Frequency offset estimation method for ubiquitous network, and system, medium and terminal

Abstract

Provided in the present invention are a frequency offset estimation method for a ubiquitous network, and a system, a medium and a terminal. The method comprises the following steps: receiving radio signals of a plurality of carriers from a plurality of satellites; constructing a satellite-to-ground geometric relationship between each satellite and a terminal; on the basis of the radio signals and the satellite-to-ground geometric relationship, constructing a frequency offset estimation equation; and on the basis of the frequency offset estimation equation, acquiring a frequency offset estimation value. The frequency offset estimation method for a ubiquitous network, the system, the medium and the terminal in the present invention can realize accurate frequency offset estimation when a ubiquitous network lacks GNSS signals, thereby ensuring the continuity and reliability of the ubiquitous network.

Description

Ubiquitous network frequency offset estimation methods, systems, media and terminals Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a method, system, medium, and terminal for estimating frequency offset in ubiquitous networks. Background Technology

[0002] Ubiquitous networks encompass an integrated network spanning air, space, land, and sea, including not only terrestrial networks but also non-terrestrial networks (NTNs), providing users with seamless coverage and ubiquitous connectivity. In NTN systems, the Doppler effect is particularly pronounced due to the high mobility of satellite platforms. For example, in a 600 km / h low Earth orbit (LEO-600) satellite scenario, the satellite's speed can reach 7.56 km / s. At lower elevation angles, the Doppler frequency offset can even exceed 20 ppm. Compared to terrestrial or maritime communication systems, satellite communication faces greater frequency offset challenges; therefore, traditional frequency synchronization technologies designed for terrestrial networks cannot be directly applied and require further enhancements tailored to the satellite communication environment.

[0003] The NTN system in the 3GPP Rel-17 / 18 standard relies on Global Navigation Satellite System (GNSS) functionality to determine its position information and calculate frequency offset compensation based on this. However, GNSS signals are susceptible to interference or spoofing. Ensuring user equipment (UE) connectivity to the ubiquitous network even when GNSS is unavailable significantly improves system robustness. During frequency synchronization, satellites can send downlink synchronization signals to each user, who then compensates for the frequency offset using local estimation, thus completing signal reception. However, in uplink communication, frequency offset differences between different users can lead to inter-user interference at the receiver, severely impacting the system's uplink performance.

[0004] In ubiquitous networks, the main sources of large carrier frequency offsets are twofold: first, the Doppler frequency offset caused by the relative motion between the satellite and the terminal; and second, the carrier frequency offset caused by errors in the terminal's local oscillator. As shown in Figure 1, the total downlink (DL) frequency offset on the UE side is F. d +F o , of which F d It is the Doppler frequency shift caused by the relative motion between the satellite and the UE, F o This is a frequency offset introduced by the oscillator. If the UE cannot distinguish F... d and F o The total frequency offset F estimated using the UE d +F oPerforming uplink frequency offset pre-compensation will generate 2F at the base station side. o Frequency offset will significantly impact uplink transmission. For UEs with GNSS support, the Doppler frequency offset between the satellite and the UE can be derived using GNSS information. This offset, combined with the total downlink frequency offset, can then be used to adjust the oscillator error, ultimately achieving frequency synchronization. However, achieving frequency synchronization when GNSS is unavailable presents a critical challenge. Summary of the Invention

[0005] In view of the shortcomings of the prior art described above, the purpose of this invention is to provide a ubiquitous network frequency offset estimation method, system, medium and terminal, which can achieve accurate frequency offset estimation in the absence of GNSS signals in ubiquitous networks, thereby ensuring the continuity and reliability of ubiquitous networks.

[0006] In a first aspect, the present invention provides a ubiquitous network frequency offset estimation method, the method comprising the following steps: receiving wireless signals from multiple carriers from multiple satellites; constructing a satellite-to-ground geometric relationship between each satellite and a terminal; constructing a frequency offset estimation equation based on the wireless signals and the satellite-to-ground geometric relationship; and obtaining a frequency offset estimate based on the frequency offset estimation equation.

[0007] In one implementation of the first aspect, the satellite-to-ground geometric relationship between each satellite and the terminal includes the relationship between the satellite velocity and the signal transmission link angle θ and the geocentric angle γ between the satellite and the terminal.

[0008] In one implementation of the first aspect, constructing the frequency offset estimation equation based on the wireless signal and the satellite-to-ground geometry includes:

[0009] Based on the satellite-to-ground geometric relationship established between the i-th satellite and the terminal, cosθ i =f(γ) i Using the function f(γ) of the geocentric angle i The Doppler frequency offset is characterized by the relative velocity between the transmitter of the i-th satellite and the terminal receiver. By linear approximation The function f(γ) of the geocentric angle i It is approximately a linear expansion of the geocentric angle, where γ i Let θ represent the geocentric angle between the i-th satellite and the terminal receiver. i This represents the angle between the velocity of the i-th satellite and the signal transmission link;

[0010] Downlink Total Frequency Offset Based on the i-th Satellite Transmitter and Terminal Receiver Constructing the Doppler frequency offset of the i-th satellite and terminal crystal frequency offset The equation is for estimating the frequency offset of unknowns.

[0011] In one implementation of the first aspect, Chebyshev polynomials are used for f(γ) i Perform a linear approximate expansion, where Where n cheby Let A be the Chebyshev order. k is the Chebyshev coefficient.

[0012] In one implementation of the first aspect, when connected to two satellites, a set of frequency offset estimation equations for the Doppler frequency shift correlation between the two satellites with the geocentric angle as the correlation relationship is constructed:

[0013] In one implementation of the first aspect, the frequency offset estimation equations are:

[0014] Where γ2 = γ1 + α, and α represents the geocentric angle between the two satellites.

[0015] In one implementation of the first aspect, the method further includes using a Kalman filter to adjust the γ1 and f calculated according to the frequency offset estimation equations over time t. o The estimated values ​​are smoothed.

[0016] In a second aspect, the present invention provides a ubiquitous network frequency offset estimation system, the system comprising a receiving module, a first construction module, a second construction module, and an estimation module;

[0017] The receiving module is used to receive wireless signals from multiple carriers from multiple satellites;

[0018] The first construction module is used to construct the satellite-to-ground geometric relationship between each satellite and the terminal;

[0019] The second building module is used to construct a frequency offset estimation equation based on the wireless signal and the satellite-to-ground geometry.

[0020] The estimation module is used to obtain the frequency offset estimate based on the frequency offset estimation equation.

[0021] Thirdly, the present invention provides a storage medium on which a computer program is stored, which, when executed by a processor, implements the above-described ubiquitous network frequency offset estimation method.

[0022] Fourthly, the present invention provides a terminal, comprising: a processor and a memory;

[0023] The memory is used to store computer programs;

[0024] The processor is used to execute the computer program stored in the memory, so that the terminal performs the ubiquitous network frequency offset estimation method described above.

[0025] As described above, the ubiquitous network frequency offset estimation method, system, medium, and device of the present invention have the following beneficial effects:

[0026] (1) It can achieve accurate frequency offset estimation in the absence of GNSS signals in ubiquitous networks, thereby ensuring the continuity and reliability of ubiquitous networks;

[0027] (2) It has the ability to access multiple satellites, can obtain the radio resources of multiple satellite nodes or carriers to estimate frequency offset, can separate and estimate the Doppler frequency shift caused by motion and the frequency offset caused by oscillator instability, thereby completing accurate uplink frequency offset pre-compensation and achieving frequency synchronization.

[0028] (3) It has a wide range of applications in the field of wireless communication for ubiquitous communication network architecture, and can provide more accurate, convenient and fast frequency offset estimation, thereby achieving more efficient, safer and wider communication services.

[0029] (4) It provides more reliable and accurate methods for fields such as physical layer parameter estimation, and is expected to advance the research progress of key technologies of ubiquitous network physical layer. Attached Figure Description

[0030] Figure 1 shows a flowchart of a ubiquitous network frequency offset estimation method of the present invention in one embodiment;

[0031] Figure 2 shows a schematic diagram of the structure of a ubiquitous network in one embodiment;

[0032] Figure 3 shows a schematic diagram of the satellite-ground geometry in one embodiment;

[0033] Figure 4 shows a structural schematic diagram of the maximum geocentric angle in one embodiment;

[0034] Figure 5 shows a schematic diagram of the ubiquitous network frequency offset estimation system of the present invention in one embodiment;

[0035] Figure 6 shows a schematic diagram of the structure of the terminal of the present invention in one embodiment. Detailed Implementation

[0036] The following specific examples illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and various details in this specification can also be modified or changed based on different viewpoints and applications without departing from the spirit of the present invention. It should be noted that, unless otherwise specified, the following embodiments and features described therein can be combined with each other.

[0037] It should be noted that the illustrations provided in the following embodiments are only schematic representations of the basic concept of the present invention. Therefore, the drawings only show the components related to the present invention and are not drawn according to the actual number, shape and size of the components in the actual implementation. In the actual implementation, the form, quantity and proportion of each component can be arbitrarily changed, and the layout of the components may also be more complex.

[0038] The following embodiments of the present invention provide a ubiquitous network frequency offset estimation method, which can be applied to terminals. The terminals described in this invention may include mobile phones with wireless charging capabilities, tablet computers, laptops, wearable devices, in-vehicle devices, augmented reality (AR) / virtual reality (VR) devices, ultra-mobile personal computers (UMPCs), netbooks, personal digital assistants (PDAs), etc. The embodiments of the present invention do not impose any restrictions on the specific type of terminal.

[0039] For example, the terminal may be a station (STAION, ST) in a WLAN with wireless charging capability, a cellular phone, cordless phone, Session Initiation Protocol (SIP) phone, Wireless Local Loop (WLL) station, Personal Digital Assistant (PDA) device, handheld device with wireless charging capability, computing device or other processing device, computer, laptop computer, handheld communication device, handheld computing device, and / or other devices for communication over a wireless system, as well as next-generation communication systems, such as mobile terminals in 5G networks, mobile terminals in future evolved Public Land Mobile Networks (PLMNs), or mobile terminals in future evolved Non-terrestrial Networks (NTNs).

[0040] For example, the terminal can communicate with networks and other devices wirelessly. The wireless communication can use any communication standard or protocol, including but not limited to Global System for Mobile communication (GSM), General Packet Radio Service (GPRS), Code Division Multiple Access (CDMA), Wideband Code Division Multiple Access (WCDMA), Long Term Evolution (LTE), email, Short Messaging Service (SMS), BT, GNSS, WLAN, NFC, FM, and / or IR technologies. The GNSS can include Global Positioning System (GPS), Global Navigation Satellite System (GLONASS), BeiDou Navigation Satellite System (BDS), Quasi-Zenith Satellite System (QZSS), and / or Satellite Based Augmentation Systems (SBAS).

[0041] The ubiquitous network frequency offset estimation terminal of the present invention accesses multiple satellites by selecting appropriate access interfaces. Based on this capability, it receives radio resources from multiple different satellites or subcarriers, and obtains auxiliary information by processing some of these radio resources. Based on the radio resources and the processed auxiliary information, it constructs an overdetermined equation, transforms the equation based on the satellite-ground geometry, and then performs a linear approximation to obtain a linear overdetermined equation for frequency offset estimation, thereby completing the estimation of N frequency offset parameters.

[0042] It should be noted that the radio resources include a Synchronization Signal Block (SSB), a Tracking Reference Signal (TRS), Channel Status Information (CSI), a Phase Tracking Reference Signal (PTRS), a Master Information Block (MIB), a System Information Block (SIB), and a custom training sequence. Different radio resources are used depending on the application scenario when performing frequency offset estimation. The auxiliary information includes carrier operating frequency, node type, and satellite ephemeris information. The satellite ephemeris information includes satellite orbital parameters, satellite velocity, satellite coordinates, and satellite elevation angle. Different auxiliary information is used depending on the application scenario when performing frequency offset estimation.

[0043] The technical solutions of the present invention will now be described in detail with reference to the accompanying drawings.

[0044] As shown in Figure 1, in one embodiment, the ubiquitous network frequency offset estimation method of the present invention includes steps S1-S4.

[0045] Step S1: Receive wireless signals from multiple carriers from multiple satellites.

[0046] Specifically, in a ubiquitous network with multiple satellites as shown in Figure 1, the UE can receive wireless signals carried by multiple carriers from multiple satellites. The UE accesses these multiple satellites by selecting a suitable access interface. The wireless signals are typically modulated and transmitted using Cyclic Prefix-Orthogonal Frequency Division Multiplexing (CP-OFDM) technology, and transmitted through a tap delay line (TDL) wireless channel model with multiple taps. The information involved in the wireless signal carried by the i-th carrier includes the receiving frequency, sampling interval, complex channel coefficients without Doppler offset, relative velocity between the satellite transmitter and the terminal receiver, variance of the received additive white Gaussian noise, oscillator accuracy offset between the satellite transmitter and the terminal receiver, reference signal, and Doppler offset caused by the relative motion between the satellite transmitter and the terminal receiver. It should be noted that the i-th satellite carries the i-th carrier.

[0047] In one embodiment, the baseband equivalent received signal r of the wireless signal carried by the i-th carrier i [n] is represented as Where f i T represents the frequency of the i-th carrier received by the terminal receiver. s i This represents the sampling interval of the i-th carrier. Let c represent the complex channel coefficients of the i-th carrier without Doppler offset, and v represent the speed of light. i w represents the relative velocity between the i-th satellite transmitter and the terminal receiver. i [n] represents the additive white Gaussian noise (AWGN) received by the terminal receiver on the i-th carrier. f i Frequency offset caused by oscillator mismatch between the satellite transmitter and the terminal receiver, s i [n] represents the reference signal on the i-th carrier; The value represents the Doppler offset caused by the relative motion between the terminal receiver and the i-th satellite transmitter, and n represents the sampling point.

[0048] Step S2: Construct the satellite-to-ground geometric relationship between each satellite and the terminal.

[0049] Specifically, the satellite-to-ground geometric relationship between each satellite and the terminal includes the relationship between the satellite velocity and the signal transmission link angle θ and the geocentric angle γ between the satellite and the terminal.

[0050] In one embodiment, as shown in Figure 2, the satellite-to-ground geometric relationship is as follows:

[0051] Where, θ i R represents the angle between the velocity of the i-th satellite and the signal transmission link. E H represents the Earth's radius. i Let θ represent the orbital altitude of the i-th satellite. i γ represents the elevation angle of the i-th satellite relative to the terminal. i This represents the geocentric angle between the i-th satellite and the terminal. This represents the slant distance between the i-th satellite and the terminal. Additionally, the geocentric angle α between the two satellites can be determined by the slant distance R between their nadir points. d and Earth's radius R E Calculated, i.e. Slope distance R of the sub-star point d It can be calculated based on the satellite's nadir coordinates in the ephemeris information.

[0052] As shown in Figure 3, the geocentric angle γ has a maximum value, which is...

[0053] Step S3: Construct a frequency offset estimation equation based on the wireless signal and the satellite-to-ground geometric relationship.

[0054] Specifically, based on the satellite-to-ground geometric relationship cosθ established between the i-th satellite and the terminal i =f(γ) i Using the function f(γ) of the geocentric angle i The Doppler frequency offset is characterized by the relative velocity between the transmitter of the i-th satellite and the terminal receiver. By linear approximation The function f(γ) of the geocentric angle i The expression is approximately a linear expansion of the geocentric angle. This is based on the total downlink frequency offset of the link between the i-th satellite transmitter and the terminal receiver. Constructing the Doppler frequency offset of the i-th satellite and terminal crystal frequency offset The equation is for estimating the frequency offset of unknowns.

[0055] Since the speed of the user terminal is negligible compared to the speed of the satellite, the Doppler frequency shift caused by the relative motion between the terminal receiver and the i-th satellite transmitter... It can be expressed as:

[0056] therefore,

[0057] To linearly correlate the Doppler frequency offset formulas of multiple satellites, for We make a linear approximation. Since the geocentric angle γ has a maximum value, its value is within a finite interval. Therefore, let... And Chebyshev polynomials were used to apply f(γ) i Perform a linear approximate expansion of a preset order. Where n cheby Let A be the Chebyshev order. k Let be the Chebyshev coefficients. Taking a 7th-order linear approximation expansion as an example, the relevant information about the geocentric angle γ is obtained. i The linear expansion is: f(γ) i )=A7γ i 7 +A6γ i 6 +A5γ i 5 +A4γ i 4 +A3γ i 3 +A2γ i 2 +A1γ i +A0

[0058] Where A k Let be the Chebyshev coefficients, k = 0, ..., 7.

[0059] To more accurately describe the frequency offset caused by oscillator mismatch between the satellite transmitter and the terminal receiver, an oscillator accuracy f is introduced. o To obtain the crystal oscillator frequency offset of the terminal for the i-th carrier. Baseband equivalent received signal r i [n] can be rewritten as in T s i This represents the sampling interval of the i-th carrier. ω represents the complex channel coefficients of the i-th carrier without Doppler offset. i [n] represents the additive white Gaussian noise received by the terminal receiver on the i-th carrier, f o Indicates the oscillator accuracy between the satellite transmitter and the terminal receiver, s i [n] represents the reference signal on the i-th carrier, and n represents the sampling point.

[0060] Assume s i [n] represents the known reference signal, and the received signal r i [n] and the known signal s i Multiplying the conjugates of [n] yields the sequence z. i [n] is as follows:

[0061] in, To eliminate the complex channel coefficients The introduced unknown phase rotation is used to perform differentiation on the sequence, and then summation is performed n-fold to obtain the sequence R. i [m i ]:

[0062] in, m i M is the differential step size of carrier i. i This is the maximum differential step size of carrier i. To reduce the impact of noise on the estimation accuracy, the receiver adjusts the result R. i [m i Perform coherent accumulation to obtain

[0063] Combining the above equations, the frequency offset estimation equation for the i-th satellite can be obtained. Represented as:

[0064] Due to the periodicity of the discrete-time exponent, the frequency offset estimation equation needs to satisfy the following condition for accurate estimation:

[0065] Due to the differential property of the estimator, the estimation range will vary with the differential step size M. i The value decreases as the value increases. The effect of timing drift can be ignored. In order to solve for the two unknowns γ in the equation... i and f o Multiple frequency offset estimation equations need to be constructed.

[0066] In one embodiment, when connected to two satellites, a set of frequency offset estimation equations is constructed:

[0067] For example, construct the following set of frequency offset estimation equations to solve for γ1 and f. o :

[0068] Where γ2 = γ1 + α, and α represents the geocentric angle between the two satellites. The above frequency offset estimation equations can be specifically expressed as the following formula:

[0069] In one embodiment, to cope with low signal-to-noise ratio environments, a Kalman filter can also be used to calculate γ1 and f according to the frequency offset estimation equations over time t. o Smoothing is performed. To simplify the formula, the same Kalman gain K is used for both. g [t], expressed by the formula:

[0070] in, It is the estimated value after Kalman filtering at time t. It is the unfiltered estimate at time t.

[0071] Step S4: Obtain the frequency offset estimate based on the frequency offset estimation equation.

[0072] Specifically, γ1 and f are solved using the frequency offset estimation equation. o Then, based on the geocentric angle α between γ1 and the two satellites, γ is obtained. i =γ1+α, thus obtaining the Doppler frequency offset estimate. With the crystal offset estimate F o =f o *f i .

[0073] In addition, frequency offset compensation is performed based on the frequency offset estimate, whereby the frequency offset compensation is the difference between the Doppler frequency offset estimate and the crystal oscillator offset estimate, i.e., F. d -F oTherefore, after obtaining the estimation results of each component of the carrier frequency offset, the pre-compensation frequency value is calculated using the downlink estimated crystal oscillator offset and Doppler frequency shift to pre-compensate the uplink frequency offset.

[0074] The scope of protection of the ubiquitous network frequency offset estimation method described in this embodiment is not limited to the execution order of the steps listed in this embodiment. Any solution implemented by adding, subtracting, or replacing steps in the prior art based on the principle of this invention is included within the scope of protection of this invention.

[0075] This invention also provides a ubiquitous network frequency offset estimation system, which can implement the ubiquitous network frequency offset estimation method described in this invention. However, the implementation device of the ubiquitous network frequency offset estimation system described in this invention includes, but is not limited to, the structure of the ubiquitous network frequency offset estimation system listed in this embodiment. All structural modifications and substitutions of the prior art made according to the principles of this invention are included within the protection scope of this invention.

[0076] As shown in Figure 5, in one embodiment, the ubiquitous network frequency offset estimation system of the present invention includes a receiving module 51, a first construction module 52, a second construction module 53, and an estimation module 54.

[0077] The receiving module 51 is used to receive wireless signals from multiple carriers from multiple satellites.

[0078] The first construction module 52 is used to construct the satellite-to-ground geometric relationship between each satellite and the terminal.

[0079] The second construction module 53 is connected to the receiving module 51 and the first construction module 52, and is used to construct a frequency offset estimation equation based on the wireless signal and the satellite-to-ground geometric relationship.

[0080] The estimation module 54 is connected to the second construction module 53 and is used to obtain the frequency offset estimate based on the frequency offset estimation equation.

[0081] The structure and principle of the receiving module 51, the first construction module 52, the second construction module 53 and the estimation module 54 correspond one-to-one with the steps in the ubiquitous network frequency offset estimation method described above, so they will not be repeated here.

[0082] In the embodiments provided by this invention, it should be understood that the disclosed systems, apparatuses, or methods can be implemented in other ways. For example, the apparatus embodiments described above are merely illustrative. For instance, the division of modules / units is only a logical functional division, and in actual implementation, there may be other division methods. For example, multiple modules or units may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be through some interfaces; the indirect coupling or communication connection of apparatuses or modules or units may be electrical, mechanical, or other forms.

[0083] The modules / units described as separate components may or may not be physically separate. The components shown as modules / units may or may not be physical modules; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules / units can be selected to achieve the objectives of the embodiments of the present invention, depending on actual needs. For example, the functional modules / units in the various embodiments of the present invention may be integrated into one processing module, or each module / unit may exist physically separately, or two or more modules / units may be integrated into one module / unit.

[0084] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementations should not be considered beyond the scope of this invention.

[0085] This invention also provides a computer-readable storage medium. Those skilled in the art will understand that all or part of the steps in the ubiquitous network frequency offset estimation method of the above embodiments can be implemented by a program instructing a processor. The program can be stored in a computer-readable storage medium, which is a non-transitory medium, such as random access memory, read-only memory, flash memory, hard disk, solid-state drive, magnetic tape, floppy disk, optical disk, and any combination thereof. The storage medium can be any available medium accessible to a computer or a data storage device such as a server or data center that integrates one or more available media. This available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., digital video disc (DVD)), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0086] This invention also provides a terminal. The terminal includes a processor and a memory.

[0087] The memory is used to store computer programs.

[0088] The memory includes various media capable of storing program code, such as ROM, RAM, magnetic disk, USB flash drive, memory card, or optical disk.

[0089] The processor is connected to the memory and is used to execute the computer program stored in the memory so that the terminal performs the ubiquitous network frequency offset estimation method described above.

[0090] Preferably, the processor can be a general-purpose processor, including a central processing unit (CPU), a network processor (NP), etc.; it can also be a digital signal processor (DSP), an application-specific integrated circuit (ASIC), a field-programmable gate array (FPGA), or other programmable logic devices, discrete gate or transistor logic devices, or discrete hardware components.

[0091] As shown in Figure 6, the terminal of the present invention is presented in the form of a general-purpose computing device. The components of the terminal may include, but are not limited to: one or more processors or processing units 61, a memory 62, and a bus 63 connecting different system components (including the memory 62 and the processing unit 61).

[0092] Bus 63 represents one or more of several bus architectures, including a memory bus or memory controller, a peripheral bus, a graphics acceleration port, a processor, or a local bus using any of the various bus architectures. For example, these architectures include, but are not limited to, the Industry Standard Architecture (ISA) bus, the Micro Channel Architecture (MAC) bus, the Enhanced ISA bus, the Video Electronics Standards Association (VESA) local bus, and the Peripheral Component Interconnect (PCI) bus.

[0093] Terminals typically include various computer system-readable media. These media can be any available media that can be accessed by the terminal, including volatile and non-volatile media, and removable and non-removable media.

[0094] Memory 62 may include computer system readable media in the form of volatile memory, such as random access memory (RAM) 621 and / or cache memory 622. The terminal may further include other removable / non-removable, volatile / non-volatile computer system storage media. By way of example only, storage system 623 may be used to read and write non-removable, non-volatile magnetic media (not shown in FIG. 6, commonly referred to as a "hard disk drive"). Although not shown in FIG. 6, disk drives for reading and writing to removable non-volatile disks (e.g., "floppy disks") and optical disk drives for reading and writing to removable non-volatile optical disks (e.g., CD-ROMs, DVD-ROMs, or other optical media) may be provided. In these cases, each drive may be connected to bus 63 via one or more data media interfaces. Memory 62 may include at least one program product having a set (e.g., at least one) of program modules configured to perform the functions of the embodiments of the present invention.

[0095] A program / utility 624 having a set (at least one) of program modules 6241 may be stored, for example, in memory 62. Such program modules 6241 include, but are not limited to, an operating system, one or more application programs, other program modules, and program data. Each or some combination of these examples may include an implementation of a network environment. Program modules 6241 typically perform the functions and / or methods described in the embodiments of the present invention.

[0096] The terminal can also communicate with one or more external devices (e.g., keyboard, pointing device, display, etc.), one or more devices that enable a user to interact with the terminal, and / or any device that enables the terminal to communicate with one or more other computing devices (e.g., network card, modem, etc.). This communication can be performed through input / output (I / O) interface 64. Furthermore, the terminal can communicate with one or more networks (e.g., local area network (LAN), wide area network (WAN), and / or public networks, such as the Internet) via network adapter 65. As shown in Figure 6, network adapter 65 communicates with other modules of the terminal via bus 63. It should be understood that, although not shown in the figures, other hardware and / or software modules can be used in conjunction with the terminal, including but not limited to: microcode, device drivers, redundant processing units, external disk drive arrays, RAID systems, tape drives, and data backup storage systems.

[0097] In summary, the ubiquitous network frequency offset estimation method, system, medium, and terminal of this invention can achieve accurate frequency offset estimation even in the absence of GNSS signals in ubiquitous networks, thereby ensuring the continuity and reliability of ubiquitous networks. It has the capability to access multiple satellites, acquiring radio resources from multiple satellite nodes or carriers for frequency offset estimation. It can separate and estimate the Doppler frequency shift caused by motion and the frequency offset caused by oscillator instability, thus achieving accurate uplink frequency offset pre-compensation and ultimately frequency synchronization. Its application prospects in the field of wireless communication for ubiquitous communication network architectures are very broad, providing more accurate, convenient, and rapid frequency offset estimation, thereby achieving more efficient, secure, and wider-ranging communication services. Therefore, this invention effectively overcomes the various shortcomings of existing technologies and has high industrial applicability.

[0098] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for estimating frequency offset in ubiquitous networks, characterized in that, The method includes the following steps: It can receive wireless signals from multiple carriers from multiple satellites. Establish the satellite-to-ground geometric relationship between each satellite and terminal; A frequency offset estimation equation is constructed based on the wireless signal and the satellite-to-ground geometric relationship; The frequency offset estimate is obtained based on the frequency offset estimation equation.

2. The ubiquitous network frequency offset estimation method according to claim 1, characterized in that, The satellite-to-ground geometric relationship between each satellite and the terminal includes: the satellite velocity and the angle between the signal transmission link. The relationship between the geocentric angle γ of the satellite and the terminal.

3. The ubiquitous network frequency offset estimation method according to claim 2, characterized in that, The frequency offset estimation equation is constructed based on the wireless signal and the satellite-to-ground geometric relationship, including: Based on the satellite-to-ground geometric relationship established between the i-th satellite and the terminal Using the function f(γ) of the geocentric angle i The Doppler frequency offset is characterized by the relative velocity between the transmitter of the i-th satellite and the terminal receiver. By linear approximation The function f(γ) of the central geocentric angle i It is approximately a linear expansion of the geocentric angle, where γ i This represents the geocentric angle between the i-th satellite and the terminal receiver. This represents the angle between the velocity of the i-th satellite and the signal transmission link; Downlink Total Frequency Offset Based on the i-th Satellite Transmitter and Terminal Receiver Constructing the Doppler frequency offset of the i-th satellite and terminal crystal frequency offset The equation is for estimating the frequency offset of unknowns.

4. The ubiquitous network frequency offset estimation method according to claim 3, characterized in that: Using Chebyshev polynomials for f(γ) i Perform a linear approximate expansion, where Where n cheby Let A be the Chebyshev order. k is the Chebyshev coefficient.

5. The ubiquitous network frequency offset estimation method according to claim 3, characterized in that, When connected to two satellites, a set of frequency offset estimation equations is constructed based on the Doppler frequency shift correlation between the two satellites with the geocentric angle as the correlation relationship:

6. The ubiquitous network frequency offset estimation method according to claim 5, characterized in that, The frequency offset estimation equation set is as follows: Where γ2 = γ1 + α, and α represents the geocentric angle between the two satellites.

7. The ubiquitous network frequency offset estimation method according to claim 6, characterized in that, It also includes using a Kalman filter to adjust the values ​​of γ1 and f calculated according to the frequency offset estimation equations over time t. o The estimated values ​​are smoothed.

8. A ubiquitous network frequency offset estimation system, characterized in that, The system includes a receiving module, a first construction module, a second construction module, and an estimation module; The receiving module is used to receive wireless signals from multiple carriers from multiple satellites; The first construction module is used to construct the satellite-to-ground geometric relationship between each satellite and the terminal; The second building module is used to construct a frequency offset estimation equation based on the wireless signal and the satellite-to-ground geometry. The estimation module is used to obtain the frequency offset estimate based on the frequency offset estimation equation.

9. A storage medium having a computer program stored thereon, characterized in that, When the program is executed by the processor, it implements the ubiquitous network frequency offset estimation method as described in any one of claims 1 to 7.

10. A terminal, characterized in that, include: Processor and memory; The memory is used to store computer programs; The processor is used to execute the computer program stored in the memory to cause the terminal to perform the ubiquitous network frequency offset estimation method according to any one of claims 1 to 7.

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