DESCRIPTION
MOVABLE BODY POSITION MEASUREMENT SYSTEM, CENTRAL STATION,
QUESTION CONTROL METHOD USED THEREIN, AND STORAGE MEDIUM
5 STORING PROGRAM THEREOF
Technical Field
[OOOl]
The present invention relates to a movable body position measurement
10 system, a central station, a question control method used therein, and a program
thereof and, in particular, to a question control method of a transmission station
used in an multilateration system (MLAT: Multilateration) and the movable body
position measurement system.
Background Art
15 [OOOZ]
MLAT is a system that receives a signal sent by a movable body in a
plurality of reception stations, and positions a position of the movable body using
a reception time in each reception station. MLAT in a case where each reception
station receives a signal that the movable body has sent voluntarily or by being
20 induced by means of another system is called passive type MLAT, and MLAT in a
case where a self-system transmits a command signal for making the movable body
generate the signal is called active type MLAT.
[0003]
Particularly, in a field of air traffic control, there is MLAT utilizing an SSR
25 (Secondary Surveillance Radar) mode S system, which is an existing air traffic
surveillance radar (for example, refer to Non Patent Literature 1).
[0004]
When the SSR mode S system transmits a prescribed question signal, an
aircraft (corresponding to the movable body) having a transponder compatible with
30 an SSR mode S sends a response signal, and thus when the SSR mode S system
exists near the MLAI' system, the passive type MLAT is achieved by the response
signal.
[0005]
In addition, the transponder may automatically send a response signal
called a squitter signal or an extended squitter signal, the response signal being
prescribed by the SSR node S system, and in that case, the passive type MLAT is
achieved utilizing the signal (for example, refer to Patent Literature 1).
[0006]
5 The active type MLAT is achieved by including in the MLAT system a
transmission station that transmits the question signal of the SSR mode S system.
Since a transmission time of the question signal can be recognized by including the
transmission station in the self-system, a reception time of a response signal from
the transponder can be predicted, and position positioning different from the
10 passive type MLAT can be performed, thus leading to improvement in positioning
accuracy (for example, refer to Non Patent Literature 2).
[0007]
When specifically explained, in the passive type MLAT, a position of the
aircraft is calculated by finding an arrival time difference between reception
15 stations, and finding intersections of hyperboloids obtained under a condition
where a distance difference between the aircraft and each reception station is
constant. It is necessary to detect a signal at least four reception stations in order
to perform three-dimensional positioning.
[OOOS]
2 0 Meanwhile, in the active type MLAT, the position of the aircraft is
calculated utilizing an ellipsoid obtained under a condition where distances among
the transmission station, the aircraft, and the reception station are constant from a
question signal transmission time by the transmission station, and a reception time
in each reception station.
25 [0009]
In the SSR mode S system relevant to the present invention, mechanical
rotation of an antenna having a strong directional beam enables surveillance of
surroundings at 360 degrees. Therefore, the transmission station transmits the
question signal when the aircraft enters within the beam. Accordingly, the system
30 performs scheduling so that the question signal is transmitted to the aircrafts in
order from an aircraft located farthest from the transmission station within the
beam, while tracking aircraft positions after detection of the aircrafts, whereby
surveillance of the aircrafts can be achieved (for example, refer to Non Patent
Literature 3).
Citation List
Patent Literature
[OO lo]
5 PTLI : Japanese Unexamined Patent Application Publication No.
2009-300146
Non Patent Literature
[OO 11)
NPLI : MULTILATERATION SYSTEM DEVELOPMENT HISTORY AND
10 PERFORMANCE AT DALALS/FT.WORTH AIRPORT, DIGITAL AVIONICS
SYSTEMS CONFERENCE, 2000.PROCEEDINGS DASC THE 1 9 ' ~V, OLUME 1
NPL2: PERFORMANCE ASSESSMENT OF MULTILATERATION
SYSTEMS-A SOLUTION TO NEXTGEN SURVEILLANCE, INTEGRATED
COMMUNICATIONS NAVIGATION AND SURVEILLANCE CONFERENCE
15 (ICNS), 2010
Summary of Invention
Technical Problem
[OO 121
2 0 In the above-mentioned MLAT, since the response signal sent from a
transmitter (transponder) of the aircraft in a wide area is received by the plurality
of reception stations, a non-directional antenna is usually used, and similarly, the
non-directional antenna is used also in the transmission station.
[00 131
2 5 When scheduling using an azimuth angle by means of the beam used in the
system relevant to the present invention is applied to the question signal
transmission in the MLAT, transmission/non-transmission of the question signal is
decided by existencelabsence of the aircraft in the azimuth angle, and a problem
occurs that the question signal is not immediately transmitted to the aircraft
30 needing it.
[00 141
In addition, when the non-directional antenna is used in the transmission
station, the transmitted questio~ls ignal reaches all the aircrafts existing in the
area. An aircraft-specific address can be specified to a question signal of tllc SSR
mode S, and the transponder of the aircraft rejects a question signal when
receiving the question signal having an address other than an aircraft's own one,
and it transmits a response signal when receiving a question signal having the
aircraft's own one.
5 [0015]
Accordingly, although the transponder of the aircraft can distinguish the
question signals, it is necessary to receive all the question signals once, decode
them, and confirm their addresses in order to distinguish them, and thus the
transponder is occupied for that. Consequently, when the non-directional antenna
10 is used in the transmission station, transponders of all the aircrafts may be
affected, and there is a regulation concerning an upper limit of a transponder
occupancy rate by question signals transmitted by the transmission station in ICAO
(International Civil Aviation Organization) ANNEX 10 vol4amendment85 6. 6. 3
issued by ICAO.
15 [0016]
Namely, an upper-limit is prescribed in the number of question signals for
each unit time that are transmitted by the transmission station. In this case, since
priority between the aircrafts cannot be taken into consideration in scheduling by
means of the azimuth angle, transmission/non-transmission is individually decided
20 to each aircraft, and when the scheduling is considered as the system, problems
occur that transmission of the question signals is limited although it is still
possible to transmit the question signals, or that the question signals are
transmitted although the number of question signals of a unit time exceeds the
upper limit.
25 [0017]
Consequently, an object of the present invention is to solve the
above-described problems, and to provide a movable body position measurement
system, a central station, a question control method used therein, and a program
thereof that can immediately transmit a question signal to an aircraft needing it
3 0 without transmitting unnecessary question signals, while keeping a prescribed
upper limit of the number of question signal transmissions.
Solution to Problem
[00 181
A movable body position measurement system according to the present
invention is the movable body position measurement system that includes: a
plurality of receptiol~ stations that receive a response signal from a movable body;
and a central station that positions a position of the movable body based on
reception times of the response signal in the plurality of reception stations, and
5 measures a geometric position of the movable body from the reception times of the
plurality of reception stations in the central station, in which
the movable body position measurement system includes at least one or
more transmission devices that transmit a question signal for obtaining the
response signal to the movable body,
10 the central station includes: question signal decision means for deciding as
question control information the question signal and a transmission time that the
transmission device should transmit; and means for transmitting to the
transmission device the question control information decided by the question
signal decision means,
15 the transmission device includes: means for receiving the question control
information; and means for transmitting the question signal specified in the
question control information when the transmission time specified in the received
question control information and a time held by the transmission device coincide
with each other,
2 0 the question signal decision means includes means for deciding a state of a
system for each first time frame, which is a time section divided by a preset time
width, and in which
the question signal decision means decides the question signal and the
transmission time that the transmission device should transmit based on the state
2 5 of the system.
[OO 191
A central station according to the present invention is the central station
included in a movable body position measurement system that includes: a plurality
of reception stations that receive a response signal from a movable body; and a
30 central station that positions a position of the movable body based on reception
times of the response signal in the plurality of reception stations, and measures a
geometric position of the movable body from the reception times of the plurality of
reception stations in the central station, in which
in the n~ovableb ody position measurement system, disposed are at least
one or more transnlission devices that transmit a question signal for obtaining the
response signal to the movable body,
the central station includes: question signal decision means for deciding as
question control information the question signal and a transmission time that the
5 transmission device should transmit; and means for transmitting to the
transmission device the question control information decided by the question
signal decision means,
in the transmission device, the following are provided: means for receiving
the question control information; and means for transmitting the question signal
1 0 specified in the question control information when the transmission time specified
in the received question control information and a time held by the transmission
device coincide with each other,
the question signal decision means includes means for deciding a state of a
system for each first time frame, which is a time section divided by a preset time
15 width, and in which
the question signal decision means decides the question signal and the
transmission time that the transmission device should transmit based on the state
of the system.
[0020]
2 0 A transmission control method according to the present invention is the
question control method used for a movable body position measurement system
that includes: a plurality of reception stations that receive a response signal from a
movable body; and a central station that positions a position of the movable body
based on reception times of the response signal in the plurality of reception
2 5 stations, and measures a geometric position of the movable body from the
reception times of the plurality of reception stations in the central station, in which
in the movable body position measurement system, at least one or more
transmission devices that transmit a question signal for obtaining the response
signal to the movable body are disposed,
3 0 the central station executes: question signal decision processing to decide
as question control information the question signal and a transmission time that the
transmission device should transmit; and processing to transmit to the transmission
device the question control information decided by the question signal decision
processing,
in the transmission device, the following are provided: means for receiving
the question control information; and means for transmitting the question signal
specified in the question control information when the transmission time specified
in the received question control information and a time held by the transmission
5 device coincide with each other,
in the question signal decision processing, processing to decide a state of a
system for each first time frame, which is a time section divided by a preset time
width, is executed, and in which
the question signal and the transmission time that the transmission device
10 should transmit are decided based on the state of the system.
[0021]
A storage medium according to the present invention is the storage medium
that a central processing unit of a central station is made to execute, the central
station being included in a movable body position measurement system that
15 includes: a plurality of reception stations that receive a response signal from a
movable body; and the central station that positions a position of the movable body
based on reception times of the response signal in the plurality of reception
stations, and measures a geometric position of the movable body from the
reception times of the plurality of reception stations in the central station, the
2 0 storage medium being characterized in that
in the movable body position measurement system, disposed are at least
one or more transmission devices that transmit a question signal for obtaining the
response signal to the movable body,
the storage medium includes: question signal decision processing to decide
2 5 as question control information the question signal and a transmission time that the
transmission device should transmit; and processing to transmit to the transmission
device the question control information decided by the question signal decision
processing,
in the transmission device, provided are: means for receiving the question
30 control information; and means for transmitting the question signal specified in the
question control information when the transmission time specified in the received
question control information and a time held by the tral~smission device coincide
with each other,
in the question signal decision processing, made to be executed is
processing to decide a state of a system for each first time frame, which is a time
section divided with a preset time width, and
the question signal and the transmission time that the transmission device
should transmit are made to be decided based on the state of the system.
5 Advantageous Effects of Invention
[0022]
According to the present invention, an effect can be obtained that by
employing the above-described configuration and operation, a question signal can
be immediately transmitted to an aircraft needing it without transmitting
10 unnecessary question signals, while keeping a prescribed upper limit of the number
of question signal transmissions.
Brief Description of the Drawings
[0023]
1 5 Fig. 1 is a block diagram showing a configuration example of the system according
to the embodiment of the present invention.
Fig. 2 is a block diagram showing a configuration example of a central station
according to the embodiment of the present invention.
Fig. 3 is a block diagram showing a configuration example of a transmission
20 station according to the embodiment of the present invention.
Fig. 4 is a block diagram showing a configuration example of a reception station
according to the embodiment of the present invention.
Fig. 5 is a sequence chart for illustrating operation of the system according to the
embodiment of the present invention.
25 Fig. 6 is a diagram for illustrating generation timing of the question control
information according to the embodiment of the present invention.
Fig. 7 is a diagram for illustrating question signal transmission control according
to the embodiment of the present invention.
3 0 Description of Embodiments
[0024]
Next, an embodiment of the present inventioi~w ill be explained with
reference to drawings. First, a movable body position measurement system
according to the present invention will be explained taking as an example a MLAT
(Multilateration) system using an SSR (Secondary Surveillance Radar) mode S
signal.
[0025]
An SSR mode S system is the system in which when a transponder mounted
5 in an aircraft (a movable body) receives a question signal, in a case where an
address specified by the question signal and an address allocated to the aircraft
coincide with each other, a response signal is automatically transmitted.
Information, such as information requested by the question signal and an address
of the aircraft, is included in the response signal.
10 [0026]
Fig. 1 is a block diagram showing a configuration example of the system
according to the embodiment of the present invention, and Fig. 2 is a block
diagram showing a configuration example of a central station according to the
embodiment of the present invention. Fig. 3 is a block diagram showing a
15 configuration example of a transmission station according to the embodiment of
the present invention, and Fig. 4 is a block diagram showing a configuration
example of a reception station according to the embodiment of the present
invention.
[0027]
2 0 In Fig. I , the system according to the embodiment of the present invention
includes: a central station 1; reception stations 2-A to 2-D; and a transmission
station 3. Note that an aircraft 4 is not a component of the system according to
the embodiment of the present invention but a component as a positioning object of
the present system.
25 [0028]
The central station 1 receives reception times of a response signal
transmitted from four reception stations 2-A to 2-D, positions a position of the
aircraft 4 that has sent the response signal based on the reception times, decides a
question signal, transmission timing, etc. that are transmitted to the aircraft 4
30 using a measurement result, and transmits a question control command for
transmitting to the transmission station 3.
[0029]
The reception stations 2-A to 2-D are the samc four reception stations, and
the individual reception station receives an RF response signal sent by the aircraft
4, measures a reception time of the RF response signal, and transmits it to the
central station 4. The transmission station 3 receives the question control
command transmitted from the central station 1, and transmits an RF question
signal to the aircraft 4 in accordance with the command. The aircraft 4 receives
5 the RF question signal transmitted from the transmission station 3, and transmits
an RF response signal to the reception stations 2-A to 2-D according to a content of
the question signal.
[0030]
In Fig. 2, the central station 1 includes: a reception station data processing
10 unit 1-1; a system state decision unit 1-2; a time counter 1-3; a question control
information decision unit 1-4; a question control information generation unit 1-5;
and a question control information transmission unit 1-6.
[003 11
The reception station data processing unit 1-1 receives from each of the
15 reception stations 2-A to 2-D the reception times of the response signal received by
the reception stations 2-A to 2-D, respectively, an address of the aircraft that has
sent the response signal, etc., performs positioning of the position of the aircraft 4
using the reception times and decoding of the response signal, and outputs the
address of the aircraft 4, a positioning result, and a decoded result.
20 [0032]
The system state decision unit 1-2 decides a state of each aircraft that is
being detected using the address of the aircraft, the positioning result, and the
decoded result input from the reception station data processing unit 1-1 at a
previously decided time with respect to a time input from the time counter 1-3, and
25 outputs states of all the aircrafts as a system state.
[003 31
The time counter 1-3 outputs a central station time of the central station 1.
The question control information decision unit 1-4 inputs a system state from the
system state decision unit 1-2 and a time from the time counter 1-3, respectively,
30 and decides and outputs question control information, such as a time to transmit
the question signal, the address of the aircraft, a type and the number of the
question signal, according to the system state.
100341
The question control informatiol~g eneration unit 1-5 converts into a
prescribed format the question control information input from the question control
information decision unit 1-4, and generates question control information data.
The question control information transmission unit 1-6 transmits the question
control information data input from the question control information generation
5 unit 1-5 to the transmission station 3 using a decided protocol.
[0035]
In Fig. 3, the transmission station 3 includes: a question control
information reception unit 3-1; an RF question signal transmission unit 3-2; and a
time counter 3-3.
1 0 [0036]
The question control information reception unit 3-1 receives and decodes
the question control information data input from the central station 1, and outputs
a content of the question control information. The RF question signal
transmission unit 3-2 inputs the question control information from the question
15 control information reception unit 3-1, generates a question signal based on the
prescribed format using the type of the question signal, the aircraft address, etc.
that are described in the question control information, and transmits the question
signal to the aircraft 4 as an RF signal when the transmission time described in the
question control information and a time input from the time counter 3-3 coincide
20 with each other. The time counter 3-3 outputs a transmission station time of the
transmission station 3.
[003 71
In Fig. 4, since the four reception stations 2-A to 2-D are assumed to have
the completely same configuration and operation, only one is described as the
25 reception station 2. The reception station 2 includes: an RF response signal
reception unit 2-1; a time counter 2-2; and a response signal information
transmission unit 2-3.
[003 81
The RF response signal reception unit 2-1 receives the RF response signal
30 sent by the aircraft 4, measures a reception time of the response signal using a time
input from the time counter 2-2, decodes the response signal to retrieve response
signal information, such as a mode S address, a mode A code, an altitude, and
aircraft dynamic state information, and outputs a measurement reception time and
the response signal information.
[0039]
The time counter 2-2 outputs a reception station time of the reception
station 2. The response signal information transmission unit 2-3 inputs the
measurement reception time and the response signal information from the RF
5 response signal reception unit 2-1, creates response signal information data based
on the prescribed format, and outputs it to the central station 1 by means of the
prescribed protocol.
[0040]
Fig. 5 is a sequence chart for illustrating operation of the system according
10 to the embodiment of the present invention. With reference to these Figs. 1 to 5,
will be explained the operation of the system according to the embodiment of the
present invention. Note that processing operation of the central station 1 shown
in Fig. 5 can be achieved by a CPU (Central Processing Unit) of the central station,
which is not shown, executing a storage medium.
15 [0041]
The MLAT system does not detect the aircraft 4 immediately after the
aircraft 4 enters a surveillance area of the MLAT system, the MLAT system
receives the RF response signal (A1 of Fig. 5) sent by the aircraft 4 (A2 of Fig. 5),
and thereby the aircraft 4 is detected. When the aircraft 4 voluntarily sends the
20 response signal, or when there is an other SSR mode S system around the MLAT
system, the response signal may be transmitted in response to the question signal
sent by the system.
[0042]
Each of the reception stations 2-A to 2-D performs reception processing of
25 the response signal, the reception time of the response signal is measured, and
creates decoded data of the response signal, such as the mode S address, the mode
A code, the altitude, and the aircraft dynamic state information, and response
signal information, such as a reception level of the RF response signal, and quality
degradation information due to an interference signal from an other aircraft (A2 of
30 Fig. 5 ) . Each of the reception stations 2-A to 2-D transmits the measurement
reception time and response signal information of the response signal to the central
station 1 by means of the prescribed protocol (A3 of Fig. 5).
[0043]
The central station 1 decides a state of the aircraft by pprocessi~lg the
response signal information and the reception time from each of the reception
stations 2-A to 2-D (A4 of Fig. 5 ) . The state of the aircraft indicates a position of
the aircraft obtained by performing MLAT calculation using a difference of the
reception times from the plurality of reception stations 2-A to 2-D, and
5 information included in the response signal information, such as a flight direction,
a flight speed, and a flight altitude. In addition, can be included a future
prediction position etc. obtained as a result of performing tracking from past
position data of the aircraft, etc.
[0044]
10 The central station 1 processes reception station data concerning each of
the plurality of aircrafts, and decides a state of each aircraft at timing when the
reception station data reaches (A4 of Fig. 5). The central station 1 integrates
states of all the aircrafts for each previously decided time interval (hereinafter
referred to as a time frame), and decides the integrated state as the state of the
1 5 system (A5 of Fig. 5).
[0045]
Fig. 6 is a diagram for illustrating generation timing of the question control
information according to the embodiment of the present invention. In Fig. 6,
shown is an example of a difference of decision timing of the state of each aircraft
2 0 and the system state. In C1, shown is the decision timing of the state of each
aircraft (movable body in Fig. 6). Reference numeral 1, 2, and ... in circles in
Fig. 6 show arrival timing of response signals of an aircraft #1 and an aircraft #2,
respectively. It may be considered that the decision timing of the state of the
aircraft in the central station 1 is also substantially the same as the arrival timing.
25 COO461
The decision timing of the system state is shown in C2. The central
station 1 decides the states of all the aircrafts for each previously decided time
interval, and sets them as the system state. Since a time when each aircraft sends
the response signal is substantially random, and there is almost no correlation also
30 between the aircrafts, it is difficult to make the decision timing of the state of the
aircraft and the system state coincide with each other, and deviation occurs.
Therefore, the deviation is minimized by using a state of the aircraft immediately
before the timing of deciding the system state.
[0047]
The central station 1 decides the system state in processing of A5 of Fig. 5,
and subsequently, decides question control information by processing of A6. The
question control information is the information serving as a basis of a command
with respect to the transmission station, the command indicating that to which
5 aircraft, what kind of question signal, how many question signals, and when the
transmission station is made to transmit the question signal.
[0048]
The question control information is decided based on the system state
decided by the processing of A5 of Fig. 5. The central station 1 creates question
10 control information data from the decided question control information in
accordance with a format previously decided between the central station 1 and the
transmission station 3 (A7 of Fig. 5), and transmits it to the transmission station 3
(A8 of Fig. 5).
[0049]
15 The transmission station 3 receives the question control information data,
and transmits an RF question signal in accordance with the question control
information (A9 of Fig. 5). When receiving the RF question signal, the aircraft 4
transmits an RF response signal according to a content of the RF question signal
(A10 of Fig. 5). The RF response signal is received and processed by the
20 reception stations 2-A to 2-D (A2 of Fig. 5).
[0050]
Note that since the aircraft 4 not only transmits the response signal due to
the question signal from the MLAT system, but may voluntarily transmit the
response signal or may respond to a question signal by an other system, and it may
2 5 be decided in the question control information decision of A6 not to transmit the
question signal, the present flow is not necessarily followed.
I005 11
Fig. 7 is a diagram for illustrating question signal transmission control
according to the embodiment of the present invention. With reference to Fig. 7,
30 will be explained a relation between time frames of the central station 1 and the
transmission station 3. R1 of Fig. 7 shows a time frame (first frame) with which
the central station 1 decides the system state, and B4 shows a time frame (second
frame) with which the transmission station 3 actually transmits the question signal.
Here, t is defined as an integer, and t-2 to t+l indicate frame numbers.
[0052]
B2 shows time relations with decision of the system state, decision,
generation, and transmission of the question control information by the central
station 1 for the transmission station 3 to transmit the question signal at a second
5 frame t-1. Since the central station 1 needs to end the decision, generation, and
transmission of the question control information before the second frame t-1 in
order to transmit the question signal at the second frame t-1, the decision of the
system state is, as shown in Fig. 7, made before Xms (however, X is a positive real
number) from a start time of the second frame t-1.
1 0 [0053]
Accordingly, the second frame is more delayed than the first frame by Xms.
Although this delay time X may be fixed for each frame number, it may be changed
for each frame number depending on a processing time needed by the central
station 1.
15 [0054]
Here, although the central station 1 needs to know a time held by the
transmission station 3 in order for the central station 1 to transmit the question
control information to the transmission station 3 before the second frame of the
transmission station 3, time synchronization of the central station 1 and the
20 transmission station 3 is assumed to be performed by related arts, such as an NTP
(Network Time Protocol) and a GPS (Global Positioning System). However,
when the central station 1 and the transmission station 3 are physically separated
from each other, it is difficult to completely make the times coincide with each
other, and a difference is generated between the second frame of the transmission
25 station 3 recognized by the central station 1 and the second frame actually held by
the transmission station 3, but operation of the present embodiment can be
achieved by recognizing the time difference at the central station 1, and specifying
a trallsmission time in consideration of the time difference.
[OOSS]
3 0 In B2, the central station 1 decides the system state at a head time of a first
frame t-1, and transmits the question control information to the transmission
station 3 during X. The transmission station 3 can transmit the question signal in
the second frame t-1 of B4. The transmission station 3 transmits the question
signal to at least one or more aircrafts within the second frame t - 1 .
[0056]
In B3, shown is a case where the transmission station 3 transmits the
question signal at the second frame t. Similarly to B2, the central station 1
decides the system state at a head of a first frame t, and transmits the question
5 control information to the transmission station 3 during X, and the transmission
station 3 transmits the question signal at a second frame t.
[0057]
In the present embodiment, by employing the configuration as described
above, it becomes possible to take into consideration priority right with respect to
10 question signal transmission among the aircrafts in consideration of the states of
the plurality of aircrafts. In addition, the present embodiment has an effect that it
becomes easy to provide the upper limit of the number of questions by performing
the control for each time frame.
LO05 81
15 As mentioned above, since the present invention takes into consideration
all the movable bodies detected by the above-described MLAT system, the priority
among the movable bodies in the question signal transmission can be taken into
consideration. Therefore, in the present invention, it becomes possible to
transmit the question signal soon to the movable body to which the question signal
20 needs to be transmitted as soon as possible, and can be obtained an effect that a
surveillance capability for the movable bodies is improved. In addition,
according to the present invention, can be obtained the effect that it becomes easy
to limit the number of questions.
[0059]
2 5 Hereinbefore, although the invention in the present application has been
explained with reference to the embodiment, the invention in the present
application is not limited by the above. Various changes that those skilled in the
art can understand within the scope of the invention can be made to the
configuration and the details of the invention in the present application.
30 [0060]
Although the present invention has been explained as a hardware
configuration in the above-mentioned embodiments, the present invention is not
limited to this. In the present invention, arbitrary processing can be achieved by
making the CPU (Central Processing Unit) execute a computer program. In this
case, the computer program can be provided by being recorded on a recording
medium, and it can also be provided by being transmitted through the Internet or
an other communication medium. In addition, a storage medium, for example,
includes: a flexible disk; a hard disk; a magnetic disk; a magnetic optical disk; a
5 CD-ROM; a DVD; a ROM cartridge; a RAM memory cartridge with battery
back-up; a flash memory cartridge; a nonvolatile RAM cartridge; etc. In
addition, the communication medium includes: a wired communication medium,
such as a telephone line; a wireless communication medium, such as a microwave
line; etc.
1 0 [0061]
Although a part or all of the above-described embodiment can be described
also as the following appendices, the present invention is not limited to the
following descriptions.
[0062]
15 Appendix 1
A central station included in a movable body position measurement system
that includes: a plurality of reception stations that receive a response signal from a
movable body; and a central station that positions a position of the movable body
based on reception times of the response signal in the plurality of reception
20 stations, and measures a geometric position of the movable body from the
reception times of the plurality of reception stations in the central station, the
central station being characterized in that
in the movable body position measurement system, disposed are at least
one or more transmission devices that transmit a question signal for obtaining the
2 5 response signal to the movable body,
the central station has: question signal decision means for deciding as
question control information the question signal and a transmission time that the
transmission device should transmit; and means for transmitting to the
transmission device the question control information decided by the question
30 signal decision means,
in the transmission device, provided are: means for receiving the question
control information; and means for transmitting the question signal specified in the
question control information when the transmission time specified in the received
question control information and a time held by the transmission device coincide
with each other,
the question signal decision means includes means for deciding a state of a
system for each first time frame, which is a time section divided with a preset time
width,
5 the question signal decision means decides the question signal and the
transmission time that the transmission device should transmit based on the state
of the system, and that
the transmission time of the question signal that the transmission device
should transmit is a second frame, which is a time section that the self-station
10 prescribes with respect to the transmission device.
[0063]
Appendix 2
The central station according to Appendix 1, wherein the first time frame
has the same time width in all times.
15 [0064]
Appendix 3
The central station according to any of Appendixes 1 to 2, wherein the state
of the system is decided based on at least either one of at least one or more
response signals from at least one or more movable bodies and a data content
2 0 superposed by the response signal from the movable body.
[0065]
Appendix 4
The central station according to Appendix 3, wherein the state of the
movable body is decided based on at least any one of a reception status in the
25 reception station of the response signal from the movable body, reception quality
in the reception station, the measured geometric position of the movable body, the
data content superposed by the response signal from the movable body, and a
future prediction position of the movable body.
[0066]
30 Appendix 5
The central station according to Appendix 1, characterized i11 that a11
upper-limit value is set to the number of questions transmitted within the second
time frame.
[0067]
Appendix 6
The central station according to any of Appendices 1 to 5 , characterized in
that the first time frame and the second time frame are changed according to the
number of movable bodies detected by the system.
5 [0068]
Appendix 7
A question control method used for a movable body position measurement
system that includes: a plurality of reception stations that receive a response signal
from a movable body; and a central station that positions a position of the movable
10 body based on reception times of the response signal in the plurality of reception
stations, and measures a geometric position of the movable body from the
reception times of the plurality of reception stations in the central station, the
question control method being characterized in that
in the movable body position measurement system, disposed are at least
15 one or more transmission devices that transmit a question signal for obtaining the
response signal to the movable body,
the central station executes: question signal decision processing to decide
as question control information the question signal and a transmission time that the
transmission device should transmit; and processing to transmit to the transmission
20 device the question control information decided by the question signal decision
processing,
in the transmission device, provided are: means for receiving the question
control information; and means for transmitting the question signal specified in the
question control information when the transmission time specified in the received
25 question control information and a time held by the transmission device coincide
with each other,
in the question signal decision processing, executed is processing to decide
a state of a system for each first time frame, which is a time section divided with a
preset time width,
3 0 the question signal and the transmission time that the transmission device
should transmit are decided based on the state of the system, and that
the transmission time of the question signal that the transmission device
should transmit is a second frame, which is a time section that the central station
prescribes with respect to the transmission device.
[0069]
Appendix 8
The question control method according to Appendix 7, characterized in that
the first time frame has the same time width in all times.
5 [0070]
Appendix 9
The question control method according to Appendix 7 or 8, characterized in
that the state of the system is decided based on at least either one of at least one or
more response signals from at least one or more movable bodies and a data content
10 superposed by the response signal from the movable body.
1007 11
Appendix 10
The question control method according to Appendix 9, characterized in that
the state of the movable body is decided based on at least any one of a reception
15 status in the reception station of the response signal from the movable body,
reception quality in the reception station, the measured geometric position of the
movable body, the data content superposed by the response signal from the
movable body, and a future prediction position of the movable body.
100721
2 0 Appendix 11
The question control method according to Appendix 7, wherein an
upper-limit value is set to the number of questions transmitted within the second
time frame.
[0073]
2 5 Appendix 12
The question control method according to any of Appendixes 7 to 11,
wherein the first time frame and the second time frame are changed according to
the number of movable bodies detected by the system.
100741
3 0 This application is based upon and claims the benefit of priority from
Japanese Patent Application No. 2012-030052, filed on February 15, 2012, the
disclosure of whicl~i s incorporated herein in its entirety by reference.
Industrial Applicability
[0075]
The present invention can be applied to an MLAT (Multilateration) system
or a WAM [Wide Area MLAT (Multilateration)] system used in a wide area.
5 Reference Signs List
[0076]
1 Central Station
1 - 1 Reception Station Data Processing Unit
1-2 System State Decision Unit
10 1-3 Time Counter
1-4 Question Control Information Decision Unit
1-5 Question Control Information Generation Unit
1-6 Question Control Information Transmission Unit
2-A to 2-D Reception Station
1 5 2-1 RF Response Signal Reception Unit
2-2 Time Counter
2-3 Response Signal Information Transmission Unit
3 TRANSMISSION STATION
3- 1 Question Control Information Reception Unit
2 0 3-2 RF Question Signal Transmission Unit
3-3 Time Counter
4 Aircraft
CLAIMS
1. A movable body position measurement system comprising at least one or
more transmission devices that transmit a question signal for obtaining a response
5 signal to a movable body, wherein
the central station has: question signal decision means for deciding as
question control information the question signal and a transmission time that the
transmission device should transmit; and means for transmitting to the
transmission device the question control information decided by the question
10 signal decision means,
the transmission device has: means for receiving the question control
information; and means for transmitting the question signal specified in the
question control information when the transmission time specified in the received
question control information and a time held by the transmission device coincide
15 with each other,
the question signal decision means includes means for deciding a state of a
system for each first time frame, which is a time section divided by a preset time
width, and
the question signal decision means decides the question signal and the
20 transmission time that the transmission device should transmit based on the state
of the system.
2. The movable body position measurement system according to Claim 1,
wherein the transmission time of the question signal that the transmission device
25 should transmit is a second frame, which is a time section that the central station
prescribes with respect to the transmission device.
3. The movable body position measurement system according to Claim 1 or 2,
wherein the first time frame has the same time width at all times.
3 0
4. The movable body position measurement system according to any of
Claims 1 to 3, wherein the state of the system is decided based on at least either
one of at least one or more response signals from at least one or more movable
bodies and a data content superposed by the response signal from the movable
body.
5 . The movable body position measurement system according to Claim 4,
wherein the state of the movable body is decided based on at least any one of a
5 reception status in the reception station of the response signal from the movable
body, reception quality in the reception station, the measured geometric position of
the movable body, the data content superposed by the response signal from the
movable body, and a future prediction position of the movable body.
1 0 6. The movable body position measurement system according to Claim 2,
wherein an upper-limit value is set to the number of questions transmitted within
the second time frame.
7. The movable body position measurement system according to any of
15 Claims 2 to 6, wherein the first time frame and the second time frame are changed
according to the number of movable bodies detected by the system.
8. A central station, wherein
in a movable body position measurement system, at least one or more
2 0 transmission devices that transmit a question signal for obtaining a response signal
to a movable body are disposed,
the central station has: question signal decision means for deciding as
question control information the question signal and a transmission time that the
transmission device should transmit; and means for transmitting to the
2 5 transmission device the question control information decided by the question
signal decision means,
in the transmission device, the following are provided: means for receiving
the question control information; and means for transmitting the question signal
specified in the question control information when the transmission time specified
30 in the received question control information and a time held by the transmission
device coincide with each other,
the question signal decision means includes means for deciding a state of a
system for each first time frame, which is a time section divided by a preset time
width, and
the question signal decision means decides the question signal and the
transmission time that the transmission device should transmit based on the state
of the system.
5 9. The central station according to Claim 8, wherein the transmission time of
the question signal that the transmission device should transmit is a second frame,
which is a time section that the self-station prescribes with respect to the
transmission device.
10 10. The central station according to Claim 8 or 9, wherein the first time frame
has the same time width at all times.
11. The central station according to any of Claims 8 to 10, wherein the state of
the system is decided based on at least either one of at least one or more response
15 signals from at least one or more movable bodies and a data content superposed by
the response signal from the movable body.
12. The central station according to Claim 11, wherein the state of the movable
body is decided based on at least any one of a reception status in the reception
20 station of the response signal from the movable body, reception quality in the
reception station, a measured geometric position of the movable body, the data
content superposed by the response signal from the movable body, and a future
prediction position of the movable body.
2 5 13. The central station according to Claim 9, wherein an upper-limit value is
set to the number of questions transmitted within the second time frame.
14. The central station according to any of Claims 9 to 13, wherein the first
time frame and the second time frame are changed according to the number of
30 movable bodies detected by the system.
15. A question control method, wherein
in a movable body position measurement system, at least one or more
transmission devices that transmit a question signal for obtaining a response signal
to a movable body are disposed,
a central station executes: question signal decision processing to decide as
question control information the question signal and a transmission time that the
transmission device should transmit; and processing to transmit to the transmission
5 device the question control information decided by the question signal decision
processing,
in the transmission device, the following are provided : means for receiving
the question control information; and means for transmitting the question signal
specified in the question control information when the transmission time specified
10 in the received question control information and a time held by the transmission
device coincide with each other,
in the question signal decision processing, processing to decide a state of
a system for each first time frame, which is a time section divided by a preset
time width, is executed, and
15 the question signal and the transmission time that the transmission device
should transmit are decided based on the state of the system.
16. The question control method according to Claim 15, wherein the
transmission time of the question signal that the transmission device should
2 0 transmit is a second frame, which is a time section that the central station
prescribes with respect to the transmission device.
17. The question control method according to Claim 15 or 16, wherein the first
time frame has the same time width at all times.
18. The question control method according to any of Claims 15 to 17, wherein
the state of the system is decided based on at least either one of at least one or
more response signals from at least one or more movable bodies and a data content
superposed by the response signal from the movable body.
3 0
19. The question control method according to Claim 18, wherein the state of
the movable body is decided based on at least any one of a reception status in the
reception station of the response signal from the movable body, a reception quality
in the reception station, a measured geometric position of the movable body, the
data content superposed by the response signal from the movable body, and a
future prediction position of the movable body.
20. The question control method according to Claim 16, wherein an upper-limit
5 value is set to the number of questions transmitted within the second time frame.
21. The question control method according to any of Claims 16 to 20, wherein
the first time frame and the second time frame are changed according to the
number of movable bodies detected by the system.
10
22. A storage medium storing a program, wherein
in a movable body position measurement system, at least one or more
transmission devices that transmit a question signal for obtaining a response signal
to a movable body are disposed,
15 the program includes: question signal decision processing to decide as
question control information the question signal and a transmission time that the
transmission device should transmit; and processing to transmit to the transmission
device the question control information decided by the question signal decision
processing,
2 0 in the transmission device, the following provided : means for receiving the
question control information; and means for transmitting the question signal
specified in the question control information when the transmission time specified
in the received question control information and a time held by the transmission
device coincide with each other,
2 5 in the question signal decision processing, processing to decide a state of a
system for each first time frame, which is a time section divided by a preset time
width, is executed, and
the question signal and the transmission time that the transmission device
should transmit are decided based on the state of the system.
30 Dated this 231d Day of July 2014
Of Anand And Anand Advocates
Agents for the Applicant