JP2005176165A - Radio transmission system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce current consumption and to shorten a communication time by quickening a response to a transmission signal. <P>SOLUTION: A transmitting side terminal transmits a block signal with a gap of a non-signal state inserted between call starting signals several times as a transmission signal. A receiving side terminal performs intermittent reception at predetermined intervals. The receiving side terminal detects a carrier and decodes a call starting signal. If the receiving side terminal recognizes a call to the terminal itself from a transmission destination ID in the call starting signal, the receiving side terminal transmits a response signal during a term of the next gap. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wireless transmission system in which one parent device terminal and a plurality of child device terminals transmit and receive data by wireless communication, and in particular, the parent device terminal can communicate with a terminal network control device that performs data communication with a center side device. The present invention relates to a data communication system in which a terminal device such as a meter is connected to a slave terminal that is connected to the base terminal and can communicate wirelessly with the master terminal.

  In a wireless transmission system, data is transmitted and received between terminals wirelessly. In general, a terminal is driven by a built-in battery, and an intermittent reception method is adopted in order to reduce current consumption. In the intermittent reception method, as described in Patent Document 1, power consumption can be reduced by intermittent reception by continuously transmitting a call start signal and receiving it for a short time at regular intervals.

  Usually, in order to extend the battery life, the interval between intermittent receptions is nearly 30 seconds. Therefore, it is necessary to transmit the call start signal for 30 seconds or more, and the longer the call start signal, the slower the response of the terminal. With this, the communication time cannot be shortened.

  Patent Document 2 describes that in the intermittent reception method, the incoming information is compared with the incoming information of the local station, and if it is not the local station, the power supply to the communication circuit is stopped.

  If there is only one system, it can be easily distinguished from its own station within that system. But in reality, many different systems are confused. In such a situation, it is very difficult to reliably determine that it is a local station. Further, the transmission side terminal does not know that the power supply has been stopped at the reception side terminal, and continues transmission. Therefore, unnecessary communication is performed and the communication time becomes long.

  Patent Document 3 describes that a frame number is sequentially assigned to a call start signal, and the terminal stops receiving operation and enters a standby state until the start of a downlink message based on the frame number.

If the microcomputer of the terminal stops operating during this standby state, operations other than communication may be restricted. For example, the microcomputer cannot receive signals from other input / output terminals, which hinders the operation of the terminal.
Japanese Patent Publication No. 3-52279 JP-A-2-79526 Japanese Patent Laid-Open No. 2001-14578

  As described above, in the wireless transmission system, the current consumption can be reduced as the intermittent period is increased by the intermittent reception method. However, it is necessary for the transmission side to transmit a call start signal for a long time, and the response on the reception side becomes slow. Therefore, the response of the entire system becomes very slow, and the number of terminals that can communicate within a unit time is reduced. In particular, in the case of a data communication system that performs one-to-many wireless communication, as the number of terminals that perform wireless communication increases, the adverse effects become more prominent, resulting in a system with poor communication efficiency.

  In view of the above, an object of the present invention is to provide a wireless transmission system that can achieve both a reduction in current consumption and a reduction in communication time.

  The present invention includes a parent device terminal and a plurality of child device terminals that perform data communication wirelessly, and the parent device terminal and the child device terminal intermittently detect a carrier and transmit a carrier when the carrier is detected. A radio transmission system for receiving a received block signal, wherein the block signal includes a plurality of call start signals and a no-signal gap between the call start signals, and the master terminal and the slave terminal When the call start signal is received, a response signal is transmitted during the gap, and when the response signal is received, transmission of the subsequent call start signal is stopped.

  In this way, a period for the receiving side terminal to return is generated by dividing the originally continuous call start signal into a plurality of parts and inserting a gap. By transmitting a response signal during this period, a link is established between the parent device terminal and the child device terminal, and both can communicate. The response of the receiving terminal is quicker and the communication time is shortened.

  The block signal includes data after a plurality of call start signals, and further includes an idle signal for setting a time for checking an error of the data in the last part. The time according to the ability of the microcomputer to be used is set by the idle signal. For low-speed microcomputers, the inspection time is set longer, and for high-speed microcomputers, the inspection time is set shorter, so that the processing is performed efficiently to reduce current consumption.

  When receiving the response signal, the master terminal and the slave terminal transmit the data without the call start signal. In other words, when the transmission side terminal receives the response signal, it immediately transmits the data. Therefore, unnecessary signals are not transmitted, communication time is shortened, and current consumption is reduced.

  When the parent device terminal and the child device terminal call other terminals, they transmit a plurality of block signals. If the transmission time of the block signal is longer than the interval of intermittent reception, the carrier can be detected without fail. Further, by transmitting such a block signal a plurality of times, the carrier can be received at the next timing even when the gap period coincides with the intermittent reception timing or when a communication error occurs. Therefore, communication can always be established, and the reliability of wireless communication is improved.

  When the master terminal and the slave terminal do not receive a response signal even if a plurality of block signals are transmitted, the master terminal and the slave terminal transmit a block signal that does not include a gap. This also makes it possible to establish communication and improve the reliability of wireless communication.

  The interval between the gap in one block signal and the gap in the next block signal is set to be different from an integral multiple of the interval of intermittent reception. When both intervals are an integral multiple, a situation occurs in which the gap period coincides with the intermittent reception timing. By preventing this, the reliability of wireless communication can be improved.

  The call start signal includes transmission source information, reception destination information, and number information indicating position information in the signal. By including the transmission source information and the reception destination information, the receiving side terminal can determine that the communication is addressed to itself in a short time. As a result, the time required for data processing can be shortened, and current consumption can be reduced.

  Then, the master terminal and the slave terminal that have received the call start signal including the number information operate in the low current consumption mode until data is transmitted. It can be recognized from which position of all signals transmitted from the number information, and the time when data is transmitted can be known. Until the data is transmitted, less operation is required for communication. Therefore, the current consumption can be reduced by operating in the low current consumption mode.

  Moreover, the call start signal is encoded by Manchester code and transmitted by the start-stop synchronization method. By using the Manchester code including the synchronization signal, it is not necessary to insert the synchronization signal, and the signal can be correctly decoded. As a result, it is possible to quickly recognize that the communication is addressed to itself.

  In Manchester code, the H state or L state does not continue for more than one bit. Therefore, by continuing the H state or the L state where the data signal is 1 bit or more, these are recognized as a stop signal and a start signal as a delimiter of the data signal. As a result, the signal can be easily decoded, the number of data can be reduced, the time required for data processing can be shortened, and the current consumption can be reduced.

  According to the present invention, by providing a gap between successive call start signals and receiving a response signal during the gap period, the response time of the entire system can be shortened, and unnecessary signal transmission can be canceled. Therefore, the reception time can be shortened and the current consumption can be reduced. Such a reduction in communication time is very useful in a data communication system that requires continuous communication from one terminal to a plurality of terminals.

  A data communication system of this embodiment is shown in FIG. This system transmits a meter reading value and security information to a center side device 2 through a communication line 1 such as a telephone line network. The center side device 2 including a host computer and a center side network control device, and a communication line 1 A terminal network control device (T-NCU) 3 connected to the center side device 2 via the network, a parent device terminal 4 connected to the terminal network control device 3 by wire, and a plurality of devices capable of wireless communication with the parent device terminal 4 And the slave terminal 5. A terminal device 6 such as a meter or a sensor is connected to the slave terminal 5. A telephone set 7 is also connected to the terminal network control device 3. In addition, a plurality of master terminals 4 may be connected.

  As shown in FIG. 2, the handset terminal 5 is configured to transmit signals between the antenna 10, the wireless communication section 11 for performing wireless communication, the control section 12 including a microcomputer that controls the entire handset, and the terminal device 6. It has an interface unit 13 that performs transmission and reception. The wireless slave unit 5 is driven by a built-in battery 14.

  The control unit 12 outputs data such as a meter reading request transmitted from the master terminal 4 to the terminal device 6 through the interface unit 13, and transmits data such as a meter reading value and security information output from the terminal device 6 to the wireless communication unit. 11 to the base unit terminal 4.

  The base terminal 4 includes an antenna 20, a wireless communication unit 21 for performing wireless communication, a control unit 22 including a microcomputer that controls the entire base unit, and a line control unit 23 for performing communication with the terminal network control device 3. have. Base unit terminal 4 is driven by a built-in battery or a power source supplied from the outside. Note that the base terminal 4 is not an independent device, and the terminal network control device 3 may be integrated so as to have the function of the base terminal 4.

  When collecting meter reading values from the center side device 2, the terminal network control device 3 is activated by a conventionally known method using no-ringing communication or a number display service. The parent device terminal 4 connected to the terminal network control device 3 transmits a signal including the parent device ID and the child device ID to the child device terminal 5. The subunit | mobile_unit terminal 5 is performing the carrier sense intermittently. When the carrier is detected, the received signal is decoded and it is confirmed whether it is addressed to itself. When it is detected that the own terminal is called, it responds to the parent terminal 4. As a result, communication is started between the parent device terminal 4 and the child device terminal 5. The handset terminal 5 transmits the meter reading data of the terminal device 6 to the parent device terminal 4, and the meter reading data is transmitted from the parent device terminal 4 to the center side device 2 through the terminal network control device 3.

  When the terminal device 6 detects an abnormality such as a gas leak, the child device terminal 5 transmits a signal including the child device ID and the parent device ID to the parent device terminal 4. Base unit terminal 4 intermittently performs carrier sense, and when a carrier is detected, decodes the signal therein. When it is detected that the terminal is called, it responds to the slave terminal 5. As a result, communication is started between the slave terminal 5 and the master terminal 4. The slave terminal 5 transmits an abnormal signal from the terminal device 6 to the center side device 2 through the master terminal 4.

  As described above, both of the parent device terminal 4 and the child device terminal 5 become the transmission side terminal and the reception side terminal. Accordingly, with respect to wireless communication, the control units 12 and 22 of the master terminal 4 and the slave terminal 5 have the same function, and drive control of the communication control units 11 and 21 is performed to transmit and receive signals. Hereinafter, the master terminal 4 and the slave terminal 5 are not distinguished from each other, and are represented by a transmitting terminal and a receiving terminal.

  Here, in order to establish a link between the parent terminal 4 and the child terminal 5, a transmission signal is transmitted from the transmitting terminal as shown in FIG. The receiving side terminal performs carrier sensing by intermittent reception and transmits a response signal to the transmitting side terminal when a transmission signal is received. In this way, a link is established between the parent device terminal 4 and the child device terminal 5, and communication can be performed.

  The transmitting side terminal continuously transmits a plurality of block signals 30 as transmission signals. Here, three block signals 30 are transmitted. The reception side terminal performs intermittent reception at a predetermined reception interval. The interval Ti of intermittent reception is set to be shorter than the transmission time Tb of one block signal 30 and preferably shorter than the transmission time Tb. Usually, in order to reduce current consumption, the intermittent reception interval Ti is set to a very long time of 30 seconds or more. Thereby, the receiving side terminal can detect a carrier by carrier sense and can receive the block signal 30 reliably.

  As shown in FIG. 4, the block signal 30 includes a call start signal 31, data 32, and an idle signal 33, which are arranged in this order. The call start signal 31 is divided into a plurality of parts, and a gap 34 is inserted between the call start signals 31. The gap 34 is in a no-signal state for a certain time. Here, there are three call start signals 31 and two gaps 34. Data 32 follows the last call start signal 31.

  Since the block signal 30 is transmitted at a time longer than the interval of intermittent reception, as shown in FIG. 4, the receiving side terminal can always detect a carrier by intermittent reception. After recognizing that there is a carrier, the receiving terminal enters a receiving state and receives the block signal 30. During this time, it is determined whether the communication is addressed to itself based on the information regarding the transmission destination in the call start signal 31.

  When receiving the call start signal 31 addressed to itself, the receiving terminal transmits a normal response signal 35 to the transmitting terminal during the first gap 34. For example, as shown in FIG. 4, when the third call start signal 31 in the block signal 30 is received, the response is made during the gap 34 that comes after the first call start signal 31 in the next block signal 30. A signal 35 is transmitted. In this case, since it was received in the middle of the third call start signal 31, the remaining call start signal 31 is received, and the subsequent data 32 is also received. When the receiving terminal determines that the call is not addressed to itself, it does not transmit the response signal 35.

  However, when the first or second call start signal 31 is received, the data 32 cannot be received unless the third call start signal 31 is received. In this case, unnecessary communication time exists. Therefore, as shown in FIG. 5, when the receiving terminal transmits a response signal 35 during the gap 34, the transmitting terminal that has received the response signal 35 omits the subsequent call start signal 31 and continues. The data 32 and the idle signal 33 are transmitted. This eliminates the need to transmit the long call start signal 31 multiple times. The receiving terminal does not need to receive unnecessary signals. Therefore, it is possible to construct a system with a very low response and low current consumption.

  Further, when the carrier sense interval of the receiving terminal is 30 seconds, the call start signal 31 is set to 11 seconds and the gap 34 is set to 0.5 seconds. As a result, the total call start signal 31 becomes 34 seconds, and the call start signal 31 can be reliably received by intermittent reception at intervals of 30 seconds. In addition, it is a probability of 0.5 / 11.5 = about 4% that reception is not possible due to the presence of the gap 34, which does not normally cause a problem.

  When the timing of intermittent reception coincides with the period of the gap 34, the transmission side terminal does not receive the normal response signal 35 during the period of the gap 34, and therefore continuously transmits the block signal 30 including the call start signal 31. The receiving terminal can detect the call start signal 31 at the next timing.

  In this case, the time Tg between the gap 34 included in the block signal 30 and the gap 34 included in the next block signal 30 is equal to the intermittent reception interval Ti so that the timing of intermittent reception does not coincide with the period of the next gap 34. It is set not to be an integer multiple of. As a result, the timing of the next intermittent reception does not coincide with the period of the gap 34, and the carrier can always be detected by intermittent reception.

  As shown in FIG. 6, there are cases where the signal cannot be received even by two consecutive block signals 30 for an unpredictable reason. For example, the carrier may be detected but the signal may not be correctly received due to noise or the like, or the response signal 35 may not be transmitted. For such a case, the third block signal 30 is a signal that does not include the gap 34 between the call start signals 31. That is, among the plurality of block signals 30, the last block signal 30 to be transmitted is assumed to be a sequence of a plurality of call start signals 31. Therefore, the receiving terminal can reliably receive the call start signal 31 in any of the block signals 30.

  By performing wireless communication using the block signal 30 as described above, the intermittent cycle of the receiving terminal is lengthened to reduce the current consumption, and at the same time, the response of the receiving terminal is prevented from slowing down. Communication time can be shortened. In addition, by appropriately selecting the gap 34 interval for intermittent reception, reception can be ensured, and the reliability of the system can be ensured.

  Next, the structure of the call start signal 31 is shown in FIG. The call start signal includes a header 40, a transmission source ID 41, a reception destination ID 42, and a serial number 43. One call start signal 31 is configured by repeating these multiple times. All three call start signals 31 have the same configuration.

  The header 40 is provided for stabilizing the wireless communication units 11 and 21 and for taking bit synchronization of signals. The next transmission source ID 41 is identification information of the transmission side terminal, and the reception destination ID 42 is identification information of the reception side terminal. As a result, the transmission source and the reception destination are clarified. The receiving side terminal can know that the own terminal is called by decoding the receiving destination ID 42 of the call start signal 31. In particular, in a system in which a terminal having the best radio wave condition is selected from a plurality of receivers depending on radio wave conditions, a transmission source ID 41 and a reception destination ID 42 are required.

  The transmission source ID 41 and the reception destination ID 42 are transmitted a plurality of times. The receiving terminal receives the same signal a plurality of times and confirms the match. Therefore, it is possible to know that the terminal is called without any signal error. When only the receiver ID 42 is included in the call start signal 31, it is difficult to know where the radio wave is coming from, and bi-directional communication becomes difficult. That is, if the call start signal 31 includes a shortened ID that is a part of the destination ID 42, the IDs may be mistakenly matched, or a signal of another system may be interpreted as the own terminal, which is unnecessary. The decoding of the signal is continued, but the above-mentioned problem can be prevented by including the transmission source ID 41 and the reception destination ID 42 in the call start signal 31.

  A serial number 43 is inserted after the receiving destination ID 42. The serial number 43 is decremented by 1 each time it appears, and the last serial number 43 that comes before the data 32 in the third call start signal 31 becomes zero. Note that the serial number 43 may be increased by one, and the last serial number 43 is a predetermined number. Further, instead of the serial number 43, any number information indicating the current position information may be used. For example, information such as symbols, kana, and alphabets may be inserted.

  Therefore, the receiving side terminal can know the current decoding position by confirming the serial number 43 when the call start signal 31 is received. Further, the time until the data 32 is received can be recognized. According to this time, the control units 12 and 22 can operate in a standby state, thereby suppressing current consumption.

  Since this system employs intermittent reception, when the receiving terminal performs carrier sense and starts decoding the signal, it is unclear from where in all the transmitted signals the decoding starts. It is. Therefore, the current decoding position can be known from the serial number 43. When the current position becomes clear, the receiving terminal can recognize the next time when the data 32 is transmitted. Until the data 32 comes, the control units 12 and 22 operate in the low speed mode, that is, the low current consumption mode. As a result, it is possible to reduce current consumption. Naturally, in the low-speed mode, operations such as reception of signals from the interface unit 13 and time counting up are possible.

  The block signal 30 is encoded using a Manchester code as shown in FIG. In the synchronous type employing the FSK method, it is necessary to insert a bit synchronization signal, a frame synchronization signal, etc. before the ID. As a result, the total number of bits becomes very large. In particular, when a radio with a low radio wave output and an unstable radio wave state is employed, it is very difficult to accurately synchronize and accurately decode the signal at the receiving terminal. In the FSK signal, when the H state or the L state continues for a long bit, the threshold level of the signal gradually changes, so that there is a problem that the signal cannot be correctly decoded.

  When the call start signal 31 is received, it is important to recognize the terminal as soon as possible. Therefore, communication is performed in an asynchronous manner using a Manchester code including a synchronization signal. As a result, it is not necessary to insert a synchronization signal separately, and the total data amount can be reduced.

  Further, in the data signal using the Manchester code, the H state or the L state does not continue for one bit or more. That is, since the Manchester code is composed of signals having different levels in the first half and the second half, the signals do not have the same level. Utilizing this fact, as shown in FIG. 8B, the H state or the L state is continued for one bit or more to form a signal delimiter. When such a state is detected, it can be recognized that the data signal is separated, and the data 32 can be easily decoded.

  In the block signal, after repeating the call start signal 31 and the gap 34 a plurality of times, data 32 and an idle signal 33 are inserted. The idle signal 33 is for setting a time for checking the error of the data 32. That is, it is necessary to consider that an error in data 32 occurs in wireless communication. Therefore, a CRC for detecting an error, a BCH code for correcting the error, and the like are used.

  By the way, in the subunit | mobile_unit terminal 5, in order to operate with the battery 14, low-current-consumption CPU is used. Such a CPU is usually used in a microcomputer having a very low capacity. In a microcomputer with low capability, it takes a very long time to calculate CRC and BCH codes. Therefore, this time is set by the idle signal 33. That is, the transmitting terminal and the receiving terminal set the idle signal 33 to H or L. If it is set to H, the time for checking the error of the data 32 is set to be long so that it can be handled by a low-speed CPU. If it is set to L, the time for checking the data error is set short, so that it can be handled by a high-speed CPU. Thus, since the inspection time can be set in accordance with the ability of the microcomputer, even a low-speed microcomputer can sufficiently perform data processing, and the reliability of the data 32 can be improved.

  In addition, this invention is not limited to the said embodiment, Of course, many corrections and changes can be added to the said embodiment within the scope of the present invention. The present invention may be applied to a centralized monitoring system in which a large number of terminal devices are monitored by a single center side device instead of the parent device terminal and the child device terminal of the wireless transmission system.

Schematic configuration diagram of the data communication system of the present embodiment Block diagram showing schematic configuration of base unit and slave unit Diagram showing transmission signal and intermittent reception timing Diagram showing details of block signal Diagram for explaining the operation when there is a response to the transmitted block signal The figure which shows the transmission signal corresponding to the case where the block signal cannot be detected The figure which shows the constitution of the call start signal (A) is a figure which shows the data encoded by the Manchester code | cord | chord, (b) is a figure which shows the division | segmentation of the signal by the encoded data.

Explanation of symbols

4 Base device terminal 5 Slave device 30 Block signal 31 Call start signal 32 Data 33 Idle signal 34 Gap 35 Response signal 41 Source ID
42 Recipient ID

Claims (8)

A base station terminal and a plurality of handset terminals that perform wireless data communication, and the base unit terminal and the handset terminal intermittently detect a carrier and transmit a block signal when the carrier is detected; The block signal includes a plurality of call start signals and a no-signal gap between the call start signals. A wireless transmission system, wherein when a start signal is received, a response signal is transmitted during the gap, and when the response signal is received, transmission of a subsequent call start signal is stopped. The block signal includes data after a plurality of call start signals, and when receiving a response signal, the master terminal and the slave terminal transmit the data by omitting the call start signal. Item 2. A wireless transmission system according to Item 1. 3. The wireless transmission system according to claim 1, wherein the base unit terminal and the slave unit terminal transmit a plurality of block signals when calling another terminal. 3. The wireless transmission system according to claim 1, wherein the base unit terminal and the mobile unit terminal transmit a block signal not including a gap when a response signal is not received even if a plurality of block signals are transmitted. 5. The wireless transmission system according to claim 3, wherein an interval between a gap in one block signal and a gap in the next block signal is set to be different from an integral multiple of an interval of intermittent reception. . The call start signal includes a number indicating position information in the signal, and the parent device terminal and the child device terminal that have received the call start signal recognize the time until data is transmitted based on the number, 5. The wireless transmission system according to claim 3, wherein the wireless transmission system operates in a low current consumption mode during this period. When the master terminal and the slave terminal encode the call start signal with Manchester code and transmit it by the start-stop synchronization method, and the data signal constituting the call start signal continues in the H state or L state of 1 bit or more 5. The wireless transmission system according to claim 3 or 4, wherein it is determined that the data signal is separated. 5. The wireless transmission system according to claim 3, wherein the block signal includes an idle signal for setting a time for checking data errors in the last part.

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