmission slot is a new transmission slot selected at random in this transmission cycle T. If it is determined that, the process proceeds to step 55. In step 55, the CPU 11 executes a slot selection process to randomly select one transmission slot and store the selected slot in the storage unit 12 as a new transmission slot. Exit.

  Further, as a result of the determination in step 52, the CPU 11 has failed to communicate with the base unit 3 in the transmission slot in the immediately preceding transmission cycle T, and this transmission slot is immediately before the previous transmission cycle T (that When it is determined that the transmission slot in the previous transmission cycle T is the transmission slot selected as the current transmission slot, communication with the base unit 3 in the transmission slot in the previous transmission cycle T has succeeded (the carrier If it is determined that a response has been received without a collision, the process proceeds to step 53.

  In this step 53, the CPU 11 continuously communicates with the base unit 3 in the same transmission slot, including the immediately preceding transmission cycle T, n times (specified number) or more (in this example, 2 times or more). In step 53, it is determined whether or not the operation has failed. As a result of the determination in step 53, the CPU 11 determines that transmission of measurement data has not failed continuously more than n times (that is, when communication with the parent device 3 in the immediately preceding transmission cycle T has been completed normally). (When not failed) and when the communication with the base unit 3 in the immediately preceding transmission cycle T is not normally completed (when failed), transmission of measurement data in this transmission cycle T When the number of consecutive measurement data transmission failures including the failure is less than n times), the CPU 11 transmits the same transmission slot as that used in the immediately preceding transmission cycle T. The slot is selected as a transmission slot to be used in the current transmission cycle T (step 56), and the transmission slot determination process is terminated.

  Further, as a result of the determination in step 53, when the CPU 11 determines that it has failed continuously n times or more, it proceeds to step 54. In this step 54, the CPU 11 executes step 55 to determine one new transmission slot randomly, or executes the same transmission slot as that used in the immediately preceding transmission cycle T by executing step 56. Any one of the transmission slots to be used in the period T is determined to have a certain probability (in this example, the probability is 50% as an example, but is not limited to this probability, and is an arbitrary probability exceeding 0% and less than 100%) Can be selected).

  As a result of the selection in step 54, when the CPU 11 selects execution of the above determination process, the CPU 11 proceeds to step 55, selects one new transmission slot at random, and transmits the current transmission cycle T. The slot is stored in the storage unit 12 (step 55), and the transmission slot determination process is terminated. Further, when the selection of the slot selection process is selected as a result of the selection in step 54, the transmission slot in the previous transmission cycle T is stored in the storage unit 12 as the transmission slot in the current transmission cycle T ( Step 56), the transmission slot determination processing 50 is terminated.

  In this case, when each child device 2 is in a hidden relationship, each child device 2 cannot detect the carrier of the other child device 2 (that is, transmission of measurement data to the parent device 3 in the other child device 2). I ca n’t figure out the timing). For this reason, when the configuration of the conventional communication terminal is adopted for each slave unit 2, all the slave units 2 that have failed to communicate with the master unit 3 always execute transmission to the master unit 3 after a random waiting time. To do. Accordingly, when a carrier collision occurs between the child device 2 of the group that has already established an appropriate timing for normal communication with the parent device 3 and the newly installed child device 2, The timing of communication with the parent device 3 is changed not only for the child device 2 installed in the mobile phone 2 but also for the child device 2 that has already established an appropriate timing. For this reason, due to this change in the timing of communication, carrier collision (parent device 3) also occurs between the child devices 2 in the group that have already established appropriate timing for normal communication with the parent device 3. Failure to communicate with the Internet) is very likely to occur immediately.

  On the other hand, in this example, by executing the transmission slot determination processing 50 described above, the slave unit 2 that has already selected an appropriate transmission slot that can normally communicate with the master unit 3, and the newly installed slave unit When a carrier collision occurs between the mobile station 2 and the newly installed slave unit 2, a new transmission slot is immediately selected. However, an appropriate transmission slot that can normally communicate with the base unit 3 is selected. In the slave unit 2 that has been selected, the same transmission slot as the transmission slot in the immediately preceding transmission cycle T is continuously selected until a carrier collision occurs n times (in this example, twice) or more continuously. . Therefore, the newly installed slave unit 2 is appropriate while avoiding the occurrence of carrier collision between the slave units 2 that have already selected an appropriate transmission slot that can normally communicate with the master unit 3. The transmission slot can be selected.

  Further, in this handset 2, even if a carrier collision has occurred n times or more in succession in the handset 2, a new transmission slot is not selected immediately, but a new transmission slot is selected. A configuration is adopted in which either one of (Step 55) and selection of the same transmission slot as the immediately preceding transmission slot (Step 56) is selected and executed with a certain probability. For example, in a configuration in which execution of selection of a new transmission slot is selected with a probability of a%, execution of selection of the same transmission slot as the immediately preceding transmission slot is selected with a probability of (100−a)%.

  As a representative example in the case where a carrier collision occurs continuously n times or more in the slave unit 2, it is already normal with the master unit 3 due to a minute variation in the time length of the transmission cycle T in each slave unit 2. This is a case where a carrier collision occurs between the slave units 2 that have already selected an appropriate transmission slot that can perform communication. In such a case, it is not always necessary to select a new transmission slot for all the slave units 2 in which a carrier collision occurs, but the same transmission slot as the immediately preceding transmission slot is selected (that is, By allowing the same transmission slot to be used continuously), a carrier collision occurs in the slave unit 2 that has already selected an appropriate transmission slot that can normally communicate with the master unit 3 It is possible to reduce the probability that a new carrier collision will occur with the handset 2 that is not. As a result, even when the number of handset 2 that communicates with one base unit 3 is increased, each transmission state has been selected after selecting an appropriate transmission slot that can normally communicate with the base unit 3. It is possible to shift the handset 2 in a short time.

  After completing the storage of the measurement data to be transmitted in the current transmission cycle T and the determination of the transmission slot used for the transmission of the measurement data in this way, the CPU 11 performs the transmission process 60 shown in FIG. Run in period T. Note that the time required for the CPU 11 to acquire measurement data from the sensor 5 and store it in the storage unit 12 and the time required for the transmission slot determination process 50 are extremely short compared to the time length of the transmission cycle T (for example, Complete in less than a few ms). For this reason, the CPU 11 also starts the transmission process 60 substantially at the beginning of the transmission cycle T.

  In this transmission process 60, the CPU 11 first repeatedly detects whether or not the transmission slot determined as described above has arrived (step 61), and the arrival of the transmission slot (specifically, the time length of the transmission slot). When the arrival of the timing for starting the measurement of T1 is detected, the measurement of the time length T1 of the transmission slot is started and the wireless communication unit 13 is activated to detect the presence or absence of a carrier from the other handset 2 (Step 62).

  When the carrier is detected in the wireless communication unit 13, the CPU 11 determines whether or not the time during which the carrier is detected has reached a predetermined maximum detection time (whether or not the time has been exceeded) ( Step 63) The presence or absence of the carrier is repeatedly detected until no carrier is detected or the time is over.

  Here, the above detection maximum time is, for example, an average value of random delay time described later (for example, 100 ms), data transmission / reception (measurement data is transmitted once, and a response from the parent device 3 is received) Time (for example, 2 seconds) and a time (42) obtained by multiplying the total value of the average value (for example, 4 seconds) of a later-described retransmission time by the maximum number of transmissions (for example, 7 times). .7 seconds (= 6.1 seconds × 7)) is subtracted from a time half of the time length T1 of one transmission slot (60 seconds in this example) (17.17 in this example). 3 seconds).

  In this case, when the CPU 11 detects that there is no carrier in step 62 before determining that the time has expired in step 63, the CPU 11 performs random delay time measurement (step 64). As an example, in this example, the CPU 11 randomly determines any one time (average value is approximately 100 ms as described above) defined at 5 ms intervals from 20 ms to 200 ms as a random delay time, and this random delay. Perform time measurement.

  After completing the measurement of the random delay time, the CPU 11 again detects the presence / absence of a radio signal (carrier) from the other slave unit 2 (step 65). As a result of this detection, when the carrier is detected, the measurement data cannot be transmitted to the master unit 3. Therefore, the CPU 11 proceeds to step 62 and executes steps 62 and 63 again.

  When the carrier is not detected as a result of the detection in step 65, the CPU 11 transmits measurement data to the parent device 3 (step 66), and then detects whether or not a response is output from the parent device 3 for a certain period of time. (Step 67). Note that the master unit 3 always outputs a response within the predetermined time when the measurement data from the slave unit 2 can be normally received. In this case, as described above, the time required for one transmission of the measurement data until the arrival of a response from the master unit 3 that has received the measurement data (the above-described fixed time for detecting the output of the response) The total time is about 2 seconds. For this reason, when the CPU 11 receives a response from the parent device 3 within the predetermined time, the CPU 11 determines that the transmission of the measurement data to the parent device 3 (communication with the parent device 3) has been normally completed, and performs this transmission. Process 60 is completed.

  On the other hand, when the response is not detected within a predetermined time in step 67, the CPU 11 executes a process of retransmitting the measurement data. In this process, the CPU 11 first determines whether or not the number of transmissions of measurement data has reached a predetermined maximum number of transmissions (step 68). The waiting time until the transmission of (also referred to as “retransmission time”) is randomly determined, and the determined retransmission time is measured (step 69). For example, when the randomly determined retransmission time is 3 seconds, the CPU 11 measures the retransmission time of 3 seconds. In addition, as above-mentioned, the average value of the retransmission time which CPU11 determines at random is prescribed | regulated so that it may become 4 second as an example in this example. When completing the measurement of the retransmission time, the CPU 11 proceeds to step 62.

  The CPU 11 determines in step 63 that the time is over, determines in step 67 that the response from the master unit 3 has been received, or determines in step 68 that the number of measurement data transmissions has reached the maximum number of transmissions. The measurement data is repeatedly transmitted to the parent device 3 by repeatedly executing the above steps 62 to 69.

  In this case, when the CPU 11 determines that the time is over in step 63 or when it is determined in step 68 that the number of transmissions of the measurement data has reached the maximum number of transmissions, the CPU 11 determines the transmission slot determination process 50 in the current transmission cycle T. It is determined that the measurement data is not normally transmitted to the base unit 3 in one transmission slot, and information indicating that the measurement data transmission in the current transmission cycle T has failed is stored in the storage unit 12. At the same time, the measurement data acquired from the sensor 5 in the current transmission cycle T is discarded (step 70), and the transmission process 60 is completed.

  When determining that the response from the parent device 3 has been received in step 67, the CPU 11 determines that the transmission of the measurement data to the parent device 3 has been normally completed as described above, and completes the transmission process 60. Let

  In this way, the measurement of the transmission period T is started at a unique timing, and one slot (transmission selected uniquely from a plurality of slots obtained by dividing the transmission period T into a plurality of times with a fixed time length T1. Slot), when the plurality of slave units 2 that transmit the measurement data acquired from the corresponding sensor 5 to one master unit 3 are sequentially installed one by one, the first slave unit 2 installed is the other slave unit 2 Since the machine 2 does not exist, the measurement data acquired from the corresponding sensor 5 is reliably transmitted to the single parent machine 3 in the transmission slot selected by itself within the transmission cycle T where the measurement is started at its own timing.

  Thereafter, in the process of sequentially installing (adding) 2 units, 3 units and the slave unit 2, the installed slave unit 2 starts measuring the transmission cycle T at a unique timing, and within the transmission cycle T. When one transmission slot is uniquely selected from a plurality of slots, the transmission slot in the slave unit 2 in which the timing of the selected transmission slot is already installed and the measurement data is transmitted to the master unit 3 There is a case where the timing does not overlap with the timing of the above, and a case where the timing overlaps.

  In each handset 2 of this example, by executing the transmission slot determination process 50 and the transmission process 60 described above, when the handset 2 installed later and the handset 2 that is already operating are exposed, The CPU 11 of the handset 2 installed later can detect the carrier of the handset 2 that is already operating. For this reason, when the transmission slots in both slave units 2 overlap, when the CPU 11 of the slave unit 2 installed later executes the transmission process 60 shown in FIG. The measurement data is discarded and the transmission process 60 is completed.

  As a result, the CPU 11 of the slave unit 2 installed later newly transmits a transmission slot at random in the immediately preceding transmission cycle T in step 52 of the transmission slot determination processing 50 shown in FIG. 3 executed at the beginning of the next transmission cycle T. And determining that transmission in the selected transmission slot has failed, the process proceeds to step 55, and a slot selection process is executed to randomly select a new transmission slot. A transmission process 60 is executed. In this way, the CPU 11 of the handset 2 installed later repeats the transmission slot determination process 50 and the transmission process 60, thereby causing a carrier collision with the handset 2 that is already operating. A transmission slot that is not to be transmitted is selected while avoiding occurrence of carrier collision.

  In this manner, the exposed slave units 2 operate in the same manner as the communication terminal described in the background art, and the slave unit 2 installed later uses its own transmission slot as the transmission slot of the slave unit 2 that is already operating. It is possible to transmit the measurement data to the master unit 3 so as not to overlap.

  On the other hand, when the slave unit 2 installed later and the slave unit 2 already operating are in a hidden relationship, the timing of the transmission slot of the slave unit 2 already operating and the slave unit installed later When the timings of the two transmission slots overlap, carrier collision occurs in the same manner as the communication terminals described in the background art. In this case, the communication terminals described in the background art remain in a state where the carrier collision is allowed (the carrier collision occurs randomly). However, the slave unit 2 of the present example is configured to reliably reduce the occurrence of carrier collision among the plurality of slave units 2 by executing the transmission slot determination process 50 and the transmission process 60 described above. ing.

  Hereinafter, a specific example will be described with reference to FIGS. In FIG. 5 to FIG. 8, in order to facilitate understanding of the invention, the transmission cycle T is divided into four slots (time length T1), and each slave unit 2 assigns one of the four slots. The transmission slot is selected at random. In addition, as an example, there are two slave units 2 (slave units 2a and 2b), which are in a hidden relationship with each other. In addition, the measurement data measured by the slave unit 2a is represented by the symbol Da1, the response from the master unit 3 to the slave unit 2a is represented by the symbol Da2, the measurement data measured by the slave unit 2b is represented by the symbol Db1, and the measurement data for the slave unit 2b is represented. It is assumed that the response from the parent device 3 is represented by the symbol Db2. In addition, measurement data and responses that can be normally transmitted and received are represented by solid lines, and measurement data and responses that cannot be normally received due to carrier collision are represented by broken lines.

  First, referring to FIG. 5, in a state in which the slave unit 2a that is already installed and activated normally executes communication with the master unit 3, the slave unit 2b that is installed later transmits its own transmission. An example will be described in which transmission of measurement data to the parent device 3 is started in a state where the slot does not overlap with the transmission slot of the child device 2a.

  In this example, in the slave unit 2a, the CPU 11 executes the transmission slot determination process 50 at the beginning of each transmission cycle T, and executes the step 56 to thereby transmit the transmission slot (this transmission cycle T in the immediately preceding transmission cycle T). In the example, the same transmission slot as the first slot) is selected, and communication with the base unit 3 (transmission of the measurement data Da1 to the base unit 3 and reception of the response Da2 from the base unit 3) is performed in this transmission slot. It is running continuously.

  In this state, in the slave unit 2b, the CPU 11 acquires the measurement data Db1 from the sensor 5 and executes the transmission slot determination process 50 at the beginning of the transmission cycle T in which measurement is started at a unique timing. The second slot among the slots is selected as a transmission slot, and transmission of the measurement data Db1 to the base unit 3 is started in this transmission slot.

  In this case, as shown in FIG. 5, since the transmission slots of the slave units 2a and 2b do not overlap, the CPUs 11 of the slave units 2a and 2b perform transmission slot determination processing 50 to be executed at the beginning of each transmission cycle T. Then, after executing steps 51, 52 and 53, step 56 is executed to select the same transmission slot as the transmission slot in the previous transmission cycle T as the transmission slot in the current transmission cycle T. Accordingly, the slave unit 2a continuously selects the same transmission slot in each transmission cycle T, repeatedly executes transmission of the measurement data Da1 and reception of the response Da2 with the master unit 3, and the slave unit 2a. 2b can also repeatedly select the same transmission slot in each transmission period T and repeatedly transmit the measurement data Da1 and receive the response Da2 with the parent device 3.

  Next, referring to FIG. 6, in a state where the already installed slave unit 2a is normally communicating with the master unit 3, the slave unit 2b installed later has its own transmission slot. An example in which transmission of measurement data to the parent device 3 is started in a state where it overlaps with the transmission slot of the child device 2a will be described.

  In this example, in the slave unit 2a, the CPU 11 executes the transmission slot determination process 50 at the beginning of each transmission cycle T, and executes the step 56 to thereby transmit the transmission slot (this transmission cycle T in the immediately preceding transmission cycle T). In the example, the same transmission slot as the first slot) is selected, and communication with the base unit 3 is continuously executed in this transmission slot.

  In this state, in the slave unit 2b, the CPU 11 executes the transmission slot determination process 50 at the beginning of the transmission cycle T (hereinafter also referred to as “transmission cycle Tb1” for the sake of explanation) where measurement is started after activation. By executing the step 55, the second slot of the four slots is newly selected as a transmission slot, and transmission of the measurement data Db1 to the base unit 3 is started in this transmission slot. In this case, as shown in FIG. 6, since the transmission slots of the slave units 2a and 2b overlap, there is a possibility that a carrier collision occurs between the slave units 2a and 2b. Is assumed to occur.

  At this time, in the slave unit 2a, the CPU 11 causes the CPU 11 to transmit a new transmission cycle T (hereinafter referred to as “transmission cycle Ta1” for the sake of description) following the transmission cycle T in which a carrier collision has occurred. In the transmission slot determination process 50 executed at the beginning of (transmission cycle Ta2), it is determined in step 51 that it is not the first time, and in step 52, transmission in the transmission slot newly selected in the immediately previous transmission cycle Ta1 is performed. Since it is determined that the transmission has not failed and it is determined in step 53 that the transmission has not failed continuously n times (twice) or more, step 56 is executed. For this reason, in this new transmission cycle T, the same transmission slot as the previous transmission cycle T is selected, and communication with the parent device 3 is executed in this transmission slot.

  On the other hand, in slave unit 2b, CPU 11 determines a transmission slot to be executed at the beginning of a new transmission cycle T (hereinafter also referred to as “transmission cycle Tb2” for explanation) after transmission cycle Tb1 in which a carrier collision has occurred. In process 50, it is determined in step 51 that it is not the first time, but in step 52, since it is determined that the transmission in the transmission slot newly selected in the immediately preceding transmission cycle T is a failure, step 55 is executed. Therefore, in this new transmission period T, a new transmission slot is selected at random (in FIG. 6, the third slot is selected as the transmission slot as an example), and measurement is performed within this new transmission slot. Transmission of the data Db1 to the parent device 3 and reception of the response Db2 from the parent device 3 are executed.

  In the figure, since the transmission slot newly selected in the slave unit 2b does not overlap with the transmission slot of the slave unit 2a, both the slave units 2a and 2b normally execute communication with the master unit 3 together. To do. Thereafter, each of the slave units 2a and 2b executes step 56 in the transmission slot determination processing 50 executed at the beginning of each transmission cycle T until the carrier collision occurs, so that the last transmission is performed. The same transmission slot as the transmission slot in the period T is selected, and communication with the parent device 3 is continued in this transmission slot.

  As in this example, when a carrier collision occurs between each of the slave units 2a and 2b, the transmission slot is maintained for the slave unit 2a that has already been installed and normally transmits measurement data to the master unit 3. However, since the priority is given to the selection of the transmission slot for the child device 2b installed later, the child that normally executes communication with the parent device 3 due to the addition of the new child device 2b. Occurrence of a situation where communication with the base unit 3 of the machine 2a is hindered is avoided. Thus, it is possible to shift the new slave unit 2b to a state in which the slave unit 2b can normally communicate with the master unit 3 while maintaining normal communication with the master unit 3 of the slave unit 2a.

  In this example, as described above, the slot defined within the transmission cycle T is the time required for data transmission / reception between the slave unit 2 and the master unit 3 (the transmission time and response time required for data transmission). A predetermined reference time T1 (specifically, a time that is at least twice as long as the time required for data transmission / reception, or a time close to double) It is prescribed. Therefore, as shown in FIG. 7, the slave unit 2a uses the first slot in the transmission cycle Ta1 as a transmission slot, and transmits data to the master unit 3 in the period W in the transmission slot. This is because the machine 2b uses the second slot in the transmission cycle Tb1 as a transmission slot and transmits data to the base unit 3 in the period W in this transmission slot, and as a result, both transmission slots overlap. Even if a carrier collision occurs, when the handset 2b selects a transmission slot for the next new transmission cycle Tb2 and a transmission slot different from the transmission slot for the previous transmission cycle Tb1, As shown, a collision with the carrier that the handset 2a transmits in the transmission slot in the next transmission cycle Ta2 is reliably avoided.

  Next, referring to FIG. 8, the transmission slots of slave units 2a and 2b that are already installed and normally transmitting measurement data to base unit 3 overlap with the passage of time, and a carrier collision occurs. An example will be described. Although each slave unit 2 is in an asynchronous state, the CPU 11 measures the same transmission cycle T based on a clock generated by, for example, a crystal oscillator. However, even if crystal oscillators with the same specification oscillation frequency are used, there is a slight variation in the time length of the transmission cycle T due to a small variation in the crystal oscillator itself or a difference in temperature at the installation location. Has occurred. For this reason, a situation occurs in which the transmission slots for the child devices 2a and 2b that are already installed and normally execute communication with the parent device 3 overlap with each other over time, and thus, between the child devices 2a and 2b. Carrier collision may occur.

  In FIG. 8, the degree of overlap of the transmission slots of the slave units 2a and 2b (the first transmission slot in the slave unit 2a and the second transmission slot in the slave unit 2b) gradually increases, and the transmission of the slave unit 2a is performed. Slot (transmission slot in transmission cycle T in FIG. 8 (hereinafter also referred to as “transmission cycle Ta1”)) and transmission slot for slave unit 2b (transmission cycle T in FIG. 8 (hereinafter referred to as “transmission cycle Tb1”). In the transmission slot), a carrier collision occurs, and each of the slave units 2a and 2b fails to communicate with the master unit 3.

  At this time, in each of the slave units 2a and 2b, each of the CPUs 11 makes a new transmission cycle T (transmission cycle Ta2 for the slave unit 2a, slave unit 2b) next to the transmission cycle Ta1 and Tb1 in which the carrier collision has occurred. In the transmission slot determination process 50 executed at the beginning of the transmission cycle Tb2), it is determined in step 51 that it is not the first time, and in step 52, it is not a failure in transmission in the newly selected transmission slot in the immediately preceding transmission cycle T. In step 53, since it is determined that the transmission has not failed continuously n times (twice) or more, step 56 is executed. For this reason, each CPU 11 of the slave units 2a and 2b uses the same transmission slot as the transmission slot in the immediately preceding transmission cycle Ta1 and Tb1 as the transmission slot in the new transmission cycles Ta2 and Tb2 (the slave unit 2a has the first In the transmission slot, transmission of the measurement data Da1, Db1 to the master unit 3 and reception of the responses Da2, Db2 from the master unit 3 are selected. Try.

  However, the timing of communication with the parent device 3 of each of the slave units 2a and 2b in the new transmission cycles Ta2 and Tb2 is almost the same as the timing in the transmission cycle Ta1 and Tb1 immediately before the carrier collision occurs. For this reason, also in the transmission cycles Ta2 and Tb2, a carrier collision occurs in the same manner as in the previous transmission cycles Ta1 and Tb1.

  Therefore, in each of the slave units 2a and 2b, each CPU 11 determines that the new transmission cycle T (the transmission cycle Ta3 and the slave unit 2b for the slave unit 2a) is next to the transmission cycle Ta2 and Tb2 in which carrier collisions occur continuously. In the transmission slot determination process 50 executed at the beginning of the transmission cycle Tb3), it is determined in step 51 that it is not the first time, and in step 52, it is not a failure in transmission in the newly selected transmission slot in the immediately preceding transmission cycle T. In step 53, since it is determined that transmission has failed continuously n times (twice) or more, step 54 is executed.

  In this step 54, each CPU 11 of the slave units 2a and 2b executes step 55 to randomly determine one new transmission slot to be used in the current transmission cycle T, or executes step 56 and immediately before Either the same transmission slot used in the transmission cycle T is determined as a transmission slot used in the current transmission cycle T with a certain probability (50% probability in this example).

  As a result, when the CPUs 11 of the slave units 2a and 2b both choose to randomly determine one new transmission slot, each CPU 11 executes step 55 and uses it in the current transmission cycle Ta3 and Tb3. Select one transmission slot. In this case, when the CPU 11 of the slave unit 2a selects the first transmission slot and the CPU 11 of the slave unit 2b selects the third transmission slot, as shown in FIG. 8, transmission is performed at each transmission cycle Ta3, Tb3. Since the overlap of the slots is eliminated, carrier collision in the slave units 2a and 2b is avoided. Thereby, both the subunit | mobile_unit 2a, 2b performs communication with the main | base station 3 normally.

  In the transmission period T after the transmission period Ta3, Tb3, each of the CPUs 11 of the slave units 2a, 2b continues to transmit slot until the occurrence of carrier collision occurs n times (in this example, twice) continuously. By executing the determination process 50, the same transmission slot as the transmission slot selected in the immediately preceding transmission cycle T is selected as the transmission slot in the next transmission cycle T, and communication with the parent device 3 is executed.

  In addition to the above example, the CPUs 11 of the slave units 2a and 2b are not shown in the figure, but only the CPU 11 of the slave unit 2a executes step 56 and is used in the immediately preceding transmission cycle Ta2. The same transmission slot as that used in the transmission cycle Ta3 is determined as the transmission slot to be used in the current transmission cycle Ta3, or only the CPU 11 of the slave unit 2b executes step 56 and used in the previous transmission cycle Tb2. Is determined as a transmission slot to be used in the current transmission cycle Tb3, or each CPU 11 of the slave units 2a and 2b uses the same transmission slot used in the previous transmission cycle Ta2 and Tb2 as the current transmission cycle Ta3 and Tb3. In some cases, the transmission slot to be used is determined.

  In any of the above four cases, when each of the CPUs 11 of the slave units 2a and 2b selects a transmission slot having the same relationship as the transmission slot in the immediately preceding transmission cycle Ta2 and Tb2, specifically, In the immediately preceding transmission cycle Ta2, Tb2, since the CPU 11 of the slave unit 2a has selected the first transmission slot and the CPU 11 of the slave unit 2b has selected the second transmission slot, this transmission cycle Ta3, At Tb3, when the CPU 11 of the slave unit 2a selects the first transmission slot and the CPU 11 of the slave unit 2b selects the second transmission slot, the CPU 11 of the slave unit 2a selects the second transmission slot. When the CPU 11 of the slave unit 2b selects the third transmission slot, the CPU 11 of the slave unit 2a selects the third transmission slot, and the slave unit 2b When the CPU11 selects 4 th transmission slot, a collision of the carrier occurs even in the transmission period Ta3, Tb3.

  In this case, each of the CPUs 11 of the slave units 2a and 2b determines a new transmission cycle next to the transmission cycle T (in this case, the transmission cycles Ta3 and Tb3) in which the carrier collision has occurred n times or more continuously. In step 53 of the transmission slot determination process 50 executed at the beginning of T, since it is determined that transmission has failed continuously n times (twice) or more, step 54 is executed. Therefore, each CPU 11 of the slave units 2a and 2b executes step 55 to randomly determine one transmission slot to be used in the current transmission cycle T, or executes step 56 to execute the previous transmission cycle T. One of the transmission slots used in the above-described transmission slot to be used in the current transmission cycle T is selected with a certain probability and executed. The CPUs 11 of the slave units 2a and 2b repeat this operation until the occurrence of carrier collision is avoided.

  Thus, in this handset 2, the CPU 11 continues continuously n times or more even when communication with the base unit 3 is good (when a response is received) and when a response cannot be received. Until reaching a state where reception is not possible, the same transmission slot as the transmission slot in the immediately preceding transmission cycle T is selected, and data transmission in the selected transmission slot is continuously executed in the transmission cycle T.

  Therefore, according to the slave unit 2, a carrier collision occurs between the slave unit 2 that has already selected an appropriate transmission slot that can normally communicate with the master unit 3 and the newly installed slave unit 2. In the slave unit 2 that has already selected an appropriate transmission slot that can normally communicate with the master unit 3, a carrier collision occurs continuously n times (two times in this example). Until this is done, it is possible to continue to select the same transmission slot as the transmission slot in the immediately preceding transmission cycle T. Therefore, according to this handset 2, it is newly installed while avoiding the occurrence of carrier collision between the handset 2 that has already selected an appropriate transmission slot that can normally communicate with the base unit 3. It is possible to cause the slave unit 2 to select an appropriate transmission slot.

  Further, in this handset 2, even when a state in which a response cannot be continuously received n times or more is reached, the slot selection process for selecting a new transmission slot is always executed in the transmission slot determination process 50. Instead, the slot selection process is executed according to a predetermined probability.

  Therefore, according to this slave unit 2, there is a slight variation in the time length of the transmission cycle T in each slave unit 2, which is a representative example in the case where a carrier collision occurs n times or more continuously in the slave unit 2. As a result, when a carrier collision occurs between the slave units 2 that have already selected an appropriate transmission slot that can normally communicate with the master unit 3, all the slaves in which the carrier conflict has occurred are generated. Rather than having the machine 2 always select a new transmission slot, leave room for selecting the same transmission slot as the previous transmission slot (that is, allowing the same transmission slot to be used continuously). Thus, a new carrier collision occurs with the slave unit 2 in which no carrier collision has occurred among the slave units 2 that have already selected an appropriate transmission slot that can normally communicate with the master unit 3. Lower the probability of Rukoto can. Thereby, according to this subunit | mobile_unit 2, even if it is a case where the number of the subunit | mobile_unit 2 which communicates between one main | base station 3 increases, the suitable transmission slot which can communicate normally with the main | base station 3 Each child device 2 can be shifted to a state in which selection has been completed in a short time.

  In addition, in the slave unit 2, when a response is not received from the master unit 3 in response to execution of data transmission in the transmission slot in the transmission cycle T immediately after startup, the slot selection process is executed according to the probability of the value 1. (Always executing) to determine a new transmission slot.

  Therefore, according to this handset 2, when there is a handset 2 that has already selected an appropriate transmission slot that can normally communicate with the base device 3, the handset 2 is newly installed. Furthermore, the slave unit 2 that has already selected an appropriate transmission slot that can normally communicate with the base unit 3 is allowed to select the same transmission slot as the transmission slot in the immediately preceding transmission cycle T (as described above). In addition, while avoiding the occurrence of a carrier collision between the slave units 2 that have already selected an appropriate transmission slot that can normally communicate with the master unit 3), for the newly installed slave unit 2 By selecting a new transmission slot, an appropriate transmission slot can be selected at an early stage.

  In addition, in said subunit | mobile_unit 2, after starting the measurement of the transmission period T after starting, the structure which performs the measurement of the transmission period T so that this transmission period T continues is employ | adopted. However, the present invention is not limited to this configuration. For example, when the CPU 11 of the slave unit 2 determines that the response from the master unit 3 has not been received (communication with the master unit 3 has failed), it does not wait for the end of the transmission cycle T currently being measured. It is also possible to adopt a configuration in which measurement of the transmission cycle T is newly started. However, when this configuration is adopted, when a carrier collision occurs even in the transmission slot selected in the transmission cycle T in which measurement is newly started, measurement of the transmission cycle T is newly started. There is a possibility that a situation occurs in which the intervals of the transmission slots are continuous at intervals less than the transmission cycle T. The occurrence of such a situation also causes a new carrier collision with the child device 2 that has already selected an appropriate transmission slot that can normally communicate with the parent device 3. Therefore, when it is determined that the response from the base unit 3 has not been received, the slave unit is newly started to measure the transmission period T without waiting for the end of the transmission period T currently being measured. When the state in which the second CPU 11 cannot receive a response from the base unit 3 occurs, it is determined whether this occurred first or continuously, and when it occurs first Only when the measurement of the transmission cycle T is newly started and continuously generated, it is preferable to adopt a configuration in which the measurement of the transmission cycle T performed at that time is continued.

1 Data collection system
2 handset
3 Master unit
T Transmission cycle

Claims (2)

Preliminarily specified with a predetermined reference time that is equal to or greater than the total time of transmission time required for wireless data transmission to the transmission target device and reception time required for wireless reception of the data transmission from the transmission target device. Performing the data transmission in the transmission slot with one slot selected from a plurality of slots obtained by dividing the transmission period into a plurality of slots,
When the response is received, and even when the response cannot be received, the data transmission in the same transmission slot is performed in the transmission period until a predetermined number of times that cannot be received continuously is reached. Continue to run,
When a state in which the response cannot be received for a predetermined number of times has been reached, a slot selection process is selected in advance, in which one slot is randomly selected from the plurality of slots and determined as a new transmission slot. Run according to the probability
When the slot selection process is executed, the data transmission is executed in the selected new transmission slot, and when the slot selection process is not executed, the data transmission in the same transmission slot is transmitted. A communication terminal that continues in a cycle.   2. The new transmission slot is determined by executing the slot selection process according to a probability of value 1 when the response is not received in response to execution of the data transmission in the transmission slot immediately after startup. The communication terminal described.

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