Communication method, communication device, computer program product and readable storage medium

Abstract

The embodiment of the invention provides a communication method, communication equipment, a computer program product and a readable storage medium, and relates to the technical field of communication. The UE accesses the first communication device, the UE can obtain the first Doppler frequency offset of the UE relative to the first communication device, and the UE obtains the second Doppler frequency offset of the UE relative to the second communication device according to the first estimated frequency offset, the second estimated frequency offset and the first Doppler frequency offset of the UE relative to the first communication device. The UE calculates a transmission distance between the UE and the second communication equipment according to the second Doppler frequency offset, and calculates a timing advance TA of the UE relative to the second communication equipment according to the transmission distance; the TA is used for communication synchronization between the UE and the second communication equipment. Thus, the UE can obtain the more accurate TA of the UE relative to the second communication equipment without accessing the second communication equipment, and the communication synchronization degree and accuracy of the UE relative to the second communication equipment are improved.

Description

Technical Field

[0001] This application relates to the field of communication technology, and in particular to a communication method, communication device, computer program product, and readable storage medium. Background Technology

[0002] Communication networks are mainly divided into terrestrial networks and non-terrestrial networks (NTNs). Non-terrestrial networks refer to networks that utilize non-terrestrial communication infrastructure such as satellites and high-altitude platforms (e.g., drones, stratospheric balloons) to achieve global communication coverage. In non-terrestrial networks, network equipment moves at high speed relative to user equipment (UE), and UEs switch connections between different network devices.

[0003] In NTN scenarios, satellites are in high-speed motion relative to the UE, and the relative position and velocity between the UE and satellite change rapidly. The UE needs to calculate the distance between itself and the satellite in real time based on both their own position information. This calculation is then used to perform data calculations for communication transmission, ensuring timely synchronization. These calculations include estimating timing advance (TA), calibrating the UE's own receive and transmit parameters based on TA, and ensuring uplink and downlink synchronization between the UE and the satellite, guaranteeing normal access to uplink and downlink services for the UE.

[0004] Existing TA calculation schemes involve the following steps: Before the UE switches from the current satellite to a neighboring satellite, a measurement event is triggered. The reference signal receiving power (RSRP) and reference signal received quality (RSRQ) are calculated using the downlink reference signal from the neighboring satellite, thus determining the path transmission loss. Then, based on the free-space path loss (FSPL), the transmission distance between the UE and the neighboring satellite is calculated, and the TA is calculated based on this distance. However, in NTN scenarios, the variation in RSRP / RSRQ is too small, resulting in a large error between the calculated transmission distance and the TA, leading to poor communication synchronization between the UE and the neighboring satellite. Summary of the Invention

[0005] This application provides a communication method, communication device, computer program product, and readable storage medium to solve the technical problem of poor communication synchronization between the UE and neighboring satellites in existing communication schemes.

[0006] To achieve the above objectives, the embodiments of this application adopt the following technical solutions:

[0007] Firstly, a communication method is provided, applied to a user equipment (UE), involving communication between the UE and a first communication device and communication between the UE and a second communication device. The first communication device is the UE's serving communication device, and the second communication device is a communication device to replace the first communication device in providing network services to the UE.

[0008] The communication scenarios applied in this application embodiment can be either terrestrial communication scenarios or non-terrestrial communication scenarios. In a terrestrial communication scenario, the first and second communication devices are fixed terrestrial base stations, and the UE is a user equipment applicable to fast-moving carriers such as high-speed trains, with the terrestrial base station moving at high speed relative to the UE. Alternatively, it can be extended to other communication scenarios where the UE and network equipment move at relatively high speeds, without limitation.

[0009] In non-terrestrial communication scenarios, the first and second communication devices can be satellites. For example, the first communication device can be a source satellite, and the second communication device can be a target satellite. Alternatively, the first and second communication devices can also be other devices deployed in high altitudes that have the capability to provide network services to the first communication device; there is no limitation. The first and second communication devices can include satellites with relatively low orbital altitudes, such as low-Earth orbit satellites with an altitude of 500-2000 km, or medium-Earth orbit satellites with an altitude of 8000-20000 km. In such communication scenarios, the frequency of UE cell handover is relatively high. The first and second communication devices operate at high speeds relative to the UE; for example, the rotational speed relative to the UE can be 7.56 km / s, etc., without limitation. It should be noted that the first and second communication devices can also be other communication devices, such as high-Earth orbit satellites, etc., without limitation.

[0010] When a UE accesses a first communication device, it can obtain a first estimated frequency offset relative to the first communication device and a second estimated frequency offset relative to a second communication device. For example, the UE can receive a downlink reference signal from the first communication device, measure the downlink reference signal, and calculate the first estimated frequency offset based on the downlink reference signal. Similarly, the UE can receive a downlink reference signal from the second communication device, measure the downlink reference signal, and calculate the second estimated frequency offset based on the downlink reference signal.

[0011] The estimated frequency offset obtained by the UE includes two parts: one part is the deviation between the frequency of the signal received by the UE and the frequency of the signal transmitted by the satellite, i.e., the Doppler frequency offset; the other part is the frequency offset caused by the UE's own devices, i.e., the local oscillator frequency offset. For example, the first estimated frequency offset includes a first Doppler frequency offset and a first local oscillator frequency offset. The first Doppler frequency offset is the deviation between the frequency of the signal received by the UE and the frequency of the signal transmitted by the first communication device. The second estimated frequency offset includes a second Doppler frequency offset and a second local oscillator frequency offset. The second Doppler frequency offset is the deviation between the frequency of the signal received by the UE and the frequency of the signal transmitted by the second communication device.

[0012] When a UE accesses a first communication device, the UE can obtain the first Doppler frequency offset of the UE relative to the first communication device. Based on the first estimated frequency offset, the second estimated frequency offset, and the first Doppler frequency offset of the UE relative to the first communication device, the UE obtains the second Doppler frequency offset of the UE relative to the second communication device.

[0013] The UE calculates the transmission distance between the UE and the second communication device based on the second Doppler frequency offset, and calculates the timing advance TA of the UE relative to the second communication device based on the transmission distance; TA is used for communication synchronization between the UE and the second communication device.

[0014] When a UE accesses a first communication device, before switching from the first to a second communication device, the UE calculates the Transmission Target (TA) relative to the second communication device. The TA is used for communication synchronization between the UE and the second communication device. The UE first obtains the second Doppler frequency offset relative to the second communication device, then calculates the transmission distance relative to the second communication device based on the second Doppler frequency offset, and calculates the TA based on the transmission distance. In this way, the UE can obtain a relatively accurate TA relative to the second communication device even without accessing the second communication device, improving the degree and accuracy of communication synchronization between the UE and the second communication device.

[0015] In another possible implementation of the first aspect, the steps for the UE to acquire the second Doppler frequency offset are further defined.

[0016] The UE obtains a first estimated frequency offset and a second estimated frequency offset. The first estimated frequency offset includes a first Doppler frequency offset and a first local oscillator frequency offset, and the second estimated frequency offset includes a second Doppler frequency offset and a second local oscillator frequency offset. The first local oscillator frequency offset is equal to the second local oscillator frequency offset. The UE calculates the difference between the first estimated frequency offset and the second estimated frequency offset to obtain the differential estimated frequency offset. Identical local oscillator frequency offsets in the first and second estimated frequency offsets cancel each other out. This differential estimated frequency offset is also the difference between the first and second Doppler frequency offsets. Based on this, the UE calculates the difference between the first Doppler frequency offset and the differential estimated frequency offset to obtain the second Doppler frequency offset.

[0017] In this implementation, the UE obtains a differential estimated frequency offset by subtracting the first estimated frequency offset from the second estimated frequency offset, thereby canceling out the identical local oscillator frequency offset that cannot be directly calculated. Then, the UE can convert the first Doppler frequency offset, which can be directly calculated, into the second Doppler frequency offset relative to the second communication device.

[0018] In this way, when the UE cannot obtain ephemeris data due to not being connected to the second communication device, and therefore cannot combine the ephemeris data and the Doppler frequency offset function to calculate the second Doppler frequency offset, an alternative calculation scheme for the second Doppler frequency offset of the UE relative to the second communication device is provided. Because the first and second communication devices rotate at high speeds relative to the UE, the change in the Doppler frequency offset of the UE relative to the second communication device is relatively large, resulting in a relatively small error in the calculated second Doppler frequency offset. This leads to relatively high accuracy of the TA calculated based on the second Doppler frequency offset.

[0019] In another possible implementation of the first aspect, the implementation scheme for the UE to obtain the first Doppler frequency offset relative to the first communication device is further specified.

[0020] The UE can determine the maximum incident angle arrival time relative to the first communication device, the cosine value of the maximum incident angle, and the time difference between the current time and the maximum incident angle arrival time.

[0021] Specifically, the first Doppler frequency offset f d s (t) satisfies:

[0022]

[0023] Among them, f c Let c represent the carrier frequency of the first communication device, and r represent the speed of light. e r represents the Earth's radius. o ω represents the orbital height of the first communication device. F Let represent the angular velocity of the first communication device. And let t represent the current time. The maximum angle of incidence between the first communication device and the UE. Indicates the time of arrival of the maximum angle of incidence. This represents the cosine value of the maximum incident angle.

[0024] In another possible implementation of the first aspect, the scheme for the UE to calculate the transmission distance between the UE and the second communication device based on the second Doppler frequency offset is further specified.

[0025] The UE fits the Doppler frequency offset function based on at least two values ​​of the second Doppler frequency offset to obtain the cosine value of the first moment when the incident angle of the second communication device relative to the UE is the first maximum incident angle and the first included angle. Then, the transmission distance is calculated based on the cosine value of the first moment and the first included angle.

[0026] The UE's method for obtaining the first moment includes: the UE linearly fitting the values ​​of the second Doppler frequency offset at at least two moments to obtain the Doppler frequency offset function of the UE relative to the second communication device. The UE calculates the first moment corresponding to the zero point value of the Doppler frequency offset function.

[0027] The scheme for the UE to obtain the cosine value of the first included angle includes: the UE calculates the cosine value of the first included angle corresponding to the first maximum incident angle based on the second Doppler frequency offset and the first time; the first included angle is the angle between the first straight line and the second straight line. The first straight line is the line connecting the sub-satellite point corresponding to the second communication device and the Earth's center, and the second straight line is the line connecting the sub-satellite point corresponding to the UE and the second communication device.

[0028] In one example, the UE calculates the cosine value of the first included angle corresponding to the first maximum incident angle based on the second Doppler frequency offset and the first time. This may include: the UE obtaining the functional relationship corresponding to the cosine value of the first included angle based on the calculation formulas of the second Doppler frequency offset, the first time, and the second Doppler frequency offset, and solving the functional relationship corresponding to the cosine value of the first included angle to obtain the cosine value of the first included angle.

[0029] The formula for calculating the second Doppler frequency offset includes:

[0030]

[0031] And, the functional relationship corresponding to the cosine value of the first included angle satisfies:

[0032]

[0033] Where, Θ(α) max ) represents the cosine of the first included angle; f c The carrier frequency of the second communication device is represented by c, the speed of light is represented by r. e r represents the Earth's radius. o ω represents the orbital height of the second communication device. F The angular velocity of the second communication device is represented by t, where t represents the current time. The first maximum angle of incidence, Indicates the first moment.

[0034] In one example, the transmission distance s between the UE and the second communication device k (t) satisfies:

[0035]

[0036] Where t represents the current time, Indicates the first moment, This represents the cosine value of the first included angle.

[0037] Furthermore, the relationship between TA and transmission distance satisfies:

[0038] Among them, s k (t) represents the transmission distance, and c represents the speed of light.

[0039] Secondly, this application provides a communication device, including: a transceiver, a memory, and a processor; the transceiver, the memory, and the processor are coupled together;

[0040] The transceiver is used to communicate with a first communication device and a second communication device. The memory is used to store computer program code, which includes computer instructions. When the computer instructions are executed by the communication device, the communication device performs a communication method as described in any of the first aspects.

[0041] Thirdly, a communication device is provided, which has the function of implementing the communication method of the first aspect described above. This function can be implemented by hardware or by hardware executing corresponding software. The hardware or software includes one or more modules corresponding to the aforementioned function.

[0042] Fourthly, a computer-readable storage medium is provided that stores instructions which, when executed on a computer, enable the computer to perform the communication method of any of the first aspects described above.

[0043] Fifthly, a computer program product containing instructions is provided, which, when run on a computer, enables the computer to execute any of the communication methods described in the first aspect above.

[0044] The technical effects of any of the design methods in aspects two through five can be found in the technical effects of different design methods in aspect one, and will not be repeated here. Attached Figure Description

[0045] Figure 1 This is a schematic diagram of a transparent transmission architecture in an NTN scenario;

[0046] Figure 2 This is a schematic diagram of a regeneration architecture in an NTN scenario;

[0047] Figure 3 This is a schematic diagram of UE handover between NTN cells on different satellites;

[0048] Figure 4 This is a schematic diagram of a process for a UE to perform NTN cell handover using the CHO method.

[0049] Figure 5 A flowchart illustrating a communication method provided in an embodiment of this application;

[0050] Figure 6 A schematic diagram illustrating the principle of the communication method provided in the embodiments of this application;

[0051] Figure 7 This is a schematic diagram of the Doppler frequency offset curve involved in the communication method provided in the embodiments of this application;

[0052] Figure 8 This is another schematic diagram of the communication method provided in the embodiments of this application;

[0053] Figure 9 A structural diagram of a communication device provided in an embodiment of this application;

[0054] Figure 10 This is another structural diagram of the communication device provided in an embodiment of this application. Detailed Implementation

[0055] The following description, in conjunction with the accompanying drawings, illustrates exemplary embodiments of this application, including various details to aid understanding. These embodiments should be considered merely exemplary. Therefore, those skilled in the art will recognize that various changes and modifications can be made to the embodiments described herein without departing from the scope of this application. Similarly, for clarity and brevity, descriptions of well-known functions and structures are omitted in the following description.

[0056] To facilitate understanding, some technical common sense involved in the embodiments of this application will be introduced first.

[0057] Communication networks are mainly divided into terrestrial networks and non-terrestrial networks (NTNs). Terrestrial networks refer to networks that achieve communication coverage through communication infrastructure built on the Earth's surface, while non-terrestrial networks utilize non-terrestrial communication infrastructure such as satellites and high-altitude platforms (e.g., drones, stratospheric balloons) to achieve global communication coverage. NTNs can include satellite communication systems, high-altitude platform systems (HAPS), and air-to-ground networks. Satellite communication systems rely on onboard platforms and mainly include low-Earth orbit (LEO), medium-Earth orbit (MEO), and geostationary earth orbit (GEO) satellites. This application's embodiments primarily use a non-terrestrial network as an example of a satellite communication system.

[0058] A communication system includes user equipment (UE) and network equipment. The network equipment provides the communication network, and the UE accesses the communication network. In terrestrial networks, the network equipment is fixed on the ground, and the UE switches connections between different network equipment while stationary or moving. In non-terrestrial networks, the network equipment moves at high speed relative to the UE, and the UE can switch connections between different networks.

[0059] As a supplement to the cellular communication provided by terrestrial networks, non-terrestrial networks enable wireless communication through satellites or high-altitude platforms in areas where terrestrial network equipment cannot cover, such as in extreme areas like deserts, oceans, and high altitudes. This improves coverage, enhances communication capabilities, and achieves full-scenario connectivity across the sky, land, and sea.

[0060] NTN scenarios involve various types of satellites, which can be classified according to their orbital altitude: low Earth orbit (LEO) satellites, medium Earth orbit (MEO) satellites, and high Earth orbit (HEO) satellites. This classification of satellite orbital altitude determines different application scenarios for satellite communication, such as global coverage, regional coverage, and polar coverage.

[0061] Low Earth Orbit (LEO) satellites orbit at altitudes of approximately 500-2000 kilometers. Their short orbital periods, typically between 90 and 120 minutes, allow for lower signal latency and higher data transmission rates. LEO satellites are suitable for Earth observation, scientific research, and new communication satellite systems such as Earth observation satellites, geodetic satellites, and space stations.

[0062] Medium Earth orbit (MEO) satellites have an orbital altitude between 8,000 and 20,000 kilometers. With a relatively long orbital period, MEO satellites are typically used to provide global coverage for satellite navigation systems such as GPS and GLONASS.

[0063] High-orbit satellites orbit at altitudes of approximately 20,000 kilometers or more, with many exceeding 36,000 kilometers.

[0064] In addition, satellites involved in the NTN scenario may also include geostationary transfer orbit (GTO), geostationary orbit (GEO), etc., which will not be elaborated further.

[0065] In the NTN scenario, satellite communication systems have two typical architectures: transparent payload and regenerative payload.

[0066] In a transparent transmission architecture, satellites are responsible for data forwarding but have no data processing capabilities. Figure 1 This is a schematic diagram of a pass-through architecture in an NTN scenario. Figure 1 As shown, the access network equipment is located on the ground, and the satellite is connected to the access network equipment through a gateway station. Data sent by user equipment to the satellite is forwarded by the satellite to the access network equipment for data processing. The link between the satellite and the user equipment is a service link, and the link between the satellite and the access network equipment is a feeder link.

[0067] In a regenerative architecture, satellites have all or part of the functions of a base station, meaning that satellites can perform data processing. Figure 2 This is a schematic diagram of a regeneration architecture in an NTN scenario. (Example) Figure 2 As shown, the data sent by the user equipment to the satellite is processed by the satellite. The link between the satellite and the user equipment is a service link.

[0068] In an NTN scenario, the cell covered by a satellite can be called an NTN cell, and the type of NTN cell is related to the satellite's orbital altitude. Based on different satellite orbital altitudes, NTN cells can be divided into: earth fixed cells, earth moving cells, quasi-earth fixed cells, etc.

[0069] Among them, fixed Earth cells correspond to high-orbit satellites (such as GEO satellites). Fixed Earth cells are achieved through high-orbit satellites, whose satellite beams are pointed at a fixed ground area, providing continuous coverage to that area. Because GEO satellites are synchronized with the Earth's rotation, they are stationary relative to the Earth's surface, thus creating cells with continuous coverage.

[0070] Earth-moving cells correspond to low-Earth orbit (LEO) satellites or medium-Earth orbit (MEO) satellites. The satellite beam moves continuously across the ground, and the coverage area changes as the satellite moves.

[0071] Quasi-Earth fixed cell: A geographical area is covered by one beam for a certain period of time, and in other periods, the area is covered by other beams, usually provided by adjustable beams generated by non-GEO satellites.

[0072] The diameter of a satellite's cell coverage area ranges from 50 km to 1000 km. Due to the satellite's relatively high rotational speed relative to the UE, the connection time between the UE and the satellite is relatively short, requiring frequent cell handovers (HO) during satellite communication. As shown in Table 1, with a cell coverage area diameter of 50 km and a satellite speed of 7.56 km / s, the handover delay for the UE can range from 6.33 s to 6.92 s, indicating a relatively high handover frequency. With a cell coverage area diameter of 1000 km, the handover delay ranges from 126.69 s to 138.38 s, indicating a relatively lower handover frequency. High-orbit satellites have relatively longer handover delays and relatively lower handover frequencies.

[0073] Table 1

[0074]

[0075] In NTN scenarios, especially those using low-Earth orbit (LEO) or medium-Earth orbit (MEO) satellites, the satellites are in high-speed motion relative to the user equipment (UE), resulting in rapid changes in the relative position between the UE and the satellites. Consequently, the UE frequently switches between different satellites. Figure 3 The diagram shown illustrates the handover process between cells on different satellites for a UE. Figure 3As shown in (1), at time T1, the UE is within the coverage area S1 of satellite 1's cell and accesses the cell of satellite 1. From time T1 to time T2, satellites 1 and 2 move at high speed. At this time, the coverage area of ​​satellite 1's cell changes to S1', and the coverage area of ​​satellite 2's cell changes from S2 to S2'. Figure 3 As shown in (2), the coverage area S1' of cell 1 of satellite 1 does not include the current location of the UE, while the coverage area S2' of cell 2 of satellite 2 can cover the current location of the UE. Therefore, the UE can disconnect from satellite 1, switch cells, and access satellite 2 from time T1 to time T2.

[0076] There are several communication methods for UE cell handover. For example, UE can handover between cells on different satellites via conditional handover (CHO). Figure 4 The diagram illustrates a process for a UE to perform cell handover using the CHO method. It mainly includes the following steps S401-S411:

[0077] S401: The UE triggers a measurement event and sends a measurement report to the source cell network device.

[0078] The UE is in RRC_Connected state and accesses the source cell network device. The UE interacts with the source cell network device via signaling to enable the UE to switch from the source cell network device to the target cell network device.

[0079] The UE measures the network equipment of the current serving cell and its neighboring cell, obtains measurement results such as reference signal receiving power (RSRP) and reference signal received quality (RSRQ), obtains a measurement report based on the measurement results, and sends the measurement report to the source cell network equipment.

[0080] S402: The source cell network device makes a cell handover decision and sends a handover request to the target cell network device.

[0081] S403: The target cell network device responds to the handover request.

[0082] S404: The source cell network device sends RRC reconfiguration information to the UE.

[0083] The source cell network device determines whether the relevant triggering conditions for a handover decision (CHO) are met based on the measurement results and other relevant information reported by the UE (such as network load and quality of service requirements). Once the source cell network device determines that the UE meets the CHO triggering conditions, it makes a CHO decision and configures the CHO for the UE, including configuring the CHO candidate cell network device (CHOCandidate Preparation) and other information. The source cell network device communicates with candidate cell network devices, including the target cell network device, to prepare for the handover process, mainly including resource reservation and context information switching.

[0084] The source cell network device sends an RRC reconfiguration message to the UE, instructing the UE to perform a CHO handover and reconfigure the cell. The RRC reconfiguration message includes the configuration information of the CHO candidate cell network device, especially the configuration information of the target cell network device.

[0085] S405: The UE sends an RRC reconfiguration complete message to the source cell network device.

[0086] The UE receives the RRC reconfiguration message from the source cell network device, retrieves the configuration information of the CHO candidate cell network device, and stores it. The UE then sends an RRC reconfiguration complete message to the source cell network device.

[0087] RRC reconfiguration information may also include execution conditions that the UE needs to meet to execute a CHO, which may include the triggering event of the CHO. After receiving the CHO configuration information, the UE begins to evaluate the execution conditions of the candidate cell network device's CHO based on signal quality, signal strength, time alignment, or other custom parameters, and executes the CHO when the execution conditions are met.

[0088] S406: UE acquisition delay.

[0089] After the UE reconfigures the cell, it obtains the latency of the UE relative to the target cell's network equipment. Specifically, the UE can obtain the downlink reference signal of the target cell's network equipment and calculate the latency based on the downlink reference signal.

[0090] S407: The UE initiates a random access request to the target cell network device.

[0091] S408: Target cell network device processing delay.

[0092] S409: The target cell network device responds to the UE's random access request.

[0093] The UE determines to perform a CHO handover, begins to detach from the source cell network device, and requests the application of target configurations.

[0094] The UE initiates a random access channel (RACH) request to the target cell network device, enabling the target cell network device to receive the UE's random access request and confirm whether to accept the connection request. Upon accepting the UE's connection request, the target cell network device sends a connection establishment confirmation message to the UE, carrying with it the resources and configuration information allocated to the UE by the target cell network device. For example, the target cell network device sends a random access response via the physical downlink control channel (PDCCH), including synchronization information and uplink authorization.

[0095] The UE initiates a random access request to the target cell network device to complete registration and resource allocation. In this way, the UE completes a CHO handover, switching from the source cell network device to the target cell network device.

[0096] S410: Handles delays.

[0097] After a UE switches from the source cell network device to the target cell network device, it can obtain the latency relative to the target network cell and perform context synchronization.

[0098] S411: The UE sends an RRC reconfiguration complete message to the target cell network device.

[0099] The RRC reconfiguration completion message indicates that the UE has completed the CHO (Cell Switch Completion) handover. Specifically, the UE can send an RRC reconfiguration completion message to the target cell network device.

[0100] Optionally, after receiving the UE's RRC reconfiguration complete message, the target cell network device confirms that the UE has successfully switched to the target cell network device and is ready to transmit data. The target cell network device sends a handover request to the core network to switch the user plane data path to the target cell network device. After confirming the successful handover of the user plane data path, the core network notifies the target cell network device. After disconnecting from the UE, the source cell network device can release the resources previously occupied by the UE.

[0101] When a UE performs a CHO handover, it can quickly respond and execute the handover when specific conditions are met, reducing its reliance on network handover commands and thus reducing handover latency and improving handover success rate. The CHO handover mechanism is particularly suitable for high-speed mobile scenarios or areas at the edge of network coverage, where signal conditions may change rapidly.

[0102] UE cell handover allows the UE to trigger handover automatically when specific conditions are met, reducing latency from waiting for network handover commands. The handover conditions adopted by the UE can more flexibly respond to changes in the radio environment, improving handover success rate and network efficiency. The UE can quickly respond to signal changes, making it suitable for high-speed mobility scenarios such as trains or cars.

[0103] Before performing a handover, the UE needs to calculate the transmission distance between the satellite and the UE in real time based on the satellite's location information and the UE's location information. Based on the transmission distance between the satellite and the UE, the UE calculates the timing advance (TA) of the data transmission for communication. Based on the TA, the UE calibrates its own receiving and transmitting parameters, as well as the uplink and downlink synchronization between the UE and the satellite, to ensure the normal access of the UE's uplink and downlink services and to ensure timely synchronization of communication.

[0104] The UE can obtain the positions of the satellite and the UE in the world coordinate system. The satellite's position (x...) SV ,y SV ,z SV The location of the satellite can be determined through broadcast information, pre-loaded ephemeris information, or positioning results from a broadcast-based Global Navigation Satellite System (GNSS) receiver. For example, the satellite's position can be determined by parsing the System Information Block (SIB) 19 in the broadcast information. The location of the ground UE (x UE ,y UE ,z UE This is mainly calculated through GNSS or Location Based Service (LBS). The UE refers to the formula... Based on the satellite's location information and the UE's location information d, the distance d between the satellite and the UE is calculated. The UE then uses the formula... Calculate TA, where c represents the speed of light.

[0105] In actual communication, the UE may not be able to obtain satellite location information or its own location information. For example, the UE needs to be equipped with a GNSS or LBS positioning module to obtain its location information, which increases the UE's power consumption and hardware costs. The openness of satellite ephemeris information mainly refers to the accessibility and usage restrictions of ephemeris data. If the openness of satellite ephemeris information is low, the satellite may not be able to accurately broadcast satellite ephemeris, thus affecting the accuracy of the UE's acquisition of satellite location information, or the UE may be unable to obtain satellite location information at all.

[0106] Poor accuracy in obtaining satellite location information by the UE, or the inability of the UE to obtain both satellite and UE location information, may result in the UE being unable to accurately calculate the distance between the satellite and the UE, and consequently, being unable to calculate the TA relatively accurately. This leads to poor communication synchronization and accuracy between the UE and the satellite.

[0107] Based on this, embodiments of this application provide a communication method applied to a UE. Before switching from the first communication device to a second communication device, the UE calculates the Transmission Time (TA) relative to the second communication device. The TA is used for communication synchronization between the UE and the second communication device. The UE first obtains the second Doppler frequency offset relative to the second communication device, then calculates the transmission distance between the UE and the second communication device based on the second Doppler frequency offset, and calculates the TA based on the transmission distance. In this way, the UE can obtain a relatively accurate TA relative to the second communication device even without connecting to the second communication device, improving the degree and accuracy of communication synchronization between the UE and the second communication device.

[0108] The communication method provided in this application embodiment can be used in the foregoing Figure 1 and Figure 2The communication system shown is applicable to the following: Third Generation Partnership Project (3GPP) communication systems, such as Long Term Evolution (LTE) systems; Fifth Generation (5G) mobile communication systems; New Radio (NR) systems; Vehicle to Everything (NR V2X) systems; LTE and 5G hybrid networking systems; Wireless Fidelity (WiFi) systems; Device-to-Device (D2D) communication systems; Machine-to-Machine (M2M) communication systems; Integrated Access and Backhaul (IBA) communication systems; Internet of Things (IoT) systems; and other future communication systems. It can also be a non-3GPP communication system.

[0109] The communication method provided in this application can be applied to various communication scenarios, such as one or more of the following communication scenarios: enhanced mobile broadband (eMBB), ultra-reliable low latency communication (URLLC), machine-type communication (MTC), massive machine-type communications (mMTC), D2D, V2X, and IoT communication scenarios.

[0110] In this embodiment, the UE can be described as a terminal. The terminal can be a device with wireless transceiver capabilities or a chip or chip system that can be installed in the device. It allows users to access the network and is a device used to provide voice and / or data connectivity to users. The UE can also be referred to as a first terminal device, user equipment (UE), subscriber unit, terminal, mobile station (MS), or mobile terminal (MT), etc.

[0111] The UE can be deployed on land, including indoors or outdoors, handheld or vehicle-mounted; it can also be deployed on water (such as on ships); and it can also be deployed in the air (such as on airplanes, balloons, and satellites). For example, the UE can be a mobile phone, a tablet computer, or a computer with wireless transceiver capabilities. UE can also be a user station, mobile station, remote station, remote terminal equipment, mobile terminal equipment, user terminal equipment, wireless communication equipment, user agent, user device, cellular phone, cordless phone, session initiation protocol (SIP) phone, wireless local loop (WLL) station, personal digital assistant (PDA), handheld device with wireless communication capabilities, computing device, processing device connected to a wireless modem, in-vehicle equipment, wearable device, terminal device in the Internet of Things (IoT), home appliance, virtual reality (VR) terminal, augmented reality (AR) terminal, wireless terminal in industrial control, wireless terminal in autonomous driving, wireless terminal in telemedicine, wireless terminal in smart grid, wireless terminal in smart city, wireless terminal in smart home, vehicle with vehicle-to-vehicle (V2V) communication capability, intelligent connected vehicle, and UAV-to-UAV communication. Unmanned aerial vehicles (UAVs) with U2U communication capabilities, terminal devices in future networks, or terminal devices in future evolved public land mobile networks (PLMNs), Wi-Fi stations (STAs), or terminal nodes (T nodes) in satellite navigation systems are not limited to these categories. Subsequent embodiments will use a UE as an example for illustration.

[0112] It is understandable that the UE and the mobile user can be completely independent. All user-related information can be stored in the subscriber identity module (SIM) card, which can be used on the UE device. The UE can interact with network-side devices by transmitting and / or receiving signals over the air interface.

[0113] The communication method provided in the embodiments of this application is applied to, for example, Figure 1In the communication system described, the first and second communication devices can be satellites. For example, the first communication device can be a source satellite, and the second communication device can be a target satellite. Alternatively, the first and second communication devices can also be other devices deployed in high altitudes that have the capability to provide network services to the first communication device; there is no limitation. The first and second communication devices can be low-Earth orbit (LEO) or medium-Earth orbit (MEO) satellites. In the NTN scenario using LEO or MEO satellites, the relative rotation speed of the satellites relative to the UE is relatively large, and the relative position changes rapidly. The UE will frequently switch between different satellites, and the UE needs to frequently calculate the TA (Tracking Aspect) relative to the satellites.

[0114] In other cases, the embodiments of this application can also be applied to certain communication scenarios of terrestrial networks. For example, the first and second communication devices are fixed terrestrial base stations, and the UE is a user equipment applicable to fast-moving carriers such as high-speed trains, with the terrestrial base station moving at high speed relative to the UE. Alternatively, it can be extended to other communication scenarios where the UE and network equipment move at relatively high speeds, without limitation.

[0115] The following is combined with Figure 1 The satellite communication system shown herein, taking the UE as the user terminal and the first and second communication devices as satellites, describes the communication method provided in this application embodiment. Actions, terminology, etc., involved in the following embodiments can be referenced interchangeably. The message names or parameter names in the messages exchanged between devices in each embodiment are merely examples, and other names may be used in specific implementations. For example, "corresponding" in the following embodiments can be replaced by "associating," and "sending" in the following embodiments can be replaced by "transmitting."

[0116] In the satellite communication scenario described in this application, there is relative motion between the satellite and the UE's receiver. According to the Doppler effect, there is a difference between the frequency of the satellite's transmitted signal and the frequency of the signal received by the UE. This difference is called the Doppler frequency offset.

[0117] Doppler frequency offset is the ratio of the product of the satellite's velocity and the user's (UE's) velocity to the frequency of the signal transmitted by the satellite. When the ground receiver is stationary, the Doppler frequency offset can be further expressed as the ratio of the satellite's velocity to the frequency of the signal transmitted by the satellite. Therefore, the Doppler frequency offset is directly proportional to the satellite's velocity and inversely proportional to the wavelength of the transmitted signal. When there is relative motion between the satellite and the ground receiver, changes in their relative velocity alter the distance between them. This causes the frequency of the signal received by the ground receiver to differ from the frequency of the signal it expects to receive, further leading to changes in the Doppler frequency offset. This reduces the system's sensitivity, thereby affecting the quality and accuracy of communication.

[0118] Based on this, in this embodiment, when the UE accesses the first communication device, before switching from the first communication device to the second communication device, it needs to calculate the transmission distance between the UE and the second communication device, and then calculate TA based on the transmission distance.

[0119] See Figure 5 This is a flowchart illustrating a communication method provided in an embodiment of this application. This method can be executed by the UE, or by a chip or functional module within the UE, without limitation. Figure 5 As shown, the provided communication method mainly includes the following steps S500-S503:

[0120] S500: The UE obtains the first estimated frequency offset of the UE relative to the first communication device and the second estimated frequency offset of the UE relative to the second communication device.

[0121] The first communication device is the communication device currently accessed by the UE, meaning it is the communication device currently providing network services to the UE. The second communication device is the communication device that the UE will soon access, meaning it will take over the network service from the first communication device.

[0122] In this application, the estimated frequency offset includes two parts: one part is the deviation between the frequency of the signal received by the UE and the frequency of the signal transmitted by the satellite, i.e., the Doppler frequency offset; the other part is the frequency offset caused by the UE's own devices, i.e., the local oscillator frequency offset. For example, the first estimated frequency offset includes a first Doppler frequency offset and a first local oscillator frequency offset. The first Doppler frequency offset is the deviation between the frequency of the signal received by the UE and the frequency of the signal transmitted by the first communication device. The second estimated frequency offset includes a second Doppler frequency offset and a second local oscillator frequency offset. The second Doppler frequency offset is the deviation between the frequency of the signal received by the UE and the frequency of the signal transmitted by the second communication device.

[0123] The local oscillator frequency offset refers to the deviation between the actual frequency and the nominal frequency of the UE's local oscillator signal. The local oscillator frequency offset caused by the UE's own devices is related to the devices themselves and is usually non-zero. Furthermore, the local oscillator frequency offset is the same for different communication devices corresponding to the same UE. In other words, the first local oscillator frequency offset included in the second estimated frequency offset is the same as the second local oscillator frequency offset included in the first estimated frequency offset; both are the UE's local oscillator frequency offset. It should be noted that the UE's first and second local oscillator frequency offsets usually cannot be directly obtained through calculation.

[0124] Optionally, the UE may receive a downlink reference signal from a first communication device, measure the downlink reference signal, and calculate a first estimated frequency offset based on the downlink reference signal. Similarly, the UE may receive a downlink reference signal from a second communication device, measure the downlink reference signal, and calculate a second estimated frequency offset based on the downlink reference signal.

[0125] The downlink reference signal may include any of the following: primary synchronization signal (PSS), secondary synchronization signal (SSS), master information block (MIB).

[0126] Taking the acquisition of the first estimated frequency offset as an example, in specific implementation, the UE can acquire the downlink reference signal broadcast by the first communication device and calculate the first estimated frequency offset based on parameters such as the phase of the downlink reference signal. This process may include:

[0127] Assume the downlink reference signal broadcast by the first communication device is s(t), and the downlink reference signal r(t) received by the UE is the signal obtained after frequency offset from the broadcast downlink reference signal, that is, the r(t) received by the UE is s(t) with frequency offset, r(t) = s(t)exp(2πΔft). Then, r(t)s'(t) = exp(2πΔft). Since the broadcast downlink reference signal s(t) and the received downlink reference signal r(t) are known to the UE, the UE can calculate the first estimated frequency offset Δf at time t based on r(t)s(t) = exp(2πΔft).

[0128] In one example, the first estimated frequency offset of the UE relative to the first communication device can be expressed as f. s (t) means that:

[0129]

[0130] in, Indicates the first Doppler frequency offset, Δf s This indicates the first oscillator frequency offset.

[0131] Similarly, following the above process, a second estimated frequency offset can be obtained, which can be represented by f. k (t) means that:

[0132]

[0133] in, Indicates the second Doppler frequency offset, Δf k The second local oscillator frequency offset, Δf s =Δf k .

[0134] When the UE accesses the first communication device, it can obtain the ephemeris data of the first communication device, and calculate the first estimated frequency offset f based on some parameters in the ephemeris data and the Doppler frequency offset calculation function. s (t) and the first Doppler frequency offset Even without access to the second communication device, the UE can still obtain the downlink reference signal sent by the second communication device and calculate the second estimated frequency offset f based on the downlink reference signal. k (t). Without access to the second communication device, the UE cannot obtain the ephemeris data from the second communication device, and therefore cannot directly calculate the second Doppler frequency offset based on the ephemeris data and the existing Doppler frequency offset calculation formula.

[0135] S501: The UE obtains the second Doppler frequency offset of the UE relative to the second communication device based on the first estimated frequency offset, the second estimated frequency offset, and the first Doppler frequency offset of the UE relative to the first communication device.

[0136] Optionally, the UE can calculate the first Doppler frequency offset included in the first estimated frequency offset, and then subtract the first estimated frequency offset and the second estimated frequency offset obtained from the above formulas (1) and (2) to obtain the difference between the first Doppler frequency offset and the second Doppler frequency offset. Furthermore, based on the calculated first Doppler frequency offset and the difference between the first Doppler frequency offset and the second Doppler frequency offset, the second Doppler frequency offset can be obtained. Specifically, S501 may include S5011-S5013:

[0137] S5011: The UE calculates the first Doppler frequency offset based on the arrival time of the maximum incident angle of the first communication device relative to the UE, the cosine value of the maximum incident angle, and the time difference between the current time and the arrival time of the maximum incident angle.

[0138] When a UE accesses a first communication device, the UE is on the Earth's surface, and the first communication device moves relative to the UE in a satellite orbit. The spatial positions of the first communication device, the UE, and the Earth satisfy certain geometric relationships in the spatial coordinate system. The UE calculates parameters such as the transmission distance and TA relative to the first communication device based on these geometric relationships.

[0139] like Figure 6 The diagram shown illustrates the principle of relative motion between the UE and the communication device in the communication method provided in this embodiment. Figure 6 As shown in (1), the communication equipment moves in the satellite orbit, and its projection onto the Earth's surface forms a sub-satellite track (SST). During the movement of the communication equipment along the satellite orbit, the spatial position of the communication equipment in the satellite orbit has a corresponding sub-satellite point in the sub-satellite track.

[0140] like Figure 6 The incident angle α between the communication device and the UE is the angle between lines AC and CB. Line AC is the line connecting the spatial point A of the communication device and the spatial point C of the UE, and line CB is the line connecting the nadir point B corresponding to the spatial point C of the UE and the spatial point A of the communication device. The incident angle α between the communication device and the UE ranges from [35°, 90°]. The incident angle α between the communication device and the UE changes in real time as the communication device moves, and reaches its maximum value when the incident angle α reaches its maximum value. max In this case, the UE is closest to the communication device, and the communication quality between the UE and the communication device reaches its highest level.

[0141] The angle γ(α) between the communication device and the UE is the angle between the straight line AO ​​containing the spatial point A and the center O of the sphere of the communication device and the straight line BO containing the sub-satellite point B and the center O of the sphere corresponding to the spatial point A.

[0142] In one implementation, when the UE accesses the first communication device, the UE calculates the first Doppler frequency offset function based on the ephemeris data of the first communication device as follows:

[0143]

[0144] Among them, f c Let c represent the carrier frequency of the first communication device, and r represent the speed of light. e r represents the Earth's radius. o ω represents the orbital height of the first communication device. F Let represent the angular velocity of the first communication device. And let t represent the current time. The angle of incidence of the first communication device relative to the UE is the maximum angle of incidence. This indicates the moment when the angle of incidence between the first communication device and the UE is at its maximum. The UE can obtain the ephemeris data of the first communication device and directly or indirectly obtain f from it. c c, r e r o ω F Equal fixed constants, and, obtain Specific values, among which, Let Θ(α) represent the cosine of the angle between the first communication device and the UE at the maximum incident angle. max )=cos(γ(α max )).

[0145] S5012: The UE calculates the difference between the first estimated frequency offset and the second estimated frequency offset to obtain the differential estimated frequency offset.

[0146] The communication method provided in this application embodiment is based on the premise that the UE has the same local oscillator frequency offset relative to both the first and second communication devices, and cancels the same local oscillator frequency offset through differential cancellation. Even when the UE is not connected to the second communication device, it can also calculate the second Doppler frequency offset relative to the second communication device using the first estimated frequency offset and the first Doppler frequency offset relative to the first communication device.

[0147] Specifically, the UE's first estimated frequency offset includes a first Doppler frequency offset and a first local oscillator frequency offset, and the UE's second estimated frequency offset includes a second Doppler frequency offset and a second local oscillator frequency offset. The UE calculates the difference between the first and second estimated frequency offsets, and the resulting estimated frequency offset is denoted as the differential estimated frequency offset. The differential estimated frequency offset cancels out the first and second local oscillator frequency offsets, leaving only the difference between the first and second Doppler frequency offsets. Therefore, the differential estimated frequency offset is equal to the difference between the first and second Doppler frequency offsets. For ease of description, the difference between the first and second Doppler frequency offsets is denoted as the differential Doppler frequency offset, and the differential Doppler frequency offset is equal to the differential estimated frequency offset.

[0148] In one example, using This represents the frequency offset of the difference estimation. The formula for calculating the frequency offset of the difference estimation is as follows:

[0149]

[0150] S5013: The UE calculates the difference between the first Doppler frequency offset and the differentially estimated frequency offset to obtain the second Doppler frequency offset.

[0151] The differentially estimated frequency offset calculated by the UE is equal to the differential Doppler frequency offset. Subtracting the differentially estimated frequency offset from the first Doppler frequency offset yields the second Doppler frequency offset. The formula for calculating the second Doppler frequency offset by the UE is as follows:

[0152]

[0153] The UE can calculate the first Doppler frequency offset at the current moment. First estimated frequency offset f s (t) and the second estimated frequency offset f k Substituting (t) into formula (5), we can calculate the value of the second Doppler frequency offset at the current moment.

[0154] S502: The UE calculates the transmission distance between the UE and the second communication device based on the second Doppler frequency offset.

[0155] If the UE connects to a second communication device, the transmission distance between the UE and the second communication device can be directly calculated using a common distance calculation formula. The common distance calculation formula is as follows:

[0156]

[0157] Wherein, s in formula (6) k (t) represents the transmission distance, r e r represents the Earth's radius. o ω represents the orbital height of the second communication device. F The angular velocity of the second communication device is represented by t, where t represents the current time. The first maximum angle of incidence of the UE relative to the second communication device. This indicates the moment when the angle of incidence of the UE relative to the second communication device is the first maximum angle of incidence, i.e., the first moment.

[0158] If the UE is not connected to the second communication device, it cannot obtain the ephemeris data of the second communication device, and therefore cannot directly calculate the first maximum incident angle and the first moment of the UE relative to the second communication device based on the ephemeris data, and cannot calculate the transmission distance between the UE and the second communication device.

[0159] In the communication scenario described in this application embodiment, the UE has not yet connected to the second communication device, therefore the UE cannot calculate the transmission distance between the UE and the second communication device using formula (6). The UE can first calculate the first maximum incident angle and the first moment, and then calculate the transmission distance between the UE and the second communication device based on the first maximum incident angle and the first moment.

[0160] In this embodiment of the application, the UE can calculate the first maximum incident angle and the first moment relative to the second communication device by the second Doppler frequency offset of the UE relative to the second communication device.

[0161] If the UE connects to the second communication device, the UE can obtain the ephemeris data of the second communication device and, based on the second Doppler frequency offset function:

[0162]

[0163] Calculate the second Doppler frequency offset of the UE relative to the second communication device. Where, f c The carrier frequency of the second communication device is represented by c, the speed of light is represented by r. e r represents the Earth's radius. o ω represents the orbital height of the second communication device. F The angular velocity of the second communication device is represented by t, where t represents the current time. The first maximum incident angle is the angle at which the UE is at its maximum relative to the second communication device. The moment when the incident angle corresponding to the second communication device is the first maximum incident angle, i.e., the first moment, Θ(α) max) represents the cosine value corresponding to the first maximum incident angle. In other words, the UE also needs to use parameters to calculate the second Doppler frequency offset using formula (6). and Θ(α) max ).

[0164] In this embodiment, the UE is not connected to the second communication device, cannot obtain the ephemeris data broadcast by the second communication device, and cannot obtain parameters from the ephemeris data. and Θ(α) max Therefore, it is impossible to substitute the second Doppler frequency offset function to calculate the second Doppler frequency offset. Based on the aforementioned S501, it is known that the UE can calculate the second Doppler frequency offset relative to the second communication device using the first estimated frequency offset and the second estimated frequency offset. The UE can fit the values ​​of the second Doppler frequency offset at at least two times to obtain a third Doppler frequency offset function that can be used to calculate the second Doppler frequency offset, and then calculate the parameters. and Θ(α) max ).

[0165] In one specific implementation, the step of the UE performing S502, which calculates the transmission distance between the UE and the second communication device based on the second Doppler frequency offset, may include S5021-S5024:

[0166] S5021: The UE obtains the third Doppler frequency offset function relative to the second communication device by linear fitting based on the values ​​of the second Doppler frequency offset at at least two times.

[0167] like Figure 7 The diagram shown illustrates the Doppler frequency offset curves involved in the communication method provided in this application embodiment. The horizontal axis represents time T (seconds), the vertical axis of curve S1 represents the Doppler frequency offset (kilohertz), and the vertical axis of curve S2 represents the incident angle (degrees) of the UE relative to the communication device. When the UE accesses the communication device, there is a Doppler frequency offset between the UE and the communication device. Figure 7 As shown in S1, the effective incident angle of the UE relative to the communication device is in the range of (35 degrees - 38 degrees), and the corresponding time period is t1-t2. During this time period, the corresponding curve of Doppler frequency offset is S3, and the Doppler frequency offset changes linearly.

[0168] Based on this, during communication between the UE and the communication equipment, the Doppler frequency offset of the UE relative to the communication equipment changes linearly. Figure 7 As shown in the Doppler frequency offset curve, the incident angle is also at its maximum when the Doppler frequency offset of the UE is 0 during the time period t1-t2. Based on this, by obtaining the zero-point value corresponding to the second Doppler frequency offset function of the UE relative to the second communication device, the first time point corresponding to the first maximum incident angle can be calculated.

[0169] The UE calculates at least two second Doppler frequency offsets and corresponding times relative to the second communication device according to S501, and then obtains the Doppler frequency offset function of the UE relative to the second communication device by fitting.

[0170] S5022: The UE calculates the first moment corresponding to the zero point value of the Doppler frequency offset function.

[0171] The first moment is the moment when the incident angle of the second communication device relative to the UE is the first maximum incident angle.

[0172] In one example, the UE can obtain the second Doppler frequency offset f at time Δt1. d (t1), the second Doppler frequency offset f at time Δt2 d The second Doppler frequency shift f at (t2) and Δt3 d (t3), based on the least squares method for linear fitting of the Doppler frequency offset function. For example, the following formula:

[0173]

[0174] By fitting the slope k and fixed bias b of the Doppler frequency offset function, the Doppler frequency offset function is obtained:

[0175]

[0176] After determining k and b, the UE can calculate the time difference using formula (9).

[0177] It should be noted that the UE can also obtain the Doppler frequency offset function by linear fitting based on the Doppler frequency offset values ​​at at least two times, without limitation.

[0178] S5023: The UE calculates the cosine value of the first included angle corresponding to the first maximum incident angle based on the second Doppler frequency offset and the first time. The first included angle is the angle between the first straight line and the second straight line. The first straight line is the line connecting the sub-satellite point corresponding to the second communication device and the Earth's center. The second straight line is the line connecting the UE and the sub-satellite point.

[0179] For the calculation formula of the second Doppler frequency offset provided by formula (7), an intermediate parameter can be introduced:

[0180]

[0181]

[0182] Substituting into formula (7), we can simplify formula (7) to:

[0183]

[0184] First convert formula (13) to After conversion, Moving to the right will give you:

[0185]

[0186] The formula can be obtained by replacing the intermediate parameters:

[0187]

[0188] Formula (14) represents the unknown variable Θ(α) max The quadratic equation in one variable can be solved to obtain:

[0189]

[0190] because And for a small angle approaching 0, then Θ(α) max The value approaches 1. Solving formula (16) yields two solutions. The solution with a value in the range [0,1] is selected from the two solutions.

[0191] In one example, such as Figure 6 As shown in (2), when the incident angle of the UE relative to the second communication device is the maximum incident angle, the UE falls exactly on the sub-satellite trajectory. And Θ(α) max =1. In this case, the angle of incidence between the UE and the second communication device is the maximum angle of incidence, the transmission distance is usually the minimum, the difference between the frequency of the signal received by the UE and the frequency transmitted by the second communication device is the minimum or even 0, that is, the second Doppler frequency offset is 0, and the communication quality of the UE is good.

[0192] S5024: The UE determines the transmission distance between the UE and the second communication device based on the cosine value of the first moment and the first included angle.

[0193] The UE obtains the first moment when the incident angle of the UE relative to the second communication device is the first maximum incident angle, and the cosine value of the first included angle corresponding to the first moment, which can be applied to the formula (6) to calculate the transmission distance.

[0194] S503: The UE calculates the TA (Transmission Aspect Ratio) relative to the second communication device based on the transmission distance.

[0195] Among them, TA is used for communication synchronization between UE and the second communication device.

[0196] The UE calculates the timing advance TA relative to the second communication device based on the transmission distance. The calculation formula is as follows:

[0197]

[0198] Among them, s k (t) represents the transmission distance, and c represents the speed of light.

[0199] In one specific example, the first communication device the UE accesses is the source satellite, and the second communication device the UE prepares to or attempts to access is the target satellite. Before switching from the source satellite to the target satellite, the UE first obtains its TA (Telematics Availability) relative to the target satellite. For example... Figure 8 The diagram shown is another flowchart illustrating the communication method provided in this application embodiment, which mainly includes the following steps:

[0200] S801: The UE calculates the first estimated frequency offset using the downlink reference signal broadcast by the source satellite.

[0201] When the UE accesses a source satellite, it can obtain downlink reference signals such as PSS, SSS, and MIB broadcast by the source satellite and calculate the first estimated frequency offset based on the signal parameters of the downlink reference signals. The specific implementation scheme for the UE to calculate the first estimated frequency offset of the source satellite can be found in the aforementioned implementation steps of S500.

[0202] S802: The UE parses the information block sent by the source satellite to obtain ephemeris data.

[0203] S803: The UE obtains the position of the source satellite from the ephemeris data and uses the positioning information to calculate the current position of the UE.

[0204] The UE can receive information broadcast by the source satellite, parse the SIB (Information Block) within the broadcast information, and obtain the ephemeris data of the source satellite. The UE can then obtain the source satellite's position from the ephemeris data and calculate its own position based on GNSS or LBS (Location Based on Service) positioning information. It should be noted that the UE can receive information broadcast by the source satellite regardless of whether it is connected to the source satellite. When connected to the source satellite, the UE can accurately and conveniently obtain both the source satellite's position and its own position.

[0205] S804: The UE calculates the maximum angle of incidence between the source satellite and the UE, as well as the time difference between the current moment and the maximum angle of incidence.

[0206] The UE combines the satellite's position and the UE's position to calculate the maximum incident angle of the source satellite and the time difference between the time corresponding to the maximum incident angle and the current time. For specific implementation details, please refer to the specific implementation steps in S5021.

[0207] S805: The UE calculates the first Doppler frequency offset between the source satellite and the UE based on the maximum incident angle and the time difference between the current time and the maximum incident angle.

[0208] Specifically, the execution process of S805 can be referenced from the specific implementation steps of S5011.

[0209] S806: The UE calculates the second estimated frequency offset using the downlink reference signal broadcast by the target satellite.

[0210] Even without access to the target satellite, the UE can receive downlink reference signals such as PSS and SSS broadcast by the target satellite and calculate the second estimated frequency offset based on the signal parameters of the downlink reference signals. The specific implementation scheme for the UE to calculate the first estimated frequency offset of the source satellite can refer to the specific implementation steps of S5011 mentioned above.

[0211] S807: UE calculates the frequency offset of the differential estimation between the source satellite and the target satellite.

[0212] The UE acquires a first estimated frequency offset relative to the source satellite and a second estimated frequency offset relative to the target satellite. The first estimated frequency offset includes a first Doppler frequency offset and a first local oscillator frequency offset, and the second estimated frequency offset includes a second Doppler frequency offset and a second local oscillator frequency offset. The first local oscillator frequency offset and the second local oscillator frequency offset are the same.

[0213] The UE can calculate the difference between the first estimated frequency offset and the second estimated frequency offset, which serves as the differential estimated frequency offset between the source satellite and the target satellite. This differential estimated frequency offset is equal to the differential Doppler frequency offset. In other words, the UE can obtain the difference between the first Doppler frequency offset of the source satellite and the second Doppler frequency offset of the target satellite. The UE can also calculate the value of the first Doppler frequency offset of the source satellite; therefore, the UE can deduce the value of the second Doppler frequency offset of the target satellite. For the specific implementation scheme of the UE obtaining the differential estimated frequency offset and obtaining the value of the second Doppler frequency offset based on it, please refer to the aforementioned implementation schemes of S5012 and S5013, which will not be elaborated upon further.

[0214] S808: The UE calculates the transmission distance between the UE and the target satellite based on the differential estimation frequency offset and the first Doppler frequency offset.

[0215] The UE acquires the values ​​of the second Doppler frequency offset of the target satellite at multiple different times. Based on the linear change characteristic of the Doppler frequency offset curve of the target satellite within a certain period, a partial function of the linear change of the Doppler frequency offset function of the target satellite is fitted. The zero point value of the Doppler frequency offset function is the first time corresponding to the maximum incident angle of the target satellite. Then, the cosine value corresponding to the maximum incident angle is calculated based on the first time. The specific implementation scheme for the UE to acquire the first time corresponding to the maximum incident angle of the target satellite and the cosine value of the maximum incident angle can be referred to the specific implementation steps of S5021-5023, and will not be elaborated here.

[0216] The UE obtains the first moment corresponding to the maximum incident angle of the target satellite and the cosine value of the maximum incident angle. Substituting these values ​​into the transmission distance calculation formula (6), the transmission distance between the UE and the target satellite can be calculated. For specific implementation schemes, please refer to S5024, which will not be elaborated further.

[0217] S809: The UE calculates the TA between the target satellite and the UE for cell handover.

[0218] The UE calculates the transmission distance between the UE and the target satellite. Based on the calculation formula corresponding to the aforementioned formula (17), the TA between the target satellite and the UE can be calculated. Based on this, the UE can switch to the NTN cell of the target satellite according to the TA to achieve communication synchronization with the target satellite.

[0219] In summary, the communication method provided in this application involves the UE calculating the Transmission Time (TA) relative to the second communication device before switching from the first communication device to the second communication device. The TA is used for communication synchronization between the UE and the second communication device. The UE first obtains the second Doppler frequency offset relative to the second communication device, then calculates the transmission distance between the UE and the second communication device based on the second Doppler frequency offset, and calculates the TA based on the transmission distance. In this way, the UE can obtain a more accurate TA, improving the degree and accuracy of communication synchronization between the UE and the second communication device. The UE can obtain an accurate TA without accessing the second communication device, and choose whether to access it based on the TA, reducing the number of times the UE switches satellites.

[0220] As one possible product form, the terminal or network device in this application embodiment can be implemented using a general bus architecture. For ease of explanation, see [link to documentation]. Figure 9 , Figure 9 This is a schematic diagram of the structure of a communication device 900 provided in an embodiment of this application. The communication device 900 includes a processor 901 and a transceiver 902. The communication device 900 can be a gNB, or a chip or chip system therein; or, the communication device 900 can be a UE, or a chip or module therein. Figure 9 Only the main components of the communication device 900 are shown. In addition to the processor 901 and transceiver 902, the communication device may further include a memory 903 and input / output devices (not shown).

[0221] Optionally, the processor 901 is mainly used to process communication protocols and communication data, control the entire communication device, execute software programs, and process the data of the software programs. The memory 903 is mainly used to store software programs and data. The transceiver 902 may include radio frequency (RF) circuitry and an antenna. The RF circuitry is mainly used for converting baseband signals to RF signals and processing RF signals. The antenna is mainly used for transmitting and receiving RF signals in the form of electromagnetic waves. Input / output devices, such as touch screens, displays, and keyboards, are mainly used to receive user input data and output data to the user.

[0222] Optionally, the processor 901, transceiver 902, and memory 903 can be connected via a communication bus.

[0223] When the communication device is powered on, the processor 901 can read the software program in the memory 903, interpret and execute the instructions of the software program, and process the data of the software program. When data needs to be transmitted wirelessly, the processor 901 performs baseband processing on the data to be transmitted and outputs the baseband signal to the radio frequency (RF) circuit. The RF circuit processes the baseband signal and transmits the RF signal outward in the form of electromagnetic waves through the antenna. When data is sent to the communication device, the RF circuit receives the RF signal through the antenna, converts the RF signal into a baseband signal, and outputs the baseband signal to the processor 901. The processor 901 converts the baseband signal into data and processes the data.

[0224] In another implementation, the radio frequency circuitry and antenna can be set up independently of the processor that performs baseband processing. For example, in a distributed scenario, the radio frequency circuitry and antenna can be arranged remotely, independent of the communication equipment.

[0225] In some embodiments, those skilled in the art will recognize that the above-described communication device 1200 can be implemented in terms of hardware. Figure 9 The communication device shown is in the form of 900.

[0226] As another possible product form, the communication device in this application can adopt... Figure 10 The shown composition structure, or including Figure 10 The components shown. Figure 10 This application provides a schematic diagram of the composition of a communication device 1000, which can be a terminal or a chip or system-on-a-chip in a terminal; or, it can be a module or chip or system-on-a-chip in a terminal or network device.

[0227] like Figure 10 As shown, the communication device 1000 includes at least one processor 1001 and at least one communication interface. Figure 10(This is merely an example illustration, using a communication interface 1004 and a processor 1001 as examples. Optionally, the communication device 1000 may also include a communication bus 1002 and a memory 1003.)

[0228] Processor 1001 may be a general-purpose central processing unit (CPU), a general-purpose processor, a network processor (NP), a digital signal processor (DSP), a microprocessor, a microcontroller, a programmable logic device (PLD), or any combination thereof. Processor 1001 may also be other devices with processing functions, such as circuits, devices, or software modules, without limitation.

[0229] The communication bus 1002 is used to connect different components in the communication device 1000, enabling communication between them. The communication bus 1002 can be a peripheral component interconnect (PCI) bus or an extended industry standard architecture (EISA) bus, etc. This bus can be divided into address bus, data bus, control bus, etc. For ease of representation, Figure 10 The bus is represented by a single thick line, but this does not mean that there is only one bus or one type of bus.

[0230] Communication interface 1004 is used for communicating with other devices or communication networks. For example, communication interface 1004 can be a module, circuit, transceiver, or any device capable of communication. Optionally, communication interface 1004 can also be an input / output interface located within processor 1001, used to implement signal input and signal output for the processor.

[0231] The memory 1003 may be a device with storage function, used to store instructions and / or data. The instructions may be computer programs.

[0232] For example, the memory 1003 may be a read-only memory (ROM) or other type of static storage device capable of storing static information and / or instructions; it may also be a random access memory (RAM) or other type of dynamic storage device capable of storing information and / or instructions; it may also be an electrically erasable programmable read-only memory (EEPROM), a compact disc read-only memory (CD-ROM) or other optical disc storage, optical disc storage (including compressed optical discs, laser discs, optical discs, digital universal optical discs, Blu-ray discs, etc.), magnetic disk storage media or other magnetic storage devices, etc., without limitation.

[0233] It should be noted that the memory 1003 can exist independently of the processor 1001, or it can be integrated with the processor 1001. The memory 1003 can be located inside or outside the communication device 1000, without limitation. The processor 1001 can be used to execute the instructions stored in the memory 1003 to implement the methods provided in the following embodiments of this application.

[0234] As an optional implementation, the communication device 1000 may also include an output device 1005 and an input device 1006. The output device 1005 communicates with the processor 1001 and can display information in various ways. For example, the output device 1005 may be a liquid crystal display (LCD), a light-emitting diode (LED) display device, a cathode ray tube (CRT) display device, or a projector, etc. The input device 1006 communicates with the processor 1001 and can receive user input in various ways. For example, the input device 1006 may be a mouse, keyboard, touchscreen device, or sensing device, etc.

[0235] In some embodiments, the hardware implementation will be apparent to those skilled in the art as described above. Figure 4 The communication device 400 shown can be adopted Figure 10 The communication device shown is in the form of 1000.

[0236] As an example, Figure 4 The functionality / implementation process of the processor in the middle can be obtained through Figure 10 The processor 1001 in the communication device 1000 shown calls computer execution instructions stored in memory 1003 to implement the function. Figure 4 The function / implementation process of the transceiver in the middle can be understood through Figure 10 This is achieved through the communication interface 1004 in the communication device 1000 shown.

[0237] It should be noted that, Figure 10 The structures shown do not constitute a specific limitation on the communication device. For example, in other embodiments of this application, the communication device may include more or fewer components than those shown, or combine some components, or split some components, or have different component arrangements. The components shown may be implemented in hardware, software, or a combination of software and hardware.

[0238] In some embodiments, this application also provides a communication device, which includes a processor for implementing the methods in any of the above method embodiments.

[0239] As one possible implementation, the communication device also includes a memory. This memory stores necessary computer programs and data. The computer program may include instructions, which a processor can invoke to instruct the communication device to execute the methods described in any of the above method embodiments. Alternatively, the memory may not be present in the communication device.

[0240] As another possible implementation, the communication device also includes an interface circuit, which is a code / data read / write interface circuit, used to receive computer execution instructions (which are stored in memory and may be read directly from memory or may be transmitted through other devices) and transmit them to the processor.

[0241] As another possible implementation, the communication device also includes a communication interface for communicating with modules outside the communication device.

[0242] It is understood that the communication device can be a chip or a chip system. When the communication device is a chip system, it can be composed of chips or may include chips and other discrete devices. This application embodiment does not specifically limit this. This application embodiment also provides a computer-readable storage medium storing a computer program, which, when run on a computer, causes the computer to execute the communication method provided in the above embodiments.

[0243] This application also provides a computer program product containing instructions that, when run on a computer, enable the computer to execute the communication method provided in the above embodiments.

[0244] The specific implementation methods and technical effects of the communication devices, computer-readable storage media, and computer program products containing instructions provided in this application can be found in the specific implementation process and technical effects of the communication methods provided in the foregoing embodiments, which will not be repeated here.

[0245] In some embodiments, as described above, those skilled in the art will clearly understand that, for the sake of convenience and brevity, the division of the functional modules described above is merely an example. In practical applications, the functions described above can be assigned to different functional modules as needed, that is, the internal structure of the device can be divided into different functional modules to complete all or part of the functions described above. The specific working process of the system, device, and unit described above can be referred to the corresponding process in the foregoing method embodiments, and will not be repeated here.

[0246] In the embodiments of this application, the functional units can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or as a software functional unit.

[0247] If the integrated unit is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solutions of the embodiments of this application, essentially, or the parts that contribute to the prior art, or all or part of the technical solutions, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) or processor to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as flash memory, portable hard disk, read-only memory, random access memory, magnetic disk, or optical disk.

[0248] The above description is merely a specific implementation of the embodiments of this application, but the protection scope of the embodiments of this application is not limited thereto. Any changes or substitutions within the technical scope disclosed in the embodiments of this application should be covered within the protection scope of the embodiments of this application. Therefore, the protection scope of the embodiments of this application should be determined by the protection scope of the claims.

Claims

1. A communication method, characterized in that, The communication method, applied to a user equipment (UE), includes: The first estimated frequency offset of the UE relative to the first communication device and the second estimated frequency offset of the UE relative to the second communication device are obtained; the first communication device is the serving communication device of the UE, and the second communication device is the communication device to take over the first communication device to provide network services to the UE; Based on the first estimated frequency offset, the second estimated frequency offset, and the first Doppler frequency offset of the UE relative to the first communication device, the second Doppler frequency offset of the UE relative to the second communication device is obtained; The transmission distance between the UE and the second communication device is calculated based on the second Doppler frequency offset. The timing advance (TA) of the UE relative to the second communication device is calculated based on the transmission distance; the TA is used for communication synchronization between the UE and the second communication device.

2. The communication method according to claim 1, characterized in that, The step of obtaining the second Doppler frequency offset of the UE relative to the second communication device based on the first estimated frequency offset, the second estimated frequency offset, and the first Doppler frequency offset of the UE relative to the first communication device includes: Calculate the difference between the first estimated frequency offset and the second estimated frequency offset to obtain the differential estimated frequency offset; The difference between the first Doppler frequency offset and the differentially estimated frequency offset is calculated to obtain the second Doppler frequency offset.

3. The communication method according to claim 2, characterized in that, The first estimated frequency offset includes the first Doppler frequency offset and the first local oscillator frequency offset, and the second estimated frequency offset includes the second Doppler frequency offset and the second local oscillator frequency offset, wherein the first local oscillator frequency offset is equal to the second local oscillator frequency offset.

4. The communication method according to claim 2 or 3, characterized in that, The first Doppler frequency offset is determined based on the arrival time of the maximum incident angle of the first communication device relative to the UE, the cosine value of the maximum incident angle, and the time difference between the current time and the arrival time of the maximum incident angle.

5. The communication method according to claim 4, characterized in that, The first Doppler frequency offset f d s (t) satisfies: Wherein, the f c The carrier frequency of the first communication device is represented by c, the speed of light is represented by r. e The radius r represents the Earth's radius. o The ω represents the orbital height of the first communication device. F This represents the angular velocity of the first communication device. And, t represents the current time, the The maximum angle of incidence of the first communication device relative to the UE, the Indicates the arrival time of the maximum incident angle, the This represents the cosine value of the maximum incident angle.

6. The communication method according to any one of claims 1-5, characterized in that, The step of calculating the transmission distance between the UE and the second communication device based on the second Doppler frequency offset includes: Based on the values ​​of the second Doppler frequency offset at at least two moments, the Doppler frequency offset function of the UE relative to the second communication device is obtained by linear fitting. Calculate the first moment corresponding to the zero point value of the Doppler frequency offset function; the first moment is the moment when the incident angle of the second communication device relative to the UE is the first maximum incident angle; Based on the second Doppler frequency offset and the first time, the cosine value of the first included angle corresponding to the first maximum incident angle is calculated; the first included angle is the angle between the first straight line and the second straight line, the first straight line is the line connecting the sub-satellite point corresponding to the second communication device and the Earth's center, and the second straight line is the line connecting the UE and the sub-satellite point corresponding to the second communication device. The transmission distance between the UE and the second communication device is determined based on the first moment and the cosine value of the first included angle.

7. The communication method according to claim 6, characterized in that, The step of calculating the cosine value of the first included angle corresponding to the first maximum incident angle based on the second Doppler frequency offset and the first time includes: The functional relationship corresponding to the cosine value of the first included angle is obtained based on the calculation formulas for the second Doppler frequency offset, the first time, and the second Doppler frequency offset. The cosine value of the first included angle is obtained by solving the functional relationship corresponding to the cosine value of the first included angle.

8. The communication method according to claim 7, characterized in that, The formula for calculating the second Doppler frequency offset includes: And / or, The function corresponding to the cosine value of the first included angle satisfies: Where, Θ(α) max ) represents the cosine value of the first included angle; the f c The carrier frequency of the second communication device is represented by c, the speed of light is represented by r. e The radius r represents the Earth's radius. o The ω represents the orbital height of the second communication device. F The angular velocity of the second communication device is represented by t, where t represents the current time. For the first maximum incident angle, the This indicates the first moment.

9. The communication method according to any one of claims 1-8, characterized in that, The first communication device includes a low-Earth orbit satellite or a medium-Earth orbit satellite; The second communication device includes a low-Earth orbit satellite or a medium-Earth orbit satellite.

10. A communication device, characterized in that, The communication device includes: a transceiver, a memory, and a processor; the transceiver, the memory, and the processor are coupled together. The transceiver is used to communicate with a first communication device and a second communication device, and the memory is used to store computer program code, the computer program code including computer instructions, which, when executed by the communication device, cause the communication device to perform the communication method as described in any one of claims 1 to 9.

11. A computer-readable storage medium, characterized in that, The computer-readable storage medium stores instructions that, when executed in a communication device, cause the communication device to perform the communication method as described in any one of claims 1 to 9.

12. A computer program product, characterized in that, The computer program product includes instructions that, when executed in a communication device, cause the communication device to perform the communication method as described in any one of claims 1 to 9.

Images