JP2009094957A - Communication system, communication apparatus, and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide techniques applicable to an automatic ticket gate system etc. , wherein a terminal performs transmitting and receiving operation intermittently while ensuring immediacy of connection with a host. <P>SOLUTION: A Wake period and a Sleep period are provided for each predetermined WakeUp interval in a terminal, which tries to transmit an entry frame in the Wake period. The host, when it is not connected to the terminal, continues to transmit non-modulated carriers until it receives any frame from the terminal. When the terminal enters into an area enabling it to receive the non-modulated carriers from the host, the terminal transmits the entry frame as a reflection wave. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a communication system, a communication apparatus, and a communication method in which a terminal (transponder) that does not have its own radio wave generation source performs non-contact data transmission with a host (reader / writer). Relates to a communication system, a communication apparatus, and a communication method for recognizing each other through a predetermined communication sequence and establishing a connection.

  More specifically, the present invention relates to a communication system, a communication apparatus, and a communication method applied to an automatic ticket gate system including an automatic ticket gate having a host function and a terminal having a credit function. The present invention relates to a communication system, a communication apparatus, and a communication method that perform transmission / reception operations intermittently while securing the immediacy of connection.

  A non-contact communication system called RFID (Radio Frequency IDentification) is known as a communication system that does not have its own radio wave generation source and transmits data wirelessly. Other names for RFID include “ID system” and “data carrier system”. The RFID system, or RFID for short, is globally common. Translated into Japanese, it becomes “a recognition system using high frequency (wireless)”. An RFID system is composed of a transponder, also called a tag, and a reader / writer that accesses the transponder. The transponder passively operates using radio waves as an energy source from the reader / writer side, and the reader / writer reads information stored in the transponder. And write information.

  Non-contact communication methods in the RFID system include an electrostatic coupling method, an electromagnetic induction method, a radio wave communication method, and the like. Among these, in the radio wave communication type RFID system, the transponder is provided with a reflector that transmits data by a reflected wave obtained by modulating a non-modulated carrier, and the reader / writer is a reflection that reads data from a modulated reflected wave signal from the reflector. It has a wave reader and performs reflected wave transmission, also called “backscatter”. When an unmodulated carrier is sent from the reflected wave reader, the reflector modulates the reflected wave based on an antenna load impedance switching operation or the like and superimposes transmission data. That is, on the reflector side, since no carrier generation source is required for data transmission, the data transmission operation is driven with low consumption. On the reflected wave reader side, such modulated reflected waves can be received and demodulated and decoded to obtain transmission data.

  The reflector basically includes an antenna that reflects incident continuous wave radio waves, a transmission data generation circuit, and an impedance change circuit that changes the load impedance of the antenna corresponding to the transmission data. The impedance change circuit is, for example, an antenna switch that switches the end of the antenna to open / ground. This antenna switch can be incorporated into a communication circuit module and configured with a CMOS (Complementary Metal Oxide Semiconductor) transistor, but separated from the circuit module and configured with a gallium arsenide (GaAs) IC (Integrated Circuit). Therefore, a high-speed switching operation with low power consumption becomes possible. In the latter case, the data transmission rate by reflected wave modulation is improved and the power consumption is suppressed to several tens of μW or less. Therefore, considering that a wireless LAN (Local Area Network) consumes several hundred mW to several watts of power during communication, reflected wave communication has an overwhelming performance difference compared to the average power consumption of a general wireless LAN. (For example, see Patent Document 1).

  Since a transponder equipped with a reflector only performs an operation of reflecting a received radio wave, it is not regarded as a radio station, and has an advantage that it is treated as not subject to legal regulations imposed on radio wave communication. In contrast, the conventional non-contact communication system uses a frequency of several MHz to several hundred MHz (for example, 13.56 MHz), whereas the reflected wave transmission method uses a 2.4 GHz band called, for example, ISM (Industry Science and Medical Band). High-speed data transmission using a high frequency band of microwaves can be realized.

  As an application example of a communication system using reflected wave transmission, a reflector as a transponder is mounted on a data source terminal such as a digital still camera or a digital video camera, and a host such as a television or printer functions as a reflected wave reader. And uploading data such as still images and moving images by reflected wave transmission, and performing display and printout processing.

  Further, in a communication system using reflected wave transmission, a communication sequence for allowing a host and a terminal to recognize each other and transition to a communicable state has been proposed. For example, Japanese Patent Application No. 2006-270365 already assigned to the present applicant discloses a service entry sequence for recognizing a partner station with which a host and a terminal can communicate with each other. In this sequence, the host intermittently transmits beacon frames at regular time intervals, and continues to transmit unmodulated carriers by providing an entry period for a predetermined time after beacon transmission. On the other hand, when a terminal enters a radio wave reachable range of a host and receives a beacon frame, the terminal acquires host information from the description content of the frame. When the terminal wants to connect to the host, the entry frame is superposed on the reflection of the unmodulated carrier using the entry period, and the entry frame is returned. In this way, the host and the terminal can recognize the existence of one or a plurality of counterpart stations that can communicate with each other.

  FIG. 7 shows an example of a service entry sequence performed between the host and the terminal. The host periodically transmits beacon frames. Further, an entry period is provided after the transmission of the beacon frame, and the host continues to transmit unmodulated carriers in the entry period. A terminal that exists within a range in which a beacon frame from a host can be received can return an entry frame superimposed on a reflected wave of an unmodulated carrier received within an entry period.

  FIG. 8 shows a sequence when a communication operation is started between the host and the terminal using the service entry sequence shown in FIG.

  The host intermittently transmits beacon frames at regular time intervals. The terminal cannot receive the beacon frame outside the radio wave reachable range, but enters the radio wave reachable range and executes the reception process when the beacon frame arrives.

  Based on the host information described in the payload of the received beacon frame, the terminal acquires information such as information on a communication frequency channel to be used and a unique ID of the host. When it is desired to connect to the host, the entry frame is superimposed on the reflection of the unmodulated carrier using the entry period, and the entry frame is returned.

  The host acquires the unique ID of the terminal, information on settable communication parameters, and the like based on the description content of the entry frame. When it is desired to communicate with the terminal, a connection request frame in which designation information such as communication parameters is described in the payload is transmitted. On the other hand, when responding to the connection request, the terminal returns a connection response frame in which the connection result or the like is described in the payload, thereby establishing the connection. Then, during the period when the connection is established, the transmission of the command frame from the host and the response frame return by the terminal corresponding to this are repeatedly executed.

  Such a service entry sequence has a terminal function in a data source such as a digital still camera or a digital video camera, and a communication system (a television or printer that outputs still images and moving images has a host function). It is preferably applied to the above), and the existence of each is notified and data exchange is possible. In addition, if the host does not receive an entry frame during the entry period after transmitting the beacon signal, no connection will be established with any terminal. Therefore, from the end of the entry period until the next beacon transmission timing During this period, communication operation can be stopped to reduce power consumption. In addition, during the low power consumption operation, no carrier is transmitted from the host and no modulated reflected wave is returned from the terminal, so that it can coexist with other communication systems in the vicinity sharing the same frequency channel. .

  As another application example of the communication system using reflected wave transmission, application to a non-contact IC card having a credit function can be cited. For example, depositing / withdrawing electronic money such as “Edy”, Or the use scene as a boarding ticket like "Mobile Suica" is assumed. For example, in Japanese Patent Application No. 2007-48289 already assigned to the present applicant, the terminal is in the form of a SIM (Subscriber Identity Module) card used in a mobile phone or the like, and the carrier handles subscriber information. A system including a SIM function and a credit function for handling information such as electronic money and a credit card is disclosed. As described above, according to the system, even if the mobile phone does not have the non-contact IC function represented by FeliCa, the non-contact credit function can be easily achieved by simply changing the SIM card with the reflected wave communication function. It becomes possible to use.

  When the reflected wave transmission communication system is applied to an automatic ticket gate system, the host function is incorporated in the automatic ticket gate and “existence confirmation”, “authentication”, “data readout” with the SIM card accommodated in the portable terminal "," Determination "," write "," confirmation ", a series of processing is realized by non-contact communication. In order to provide a service without stopping the user passing through the automatic ticket gate, it is necessary to complete these processes in less than 200 milliseconds (see, for example, Non-Patent Document 1).

  By the way, since the portable terminal is driven by a battery such as a lithium ion battery, there is a demand for reducing the power consumption of the wireless communication system as much as possible. The terminal of the above-described reflected wave transmission system consumes about several μW of power for transmission / reception control of the antenna switch (that is, modulation processing of the reflected wave) at the time of transmission, and ASK (Amplitude Shift) received from the host at the time of reception. Keying) Electric power of about several mW is consumed for detection of the modulated wave signal. Although the power consumption associated with the communication operation of the terminal is sufficiently low compared to other wireless systems, considering that the user passes through the automatic ticket gate several times a day, the terminal receives it all day. Staying in the standby state is not preferable from the viewpoint of power consumption. Generally, a technique of reducing power consumption by intermittently performing a reception standby operation is employed.

  Here, in the reflected wave transmission system in which the terminal and the host establish a connection by the service entry sequence shown in FIGS. 7 to 8, a case where the terminal intermittently performs a reception waiting operation will be described with reference to FIG. Let's consider it.

  In the service entry sequence, since the terminal 2 receives a beacon frame transmitted from the host at every beacon interval, the connection operation between the two is started. For this reason, the terminal waits for a beacon frame intermittently. In the operation example illustrated in FIG. 9, the WakeUp interval 401 represents a time interval at which the terminal periodically starts reception, and one WakeUp interval 401 includes a beacon reception waiting period 402 and a transmission / reception stop period 403. The terminal performs an intermittent reception waiting operation in which reception of a beacon frame is periodically started every WakeUp interval 401. When the terminal waits for the arrival of a beacon frame from the host in the beacon frame reception waiting period 402 and does not receive a beacon frame (or does not return an entry frame in response to the beacon frame), the terminal A transmission / reception stop period 403 in which the transmission / reception operation is stopped is entered until the WakeUp interval 401, and reception of a beacon frame is again waited for at the next WakeUp timing. The transmission / reception stop period 403 represents a period during which the transmission / reception operation of the communication system is stopped, and other communication systems sharing the same frequency can perform communication (that is, coexistence with an adjacent communication system is possible). .

  Consider further the configuration method of the WakeUp interval 401. By reducing the ratio of the beacon reception waiting period 402 to the WakeUp interval 401, the terminal can reduce the power consumed by the reception waiting. On the other hand, in order to ensure the immediacy of the connection between the host and the terminal, it is desirable that the beacon reception waiting period 402 of the terminal 2 is at least longer than the beacon interval on the host side. This is because an opportunity to receive a beacon is obtained once during one beacon reception waiting period 402. If the beacon reception waiting period 402 is shorter than the beacon interval, there is a possibility that a chance to receive a beacon will not be reached unless the WakeUp interval 401 is repeated several times, and the immediacy of the connection between the host and the terminal is lost. End up.

  Thus, since the minimum time length of the beacon reception waiting period 402 is limited in order to maintain the immediacy of the connection between the host and the terminal, the consumption can be further reduced by adjusting the ratio of the beacon reception waiting period 402 to the WakeUp interval 401. To achieve this, it is necessary to extend the WakeUp interval 401 and the transmission / reception stop period 403. However, since the terminal may not receive a beacon only during the transmission / reception stop period 403 + beacon interval, if the transmission / reception stop period 403 is extended, the immediacy of the connection between the host and the terminal is lost.

  In short, in a communication system that performs a service entry sequence based on the beacon interval as shown in FIGS. 7 to 8, the power consumption is reduced by intermittent transmission / reception operations at the terminal and the connection with the host is reduced. There is a problem that immediacy is difficult to achieve. That is, it can be said to be suitable for data transfer from a digital still camera or digital video camera to a television or printer, but not suitable for an application similar to a ticket service at a ticket gate.

Japanese Patent Laying-Open No. 2005-064822 Introduction of contactless IC card / Suica ticket gate system (IEEE Trans. SM, Vol. 123, No. 8, 2003)

  An object of the present invention is to provide an excellent communication system in which a terminal (transponder) that does not have its own radio wave generation source can suitably perform data transmission without contact with a host (reader / writer). is there.

  It is a further object of the present invention to provide an excellent communication system, communication apparatus, and communication method in which a terminal and a host can recognize each other through a predetermined communication sequence and smoothly establish a connection. .

  A further object of the present invention is to provide an excellent communication system, communication apparatus, and communication method that can be suitably applied to an automatic ticket gate system including an automatic ticket gate having a host function and a terminal having a credit function. There is.

  A further object of the present invention is to provide an excellent communication system, a communication apparatus, and a communication method capable of ensuring immediacy of connection with a host while achieving low power consumption by intermittent transmission / reception operations of a terminal. There is to do.

The present invention has been made in consideration of the above-described problems, and is a communication system in which a terminal having a transponder function that does not have its own radio wave generation source performs data transmission with a host having a reader / writer function. And
The host transmits an unmodulated carrier until it receives any frame from the terminal in a state where it is not connected to the terminal,
In a state in which the terminal is not connected to the host, the terminal provides a Wake period in which transmission / reception operation is performed every predetermined WakeUp interval and a Sleep period in which the transmission / reception operation is stopped. In the Wake period, the terminal Attempt to send an entry frame to announce its existence,
This is a communication system characterized by the above.

  However, “system” here refers to a logical collection of a plurality of devices (or functional modules that realize specific functions), and each device or functional module is in a single housing. It does not matter whether or not.

  The present invention relates to a non-contact communication system in which a transponder that does not have its own radio wave generation source operates passively using radio waves from a reader / writer as an energy source. For example, the transponder receives an unmodulated carrier and receives data. A reflector for transmitting the superimposed modulated reflected wave is mounted, and the reader / writer is composed of a reflected wave reader for reading data from the modulated reflected wave. According to a communication system using reflected wave transmission, since no carrier generation source is required on the reflector side, data transmission is performed while dramatically reducing power consumption compared to existing wireless communication technologies such as wireless LAN. Can be performed.

  In order to start data transmission between the transponder and the reader / writer, a communication sequence for establishing a connection between them is required. For example, in a communication system in which a terminal serving as a data source such as a digital still camera or a digital video camera serves as a transponder and a host such as a television or printer serves as a reader / writer, a service entry sequence (for example, a beacon interval) (for example, Japanese Patent Application No. 2006-270365 is effective. However, when the host function is applied to an automatic ticket gate system that is installed in an automatic ticket gate, a terminal equipped with a transponder function has low power consumption and a smooth connection is established while passing through the ticket gate. Although it is necessary to complete the data transmission processing, there is a problem that it is difficult to achieve both low power consumption by intermittent transmission / reception operation of the terminal and immediacy of connection with the host.

  On the other hand, the communication system according to the present invention assumes an application similar to a ticket service at a ticket gate, and reduces power consumption and immediate connection with a one-to-one terminal and host. Service entry sequence is considered.

  In a state where the terminal is not connected to the host, the terminal can basically transit to the sleep state in which the transmission / reception operation is stopped. However, a wake period in which the transmission / reception operation can be performed is provided for each WakeUp interval, and the intermittent transmission / reception operation is performed. To reduce power consumption.

  In addition, the terminal attempts to transmit an entry frame for notifying the host of its presence during the Wake period. On the other hand, the host transmits an unmodulated carrier until it receives any frame from the terminal in a state where it is not connected to the terminal. Therefore, the terminal can transmit the entry frame as a reflected wave when entering the area where the unmodulated carrier from the host can be received, so that the terminal can smoothly connect while performing intermittent transmission / reception operations. Thus, it is possible to ensure the immediacy of the connection.

  The terminal attempts to receive a frame from the host in the remaining Wake period in response to the fact that the entry frame can be transmitted using the unmodulated carrier from the host.

  The host transmits a connection request frame to the terminal in response to receiving the entry frame from the terminal.

  Here, when the terminal cannot receive the frame from the host in the remaining Wake period after transmitting the entry frame, the terminal enters the Sleep period and stops the transmission / reception operation. In a general frame format, a preamble is followed by a bit for frame synchronization. When the terminal cannot detect the frame synchronization bit of the connection request frame in the frame reception period after transmitting the entry frame, the terminal immediately stops reception and enters the sleep period to further reduce power consumption. Can do.

  On the other hand, the terminal can know the presence of a communicable host by receiving the connection request frame from the host during the frame reception period after transmitting the entry frame. Thereafter, the terminal enters a connection state with the host.

  In this connection state, a frame transmission period from the terminal and a frame transmission period from the host (a frame reception period for the terminal) can be alternately provided, and frame transmission / reception can be performed alternately. The host transmits an unmodulated carrier in the frame transmission period of the terminal after transmitting the frame itself, and the terminal performs frame transmission using the unmodulated carrier.

  For example, after transmitting a connection request frame in response to receiving an entry frame, the host performs unmodulated wave carrier transmission for the terminal to transmit the frame. Further, in response to receiving a frame other than the entry frame from the terminal, the host determines that the terminal is connected and transmits / receives a frame.

  According to the present invention, a terminal (transponder) that does not have a radio wave generation source itself can recognize the presence of each other through a predetermined communication sequence with a host (reader / writer) and smoothly establish a connection. An excellent communication system, communication apparatus, and communication method can be provided.

  Further, according to the present invention, the terminal is intermittently applied in an application similar to a ticket service at a ticket gate applied to an automatic ticket gate system including an automatic ticket gate having a host function and a terminal having a credit function. It is possible to provide an excellent communication system, communication apparatus, and communication method that can secure immediacy of connection with a host while reducing power consumption by a typical transmission / reception operation.

  Other objects, features, and advantages of the present invention will become apparent from more detailed description based on embodiments of the present invention described later and the accompanying drawings.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  Non-contact communication methods include electrostatic coupling method, electromagnetic induction method, radio wave communication method, etc., but in the following, assuming the embodiment to apply the radio wave communication method, reflected wave transmission called “backscatter” is performed. Shall be done. The reflected wave transmission method is characterized in that, for example, low power consumption can be realized in a communication mode in which the transmission ratio from the transponder (reflector) side occupies most of the communication.

  FIG. 1 schematically shows a configuration of a communication system according to an embodiment of the present invention. The communication system according to this embodiment includes a host 1 (as a reader / writer) provided with the reflected wave reader shown in FIG. 1A and a terminal 2 (as a transponder) provided with the reflector shown in FIG. 1B. .

  First, a case where data is transmitted from the host 1 to the terminal 2 will be described. On the host 1 side, transmission data supplied from the host function unit 13 is modulated by the modulation function unit 121 of the host communication control function unit 22 via the control interface 14. The modulation signal 16 is placed on the carrier 31 generated by the carrier generation source 111 of the RF function unit 11 by the mixer 112, further amplified by the power amplification amplifier 113, and then the modulated wave signal via the circulator 117 and the antenna 14. 31 is transmitted to the terminal 2. On the other hand, when receiving the modulated wave signal 31, the RF function unit 21 of the terminal 2 demodulates the signal to obtain a demodulated signal 25. The demodulation function unit 223 demodulates the demodulated signal 25 and passes it to the terminal function unit 23 via the control interface 25. The terminal function unit 23 stores received data, displays it on the screen, and notifies the user of reception as necessary.

  Next, a case where data is transmitted from the terminal 2 to the host 1 will be described. Transmission data supplied from the terminal function unit 23 of the terminal 2 is modulated by the modulation function unit 222 of the communication control function unit 22. The load impedance of the antenna 24 is switched by turning on / off the antenna switch 211 of the RF function unit 21 according to the modulation signal 26. At this time, a modulated reflected wave signal 32 obtained by reflecting the carrier 31 received from the host 1 side is transmitted to the host 1. On the other hand, when the RF function unit 11 on the host 1 side receives the reflected wave 32, it is amplified by the low noise amplifier 114, and further multiplied by the local signal from the carrier generation source 111 by the quadrature demodulator 115 to obtain the demodulated signal 16 Get. The demodulated signal 16 is subjected to gain adjustment by an AGC (Auto Gain Control) 116, demodulated by the demodulation function unit 123, and passed to the host function unit 13 via the control interface 14. The host function unit 13 stores received data, displays it on the screen, and notifies the user of reception as necessary.

  Further, in addition to the data transmission / reception function described above, the protocol control units 121 and 221 that mutually function in the host 1 and the terminal 2 are provided in the communication control functions 12 and 22, so that the host 1 and the terminal 2 can be connected, disconnected, Protocol control such as is realized.

  In a communication system using reflected wave transmission, since no carrier generation source is required for the RF function unit 21 of the terminal 2, the system can be driven with low consumption. Further, data modulation on the terminal 2 side is subjected to multilevel modulation such as QPSK (Quadrature Phase Shift Keying) or QAM (Quadrature Amplitude Modulation) (for example, refer to Japanese Patent Application Laid-Open No. 2005-136944), and the host 2 to the host High-speed communication can be realized in one direction (uplink). However, since the modulation in the host 1 uses ASK modulation in consideration of the ease of detection on the terminal 2 side, the direction from the host 1 to the terminal 2 (downlink) has a low data rate.

  In the illustrated system, it is assumed that the protocol control function units 121 and 221 of the host 1 and the terminal 2 respectively perform protocol sequence control and control of a communication state according to the sequence. The transmission frame configuration may be the same as the configuration shown in FIG. 7 of Japanese Patent Application No. 2006-270365 (see FIG. 10).

  The reflected wave transmission communication system as shown in FIG. 1 is not only used for large-capacity data transmission applications between terminals that are data sources such as digital still cameras and digital video cameras, and hosts such as televisions and printers. Application to an application similar to a ticket service at a ticket gate is assumed. In particular, in the latter case, it is necessary to suppress the power consumption required for the reception waiting of the terminal and not impair the immediacy of the connection between the host and the terminal.

  In the present embodiment, the communication system includes a plurality of service entry sequences for allowing the host 1 and the terminal 2 to recognize each other.

  The first service entry sequence assumes an application that uploads a still image or video from a terminal such as a digital still camera or a digital video camera to a host such as a television or printer, and the terminal and the host have multiple partners. One-to-one communication can be performed by selecting a connection partner from a station. Since the first service entry sequence is the same as that described in Japanese Patent Application No. 2006-270365 (described above), description thereof will be omitted below.

  On the other hand, the second service entry sequence assumes an application similar to a ticket service at the ticket gate, and reduces power consumption and connection in a state where the terminal and the host are limited to one-to-one. This is a sequence that is considered to be immediate.

  FIG. 2 shows how frames are exchanged between the host 1 and the terminal 2 in the second service entry sequence. However, between the frame transmission period from the host 1 and the transmission period from the terminal 2, a processing time for performing the next transmission based on the received frame is taken into consideration, and a guard interval of a predetermined length (transmission of the terminal 2) The guard time “Up to Down (U2D)” is used during the switching from the period to the transmission period of the host 1, and the guard time “Down to Up (D2U)” is used during the switching from the transmission period of the host 1 to the transmission period of the terminal 2. ) Is provided.

  In a state where the host 1 is not connected to the terminal 2, the host 1 is in a state (501) of transmitting an unmodulated carrier and receiving a reflected wave until it can receive a reflected wave (some frame) from the terminal 2. In other words, this is different from the first service entry sequence (see FIG. 7) in which the host 1 transmits an unmodulated carrier for a fixed entry period provided at regular beacon intervals.

  On the other hand, the terminal 2 can basically transit to the sleep state in which the transmission / reception operation is stopped in a state in which the terminal 2 is not connected to the host 1, but a wake period in which the transmission / reception operation can be performed at every WakeUp interval (502). (503) is provided. That is, power consumption can be reduced by an intermittent operation in which the Wake period (503) and the Sleep period (507) are alternately repeated every WakeUp interval (502). In the Wake period, a frame transmission (Tx) period in which the terminal 2 performs a transmission operation and a frame reception (Rx) period (505) in which a reception operation is performed are alternately provided with a predetermined guard interval.

  In a state in which the connection with the host 1 is not established, the terminal 2 transmits an entry frame for making the host 1 recognize its existence in the first frame transmission period (504) in the Wake period. Try. The host 1 continues to send an unmodulated carrier while the connection with the terminal 2 is not established (until some frame can be received from the terminal 2). Therefore, when the terminal 2 enters an area where the unmodulated carrier from the host 1 can be received, the terminal 2 can transmit the entry frame as a reflected wave in the entry period (504). The terminal 2 tries to receive a frame composed of an ASK modulated wave from the host 1 in a frame reception period (505) that continues through the guard interval.

  When the host 1 receives the entry frame, the host 1 knows the existence of the communicable terminal 2 and transmits a connection request frame (506) to the terminal 2 using the ASK modulated wave.

  Here, if the terminal 2 cannot receive the connection request frame (506) in the frame reception period (505) following the entry period (504), the terminal 2 enters the sleep period (507) and stops the transmission / reception operation. When the terminal 2 cannot detect the frame synchronization bit of the connection request frame in the reception period (505), the terminal 2 can immediately stop the reception and enter the sleep period (507), thereby further reducing power consumption.

  When the terminal 2 enters the Wake period again after the Sleep period (507), the terminal 2 tries to transmit the entry frame in the same manner as described above. Thereafter, the terminal 2 repeats the operation for each WakeUp interval (502) as described above until the connection request frame can be received from the host 1.

  Then, after transmitting the entry frame in the entry period within the subsequent Wake period, the terminal 2 receives the connection request frame from the host 1 in the reception period provided through the guard interval, thereby enabling communication with the host 1 Can know the existence of Thereafter, the terminal 2 is connected to the host 1 and alternately provides frame transmission periods and frame reception periods, and performs frame transmission / reception alternately.

  After transmitting the connection request frame (506), the host 1 enters the reflected wave reception (non-modulated wave carrier transmission) state again. If the host 1 receives the entry frame, the host 1 repeats the connection request frame transmission and the reflected wave reception (unmodulated wave carrier transmission for the terminal to transmit the frame). If the frame received from the terminal 2 is other than the entry frame, it is determined that the terminal 2 is connected, and the frame is transmitted / received. For example, in an application similar to a ticket service at the ticket gate, a series of frame exchanges for “existence confirmation”, “authentication”, “data read”, “judgment”, “write”, “confirmation”, etc. Between the host 1 and the terminal 2.

  In the connected state, a frame transmission period from the terminal 2 and a frame transmission period from the host 1 (a frame reception period for the terminal 2) are alternately provided. The host 1 transmits an unmodulated carrier in the frame transmission period by the terminal 2 after transmitting the frame itself. The terminal 2 can perform frame transmission using this unmodulated carrier.

  As described above, since the host 1 continues to transmit the unmodulated carrier when not connected to the terminal 2, the terminal 2 transmits the entry frame when entering the area where the unmodulated carrier from the host 1 arrives. Thus, the procedure for connection can be started immediately, thereby ensuring the immediacy of the connection with the host.

The terminal 2 is controlled by the terminal function unit 23 to select the first service entry sequence or the second service entry sequence via the control interface 25. Alternatively, a non-volatile memory such as E ² PROM (Electrically Erasable and Programmable Read Only Memory) may be provided, and a value written on this memory may be read and determined when the wireless communication system is activated.

  FIG. 3 shows a service entry sequence in the communication system shown in FIG. The terminal 2 transmits an entry frame to notify the presence of its own station (a). On the other hand, the host 1 that has received the entry frame transmits a connection request frame to inform the terminal that the existence of the terminal has been confirmed, and makes a request for starting the connection (b).

  FIG. 4 shows a state transition diagram of the host 1 for performing service entry sequence control in the communication system shown in FIG.

  The protocol control unit 121 of the host 1 is in a standby state (700) after power-on, and receives an entry frame reception request from the host function unit 13. The protocol control unit 121 sets the communication frequency channel of the RF function unit 11 in accordance with the entry frame reception request, and transitions to the connected state (701).

  In the connected state (701), an entry frame from the terminal 2 is waited for reception, and when an entry frame is received, a connection request frame is transmitted. FIG. 5 shows a transition diagram of the transmission / reception state of the host 1 in the connected state (701). In the connected state (701), the transmission / reception state of the host 1 starts from the reception state (800). In the reception state (800), the host 1 continues to transmit unmodulated carriers.

  When the host 1 receives the entry frame in the reception state (800), it waits for the guard time Up to Down time in the guard time U2D state (801), and then transitions to the transmission state (802).

  In the transmission state (802), the host 1 transmits a connection request frame to the terminal 2 that is the transmission source of the entry frame received in the reception state (800). When the transmission of this connection request frame is completed, the host 1 waits for the guard time Down to Up time in the guard time D2U state (803), and then transitions to the reception state (800) again.

  When the host 1 receives a frame addressed to itself from the terminal 2 that is the transmission destination of the connection request frame in the reception state (800) in the connection state (701), the host 1 transits to the connection state (702), and the terminal 2 Exchange of data frames with.

  Further, in the communication system shown in FIG. 1, the state transition diagram for performing the service entry sequence control is represented in the same manner as the state transition diagram on the host 1 side shown in FIG.

  The protocol control unit 221 of the terminal 2 is in a standby state (700) after the power is turned on, and receives an entry transmission request from the terminal function unit 23. In accordance with the entry transmission request, the protocol control unit 221 sets the length of the WakeUp interval and the ratio between the Wake period in which transmission / reception operation is performed and the Sleep period in which transmission / reception operation is stopped within this WakeUp interval, and the connected state (701) Transition to.

  The connected state (701) is a state in which an entry frame is transmitted using an intermittent Wake period and reception of a connection request frame from the host is awaited. FIG. 6 shows a transition diagram of the transmission / reception state of the terminal 2 in the connected state (701). In the connected state (701), the transmission / reception state of the terminal 2 starts from the transmission state (900) (symmetric with the transmission / reception state of the host 1 starting from the reception state).

  When the terminal 2 transmits the entry frame in the transmission state (900), it waits for the guard time Up to Down time in the guard time U2D state (901), and then transitions to the reception state (902).

  When the terminal 2 receives a connection request frame addressed to itself from the host 1 in the reception state (902) of the connection state (701), the terminal 2 transits to the connection state (702). The transmission / reception state is the guard time D2U state (903), waits for the guard time Down to Up time to elapse, then transitions to the transmission state (900), and the transmission source of the connection request frame received in the reception state (902) It is possible to exchange frames with the host 1 as the destination.

  On the other hand, in the reception state (902) of the connected state (701), the terminal 2 cannot receive the frame synchronization bit by the time to receive it, or there is a bit error in the header, or in the frame addressed to itself. If any event occurs, that is, there is no connection request frame, the reception is aborted at that time, and the state transits to the sleep state (904). Also, the terminal 2 receives the frame synchronization bit by the time when it should be received, there is no bit error in the header, it is a frame addressed to itself, and there is a bit error in the data even if it is a connection request frame In addition, the state transits to the sleep state (904).

  When the timing of the next Wake period arrives, the terminal 2 exits the sleep state (904) and transmits the entry frame again in the transmission state (900).

  Here, when the terminal 2 performs an intermittent transmission / reception operation in the first service entry sequence (see FIG. 9), the terminal 2 performs an intermittent transmission / reception operation in the second service entry sequence. Compare the immediacy of the connection with the host when doing (see Figure 2). However, the frame lengths of the beacon frame, the connection request frame, and the entry frame are all 200 microseconds, and the guard intervals are 50 microseconds for both Up to Down and Down to Up.

  In the second service entry sequence shown in FIG. 2, the length of the frame reception period 505 of the terminal 2 is 200 microseconds as long as it can receive the connection request frame (in practice, a predetermined margin α is provided). 200 microseconds + α, but no margin is considered here). If the WakeUp interval 502 is 50 milliseconds, the ratio of the reception interval to the WakeUp interval is 0.4%. In a situation where the terminal 2 is not in an area where communication with the host 1 is possible and the frame synchronization bit of the connection request frame cannot be detected, the frame reception period 505 can be quickly terminated and the sleep period 507 can be extended accordingly. The above ratio can be further reduced, and power consumption can be further reduced.

  On the other hand, in the first service entry sequence shown in FIG. 9, the beacon interval length that the host can make the shortest is beacon frame length + guard interval (Down to Up) + entry frame length + guard. The interval (Up to Down) is 500 microseconds under the above-described conditions. In order to allow the terminal to receive a beacon frame at least once during the beacon reception waiting period 402 (as described above), the beacon reception waiting period 402 is 500 microseconds equal to the beacon interval. If the WakeUp interval 401 is set to 50 milliseconds in the same manner as in the second service entry sequence, the ratio of the reception interval to the WakeUp interval is 1%. Further, in order to set the ratio to 0.4% equivalent to the second service entry sequence, the transmission / reception stop period 403 must be set to 125 milliseconds, and the immediacy of the connection deteriorates.

  As described above, it can be understood that the second service entry sequence is more appropriate for an application in which a reflected wave transmission type communication system is similar to a ticket service at a ticket gate.

  The present invention has been described in detail above with reference to specific embodiments. However, it is obvious that those skilled in the art can make modifications and substitutions of the embodiment without departing from the gist of the present invention.

  In the present specification, the embodiment applied to a communication system that performs reflected wave transmission in which the transponder serves as a reflector and the reader / writer serves as a reflected wave reader has been mainly described. However, the gist of the present invention is not limited thereto. It is not something. For example, the present invention can be similarly applied to various communication systems such as an electrostatic coupling method and an electromagnetic induction method in which a transponder that does not have its own radio wave generation source performs a data transmission operation without contact with a reader / writer.

  In short, the present invention has been disclosed in the form of exemplification, and the description of the present specification should not be interpreted in a limited manner. In order to determine the gist of the present invention, the claims should be taken into consideration.

FIG. 1A is a diagram schematically showing a configuration of a host 1 in a communication system according to an embodiment of the present invention. FIG. 1B is a diagram schematically showing the configuration of the terminal 2 in the communication system according to the embodiment of the present invention. FIG. 2 is a diagram showing how frames are exchanged between a host and a terminal in a service entry sequence when an application similar to a ticket service at the ticket gate of the communication system shown in FIG. 1 is assumed. is there. FIG. 3 is a diagram showing a service entry sequence in the communication system shown in FIG. FIG. 4 is a state transition diagram of the host 1 for performing service entry sequence control in the communication system shown in FIG. FIG. 5 is a transition diagram of the transmission / reception state of the host 1 in the connected state (701). FIG. 6 is a transition diagram of the transmission / reception state of the terminal 2 in the connected state (701). FIG. 7 is a diagram showing an example of a service entry sequence performed between the host and the terminal. FIG. 8 is a diagram showing a sequence when a communication operation is started between the host and the terminal using the service entry sequence shown in FIG. FIG. 9 is a diagram illustrating a state in which a terminal intermittently performs a reception waiting operation in a reflected wave transmission system in which a terminal and a host establish a connection by the service entry sequence illustrated in FIGS. 7 to 8. FIG. 10 is a diagram showing an example of a frame format exchanged between the host 1 and the terminal 2.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Host 11 ... RF functional part 111 ... Carrier generation source 112 ... Mixer 113 ... Power amplification amplifier 114 ... Low noise amplifier 115 ... Quadrature demodulator 116 ... AGC
DESCRIPTION OF SYMBOLS 117 ... Circulator 12 ... Communication control function part 121 ... Protocol control part 122 ... Modulation function part 123 ... Demodulation function part 13 ... Host function part 14 ... Antenna 2 ... Terminal 21 ... RF function part 211 ... Antenna switch 212 ... Antenna load impedance 213: Band pass filter (BPF)
214 ... ASK detection unit 22 ... Communication control function unit 221 ... Protocol control unit 222 ... Modulation function unit 223 ... Demodulation function unit 23 ... Terminal function unit 24 ... Antenna

Claims (21)

A communication system in which a terminal having a transponder function that does not have its own radio wave generation source performs data transmission with a host having a reader / writer function,
The host transmits an unmodulated carrier until it receives any frame from the terminal in a state where it is not connected to the terminal,
In a state in which the terminal is not connected to the host, the terminal provides a Wake period in which transmission / reception operation is performed every predetermined WakeUp interval and a Sleep period in which the transmission / reception operation is stopped. In the Wake period, the terminal Attempt to send an entry frame to announce its existence,
A communication system characterized by the above. The terminal attempts to receive a frame from the host in the remaining Wake period in response to the fact that an entry frame can be transmitted using an unmodulated carrier from the host.
The communication system according to claim 1. In response to receiving an entry frame from the terminal, the host transmits a connection request frame to the terminal.
The communication system according to claim 2. When the terminal fails to receive a connection request frame from the host in the remaining Wake period after transmitting the entry frame, the terminal enters a Sleep period and stops transmission / reception operations.
The communication system according to claim 2. In a frame format exchanged between the host and the terminal, a preamble is followed by a bit for frame synchronization,
In the frame reception period after transmitting the entry frame, the terminal stops frame reception at the time when the frame synchronization bit of the connection request frame cannot be detected, and enters the Sleep period.
The communication system according to claim 4. The terminal recognizes that it can communicate with the host by receiving a connection request frame from the host in a frame reception period after transmitting an entry frame, and enters a connection state.
The communication system according to claim 3. In the connected state, a frame transmission period from the terminal and a frame transmission period from the host (frame reception period for the terminal) are alternately provided,
The host transmits an unmodulated carrier in a frame transmission period by the terminal after transmitting a frame by itself, and the terminal performs frame transmission using the unmodulated carrier.
The communication system according to claim 6. The host performs unmodulated wave carrier transmission for the terminal to transmit a frame after transmitting a connection request frame in response to receiving the entry frame.
The communication system according to claim 7. In response to receiving a frame other than an entry frame from the terminal, the host determines that the terminal is in a connected state, and transmits and receives frames.
The communication system according to claim 7. A communication device that operates as a host having a reader / writer function and performs data transmission with a terminal having a transponder function that does not have a radio wave generation source.
Transmitting means for performing transmission processing of a frame composed of a modulated signal to the terminal;
A receiving means for transmitting a non-modulated carrier and for receiving a frame transmitted by the terminal using the non-modulated carrier;
Protocol control means for controlling operations related to connection and frame exchange with the terminal in response to a request from an upper layer protocol,
The protocol control means transitions between a standby state, a connected state in which an unmodulated carrier is sent and an entry frame is received from the terminal, and a connection state in which data frames can be exchanged with the terminal. Control,
A communication device. The protocol control means transmits a connection request frame to the terminal in response to receiving an entry frame from the terminal in the connected state.
The communication apparatus according to claim 10. The protocol control means transmits a connection request frame to the terminal in the connected state, then sends an unmodulated carrier and waits to receive a frame from the terminal.
The communication device according to claim 11. The protocol control means shifts to the connected state in response to receiving a frame from the terminal that is a transmission destination of a connection request frame in the connected state.
The communication device according to claim 12. In the connected state, the protocol control means alternately provides a frame transmission period from the terminal and a frame transmission period from the host (frame reception period for the terminal), and the terminal after transmitting the frame itself Transmit unmodulated carrier in the frame transmission period by
The communication apparatus according to claim 10. A communication method for performing data transmission with a terminal having a transponder function that operates as a host having a reader / writer function and does not have a radio wave generation source.
Sending an unmodulated carrier and waiting to receive an entry frame from the terminal;
In response to receiving an entry frame from the terminal, transmitting a connection request frame to the terminal;
After transmitting a connection request frame, sending a non-modulated carrier and waiting to receive a frame from the terminal;
In response to receiving a frame from the terminal that is a transmission destination of a connection request frame, the step of entering a connection state capable of exchanging data frames with the terminal,
In the connected state, a frame transmission period from the terminal and a frame transmission period from the host (frame reception period for the terminal) are alternately provided, and there is no frame transmission period by the terminal after transmitting the frame itself. Send modulated carrier,
A communication method characterized by the above. A communication device that operates as a terminal having a transponder function that does not have a radio wave source by itself and performs data transmission with a host having a reader / writer function,
Transmission means for performing frame transmission processing using an unmodulated carrier from the host;
Receiving means for receiving a frame composed of a modulated signal transmitted from the host;
Protocol control means for controlling connection with the host and frame exchange in response to a request from an upper layer protocol,
The protocol control means includes a standby state, a wake period during which transmission / reception operations are performed every predetermined WakeUp interval, and a connection state during which intermittent transmission / reception operations are performed with a sleep period during which transmission / reception operations are stopped, Control transitions between connection states where frames can be exchanged,
A communication device. In the connected state, the protocol control means waits for reception of a connection request frame from the host after attempting to transmit an entry frame in a Wake period.
The communication apparatus according to claim 16. The protocol control means shifts to the connection state in response to receiving a connection request frame from the host after transmitting an entry frame in the Wake period in the connection state.
The communication device according to claim 17. The protocol control means alternately provides a frame transmission period from the terminal and a frame transmission period from the host (frame reception period for the terminal) in the connected state.
The communication apparatus according to claim 16. The protocol control means enters a sleep period when the connection request frame is not successfully received in the period of waiting to receive a connection request frame from the host after transmitting an entry frame in the connected state. ,
The communication device according to claim 17. A communication method for operating as a terminal having a transponder function that does not have a radio wave source and performing data transmission with a host having a reader / writer function, and transmitting and receiving at every predetermined WakeUp interval When performing a intermittent transmission / reception operation by providing a wake period for performing the transmission and a Sleep period for stopping the transmission / reception operation,
Waiting to receive a connection request frame from the host after attempting to transmit an entry frame in the Wake period;
After transmitting the entry frame, in response to receiving a connection request frame from the host, transitioning to a connection state in which data frames can be exchanged with the host;
A step of entering a sleep period when a connection request frame is not successfully received in a period of waiting to receive a connection request frame from the host after transmitting an entry frame;
A communication method comprising:

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