Block Design And Coding Modulation Ldpc Coding Technology Research,

With the development of audio, video and some other media applications, people around the world have gotten higher requirements for digital communication system. The technology of channel error-correcting coding is one of the effective methods to assure the transmission dependability in our system. This kind of technology could not just decrease the information error rate, but also with the low complexity to implement.Low-density parity-check (LDPC) codes, which was first discovered in the 60's last century, is a kind of linear block codes with the parity-check matrix containing mostly 0's and relatively few 1's. Later in 1990's they were rediscovered and soon became the focus in channel code fields because of their remarkable performance close to Shannon limit with iterative decoding and their structures for parallel decoding.There are two families of LDPC codes. One is random codes, which is constructed by computer search, their advantages include flexible construction and perfect performance; another is constructed codes, which are constructed based on geometric, algebraic or combinatoric design approach.The random generated LDPC code lacks the analytical theory and looks very difficult to implement in hardware, so it become the choke point of LDPC applications. For predigesting the complexity, many constructed LDPC codes have been tabled lately.In this article, two kinds of methods - Balanced Incomplete Block Design (BIBD) and Coded Modulation (CM) are used in the construction of LDPC codes. The BIBD-LDPC codes could get the base incidence vectors with computer search, and the remainder incidence vectors are gotten by cyclically shifting these base incidence vectors. This kind of parity-check matrix gets standard circular structure and looks very easy to implement with simple linar feedback shifting register. The simulation results demonstrate that the BIBD-LDPC codes based on this method work quite well.The technology of CM which processes encoder and modulator together is regarded as a landmark in the development of channel coding. This article discuss a way mapping subcodes with different levels in concatenated Single Parity Check (SPC) codes to different bit positions in modulated signal. This way could adjust relative positions for signals of modulating constellation, so it's with better performance and with easier coding way to implement. The performance of concatenated SPC codes with TCM which with the BER of 10-5 is 2dB better than those without CM.The construction the LDPC codes with BIBD and CM could make the encoding process very simple and also have great performance in simulating test. As one of the most important findings in channel coding field, LDPC codes are the nearest codes to Shannon limit. There will be a promising application foreground ahead.