Automatic wake-up device for radio automatic recognition terminal and communication method using the terminal

An automatic wake-up device for a radio automatic recognition terminal mounted in a vehicle and a communication method using the terminal are provided in an electronic toll collecting system. The terminal wakes up in response to various modes of automatically waking up the terminal included in the vehicle. The automatic wake-up device includes a circuit responding to a first mode which transmits a wake-up signal having a frequency different from a communication frequency to a wake-up zone when the wake-up zone and communication zone are separately located, and the circuit responds to a second mode which alternately transmits data for communication and data for waking-up the terminal to the communication zone so as to wake up the vehicle terminal without differentiating between the communication zone and the wake-up zone.

CLAIM OF PRIORITY
 This application makes reference to, incorporates the same herein, and
 claims all benefits accruing 35 U.S.C..sctn.119 from an application
 entitled AUTOMATIC WAKE-UP DEVICE OF RADIO AUTOMATIC RECOGNITION TERMINAL
 AND COMMUNICATION METHOD USING THE TERMINAL earlier filed in the Korean
 Industrial Property Office on Aug. 31, 1997, and there duly assigned Ser.
 No.97-45398 by that Office.
 BACKGROUND OF THE INVENTION
 1. Technical Field
 The present invention relates to an automatic wake-up device for a radio
 automatic recognition terminal and a communication method using the
 terminal. More particularly, the invention relates to an automatic wake-up
 device for a radio automatic recognition terminal and a communication
 method using the terminal, in which the radio automatic recognition
 terminal wakes up in response to various modes of waking up a terminal
 included in a vehicle in an electronic toll collection system.
 2. Related Art
 Recently, there has been proposed an electronic toll collection system
 (ETCS) which reduces the number of men and the time required for
 collecting tolls on a highway in order to smooth the flow of vehicle
 traffic.
 Typically, an ETCS employs a communication beacon which transmits a radio
 signal to a communication zone through which a vehicle must pass. The
 vehicle includes a radio automatic recognition terminal which responds to
 a polling signal transmitted via the communication beacon as the vehicle
 passes through the communication zone so that a corresponding toll is
 automatically collected.
 Most vehicle terminals include batteries which operate in a sleep mode at
 ordinary times, that is, when the vehicle is not near a toll station. The
 vehicle terminal is awakened when the vehicle approaches the communication
 beacon and then returns to the sleep mode after communicating with the
 communication beacon.
 Two different wake-up arrangements are utilized in such systems. In a first
 arrangement, a wake-up beacon is disposed separate from the communication
 beacon, and the two beacons transmit on different frequencies. Such an
 arrangement has the disadvantage that, if the vehicle stops at the
 boundary between the wake-up zone and the communication zone for an
 extended period of time (such as due to a traffic jam), communication is
 disabled between the terminal and the beacon, and the vehicle terminal
 returns to the sleep mode.
 A second arrangement does not employ separate beacons, but rather
 communication data and wake-up data are separately and distinctly encoded
 and transmitted from the same beacon. However, such an arrangement has the
 disadvantage that, when vehicles are traveling at high speed and the
 communication zone is too wide, a large number of vehicle terminals can be
 in the communication zone at the same time, and this disturbs normal
 communication.
 Therefore, there is a need for the development of an automatic wake-up
 device for a radio automatic recognition terminal and related
 communication method that eliminate the problems stated above.
 SUMMARY OF THE INVENTION
 Accordingly, the present invention is directed to an automatic wake-up
 device for a radio automatic recognition terminal and a communication
 method using the terminal that substantially obviate one or more of the
 problems, limitations and disadvantages set forth above.
 An object of the present invention is to provide an automatic wake-up
 device for a radio automatic recognition terminal and a communication
 method using the terminal, in which a vehicle terminal in the normal mode
 can wake up in response to either of the two waking-up methods described
 herein, and in which a vehicle terminal in the sleep mode can wake up
 again after passing a wake-up zone.
 To accomplish the object of the present invention, there is provided an
 automatic wake-up device for a radio automatic recognition terminal,
 comprising: an antenna for picking up a radio signal; a band pass filter
 for filtering the radio signal picked up by the antenna to obtain a signal
 having a frequency corresponding to the frequency band of a wake-up
 signal; a first low pass filter for smoothing the signal which passed the
 band pass filter so as to generate an average DC level; a first comparator
 for comparing the signal level obtained by the first low pass filter with
 a predetermined reference level to determine if it is the wake-up signal,
 and for generating a corresponding result; a second low pass filter for
 detecting the DC level of data for waking-up, as amplified by the antenna;
 a second comparator for comparing the DC level of data for waking-up
 detected by the second low pass filter with a predetermined reference
 level to determine if it is the wake-up signal; a CPU for controlling the
 overall operation of a vehicle terminal, the CPU being normally in a sleep
 mode; a wake-up controller for waking up the CPU when the first comparator
 or the second comparator detects the normal wake-up signal; and a power
 switch which is turned on under the control of the CPU after waking-up of
 the CPU to provide power to other portions of the vehicle terminal.
 To accomplish the objects of the invention, there is also provided a
 communication method using a radio automatic recognition terminal. In
 accordance therewith, a communication zone is located in a predetermined
 area of a lane, and a polling signal is transmitted to the communication
 zone to process a radio signal related to toll collection when a radio
 automatic recognition terminal included in a vehicle passing through the
 communication zone responds to the polling signal. Toll collection is then
 performed. The method comprises the steps of waiting for a predetermined
 period of time after the transmission of the polling signal, and then
 transmitting a radio signal to wake up the terminal for a predetermined
 period of time when the radio automatic recognition terminal does not
 respond to the polling signal within the waiting time.
 It is to be understood that both the foregoing general description and the
 following detailed description are exemplary and explanatory and are
 intended to provide further explanation of the invention as claimed.

DETAILED DESCRIPTION OF THE INVENTION
 Reference will now be made in detail to the preferred embodiments of the
 present invention, examples of which are illustrated in the accompanying
 drawings.
 FIG. 1 roughly illustrates the configuration of a lane-side device for an
 ETCS. Referring to FIG. 1, a gantry 1 is placed over a lane 4, and has
 communication beacon 2 which transmits a radio signal to a specific zone
 (referred to hereinafter as communication zone 5) of lane 4. A vehicle
 includes a radio automatic recognition terminal (referred to hereinafter
 as a vehicle terminal) which radio-communicates with communication beacon
 2. With communication beacon 2 transmitting a polling signal to
 communication zone 5 in a predetermined cycle, the vehicle responds to
 this polling signal when it passes through communication zone 5 so that a
 corresponding toll is automatically collected.
 Communication beacon 2 is directed only toward a predetermined point. Thus,
 vehicle terminals which include batteries operate in the sleep mode at
 ordinary times, but wake when they are close to communication beacon 2,
 and then return to the sleep mode after communicating with communication
 beacon 2, thereby reducing consumption of battery power. A wake-up beacon
 3 is disposed on gantry 1 separate from communication beacon 2 to transmit
 a wake-up signal, having a frequency different from that of the
 communication signal, to a wake-up zone 6 in front of communication zone
 5, thereby waking up the vehicle terminal before it reaches communication
 zone 5. With this wake-up method, however, the vehicle terminal returns to
 the sleep mode when the vehicle stops at the boundary between the wake-up
 zone and communication zone for an extended period of time (e.g., due to
 traffic jam), thereby disabling communication between the vehicle terminal
 and the communication beacon. Furthermore, communication is not possible
 when the transmission antenna of the wake-up beacon is out of order.
 There is another method of waking up a vehicle terminal without using a
 separate wake-up beacon and establishing a wake-up zone. Under that
 method, data for communication and data for waking-up are encoded
 differently and are transmitted from the same communication beacon to the
 communication zone. With a system such as the ETCS performing radio
 communication with vehicles traveling at high speed, when the
 communication zone is too wide, there are a lot of vehicle terminals in
 the communication zone, and this disturbs normal communication. To prevent
 this, the communication zone is limited to approximately five square
 meters. This reduces the time, exclusive of time for waking up, required
 to carry out communication for toll collection. In terms of the vehicle
 terminal, a wake-up device which responds to only one of the above two
 methods does not wake up in a system employing the other method, being
 disabled in communication.
 FIG. 2 is a block diagram of an automatic wake-up device for a radio
 automatic recognition terminal according to the present invention.
 Referring to FIG. 2, the automatic wake-up device for a radio automatic
 recognition terminal according to the present invention includes a circuit
 responsive to a mode (referred to hereinafter as the first mode) which
 transmits a wake-up signal, with a frequency different from a
 communication frequency, to a wake-up zone when the wake-up zone and
 communication zone are separately located, and a circuit responsive to
 another mode (referred to hereinafter as the second mode) which
 alternately transmits data for communication and data for waking-up to the
 communication zone to wake up the vehicle terminal without differentiating
 the communication zone and the wake-up zone from each other.
 The circuit responsive to the first mode includes: an antenna 10 for
 picking up a radio signal; an amplifier 12 for amplifying the radio signal
 to a level where the signal can be processed; a band pass filter 14 for
 filtering the radio signal amplified by amplifier 12 to obtain a signal
 having a frequency corresponding to the frequency band of the wake-up
 signal; a low pass filter 16 for smoothing the signal which has passed
 band pass filter 14 to generate an average direct current (DC) level; a
 first comparator 18 for comparing the average DC level of the signal from
 filter 16 with a predetermined reference level (Vref1) to determine if the
 signal is a wake-up signal, and for generating a corresponding result; a
 CPU 26, which stands by in sleep mode at ordinary times, and which
 controls the overall operation of the vehicle terminal; a wake-up
 controller 24 for waking up CPU 26 when first comparator 18 detects the
 normal wake-up signal; and a power switch (not shown) which is turned on
 under the control of CPU 26 after the CPU 26 wakes up to provide power to
 other portions of the vehicle terminal. The circuit responding to the
 second mode includes: a low pass filter 20 for filtering the signal picked
 up by antenna 10 and amplified by amplifier 12 to detect the DC level of
 data for waking-up; a second comparator 22 for comparing the DC level of
 the data for waking-up detected by low pass filter 20 with a predetermined
 reference level (Vref2) to determine if it is the wake-up signal; wake-up
 controller 24; CPU 26; and a power switch (not shown).
 The operation of the automatic wake-up device of the radio automatic
 recognition terminal and the communication method using the terminal
 according to the present invention will now be explained. FIG. 3 is a flow
 diagram showing a communication method using the radio automatic
 recognition terminal according to the present invention. In the first
 mode, in which a wake-up signal having a wake-up frequency different from
 the communication frequency is transmitted to wake up the vehicle
 terminal, wake-up beacon 3 continuously transmits a wake-up signal coded
 to have a specific duty ratio to wake-up zone 6. When a vehicle arrives in
 wake-up zone 6, antenna 10 of its terminal picks up the wake-up signal
 transmitted from wake-up beacon 3. This signal is then amplified to a
 predetermined level by amplifier 12. The amplified signal includes
 communication signals and noise, as well as the wake-up signal. Band pass
 filter 14 filters the amplified signal to obtain a signal corresponding to
 the frequency component of the wake-up signal. Thereafter, low pass filter
 16 integrates the wake-up signal to generate the average DC level which is
 compared with the predetermined reference level (Vref1) by first
 comparator 18 in order to determine if it is the wake-up signal. When it
 is, wake-up controller 24 controls CPU 26, which has been standing by in
 sleep mode, and the power switch (not shown) to provide power to the
 communication circuit and display circuit of the vehicle terminal,
 allowing communication to be performed in communication zone 5.
 In the case of the second mode, the vehicle terminal wakes up only when the
 vehicle reaches communication zone 5. With the first mode, when the
 vehicle stops at the boundary between wake-up zone 6 and communication
 zone 5 for a long period of time, the vehicle terminal may return to the
 sleep mode. Even in this case, the vehicle terminal can wake up if the
 vehicle arrives in communication zone 5. This is described below in more
 detail with reference to FIG. 3.
 Communication beacon 2 polls the vehicle in communication zone 5 at step
 S10, waits for response from the vehicle terminal for a predetermined
 period of time t1 at step S12, and then determines whether there is a
 response from the terminal at step S14. The vehicle terminal cannot
 respond to the communication beacon at step S14 if it does not wake up. In
 this case, communication beacon 2 transmits data for waking-up to
 communication zone 5 for a predetermined period of time t2 to wake up the
 vehicle terminal in step S16, and then returns to step S10. When the
 vehicle terminal is already in the wake-up state so that it can respond at
 step S14, communication is performed through steps S18 and S20 to collect
 the toll.
 It will be apparent to those skilled in the art that various modifications
 and variations can be made in the automatic wake-up device of a radio
 automatic recognition terminal and communication method using the terminal
 of the present invention without departing from the spirit or scope of the
 invention. For example, the device of the present invention can be used in
 a system for providing traffic information as well as ETCS.
 According to the present invention, the vehicle terminal in sleep mode can
 wake up in response to various wake-up methods. Furthermore, it is
 possible to wake up the vehicle terminal which returns to the sleep mode
 after passing the wake-up zone.