JPH05218932A - Satellite communication equipment - Google Patents

Abstract

PURPOSE:To facilitate the revision of an offset value when a terrestrial station is moved by coupling electrically a position measurement device and a transmitter, fetching a reference timing being a reference when a burst signal is sent, and offsetting the reference timing by the offset calculated in the transmitter. CONSTITUTION:The latitude and the longitude of the terrestrial station measured by a position measurement device 1 are converted into an electric interface signals by the device 1 and the resulting information 4 is sent to an interface section 5 in the inside of a transmitter 2, in which the information is converted into a common electric signal used in the inside of the transmitter 2. Then the converted longitude and latitude information is sent to an offset calculation section 11, and the information and latitude 6 and altitude 7 of the communication satellite stored in advance in a memory section 8 are used to calculate a propagation delay from the terrestrial station till the satellite. That is, an offset value 10 calculated by an offset calculation section 11 is sent to a transmission timing generating section 13 and the timing is shifted by the offset value 10 calculated with respect to the reference timing 3 to decide the transmission timing 12 of the burst signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a satellite communication device,
In particular, it relates to a satellite communication device for transmitting and receiving digitally modulated burst signals.

[0002]

2. Description of the Related Art A satellite communication system of digital multiple access for performing communication on a common channel via a communication satellite, for example, a well-known time division multiple access (TDMA) communication system, a pure Aloha communication system, and a slot. In the attached Aloha communication system and the like, burst signals must be transmitted and received among the geographically dispersed earth stations participating in the communication system.

Generally, in satellite communication, a certain delay occurs until a signal transmitted from an earth station is received again by the earth station via a communication satellite located in outer space. In particular, it is well known that the time required by geostationary satellites is approximately 300 msec because radio waves travel back and forth over a distance of approximately 36,000 km above the ground. This delay is called a round trip delay and can be said to be one of the typical characteristics of satellite communication.

The round trip delay depends on the distance between each earth station transmitting and receiving signals and the communication satellite, and the distance is uniquely determined by the latitude and longitude where each earth station is located. The distance between the earth station and the communication satellite is "Revision of satellite communication technology, published by Institute of Electronics and Communication Engineers, Kenichi Miya, Showa 60
As shown on pages 7-8, it is represented by the following formula.

L = {R ² + (R + H) ² −2R (R + H) cos β} ^1/2 (1)

Cos β = cos γ · cos Δφ (2)

Here, L is the distance between the earth station and the communication satellite, R is the radius of the earth (6,378 km), H is the distance from the ground to the communication satellite, γ is the latitude of the earth station, and Δφ. Shows the longitude difference between the communication satellite and the earth station.

Therefore, the propagation delay D from the earth station to the communication satellite is given by the following equation.

D = L / c (sec) (3)

Here, c is the velocity of light in free space (about 3 × 10 ⁸ m / sec).

Thus, the propagation delay from the earth station to the communication satellite is determined by the latitude and longitude where the earth station is located.

On the other hand, in recent years, the use of a digital multiple access satellite communication system such as a time division multiple access (TDMA) communication system and an Aloha communication system with a slot for performing communication on a common channel via a communication satellite has increased. A bucket type VSAT system and a mobile satellite communication system are examples of this. In these systems, burst signals are transmitted and received among the earth stations dispersed geographically over a wide area.

At this time, in order to demodulate the burst signal at the receiving side with high efficiency, it is desirable to know the approximate arrival position of the burst signal. For that purpose, burst signals transmitted from a plurality of earth stations are required to be arranged on a common time slot on the time axis of the communication satellite. If burst signals that access a common channel are arranged on the time axis of the communication satellite without being projected on the time slot, any station participating in the system will receive the burst signal on the time slot. Since they are arranged side by side, the arrival position of the burst signal is within this time slot.

In order to arrange burst signals transmitted from a plurality of earth stations on a common time slot on the time axis of a communication satellite, individual earths in which a guard time in a unit time slot is widely dispersed It is conceivable to set all the propagation delays from the earth station of the station to the communication satellite as long as possible, but this is not preferable because the data transmission efficiency deteriorates.

Therefore, the "time difference" between the reference timing signal and the transmission timing for transmitting the burst signal is optimized in accordance with the propagation delay unique to the earth station from the earth station to the communication satellite. It becomes necessary to adjust.

This will be described with reference to the drawings. 3 to 4 are explanatory diagrams for arranging burst signals on a common time slot on the time axis of a communication satellite.

Of these, FIG. 3 shows an example in which earth stations located at different locations send burst signals according to a common reference timing. In this case, it can be seen that the burst signals do not line up in a common time slot on the time axis of the communication satellite because the propagation delay from the earth station to the communication satellite is different.

FIG. 4 shows an example in which earth stations located at different places send burst signals by giving their own unique offset values to common reference timings. In this case, it can be seen that the burst signals can be arranged in a common time slot on the time axis of the communication satellite even if the propagation delay from the earth station to the communication satellite is different.

FIG. 2 shows a concrete example of the prior art. In FIG. 2, reference numeral 101 is a transmitter, reference numeral 102 is an offset parameter, and reference numeral 103 is a reference timing. The transmitter 101 includes a transmission timing generation unit 104,
Output 105, data generator 106, output 10
7, buffer unit 108, its output 109, modulator unit 110
Has become.

The operation will be briefly described. Transmitter 101
An offset parameter 102 and a reference timing 103 are input from the outside. The offset parameter 102 is calculated after obtaining the latitude and longitude where the earth station is located,
The propagation delay from the earth station to the communication satellite is calculated by the above equations (1), (2) and (3), and the reference timing 103
The "time difference" between and is further calculated.

After that, this is converted into a parameter that can be easily handled by the circuit configuration of the transmission timing generation unit 104 inside the transmitter 101 and input. Inside the transmitter 101,
Burst-shaped data 10 created by the data generation unit 106
7 is temporarily stored in the buffer unit 108, and is output according to the transmission timing 105 sent from the transmission timing generation unit. The modulator 110 receives this, digitally modulates it, and then outputs it.

[0022]

The "time lag" in the above-mentioned conventional example is different for each earth station. For this reason, it has conventionally been necessary to obtain accurate latitude and longitude where the earth station is located, perform troublesome calculation, and input relevant parameters to the satellite communication device based on the calculation result. It is not easy to know the exact latitude and longitude of the place where the earth station is located. Moreover, when the earth station was moved to another place, the same calculation had to be calculated again according to the new position. This is because in the mobile satellite communication devices that have been put into practical use one after another in recent years, since communication is performed while moving, it is practically impossible to process this in real time.

[0023]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a satellite communication device capable of improving the disadvantages of the conventional example, and in particular, capable of automatically changing and setting the offset value even if the earth station is moved to another location. To that end.

[0024]

According to the present invention, a positioning device for measuring the latitude and longitude of an earth station, converting the measured latitude and longitude into an electric signal and outputting the electric signal, and information from the positioning device are input and digitally modulated. And a transmitter for transmitting a burst signal, the transmitter stores the latitude and longitude information from the output of the positioning device and the longitude and altitude of the communication satellite used by the system. Input the information output from the memory unit and the interface unit and the longitude and altitude of the communication satellite used by the system, which is given in advance in the memory unit, and calculate the offset value between the reference timing and the transmission timing from these Offset calculation section and the reference timing separately input based on the offset value calculated by this offset calculation section Transmission timing generating section shifted by preparative value amount to generate a transmission timing of the burst signal,
A data generation unit that shapes and outputs data to be transmitted in a burst form, and output data from this data generation unit is temporarily stored and output as burst-like data for transmission according to the transmission timing sent from the transmission timing generation unit. And a modulator that digitally modulates and outputs the output of the buffer. This aims to achieve the above-mentioned object.

[0025]

The positioning device 1 is electrically coupled to the transmitter 2, and the transmitter 2 takes in the reference timing 3 which serves as a reference when transmitting the burst signal, and calculates it in the offset calculation unit 11 inside the transmitter 2. The reference timing 3 is offset by the offset thus set, and the burst signal is modulated and transmitted using this as the transmission timing 12.

[0026]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In FIG. 1, reference numeral 1 is a positioning device for measuring the latitude and longitude of an earth station and converting it into an electric signal for output, reference numeral 2 is a transmitter for transmitting a digitally modulated burst signal, and reference numeral 3 is a burst. The reference timing, which is the reference for generating the signal transmission timing, is shown.

The transmitter 2 stores an interface unit 5 for reading the latitude and longitude information 4 measured by the positioning device and converted into an electric signal, and a longitude 6 and an altitude 7 of a communication satellite used by the system. Memory section 8 to hold
And a reference timing and a transmission timing based on the longitude 6 and altitude 7 information of the communication satellite for the system, which receives the earth station latitude and longitude signals 9 output from the interface unit 5 and is given in advance in the memory unit 8. An offset calculation unit 11 for calculating an offset value of 10 and a transmission timing generation unit 13 for generating a transmission timing 12 of a burst signal by shifting the reference timing 3 using the offset value 10 calculated by the offset calculation unit 11. I have it. Further, the transmitter 2 receives the data to be transmitted or receives it from the outside, shapes it into a burst and outputs it, and the burst data 15 output from the data generator and receives it. Is temporarily stored and receives the transmission timing 12 sent from the transmission timing generation unit 13 and outputs the burst data 16 for transmission in accordance therewith, and the output 16 of the buffer unit 17 is received and digitally modulated. It is composed of a modulator 18 for outputting the output.

Next, the operation of the above embodiment will be described.

The latitude and longitude of the earth station measured by the positioning device 1 are converted into an electrical interface specific to the positioning device and output to the transmitter 2.

As the positioning device 1, a relatively inexpensive positioning device for measuring the position by wireless is usually used, and examples thereof include those using the Loran C system and the Omega system. In addition, a positioning device that uses a satellite among wireless devices has been easily used in recent years, and a typical one is GPS. For example, "Electronic Life September 1991 issue
Page 37-90 ", GP easily available as of September 1991
You can see all of the S receivers. It is also well known that there is a system that measures the position using two communication satellites as a positioning device using satellites. The outputs of these positioning devices have their own electrical interfaces, and for example, the interfaces specified by ARINC and NMEA are used as standard.

The latitude / longitude information 4 converted into an electric signal is sent to the interface section 5 inside the transmitter 2. Here, the latitude / longitude information 4 sent by the unique interface is converted into a common electric signal used inside the transmitter 2. Usually, a microprocessor is used in the offset calculation unit 11 described later, and thus the converted signal is a TTL or CMOS level bus signal.

The converted latitude / longitude information 5 is then sent to the offset calculation unit 11 inside the transmitter 2. If burst signals that access a common channel are arranged on the time axis of the communication satellite without being projected on the time slot, any station participating in the system will receive the burst signal on the time slot. Since they are arranged side by side, here, the latitude 6 and longitude 7 of the communication satellite used by the system which is stored in advance in the memory unit 8 is received and the position and position of the satellite are measured. Using the information 5 of 1., the propagation delay from the earth station to the communication satellite is obtained by the equations (1), (2) and (3). A reference timing 3 input to a transmission timing generation unit 13 described later is a reference timing signal for transmitting a burst signal, and the offset calculation unit 11 includes a reference timing 3 and a transmission timing 12 that is a transmission timing. The "time difference", that is, the offset value 10, is calculated from the obtained propagation delay from the earth station to the communication satellite.

The offset calculation section 11 needs to perform many complicated calculations at high speed and needs flexibility, and therefore is suitable for use with a microprocessor. Also,
The offset value calculated here is of course time, but due to the ease of handling and the practicability when implementing the device,
It is represented by the number of bits converted into a transmission rate.

The above-mentioned reference timing 3 is commonly distributed to all earth stations participating in the system, and may be distributed using, for example, a common satellite channel.
If the reference timing is distributed by the common satellite channel, the phase will be different among the receiving earth stations due to the propagation delay from the earth station to the communication satellite, and further from the communication satellite to the earth station. It cannot be used as the timing, but if the propagation delay from the communication satellite to the earth station is known, the phase can be corrected by the same method as described above, and the system can be used by using the corrected reference timing. It can be regarded as a common timing for all earth stations participating in.

The offset value 10 calculated by the offset calculation section 11 is sent to the transmission timing generation section 13, and the reference timing 3 obtained as described above is shifted by the calculated offset to generate a burst signal. The transmission timing 12 used for transmitting is generated.

On the other hand, the data to be transmitted is the data generator 1
4 is generated, or is input here from the outside. The data generation unit 14 shapes this into a burst shape and then outputs it to the buffer unit 17. Buffer unit 17
Then, the burst data 15 created by the data generation unit 14 is temporarily stored, and the burst data 16 for transmission is output according to the transmission timing 12 sent from the transmission timing generation unit 13. The modulator 18 receives this and performs digital modulation to output it.

As described in the above embodiments, in the present invention, by using the positioning device electrically coupled to the transmitter, the propagation from the earth station to the communication satellite, which is conventionally performed for each earth station, is performed. It is possible to omit the troublesome calculation of the delay and the input work of the related parameters based on the calculation result. Also, even if you move the earth station to another place,
The offset value can be changed promptly without new position information from others. Further, even in mobile satellite communication in which communication is performed while moving, there is an advantage that position information that changes from time to time can be taken in at any time and the offset value can be dynamically changed.

[0038]

As described above, according to the present invention,
By electrically interfacing the positioning device and the transmitter,
The offset value between the reference timing as the reference and the transmission timing for actually transmitting the burst signal is automatically calculated inside the transmitter, and the reference timing is offset according to the calculated offset value to generate the transmission timing. Therefore, the complicated calculation for obtaining the propagation delay from the earth station to the communication satellite, which was conventionally performed for each earth station,
Also, it is possible to omit the work of inputting the related parameters based on the calculation result, and to change the offset value promptly without new position information from others even when the earth station is moved to another place. (EN) An excellent satellite communication device that has not been available in the past, in which the position information that changes from time to time can be taken in and the offset value can be dynamically changed even in mobile satellite communication in which communication is performed while moving. be able to.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a block diagram showing a conventional example.

3 to 4 are explanatory diagrams for arranging burst signals on common time slots on a time axis of a communication satellite.

[Explanation of symbols]

 1 Positioning Device 2 Transmitter 3 Reference Timing 4 Latitude / Longitude Information Converted to Electrical Signals 5 Interface 6 Longitude of Communication Satellite Used by System 7 Altitude of Communication Satellite Used by System 8 Memory 10 Offset Value 11 Offset calculation unit 13 Transmission timing generation unit 14 Data generation unit 17 Buffer unit 18 Modulation unit

Claims (1)

[Claims] 1. A positioning device for measuring the latitude and longitude of an earth station, converting it into an electric signal and outputting the electric signal, and a transmitter for inputting information from the positioning device and transmitting a digitally modulated burst signal. This transmitter has an interface unit that reads latitude and longitude information from the output of the positioning device, a memory unit that stores and holds the longitude and altitude of a communication satellite used by the system, and the interface unit. An output calculator and an offset calculator that calculates the offset value between the reference timing and the transmission timing by inputting information on the longitude and altitude of the communication satellite used by the system, which is given in advance in the memory unit, Based on the offset value calculated by this offset calculation unit, the separately input reference timing is shifted by the offset value. A transmission timing generation unit that generates a transmission timing of a burst signal, a data generation unit that shapes and outputs data to be transmitted in a burst form, and output data from the data generation unit that is temporarily stored and transmitted from the transmission timing generation unit. A buffer unit that outputs as burst-like data for transmission according to the transmitted transmission timing,
A satellite communication device comprising: a modulator that digitally modulates and outputs the output of the buffer unit.