An aircraft on-demand access and time synchronization fusion design method

Abstract

The application relates to a kind of aircraft access and time synchronization fusion design method, which can simultaneously realize the needs of access and high-precision measurement, and the time reference of user spacecraft is synchronized to Beidou by using the clock difference adjustment of two-way measurement distance result calculation clock, and the link can also satisfy the low-speed communication ability of user spacecraft and target spacecraft.The application can satisfy the scene of multi-user spacecraft time synchronization, uses burst signal to scan in different space, realizes the ability of navigation message broadcast, access, high-precision measurement, can also satisfy the ability of multi-user simultaneous access and time synchronization, changes the situation that access process and time synchronization process are designed according to two stages in the past.

Description

Technical Field

[0001] This invention belongs to the field of communication and measurement technology, and relates to a design method for the fusion of on-the-fly access and time synchronization for aircraft. Background Technology

[0002] The integrated communication and navigation technology is developing rapidly, requiring the technical integration of the communication and navigation fields. When designing integrated communication and navigation systems in vast airspace, two technical challenges arise: on-the-spot access and time synchronization. Previously, on-the-spot access and time synchronization were addressed independently.

[0003] Ad-hoc access technology is a specialized technology in the field of communications, addressing a primary issue for user terminals accessing communication networks. Time synchronization is a problem to be solved in the fields of time and frequency measurement. Patent CN109150284A, "Multi-Scenario Ad-hoc Access Method for Telemetry and Control Communication Systems," discloses a method for multi-scenario ad-hoc access in telemetry and control communication systems, aiming to solve the problem that existing planned access telemetry and control methods cannot meet the future telemetry and control needs of aerospace systems. When the application scenario is a multi-beam full-space scanning access method, the spacecraft continuously transmits telemetry signals, and the telemetry and control communication system calls the scanning beam to perform full-space target search, identifying the received telemetry signals. When it is a cooperative spacecraft, a remote control signal is transmitted to that spacecraft. This method requires an omnidirectional antenna for assistance. This patent is representative of the ad-hoc access technology field.

[0004] Time synchronization is a problem that needs to be solved in the fields of time and frequency measurement. Patent CN110793528A, "An Adaptive Networking Method for Time Synchronization Based on GNSS Satellite Shared View," provides a method for adaptive networking of time synchronization based on GNSS satellite shared view. By leveraging GNSS satellite shared view, it achieves high-precision wireless time comparison between nodes, solving the problem of high-precision time comparison between nodes within a time network. Furthermore, by adaptively selecting multiple comparison reference points among nodes within the network, it addresses the problem of self-monitoring and judging the synchronization performance integrity of each node. This patent addresses the time synchronization problem under shared view conditions and has already seen widespread application.

[0005] Traditionally, user spacecraft time synchronization links and on-demand access are designed separately. However, for scenarios involving target spacecraft serving large-scale airspace scans, long scan cycles, and uncontrollable access times, independent design of on-demand access and time synchronization is no longer sufficient to meet the requirements of lunar and deep space applications. Summary of the Invention

[0006] The technical problem solved by this invention is to overcome the shortcomings of the prior art and propose a design method for the integration of on-demand access and time synchronization for spacecraft, so as to realize the two processes of on-demand access and time synchronization, and provide space-time reference and communication access services for spacecraft in the Earth-Moon space.

[0007] The solution of the present invention is:

[0008] A design method for integrating on-demand access and time synchronization for aircraft includes:

[0009] The target aircraft divides the service airspace into multiple wave positions according to the service space to achieve complete coverage;

[0010] The target aircraft divides its working time slot into a receiving time slot and a transmitting time slot. In the transmitting time slot, after broadcasting the complete navigation message and access capability information based on the wave position information in the first wave position, the target aircraft switches to the second wave position, updates the navigation message and access capability information based on the second wave position information and broadcasts it, and so on, until all wave positions are scanned and then switches to the receiving time slot.

[0011] The user aircraft divides its working time slots into receive time slots and transmit time slots. In the receive time slot, the user aircraft receives the navigation message and access capability information of the target aircraft, then calculates the target aircraft's position and determines its access capability. If the target aircraft has access capability, it determines and adjusts the antenna pointing. In the transmit time slot, the user aircraft continuously sends access requests and its own position information to the target aircraft.

[0012] The target aircraft receives signals transmitted by the user aircraft in the receiving time slot, obtains information about the user aircraft requesting access, and measures the pseudorange T of the user aircraft requesting access. A And allocate communication resources to it, and during the transmission time slot, the pseudorange T A The communication resources are sent as an acknowledgment signal to the corresponding user aircraft, enabling the user aircraft to access the system on demand.

[0013] The user aircraft receives the acknowledgment signal from the target aircraft in the receiving time slot, and analyzes the pseudorange T through the acknowledgment signal. A The pseudorange T of the target aircraft is measured using a local time reference. B Based on the two-way pseudorange measurement results, a two-way time comparison calculation is performed to unify the user aircraft's time reference with the target aircraft's time reference, thereby achieving time synchronization between the user aircraft and the target aircraft.

[0014] Preferably, initially, the user spacecraft is preloaded with the ephemeris information of the target spacecraft, which can roughly determine the position of the target spacecraft. Based on the position of the target spacecraft, the user spacecraft determines the pointing direction of the receiving antenna, adjusts the attitude of the antenna to point at the target spacecraft, and puts it in a constant receiving state.

[0015] Preferably, the user aircraft performs two-way time comparison calculations based on the two-way pseudorange measurement results to unify the user aircraft's time reference with the target aircraft's time reference in the following manner:

[0016] The user aircraft will analyze the pseudorange T A And the measured pseudorange T of the target aircraft B Perform normalization processing;

[0017] The liasion positioning method is used to determine the orbital position of the user's spacecraft.

[0018] Obtain the clock difference between the user's aircraft and the target aircraft;

[0019] The user aircraft uses the clock difference to unify its time base with the target aircraft's time base.

[0020] Preferably, the user aircraft resolved pseudorange T A and the target aircraft pseudorange T measured using a local time reference B It is expressed as follows:

[0021]

[0022]

[0023] in:

[0024] T AB (t1): At time t1, the pseudorange T of the user aircraft requesting access, measured by the target aircraft. A ;

[0025] T BA (t2): At time t2, the pseudorange T of the target aircraft is measured by the user aircraft using the local time reference. B ;

[0026] The three-dimensional position vector of the target aircraft at time t2;

[0027] The three-dimensional position vector of the user's spacecraft at time t1;

[0028] δ A (t2): The clock difference of the target aircraft at time t2;

[0029] δ B (t1): The clock difference of the user's spacecraft at time t1;

[0030] δ rel-AB δ rel-BA Relativistic effects of satellite clock periodicity;

[0031] User aircraft receiver latency;

[0032] Target vehicle launch delay;

[0033] User spacecraft transmitter latency;

[0034] Target aircraft receiver latency;

[0035] ε AB and ε BA It is random noise.

[0036] Preferably, the user aircraft will resolve the pseudorange T A And the measured pseudorange T of the target aircraft B Normalization is performed as follows:

[0037] Analyze pseudorange T of user aircraft A and the target aircraft pseudorange T measured using a local time reference B Normalized to t0 (t0≤t2<t1), then

[0038]

[0039]

[0040] T AB (t0): The pseudorange normalized value of the user aircraft requesting access, measured by the target aircraft at time t0;

[0041] T BA (t0): The normalized pseudorange value of the target aircraft measured by the user aircraft using the local time base at time t2;

[0042] dT AB The relative clock difference of the target aircraft at time t1;

[0043] dT BA The relative clock difference of the user's spacecraft at time t1;

[0044] c: speed of light;

[0045] The three-dimensional position vector of the target aircraft at time t0;

[0046] The three-dimensional position vector of the user's spacecraft at time t0;

[0047] δ A (t0): The clock difference of the target aircraft at time t0;

[0048] δ B (t0): The clock difference of the user's spacecraft at time t0.

[0049] Preferably, the liaison positioning method is used to determine the orbital position of the user spacecraft. The formula is as follows:

[0050]

[0051] Preferably, the clock difference between the user aircraft and the target aircraft is obtained using the following formula.

[0052]

[0053] Preferably, the user aircraft uses the clock difference to adjust its local 1pps time, unifying the time base with the target aircraft's time base, thus achieving synchronization with the target aircraft's BeiDou time.

[0054] Preferably, the target aircraft's transmission and reception time slots use the same signal structure, and each time slot contains one frame of data.

[0055] Preferably, the random access channel multiplexing for the target aircraft and the user aircraft adopts the SDMA+CDMA method.

[0056] The advantages of this invention compared to the prior art are:

[0057] (1) This invention proposes a method for simultaneous time synchronization and on-demand access. This method can simultaneously meet the requirements of on-demand access and high-precision measurement. When the time reference of the user spacecraft is synchronized to BeiDou by calculating the clock difference using the bidirectional measurement distance results, the link can also meet the low-speed communication capability of the user spacecraft and the target spacecraft.

[0058] (2) This invention can meet the scenario of time synchronization of multiple users spacecraft. It uses burst signals to scan in different Earth-Moon spaces to achieve the ability to broadcast navigation messages, access anytime, and measure with high precision. At the same time, it can meet the ability of multiple users to access and synchronize time simultaneously, changing the previous situation where bidirectional time comparison could only be performed when viewed from the same point of view. Attached Figure Description

[0059] Figure 1 A schematic diagram showing the positions of the target aircraft and the user aircraft;

[0060] Figure 2 A schematic diagram illustrating the communication interaction between the target aircraft and the user aircraft.

[0061] Figure 3 Designed for transmit and receive time slots;

[0062] Figure 4 Designed for ubiquitous signal access;

[0063] Figure 5The results are from a time-synchronized simulation. Detailed Implementation

[0064] The invention will now be further described with reference to the accompanying drawings.

[0065] Deploying a target spacecraft at a Lagrange point can provide spatiotemporal reference and access communication services for lunar user spacecraft. The target spacecraft can provide a BeiDou time reference, using beam scanning to serve the entire Earth-Moon space. User spacecraft require the target spacecraft to provide a time reference and simultaneously request access services from the target spacecraft, utilizing communication channel resources. However, target spacecraft have drawbacks such as a large service range, long scanning cycle, and uncontrollable access time. This invention designs a method for integrating on-demand access and time synchronization, which can simultaneously meet the needs for communication channel resources and high-precision time synchronization.

[0066] The target aircraft is deployed at a Lagrange point and can provide user aircraft with spatiotemporal reference and access communication services. The target aircraft scans according to different wavefronts; a wavefront diagram of the scan is shown below. Figure 1 As shown, a total of N wave positions are scanned. The target aircraft operates in a rotating manner, using both receive and transmit time slots, as described in the diagram. Figure 3 As shown. During the transmission time slot, the target aircraft operates in the signal transmission state. During the reception time slot, the target aircraft operates in the signal reception state. The duration of the transmission time slot and the duration of the reception time slot are T, respectively. S Second. Figure 2 This is a schematic diagram illustrating the communication interaction between the target aircraft and the user aircraft.

[0067] The transmit and receive time slots use the same signal structure. The effective signal length is 2 seconds, and each time slot contains one frame of data. Access channel multiplexing uses SDMA+CDMA.

[0068] Channel multiplexing: SDMA+CDMA;

[0069] Duplex mode: Time Division Duplex (TDD), transmit time slot 2s;

[0070] Signal frame structure as follows Figure 4 As shown, the synchronization segment and the fine tracking segment are unmodulated data. The synchronization segment is 400ms and the fine tracking segment is 212ms. The synchronization segment includes a preamble segment and a capture segment. The synchronization header preamble segment is 200ms of single-carrier data.

[0071] The data segment of the signal transmitted from the target aircraft to the user aircraft includes broadcast navigation information and access confirmation information. The data segment of the signal transmitted from the user aircraft to the target aircraft includes the link for requesting access and pseudorange measurement, and these two links are implemented in a time-division multiplexing manner on the same frequency.

[0072] The design of unrestricted access and time synchronization fusion for aircraft specifically includes four steps:

[0073] (1) Target aircraft broadcast navigation messages and access capability information:

[0074] The target aircraft will be divided into multiple wave positions according to the service range to achieve complete coverage and ensure that all user aircraft can establish links with the target aircraft.

[0075] The target spacecraft uses the same time reference as BeiDou and divides its working time slots into receive and transmit time slots. The target spacecraft continuously switches between these transmit and receive time slots. The duration of both transmission and reception requires scanning the entire Earth-Moon spaceband. Within the transmit time slot, the target spacecraft continuously broadcasts navigation messages based on the bandband. After broadcasting the complete navigation message and access capability information for a bandband, it switches to the next bandband, updates the message and access capability information, and then broadcasts again, until the bandband scan is completed and it switches to the receive time slot.

[0076] (2) Service Application

[0077] The user spacecraft divides its operating time slots into receive and transmit time slots. During service access requests, the user spacecraft remains in receive mode. The user spacecraft carries the target spacecraft's ephemeris information, and its established time reference error is on the order of seconds, allowing it to roughly determine the target spacecraft's location. Based on the target spacecraft's location, the user spacecraft determines the pointing orientation of its receiving antenna, adjusts the antenna's attitude to point towards the target spacecraft, and maintains a constant receiving state.

[0078] The user aircraft receives navigation messages and access capability information from the target aircraft. After receiving the navigation messages, the user aircraft calculates the target aircraft's position and determines its access capability. If access capability is available, the user aircraft adjusts its antenna pointing more accurately and sends an access request to the target aircraft, while also transmitting its own position. The user aircraft continues to transmit its position and request information until a complete transmission time slot is reached.

[0079] (3) Service Request Response Receipt

[0080] The target aircraft receives the signal transmitted by the user aircraft in the receiving time slot, obtains the user aircraft information based on the request information, and measures the pseudorange T of the requesting user. ASimultaneously, pseudorange measurements are transmitted and communication resources are allocated for response acknowledgments. The target aircraft waits for the launch slot to send an acknowledgment signal to itself.

[0081] (4) Two-way time comparison

[0082] The user aircraft uses a local time reference to measure the pseudorange T of the target aircraft. B The user aircraft analyzes the pseudorange T using the feedback signal. A Based on the two-way pseudorange measurement results, a two-way time comparison calculation is performed.

[0083] The two-way comparison and calculation are implemented on the user aircraft. The target aircraft can provide the BeiDou time reference and satellite ephemeris. The target aircraft receives navigation messages and parses the information content. When it receives confirmation information from its own access acknowledgment, the user aircraft extracts the two-way measurement pseudorange, where T... AB (t) represents the measured pseudorange received by the target aircraft at time t from the signal transmitted by the user aircraft. BA (t) represents the measured pseudorange received by the user aircraft at time t, based on the signal transmitted by the target aircraft.

[0084] The target spacecraft and the user spacecraft employ a two-way satellite measurement mode. The two satellites transmit signals to each other for ranging, exchanging measurement data and performing calculations to obtain the relative clock difference and inter-satellite distance measurements. This eliminates most of the systematic and correlation errors affecting inter-satellite ranging. It is difficult for the two satellites to simultaneously transmit and receive ranging data. For time comparison, the two-way pseudorange needs to be normalized to the same epoch.

[0085] The link measurements between the target aircraft and the user aircraft can be represented as follows:

[0086]

[0087]

[0088] In the above formula:

[0089] T AB (t1): The pseudorange measured by the target aircraft at time t1 is the signal transmitted by the user aircraft.

[0090] T BA (t2): The pseudorange measured by the user aircraft at time t2 is the signal transmitted by the target aircraft.

[0091] The three-dimensional position vector of the target aircraft at time t1;

[0092] The three-dimensional position vector of the user's spacecraft at time t2;

[0093] δ A (t1): The clock difference of the target aircraft at time t1;

[0094] δ B (t2): The clock difference of the user's spacecraft at time t2;

[0095] δ rel-AB δ rel-BA Relativistic effects of satellite clock periodicity;

[0096] User aircraft receiver latency;

[0097] Target vehicle launch delay;

[0098] User spacecraft transmitter latency;

[0099] Target aircraft receiver latency;

[0100] ε AB and ε BA It is random noise.

[0101] After correcting and compensating for relativistic effect errors and transmission / reception delays, and reducing the ranging values ​​measured at t1 and t2 to t0 (t0≤t2<t1), the link measurement values ​​can be expressed as follows:

[0102]

[0103]

[0104] T AB (t0) and T BA Adding (t0) eliminates satellite clock bias information, leaving only constraints on satellite orbital parameters. The distance measurement value is then used to determine the orbital position of the user's spacecraft using the liasion positioning method.

[0105]

[0106] T AB (t0) and T BA The difference between (t0) and (t0) can eliminate satellite orbit information and be used directly for clock error determination.

[0107]

[0108] This clock difference information is used to adjust the user's local 1pps time to achieve synchronization with the target aircraft's BeiDou time. The result of time synchronization using the above method is as follows: Figure 5As shown, time synchronization achieved high accuracy, and the user's aircraft also achieved the goal of access.

[0109] This invention provides a method for seamless access and time synchronization that can be used not only in lunar space but also in near-Earth space. It can be used not only in the time-division multiplexing method but also in the frequency-division multiplexing method. This design enables multiple users to access target spacecraft for communication and high-precision measurement, significantly optimizing the access and time synchronization process.

[0110] This invention, through the design of a signal system and a link establishment method, enables the low-cost realization of lunar space time reference and communication access services, providing technical support for my country's lunar and deep space exploration.

[0111] Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solutions of the present invention by utilizing the methods and techniques disclosed above without departing from the spirit and scope of the present invention. Therefore, any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the content of the technical solutions of the present invention shall fall within the protection scope of the technical solutions of the present invention.

Claims

1. A design method for integrating on-the-fly access and time synchronization for aircraft, characterized in that, include: The target aircraft divides the service airspace into multiple wave positions according to the service space to achieve complete coverage; The target aircraft divides its working time slot into a receiving time slot and a transmitting time slot. In the transmitting time slot, after broadcasting the complete navigation message and access capability information based on the wave position information in the first wave position, the target aircraft switches to the second wave position, updates the navigation message and access capability information based on the second wave position information and broadcasts it, and so on, until all wave positions are scanned and then switches to the receiving time slot. The user aircraft divides its working time slots into receive time slots and transmit time slots. In the receive time slot, the user aircraft receives the navigation message and access capability information of the target aircraft, then calculates the target aircraft's position and determines its access capability. If the target aircraft has access capability, it determines and adjusts the antenna pointing. In the transmit time slot, the user aircraft continuously sends access requests and its own position information to the target aircraft. The target aircraft receives signals transmitted by the user aircraft in the receiving time slot, obtains information about the user aircraft requesting access, and measures the pseudorange T of the user aircraft requesting access. AB And allocate communication resources to it, and during the transmission time slot, the pseudorange T AB The communication resources are sent as an acknowledgment signal to the corresponding user aircraft, enabling the user aircraft to access the system on demand. The user aircraft receives the acknowledgment signal from the target aircraft in the receiving time slot, and analyzes the pseudorange T through the acknowledgment signal. AB The pseudorange T of the target aircraft is measured using a local time reference. BA Based on the two-way pseudorange measurement results, a two-way time comparison calculation is performed to unify the user aircraft time reference with the target aircraft time reference, thereby achieving time synchronization between the user aircraft and the target aircraft. The user aircraft performs two-way time comparison calculations based on the two-way pseudorange measurement results, and the method for unifying the user aircraft's time reference to the target aircraft's time reference is as follows: The user aircraft will analyze the pseudorange T AB And the measured pseudorange T of the target aircraft BA Perform normalization processing; The liasion positioning method is used to determine the orbital position of the user's spacecraft. Obtain the clock difference between the user's aircraft and the target aircraft; The user aircraft uses the clock difference to unify its time base with the target aircraft's time base.

2. The design method for the fusion of on-demand access and time synchronization for aircraft according to claim 1, characterized in that, Initially, the user spacecraft is preloaded with the ephemeris information of the target spacecraft, which allows it to roughly determine the target spacecraft's position. Based on the target spacecraft's position, the user spacecraft determines the pointing direction of the receiving antenna, adjusts the antenna's attitude to point at the target spacecraft, and puts it in a constant receiving state.

3. The design method for the fusion of on-demand access and time synchronization for aircraft according to claim 1, characterized in that, User aircraft analyzes pseudorange T AB and the target aircraft pseudorange T measured using a local time reference BA It is expressed as follows: in: : At any given moment, the pseudorange of the user aircraft requesting access is measured by the target aircraft; : At any given moment, the user aircraft uses its local time reference to measure the target aircraft's pseudorange; : Target aircraft in The three-dimensional position vector at time t; User aircraft in The three-dimensional position vector at time t; : Target aircraft in The time difference; User aircraft in The time difference; , Relativistic effects of satellite clock periodicity; User aircraft receiver latency; : Target spacecraft launch delay; User spacecraft transmitter latency; : Target aircraft receiver latency; and It is random noise; Speed ​​of light.

4. The design method for the fusion of on-demand access and time synchronization of an aircraft according to claim 3, characterized in that, The user aircraft will analyze the pseudorange T AB And the measured pseudorange T of the target aircraft BA Normalization is performed as follows: Analyze the pseudorange T of the user's aircraft AB and the target aircraft pseudorange T measured using a local time reference BA Normalization to ( ),but : At any given moment, the target aircraft measures the normalized pseudorange value of the user aircraft requesting access. : At any given time, the user aircraft uses a local time reference to measure the target aircraft's pseudorange normalized value; The relative clock difference of the target aircraft at time t1; The relative clock difference of the user's spacecraft at time t1; Speed ​​of light; : Target aircraft in The three-dimensional position vector at time t; User aircraft in The three-dimensional position vector at time t; : Target aircraft in The time difference; User aircraft in The time difference.

5. The design method for the fusion of on-demand access and time synchronization for aircraft according to claim 4, characterized in that, Use liaison positioning methods to determine the orbital position of the user spacecraft. The formula is as follows: 。 6. The design method for the fusion of on-demand access and time synchronization for aircraft according to claim 5, characterized in that, The clock difference between the user aircraft and the target aircraft can be obtained using the following formula.

7. The design method for the fusion of on-demand access and time synchronization for aircraft according to claim 6, characterized in that, The user aircraft uses the clock difference to adjust its local 1pps time, unifying the time base with the target aircraft's time base, thus achieving synchronization with the target aircraft's BeiDou time.

8. The design method for the fusion of on-demand access and time synchronization of an aircraft according to claim 1, characterized in that, The target aircraft uses the same signal structure for both the transmission and reception time slots, and each time slot contains one frame of data.

9. The design method for the fusion of on-demand access and time synchronization of an aircraft according to claim 1, characterized in that, The random access channel multiplexing for target aircraft and user aircraft adopts the SDMA+CDMA method.

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