利用matlab仿真了改进的二类选择重传HARQ机制的吞吐量与误比特率之间的关系。在仿真中对于编码和解码过程进行了简化：根据误比特率按概率模拟传输过程中码字的出错位数，在接收端只判断码字错误的位数是否在可纠错得范围之内。每发送一个码字，接收端根据出错位数信息检验其是否出错，没有出错则接收，否则要求重发，程序中利用alternate值交替发送信息码字和校验码字。当校验码字到来后，若校验码与原码组成的新码字能够纠错，则正确接收，否则要求重传。 -Retransmission the HARQ mec

This matlab code can be used to generate a parity check matrix for the LDPC code and further encoded and decoded in a complete communication system.

在matlab环境下，构造LDPC码的校验矩阵的各种方法，包括Gallager构造法，Mackay构造法，PEG构造法，对以后的编译码算法有很大的帮助。-In the matlab environment, various methods LDPC code parity check matrix structure, including Gallager construction law, Mackay construction law, PEG construction method, af

File is used for counting short cycle of ldpc codes. You must give parity check matrix of ldpc code in text file and then use cycle count file of matlab for counting of short cycle of given length.