Abstract: This paper designs an adjustable rate LDPC with nesting structure.This code can use a differential encoder which is easy in circuit implementation.There are several codes with different rates because of the nesting structure in parity check matrix，so we can send different rate code in different channel condition to improve the system performance.This coding method is also suitable in the Automatic Repeat Request（ARQ） system.Simulation results indicate that these codes perform as well as regular low density parity check codes based on completely random matrix constructions.

Key words: Low-Density Parity-Check（LDPC） Code, nesting structure, encoding

摘要： 设计了一种码率可调的嵌套LDPC码。该码具有差分编码结构，易于硬件实现。校验矩阵采用嵌套结构，同一系统中可以含有多种码率的码字。对于不同信道情况，可以传送不同码率的码字，以提高系统性能。这种码率可调的编码也适合于出错重发系统。仿真结果表明，该构造方法确定的码字同通过复杂方法随机构造出来的码字性能接近。

关键词: LDPC码, 嵌套结构, 编码