Abstract: A method for overcoming rain attenuation in a return link in a satellite communication system is provided. The method may include periodically receiving channel state information from a terminal, estimating a signal-to-noise ratio (SNR) based on the channel state information, determining, based on the estimated SNR, whether rain attenuation is to be compensated for, analyzing the channel state information and determining a rain attenuation compensation scheme, and transmitting an operating mode change command corresponding to the rain attenuation compensation scheme to the terminal.

Abstract: A satellite communication system and a method of cancelling interference in the satellite communication system are disclosed. The method of cancelling interference in the satellite communication system may include receiving a signal by a central station from a terminal via a satellite transponder, estimating, from the signal, a nonlinear characteristic associated with a central station signal transmitted from the central station, and cancelling an interference signal from the signal using the estimated nonlinear characteristic.

Abstract: A first terminal according to the present invention is a first terminal among a plurality of terminals which is connected to a district center network management device in a VSAT (very small aperture terminal) system, including: a communication unit which connects the first terminal to the district center network management device through a star network; and a control unit which creates SCPC call establishment request information, transmits the created SCPC call establishment request information to the district center network management device through the communication unit, and performs SCPC connection with another terminal based on SCPC call establishment information which is transmitted from the district center network management device in response to the transmitted SCPC call establishment request information when SCPC (single channel per carrier) connection is desired to be performed with another terminal among the plurality of terminals.

Abstract: Provided is a system and method for synchronization between digital-to-analog converters (DAC) for high speed signal processing. A synchronization method of a multi-DAC apparatus may include: inputting a clock to a multiplexer (MUX) DAC; dividing the clock into a first clock and a second clock; transferring a phase difference between the first clock and the second clock to a D flip-flop; and synchronizing the first clock and the second clock by processing the phase difference.

Abstract: Provided are a phase locked loop (PLL) apparatus and an operating method of the PLL apparatus including a PLL unit to provide a fixed frequency signal, a converter to convert, using the fixed frequency signal, a frequency of a first signal oscillated by a first voltage-controlled oscillator (VCO) based on a first control voltage, a first frequency divider to divide the converted frequency of the first signal, and a first phase comparator to compare the divided frequency of the first signal to an input first reference frequency and detect a first phase difference, wherein the first VCO may adjust the first control voltage based on the detected first phase difference to equalize the divided frequency of the first signal to the first reference frequency.

Abstract: An adaptive coding and modulation (ACM) apparatus and method for a forward link in satellite communication is provided. The ACM apparatus may include a receiving unit to receive a signal-to-noise ratio (SNR) of a received signal, a determination unit to determine whether the SNR of the received signal is less than or equal to a threshold value, and a processing unit to execute a channel prediction algorithm when the SNR of the received signal is determined to be less than or equal to the threshold value.

Abstract: Provided is a system and method for synchronization between digital-to-analog converters (DAC) for high speed signal processing. A synchronization method of a multi-DAC apparatus may include: inputting a clock to a multiplexer (MUX) DAC; dividing the clock into a first clock and a second clock; transferring a phase difference between the first clock and the second clock to a D flip-flop; and synchronizing the first clock and the second clock by processing the phase difference.

Abstract: Provided are an adaptive coding modulation (ACM)-based simulcast transmission and reception apparatus and method. The apparatus includes a transmitter configured to analyze whether or not it is raining in a region where a receiver is present on the basis of channel state information (CSI) provided by the receiver, encode and/or modulate an image signal according to the analysis result, and provide the encoded and/or modulated image signal through a single band or multiple bands. On the basis of a result of analyzing whether or not it is raining in a region where a receiver is present, it is possible to effectively prevent signal attenuation caused by rain by providing image signals having different resolutions through multiple bands when the region is in a rainfall state.

Abstract: Provided is a multilevel satellite broadcasting system for providing a hierarchical satellite broadcasting, including a demodulator to demodulate a transmitted multilevel compression stream based on a modulation parameter, a hierarchical video decoder to receive the demodulated multilevel compression stream, and a channel predicting and controlling unit to process at least one of channel prediction and channel control with respect to the demodulated multilevel compression stream based on channel information of the demodulator.

Abstract: Provided is an apparatus and a method for receiving a satellite broadcast. The method may include estimating a channel using signal-to-noise ratio (SNR) information being received, determining a video signal to be received among at least two video signals based on the estimated channel, and controlling selective reception of the determined video signal.

Abstract: A phase locked loop includes: a loop filter; a voltage controlled oscillating unit configured to output a frequency varying according to an output voltage of the loop filter; a frequency down-converting unit configured to down-convert an output frequency of the voltage controlled oscillating unit according to a band of the output frequency of the voltage controlled oscillating unit; and a frequency divider configured to divide a frequency down-converted by the frequency down-converting unit. The output frequency of the voltage controlled oscillating unit varies according to the output voltage of the loop filter and a control signal compensating the frequency down-converted by the frequency down-converting unit.

Abstract: An adaptive coding and modulation (ACM) apparatus and method for a forward link in satellite communication is provided. The ACM apparatus may include a receiving unit to receive a signal-to-noise ratio (SNR) of a received signal, a determination unit to determine whether the SNR of the received signal is less than or equal to a threshold value, and a processing unit to execute a channel prediction algorithm when the SNR of the received signal is determined to be less than or equal to the threshold value.

Abstract: Provided are an adaptive coding modulation (ACM)-based simulcast transmission and reception apparatus and method. The apparatus includes a transmitter configured to analyze whether or not it is raining in a region where a receiver is present on the basis of channel state information (CSI) provided by the receiver, encode and/or modulate an image signal according to the analysis result, and provide the encoded and/or modulated image signal through a single band or multiple bands. On the basis of a result of analyzing whether or not it is raining in a region where a receiver is present, it is possible to effectively prevent signal attenuation caused by rain by providing image signals having different resolutions through multiple bands when the region is in a rainfall state.

Abstract: Provided are a method and apparatus for measuring a time delay in an envelope elimination and restoration (EER) transmitter. A method of measuring a time delay in an EER transmitter includes receiving a modulated sinusoidal signal and distributing the modulated sinusoidal signal to be transmitted through transmission lines separated from each other, extracting an amplitude modulation signal and a phase modulation signal from the modulated sinusoidal signal, and detecting envelops of the amplitude and phase modulation signals and determining a difference in time between the amplitude and phase modulation signals. In the EER transmitter, to measure a time delay between input and output signals, time delays of paths of amplitude and phase modulation signals of the input signal are compared, thereby determining a difference in time between the amplitude and phase modulation signals.

Abstract: A center district network synchronization acquisition apparatus and method capable of accommodating both a GPS mode based terminal and an NCR mode based terminal. The center district network synchronization acquisition apparatus for a satellite communication system according to an exemplary embodiment includes: a timing generating unit configured to generate an interrupt signal by being synchronized with a PPS (pulse per second) signal received from a reference clock generation module, an NCR counter configured to extract a corresponding NCR (network clock reference) value at a timing indicated by the interrupt signal, and a packet generating unit configured to generate an MPEG2-TS packet including the NCR value extracted according to the interrupt signal. Therefore, this apparatus can accommodate both a GPS mode based terminal and an NCR mode based terminal. As a result, the satellite communication system can operate regardless of the network synchronization mode performed by the terminal.

Abstract: A phase locked loop includes: a loop filter; a voltage controlled oscillating unit configured to output a frequency varying according to an output voltage of the loop filter; a frequency down-converting unit configured to down-convert an output frequency of the voltage controlled oscillating unit according to a band of the output frequency of the voltage controlled oscillating unit; and a frequency divider configured to divide a frequency down-converted by the frequency down-converting unit. The output frequency of the voltage controlled oscillating unit varies according to the output voltage of the loop filter and a control signal compensating the frequency down-converted by the frequency down-converting unit.

Abstract: Disclosed relates to a microstrip antenna, particularly, relates to a dual band microstrip antenna including two slots. The microstrip antenna includes a conductor plate having a first hole and a substrate having a microstrip patch where slots of two different sizes are positioned, the substrate being located on a top of the conductor plate.

Abstract: Provided are a forward link rain attenuation compensating apparatus using an adaptive transmission scheme in an interactive satellite communication system and a method thereof. The apparatus separates the mobile stations into clear-sky mobile stations and mobile stations in the state of rain attenuation and makes the clear-sky mobile stations receive data having a high data transmission efficiency at a high-speed while making the rain attenuation mobile stations receive the data continuously although the data transmit rate is low by making each of the two kinds of mobile stations receive data frames of a different transmission method, and provides a method therefor. The apparatus includes: a resource manager, a transmitting data format converter, a forward modulator, a backward demodulator, a receiving data format converter.

Abstract: Provided are a 3-port orthogonal mode transducer, and a receiver and receiving method using the same. The 3-port orthogonal mode transducer includes: a transmission port having a rectangular shape elongated in a horizontal direction and configured to transmit a Ka-band (30 GHz) vertical polarization signal; a first reception port having a rectangular shape inclined at about +45 degrees at a location being at about +45 degrees with respect to the transmission port and configured to receive a K-band (20 GHz) vertical or horizontal polarization signal phased-delayed about +45 degrees; and a second reception port having a rectangular shape inclined at about ?45 degrees at a location being at about ?45 degrees with respect to the transmission port and configured to receive a K-band (20 GHz) vertical or horizontal polarization signal phase-delayed about ?45 degrees.

Abstract: Provided is a frequency error estimating method of a communication system. The method includes receiving a frame, and calculating a frequency error from a SOF field of the received frame.