Analysis For LDPC Based On The IEEE 802.16e Standards In The Underwater Laser Communication System

The LDPC code based on the current IEEE802.16e standard is a kind of forward error correction codes which with low complexity decoding algorithms and plenty of small girth, its application system also has higher parallel degree and decode throughput.This paper has studied the IEEE802.16e standard deeply, and presents a new scheme of designing the LDPC code. In the proposed scheme, the design has modified the sub-parity check matrix under the frame of the IEEE802.16e Standard. The proposed check matrix with the spreading factor (zf=48) is constructed with quasi-cyclic matrix method and finite geometry method. Then an optimized encoding algorithm is applied which can support such improved shorten LDPC codes based on IEEE802.16e standard by the way of comparing and analyzing three encoding algorithms, which have been proposed in IEEE802.16e standard currently.Moreover the paper has finished the analysis of the improved decoding algorithms .With the help of simulation and discussion of belief propagation and the log-BP decoding algorithms. By comparing many decoding algorithms, the author has designed an improved min-sum algorithm based on the log-BP.Finally, The results of simulation in the AWGN channels show that the improved LDPC code with the code rate approaching to 0.5, can fast encode as excellent as the IEEE802.16e protocol contains, and the system has a better BER performance under the 10-5 in such channel.