JPH11312285A - Emergency emergency call system capable of simultaneous data / voice communication or communication switching - Google Patents

Abstract

(57) [Summary] [Problem] To provide an accident emergency notification system that can inform an emergency rescue center of detailed accident contents. SOLUTION: When an emergency occurs in a vehicle due to an accident or the like, first, position information and accident information of the own vehicle by first wireless transmission means 33, and vehicle ID, occupant ID information and the like stored in advance. The emergency information is transmitted to the emergency rescue center by wireless data communication, and when the data communication is completed, the second wireless transmission means 35 automatically switches to voice communication to inform the emergency rescue center of the details of the accident. .

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an accident emergency reporting system, and more particularly to a system for transmitting emergency information by data communication.
It is configured to perform voice communication by automatic switching or to enable simultaneous data / voice communication.

[0002]

2. Description of the Related Art Conventionally, an emergency notification system capable of transmitting the occurrence of an abnormality to the outside together with the position of the vehicle even when the driver becomes unable to communicate with the outside due to an accident of a vehicle such as an automobile or the like is known. This is disclosed in Japanese Unexamined Patent Publication No. 9-198592. According to this, a self-position is measured every predetermined time by using a navigation system that measures the self-position based on the position information from the GPS, and the measured value and the measurement time are stored in the storage means. An abnormality occurrence message created based on the latest measurement value and measurement time stored in the storage means when detected by the abnormality detection means is transmitted to a predetermined receiving device via a wireless public telephone line. ing.

This system is capable of accurately informing the details of an accident by simply communicating the latest abnormality occurrence message created based on the self-location data and the time data in which the self-location is stored to a predetermined report destination. There was a problem that it was not possible.

[0004]

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to solve the above-mentioned problems, and when an emergency occurs in a vehicle due to an accident or the like, first, the position information of the own vehicle and the accident information, and furthermore, Emergency information such as vehicle ID and occupant ID information stored in advance is transmitted to the emergency rescue center by wireless data communication and automatically switched to voice communication at the end of the data communication, or simultaneous data / voice communication means is used. do it,
It is an object of the present invention to provide an accident emergency notification system that can notify an emergency rescue center of detailed accident contents.

[0005]

An accident emergency notification system according to the present invention comprises: an accident detecting means for detecting an accident of the own vehicle by a sensor such as a gravitational acceleration or an inclination of the own vehicle; Own vehicle position specifying means for specifying the position of the own vehicle from the information; the above-mentioned own vehicle position information and accident information;
A vehicle having at least wireless communication means for wirelessly communicating emergency information such as D information to an emergency rescue center to be described later, or data / voice simultaneous transmission means capable of simultaneously transmitting data and voice; And an emergency rescue center for requesting the dispatch of an emergency vehicle to the place where the vehicle is located based on the contents thereof. First wireless transmission means for transmitting emergency information to the emergency rescue center by data communication, and automatic switching at the end of data communication by the first wireless transmission means enables voice communication from the vehicle to the emergency rescue center. It is characterized by having at least a second wireless transmission means.

[0006] Further, the data communication and the voice communication can be performed simultaneously in parallel by providing data / voice simultaneous transmission means.

With this configuration, first, emergency information is transmitted by wireless data communication, and then automatic switching to voice communication or simultaneous data / voice communication is performed, so that detailed accident details can be accurately notified. The emergency information can be transmitted to the emergency rescue center by data communication even in the worst case, so that a quicker and more accurate rescue and support system can be established.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to an accident detecting means for detecting an accident of the own vehicle by a sensor such as a gravitational acceleration or an inclination of the own vehicle, and a GPS, gyro, vehicle speed sensor and the like. Own-vehicle position specifying means for specifying the position of the own vehicle from the sense information; emergency rescue described later; emergency information such as the above-mentioned own vehicle position information and accident information; and prestored vehicle ID and occupant ID information. A vehicle having at least wireless communication means for wirelessly communicating with a center or data / voice simultaneous transmission means capable of simultaneously transmitting data and voice; And an emergency rescue center for requesting the dispatch of an emergency vehicle to the location where the emergency rescue center is located. A first wireless transmission means for transmitting emergency information in the data communication to the printer, the enabling voice communication to the emergency rescue center from the vehicle by the automatic switching at the first end by the wireless transmission unit data communication 2
This is an accident emergency notification system characterized by having at least a wireless transmission means, which can accurately inform the details of the accident and transmit emergency information by data communication to the emergency rescue center even in the worst case It has the effect of being able to do so.

According to a second aspect of the present invention, there is provided an accident emergency notification system according to the first aspect, wherein the line is controlled under the initiative of the emergency rescue center during data communication and voice communication. This has the effect that the emergency rescue center can take the initiative in disconnecting the line so that the emergency notification device does not disconnect the connected line.

[0010] The invention according to claim 3 is the second invention.
If a new high-priority data communication request occurs during voice communication by the wireless transmission means, the voice communication by the second wireless transmission means is interrupted, and data communication by the first wireless transmission means is enabled. The accident emergency notification system according to claim 1, characterized in that, even after switching to voice communication, switching to data communication can be performed again for a newly invited situation. Has the effect of being able to.

The invention according to claim 4 is the data / voice simultaneous communication means, wherein frequency division multiplexing, time division multiplexing, or space division multiplexing (spread spectrum method) is used to simultaneously perform voice communication during data communication. The accident emergency notification system according to claim 1, wherein the communication is configured to be transmitted so that when switching from data communication to voice communication, voice communication can be started quickly by a driver's will. It has the action of:

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a schematic configuration of an accident emergency notification system according to each embodiment of the present invention. In FIG. 1, the accident emergency notification system has at least GP
The vehicle 1 equipped with the emergency notification device which obtains and records the position information of the own vehicle from S and can notify the emergency rescue center 2 via a network (base station, switching network) when an accident occurs. I have. The emergency rescue center 2 grasps the situation of the accident on the basis of the report from the vehicle 1, arranges a hospital, requests the nearest police station and fire department to dispatch an emergency vehicle to the site, and requests post-processing. Further, since the emergency rescue center 2 provides an emergency rescue service by contract with the vehicle owner, at least data communication for confirming the safety of the vehicle 2 with respect to the vehicle 2 is automatically performed by data communication. I have.

FIG. 2 shows an outline of the configuration of a vehicle equipped with an emergency notification device. In FIG. 2, an accident detecting means 21 for detecting an accident of the own vehicle by a sensor such as a gravitational acceleration or an inclination of the own vehicle, and an own vehicle position specifying device for specifying the position of the own vehicle from sense information of a GPS, a gyro, a vehicle speed sensor, and the like. Means22
Wireless communication means 23 for wirelessly communicating the above-mentioned position information and accident information of the own vehicle, and emergency information such as vehicle ID and occupant ID information stored in advance to the emergency rescue center.
Or, it comprises a data / voice simultaneous communication means 27, a storage means 24 including ROM and RAM, a CPU 25, and a power supply 26.

(First Embodiment) The first embodiment of the present invention will be described with reference to the configuration of a vehicle equipped with the above-mentioned accident emergency notification system and emergency notification device. As shown in FIG.
And a normal mobile phone unit (mobile phone main body unit related to transmission and reception excluding the transmitting / receiving unit and the antenna unit) 32. Further, the mobile phone unit 32 is connected to a modem 34 via a changeover switch (described later). Wireless transmission means for connecting
33 and a second wireless transmission means 35 for connecting to a handset (or hands-free) 36 via a changeover switch (described later). Note that, in FIG. 3, a dotted line indicates that the emergency notification device is controlled by the CPU.

FIG. 4 shows the configuration of the emergency notification device according to the first embodiment of the present invention and the configuration of the above-mentioned wireless communication means in more detail. In FIG. 4, a changeover switch portion and a modem portion of the wireless communication means are included in the emergency notification device, but the other portions are provided outside the emergency notification device. And the emergency call device has a CP
U41, Flash ROM42, RAM43, Gyro sensor
44, a GPS receiver 45, a rollover sensor 46, a power supply unit 47, a modem 48, a changeover switch 49, and an echo canceller 50 are provided. Further, the CPU 41 receives ON / OFF information of a key switch, information of a crash sensor, information of a speed sensor, and the like.

FIG. 5 shows a schematic configuration of an emergency rescue center according to an embodiment of the present invention. The emergency rescue center includes a communication means 51, a communication control means 52, and a database.
53 and a display / communication means 54 are provided, and the communication control means 52 can exchange data with the database 53 and the display / communication means 54 via the LAN.
The communication unit 51 includes an exchange, and is connected to and controlled by the communication control unit 52 via a link. The database 53 stores and holds customer management data, map data, emergency call data, and the like for the owner of the vehicle.

The communication means (switch) 51 is connected to the vehicle via a public wired line, a public wireless line, or the like provided by a common carrier, and is capable of receiving emergency information from the vehicle. The communication control means 52 decodes the emergency information at the time of receiving the emergency information from the vehicle, and decodes the time information / position data, the accident information, and the vehicle ID stored in advance.
The occupant ID information and the like are taken out, the occurrence of the accident is notified to the display / call means 54 where the operator is present, and the map data taken out from the database 53 is subjected to map matching and displayed on the display / call means 54. The operator can form a quick emergency support system, such as requesting the dispatch of an emergency car or arranging an emergency hospital, by looking at the displayed content of the accident.

Next, the operation of the accident emergency notification system according to the first embodiment of the present invention will be described.

The vehicle position specifying means 22 shown in FIG. 2 periodically obtains position information from the GPS at the GPS receiver 45 as shown in FIG.
It is stored in the flash ROM 42 in the emergency call device. FIG.
The accident detection means 21 detects the occurrence of an accident by detecting the occurrence of an accident by the operation of a crash sensor due to the gravitational acceleration applied to the vehicle 1 or the rollover sensor 46 sensing an unnecessary inclination of the vehicle 1. To the CPU 41 of the emergency notification device and flash ROM
Store in 42.

C of the emergency notification device that has been notified of the occurrence of the accident
The PU 41 operates the first wireless transmission means 33 of FIG. 3 to store information regarding the accident in the flash ROM 42, that is, the position information of the vehicle 1, the time information, the sense information indicating the details of the accident from various sensors, and furthermore, Is the flash ROM 42 in advance.
And read out the vehicle ID, occupant ID information, etc. at the same time, set a predetermined transmission format,
49 is switched to the modem side to connect the cellular phone unit and the modem 48, and the data is transmitted to the emergency rescue center 2 as emergency information via the antenna TEL via the public line to the emergency rescue center 2.

When the communication control means 52 of the emergency rescue center 2 detects the end of the data transmission of the emergency information in the data communication format, an ACK indicating that the vehicle 1 has received the data is received.
Will be returned. Thus, the CPU of the emergency notification device of the vehicle 1
41 operates the second wireless transmission means 35 of FIG. 3 to automatically switch the changeover switch 49 to the handset or hands-free, and connects the mobile phone unit to the handset or hands-free to start voice communication. .

Thus, it is possible to make a voice communication between the occupant in the vehicle and the operator present at the display / communication means 54 of the emergency rescue center 2 by voice communication.

The above communication sequence can be represented as shown in FIG.

During the voice communication in the voice communication format, if a state to perform data communication is detected due to the occurrence of a new high priority situation, the CPU 41 of the emergency notification device
Can operate the first wireless transmission means 33 again to transmit the emergency information again in the data communication format.

In the emergency rescue center 2, the emergency information transmitted in the data communication format is received by the communication control means 52 for controlling the exchange via the exchange as the communication means 51. Communication control means
The control unit 52 first decodes the emergency information transmitted in the data communication format, specifies the content of the accident, and controls the communication control unit 52 to control the disconnection of the line. Thereafter, the present position and time of the vehicle in which the accident occurred, the operation status of the accident sensor, the vehicle ID, the occupant ID, and the like are decoded, and the results are displayed on the map data from the database 53 while map matching is performed. To be displayed.

Next, the end of the data communication format is detected by the communication control means 52, and the emergency rescue center sends the AC to the vehicle.
K is returned. This ACK is detected by the CPU 41 on the vehicle side, and the vehicle side operates the second wireless transmission means 35 to automatically switch to voice communication. On the emergency rescue center side, the communication means 51 switches to an extension and conducts a voice communication type call with the occupant of the vehicle using the operator telephone. Since voice communication can be automatically performed with the occupant of the vehicle, the accident situation can be complemented, and the accident situation can be grasped more accurately.

The operator of the emergency rescue center who has grasped the accident situation as described above looks at the contents displayed on the display / communication means 54, and places the vehicle in the place where the vehicle is located via the communication means 51. Request the dispatch of emergency vehicles such as emergency and ambulance vehicles, and also prevent the occurrence of secondary disasters and arrange hospitals.

(Second Embodiment) A second embodiment of the present invention will be described below with reference to the drawings. The configuration of the accident emergency notification system, the vehicle equipped with the emergency notification device, and the emergency rescue center has already been described, and will not be described again here. The description of the same configuration as that of the first embodiment is omitted.

As shown in FIG. 7, the simultaneous data / voice communication means comprises an antenna 31 and a normal portable telephone unit (a portable telephone main body unit for transmission and reception excluding the transmitting / receiving unit and the antenna unit).
The mobile phone unit 32 is connected to a speed conversion / command processing unit 38 via a data / voice simultaneous transmission unit 37, and is connected to a data / voice simultaneous transmission unit.
A handset (or hands-free) 36 can be connected via 37.

Although there are various methods for realizing simultaneous data / voice communication, some examples will be briefly described.
A first technique is a frequency division multiplexing method. This method is further divided into (a) the DTMF method and (b) the FSK method. (A) In the DTMF method, a DTMF (Dual Tone Mu) is transmitted during a normal voice transmission mode.
lti-Frequency) to superimpose data transmission at low speed. On the other hand, (b) the FSK method superimposes low-speed data transmission by FSK (Frequency Shift Keying) during a normal voice transmission mode.

Next, as a second method, there is a time division multiplexing method. This method is used, for example, as a data transmission rate.
This is realized by using a line that can transmit 9600 bits data divided into 4800 bits each for data and voice. In this case, needless to say, a CODEC (encoder / decoder) having a low bit rate of about 4.8 kb / s is required for voice transmission. In addition, voice calls are generally about 1 /
Since only 3 is occupied, the remaining about 2/3 has a silence period, so data transmission can be performed during that period. However, since the silence period is not constant, the speed of flow control etc. It is necessary to perform a matching process. For this purpose, it is necessary to provide a silence detecting unit in a voice part, and to provide a speed matching / command processing unit in a data transmission unit.

As a third method, there is a space division multiplexing (spread spectrum method) method. This system is usually already realized by the mobile phone system as the CDMA system, and the transmission band can be dramatically improved, so that not only data / voice but also image data can be transmitted. .

The above-mentioned "command processing" generally refers to the control of the MODEM operation mode, such as the transmission speed of an AT command and the like, the error detection and correction method, the flow control method, etc., mounted on the MODEM. This process is a well-known process.

FIG. 8 shows in more detail the configuration of the emergency notification device according to the second embodiment of the present invention and the configuration of the data / voice simultaneous communication means described above. In FIG. 8, the data / voice simultaneous transmission means, the changeover switch, and the speed conversion / command processing unit are included in the emergency notification device, but the other components are provided outside the emergency notification device. The emergency notification device includes a CPU 41, a flash ROM 42, a RAM 43, a gyro sensor 44, a GPS receiver 45, a rollover sensor 46, a power supply unit 47, an echo canceller 50, a data / voice simultaneous transmission unit 55, a speed conversion /
A command processing unit 56 is provided. Further, the CPU 41 receives ON / OFF information of a key switch, information of a crash sensor, information of a speed sensor, and the like.

Next, the operation of the accident emergency notification system according to the second embodiment of the present invention will be described.

The own-vehicle position specifying means 22 shown in FIG. 2 periodically obtains position information from the GPS at the GPS receiver 45 as shown in FIG.
It is stored in the flash ROM 42 in the emergency call device. FIG.
The accident detection means 21 detects the occurrence of an accident by detecting the occurrence of an accident by the operation of a crash sensor due to the gravitational acceleration applied to the vehicle 1 or the rollover sensor 46 sensing an unnecessary inclination of the vehicle 1. To the CPU 41 of the emergency notification device and flash ROM
Store in 42.

C of the emergency notification device that has been notified of the occurrence of the accident
The PU 41 operates the speed conversion / command processing unit 38 shown in FIG.
That is, the position information of the vehicle 1, the time information, the sense information indicating the details of the accident from various sensors, and the flash R
The mobile phone unit and the speed conversion / command processing unit 38 are connected at the same time as reading out the vehicle ID, the occupant ID information, etc. stored in the OM 42, and the emergency rescue center 2 is sent as emergency information via the public line via the antenna TEL. It is transmitted in the data communication format to the user.

When the communication control means 52 of the emergency rescue center 2 detects the end of the data transmission of the emergency information in the data communication format, an ACK indicating that the vehicle 1 has received the data is received.
Will be returned. Thus, the CPU of the emergency notification device of the vehicle 1
Reference numeral 41 automatically switches to the handset or hands-free of FIG. 7 and starts the voice communication by connecting the mobile phone unit to the handset or hands-free.

Thus, a voice communication between the occupant in the vehicle and the operator present at the display / communication means 54 of the emergency rescue center 2 can be made.

If the above communication sequence is shown, it can be represented as shown in FIG.

During the voice communication in the voice communication format, if a state to perform data communication is detected due to the occurrence of a new high priority situation, the CPU 41 of the emergency notification device
Can operate the speed conversion / command processing unit 38 to transmit the emergency information again in the data communication format.

In the emergency rescue center 2, the emergency information transmitted in the data communication format is received by the communication control means 52 for controlling the exchange via the exchange as the communication means 51. Communication control means
The control unit 52 first decodes the emergency information transmitted in the data communication format, specifies the content of the accident, and controls the communication control unit 52 to control the disconnection of the line. Thereafter, the present position and time of the vehicle in which the accident occurred, the operation status of the accident sensor, the vehicle ID, the occupant ID, and the like are decoded, and the results are displayed on the map data from the database 53 while map matching is performed. To be displayed.

Next, the end of the data communication format is detected by the communication control means 52, and the AC is sent from the emergency rescue center to the vehicle.
K is returned. This ACK is detected by the CPU 41 on the vehicle side, and the vehicle side operates the second wireless transmission means 35 to automatically switch to voice communication. On the emergency rescue center side, the communication means 51 switches to an extension and conducts a voice communication type call with the occupant of the vehicle using the operator telephone. Since voice communication can be automatically performed with the occupant of the vehicle, the accident situation can be complemented, and the accident situation can be grasped more accurately.

The operator of the emergency rescue center, having grasped the accident situation as described above, looks at the contents displayed on the display / communication means 54, and places the vehicle in the place where the vehicle is located via the communication means 51. Requests to dispatch emergency vehicles such as emergency and ambulances, as well as preventing the occurrence of secondary disasters and arranging hospitals.

In the above-described first and second embodiments, the wireless information for wirelessly communicating the emergency information such as the vehicle ID and the occupant ID information stored in advance shown in FIG. Although the communication means 23 and the data / voice simultaneous communication means 27 are described as being provided alternatively, the above two communication means may be provided at the same time, and either of them may be freely selected by changing the mode.

[0047]

As described above, according to the accident emergency notification system of the present invention, it is possible to accurately inform the details of the accident and to transmit emergency information by data communication to the emergency rescue center even in the worst case. There is an effect of getting.

Further, according to the accident emergency notification system of the present invention, even after switching to voice communication, there is an effect that switching to data communication can be performed again for a newly invited situation.

Further, according to the accident emergency notification system of the present invention, since data communication and voice communication can be performed simultaneously, it is possible to quickly respond to a newly introduced situation by voice communication. is there.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a schematic configuration of an accident emergency notification system according to each embodiment of the present invention;

FIG. 2 is a block diagram showing an outline of a configuration of a vehicle equipped with the emergency notification device according to each embodiment of the present invention;

FIG. 3 is a block diagram showing a configuration of a wireless communication unit according to the first embodiment of the present invention;

FIG. 4 is a configuration block diagram showing the configuration of the emergency notification device and the configuration of the wireless communication unit according to the first embodiment of the present invention in more detail;

FIG. 5 is a block diagram showing a schematic configuration of an emergency rescue center according to each embodiment of the present invention;

FIG. 6 is a diagram showing a communication sequence between the emergency notification device and the emergency rescue center according to each embodiment of the present invention;

FIG. 7 is a block diagram showing a configuration of a data / voice simultaneous communication unit according to a second embodiment of the present invention;

FIG. 8 is a block diagram showing a configuration of an emergency notification device and a configuration of a data / voice simultaneous communication unit according to a second embodiment of the present invention in more detail.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Vehicle equipped with emergency notification device 2 Emergency rescue center 21 Accident detection means 22 Own vehicle position specifying means 23 Wireless communication means 24 Storage means 25, 41 CPU 26 Power supply 27 Data / voice simultaneous communication means 31 ANT 32 Mobile phone unit 33 1 wireless transmission means 34, 48 modem 35 second wireless transmission means 36 handset / hands-free 37, 55 simultaneous data / voice transmission means 38, 56 speed conversion / command processing unit 42 flash ROM 43 RAM 44 gyro sensor 45 GPS receiver 46 Rollover sensor 47 Power supply unit 49 Selector switch 50 Echo canceller 51 Communication means 52 Communication control means 53 Database 54 Display / communication means

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Tatsuyuki Negishi 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture Inside Matsushita Communication Industrial Co., Ltd. (72) Inventor Kenji Matsumoto Tsunashima-Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture 4-3-1, Matsushita Communication Industrial Co., Ltd. (72) Inventor Takashi Kawazato 4-3-1 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture Matsushita Communication Industrial Co., Ltd. (72) Inventor Tatsunori Kato Yokohama, Kanagawa Matsushita Communication Industrial Co., Ltd., 4-3-1 Tsunashima Higashi, Kohoku-ku, Tokyo (72) Inventor Yukio Ichikawa 4-1-1 Tsunashima Higashi, Kohoku-ku, Yokohama, Kanagawa Prefecture Matsushita Communication Industrial Co., Ltd. (72) Inventor Onuki Masahiro 4-3-9 Toranomon, Minato-ku, Tokyo Daimler-Benz Interservice Telematic Japan Co., Ltd. (72) Masakatsu Toranomon, Minato-ku, Tokyo chome No. 3 No. 9 Daimler Benz inter-service telematic Japan within Co., Ltd.

Claims (4)

[Claims] 1. An accident detecting means for detecting an accident of the own vehicle by a sensor such as a gravitational acceleration or an inclination of the own vehicle, and an own vehicle position identification for identifying a position of the own vehicle from sense information of a GPS, a gyro, a vehicle speed sensor, and the like. Means, the position information and the accident information of the own vehicle, the vehicle ID stored in advance, and the occupant I
A vehicle having at least wireless communication means for wirelessly communicating emergency information such as D information to an emergency rescue center to be described later, or a data / voice simultaneous transmission means capable of simultaneously transmitting data and voice; And an emergency rescue center for requesting the dispatch of an emergency vehicle to the place where the vehicle is located based on the contents thereof, wherein the emergency communication system comprises: The first to transmit emergency information to emergency rescue center by data communication
Wireless transmission means, and at least a second wireless transmission means or a data / voice simultaneous transmission means for enabling voice communication from the vehicle to the emergency rescue center by automatic switching at the end of data communication by the first wireless transmission means. An accident emergency call system characterized by having. 2. The accident emergency notification system according to claim 1, wherein during data communication and voice communication, line disconnection control is performed under the initiative of the emergency rescue center. 3. If a new high-priority data communication request occurs during voice communication by the second wireless transmission means, the voice communication by the second wireless transmission means is interrupted and the first wireless transmission is performed. The accident emergency notification system according to claim 1, wherein data communication by means is enabled. 4. The data / voice simultaneous communication means includes:
The accident emergency notification system according to claim 1, wherein voice communication is simultaneously transmitted during data communication by frequency division multiplexing, time division multiplexing, or space division multiplexing (spread spectrum method).