中文摘要：

面向单信源异构信宿网络，研究了层间等级网络编码的编码类型优化。基于遗传算法，提出了一种最优编码类型的快速搜索方案。该方案充分考虑了信源输出链路上进行的层间等级网络编码的编码类型对整个网络传输性能的影响，将网络总吞吐量作为评价编码类型优劣的标准，设计了符合层间等级网络编码本质特性的遗传操作。实验结果表明，与分层组播网络编码和基于现有启发式算法的层间等级网络编码相比，基于本文方案实现的层间等级网络编码能够为单信源异构信宿网络获得更高的网络总吞吐量。

英文摘要：

The coding type optimization of the inter-layer hierarchical network coding for single-source heterogeneous-receivers networks was investigated. Based on the genetic algorithm, a strategy for fast searching the optimum coding type was proposed. This strategy emphasizes the optimization of the coding types on the outgoing links of the source node, and takes the maximization of the overall network throughput as the optimization objective. Special genetic processes were designed according to the characteristics of inter-layer hierarchical network codes. The experimental results show that compared to the layered multicast network coding and the inter-layer hierarchical network coding using the existing heuristic method, the inter-layer hierarchical network coding using the proposed optimization strategy can achieve the higher overall network throughputs for single-source heterogeneous-receiver networks.