Low-orbit constellation multi-beam mode time-varying hopping beam scheduling method

Abstract

The invention discloses a low-orbit constellation multi-beam mode time-varying beam hopping scheduling method, which comprises the following steps that: firstly, a user feeds back user state information including a user rate demand, a user terminal beam quantity, each beam channel gain, a user position and the like to a satellite through a control channel; and the satellite determines a beam mode, the number of accessed users, scheduling of beams in each time slot and a power distribution strategy based on the user state information. The satellite generates beams according to the selected mode and sends data, beam space-time resource allocation can be carried out according to non-uniform user requirements, changing user requirements are adapted, and the satellite network capacity is improved.

Description

Technical Field

[0001] The invention relates to a time-varying beam-hopping scheduling method for a low-orbit constellation multi-beam mode, and belongs to the technical field of satellite communications. Background Art

[0002] As an important part of 5G NTN and 6G networks, space-based networks can achieve seamless global coverage. Low-orbit satellite communication systems have become the main form of space-based networks due to their strong coverage, short latency and high transmission capacity.

[0003] Among the several influential low-orbit constellations, the least planned satellites have thousands of satellites, and the satellites are all equipped with intersatellite networking payloads and multi-beam antenna payloads as core payloads. Low-orbit satellites use multi-beam technology to launch several high-power beams with smaller coverage to the ground, thereby providing services to multiple users on the ground at the same time, which can greatly enhance the service capabilities of satellite communication systems.

[0004] In low-orbit multi-beam satellite systems, traditional fixed multi-beam coverage is a space-centered average coverage mode with the characteristics of simple beam control. In low-orbit satellite systems, due to the uneven distribution of user traffic, the traffic distribution between beams or users is often uneven. Fixed beam patterns cannot adapt to dynamically changing and unevenly distributed traffic distribution scenarios, and there are problems such as mismatch between resources and demand and limited overall system performance. Since the payload mass and power of satellites are subject to stricter restrictions, the energy efficiency optimization problem of low-orbit satellite communication systems has important research and engineering significance. Adaptive transmit beamforming is the key to improving spectrum and energy efficiency when user rate demands are unevenly distributed.

[0005] However, for higher frequency bands, the number of satellite array elements is relatively large, and the amount of calculation required for on-orbit on-demand beamforming is large. The beamforming coefficients cannot be calculated in real time, making it difficult to apply in practice. At the same time, considering that satellite multi-beam systems operating in higher frequency bands mainly use analog beamforming technology, the number of beams that can work simultaneously is limited, and beam hopping is required to complete coverage in a time-sharing manner. The complexity of beam mode selection and beam hopping scheduling in low-orbit satellite systems is exponential, and traditional methods are difficult to solve. Summary of the invention

[0006] The technical problem solved by the present invention is: in view of the deficiencies existing in the current prior art, a time-varying beam-hopping scheduling method for a multi-beam mode of a low-orbit constellation is proposed.

[0007] The present invention solves the above technical problem by the following technical solution: a time-varying beam hopping scheduling method for a multi-beam mode of a low-orbit constellation, comprising:

[0008] Feedback user status information to the satellite via the control channel;

[0009] For each satellite, determine the candidate satellite beam hopping scheme that meets the spatial isolation conditions. For beams with inter-satellite beam interference, avoid interference by arranging the interfering beams in different time slots.

[0010] Each scheduling period is divided into time slots of equal length, and beam hopping is controlled in units of time slots; in each scheduling period, for each beam of each user terminal, satellite beam mode and user access satellite beam selection are performed in turn;

[0011] For each time slot, for the satellite terminal beam accessed by each beam of the satellite, the rate of the beam of each user terminal in the time slot is calculated in combination with the channel gain when the satellite transmission power is determined, and the first N beams whose user demand rate is closest to the user allocation rate in the satellite beam hopping candidate scheme are selected as working beams, where N is the maximum number of simultaneously operable beams of the satellite; the user allocation rate is the sum of the rates of each user terminal in the time slot plus the rate that has been allocated to the user before the time slot;

[0012] For a set of satellites whose user allocation rate is greater than the user's required rate, the satellite transmission power is calculated based on the user's required rate and the channel gain;

[0013] The satellite sends the selected satellite beam mode, the user access satellite beam selection result and the working beam to the user terminal through the control channel;

[0014] The user terminal controls its own beam to point to the corresponding satellite according to the user access satellite beam selection result.

[0015] The corresponding satellite sends data to the target user in time slots according to the selected working beam, beam mode and satellite transmission power;

[0016] The user terminal combines the data obtained by each beam to obtain the data it needs.

[0017] Preferably, the user status information includes: user required rate, number of user terminal beams, channel gain of each beam of the user terminal, and user location.

[0018] Preferably, the specific calculation method of the channel gain of each beam of the user terminal is: the sum of the user antenna gain when the user beam points to the satellite and the gain of each beam pattern of the satellite antenna in the direction of the user position, minus the channel loss measured by the user.

[0019] Preferably, a specific method for determining a candidate beam hopping solution that meets the spatial isolation condition is:

[0020] For each satellite, let the number of satellite positions be M, define the beam interference matrix A of size M×M, and the element a ij∈{0,1} indicates whether beam i interferes with beam j. ij =1, do not interfere with a ij =0, the diagonal elements are 0; suppose the number of beams that can work simultaneously on a satellite is N, for beams with inter-satellite beam interference, interference avoidance is performed by time slot sharing, and for beams with inter-satellite beam interference, a is set in the time slot where the satellite cannot work. ij =1;

[0021] Define the row vector b of size M as the candidate beam hopping solution, element b i ∈{0,1} to indicate whether the beam at wave position i is working, b i =1 indicates that the wave position beam is working, b i =0 means that the beam position is not working;

[0022] Select bAb T b with = 0 is a beam hopping candidate solution.

[0023] Preferably, the beam hopping candidate scheme is a pre-allocated scheme.

[0024] Preferably, in each scheduling period, the specific method of selecting the satellite beam mode and the user access satellite beam is:

[0025] S1. For each beam of each satellite, first select the beam mode with the largest beam coverage;

[0026] S2. The combinations of each user and each beam of each satellite are sorted by the product of the user rate requirement and the channel gain of the user on each beam of each satellite; each beam of each satellite selects the first U users to access, where U is the maximum number of users allowed to access a single beam;

[0027] S3. After determining the satellite beam to which the user is accessed, for each beam of each satellite and each beam mode in which the beam can operate, the sum of the channel gains of all users in each beam mode is calculated, and the beam mode corresponding to the maximum sum is taken as the operating beam mode;

[0028] S4. Repeat S2-S3 until the beam pattern and the user access beam no longer change or the maximum number of iterations is reached.

[0029] Preferably, the value of U is based on the service satisfaction rate of the last D scheduling cycles. When the service satisfaction rate is less than 100%, the value of U decreases, and when the service satisfaction rate is 100%, the value of U increases. The value of D is 2-10.

[0030] Preferably, each beam of each satellite in the satellite beam mode may be different, and the satellite beam mode is stored in the on-board beam control machine in the form of amplitude and phase coefficients, and the beam mode is controlled by the beam control machine according to the satellite beam mode selection result.

[0031] Preferably, the satellite beams are of the same frequency or different frequencies; when they are of different frequencies, the user terminal configures multiple beams to simultaneously access different beams in different frequency bands, and these beams belong to the same satellite or different satellites; when they are of the same frequency, the user terminal configures multiple beams to simultaneously access beams of different satellites in the same frequency band.

[0032] The advantages of the present invention compared with the prior art are:

[0033] The present invention proposes a solution to the joint optimization problem of beam mode selection, satellite user access and beam scheduling. By arranging beams in time slots, beam pointing and selecting beam modes, the designed satellite beam scheduling is matched with the uneven rate requirements of users, while avoiding interference between beams, supporting users' diversified services and ensuring service quality.

[0034] The present invention can coordinate beam power and coverage space with a limited number of beams and minimize transmission power consumption with fewer pre-stored beam modes, reduce interference between beams, and meet user needs to the greatest extent.

[0035] For multi-beam satellites with higher frequency bands, there are many satellite antenna array elements. Traditional heuristic learning algorithms, particle swarm algorithms, and genetic algorithms are unable to perform real-time beamforming calculations on-orbit. This solution adjusts and selects different beam modes so that data transmission in the satellite system can adapt to uneven traffic distribution, reduce interference between beams, and meet system requirements at the same time.

[0036] Traditional methods are all beam hopping methods with unchanged beam patterns, while the present invention solves the dual problems of beam deployment and beam pattern selection. Due to the strong coupling between beam pattern selection and beam hopping scheduling in low-orbit satellite systems, conventional methods are difficult to solve in the case of multi-satellite interference, large number of beam positions, and simultaneous multi-beams. The present invention proposes a method for joint optimization of beam pattern selection and beam scheduling by time slot, so that beams with the same frequency are just avoided from the time slot. Complex signaling between satellites is not required, which avoids a large amount of centralized scheduling, and each satellite can be scheduled in parallel independently. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 A flowchart of the steps of a time-varying beam-hopping scheduling method for a multi-beam mode of a low-orbit constellation provided by the invention; DETAILED DESCRIPTION

[0038] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] Example:

[0040] The multiple beams of a multi-beam satellite can be realized in various forms such as on-board phased array multi-beam antenna, lens multi-beam antenna, conventional reflector multi-beam antenna and phased array fed reflector multi-beam antenna, for phased array antennas with higher operating frequency bands.

[0041] In the embodiment, there are 4 low-orbit satellites, each of which can work on 4 beams at the same time, with an operating frequency band of 18 GHz, an operating bandwidth of 400 MHz, a maximum transmission power of 50 dBm, and a terminal receiving antenna gain of 30 dBi. A scheduling period is 100 ms, a time slot length of 10 ms, and a satellite orbit altitude of 500 km. The number of wave positions that each satellite can work on is 37, and the beam mode is a circular beam with a 3 dB beam width of [1.8°, 2.6°, 3.5°]. The terminal uses a phased array antenna that can accurately point to the satellite, so the gain is fixed. The terminal supports multiple frequency bands, so it can access different satellite beams in different frequency bands. The beams can belong to the same satellite or to different satellites. Assume that the number of user terminals covered by 4 satellites is 50, and the rate requirement of each user terminal is between 5 Mbps and 500 Mbps. The user terminal described in the present invention includes terminals deployed on drones, roofs, aircraft, ships, vehicles, etc.

[0042] The idea of ​​the present invention is that the user first feeds back the user status information, including user rate requirements, number of user terminal beams, channel gain of each beam, user location, etc., to the satellite through the control channel. Based on the user status information, the satellite determines the beam mode, the number of connected users, the scheduling of beams in each time slot, and the power allocation strategy. The satellite generates beams and sends data according to the selected mode, and can allocate beam space-time resources according to non-uniform user needs, adapt to changing user needs, and improve satellite network capacity.

[0043] like Figure 1 As shown, the specific implementation process of the present invention is as follows:

[0044] (1) Feedback the user status information, including the user required rate, the number of user terminal beams (e.g., 4), the channel gain of each user terminal beam, and the user position in the form of longitude and latitude, to the satellite through the control channel.

[0045] (2) For each satellite, determine the candidate satellite beam hopping scheme that meets the spatial isolation conditions. For beams with inter-satellite beam interference, avoid interference by arranging the interfering beams in different time slots.

[0046] Since the number of operable beams, 4, is relatively small compared to the number of beam positions, 37, the interfering beams between different satellites can be staggered in terms of time slots, and this staggering is pre-allocated and does not require negotiation during system operation.

[0047] (3) Each scheduling cycle of 100ms is divided into 10 time slots of equal length, each time slot is 10ms, and beam hopping is controlled in time slots. In each scheduling cycle, for each beam of each user terminal, satellite beam mode and user access satellite beam selection are performed in turn. The process is as follows:

[0048] (31) For each beam of each satellite, the beam mode with the largest beam coverage is first selected.

[0049] (32) The combination of each user and each beam of each satellite is sorted by the product of the user demand rate and the channel gain of the user on each beam of each satellite. Each beam of each satellite selects the first U users for access, where U is the maximum number of users allowed to access a single beam. The value of U is based on the service satisfaction rate of the last D = 5 scheduling cycles. When the service satisfaction rate is less than 100%, the value of U is reduced by 1. When the service satisfaction rate is 100%, the value of U is increased by 1.

[0050] (33) After determining the satellite beam to which the user is accessed, for each beam of each satellite and for each beam mode in which the beam can operate, the sum of the channel gains of all users in the beam mode is calculated, and the beam mode corresponding to the maximum sum is taken as the operating beam mode.

[0051] (34) Repeat (32)-(33) until the beam pattern and the user access beam no longer change or the maximum number of iterations is reached. Here, the maximum number of iterations is 10.

[0052] (4) For each time slot, for each satellite terminal beam accessed by each satellite beam, the satellite transmit power is determined to be 50 dBm, and the rate of each user terminal in this beam in this time slot is calculated in combination with the channel gain. The channel gain from satellite s to user k is in is the antenna gain of satellite s pointing to user k in beam mode n, is the receiving antenna gain of user k, The total channel loss from satellite s to user k measured for user k.

[0053] The rate at which satellite s transmits to user k in time slot is R skt=B log(1+γ skt ), where γ skt is the SINR of communication between satellite s and terminal k, which is calculated by the channel gain G from satellite s to user k, interference and noise of other beams, and B is the bandwidth allocated to the user. In this embodiment, users accessing the beam are evenly allocated the total bandwidth of the beam.

[0054] The capacity provided by the satellite network for user k is where x skt ∈{0, 1}, if the beam of satellite s serves user k in time slot t, then x skt =1, otherwise x skt =0.

[0055] From the valid beam-hopping candidate schemes determined in step (2), the first N=4 beams whose user demand rates are closest to the user allocation rates (the sum of the rates of each user terminal in this time slot plus the rates that have been allocated to the user before this time slot) are selected as working beams, where N is the maximum number of simultaneously operable beams of the satellite, which is 4 in this embodiment.

[0056] In each time slot, there is There are many beam combinations, but not all candidate beam solutions can meet the spatial isolation between beams. In order to reduce inter-beam interference, it is necessary to select effective candidate beam solutions with spatial isolation conditions from all candidate beam solutions. The above effective candidate beam solution determination method is as follows: for each satellite, the number of satellite positions M = 37, define a beam interference matrix A of size M × M, and the element a ij ∈{0,1} indicates whether beam i interferes with beam j. ij =1, do not interfere with a ij =0, and the diagonal elements are 0. The number of beams that can be operated simultaneously by the satellite is N=4. For beams with inter-satellite beam interference, interference avoidance is performed through time slot time sharing. For beams with inter-satellite beam interference, a is set in the time slot where the satellite cannot work. ij =1.

[0057] Define a row vector b of size M = 37 as a candidate beam hopping solution, element b i ∈{0,1} to indicate whether the beam at wave position i is working, b i =1 indicates that the wave position beam is working, b i = 0 means that the wave position beam is not working, and the number of 1s in the row vector b is not greater than N = 4. Select bAb T b with = 0 is a beam hopping candidate solution.

[0058] (5) For a set of satellites whose user allocation rate is greater than the user's required rate, the satellite transmit power is calculated based on the required rate and channel gain.

[0059] (6) The satellite sends the selected beam mode, the user access satellite beam selection result, and the working beam to the user terminal through the control channel.

[0060] (7) The user terminal controls its own beam to point to the corresponding satellite according to the user access satellite beam selection result.

[0061] (8) The corresponding satellite sends data to the target user in time slots according to the selected mode and satellite transmission power.

[0062] (9) The user terminal combines the data obtained from the working beams of each satellite it accesses to obtain the data it needs.

[0063] Although the present invention has been disclosed as above in the form of a preferred embodiment, it is not intended to limit the present invention. Any person skilled in the art may make possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solution of the present invention shall fall within the protection scope of the technical solution of the present invention.

[0064] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A time-varying beam-hopping scheduling method for multi-beam modes of low-orbit constellations, characterized in that include: Feedback user status information to the satellite via the control channel; For each satellite, determine the candidate satellite beam hopping scheme that meets the spatial isolation conditions. For beams with inter-satellite beam interference, avoid interference by arranging the interfering beams in different time slots. Each scheduling cycle is divided into time slots of equal length, and beam hopping is controlled in units of time slots; In each scheduling period, for each beam of each user terminal, satellite beam mode and user access satellite beam selection are performed in turn; For each time slot, for the satellite terminal beam accessed by each beam of the satellite, the rate of the beam of each user terminal in the time slot is calculated in combination with the channel gain when the satellite transmission power is determined, and the first N beams whose user demand rate is closest to the user allocation rate in the satellite beam hopping candidate scheme are selected as working beams, where N is the maximum number of simultaneously operable beams of the satellite; the user allocation rate is the sum of the rates of each user terminal in the time slot plus the rate that has been allocated to the user before the time slot; For a set of satellites whose user allocation rate is greater than the user's required rate, the satellite transmission power is calculated based on the user's required rate and the channel gain; The satellite sends the selected satellite beam mode, the user access satellite beam selection result and the working beam to the user terminal through the control channel; The user terminal controls its own beam to point to the corresponding satellite according to the user access satellite beam selection result. The corresponding satellite sends data to the target user in time slots according to the selected working beam, beam mode and satellite transmission power; The user terminal combines the data obtained by each beam to obtain the data it needs.

2. The method for time-varying beam hopping scheduling of a low-orbit constellation multi-beam mode according to claim 1, characterized in that: The user status information includes: user required rate, number of user terminal beams, channel gain of each beam of the user terminal, and user location.

3. The method for time-varying beam hopping scheduling of a multi-beam mode of a low-orbit constellation according to claim 2, characterized in that: The specific calculation method of the channel gain of each beam of the user terminal is: the sum of the user antenna gain when the user beam points to the satellite and the gain of each beam pattern of the satellite antenna in the direction of the user position, minus the channel loss measured by the user.

4. The method for time-varying beam hopping scheduling of a multi-beam mode of a low-orbit constellation according to claim 1, characterized in that: The specific method for determining the candidate beam hopping schemes that meet the spatial isolation conditions is as follows: For each satellite, let the number of satellite positions be M, define the beam interference matrix A of size M×M, and the element a ij ∈{0,1} indicates whether beam i interferes with beam j. ij =1, do not interfere with a ij =0, the diagonal elements are 0; suppose the number of beams that can work simultaneously on a satellite is N, for beams with inter-satellite beam interference, interference avoidance is performed by time slot sharing, and for beams with inter-satellite beam interference, a is set in the time slot where the satellite cannot work. ij =1; Define the row vector b of size M as the candidate beam hopping solution, element b i ∈{0,1} to indicate whether the beam at wave position i is working, b i =1 indicates that the wave position beam is working, b i =0 means that the beam position is not working; Select bAb T b with = 0 is a beam hopping candidate solution.

5. The method for time-varying beam hopping scheduling of a low-orbit constellation multi-beam mode according to claim 1 or 4, characterized in that: The beam hopping candidate scheme is a pre-assigned scheme.

6. The method for time-varying beam hopping scheduling of a low-orbit constellation multi-beam mode according to claim 1, characterized in that: In each scheduling cycle, the specific method of satellite beam mode and user access satellite beam selection is as follows: S1. For each beam of each satellite, first select the beam mode with the largest beam coverage; S2. The combinations of each user and each beam of each satellite are sorted by the product of the user rate requirement and the channel gain of the user on each beam of each satellite; each beam of each satellite selects the first U users to access, where U is the maximum number of users allowed to access a single beam; S3. After determining the satellite beam to which the user is connected, for each beam of each satellite and each beam mode in which the beam can operate, calculate the sum of the channel gains of all users in each beam mode, and take the beam mode corresponding to the maximum sum as the operating beam mode; S4. Repeat S2-S3 until the beam pattern and the user access beam no longer change or the maximum number of iterations is reached.

7. The method for time-varying beam hopping scheduling of a multi-beam mode of a low-orbit constellation according to claim 6, characterized in that: The value of U is based on the service satisfaction rate of the last D scheduling cycles. When the service satisfaction rate is less than 100%, the value of U decreases. When the service satisfaction rate is 100%, the value of U increases. The value of D is 2-10.

8. The method for time-varying beam hopping scheduling of a low-orbit constellation multi-beam mode according to claim 1 or 6, characterized in that: Each beam of each satellite in the satellite beam mode can be different. The satellite beam mode is stored in the on-board beam control machine in the form of amplitude and phase coefficients. The beam mode is controlled by the beam control machine according to the satellite beam mode selection result.

9. The method for time-varying beam hopping scheduling of a low-orbit constellation multi-beam mode according to claim 1, characterized in that: The satellite beams are of the same frequency or different frequencies. When the frequencies are different, the user terminal configures multiple beams to simultaneously access different beams in different frequency bands. These beams belong to the same satellite or different satellites. When the frequencies are the same, the user terminal configures multiple beams to simultaneously access beams of different satellites in the same frequency band.

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