CN114978276B - Multi-path collaborative software defined satellite network continuous data return method and system - Google Patents
Multi-path collaborative software defined satellite network continuous data return method and system Download PDFInfo
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- H04B7/14—Relay systems
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- H04B7/185—Space-based or airborne stations; Stations for satellite systems
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- H04L1/12—Arrangements for detecting or preventing errors in the information received by using return channel
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- H04L5/0053—Allocation of signalling, i.e. of overhead other than pilot signals
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Abstract
The invention provides a multipath collaborative software defined satellite network continuous data return method and system, comprising the following steps: the controller calculates a cooperative satellite set and a cooperative transmission amount, and estimates the number of data packets capable of being cooperatively relayed; the controller plans a plurality of paths between the source satellite and the cooperative satellite set; the source satellite encodes the data packet and transmits the data packet through multiple paths; the intermediate node receives the data packet to encode and forward 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 invention ensures continuous uninterrupted return of satellite data based on cooperative transmission among satellites, reduces end-to-end time delay and improves the throughput rate of the network; the path coordination and management cost required by the traditional multipath transmission scheme is avoided; the invention has no ACK mechanism such as end-to-end stop, obviously reduces the expenditure brought by the acknowledgement 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 collaborative software defined satellite network continuous data return method and system.
Background
The satellite has the characteristics of long communication distance, wide coverage range and the like compared with the ground node, and a plurality of satellites cooperate and relay through inter-satellite links, so that global communication coverage is easy to realize, the satellite can become an important component of a future 6G system, and the satellite plays an irreplaceable role in the fields of remote sensing monitoring, ground observation and the like. However, because satellites continue to move at high speed on a space-time large scale, the communication window between a single medium-low orbit satellite and an earth station is only about 20 minutes; most of the existing satellite systems adopt an over-top transmission mechanism, so that intermittent transmission, large time delay and interval and low satellite resource utilization rate are caused, and broadband and continuous information service is difficult to support. Therefore, based on cooperation among a plurality of satellites, a source satellite which needs to download data transmits the data to a group of satellites which can directly communicate with an earth station along an inter-satellite link (the invention is called a cooperative satellite), and the latter continuously returns to the earth station, so that the method is a necessary route for broadband and continuous satellite service in the future. Here, the cooperative satellites are constantly changing. On the other hand, in order to support intelligent management of satellite networks, future satellite networks will use a logically centralized control plane to perform fine control on satellite resources based on software definition technology, maintain satellite network states based on controllers, plan paths accordingly, balance loads, and the like.
Multipath is an effective technique for improving network throughput, reducing end-to-end delay, and improving transmission quality in unstable environments. In the multipath transmission scheme based on network coding, the data packets are continuously coded on the transmission path, and the destination end can analyze the source data packets only by receiving enough coded data packets. Meanwhile, the coded data packet can participate in source data packet analysis no matter which path is transmitted from, and the data packet is transmitted to the destination end. But it is now difficult to provide effective support for broadband, continuous data backhaul for satellite networks.
The scholars Chachulski and the like (Szymon Chachulski,Michael Jennings,Sachin Katti et al.Trading Structure for Randomness in Wireless Opportunistic Routing.SIGCOMM Comput.Commun.Rev.2007:169–180.) firstly propose to combine network coding and opportunistic routing to improve the throughput of a wireless network, and design a multipath protocol MORE oriented to the wireless network, wherein the basic idea is that a source node broadcasts a packet, and a neighbor node recodes a data packet and recursively broadcasts the data packet; once the destination node receives a sufficient number of packets belonging to one Batch (Batch), it will parse the Batch data packet and send an ACK to inform the source to send the next Batch of packets. The network coding protocol CCACK was designed based on MORE, koutsonikolas, et al (Dimitrios Koutsonikolas,Chih-Chun Wang and Y.Charlie Hu.CCACK:Efficient Network Coding Based Opportunistic Routing Through Cumulative Coded Acknowledgments.In INFOCOM 2010:2919–2927.), and it is critical to employ accumulated coded acknowledgements from downstream nodes to reduce the amount of transmission redundancy, i.e., once a sufficient number of coded packets are received by a downstream node, the upstream node will not send the batch of packets.
Furthermore, document (Xinyu Zhang and Baochun Li."Optimized multipath network coding in lossy wireless networks".IEEE Journal on Selected Areas in Communications,2009,27(5):622–634) proposes a network coding based multipath protocol OMNC that allocates transmission rates to source nodes based on distributed optimization to improve the throughput of noisy wireless networks with the aim of optimizing the gains of network coding.
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 waste of inter-satellite link resources and low performance of the satellite network, and are difficult to be suitable for the satellite network. The invention is based on the cooperative transmission among satellites, solves the transmission interruption caused by the overhead transmission of the existing satellite system, ensures the continuous return of satellite data, reduces the end-to-end time delay and improves the throughput rate of the network; meanwhile, the multipath cooperative transmission scheme based on network coding avoids coordination and management cost among paths required by the traditional multipath transmission scheme; the proposed end-to-end ACK mechanism without stop and the like obviously reduces the expenditure brought by the acknowledgement mechanism and improves the utilization rate of the inter-satellite links.
Patent document CN113644962a (application number: cn202110866297. X) discloses a low-speed, non-real-time satellite internet of things terminal data backhaul method and system, wherein the method comprises: step 1, a cooperative network control center establishes a communication link with a user terminal; step 2, the user terminal accesses the network control center according to the communication link; and step 3, the user terminal and the network control center carry out data feedback according to the requirements. However, the method for transmitting the data back of the internet of things at a low speed and in a non-real time manner cannot guarantee continuous and uninterrupted data back of the satellite, and the problems of intermittent transmission, large time delay and interval, low satellite resource utilization rate and the like are not solved.
The invention ensures continuous uninterrupted return of satellite data based on cooperative transmission among satellites, reduces end-to-end time delay and improves the throughput rate of the network; the path coordination and management cost required by the traditional multipath transmission scheme is avoided; the invention has no ACK mechanism such as end-to-end stop, obviously reduces the expenditure brought by the acknowledgement mechanism and improves the utilization rate of the inter-satellite link.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide a multi-path collaborative software defined satellite network continuous data return method and system.
The invention provides a multipath collaborative software defined satellite network continuous data return method, which comprises the following steps:
step S1: the controller calculates a cooperative satellite set and a cooperative transmission amount, and estimates the number of data packets capable of being cooperatively relayed;
step S2: the controller plans a plurality of paths between the source satellite and the cooperative satellite set;
step S3: the source satellite encodes the data packet and transmits the data packet through multiple paths;
Step S4: the intermediate node receives the data packet to encode and forward 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 said step S1:
Step S1.1: computing a collaborative satellite set:
In a software-defined satellite network, when a source satellite s needing to download data sends a transmission request to a controller thereof, the controller calculates a cooperative satellite set CS positioned above an earth station at the moment based on a constellation movement mode;
step S1.2: calculating the cooperative transmission amount:
The cooperative transmission amount CTT i is the number of packets that the cooperative node cs i can transmit in one time window.
Preferably, in said step S1.2:
Step s1.2.1: based on the load and the data arrival rate of the cooperative satellite, estimating the number of data packets which can be cooperatively relayed by the cooperative satellite:
The amount of cooperative transmission is limited by two factors: a time window for maintaining communication with the earth station; secondly, the load exists in the buffer area;
let Deltat i denote the (i-1) th data packet and the time interval for the i-th data packet to reach the cooperating node; t o denotes the propagation delay from the source to the cooperating satellites, then:
wherein L is the total length of the collaborative satellite buffer queue; r s is the transmission rate of the source satellite s;
The packet entry rate r i (t) and the exit rate r o (t) of the collaborative satellite buffer are time dependent, and the number of packets l i in the buffer of the collaborative satellite cs i is increased within the time interval Δt i as follows:
The maximum transmission window of the cooperative satellite cs i is tw i, and the maximum transmission window is the longest time that cs i is directly communicated with the earth station; when source s begins transmitting, cs i has an available transmission time of The cs i buffer has l 0 packets; when cs i receives x data packets, the available transmission time t (x) of cs i is:
Wherein B i is the transmission rate of the cooperative satellite cs i;
step S1.2.2: maximum cooperative relay amount of single satellite:
Considering the maximum communication time window of each cooperative satellite over the earth station, the maximum cooperative transmission amount CTT i of any one cooperative satellite cs i is:
Where tw i is the longest time that the cooperative satellite cs i is in one continuous communication with the earth station.
Preferably, in said step S2:
planning a plurality of orthogonal paths between the source satellite and the set of cooperating satellites comprises the steps of:
Step S2.1: evaluating link transmission cost:
Calculating link transmission cost by using broadband and node load based on link quality of satellite network and ground network;
Wherein, For a linkCost of transmission on; Representing links On packet loss rate, reflecting linkTransmission quality on; And Respectively linksBandwidth used above and its total bandwidth;
step S2.2: calculating path transmission cost:
According to the calculated link transmission cost, calculating the end-to-end transmission cost of all paths between the source node and each cooperative satellite;
for one transmission path p:
Wherein, Representing different links making up path pThe partial order relation exists between the two paths, and the expression of the path transmission cost C p on the path p is as follows:
step S2.3: multipath planning:
taking the path transmission cost as a routing mechanism and the transmission cost as the minimum principle, planning N orthogonal paths P between a source satellite and each cooperative satellite set:
where s is the source satellite and cs i is the cooperative satellite.
Preferably, in said step S3:
The source satellite performs data transmission based on network coding, which comprises the following steps:
step S3.1: a source satellite codes a data packet, takes a batch as a basic coding unit, and codes a batch of source data;
Step S3.2: transmitting the coded data packet, and coding the coded data packet M continuous sending on each path, and put into buffer zone, select another group of random coding vector, code the next batch of source data packet;
step S3.3: when receiving the coded data packet The acknowledgement message ACK, a batch of packets of the acknowledgement message is removed from the buffer.
Preferably, the step S3.1 comprises the steps of:
step S3.1.1: encoding vector generation:
Each batch of source data packets is encoded by adopting a random linear network coding scheme on a finite field GF (256), each batch comprises N data packets, op i represents any source data packet, cp i represents one coded data packet, then a coding vector is randomly generated from GF (256), and the coding vector of the jth data packet
Wherein a j,i (1.ltoreq.i.ltoreq.N) is randomly selected from [0, 255 ];
Step S3.1.2: data packet coding with batch as basic unit:
for a batch of source packets OP:
OP＝{op1,op2,…,opN}
Generating a batch of coded data packets CP:
CP＝{cp1,cp2,…,cpN}
The encoded data packet cp j of the j-th data packet is generated in the following manner:
cpj＝aj,1op1+aj,2op2+…+aj,NopN,1≤j≤N (7)
Namely:
CP＝A*OP
Wherein a= Σ 1≤j≤N∑1≤i≤Naj,i.
Preferably, the step S3.2 comprises the steps of:
Step S3.2.1: the transmission mode is as follows:
In the multi-path cooperative transmission based on network coding, continuously transmitting 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 same batch of data packets transmitted on each path:
the source end independently transmits the data packet to the cooperative satellite from each path, and if the data packet transmitted by the source end is less than a preset value, the destination end cannot decode;
Link The packet loss rate is as follows Delivery success ratePathThe successful delivery rate of (2) isThe source node transmits a batch of coded data packets CP from a plurality of independent paths P i E P at the same time;
Wherein,
The total transmission success rate of a batch of coded data packets on each path isThe I P I represents the number of paths in the path set P;
The source satellite transmits m data packets on each path, and the cooperative node will receive A data packet;
In order to decode N source packets in a batch, the cooperating node must receive at least N encoded packets, and therefore the number of packets m that the source node should send on each path should satisfy:
after m coded data packets are sent by a source satellite on each path, continuously sending m|P| data packets on multiple paths for each batch, and starting to send the next batch;
step S3.2.3: transmitting the encoded data packet to the next hop:
The source satellite continuously transmits m coded data packets; encoding and transmitting the next batch of data packets in the same mode;
Step S3.2.4: source satellite retransmission:
When a source satellite is required to retransmit a batch of messages, the source records the number of data packets which are transmitted again on each path by the source and the cooperative satellite receives m 0 linearly independent messages The method comprises the following steps:
otherwise, step S3.2.4 is skipped;
Wherein m 0 is the number of linearly independent messages that the cooperative satellite has received.
Preferably, in said step S4:
the data forwarding of the intermediate node based on network coding comprises the following steps:
step S4.1: the intermediate node encodes the received data packet:
The intermediate node receives the same batch of m coded data packets Recoding to form a new data packet using a new coding vector randomly generated between [0, 255]
Step S4.2: the intermediate node encodes the data packetTo its downstream nodes.
Preferably, in said step S5:
The cooperative satellite decoding and validation includes the steps of:
Step S5.1: parsing source packets in the same batch:
when the cooperative satellite cs i receives at least N coded packets from the same batch, gao Sixiao-element is carried out on the coded packets to analyze a source data packet OP
OP＝{op1,op2,…,opN}
Cs i judges the change of the rank based on Gao Sixiao yuan, when cs i collects N linear irrelevant packets, the rank is N, the source data packet is analyzed and transmitted to an upper layer;
Step S5.2: returning a certain batch of acknowledgement messages ACK:
After cs i analyzes N source data packets OP in a batch and transmits the N source data packets OP to an upper layer, feeding back a batch acknowledgement message ACK along the opposite direction of a transmission path;
step S5.3: returning an unsuccessful message:
When cs i receives only m 0 coded packets (m 0 < N), the source data packets OP in a batch cannot be analyzed, and the number m 0 of the received coded packets is fed back along the opposite direction of the transmission path;
When not less than N coded packets belonging to the same batch are received, this step is skipped.
According to the software defined satellite network continuous data return system with multipath cooperation provided by the invention, the software defined satellite network continuous data return method with multipath cooperation is executed, and the method comprises the following steps:
The controller module M1: determining a cooperative set of satellites and multipath comprises: determining a cooperative satellite set and a forwarding amount of each cooperative satellite; planning a disjoint path set 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, including: a group of source data packets in units of a batch; transmitting the encoded packet on each path; buffering unacknowledged encoded packets and deleting the buffer when receiving an ACK;
Intermediate satellite module M3: performing network coding-based data forwarding, including: after receiving the same batch of coded data packets, recoding the data packets and transmitting the recoded data packets to a downstream satellite;
cooperative satellite module M4: parsing and validating the encoded data packet, including: analyzing the coded data packet and restoring the source data packet; sending ACK; and when the analysis is unsuccessful, sending a failure message and the number of received coded packets.
Compared with the prior art, the invention has the following beneficial effects:
1. The continuous data return scheme based on the cooperation among satellites ensures continuous uninterrupted return of satellite data, solves the problems of transmission interruption, large time delay and interval, low satellite resource utilization rate and the like caused by overhead transmission of the existing satellite system, and improves the throughput rate of a network while reducing the end-to-end time delay;
2. according to the multi-path cooperative transmission scheme based on network coding, coordination and management cost among paths required by the traditional multi-path transmission scheme are avoided;
3. the ACK mechanism without stop and the like designed in the invention ensures the delivery rate, obviously reduces the expenditure brought by ACK confirmation and improves the utilization rate of the inter-satellite links.
Drawings
Other features, objects and advantages of the present invention will become more apparent upon reading of the detailed description of non-limiting embodiments, given with reference to the accompanying drawings in which:
FIG. 1 is a flow chart of a software defined satellite network continuous data return method based on multipath cooperation in an embodiment of the 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 links between the controller and the satellite switching nodes are not shown;
Fig. 3 is a block diagram of a software defined satellite network continuous data backhaul system based on multipath 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 present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.
Example 1:
According to the invention, as shown in fig. 1-3, a continuous data return method of a software defined satellite network for multipath cooperation comprises the following steps:
step S1: the controller calculates a cooperative satellite set and a cooperative transmission amount, and estimates the number of data packets capable of being cooperatively relayed;
Specifically, in the step S1:
Step S1.1: computing a collaborative satellite set:
In a software-defined satellite network, when a source satellite s needing to download data sends a transmission request to a controller thereof, the controller calculates a cooperative satellite set CS positioned above an earth station at the moment based on a constellation movement mode;
step S1.2: calculating the cooperative transmission amount:
The cooperative transmission amount CTT i is the number of packets that the cooperative node cs i can transmit in one time window.
Specifically, in said step S1.2:
Step s1.2.1: based on the load and the data arrival rate of the cooperative satellite, estimating the number of data packets which can be cooperatively relayed by the cooperative satellite:
The amount of cooperative transmission is limited by two factors: a time window for maintaining communication with the earth station; secondly, the load exists in the buffer area;
let Deltat i denote the (i-1) th data packet and the time interval for the i-th data packet to reach the cooperating node; t o denotes the propagation delay from the source to the cooperating satellites, then:
wherein L is the total length of the collaborative satellite buffer queue; r s is the transmission rate of the source satellite s;
The packet entry rate r i (t) and the exit rate r o (t) of the collaborative satellite buffer are time dependent, and the number of packets l i in the buffer of the collaborative satellite cs i is increased within the time interval Δt i as follows:
The maximum transmission window of the cooperative satellite cs i is tw i, and the maximum transmission window is the longest time for xs i to directly communicate with the earth station; when source s begins to transmit, the available transmission time of xs i is The xs i buffer has l 0 packets; when xs i receives x data packets, the available transmission time t (x) of xs i is:
Wherein B i is the transmission rate of the cooperative satellite cs i;
step S1.2.2: maximum cooperative relay amount of single satellite:
Considering the maximum communication time window of each cooperative satellite over the earth station, the maximum cooperative transmission amount CTT i of any one cooperative satellite cs i is:
Where tw i is the longest time that the cooperative satellite cs i is in 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 a plurality of orthogonal paths between the source satellite and the set of cooperating satellites comprises the steps of:
Step S2.1: evaluating link transmission cost:
Calculating link transmission cost by using broadband and node load based on link quality of satellite network and ground network;
Wherein, For a linkCost of transmission on; Representing links On packet loss rate, reflecting linkTransmission quality on; And Respectively linksBandwidth used above and its total bandwidth;
step S2.2: calculating path transmission cost:
According to the calculated link transmission cost, calculating the end-to-end transmission cost of all paths between the source node and each cooperative satellite;
for one transmission path p:
Wherein, Representing different links making up path pThe partial order relation exists between the two paths, and the expression of the path transmission cost C p on the path p is as follows:
step S2.3: multipath planning:
taking the path transmission cost as a routing mechanism and the transmission cost as the minimum principle, planning N orthogonal paths P between a source satellite and each cooperative satellite set:
where s is the source satellite and cs i is the cooperative satellite.
Step S3: the source satellite encodes the data packet and transmits the data packet through multiple paths;
Specifically, in the step S3:
The source satellite performs data transmission based on network coding, which comprises the following steps:
step S3.1: a source satellite codes a data packet, takes a batch as a basic coding unit, and codes a batch of source data;
Step S3.2: transmitting the coded data packet, and coding the coded data packet M continuous sending on each path, and put into buffer zone, select another group of random coding vector, code the next batch of source data packet;
step S3.3: when receiving the coded data packet The acknowledgement message ACK, a batch of packets of the acknowledgement message is removed from the buffer.
Specifically, the step S3.1 includes the steps of:
step S3.1.1: encoding vector generation:
Each batch of source data packets is encoded by adopting a random linear network coding scheme on a finite field GF (256), each batch comprises N data packets, op i represents any source data packet, op i represents one coded data packet, then a coding vector is randomly generated from the GF (256), and the coding vector of the jth data packet
Wherein a j,i (1.ltoreq.i.ltoreq.N) is randomly selected from [0, 255 ];
Step S3.1.2: data packet coding with batch as basic unit:
for a batch of source packets OP:
OP＝{op1,op2,…,opN}
Generating a batch of coded data packets CP:
CP＝{cp1,cp2,…,cpN}
The encoded data packet cp j of the j-th data packet is generated in the following manner:
cpj＝aj,1op1+aj,2op2+…+aj,NopN,1≤j≤N (7)
Namely:
CP＝A*OP
Wherein a= Σ 1≤j≤N∑1≤i≤Naj,i.
Specifically, the step S3.2 includes the steps of:
Step S3.2.1: the transmission mode is as follows:
In the multi-path cooperative transmission based on network coding, continuously transmitting 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 same batch of data packets transmitted on each path:
the source end independently transmits the data packet to the cooperative satellite from each path, and if the data packet transmitted by the source end is less than a preset value, the destination end cannot decode;
Link The packet loss rate is as follows Delivery success ratePathThe successful delivery rate of (2) isThe source node transmits a batch of coded data packets CP from a plurality of independent paths P i E P at the same time;
Wherein,
The total transmission success rate of a batch of coded data packets on each path isThe I P I represents the number of paths in the path set P;
The source satellite transmits m data packets on each path, and the cooperative node will receive A data packet;
In order to decode N source packets in a batch, the cooperating node must receive at least N encoded packets, and therefore the number of packets m that the source node should send on each path should satisfy:
after m coded data packets are sent by a source satellite on each path, continuously sending m|P| data packets on multiple paths for each batch, and starting to send the next batch;
step S3.2.3: transmitting the encoded data packet to the next hop:
The source satellite continuously transmits m coded data packets; encoding and transmitting the next batch of data packets in the same mode;
Step S3.2.4: source satellite retransmission:
When a source satellite is required to retransmit a batch of messages, the source records the number of data packets which are transmitted again on each path by the source and the cooperative satellite receives m 0 linearly independent messages The method comprises the following steps:
otherwise, step S3.2.4 is skipped;
Wherein m 0 is the number of linearly independent messages that the cooperative satellite has received.
Step S4: the intermediate node receives the data packet to encode and forward the data packet;
specifically, in the step S4:
the data forwarding of the intermediate node based on network coding comprises the following steps:
step S4.1: the intermediate node encodes the received data packet:
The intermediate node receives the same batch of m coded data packets Recoding to form a new data packet using a new coding vector randomly generated between [0, 255]
Step S4.2: the intermediate node encodes the data packetTo 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 includes the steps of:
Step S5.1: parsing source packets in the same batch:
when the cooperative satellite cs i receives at least N coded packets from the same batch, gao Sixiao-element is carried out on the coded packets to analyze a source data packet OP
OP＝{op1,op2,…,opN}
Cs i judges the change of the rank based on Gao Sixiao yuan, when cs i collects N linear irrelevant packets, the rank is N, the source data packet is analyzed and transmitted to an upper layer;
Step S5.2: returning a certain batch of acknowledgement messages ACK:
After cs i analyzes N source data packets OP in a batch and transmits the N source data packets OP to an upper layer, feeding back a batch acknowledgement message ACK along the opposite direction of a transmission path;
step S5.3: returning an unsuccessful message:
When cs i receives only m 0 coded packets (m 0 < N), the source data packets OP in a batch cannot be analyzed, and the number m 0 of the received coded packets is fed back along the opposite direction of the transmission path;
When not less than N coded packets belonging to the same batch are received, this step is skipped.
According to the software defined satellite network continuous data return system with multipath cooperation provided by the invention, the software defined satellite network continuous data return method with multipath cooperation is executed, and the method comprises the following steps:
The controller module M1: determining a cooperative set of satellites and multipath comprises: determining a cooperative satellite set and a forwarding amount of each cooperative satellite; planning a disjoint path set 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, including: a group of source data packets in units of a batch; transmitting the encoded packet on each path; buffering unacknowledged encoded packets and deleting the buffer when receiving an ACK;
Intermediate satellite module M3: performing network coding-based data forwarding, including: after receiving the same batch of coded data packets, recoding the data packets and transmitting the recoded data packets to a downstream satellite;
cooperative satellite module M4: parsing and validating the encoded data packet, including: analyzing the coded data packet and restoring the source data packet; sending ACK; and when the analysis is unsuccessful, sending a failure message and the number of received coded packets.
Example 2:
Example 2 is a preferable example of example 1 to more specifically explain the present invention.
Aiming at the defects in the prior art, the invention provides a data returning method and a system based on multipath cooperation in a software defined satellite network, which can continuously return large-capacity satellite data by taking a satellite capable of directly communicating with an earth station as a cooperation relay through an inter-satellite link, thereby not only supporting satellite application with real-time requirements (such as real-time forest fire monitoring based on remote sensing data) but also improving the throughput rate of a satellite system.
The invention provides a satellite network broadband real-time data return method and a system based on multipath cooperation in a software defined satellite network, which are characterized in that through cooperation relay of direct communication satellites with earth stations, the satellite data continuously and real-time transmits the large-capacity satellite data back to the earth station through a plurality of paths of inter-satellite links, and compared with the traditional overhead transmission, the method not only fully utilizes the inter-satellite links, but also supports real-time application based on satellites.
The invention provides a software defined satellite network continuous data return method and system based on multipath cooperation, comprising the following steps: step S1: the controller determines a set of cooperative satellites currently in direct communication with the earth station Then, calculating the cooperative transmission quantity which can be downloaded to the earth station by each cooperative satellite cs i at present; step S2: planning a plurality of orthogonal transmission paths between a source satellite requesting data downloading and a cooperative satellite set by taking the lowest transmission cost as a strategy; step S3: the source satellite takes Batch (Batch) as a basic unit, encodes a group of data packets, and then transmits m encoded data packets on each path; and put into the buffer until receiving the acknowledgement message ACK for the batch, remove it from the buffer; step S4: the intermediate node encodes and transmits data packets in a similar manner, and buffers the data packets until receiving acknowledgement messages ACK from the cooperative satellites; step S5: the cooperative satellites decode the received encoded data packets in units of batches, parse out the original data packets, and send acknowledgement messages ACK for the batches to the source satellite.
The detailed steps are as follows:
Step S1: the controller calculates a cooperative satellite set and a cooperative transmission amount. Cooperative satellites (cooperative satellite) refer to satellite nodes that can communicate directly with earth stations; as shown in FIG. 2, at the same time, a plurality of such cooperative satellites are located above an earth station, which constitute a cooperative satellite set Because the satellites move at high speeds relative to the earth station, each cooperative satellite cs i can download the data amount to the earth station in the same movement period, which is called its cooperative transmission amount ct i (cooperative transmission).
Preferentially, the step S1 employs:
Step S1.1: and (5) calculating a collaborative satellite set. The world network is networked in a software defined architecture, and the controller (itself a satellite node) manages a set of satellites for which network management such as path planning, traffic scheduling, etc. (fig. 2). When the source satellite S, which needs to download data, sends a transmission request to its controller, the controller calculates a set of cooperative satellites CS, which are now located above the earth station, based on the constellation movement pattern.
Step S1.2: and calculating the cooperative transmission quantity. The cooperative transmission amount CTT i (cooperative transmission traffic) is used to represent the number of packets that the cooperative node cs i can transmit in a time window. Due to the high speed motion of the cooperative satellites to the earth stations, the amount of data that the cooperative satellites can forward is limited and excessive packets will be lost. The steps are further divided into:
step s1.2.1: based on the load and the data arrival rate of the cooperative satellite, the number of data packets that it can cooperatively relay is estimated. The amount of cooperative transmission is limited by two factors: the first is a time window in which it remains in communication with the earth station; and secondly, the load is already in the buffer area.
Let Deltat i denote the (i-1) th packet and the time interval for the i-th packet to reach the cooperating node; t o represents the propagation delay from the source to the cooperating satellite, thenWherein L is the total length of the collaborative satellite buffer queue; r s is the transmission rate of the source satellite s.
Considering that a cooperative satellite may receive multiple concurrent forwarding requests, the packet entry in its buffer is related to the sending speed and time, denoted as r i (t) and r o (t), respectively. The number of data packets in the buffer of the cooperative satellite cs i is increased to be within the time interval Δt i
Assume that the maximum transmission time window of cs i (transmission window, the maximum time that cs i can directly communicate with the earth station) is tw i; when the source satellite s begins transmitting, the available transmission time of cs i isThe cs i buffer already has l 0 packets. Then after cs i receives the x data packets, the available transmission time for cs i 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, the maximum cooperative transmission amount of any cs i is:
Wherein tw i is the maximum time for which the cooperative satellite cs i can continuously communicate with the earth station once (also called a transmission window: transmission window);
step S2: multiple transmission paths between the source satellite (i.e., the requesting data download node) and the cooperating set of 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 on the basis of the lowest cost.
Preferably, the step S2 employs:
Step S2.1: and (5) evaluating the link transmission cost. Calculating link transmission cost based on link quality of satellite network and ground network, available broadband and node load;
Wherein, For a linkCost of transmission on; Representing links On packet loss rate, reflecting linkTransmission quality on; And Respectively linksBandwidth used above and its total bandwidth;
Step S2.2: and calculating the path transmission cost. According to the calculated link transmission cost, calculating the end-to-end transmission cost of all paths between the source node and each cooperative satellite;
for one transmission path (Here,Representing different links making up path pAnd a partial order relation exists between the two paths), and the path transmission cost expression on the path p is as follows:
Wherein, Representing different links making up path pThere is a partial order relation between
Step S2.3: and (5) multipath planning. Taking the path transmission cost as a routing mechanism and the transmission cost as the minimum principle, planning N orthogonal paths between a source satellite and each cooperative satellite set:
step S3: the source satellite performs network-based coded data transmission. First, source satellite encodes a data packet; and secondly, transmitting the coded data packet.
Preferentially, the step S3 employs:
step S3.1: the source satellite encodes a data packet, and a batch (batch) is taken as a basic coding unit to encode a batch of source data. Comprising the following steps:
step S3.1.1: the encoded vector is generated. Each batch of source packets is encoded using a random linear network coding scheme over a finite field GF (256). Each batch contains N data packets, op i represents any source data packet (original packet), cp i represents a coded packet (coded packet), then the coding vector is randomly generated from GF (256), and the coding vector of the jth data packet Wherein a j,i (1.ltoreq.i.ltoreq.N) is randomly selected from [0, 255 ]. The random system ensures that the encoded data packet is linearly uncorrelated with the source data packet.
Step S3.1.2: packet encoding in batch units. For a batch of source packets op= { OP 1,op2,…,opN }, a batch of encoded packets cp= { CP 1,cp2,…,cpN }, the encoded packet CP j of the j-th packet is:
cpj＝aj,1op1+aj,2op2+…+aj,NopN,1≤j≤N (7)
I.e. cp=a×op, where a= Σ 1≤j≤N∑1≤i≤Naj,i
Step S3.2: and transmitting the coded data packet. Will encode the next batch of data packetsM are sent consecutively on each path and put into the buffer. Then, another set of random encoding vectors is selected to encode the next batch of source packets.
Preferably, step S3.2 is further divided into:
step S3.2.1: transmission mode. In the multi-path cooperative transmission based on network coding, a data packet takes a batch (batch) as a basic coding and transmitting unit; for a batch of encoded linear independent data packets, m data packets are continuously transmitted on each path.
Step S3.2.2: and sending the determination of the number m of the same batch of data packets on each path. The source transmits the data packets from each path individually to the cooperating satellites. If the source end sends too few data packets, the destination end cannot decode; conversely, receiving too many redundant packets wastes bandwidth resources.
The end-to-end success rate of message transmission depends on the path stability. LinkThe packet loss rate is as followsI.e.Delivery success rateThus, the pathThe successful delivery rate of (2) isThe source node simultaneously transmits a coded batch of data packets CP from a plurality of independent paths P And (5) up-transmitting. Thus, the encoded batch of data packets has an overall transmission success rate ofHere, |p| represents the number of elements in the set P.
Whenever a source satellite transmits m packets on each path, the cooperating node will receiveAnd data packets. On the other hand, in order to decode N source packets in a batch, the cooperative node must receive at least N encoded packets, so the number of packets m that the source node should send on each path should satisfy:
Thus, after m encoded packets are sent on each path by the source satellite, i.e., after m|p| packets are continuously sent on multiple paths for each batch, the next batch is started.
Step S3.2.3: and sending the encoded data packet to the next hop. The source satellite continuously transmits m coded data packets; the next batch of packets is then encoded and transmitted in the same manner.
Step S3.2.4: source satellite retransmission. When a source satellite is required to retransmit a batch of messages, assuming that the source terminal records that the cooperative satellite has received m 0 linearly independent messages, the number of data packets which are only required to be transmitted on each path by the source terminal is as follows:
otherwise, this step is skipped.
Step S3.3: when receiving the coded data packetThe acknowledgement message ACK removes the batch from the buffer.
Step S4: the intermediate node forwards the data based on the network coding. Firstly, the intermediate node encodes a data packet; and secondly, transmitting the coded data packet.
Preferentially, the step S4 employs:
Step S4.1: the intermediate node encodes the received data packet. Once the intermediate node receives the same batch of m coded data packets It also re-encodes to form new data packets using new encoding vectors randomly generated between [0, 255]
Step S4.2: the intermediate node encodes the data packetTo its downstream nodes.
Step S5: and (5) collaborative satellite decoding and confirmation. Firstly, the cooperative satellite receives the 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 message ACK to the source satellite.
Preferably, step S5 comprises:
Step S5.1: source packets in the same batch are parsed. When the cooperative satellite cs i receives not less than N coded packets from the same batch, gao Sixiao-element is carried out on the coded packets, and a source data packet OP= { OP 1,op2,…,opN } is analyzed. To determine whether the new packet is linearly independent, cs i determines a rank change based on Gao Sixiao bits. When cs i collects N linearly independent packets, i.e., the rank is N, it will successfully parse out the source packet and pass it to the upper layer.
Step S5.2: a certain batch of acknowledgement messages ACK is returned. After cs i delivers a batch of parsed N source data packets OP to the upper layer, a batch acknowledgement message ACK is fed back to the opposite direction of the transmission path.
Step S5.3: an unsuccessful message is returned. When cs i receives only m 0 encoded packets (m 0 < N), it cannot parse the source packets OP in a batch, and feeds back the number of received encoded packets m 0 along the opposite direction of the transmission path. When not less than N coded packets belonging to the same batch are received, this step is skipped.
According to the invention, a software defined satellite network continuous data return system based on multipath cooperation is provided, comprising:
The controller module M1: determining a cooperative set of satellites and multipath comprises: the controller determines the forwarding quantity of the cooperative satellite set CS and 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, including: a group of source data packets in units of a batch; transmitting m encoded packets on each path; the unacknowledged encoded packets are buffered and the buffer is deleted upon receipt of an ACK.
Intermediate satellite module M3: performing network coding-based data forwarding, including: after receiving the same batch of m coded data packets, recoding the data packets and transmitting the data packets to a downstream satellite.
Cooperative satellite module M4: parsing and validating the encoded data packet, including: analyzing the coded data packet and restoring the source data packet; sending ACK; and when the analysis is unsuccessful, sending a failure message and receiving the number m 0 of the coded packets.
Those skilled in the art will appreciate that the systems, apparatus, and their respective modules provided herein may be implemented entirely by logic programming of method steps such that the systems, apparatus, and their respective modules are implemented as logic gates, switches, application specific integrated circuits, programmable logic controllers, embedded microcontrollers, etc., in addition to the systems, apparatus, and their respective modules being implemented as pure computer readable program code. Therefore, the system, the apparatus, and the respective modules thereof provided by the present invention may be regarded as one hardware component, and the modules included therein for implementing various programs may also be regarded as structures within the hardware component; modules for implementing various functions may also be regarded as being either software programs for implementing the methods or structures within hardware components.
The foregoing describes specific embodiments of the present application. It is to be understood that the application is not limited to the particular embodiments described above, and that various changes or modifications may be made by those skilled in the art within the scope of the appended claims without affecting the spirit of the application. The embodiments of the application and the features of the embodiments may be combined with each other arbitrarily without conflict.
Claims (9)
1. A software defined satellite network continuous data backhaul method for multipath collaboration, comprising:
step S1: the controller calculates a cooperative satellite set and a cooperative transmission amount, and estimates the number of data packets capable of being cooperatively relayed;
step S2: the controller plans a plurality of paths between the source satellite and the cooperative satellite set;
step S3: the source satellite encodes the data packet and transmits the data packet through multiple paths;
Step S4: the intermediate node receives the data packet to encode and forward the data packet;
Step S5: the cooperative satellite receives and decodes the data packet forwarded by the intermediate node and sends a confirmation message to the source satellite;
In the step S2:
planning a plurality of orthogonal paths between the source satellite and the set of cooperating satellites comprises the steps of:
Step S2.1: evaluating link transmission cost:
Calculating link transmission cost by using broadband and node load based on link quality of satellite network and ground network;
Wherein, For a linkCost of transmission on; Representing links On packet loss rate, reflecting linkTransmission quality on; And Respectively linksBandwidth used above and its total bandwidth;
step S2.2: calculating path transmission cost:
According to the calculated link transmission cost, calculating the end-to-end transmission cost of all paths between the source node and each cooperative satellite;
for one transmission path p:
Wherein, Representing different links making up path pThe partial order relation exists between the two paths, and the expression of the path transmission cost C p on the path p is as follows:
step S2.3: multipath planning:
taking the path transmission cost as a routing mechanism and the transmission cost as the minimum principle, planning N orthogonal paths P between a source satellite and each cooperative satellite set:
where s is the source satellite and cs i is the cooperative satellite.
2. The method for continuous data transmission back in a software defined satellite network according to claim 1, wherein in step S1:
Step S1.1: computing a collaborative satellite set:
In a software-defined satellite network, when a source satellite s needing to download data sends a transmission request to a controller thereof, the controller calculates a cooperative satellite set CS positioned above an earth station at the moment based on a constellation movement mode;
step S1.2: calculating the cooperative transmission amount:
The cooperative transmission amount CTT i is the number of packets that the cooperative node cs i can transmit in one time window.
3. The method for continuous data backhaul in a software defined satellite network with multipath cooperation according to claim 2, wherein:
in said step S1.2:
Step s1.2.1: based on the load and the data arrival rate of the cooperative satellite, estimating the number of data packets which can be cooperatively relayed by the cooperative satellite:
The amount of cooperative transmission is limited by two factors: a time window for maintaining communication with the earth station; secondly, the load exists in the buffer area;
let Deltat i denote the (i-1) th data packet and the time interval for the i-th data packet to reach the cooperating node; t o denotes the propagation delay from the source to the cooperating satellites, then:
wherein L is the total length of the collaborative satellite buffer queue; r s is the transmission rate of the source satellite s;
The packet entry rate r i (t) and the exit rate r o (t) of the collaborative satellite buffer are time dependent, and the number of packets l i in the buffer of the collaborative satellite cs i is increased within the time interval Δt i as follows:
The maximum transmission window of the cooperative satellite cs i is tw i, and the maximum transmission window is the longest time that cs i is directly communicated with the earth station; when source s begins transmitting, cs i has an available transmission time of The cs i buffer has l 0 packets; when cs i receives x data packets, the available transmission time t (x) of cs i is:
Wherein B i is the transmission rate of the cooperative satellite cs i;
step S1.2.2: maximum cooperative relay amount of single satellite:
Considering the maximum communication time window of each cooperative satellite over the earth station, the maximum cooperative transmission amount CTT i of any one cooperative satellite cs i is:
Where tw i is the longest time that the cooperative satellite cs i is in one continuous communication with the earth station.
4. The method for continuous data transmission back in a software defined satellite network according to claim 1, wherein in step S3:
The source satellite performs data transmission based on network coding, which comprises the following steps:
step S3.1: a source satellite codes a data packet, takes a batch as a basic coding unit, and codes a batch of source data;
Step S3.2: transmitting the coded data packet, and coding the coded data packet M continuous sending on each path, and put into buffer zone, select another group of random coding vector, code the next batch of source data packet;
step S3.3: when receiving the coded data packet The acknowledgement message ACK, a batch of packets of the acknowledgement message is removed from the buffer.
5. The method for continuous data transmission back in a software defined satellite network with multipath cooperation according to claim 4, wherein:
The step S3.1 comprises the steps of:
step S3.1.1: encoding vector generation:
Each batch of source data packets is encoded by adopting a random linear network coding scheme on a finite field GF (256), each batch comprises N data packets, op i represents any source data packet, cp i represents one coded data packet, then a coding vector is randomly generated from GF (256), and the coding vector of the jth data packet
Wherein a j,i (1.ltoreq.i.ltoreq.N) is randomly selected from [0, 255 ];
Step S3.1.2: data packet coding with batch as basic unit:
for a batch of source packets OP:
OP＝{op1,op2,…,opN}
Generating a batch of coded data packets CP:
CP＝{cp1,cp2,…,cpN}
The encoded data packet cp j of the j-th data packet is generated in the following manner:
cpj＝aj,1op1+aj,2op2+…+aj,NopN，1≤j≤N (7)
Namely:
CP＝A*OP
wherein a= Σ 1≤j≤N∑1≤i≤Naj,i.
6. The method for continuous data transmission back in a software defined satellite network with multipath cooperation according to claim 4, wherein:
the step S3.2 comprises the steps of:
Step S3.2.1: the transmission mode is as follows:
In the multi-path cooperative transmission based on network coding, continuously transmitting 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 same batch of data packets transmitted on each path:
the source end independently transmits the data packet to the cooperative satellite from each path, and if the data packet transmitted by the source end is less than a preset value, the destination end cannot decode;
Link The packet loss rate is as followsDelivery success ratePathThe successful delivery rate of (2) isThe source node transmits a batch of coded data packets CP from a plurality of independent paths P i E P at the same time;
Wherein, Is the path between s and cs i;
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 transmits m data packets on each path, and the cooperative node will receive A data packet;
In order to decode N source packets in a batch, the cooperating node must receive at least N encoded packets, and therefore the number of packets m that the source node should send on each path should satisfy:
after m coded data packets are sent by a source satellite on each path, continuously sending m|P| data packets on multiple paths for each batch, and starting to send the next batch;
step S3.2.3: transmitting the encoded data packet to the next hop:
The source satellite continuously transmits m coded data packets; encoding and transmitting the next batch of data packets in the same mode;
Step S3.2.4: source satellite retransmission:
When a source satellite is required to retransmit a batch of messages, the source records the number of data packets which are transmitted again on each path by the source and the cooperative satellite receives m 0 linearly independent messages The method comprises the following steps:
otherwise, step S3.2.4 is skipped;
Wherein m 0 is the number of linearly independent messages that the cooperative satellite has received.
7. The method for continuous data transmission back in a software defined satellite network according to claim 1, wherein in step S4:
the data forwarding of the intermediate node based on network coding comprises the following steps:
step S4.1: the intermediate node encodes the received data packet:
The intermediate node receives the same batch of m coded data packets Recoding to form a new data packet using a new coding vector randomly generated between [0, 255]
Step S4.2: the intermediate node encodes the data packetTo its downstream nodes.
8. The method for continuous data transmission back in a software defined satellite network according to claim 1, wherein in step S5:
The cooperative satellite decoding and validation includes the steps of:
Step S5.1: parsing source packets in the same batch:
When the cooperative satellite cs i receives at least N coded packets from the same batch, gao Sixiao-element is carried out on the coded packets to analyze the source data packet 0P
OP＝{op1,op2,…,opN}
Cs i judges the change of the rank based on Gao Sixiao yuan, when cs i collects N linear irrelevant packets, the rank is N, the source data packet is analyzed and transmitted to an upper layer;
Step S5.2: returning a certain batch of acknowledgement messages ACK:
After cs i analyzes N source data packets OP in a batch and transmits the N source data packets OP to an upper layer, feeding back a batch acknowledgement message ACK along the opposite direction of a transmission path;
step S5.3: returning an unsuccessful message:
When cs i receives only m 0 coded packets (m 0 is less than N), the source data packets OP in a batch cannot be analyzed, and the number m 0 of the received coded packets is fed back along the opposite direction of the transmission path;
When not less than N coded packets belonging to the same batch are received, this step is skipped.
9. A software defined satellite network continuous data backhaul system for multipath collaboration, wherein the software defined satellite network continuous data backhaul method for performing multipath collaboration of claim 1 comprises:
The controller module M1: determining a cooperative set of satellites and multipath comprises: determining a cooperative satellite set and a forwarding amount of each cooperative satellite; planning a disjoint path set 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, including: a group of source data packets in units of a batch; transmitting the encoded packet on each path; buffering unacknowledged encoded packets and deleting the buffer when receiving an ACK;
Intermediate satellite module M3: performing network coding-based data forwarding, including: after receiving the same batch of coded data packets, recoding the data packets and transmitting the recoded data packets to a downstream satellite;
cooperative satellite module M4: parsing and validating the encoded data packet, including: analyzing the coded data packet and restoring the source data packet; sending ACK; and when the analysis is unsuccessful, sending a failure message and the number of received coded packets.
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