Abstract:
A transmitting apparatus is provided. The transmitting apparatus includes: an encoder configured to generate a low density parity check (LDPC) codeword by LDPC encoding based on a parity check matrix; an interleaver configured to interleave the LDPC codeword; and a modulator configured to map the interleaved LDPC codeword onto a modulation symbol, wherein the modulator is further configured to map a bit included in a predetermined bit group from among a plurality of bit groups constituting the LDPC codeword onto a predetermined bit of the modulation symbol.
Abstract:
A frame header of Forward Error Correction (FEC) is provided, suitable for using in the DVB-C2 Standard. In the DVB-C2 Standard, Adaptive Coding and Modulation (ACM) or Variable Coding and Modulation (VCM) is applied to each FEC block to provide as much flexibility as possible. As a result, a frame header is attached in front of each FEC frame to inform the coding rate, modulation type and physical layer pipe identifier. Besides the signaling of physical layer related information, the FEC frame header has to provide a structure so that it can be easily and reliably detected in the receiver. Motivated by the need in DVB-C2 Standard, an efficient and reliable FEC header suitable for DVB-C2 Standard is provided in at least one implementation in this disclosure that combines use of two different modulation types for the header information. In addition, the detection Method of the FEC header is described.
Abstract:
A transmitter transmits payload data using Orthogonal Frequency Division Multiplexed (OFDM) symbols. The transmitter comprises a frame builder configured to receive the payload data to be transmitted and to receive signalling data for use in detecting and recovering the payload data at a receiver, and to form the payload data with the signalling data into frames for transmission. A modulator is configured to modulate a first OFDM symbol with the signalling data forming a part of each of the frames and to modulate one or more second OFDM symbols with the payload data to form one or more of the frames, and a transmission unit for transmitting the first and second OFDM symbols. The first OFDM symbol is a first type having a number of sub-carriers which is less than or equal to the number of sub-carriers of the one or more second OFDM symbols of a second type and a guard interval for the first OFDM symbol is selected in dependence upon the longest possible guard interval of the second OFDM symbol. Accordingly an OFDM communications system can be formed in which data is transmitted using a frame structure in which a guard interval is adapted to allow a mix of different types of OFDM symbols. The mix of OFDM symbols allows the signalling data to be carried by the OFDM symbol of the first type and the payload data to be carried by the OFDM symbol of the second type, and the number of sub-carriers of the OFDM symbols of first type carrying the signalling data is less than or equal to the number of sub-carriers of the OFDM symbol of the second type. If the number of sub-carriers of the OFDM symbol of the first type is less than the number of OFDM symbols of the second type then there is an improved likelihood of the signalling data being detected and recovered before the payload data, so that a more robust communications system can be formed.