CN118199711A - Multi-attribute decision-making switching method for giant inclined Walker-Delta low-orbit satellite networks - Google Patents
Multi-attribute decision-making switching method for giant inclined Walker-Delta low-orbit satellite networks Download PDFInfo
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Abstract
The invention discloses a multi-attribute decision switching method for a giant inclined Walker-Delta low-orbit satellite network, relates to the technical field of satellite communication, and particularly relates to a multi-attribute decision switching method in a low-orbit satellite network. The invention aims to solve the problems that in a giant inclined Walker-Delta low-orbit satellite network, the end-to-end route delay fluctuation before and after user switching is large and the switching is interrupted due to the existence of an ascending orbit surface and a descending orbit surface. The multi-attribute decision switching method adopts a conditional switching mode proposed by 3GPP, can improve the switching continuity and reduce the switching interruption probability; the switching utility function is designed, the route hop count is used as an important switching criterion, and the switching problem is converted into a multi-attribute joint decision problem, so that the end-to-end delay of both communication parties can be effectively reduced.
Description
Technical Field
The invention relates to the technical field of satellite communication, in particular to a multi-attribute decision switching method in a low-orbit satellite network.
Background
Giant low orbit satellite (LEO) constellations are rapidly deploying, making significant contributions to sixth generation (6G) mobile networks, such as StarLink, oneWeb and Kuiper. The low-orbit satellites move continuously at a high speed of about 7.56km/s, with a connection time between the terminal and each satellite of only a few minutes. Terminals need to frequently handoff from one satellite to another, known as satellite handoff or inter-satellite handoff. Such a handover would result in communication interruption, increased end-to-end delay and higher signaling overhead. Therefore, it is necessary to design a handover strategy to improve the quality of experience (QoE) of the user.
Many satellite handoff studies have focused on handoff standards. The three most common basic switching strategies are the maximum elevation strategy, the maximum remaining time strategy and the most available channel strategy. The maximum elevation angle strategy means that the user selects the satellite with the largest communication elevation angle from all available satellites to switch, and the user can obtain the best communication quality. The maximum remaining time policy refers to that the user selects the satellite with the longest remaining service time in the handover process, which reduces the number of handovers and the probability of communication interruption. The most available channel strategy refers to that a user selects a satellite with the most available channels for handoff, and the collision probability of user access can be reduced. However, a single handover criteria policy may cause performance bottlenecks in some aspect of the network. This has prompted the study of multi-attribute switching strategies. The challenges of multi-attribute switching are often translated into optimization problems, and the problems are solved by reinforcement learning, graph theory, convex optimization theory and the like. Existing multi-attribute switching strategies are basically considered for a communication party to pursue the maximum QoE of the communication party. However, in the giant inclined Walker-Delta low-orbit satellite network, the whole constellation has an ascending track plane and a descending track plane, if both communication parties are connected to the ascending track plane at the same time or connected to the descending track plane at the same time, most users can establish connection through fewer route hops, otherwise, the users need to establish communication through more routes by hops. Therefore, selecting different handoff satellites during handoff may cause a drastic change in the number of hops between the two parties.
In the current switching strategy, the influence of a communication party on the other party when the communication party initiates the switching is not considered, and how to reduce the end-to-end delay in the satellite switching process in the giant inclined Walker-Delta low orbit satellite network is still a pending problem.
Disclosure of Invention
The invention aims to solve the problems of large end-to-end route delay fluctuation and switching interruption before and after user switching caused by the existence of an ascending track surface and a descending track surface in a giant inclined Walker-Delta low-orbit satellite network, and provides a multi-attribute decision switching method for the giant inclined Walker-Delta low-orbit satellite network.
The multi-attribute decision switching method for the giant inclined Walker-Delta low-orbit satellite network comprises the following specific processes:
Step one: the MN sends a Radio Resource Control (RRC) measurement report of all satellites in the MN self-switching satellite set S MN to a source satellite of the MN;
The MN is a mobile node;
The source satellite of the MN is a satellite originally accessed by the MN;
Step two: after receiving Radio Resource Control (RRC) measurement reports of all satellites in the MN self switching satellite set S MN, a source satellite of the MN sends a switching information inquiry request to the CN through a source satellite of the CN;
after receiving the handover information inquiry request, the CN sends a radio resource control RRC measurement report of all satellites in the CN' S own handover satellite set S CN to the source satellite of the MN;
The CN is a communication opposite-end node;
Step three: after receiving Radio Resource Control (RRC) measurement reports of all satellites in the CN self-switching satellite set S CN, the source satellite of the MN calculates switching gain g (i, j) of a satellite i in the MN self-switching satellite set S MN and a satellite j in the CN self-switching satellite set S CN;
taking a satellite i corresponding to the maximum value of the switching gain g (i, j) as a target satellite of the MN;
taking a satellite j corresponding to the maximum value of the switching gain g (i, j) as a target satellite of CN;
the target satellite of the MN is a satellite to be switched by the MN;
the target satellite of the CN is a satellite to be switched by the CN;
step four: the source satellite of the MN sends a conditional switching CHO switching request to the destination satellite of the MN;
meanwhile, the source satellite of the MN sends a conditional switching CHO decision result to the source satellite of the CN, and after receiving the conditional switching decision result, the source satellite of the CN sends a conditional switching CHO request to the target satellite of the CN;
After receiving a conditional switching CHO request, a target satellite of the MN judges whether resources can support the switching of the MN or not, and if so, the target satellite of the MN sends confirmation information for permitting the switching to a source satellite of the MN; if not, the switching fails;
After receiving a conditional switching CHO request, the target satellite of the CN receives a determination whether resources can support MN switching or not, and if so, the target satellite of the CN sends confirmation information for permitting switching to the source satellite of the CN; if not, the switching fails;
step five: the source satellite of the MN sends a Radio Resource Control (RRC) reconfiguration message to the MN;
the source satellite of the CN sends a radio resource control RRC reconfiguration message to the CN;
Step six: the MN keeps connection with a source satellite of the MN, monitors the condition of a target satellite of the MN, and when the condition reaches the switching condition, the target satellite of the MN makes a decision of agreeing to the conditional switching request CHO, and the seventh step is executed; when the condition does not reach the switching condition, the switching fails;
The CN keeps connection with a source satellite of the CN, monitors the condition of a target satellite of the CN, and when the condition reaches the switching condition, the target satellite of the CN makes a decision of agreeing to the condition switching request CHO, and executes the step seven; when the condition does not reach the switching condition, the switching fails;
step seven: the MN is separated from a source satellite of the MN, then the MN establishes connection with a target satellite of the MN, and the MN sends an RRC reconfiguration completion message to the target satellite of the MN;
the CN is separated from a source satellite of the CN, then the CN establishes connection with a target satellite of the CN, and the MN sends RRC reconfiguration completion information to the target satellite of the CN;
Step eight: if the target satellite detection condition switching CHO of the MN is completed, the target satellite of the MN sends a context release message of the MN to a source satellite of the MN to complete link switching;
If the target satellite detection condition of the MN is not switched CHO, the switching fails;
If the target satellite of the CN checks that the condition switching CHO is completed, the target satellite of the CN sends a context release message of the CN to a source satellite of the CN to complete the link switching;
If the target satellite checking condition of the CN is not switched to CHO, the switching is failed;
step nine: if the source satellite detection condition switching CHO of the MN is completed, releasing the radio link resource related to the MN;
the radio link resources related to the MN are: channel resources and spectrum resources;
If the source satellite detection condition of the MN is not switched CHO, the switching fails;
if the source satellite checking condition switching CHO of the CN is completed, releasing the radio link resource related to the CN;
The radio link resources related to the CN are as follows: channel resources and spectrum resources;
If the source satellite checking condition of CN is not switched CHO, the switching fails.
The beneficial effects of the invention are as follows:
The multi-attribute decision switching method adopts a conditional switching (CHO) mode proposed by 3GPP, can improve the continuity of switching and reduce the switching interruption probability.
The invention mainly solves the problem of end-to-end delay fluctuation in the satellite switching process in the giant inclined Walker-Delta constellation, designs a switching utility function (formula 1), takes the number of route hops as an important switching criterion, converts the switching problem into a multi-attribute joint decision problem, and can effectively reduce the end-to-end delay of both communication parties.
The invention provides a general flow of joint switching (MN and CN) of two communication parties, designs a shortest path with low complexity, and assists a switching decision by a hop count algorithm, and further reduces the end-to-end time delay of the two communication parties while reducing the calculated amount of the switching decision.
Drawings
FIG. 1 is a general flow of a multi-attribute decision switching method of the present invention;
Fig. 2 is a diagram of a skewed orbital constellation orbital relationship model according to the invention.
Detailed Description
The first embodiment is as follows: the multi-attribute decision switching method for the giant inclined Walker-Delta low-orbit satellite network in the embodiment comprises the following specific processes:
Step one: the MN sends a Radio Resource Control (RRC) measurement report of all satellites in an MN self-switching satellite set S MN (a set formed by the MN accessible satellites) to a source satellite of the MN;
the MN is a mobile node and can be understood as a mobile terminal, such as a mobile phone;
The source satellite of the MN is a satellite originally accessed by the MN;
Step two: after receiving Radio Resource Control (RRC) measurement reports of all satellites in the MN self switching satellite set S MN, a source satellite of the MN sends a switching information inquiry request to the CN through a source satellite of the CN;
after receiving the handover information inquiry request, the CN sends a radio resource control RRC measurement report of all satellites in the CN' S own handover satellite set S CN to the source satellite of the MN;
The CN is a communication opposite terminal node, and can be also understood as a mobile phone or terminal equipment capable of directly establishing communication with a satellite;
Step three: after receiving Radio Resource Control (RRC) measurement reports of all satellites in the CN self-switching satellite set S CN, the source satellite of the MN calculates switching gain g (i, j) of a satellite i in the MN self-switching satellite set S MN and a satellite j in the CN self-switching satellite set S CN;
taking a satellite i corresponding to the maximum value of the switching gain g (i, j) as a target satellite of the MN;
taking a satellite j corresponding to the maximum value of the switching gain g (i, j) as a target satellite of CN;
the target satellite of the MN is a satellite to be switched by the MN;
the target satellite of the CN is a satellite to be switched by the CN;
step four: the source satellite of the MN sends a conditional switching CHO switching request to the destination satellite of the MN;
meanwhile, the source satellite of the MN sends a conditional switching CHO decision result to the source satellite of the CN, and after receiving the conditional switching decision result, the source satellite of the CN sends a conditional switching CHO request to the target satellite of the CN;
after receiving the conditional switching CHO request, the target satellite of the MN judges whether the target satellite of the MN has resources capable of supporting the switching of the MN or not, and if so, the target satellite of the MN sends confirmation information for permitting the switching to the source satellite of the MN (step five); if not, the switching fails;
after receiving the conditional switching CHO request, the CN destination satellite receives and judges whether the source can support MN switching, if so, the CN destination satellite sends confirmation information for permitting switching to the CN source satellite (step five); if not, the switching fails;
step five: the source satellite of the MN sends a Radio Resource Control (RRC) reconfiguration message to the MN;
the source satellite of the CN sends a radio resource control RRC reconfiguration message to the CN;
Step six: the MN keeps connection with a source satellite of the MN, monitors the condition (timing condition or position condition) of a target satellite of the MN, and when the condition reaches the condition of switching, the target satellite of the MN makes a decision of agreeing to a conditional switching request CHO, and executes a step seven; when the condition does not reach the switching condition, the switching fails;
The CN keeps connection with a source satellite of the CN, monitors the condition of a target satellite of the CN, and when the condition reaches the switching condition, the target satellite of the CN makes a decision of agreeing to the condition switching request CHO, and executes the step seven; when the condition does not reach the switching condition, the switching fails;
Status: whether the condition for switching is reached or not, a timing condition or a position condition can be reached or not, and various choices can be made;
step seven: the MN is separated from a source satellite of the MN, then the MN establishes connection with a target satellite of the MN, and the MN sends an RRC reconfiguration completion message to the target satellite of the MN;
the CN is separated from a source satellite of the CN, then the CN establishes connection with a target satellite of the CN, and the MN sends RRC reconfiguration completion information to the target satellite of the CN;
Step eight: if the target satellite detection condition switching CHO of the MN is completed, the target satellite of the MN sends a context release message of the MN to a source satellite of the MN to complete link switching;
If the target satellite detection condition of the MN is not switched CHO, the switching fails;
If the target satellite of the CN checks that the condition switching CHO is completed, the target satellite of the CN sends a context release message of the CN to a source satellite of the CN to complete the link switching;
If the target satellite checking condition of the CN is not switched to CHO, the switching is failed;
step nine: if the source satellite detection condition switching CHO of the MN is completed, releasing the radio link resource related to the MN;
the radio link resources related to the MN are: channel resources, spectrum resources, etc.;
If the source satellite detection condition of the MN is not switched CHO, the switching fails;
if the source satellite checking condition switching CHO of the CN is completed, releasing the radio link resource related to the CN;
the radio link resources related to the CN are as follows: channel resources, spectrum resources, etc.;
If the source satellite checking condition of CN is not switched CHO, the switching fails.
The second embodiment is as follows: the first difference between this embodiment and the specific embodiment is that the source satellite and the destination satellite are satellites in a Walker-Delta constellation;
the Walker-Delta constellation consists of N p×Mp satellites;
Wherein N p is the number of tracks, the tracks having the same track inclination angle θ are uniformly distributed along the equator;
the right-hand rising intersection point right-hand warp (RAAN) difference between adjacent planes is deltaomega=2pi/N p;
Each orbit comprises M p satellites, M p satellites are uniformly distributed, and the phase difference between adjacent satellites is delta phi=2pi/M p;
The phase difference between adjacent satellites of adjacent planes is
Wherein F is a phase factor;
Thus, the Walker-Delta constellation is described as θ:M p/Np/F.
The invention is suitable for various low orbit satellite constellations, in particular for giant inclined Walker-Delta constellations.
Other steps and parameters are the same as in the first embodiment.
And a third specific embodiment: the difference between the present embodiment and the first or second embodiment is that, in the third step, the source satellite of the MN calculates a switching gain g (i, j) between the satellite i in the MN self-switching satellite set S MN and the satellite j in the CN self-switching satellite set S CN; the specific process is as follows:
The MN' S own set of potential handoff satellites is denoted S MN＝{sm,1,sm,2,sm,3,…,sm,M;
Wherein s m,1 represents the 1 st satellite in the MN's own handoff satellite set, s m,2 represents the 2 nd satellite in the MN's own handoff satellite set, s m,3 represents the 3 rd satellite in the MN's own handoff satellite set, and s m,M represents the M-th satellite in the MN's own handoff satellite set;
the CN' S own set of potential handoff satellites is denoted S CN＝{sc,1,sc,2,sc,3,…,sc,N;
Wherein s c,1 represents the 1 st satellite in the CN self switching satellite set, s c,2 represents the 2 nd satellite in the CN self switching satellite set, s c,3 represents the 3 rd satellite in the CN self switching satellite set, and s c,N represents the N th satellite in the CN self switching satellite set;
The invention mainly considers the influence of two aspects during switching: firstly, the communication quality of users, including their transmission rate and switching times; and secondly, the communication pressure on the network can be measured by using end-to-end time delay. The goal is to transmit the user's data as quickly as possible to reduce network congestion.
Therefore, the present invention mainly considers the use of the elevation angle of the switched users (MN and CN), the remaining service time of the users and the number of route hops to perform joint switching;
The switched gain function g (i, j) is defined as follows:
Wherein i e S MN,j∈SCN;wθ、wt and w r are weighting coefficients, satisfying w θ+wt+wr =1;
is the elevation gain,/> For the remaining service time gain,Gain for the number of route hops;
Gamma is a switching discount coefficient, which indicates the influence of switching on the overall communication quality and satisfies gamma epsilon [0,1]; p i,j is the discount matrix.
Other steps and parameters are the same as in the first or second embodiment.
The specific embodiment IV is as follows: this embodiment differs from one to three embodiments in that the discount matrix p i,j is determined by formula (2):
Wherein k is the kth satellite in the switching satellite set of the CN, S c,k is the kth satellite in the switching satellite set of the MN, and S m,k is the kth satellite in the switching satellite set of the MN;
The switching gain function is defined as a combination of three gain functions: elevation gain (g θ), remaining service time gain (g t), and route hop count gain (g r).
Other steps and parameters are the same as in one to three embodiments.
Fifth embodiment: this embodiment differs from the embodiments by one to four in that the elevation gainThe acquisition process comprises the following steps:
Assuming that the users MN and CN have a positioning function and know ephemeris information of satellites, obtaining position coordinates of the MN, the CN, the satellite i and the satellite j by converting latitude, longitude and altitude of the MN and the CN into Cartesian coordinates;
the position coordinates of the MN, the CN, the satellite i and the satellite j are x m,ym,zm、xc,yc,zc、xi,yi,zi and x j,yj,zj respectively;
the satellite elevation calculation expression for MN and satellite i is:
Where h is the orbital altitude of the satellite and R e is the radius of the earth; d m,i is the distance from MN to satellite i, expressed as:
the elevation calculation expression for CN and satellite j is:
where d c,j is the distance from CN to satellite j, expressed as:
Thus elevation gain Expressed as:
Satellite i and satellite j have many, so many θ m,i and many θ c,j, so there is a maximum.
Other steps and parameters are the same as in one to four embodiments.
Specific embodiment six: this embodiment differs from one to five of the embodiments in that the remaining service time gainThe acquisition process comprises the following steps:
the user reduces the handoff time by selecting satellites with longer remaining service times.
1) The maximum service time of MN in satellite i is
Where w is the angular velocity of the satellite in the geocentric earth fixed coordinate system, w=w s-we cos (θ), θ is the orbital tilt angle, w s is the angular velocity of the satellite in the geocentric inertial coordinate system, w e is the rotational angular velocity of the earth in the geocentric inertial coordinate system, w e≈7.292115×10-5 (rad/s),Rad/s is angular velocity per second, u is kepler constant, u= 398600km 2/s2; r is the distance of the satellite from the earth center, r=r e +h;
θ min is the minimum elevation angle of the user (MN or CN, 1) MN, 2) CN) with satellite communication, constant;
Is an intermediate variable,/>
R is the distance of the satellite from the earth center, r=r e +h;
D m,i is the shortest distance between MN and the plane formed by the satellite i's understar trajectory and the earth center (the points and lines can define a plane, representing the shortest distance between MN and this plane, expressed as:
The coordinates of the projection points (obtained by ephemeris) of the point track under the satellite i for the MN;
2) The maximum service time of the same CN in the satellite j is
Is an intermediate variable,
D c,j is the shortest distance from CN to the plane formed by the satellite j's understar trajectory and the earth center, expressed as:
the coordinates of the projection points (obtained by ephemeris) of the point track of the CN under the satellite i star are obtained;
3) The remaining service time of MN in satellite i is The time that the MN has served in satellite i;
The remaining service time of CN in satellite j is The time that the MN has served in satellite j;
4) Residual service time gain Expressed as:
other steps and parameters are the same as in one of the first to fifth embodiments.
Seventh embodiment: this embodiment differs from one to six of the embodiments in that the route hop count gainThe acquisition process comprises the following steps:
The handoff gain function also considers the number of route hops as an important criterion, H (i, j) representing the number of hops from handoff satellite i of the MN to handoff satellite j of the CN;
Route hop count gain Expressed as:
Where H (i, j) represents the number of hops from satellite i in handoff satellite set S MN of the MN to satellite j in handoff satellite set S CN of the CN.
Other steps and parameters are the same as in one of the first to sixth embodiments.
Eighth embodiment: the present embodiment is different from one of the first to seventh embodiments in that the step of obtaining the hop count H (i, j) is:
The model of the orbital relationship of Walker-Delta constellation θ to M p/Np/F is shown in FIG. 2.
1) The Walker-Delta constellation consists of N p×Mp satellites;
N p is the number of tracks, the tracks having the same track inclination angle θ being uniformly distributed along the equator;
each orbit comprises M p satellites, and M p satellites are uniformly distributed;
s0101, S0102, …, S01M p are provided on track surface 1;
s0201, S0202, …, S02M p are provided on the track surface 2;
SN p01、SNp02、…、SNpMp is provided on the track surface N p;
s0101 denotes the 1 st satellite of the 1 st orbit, S0102 denotes the 2 nd satellite of the 1 st orbit, and S01M p denotes the M p st satellite of the 1 st orbit;
S0201 represents the 1 st satellite in the 2 nd orbit, S0202 represents the 2 nd satellite in the 2 nd orbit, S02M p represents the M p st satellite in the 2 nd orbit;
SN p 01 denotes the 1 st satellite in the N p th orbit, SN p 02 denotes the 2 nd satellite in the N p th orbit, and SN pMp denotes the M p th satellite in the N p th orbit;
The S0101 is positioned at the intersection point of the 1 st orbit and the equator; s0102 and S01M p are positioned on two sides of the equator;
the S0201 and the S02M p are positioned on two sides of the equator;
The SN p01、SNpMp is positioned at two sides of the equator;
The connection line length between S0101 and SN pMp is L 1;
the length of the connecting line of S0101 and S0202 is L 1;
The connection line length between S0101 and SN p 01 is L 2;
the connection line length between S0101 and S02M p is L 2;
The length of a connecting line of the S0101 crossing point with the N p track along the equatorial direction is L 3;
the length of the connecting line of the intersection point of the S0101 and the 2 nd track along the equatorial direction is L 3;
The connecting line length of the SN pMp along the N p track direction and the intersection point of the equator is L 4;
the connecting line length of S0201 along the intersection point of the 2 nd track direction and the equator is L 4;
The connecting line length of the SN p 01 along the N p track direction and the intersection point of the equator is L 5;
The connecting line length of S02M p along the intersection point of the 2 nd track direction and the equator is L 5;
2) Calculating L 3、L4 and L 5 according to the geometric relationship and the orbit parameters of the constellation by using a formula (12), a formula (13) and a formula (14);
L3＝2sin(ΔΩ)×(Re+h) (12)
L4＝2sin(Δφ)×(Re+h)/Np (13)
L5＝2(Np-1)sin(Δφ)×(Re+h)/Np (14)
Then, L 1 and L 2 are given by equation (15) and equation (16), respectively:
wherein θ is the orbit inclination θ; ΔΩ is the right-hand rising intersection right-hand warp (RAAN) difference between adjacent tracks, ΔΩ=2pi/N p; Δφ is the phase difference between adjacent satellites, Δφ=2π/M p;
3) Defining two new variables And
Indicating the difference between the satellite number of the k+1th orbit and the satellite number of the k orbit when the satellite of the k orbit is connected with the satellite of the k+1th orbit; for example, in the case of L 1≥L2, satellite S0102 is linked to satellite S0201, where S0102 represents the 2 nd satellite in orbit 1 and S0201 represents the 1 st satellite in orbit 2, then
Indicating the difference between the satellite number of the 1 st orbit and the satellite number of the N p th orbit when the satellite of the N p th orbit is connected with the satellite of the 1 st orbit; for example, in the case of L 1≥L2, satellite SN p 01 is connected to satellite S0101, S0101 represents the 1 st satellite in the 1 st orbit, and SN p 01 represents the 1 st satellite in the N p th orbit, then
AndExpressed as:
4) Given two satellites S 1 and S 2, the positions of satellites S 1 and S 2 are represented by two-dimensional coordinates, the position of satellite S 1 is the nth 1 satellite of the p 1 th orbit, denoted S 1(p1,n1), the position of satellite S 2 is the nth 2 satellite of the p 2 th orbit, denoted S 2(p2,n2), assuming p 1≤p2;
5) Calculating the number of routes between the satellite S 1 and the satellite S 2; the specific process is as follows:
51 Calculating an orbit difference Δp c between satellite S 1 and satellite S 2, and a satellite number difference Δn c between satellite S 1 and satellite S 2;
Δpc＝p2-p1 (19)
if Δn c is less than or equal to 0, Δn c＝Δnc+Mp;
If Δn c≥Mp, Δn c＝Δnc-Mp;
52 Calculating two possible route hops H 1 and H 2):
H1＝Δpc+|Δnc-n2| (21)
H2＝Δpc+Mp-|Δnc-n2| (22)
The orbit difference Δp a between satellite S 1 and satellite S 2, and the satellite number difference Δn a between satellite S 1 and satellite S 2, may also be calculated from the opposite direction;
Δpa＝Np-Δpc (23)
if Δn a is less than or equal to 0, Δn a＝Δna+Mp;
If Δn a≥Mp, Δn a＝Δna-Mp;
53 Calculating two possible route hops H 3 and H 4):
H3＝Δpa+|Δna-n2| (25)
H4＝Δpa+Mp-|Δna-n2| (26)
54 The shortest route hop count between the satellite S 1 and the satellite S 2 is obtained as h=min { H 1,H2,H3,H4 }, H being the minimum value among { H 1,H2,H3,H4 }.
This procedure is described in algorithm 1 below. The computational complexity of the algorithm is independent of the constellation size.
Other steps and parameters are the same as those of one of the first to seventh embodiments.
The present invention is capable of other and further embodiments and its several details are capable of modification and variation in light of the present invention, as will be apparent to those skilled in the art, without departing from the spirit and scope of the invention as defined in the appended claims.
Claims (8)
1. The multi-attribute decision switching method for the giant inclined Walker-Delta low-orbit satellite network is characterized by comprising the following steps of: the method comprises the following specific processes:
Step one: the MN sends a Radio Resource Control (RRC) measurement report of all satellites in the MN self-switching satellite set S MN to a source satellite of the MN;
The MN is a mobile node;
The source satellite of the MN is a satellite originally accessed by the MN;
Step two: after receiving Radio Resource Control (RRC) measurement reports of all satellites in the MN self switching satellite set S MN, a source satellite of the MN sends a switching information inquiry request to the CN through a source satellite of the CN;
after receiving the handover information inquiry request, the CN sends a radio resource control RRC measurement report of all satellites in the CN' S own handover satellite set S CN to the source satellite of the MN;
The CN is a communication opposite-end node;
Step three: after receiving Radio Resource Control (RRC) measurement reports of all satellites in the CN self-switching satellite set S CN, the source satellite of the MN calculates switching gain g (i, j) of a satellite i in the MN self-switching satellite set S MN and a satellite j in the CN self-switching satellite set S CN;
taking a satellite i corresponding to the maximum value of the switching gain g (i, j) as a target satellite of the MN;
taking a satellite j corresponding to the maximum value of the switching gain g (i, j) as a target satellite of CN;
the target satellite of the MN is a satellite to be switched by the MN;
the target satellite of the CN is a satellite to be switched by the CN;
step four: the source satellite of the MN sends a conditional switching CHO switching request to the destination satellite of the MN;
meanwhile, the source satellite of the MN sends a conditional switching CHO decision result to the source satellite of the CN, and after receiving the conditional switching decision result, the source satellite of the CN sends a conditional switching CHO request to the target satellite of the CN;
After receiving a conditional switching CHO request, a target satellite of the MN judges whether resources can support the switching of the MN or not, and if so, the target satellite of the MN sends confirmation information for permitting the switching to a source satellite of the MN; if not, the switching fails;
After receiving a conditional switching CHO request, the target satellite of the CN receives a determination whether resources can support MN switching or not, and if so, the target satellite of the CN sends confirmation information for permitting switching to the source satellite of the CN; if not, the switching fails;
step five: the source satellite of the MN sends a Radio Resource Control (RRC) reconfiguration message to the MN;
the source satellite of the CN sends a radio resource control RRC reconfiguration message to the CN;
Step six: the MN keeps connection with a source satellite of the MN, monitors the condition of a target satellite of the MN, and when the condition reaches the switching condition, the target satellite of the MN makes a decision of agreeing to the conditional switching request CHO, and the seventh step is executed; when the condition does not reach the switching condition, the switching fails;
The CN keeps connection with a source satellite of the CN, monitors the condition of a target satellite of the CN, and when the condition reaches the switching condition, the target satellite of the CN makes a decision of agreeing to the condition switching request CHO, and executes the step seven; when the condition does not reach the switching condition, the switching fails;
step seven: the MN is separated from a source satellite of the MN, then the MN establishes connection with a target satellite of the MN, and the MN sends an RRC reconfiguration completion message to the target satellite of the MN;
the CN is separated from a source satellite of the CN, then the CN establishes connection with a target satellite of the CN, and the MN sends RRC reconfiguration completion information to the target satellite of the CN;
Step eight: if the target satellite detection condition switching CHO of the MN is completed, the target satellite of the MN sends a context release message of the MN to a source satellite of the MN to complete link switching;
If the target satellite detection condition of the MN is not switched CHO, the switching fails;
If the target satellite of the CN checks that the condition switching CHO is completed, the target satellite of the CN sends a context release message of the CN to a source satellite of the CN to complete the link switching;
If the target satellite checking condition of the CN is not switched to CHO, the switching is failed;
step nine: if the source satellite detection condition switching CHO of the MN is completed, releasing the radio link resource related to the MN;
the radio link resources related to the MN are: channel resources and spectrum resources;
If the source satellite detection condition of the MN is not switched CHO, the switching fails;
if the source satellite checking condition switching CHO of the CN is completed, releasing the radio link resource related to the CN;
The radio link resources related to the CN are as follows: channel resources and spectrum resources;
If the source satellite checking condition of CN is not switched CHO, the switching fails.
2. The multi-attribute decision switching method for a giant-tilt Walker-Delta low-orbit satellite network according to claim 1, wherein the method comprises the following steps: the source satellite and the destination satellite are satellites in a Walker-Delta constellation;
the Walker-Delta constellation consists of N p×Mp satellites;
Wherein N p is the number of tracks, the tracks having the same track inclination angle θ are uniformly distributed along the equator;
The right-hand rising intersection point right-hand warp difference value between adjacent planes is delta omega=2pi/N p;
Each orbit comprises M p satellites, M p satellites are uniformly distributed, and the phase difference between adjacent satellites is delta phi=2pi/M p;
The phase difference between adjacent satellites of adjacent planes is
Wherein F is a phase factor;
Thus, the Walker-Delta constellation is described as θ:M p/Np/F.
3. The multi-attribute decision switching method for a giant-tilt Walker-Delta low-orbit satellite network according to claim 2, wherein the method comprises the following steps: in the third step, the source satellite of the MN calculates a switching gain g (i, j) of a satellite i in the MN self-switching satellite set S MN and a satellite j in the CN self-switching satellite set S CN; the specific process is as follows:
the MN' S own set of handoff satellites is denoted S MN＝{sm,1,sm,2,sm,3,…,sm,M;
Wherein s m,1 represents the 1 st satellite in the MN's own handoff satellite set, s m,2 represents the 2 nd satellite in the MN's own handoff satellite set, s m,3 represents the 3 rd satellite in the MN's own handoff satellite set, and s m,M represents the M-th satellite in the MN's own handoff satellite set;
The CN' S own set of handoff satellites is denoted S CN＝{sc,1,sc,2,sc,3,…,sc,N;
Wherein s c,1 represents the 1 st satellite in the CN self switching satellite set, s c,2 represents the 2 nd satellite in the CN self switching satellite set, s c,3 represents the 3 rd satellite in the CN self switching satellite set, and s c,N represents the N th satellite in the CN self switching satellite set;
The switched gain function g (i, j) is defined as follows:
Wherein i e S MN,j∈SCN;wθ、wt and w r are weighting coefficients, satisfying w θ+wt+wr =1;
is the elevation gain,/> For the remaining service time gain,Gain for the number of route hops;
gamma is a switching discount coefficient, and satisfies gamma epsilon [0,1]; p i,j is the discount matrix.
4. The multi-attribute decision switching method for a giant-tilt Walker-Delta low-orbit satellite network according to claim 3, wherein the method comprises the following steps: the discount matrix p i,j is determined by equation (2):
wherein k is the kth satellite in the switching satellite set of the CN, S c,k is the kth satellite in the switching satellite set of the MN, and S m,k is the kth satellite in the switching satellite set of the MN.
5. The multi-attribute decision switching method for a giant-tilt Walker-Delta low-orbit satellite network according to claim 4, wherein the method comprises the following steps: the elevation gainThe acquisition process comprises the following steps:
the position coordinates of the MN, the CN, the satellite i and the satellite j are x m,ym,zm、xc,yc,zc、xi,yi,zi and x j,yj,zj respectively;
the satellite elevation calculation expression for MN and satellite i is:
Where h is the orbital altitude of the satellite and R e is the radius of the earth; d m,i is the distance from MN to satellite i, expressed as:
the elevation calculation expression for CN and satellite j is:
where d c,j is the distance from CN to satellite j, expressed as:
Thus elevation gain Expressed as:
6. The multi-attribute decision switching method for a giant-tilt Walker-Delta low-orbit satellite network according to claim 5, wherein the method comprises the following steps: the remaining service time gain The acquisition process comprises the following steps:
1) The maximum service time of MN in satellite i is
Wherein w is the angular velocity of the satellite in the geocentric and geodetic fixed coordinate system;
θ min is the minimum elevation angle at which the user communicates with the satellite;
Is an intermediate variable,/>
R is the distance of the satellite from the earth center, r=r e +h;
D m,i is the shortest distance from MN to the plane formed by the satellite i's understar trajectory and the earth center, expressed as:
the projection point coordinates of the point track under the satellite i star are given to the MN;
2) The maximum service time of CN in satellite j is
Is an intermediate variable,
D c,j is the shortest distance from CN to the plane formed by the satellite j's understar trajectory and the earth center, expressed as:
The projection point coordinates of the point track of the CN under the satellite i star are obtained;
3) The remaining service time of MN in satellite i is The time that the MN has served in satellite i;
The remaining service time of CN in satellite j is The time that the MN has served in satellite j;
4) Residual service time gain Expressed as:
7. The multi-attribute decision switching method for a giant-tilt Walker-Delta low-orbit satellite network according to claim 6, wherein the method comprises the following steps: the route hop count gain The acquisition process comprises the following steps:
Route hop count gain Expressed as:
Where H (i, j) represents the number of hops from satellite i in handoff satellite set S MN of the MN to satellite j in handoff satellite set S CN of the CN.
8. The multi-attribute decision switching method for a giant-tilt Walker-Delta low-orbit satellite network according to claim 7, wherein the method comprises the following steps: the acquisition process of the hop count H (i, j) comprises the following steps:
1) The Walker-Delta constellation consists of N p×Mp satellites;
N p is the number of tracks, the tracks having the same track inclination angle θ being uniformly distributed along the equator;
each orbit comprises M p satellites, and M p satellites are uniformly distributed;
s0101, S0102, …, S01M p are provided on track surface 1;
s0201, S0202, …, S02M p are provided on the track surface 2;
SN p01、SNp02、…、SNpMp is provided on the track surface N p;
s0101 denotes the 1 st satellite of the 1 st orbit, S0102 denotes the 2 nd satellite of the 1 st orbit, and S01M p denotes the M p st satellite of the 1 st orbit;
S0201 represents the 1 st satellite in the 2 nd orbit, S0202 represents the 2 nd satellite in the 2 nd orbit, S02M p represents the M p st satellite in the 2 nd orbit;
SN p 01 denotes the 1 st satellite in the N p th orbit, SN p 02 denotes the 2 nd satellite in the N p th orbit, and SN pMp denotes the M p th satellite in the N p th orbit;
The S0101 is positioned at the intersection point of the 1 st orbit and the equator; s0102 and S01M p are positioned on two sides of the equator;
the S0201 and the S02M p are positioned on two sides of the equator;
The SN p01、SNpMp is positioned at two sides of the equator;
The connection line length between S0101 and SN pMp is L 1;
the length of the connecting line of S0101 and S0202 is L 1;
The connection line length between S0101 and SN p 01 is L 2;
the connection line length between S0101 and S02M p is L 2;
The length of a connecting line of the S0101 crossing point with the N p track along the equatorial direction is L 3;
the length of the connecting line of the intersection point of the S0101 and the 2 nd track along the equatorial direction is L 3;
The connecting line length of the SN pMp along the N p track direction and the intersection point of the equator is L 4;
the connecting line length of S0201 along the intersection point of the 2 nd track direction and the equator is L 4;
The connecting line length of the SN p 01 along the N p track direction and the intersection point of the equator is L 5;
The connecting line length of S02M p along the intersection point of the 2 nd track direction and the equator is L 5;
2) Calculating L 3、L4 and L 5 by using formula (12), formula (13) and formula (14), respectively;
L3＝2sin(ΔΩ)×(Re+h) (12)
L4＝2sin(Δφ)×(Re+h)/Np (13)
L5＝2(Np-1)sin(Δφ)×(Re+h)/Np (14)
Then, L 1 and L 2 are given by equation (15) and equation (16), respectively:
Wherein θ is the orbit inclination θ; ΔΩ is the right-hand rising intersection right-hand warp difference between adjacent tracks, ΔΩ=2pi/N p; Δφ is the phase difference between adjacent satellites, Δφ=2π/M p;
3) Defining two new variables And
Indicating the difference between the satellite number of the k+1th orbit and the satellite number of the k orbit when the satellite of the k orbit is connected with the satellite of the k+1th orbit;
Indicating the difference between the satellite number of the 1 st orbit and the satellite number of the N p th orbit when the satellite of the N p th orbit is connected with the satellite of the 1 st orbit;
And/> Expressed as:
4) Given two satellites S 1 and S 2, the positions of satellites S 1 and S 2 are represented by two-dimensional coordinates, the position of satellite S 1 is the nth 1 satellite of the p 1 th orbit, denoted S 1(p1,n1), the position of satellite S 2 is the nth 2 satellite of the p 2 th orbit, denoted S 2(p2,n2), assuming p 1≤p2;
5) Calculating the number of routes between the satellite S 1 and the satellite S 2; the specific process is as follows:
51 Calculating an orbit difference Δp c between satellite S 1 and satellite S 2, and a satellite number difference Δn c between satellite S 1 and satellite S 2;
Δpc＝p2-p1 (19)
if Δn c is less than or equal to 0, Δn c＝Δnc+Mp;
If Δn c≥Mp, Δn c＝Δnc-Mp;
52 Calculating two route hops H 1 and H 2):
H1＝Δpc+|Δnc-n2| (21)
H2＝Δpc+Mp-|Δnc-n2| (22)
The orbit difference Δp a between satellite S 1 and satellite S 2, and the satellite number difference Δn a between satellite S 1 and satellite S 2, may also be calculated from the opposite direction;
Δpa＝Np-Δpc (23)
if Δn a is less than or equal to 0, Δn a＝Δna+Mp;
If Δn a≥Mp, Δn a＝Δna-Mp;
53 Calculating two possible route hops H 3 and H 4):
H3＝Δpa+|Δna-n2| (25)
H4＝Δpa+Mp-|Δna-n2| (26)
54 The shortest route hop count between the satellite S 1 and the satellite S 2 is obtained as h=min { H 1,H2,H3,H4 }, H being the minimum value among { H 1,H2,H3,H4 }.
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