Multicast routing algorithms with high bandwidth efficiency for LEO satellite networks

To resolve the channel resources waste problem of the typical source-based multicast routing algorithm in low earth orbit (LEO) satellite IP networks, this paper proposes a new core-based shared tree algorithm called the core-cluster combination shared tree (CCST) algorithm and its improved version (i.e. the w-CCST algorithm). The CCST algorithm consists of the dynamic approximate center (DAC) core selection method and the core-cluster combination multicast route construction method. The DAC method can adaptively select the optimal core node according to group distribution in the network. And the core-cluster combination method takes core node and its nearest group member in hops as initial core-cluster, and expands it to construct entire multicast tree with the lowest tree cost stepwise by a shortest path scheme between newly-generated core-cluster and surplus group members, which can greatly improve transport bandwidth utilization and transport efficiency. In the w-CCST algorithm, a weighted factor is used to make tradeoff between tree cost and end-to-end propagation delay. Therefore, tree cost can be increased a bit and meanwhile end-to-end propagation delay is decreased slightly to meet strict end-to-end delay requirements of some real-time multicast applications by adjusting the weighted factor. Performance of the CCST and w-CCST algorithms is compared with several other algorithms. And simulation results show that average tree cost of the CCST multicast tree is greatly lower than that of multicast tree of other algorithms, and its average end-to-end propagation delay is a bit higher than that of others, while average end-to-end propagation delay of the w-CCST multicast tree is lower than that of the CCST multicast tree.