Method and apparatus for supporting the estimation of link acquisition time in a satellite-based network

Abstract

The present disclosure provides a method and apparatus for supporting the estimation of the inter-satellite link acquisition time in a satellite constellation. The method includes calculating or generating an indication of a statistical model based on observations of previous link acquisition times. The method further includes transmitting the indication, such as a statistical model of the link acquisition time or related parameters or a combination thereof, over a communication network. The indication may be transmitted using one or more transmission techniques or protocols, such as flooding, link state protocols, or gossip protocols. Based on the propagated indication, future link acquisition times may be predicted by satellites in the satellite constellation. Embodiments of the present disclosure use statistical-based computational methods, such as regression modeling or random variable modeling, to estimate the link acquisition time or associated estimation parameters. Then, the estimated values or associated estimation parameters may be propagated through the constellation.

Description

[0001] Cross - reference to related applications

[0002] This application claims priority to U.S. Non - Provisional Patent Application No. 16 / 896,285, filed on June 9, 2020, with the title "Methods and Apparatus for Supporting Estimation of Link Acquisition Time in Satellite - based Networks". Technical Field

[0003] The present disclosure relates to satellite - based networks, such as optical satellite mesh networks, and particularly to a method and apparatus for estimating the acquisition time of satellite links in such networks and for propagating related information through the network. Background Art

[0004] Low Earth Orbit (LEO) satellite constellations are being developed to provide Internet routing services, among other things. A LEO constellation can be considered a group of satellites distributed in space such that they can be organized into a mesh network. Free - space optical (i.e., laser) links can be used to provide inter - satellite links (ISLs). A LEO constellation with ISLs and ground links can be used to provide high - bandwidth networks. Other types of ISLs may also be employed, such as radiofrequency (RF) or microwave - based links. One of the technical problems with ISLs in a polar - orbiting LEO constellation is that due to the relative motion of the satellites in the constellation, the inter - satellite links periodically experience signal loss. For example, this occurs when satellite orbits intersect (e.g., at or near the poles) and the east - west links are swapped. Other examples occur at the seams of a polar - orbiting constellation and at the east - west links of a constellation with orbits deviating from the poles (such as a Walker Delta constellation). For example, a seam is a boundary such that on one side of the boundary are satellites in one of two counter - rotating hemispheres or spheres, and on the other side of the boundary are satellites in the other of the two counter - rotating hemispheres or spheres. The communication link between satellites in different hemispheres or spheres of the two counter - rotating hemispheres or spheres intersects the seam.

[0005] Re - acquiring an inter - satellite link after a disconnection can be a time - consuming process. In the current literature, the estimated current optical link acquisition time (e.g., space acquisition time) is between 10 and 60 seconds. Most of this time is due to the need for a space acquisition operation in which the communication lasers on adjacent satellites are correctly aimed at the corresponding receivers.

[0006] Since, in many cases, the link acquisition time is relatively long in the context of the link's lifetime, link interruptions can have an impact on network operation. Therefore, a method and apparatus for estimating link acquisition time and propagating relevant information through a network are needed so that the impact of link interruptions can be mitigated.

[0007] This background information is provided to disclose information that the applicant believes may be relevant to the present disclosure. It is not necessary to admit and should not be construed as any of the foregoing information constituting prior art relative to the present disclosure. Summary of the Invention

[0008] An object of embodiments of the present disclosure is to provide a method and apparatus for supporting the estimation of inter-satellite link acquisition time in a satellite constellation. The method and apparatus are provided for estimating satellite communication link acquisition time, for propagating information such as link acquisition time or related parameters through a communication network, or a combination thereof. Embodiments of the present disclosure use a statistical-based calculation method to estimate link acquisition time or associated estimation parameters. Then, the estimated value or associated estimation parameters can be propagated through the constellation. The estimation of inter-satellite link acquisition time can be performed locally, remotely, or a combination thereof.

[0009] According to an embodiment of the present disclosure, a method for supporting the estimation of inter-satellite link acquisition time in a satellite constellation is provided. The method can be executed by a suitable device, such as a computing and communication device of a first satellite of a satellite constellation. The method includes determining an indication of a statistical model. The indication can be determined based on observations of previous inter-satellite link acquisitions involving the first satellite. The statistical model is used to estimate future inter-satellite link acquisition time involving the first satellite. The method further includes transmitting the indication of the statistical model to one or more other satellites in the satellite constellation. Then, the indication can be used by one or more other satellites or one or more other network entities to operate the statistical model to estimate future inter-satellite link acquisition time involving the first satellite.

[0010] According to an embodiment of the present disclosure, an apparatus for a satellite of a satellite constellation is provided for supporting the estimation of inter-satellite link acquisition time in a satellite constellation. The apparatus includes suitable computing electronics, such as a processor and a memory storing machine-executable instructions. For example, through the configuration of instructions, the apparatus is configured to calculate an indication of a statistical model and transmit the indication of the statistical model. The calculation is based on observations of previous inter-satellite link acquisitions involving the satellite. The statistical model is used to estimate future inter-satellite link acquisition time involving the satellite. The indication of the statistical model is transmitted to one or more other satellites in the satellite constellation. Then, the indication can be used by one or more other satellites or one or more other network entities to operate the statistical model to estimate future inter-satellite link acquisition time involving the satellite.

[0011] According to an embodiment of the present disclosure, there is provided an apparatus for supporting the estimation of the inter-satellite link acquisition time in a satellite constellation. The apparatus includes suitable computing electronics, such as a processor and a memory storing machine-executable instructions. For example, by the configuration of the instructions, the apparatus is configured to receive an indication of a statistical model and operate the statistical model. The statistical model is calculated based on observations of previous inter-satellite link acquisitions involving remote satellites. The statistical model is used to estimate the future inter-satellite link acquisition time involving remote satellites. The indication is used to operate the statistical model to estimate the future inter-satellite link acquisition time involving remote satellites.

[0012] The embodiments described above in connection with the aspects of the present disclosure may be implemented based on these aspects. Those skilled in the art will understand that the embodiments may be implemented in combination with the aspects that describe them, but may also be implemented with other embodiments of that aspect. When the embodiments are mutually exclusive or incompatible with each other, this will be obvious to those skilled in the art. Some embodiments may be described in combination with one aspect, but may also be applicable to other aspects, which will be obvious to those skilled in the art. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] In combination with the accompanying drawings, through the following detailed description, further features and advantages of the present disclosure will become apparent, in which:

[0014] Figure 1 An example of a satellite network integrated with a terrestrial network is shown.

[0015] Figure 2 The unpredictability of the link acquisition time in a satellite network and its potential impact on network operation are shown.

[0016] Figure 3 A method for supporting the estimation of the inter-satellite link acquisition time in a satellite constellation provided by an embodiment of the present disclosure is shown in a flowchart.

[0017] Figure 4 A part of a satellite constellation provided by an embodiment of the present disclosure is shown in a block diagram, in which a plurality of satellites are connected together in a mesh network.

[0018] Figure 5 An electronic device provided by an embodiment of the present disclosure is shown in a schematic diagram.

[0019] It should be noted that in all the drawings, the same features are identified by the same reference numerals. DETAILED DESCRIPTION

[0020] The term "about" as used herein should be understood to include variations from the nominal value, e.g., variations of + / - 10% from the nominal value. It should be understood that given values provided herein always include such variations whether or not specifically mentioned.

[0021] Figure 1 An example of a satellite network integrated with a terrestrial network is shown. Referring Figure 1 , a satellite network 100 integrated with a terrestrial network is provided. The satellite network 100 includes LEO satellites 110 and 120 in a satellite constellation. The LEO satellites 110 and 120 can be placed in different orbits. The LEO satellites 110 and 120 can be interconnected by optical crosslink links. The LEO satellites 110 and 120 are connected to terrestrial user terminals. The optical fiber 135 and the wireless network 130 are interconnected with the satellites through a gateway 140 to form a global heterogeneous network. A data network based on such a LEO constellation topology shown in the figure can provide data network services, especially in areas with poor or congested terrestrial infrastructure deployments.

[0022] Low Earth Orbit (LEO) satellite constellations are capable of providing Internet routing services, etc. To provide Internet routing services, link state routing is mainly used as an internal gateway routing method in satellite network operations because link state routing takes into account the conditions of network links when performing routing calculations.

[0023] For example, due to operational problems or satellite positions, satellite links may be interrupted occasionally or periodically. Then, the interrupted link needs to be reacquired. Since the link cannot be used during its acquisition process, it is useful to notify other satellites in the constellation or network of the time when the link acquisition is completed or expected to be completed. This helps these satellites make correct routing decisions involving reacquiring the link.

[0024] Existing methods, such as the US patent application with publication number 2003 / 0137930, provide methods and apparatuses for routing information in a satellite (communication) network. Some existing methods use satellite ephemeris data to predict link state changes in a satellite grid or constellation that organizes LEO satellites. Satellite ephemeris data can include information related to satellite trajectories, such as the position (or velocity) of a satellite over time, and information related to the satellite state.

[0025] In existing methods, it is proposed to use almanac data for network nodes (such as satellites) that are not adjacent (e.g., far away) from a satellite link whose state changes in order to predict satellite link state changes. Almanac data can include the approximate orbits and state information of each satellite in a satellite constellation. On the other hand, network nodes adjacent to a satellite link whose state changes suppress updating their link states.

[0026] In an embodiment, the ephemeris data may refer to information about the operating information of satellites in a constellation. The operating information may include orbit (e.g., position and velocity) information, satellite status information, coarse communication link capacity information, etc.

[0027] The purpose of this disclosure in presenting such a method is to avoid the continuous flooding of link state updates, thereby making link state changes predictable. Regarding link state changes, the prior art does not consider the random nature of satellite link acquisition because they assume that link state updates occur due to the known movement of satellites.

[0028] However, link state changes are not always easily predictable. This is because the link acquisition time can vary over a relatively wide range and is thus unpredictable, as Figure 2 shown. In addition, satellite simulators typically model the link acquisition time as a random variable. This makes it more difficult to predict when a link will become active. Figure 2 illustrates the unpredictability of link acquisition time in a satellite network and its potential impact on network operation. In particular, Figure 2 illustrates the time 205 when the link is disconnected and the time 210 when a new link acquisition operation starts. Although the worst-case link acquisition time 220 may be known and predictable, the actual link acquisition time 215 is not necessarily predictable, other than knowing that it is before the worst-case link acquisition time 220. During the time 225 between the actual link acquisition time 215 and the worst-case link acquisition time 220, the link is ready for use but unavailable because the network is configured to wait until the worst-case link acquisition time 220 to use the link.

[0029] However, simply using the worst-case link acquisition time is not an ideal option because it will reduce network throughput and utilization. Referring to Figure 2 , using the worst-case link acquisition time may cause unnecessary delays in the entire network (e.g., the link is ready but cannot be used by the network), especially when the link re-acquisition time is earlier than the worst link acquisition time. On the other hand, if the link re-acquisition is declared too early, the premature declaration may lead to routing black holes, packet loss, and their subsequent impacts.

[0030] According to various embodiments, a computing device associated (e.g., onboard) with a satellite can be used to record a history of link acquisition times (e.g., previous link acquisition times), possibly along with related information. For example, the related information may include absolute satellite position, relative satellite position with respect to other satellites, time, distance, position, and / or velocity of the satellite, distance, position, and / or velocity of the satellite at the far end of the link, etc. In some embodiments, the computing device associated with the satellite may be located away from the satellite while being communicatively connected to the satellite.

[0031] Historical records (e.g., previous link acquisition times) can be used to estimate future link acquisition times. In some cases, the estimate can be substantially independent of other observations. For example, if the link acquisition times have historically been close to a Gaussian distribution with a mean of and a variance of , then the link acquisition time can be estimated based on this distribution. For example, based on standard statistical analysis, the link acquisition time can be estimated to be less than or equal to with a probability of approximately 0.9545. In some cases, the estimate may depend on other observations. For example, the historical records can be processed to infer that the link acquisition times are distributed according to a particular probability distribution that has parameters as a function of one or more other observables, such as satellite position (e.g., the absolute position of the satellite or the relative position of the satellite with respect to other satellites) and inter-satellite distance. Thus, the link acquisition time can be estimated based on this distribution while taking into account the current values of such observables.

[0032] More generally, historical records can be used to determine an indication of a model that can be used to estimate future link acquisition times involving a given satellite. The indication can be the model itself or a parameter of the model. The model typically refers to a statistical model, which can involve one or more methods such as regression, statistical filtering, maximum likelihood estimation, maximum a posteriori estimation, expectation maximization, hidden Markov models, or other methods. The parameters can be parameters of a statistical distribution (e.g., mean and variance), or state transition probabilities in a hidden Markov model, parameters that describe the behavior of random variables or the correlation between variables, etc.

[0033] In some embodiments, each satellite will need to have a routing engine that makes routing decisions based on the state of remote links (e.g., links that do not originate or terminate on the relevant satellite) in a satellite network system. The state of a remote link is closely related to whether the link acquisition process for the remote link is complete. Embodiments of the present disclosure provide methods and apparatuses for estimating the probability that a remote link will be reacquired (e.g., link acquisition is complete) at a particular time and will operate after a link interruption. This estimate can be used to make informed routing decisions.

[0034] According to various embodiments, a satellite routing engine estimates the link acquisition time based on observations and calculations. Then, relevant information (e.g., parameters of a statistical model) is distributed through the constellation. Other satellites, after receiving the information, use the information to more accurately predict the remote link acquisition time. It should be noted that satellites do not necessarily need to predict the local link acquisition times because these times are directly observable. Those skilled in the art will understand that "satellite" can be generally used instead of "satellite routing engine".

[0035] Figure 3Illustrates a method provided by an embodiment of the present disclosure for supporting the estimation of the inter-satellite link acquisition time in a satellite constellation. Figure 3 The method shown can be executed by one or more computing and communication devices of a satellite in a satellite constellation. In some embodiments, the computing and communication devices may be integrated with a part of the satellite. In some embodiments, the computing and communication devices may be separate from the satellite but communicatively connected to the satellite. Referring to Figure 3 , embodiments of the present disclosure relate to a first satellite or other satellites learning (310) information indicating the link acquisition time based on observations. In at least one embodiment, a satellite or a routing engine of the satellite learns about link acquisitions associated with links originated or terminated at the same satellite. The link acquisition information may be carried in the form of a statistical model or its parameters. Embodiments also relate to the first satellite or other satellites transmitting (320) information indicating the link acquisition time (i.e., an indication of the statistical model of the link acquisition time) to the first satellite or other satellites in the satellite constellation. Embodiments also relate to the first satellite or other satellites predicting (330) the link acquisition time, for example, based on the received information indicating the link acquisition time.

[0036] The observations can be performed by the first satellite or other network entities (such as network nodes, other satellites) remote from the first satellite. If the observations are made by a network entity other than the first satellite, the network entity operates or is communicatively connected to the first satellite. In this case, the observation results obtained by the network entity other than the first satellite can be sent to the first satellite. The observation results may include information regarding the link acquisition time of the first satellite.

[0037] The information indicating the link acquisition time may include an estimated value of the link acquisition time. The information indicating the link acquisition time may include a statistical model or its parameters for estimating or predicting the link acquisition time. The parameters may be statistical parameters (such as mean, variance, distribution type), model parameters (such as the structure of the model for estimating the link acquisition time), etc.

[0038] Learning based on observations (310) for link acquisition information may include receiving or collecting observations and processing the observations. The processing may also include calculating an indication of a statistical model (for link acquisition time) based on observations obtained from a previous inter-satellite link involving the first satellite. Observations (or observations results) may include the distance between satellites, absolute and relative satellite velocities, the intensity of a laser transmitter, etc. In some embodiments, the information may be specific to a particular pairing of satellites. In various embodiments, the processing may be performed by the first satellite. In some embodiments, the processing may be performed by other network entities remote from the first satellite (e.g., one or more other satellites, network entities of a terrestrial network). In such a case, the observations obtained by the first satellite may be sent to one or more network entities other than the first satellite, such that the one or more network entities may perform the processing using the observations received from the first satellite. The indication of the statistical model may include the statistical model itself or the parameters of the statistical model. The processing may be based on statistical techniques, such as regression modeling, random variable modeling, or other computational methods for estimating relationships between variables. For example, in some embodiments, regression modeling may be used to generate a statistical model of link acquisition time based on independent variables. For example, the independent variables may indicate some or all of the following: the distance between satellites; the relative satellite velocity; and the intensity of the laser transmitter.

[0039] In some embodiments, the link acquisition time may be treated as a random variable that has been modeled (e.g., using statistical modeling). To model the random variable (e.g., link acquisition time), statistical functions, such as probability density functions, may be used. The parameters of the statistical function (e.g., probability density function parameters) may be estimated using statistical inference techniques, such as maximum likelihood estimation, maximum a posteriori estimation, expectation maximization, hidden Markov models, or other techniques. For example, using a maximum likelihood estimator, the parameter values of the probability density function will be determined such that the value of the parameter maximizes the output of the likelihood (or probability) function (i.e., the parameter value that maximizes the data likelihood). The likelihood function may be expressed as , where X represents a sampled data set of link acquisition times, represents the parameters of the probability density function. In other words, using a maximum likelihood estimator, the probability density function parameters will be selected such that the likelihood (i.e., L) of the link acquisition time (i.e., X) is maximized. According to an embodiment, the statistical model may specify the probability distribution of such a random variable, such as a truncated normal (Gaussian) distribution (truncated on the left), an exponential distribution, or other suitable probability distributions, with certain known or unknown parameters (e.g., distribution type, mean, and variance).

[0040] Transmission (320) of information indicating a link acquisition time (i.e., an indication of a statistical model of link acquisition time) can involve transmitting a statistical model of link acquisition time or a parameter of such a statistical model. In various embodiments, the transmission (320) can be performed by a first satellite. In some embodiments, the transmission (320) can be performed by other network entities remote from the first satellite (e.g., one or more other satellites, network entities of a terrestrial network). For example, when these network entities process observations transmitted from the first satellite, the transmission (320) can be performed by a network entity other than the first satellite. In such cases, the observations can be processed as described above (e.g., processing the observations based on statistical techniques such as regression modeling, random variable modeling, or other computational methods for estimating relationships between variables). In some embodiments, the transmission can be a first satellite transmitting link acquisition information. Such a transmission can be directed to one or more neighboring satellites using an inter-satellite link. In some embodiments, such a transmission can be accomplished using a terrestrial link to a terrestrial node, which can aggregate this information from multiple different satellites and redistribute this information in any of a variety of forms (including as part of an almanac).

[0041] According to an embodiment, an indication of the statistical model can be transmitted via one or more protocols. These protocols can include flooding, link state protocols, or gossip protocols. In some embodiments, flooding techniques can be used to transmit the indication to other network nodes (e.g., the first satellite, other satellites, or other network entities of a terrestrial network). In some embodiments, flooding techniques can be integrated with link state protocols. In some embodiments, gossip protocols can be used to transmit the indication. Gossip protocols can be similar to flooding techniques, but with reduced message passing. In some embodiments, an entity of a terrestrial network (e.g., a terrestrial site) can be used to transmit the indication to other network nodes (e.g., the first satellite, other satellites, or other network entities of a terrestrial network).

[0042] Once an indication of the statistical model of the link acquisition time has been transmitted, e.g., based on received information indicating the link acquisition time (i.e., the indication of the statistical model of the link acquisition time), a prediction (330) is made regarding the future link acquisition time of the first satellite. According to an embodiment, the indication of the statistical model of the link acquisition time can be used by a satellite (e.g., the first satellite or another satellite) or other network entity (e.g., a network entity of a terrestrial network) to operate a statistical model for estimating the future inter-satellite link acquisition time regarding the first satellite. Thus, the estimation of the future inter-satellite link acquisition time can be performed locally, remotely, or in combination thereof. The remote estimation of the future acquisition time can include an estimation performed at least in part by an entity of the terrestrial network (e.g., an entity on the ground). Some embodiments can use the indication of the statistical model to predict (330) the probability that the link acquisition will be completed at a specific time. In various embodiments, the prediction (330) can be performed by a satellite other than the above-mentioned first satellite in a satellite constellation. However, in some embodiments, the prediction (330) can also be performed by the first satellite.

[0043] According to an embodiment, the nominal link acquisition time can be determined based on the indication of the statistical model transmitted in step 320 above. The indication can include the statistical model itself or the parameters of the statistical model. The parameter values of the statistical model can be provided or determined during the execution of step 310 above.

[0044] In one case, a satellite remote from the satellite providing the indication of the statistical model can use the indication of the statistical model (e.g., a regression model) to predict the future link acquisition time regarding the first satellite. The indication can include the statistical model itself or its parameters. The remote satellite can use ephemeris data (e.g., the approximate orbits and status information of each satellite (any satellite) in the satellite constellation) to determine the nominal link acquisition time. Then, the nominal link acquisition time can be adjusted using the indication of the statistical model.

[0045] In another case, a satellite remote from the satellite providing the indication of the statistical model (e.g., the first satellite) can use the indication of the statistical model (e.g., a random variable model) to predict the probability that the link acquisition will be completed. The indication can include the statistical model itself or its parameters. The remote satellite can determine the nominal link acquisition time based on the probability density function. For example, the nominal link acquisition time can be determined such that the probability of completing the inter-satellite link acquisition (i.e., such that the link is ready to be used) is 0.9 (or some other suitable high value). The parameters of the probability density function can be estimated in step 310 above using statistical inference techniques such as maximum likelihood estimation, maximum a posteriori estimation, expectation maximization, or hidden Markov models or other techniques.

[0046] In some embodiments, the determined nominal link acquisition time can be transmitted as needed to the rest of the satellite network (e.g., other satellites in a satellite constellation, entities communicatively or operationally connected to satellites in the satellite constellation).

[0047] It should be understood that in repeated instances of step 330, nodes at the far end of the first satellite receive link acquisition information from the first satellite and multiple other satellites. When determining routes from the nodes, the link acquisition times of multiple different links in the network can be used to determine the likelihood of a link being available, and this information can be used in the path selection process.

[0048] Figure 4 is a block diagram showing a portion of a satellite constellation 400 provided by an embodiment of the present disclosure, where multiple satellites are connected together in a rectangular grid. Refer Figure 4 , to the left of the seam 440 are five satellites, denoted by the general reference numerals 410 and 420, and to the right of the seam 440 are two satellites 430. The seam 440 refers to the boundary that divides the satellites into two groups such that satellites 410 and 420 are in one of two counter-rotating hemispheres and satellites 430 are in the other of the two counter-rotating hemispheres. The satellites in each hemisphere rotate counter to each other. Satellites 410, 420, and 430 can be operationally or communicatively connected to each other, as Figure 4 shown. Communication links between satellites in different hemispheres of the two counter-rotating hemispheres (i.e., satellites 410, 420 and satellites 430) can cross the seam 440. The satellites can also be arranged in other ways, such as arranged in two or more counter-rotating spheres.

[0049] Satellite 410 can include a router 411, an ephemeris function 412, a link state database 413, and an observation database 414. The router 411 can be a network interface that receives data from other satellites and sends data to other satellites. The ephemeris function 412 can collect or provide ephemeris data for each satellite in the satellite constellation, such as rough orbit and status information. The link state database 413 can be operationally or communicatively connected to the router 411. The link state database 413 can store information describing the satellite network topology, including the current state of the links in the network. The information stored in the link state database 413 can be very detailed such that the shortest path to a network node can be calculated based on the latest information available from the link state database 413. The observation database 414 can be part of the link state database 413 of the router 411, as shown. In some embodiments, the observation database 414 is not part of the link state database 413 but is a separate database. Although marked differently, satellites 420 and 430 have the same or similar components as satellite 410.

[0050] According to an embodiment, the satellite 410 may acquire and measure the link acquisition time according to the need to observe the inter-satellite link. The measured link acquisition time may be stored in the observation database 414. The link acquisition time stored in the observation database 414 may be retrieved to calculate an indication of a statistical model (e.g., a regression model). The statistical model may be used to estimate a future inter-satellite link acquisition time involving the satellite 410.

[0051] When retrieving the link acquisition time from the observation database 414, the satellite 410 may calculate or generate an indication of a statistical model of the link acquisition time. The indication of the statistical model may include the statistical model or its parameters for estimating or predicting the link acquisition time. The parameters may include statistical parameters such as the average link acquisition time, variance, distribution type, or more generally, the probability distribution parameters of a random variable representing a quantity (e.g., but not limited to the link acquisition time). The parameters may include model parameters such as the structure of the model for estimating the link acquisition time. The model parameters may indicate one or more variables such as the random variable to be predicted or (partially or fully) observable quantities. The observable quantities may include satellite position, velocity, time, distance, laser intensity, signal intensity, etc. The model parameters may indicate the causal or statistical relationship between these variables. For example, the model parameters may indicate the numerical relationship between the link acquisition time and observable quantities such as the inter-satellite distance, satellite position, velocity, and signal intensity. The numerical relationship may be represented in the form of a mathematical model such as a Bayesian network, hidden Markov model, stochastic equation, or differential equation, etc. According to an embodiment, the link acquisition time may be modeled using one or more statistical techniques such as regression modeling, random variable modeling, and other computational methods. In some embodiments, the link acquisition time may be modeled as a function of the relative velocity of two satellites.

[0052] In some embodiments, the parameters of the statistical model of the link acquisition time may be calculated using statistical inference techniques such as maximum likelihood estimation, maximum a posteriori estimation, expectation maximization, hidden Markov model, or other techniques. For example, using a maximum likelihood estimator, the parameter values of the statistical model of the link acquisition time will be determined such that the value of the parameter maximizes the output of the likelihood (or probability) function (i.e., the parameter value that maximizes the data likelihood). The likelihood function may be expressed as , where X represents the sampled data set of the link acquisition time, represents the parameters of the statistical model. In other words, using a maximum likelihood estimator, the parameters of the statistical model will be selected such that the likelihood (i.e., L) of the link acquisition time (i.e., X) is maximized.

[0053] When the satellite 410 finishes computing or generating an indication of a statistical model (e.g., a regression model, a random variable model) of the link acquisition time, the satellite 410 can transmit the indication to other satellites (e.g., satellites 420 and 430) in the satellite constellation. Similarly, for example, the indication can include model parameters. When forwarding the statistical model to satellites 420 and 430, one or more routing techniques or transport protocols can be used. Potential routing techniques or transport protocols include flooding, link state protocols, and gossip protocols. In some embodiments, the flooding technique can be integrated with the link state protocol. In some embodiments, the statistical model can be transmitted or propagated to other satellites (e.g., satellites 420 and 430) as part of a link state protocol data unit (PDU) message.

[0054] When satellites 420 and 430 receive an indication of the statistical model of the link acquisition time, these satellites can use the received indication to reconstruct and execute the statistical model in order to estimate the time at which the link involving satellite 410 will compute its link acquisition phase. To this end, satellites 420 and 430 can predict the future link acquisition time of the link involving satellite 410. In some embodiments, satellites 420 and 430 can use the indication of the statistical model to predict the probability that the link acquisition involving satellite 410 will be completed at a specific time.

[0055] According to an embodiment, satellites 420 and 430 can use almanac data (e.g., the approximate orbits and status information of each satellite in the satellite constellation) provided by their almanac function (i.e., a component equivalent to the almanac function 412) to determine the nominal link acquisition time. The nominal link acquisition time can be adjusted using the indication of the statistical model to obtain the future link acquisition time involving satellite 410.

[0056] When estimating the future link acquisition time or the probability of completing the link acquisition, satellites 410, 420, and 430 can use this data to update their local link state databases (e.g., link state database 413). Satellites 410, 420, and 430 can also trigger new routing calculations based on this data.

[0057] Figure 5 FIG. is a schematic diagram of an electronic device 500 provided by different embodiments of the present disclosure, and the electronic device 500 can perform any or all of the operations and features of the above methods explicitly or implicitly described herein. For example, a computer equipped with satellite or network functions can be configured as the electronic device 500.

[0058] As shown in the figure, the device includes a processor 510 (e.g., a central processing unit (CPU) or a dedicated processor such as a digital signal processor (DSP) or other such processor unit), a memory 520, a non-transitory mass storage 530, an I / O interface 540, a network interface 550, and a transceiver 560, all of which are communicatively coupled via a bidirectional bus 570. According to certain embodiments, any or all of the described elements may be used, or only a subset of these elements. Additionally, the device 500 may include multiple instances of certain elements, such as multiple processors, memories, or transceivers. Further, the elements of the hardware device may be directly coupled to other elements without a bidirectional bus. Additionally or alternatively, other electronic devices such as integrated circuits may be employed to perform the required logic operations in addition to the processor and the memory.

[0059] The memory 520 may include any type of non-transitory memory, such as static random access memory (SRAM), dynamic random access memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM), or any combination thereof. The mass storage 530 may include any type of non-transitory storage device, such as a solid state drive, a hard disk drive, a disk drive, an optical drive, a USB drive, or any computer program product configured to store data and machine-executable program code. According to certain embodiments, the memory 520 or the mass storage 530 may record statements and instructions executable by the processor 510 for performing any of the method operations described above.

[0060] Embodiments of the present disclosure provide advantages for operating a satellite network system. For example, the embodiments enable the satellite network system to avoid using open-loop estimates of link acquisition times. This can reduce network downtime due to signal loss on the satellite network link, thereby improving network throughput and utilization. Given the random nature of satellite link acquisition, without the proposed methods and embodiments, each satellite may take a very conservative approach to estimating the time when an inter-satellite link will be reacquired or made available for use.

[0061] It should be understood that although specific embodiments of the technology have been described herein for purposes of illustration, various modifications can be made without departing from the scope of the technology. The specification and drawings are to be regarded only as an illustration of the disclosure as defined by the appended claims and are considered to cover any and all modifications, variations, combinations, or equivalents that fall within the scope of this specification. Specifically, a computer program product or program element for storing machine-readable signals, or a program storage or memory device such as a magnetic or optical tape, disk, or the like, is within the scope of the present technology for controlling the operation of a computer according to the method of the present technology and / or constructing some or all of its components according to the system of the present technology.

[0062] The actions associated with the method described herein can be implemented as encoded instructions in a computer program product. In other words, a computer program product is a computer-readable medium on which software code is recorded to perform the method when the computer program product is loaded into memory and executed on the microprocessor of a wireless communication device.

[0063] The actions associated with the method described herein can be implemented as encoded instructions in multiple computer program products. For example, the first part of the method can be executed using one computing device, and the second part of the method can be executed using another computing device, server, etc. In such a case, each computer program product is a computer-readable medium on which software code is recorded to perform the appropriate part of the method when the computer program product is loaded into memory and executed on the microprocessor of a computing device.

[0064] In addition, each operation of the method can be executed on any computing device (such as a personal computer, server, PDA, etc.) according to one or more program elements, modules, or objects generated from any programming language (such as C++, Java, etc.), or a part of one or more program elements, modules, or objects. In addition, each operation or the file or object, etc. implementing each such operation can be executed by dedicated hardware or a circuit module designed for this purpose.

[0065] Through the description of the above embodiments, the present disclosure can be implemented only by hardware, or can be implemented by software and a necessary general hardware platform. Based on such an understanding, the technical solution of the present disclosure can be embodied in the form of a software product. The software product can be stored in a non-volatile or non-transitory storage medium, and the non-volatile or non-transitory storage medium can be a compact disk read-only memory (CD-ROM), a USB flash drive, or a removable hard disk. The software product includes a number of instructions that enable a computer device (a personal computer, a server, or a network device) to execute the methods provided in the embodiments of the present disclosure. For example, such an execution can correspond to an emulation of the logical operations as described herein. According to an embodiment of the present disclosure, additionally or alternatively, the software product can include a number of instructions that enable a computer device to perform operations for configuring or programming a digital logic device.

[0066] Although the present disclosure has been described with reference to specific features and embodiments of the present disclosure, it is obvious that various modifications and combinations of the present disclosure can be made without departing from the present disclosure. The specification and the drawings are only to be regarded as illustrative of the present disclosure as defined by the appended claims and are considered to cover any and all modifications, variations, combinations, or equivalents within the scope of this description.

Claims

1. A method for supporting the estimation of the acquisition time of inter-satellite links in a satellite constellation, characterized in that, Comprising: Performed by the computing and communication equipment of the first satellite of the satellite constellation: Determining an indication of a statistical model based on observations obtained from previous inter-satellite links involving the first satellite, the statistical model being used to estimate the future inter-satellite link acquisition time involving the first satellite; And Transmitting the indication of the statistical model to one or more other satellites in the satellite constellation, the indication being used by the one or more other satellites or one or more other network entities to operate the statistical model to estimate the future inter-satellite link acquisition time involving the first satellite.

2. The method according to claim 1, wherein The transmitted indication includes information enabling the one or more other satellites to estimate the future inter-satellite link acquisition time.

3. The method according to claim 1 or 2, characterized in that, Data related to the first satellite or the one or more other satellites includes ephemeris data.

4. The method according to claim 1 or 2, characterized in that The one or more other satellites estimate the probability of completing an inter-satellite link acquisition involving the first satellite at a specific time based on the indication.

5. The method according to claim 1 or 2, characterized in that, The indication includes the statistical model.

6. The method according to claim 1 or 2, characterized in that The indication includes one or more parameters of the statistical model.

7. The method according to claim 6, wherein The parameters include one or both of the following parameter types: probability distribution parameters of random variables; and causal or statistical relationships between random variables, observables, or combinations thereof.

8. The method according to claim 1 or 2, characterized in that, The indication of the statistical model is transmitted using one or more of flooding, link state protocols, gossip protocols, and link state protocol data unit (PDU) messages.

9. The method according to claim 1 or 2, characterized in that The indication is calculated using one or more statistical inference methods.

10. The method according to claim 9, wherein The one or more statistical inference methods include regression analysis, regression modeling, random variable modeling, maximum likelihood estimation (MLE), maximum a posteriori (MAP) estimation, expectation maximization (EM), and hidden Markov models.

11. The method according to claim 1 or 2, characterized in that, Transmitting the indication further includes sending the indication to a node in the terrestrial network.

12. The method according to claim 1 or 2, characterized in that The inter-satellite link is between the first satellite and a second satellite placed in the same orbit as the first satellite, or wherein the inter-satellite link is between the first satellite and a second satellite placed in a different orbit from the first satellite, or wherein the inter-satellite link is between the first satellite and a second satellite that communicates across a seam with the first satellite.

13. A device for supporting the estimation of the inter-satellite link acquisition time in a satellite constellation, characterized in that, Comprising: A processor; A memory storing machine-executable instructions that, when executed by the processor, configure the device to: Calculate an indication of a statistical model based on observations obtained from previous inter-satellite links involving a satellite, the statistical model being used to estimate the future inter-satellite link acquisition time involving the satellite; And Transmit the indication of the statistical model to one or more other satellites in the satellite constellation, the indication being used by the one or more other satellites or one or more other network entities to operate the statistical model to estimate the future inter-satellite link acquisition time involving the satellite.

14. The device according to claim 13, characterized in that, The indication includes the statistical model.

15. The device according to claim 13 or 14, characterized in that The indication includes one or more parameters of the statistical model.

16. The device according to claim 15, characterized in that, The parameters include one or both of the following parameter types: probability distribution parameters of random variables; and causal or statistical relationships between random variables, observables, or combinations thereof.

17. The device according to claim 13 or 14, characterized in that, The indication of the statistical model is transmitted using one or more of flooding, link state protocols, gossip protocols, and link state protocol data unit (PDU) messages.

18. The device according to claim 13 or 14, characterized in that, The indication is calculated using one or more statistical inference methods.

19. The device according to claim 18, characterized in that, The one or more statistical inference methods include regression analysis, regression modeling, random variable modeling, maximum likelihood estimation (MLE), maximum a posteriori (MAP) estimation, expectation maximization (EM), and hidden Markov models.

20. The device according to claim 13 or 14, characterized in that, The indication is transmitted at least in part via a terrestrial network.

21. An apparatus for supporting the estimation of the inter-satellite link acquisition time in a satellite constellation, characterized in that, The apparatus includes: a processor; and a memory storing machine-executable instructions that, when executed by the processor, configure the apparatus to: receive an indication of a statistical model that is calculated based on observations obtained from previous inter-satellite links involving a remote satellite, the statistical model being for estimating a future inter-satellite link acquisition time involving the remote satellite; and operate the statistical model using the indication to estimate the future inter-satellite link acquisition time involving the remote satellite.

22. The device according to claim 21, characterized in that, The instructions, when executed by the processor, further configure the apparatus to: estimate the future inter-satellite link acquisition time based on the indication and data related to the remote satellite or other satellites in the satellite constellation.

23. The device according to claim 22, characterized in that, The data related to the remote satellite or other satellites in the satellite constellation includes ephemeris data.

24. The device according to any one of claims 21 or 22, characterized in that The instructions, when executed by the processor, further configure the apparatus to: use the indication to estimate the probability of completing an inter-satellite link acquisition involving the remote satellite at a specific time.

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