JP2007306525A - Wireless communication system and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To decrease the power consumption in a wireless communication system driven by a battery or the like. <P>SOLUTION: The wireless communication system driven by a DC power supply includes: an antenna 1 for transmitting/receiving a wireless signal; a detection modulation detection circuit 3-1 that detects the wireless signal received by the antenna and transmits a detection signal when detecting that the amplitude of the detection signal is a predetermined threshold value or over; a switching circuit 3-3 for outputting a prescribed power supply voltage from the DC power supply depending on an input of the detection signal; a first internal circuit 3-4 with a central processing section activated through the application of the prescribed power supply voltage in response to an output of the switching circuit; and a second internal circuit 3-5 for transmitting data stored in a storage section to the first internal circuit in response to a request signal from the activated first internal circuit. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a wireless communication system driven by a battery or the like, and more particularly to a wireless communication system and a wireless communication method for realizing low power consumption.

  In recent years, wireless communication systems driven by batteries or the like have become widespread. In such wireless communication systems, it is important to reduce power consumption during operation, that is, during standby, and to reduce power consumption. It is coming.

  2. Description of the Related Art Conventionally, as a technique for realizing low power consumption, there is a portable wireless terminal device that reduces power consumption by stopping power feeding under the control of a CPU (Patent Document 1). Similarly, there is a semiconductor device that reduces power consumption by supplying a low-voltage power supply to a logic circuit in a standby state based on an external control signal (Patent Document 2). Furthermore, there is a wireless device that uses a non-volatile memory that does not lose written contents even when the power is stopped, reduces the amount of volatile memory, and reduces power consumption (Patent Document 3).

  In the technique described in Patent Document 1, whether a part of the memory is stopped or operated is controlled by the CPU. For this reason, it is necessary to always operate the CPU, and there is a limit in reducing power consumption. In the technology described in Patent Document 2, a low voltage power supply is supplied to the logic circuit in a standby state. However, the logic circuit is always supplied with power even though it is a low voltage, and does not require power supply. Wasteful power is also supplied to the circuit section.

  The technique described in Patent Document 3 uses an MRAM in which written contents are not lost even when the power supply is stopped, and power consumption can be reduced because the power supply is stopped, but a special memory is newly added in the manufacturing process. Will add to the cost.

Such a wireless communication system driven by a battery or the like can be applied to a smart plate. The smart plate is the name of a license plate of an automobile equipped with an IC chip on which vehicle information, vehicle user information, and the like are written. This smart plate wirelessly transmits information on a license plate of a car to a road device based on power supply from a built-in battery. Such smart plates are used, for example, for business vehicle entry / exit management. The smart plate is required to operate normally without maintenance / maintenance from system installation to at least vehicle inspection (usually 2 years, 3 years for new vehicles).
JP 2002-26803 A JP 2004-88264 A JP 2005-26912 A

  For example, when the technologies of Patent Documents 1 to 3 described above are used for a smart plate system, the power consumption may not be sufficiently reduced.

  A radio communication system according to an aspect of the present invention is a radio communication system driven by a DC power source, and detects an antenna that transmits and receives a radio signal, a radio signal received by the antenna, and a detection signal has a predetermined threshold value. A detection modulation detection circuit that sends out a detection signal when the above amplitude is detected, a switching circuit that outputs the DC power supply as a predetermined power supply voltage in response to an input of the detection signal, and a response to the output of the switching circuit In response to a request signal from the activated first internal circuit and a first internal circuit having a central processing unit activated by being supplied with a predetermined power supply voltage, On the other hand, it has a second internal circuit for sending data held in the storage unit.

  A control method for a radio communication system according to an aspect of the present invention is a control method for a radio communication system driven by a DC power source, and a detection output of a received radio signal is greater than or equal to a predetermined threshold value. The first internal circuit having a central processing unit is activated, the first internal circuit processes data read from the second internal circuit based on the received radio signal, and the first internal circuit The internal circuit outputs a processing end signal based on completion of processing of the read data, and the second internal circuit deactivates the first internal circuit based on the processing end signal. It is characterized by outputting a signal to be converted.

  It is possible to reduce power consumption in a wireless communication system driven by a battery or the like.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing a wireless communication system of the present invention. The wireless communication system shown in FIG. 1 includes an antenna 1, a power supply 2 and an LSI 3. The antenna 1 transmits and receives radio signals to and from the outside. The power source 2 is, for example, a battery built in the smart plate, and supplies power to the LSI 3. The LSI 3 is an integrated circuit that performs necessary processing based on, for example, holding of vehicle information and a radio signal. The LSI 3 includes a detection / modulation detection circuit 3-1, a power supply circuit 3-2, a switching circuit 3-3, a first internal circuit 3-4, and a second internal circuit 3-5.

  The detection modulation detection circuit 3-1 detects a radio signal received by the antenna 1, and sends a radio detection signal (see FIG. 1, A) when the detection signal detects an amplitude equal to or greater than a predetermined threshold. The detected and demodulated signal (see FIG. 1, B) is sent to the first internal circuit. Further, a signal (see E in FIG. 1) from the first internal circuit 3-4 is modulated, and a radio signal is transmitted via the antenna 1. The power supply circuit 3-2 receives the DC voltage from the power supply 2, converts it to a predetermined DC voltage, and supplies it to the switching circuit 3-3. If the DC voltage from the power supply 2 is equal to a predetermined DC voltage supplied to the inside, the power supply circuit 3-2 is not necessary.

  The switching circuit 3-3 outputs the above-described DC voltage to the first internal circuit 3-4 in response to a radio detection signal or a signal (see FIG. 1, D) input from the second internal circuit 3-5. This is a circuit for switching whether or not to perform. The first internal circuit includes a central processing unit (hereinafter referred to as CPU) and is a circuit that operates at high speed. This first internal circuit is activated or deactivated by the output of the switching circuit 3-3. The second internal circuit 3-5 is a circuit that includes a memory as a storage unit and holds data and programs. In response to a request signal (see FIG. 1, F) from the activated first internal circuit 3-4, the second internal circuit sends data or a program (see FIG. 1) to the first internal circuit 3-4. 1 and G). Further, the second internal circuit sends a switching request signal (see FIG. 1, D) to the switching circuit 3-3 according to the operation status. In the present embodiment, the second internal circuit is composed of a volatile memory such as SRAM or DRAM.

  FIG. 2 is a diagram illustrating an operation flow of the wireless communication system according to the present embodiment. FIG. 3 schematically shows signals exchanged based on this operation flow. In FIG. 3, the operating state of the first internal circuit in the present embodiment is shown using the lowermost stage. Hereinafter, the operation of the radio communication system according to the present embodiment will be described with reference to FIGS. 1 to 3. First, in step S0 of FIG. 2, the detection / modulation detection circuit 3-1 is always supplied with power from the external power source 2, and the system is in a standby state.

  When the wireless communication system receives a wireless signal from the outside via the antenna 1 in step S1 in FIG. 2, detection and demodulation of the signal received by the detection / modulation detection circuit 3-1 in step S2 in FIG.

  In step S3 of FIG. 2, when the detection / modulation detection circuit 3-1 detects an amplitude of the detection signal equal to or greater than a predetermined threshold value, the radio detection signal (see FIGS. 1 and 3 and A) is immediately switched. Send to circuit 3-3. When the wireless detection signal is input, the switching circuit 3-3 supplies the predetermined power supply voltage generated by the power supply circuit 3-2 to the first internal circuit 3-4 (FIGS. 1 and 3, C reference). The first internal circuit is activated because the power supply voltage is supplied (see the lowest stage in FIG. 3).

  In steps S4 and S5 in FIG. 2, the activated CPU in the first internal circuit reads a request signal (for reading out data and programs required for restarting the operation held in the second internal circuit 3-5). 1 and FIG. 3, F) are sent to the second internal circuit 3-5. The second internal circuit 3-5 sends data and a program (see FIGS. 1 and 3, G) to the first internal circuit 3-4 in accordance with the request signal.

  In step S6 of FIG. 2, the CPU in the first internal circuit executes processing of the signal (see FIGS. 1 and 3, B) detected and demodulated by the detection / modulation detection circuit 3-1, based on data and a program. . At this time, the CPU can immediately perform processing using the read data or program without executing the initialization operation.

  In step S7 of FIG. 2, the CPU in the first internal circuit further sends a signal (see FIGS. 1 and 3, E) processed in step S6 to the detection / modulation detection circuit 3-1. In the detection / modulation detection circuit 3-1, the signal output from the first internal circuit is modulated.

  In step S8 of FIG. 2, the modulated signal is transmitted from the antenna 1 to the outside. That is, it is transmitted to the outside as information in response to the input.

  In step S9 in FIG. 2, the CPU in the first internal circuit sends a signal (see FIGS. 1 and 3, F) indicating that the processing has been completed to the second internal circuit. In step S10 in FIG. 2, the second internal circuit 3-5 sends a switching request signal (see FIGS. 1 and 3 and D) to the switching circuit 3-3 based on the processing end notification in step S8. Based on this switching request signal, the switching circuit 3-3 switches so as to stop the power supply to the first internal circuit 3-4.

  Then, in step S11 of FIG. 2, the first internal circuit 3-4 is deactivated because the power is turned off. As in step S0, the LSI 3 is in a standby state until the next input signal is detected.

  That is, in the wireless communication system of the present embodiment, the first internal circuit 3-4 is activated after reception of a wireless signal is started, performs processing, and transmits a signal in response to an input to the outside. Thereafter, power is not supplied to the first internal circuit, and the first internal circuit is turned off. That is, the first internal circuit 3-4 that operates at high speed and consumes the largest amount of power performs only the minimum necessary operation. Thus, since the first internal circuit starts operating only when the received radio signal is equal to or higher than a predetermined threshold value, it is possible to suppress wasteful power consumption. Further, depending on the request included in the received radio signal, some signals may be transmitted continuously. In this case, the first internal circuit 3-4 may be activated for a while, and the power may be turned off after a predetermined time has elapsed.

  In the present embodiment, since the second internal circuit uses an example in which a volatile memory such as SRAM or DRAM is used in FIG. 1, the power is always supplied from the external power source 2. Non-volatile memory such as MRAM that does not need to be applied may be used. However, in this case, there is a case where the cost of the LSI is increased due to an increase in the manufacturing process and the reading speed of data and programs is a problem.

  In the wireless communication system of the present embodiment, new data and programs can be stored in the memory of the second internal circuit 3-5 by an external input signal in wireless communication. That is, new information can be added, data and programs can be upgraded.

  Next, a smart plate will be described as a more specific example of the present invention. This example is a case where the entry of a business vehicle into a predetermined area is managed. As described above, the smart plate is a system in which a device capable of wireless communication is mounted on a license plate of a vehicle and communication is performed between a road machine installed on the road and the license plate.

  FIG. 4 shows the smart plate system. As shown in FIG. 4, the smart plate system has a road machine 20 and a smart plate 10.

  The roadside device 20 is a device that transmits a modulated radio signal including data and a carrier wave to the smart plate 10 and receives a radio signal transmitted from the smart plate 10. The road machine 20 is connected to the information processing computer 30 through, for example, a network cable, and sends data necessary for managing entry / exit to the information processing computer 30.

  The road machine 20 is installed, for example, on the side of a road. As shown in FIG. 4, the road machine 20 includes an antenna 21, a radio unit 22, a control unit 23, and a memory 24. The wireless unit 22 receives a signal from the smart plate 10 via the antenna 21 and transmits a signal such as a command to the smart plate 10 via the antenna 21. The control unit 23 is constituted by a microcomputer or the like, and performs processing for sending various information sent from the smart plate 10 to the information management computer 30. Further, the memory is composed of a flash memory, a RAM, and the like, and stores data accompanying processing of the control unit 23 in addition to the computer program.

  The smart plate 10 demodulates the received radio signal and performs processing based on the command data included therein. In addition, the smart plate 10 transmits response data to the received command data to the road unit 20.

  As shown in FIG. 4, the smart plate includes an antenna 11, a battery 12, and an LSI 13. The LSI 13 is supplied with power from the battery 12. The LSI 13 receives a received signal from the roadside device 20 via the antenna, performs processing according to the received signal, and transmits the processed result from the antenna 11 to the roadside device as a transmission signal. The LSI 13 includes a detection modulation detection circuit 13-1, a switching circuit 13-3, a first internal circuit 13-4, and a second internal circuit 13-5. The detection modulation detection circuit 13-1 and the switching circuit 13-3 are the same as those in FIG.

  The first internal circuit 13-4 includes a CPU that transmits vehicle data based on a request from the road unit 20. The second internal circuit 13-5 includes a memory such as an SRAM or a DRAM that stores various types of vehicle data (for example, low-emission vehicle identification data) including computer programs, data associated with processing, vehicle ID codes, and the like. ing. Here, as the ID code, the registration number of the vehicle constituting the information of the license plate is used. The low pollution vehicle identification data is data for identifying whether or not the vehicle is a low pollution vehicle.

  Next, the system of this embodiment will be described with reference to FIG. FIG. 5 is a flowchart showing the relationship between the communication process of the control unit 23 of the road machine 20 and the communication process of the smart plate 10.

  In step S501, the control unit 23 of the road unit 20 automatically transmits a call signal for the smart plate 10 from the wireless unit at regular intervals (see FIG. 5, (1)). While the call signal is being transmitted, when the vehicle equipped with the smart plate 10 enters the communication area of the road unit 20 and the vehicle approaches the road unit 20, the input level of the detection signal received by the antenna 11 of the smart plate 10 Rises. When the input level of the detection signal becomes equal to or higher than a certain threshold value, the first internal circuit 13-4 of the smart plate is activated.

  In step S508, on the smart plate 10 side, the first internal circuit 13-4 reads the computer program and data associated with the processing from the second internal circuit 13-5 and starts processing according to the input signal. Then, the processing result is transmitted from the antenna 11. In this processing result, the first internal circuit detects that a signal has been transmitted from the road unit 20, and also includes an SP identification signal indicating that it is a response signal from the smart plate 10 (FIG. 5). (See (2)).

  In step S502, when the road unit 20 receives the response signal from the smart plate 10, the control unit 23 of the road unit 20 determines whether the response is from the smart plate 10 based on the SP identification information included in the response signal. Determine if. If the response includes the SP identification signal, in step S503, the control unit 23 of the road unit 20 transmits a signal including road identification information from the radio unit 22 (see FIG. 5, (3)). Here, the road identification information is for indicating that a signal is sent from the road machine 20.

  In step S509, the smart plate 10 receives the response signal from the roadside device 20. As in the case of responding to the call signal, if the input level of the road identification information is a signal level equal to or higher than a certain threshold, the first internal circuit of the smart plate receives a computer program or data associated with processing from the second internal circuit. Reading and processing according to the input signal. The smart plate 10 transmits the processing result from the antenna (see FIGS. 5 and 4). That is, here, it is determined that the signal is a response from the road device based on the road identification information included in the input signal. The smart plate transmits its own ID code from the antenna. As the ID code, information on the number plate of the vehicle is used.

  As described above, the road unit 20 and the smart plate 10 recognize that communication is established with each other based on the transmitted signal and the response signal. After that, when the ID code from the smart plate 10 is received by the wireless unit 22 of the road machine 20 in step S504, the control unit 23 of the road machine 20 requests the vehicle data on the road machine side. Is transmitted from the radio unit (see FIGS. 5 and 5). Thereafter, in step S506, the roadside machine 20 side enters a standby state.

  Then, in step S511, when the smart plate 10 side receives a request signal from the road machine 20 with an antenna, it determines that the road machine is requesting vehicle data, and is a business vehicle to a predetermined area. The vehicle data indicating this is called from the second internal circuit, and the called vehicle data is transmitted (see FIGS. 5 and 6).

  When the vehicle data from the smart plate 10 is received by the radio unit 22 of the road unit, the road unit control unit 23 transmits the vehicle data together with the ID code to the information management computer (see FIG. 5 (7)). Thereby, the vehicle data of the vehicle which passed the vicinity of the roadside machine is collected for each vehicle by the information management computer. Here, if the permission of entering the area is registered in advance for each vehicle, for example, the gate for entering the area is opened, and if not, the gate is not opened. In the application example of the present invention to the smart plate, since the LSI in the smart plate is in a stopped state until the vehicle approaches the road device, no wasteful power consumption occurs. In addition, after the communication with the roadside device is completed, the LSI in the smart plate shifts to the stop state, so that no unnecessary power consumption occurs.

  As described above in detail with reference to the embodiments, the battery-driven wireless communication system of the present invention detects (detects) an initial weak signal from an antenna and outputs an initial weak signal equal to or greater than a threshold value. At the time of detection, power is supplied to the built-in circuit 1 by a switching signal from the detection circuit to realize a high-speed operation mode. This operation enables normal reception from the beginning of the received data, receives the necessary wireless data, and when the high-speed operation becomes unnecessary, the switching signal from the second internal circuit that does not require high-speed operation. The power supply to the first internal circuit is stopped. Or, after detecting the initial weak signal, if the next radio signal is not detected within an arbitrary time, the power supply is cut off, thereby reducing the power consumption and extending the time for driving the LSI by the battery. Is possible.

  The present invention is not limited to this embodiment, and various modifications can be made. For example, in the above specific example, the example of transmitting information related to permission of warehousing from the smart plate side has been described as the management of warehousing and warehousing. If there is, it is possible to set so that no further request signal or the like is issued from the road unit side to the smart plate side when step S504 in FIG. 5 is completed.

  The design of the present invention can be changed as appropriate by those skilled in the art without departing from the gist of the present invention.

It is a block diagram which shows the radio | wireless communications system of embodiment of this invention. It is a figure which shows the operation | movement flow of the radio | wireless communications system of embodiment of this invention. It is a schematic diagram of the signal at the time of operation | movement of embodiment. It is a block diagram of the system which applied this invention to the smart plate. It is a figure which shows the operation | movement flow in a smart plate system.

Explanation of symbols

1, 11 Antenna 2, 12 DC power supply 3, 13 LSI
3-1, 13-1 detection modulation detection circuit 3-2 power supply circuit 3-3, 13-3 switching circuit 3-4, 13-4 first internal circuit 3-5, 13-5 second internal circuit DESCRIPTION OF SYMBOLS 10 Smart plate 20 Roadside device 21 Antenna 22 Radio | wireless part 23 Control part 24 Memory 30 Information management computer

Claims (10)

A wireless communication system driven by a DC power source,
An antenna for transmitting and receiving radio signals;
A detection modulation detection circuit for detecting a radio signal received by the antenna and transmitting a detection signal when the detection signal detects an amplitude equal to or greater than a predetermined threshold;
A switching circuit that outputs the DC power supply as a predetermined power supply voltage in response to an input of the detection signal;
A first internal circuit having a central processing unit activated by being supplied with a predetermined power supply voltage in accordance with an output of the switching circuit;
A wireless communication system having a second internal circuit that sends data held in a storage unit to the first internal circuit in response to a request signal from the activated first internal circuit.   2. The second internal circuit sends a signal for deactivating the first internal circuit to the switching circuit based on a processing end signal from the first internal circuit. The wireless communication system described.   3. The radio communication system according to claim 1, wherein the detection / modulation detection circuit further sends a detected and demodulated signal to the activated first internal circuit. 4.   4. The detection circuit according to claim 1, wherein the detection modulation detection circuit further modulates a signal from a first internal circuit and transmits the modulated radio signal from the antenna. 5. Wireless communication system.   The wireless communication system further includes a power supply circuit, wherein the power supply circuit converts a DC voltage from the DC power source into a predetermined DC voltage and supplies the DC voltage to the switching circuit. Item 5. The wireless communication system according to any one of Items 1 to 4.   The second internal circuit sends a signal for deactivating the first internal circuit to the switching circuit after a predetermined time has elapsed since the reception of the processing end signal from the first internal circuit. The wireless communication system according to any one of claims 1 to 5. 7. The first internal circuit ends processing based on a radio signal received by the antenna, and sends a processing end signal to the second internal circuit after a predetermined time. The wireless communication system according to any one of the above.   The wireless communication system according to any one of claims 1 to 7, wherein the threshold value predetermined by the detection / modulation detection circuit can be changed by a wireless signal received by the antenna.   9. A radio communication apparatus comprising: the radio communication system according to claim 1; and a DC power source that drives the radio communication system. A control method for a wireless communication system driven by a DC power source,
When the detection output of the received radio signal is equal to or greater than a predetermined threshold value, the first internal circuit having the central processing unit is activated,
The first internal circuit processes data read from the second internal circuit based on the received radio signal;
The first internal circuit outputs a processing end signal based on the end of processing of the read data,
The method for controlling a wireless communication system, wherein the second internal circuit outputs a signal for deactivating the first internal circuit based on the processing end signal.

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