Both constant and variable Forward Error Correcting (FEC) coding is provided by the DVB-S2 system.
Variable FEC can be used for different levels of error protection according to different applications. DVB-S2 system [15] is intended to provide interactive services, which are mainly point-to-point or point-to multipoint, where variable FEC may be combined with the use of return channels, to achieve Adaptive Coding. The novel idea explained in this paper, introduces a well-structured
Low Density Parity Check (LPDC) codes, which enables the system to switch between LDPC codes of different rates (9/10, 8/9, 5/6, 4/5…) derived from a base parity check matrix. We introduce a method to achieve variable rate codes starting from higher rate to lower rate codes based on matrix expansion.