Abstract: A Second Generation Digital Video Broadcasting via Satellite (DVB-S2) system is provided. More particularly, a method and apparatus for maintaining synchronization of a signal by changing an Adaptive Coding and Modulation (ACM) method that is used for a conventional DVB-S2 system are provided. In the apparatus and method, an FEC frame of a variable length is formed by turbo encoding rather than Bose-Chaudhuri-Hocquenghem (BCH) and Low Density Parity Check (LDPC) encoding, and a Physical Layer (PL) frame of a specific length is formed regardless of a modulation method, so that a satellite terminal receives a signal transmitted at a specific length regardless of a modulation method or a coding rate to easily maintain synchronization without interruption and efficiently transmit the signal.

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 is a decoding method for detecting Physical Layer Signaling Codes (PLSCs) from frames of a satellite broadcasting system. The method includes: a) acquiring a summation vector and a subtraction vector from an inputted symbol vector; b) performing parallel Reed-Muller (32,6) decoding onto the summation and subtraction vectors based on a Hadamard matrix and estimating message bits of the summation and subtraction vectors; c) performing PLSC coding and modulation onto the message bits of the summation and subtraction vectors; d) calculating a first difference between symbols of the received symbol vector and the summation vector symbols, and a second difference between the symbols of the received symbol vector and the subtraction vector symbols; and e) when the first difference is smaller than the second difference, determining a Reed-Muller codeword is repeated, or when the first difference is larger than the second difference, determining that the Reed-Muller codeword is inverted.

Abstract: Provided is a correlation scheme selecting apparatus and method that can acquire initial synchronization efficiently by calculating frequency error criterion threshold between correlation schemes and selecting a correlation scheme for each region when a correlation value is calculated for initial sync in a communication system with carrier frequency errors. The method for selecting a correlation scheme based on a carrier frequency error includes: calculating mis-detection probability values based on a normalized frequency offset for each correlation scheme; determining as a frequency-error criterion threshold a crossing point of graphs of the calculated mis-detection probability values for each correlation scheme; and selecting a correlation scheme based on the determined frequency-error criterion threshold.

Abstract: Provided are repetition apparatus and method for repeatedly transmitting and receiving a data packet using different puncturing patterns to overcome signal attenuation and fading in a high speed mobile environment by repeatedly transmitting the duplicated information bit sequences with parity bits having a different puncturing pattern after channel-encoding the duplicated information bit. The repetition apparatus for repeatedly transmitting a data packet, includes a dual data generator for generating duplicated information bit sequences identical to each of information bit sequences to transmit, a channel encoder for dividing each of the duplicated information bit sequences into a plurality of information bits, and generating coded data packets alternately having a plurality of parity bits according to different puncturing patterns for each of the divided information bits, and a transmitter for transmitting the generated coded data packets sequentially.

Abstract: Provided is a method for handover between heterogeneous networks using a link trigger signal in a multi-interface mobile router. The method includes: maintaining a state of a second network access interface in a sleep state, activating a first network access interface, receiving and transmitting the first network service to a subordinate node in the mobile router located in a first network; when the mobile router senses a second network link-up trigger signal while moving to the second network, changing the state of the second network access interface into an active state and performing handover; and receiving a second network service through the activated second network access interface in the mobile router performing the handover and transmitting the second network service to the subordinate node.

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 sealer 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 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: Provided are a method and apparatus for hierarchical modulation and demodulation in a Digital Multimedia Broadcasting (DMB) system. The method for hierarchical modulation in a digital broadcast signal transmitter includes the steps of: receiving a first broadcast signal and a second broadcast signal from outside, and encoding the broadcast signals by a first method and a second method, respectively; synthesizing the encoded first and second broadcast signals; determining a modulation point using a constellation diagram of an I-Q plane corresponding to the synthesized signal; and hierarchically phase-shift modulating the synthesized signal using the determined modulation point. Here, in the I-Q plane, the modulation point is deviated by a predetermined deviation angle from a phase axis passing through a modulation point of the first broadcast signal and an origin of the I-Q plane.

Abstract: Disclosed is a soft decision decoder, and a log likelihood ratio calculator for soft decision decoding and a method thereof, for realizing a generalized log likelihood ratio algorithm in consideration of channel estimation errors for performing soft decision decoding on QAM signals, which comprises multipliers for multiplying reference signals and channel estimation signals, subtractors for subtracting a receive signal of a receiver from output signals of the multipliers, first and second square calculators for squaring the subtractors' output signals and reference signals, dividers for dividing output signals of the first and second square calculators by addition values, and a comparator for comparing output signals of the dividers.

Abstract: Provided is a frame synchronization method for synchronizing frames with pilot blocks added thereto based on differential correlation information in a satellite communication system. The method can acquire a highly reliable frame synchronization estimation value by achieving a multi-step threshold value test using pilot blocks after a correlation analysis and a threshold test based on a sync signal in order to resolve the problem of a low signal-to-noise ratio and a large frequency error and acquire highly reliable frame synchronization performance, and can overcome distortion of a correlation analysis value caused by the frequency error by analyzing correlation based on differential information. The method includes the steps of: a) performing correlation analysis and a threshold test by using a sync word; and b) performing a multi-step correlation value test by using the pilot blocks added to the frames prior to the sync word.

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 is a decoding method for detecting Physical Layer Signaling Codes (PLSCs) from frames of a satellite broadcasting system. The method includes: a) acquiring a summation vector and a subtraction vector from an inputted symbol vector; b) performing parallel Reed-Muller (32,6) decoding onto the summation and subtraction vectors based on a Hadamard matrix and estimating message bits of the summation and subtraction vectors; c) performing PLSC coding and modulation onto the message bits of the summation and subtraction vectors; d) calculating a first difference between symbols of the received symbol vector and the summation vector symbols, and a second difference between the symbols of the received symbol vector and the subtraction vector symbols; and e) when the first difference is smaller than the second difference, determining a Reed-Muller codeword is repeated, or when the first difference is larger than the second difference, determining that the Reed-Muller codeword is inverted.

Abstract: Provided is a frame synchronization method for synchronizing frames with pilot blocks added thereto based on differential correlation information in a satellite communication system. The method can acquire a highly reliable frame synchronization estimation value by achieving a multi-step threshold value test using pilot blocks after a correlation analysis and a threshold test based on a sync signal in order to resolve the problem of a low signal-to-noise ratio and a large frequency error and acquire highly reliable frame synchronization performance, and can overcome distortion of a correlation analysis value caused by the frequency error by analyzing correlation based on differential information. The method includes the steps of: a) performing correlation analysis and a threshold test by using a sync word; and b) performing a multi-step correlation value test by using the pilot blocks added to the frames prior to the sync word.

Abstract: Provided are a soft decision demapping method suitable for higher-order modulation for an iterative decoder and an error correction apparatus using the same, which are capable of preventing performance deterioration of repetition codes using an efficient technique.

Abstract: Provided are an apparatus and method for correcting a frequency offset in a satellite digital video broadcasting system.

Abstract: Provided is a digital satellite broadcasting set-top box and a home network control system employing the same. The set-top box includes: a satellite signal receiving unit for receiving a satellite signal including a home network control signal for controlling the household appliances through a satellite broadcasting network from a remote terminal; and a control unit for extracting a household appliances control signal included in the satellite signal transmitted from the satellite signal receiving unit and commanding a power line converter to transmit the household appliances control signal to a corresponding household appliance, wherein the power line converter converts the household appliances control signal transmitted from the digital satellite broadcasting set-top box into a power line communication signal and transmits the power line communication signal on the home network through a power line.

Abstract: An apparatus for independently extracting streams from a hierarchically-modulated signal and performing a soft-decision, and a method thereof are provided. The apparatus includes: a synchronizing unit for receiving a hierarchically-modulated signal configured of an I-channel signal and a Q-channel signal from an external device and performing a synchronizing process on the received signal; a divaricating unit 410 for divaricating the synchronized signal configured of the I-channel signal and the Q-channel signal from the synchronizing unit; a high priority (HP) stream extracting and soft-decision unit for extracting a HP stream from one of the divaricated signals, and performing a soft-decision; a processing unit for processing the other of the divaricated signals to allow constellation points to be distinguished; and a low priority (LP) stream extracting and soft-decision unit for extracting a LP stream from the processed signal from the processing unit and performing a soft-decision.

Abstract: An apparatus and a method for demodulation using detection of channel adaptive modulation scheme are disclosed. The apparatus includes: a receiving unit for receiving a signal modulated based on the channel adaptive modulation scheme from an external; a demodulating unit for demodulating the modulated signal according to modulation scheme information; a modulation scheme detecting unit for determining modulation scheme information by detecting mapping information from the demodulated signal and outputting the modulation scheme information to the demodulating unit; and a decoding unit for performing an error correction on the demodulated signal and decoding the demodulated signal by using the determined modulation scheme information.

Abstract: An apparatus for resolution of phase ambiguity is disclosed. The apparatus receives a modulated signal and resolves a phase ambiguity of the modulated signal while recovering the modulated signal to original data, wherein the apparatus includes a phase ambiguity detector for receiving demodulated data and frame synchronization information, and detecting a phase ambiguity value from the demodulated data based on a frame synchronization information; a phase ambiguity eliminator for receiving the phase ambiguity value and the demodulated data, and generating a phase ambiguity eliminated data by inverting the phase ambiguity value and multiplying the inverted phase ambiguity value and the demodulated data. The present invention can resolve a phase ambiguity occurred in various modulation modes including a burst mode communication with the same algorithm so it can effectively be implemented to an adaptive MODEM.