Abstract: Network coding become the research focus of widespread concerning. Because of it can improve the network throughput, has better robustness, and effectively improve the efficiency of forwarding by relay nodes. Therefore, in the relay node, a joint design of network-channel coding can further improve BER performance of the system BER performance. Based on the research of Razaghi, who designed the two kinds of Bilayer-LDPC codes（divided into Expurgated and Lengthened type）, proposes a kind of network-channel coding called NBL-LDPC code（Network Bilayer Lengthened LDPC, referred to as the NBL-LDPC）. Meanwhile, This paper shows the process of encoding and decoding, and for this code, the Gaussian density evolution algorithm has to be improved, so the BER performance can be calculated and simulated. Simulation results show that the proposed coding scheme performs better than the NBE-LDPC code（Network Bilayer Expurgated LDPC, referred to as NBE-LDPC）.

Key words: communications technology, network-bilayer LDPC, Gaussian approximation, Bit Error Rate（BER）

摘要： 网络编码技术由于其能提高网络吞吐量、具有较好的鲁棒性、能有效提高中继节点转发效率等优点成为目前广泛关注的研究热点。在中继节点上，采用网络-信道编码联合设计方案能进一步提高系统的误码性能。基于Razaghi等人研究的两种双层LDPC码（Bilayer LDPC，分为删余型和延长型），设计了一种在中继节点上联合设计的网络双层LDPC延长码（Network Bilayer Lengthened LDPC，NBL-LDPC）。给出了此码的编译码过程，并针对此码，对高斯密度进化算法进行改进，计算误码率并完成误码性能仿真。仿真结果表明，所提出的编码方案性能要优于利用双层LDPC删余码设计的网络双层LDPC删余码（Network Bilayer Expurgated LDPC，NBE-LDPC）。

关键词: 通信技术, 网络双层LDPC码, 高斯近似算法, 误码性能