中文摘要：

网络编码是一种允许信息在中间节点进行编码的新型网络信息传输方式．它相较于传统路由的“存储-转发”方式，能够充分利用网络的信道容量，提高信息的传输效率．采用Jaggi—Sanders算法可以在单源无圈网络上构造出能够达到网络最大流界的线性多播网络编码．但要构造出更强的线性广播和线性扩散，此前的方法是对原网络按一定方式进行扩展，再通过构造新网络上的线性多播和线性广播来得到原网络上的线性广播和线性扩散．文章通过对Jaggi—Sanders算法进行改进，使得不需要进行网络扩展便可在网络上直接构造出线性广播和线性扩散，并且减少了构造所需的时间消耗．

英文摘要：

Network coding is a new way of transmitting information which allows intermediate nodes code the messages received. Compared with ＂store-and-forward＂ of routing, network coding can utilize the full capacity of the network and improve the information rate. For a single source acyclic network, Jaggi-Sanders algorithm can construct network code called linear multicast, with which the throughput of the network reaches its upper bound. When constructing linear broadcast or linear dispersion further, it is necessary to extend the network in some way before using Jaggi-Sanders algorithm. In this paper, we propose some improvements on Jaggi- Sanders algorithm. The improved algorithms can construct linear broadcast and linear dispersion without extending the network, and reduce the cost of time.