JPS593047B2 - Message communication system for ships using satellites - Google Patents

Description

Detailed Description of the Invention The present invention realizes expansion of applicability to include small ships, effective use of satellite radiated power, increase in communication capacity, and effective use of frequencies in a ship communication system for public communication using satellites. This article relates to the configuration of a message communication system.

The conventional maritime communication system for public communication using satellites is for telephone, 50 baud telex, and data communication, and the ship station equipment also uses a large antenna with a diameter of 1.2 m, and the voice "5" is analog. The transmission system, telex, etc., is an expensive configuration that uses a digital transmission system.

As a result, the subscriber's usage fee is expensive, and furthermore, it is physically difficult to install the ship station equipment on small ships. In addition, since this method radiates satellite radio waves for ships as a global beam over the entire area of the service area, it has the advantage of simplifying the configuration of the satellite. There was a problem. At the same time, repeated use of frequencies was not possible due to the use of a global single beam. The present invention aims to solve these drawbacks, and its features are as follows: 1) communication can be achieved with a small amount of information required to be transmitted, transmission delay can be ignored, and real-time 30-way two-way communication is not always possible; The purpose of the present invention is to use a method for message communication that does not require message communication, and ii) efficiently radiate satellite radio waves for ships using beam scanning or multi-beam methods, thereby maximizing the use of satellite capabilities.

Embodiments will be described below with reference to the drawings.

FIG. 1 shows one embodiment of the application of the beam scanning method in the message communication system according to the present invention, in which 1 is a coast station, 2 is a satellite, 3 is a service area sea area, and 4 is a satellite beam area at a certain time. , 5 shows the scanning line of the scanning beam, 6 shows the ship A, and 7 shows the ship B.

Compared to mobile communications that target moving objects such as cars and people on land, sea-land-ship communications have a characteristic that the number of moving objects per unit area within the service area, that is, the traffic density per unit area, is extremely low. have. For example, there are no more than 4,000 Japanese-flagged international vessels (including fishing boats). For this reason, in the conventional method of emitting satellite radio waves evenly and simultaneously throughout the service area, the usage rate of satellite radio waves is extremely low. In FIG. 1, powerful radio waves are concentrated in a narrow area and each ship communicates when its position is illuminated by the beam. The required transmission time for message transmission in 2Kb/S packet format is only about 0.5 seconds, so by appropriately selecting the beam scanning speed of the satellite, each ship can communicate while it is being irradiated. can be completed.

Beam scanning can be realized in a satellite antenna device by an electronic method using a phased array or the like, or by a mechanical method. Furthermore, in areas with high ship density, the beam width should be widened (
Further efficiency can be achieved by adopting a method such as a variable beam width beam scanning method) or a slow adjustment of the scanning speed (variable scan speed beam scanning). Here, the ratio of the area of the service area 3 to the area of the beam 4 is the communication capacity increase gain of the present invention, and the ship station equipment (antenna, transmitting function, etc.) can be made smaller and have lower power consumption by this amount. I can do it. Next, the case of message transmission from ship to land and ship to ship will be explained.

Ship A detects that the beam has arrived in its own sea area by receiving beacon waves or other methods, and transmits a message signal in packet format to the land side via a satellite. Furthermore, a message from ship A to ship B can also be transmitted via a satellite or coast station, etc. by using the same method and by providing the satellite or coast station with a memory function. For example, when the service area is the Pacific Ocean region including the sea near Japan, the communication capability increase gain by the present invention is on the order of 100 times when scanning with a beam of several hundred and one diameter. By focusing on downsizing, etc., it will be possible to significantly reduce charges. Figure 2 shows an example of using multi-beams and repeating frequencies for ships in order to make early use of frequencies and increase communication capacity, where 10 is a satellite and 11 is a service area. ,1
2 indicates a beam irradiation area in which the service area is divided into multiple beams.

A, B, C, and D in the figure indicate the different frequencies used and indicate that they are used repeatedly. The greater the number of beams, the higher the frequency utilization rate. In the case shown in the figure, if the ship station has four communication channels of frequencies A, B, C, and D, it can communicate by switching channels no matter where it is in the sea area within its service area. Even in this case,
A gain can be obtained depending on the ratio of the service area area to the area of each beam. This gain can be used to make the ship station more compact and economical, as in the case of the embodiment shown in FIG. The invention of the embodiment shown in FIG. ) and the features of the scanning spot beam method (radiation energy is concentrated in a small area, so the rate of use of radio wave energy that impedes communication is extremely high; in other words, the satellite transmitter output is reduced and It integrates the antenna and transmitter of the ship station (small, low power, and economical), and is an extremely low-cost ship communication method for public communications as a means of communication between ships and land, and between ships. method can be realized.

For example, in the case of a spot beam with an area ratio of 1/100, the transmitter power may be 1/100 of that of a conventional global beam. The embodiment shown in FIG. 2 also has the benefit of simplifying the ship's station equipment in inverse proportion to the increase in satellite antenna gain from the perspective of the ship (at the expense of the user). Brief Description of the Drawings FIG. 1 shows an embodiment of a message communication system for ships using beam scanning according to the present invention, and FIG. 2 shows an example of a message communication system for ships using multi-beam irradiation.

1...Coast station, 2...Satellite, 3...
... Service area sea area, 4 ... Scanning beam at a certain time, 5 ... Scanning line of scanning beam, 6 ... Vessel A, 7 ...
...Ship B, 10...Satellite, 11...
...Service area sea area, 12...One beam in the spot beam.

Claims (1)

[Claims] 1. In a message communication system between a ship and land or between ships via a satellite, the beam area of the satellite is narrower than the service area area on earth, and the satellite beam scans the service area according to the density of ships. Using a satellite, which scans sequentially using a variable scanning speed beam scanning method in which the speed is controlled, and the messages transmitted are in the form of packets, which are transmitted via the satellite as the ship is scanned by the satellite beam. Ship message communication system. 2. In a message communication system between a ship and land or between ships via a satellite, the beam area of the satellite is narrower than the service area area on Earth, and the beam width of the satellite beam is controlled according to the density of ships in the service area. A message communication system for ships using a satellite, which is characterized in that sequential scanning is performed using a variable width beam scanning method, and the transmitted messages are in packet format, and are transmitted via the satellite when the ship is scanned by the satellite beam. . 3. In a message communication system between a ship and land or between ships via satellite, the satellite beam that illuminates the service area is a multi-spot beam, and the same frequency is used repeatedly in multiple beams to transmit messages. is a message communication system for ships using satellites, which is characterized by being carried out in packet format.