Abstract: A communication apparatus for a continuous phase modulation signal. The communication apparatus includes a first processing unit configured to generate first information of the continuous phase modulation signal using first symbol data; a symbol converting unit configured to convert the first symbol data into second symbol data or convert the second symbol data into the first symbol data; a symbol storage unit configured to store the second symbol data; a second processing unit configured to second information of the continuous phase modulation signal using the second symbol data stored in the symbol storage unit; a third processing unit configured to generate third information of the continuous phase modulation signal using a modulo operation of an integer related to a modulation index; and an output unit configured to add an output from the third processing unit and an output from the first processing unit and generate the continuous phase modulation signal.

Abstract: When errors occur in a packet received from a satellite terminal device, a modulation and coding (MODCOD) value is calculated according to a result of the detection, and a calculated MODCOD value is transmitted to the satellite terminal device, so that packet loss is reduced based on the yield of actual traffic when the satellite terminal device transmits a return link packet. An occurrence of a packet error is detected by generating a first return link packet by sequentially assembling the plurality of return link packets from the satellite terminal device and performing a comparison analysis by comparing the first return link packet with a newly received second return link packet.

Abstract: An apparatus and method for producing error correction code and error correction decoding are provided. The method for producing error correction code includes generating an asymmetric matrix by arranging input data bits in a matrix of a predefined size and adding a zero bit column and/or a zero bit row, each of the column and the row consisting of zero bits, to the matrix; primarily encoding the asymmetric matrix by adding one or more parity bits to each row; and secondarily encoding the primarily encoded matrix by adding one or more parity bits to each column of the encoded matrix.

Abstract: A technology for modulating and demodulating a burst signal in a return link of a satellite system, in which the burst signal is modulated and transmitted from a transmission end of the return link and a symbol of the burst signal is identified and demodulated at a receiving end. The method includes estimating symbol timing of a burst received through the return link and synchronizing the estimated symbol timing of the burst to reference symbol timing; synchronizing a location of the timing-synchronized burst having the symbol timing synchronized to a location of a reference burst using a preamble symbol and a post-amble symbol of the timing-synchronized burst; and recovering a carrier of the location-synchronized burst whose location has been synchronized to the location of the reference burst using a pilot symbol of the location-synchronized burst.

Abstract: Provided is a frame synchronization apparatus capable of reducing the amount of total computation and computation delays when a receiver of a satellite communication system calculates correlation between an input signal for frame synchronization and a signal sequence of the receiver, since the receiver uses no multiplier. The frame synchronization apparatus includes a correlator to obtain a correlation value of a unique word of a receiver with respect to a symbol data stream of a frame received from a transmitter of the satellite communication system, a comparator to compare the correlation value to a predetermined threshold value, and a determiner to determine whether the frame has been synchronized, based on the result of the comparison by the comparator.

Abstract: Provided is a method for detecting frame sync and frame structure in a satellite broadcasting system, which acquires an estimated value for detecting frame structure and frame sync and overcomes distortion of correlation analysis values by summing differential correlation values for SOF positions in consideration of the variable frame length, and selecting a maximum value in a channel environment with low signal-to-noise ratio and high frequency error. SOF is a sync word indicating the start point of a frame. The method includes the steps of: acquiring SOF differential correlation value sequences; acquiring sums (di,t) of the correlation values normalized for SOF positions based on the number of symbols per frame by using the above-generated SOF differential correlation value sequences; and selecting a maximum value (dz,x) among the sums of correlation values, detecting z as a frame sync position, and detecting x as a frame structure index.

Abstract: An apparatus and method for acquiring reliable frame synchronization performance and frequency synchronization simultaneously in a communication system includes a differential correlator outputting a result value obtained by performing a differential operation based on an input signal having symbol timing synchronization and a value pre-defined with a sender sending the input signal, a frequency error calculator compensating for a frequency error based on the result value of the differential correlator and a frequency compensation control signal, and a frame synchronization determiner outputting the frequency compensation control signal if the result value of the differential correlator is greater than a threshold set having at least one value. By introducing a correlation scheme, i.e.

Abstract: Provided is a frame synchronization apparatus capable of reducing the amount of total computation and computation delays when a receiver of a satellite communication system calculates correlation between an input signal for frame synchronization and a signal sequence of the receiver, since the receiver uses no multiplier. The frame synchronization apparatus includes a correlator to obtain a correlation vale of a unique word of a receiver with respect to a symbol data stream of a frame received from a transmitter of the satellite communication system, a comparator to compare the correlation value to a predetermined threshold value, and a determiner to determine whether the frame has been synchronized, based on the result of the comparison by the comparator.

Abstract: A technology in which it is detected whether errors occur in a packet received from a satellite terminal device, a modulation and coding (MODCOD) value is calculated according to a result of the detection and the calculated MODCOD value is transmitted to the satellite terminal device, so that pack loss is reduced based on the yield of actual traffic when the satellite terminal device transmits a return link packet. A plurality of return link packets are received from the satellite terminal device. An occurrence of a packet error is detected by generating a first return link packet by sequentially assembling the plurality of return link packets and performing a comparison analysis by comparing the first return link packet with a second return link packet that is newly received.

Abstract: A technology for modulating and demodulating a burst signal in a return link of a satellite system, in which the burst signal is modulated and transmitted from a transmission end of the return link and a symbol of the burst signal is identified and demodulated at a receiving end. The method includes estimating symbol timing of a burst received through the return link and synchronizing the estimated symbol timing of the burst to reference symbol timing; synchronizing a location of the timing-synchronized burst having the symbol timing synchronized to a location of a reference burst using a preamble symbol and a post-amble symbol of the timing-synchronized burst; and recovering a carrier of the location-synchronized burst whose location has been synchronized to the location of the reference burst using a pilot symbol of the location-synchronized burst.

Abstract: An apparatus and method for producing error correction code and error correction decoding are provided. The method for producing error correction code includes generating an asymmetric matrix by arranging input data bits in a matrix of a predefined size and adding a zero bit column and/or a zero bit row, each of the column and the row consisting of zero bits, to the matrix; primarily encoding the asymmetric matrix by adding one or more parity bits to each row; and secondarily encoding the primarily encoded matrix by adding one or more parity bits to each column of the encoded matrix.

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 communication apparatus for a continuous phase modulation signal. The communication apparatus includes a first processing unit configured to generate first information of the continuous phase modulation signal using first symbol data; a symbol converting unit configured to convert the first symbol data into second symbol data or convert the second symbol data into the first symbol data; a symbol storage unit configured to store the second symbol data; a second processing unit configured to second information of the continuous phase modulation signal using the second symbol data stored in the symbol storage unit; a third processing unit configured to generate third information of the continuous phase modulation signal using a modulo operation of an integer related to a modulation index; and an output unit configured to add an output from the third processing unit and an output from the first processing unit and generate the continuous phase modulation signal.

Abstract: Provided is a low-density parity-check (LDPC) decoding apparatus and method using a type-classified index. The apparatus includes: a memory allocating unit for multiplying reception data by an estimated channel value and storing a multiplied value in a memory including a plurality of memory block; an index storing unit for storing a Read Only Memory (ROM) index, an address index and a permutation index for the stored data; a check node updating unit for bring the stored data in parallel based on the ROM index, the address index, and the permutation index and updating a check node; and a bit node updating unit for updating a bit node based on the data stored in the memory and check node information updated in the check node updating unit.

Abstract: Provided are an apparatus and method for generating a soft bit metric and a multi-level (M-ary) Quadrature Amplitude Modulation (QAM) receiving system using the same. The apparatus includes an analog to digital converter for converting an analog symbol signal of a demodulated I (Inphase) or Q (Quadrature) channel into a digital signal, a scaler for scaling the converted digital signal based on a reference value used for determining a space between symbols, a positive integer converter for calculating a positive integer of the scaled digital I or Q channel symbol signal, a sign determinator for determining a sign of the scaled digital I or Q channel symbol signal, and a bit information converter for converting the scaled digital I or Q channel symbol signal into soft bit metric information per bit on the basis of the calculated positive integer and the determined sign value.

Abstract: Provided is a method for detecting frame sync and frame structure in a satellite broadcasting system. The method for detecting frame sync and frame structure includes the steps of: calculating differential correlation values of reception symbols; generating index sequences of reception symbols whose differential correlation values calculated above exceed a threshold value; calculating positions estimated as frame start points which correspond to a total frame number based on the number of symbols per frame for each frame structure; and detecting frame sync and frame structure based on the umber of positions where the above-calculated frame start point estimated positions and the above-generated index sequences are matched.

Abstract: Provided are an apparatus for estimating a phase error and a phase error correcting system using the phase error estimating apparatus. The apparatus includes: a probability value estimating unit for estimating a negative log probability value for each transmission symbol by transforming a soft output information transferred from the outside to a log A posterior probability ratio (LAPPR) value; an APP value calculating unit for calculating a posterior probability (APP) value by applying a negative exponential function to the transmission symbol; an average value deciding unit for deciding an average value for each transmission symbol using the probability information entirely, partially, or selectively according to a probability information type; and a symbol phase estimating unit for estimating a phase of a symbol based on the decided average value.

Abstract: Provided are an apparatus and method for deciding a transmission format using a variable frame length and a decoding method using the same. The apparatus for deciding the transmission format using the variable frame length includes: a frame synchronization acquiring unit for acquiring a frame synchronization of a received transmission frame; a correlation analyzing unit for performing a correlation analysis with respect to the transmission frame whose synchronization is acquired, considering frame lengths of respective frame structures; and a transmission frame structure deciding unit for deciding the structure of the received transmission frame using the analyzed correlation. Accordingly, a physical layer signaling code (PLSC) demodulation and decoding performance can be enhanced by determining the structure of the transmitted frame without carrying out a PLSC decoding in such a state that a frequency synchronization is not acquired.

Abstract: There are provided an apparatus and method for traffic performance improvement and traffic security in an interactive satellite communication system. The method for traffic performance improvement of an interactive satellite communication system includes the steps of: a) storing an Internet protocol (IP) packet that is received from a user terminal connected to a satellite mobile terminal of the interactive satellite communication system and is to be transmitted to a central station through a satellite; b) transmitting acknowledgement for the stored IP packet to the user terminal by acting for the central station, before the stored IP packet is transmitted to the central station; and c) transmitting the stored IP packet through the satellite to the central station, and retransmitting an unacknowledged IP packet according to a retransmission request of the central station.

Abstract: Provided is a method for detecting frame sync and frame structure in a satellite broadcasting system, which acquires an estimated value for detecting frame structure and frame sync and overcomes distortion of correlation analysis values by summing differential correlation values for SOF positions in consideration of the variable frame length, and selecting a maximum value in a channel environment with low signal-to-noise ratio and high frequency error. SOF is a sync word indicating the start point of a frame. The method includes the steps of: acquiring SOF differential correlation value sequences; acquiring sums (di,t) of the correlation values normalized for SOF positions based on the number of symbols per frame by using the above-generated SOF differential correlation value sequences; and selecting a maximum value (dz,x) among the sums of correlation values, detecting z as a frame sync position, and detecting x as a frame structure index.