[0037] The present invention will be described in detail below with reference to the specific embodiments. The following examples will help to further understand the present invention in any form of technicrat, it will be further understood by those skilled in the art. It should be noted that several deformations and improvements can be made without departing from the concept of the present invention without departing from the present invention. These are all of the scope of protection of the present invention.
[0038] The technical solutions in the present invention will be described in more detail below in conjunction with specific embodiments.
[0039] Step S1: Establish the MEO / LEO dual-layer satellite network system model, based on the initial load balancing preset according to the global business flow model; establish a MEO / LEO double satellite network topology, such as figure 1As shown, it is known from the cover belt parameter and topology of the satellite constellation, and the low orbit LEO satellite covers 40-70 satellites throughout the earth. Therefore, in the present invention, the global region is divided into 60 business districts, such as figure 2 As shown in 30 ° latitude, 36 ° longitude as a region z xy. Z xy , X ∈ [1, 10] and y∈ [1, 6]. Combining the geographical location, development degree, population density, infrastructure and other factors, set the business flow density level for each region. xy. Calculate each zone z xy Total daily traffic flow xy as follows.
[0040]
[0041] Among them, n = 6, m = 10, f total For the total number of daily traffic, α is used to represent business daily volatility, randomly value in the range [-0.2, 0.2], indicating fluctuation of regional satellite network traffic flow.
[0042] According to the flow distribution of various regions, the initial load balance preset is performed, and the flow distribution is performed according to the flow distribution of the flow data within a certain period of time. By dividing the different business priority, setting a cost due to δ allows the low-priority to give the low-load satellite link, reducing the load condition of high load satellite. The specific rules are:
[0043] Cost factor δ Level1 Level2 Level3 Level4 Level5 High priority business p p p p p Low priority business P + C P + 2C P + 3C P + 4C P + 5C
[0044] 1. High priority business has no additional consideration through any satellite;
[0045] 2. The low priority service is calculated by the cost of consumer factor by the cost of high-load satellite.
[0046] Satellite load is divided into (1, ..., 5) five grades through the global business flow model, and the business is divided into two, high priority services and low priority services. Its cost factor is set as above. image 3 It is a simple example of load balancing preset, and the next hop route selection of the satellite node SL1 has two SL2 and the SL3 of the service density level of 5, respectively, and the delay cost of the two is T. And 1.5T, both the two will select high-load SL2 as the next hop target, and the low priority service will prior to low load SL3 through the cost of the cost factor. This mechanism is the weighted setting of the final routing table, which has no effect on the routing calculation process.
[0047] Step S2: According to the coverage of the LEO layer satellite according to the MEO layer satellite, the LEO layer satellite is divided into multiple control fields. Each control domain selects a manager's MEO satellite; MEO satellite relative to Leo satellite, less, overwritten The range is larger. In some embodiments, depending on the shortest path routing strategy, each LEO is linked to the MEO satellite from yourself, and the present invention is based on this basis. The LeO satellite is divided into multiple control fields, and the LEO satellite links in each control domain are connected to the same MEO satellite, called managers from this Leo satellite control domain. The manager is responsible for the routing table generation, calculation, forwarding, and link information of the link information within the control domain.
[0048] Due to the dynamicity of the satellite network, the difference between the MEO satellite and the LeO satellite orbital speed, the LEO satellite covered by the Manage MEO satellite changes over time, and therefore the present invention performs control domain division at the start time of each topological snapshot cycle. It is particularly noted that the polar orbit constellation is inverse, i.e., when the satellite track is opposite to the direction of movement of the pole, there is a case where two adjacent track motion reverse opposite. Since the relative movement of the LEO satellite is high, after using a polar orbit constellation, the two satellites are poorly stabilized, so when the control field is divided, avoiding the satellite on both sides of the reverse sewing in the same Inside the domain.
[0049] In theory, in a static topology snapshot, N X × N Y MEO satellite and N x × N y Leo satellite can divide N X × N Y Domain, the number of LEO satellites in each control domain is However, in fact, the number of LEO satellites included in the coverage of the MEO satellite is usually greater than Thus in other embodiments, the candidate MEO satellite selected from the shortest path routing policy is different. In the hierarchical architecture, the control domain division according to the coverage field of the MEO is divided according to the load of the MEO satellite, the Leo transmission price The parameters selection managers MEO satellites, reduce the number of control domains, liberate a certain number of MEO satellites, and increase resource utilization. Suppose the number of LEO satellites covered by a single MEO satellite is n L The minimum number of control domains required to cover the LEO layer can be obtained (the number of seniors of the person in charge) is Then you can get the number of LEO satellites in a single control domain. The range of control domains is Here, the size and quantity of the control field is determined according to the number of LEO satellites in the control domain. Take the number of LEO satellites in a single control area N CZ for:
[0050]
[0051] Where m, n is a variable parameter, determined by a specific simulation environment. At the same time, there is a control domain
[0052] Suppose the number of MEO satellites in the MEO satellite coverage area at a single Leo is N M. According to the symmetry visible between the LEO satellite and the MEO satellite, it is:
[0053]
[0054] From this, the number of MEO satellites contained in one LeO satellite control domain is in the range of [1, N " M ], Remove the managers MEO satellites, and compare redundant MEO satellites as a relay forwarding satellite, used as data forwarding or load balancing. It is worth noting that the administrator MEO satellites in the domain can also be considered a relay forwarding satellite. After each Leo satellite domain selects a manager's MEO satellite, unless the domain administrator MEO satellite is compiled into a relay forwarding satellite, sorted according to the transfer price, the Leo satellite is in the transmission link state to the manager MeO When the satellite will communicate with the ILLs between the relay forwarding satellite, the load is uploaded as part of the report. Managers MEO satellites are considering the link conditions of the relay forwarding satellites in the report when performing routing tables.
[0055] Step S3: Establish a network time delay model, manager MEO satellite computational routing table and distribute to the LEO layer, perform a cross-layer routing algorithm; when the routing decision makes it, it is often considered the cost of each route to pay, in different Under optimization goals, the weight between different costs is different. The network delay is an extremely important optimization target, which simultaneously reflects the factors such as network capacity, satellite physical distance, and traffic density in the network. In the network topology of this article, modeling network delay, mainly considering data propagation delays, data transmission delay, queuing delay.
[0056] The relative distance is obtained by the coordinates of the two satellites, and the propagation delay is obtained. which is
[0057]
[0058] Among them, (x s Y s ,z s ) And (x d Y d ,z d ) The coordinates of the source satellite and target satellite respectively, and C represents the light speed constant.
[0059] Regarding the queuing time, it is assumed that the data packet processing capability of the node is μ, the packet reaches the Poisson distribution of λ from the parameters. When the processing capacity of the node is sufficient, the theory of steady-state delay parameters can be obtained:
[0060]
[0061] Where C is satellite link capacity, packet size Indicates the size of the packet.
[0062] Transmission time delay is related to the link bandwidth, expressed as In the satellite network, because of the satellite, the distance between the satellite and the ground station is far, and the satellite capacity is large, so transmission time delay relative to propagation D trans Delay can be ignored with satellite treatment. Therefore, the delay cost function for transmitting data to another satellite can be expressed as:
[0063] Di total = D s2d + D que + D trans ≈D s2d + D que
[0064] The processing capability of the MEO satellite is higher than the LEO satellite, and the distance between the MEO satellite and the LEO satellite is longer than the distance between the same space, so this article is made for the IOLS link between the Leo satellite and the MEO satellite. Simplified processing, assuming that the bandwidth of the IOLS link is unlimited, and the forwarding process delay and transmission of the MEO satellite are negligible for transmission. This allows the delay cost function D of the Leo to the MEO satellite. M for:
[0065] Di M ≈D s2d
[0066] For the person in charge of the MEO satellite, it is necessary to calculate the LEO routing table in the control domain, so it is necessary to quantify the time delay D of the LEO routing table. calculate , The number of LEO satellites in a single control domain is known to N CZ The satellite node processing capacity is μ, and the packet of a single satellite node to the Poisson distribution of the parameter is λ. From this to the calculation time D calculate The expression is:
[0067]
[0068] Next, the specific content and processes of routing calculations are introduced, first introduces three data structures used by cross-layer routing algorithms:
[0069] LEO routing table. The next hop includes the ground station, can reaches the LEO satellite, can reach the MEO satellite. The LEO layer satellite status is collected by the manager MEO satellite to generate the Leo routing table.
[0070] MEO routing table. The MEO routing table is calculated by the MEO satellite, and the MEO satellite exchanges the route state through the flood mechanism, and the global routing table of the MEO layer is propagated throughout the MEO layer, generating the MEO layer routing table.
[0071] Leo / MEO Collaborative Table. Each LeO satellite maintains an Leo / Meo collaborative table, records the management of the management domain in which you are in the control domain, and forward redundant relay forwarding the MEO satellite, sort by transmission costs and MeO load (cost function).
[0072] After introducing the main data structures in the three routing algorithms, the specific implementation process of the routing algorithm is described below, with reference to the flow Figure 4.
[0073] 1.leo satellite control domain division: dynamic satellite networks are divided into multiple static topology snapshots Tk In every T k At the beginning of the stage, the Leo satellite is divided into a plurality of Leo satellite control fields according to their own candidate MEO satellites, and the MEO satellite coverage. Each satellite selects a manager MEO satellite, and records the Leo / Meo collaboration in itself. surface.
[0074] 2. At the same time at each T k At the beginning of the stage, all LEO satellites and MEO satellites calculate their own link status based on the consumer function, and generate link status reports based on the consumer function, and generate link status reports based on the link state of contiguous satellite links in their layers. After the MEO satellite itself calculates the initial routing table, the MEO routing table is formed by flooding in the MEO layer. LEO satellites send their own link status report to managers after selecting managers MEO satellites.
[0075] 3. Manager MEO Satellite Set the timer T. After the end, the default all link status report is received. Manager MEO Satellite exchanges link status reports in each domain in the MEO layer, calculates the LEO routing table, and issues to the LEO satellites within their respective controls, and inform all managers MEO satellites in the timer cycle.
[0076] 4. LEO Satellite Plexine with its own JOS satellite table based on the received manager MEO number, and sequencing records in accordance with the price size, re-forwarding the MEO satellite, updating the Leo / Meo Collaborative Table.
[0077] Step S4: Figure 5 As shown, the satellite continues to perform a load balancing operation based on the load balancing model in accordance with the load of the T cycle as the cycle. Suppose the current satellite buffer queue length is Q cur The total length of the queue is Q 0 So you can get the queue overflow time, that is, the packet loss time D is:
[0078]
[0079] As can be seen from the above formula, the greater D, the more serious the satellite load. To this turn, the load level is set to perform different split operations.
[0080] LL (Light Load): D> T. Indicates that the satellite has no load pressure in this cycle T, without performing load balancing operation, all packets are sent in the original path.
[0081] ML (MODERATE LOAD): Indicates that the satellite has a certain load pressure, and the load balancing operation is started, and the data traffic transmitted in the original path is maintained, and the relay forwarding MEO satellite forwarding load is enabled. At the same time, the routing table is updated and the forwarding cost is increased.
[0082] HL (Heavy Load): Indicates that the satellite load pressure is extremely large, performs more permissions load balancing operations to reduce the forwarding rate of the current buffer queue length in the original path to send traffic, and the remaining flow is forwarded by relay forwarding MEO satellite forwarding. At the same time, the routing table is updated and the forwarding cost is increased.
[0083] During the entire satellite network transmission, the satellite continues to perform the load of the cycle detection node in the T cycle, and the load balancing is achieved according to the load balance forwarding model in the previous section. The core idea of its algorithm is as follows:
[0084] 1. When the load level is LL, D> T indicates that there is no overload in this period, indicating that the LEO satellite has no load pressure, so the node load traffic is forwarded by the source path, and the Leo routing table does not need to be modified.
[0085] 2. When the load level is ml, Indicates that if the load balancing operation is not performed, an overload occurs during the second half of this cycle, indicating that the Leo satellite has a load pressure and requires load balancing operation. Leo satellite queries its own storage MEO / LEO collaborative table, selecting the minimum relay forwarding MEO satellite in the table, remembering the application trans , Part of the data package by M trans Forward, the size is Where is Q in -Q out Represents traffic in the queue, and It is proportional to the link load to adjust the amount of forwarding the data package. If the MEO / LEO collaborative table does not have a relay forwarding MEO satellite, update the LeO routing table of the Leo satellite and neighboring nodes, calculate the new routing path, forward the overload packet.
[0086] 3. When the load level is HL, Indicates that if the load balancing operation is not performed, overloading occurs in the first half of this cycle, indicating that the LEO satellite load pressure is large, and the current buffer queue is required. The same 2 is the same, just forwarding the packet for q in. And when the MEO / LEO collaborative table does not have a relay transfer of the MEO satellite, enable the administrator MEO satellite M manager Perform a packet forward and reclaim the calculation of the MEO / LEO collaborative table.
[0087] 4. For the MEO satellite bandwidth, do not consider overload problems, when the packet is received, the forwarding according to the MEO routing table, including two choices, if the target is in the control domain of its own management, the LEO within the control domain is directly issued. Satellite; if the target is not within the control domain of its own management, it is forwarded to the corresponding MEO satellite.
[0088] 5. LEO Satellite Periodically Update its own MEO / LEO collaborative table, renovate the MEO satellite in the table.
[0089] Embodiments of the present invention also include a communication system based on a MeO / Leo dual-layer satellite network comprising a MEO satellite and a LEO satellite, and is routed with a cross-layer routing method based on the above-described MEO / LEO dual satellite network.
[0090] The specific embodiments of the present invention will be described above. It is to be understood that the invention is not limited to the specific embodiments described above, and those skilled in the art can make various changes or modifications within the scope of the claims, which does not affect the substantial content of the present invention. In the case of an unable conflict, the features of the present application and the features in the embodiments may be combined with each other.
