CN114978276A - Multi-path cooperative software-defined satellite network continuous data return method and system - Google Patents
Multi-path cooperative software-defined satellite network continuous data return method and system Download PDFInfo
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- CN114978276A CN114978276A CN202210427803.XA CN202210427803A CN114978276A CN 114978276 A CN114978276 A CN 114978276A CN 202210427803 A CN202210427803 A CN 202210427803A CN 114978276 A CN114978276 A CN 114978276A
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/14—Relay systems
- H04B7/15—Active relay systems
- H04B7/185—Space-based or airborne stations; Stations for satellite systems
- H04B7/18521—Systems of inter linked satellites, i.e. inter satellite service
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0032—Distributed allocation, i.e. involving a plurality of allocating devices, each making partial allocation
- H04L5/0035—Resource allocation in a cooperative multipoint environment
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L5/00—Arrangements affording multiple use of the transmission path
- H04L5/003—Arrangements for allocating sub-channels of the transmission path
- H04L5/0053—Allocation of signaling, i.e. of overhead other than pilot signals
- H04L5/0055—Physical resource allocation for ACK/NACK
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
- Y02D30/00—Reducing energy consumption in communication networks
- Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks
Abstract
The invention provides a continuous data returning method and a continuous data returning system of a multi-path cooperative software-defined satellite network, which comprise the following steps: the controller calculates the cooperative satellite set and the cooperative transmission quantity and estimates the number of data packets capable of being relayed in a cooperative mode; the controller plans a plurality of paths between the source satellite and the cooperative satellite set; encoding a data packet by a source satellite and transmitting the data packet by multiple paths; the intermediate node receives the data packet, encodes the data packet and forwards the data packet; and the cooperative satellite receives and decodes the data packet forwarded by the intermediate node, and sends a confirmation message to the source satellite. The method is based on cooperative transmission among satellites, continuous and uninterrupted return of satellite data is guaranteed, end-to-end time delay is reduced, and the throughput rate of a network is improved; the path coordination and management cost required by the traditional multi-path transmission scheme is avoided; the end-to-end stop-free ACK mechanism obviously reduces the overhead brought by the confirmation mechanism and improves the utilization rate of the inter-satellite link.
Description
Technical Field
The invention relates to the field of satellite network broadband real-time data transmission, in particular to a multipath cooperative software-defined satellite network continuous data returning method and system.
Background
The satellite has the characteristics of long communication distance, wide coverage range and the like compared with a ground node, a plurality of satellites carry out cooperative relaying through inter-satellite links, global communication coverage is easy to realize, the satellite becomes an important component of a future 6G system, and the satellite plays an irreplaceable role particularly in the fields of remote sensing monitoring, ground observation and the like. However, because the satellite continuously moves at a large space-time scale at a high speed, the communication window between a single middle-low orbit satellite and a single earth station is only about 20 minutes; most of the existing satellite systems adopt an over-the-top transmission mechanism, thereby causing discontinuous transmission, large time delay and interval, low satellite resource utilization rate and difficulty in supporting broadband and continuous information service. Therefore, based on cooperation among multiple satellites, a source satellite needing to download data transmits the data to a group of satellites (referred to as cooperative satellites in the invention) capable of directly communicating with earth stations along inter-satellite links, and the latter continuously transmits back to the earth stations, which is a necessary route for future broadband and continuous satellite services. Here, the cooperative satellites are constantly changing. On the other hand, in order to support intelligent management of a satellite network, the future satellite network is based on a software definition technology, a logically centralized control plane is used for finely controlling satellite resources, a satellite network state is maintained based on a controller, and a path, a load and the like are planned according to the satellite network state.
Multipath is an effective technique for improving the throughput rate of a network, reducing the end-to-end delay and improving the transmission quality in an unstable environment. In the multi-path transmission scheme based on network coding, data packets are continuously coded on a transmission path, and a destination terminal can analyze a source data packet as long as receiving a sufficient number of coded data packets. Meanwhile, no matter which path the coded data packet is sent from, the coded data packet can participate in the analysis of the source data packet as long as the coded data packet is transmitted to a destination end. But the existing achievements are difficult to provide effective support for broadband and continuous data back transmission of a satellite network.
Scholars, Chachulski et al (Szymon Chachulski, Michael Jennings, Sachin Katti et al. mapping Structure for random in Wireless Access reporting routing. SIGCMM Comp. Commun. Rev.2007: 169-180.) first propose to improve the throughput of Wireless network by combining network coding and Opportunistic routing, and design a Wireless network-oriented multipath protocol MORE, whose basic idea is that a source node broadcasts a packet, and a neighbor node re-encodes a data packet and broadcasts it recursively; once the destination node receives a sufficient number of packets belonging to a Batch (Batch), it will parse the Batch packet and send an ACK to inform the source to send the next Batch of packets. Network Coding protocol CCACK is designed Based on MORE, Koutsonikolas, etc. (Dimitrios Koutsonikolas, Chih-Chun and Y. Charlie Hu. CCACK: Efficient Network Coding Based on optical Routing Through Cumulative Coding and decoding in INFOCOM 2010: 2919-2927.) the key point is to reduce the amount of transmission redundancy using Cumulative Coding acknowledgements from downstream nodes, i.e., once a sufficient number of Coded data packets are received by a downstream node, the upstream node will not send the batch of data packets any MORE.
Furthermore, the literature (Xinyu Zhang and Baochun Li., "Optimized multipath network coding in less networks". IEEE Journal on Selected Areas in Communications,2009,27(5): 622-.
However, because the single-hop delay of the inter-satellite link is far greater than that of the ground link, the data transmission and confirmation mechanisms of the existing protocols cause serious resource waste of the inter-satellite link and low performance of the satellite network, and are difficult to be applied to the satellite network. The method is based on cooperative transmission among satellites, solves the problem of transmission discontinuity caused by 'over-the-top transmission' of the conventional satellite system, ensures the continuous return of satellite data, reduces the end-to-end time delay and improves the throughput rate of a network; meanwhile, the multi-path cooperative transmission scheme based on network coding avoids the coordination and management cost among paths required by the traditional multi-path transmission scheme; the proposed end-to-end stop-free ACK mechanism obviously reduces the overhead brought by the acknowledgement mechanism and improves the utilization rate of the inter-satellite link.
Patent document CN113644962A (application number: cn202110866297.x) discloses a low-speed, non-real-time satellite internet of things terminal data returning method and system, wherein the method includes: step 1, establishing a communication link between a cooperative network control center and a user terminal; step 2, the user terminal accesses to a network control center according to the communication link; and 3, the user terminal and the network control center return data according to the requirement. However, the low-speed non-real-time internet of things data returning method cannot ensure continuous and uninterrupted returning of satellite data, and does not solve the problems of discontinuous transmission, large time delay and interval, low satellite resource utilization rate and the like.
The invention is based on cooperative transmission among satellites, ensures continuous and uninterrupted return of satellite data, reduces end-to-end time delay and improves the throughput rate of a network; the path coordination and management cost required by the traditional multi-path transmission scheme is avoided; the end-to-end stop-free ACK mechanism obviously reduces the overhead brought by the confirmation mechanism and improves the utilization rate of the inter-satellite link.
Disclosure of Invention
In view of the defects in the prior art, the present invention provides a continuous data backhaul method and system for a multi-path cooperative software-defined satellite network.
The invention provides a continuous data returning method of a multi-path cooperative software defined satellite network, which comprises the following steps:
step S1: the controller calculates the cooperative satellite set and the cooperative transmission quantity and estimates the number of data packets capable of being relayed in a cooperative mode;
step S2: the controller plans a plurality of paths between the source satellite and the cooperative satellite set;
step S3: encoding a data packet by a source satellite and transmitting the data packet by multiple paths;
step S4: the intermediate node receives the data packet, encodes the data packet and forwards the data packet;
step S5: and the cooperative satellite receives and decodes the data packet forwarded by the intermediate node, and sends a confirmation message to the source satellite.
Preferably, in the step S1:
step S1.1: calculating a cooperative satellite set:
in the software defined satellite network, when a source satellite s needing to download data sends a transmission request to a controller of the source satellite s, the controller calculates a cooperative satellite set CS positioned above an earth station at the moment based on a constellation motion mode;
step S1.2: calculating the cooperative transmission quantity:
cooperative traffic CTT i Is a cooperative node cs i The number of data packets that can be transmitted within a time window.
Preferably, in said step S1.2:
step S1.2.1: estimating the number of data packets which can be cooperatively relayed by the cooperative satellite based on the load and the data arrival rate of the cooperative satellite:
the cooperative transmission amount is limited by two factors: first, a time window for maintaining communication with the earth station; secondly, the buffer area has a load;
at Δ t i Representing the (i-1) th data packet and the time interval of arrival of the ith data packet at the cooperative node; t is t o Representing the propagation delay from the source to the cooperating satellite, then:
wherein, L is the total length of the cooperative satellite buffer queue; r is s Is the transmission rate of the source satellite s;
packet ingress rate r for cooperative satellite buffers i (t) and emission rate r o (t) is time dependent, at time interval Δ t i Internal and cooperative satellite cs i In the buffer area of (2) increasing the number of data packets l i Comprises the following steps:
cooperative satellite cs i Has a maximum transmission window of tw i The maximum transmission window is cs i Maximum time to communicate directly with earth stations; when source s starts to transmit, cs i The available transmission time is
cs i Buffer has been 0 A data packet; when cs i After receiving x data packets, cs i Available transmission time oft (x) is:
wherein, B i For a cooperative satellite cs i The sending rate of (d);
step S1.2.2: maximum cooperative relay capacity of a single satellite:
considering the maximum communication time window of each cooperative satellite over the earth station, any one cooperative satellite cs i Maximum cooperative transmission capacity CTT i Comprises the following steps:
wherein, tw i For a cooperative satellite cs i The longest time of one continuous communication with the earth station.
Preferably, in the step S2:
planning multiple orthogonal paths between a source satellite and a set of cooperating satellites includes the steps of:
step S2.1: and evaluating link transmission cost:
calculating link transmission cost based on link quality of a satellite network and a ground network, and by using a broadband and a node load;
wherein the content of the first and second substances,
is a link
A transmission cost of;
indicating a link
Packet loss rate on, reflecting link
The quality of transmission over;
and
are respectively a link
The bandwidth already used and its total bandwidth;
step S2.2: calculating the path transmission cost:
calculating the end-to-end transmission cost of all paths between the source node and each cooperative satellite according to the calculated link transmission cost;
for one transmission path p:
wherein the content of the first and second substances,
representing different links constituting a path p
There is a partial order relationship between them, the path transmission cost C on the path p p The expression is as follows:
step S2.3: and (3) multipath planning:
and planning N orthogonal paths P between the source satellite and each cooperative satellite set by taking the path transmission cost as a routing mechanism and taking the transmission cost as the lowest principle:
wherein s is a source satellite, cs i Are cooperative satellites.
Preferably, in the step S3:
the source satellite carries out data transmission based on network coding and comprises the following steps:
step S3.1: the source satellite encoding data packet takes batches as basic encoding units and encodes a batch of source data;
step S3.2: transmitting the encoded data packet, and encoding the data packets
Continuously sending m data packets on each path, placing the data packets in a buffer area, selecting another group of random coding vectors, and coding the next group of source data packets;
step S3.3: when a batch of data packets after encoding is received
The acknowledgement message ACK removes a batch of data packets of the acknowledgement message from the buffer.
Preferably, said step S3.1 comprises the steps of:
step S3.1.1: and (3) generating a coding vector:
each batch of source data packets is coded by adopting a random linear network coding scheme on a finite field GF (256), and each batch comprises N data packets and op i Indicates any source packet, cp i Representing an encoded packet, the code vector is randomly generated from GF (256), the code vector for the jth packet
Wherein, a j,i (1. ltoreq. i. ltoreq.N) from [0, 255]Selecting randomly;
step S3.1.2: packet coding with batch as basic unit:
for a batch of source packets OP:
OP＝{op 1 ,op 2 ,…,op N }
generating a batch of encoded data packets CP:
CP＝{cp 1 ,cp 2 ,…,cp N }
the coded data packet cp of the jth data packet j Generated in the following manner:
cp j ＝a j,1 op 1 +a j,2 op 2 +…+a j,N op N ,1≤j≤N (7)
namely:
CP＝A*OP
wherein A ═ Σ 1≤j≤N ∑ 1≤i≤N a j,i 。
Preferably, said step S3.2 comprises the steps of:
step S3.2.1: the sending mode is as follows:
in multi-path cooperative transmission based on network coding, continuously sending m data packets on each path for a batch of coded linear irrelevant data packets;
step S3.2.2: determining the number m of the data packets sent in the same batch on each path:
the source end sends the data packet to the cooperative satellite from each path independently, and if the data packet sent by the source end is less than a preset value, the destination end cannot decode;
link circuit
Has a packet loss rate of
The delivery success rate is
Route of travel
Has a successful delivery rate of
The source node simultaneously transmits a batch of encoded data packets CP from a plurality of independent paths p i E, sending on P;
wherein the content of the first and second substances,
the total transmission success rate of a batch of coded data packets on each path is
| P | represents the number of paths in the path set P;
the source satellite sends m data packets on each path, and the cooperative nodes receive the data packets
A data packet;
in order to decode N source packets in a batch, the cooperative node must receive at least N encoded packets, and therefore, the number m of packets that the source node should send on each path should satisfy:
after the source satellite sends m coded data packets on each path, continuously sending m x | P | data packets on each batch on a multipath, and starting to send the next batch;
step S3.2.3: and sending the coded data packet to the next hop:
the source satellite continuously transmits m coded data packets; coding and sending next batch of data packets in the same way;
step S3.2.4: retransmission by the source satellite:
when a source satellite is required to retransmit a batch of messages, the source end records the reception m of the cooperative satellite 0 For linearly independent packets, the source sends the number of packets on each path again
Comprises the following steps:
otherwise, step S3.2.4 is skipped;
wherein m is 0 The number of linearly independent messages that have been received for the cooperative satellite.
Preferably, in the step S4:
the data forwarding of the intermediate node based on the network coding comprises the following steps:
step S4.1: the intermediate node encodes the received data packet:
the intermediate node receives m coded data packets of the same batch
Using [0, 255]Randomly generating new code vector, and re-encoding to form new data packet
Step S4.2: the intermediate node encodes the data packet
To its downstream nodes.
Preferably, in the step S5:
the cooperative satellite decoding and validation comprises the following steps:
step S5.1: analyzing source packets in the same batch:
cooperative satellite cs i When not less than N code packets from the same batch are received, Gaussian elimination is carried out on the batch of code packets, and a source data packet OP is analyzed
OP＝{op 1 ,op 2 ,…,op N }
cs i Based on Gaussian elimination, the change of rank is judged when cs i Collecting N linear irrelevant groups, wherein the rank is N, and analyzing a source data packet and transmitting the source data packet to an upper layer;
step S5.2: and returning some batch of acknowledgement messages ACK:
when cs is i After N source packets OP in a batch are analyzed and transmitted to an upper layer, feeding back a batch acknowledgement message ACK along the opposite direction of a transmission path;
step S5.3: and returning an unsuccessful message:
when cs is i Receive only m 0 A code packet (m) 0 <N), source packets OP in a batch cannot be analyzed, and the number m of received coded packets is fed back in the opposite direction of the transmission path 0 ；
When not less than N coded packets belonging to the same batch are received, the step is skipped.
According to the continuous data returning system of the multi-path cooperative software defined satellite network, provided by the invention, the continuous data returning method of the multi-path cooperative software defined satellite network is executed, and comprises the following steps:
controller module M1: determining a set of cooperating satellites and multipaths, comprising: determining a cooperative satellite set and the forwarding amount of each cooperative satellite; planning a disjoint path set between a source node and a cooperative node set based on the path transmission cost;
source satellite module M2: performing network coding-based data transmission, comprising: a group of source packets in a batch; transmitting the encoded packet on each path; buffering the unacknowledged coded packets, and deleting the buffer when the ACK is received;
intermediate satellite module M3: performing network coding-based data forwarding, comprising: after receiving the same batch of coded data packets, coding the data packets again and sending the coded data packets to a downstream satellite of the coded data packets;
cooperative satellite module M4: parsing and validating the encoded data packet, comprising: analyzing the coded data packet and restoring a source data packet; sending ACK; when the parsing is unsuccessful, a failure message is sent along with the number of received encoded packets.
Compared with the prior art, the invention has the following beneficial effects:
1. the data continuous return scheme based on cooperation among satellites designed by the invention ensures continuous and uninterrupted return of satellite data, solves the problems of discontinuous transmission, large time delay and interval, low satellite resource utilization rate and the like caused by 'over-the-top transmission' of the conventional satellite system, and improves the throughput rate of a network while reducing the end-to-end time delay;
2. the multi-path cooperative transmission scheme based on network coding avoids the coordination and management cost among paths required by the traditional multi-path transmission scheme;
3. the invention designs the non-stop ACK mechanism, which ensures the delivery rate, obviously reduces the overhead brought by ACK confirmation and improves the utilization rate of the inter-satellite link.
Drawings
Other features, objects and advantages of the invention will become more apparent upon reading of the detailed description of non-limiting embodiments with reference to the following drawings:
FIG. 1 is a block diagram illustrating a flow chart of a continuous data backhaul method for a software defined satellite network based on multi-path cooperation according to an embodiment of the present invention;
FIG. 2 is a schematic diagram of a software-defined heaven-earth integrated network structure according to an embodiment of the present invention; wherein the link between the controller and the satellite switching node is not shown;
fig. 3 is a block diagram illustrating a continuous data backhaul system of a software-defined satellite network based on multi-path cooperation according to an embodiment of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the invention, but are not intended to limit the invention in any way. It should be noted that it would be obvious to those skilled in the art that various changes and modifications can be made without departing from the spirit of the invention. All falling within the scope of the invention.
Example 1:
the continuous data backhaul method for the multi-path cooperative software-defined satellite network according to the present invention, as shown in fig. 1 to 3, includes:
step S1: the controller calculates the cooperative satellite set and the cooperative transmission quantity and estimates the number of data packets capable of being relayed in a cooperative mode;
specifically, in the step S1:
step S1.1: calculating a cooperative satellite set:
in the software defined satellite network, when a source satellite s needing to download data sends a transmission request to a controller of the source satellite s, the controller calculates a cooperative satellite set CS positioned above an earth station at the moment based on a constellation motion mode;
step S1.2: calculating the cooperative transmission quantity:
cooperative traffic CTT i Is a cooperative node cs i The number of data packets that can be transmitted within a time window.
Specifically, in said step S1.2:
step S1.2.1: estimating the number of data packets which can be cooperatively relayed by the cooperative satellite based on the load and the data arrival rate of the cooperative satellite:
the cooperative transmission amount is limited by two factors: first, a time window for maintaining communication with the earth station; secondly, the buffer area has a load;
at Δ t i Representing the (i-1) th data packet and the time interval of arrival of the ith data packet at the cooperative node; t is t o Representing the propagation delay from the source to the cooperating satellite, then:
wherein, L is the total length of the cooperative satellite buffer queue; r is s Is the transmission rate of the source satellite s;
packet ingress rate r for cooperative satellite buffers i (t) and emission rate r o (t) is time dependent, at time interval Δ t i Internal and cooperative satellite cs i In the buffer area of (2) increasing the number of data packets l i Comprises the following steps:
cooperative satellite cs i Has a maximum transmission window of tw i The maximum transmission window is xs i Maximum time to communicate directly with earth stations; when source s starts to transmit, xs i The available transmission time is
xs i Buffer already has 0 A data packet; when xs i After receiving x data packets, xs i The available transmission time t (x) is:
wherein, B i For a cooperative satellite cs i The sending rate of (d);
step S1.2.2: maximum cooperative relay capacity of a single satellite:
considering the maximum communication time window of each cooperative satellite over the earth station, any cooperative satellite cs i Maximum cooperative transmission capacity CTT i Comprises the following steps:
wherein, tw i As a cooperative satellite cs i The longest time of one continuous communication with the earth station.
Step S2: the controller plans a plurality of paths between the source satellite and the cooperative satellite set;
specifically, in the step S2:
planning multiple orthogonal paths between a source satellite and a set of cooperating satellites includes the steps of:
step S2.1: and (3) evaluating link transmission cost:
calculating link transmission cost based on link quality of a satellite network and a ground network, and by using a broadband and a node load;
wherein the content of the first and second substances,
is a link
A transmission cost of;
indicating a link
Packet loss rate on, reflecting link
The quality of transmission over;
and
are respectively a link
The bandwidth already used and its total bandwidth;
step S2.2: calculating the path transmission cost:
calculating the end-to-end transmission cost of all paths between the source node and each cooperative satellite according to the calculated link transmission cost;
for one transmission path p:
wherein the content of the first and second substances,
representing different links constituting a path p
There is a partial order relationship between them, the path transmission cost C on the path p p The expression is as follows:
step S2.3: and (3) multipath planning:
and planning N orthogonal paths P between the source satellite and each cooperative satellite set by taking the path transmission cost as a routing mechanism and taking the transmission cost as the lowest principle:
wherein s is a source satellite, cs i Are cooperative satellites.
Step S3: encoding a data packet by a source satellite and transmitting the data packet by multiple paths;
specifically, in the step S3:
the source satellite carries out data transmission based on network coding and comprises the following steps:
step S3.1: the source satellite encoding data packet takes batches as basic encoding units and encodes a batch of source data;
step S3.2: transmitting the encoded data packet, and encoding the data packets
Continuously sending m data packets on each path, putting the data packets into a buffer area, selecting another group of random coding vectors, and coding the next group of source data packets;
step S3.3: when a batch of data packets after encoding is received
The acknowledgement message ACK removes a batch of data packets of the acknowledgement message from the buffer.
In particular, said step S3.1 comprises the following steps:
step S3.1.1: and (3) generating a coding vector:
each batch of source data packets is coded by adopting a random linear network coding scheme on a finite field GF (256), and each batch comprises N data packets and op i Representing any source packet, op i Representing an encoded packet, the code vector is randomly generated from GF (256), the code vector for the jth packet
Wherein, a j,i (1. ltoreq. i. ltoreq.N) from [0, 255]Selecting randomly;
step S3.1.2: packet coding with batch as basic unit:
for a batch of source packets OP:
OP＝{op 1 ,op 2 ,…,op N }
generating a batch of encoded data packets CP:
CP＝{cp 1 ,cp 2 ,…,cp N }
the coded data packet cp of the jth data packet j Generated in the following manner:
cp j ＝a j,1 op 1 +a j,2 op 2 +…+a j,N op N ,1≤j≤N (7)
namely:
CP＝A*OP
wherein A ═ Σ 1≤j≤N ∑ 1≤i≤N a j,i 。
In particular, said step S3.2 comprises the following steps:
step S3.2.1: the sending mode is as follows:
in multi-path cooperative transmission based on network coding, continuously sending m data packets on each path for a batch of coded linear irrelevant data packets;
step S3.2.2: determining the number m of the data packets sent in the same batch on each path:
the source end sends the data packet to the cooperative satellite from each path independently, and if the data packet sent by the source end is less than a preset value, the destination end cannot decode;
link circuit
Has a packet loss rate of
The delivery success rate is
Route of travel
Has a successful delivery rate of
The source node simultaneously transmits a batch of encoded data packets CP from a plurality of independent paths p i E, sending on P;
wherein the content of the first and second substances,
a batch of data packets after being codedThe total transmission success rate on each path is
| P | represents the number of paths in the path set P;
the source satellite sends m data packets on each path, and the cooperative nodes receive the data packets
A data packet;
in order to decode N source packets in a batch, the cooperative node must receive at least N encoded packets, and therefore, the number m of packets that the source node should send on each path should satisfy:
after the source satellite sends m coded data packets on each path, continuously sending m x | P | data packets on each batch on a multipath, and starting to send the next batch;
step S3.2.3: and sending the coded data packet to the next hop:
the source satellite continuously transmits m coded data packets; coding and sending next batch of data packets in the same way;
step S3.2.4: retransmission by the source satellite:
when a source satellite is required to retransmit a batch of messages, the source end records the reception m of the cooperative satellite 0 For linearly independent packets, the source sends the number of packets on each path again
Comprises the following steps:
otherwise, step S3.2.4 is skipped;
wherein m is 0 The number of linearly independent messages that have been received for the cooperative satellite.
Step S4: the intermediate node receives the data packet, encodes the data packet and forwards the data packet;
specifically, in the step S4:
the data forwarding of the intermediate node based on the network coding comprises the following steps:
step S4.1: the intermediate node encodes the received data packet:
the intermediate node receives m coded data packets of the same batch
Using [0, 255]Randomly generating new code vector, and re-encoding to form new data packet
Step S4.2: the intermediate node transmits the encoded data packet
To its downstream nodes.
Step S5: and the cooperative satellite receives and decodes the data packet forwarded by the intermediate node, and sends a confirmation message to the source satellite.
Specifically, in the step S5:
the cooperative satellite decoding and validation comprises the following steps:
step S5.1: analyzing source packets in the same batch:
cooperative satellite cs i When not less than N code packets from the same batch are received, Gaussian elimination is carried out on the batch of code packets, and a source data packet OP is analyzed
OP＝{op 1 ,op 2 ,…,op N }
cs i Based on Gaussian elimination, the change of rank is judged when cs i Collecting N linear independent groups with the rank of N, analyzing a source data packet and transmittingTransferring to the upper layer;
step S5.2: and returning some batch of acknowledgement messages ACK:
when cs is i After N source packets OP in a batch are analyzed and transmitted to an upper layer, feeding back a batch acknowledgement message ACK along the opposite direction of a transmission path;
step S5.3: and returning an unsuccessful message:
when cs is i Receive only m 0 A code packet (m) 0 <N), source packets OP in a batch cannot be analyzed, and the number m of received coded packets is fed back in the opposite direction of the transmission path 0 ；
When not less than N coded packets belonging to the same batch are received, the step is skipped.
According to the continuous data returning system of the multi-path cooperative software defined satellite network provided by the invention, the continuous data returning method of the multi-path cooperative software defined satellite network is executed, and the method comprises the following steps:
controller module M1: determining a set of cooperating satellites and multipaths, comprising: determining a cooperative satellite set and the forwarding amount of each cooperative satellite; planning a disjoint path set between a source node and a cooperative node set based on the path transmission cost;
source satellite module M2: performing network coding-based data transmission, comprising: grouping source packets in batches; transmitting the encoded packet on each path; buffering the unacknowledged coded packets, and deleting the buffer when the ACK is received;
intermediate satellite module M3: performing network coding-based data forwarding, comprising: after receiving the same batch of coded data packets, coding the data packets again and sending the coded data packets to a downstream satellite of the same batch of coded data packets;
cooperative satellite module M4: parsing and validating the encoded data packet, comprising: analyzing the coded data packet and restoring a source data packet; sending ACK; when the parsing is unsuccessful, a failure message is sent along with the number of received encoded packets.
Example 2:
example 2 is a preferred example of example 1, and the present invention will be described in more detail.
Aiming at the defects in the prior art, the invention provides a data returning method and a data returning system based on multipath cooperation in a software defined satellite network.
The invention provides a satellite network broadband real-time data returning method and a system based on multipath cooperation in a software defined satellite network.
The invention provides a software defined satellite network continuous data returning method and system based on multipath cooperation, which comprises the following steps: step S1: the controller determines a set of cooperating satellites currently in direct communication with the earth station
Then, calculating each cooperative satellite cs i A cooperative transmission volume currently available for download to the earth station; step S2: planning a plurality of orthogonal transmission paths between a source satellite and a cooperative satellite set for requesting data downloading by taking the lowest transmission cost as a strategy; step S3: the source satellite encodes a group of data packets by taking Batch (Batch) as a basic unit, and then sends m encoded data packets on each path; and put into the buffer zone, until receiving the acknowledgement message ACK to the batch, remove it from the buffer zone; step S4: the intermediate node encodes and transmits the data packet in a similar way, and buffers the data packet until receiving the acknowledgement message ACK from the cooperative satellite; step S5: the cooperative satellite decodes the received coded data packet by taking batch as a unit, analyzes the original data packet and sends the original data packet to the source satelliteAn acknowledgement message ACK for the batch is sent.
The detailed steps are as follows:
step S1: the controller calculates a set of cooperative satellites and a cooperative transmission volume. A cooperative satellite (cooperative satellite) refers to a satellite node that can communicate directly with an earth station; as shown in FIG. 2, a plurality of such cooperative satellites are spaced over an earth station at the same time and form a cooperative satellite set
Each of the cooperating satellites cs is moved at high speed relative to the earth station i The quantity of data that can be downloaded to the earth station in the same movement cycle, called its cooperative transmission quantity ct i (cooperative transmission)。
Preferably, the step S1 adopts:
step S1.1: and calculating a cooperative satellite set. The heaven and earth network is networked in a software defined structure, and a controller (which is also a satellite node) manages a group of satellites, plans paths for the satellites, schedules traffic and other network management (fig. 2). When a source satellite S that needs to download data sends a transmission request to its controller, the controller calculates a set of cooperating satellites CS that are now located overhead the earth stations based on the constellation motion pattern.
Step S1.2: and calculating the cooperative transmission amount. Cooperative traffic CTT i (cooperative transmission traffic) is used to represent the cooperative node cs i The number of data packets that can be transmitted within a time window. Due to the high speed of the earth station movement of the cooperative satellites, the amount of data that can be forwarded by the cooperative satellites is limited and too many data packets will be lost. The steps are further divided into:
step S1.2.1: and estimating the number of data packets which can be cooperatively relayed by the cooperative satellite based on the load and the data arrival rate of the cooperative satellite. The cooperative transmission amount is limited by two factors: first, a time window in which it remains in communication with the earth station; second, there is a load in its buffer.
By Δ t i Indicating the (i-1) th data packet and the time interval of arrival of the ith data packet at the cooperative node; t is t o Represents fromPropagation delay between source and cooperative satellite, then
Wherein, L is the total length of the cooperative satellite buffer queue; r is s Is the transmission rate of the source satellite s.
Considering that the cooperative satellite may receive multiple concurrent forwarding requests, the data packet entering and sending speed of its buffer are related to time, which are respectively denoted as r i (t) and r o (t) of (d). At time interval Δ t i Internal and cooperative satellite cs i In the buffer area, the number of data packets is increased to
Suppose cs i Maximum transmission time window (cs) i The longest time that can be directly connected to the earth station) is tw i (ii) a When the source satellite s starts transmitting, cs i The available transmission time is
cs i Buffer already has 0 A packet of data. When cs is i After receiving x data packets, cs i The available transmission time of (c) is:
step S1.2.2: maximum cooperative relay capacity for a single satellite. Considering the maximum communication time window of each cooperative satellite over the earth station, any one cs i The maximum cooperative transmission amount of (c) is:
wherein, tw i For a cooperative satellite cs i Maximum time of one continuous communication with earth station (also called transmission window)Transmission window);
step S2: multiple transmission paths between the source satellite (i.e., the requesting data download node) and the set of cooperating satellites are planned. Firstly, calculating link transmission cost; secondly, calculating the end-to-end transmission cost of all disjoint paths between the source node and each cooperative satellite; and finally, planning a plurality of orthogonal paths between the source satellite and each cooperative satellite set by using the lowest cost as a principle.
Preferably, the step S2 adopts:
step S2.1: and evaluating link transmission cost. Calculating link transmission cost based on link quality, available broadband and node load of a satellite network and a ground network;
wherein the content of the first and second substances,
is a link
A transmission cost of;
indicating a link
Packet loss rate on, reflecting link
The quality of transmission over;
and
are respectively a link
The bandwidth already used and its total bandwidth;
step S2.2: and calculating path transmission cost. Calculating the end-to-end transmission cost of all paths between the source node and each cooperative satellite according to the calculated link transmission cost;
for one transmission path
(here, the number of the first and second electrodes,
representing different links constituting a path p
There is a partial order relationship between the paths), the path transmission cost expression on the path p is:
wherein the content of the first and second substances,
representing different links constituting a path p
Have partial order relationship between them
Step S2.3: and (4) planning multiple paths. And planning N orthogonal paths between the source satellite and each cooperative satellite set by taking the path transmission cost as a routing mechanism and taking the transmission cost as the lowest principle:
step S3: the source satellite performs data transmission based on network coding. Firstly, a source satellite encodes a data packet; next, the encoded data packet is transmitted.
Preferably, the step S3 adopts:
step S3.1: the source satellite encodes a data packet, and a batch (batch) is used as a basic encoding unit to encode a batch of source data. The method comprises the following steps:
step S3.1.1: and generating a coding vector. Each batch of source packets is encoded using a random linear network coding scheme over a finite field GF (256). Each batch contains N packets, in ops i Indicates any source packet (original packet), cp i Representing a coded packet, the coded vector being randomly generated from GF (256), the coded vector for the jth packet
Wherein, a j,i (1. ltoreq. i. ltoreq.N) from [0, 255]Is randomly selected. The stochastic system ensures that the encoded data packets are linearly uncorrelated with the source data packets.
Step S3.1.2: packet encoding in units of batches (batch). For a batch of source packets OP ═ OP 1 ,op 2 ,…,op N And generating a batch of coded data packets CP ═ CP 1 ,cp 2 ,…,cp N H, the coded data packet cp of the jth data packet j Comprises the following steps:
cp j ＝a j,1 op 1 +a j,2 op 2 +…+a j,N op N ,1≤j≤N (7)
i.e. CP ═ a × OP, where a ═ Σ 1≤j≤N ∑ 1≤i≤N a j,i
Step S3.2: the encoded packet is transmitted. A batch of data packets after being coded
M are sent consecutively on each path and put into a buffer. Another set of random encoding vectors is then selected to encode the next set of source packets.
Preferably, step S3.2 can be further divided into:
step S3.2.1: and (4) a sending mode. In the multipath cooperative transmission based on network coding, a data packet takes batch (batch) as a basic coding and sending unit; and for a batch of encoded linear irrelevant data packets, continuously sending m data packets on each path.
Step S3.2.2: and determining the number m of the data packets sent in the same batch on each path. The source transmits the data packets from each path individually to the cooperating satellite. If the source end sends too few data packets, the destination end cannot decode; conversely, receiving too many redundant packets wastes bandwidth resources.
The success rate of end-to-end transmission of packets depends on the path stability. Link circuit
Has a packet loss rate of
Namely, it is
The delivery success rate is
Thus, the path
Has a successful delivery rate of
The source node simultaneously transmits a batch of encoded data packets CP from a plurality of independent paths P
And (4) sending. Therefore, the total transmission success rate of a batch of coded data packets on each path is
Here, | P | represents the number of elements in the set P.
Whenever the source satellite transmits m packets per path, the cooperative node will receive
And (4) a data packet. On the other hand, in order to decode N source packets in a batch, the cooperative node must receive at least N encoded packets, and therefore, the number m of packets that the source node should send on each path should satisfy:
thus, after the source satellite transmits m encoded data packets per path, i.e., continues to transmit m x | P | data packets per batch over multiple paths, the source satellite begins transmitting the next batch.
Step S3.2.3: and sending the encoded data packet to a next hop. The source satellite continuously transmits m coded data packets; then, the next batch of data packets are encoded and transmitted in the same way.
Step S3.2.4: and (5) retransmitting by the source satellite. When a source satellite is required to retransmit a batch of messages, assume that the source end records that the cooperative satellite has received m 0 For a linearly independent packet, the number of data packets that the source end needs to send on each path is:
otherwise, this step is skipped.
Step S3.3: when a batch of data packets after encoding is received
The acknowledgement message ACK, the batch is removed from the buffer.
Step S4: the intermediate node forwards the data based on network coding. Firstly, an intermediate node encodes a data packet; next, the encoded data packet is transmitted.
Preferably, the step S4 adopts:
step S4.1: the intermediate node encodes the received data packet. Intermediate node onceReceiving m coded data packets of the same batch
It also uses [0, 255 ]]Randomly generating new code vector, and re-encoding to form new data packet
Step S4.2: the intermediate node encodes the data packet
To its downstream nodes.
Step S5: and decoding and confirming the cooperative satellite. Firstly, a cooperative satellite receives a coded data packet and analyzes the data packet based on the same coding scheme; and secondly, after the analysis is successful, obtaining an original data packet and sending an Acknowledgement (ACK) to the source satellite.
Preferably, step S5 includes:
step S5.1: and parsing the source packets in the same batch. Cooperative satellite cs i When not less than N code packets from the same batch are received, Gaussian elimination is carried out on the batch of code packets, and a source data packet OP (OP) is analyzed 1 ,op 2 ,…,op N }. To determine whether a new packet is linearly independent, cs i The change of rank is judged based on gaussian elimination. When cs is i Collect N linearly independent packets, i.e. with rank N, it will successfully parse out the source packets and pass to the upper layer.
Step S5.2: and returning some batch of acknowledgement messages ACK. When cs is i And after transmitting a batch of analyzed N source packets OP to an upper layer, feeding back a batch acknowledgement message ACK to the reverse direction of the transmission path.
Step S5.3: an unsuccessful message is returned. When cs is i Receive only m 0 A code packet (m) 0 <N) that cannot resolve the source packets OP in a batch, and feeds back the number m of received code packets in the opposite direction of the transmission path 0 . When not less than N coded packets belonging to the same batch are received, the step is skipped.
The invention provides a software defined satellite network continuous data return system based on multi-path cooperation, which comprises:
controller module M1: determining a set of cooperating satellites and multipaths, comprising: the controller determines a cooperative satellite set CS and the forwarding amount of each cooperative satellite; and planning a plurality of disjoint path sets P (P is less than or equal to CS) between the source node and the cooperative node set based on the path transmission cost.
Source satellite module M2: performing network coding-based data transmission, comprising: a group of source packets in a batch; transmitting m coded packets on each path; the unacknowledged coded packets are buffered and the buffer is removed when an ACK is received.
Intermediate satellite module M3: performing network coding-based data forwarding, comprising: and after m encoded data packets of the same batch are received, encoding the data packets again and sending the data packets to a downstream satellite.
Cooperative satellite module M4: parsing and validating the encoded data packet, comprising: analyzing the coded data packet and restoring a source data packet; sending ACK; when the analysis is not successful, sending failure message and the number m of received code packets 0 。
Those skilled in the art will appreciate that, in addition to implementing the systems, apparatus, and various modules thereof provided by the present invention in purely computer readable program code, the same procedures can be implemented entirely by logically programming method steps such that the systems, apparatus, and various modules thereof are provided in the form of logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers and the like. Therefore, the system, the device and the modules thereof provided by the present invention can be considered as a hardware component, and the modules included in the system, the device and the modules thereof for implementing various programs can also be considered as structures in the hardware component; modules for performing various functions may also be considered to be both software programs for performing the methods and structures within hardware components.
The foregoing description of specific embodiments of the present invention has been presented. It is to be understood that the present invention is not limited to the specific embodiments described above, and that various changes or modifications may be made by one skilled in the art within the scope of the appended claims without departing from the spirit of the invention. The embodiments and features of the embodiments of the present application may be combined with each other arbitrarily without conflict.
Claims (10)
1. A continuous data backhaul method for a multi-path cooperative software-defined satellite network, comprising:
step S1: the controller calculates the cooperative satellite set and the cooperative transmission quantity and estimates the number of data packets capable of being relayed in a cooperative mode;
step S2: the controller plans a plurality of paths between the source satellite and the cooperative satellite set;
step S3: encoding a data packet by a source satellite and transmitting the data packet by multiple paths;
step S4: the intermediate node receives the data packet, encodes the data packet and forwards the data packet;
step S5: and the cooperative satellite receives and decodes the data packet forwarded by the intermediate node, and sends a confirmation message to the source satellite.
2. The multi-path cooperative software-defined satellite network continuous data backhaul method according to claim 1, wherein in said step S1:
step S1.1: calculating a cooperative satellite set:
in the software defined satellite network, when a source satellite s needing to download data sends a transmission request to a controller of the source satellite s, the controller calculates a cooperative satellite set CS positioned above an earth station at the moment based on a constellation motion mode;
step S1.2: calculating the cooperative transmission quantity:
cooperative traffic CTT i Is a cooperative node cs i The number of data packets that can be transmitted within a time window.
3. The method of claim 2, wherein the method further comprises:
in said step S1.2:
step S1.2.1: estimating the number of data packets which can be cooperatively relayed by the cooperative satellite based on the load and the data arrival rate of the cooperative satellite:
the cooperative transmission amount is limited by two factors: first, a time window for maintaining communication with the earth station; secondly, the buffer area has a load;
at Δ t i Representing the (i-1) th data packet and the time interval of arrival of the ith data packet at the cooperative node; t is t o Representing the propagation delay from the source to the cooperating satellite, then:
wherein, L is the total length of the cooperative satellite buffer queue; r is s Is the transmission rate of the source satellite s;
packet ingress rate r for cooperative satellite buffers i (t) and emission rate r o (t) is time dependent, at time interval Δ t i Internal and cooperative satellite cs i In the buffer area of (2) increasing the number of data packets l i Comprises the following steps:
cooperative satellite cs i Has a maximum transmission window of tw i The maximum transmission window is cs i Maximum time to communicate directly with earth stations; when source s starts to transmit, cs i The available transmission time is
cs i Buffer has been 0 A data packet; when cs is i After receiving x data packets, cs i The available transmission time t (x) is:
wherein, B i For a cooperative satellite cs i The sending rate of (c);
step S1.2.2: maximum cooperative relay capacity of a single satellite:
considering the maximum communication time window of each cooperative satellite over the earth station, any one cooperative satellite cs i Maximum cooperative transmission capacity CTT i Comprises the following steps:
wherein, tw i For a cooperative satellite cs i The longest time of one continuous communication with the earth station.
4. The multi-path cooperative software-defined satellite network continuous data backhaul method according to claim 1, wherein in said step S2:
planning multiple orthogonal paths between a source satellite and a set of cooperating satellites includes the steps of:
step S2.1: and (3) evaluating link transmission cost:
calculating link transmission cost based on link quality of a satellite network and a ground network, and by using a broadband and a node load;
wherein the content of the first and second substances,
is a link
A transmission cost of;
indicating a link
Packet loss rate on, reflecting link
The quality of transmission over;
and
are respectively a link
The bandwidth already used and its total bandwidth;
step S2.2: calculating the path transmission cost:
calculating the end-to-end transmission cost of all paths between the source node and each cooperative satellite according to the calculated link transmission cost;
for one transmission path p:
wherein the content of the first and second substances,
representing different links constituting a path p
There is a partial order relationship between them, the path transmission cost C on the path p p The expression is as follows:
step S2.3: and (3) multipath planning:
and planning N orthogonal paths P between the source satellite and each cooperative satellite set by taking the path transmission cost as a routing mechanism and taking the lowest transmission cost as a principle:
wherein s is a source satellite, cs i Are cooperative satellites.
5. The multi-path cooperative software-defined satellite network continuous data backhaul method according to claim 1, wherein in said step S3:
the source satellite carries out data transmission based on network coding and comprises the following steps:
step S3.1: the source satellite encoding data packet takes batches as basic encoding units and encodes a batch of source data;
step S3.2: transmitting the encoded data packet, and encoding the data packets
Continuously sending m data packets on each path, putting the data packets into a buffer area, selecting another group of random coding vectors, and coding the next group of source data packets;
step S3.3: when a batch of data packets after encoding is received
The acknowledgement message ACK, a batch of packets of the acknowledgement message is removed from the buffer.
6. The method as claimed in claim 5, wherein the method further comprises:
said step S3.1 comprises the steps of:
step S3.1.1: and (3) generating a coding vector:
each batch of source data packets is coded by a random linear network coding scheme over a finite field GF (256), wherein each batch comprises N data packets, and opi represents any source numberPacket, cpi represents an encoded packet, the code vector is randomly generated from GF (256), the code vector for the jth packet
Wherein, a j,i (1. ltoreq. i. ltoreq.N) from [0, 255]Selecting randomly;
step S3.1.2: packet coding with batch as basic unit:
for a batch of source packets OP:
OP＝{op 1 ,op 2 ,…,op N }
generating a batch of encoded data packets CP:
CP＝{cp 1 ,cp 2 ,…,cp N }
the coded data packet cp of the jth data packet j Generated in the following manner:
cp j ＝a j,1 op 1 +a j,2 op 2 +…+a j,N op N ,1≤j≤N (7)
namely:
CP＝A*OP
wherein A ═ Σ 1≤j≤N ∑ 1≤i≤N a j,i 。
7. A multi-path cooperative method as claimed in claim 5, wherein the method comprises:
said step S3.2 comprises the steps of:
step S3.2.1: the sending mode is as follows:
in multi-path cooperative transmission based on network coding, continuously sending m data packets on each path for a batch of coded linear irrelevant data packets;
step S3.2.2: determining the number m of the data packets sent in the same batch on each path:
the source end sends the data packet to the cooperative satellite from each path independently, and if the data packet sent by the source end is less than a preset value, the destination end cannot decode;
link circuit
Has a packet loss rate of
The delivery success rate is
Route of travel
Has a successful delivery rate of
The source node simultaneously transmits a batch of encoded data packets CP from a plurality of independent paths p i E, sending on P;
wherein the content of the first and second substances,
the total transmission success rate of a batch of coded data packets on each path is
The | P | represents the number of paths in the path set P;
the source satellite sends m data packets on each path, and the cooperative nodes receive the data packets
A data packet;
in order to decode N source packets in a batch, the cooperative node must receive at least N encoded packets, and therefore, the number m of packets that the source node should send on each path should satisfy:
after the source satellite sends m coded data packets on each path, continuously sending m x | P | data packets on each batch on a multipath, and starting to send the next batch;
step S3.2.3: and sending the coded data packet to the next hop:
the source satellite continuously transmits m coded data packets; coding and sending next batch of data packets in the same way;
step S3.2.4: retransmission by the source satellite:
when a source satellite is required to retransmit a batch of messages, the source end records the reception m of the cooperative satellite 0 For linearly independent packets, the source sends the number of packets on each path again
Comprises the following steps:
otherwise, step S3.2.4 is skipped;
wherein m is 0 The number of linearly independent messages that have been received for the cooperative satellite.
8. The multi-path cooperative software-defined satellite network continuous data backhaul method according to claim 1, wherein in said step S4:
the data forwarding of the intermediate node based on the network coding comprises the following steps:
step S4.1: the intermediate node encodes the received data packet:
the intermediate node receives m coded data packets of the same batch
Using [0, 255]Randomly generating new code vector, and re-encoding to form new data packet
Step S4.2: the intermediate node encodes the data packet
To its downstream nodes.
9. The multi-path cooperative software-defined satellite network continuous data backhaul method according to claim 1, wherein in said step S5:
the cooperative satellite decoding and validation comprises the following steps:
step S5.1: analyzing source packets in the same batch:
cooperative satellite cs i When not less than N code packets from the same batch are received, Gaussian elimination is carried out on the batch of code packets, and a source data packet OP is analyzed
OP＝{op 1 ,op 2 ,…,op N }
cs i Based on Gaussian elimination, the change of rank is judged when cs i Collecting N linear irrelevant groups, wherein the rank is N, and analyzing a source data packet and transmitting the source data packet to an upper layer;
step S5.2: and returning some batch of acknowledgement messages ACK:
when cs i After N source packets OP in a batch are analyzed and transmitted to an upper layer, feeding back a batch acknowledgement message ACK along the opposite direction of a transmission path;
step S5.3: and returning an unsuccessful message:
when cs is i Receive only m 0 Code ofBags (m) 0 <N), source packets OP in a batch cannot be analyzed, and the number m of received coded packets is fed back in the opposite direction of the transmission path 0 ；
When not less than N coded packets belonging to the same batch are received, the step is skipped.
10. A multi-path cooperative continuous data backhaul system for a software defined satellite network, wherein the multi-path cooperative continuous data backhaul method for a software defined satellite network according to claim 1 is performed, comprising:
controller module M1: determining a set of cooperating satellites and multipaths, comprising: determining a cooperative satellite set and the forwarding amount of each cooperative satellite; planning a disjoint path set between a source node and a cooperative node set based on the path transmission cost;
source satellite module M2: performing network coding-based data transmission, comprising: a group of source packets in a batch;
transmitting the encoded packet on each path; buffering the unacknowledged coded packets, and deleting the buffer when the ACK is received;
intermediate satellite module M3: performing network coding-based data forwarding, comprising: after receiving the same batch of coded data packets, coding the data packets again and sending the coded data packets to a downstream satellite of the coded data packets;
cooperative satellite module M4: parsing and validating the encoded data packet, comprising: analyzing the coded data packet and restoring a source data packet; sending ACK; when the parsing is unsuccessful, a failure message is sent along with the number of received encoded packets.
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