JPH0525309B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a mobile satellite communication/positioning system, and particularly to a mobile satellite communication/positioning system in which one or more base stations perform two-way communication with a large number of mobile objects via communication satellites. The present invention relates to a mobile satellite communication/positioning method that can measure the position of a mobile object and transmit the position to the mobile object using two communication satellites.

(Prior Art) As satellite communication technology advances, great expectations are placed on mobile satellite communication systems. When constructing this mobile satellite communication system, it is important to take advantage of the wide-area characteristics of satellite communication and realize communication/positioning functions that can perform positioning of mobile objects in parallel with communication with mobile objects. This has become a development issue, and for example, a mobile satellite communication/positioning system as shown in FIG. 2 has been proposed.

This system was developed by the American company GEOSTAR (US Patent No. 4359733), and uses the code division multiplexing (CDM) system based on spread spectrum technology to transmit two communication satellites, 1-1 and 1-2. One of the communication satellites (first communication satellite) 1-
The mobile unit 2 and the base station 3 communicate via the mobile unit 1, and the base station 3 communicates with the mobile unit using two communication satellites including the other communication satellite (second communication satellite) 1-2. This is a mobile satellite communication/positioning method that performs positioning as described in Section 2 and transmits it to the corresponding mobile object.

The mobile body 2 includes a mobile antenna 2-1 consisting of a low-directivity antenna, a duplexer 2-2, a low-noise amplifier 2-3, a down converter 2-4, a spread spectrum demodulator 2-5, and a data demodulator. a receiving section consisting of a receiver 2-6, a mobile terminal 2-7, a data modulator 2-8, a spread spectrum modulator 2-9, an up converter 2-10 and a high power amplifier 2-11.
and a transmitting section.

The base station 3 also has two communication satellites (1-1,
A base station antenna 3- consisting of a highly directional antenna provided in one-to-one correspondence with each of 1-2).
1 and 3-2, the duplexer 3-3, and the first receiving section (low noise amplifier 3-4, down converter 3
-5, spread spectrum demodulator 3-6 and data demodulator 3-7), and a transmitter (data modulator 3-7);
8, spread spectrum modulator 3-9, up converter 3-10 and high power amplifier 3-11);
Second receiving section (low noise amplifier 3-12, down converter 3-13 and spread spectrum demodulator 3)
-14) and a communication/positioning operation terminal 3-15.

The gist of this conventional system is as described above, and the detailed explanation will be omitted as the reference will be made to the above-mentioned US patent, but the outline will be listed as follows.

(1) To improve measurement accuracy, use spread spectrum modulation with high-speed PN codes (random codes) and use the full bandwidth (14MHz) of the satellite repeater.

(2) In the base station 3, a transmission timing signal is issued from the communication/positioning operation terminal 3-15 to the spread spectrum modulator 3-9, and in response to this, the output signal of the data modulator 3-8 is spread spectrum modulated. , which is transmitted to the communication satellite 1-1 via an up-converter 3-10, a high-power amplifier 3-11, a duplexer 3-3, and a base station antenna 3-1.

In the mobile unit 2, high-speed PN code synchronization is established in the spread spectrum demodulator 2-5 of the receiving section via the mobile antenna 2-1 and the demultiplexer 2-2, and despreading processing is performed, and the result is transmitted as data. is applied to the demodulator 2-6, and a reception timing signal of the established PN code is applied to the spread spectrum modulator 2-9. The data demodulator 2-6 reproduces the data and provides it to the mobile terminal 2-7.

(3) Next, in the mobile unit 2, the data transmitted by the mobile terminal 2-7 is transmitted to the data modulator 2-8.
into the spread spectrum modulator 2-9 via
Here, it is spread spectrum modulated by the transmission PN code. At this time, the spread spectrum modulator 2
-9 transmit PN code chip clock and
PN code timing is spread spectrum demodulator 2
Based on the output of -5, that is, regarding the PN code timing, it is equivalent to returning and transmitting the base station transmission signal as it is.

The output of the spread spectrum modulator 2-9 is connected to an up converter 2-10, a high power amplifier 2-11,
The signal is transmitted to two communication satellites via a duplexer 2-2 and a mobile antenna 2-1.

(4) The base station transmits the mobile transmission signal to the communication satellite 1-
The spectrum of the first receiving section is received separately by the high directional antenna 3-1 via the communication satellite 1 and the high directional antenna 3-2 via the communication satellite 1-2. Spreading demodulator 3-6
and a spread spectrum demodulator 3 of the second receiving section.
-14, PN synchronization is established separately and despread demodulation is performed. The data demodulator 3-7 receives the output of the spread spectrum demodulator 3-6 and reproduces the data. In addition, communication/positioning operation terminal 3-1
5, the transmission timing supplied to the spread spectrum modulator 3-9 and the spread spectrum demodulator 3-
6 and 3-14, the position of the moving object is determined by the principle of triangulation based on the position information of known communication satellites, and the information is transmitted to the moving object.

(5) Since each mobile unit transmits using the entire bandwidth (14MHz), the entire power of the satellite is used, and the satellite's repeater is used in a time-sharing manner. In other words, a random access method using packet communication is used.

(Problems to be Solved by the Invention) As explained above, the method proposed by GEOSTAR is a wideband communication that uses the entire band (14MHz) of the satellite repeater using spread spectrum technology. It is possible to measure time with very high precision and to determine position with an accuracy of several meters.

However, since this method uses a spread spectrum modulator and a spread spectrum demodulator, the circuit scale increases, making it unsuitable for mobile objects that are designed to be small and lightweight. Furthermore, since communication is performed in a time-division manner, the signals are in a burst form, making real-time communication such as voice communication impossible.

In short, this method has a problem in that the emphasis is placed on the positioning function, and the communication function is extremely limited.

The present invention was made in view of these problems, and its purpose is not only to enable voice communication and data communication without increasing the circuit scale, but also to
The object of the present invention is to provide a mobile satellite communication/positioning method that can also perform positioning.

(Means for Solving the Problems) In order to achieve the above object, the mobile satellite communication/positioning system of the present invention has the following configuration.

That is, the mobile satellite communication/positioning method of the present invention is as follows:
It is composed of two communication satellites, a first and a second, one or a plurality of mobile bodies, and at least one base station; transmits communication signals from the low-directivity antenna toward the two communication satellites on the communication frequency channel assigned to its own station, and also receives signals from multiple frequency channels received by the low-directivity antenna. a first mobile transmitting/receiving means for frequency-selectively receiving signals of communication frequency channels assigned to the own station and taking them in as communication signals for the own station; a plurality of frequency channels received by the low directional antenna during positioning; A second movement in which the pilot signal of a specific frequency channel is frequency-selectively received from the signal of the station, inserted into the frequency channel assigned to the own station, and then transmitted back from the low directional antenna toward the two communication satellites. The base station includes two highly directional antennas that transmit and receive radio waves in a one-to-one correspondence with each of the two communication satellites; The signals of the plurality of frequency channels, which are composed of a plurality of communication frequency channels and the specific frequency channel into which a pilot signal is inserted, are transmitted from one of the two highly directional antennas to the corresponding one of the two communication satellites. a base station transmitting/receiving means for frequency-selectively receiving signals of one or more communication frequency channels transmitted to a communication satellite, received by one of the highly directional antennas, and capturing the signals as communication signals from a mobile body; a pilot signal receiving means for receiving and processing each pilot signal of a communication frequency channel individually received by the two highly directional antennas via the corresponding first and second communication satellites during positioning; Based on the time difference between the reception timing of the received and processed pilot signals of the two systems and the transmission timing of the pilot signal by the specific frequency channel, the positioning of the mobile object and the two
positioning calculation means for determining the position of the mobile body based on the principle of triangulation by calculating the distance to each communication satellite, and providing the positioning result to the base station transmitting/receiving means in order to transmit the positioning result to the corresponding mobile body; It is characterized by having the following.

(Operation) Next, the operation of the mobile satellite communication/positioning system of the present invention configured as described above will be explained.

First, two-way communication (voice/
data) is performed as follows. At the base station,
The transmitting unit of the base station transmitting/receiving means transmits signals of a plurality of frequency channels consisting of one or more communication frequency channels into which a communication signal is inserted and the specific frequency channel into which a pilot signal is inserted, to two highly directional antennas. The data is transmitted from one of the two communication satellites to the corresponding one of the two communication satellites, for example, the first communication satellite. In other words, the base station transmits communication signals and pilot signals using frequency division multiplexing (FDM).
The FDM signal associated with the base station transmission is transmitted from the first communications satellite in broadcast mode to one or more mobile units. Therefore, in the mobile body, the receiving section of the first mobile body transmitting/receiving means frequency-selectively receives the signal of the communication frequency channel assigned to the own station from among the signals of the plurality of frequency channels received by the low-directivity antenna. Capture it as a communication signal for your own station.

Conversely, in the mobile body, the transmitting section of the first mobile body transmitting/receiving means transmits the communication signal from the low directivity antenna to the two communication satellites on the communication frequency channel assigned to the mobile body. Communication signals related to this mobile transmission are sent to two base stations via two communication satellites.
However, at the base station, the receiving section of the base station transmitting/receiving means receives one or more communications received by one of the two high-directivity antennas. It performs frequency selective reception of signals on frequency channels and captures them as communication signals from mobile bodies.

Then, positioning is performed as follows. It goes without saying that certain procedures are required between the mobile body and the base station in order to measure the position of the mobile body.
Since the need for positioning usually occurs on the mobile body side, firstly, when positioning the mobile body, the second
The transmitting/receiving means frequency-selectively receives a pilot signal of a specific frequency channel from the signals of a plurality of frequency channels received by the low-directivity antenna, inserts it into the frequency channel assigned to its own station, and transmits the pilot signal from the low-directivity antenna to the second frequency channel. The signal is then sent back to each communication satellite. In other words, the base station receives this folded pilot signal via two different propagation paths. The form in which the base station receives signals via two different propagation paths is similar to that of normal communication, but the difference is that during positioning, the pilot signal receiving means and positioning calculating means operate.

The pilot signal receiving means performs reception processing on each of the pilot signals of the communication frequency channel individually received by the two highly directional antennas via the corresponding first and second communication satellites during positioning, It gives it to the positioning calculation means.

The positioning calculation means uses the time difference between the reception timing of the two systems of pilot signals that have been received and processed and the transmission timing of the pilot signal through the specific frequency channel to determine whether the mobile object related to the positioning and the two
The distance to each communication satellite is calculated to determine the position of the mobile body based on the principle of triangulation, and the positioning result is provided to the base station transmitting/receiving means for transmitting the positioning result to the corresponding mobile body. Here, positioning can be performed with sufficient accuracy for practical purposes.

Note that it is clear from the above description that there may be two or more base stations.

As described above, according to the mobile satellite communication/positioning method of the present invention, the normal SCPC (Single Carrier Per
Channel) - In the FDMA (Frequency Division Multiple Access) system, one inserts a pilot signal into the frequency channel and loops it back.
Not only can voice communication and data communication be performed without increasing the circuit scale on the mobile side, but also side communication can be performed concurrently.

According to the system of the present invention, the ability to provide two or more base stations has the effect of making it possible to construct a global mobile satellite communication/positioning system.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 shows a mobile satellite communication/positioning system according to an embodiment of the present invention. Components that are the same as those of the conventional example shown in FIG. 2 are designated by the same reference numerals.

In FIG. 1, a mobile body 20 of the present invention includes a mobile body antenna 2-1 consisting of a low directivity antenna,
A receiving section consisting of a duplexer 2-2, a low-noise amplifier 3-3, a down converter 2-4, a frequency conversion circuit 20-5, and a data demodulator 2-6, a mobile terminal 20-7, and a data modulator. device 2-8, selection circuit 2
0-9, a frequency conversion circuit 20-10, an up converter 2-10, and a high power amplifier 2-11.

The base station 30 also has two communication satellites (1-
The base station antennas 3-1 and 3-2, each consisting of a highly directional antenna provided in one-to-one correspondence with each of the base station antennas 3-1 and 1-2), the branching filter 3-3, and the first receiving section ( Low noise amplifier 3-4, down converter 3-5, signal branch circuit 30-1, frequency conversion circuits 30-2-1 to 30-2-N, data demodulator 3
0-3-1 to 30-3-N), a transmitter (data modulators 30-4-0 to 30-4-N, frequency conversion circuits 30-5-0 to 30-5-N, signal synthesis circuit 30-6, up converter 3-10, high power amplifier 3-11), and second receiving section (low noise amplifier 3-12, down converter 3-13, signal branch circuit 30-7, frequency conversion Circuit 30-8-
1 to 30-8-L, data demodulator 30-9-1
~30-9-L) and positioning calculation section 30-10
and a base station terminal 30-11.

As is clear from the above configuration, the mobile satellite communication/positioning system of the present invention is based on the well-known SCPC-FDMA system. In this embodiment, the base station has a transmitter having N+1 frequency channels, and transmits one of the frequency channels to the outputs of the positioning calculation units 30- and 10 (for example, a modulated data sequence obtained by digitally modulating a specific signal sequence). The remaining N frequency channels (Ch1 to ChN) are designated as a specific frequency channel (pilot channel: ChP) into which a pilot signal consisting of
1 (a communication signal consisting of an audio signal, a data signal, etc.) is inserted into a communication frequency channel.

Further, the first receiving section has the N communication frequency channels (Ch1 to ChN). This configuration is designed with bidirectional communication with a large number of mobile objects in mind.
On the other hand, the second receiving section has L communication frequency channels (Ch1 to ChL). Since this second receiving section is configured with positioning in mind, the relationship between N and L is N>>L. The transmitter, the first receiver, and the base station terminal 30-11 collectively constitute a base station transmitting/receiving means, and the first receiver, the second receiver, and the base station terminal 30-11 collectively constitute a pilot. It constitutes a signal receiving means.

Further, in the mobile body 20, the frequency conversion circuit 20-5 of the receiving section receives the command a from the mobile terminal 20-7.
Then, during two-way communication, the communication frequency channel assigned to the own station is selected and the communication signal contained therein is given to the data demodulator 2-6, and during positioning, the frequency of the pilot channel ChP is selected and the communication signal contained therein is selected. The selected pilot signal is taken out and applied as it is to the selection circuit 20-9. On the other hand, in the transmitter, the frequency conversion circuit 20-10 is set to the communication frequency channel Chn assigned to the own station, and the selection circuit 20-9 provided in the previous stage receives the command b from the mobile terminal 20-7. During bidirectional communication, the output (communication signal) of data modulator 2-8 is
During positioning, the outputs (pilot signals) of the frequency conversion circuit 20-5 are selected and applied to the frequency conversion circuit 20-10. Therefore, the receiving section, the transmitting section, and the mobile terminal 20-7 as a whole are connected to the first
and constitutes a second mobile body transmitting/receiving means.

In the above configuration, in the base station 30, the communication signal output from the base station terminal 30-11 is inserted into the corresponding channel of N communication frequency channels (Ch1 to ChN), and the positioning calculation unit 30-10 outputs the communication signal. The pilot signals for the
The signal is subjected to FDM and transmitted to the communication satellite 1-1 via an up-converter 3-10, a high-power amplifier 3-11, a duplexer 3-3, and a base station antenna 3-1. The pilot signal is constantly transmitted in broadcast mode.

Since the mobile unit 20 is not performing "positioning", the frequency conversion circuit 20-5 is set to the communication frequency channel assigned to the mobile unit 20, and takes in the signal of the communication frequency channel as the communication signal for the mobile unit.

Furthermore, in the mobile unit 20, the communication signal output from the mobile terminal 20-7 is converted into a communication frequency channel assigned to the own station in the frequency conversion circuit 20-10.
Chn, and it is transmitted from the mobile antenna 2-1 to the two communication satellites (1-1, 1-2).

At the base station, base station antennas 3-1 and 3-2
Although it is received by both, it is not "positioning", so
The base station terminal 30-11 receives input from the first receiving section as a communication signal related to mobile transmission.

In this way, in the process of two-way communication,
When the need for positioning arises on the mobile body 20 side, the mobile body 20 sends a positioning request using a communication signal from the base station 30, and similarly receives an instruction to receive a pilot signal from the base station 30 using a communication signal. Then, the mobile terminal 20-7 changes the contents of commands a and b to positioning.

Then, the pilot signal received on the pilot channel ChP is transferred to the own station's communication frequency channel Chn.
and is returned to the base station 30.

Here, since the pilot signal is simply frequency-converted and returned, the time delay here can be ignored.

On the other hand, in the base station 30, the transmission signal of the mobile object is received by both the base station antennas 3-1 and 3-2, but since it is "positioning", the base station terminal 30-
11 detects the signal (pilot signal) of the frequency channel of the mobile object 20 from among the outputs of the first and second receiving sections, and transmits it to the positioning calculation section 30-
Give to 10. The positioning calculation unit 30-10 determines whether the mobile object 20 and the two communication satellites (1-1, 1-2), the position of the mobile object 20 is determined based on the conventional triangulation method, and the result is given to the base station terminal 30-11. Since the base station terminal 30-11 inserts the positioning result into the corresponding communication frequency channel, the positioning result is transmitted to the mobile unit 20 and taken into the mobile terminal 20-7.

Note that it is rare for all channels to be used for positioning, so as mentioned above, N≫L is sufficient, and base station 3
0 circuit scale can be reduced.

Next, the positioning accuracy according to the method of the present invention can be explained as follows.

Now, if the transmission speed is 4.8Kb/s, base station 3
It is sufficiently possible to measure time with a phase error of ±3.6 (1/100 of one cycle) by clock reproduction at 0, so the measurement time accuracy is Δt = 1/4.8 (KHz) x 100 = 2.08 x 10 ^-6 (sec) Therefore, the measurement distance accuracy is as follows, where C is the speed of light: Δl=C·Δt=625 (m) In other words, a measurement distance accuracy of 1 km or less can be obtained, which is sufficient for normal applications.

(Effects of the Invention) As detailed above, according to the mobile satellite communication/positioning system of the present invention, the normal SCPC (Single
Carrier Per Channel) - In the FDMA (Frequency Division Multiple Access) system, a pilot signal is inserted into one frequency channel and then looped back, allowing voice and data communications to be carried out without increasing the circuit scale on the mobile side. Not only can this be done, but positioning can also be done at the same time.

According to the system of the present invention, the ability to provide two or more base stations has the effect of making it possible to construct a global mobile satellite communication/positioning system.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a mobile satellite communication/positioning system according to an embodiment of the present invention, and FIG. 2 is a block diagram of a conventional mobile satellite communication/positioning system. 1-1, 1-2... Communication satellite, 2, 20... Mobile object, 3, 30... Base station.

Claims (1)

[Claims] 1 Consists of two communication satellites, a first and a second, one or a number of mobile objects, and at least one base station; Directional antenna; transmits communication signals from a low directional antenna toward the two communication satellites on a communication frequency channel assigned to its own station, and receives signals from multiple frequency channels by the low directional antenna. The first step is to frequency-selectively receive the signal of the communication frequency channel assigned to the own station from the station and take it in as a communication signal for the own station.
A mobile transmitting/receiving means; frequency selectively receives a pilot signal of a specific frequency channel from signals of multiple frequency channels received by a low directivity antenna during positioning, inserts it into the frequency channel assigned to the own station, and performs low directivity. a second mobile body transmitting/receiving means for returning transmission from a mobile antenna to the two communication satellites, and the base station transmits and receives radio waves in a one-to-one correspondence with each of the two communication satellites. two high-directivity antennas that transmit signals of the plurality of frequency channels consisting of one or more communication frequency channels into which a communication signal is inserted and the specific frequency channel into which a pilot signal is inserted; transmitting signals from one of the directional antennas toward a corresponding one of the two communication satellites, and transmitting signals of one or more communication frequency channels received by one of the high directional antennas; a base station transmitting/receiving means for selectively receiving a frequency and taking it in as a communication signal from a mobile body; during positioning, the two highly directional antennas individually receive signals via the corresponding first and second communication satellites; a pilot signal receiving means for receiving and processing each of the pilot signals of the communication frequency channels; and determining the position based on the time difference between the reception timing of the two systems of pilot signals subjected to the reception processing and the transmission timing of the pilot signal by the specific frequency channel. The distance between the mobile object and the two communication satellites is calculated, the position of the mobile object is determined based on the principle of triangulation, and the positioning result is transmitted to the base station transmitting/receiving means to the corresponding mobile object. A mobile satellite communication/positioning system characterized by comprising: positioning calculation means for providing;