CN101299713A - Method for setting multilayer satellite network system route - Google Patents

Abstract

The present invention relates to a method for setting multilayer satellite network system route, including steps of: 1. setting parameters for the network initialization; 2. fixing a time, solving satellite orbit parameters in the interval of time, calculating the location coordinates of the satellite and the length of the link between stars, and establishing a network topological structure; 3. calculating the load of link between stars of the multi-layer satellite network; 4. calculating the process and exchange time delay on stars according to the queuing theory; 5. searching source satellite and object satellite of each satellite layer; 6. selecting the satellite layer for transporting services according to the communication service instruction requirement and network states, and searching an optimum route according to routing algorithm. Relative to traditional stationary orbit satellite, the present invention has small transmission delay, and high validity. The system has advantages of more flexible routing, effective guaranty of service quality, multiple replaceable chain circuits, stronger survivability, a capacity of processing and exchanging on star, optical or microwave links between stars, and capability of providing wideband synthetic service for users in global scope.

Description

A kind of method for setting multilayer satellite network system route

Technical field

The invention belongs to the deep space communication field, be specifically related to a kind of method for setting multilayer satellite network system route.

Background technology

Single satellite is often adopted in early stage satellite communication, and this satellite orbital altitude is about 35786 kms, and orbit inclination angle 0 degree is positioned on the overhead certain longitude station in equator, and ground is static relatively.Satellite track height, coverage are big, but because the communication distance between star-ground is big, link is easily impaired, does not support small-power users such as ground hand-held set.Because the satellite orbit inclination angle is 0 degree, can not cover the arctic regions simultaneously, the high latitude area communication elevation angle is little, communication quality is difficult to guarantee.The appearance of satellite inter-satellite link technology makes satellite constitute network, can communicate between star.Satellite Network Design method is comparatively simple, as long as determine can be made of several satellites the longitude station at network, satellite place, other parameters all are to determine relatively.

Middle rail satellite is on the track between two Van Allen belts, and constellation generally is made of tens satellites, and single visual time reaches 1～2 hour.As trading off of satellite and low orbit satellite, middle rail satellite double jump propagation delay time is greater than low orbit satellite, but as a network, consider factor such as processing and uplink downlink on whole inter-satellite link length, the star, middle track satellite network delay performance may be better than low-track satellite network.Simultaneously, with respect to low orbit satellite, middle rail satellite switching probability is low, Doppler effect is less, and control system and antenna generally can obtain 20～30 degree communication elevations angle with taking aim at system simplification.

Low orbit satellite is distributed on the circle or elliptic orbit of 500～2000 kms, increases a satellite communication network and generally is made up of tens satellites.Single visible time of satellite is short, needs wave beam to switch and the satellite switching.The low orbit satellite advantage is a lot, because track is low, and the inter-satellite link superior performance, propagation delay time is little, and the moonlet The Application of Technology makes that the satellite volume is less simultaneously, is convenient to emission.But the networking cycle that low orbit satellite is formed is long, spatial control system relative complex, and system's investment is huge.Simultaneously, numerous gateway station needs to follow fast the system that takes aim at, and needs to consider Doppler effect.Satellite orbit is low, and the communication elevation angle is that because the quick variation at the elevation angle, signal transmission path is variant about 10 degree.

Consider the track of pole orbit or proximal pole track such as π type constellation, have " slit " at the interorbital of move toward one another, at both sides, slit satellite because move toward one another can't be set up the interorbital link; The interorbital link will be closed in the sky, polar region simultaneously, because in the sky, polar region, the adjacent satellite track intersects, and interstellar distance changes rapidly, can't set up inter-satellite link.

In addition, in research process, find, particularly low rail (LEO:Low EarthOrbit) of individual layer satellite network and middle rail (MEO:Medium Earth Orbit) satellite network, two satellite spatial distances are very near, but because there is not inter-satellite link (ISL:Inter-Satellite Link) directly to connect, making can not direct communication, must just can finish communication by the satellite path that some ISL set up, so not only can not satisfy communication service instruction (QoS:Quality of Service), and wasted resource on a large amount of systems and the star, even cause link obstructions.

In order effectively to solve the problems of the technologies described above many research institutions in the test of carrying out satellite interlayer link, LEO satellite SPOT IV passes through the rate communication of the inter-satellite link of 0.8 μ m with 50Mbps with GEO satellite Artemis in the SILEX test of Europe, follow-up experiment is finished by communication experiment between the star that carries out of OICETS satellite of Artemis and Japan, the ISL of two experiments is LEO to GEO satellite optical link, and the U.S. has also carried out similar ISL test.Other the plan as Motorola with Celestri low orbit satellite system with the combination of GEO satellite, constitute the mixed satellite network, 13 LEO satellites and 6 MEO satellites have been formed the Rostelesat constellation jointly, and GESN, GNSS/Galileo and West system are by different MEO/GEO satellite formation of number etc.

Multilayer satellite network (MLSN:Multi layer satellite networks) becomes the focus of research in the later stage nineties in last century.Kimura proposes a kind of bilayer (LEO and MEO) satellite constellation, has compared the difference of pole orbit and inclined plane constellation, by the method at the many coverings and the increase elevation angle, guarantee the reliability requirement of communication, but number of satellite is huge.

Summary of the invention

For solve the satellite network system that exists in the prior art huge, cause the wasting of resources on a large amount of systems and the star, prolong, cause easily technical problems such as link obstructions in the time of in the transmission course, the invention provides a kind of method for setting multilayer satellite network system route.

The present invention solves scheme that the prior art problem adopted for a kind of method for setting multilayer satellite network system route is provided, and described route establishing method comprises step: the first step, setup parameter, carry out netinit; Second goes on foot, fixes a moment t _k, at this time interval Δ t, find the solution the satellite orbit parameter, calculate satellite position coordinate and inter-satellite link length, set up network topology structure; The 3rd step, according to the business model of setting, the inter-satellite link load of calculating described multilayer satellite network.The 4th goes on foot, calculates according to queuing theory the time delay of handling and exchanging on the star; The 5th the step, according to the ground-level source target location, seek source satellite and target satellite in each satellite layer; The 6th step, select the satellite layer of transport service,, seek optimal path according to routing algorithm according to communication service instruction demand and network state.

According to a preferred embodiment of the invention: the parameter of setting in the described first step comprises: number of satellite, inter-satellite link bar number, each satellite orbit type, orbit altitude, orbit inclination angle and number of tracks in the multilayer satellite network number of plies, each layer.

According to a preferred embodiment of the invention: described the 3rd step further comprises substep: one, under the non-uniform Distribution model, consider the difference that land and ocean, desert peace original subscriber distribute, the density of population is divided into 5 grades, with the density of population in each zone of numeral; Two, earth surface is divided into 48 and part, adopts to be parallel to parallel, favour the division methods of warp, 8 oblique lines are 52 with parallel and spend.Longitude 360 degree are divided into 8 parts, and latitude is divided into 6 parts; Establish a ground station in each zone, ground station is positioned at north and south latitude 15 degree, 45 degree and 68 degree, and number is 48; Adopt the maximum access scheme in the elevation angle to insert; Three, under statistical distribution pattern, consider the difference of user's distribution density, the source and target position and the density variation of calling, draw the channel occupancy situation of every inter-satellite link in the network.

According to a preferred embodiment of the invention: described the 4th step further comprises substep: one, according to queuing theory, every inter-satellite link can be regarded as the mixed queuing model M/M/l/m of single service window, every inter-satellite link only contains single service window, obey negative exponent the blanking time that " client " arrives and distribute, parameter is β; Be that parameter is that μ is that negative exponent distributes service time; Every inter-satellite link has m queueing capacity.When having m packet in the system, new packet no longer enters queuing, has: ρ=β/μ; Two, the average waiting time delay of packet is $W=\frac{1}{\mathrm{\μ}\·(1-\mathrm{\ρ})}-\frac{m\·{\mathrm{\ρ}}^m}{\mathrm{\μ}\·(1-{\mathrm{\ρ}}^m)}.$

According to a preferred embodiment of the invention: the routing algorithm in described the 6th step is the FBellman-Ford routing algorithm.

According to a preferred embodiment of the invention: described the 6th step specifically comprises substep: 61 steps, default business are low rail layer at described multilayer satellite network system, if middle rail source satellite, target satellite are identical, and low rail source satellite, target satellite difference, six or four steps of execution in step; If stationary orbit source satellite, target satellite are identical, and low rail and middle rail source satellite, target satellite are different, six or five steps of execution in step; Otherwise, six or two steps of execution in step; Six or two steps: be less than or equal to the low rail thresholding of inter-satellite link, six or three steps of execution in step if should low rail layer path comprise inter-satellite link quantity; If described low rail layer path comprises inter-satellite link quantity greater than the low rail thresholding of inter-satellite link, and middle rail layer path comprises inter-satellite link quantity and is less than or equal to rail thresholding in the inter-satellite link, six or four steps of execution in step; Otherwise, six or five steps of execution in step; Six or three steps: set up low orbit satellite layer optimal communication path, finish transformation task; Six or four steps: rail satellite layer optimal communication path in the foundation, finish transformation task; Six or five steps: set up satellite layer optimal communication path, finish transformation task; Six or six steps: add up the characteristic parameter of multitiered network in the described multilayer satellite network system, the phase-split network performance; Six or seven steps: update time the interval, finish new routing table and calculate and finish the satellite handover.

According to a preferred embodiment of the invention: the bellman-ford routing algorithm that described three steps of step 6, six or four steps and six or five steps are applied to, this algorithm comprises substep: step 1: the T index value that makes all non-beginning nodes in the network is ∞, i.e. T (i)=∞; The order beginning P label of node is 0, i.e. P (s)=0; Step 2: with new described P label is the beginning node i, checks with i to be whether each terminal point j on limit of beginning node exists [P (i)+d (i, j)]＜P (j) or [P (i)+d (i, j)]＜T (j), if exist, and execution in step 3, otherwise keep former label; Step 3: with the T label at j point place or P label change into new T label T (j)=P (i)+d (i, j) or T (i)+d (i, j).Get the minimum value of existing T label point in the network, be decided to be new P label point, repeated execution of steps 2; Step 4: when all nodes of network all were the P label point, algorithm finished.

According to a preferred embodiment of the invention: the described characteristic parameter that needs in described six or six steps to add up comprises: the memory usage percentage of each satellite node, inter-satellite link length and blocking probability.

Beneficial effect of the present invention is: with respect to traditional stationary orbit (GEO:GeostationaryEarth Orbit) satellite, constituted the network of global covering by low rail (LEO:Low Earth Orbit) and middle rail (MEO:MediumEarth Orbit) satellite, transmission delay is little, the validity height.Satellite has on the star to be handled and exchange capacity, has microwave or optical link between star, and the integrated service in broadband can be provided for the user in the global range, effectively guaranteed service quality, and Path selection is more flexible, and replaceable link is many, and survivability can be stronger.

Description of drawings

Fig. 1. the covering crack structure schematic diagram of pole orbit or proximal pole track constellation;

Fig. 2. overhead pole orbit in polar region or proximal pole track constellation adjacent orbit cross reference schematic diagram;

Fig. 3 .Walker delta constellation medium and low earth orbit satellites 11 is to the shortest path schematic diagram between the low orbit satellite 54;

Fig. 4. the orbit parameter schematic diagram in the constellation;

Fig. 5. multilayer satellite network system structural representation in a kind of multilayer satellite network system of the present invention and the route establishing method thereof;

Fig. 6. multilayer satellite network system space structure schematic diagram of the present invention;

Fig. 7. satellite inter-satellite link computational mathematics model schematic diagram;

Fig. 8. average delay and inter-satellite link number concerns schematic diagram in the multilayer satellite network;

Fig. 9. multilayer satellite network normalization link load changes schematic diagram with the inter-satellite link channel capacity;

Figure 10. multilayer satellite network normalization link load changes schematic diagram with Internet traffic;

Figure 11. multilayer satellite network normalization link load changes schematic diagram in time;

Figure 12. packet loss changes schematic diagram with the packet average length;

Figure 13. the comprehensive link weight of multilayer satellite network changes schematic diagram in time;

Figure 14. multilayer satellite network user distribution density map;

Figure 15. route establishing method flow chart in a kind of multilayer satellite network system of the present invention and the route establishing method thereof.

Embodiment:

Below in conjunction with accompanying drawing and concrete execution mode the present invention is done explanation in further detail:

A key of satellite network is the special satellite network routing algorithm of development, to adapt to the dynamic characteristic of satellite network.Along with the develop rapidly of internet, need a kind of seamless routing policy in the satellite network, the same with ground network, the IP switch is arranged on the satellite, can independently transport the IP bag, switch links to each other by ISL on the star.Packet switch routing policy based on the non-geo satellite system is widely studied, but because satellite is with terrestrial user relative motion constantly, the continuous variation of ISL length, terrestrial user distributes non-homogeneous, reasons such as the last volume variance of ISL is very big, no matter collateral security QoS of customer angle is still optimized the Internet resources angle from system maintenance person, set up effective multilayer satellite network system and it is carried out route set and for the ISL backbone network, be absolutely necessary.

Low rail, middle rail and satellite are to divide according to orbit altitude, and characteristics are separately arranged.For a long time, the pluses and minuses of the satellite network that makes up respectively with various satellites also obtain comparison and balance, are used for supporting different quality of service requirements.By the satellite communication network operation around the earth that low orbit satellite and middle rail satellite make up respectively, the foundation of inter-satellite link makes the communication between the satellite become a reality, and has constituted network truly, such as Iridium and Milstar-2 satellite network.Time-delay index by the higher satellite network service of the individual layer satellite network, particularly orbit altitude of various satellites structures is too high, and the multilayer satellite network helps solving the contradiction between switching probability and the time delay; In the individual layer satellite network, for realizing the seamless covering in the whole world, usually use the constellation of pole orbit and proximal pole classification of track, this can cause the phenomenon with the increase of switching probability, blocking probability of closing of inter-satellite link, each interlayer complementation in the multilayer satellite network, can on the basis of inclined plane, realize global seamless covering, avoid the problems referred to above; Individual layer satellite network survivability is relatively poor, the individual layer satellite network is difficult for finding and satisfies the alternative route that original singal reporting code requires under the situation of satellite or inter-satellite link damage, and the backup link that can substitute in the multilayer satellite network has a lot, can not cause the decline significantly of communication quality; And individual layer satellite network particularly spaceborne the following of network of low orbit satellite formation is taken aim at the system design difficulty, because the pole orbit that low-track satellite network often adopts.In multilayer satellite network, relaying by middle rail and satellite, satellite network does not need to keep reverse interorbital inter-satellite link in the low orbit constellation again, even can adopt inclined plane to realize low-track satellite network, has reduced spaceborne with the requirement of taking aim at system.

Provided by the inventionly provide a kind of method for setting multilayer satellite network system route, described route establishing method comprises step: the first step, setup parameter, carry out netinit; Second goes on foot, fixes a moment t _k, at this time interval Δ t, find the solution the satellite orbit parameter, calculate satellite position coordinate and inter-satellite link length, set up network topology structure; The 3rd step, according to the business model of setting, the inter-satellite link load of calculating described multilayer satellite network.The 4th goes on foot, calculates according to queuing theory the time delay of handling and exchanging on the star; The 5th the step, according to the ground-level source target location, seek source satellite and target satellite in each satellite layer; The 6th step, select the satellite layer of transport service,, seek optimal path according to routing algorithm according to communication service instruction demand and network state.

Wherein, the parameter of setting in the described first step comprises: number of satellite, inter-satellite link bar number, each satellite orbit type, orbit altitude, orbit inclination angle, number of tracks in the multilayer satellite network number of plies, each layer.Described the 3rd step further comprises substep: one, under the non-uniform Distribution model, consider the difference that land and ocean, desert peace original subscriber distribute, the density of population is divided into 5 grades, with the density of population in each zone of numeral; Two, earth surface is divided into 48 and part, adopts to be parallel to parallel, favour the division methods of warp, 8 oblique lines are 52 with parallel and spend.Longitude 360 degree are divided into 8 parts, and latitude is divided into 6 parts; Establish a ground station in each zone, ground station is positioned at north and south latitude 15 degree, 45 degree and 68 degree, and number is 48; Adopt the maximum access scheme in the elevation angle to insert; Three, under statistical distribution pattern, consider the difference of user's distribution density, the source and target position and the density variation of calling, draw the channel occupancy situation of every inter-satellite link in the network.Described the 4th step further comprises substep: one, according to queuing theory, every inter-satellite link can be regarded as the mixed queuing model M/M/l/m of single service window, every inter-satellite link only contains single service window, obeys negative exponent the blanking time that " client " arrives and distributes, and parameter is β; Be that parameter is that μ is that negative exponent distributes service time; Every inter-satellite link has m queueing capacity.When having m packet in the system, new packet no longer enters queuing, and packet is dropped, and has: ρ=β/μ; Two, the average waiting time delay of packet is $W=\frac{1}{\mathrm{\μ}\·(1-\mathrm{\ρ})}-\frac{m\·{\mathrm{\ρ}}^m}{\mathrm{\μ}\·(1-{\mathrm{\ρ}}^m)}.$ Routing algorithm in described the 6th step is the FBellman-Ford routing algorithm.

According to a preferred embodiment of the invention: described the 6th step specifically comprises substep: 61 steps, default business are low rail layer at described multilayer satellite network system, if middle rail source satellite, target satellite are identical, and low rail source satellite, target satellite difference, six or four steps of execution in step; If stationary orbit source satellite, target satellite are identical, and low rail and middle rail source satellite, target satellite are different, six or five steps of execution in step; Otherwise, six or two steps of execution in step; Six or two steps: be less than or equal to the low rail thresholding of inter-satellite link, six or three steps of execution in step if should low rail layer path comprise inter-satellite link quantity; If described low rail layer path comprises inter-satellite link quantity greater than the low rail thresholding of inter-satellite link, and middle rail layer path comprises inter-satellite link quantity and is less than or equal to rail thresholding in the inter-satellite link, six or four steps of execution in step; Otherwise, six or five steps of execution in step; Six or three steps: set up low orbit satellite layer optimal communication path, finish transformation task; Six or four steps: rail satellite layer optimal communication path in the foundation, finish transformation task; Six or five steps: set up satellite layer optimal communication path, finish transformation task; Six or six steps: add up the characteristic parameter of multitiered network in the described multilayer satellite network system, the phase-split network performance; Six or seven steps: update time the interval, finish new routing table and calculate and finish the satellite handover.The bellman-ford routing algorithm that described three steps of step 6, six or four steps and six or five steps are applied to, this algorithm comprises substep: step 1: the T index value that makes all non-beginning nodes in the network is ∞, i.e. T (i)=∞; The order beginning P label of node is 0, i.e. P (s)=0; Step 2: with new described P label is the beginning node i, checks with i to be whether each terminal point j on limit of beginning node exists [P (i)+d (i, j)]＜P (j) or [P (i)+d (i, j)]＜T (j), if exist, and execution in step 3, otherwise keep former label; Step 3: with the T label at j point place or P label change into new T label T (j)=P (i)+d (i, j) or T (i)+d (i, j).Get the minimum value of existing T label point in the network, be decided to be new P label point, repeated execution of steps 2; Step 4: when all nodes of network all were the P label point, algorithm finished.The described characteristic parameter that needs in described six or six steps to add up comprises: the memory usage percentage of each satellite node, inter-satellite link length and blocking probability.

Consider the track of pole orbit or proximal pole track such as π type constellation, have " slit " at the interorbital of move toward one another, at both sides, slit satellite because move toward one another can't be set up the interorbital link; The interorbital link will be closed in the sky, polar region simultaneously, because in the sky, polar region, the adjacent satellite track intersects, interstellar distance changes rapidly, can't set up ISL, shown in the overhead pole orbit of covering crack structure schematic diagram and accompanying drawing 2 polar regions or proximal pole track constellation adjacent orbit cross reference schematic diagram of accompanying drawing 1 pole orbit or proximal pole track constellation.The communication network satellite relative position that Walker delta-2 π type inclination circular orbit constellation constitutes is fixed, and the ISL geometry is simple, stable performance.Multilayer satellite network can solve Walker delta type LEO constellation high latitude area and cover not enough problem.

In addition, in research process, find, the individual layer satellite network is LEO and MEO satellite network particularly, two satellite spatial distances are very near, but because there is not ISL directly to connect, making can not direct communication, must just can finish communication by the satellite path that some ISL set up, so not only can not satisfy communication QoS, and wasted resource on a large amount of systems and the star, even cause link obstructions, as Fig. 3 Walker delta constellation medium and low earth orbit satellites 11 in the Walker delta constellation shown in the shortest path schematic diagram between the low orbit satellite LEO satellite 11 to the shortest path between the LEO satellite.

The multilayer satellite network of hierarchy not only can address the above problem, and advantage that can comprehensive three kinds of individual layer satellites, brings into play its huge advantage at aspects such as coverage, inter-satellite link, delay requirements, satisfies the requirement of miscellaneous service.Multilayer satellite network is more effective than single layer network, and its Path selection is more flexible, and replaceable link is many, and survivability can be stronger.

Fig. 4 is an individual layer inclination circular orbit satellite constellation covering performance schematic diagram.It is that γ highly is the circular orbit of h that satellite constellation comprises l bar inclination angle, m equally distributed satellite arranged on each track, phase difference δ=2 π/m, each ascending node of orbit right ascension difference Ω=2 π/l, the relative position of adjacent orbit satellite can represent that Δ M is the initial phase with respect to reference satellite 11 with a and ω.Can calculate of the covering of single satellite with following formula to the earth:

$\mathrm{\φ}=\mathrm{\π}/2-\mathrm{\ϵ}-{\sin }^{-1}(\frac{r_E}{r_E+h}\·\cos \mathrm{\ϵ})---\left(1\right)$

ε represents the elevation angle of communicating by letter, r in the formula (1) _EThe expression earth radius, result of calculation

Half of the geocentric angle of expression overlay area correspondence.For multilayer satellite network, need to consider that the upper strata satellite covers the situation of lower floor's satellite.Can calculate according to formula (2):

${\mathrm{\φ}}_i=\mathrm{\π}/2-{\mathrm{\ϵ}}_i-{\sin }^{-1}(\frac{r_i}{r_i+h_i}\·\cos {\mathrm{\ϵ}}_i)$ i＝1，2，3... (2)

The situation of i=2 in the expression (2) in the multilayer satellite network system structural representation in a kind of multilayer satellite network system of Fig. 5 the present invention and the route establishing method thereof: ε wherein ₂=θ, r ₂=r _Lr _L, r _MExpression LEO and MEO satellite orbit radius, h ₁Expression LEO satellite altitude, h ₂Represent the poor of MEO and LEO satellite orbital altitude, s ¹ _L, s ² _L, s ⁿ _LAnd s ¹ _M, s ^N _MThe expression satellite, d ₁, d ₂, d ₃The expression interstellar distance, θ represents the minimum angle of elevation that LEO communicates by letter with MEO, and top shadow representation MEO satellite promptly can be set up the scope of ISL to the coverage of LEO satellite layer among the figure, and following shadow representation LEO satellite is to ground coverage.Calculate interstellar distance and only co-ordinates of satellite need be brought into (3) formula:

$d=\sqrt{{(x_1-x_2)}^2+{({\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="A20081006614000212.png,A20081006614000241.png"\; state="\{\{state\}\}">y</figure-callout>}}_1+y_2)}^2+{({\mathrm{<figure-callout\; id="1"\; label="z"\; filenames="A20081006614000212.png,A20081006614000241.png"\; state="\{\{state\}\}">z</figure-callout>}}_1+z_2)}^2}---\left(3\right)$

Wherein the coordinate of satellite in earth fixed coordinate system (x, y z) can calculate by through type (4):

$\left\{\begin{array}{c}x=(r_E+h)\&CenterDot;[\cos \mathrm{\&xi;}\&CenterDot;\cos \mathrm{\&rho;}-\sin \mathrm{\&xi;}\&CenterDot;\sin \mathrm{\&rho;}\&CenterDot;\cos \mathrm{\&gamma;}]\\ y=(r_E+h)\&CenterDot;[\cos \mathrm{\&xi;}\&CenterDot;\sin \mathrm{\&rho;}+\sin \mathrm{\&xi;}\&CenterDot;\cos \mathrm{\&rho;}\&CenterDot;\cos \mathrm{\&gamma;}]\\ z=(r_E+h)\&CenterDot;\sin \mathrm{\&xi;}\&CenterDot;\sin \mathrm{\&gamma;}\end{array}\right.---\left(4\right)$

In the formula (4)

ξ＝ω ₀+v ₀+v·(t-t ₀) (5)

ρ＝ζ-v _E·(t-t ₀) (6)

ω ₀Be argument of perigee, v ₀Be the initial true anomaly of satellite, v is a satellite motion angular speed, wherein $v=\sqrt{\mathrm{\&mu;}/{\mathrm{<figure-callout\; id="3"\; label="r"\; filenames="A20081006614000212.png,A20081006614000242.png"\; state="\{\{state\}\}">r</figure-callout>}}^3},$ μ is the terrestrial gravitation constant, and r is the satellite orbit radius, t-t ₀Be satellite transit time, t ₀Be initial time, ξ is a true anomaly, and ζ is a right ascension of ascending node, v _EBe rotational-angular velocity of the earth.

Table 1:

The satellite layer	GEO	MEO	LEO
				Number of satellite ()	3	12	48
Orbit altitude (km)	35786	10355	1400
				Orbit inclination angle (degree)	0.0	55.0	52.0
Orbital period	24 hours	6 hours	114 minutes
				Number of tracks	1	3	8
Constellation types	Geo-stationary orbit	Walker delta constellation	Walker delta constellation
				The interlayer link (bar /)	GEO-＞MEO 4	MEO-＞GEO 1 MEO-＞LEO 4	LEO-＞MEO 1
A same layer link (bar /)	2	In 2 tracks+2 interorbitals	In 2 tracks+2 interorbitals
				The interlayer Link State	Impermanency	Impermanency	Impermanency
With layer Link State	Permanent	Permanent	Permanent
				The communication elevation angle (degree)	20	22	10
Coverage	± 61.8 ° of scopes	The whole world covers	± 68.1 ° of scopes

The GEO satellite can be selected as required, as cover Chinese surrounding area (67.5 ° to 172.5 ° of east longitudes, 54 ° of scopes of north and south latitude comprise areas such as the Central Asia, East Asia and Oceania) if adopt one to be used for the zone covering, and satellite is positioned at 120.0 ° of sky of east longitude.If covering the whole world, three GEO satellites in the multilayer satellite network that proposes such as this paper are positioned at 0.0 ° of east longitude, 120.0 ° and 240.0 °.Table 1 provides the multilayer satellite network structural parameters, and MLSN space structure figure is shown in Fig. 6 satellite inter-satellite link computational mathematics model schematic diagram.

Every MEO satellite has 4 permanent ISLs in the MEO layer, the ISLs geometric parameters are fixed in two tracks, becomes during the permanent ISLs geometric parameter of two interorbitals.The ISL situation of other MEO satellite is similar with MEO satellite 11, and initial phase is variant.Contain 24 ISLs in the MEO satellite layer altogether.Same every LEO satellite has 4 permanent ISLs in layer, in two tracks with two interorbital.Contain 96 ISLs in the LEO satellite layer altogether.

For the interlayer link, though visible simultaneously many MEO of every LEO satellite and GEO satellite, for simplified structure with consider the practical communication demand, every LEO satellite selects a MEO satellite, every also only same GEO satellite of MEO satellite to set up a link.ISLs geometric parameter checkout result such as table 2 between the LEO/MEO satellite orbit are example with satellite 11.

Satellite ISL computational mathematics model is shown in Fig. 7 satellite inter-satellite link computational mathematics model schematic diagram, and the relation of average delay and ISL the concerning shown in the schematic diagram of average delay and inter-satellite link number in Fig. 8 multilayer satellite network in the multilayer satellite network.ISL quantity is almost linear on average delay and the path, as can be seen, the GEO satellite is not suitable for the transporting speech business, because voice service requires time delay less than 200ms, if and MEO network transporting speech business, the maximum ISL in delay requirement path, certainly, if the path comprises 6 above ISL average delays also greater than 200ms in the LEO network.For the 400ms propagation delay time of CCITT suggestion, LEO and MEO network can both satisfy.

Table 2

Route calculate to adopt behind the Bellman-Ford to algorithm, declaring of optimal path then is the comprehensive weight in this path (TPW:Total path weight), TPW has represented the time delay and the bandwidth occupancy combination property of a paths, consideration also be effective and reliable combination property.TPW is made up of three parts, the up link time delay D _u, downlink delay D _dWith each ISLw on the path _iThe link weight The set W={w of ISL on the expression path ₁, w ₂... w _i... w _Ns-1, | W|=n _s-1 this paths of expression comprises n _sArticle-1, ISL, n _sBe the number of satellite on this path (comprising source satellite and target satellite).After wherein ground-level source and target location are determined, adopt selected source satellite of the maximum access scheme in the elevation angle and target satellite, so that constitute an end-to-end link.

$\mathrm{TPW}=\underset{w_i\&Element;W}{\mathrm{\&Sigma;}}{\mathrm{LW}}_{w_i}+D_u+D_d---\left(7\right)$

Wherein

${\mathrm{LW}}_{w_i}=D_{w_i}+f\&CenterDot;W_{w_i}---\left(8\right)$

Expression

Propagation delay time,

Expression average waiting time delay, f is the amount of information weight parameter.D _u, D _dWith

only find the solution and need know the satellite spatial position coordinates, get final product divided by transmission speed with linkage length, need not superfluous stating.

According to the Jackson principle, every ISL can be regarded as the mixed queuing model M/M/l/m of single service window, to obey negative exponent the blanking time that packet arrives and distribute, parameter is β; Be that parameter is that μ is that negative exponent distributes service time; Every ISL has m queueing capacity.When having m packet in the system, new packet will be transferred to other satellite to be handled.

Have

ρ=β/μ (9)

The average waiting time delay of packet is

$W=\frac{1}{\mathrm{\&mu;}\&CenterDot;(1-\mathrm{\&rho;})}-\frac{m\&CenterDot;{\mathrm{\&rho;}}^m}{\mathrm{\&mu;}\&CenterDot;(1-{\mathrm{\&rho;}}^m)}---\left(10\right)$

Multilayer satellite network self adaptation IP routing policy has following feature: professional by LEO source satellite and target satellite access satellite system, select this professional satellite layer of transmission according to QoS needs and network state, if LEO layer network resource can not satisfy this business need, just this business is forwarded to the transmission of MEO layer, even the transmission of GEO layer.Directly insert MEO or GEO satellite situation for ground-level source/target, simple because routing algorithm is realized, so do not make labor.Concerning shown in schematic diagram and the simulation result according to average delay in Fig. 8 multilayer satellite network and inter-satellite link number in addition, if the path of LEO layer comprises 6 or 7 ISLs, time delay will be greater than 200ms, if at this moment this business is transferred to MEO, transmission time is shorter, takies on the star resource still less.And if ground-level source and target location are covered by same MEO or GEO satellite, this is just this business to be forwarded to MEO and GEO transmission, with taking of resource on the minimizing star.This strategy is considered time delay index and ISL bandwidth occupancy situation, and optimal route selection is taken into account satellite system validity and reliability.Other parameter parameter settings such as the following table 3 that in the algorithm computation process, need.Calling percentage such as table 4 between call source one target area.

Table 3

Parameter

Numerical value

ISL channel capacity (Kbps)	400～10,000
		Network total traffic capacity (packets/s)	2000～100,000
Packet average length (bytes)	200～20,000
		Data packet length mean square deviation (bytes)	30～3,000
Simulation time (min)	114/360
		Amount of information weight parameter f	{0，1，10，100}
ISL buffering area (packets)	25
		The ISL_LEO thresholding	5
The ISL_MEO thresholding	2

Table 4

Sandwich construction has effectively been shared offered load, at other relevant parameter all under the same case, can reduce TPW, change shown in the schematic diagram with the inter-satellite link channel capacity as Fig. 9 multilayer satellite network normalization link load, no matter compare with LEO network or MEO network, the path TPW of MLSN is all less than the individual layer satellite network.The multilayer satellite network that Walker delta constellation constitutes has permanent ISL, can guarantee the validity of satellite network, and has higher reliability than the individual layer satellite network, under the situation of satellite node or communication link damage, have more alternative path, can not cause service performance to decline to a great extent.Self adaptation IP routing policy is considered the information loads situation of change of all ISL in the network under the Distribution Statistics business model, selects optimal path adaptively.Multilayer satellite network can satisfy the different quality of service requirement of miscellaneous service, particularly under the situation that does not increase propagation delay time and delay variation, obtain less comprehensive path weight value, reduce drop probabilities, be fit to constitute the bigger different military satellite communication networks of the comprehensive network of multiple business of QoS requirement difference with priority.

Technology of the present invention is with respect to traditional satellite, and by hanging down the network that rail and middle rail satellite have constituted global covering, transmission delay is little, the validity height.Satellite has on the star to be handled and exchange capacity, has microwave or optical link between star, and the integrated service in broadband can be provided for the user in the global range, effectively guaranteed service quality, and Path selection is more flexible, and replaceable link is many, and survivability can be stronger.

Above content be in conjunction with concrete preferred implementation to further describing that the present invention did, can not assert that concrete enforcement of the present invention is confined to these explanations.For the general technical staff of the technical field of the invention, without departing from the inventive concept of the premise, can also make some deduction or replace, all should be considered as belonging to protection scope of the present invention.

Claims (8)

1. method for setting multilayer satellite network system route, it is characterized in that: described route establishing method comprises step:

A: setup parameter, carry out netinit;

B: fix a moment t _k, at this time interval Δ t, find the solution the satellite orbit parameter, calculate satellite position coordinate and inter-satellite link length, set up network topology structure;

C: according to the business model of setting, the inter-satellite link load of calculating described multilayer satellite network;

D: calculate the time delay of handling and exchanging on the star according to queuing theory;

E:, seek source satellite and target satellite in each satellite layer according to the ground-level source target location;

F:,, seek optimal path according to routing algorithm according to the satellite layer of communication service instruction demand and network state selection transport service.

2. according to the described method for setting multilayer satellite network system route of claim 1, it is characterized in that: the parameter of setting in the described steps A comprises: number of satellite, inter-satellite link bar number, each satellite orbit type, orbit altitude, orbit inclination angle and number of tracks in the multilayer satellite network number of plies, each layer.

3. according to the described method for setting multilayer satellite network system route of claim 1, it is characterized in that: described step C further comprises substep:

C1: under the non-uniform Distribution model, the density of population is divided into 5 grades, with the density of population in each zone of numeral;

C2: earth surface is divided into 48 and part, adopts to be parallel to parallel, favour the division methods of warp, 8 oblique lines are 52 degree with parallel, longitude 360 are spent be divided into 8 parts, and latitude is divided into 6 parts; Establish a ground station in each zone, ground station is positioned at north and south latitude 15 degree, 45 degree and 68 degree, and number is 48; Adopt the maximum access scheme in the elevation angle to insert;

C3: under statistical distribution pattern, consider the difference of user's distribution density, the source and target position and the density variation of calling, draw the channel occupancy situation of every inter-satellite link in the network.

4. according to the described method for setting multilayer satellite network system route of claim 1, it is characterized in that: described step D further comprises substep:

D1: according to queuing theory, regard every inter-satellite link as single service window mixed queuing model M/Ml/m, every inter-satellite link only contains single service window, obeys negative exponent the blanking time that " client " arrives and distributes, and parameter is β; Be that parameter is that μ is that negative exponent distributes service time; Every inter-satellite link has m queueing capacity, and when having m packet in the system, new packet no longer enters queuing, has: ρ=β/μ;

D2: the average waiting time delay of packet is $W=\frac{1}{\mathrm{\&mu;}\&CenterDot;(1-\mathrm{\&rho;})}-\frac{m\&CenterDot;{\mathrm{\&rho;}}^m}{\mathrm{\&mu;}\&CenterDot;(1-{\mathrm{\&rho;}}^m)}.$

5. according to the described method for setting multilayer satellite network system route of claim 1, it is characterized in that: the routing algorithm in the described step F is the FBellman-Ford routing algorithm.

6. according to claim 1 or 5 described method for setting multilayer satellite network system route, it is characterized in that: described step F specifically comprises substep:

F1: default business is low rail layer at described multilayer satellite network system, if middle rail source satellite, target satellite are identical, and low rail source satellite, target satellite difference, execution in step F4; If stationary orbit source satellite, target satellite are identical, and low rail and middle rail source satellite, target satellite are different, execution in step F5; Otherwise, execution in step F2;

F2: be less than or equal to the low rail thresholding of inter-satellite link, execution in step F3 if this low rail layer path comprises inter-satellite link quantity; If described low rail layer path comprises inter-satellite link quantity greater than the low rail thresholding of inter-satellite link, and middle rail layer path comprises inter-satellite link quantity and is less than or equal to rail thresholding in the inter-satellite link, execution in step F4; Otherwise, execution in step F5;

F3: set up low orbit satellite layer optimal communication path, finish transformation task;

F4: rail satellite layer optimal communication path in the foundation, finish transformation task;

F5: set up satellite layer optimal communication path, finish transformation task;

F6: add up the characteristic parameter of multitiered network in the described multilayer satellite network system, the phase-split network performance;

F7: update time the interval, finish new routing table and calculate and finish the satellite handover.

7. want 6 described method for setting multilayer satellite network system route according to right, it is characterized in that: the described bellman-ford routing algorithm that described step F 3, F4 and F5 are applied to, this algorithm comprises substep:

Step 1: the T index value that makes all non-beginning nodes in the network is ∞, i.e. T (i)=∞; The order beginning P label of node is 0, i.e. P (s)=0;

Step 2: with new described P label is the beginning node i, checks with i to be whether each terminal point j on limit of beginning node exists [P (i)+d (i, j)]＜P (j) or [P (i)+d (i, j)]＜T (j), if exist, and execution in step 3, otherwise keep former label;

Step 3: with the T label at j point place or P label change into new T label T (j)=P (i)+d (i, j) or T (i)+d (i, j).Get the minimum value of existing T label point in the network, be decided to be new P label point, repeat described step 2;

Step 4: when all nodes of network all were the P label point, algorithm finished.

8. want 6 described method for setting multilayer satellite network system route according to right, it is characterized in that: the characteristic parameter that needs to add up in the described step F 6 comprises: the memory usage percentage of each satellite node, inter-satellite link length and blocking probability.

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