TDD-based low-orbit satellite communication system time slot resource allocation method

Abstract

The invention provides a time slot resource allocation method for a low-orbit satellite communication system based on TDD (Time Division Duplex), which adopts a flexible on-demand frame structure, schedules uplink and downlink time slots of a terminal by a satellite on demand, and ensures that no interference is generated among the time slots allocated to the terminal when the satellite schedules. According to the invention, for a random access process, an RO allocation problem considering a resource utilization rate is constructed and the optimal RO configuration is solved; for a data transmission process, time slot resource allocation optimization problems oriented to a single-satellite system and a multi-satellite system are respectively established so as to maximize a system resource utilization rate, auxiliary variables are introduced to convert non-interference constraints, and finally an optimal allocation result of time slot resources is obtained. According to the invention, uplink and downlink transmission is flexibly scheduled to avoid interference, a long guard interval does not need to be set, the utilization rate of system resources can be fully improved, and a feasible solution is provided for application of TDD in a low-orbit satellite communication system.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of satellite communication, and particularly relates to a time slot resource allocation method for a low-orbit satellite communication system based on TDD. BACKGROUND

[0002] Low-orbit satellite communication systems have become an important supplement to ground networks and are regarded as one of the key enabling technologies for 6G due to their shorter propagation delay and larger capacity. Time division duplexing (TDD) mode can flexibly support asymmetric services and help reduce satellite load and power consumption due to its simple radio frequency circuit and low cost, thus having broad application prospects in future satellite communication systems. However, due to the differences between satellite channel conditions and the ground, direct application of TDD in low-orbit satellite communication systems will cause serious uplink and downlink interference and resource utilization rate reduction.

[0003] In a TDD system, uplink and downlink transmissions use the same frequency resources, and bidirectional communication is achieved through time division. To avoid uplink and downlink interference, a guard interval of no less than the maximum round-trip delay in the system is set in the TDD frame structure of the base station. In the low-orbit satellite scenario, the propagation delay is significantly increased, and a long guard interval will cause serious resource waste. Most existing researches improve resource utilization by extending the frame period, but the improvement effect brought by this method is limited, and it is difficult to achieve high resource utilization while ensuring system interference-free. SUMMARY

[0004] The purpose of the present application is to provide a time slot resource allocation method for a low-orbit satellite communication system based on TDD, which can significantly improve the resource utilization of the system when the number of users is large.

[0005] Technical scheme: To achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0006] In the first aspect, the present application provides a time slot resource allocation method for a low-orbit satellite communication system based on TDD. For the RO allocation problem in the access process, a flexible on-demand frame structure is adopted, and the uplink and downlink time slots of the terminal are scheduled by the satellite on demand. The satellite ensures that there is no interference between the time slots allocated to the terminal during scheduling. The RO allocation includes the following steps:

[0007] The transmission intervals of RO and various system broadcast signals in the base station side during synchronization and access are analyzed, and the transmission intervals of the base station side are mapped to the user side according to the propagation delay range of each wave position, to obtain the interference-free constraint conditions of RO and various system broadcast signals.

[0008] Construct a RO allocation optimization problem that considers resource utilization. The optimization objective is to maximize the average RO utilization of all beams. Constraints include: effective ROs do not interfere with broadcast signals of various systems; effective ROs under a beam are available for each beam position; each beam has at least one effective RO; and effective ROs are restricted to be located within the uplink time slot of the base station.

[0009] Traverse the candidate RO configuration set, solve the optimization problem, obtain the optimal RO utilization rate and the corresponding optimal configuration set, as well as the effective RO indicator vector of each beam under the optimal configuration.

[0010] Furthermore, the step of traversing the candidate RO configuration set to solve the optimization problem includes:

[0011] In a given candidate RO configuration The minimum common period of various signals is determined, and the RO transmission interval set is constructed.

[0012] For each beam, an effective RO (Resource Optimizer) that does not interfere with the downlink signal is identified, and the average RO utilization of all beams under that candidate RO configuration is obtained; where, for each beam Each wave position Based on the propagation delay range, it is determined whether the RO interferes with various system broadcast signals in turn, and the waveform is obtained. Effective RO transmission interval set Thus, the beam is obtained. Effective RO transmission interval set ;like Discard configuration Set the average RO utilization rate to 0; otherwise, obtain the configuration. Average RO utilization rate ;in, For satellite beam sets; For beam The set of wave positions served For the number of beams, Configure the base station in RO The set of RO intervals below, Describes the cardinality of a set;

[0013] Compare all candidate RO configurations and select the configuration with the highest utilization.

[0014] Secondly, the present invention provides a time slot resource allocation method for a low-Earth orbit satellite communication system based on TDD. Addressing the transmission resource allocation problem of a single-satellite system, it adopts a flexible, on-demand frame structure. The uplink and downlink time slots of the terminal are scheduled by the satellite on demand, and the satellite ensures that no interference occurs between time slots allocated to the terminal during scheduling. The transmission resource allocation includes the following steps:

[0015] Based on the user's propagation delay, the time intervals for receiving downlink signals from the base station and sending uplink signals to the base station are obtained. By ensuring that these two intervals do not overlap, the constraint condition of no interference between the uplink and downlink time slots allocated to the user is obtained.

[0016] This paper proposes an optimization problem for time slot allocation in a single-satellite system. The optimization objective is to maximize the number of allocated time slots within a given scheduling period. ;in, Indicates the first Is the first time slot allocated to the first... For each user, 1 indicates allocation and 0 indicates no allocation; constraints include: each time slot can be allocated to at most one user, the number of downlink and uplink time slots required for each user's allocation, and there is no interference between the uplink and downlink time slots allocated to each user.

[0017] By introducing auxiliary variables to transform the uplink and downlink interference-free constraints, the original optimization problem is transformed into an integer programming form;

[0018] The optimization problem after transformation is solved to obtain the user's time slot allocation result.

[0019] Furthermore, the constraint condition for no interference between uplink and downlink time slots is as follows: ;in, The downlink time slot number within the scheduling period. This is the uplink timeslot number. For users' satellite-to-ground propagation latency, The corresponding parameter is the subcarrier spacing.

[0020] Furthermore, by multiplying the inequality on the left... The restriction applies if and only if and That is, the base station allocates the corresponding time slot to the user. This constraint is only satisfied within the allocated time slots; otherwise, the constraint always holds. The introduction of auxiliary variables transforms the uplink / downlink interference-free constraint, and the transformed constraints include:

[0021]

[0022]

[0023] in, For the first Propagation delay per user, For the set of downlink time slot numbers, For the set of uplink timeslot numbers, For the set of user IDs, Auxiliary variables of 0-1 It is a preset positive number.

[0024] Thirdly, the present invention provides a time slot resource allocation method for a low-Earth orbit satellite communication system based on TDD. Addressing the transmission resource allocation problem in multi-satellite systems, it adopts a flexible, on-demand frame structure. The uplink and downlink time slots of the terminal are scheduled by the satellite on demand, and the satellite ensures that no interference occurs between time slots allocated to the terminal during scheduling. The transmission resource allocation includes the following steps:

[0025] Based on the allocated time slot number and the user's propagation delay, the interference-free constraint condition for the multi-star system is obtained by ensuring that the time intervals of the signals that will cause interference do not overlap.

[0026] The optimization problem of time slot allocation in a multi-satellite system is proposed, with the objective of maximizing the number of allocated time slots within a given scheduling period for all satellites. ;in, Indicates the first Will the first satellite be the first? The time slot is allocated to the first For each user, 1 indicates allocation, and 0 indicates no allocation; constraints include: each user can only communicate with one satellite, users can only communicate with a satellite within its coverage area, the satellite that allocates time slots to users is the same satellite that users choose to communicate with, each satellite can allocate at most one time slot, each user is allocated the required number of downlink and uplink time slots, there is no interference between the uplink and downlink time slots allocated to each user, and there is no interference between downlink signals and between uplink signals in the time slots allocated to users;

[0027] By introducing auxiliary variables to transform the unobstructed constraints, the original optimization problem is transformed into an integer programming form;

[0028] The transformed optimization problem is solved to obtain the user's time slot allocation results and the communication relationship between the user and the satellite.

[0029] Furthermore, the interference constraints between downlink signals in a multi-satellite system are as follows: ,in and Number the satellite. For the satellite and satellite User ID within the overlapping coverage area For satellite Assigned to user downlink slot number, For satellite Downlink time slot numbers assigned to other users For satellite With users The propagation delay between satellites and the ground is the satellite number, is the start time slot time in the scheduling period relative to the satellite is the value of the delay, is the corresponding parameter for the subcarrier spacing; the interference constraint condition between the uplink signals of the multi-satellite system is wherein is the satellite number, is the uplink time slot number allocated to the user , is the satellite number, is the uplink time slot number allocated to other users.

[0030] Further, an auxiliary variable is introduced to convert the non-interference constraint, and the converted non-interference constraint includes:

[0031]

[0032] wherein, is the satellite number, is the satellite-ground propagation delay between the satellite and the user , represents whether the user is located in the coverage range of the satellite , 1 represents being located in the coverage area, and 0 represents not being located, is the downlink time slot number set of the satellite , is the uplink time slot number set of the satellite , is the satellite number, is the user number set, , is a 0-1 auxiliary variable, is a preset positive number.

[0033] Further, for a single-satellite system, if a feasible solution cannot be obtained, the scheduling period expansion solution space is increased, the downlink time slot number set and the uplink time slot number set are recalculated, and a new optimization problem is solved; for a multi-satellite system, if a feasible solution cannot be obtained, the scheduling period of the satellite is sequentially increased, the downlink time slot number set and the uplink time slot number set of each satellite are recalculated, and a new optimization problem is solved.

[0034] The application also provides a computer system, including a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the computer program is executed by the processor to realize the steps of the TDD-based low-orbit satellite communication system time slot resource allocation method.

[0035] Beneficial effects: The TDD-based low-orbit satellite communication system time slot resource allocation method provided by the application derives the interference constraint and establishes a corresponding resource allocation optimization problem, so as to realize reasonable allocation of system access resources and transmission resources. Compared with the prior art, the method avoids interference by flexible scheduling of uplink and downlink transmission, does not need to set a long guard interval, and can fully improve the resource utilization rate of the system. BRIEF DESCRIPTION OF DRAWINGS

[0036] Figure 1 It is a flexible on-demand frame structure diagram.

[0037] Figure 2 It is a system schematic diagram of the access process in the beam hopping scenario.

[0038] Figure 3 It is an effective RO schematic diagram without interference with SSB.

[0039] Figure 4 It is a RO allocation problem solving flowchart.

[0040] Figure 5 It is a single-satellite multi-user scenario schematic diagram.

[0041] Figure 6 It is a multi-satellite multi-user scenario schematic diagram. DETAILED DESCRIPTION

[0042] The application will be further described below in combination with the drawings and specific embodiments, which are only used to illustrate the application and are not a limitation on the protection scope of the application.

[0043] The application provides a TDD-based low-orbit satellite communication system time slot resource allocation method, which adopts a flexible on-demand frame structure, as shown in the figure. Figure 1 The uplink and downlink time slots of the terminal are scheduled by the satellite on demand and are not limited by the 5G frame structure, so the base station side does not need to set a guard interval. The satellite needs to ensure that there is no interference between the time slots allocated to the terminal when scheduling, so as to improve the resource utilization rate and ensure the reliability of the system. If the base station allocates the second downlink time slot and the first uplink time slot to UE1 at the same time, the uplink and downlink signals of UE1 will overlap, thereby causing interference, so the base station can select to allocate the first uplink time slot to UE2. By optimizing the time slot allocation scheme, the resource utilization rate of the system is improved without causing interference.

[0044] The TDD-based low-orbit satellite communication system time slot resource allocation method provided by the embodiment of the application includes the following steps for the RO allocation problem of the access process:

[0045] transmission intervals of RO and various system broadcast signals in the base station side during the synchronization and access processes are analyzed, and the transmission intervals of the base station side are mapped to the user side according to the propagation delay range of each beam position, to obtain the non-interference constraint conditions of RO and various system broadcast signals;

[0046] An RO allocation optimization problem considering resource utilization is constructed, and the optimization objective is to maximize the average RO utilization rate of all beams, and the constraints include: the effective RO does not interfere with various system broadcast signals, the effective RO under each beam is available for each beam position, and there is at least one effective RO for each beam, and the effective RO is limited to be located in the uplink time slot of the base station;

[0047] The candidate RO configuration set is traversed to solve the optimization problem, to obtain the optimal RO utilization rate and the corresponding optimal configuration set, and the effective RO indication vector of each beam under the optimal configuration.

[0048] The RO allocation of the access process will be described in detail in combination with a specific scenario.

[0049] Figure 2 The system diagram for the access process is shown in the following figure. A low-orbit satellite communication system working in TDD mode is considered, and the satellite can simultaneously transmit beams to light up beam positions in turn, and the corresponding beam set is denoted as Each beam includes SSBs in the SSB burst, and the corresponding beam position set is denoted as Therefore, is obtained. Denote the beam serving the beam position as , and the time delay range of can be determined by the satellite coordinates, beam position center coordinates, and beam position radius. In the TDD mode, the terminal cannot transmit and receive at the same time, so the uplink and downlink time slots allocated to the terminal cannot overlap in the time domain. Therefore, in the access process, the effective RO should not only be located in the uplink time slot, but also avoid interfering with various system broadcast signals, for example, according to the 3GPP protocol, the RO needs to avoid interfering with SSB, SIB1, and SIB19, and the non-interference condition of SSB and RO is shown in Figure 3 . Since various signals are periodically configured, and the behavior in different periods is repeated, it is only necessary to analyze the minimum common period of the above signals analyzing their interference relationship in time domain. In the period, the validity of the RO is determined, and the determination result is repeated along the period. The allocation method for the RO includes the following steps:

[0050] Let the starting time of base station frame 0 be Due to the influence of propagation delay, for the RO in The downlink signal that may interfere with it comes from the interval .

[0051] S11: Calculate the SSB transmission interval

[0052] In , the frame number and slot number of the SSB numbered and , the corresponding transmission interval is recorded as , where is the subcarrier spacing parameter, is the length of each radio frame. Therefore, the SSB transmission interval set of wave bit can be expressed as

[0053]

[0054] where is the number of SSB burst set repetitions in , and ensures coverage of all SSBs in . On the user side, these transmission intervals need to consider the propagation delay, which can be expressed as

[0055]

[0056] S12: Calculate the SIB1 transmission interval

[0057] In , the frame number and slot number of the SSB corresponding SIB1 are and , and its transmission interval is recorded as . Therefore, the SIB1 transmission interval set of wave bit can be expressed as

[0058]

[0059] where is the number of SIB1 repetitions in , and ensures coverage of all SIB1s in . On the user side, the transmission interval set of SIB1 can be expressed as

[0060]

[0061] S13: Calculate SIB19 transmission interval

[0062] Let SSBs in SI-window where SIB19 is transmitted The number of corresponding SIB19 transmission opportunities is . The frame number and time slot number of the th transmission opportunity in are and respectively, and the corresponding transmission interval of this SIB19 is . Therefore, the SIB19 transmission interval set of beam can be expressed as

[0063]

[0064] where is the number of SIB19 repetitions in , and ensures that all SIB19s in are covered. On the user side, the SIB19 transmission interval set can be expressed as

[0065]

[0066] S14: Calculate RO transmission interval and derive interference-free condition

[0067] Let the candidate RO configuration set be , where is the number of candidate configurations. For a certain configuration , take format 0 as an example, the frame number and subframe number of the th RO in are and respectively, where , is the number of RO time-domain transmission opportunities in each configuration period. Accordingly, the transmission interval of the th RO is , where is the length of each subframe. Then the RO transmission interval set in is

[0068]

[0069] where is the number of RO configuration repetitions in . On the user side, the RO transmission interval set can be expressed as ​​​​​​

[0070]

[0071] After the transmission interval of each signal is determined, the interference-free condition that the RO configuration needs to meet can be obtained. Let be the set of valid RO transmission intervals on the base station side, and be the set of valid RO transmission intervals on the user side corresponding to should meet

[0072]

[0073] where , output a set whose elements are the intersection of each interval element in and , for example, when and , we get .

[0074] S15: Construct the RO allocation optimization problem, whose optimization objective is to maximize the average RO utilization rate of all beams, expressed as follows:

[0075]

[0076] where ensure that the valid RO does not interfere with SSB, SIB1 or SIB19; denote the valid RO under the beam available for each wave position; ensure that there is at least one valid RO for each beam; limit the valid RO to be located in the uplink time slot of the base station, where is the set of RO transmission intervals in located in the uplink time slot.

[0077] S16: Solve the optimization problem

[0078] Under a given RO configuration, first determine the minimum common period of each type of signal and construct its transmission interval set. Then, for each beam, determine the valid RO that does not interfere with the downlink signal, and obtain the average RO utilization rate of all beams under this configuration. Finally, compare all candidate RO configurations and select the configuration with the highest utilization rate. Figure 4 The flowchart for solving is as follows:

[0079] S161: Parameter initialization

[0080] Determine the scene parameters, including the set of beams , the set of wave positions of each beam and the corresponding propagation delay range. The base station configuration parameters include the configuration of SSB, SIB1, SIB19, and the TDD frame structure of the base station. The candidate RO configuration set is , the optimal configuration set is empty.

[0081] S162: traverse the RO configuration scheme

[0082] 1) calculate the interference judgment period .

[0083] 2) generate the RO transmission interval set , select the interval located in the uplink slot to form the set .

[0084] 3) calculate the average RO utilization rate of all beams . Including:

[0085] 31) traverse the beam

[0086] 32) traverse the wave position

[0087] 321) according to the SSB index corresponding to the wave position, generate the transmission interval set of SSB, SIB1 and SIB19 , and .

[0088] 322) based on the propagation delay range , judge whether the RO interferes with SSB, SIB1 and SIB19 in turn, and obtain the effective RO transmission interval set of the wave position .

[0089] 33) obtain the effective RO transmission interval set of the beam .

[0090] 34) if , discard the configuration, let ; otherwise, obtain the average RO utilization rate of the configuration .

[0091] S163: obtain the optimal RO utilization rate and the corresponding optimal configuration set , and the effective RO indication vector of each beam in under these configurations, that is, the binary vector , A value of 1 indicates that the RO is valid. for Internal configuration The total number of time-domain ROs.

[0092] After determining the optimal RO configuration, the base station can indicate to the user which ROs are valid. During random access, the user can only select these valid ROs to send preamble signals, thereby avoiding interference with signals such as SSB and ensuring that users on all wavelengths can successfully complete access.

[0093] This invention provides a time slot resource allocation method for a low-Earth orbit satellite communication system based on TDD, addressing the transmission resource allocation problem of a single-satellite system, and includes the following steps:

[0094] Based on the user's propagation delay, the time intervals for receiving downlink signals from the base station and sending uplink signals to the base station are obtained. By ensuring that these two intervals do not overlap, the constraint condition of no interference between the uplink and downlink time slots allocated to the user is obtained.

[0095] This paper proposes an optimization problem for time slot allocation in a single-satellite system. The optimization objective is to maximize the number of allocated time slots within a given scheduling period. ;in, Indicates the first Is the first time slot allocated to the first... For each user, 1 indicates allocation and 0 indicates no allocation; constraints include: each time slot can be allocated to at most one user, the number of downlink and uplink time slots required for each user's allocation, and there is no interference between the uplink and downlink time slots allocated to each user.

[0096] By introducing auxiliary variables to transform the uplink and downlink interference-free constraints, the original optimization problem is transformed into an integer programming form;

[0097] The optimization problem after transformation is solved to obtain the user's time slot allocation result.

[0098] The following section provides a detailed explanation of the transmission resource allocation for the single-satellite system using a specific scenario.

[0099] Figure 5 This is a schematic diagram of a single-satellite system. The satellite has base station functionality. The satellite-to-ground propagation delay for an individual user is defined as the one-way delay from signal transmission from the satellite to the user. The total number of users in the system is The user ID set is Assuming the base station knows the uplink and downlink traffic requirements of all users, the first... The number of downlink and uplink time slots required by each user are respectively and In addition, in the case of short scheduling period, the time delay change caused by satellite mobility is not considered. The time slot allocation method for single satellite system includes the following steps:

[0100] S21: Based on the traffic demand of users, the number of scheduling periods of the system is first given The total number of time slots in the scheduling period is The total number of time slots in the scheduling period is The time slots are numbered from 1 to , and the downlink time slot number set is obtained.

[0101] Suppose the base station allocates downlink time slot and uplink time slot to a user, according to the propagation time delay of the user , the time interval for the user to receive the base station downlink signal is , and the time interval for the user to send uplink signal to the base station is , and the two intervals are not overlapped, so that the constraint condition of no interference between the uplink and downlink time slots allocated to the user is obtained .

[0102] S22: Construct the optimization problem of single satellite system time slot allocation, the optimization objective of the optimization problem is to maximize the number of allocated time slots in the scheduling period , wherein indicates whether the th time slot is allocated to the th user, and the expression is as follows:

[0103]

[0104] The optimization problem is expressed as:

[0105]

[0106] , wherein indicates that each time slot is allocated to at most one user; and indicate the number of downlink and uplink time slots required by each user; indicates that there is no interference between the uplink and downlink time slots allocated to each user. In , by multiplying on the left side of the inequality and , that is, when the base station allocates the corresponding time slot to the user , the allocated time slots satisfy this constraint, otherwise the constraint is always true.

[0107] S23: Introducing auxiliary variables transforms the interference-free constraints in the original optimization problem, resulting in the transformed optimization problem:

[0108]

[0109] in, Auxiliary variables of 0-1 It is a sufficiently large positive number. When At that time, the optimization problem satisfies ,and Due to the large The existence of something is always true; when At that time, the optimization problem satisfies , Heng was established.

[0110] S24: Solve the transformed optimization problem to obtain the user's time slot allocation result. If a feasible solution cannot be obtained, the scheduling cycle is increased to expand the solution space, and the set is recalculated. and The new optimization problem is then solved.

[0111] This invention provides a time slot resource allocation method for a low-Earth orbit satellite communication system based on TDD, addressing the transmission resource allocation problem in multi-satellite systems, and includes the following steps:

[0112] Based on the allocated time slot number and the user's propagation delay, the interference-free constraint condition for the multi-star system is obtained by ensuring that the time intervals of the signals that will cause interference do not overlap.

[0113] The optimization problem of time slot allocation in a multi-satellite system is proposed, with the objective of maximizing the number of allocated time slots within a given scheduling period for all satellites. ;in, Indicates the first Will the first satellite be the first? The time slot is allocated to the first For each user, 1 indicates allocation, and 0 indicates no allocation; constraints include: each user can only communicate with one satellite, users can only communicate with a satellite within its coverage area, the satellite that allocates time slots to users is the same satellite that users choose to communicate with, each satellite can allocate at most one time slot, each user is allocated the required number of downlink and uplink time slots, there is no interference between the uplink and downlink time slots allocated to each user, and there is no interference between downlink signals and between uplink signals in the time slots allocated to users;

[0114] By introducing auxiliary variables to transform the unobstructed constraints, the original optimization problem is transformed into an integer programming form;

[0115] The transformed optimization problem is solved to obtain the user's time slot allocation results and the communication relationship between the user and the satellite.

[0116] The following section provides a detailed explanation of the transmission resource allocation of the multi-satellite system using a specific scenario.

[0117] Figure 6 This is a schematic diagram of a multi-satellite system. The total number of satellites in the system is... The satellite number set is The total number of users is The user ID set is Assume that all satellites communicate with users using the same frequency band, and that users located within the overlapping coverage area of ​​multiple satellites can only communicate with one satellite. Among these, the first... The number of downlink and uplink time slots required by each user are respectively and ,satellite With users The propagation delay between satellites and the ground is The time slot allocation method for multi-satellite systems specifically includes the following steps:

[0118] S31: Based on user traffic demands, first specify the data usage of each satellite within the system. Number of scheduling cycles Then the total number of time slots within all satellite scheduling cycles is ,in For satellite The frame period. For each satellite The time slots within the scheduling period are numbered consecutively starting from 1 to obtain the set of downlink time slot numbers. and uplink timeslot number set For all users within the coverage area All users must meet the uplink and downlink interference-free constraints; for users in areas with overlapping coverage by multiple satellites, the following two interference constraints must also be met.

[0119] Interference constraints between downlink signals: Figure 6 In this context, let's define users located within the overlapping coverage area. With satellite To conduct communication. Then the user Not only will it receive from satellites The downlink signal will also receive satellite signals. When downlink signals sent to other users overlap in time, interference occurs. Assume a satellite... Downlink time slot Assigned to user ,satellite Downlink time slot Assigned to other users, and received by users Receive satellite The time interval of the downlink signal is ,user Receive satellite The time interval of the downlink interference signal is ,in For satellite The start time slot time within the scheduling cycle relative to the satellite The value of the delay. Assuming these two intervals do not overlap, the multi-star interference-free constraint condition is obtained as follows: .

[0120] Interference constraints between uplink signals: satellite When receiving uplink signals from other users, it will also receive user signals. Send to satellite If the uplink signals of two satellites overlap in time, interference occurs. Assume the satellite... Uplink time slot Assigned to user ,satellite Uplink time slot Satellites were allocated to other users. Received user The time interval of the uplink interference signal is ,satellite The time interval for receiving uplink signals from other users is Ensuring these two intervals do not overlap, we obtain the multi-star interference-free constraint condition as follows: .

[0121] S32: Construct a multi-satellite system time slot allocation optimization problem. The optimization objective of this problem is to maximize the number of time slots allocated within all satellite scheduling cycles. .in, Indicates the first Will the first satellite be the first? The time slot is allocated to the first For each user, the expression is as follows:

[0122]

[0123] To represent the communication relationship between the satellite and the user, a variable is defined. The expression is as follows:

[0124]

[0125] To represent the coverage relationship between satellites and users, define variables. This value can be calculated in advance using satellite and user coordinates. The expression is as follows:

[0126]

[0127] The optimization problem is represented as:

[0128]

[0129] in, This means that each user can only communicate with one satellite; This means that users can only communicate with the satellite within its coverage area; This indicates that the satellite to which the user is assigned a time slot is the same satellite that the user has selected for communication. This means that each time slot of the satellite can be allocated to at most one user; and This indicates the number of downlink and uplink time slots required for each user; This indicates that there is no interference between the uplink and downlink time slots allocated to each user; and This indicates that the time slots allocated to users do not contain the interference from the two multi-satellite scenarios mentioned in step (1). For interference constraints such as... , Introduction , For sufficiently large positive numbers, the restriction is that if and only if and That is, this constraint is only satisfied when the satellite allocates the corresponding time slot to the user; otherwise, the constraint always holds. Further, a term is introduced... The restriction applies if and only if and That is, users Located in satellite and satellite This constraint is only required when the area is within the overlapping coverage region; otherwise, the constraint always holds.

[0130] S33: Introducing auxiliary variables transforms the interference-free constraints in the original optimization problem, resulting in the transformed optimization problem:

[0131]

[0132] in, , and It is a 0-1 auxiliary variable.

[0133] S34: Solve the transformed optimization problem to obtain the user's time slot allocation result. And the communication relationship between users and satellites. If no feasible solution can be obtained, the scheduling period of the satellite is increased in sequence, and the set is recalculated and The new optimization problem is solved, and if the system resource utilization rate obtained is too low, the scheduling period is reduced.

[0134] The application provides a time slot resource allocation method for a TDD-based low-orbit satellite communication system, adopts a flexible on-demand frame structure design, time slot resources of a terminal can be flexibly scheduled and allocated by a satellite, is not limited by a 5G frame structure, and only needs to meet a derived interference-free constraint, so a guard interval does not need to be arranged in a base station frame structure. The above embodiment constructs a RO allocation problem considering resource utilization for a random access process and solves the problem; for a data transmission process, time slot resource allocation optimization problems for a single-satellite system and a multi-satellite system are respectively established to maximize system resource utilization, auxiliary variables are introduced to convert the interference-free constraint, and finally, an optimal allocation result of the time slot resource is obtained. The method can simultaneously avoid interference and improve system resource utilization, and provides a feasible solution for application of TDD in a low-orbit satellite communication system.

[0135] The embodiment of the application further provides a computer system, including a memory, a processor and a computer program stored on the memory and capable of running on the processor, and the computer program realizes the steps of the time slot resource allocation method for the TDD-based low-orbit satellite communication system according to any one of the preceding embodiments when executed by the processor.

Claims

1. A time slot resource allocation method for a TDD-based low-orbit satellite communication system, aiming at RO allocation problem in an access procedure, characterized in that, The uplink and downlink time slots of the terminal are scheduled by the satellite on demand, and the satellite ensures that no interference occurs between the time slots allocated to the terminal during scheduling; the RO allocation includes the following steps: The transmission intervals of the RO and various types of system broadcast signals at the base station side during synchronization and access are analyzed, and the transmission intervals at the base station side are mapped to the user side according to the propagation delay range of each wave position, to obtain the non-interference constraint conditions of the RO and various types of system broadcast signals; An RO allocation optimization problem considering resource utilization is constructed, the optimization objective is to maximize the average RO utilization of all beams, and the constraints include: the effective RO does not interfere with various types of system broadcast signals, the effective RO under the beam is available for each wave position, there is at least one effective RO for each beam, and the effective RO is limited to be located in the uplink time slot of the base station; The candidate RO configuration set is traversed to solve the optimization problem, to obtain the optimal RO utilization and the corresponding optimal configuration set, and the effective RO indicator vector of each beam under the optimal configuration.

2. The time slot resource allocation method for a low-Earth orbit satellite communication system based on TDD according to claim 1, characterized in that, The candidate RO configuration set is traversed to solve the optimization problem, including: In a given candidate RO configuration Next, the minimum common period of each type of signal is determined, and a set of RO transmission intervals is constructed; For each beam, an effective RO (Resource Optimizer) that does not interfere with the downlink signal is identified, and the average RO utilization of all beams under that candidate RO configuration is obtained; where, for each beam Each wave position Based on the propagation delay range, it is determined whether the RO interferes with various system broadcast signals in turn, and the waveform is obtained. Effective RO transmission interval set Thus, the beam is obtained. Effective RO transmission interval set ;like Discard configuration Set the average RO utilization rate to 0; otherwise, obtain the configuration. Average RO utilization rate ;in, For satellite beam sets; For beam The set of wave positions served For the number of beams, Configure the base station in RO The set of RO intervals below, Describes the cardinality of a set; All candidate RO configurations are compared, and the configuration with the highest utilization rate is selected.

3. A time slot resource allocation method for a TDD-based low-orbit satellite communication system, aiming at the transmission resource allocation problem of a single-satellite system, characterized in that, The uplink and downlink time slots of the terminal are scheduled by the satellite on demand, and the satellite ensures that no interference occurs between the time slots allocated to the terminal during scheduling; the transmission resource allocation includes the following steps: According to the propagation delay of the user, the time intervals for receiving the downlink signal of the base station and sending the uplink signal to the base station are obtained, and the two intervals are made non-overlapping to obtain the non-interference constraint condition between the uplink and downlink time slots allocated to the user; This paper proposes an optimization problem for time slot allocation in a single-satellite system. The optimization objective is to maximize the number of allocated time slots within a given scheduling period. ;in, Indicates the first Is the first time slot allocated to the first... For each user, 1 indicates allocation and 0 indicates no allocation; constraints include: each time slot can be allocated to at most one user, the number of downlink and uplink time slots required for each user's allocation, and there is no interference between the uplink and downlink time slots allocated to each user. Auxiliary variables are introduced to convert the uplink and downlink non-interference constraints, and the original optimization problem is converted into an integer programming form; The converted optimization problem is solved to obtain the time slot allocation result of the user.

4. The method of claim 3, wherein, The constraint condition of no interference between the uplink and downlink time slots is ; wherein, is the downlink time slot number within the scheduling period, is the uplink time slot number, is the user's satellite-ground propagation delay, is the corresponding parameter of the subcarrier spacing.

5. The method of claim 4, wherein, By multiplying on the left side of the inequality The constraint holds if and only if and i.e. the base station will assign to the user the assigned time slots satisfy this constraint, otherwise the constraint holds constantly; The converted non-interference constraints include: ； wherein, is the propagation delay for the user, is a set of downlink slot numbers, is a set of uplink slot numbers, is a set of user numbers, is a 0-1 auxiliary variable, is a predetermined positive number.

6. A time slot resource allocation method for a TDD-based low-orbit satellite communication system, aiming at the transmission resource allocation problem of a multi-satellite system, characterized in that, The uplink and downlink time slots of the terminal are scheduled by the satellite on demand, and the satellite ensures that no interference occurs between the time slots allocated to the terminal during scheduling; the transmission resource allocation includes the following steps: According to the allocated time slot number and the propagation delay of the user, the time intervals of the signals that will cause interference are made non-overlapping to obtain the non-interference constraint condition of the multi-satellite system; The optimization problem of time slot allocation in multi-satellite system is constructed, and the optimization goal is to maximize the number of allocated time slots in a given scheduling period of all satellites ; wherein, represents the th satellite whether to allocate the th time slot to the th user, 1 represents allocation, and 0 represents non-allocation; the constraints include: each user can communicate with only one satellite, the user can communicate with the satellite only when the user is in the coverage area of the satellite, the satellite allocating time slots to the user is consistent with the satellite selected by the user to communicate, each time slot of the satellite is allocated to at most one user, the number of required downlink and uplink time slots is allocated to each user, there is no interference between the uplink and downlink time slots allocated to each user, and there is no interference between the downlink signals and the uplink signals allocated to the user; Auxiliary variables are introduced to convert the non-interference constraints, and the original optimization problem is converted into an integer programming form; The converted optimization problem is solved to obtain the time slot allocation result of the user, and the communication relationship between the user and the satellite.

7. The method of claim 6, wherein, Interference constraints between downlink signals in a multi-satellite system are as follows: ,in and Number the satellite. For the satellite and satellite User ID within the overlapping coverage area For satellite Assigned to user downlink slot number, For satellite Downlink time slot numbers assigned to other users For satellite With users The propagation delay between satellites and the ground For satellite The start time slot time within the scheduling cycle relative to the satellite The value of the delay, Here are the corresponding parameters for the subcarrier spacing; the interference constraints between uplink signals in a multi-satellite system are... ,in For satellite Assigned to user The uplink timeslot number, For satellite Uplink time slot numbers assigned to other users.

8. The method of claim 7, wherein, The converted non-interference constraints include: ； wherein, is a satellite is a satellite is a satellite is a satellite is a satellite is a satellite is a satellite is a satellite is a satellite is a satellite is a satellite is a satellite , and is a 0-1 auxiliary variable, is a predetermined positive number.

9. The method of claim 3 or 6, wherein, For a single-satellite system, if a feasible solution cannot be obtained, the scheduling period is expanded to expand the solution space, the downlink time slot number set and the uplink time slot number set are recalculated, and the new optimization problem is solved; for a multi-satellite system, if a feasible solution cannot be obtained, the scheduling period of each satellite is sequentially increased, the downlink time slot number set and the uplink time slot number set of each satellite are recalculated, and the new optimization problem is solved.

10. A computer system comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, wherein the computer program comprises computer program code configured to cause the processor to perform the method of any one of claims 1 to 9. The computer program, when executed by a processor, implements the steps of the method for allocating time slot resources in a TDD-based low-orbit satellite communication system according to any one of claims 1-9.

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