Downlink satellite resource scheduling method and system

Abstract

The invention discloses a downlink satellite resource scheduling method and system, and the method comprises the steps: analyzing the relation between a data packet effective service decision variable and a decision variable related to time slot resource distribution in a data packet transmission process, and constructing an association constraint between decision variables related to Link ID, channel and DC channel selection in the data packet transmission process; analyzing a relationship between data packet transmission and the effective service decision variable, and constructing a nonlinear association constraint of the Link ID, channel selection and the effective service decision variable; and analyzing the relation between the resource allocation scheme and a data packet transmission optimization target, and constructing a VDE-SAT-oriented downlink satellite resource optimization scheduling model taking the system throughput, the bandwidth resource utilization rate and the service reception rate as targets. In the scheme provided by the invention, the characteristics of the VDES system are considered, the downlink satellite time slot resource allocation optimization model of the VDE-SAT is established, the Link ID, channel and DC channel allocation method of the downlink complete data packet is optimized, and the rationality of the allocation scheme is improved.

Description

Technical Field

[0001] The present invention relates to the field of satellite communication technology, and in particular to a downlink satellite resource scheduling method system. Background Art

[0002] The VHF Data Exchange System (VDES) is an enhanced and upgraded version of the Automatic Identification System (AIS). It integrates the existing AIS functions and adds application-specific messages (ASM) and broadband VHF data exchange (VDE) functions. It can effectively alleviate the pressure of existing AIS data communications and meet the needs of all data exchange services between ship and ship, ship and shore, ship and satellite, and shore and satellite. It belongs to the third generation maritime communication system.

[0003] The automatic identification system of ships plays a vital role in the traffic safety, tracking and management of marine ships. However, with the expansion of ship size, the increase in the number of AIS users, and the diversification of user needs, the message collision problem faced by the AIS system is becoming increasingly serious. To address this challenge, in 2013, the International Maritime Organization, the International Association of Lighthouse Authorities and the International Telecommunication Union jointly initiated the research and design of the VDES system and launched the future maritime communication platform - the VDES plan. The design of the VDES system takes into account two major subsystems: terrestrial (VDE-Terrestrial, VDE-TER) and satellite (VDE-Satellite, VDE-SAT). VDE-TER provides high-speed and reliable data transmission for a large number of users in offshore areas, and VDE-SAT provides very high frequency data exchange functions for areas outside the signal coverage of land shore stations and areas where there are no land shore station facilities. Combining satellite communication technology with VDES can achieve global coverage and long-distance tracking, giving it a unique advantage in the field of marine supervision.

[0004] At present, VDES is still in the pre-research stage, and many technologies and performances are still to be studied. In the VDES system, the VDE-SAT subsystem is particularly important, because a large part of ship communications is at sea far away from the coverage of shore stations. ITU-RM.2092-1 gives certain suggestions on the use of frequency and time slot resources. For example, multiple Link IDs are defined in the uplink and downlink of the VDE-SAT communication system, and the physical layer parameter settings of different Link IDs are different, including modulation mode, coding rate, spread spectrum mode, etc. The VDE-SAT system supports duplex communication and uses Turbo code technology. The default bulletin board defines 6 channel pairs, marked as A to F, of which channel pairs A and B use the VDE satellite dedicated frequency bands 1026, 1086, 2026, 2086, and channel pairs C to F use the VDE satellite and ground shared frequency bands 1024, 1084, 1025, 1085, 2024, 2084, 2025, 2085. In the VDE-SAT system, the Time Division Multiple Access (TDMA) technology is used, that is, the communication resources are divided into time slots; and the logical channel is a description of the function of the time slot. According to the different functions of the time slot, the logical channel is divided into two categories: signaling channel and data channel (DC). The former is used to transmit signaling, and the latter is dedicated to exchanging data. The allocation of VDE-SAT communication resources can be defined as resource requests initiated by multiple known user terminals (data packets to be transmitted). With the goal of optimizing bandwidth utilization and service quality, DC channels are allocated to user terminals, where the channel and Link ID on each DC channel are uniquely determined, and the number of time slots occupied by the DC channel is the time slot resource allocated to the user.

[0005] In the existing technology, satellite communications basically use multiple access methods such as time division multiple access, frequency division multiple access (FDMA), code division multiple access and space division multiple access, each of which has different application scenarios. With the continuous development of communication networks, the number of users has increased sharply, the types of services have become more diverse, and all kinds of information have exploded. Due to its own limitations, traditional multiple access methods can no longer meet the requirements of multiple users and multiple services. Summary of the invention

[0006] The present invention provides a downlink satellite resource scheduling method and system, constructs a satellite resource intelligent scheduling optimization model for a VDE-SAT system, satisfies some relatively complex practical applications, and maximizes the use of satellite resources.

[0007] According to one aspect of the present invention, a downlink satellite resource scheduling method is provided, comprising the following steps:

[0008] Step 1: Introduce data packet effective service decision variables and decision variables related to link ID, channel and DC channel selection into the satellite resource optimization scheduling model;

[0009] Step 2: Analyze the relationship between the decision variables of effective service of data packets and the decision variables related to time slot resource allocation during data packet transmission, and construct the association constraints between the decision variables related to Link ID, channel and DC channel selection during data packet transmission;

[0010] Step 3: Analyze the relationship between data packet transmission and effective service decision variables, and construct nonlinear association constraints between Link ID, channel selection and effective service decision variables;

[0011] Step 4: Analyze the relationship between the resource allocation scheme and the data packet transmission optimization goal, and construct a downlink satellite resource optimization scheduling model for VDE-SAT with the goals of system throughput, bandwidth resource utilization and service reception rate; the decision variables of the satellite resource optimization scheduling model include effective service decision variables, Link ID selection decision variables, channel selection decision variables, and DC channel selection decision variables.

[0012] The step 1 specifically includes:

[0013] Effective service decision variables: y u Indicates whether data packet u is a valid service;

[0014] Decision variables related to Link ID, channel and DC channel selection: z u，c，l Indicates whether data packet u uses Link ID1 service on DC channel c; u，c，f Indicates whether data packet u occupies channel f on DC channel c.

[0015] The step 2 specifically includes:

[0016] Link ID selection constraint: The channel quality CQI value based on which the data packet u selects the Link ID is the average of the channel quality of 6 consecutive DC channels in a TDMA subframe; the CQI value of the selected Link ID should not be greater than the CQI value calculated by the link;

[0017] The allocated Link ID meets the channel bandwidth constraint, that is, the bandwidth required by the Link ID used on the channel should be less than or equal to the channel bandwidth;

[0018] Link ID selection satisfies the requirement that the number of time slots for a trigger is less than or equal to the number of time slots of the DC channel; the specific expression is:

[0019]

[0020]

[0021] Among them, CQI u，c represents the CQI mean of data packet u in a TDMA subframe; CQI(u,c) represents the channel quality of data packet u on DC channel c; bw l and BW f denote Link ID1 and the bandwidth of channel f respectively; t c Indicates the number of time slots occupied by DC channel c; Indicates the number of time slots in a burst of Link ID l;

[0022] Channel selection constraints: The access technology uses MF-TDMA multiple access mode. At the same time, the DC channel can access multiple data packets for transmission, allowing multiple channels to be used simultaneously, but the channels used by these data packets must not overlap in frequency.

[0023] Construct the channel matrix F f，j , if F f，j =1 indicates that channel f occupies carrier j; otherwise, F f，j =0;

[0024] The frequency non-overlap constraint is stated as follows:

[0025]

[0026] Among them, F f represents the carrier occupied by channel f; E represents a 1×|J| all-1 matrix.

[0027] The step three specifically includes:

[0028] definition Indicates the maximum amount of data that can be transmitted by data packet u in a DC channel c using Link ID l; if data packet u is a valid service, that is, y u =1, the data packet transmission process occupies at least one DC channel and uses Link ID and channel for transmission; the data packet transmission is completed within a one-minute scheduling cycle; if data packet u is an invalid service, that is, y u =0, there are two situations: one is that data packet u has not started to be transmitted; the other is that the transmission of data packet u has not been completed;

[0029] Construct the following constraints:

[0030]

[0031]

[0032] in, Indicates the number of bytes transmitted in a burst time slot of Link ID1; Indicates the maximum number of times Link ID l is triggered on DC channel c. Indicates rounding down, d u Indicates the data volume of data packet u;

[0033] Because z u，c，l ,y u All of them are decision variables, which leads to the above four formulas are all nonlinear constraints. To facilitate the solution, they are converted into linear constraints by the following method:

[0034]

[0035] Where M represents a very large positive integer.

[0036] The step 4 specifically includes:

[0037] If data packet u is a valid service within the scheduling period, the transmission data volume of data packet u is d u ; otherwise the amount of data transferred is calculated as The total throughput TC of the system is:

[0038]

[0039] The system bandwidth resource utilization is expressed as:

[0040]

[0041] Among them, |U| represents the number of data packets, B w Indicates the total system bandwidth;

[0042] The service reception rate is expressed as:

[0043]

[0044] The downlink satellite resource allocation optimization model for VDE-SAT is:

[0045]

[0046] Among them, TC is the total system throughput; R B is the system bandwidth resource utilization; R R is the service receiving rate; ω T ,ω B and ω R are the weight coefficients of the corresponding targets respectively.

[0047] The method further comprises:

[0048] Step five: Analyze the relationship between decision variables and objectives in the constructed satellite resource optimization scheduling model, and optimize the model.

[0049] The step five specifically includes:

[0050] The satellite resource optimization scheduling model is regarded as a packing problem and described by a set covering problem;

[0051] In the full set N = {n1, n2, ..., n I} and its subset V = {v1, v2, ..., v s}, a subset of V corresponds to a weight ε m ,The goal of the set covering problem is to find a set of subsets of the whole set N, so that the union of these subsets is equal to the whole set N and the total weight is the largest or smallest;

[0052] The set coverage problem is reduced to the satellite time slot resource scheduling problem, and the following settings are made:

[0053] The full set N corresponds to the allocation set of the system in a scheduling period, i.e., a frame;

[0054] The subset V = {v1, v2, ..., v2} consists of the time slot allocation schemes of each data packet;

[0055] Each v n The improvement in the updated objective function value after allocation is regarded as the weight of its corresponding subset;

[0056] From the reduced set cover problem, we know that y u 、z u，c，l and δ u，c，f represents the allocation of user services and satellite resources, then each allocation scheme in the set V can be represented by the set {A 1，c，l，f , A 2，c，l，f , ..., A |U|，c，l，f}, get A u，c，l，f The corresponding weight value;

[0057] The problem of the satellite resource optimization scheduling model is transformed into selecting a set of subsets And it satisfies v1∪v2∪...∪v s =N makes the total objective function value maximum;

[0058] In the scenario where |U| data packets to be transmitted, |L| Link IDs, |F| channels, and |C| DC channels, there are a total of |U|·|L|·|F|·|C| resource allocation schemes, and the solution time complexity is O(|U| 4); With the increase of terminal requests, the number of carrier channels and time slot resources increases, the scale of the problem increases accordingly, the search space of the combinatorial optimization problem also expands dramatically, and the model is optimized.

[0059] Prior to the method, the method further includes:

[0060] Define the set of data packets to be transmitted in the network as U, the set of Link ID working modes as L, and the total system bandwidth as R w , a total of |J| carriers are divided;

[0061] Multiple continuous carriers can form different channels, and the channel division method set is F;

[0062] One frame is divided into three TDMA subframes, each subframe is divided into six DC channels, and the number of time slots contained in the DC channel is 30 or 60;

[0063] The satellite time slot resource scheduling period is one frame, so there are 18 DC channels in the scheduling period, and the DC channel set is defined as C;

[0064] Define the Link ID selection mechanism; the channel quality is represented by CQI. The larger the CQI, the better the channel quality. The calculation formula is as follows:

[0065] CQI=40+4·SINR

[0066] C / (N0+I0)=SINR+10log 10 R s

[0067] Among them, SINR represents the ratio of signal to interference plus noise level, N0 represents the received signal level, I0 represents the interference signal level, R s Indicates the symbol rate;

[0068] The workflow of ACM is as follows:

[0069] The system runs; the receiving end feeds back the current channel status information to the transmitting end so that the transmitting end can adjust its own communication mode;

[0070] Calculate the CQI value, obtain the link signal to interference and noise ratio during data transmission, and obtain the CQI value of the channel according to the above formula;

[0071] Link ID selection: compare the CQI with the interval value corresponding to the nth type. If its value is exactly within the interval, the nth Link ID is selected; if its CQI value is not within the interval of the nth group, it is compared with the interval value of the n-1 group until a suitable Link ID is found;

[0072] If the interval corresponding to the CQI value of the current channel is group 0, the terminal interrupts the communication transmission.

[0073] According to another aspect of the present invention, there is provided a downlink satellite resource scheduling system, comprising:

[0074] A decision variable selection unit, used for introducing a data packet effective service decision variable and decision variables related to link ID, channel and DC channel selection in a satellite resource optimization scheduling model;

[0075] A decision variable constraint unit is used to analyze the relationship between the decision variables of effective service of data packets and the decision variables related to time slot resource allocation during data packet transmission, and to construct the association constraints between the decision variables related to Link ID, channel and DC channel selection during data packet transmission;

[0076] Nonlinear constraint unit, used to analyze the relationship between data packet transmission and effective service decision variables, and to construct nonlinear association constraints between Link ID, channel selection and effective service decision variables;

[0077] The model building unit is used to analyze the relationship between the resource allocation scheme and the data packet transmission optimization target, and to build a downlink satellite resource optimization scheduling model for VDE-SAT with the targets of system throughput, time slot resource utilization and service reception rate; the decision variables of the satellite resource optimization scheduling model include effective service decision variables, Link ID selection decision variables, channel selection decision variables and DC channel selection decision variables.

[0078] The system further comprises:

[0079] The model optimization unit is used to analyze the relationship between decision variables and objectives in the constructed satellite resource optimization scheduling model and to optimize the model.

[0080] In the scheme proposed by the present invention, effective service decision variables of data packets and decision variables related to link ID, channel and DC channel selection are introduced into the satellite resource optimization scheduling model; the relationship between effective service decision variables of data packets and decision variables related to time slot resource allocation in the data packet transmission process is analyzed, and the association constraints between decision variables related to Link ID, channel and DC channel selection in the data packet transmission process are constructed; the relationship between data packet transmission and effective service decision variables is analyzed, and nonlinear association constraints between Link ID, channel selection and effective service decision variables are constructed; the connection between resource allocation scheme and data packet transmission optimization target is analyzed, and a downlink satellite resource optimization scheduling model for VDE-SAT is constructed with system throughput, bandwidth resource utilization and service reception rate as the targets. A downlink satellite time slot resource intelligent scheduling scheme for VDE-SAT is proposed, and the characteristics of the VDES system are considered to establish a downlink satellite time slot resource allocation optimization model for VDE-SAT, optimize the Link ID, channel and DC channel allocation method of the downlink complete data packet, and improve the rationality of the allocation scheme.

[0081] The technical solution of the present invention is further described in detail below through the accompanying drawings and embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0082] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0083] Figure 1 This is a principle flow chart of a downlink satellite resource scheduling method according to an embodiment of the present invention;

[0084] Figure 2 Schematic diagram of the structure of a downlink satellite resource scheduling system in an embodiment of the present invention. DETAILED DESCRIPTION

[0085] The preferred embodiments of the present invention are described below in conjunction with the accompanying drawings. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0086] In the early 1990s, Multi-Frequency Time-Division Multiple Address (MF-TDMA) technology was first proposed. MF-TDMA is a hybrid multiple access method that combines FDMA and TDMA systems. It allows many user terminals to share a series of carriers with different rates, each carrier is divided into time slots, and flexible resource allocation is achieved through comprehensive scheduling of time-frequency two-dimensional resources. Compared with other multiple access methods, MF-TDMA has the advantages of both TDMA and FDMA. Through carrier frequency hopping, rate variation and virtual circuit technology, it has the characteristics of strong transmission capacity, high resource utilization, flexible networking, strong scalability, etc. It is suitable for multiple types of terminals and services, and can meet the QoS requirements of different services.

[0087] At present, although many scholars have studied MF-TDMA technology, no research has combined this technology with the characteristics of the VDES system to build a VDE-SAT communication resource allocation model from an optimization perspective. In addition, most of the existing research on MF-TDMA multiple access technology focuses on the flexible allocation of bandwidth and time slot resources, and no research has considered the joint allocation of modulation methods, frequency resources, and time slot resources from the perspective of system optimization. Therefore, with the vigorous development of VDES, in order to ensure the high-quality operation of the VDE-SAT system, an optimized resource allocation method is urgently needed to make certain allocations of VDE-SAT's communication resources such as frequency and time slot resources, so as to maximize the satisfaction of resource requests while maintaining a certain fairness among all users.

[0088] In view of the shortcomings of the above-mentioned prior art, the embodiments of the present invention take into account the characteristics of the VDES system, establish a downlink satellite time slot resource allocation optimization model for VDE-SAT, optimize the Link ID, channel and DC channel allocation method of the downlink complete data packet, and improve the rationality of the allocation scheme.

[0089] The embodiments of the present invention involve multiple mathematical calculation steps and multiple mathematical formulas, in which various parameters are either specific physical values ​​or just letter symbols required for conventional mathematical calculations. For values ​​with actual physical meanings, the embodiments of the present invention provide specific explanations and elaborations of physical meanings. For symbols, letters, etc. involved in conventional mathematical calculations, the conventional usage in the prior art shall prevail, and the embodiments of the present invention will not provide specific meaning explanations one by one.

[0090] Figure 1 FIG. 1 is a flowchart of downlink satellite resource scheduling in Embodiment 1 of the present invention. Figure 1 As shown, the downlink satellite resource scheduling process includes the following steps:

[0091] Step 101: Introduce data packet effective service decision variables and decision variables related to link ID, channel and DC channel selection into the satellite resource optimization scheduling model.

[0092] In one embodiment of the present invention, in the satellite resource allocation problem, the data packet selects LinkID and channel on the DC channel using binary selection decision variables z and z. u，c，l and δ u，c，f The number of completed data packets within the scheduling time range is expressed as the effective service binary decision variable y u Considering that VDE-SAT uses MF-TDMA multiple access technology, it is assumed that the transmission process of any data packet can use different Link IDs, select different channels, and span multiple DC channels. The above decision variables have the following relationship: if data packet u is effectively transmitted, that is, y u =1, then during the data transmission process, at least one DC channel c is occupied and a channel f is allocated and a Link ID l is used, that is, z ucl =1 and δ ucf =1. In addition, the following constraints need to be satisfied: the bandwidth occupied by channel f should be greater than the bandwidth required by Link ID l; the time slots triggered by Link ID l used at one time should be less than the number of time slots occupied by the DC channel; the channel frequencies occupied at the same time (DC channel) do not overlap. In addition, the goal of satellite resource allocation is to provide efficient and high-quality services to as many users (data packets) as possible with limited communication resources. Therefore, the consistency of the optimization objectives and the correlation between decision variables ensure the feasibility of constructing a downlink satellite time slot resource allocation optimization method for VDE-SAT.

[0093] Based on the above analysis, first, define the set of data packets to be transmitted in the network as U, the set of Link ID working modes as L, and the total system bandwidth as B. w , a total of |J| carriers are divided. Multiple continuous carriers can form different channels, and the channel division method set is F. In addition, according to the frame structure method of VDE-SAT recommended in Recommendation ITU-R M.2092-1, one frame is divided into 3 TDMA subframes, each subframe is divided into 6 DC channels, and the number of time slots contained in the DC channel is 30 or 60. The present invention assumes that the satellite time slot resource scheduling period is one frame, then there are 18 DC channels in the scheduling period, and the DC channel set is defined as C.

[0094] Secondly, define the Link ID selection mechanism. To ensure the reliability of data transmission, the Adaptive Coding and Modulation (ACM) mechanism is used in the transmission process to automatically adjust the modulation and coding methods according to the channel quality. For example, when the channel conditions are good, high-order modulation and high-code rate coding can be used to increase the data transmission rate; when the channel quality is poor, low-order modulation and low-code rate coding are required to ensure the reliability of data transmission. Channel quality is represented by CQI. The larger the CQI, the better the channel quality. The calculation formula is as follows:

[0095] CQI = 40 + 4 SINR (1)

[0096] C / (N0+I0)=SINR+10log 10 R s (2)

[0097] Among them, SINR represents the ratio of signal to interference plus noise level, N0 represents the received signal level, I0 represents the interference signal level, R s Indicates the symbol rate.

[0098] The workflow of ACM is as follows:

[0099] (1) System operation: The receiver feeds back the current channel status information to the transmitter so that the transmitter can adjust its own communication mode.

[0100] (2) Calculate the CQI value. Obtain the link signal-to-interference-and-noise ratio during data transmission, and obtain the CQI value of the channel according to calculation formulas (1) and (2).

[0101] (3) Link ID selection. First, the CQI is compared with the interval value corresponding to the nth type (the Link ID corresponding to the best channel condition). If its value is exactly within the interval, the nth Link ID is selected; if its CQI value is not within the interval of the nth group, it is compared with the interval value of the n-1 group until a suitable Link ID is found.

[0102] (4) If the interval corresponding to the CQI value of the current channel is group 0, the terminal interrupts the communication transmission.

[0103] In one embodiment of the present invention, the decision variables of the satellite time slot resource allocation optimization model include:

[0104] Effective service decision variables: y u Indicates whether data packet u is a valid service;

[0105] Decision variables related to Link ID, channel and DC channel selection: z u，c，l Indicates whether data packet u uses Link ID l service on DC channel c; u，c，f Indicates whether data packet u occupies channel f on DC channel c.

[0106] Step 102, analyzing the relationship between the effective service decision variables of the data packet and the decision variables related to the time slot resource allocation during the data packet transmission process, and constructing the association constraints between the decision variables related to the Link ID, channel and DC channel selection during the data packet transmission process.

[0107] In one embodiment of the present invention, the specific process is:

[0108] (1) Link ID selection constraints:

[0109] Under the premise of following the above-mentioned ACM mechanism, according to the requirements of Recommendation ITU-R M.2092-1, the CQI value used by data packet u when selecting Link ID is the channel quality average of one TDMA subframe, that is, 6 consecutive DC channels, as shown in formula (3); at the same time, the CQI value of the selected Link ID should not be greater than the CQI value calculated by the link, as shown in formula (4). The allocated Link ID must meet the channel bandwidth constraint, that is, the bandwidth required for the Link ID used on the channel should be less than or equal to the channel bandwidth (Formula 5). In addition, since different DC channels occupy different numbers of time slots, and the Link ID can be triggered multiple times on a DC channel, the Link ID selection must meet the requirement that the number of time slots triggered once is less than or equal to the number of time slots of the DC channel (Formula 6). The above can be expressed as:

[0110]

[0111]

[0112]

[0113] Among them, CQI u，c represents the CQI mean of data packet u in a TDMA subframe; CQI(u,c) represents the channel quality of data packet u on DC channel c; bw l and BW f Respectively represent the bandwidth of Link ID l and channel f; t c Indicates the number of time slots occupied by DC channel c; Indicates the number of time slots in a burst of Link ID 1.

[0114] (2) Channel selection constraints:

[0115] VDE-SAT's access technology uses MF-TDMA multiple access, which means that multiple data packets can be accessed at the same time (DC channel), that is, multiple channels can be used simultaneously, but the channels used by these data packets must not overlap in frequency. Considering the channel settings recommended in Recommendation ITU-R M.2092-1, the channel matrix F is constructed. f，j , if F f，j =1 indicates that channel f occupies carrier j; otherwise, F f，j = 0. Therefore, the frequency non-overlap constraint is expressed as follows:

[0116]

[0117] Among them, F f represents the carrier occupied by channel f; E represents a 1×|J| all-1 matrix.

[0118] Step 103: Analyze the relationship between data packet transmission and effective service decision variables, and construct nonlinear association constraints among Link ID, channel selection and effective service decision variables.

[0119] In one embodiment of the present invention, the specific process is:

[0120] Considering that during the data transmission process, the amount of remaining data to be transmitted changes as the data is transmitted in each TDMA subframe. Definition Indicates the maximum amount of data that can be transmitted by data packet u in a DC channel c using Link IDl. If data packet u is a valid service, that is, y u =1, the data packet transmission process occupies at least one DC channel and uses Link ID and channel for transmission; at the same time, the data packet transmission is completed within a one-minute scheduling cycle. If data packet u is an invalid service, that is, y u = 0, there are two situations: one is that data packet u has not started to be transmitted; the other is that data packet u has not been transmitted. Therefore, the following constraints can be constructed:

[0121]

[0122] in, Indicates the number of bytes transmitted in one burst time slot of Link ID 1; Indicates the maximum number of times Link ID l is triggered on DC channel c. Indicates rounding down, d u represents the amount of data in data packet u. u，c，l ,y u All of them are decision variables, which leads to the above four equations are all nonlinear constraints. For the convenience of solving, they can be converted into linear constraints by the following method:

[0123]

[0124] Where M represents a very large positive integer.

[0125] Step 104, analyzing the relationship between the resource allocation scheme and the packet transmission optimization goal, and constructing a downlink satellite resource optimization scheduling model for VDE-SAT with the goals of system throughput, bandwidth resource utilization and service reception rate.

[0126] In one embodiment of the present invention, the decision variables of the satellite resource optimization scheduling model include effective service decision variables, Link ID selection decision variables, channel selection decision variables, and DC channel selection decision variables.

[0127] The goal of satellite resource allocation optimization is to maximize the satisfaction of resource requests / data packet services while maintaining a certain degree of fairness among all users (data packets). Ensuring user satisfaction is also an important goal of optimization. Therefore, system throughput, bandwidth utilization and service reception rate are important indicators for evaluating satellite resource allocation schemes. The optimization goals of the downlink satellite resource allocation optimization model for VDE-SAT constructed by the present invention are:

[0128] (1) Throughput is an important indicator for measuring the performance of a communication system. The value depends on the allocation of time slot resources. If data packet u is effectively served during the scheduling period, the amount of data transmitted by data packet u is d u ; otherwise the amount of data transferred is calculated as Therefore, the total throughput TC of the system is:

[0129]

[0130] (2) The system bandwidth resource utilization reflects the use of frequency resources and, to a certain extent, the quality of channel division. It can be expressed as:

[0131]

[0132] Among them, |U| represents the number of data packets, B w Indicates the total system bandwidth.

[0133] (3) The service reception rate shows the satisfaction of the receiving end with receiving data from another aspect. It is the ratio of the actual transmission service data volume to the data packet. This value reflects whether the allocation method can meet the transmission requirements of each data packet. The range is between 0 and 1. The larger the value, the more data packets can meet its transmission requirements. It can be expressed as:

[0134]

[0135] The downlink satellite resource allocation optimization model for VDE-SAT constructed by the present invention is:

[0136]

[0137] Among them, TC is the total system throughput; R B is the system bandwidth resource utilization; R R is the service receiving rate; ω T ,ω B and ω R are the weight coefficients of the corresponding targets respectively.

[0138] In one embodiment of the present invention, an optimization analysis process may also be included. The relationship between the decision variables and the target in the constructed model is analyzed, and the model is optimized. The model of the present invention can be regarded as a variant model of the packing problem, which is obviously an NP-hard problem. Next, the NP-hard property of the model of the present invention is derived and proved.

[0139] First, the set cover problem can be described as follows: In the set N = {n1, n2, ..., n I} and its subset V = {v1, v2, ..., v s}, a subset of V corresponds to a weight ε m The goal of the set covering problem is to find a set of subsets of the whole set N, so that the union of these subsets is equal to the whole set N and the total weight is the largest or smallest.

[0140] Next, the following settings need to be made when reducing the set coverage problem to a satellite time slot resource scheduling problem:

[0141] (1) The full set N corresponds to the allocation set of the system in a scheduling period, i.e., a frame;

[0142] (2) The subset V = {v1, v2, ..., v2} consists of the time slot allocation schemes of each data packet, for example, v1 = {A 1，c，l，f ={y1, z 1，c，l , δ 1，c，f}={1,(z 1，0，0 , z 1，1，0 ), (δ 1，0，3 , δ 1，1，2 )} indicates that data packet 1 is effectively served, and DC channel 0 and DC channel 1 are allocated in sequence during the data transmission process, and Link ID 0 is used on DC channel 0 and channel 3 is occupied, and Link ID 0 is used on DC channel 1 and channel 2 is occupied.

[0143] (3) Each v nThe improvement of the updated objective function value after allocation is regarded as the weight of its corresponding subset. From the above reduced set cover problem, we can see that y u 、z u，c，l and δ u，c，f represents the allocation of user services and satellite resources, then each allocation scheme in the set V can be represented by the set {A 1，c，l，f , A 2，c，l，f , ..., A |U|，c，l，f}, and based on formula (19) we get A u，c，l，f The corresponding weight value. The modeling problem in this paper can be transformed into selecting a set of subsets And it satisfies v1∪v2∪...∪v s =N makes the total objective function value maximum.

[0144] For the above problem, in the scenario of |U| data packets to be transmitted, |L| Link IDs, |F| channels, and |C| DC channels, there are a total of |U|·|L|·|F|·|C| resource allocation schemes. Therefore, it can be seen that the time complexity of solving this type of problem is O(|U| 4 ). As the number of terminal requests increases, the number of carrier channels and time slot resources increases, the scale of the problem increases accordingly, and the search space of the combinatorial optimization problem also expands dramatically.

[0145] The following Tables 1 and 2 show the correspondence of satellite link resources after specific optimization scheduling.

[0146] Table 1 Link ID working mode

[0147]

[0148] Table 2 Downlink channel division

[0149]

[0150] In the scheme proposed by the present invention, effective service decision variables of data packets and decision variables related to link ID, channel and DC channel selection are introduced into the satellite resource optimization scheduling model; the relationship between effective service decision variables of data packets and decision variables related to time slot resource allocation in the data packet transmission process is analyzed, and the association constraints between decision variables related to Link ID, channel and DC channel selection in the data packet transmission process are constructed; the relationship between data packet transmission and effective service decision variables is analyzed, and nonlinear association constraints between Link ID, channel selection and effective service decision variables are constructed; the connection between resource allocation scheme and data packet transmission optimization target is analyzed, and a downlink satellite resource optimization scheduling model for VDE-SAT is constructed with system throughput, bandwidth resource utilization and service reception rate as the targets. A downlink satellite time slot resource intelligent scheduling scheme for VDE-SAT is proposed, and the characteristics of the VDES system are considered to establish a downlink satellite time slot resource allocation optimization model for VDE-SAT, optimize the Link ID, channel and DC channel allocation method of the downlink complete data packet, and improve the rationality of the allocation scheme.

[0151] In order to implement the above process, the technical solution of the present invention also provides a downlink satellite resource scheduling system, such as Figure 2 As shown, the downlink satellite resource scheduling system includes:

[0152] A decision variable selection unit 21 is used to introduce a data packet effective service decision variable and decision variables related to link ID, channel and DC channel selection in the satellite resource optimization scheduling model;

[0153] A decision variable constraint unit 22, used to analyze the relationship between the decision variables for effective service of data packets and the decision variables related to time slot resource allocation during data packet transmission, and to construct association constraints between the decision variables related to Link ID, channel and DC channel selection during data packet transmission;

[0154] A nonlinear constraint unit 23, used to analyze the relationship between data packet transmission and effective service decision variables, and to construct nonlinear association constraints between Link ID, channel selection and effective service decision variables;

[0155] The model building unit 24 is used to analyze the relationship between the resource allocation scheme and the data packet transmission optimization target, and to build a downlink satellite resource optimization scheduling model for VDE-SAT with the targets of system throughput, bandwidth resource utilization and service reception rate; the decision variables of the satellite resource optimization scheduling model include effective service decision variables, Link ID selection decision variables, channel selection decision variables, and DC channel selection decision variables.

[0156] The system further comprises:

[0157] The model optimization unit 25 is used to analyze the relationship between the decision variables and the objectives in the constructed satellite resource optimization scheduling model, and to optimize the model.

[0158] In summary, the technical solution of the present invention proposes a downlink satellite resource scheduling scheme, introduces data packet effective service decision variables and decision variables related to link identification Link ID, channel and DC channel selection into the satellite resource optimization scheduling model; analyzes the relationship between the data packet effective service decision variables and the decision variables related to time slot resource allocation during data packet transmission, and constructs the association constraints between the decision variables related to Link ID, channel and DC channel selection during data packet transmission; analyzes the relationship between data packet transmission and effective service decision variables, and constructs nonlinear association constraints between Link ID, channel selection and effective service decision variables; analyzes the connection between the resource allocation scheme and the data packet transmission optimization goal, and constructs a downlink satellite resource optimization scheduling model for VDE-SAT with system throughput, bandwidth resource utilization and service reception rate as the goals.

[0159] The technical solution of the present invention realizes the accurate model representation of the satellite resource allocation method of the VDE-SAT system, analyzes the principle of resource scheduling, and has the following advantages:

[0160] Starting from the traditional MF-TDMA channel model and combining the technical characteristics of the VDE-SAT system, the satellite resource optimization problem of the VDE-SAT system is studied for the first time, and a satellite resource intelligent scheduling optimization model for the VDE-SAT system is constructed. The constructed model is accurate, simple in form, and has good expansion space to meet some more complex practical applications.

[0161] From the perspective of system optimization, the system throughput, bandwidth utilization and service reception rate are targeted, while the selection of Link ID, the use of channel and time slot resources are optimized. The restrictions and conflict constraints encountered in the resource scheduling process are described in detail and mathematical models are developed to maximize the utilization of satellite resources.

[0162] Those skilled in the art will appreciate that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage and optical storage, etc.) containing computer-usable program code.

[0163] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0164] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0165] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0166] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A downlink satellite resource scheduling method, characterized in that: The following steps are involved: Step 1: Introduce data packet effective service decision variables and decision variables related to link ID, channel and DC channel selection into the satellite resource optimization scheduling model; Step 2: Analyze the relationship between the decision variables of effective service of data packets and the decision variables related to time slot resource allocation during data packet transmission, and construct the association constraints between the decision variables related to Link ID, channel and DC channel selection during data packet transmission; Step 3: Analyze the relationship between data packet transmission and effective service decision variables, and construct nonlinear association constraints between Link ID, channel selection and effective service decision variables; Step 4: Analyze the relationship between the resource allocation scheme and the data packet transmission optimization goal, and construct a downlink satellite resource optimization scheduling model for VDE-SAT with the goals of system throughput, bandwidth resource utilization and service reception rate; the decision variables of the satellite resource optimization scheduling model include effective service decision variables, Link ID selection decision variables, channel selection decision variables, and DC channel selection decision variables.

2. A downlink satellite resource scheduling method according to claim 1, characterized in that: The step 1 specifically includes: Effective service decision variables: y u Indicates whether the data packet u is a valid service; Decision variables related to Link ID, channel and DC channel selection: z u，c，l Indicates whether data packet u uses Link ID l service on DC channel c; u，c，f Indicates whether data packet u occupies channel f on DC channel c.

3. A downlink satellite resource scheduling method according to claim 1 or 2, characterized in that: The step 2 specifically includes: Link ID selection constraint: The channel quality CQI value based on which the data packet u selects the Link ID is the average of the channel quality of 6 consecutive DC channels in a TDMA subframe; the CQI value of the selected Link ID should not be greater than the CQI value calculated by the link; The allocated Link ID meets the channel bandwidth constraint, that is, the bandwidth required by the Link ID used on the channel should be less than or equal to the channel bandwidth; Link ID selection satisfies the requirement that the number of time slots for a trigger is less than or equal to the number of time slots of the DC channel; the specific expression is: Among them, CQI u，c represents the CQI mean of data packet u in a TDMA subframe; CQI(u,c) represents the channel quality of data packet u on DC channel c; bw l and BW f denote Link ID1 and the bandwidth of channel f respectively; t c Indicates the number of time slots occupied by DC channel c; Indicates the number of time slots of a burst of Link ID1; Channel selection constraints: The access technology uses MF-TDMA multiple access mode. At the same time, the DC channel can access multiple data packets for transmission, allowing multiple channels to be used simultaneously, but the channels used by these data packets must not overlap in frequency. Construct the channel matrix F f，j , if F f，j =1 indicates that channel f occupies carrier j; otherwise, F f，j =0; The frequency non-overlap constraint is stated as follows: Among them, F f represents the carrier occupied by channel f; E represents a 1×|J| all-1 matrix.

4. A downlink satellite resource scheduling method according to claim 1 or 3, characterized in that: The step three specifically includes: definition Indicates the maximum amount of data that can be transmitted by data packet u in a DC channel c using Link ID l; if data packet u is a valid service, that is, y u =1, the data packet transmission process occupies at least one DC channel and uses Link ID and channel for transmission; the data packet transmission is completed within a one-minute scheduling cycle; if data packet u is an invalid service, that is, y u =0, there are two situations: one is that data packet u has not started to be transmitted; the other is that the transmission of data packet u has not been completed; Construct the following constraints: in, Indicates the number of bytes transmitted in a burst time slot of Link ID1; Indicates the maximum number of times Link ID l is triggered on DC channel c. Indicates rounding down, d u Indicates the data volume of data packet u; Because z u，c，l ,y u All of them are decision variables, which leads to the above four formulas are all nonlinear constraints. To facilitate the solution, they are converted into linear constraints by the following method: Where M represents a very large positive integer.

5. A downlink satellite resource scheduling method according to claim 1 or 4, characterized in that: The step 4 specifically includes: If data packet u is a valid service within the scheduling period, the transmission data volume of data packet u is d u ; Otherwise, the amount of data transferred is calculated as The total throughput TC of the system is: The system bandwidth resource utilization is expressed as: Among them, |U| represents the number of data packets, B w Indicates the total system bandwidth; The service reception rate is expressed as: The downlink satellite resource allocation optimization model for VDE-SAT is: Among them, TC is the total system throughput; R B is the system bandwidth resource utilization; R R is the service receiving rate; ω T ,ω B and ω R are the weight coefficients of the corresponding targets respectively.

6. A downlink satellite resource scheduling method according to claim 1, characterized in that: The method further comprises: Step five: Analyze the relationship between decision variables and objectives in the constructed satellite resource optimization scheduling model, and optimize the model.

7. A downlink satellite resource scheduling method according to claim 6, characterized in that: The step five specifically includes: The satellite resource optimization scheduling model is regarded as a packing problem and described by a set covering problem; In the full set N = {n1, n2, ..., n I } and its subset V = {v1, v2, ..., v s }, a subset of V corresponds to a weight ε m ,The goal of the set covering problem is to find a set of subsets of the whole set N, so that the union of these subsets is equal to the whole set N and the total weight is the largest or smallest; The set coverage problem is reduced to the satellite time slot resource scheduling problem, and the following settings are made: The full set N corresponds to the allocation set of the system in a scheduling period, i.e., a frame; The subset V = {v1, v2, ..., v2} consists of the time slot allocation schemes of each data packet; Each v n The improvement in the updated objective function value after allocation is regarded as the weight of its corresponding subset; From the reduced set cover problem, we know that y u 、z u，c，l and δ u，c，f represents the allocation of user services and satellite resources, then each allocation scheme in the set V can be represented by the set {A 1，c，l，f , A 2，c，l，f , ..., A |U|，c，l，f }, get A u，c，l，f The corresponding weight value; The problem of the satellite resource optimization scheduling model is transformed into selecting a set of subsets And it satisfies v1∪v2∪...∪v s =N makes the total objective function value maximum; In the scenario where |U| data packets to be transmitted, |L| Link IDs, |F| channels, and |C| DC channels, there are a total of |U|·|L|·|F|·|C| resource allocation schemes, and the solution time complexity is O(|U| 4 ); With the increase of terminal requests, the number of carrier channels and time slot resources increases, the scale of the problem increases accordingly, the search space of the combinatorial optimization problem also expands dramatically, and the model is optimized.

8. A downlink satellite resource scheduling method according to claim 1, characterized in that: Prior to the method, the method further includes: Define the set of data packets to be transmitted in the network as U, the set of Link ID working modes as L, and the total system bandwidth as B w , a total of |J| carriers are divided; Multiple continuous carriers can form different channels, and the channel division method set is F; One frame is divided into three TDMA subframes, each subframe is divided into six DC channels, and the number of time slots contained in the DC channel is 30 or 60; The satellite time slot resource scheduling period is one frame, so there are 18 DC channels in the scheduling period, and the DC channel set is defined as C; Define the Link ID selection mechanism; the channel quality is represented by CQI. The larger the CQI, the better the channel quality. The calculation formula is as follows: CQI=40+4·SINR C / (N0+I0)=SINR+10log 10 R s Among them, SINR represents the ratio of signal to interference plus noise level, N0 represents the received signal level, I0 represents the interference signal level, R s Indicates the symbol rate; The workflow of ACM is as follows: The system runs; the receiving end feeds back the current channel status information to the transmitting end so that the transmitting end can adjust its own communication mode; Calculate the CQI value, obtain the link signal to interference and noise ratio during data transmission, and obtain the CQI value of the channel according to the above formula; Link ID selection: compare the CQI with the interval value corresponding to the nth type. If its value is exactly within the interval, the nth Link ID is selected; if its CQI value is not within the interval of the nth group, it is compared with the interval value of the n-1 group until a suitable Link ID is found; If the interval corresponding to the CQI value of the current channel is group 0, the terminal interrupts the communication transmission.

9. A downlink satellite resource scheduling system, characterized in that: include: A decision variable selection unit, used for introducing a data packet effective service decision variable and decision variables related to link ID, channel and DC channel selection in a satellite resource optimization scheduling model; A decision variable constraint unit is used to analyze the relationship between the decision variables of effective service of data packets and the decision variables related to time slot resource allocation during data packet transmission, and to construct the association constraints between the decision variables related to Link ID, channel and DC channel selection during data packet transmission; A nonlinear constraint unit is used to analyze the relationship between data packet transmission and effective service decision variables, and to construct nonlinear association constraints between LinkID, channel selection and effective service decision variables; The model building unit is used to analyze the relationship between the resource allocation scheme and the data packet transmission optimization target, and to build a downlink satellite resource optimization scheduling model for VDE-SAT with the targets of system throughput, bandwidth resource utilization and service reception rate; the decision variables of the satellite resource optimization scheduling model include effective service decision variables, Link ID selection decision variables, channel selection decision variables and DC channel selection decision variables.

10. A downlink satellite resource scheduling system according to claim 9, characterized in that: The system further comprises: The model optimization unit is used to analyze the relationship between decision variables and objectives in the constructed satellite resource optimization scheduling model and to optimize the model.

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