JPS62199130A - Satellite communication system - Google Patents

Abstract

PURPOSE:To realize the communication service of the same inoperation rate by setting each transmission power from satellites so as to cancel the deviation of the margin based on rainfall attenuation thereby using an earth station of the same scale nationally. CONSTITUTION:A transmission power per channel in spot beams 1-6 from a communication satellite 7 is set respectively to P1-P6 and earth stations 1c-6c in the service area of each spot beam are provided with the same diame ter of antenna. The transmission power beams P1-P6 are set to offset the deviation among the spot beams in the line margin of down-like. The said setting is realized by using an attenuator to change the gain of a satellite repeater connected to each spot beam. As a result, the equipment of the earth station side is made all the same in scale and the equipments are operated in the inoperation rate.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a satellite communication system, and relates to a satellite communication system in which communication is carried out between earth stations via a geostationary communication satellite equipped with a multi-beam antenna on 1%.

[Conventional technology]

Conventionally, one effective method for configuring a satellite communication system for domestic use is to mount a multi-beam antenna on a geostationary satellite to increase the satellite's equivalent isotropic radiated power (EI 几P) and to make the earth station smaller. A plan to do so is presented.

When establishing a satellite communication system using quasi-millimeter wave band (Ka, Ku band) frequencies, radio wave attenuation due to rain (
rain attenuation) is an important factor in line planning. in general,
The reliability of satellite communication systems using such quasi-millimeter wave bands is expressed as the annual percentage of time that lines are disconnected due to rain attenuation (outage rate). The necessary value of this unavailability rate is determined depending on the purpose of use of the line, but it is usually necessary to secure a value of about 0.05%.

The rainfall attenuation required for planning a satellite communication system using the sub-millimeter wave band is now estimated based on 10 years of rainfall data for each region of the country (Research Practical Report 2 Nippon Telegraph) Telephone Corporation Telecommunications Research Institute, Volume 28,
No. 8, pp. 1667-1676), circuit design is usually performed using this estimated value. Table 1 shows major 1 nationwide
Ku-band downlink frequency (115 GHz) corresponding to a 10-year average time rate of 0.05% in the two cities
Rainfall attenuation measurement in 9. The amount of increase ΔN in reception noise temperature at that time, the line margins M and D (= 1., +ΔN) required for downlink from the above, and the line margin with Kochi as the reference (Oda) showing the maximum rain attenuation. , the rainfall attenuation amount L10 at the uplink frequency (14.5 GHz) (this is the line margin required for uplink), and the deviation thereof in units of t-dB. These values determine the orbital position of the satellite at 1 east longitude.
Calculations were made using the above literature assuming that the noise temperature of the earth station receiving device was 50 degrees Celsius and 200 degrees Celsius.

The unit of each numerical value in the following margin is d LI: Downlink rain attenuation amount ΔN = Noise temperature increase amount when the above rain attenuation amount M □: Downlink line margin (Lm * + ΔN) L □ Near link rain attenuation amount Figure 2 is a coverage map showing the service area of each spot beam of a communications satellite that emits six spot beams with equal beam widths: Hokkaido beam, Tohoku beam, Kanto/Chubu beam, and Kansai/Chushikoku beam.

The 6-spot beam of the previous beam, Okinawa Beam, is set to cover all of Japan. 12~ shown in the figure
The circles 6a each represent the Chibis area of each beam, and each of the 12 major cities shown in Table 1 belongs to one of the service areas.

Table 2 shows the deviation (in dB based on Kansai and Chugoku-Shikoku spots) of the line margin required for downlink and uplink for each spot beam corresponding to each service area in Figure 2. ) is determined from Table 1 and is shown here. If the service area includes multiple cities, the value of the city with the largest amount of rainfall attenuation is used to display the target area within the service area. Such values are normally used at the system planning stage in order to ensure the necessary line reliability in all cities in the area.

If the transmission power per channel transmitted from the satellite is the same for all spot beams, the downtime rate at each earth station is 0.
The degree of margin necessary to secure 0.5% or more is the second
From the table, the Hokkaido beam earth station requires +5 dB less in the downlink and 9.5 dB less in the uplink than the Kansai/Chushikoku beam earth station.

Table 2 M. The unit of deviation 1M1 deviation is dB.To deal with uplink rain attenuation, transmission power control is performed to increase the earth station's transmission power during rain so that the received power of the satellite remains constant even during rain. There is no suitable control means for link rain attenuation, and it is generally necessary to provide the necessary margin for the performance of the earth station receiving equipment.
It's been well taken care of. Table 2 shows what is necessary to ensure the same unavailability rate when the noise temperature of the earth station low-noise amplifier is constant and only the antenna diameter is changed to deal with deviations in downlink line margin M. antenna diameter ratio,
The diameter of the Hokkaido beam earth station with the least rainfall attenuation is 1.
It is shown as follows.

Figure 3 is a system conceptual diagram showing the concept of the system configuration of a conventional satellite communication system using six spot beams.
Each of the spot beams 1 to 6 of the communication satellite 7a transmits the same transmission power P0 per channel, and the antennas of the earth stations 1b to 6b corresponding to each spot beam are configured with a diameter ratio as shown in the figure. There is. For example, the antenna diameter of earth station 4b (Kochi) corresponding to Kansai/Chugoku-Shikoku beam 4 is 37 times the antenna diameter of earth station 1b (Sapporo) corresponding to Hokkaido beam 1. In this way, by changing the diameter of the earth station antenna, the system is configured to maintain the same annual downtime rate of 0.05% in all regions.

[Problem that the invention seeks to solve]

In the conventional satellite communication system mentioned above, in order to maintain a constant annual downtime rate, the antenna diameter of the earth station must be changed depending on the region, and the problem is that the same size earth station cannot be used nationwide. There is.

Conversely, when earth stations of the same size are used, there is a problem that the downtime rate varies depending on the region and it is not possible to ensure the same level of reliability.

An object of the present invention is to provide a satellite communication system that eliminates the above-mentioned problems and allows communication services with the same downtime rate to be received in any region of the country using earth stations of the same scale.

[Means for solving problems]

The satellite communication system of the present invention is a satellite communication system in which communication is carried out between earth stations via a communication satellite in a geostationary orbit equipped with a multi-beam antenna that emits a plurality of spot beams. , rather than canceling out the difference in the downlink line margin between the respective spot beams, which is necessary to keep the downlink line margin below a predetermined value, the communication channel transmission transmitted by the communication satellite to each of the spot beams is The power is set and configured.

〔Example〕

Next, the present invention will be explained in detail based on examples.

FIG. 1 is a conceptual system diagram showing the concept of the system configuration of an embodiment of the present invention. In Figure 1, communication satellite 7
The transmission power for each channel transmitted to each spot beam 1 to 6 is not the same, but is set to PI to P6, and the earth stations 1c to 6c within the service area of each spot beam are all equipped with antennas of the same diameter. It is configured. The transmission power Pl to P6 of each beam is set so as to cancel the deviation between each spot beam of the downlink line margin M shown in Table 2, P1=P4-&5da, P=: P4
6.8 dB* Ps ””4 3.5'B + P
s= P4 0.4dB, P@: P4 g,
It is set to gda. This setting can be easily implemented, for example, by changing the gain of a satellite repeater connected to each spot beam using an attenuator or the like.

As is clear from the above explanation, the transmission power Pl-P sent from the satellite to each spot beam is not the same, but is set to offset the deviation of the line margin M based on rain attenuation. In addition, it is possible to ensure the same downtime rate by setting all the earth stations to the same scale. By configuring such a system, equipment for earth stations that are used in large numbers can be mass-produced according to unified standards, and an economical system configuration becomes possible. Furthermore, portable stations and mobile stations have the advantage of being able to operate with the same downtime rate no matter where they are moved across the country. Note that in order to prevent uplink rain attenuation, it is necessary to control the earth station transmission power as in the past.

Above, Ku emits 6 spot beams with the same beam width.
Although the case of a satellite communication system in the Ku band has been described, the technical idea of the present invention can also be applied to the case where spot beams with different beam widths are used together, and it goes without saying that it can also be applied to the case of the Ka band. stomach.

〔Effect of the invention〕

As explained in detail above, according to the satellite communication system of the present invention, the earth station standards can be made the same throughout the country and can be operated with the same downtime rate, and the earth station equipment can be made more economical. Mobile stations and portable stations have the advantage of being able to operate with the same downtime rate no matter which region of the country they are moved to.

[Brief explanation of drawings]

Fig. 1 is a system conceptual diagram showing the system configuration of an embodiment of the present invention, Fig. 2 is an overlapping diagram showing the service area of each spot beam, and Fig. 3 is a system conceptual diagram showing an example of the conventional system configuration. . 1-6...Spot beam, la-6a...
...Service area, 1b to 5b, lc to 6C...
...Earth station, 7°7a...Communication satellite. Agent: Susumu Uchihara, patent attorney! @

Claims (1)

[Claims] In order to keep the annual downtime rate below a predetermined value in a satellite communication system that communicates between earth stations via a communication satellite in geostationary orbit equipped with a multi-beam antenna that emits multiple spot beams. A satellite communication system characterized in that the transmission power per communication path transmitted by the communication satellite to each of the spot beams is set so as to offset the difference in required downlink line margin between the spot beams. .