Routing and Multicast Algorithms for LEO Satellite Networks

低地球轨道（LEO）卫星系统提供具有短往返延迟的全球覆盖。 凭借这些特性，它们将在全球互联网中发挥至关重要的作用，以支持实时和非实时应用。 LEO卫星系统中的路由和组播是支持这些业务的关键问题。 非实时应用的特征是延迟界限宽松。 它们对延迟的变化也不敏感。 因此，基于数据报的路由方案可以用于支持这种类型的业务。 提出了半集中式数据报路由协议（SC-DRP）以支持LEO卫星网络中的无连接路由。 SC-DRP的目标是在LEO卫星网络中的最小延迟路径上转发数据包。 SC-DRP利用LEO和MEO/GEO卫星来计算路由表，这将提高数据报业务在卫星网络中的可靠性和延迟性能，其中数据业务在LEO卫星网络中承载。 数据报多播协议（DatagramMulticastProtocol，简称RTP）是为了支持无连接多播而提出的。 它基于SC-DRP，创建最短路径树。 实时应用对延迟有严格的限制，并且对延迟变化很敏感。 因此，面向连接的路由方案可以支持实时流量。 在低轨卫星网络中，卫星连接模式的变化会影响到已建立的路径。 因此，确定稳定路径非常重要。 针对低轨卫星网络中面向连接的路由问题，提出了时延耦合概率路由协议（DC-PRP）。 DC-PRP计算符合连接的延迟和延迟抖动界限的路径。 面向连接的多播协议LEOCOM（Connection Oriented Multicast Protocol）是针对面向连接的多播而提出的，它建立了时延受限的多播树。 使用贪婪搜索算法优化组播树长度。

Low Earth Orbit (LEO) satellite systems provide global coverage with short round trip delays. With these properties they will play a crucial role in the global Internet to support real-time and non-real-time applications. Routing and multicasting in LEO satellite systems are the key issues to support these services. Non-real-time applications are characterized by relaxed delay bounds. They are also insensitive to the variations in delay. Thus, datagram-based routing schemes can be used to support this type of traffic. the Semi-Centralized Datagram Routing Protocol (SC-DRP) is proposed to support connectionless routing in LEO satellite networks. The SC-DRP aims to foward the packets in the LEO satellite network on minimum delay paths. SC-DRP utilized LEO and MEO/GEO satellites to calculate routing tables, which will increase the reliability and delay performance of datagram traffic in satellite networks, where the data traffic is carried in the LEO satellite network. The Datagram Multicast Protocol (DMP) is proposed to support connectionless multicasting. DMP is based on the SC-DRP and creates shortest path trees. Real-time applications impose strict delay bounds and are sensitive to delay varations. Thus, real-time traffic can be supported by connection-oriented routing schemes. The changing connectivity pattern of satellites affects the estbalished paths in LEO satellite networks. Thus, determining stable paths is very important. The Delay-Coupled Probabilistic Routing Protocol (DC-PRP) is proposed for connection-oriented routing in LEO satellite networks. DC-PRP computes paths conforming to the delay and delay jitter bounds of the connections. The Connection-Oriented Multicast Protocol (LEOCOM) is proposed for the connection-oriented multicasting, which creates delay-constrained multicast trees. The multicast tree length is optimized using a greedy search algorithm.