技术领域technical field
本发明涉及卫星网络通信领域，尤其涉及一种基于网络编码的双层卫星网络多径路由方法。The invention relates to the field of satellite network communication, in particular to a network coding-based double-layer satellite network multipath routing method.
背景技术Background technique
卫星通信网络为全球范围内分散分布的用户提供多样化的数据传送服务，其在全球通信服务领域中具有巨大的潜力。卫星通信网络不仅具有良好的全球覆盖性，而且能够提供高效实时的数据通信服务，因此卫星通信网络的应用对人迹罕至及地理环境恶劣的区域具有重大的意义。The satellite communication network provides diversified data transmission services for users scattered around the world, and it has great potential in the field of global communication services. The satellite communication network not only has good global coverage, but also can provide efficient and real-time data communication services. Therefore, the application of satellite communication network is of great significance to areas with inaccessible and harsh geographical environments.
基于卫星通信网络的广阔应用前景，针对卫星通信网络而设计的具有高效能且兼顾服务质量的网络路由算法称为卫星网络通信领域的一大重要课题。卫星沿各自轨道平面不间断运行，按轨道高度的不同，卫星被划分为低地球轨道、中地球轨道与地球同步轨道卫星。卫星的轨迹运动导致了卫星通信网络拓扑的时变性，进而增加了卫星网络路由的复杂性；而真空中卫星节点之间高带宽低延时的星间链路的建立，又为卫星通信网络的通信提供了高容量、高吞吐量的潜质。Based on the broad application prospects of satellite communication networks, the network routing algorithm designed for satellite communication networks with high performance and quality of service is an important topic in the field of satellite network communication. Satellites operate continuously along their respective orbital planes. According to different orbital heights, satellites are divided into low-earth orbit, medium-earth orbit and geosynchronous orbit satellites. The trajectory movement of satellites leads to the time-varying nature of the satellite communication network topology, which increases the complexity of satellite network routing; and the establishment of high-bandwidth and low-delay inter-satellite links between satellite nodes in a vacuum provides a new foundation for the satellite communication network. Communications offer the potential for high capacity, high throughput.
卫星网络的拓扑结构决定着卫星网络中的星间链路数目以及数据包的传输路径等，目前依靠单一轨道上的卫星节点组成的单层卫星网络因其网络阻塞概率大、抗毁性差、节点时延积累等因素，已经难以满足日益增长的信息服务需求。相较之下，多层卫星网络的拓扑结构具有较高的连通度，增加了卫星网络的可靠性，在卫星节点之间存在可供选择的备用链路，其通过结合不同轨道平面的卫星，可更加充分地利用卫星网络资源。在双层卫星网络拓扑结构中，MEO/LEO双层卫星网络具备诸多优势，网络中LEO卫星与MEO卫星均具有数据交换功能，层内可建立稳定的永久星间链路，通过MEO卫星节点对LEO卫星节点的覆盖特性，可以在层间建立用以数据转发的星间链路，通过两层卫星节点的协作，对网络中的数据进行转发，从而提高网络的数据传输效率，也可实现多径路由方法的应用。MEO/LEO双层卫星网络拓扑结构能够实现对地面用户的广泛覆盖，并且相较于其他卫星网络拓扑结构，具备传输时延低、数据链路损耗小等特点，能够更好地满足数据传输服务对通信质量的需求。The topology of the satellite network determines the number of inter-satellite links and the transmission path of data packets in the satellite network. At present, the single-layer satellite network composed of satellite nodes on a single orbit has a high probability of network blocking, poor invulnerability, and node Factors such as time delay accumulation have made it difficult to meet the growing demand for information services. In contrast, the topology of the multi-layer satellite network has high connectivity, which increases the reliability of the satellite network. There are optional backup links between satellite nodes. By combining satellites of different orbital planes, Satellite network resources can be more fully utilized. In the double-layer satellite network topology, the MEO/LEO double-layer satellite network has many advantages. Both the LEO satellite and the MEO satellite in the network have the function of data exchange, and a stable permanent inter-satellite link can be established in the layer. The coverage characteristics of LEO satellite nodes can establish an inter-satellite link for data forwarding between layers. Through the cooperation of two layers of satellite nodes, the data in the network can be forwarded, thereby improving the data transmission efficiency of the network and realizing multi- The path is applied by the method. MEO/LEO double-layer satellite network topology can achieve extensive coverage of ground users, and compared with other satellite network topologies, it has the characteristics of low transmission delay and low data link loss, which can better meet data transmission services The need for communication quality.
卫星网络的路由方法设计旨在充分利用丰富的网络资源，提升网络的传输性能与可靠性。针对卫星网络中无线信道所具有的广播、时变以及丢失等特性，相较于传统路由方法，多径路由通过应用在多个潜在中继节点中竞争、选择下一跳节点的方法，可以在数据转发的过程当中，通过路由算法的应用优先选择可用度更高的路径，提高了网络的吞吐量与传输的可靠性。与此同时，网络编码技术的提出似的网络中的节点能够相互协作转发数据包，充分地利用了双层卫星网络的空间关系及其丰富的网络资源，网络编码技术的应用允许节点对来自不同链路的数据包进行编码组合，当目的节点收到的编码数据包数达到一定数量，就可解码获得原始数据包，这相比原始的多径路由算法又进一步提高了网络的吞吐量。因此，在卫星网络路由方法的设计过程中，需要充分考虑卫星通信网络区别于其他网络的特性，并对其自身的显著优点加以利用，在时变的网络拓扑与高校的路由性能中寻求平衡，以期得到满足业务需求、具有优秀通信性能的卫星通信网络路由方法。The routing method of the satellite network is designed to make full use of abundant network resources and improve the transmission performance and reliability of the network. In view of the characteristics of broadcasting, time-varying and loss in the wireless channel in the satellite network, compared with the traditional routing method, multi-path routing can be used in multiple potential relay nodes to select the next-hop node by competing in the method. In the process of data forwarding, the application of the routing algorithm preferentially selects the path with higher availability, which improves the throughput of the network and the reliability of transmission. At the same time, the network coding technology allows nodes in the network to cooperate with each other to forward data packets, making full use of the spatial relationship of the double-layer satellite network and its rich network resources. The application of network coding technology allows nodes to The data packets of the link are encoded and combined. When the number of encoded data packets received by the destination node reaches a certain number, the original data packets can be decoded, which further improves the throughput of the network compared with the original multipath routing algorithm. Therefore, in the design process of the satellite network routing method, it is necessary to fully consider the characteristics of the satellite communication network that are different from other networks, and use its own significant advantages to seek a balance between the time-varying network topology and the routing performance of universities. In order to obtain a satellite communication network routing method that meets business requirements and has excellent communication performance.
发明内容Contents of the invention
本发明提出了一种基于网络编码的双层卫星网络多径路由方法，包括如下步骤：The present invention proposes a double-layer satellite network multipath routing method based on network coding, comprising the following steps:
步骤一：构建具有双层卫星星座的卫星网络拓扑，结合中、低地球轨道的特性建立星间链路，根据卫星数目与卫星网络容量的关系确定卫星网络结构；Step 1: Construct a satellite network topology with a double-layer satellite constellation, establish an inter-satellite link based on the characteristics of medium and low earth orbits, and determine the satellite network structure according to the relationship between the number of satellites and the capacity of the satellite network;
步骤二：根据卫星网络实时状态进行网络路由设置，以路由请求为驱动，在源端节点与目的端节点之间进行星间链路与沿途卫星节点的可用度权值计算，并据此获取响应路由请求的局部网络路由状态；Step 2: Set the network routing according to the real-time status of the satellite network. Driven by the routing request, calculate the availability weight of the inter-satellite link and the satellite nodes along the way between the source node and the destination node, and obtain the response accordingly The local network routing state of the routing request;
步骤三：结合网络编码与多径路由的方法优化卫星通信网络的性能，通过计算参与转发的卫星节点列表，结合数据传送过程中的编码操作与目的端完成数据传送后的解码操作，在网络中建立满足业务需求的有效链接；Step 3: Optimize the performance of the satellite communication network by combining network coding and multi-path routing. By calculating the list of satellite nodes participating in the forwarding, combining the coding operation during data transmission and the decoding operation after the destination end completes data transmission, in the network Establish effective links that meet business needs;
步骤四：根据卫星网络的拥塞状况，网络中各卫星节点及其星间链路的可用度权值，优先选择传送数据总代价较小的路由路径进行数据转发，提高卫星网络的吞吐量。Step 4: According to the congestion status of the satellite network, the availability weight of each satellite node and its inter-satellite link in the network, the routing path with the lower total cost of transmitting data is preferentially selected for data forwarding, and the throughput of the satellite network is improved.
本发明提出的所述基于网络编码的双层卫星网络多径路由方法中，步骤一中建立双层卫星网络拓扑包括如下步骤：In the network coding-based double-layer satellite network multipath routing method proposed by the present invention, the establishment of a double-layer satellite network topology in step 1 includes the following steps:
步骤1a：分析不同运行轨道中卫星的特性，根据本算法中提高网络吞吐量的要求，选定中地球轨道与低地球轨道两者结合构建双层卫星通信网络拓扑；Step 1a: Analyze the characteristics of satellites in different orbits, and according to the requirements of improving network throughput in this algorithm, select the combination of medium earth orbit and low earth orbit to construct a two-layer satellite communication network topology;
步骤1b：基于卫星通信网络中常用的轨道平面倾角，设定合理可行的卫星节点运行轨道平面，本算法中确定6个轨道倾角为86.4°的低地球轨道平面与3个轨道倾角为45°的中地球轨道平面；Step 1b: Based on the orbital plane inclination commonly used in satellite communication networks, set reasonable and feasible orbital planes for satellite nodes. In this algorithm, 6 low-Earth orbit planes with an orbital inclination of 86.4° and 3 low-Earth orbital planes with an orbital inclination of 45° are determined. Middle Earth orbit plane;
步骤1c：根据卫星通信网络中网络容量与在网卫星数目的关系，分析选定双层卫星网络中适用的卫星节点数目，本算法中选定66颗低地球轨道卫星与18颗中地球轨道卫星；Step 1c: According to the relationship between the network capacity and the number of satellites in the satellite communication network, analyze the number of satellite nodes applicable in the selected double-layer satellite network. In this algorithm, 66 low-earth orbit satellites and 18 medium-earth orbit satellites are selected ;
步骤1d：在构建的双层卫星网络拓扑中，依据卫星仰角、天线角度、轨道平面夹角等参数，计算层间卫星之间的可见性，并据此建立星间链路，以实现数据通信功能。Step 1d: In the constructed two-layer satellite network topology, calculate the visibility between satellites between layers based on parameters such as satellite elevation angle, antenna angle, and orbital plane angle, and establish inter-satellite links based on this to realize data communication Function.
本发明提出的所述基于网络编码的双层卫星网络多径路由方法中，步骤1d中依据卫星仰角、天线角度、轨道平面夹角等参数，计算层间卫星之间的可见性，判定两卫星彼此可见的条件以如下公式表示：In the network coding-based double-layer satellite network multipath routing method proposed by the present invention, in step 1d, according to parameters such as satellite elevation angle, antenna angle, and orbital plane angle, the visibility between satellites between layers is calculated, and the two satellites are determined. The condition of being visible to each other is expressed by the following formula:
θ≤αθ≤α
上式中，θ表示两层间卫星分别所处的低地球轨道与中地球轨道平面夹角，α表示低地球轨道卫星可见中地球轨道卫星的视野范围，β表示低地球轨道卫星天线角度，hL与hM分别表示低地球轨道与中地球轨道平面的海拔高度，rE表示地球半径。In the above formula, θ represents the angle between the low-earth orbit and the medium-earth orbit plane where the two layers of satellites are respectively located, α represents the field of view of the low-earth orbit satellite visible to the medium-earth orbit satellite, β represents the antenna angle of the low-earth orbit satellite, hL and hM represent the altitudes of the low-earth orbit and medium-earth orbit planes, respectively, and rE represents the radius of the earth.
则以上公式表示，当且仅当层间卫星所处平面的夹角小于等于两者中低地球轨道的视野范围时，两个层间卫星被判定为彼此可见，即此时可以建立有效的层间星间链路，可以在该两颗卫星节点之间实现数据通信。Then the above formula indicates that two interlayer satellites are judged to be visible to each other if and only when the angle between the planes where the interlayer satellites are located is less than or equal to the field of view of the low earth orbit of the two, that is, an effective layer can be established at this time The inter-satellite link can realize data communication between the two satellite nodes.
本发明提出的所述基于网络编码的双层卫星网络多径路由方法中，步骤二中结合卫星网络实时状态与路由请求信息进行路由设置包括如下步骤：In the double-layer satellite network multi-path routing method based on network coding proposed by the present invention, in step 2, carrying out routing setting in combination with satellite network real-time status and routing request information includes the following steps:
步骤2a：当一个新批次的数据包开始传送，源端节点产生路由请求，向网络中广播RQS数据包，在RQS数据包中，设置TTL初始值为20；Step 2a: When a new batch of data packets starts to be transmitted, the source node generates a routing request and broadcasts an RQS data packet to the network. In the RQS data packet, set the TTL initial value to 20;
步骤2b：RQS数据包在网络中广播直到到达目的端节点，RQS包广播过程中，每到达一个中继节点，其TTL值即减1，TTL值小于或等于零的RQS数据包将被丢弃；Step 2b: The RQS data packet is broadcast in the network until it reaches the destination end node. During the broadcasting process of the RQS packet, each time it reaches a relay node, its TTL value is reduced by 1, and the RQS data packet with a TTL value less than or equal to zero will be discarded;
步骤2c：当目的端节点收到RQS包时，其生成UPD数据包并向网络广播，在UPD数据包中，设置TTL初始值为20，Dc初始值为1；Step 2c: When the destination end node receives the RQS packet, it generates a UPD packet and broadcasts it to the network. In the UPD packet, set the initial value of TTL to 20, and the initial value of Dc to 1;
步骤2d：UPD数据包在网络中回传，更新并记录沿途卫星节点的路由信息，UPD数据包每到达一个中继节点，其TTL值即减1，更新Dc值为本数据包Dc值与本地节点ENT值之和，中继节点将自身节点ID与距离目的端节点的Dc值写入记录路由信息的节点列表，并对更新后的UPD数据包进行转发；Step 2d: The UPD data packet is transmitted back in the network, and the routing information of the satellite nodes along the way is updated and recorded. Every time the UPD data packet reaches a relay node, its TTL value is reduced by 1, and the updated Dc value is the Dc value of the data packet With the sum of the local node ENT value, the relay node writes its own node ID and theDc value of the distance from the destination node to the node list for recording routing information, and forwards the updated UPD packet;
步骤2e：源端节点收到UPD数据包时，UPD数据包中已包含在源端节点与目的端节点之间经由的卫星节点的路由信息，源端节点将据此信息生成参与数据转发的节点列表，将所有Dc值小于自身的节点写入转发节点列表，完成网络的路由设置阶段。Step 2e: When the source node receives the UPD data packet, the UPD data packet already contains the routing information of the satellite node between the source node and the destination node, and the source node will generate a node that participates in data forwarding based on this information List, write all the nodes whoseDc value is smaller than itself into the forwarding node list, and complete the routing setting stage of the network.
本发明提出的所述基于网络编码的双层卫星网络多径路由方法中，步骤2d中卫星网络节点的ENT值的计算以如下公式表示：In the double-layer satellite network multipath routing method based on network coding proposed by the present invention, the calculation of the ENT value of the satellite network node in step 2d is expressed by the following formula:
pr＝1-∏k＞j(1-μkλj)pr ＝1-∏k＞j (1-μk λj )
pd＝1-∏i＜j(1-μjλi)pd ＝1-∏i<j (1-μj λi )
上式中，λj表示节点j成功接收一次数据传送的概率，λj由节点之间互相发送探测数据包计算而得，每个卫星节点以一定周期τ(本算法中设定为1s)广播探测数据包，count(t)表示在给定t时间内节点j接收到的探测数据包数目，则λj可由以上公式计算得到；同理，节点j成功发送一次数据的概率μj也可由此方法测得。In the above formula, λj represents the probability that node j successfully receives a data transmission, λj is calculated by sending detection packets between nodes, and each satellite node broadcasts at a certain period τ (set as 1s in this algorithm) Detection data packets, count(t) represents the number of detection data packets received by node j within a given time t, then λj can be calculated by the above formula; similarly, the probability μj of node j successfully sending data once can also be obtained by method measured.
pr表示节点j成功接收到上游节点传送的至少一个数据包的概率，pd表示节点j成功向下游节点发送至少一个数据包的概率，则节点j成功参与当前数据流的转发所需要的期望传输次数ENT可由以上概率计算而得。pr represents the probability that node j successfully receives at least one data packet transmitted by the upstream node, pd represents the probability that node j successfully sends at least one data packet to the downstream node, then node j successfully participates in the forwarding of the current data flow. The number of transmissions ENT can be calculated from the above probabilities.
本发明提出的所述基于网络编码的双层卫星网络多径路由方法中，步骤三中所述在卫星通信网络中结合网络编码的多径路由算法包括如下步骤：In the double-layer satellite network multi-path routing method based on network coding proposed by the present invention, the multi-path routing algorithm combined with network coding in the satellite communication network described in step 3 includes the following steps:
步骤3a：当步骤二的路由设置过程完成后，源端节点将数据流中的每M(本算法中设定M＝32)个原始数据包划分为一个批次；Step 3a: after the route setting process of step 2 is completed, the source node divides every M (setting M=32 in this algorithm) original data packets in the data stream into a batch;
步骤3b：源端节点将同一批次的原始数据包进行线性随机编码，并向编码后的编码数据包中添加写有网络路由信息的NCMP头文件；Step 3b: The source node performs linear random encoding on the same batch of original data packets, and adds an NCMP header file with network routing information to the encoded encoded data packets;
步骤3c：源端节点持续传送当前批次的文件，直到其接收到目的端节点发送的ACK数据包，此时转至下一批次数据包的传送；Step 3c: The source node continues to transmit the current batch of files until it receives the ACK data packet sent by the destination node, and then transfers to the transmission of the next batch of data packets;
步骤3d：中继节点监听网络中的所有数据传送，每当接收到一个数据包，中继节点首先检查自己是否在转发节点的列表之中，如果在，则比对当前数据包的批次与本地存储数据包的批次，中继节点只转发最新批次的数据包，丢弃不符要求的编码数据包；Step 3d: The relay node monitors all data transmissions in the network. Whenever a data packet is received, the relay node first checks whether it is in the list of forwarding nodes, and if so, compares the batch of the current data packet with The batches of data packets are stored locally, and the relay node only forwards the latest batch of data packets, and discards the encoded data packets that do not meet the requirements;
步骤3e：对于符合步骤3d所述要求的数据包，中继节点继续检查当前数据包与本地数据包的线性独立性，这一检查通过对编码向量的运算实现，中继节点重编码线性独立的数据包，丢弃冗余信息；Step 3e: For the data packets that meet the requirements described in step 3d, the relay node continues to check the linear independence of the current data packet and the local data packet. This check is realized through the operation of the encoding vector, and the relay node re-encodes the linearly independent Data packets, discarding redundant information;
步骤3f：中继节点将编码后的数据包在网络中广播，同时对本地数据包进行预编码操作；Step 3f: the relay node broadcasts the encoded data packet in the network, and at the same time pre-encodes the local data packet;
步骤3g：当目的端节点收到编码数据包时，其同样如步骤3e所述检查数据的线性独立性，当接收到线性独立的数据包，其查看本地是否已经收到一个完整批次的数据包，如果数据包数目达到M，则目的端节点即刻向源端节点发送一个具有最高优先级的ACK数据包，并同时开始对当前批次编码数据包的解码操作。Step 3g: When the destination end node receives the encoded data packet, it also checks the linear independence of the data as described in step 3e. When receiving a linearly independent data packet, it checks whether a complete batch of data has been received locally If the number of data packets reaches M, the destination end node immediately sends an ACK data packet with the highest priority to the source end node, and at the same time starts to decode the current batch of encoded data packets.
步骤3h：结束当前批次的数据传送，更新卫星网络状态，等待下一次路由请求。Step 3h: End the current batch of data transmission, update the status of the satellite network, and wait for the next routing request.
本发明提出的所述基于网络编码的双层卫星网络多径路由方法中，步骤三中在卫星网络中转发数据过程中应用的网络编码及解码操作以如下公式表示：In the network coding-based double-layer satellite network multipath routing method proposed by the present invention, the network coding and decoding operations applied in the process of forwarding data in the satellite network in step 3 are represented by the following formula:
上式中，表示从有限域＝28中随机抽取的编码向量，pcj表示经过编码操作的编码数据包，pi表示源端节点生成的原始数据包。In the above formula, Indicates the encoding vector randomly extracted from the finite field = 28 , pcj indicates the encoded data packet after the encoding operation, andpi indicates the original data packet generated by the source end node.
步骤3f所述在目的端节点进行的数据包解码操作以如下矩阵运算表示：The packet decoding operation performed at the destination end node described in step 3f is represented by the following matrix operation:
通过上式的矩阵运算，可以在目的端节点实现从接收到的编码数据包中还原原始数据包的操作，该编码与解码的过程保证了原始数据包在网络中传送的稳定性与安全性。Through the matrix operation of the above formula, the operation of restoring the original data packet from the received encoded data packet can be realized at the destination end node. The process of encoding and decoding ensures the stability and security of the original data packet transmitted in the network.
本发明通过对不同类型卫星节点的通信特性分析，确定一种结合低地球轨道与中地球轨道的双层卫星网络拓扑，网络构架中的卫星节点数目能够提供数据通信所需的网络容量。在所述的卫星网络拓扑中，本算法提出一种结合网络编码方法的多径路由方法。网络编码方法的运用能够提高卫星通信网络的吞吐量，而多径路由方法则有效弥补了卫星轨迹运动带来的网络拓扑的高时变性。本算法充分考虑了卫星网络自身的特性，对数据进行编码后在网络中多条路径协同转发，提高网络效能，降低数据传送的成本，从而为卫星网络的通信提供切实可行的路由方法。本算法将网络编码技术应用于卫星网络的路由算法之中，网络编码技术能够提高网络的吞吐量与可靠性；本发明中的路由算法通过引入网络编码解决了卫星网络数据传输过程中节点相互协作的难题，充分地利用了卫星网络的空间关系，通过多个卫星节点的协作对数据包进行转发；与此同时，本路由算法通过引入路由请求时限标签TTL以及ACK确认机制，提高了网络的吞吐量，能够在双层卫星网络中建立多条有效的路由路径，适应时变拓扑的网络环境，优化双层卫星网络的路由性能The present invention determines a double-layer satellite network topology combining low-earth orbit and medium-earth orbit by analyzing communication characteristics of different types of satellite nodes, and the number of satellite nodes in the network framework can provide network capacity required for data communication. In the above-mentioned satellite network topology, this algorithm proposes a multi-path routing method combined with network coding method. The application of the network coding method can improve the throughput of the satellite communication network, and the multipath routing method can effectively compensate for the high time-varying network topology caused by the satellite trajectory movement. This algorithm fully considers the characteristics of the satellite network itself, encodes the data and forwards them cooperatively in multiple paths in the network, improves network efficiency, reduces the cost of data transmission, and thus provides a feasible routing method for satellite network communication. This algorithm applies network coding technology to the routing algorithm of the satellite network. The network coding technology can improve the throughput and reliability of the network; the routing algorithm in the present invention solves the mutual cooperation of nodes in the process of satellite network data transmission by introducing network coding It makes full use of the spatial relationship of the satellite network and forwards data packets through the cooperation of multiple satellite nodes; at the same time, this routing algorithm improves the throughput of the network by introducing the routing request time limit label TTL and ACK confirmation mechanism It can establish multiple effective routing paths in the double-layer satellite network, adapt to the network environment of time-varying topology, and optimize the routing performance of the double-layer satellite network
附图说明：Description of drawings:
图1是本发明的MEO/LEO双层卫星网络拓扑结构图。Fig. 1 is a topological structure diagram of the MEO/LEO double-layer satellite network of the present invention.
图2是本发明的流程示意图。Fig. 2 is a schematic flow chart of the present invention.
图3a是本发明的卫星网络数据传送过程路由算法源端的流程示意图。Fig. 3a is a schematic flowchart of the source end of the routing algorithm of the satellite network data transmission process of the present invention.
图3b是本发明的卫星网络数据传送过程路由算法数据接收端的流程示意图。。Fig. 3b is a schematic flowchart of the data receiving end of the routing algorithm in the satellite network data transmission process of the present invention. .
具体实施方式Detailed ways
结合以下具体实施例和附图，对本发明作进一步的详细说明。实施本发明的过程、条件、实验方法等，除以下专门提及的内容之外，均为本领域的普遍知识和公知常识，本发明没有特别限制内容。The present invention will be further described in detail in conjunction with the following specific embodiments and accompanying drawings. The process, conditions, experimental methods, etc. for implementing the present invention, except for the content specifically mentioned below, are common knowledge and common knowledge in this field, and the present invention has no special limitation content.
本发明公开了一种基于网络编码的双层卫星网络多径路由方法，其特征在于，包括如下步骤：The invention discloses a network coding-based double-layer satellite network multi-path routing method, which is characterized in that it comprises the following steps:
步骤一：构建具有双层卫星星座的卫星网络拓扑，结合中、低地球轨道的特性建立星间链路，根据卫星数目与卫星网络容量的关系确定卫星网络结构。Step 1: Construct a satellite network topology with a double-layer satellite constellation, establish an inter-satellite link based on the characteristics of medium and low earth orbits, and determine the satellite network structure according to the relationship between the number of satellites and the capacity of the satellite network.
具体包括以下步骤：Specifically include the following steps:
步骤一中建立双层卫星网络拓扑包括如下步骤：The establishment of a two-tier satellite network topology in step 1 includes the following steps:
步骤1a：分析不同运行轨道中卫星的特性，根据本算法中提高网络吞吐量的要求，选定中地球轨道与低地球轨道两者结合构建双层卫星通信网络拓扑；Step 1a: Analyze the characteristics of satellites in different orbits, and according to the requirements of improving network throughput in this algorithm, select the combination of medium earth orbit and low earth orbit to construct a two-layer satellite communication network topology;
步骤1b：基于卫星通信网络中常用的轨道平面倾角，设定合理可行的卫星节点运行轨道平面；Step 1b: Based on the orbital plane inclination commonly used in satellite communication networks, set a reasonable and feasible satellite node operating orbital plane;
步骤1c：根据卫星通信网络中网络容量与在网卫星数目的关系，分析选定双层卫星网络中适用的卫星节点数目；Step 1c: According to the relationship between the network capacity and the number of satellites in the satellite communication network, analyze the number of satellite nodes applicable in the selected double-layer satellite network;
步骤1d：在构建的双层卫星网络拓扑中，依据卫星仰角、天线角度、轨道平面夹角参数，计算层间卫星之间的可见性，并据此建立星间链路，以实现数据通信功能。Step 1d: In the constructed two-layer satellite network topology, calculate the visibility between interlayer satellites based on satellite elevation angle, antenna angle, and orbital plane angle parameters, and establish inter-satellite links based on this to realize data communication functions .
步骤1d中依据卫星仰角、天线角度、轨道平面夹角等参数，计算层间卫星之间的可见性，判定两卫星彼此可见的条件以如下公式表示：In step 1d, according to the parameters such as satellite elevation angle, antenna angle, and orbital plane angle, the visibility between interlayer satellites is calculated, and the conditions for judging that two satellites are visible to each other are expressed by the following formula:
θ≤αθ≤α
上式中，θ表示两层间卫星分别所处的低地球轨道与中地球轨道平面夹角，α表示低地球轨道卫星可见中地球轨道卫星的视野范围，β表示低地球轨道卫星天线角度，hL与hM分别表示低地球轨道与中地球轨道平面的海拔高度，rE表示地球半径；In the above formula, θ represents the angle between the low-earth orbit and the medium-earth orbit plane where the two layers of satellites are respectively located, α represents the field of view of the low-earth orbit satellite visible to the medium-earth orbit satellite, β represents the antenna angle of the low-earth orbit satellite, hL and hM represent the altitude of the low earth orbit and medium earth orbit plane respectively, and rE represents the radius of the earth;
则以上公式表示，当且仅当层间卫星所处平面的夹角小于等于两者中低地球轨道的视野范围时，两个层间卫星被判定为彼此可见，即此时可以建立有效的层间星间链路，可以在该两颗卫星节点之间实现数据通信。Then the above formula indicates that two interlayer satellites are judged to be visible to each other if and only when the angle between the planes where the interlayer satellites are located is less than or equal to the field of view of the low earth orbit of the two, that is, an effective layer can be established at this time The inter-satellite link can realize data communication between the two satellite nodes.
步骤二：根据卫星网络实时状态进行网络路由设置，以路由请求为驱动，在源端节点与目的端节点之间进行星间链路与沿途卫星节点的可用度权值计算，并据此获取响应路由请求的局部网络路由状态。具体包括以下步骤：Step 2: Set the network routing according to the real-time status of the satellite network. Driven by the routing request, calculate the availability weight of the inter-satellite link and the satellite nodes along the way between the source node and the destination node, and obtain the response accordingly The local network routing state for routing requests. Specifically include the following steps:
步骤2a：当一个新批次的数据包开始传送，源端节点产生路由请求，向网络中广播RQS数据包，在RQS数据包中，设置TTL初始值为20；Step 2a: When a new batch of data packets starts to be transmitted, the source node generates a routing request and broadcasts an RQS data packet to the network. In the RQS data packet, set the TTL initial value to 20;
步骤2b：RQS数据包在网络中广播直到到达目的端节点，RQS包广播过程中，每到达一个中继节点，其TTL值即减1，TTL值小于或等于零的RQS数据包将被丢弃；Step 2b: The RQS data packet is broadcast in the network until it reaches the destination end node. During the broadcasting process of the RQS packet, each time it reaches a relay node, its TTL value is reduced by 1, and the RQS data packet with a TTL value less than or equal to zero will be discarded;
步骤2c：当目的端节点收到RQS包时，其生成UPD数据包并向网络广播，在UPD数据包中，设置TTL初始值为20，Dc初始值为1；Step 2c: When the destination end node receives the RQS packet, it generates a UPD packet and broadcasts it to the network. In the UPD packet, set the initial value of TTL to 20, and the initial value of Dc to 1;
步骤2d：UPD数据包在网络中回传，更新并记录沿途卫星节点的路由信息，UPD数据包每到达一个中继节点，其TTL值即减1，更新Dc值为本数据包Dc值与本地节点ENT值之和，中继节点将自身节点ID与距离目的端节点的Dc值写入记录路由信息的节点列表，并对更新后的UPD数据包进行转发；Step 2d: The UPD data packet is transmitted back in the network, and the routing information of the satellite nodes along the way is updated and recorded. Every time the UPD data packet reaches a relay node, its TTL value is reduced by 1, and the updated Dc value is the Dc value of the data packet With the sum of the local node ENT value, the relay node writes its own node ID and theDc value of the distance from the destination node to the node list for recording routing information, and forwards the updated UPD packet;
步骤2e：源端节点收到UPD数据包时，UPD数据包中已包含在源端节点与目的端节点之间经由的卫星节点的路由信息，源端节点将据此信息生成参与数据转发的节点列表，将所有Dc值小于自身的节点写入转发节点列表，完成网络的路由设置阶段。Step 2e: When the source node receives the UPD data packet, the UPD data packet already contains the routing information of the satellite node between the source node and the destination node, and the source node will generate a node that participates in data forwarding based on this information List, write all the nodes whoseDc value is smaller than itself into the forwarding node list, and complete the routing setting stage of the network.
步骤三：结合网络编码与多径路由的方法优化卫星通信网络的性能，通过计算参与转发的卫星节点列表，结合数据传送过程中的编码操作与目的端完成数据传送后的解码操作，在网络中建立满足业务需求的有效链接；Step 3: Optimize the performance of the satellite communication network by combining network coding and multi-path routing. By calculating the list of satellite nodes participating in the forwarding, combining the coding operation during data transmission and the decoding operation after the destination end completes data transmission, in the network Establish effective links that meet business needs;
具体包括以下步骤：Specifically include the following steps:
步骤3a：当步骤二的路由设置过程完成后，源端节点将数据流中的每M个原始数据包划分为一个批次；Step 3a: After the routing setting process in step 2 is completed, the source node divides every M original data packets in the data stream into a batch;
步骤3b：源端节点将同一批次的原始数据包进行线性随机编码，并向编码后的编码数据包中添加写有网络路由信息的NCMP头文件；Step 3b: The source node performs linear random encoding on the same batch of original data packets, and adds an NCMP header file with network routing information to the encoded encoded data packets;
步骤3c：源端节点持续传送当前批次的文件，直到其接收到目的端节点发送的ACK数据包，此时转至下一批次数据包的传送；Step 3c: The source node continues to transmit the current batch of files until it receives the ACK data packet sent by the destination node, and then transfers to the transmission of the next batch of data packets;
步骤3d：中继节点监听网络中的所有数据传送，每当接收到一个数据包，中继节点首先检查自己是否在转发节点的列表之中，如果在，则比对当前数据包的批次与本地存储数据包的批次，中继节点只转发最新批次的数据包，丢弃不符要求的编码数据包；Step 3d: The relay node monitors all data transmissions in the network. Whenever a data packet is received, the relay node first checks whether it is in the list of forwarding nodes, and if so, compares the batch of the current data packet with The batches of data packets are stored locally, and the relay node only forwards the latest batch of data packets, and discards the encoded data packets that do not meet the requirements;
步骤3e：对于符合步骤3d所述要求的数据包，中继节点继续检查当前数据包与本地数据包的线性独立性，这一检查通过对编码向量的运算实现，中继节点重编码线性独立的数据包，丢弃冗余信息；Step 3e: For the data packets that meet the requirements described in step 3d, the relay node continues to check the linear independence of the current data packet and the local data packet. This check is realized through the operation of the encoding vector, and the relay node re-encodes the linearly independent Data packets, discarding redundant information;
步骤3f：中继节点将编码后的数据包在网络中广播，同时对本地数据包进行预编码操作；Step 3f: the relay node broadcasts the encoded data packet in the network, and at the same time pre-encodes the local data packet;
步骤3g：当目的端节点收到编码数据包时，其同样如步骤3e所述检查数据的线性独立性，当接收到线性独立的数据包，其查看本地是否已经收到一个完整批次的数据包，如果数据包数目达到M，则目的端节点即刻向源端节点发送一个具有最高优先级的ACK数据包，并同时开始对当前批次编码数据包的解码操作；Step 3g: When the destination end node receives the encoded data packet, it also checks the linear independence of the data as described in step 3e. When receiving a linearly independent data packet, it checks whether a complete batch of data has been received locally If the number of data packets reaches M, the destination end node immediately sends an ACK data packet with the highest priority to the source end node, and at the same time starts to decode the current batch of encoded data packets;
步骤3h：结束当前批次的数据传送，更新卫星网络状态，等待下一次路由请求。Step 3h: End the current batch of data transmission, update the status of the satellite network, and wait for the next routing request.
本发明的核心内容是依据数据通信业务的需求，构建大容量双层卫星通信网络拓扑结构，并在此卫星网络中，结合卫星节点的相互可见性、卫星网络数据传播的特性等，设计符合业务需求、适应卫星网络结构的路由算法，以实现对卫星通信网络性能指标的优化。The core content of the present invention is to construct a large-capacity double-layer satellite communication network topology according to the needs of data communication services, and in this satellite network, combined with the mutual visibility of satellite nodes and the characteristics of satellite network data transmission, etc., the design conforms to the business Requirements and routing algorithms adapted to the satellite network structure to optimize the performance indicators of the satellite communication network.
本算法应用的MEO/LEO双层卫星网络拓扑模型如图1所示，图中可见六条低地球轨道运行轨迹以及三条中地球轨道运行轨迹，其轨道平面具体参数详见以下表1：The MEO/LEO two-layer satellite network topology model applied by this algorithm is shown in Figure 1. In the figure, six low-Earth orbit trajectories and three medium-Earth orbit trajectories can be seen. The specific parameters of the orbital plane are shown in Table 1 below:
表1 MEO/LEO卫星网络的参数配置Table 1 Parameter configuration of MEO/LEO satellite network
在上述MEO/LEO双层卫星网络中，涉及数据传送的链路可划分为层内星间链路、层间星间链路以及卫星与地面节点之间的链路，在本算法中设置网络参数详见以下表2：In the above-mentioned MEO/LEO double-layer satellite network, the links involved in data transmission can be divided into intra-layer inter-satellite links, inter-layer inter-satellite links, and links between satellites and ground nodes. In this algorithm, the network The parameters are detailed in Table 2 below:
表2 网络链路的参数配置Table 2 Parameter configuration of network link
在卫星通信网络中，数据的通信通过星间链路实现，星间链路的建立则与卫星仰角、天线角度、轨道平面夹角等参数有关，卫星节点在层内分别与其东西南北四个方位的邻居节点建立四条星间链路，而层间星间链路的建立则需要首先计算层间卫星之间的可见性，判定两卫星彼此可见；判定两颗层间卫星节点相互可见的条件以如下公式表示：In the satellite communication network, data communication is realized through the inter-satellite link, and the establishment of the inter-satellite link is related to parameters such as satellite elevation angle, antenna angle, and orbital plane angle. Neighbor nodes establish four inter-satellite links, and the establishment of an inter-layer inter-satellite link needs to first calculate the visibility between the inter-layer satellites, and determine that the two satellites are visible to each other; determine the conditions for the mutual visibility of the two inter-layer satellite nodes The following formula expresses:
θ≤αθ≤α
上式中，θ表示两层间卫星分别所处的低地球轨道与中地球轨道平面夹角，α表示低地球轨道卫星可见中地球轨道卫星的视野范围，β表示低地球轨道卫星天线角度，hL与hM分别表示低地球轨道与中地球轨道平面的海拔高度，rE表示地球半径。则以上公式表示，当且仅当层间卫星所处平面的夹角小于等于两者中低地球轨道的视野范围时，两个层间卫星被判定为彼此可见，即此时可以建立有效的层间星间链路，可以在该两颗卫星节点之间实现数据通信。In the above formula, θ represents the angle between the low-earth orbit and the medium-earth orbit plane where the two layers of satellites are respectively located, α represents the field of view of the low-earth orbit satellite visible to the medium-earth orbit satellite, β represents the antenna angle of the low-earth orbit satellite, hL and hM represent the altitudes of the low-earth orbit and medium-earth orbit planes, respectively, and rE represents the radius of the earth. Then the above formula indicates that two interlayer satellites are judged to be visible to each other if and only when the angle between the planes where the interlayer satellites are located is less than or equal to the field of view of the low earth orbit of the two, that is, an effective layer can be established at this time The inter-satellite link can realize data communication between the two satellite nodes.
完成星间链路的建立后，卫星网络拓扑基本构建完成，在网络产生数据传送需求的情况下，本算法首先需要结合卫星网络实时状态与路由请求信息进行网络路由设置，其算法如下所示，After the establishment of the inter-satellite link, the basic construction of the satellite network topology is completed. When the network generates data transmission requirements, the algorithm first needs to combine the real-time status of the satellite network and routing request information to set the network routing. The algorithm is as follows,
如图2、3a、3b所示，当一个新批次的数据包开始传送，源端节点产生路由请求，向网络中广播RQS数据包，在RQS数据包中，设置TTL初始值为20。由源端节点发送的RQS数据包在网络中持续广播直到到达目的端节点，RQS数据包广播过程中，每到达一个中继节点，其TTL值即减1，TTL值小于或等于零的RQS数据包将被丢弃。当目的端节点收到RQS包时，其生成UPD数据包并向网络广播，在UPD数据包中，设置TTL初始值为20，Dc初始值为1。目的端节点发出的UPD数据包在网络中回传，更新并记录沿途卫星节点的路由信息，UPD数据包每到达一个中继节点，其TTL值即减1，更新Dc值为本数据包Dc值与本地节点ENT值之和，中继节点将自身节点ID与距离目的端节点的Dc值写入记录路由信息的节点列表，并对更新后的UPD数据包进行转发。当源端节点收到UPD数据包时，UPD数据包中已包含在源端节点与目的端节点之间经由的卫星节点的路由信息，源端节点将据此信息生成参与数据转发的节点列表，将所有Dc值小于自身的节点写入转发节点列表，完成网络的路由设置阶段。As shown in Figures 2, 3a, and 3b, when a new batch of data packets starts to be transmitted, the source node generates a routing request and broadcasts RQS data packets to the network. In the RQS data packets, set the initial value of TTL to 20. The RQS data packet sent by the source node continues to broadcast in the network until it reaches the destination node. During the broadcasting process of the RQS data packet, each time it reaches a relay node, its TTL value is reduced by 1, and the RQS data packet with a TTL value less than or equal to zero will be discarded. When the destination end node receives the RQS packet, it generates a UPD packet and broadcasts it to the network. In the UPD packet, the initial value of TTL is set to 20, and the initial value of Dc is 1. The UPD data packet sent by the destination end node is transmitted back in the network, and the routing information of the satellite nodes along the way is updated and recorded. Every time the UPD data packet reaches a relay node, its TTL value is reduced by 1, and the updated Dc value is the data packet D The sum of thec value and the ENT value of the local node, the relay node writes its own node ID and the Dc value of the distance to the destination node into the node list recording routing information, and forwards the updated UPD packet. When the source node receives the UPD data packet, the UPD data packet already contains the routing information of the satellite node passed between the source node and the destination node, and the source node will generate a list of nodes participating in data forwarding based on this information, Write all nodes whose Dc value is smaller than itself into the forwarding node list, and complete the routing setting stage of the network.
在上述网络路由设置过程中提及的卫星网络节点的ENT值的计算以如下公式表示：The calculation of the ENT value of the satellite network node mentioned in the above network routing setting process is expressed by the following formula:
pr＝1-∏k＞j(1-μkλj)pr ＝1-∏k＞j (1-μk λj )
pd＝1-∏i＜j(1-μjλi)pd ＝1-∏i<j (1-μj λi )
上式中，λj表示节点j成功接收一次数据传送的概率，λj由节点之间互相发送探测数据包计算而得，每个卫星节点以一定周期τ(本算法中设定为1s)广播探测数据包，count(t)表示在给定t时间内节点j接收到的探测数据包数目，则λj可由以上公式计算得到；同理，节点j成功发送一次数据的概率μj也可由此方法测得。pr表示节点j成功接收到上游节点传送的至少一个数据包的概率，pd表示节点j成功向下游节点发送至少一个数据包的概率，则节点j成功参与当前数据流的转发所需要的期望传输次数ENT可由以上概率计算而得。In the above formula, λj represents the probability that node j successfully receives a data transmission, λj is calculated by sending detection packets between nodes, and each satellite node broadcasts at a certain period τ (set as 1s in this algorithm) Detection data packets, count(t) represents the number of detection data packets received by node j within a given time t, then λj can be calculated by the above formula; similarly, the probability μj of node j successfully sending data once can also be obtained by method measured. pr represents the probability that node j successfully receives at least one data packet transmitted by the upstream node, pd represents the probability that node j successfully sends at least one data packet to the downstream node, then node j successfully participates in the forwarding of the current data flow. The number of transmissions ENT can be calculated from the above probabilities.
上述网络路由设置过程协助源端节点建立一张转发节点列表，这张转发节点列表包含了所有距离目的端节点Dc值小于源端节点的沿途卫星节点信息，下一步的数据传送过程就通过列表中所涵盖卫星节点组成的路由路径实现。The above network routing setting process assists the source node to establish a list of forwarding nodes. This list of forwarding nodes contains information on all satellite nodes along the route whose distance from the destination nodeDc value is less than the source node. The next step of the data transmission process is through the list Routing paths composed of satellite nodes covered in .
当上述建立好转发节点列表后，源端节点将数据流中的每M(本算法中设定M＝32)个原始数据包划分为一个批次，继而将同一批次的原始数据包进行线性随机编码，并向编码后的编码数据包中添加写有网络路由信息的NCMP头文件，该网络编码操作以如下公式表示：After the above-mentioned forwarding node list is established, the source node divides every M (set M=32 in this algorithm) original data packets in the data stream into a batch, and then performs linear processing on the same batch of original data packets. Randomly encode, and add an NCMP header file with network routing information to the encoded encoded data packet. The network encoding operation is expressed by the following formula:
上式中，表示从有限域＝28中随机抽取的编码向量，pcj表示经过编码操作的编码数据包，pi表示源端节点生成的原始数据包。In the above formula, Indicates the encoding vector randomly extracted from the finite field = 28 , pcj indicates the encoded data packet after the encoding operation, andpi indicates the original data packet generated by the source end node.
在完成数据包的编码后，源端节点持续传送当前批次的文件，直到其接收到目的端节点发送的ACK数据包，此时转至下一批次数据包的传送。After the encoding of the data packet is completed, the source node continues to transmit the current batch of files until it receives the ACK data packet sent by the destination node, and then transfers to the transmission of the next batch of data packets.
网络中的每个中继节点监听网络中的所有数据传送，每当接收到一个数据包，中继节点首先检查自己是否在转发节点的列表之中，如果在，则比对当前数据包的批次与本地存储数据包的批次，中继节点只转发最新批次的数据包，丢弃不符要求的编码数据包。对于符合这些要求的数据包，中继节点继续检查当前数据包与本地数据包的线性独立性，这一检查通过对编码向量的运算实现，中继节点重编码线性独立的数据包，丢弃冗余信息。中继节点将编码后的数据包在网络中广播，同时对本地数据包进行预编码操作。Each relay node in the network listens to all data transmissions in the network. Whenever a data packet is received, the relay node first checks whether it is in the list of forwarding nodes, and if so, compares the current data packet batch The relay node only forwards the latest batch of data packets and discards the encoded data packets that do not meet the requirements. For data packets that meet these requirements, the relay node continues to check the linear independence of the current data packet and the local data packet. This check is realized through the operation of the encoding vector. The relay node re-encodes the linearly independent data packets and discards redundant information. The relay node broadcasts the encoded data packets in the network, and at the same time pre-encodes the local data packets.
当目的端节点收到编码数据包时，其同样如步骤3e所述检查数据的线性独立性，当接收到线性独立的数据包，其查看本地是否已经收到一个完整批次的数据包，如果数据包数目达到M，则目的端节点即刻向源端节点发送一个具有最高优先级的ACK数据包，并同时开始对当前批次编码数据包的解码操作，解码操作以如下矩阵运算表示：When the destination end node receives the encoded data packet, it also checks the linear independence of the data as described in step 3e. When receiving a linearly independent data packet, it checks whether a complete batch of data packets has been received locally. If When the number of data packets reaches M, the destination end node immediately sends an ACK data packet with the highest priority to the source end node, and at the same time starts the decoding operation of the current batch of encoded data packets. The decoding operation is represented by the following matrix operation:
通过上式的矩阵运算，可以在目的端节点实现从接收到的编码数据包中还原原始数据包的操作，该编码与解码的过程保证了原始数据包在网络中传送的稳定性与安全性。目的端节点完成解码操作后，则结束当前批次的数据传送，更新卫星网络状态，等待下一次路由请求。Through the matrix operation of the above formula, the operation of restoring the original data packet from the received encoded data packet can be realized at the destination end node. The process of encoding and decoding ensures the stability and security of the original data packet transmitted in the network. After the destination end node completes the decoding operation, it ends the current batch of data transmission, updates the status of the satellite network, and waits for the next routing request.
本发明通过对不同类型卫星节点的通信特性分析，确定一种结合低地球轨道与中地球轨道的双层卫星网络拓扑，网络构架中的卫星节点数目能够提供数据通信所需的网络容量。在所述的卫星网络拓扑中，本算法提出一种结合网络编码方法的多径路由方法。网络编码方法的运用能够提高卫星通信网络的吞吐量，而多径路由方法则有效弥补了卫星轨迹运动带来的网络拓扑的高时变性。本算法充分考虑了卫星网络自身的特性，对数据进行编码后在网络中多条路径协同转发，提高网络效能，降低数据传送的成本，从而为卫星网络的通信提供切实可行的路由方法。本算法将网络编码技术应用于卫星网络的路由算法之中，网络编码技术能够提高网络的吞吐量与可靠性；本发明中的路由算法通过引入网络编码解决了卫星网络数据传输过程中节点相互协作的难题，充分地利用了卫星网络的空间关系，通过多个卫星节点的协作对数据包进行转发；与此同时，本路由算法通过引入路由请求时限标签TTL以及ACK确认机制，提高了网络的吞吐量，能够在双层卫星网络中建立多条有效的路由路径，适应时变拓扑的网络环境，优化双层卫星网络的路由性能The present invention determines a double-layer satellite network topology combining low-earth orbit and medium-earth orbit by analyzing communication characteristics of different types of satellite nodes, and the number of satellite nodes in the network framework can provide network capacity required for data communication. In the above-mentioned satellite network topology, this algorithm proposes a multi-path routing method combined with network coding method. The application of the network coding method can improve the throughput of the satellite communication network, and the multipath routing method can effectively compensate for the high time-varying network topology caused by the satellite trajectory movement. This algorithm fully considers the characteristics of the satellite network itself, encodes the data and forwards them cooperatively in multiple paths in the network, improves network efficiency, reduces the cost of data transmission, and thus provides a feasible routing method for satellite network communication. This algorithm applies network coding technology to the routing algorithm of the satellite network. The network coding technology can improve the throughput and reliability of the network; the routing algorithm in the present invention solves the mutual cooperation of nodes in the process of satellite network data transmission by introducing network coding It makes full use of the spatial relationship of the satellite network and forwards data packets through the cooperation of multiple satellite nodes; at the same time, this routing algorithm improves the throughput of the network by introducing the routing request time limit label TTL and ACK confirmation mechanism It can establish multiple effective routing paths in the double-layer satellite network, adapt to the network environment of time-varying topology, and optimize the routing performance of the double-layer satellite network
本发明的保护内容不局限于以上实施例。在不背离发明构思的精神和范围下，本领域技术人员能够想到的变化和优点都被包括在本发明中，并且以所附的权利要求书为保护范围。The protection content of the present invention is not limited to the above embodiments. Without departing from the spirit and scope of the inventive concept, changes and advantages conceivable by those skilled in the art are all included in the present invention, and the appended claims are the protection scope.
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