Description

APPARATUS AND METHOD OF CONTROLLING INTERFERENCE IN SATELLITE COMMUNICATION SYSTEM

Technical Field

[1] The present invention relates to a method and apparatus of controlling interference in a communication system. More particularly, the present invention relates to an interference control method and apparatus that are capable of reducing interference signals transmitted to another communication system.

[2] The present invention was supported by the IT R&D program of MIC/IIT

[2005-S-014-03, Development of Satellite IMT2000+ Technology]. Background Art

[3] It has been considered to operate a service system using satellite communication in order to transmit a large amount of multimedia data to a wide service area. Satellite communication uses a satellite in space to perform communication between earth stations. Satellite communication provides a communication service and a broadcasting service using a high frequency bandwidth, such as a millimeter wave band.

[4] Since frequency resources are limited, the communication system using the satellite communication may use the same frequency bandwidth as that of another satellite communication system and another ground communication system. In this case, during communication between an earth station and a satellite, interference signals may be transmitted to another satellite communication system or another ground communication system. The interference signals cause the performance of another satellite communication system or another ground communication system to deteriorate, and the deterioration of the performance in another satellite communication system or another communication system may cause deterioration of the performance of a satellite communication system including the earth station that communicates with the satellite.

[5] The performance of the beam pattern of an antenna of the satellite or the ground terminal is improved in order to solve the interference problems. However, a high-gain antenna has limitations in reducing the interference signals due to errors in beam directivity, and amplitude distribution and phase distribution errors on an antenna aperture.

Disclosure of Invention Technical Problem

[6] The present invention has been made in an effort to provide an interference control method and apparatus in a satellite communication system that are capable of ef-

fectively reducing interference signals transmitted to another satellite communication network or another wireless communication network. Technical Solution

[7] According to an aspect of the present invention, there is provided a method of controlling interference transmitted from a first communication system to a second communication system. The method includes estimating a power of a received signal, determining a transmission power of a transmission signal on the basis of a difference between the power of the received signal and a reference power, forming a transmission beam according to a direction in which the transmission signal is transmitted, and transmitting the transmission signal with the transmission power along the transmission beam.

[8] According to another aspect of the present invention, there is provided an apparatus of controlling interference transmitted from a first communication system to a second communication system. The apparatus includes a power controller, a transmission beam forming unit, and a transmission power amplifier. The power controller estimates conditions of a channel for a received signal, and determines a level of a transmission power of a transmission signal on the basis of the conditions of the channel. The transmission beam forming unit forms a transmission beam according to a direction in which the transmission signal is transmitted. The transmission power amplifier outputs the transmission signal with the transmission power level along the transmission beam.

Advantageous Effects

[9] According to the above-mentioned aspects of the present invention, it is possible to share frequencies between satellite communication systems or between a satellite communication system and another communication system using the same frequency bandwidth by changing the power of a transmission signal according to channel conditions. As a result, it is possible to efficiently use limited frequency resources. Brief Description of the Drawings

[10] FIG. 1 is a diagram schematically illustrating a satellite communication system to which the present invention is applied;

[11] FIG. 2 is a block diagram illustrating the structure of interference control apparatuses of a satellite and a satellite terminal according to an exemplary embodiment of the present invention;

[12] FIG. 3 is a block diagram illustrating the structure of a power controller shown in

FIG. 2;

[13] FIG. 4 is a flowchart illustrating the operation of the power controller shown in FIG.

2; and

[14] FIG. 5 is a diagram illustrating a method of determining transmission power in the

power controller shown in FIG. 2. Mode for the Invention

[15] In the following detailed description, only certain exemplary embodiments of the present invention have been shown and described, simply by way of illustration. As those skilled in the art would realize, the described embodiments may be modified in various different ways, all without departing from the spirit or scope of the present invention. Accordingly, the drawings and description are to be regarded as illustrative in nature and not restrictive. Like reference numerals designate like elements throughout the specification.

[16] In the specification and claims, unless explicitly described to the contrary, the word

"comprise" and variations such as "comprises" or "comprising" will be understood to imply the inclusion of stated elements but not the exclusion of any other elements. In addition, the terms "-er", "-or", and "module" described in the specification mean units for processing at least one function and operation, and can be implemented by hardware components or software components, and combinations thereof.

[17] Hereinafter, an apparatus and method for controlling interference in a satellite communication system according to exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[18] FIG. 1 is a diagram schematically illustrating a satellite communication system to which the present invention is applied, and FIG. 2 is a block diagram illustrating the structure of interference control apparatuses of a satellite and a satellite terminal according to an exemplary embodiment of the present invention.

[19] As shown in FIG. 1, the satellite communication system includes a satellite 100 and a satellite terminal 200.

[20] The satellite 100 receives signals from one satellite terminal 200, amplifies the received signals, and retransmits the amplified signals to another satellite terminal 200.

[21] The satellite terminal 200 is a terminal that is capable of transmitting/receiving signals to/from the satellite 100.

[22] In this case, satellite links that connects the satellite terminals 200 through the satellite includes a downlink (DL) from the satellite 100 to the satellite terminal 200 and an uplink (UL) from the satellite terminal 200 to the satellite 100. In general, in a satellite communication system, the frequency of the signal transmitted through the uplink is higher than that of the signal transmitted through the downlink.

[23] Interference signals transmitted from the satellite terminal 200 through sidelobes of an antenna beam pattern may be transmitted to another satellite 10 of another satellite communication network through the uplink (UL). The interference signals transmitted from the satellite 100 through the sidelobes of the antenna beam pattern may be

transmitted to another wireless communication network 20 using the same frequency as that of the satellite communication system through the downlink.

[24] As shown in FIG. 2, the interference control apparatuses of the satellite 100 and the satellite terminal 200 for reducing the interference signals transmitted to another satellite 10 and another wireless communication network 20 include receivers 110 and 210, reception beam forming units 120 and 220, transmission/reception signal processing units 130 and 230, transmission beam forming units 140 and 240, transmitters 150 and 250, power controllers 160 and 260, and transmission power amplifiers 170 and 270, respectively. The interference control apparatus of the satellite 100 reduces the interference signals transmitted from the satellite 100 to another wireless communication network 20, and the interference control apparatus of the satellite terminal 200 reduces the interference signals transmitted from the satellite terminal 200 to the satellite 10 in another satellite network.

[25] As can be seen from FIG. 2, in the interference control apparatus of the satellite 100, the receiver 110 receives the signals transmitted from the satellite terminal 200, and the reception beam forming unit 120 forms a reception beam according to the direction in which signals are received.

[26] The transmission/reception signal processing unit 130 processes the received signal and generates transmission signals, and the transmission beam forming unit 140 forms a transmission beam according to the direction in which signals are transmitted. According to this exemplary embodiment of the present invention, the transmission beam forming unit 140 calculates a weight value required for each antenna from a desired satellite direction and satellite direction data of another satellite 10, and applies the weight value to each antenna, thereby forming a main transmission beam in the desired direction and a very low antenna beam in a non-desired direction.

[27] The transmitter 150 transmits a transmission signal to the transmission power amplifier 170. The power controller 160 estimates reception power from the received signal, checks channel conditions from the estimated reception power, and determines a transmission power level. The transmission power amplifier 170 changes the level of the transmission signal to the determined transmission power level, and transmits the signal to the satellite terminal 100 along the transmission beam. In this case, the transmission power amplifier 170 has power level taps to change the power level of the transmission signal to a plurality of power levels according to the determined transmission power level.

[28] In the interference control apparatus of the satellite terminal 200, the receiver 210, the reception beam forming unit 220, the transmission/reception signal processing unit 230, the transmission beam forming unit 240, the transmitter 250, the power controller 260, and the transmission power amplifier 270 have the same functions as the receiver

110, the reception beam forming unit 120, the transmission/reception signal processing unit 130, the transmission beam forming unit 140, the transmitter 150, the power controller 160, and the transmission power amplifier 170 in the interference control apparatus of the satellite. However, the interference control apparatus of the satellite terminal differs from the interference control apparatus of the satellite in that the receiver 210 receives the signals transmitted from the satellite 100, and the transmission power amplifier 270 transmits a transmission signal having a variable transmission power level to the satellite 100.

[29] FIG. 3 is a block diagram illustrating the structure of the power controller shown in

FIG. 2, and FIG. 4 is a flowchart illustrating the operation of the power controller shown in FIG. 2. FIG. 5 is a diagram illustrating a method of determining transmission power in the power controller shown in FIG. 2. FIG. 3 shows only the power controller 160 of the interference control apparatus of the satellite 100, and the power controller 260 of the interference control apparatus of the satellite terminal 200 has the same structure as that of the power controller 160.

[30] As shown in FIG. 3, the power controller 160 includes a power estimating unit 162, a comparing unit 164, and a power level determining unit 166.

[31] As shown in FIG. 4, the power estimating unit 162 estimates the power of the signal received by the receiver 110 (S410).

[32] The comparing unit 164 compares the estimated power and a reference power

(S420).

[33] The power level determining unit 166 determines the power level of a transmission signal required for the current channel conditions on the basis of the difference between the estimated power and the reference power according to the comparison result of the comparing unit 164 (S430).

[34] As shown in FIG. 5, the power level determining unit 166 increases the transmission power level as the difference between the estimated power and the reference power increases. That is, if the power loss of a corresponding channel is large, the power level determining unit 166 increases the transmission power level. If the power loss of a corresponding channel is small, the power level determining unit 166 decreases the transmission power level. In this way, it is possible to reduce the interference signals transmitted to another wireless communication network (reference numeral 20 in FIG. 1). As a result, it is possible to share frequencies between satellite communication systems or between a satellite communication system and another communication system using the same frequency bandwidth.

[35] In this exemplary embodiment of the present invention, the satellite communication system is used as an example of the communication system, but the invention is not limited thereto. For example, the interference control apparatus according to the above-

described exemplary embodiment of the invention may be applied to different communication systems using the same frequency bandwidth.

[36] The above-described exemplary embodiment of the present invention can be applied to programs that allow computers to execute functions corresponding to the configurations of the exemplary embodiments of the invention or recording media including the programs as well as the method and apparatus. Those skilled in the art can easily implement the applications from the above-described exemplary embodiments of the present invention.

[37] While this invention has been described in connection with what is presently considered to be practical exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.