OFDM (Orthogonal Frequency Division Multiplexing)-based conduction integrated signal construction method and system, electronic equipment and medium

Abstract

The invention belongs to the technical field of satellite communication and navigation, and particularly relates to an OFDM (Orthogonal Frequency Division Multiplexing)-based conduction integrated signal construction method and system, electronic equipment and a medium. The construction method comprises the following steps: constructing a reference signal, called MLBOC, of a mixed linear offset carrier and a binary offset carrier, so that the navigation performance of the signal is improved; then, the MLBOC is embedded into an OFDM communication signal, a novel communication and navigation integrated signal OFDM-M is generated, and parameter configuration of the OFDM-M is determined for the optimal communication and navigation performance. A simulation experiment shows that compared with other ICAN signals, the OFDM-M signal provided by the invention has better communication performance and navigation performance.

Description

Technical Field

[0001] The present invention belongs to the technical field of satellite communication and navigation, and in particular relates to a communication and navigation integrated signal construction method, system, electronic equipment and medium based on OFDM. Background Art

[0002] In recent years, low-Earth Orbit (LEO) constellations have been booming. They are mainly designed to provide broadband Internet communication services, and also provide opportunities to enhance the positioning, navigation and timing services of the Global Navigation Satellite System (GNSS). Many studies use the communication signals broadcast by LEO constellations as opportunity signals to provide navigation services, but without the authorization of LEO satellite operators, opportunity navigation is non-cooperative and has low accuracy. The cooperative navigation mode can solve this problem well. Cooperative users can easily obtain the precise orbit and signal structure of LEO satellites, and activate satellite signals according to the needs of cooperative users, thereby improving navigation accuracy. Therefore, studying the design issues of LEO satellite transmission signals has become the key to LEO constellations providing integrated communication and navigation (ICAN) services.

[0003] Orthogonal Frequency Division Multiplexing (OFDM), as a modulation technology with superior performance, has been used in the downlink signal of the Starlink low-orbit constellation. Some studies have attempted to design integrated communication and navigation signals based on OFDM. For example, the navigation signal is superimposed on the OFDM communication signal through time division and code division multiplexing, and the time division and code division OFDM (TC-OFDM) technology is developed; the frequency of the navigation signal is moved to the sideband of the OFDM communication signal by using frequency division multiplexing, thus developing the binary offset carrier (BOC) assisted OFDM (BA-OFDM) technology.

[0004] There are several limitations in the design of existing OFDM-type integrated communication and navigation signals: (1) There is no research on using navigation signals as OFDM reference signals. The existing reference signals are designed for channel estimation and their navigation performance is not optimal. (2) Existing research mainly multiplexes separately designed communication signals and navigation signals through time division, frequency division or code division. There is mutual interference between communication signals and navigation signals, and their compatibility is poor. Summary of the invention

[0005] The purpose of the present invention is to provide a method, system, electronic device and medium for constructing an OFDM-based communication and navigation integrated signal, which solves the limitation problem of the existing OFDM-type communication and navigation integrated signal.

[0006] The present invention is achieved through the following technical solutions: The present invention discloses a communication and guidance integrated signal construction method based on OFDM, comprising the following steps: S1. Construct a reference signal of a mixed linear offset carrier and a binary offset carrier, called an MLBOC signal; S2. Embed the MLBOC signal into the OFDM communication signal to generate the communication and navigation integrated signal OFDM-M.

[0007] Further, assuming that the number of subcarriers of the OFDM communication signal is , the subcarrier numbering starts from arrive , the subcarrier frequency spacing is ; In S1, MLBOC signal The expression is:

[0008] in, is the OFDM symbol time; n Indicates the OFDM symbol number; k Indicates the subcarrier number; t To indicate a moment; Indicates that the reference signal is n symbol time k The modulated data on the subcarriers is a predefined pseudo-random sequence; Indicates reference data The location set of The support time is The rectangular function of It is k The expression of the subcarrier waveform.

[0009] further, Abbreviated as , is a rectangular function, defined as: .

[0010] further, Abbreviated as , It has two forms of expression. kThe waveform of the subcarrier with a smaller absolute number adopts LOC, and the waveform of the subcarrier with a larger absolute number adopts BOC. The specific expression is:

[0011] in, is the threshold index, represents the imaginary unit, is a sign function, Indicates the subcarrier frequency spacing.

[0012] further, The value is ,in Represents the ceiling function.

[0013] Furthermore, S2 is specifically as follows: by replacing the traditional OFDM reference signal with the MLBOC signal, a new multi-carrier modulation scheme is established to obtain OFDM with MLBOC signal, called OFDM-M, which is expressed as:

[0014] in, Represents communication signals, represents the reference signal after replacement.

[0015] Furthermore, the power spectral density of the MLBOC signal is denoted as , is the sum of all subcarrier power spectral densities, expressed as:

[0016] in, f is the frequency independent variable, It is k The power spectral density of the subcarriers; MLBOC signals have two types of subcarrier waveforms, LOC and BOC. The power spectrum density of the subcarriers is divided into two categories:

[0017] in, f represents the frequency independent variable, It is k The power spectral density of the LOC subcarriers, It is k The power spectral density of BOC subcarriers; It is k The spectrum of the subcarriers of type LOC, It is k The spectrum of the subcarriers of BOC type; is the chip duration of the pseudo-random sequence, which is equal to ; is the threshold index, k Indicates the subcarrier number.

[0018] The present invention also discloses a communication and guidance integrated signal construction system based on OFDM, comprising: A reference signal building module is used to construct a reference signal of a mixed linear offset carrier and a binary offset carrier, called an MLBOC signal; The signal embedding module is used to embed the MLBOC signal into the OFDM communication signal to generate the communication and navigation integrated signal OFDM-M.

[0019] The present invention also discloses a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the OFDM-based communication and guidance integrated signal construction method are implemented.

[0020] The present invention also discloses a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the OFDM-based communication and guidance integrated signal construction method are implemented.

[0021] Compared with the prior art, the present invention has the following beneficial technical effects: The present invention proposes a method for constructing an integrated communication and navigation signal based on OFDM. By designing the reference signal of OFDM, it can be used for synchronization and channel equalization of communication signals and for capture and tracking of navigation signals, so as to have good communication and navigation performance at the same time. In the design of this new ICAN signal, the reference signal is constructed by mixing a linear offset carrier LOC and a binary offset carrier BOC, referred to as MLBOC. By embedding the BOC commonly used in navigation signal design into the reference signal, the navigation performance of the reference signal can be enhanced. Then, the OFDM communication signal is combined with the reference signal MLBOC to generate this new ICAN signal, called OFDM-M. The OFDM-M signal proposed by the present invention is a combination of the OFDM communication signal and the MLBOC reference signal without conflict, and there is no mutual interference between the two, thereby improving the compatibility between the communication signal and the navigation signal, which provides a pioneering multiplexing method for the ICAN signal. In addition, the difference between OFDM-M signals and standard OFDM communication signals lies mainly in the reference signal. The two maintain good compatibility and can be easily upgraded to OFDM-M signals by changing the standard OFDM signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 is a resource grid of OFDM signal; Figure 2 Normalized (a) autocorrelation function and (b) power spectral density of MLBOC signal; Figure 3 This is the curve of BER changing with LEO satellite transmission power; Figure 4 This is the curve of the variation of ranging accuracy with the transmission power of LEO satellite; Figure 5 is the bit error rate curve of different ICAN signals; Figure 6 is the NELP code tracking error of different ICAN signals; Figure 7 The present invention is a flowchart of a method for constructing an OFDM-based integrated communication and guidance signal. DETAILED DESCRIPTION

[0023] In order to make the purpose, technical solution and advantages of the present invention more clear, the following is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the embodiments described are only part of the embodiments of the present invention, not all embodiments.

[0024] The components described and shown in the drawings and embodiments of the present invention may be arranged and designed in various configurations. Therefore, the detailed description of the embodiments of the present invention provided in the following drawings is not intended to limit the scope of the claimed invention, but merely represents a selected embodiment of the present invention. Based on the drawings and embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0025] It should be noted that the terms "comprises", "includes" or any other variations are intended to cover non-exclusive inclusion, so that a process, element, method, article or equipment that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to the process, element, method, article or equipment.

[0026] The features and performances of the present invention are further described in detail below in conjunction with the embodiments.

[0027] Example 1 like Figure 7 As shown, the present invention discloses a method for constructing a communication and guidance integrated signal based on OFDM, comprising the following steps: S1. Construct a reference signal of a mixed linear offset carrier and a binary offset carrier, called an MLBOC signal; S2. Embed the MLBOC signal into the OFDM communication signal to generate the communication and navigation integrated signal OFDM-M.

[0028] The OFDM-M signal proposed in the present invention is a combination of an OFDM communication signal and an MLBOC reference signal without conflict, and there is no mutual interference between the two, thereby improving the compatibility between the communication signal and the navigation signal, which provides a groundbreaking multiplexing method for ICAN signals. In addition, the difference between the OFDM-M signal and the standard OFDM communication signal mainly lies in the reference signal, and the two maintain good compatibility. By changing the standard OFDM signal, it can be easily upgraded to an OFDM-M signal.

[0029] Example 2 The following is a detailed introduction to the construction method of the reference signal MLBOC and some of its details.

[0030] Assume that the number of subcarriers of OFDM communication signal is , the subcarrier numbering starts from arrive , the subcarrier frequency spacing is The resource grid is the core of the OFDM signal, representing the composition of the modulated data on each carrier at each time: communication data or reference signal, such as Figure 1 As shown. Indicates reference data The location set, Indicates that the reference signal is n symbol time k The modulated data on the subcarriers is a predefined pseudo-random sequence.

[0031] The traditional OFDM reference signal is designed for channel estimation and equalization. In order to enhance the navigation performance, the present invention proposes a new OFDM reference signal, referred to as MLBOC, which stands for the mixture of linear offset carrier LOC and binary offset carrier BOC and can be expressed by a mathematical formula: (1) in, is the OFDM symbol time; n Indicates the OFDM symbol number; k Indicates the subcarrier number; t Indicates a moment. Indicates that the reference signal is n symbol time k The modulated data on the subcarriers is a predefined pseudo-random sequence; Indicates reference data A collection of locations. The support time is The rectangular function of It is k The expression of the subcarrier waveform.

[0032] Abbreviated as , is a rectangular function, defined as: (2) Specifically, The corresponding expression is abbreviated as , It has two forms of expression. k The waveform of the subcarrier with a smaller absolute number adopts LOC, and the waveform of the subcarrier with a larger absolute number adopts BOC. The specific expression is: (3) in, is the threshold index; represents an imaginary unit; is a sign function; Indicates the subcarrier frequency spacing.

[0033] Example 3 The following is a detailed description of the threshold index Discussion of values.

[0034] The present invention selects the navigation tracking accuracy and communication performance based on these two factors. On the one hand, when When it decreases, the number of BOC subcarriers increases, and the tracking accuracy improves accordingly; on the other hand, in order to ensure communication performance, It cannot be reduced infinitely because when the harmonics of the BOC subcarrier overlap with another subcarrier frequency of the OFDM signal, it will interfere with the communication signal, resulting in a decrease in the bit error rate. If the minimum index of the BOC subcarrier in the MLBOC signal is , through Fourier analysis, we know that the minimum frequency of the harmonics of the MLBOC signal is To avoid interference with other subcarriers, the harmonics of the MLBOC signal should be outside the main lobe bandwidth of the OFDM signal. In other words, its minimum frequency should be greater than the maximum frequency of the subcarrier, that is, (4) in Indicates the maximum index of a subcarrier.

[0035] Therefore, in order to avoid subcarrier interference, it can be derived from formula (4): The following conditions should be met: (5) in Represents the ceiling function.

[0036] Based on the above analysis, the present invention will The value is set to , so that the signal has optimal communication and navigation performance.

[0037] Example 4 The following is a detailed introduction to the construction method of ICAN signal OFDM-M and some of its details.

[0038] By replacing the traditional OFDM reference signal with the MLBOC signal, a new multi-carrier modulation scheme can be established, namely OFDM with MLBOC signal, called OFDM-M, which can be expressed in mathematical symbols as: (6) in, Represents communication signals, represents the reference signal after replacement.

[0039] OFDM-M and OFDM basically have similar signal structures. OFDM-M can be obtained by modifying the subcarrier waveform of the OFDM reference signal. Therefore, OFDM-M and OFDM have good compatibility. In addition, due to the use of MLBOC, OFDM-M has higher navigation accuracy than OFDM, while also improving the channel estimation quality and reducing the bit error rate.

[0040] Example 5 The power spectral density of the MLBOC signal is introduced in detail below.

[0041] Power spectral density is an important tool for analyzing the navigation performance of reference signals. The present invention derives the power spectral density of the MLBOC signal. The pseudo-random sequence used in the MLBOC signal ensures that all subcarriers are orthogonal within a long integration time. Therefore, the power spectral density of the MLBOC signal is denoted as , is the sum of the power spectral densities of all subcarriers, that is, (7) in, f is the frequency independent variable, It is k The power spectral density of the subcarriers can be obtained from the power spectral density of the pseudo-random sequence and spectrum of the subcarrier waveform Derived from this: (8) in, is the chip duration of the pseudo-random sequence, which in OFDM-M is equal to When the pseudo-random sequence is an ideal white noise sequence, .

[0042] For k LOC type subcarriers, whose spectrum for: (9) in, It is k The subcarrier frequency, represents the sinc function, represents an imaginary unit; is the chip duration of the pseudo-random sequence.

[0043] Similarly, k The spectrum of the BOC type subcarriers for: (10) in, It is k The frequency of the subcarriers; is the chip duration of the pseudo-random sequence.

[0044] Since the MLBOC signal has two types of subcarrier waveforms, LOC and BOC, the power spectrum density of the subcarrier is divided into two categories: (11) in, and They are k The power spectral density of the LOC and BOC subcarriers.

[0045] like Figure 2 As shown in Figure 1, a normalized autocorrelation function and power spectrum density diagram of an MLBOC signal is given. Figure 2 It can be seen that the properties of the MLBOC signal are similar to those of the standard OFDM reference signal, indicating that the OFDM-M signal has good compatibility with the standard OFDM signal.

[0046] The performance analysis part of the OFDM-M signal finally designed by the present invention is introduced below.

[0047] 1. Performance comparison between OFDM-M and OFDM signals In order to illustrate the advantages of OFDM-M signals over traditional OFDM signals, their communication and navigation performances are compared. The two signals are received using the same method: the signal synchronization module uses a code tracking loop (Delay Lock Loop, DLL) to achieve communication synchronization and navigation delay estimation.

[0048] (1) Communication performance The present invention uses the bit error rate (BER) to evaluate the communication performance of the two signals. Figure 3 As shown. Figure 3 The following conclusions can be drawn: the BER curve of the OFDM-M signal is below the BER curve of the traditional OFDM signal. When the transmission power is 60 dBm, the BER of the OFDM-M signal is reduced by 10% compared with the OFDM signal, indicating that the communication reliability of the OFDM-M signal is better.

[0049] (2) Navigation performance Estimation error of time delay For characterizing navigation performance, the estimated time delay and the actual time delay Derived from this: (12) The present invention utilizes the estimation error The standard deviation (STD) of OFDM-M signal is used to compare the navigation performance of OFDM signal with that of OFDM signal. The results are as follows: Figure 4 As shown. Figure 4 The following conclusions can be drawn: Compared with the traditional OFDM signal, the estimation error STD of the OFDM-M signal is significantly lower. When the transmission power is 60dBm, the estimation error STD of the OFDM-M signal is 24% lower than that of the traditional OFDM signal, indicating that the OFDM-M signal has better navigation accuracy.

[0050] 2. Comparison between OFDM-M signal and other ICAN signals The present invention compares OFDM-M signals with other OFDM-like ICAN signals TC-OFDM and BA-OFDM to demonstrate the advantages of OFDM-M. For a fair comparison, TC-OFDM, BA-OFDM and OFDM-M all use the same receiver architecture, and these ICAN signals have the same main lobe bandwidth and the same OFDM configuration parameters and transmission power.

[0051] (1) Communication performance The relationship between the bit error rate of the three signals and the satellite transmission power is as follows: Figure 5 As shown. Figure 5 The following conclusions can be drawn: compared with TC-OFDM, OFDM-M signal has a lower bit error rate; compared with BA-OFDM, the bit error rate of OFDM-M signal is similar, indicating that OFDM-M has good communication reliability.

[0052] (2) Navigation performance Navigation performance can be evaluated by tracking accuracy, and NELP code tracking error is used to further evaluate tracking accuracy. The calculation results of NELP code tracking error are as follows: Figure 6 As shown, from Figure 6 The following conclusions can be drawn: the proposed OFDM-M signal has the lowest code tracking error and the highest tracking accuracy. When the transmit power is 60 dBm, OFDM-M reduces the code tracking error by 90.8% and 49.6% compared with TC-OFDM and BA-OFDM, respectively.

[0053] In summary, compared with the existing ICAN signal, the OFDM-M signal proposed in the present invention has better communication performance and navigation performance.

[0054] The present invention also discloses a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the processor executes the computer program, the steps of the OFDM-based integrated communication and guidance signal construction method are implemented. The memory may include a memory, such as a high-speed random access memory, and may also include a non-volatile memory, such as at least one disk memory, etc. The processor, the network interface, and the memory are interconnected through an internal bus, and the internal bus may be an industrial standard architecture bus, a peripheral component interconnection standard bus, an extended industrial standard structure bus, etc. The bus may be divided into an address bus, a data bus, a control bus, etc. The memory is used to store programs. Specifically, the program may include a program code, and the program code includes computer operation instructions. The memory may include a memory and a non-volatile memory, and provide instructions and data to the processor.

[0055] The present invention also discloses a computer-readable storage medium, wherein the computer-readable storage medium stores a computer program, and when the computer program is executed by a processor, the steps of the OFDM-based integrated communication and guidance signal construction method are implemented. Specifically, the computer-readable storage medium includes, but is not limited to, for example, a volatile memory and / or a non-volatile memory. The volatile memory may include a random access memory and / or a cache memory, etc. The non-volatile memory may include a read-only memory, a hard disk, a flash memory, an optical disk, a magnetic disk, etc.

[0056] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, optical storage, etc.) containing computer-usable program code.

[0057] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0058] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0059] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 The steps for the functions specified in one or more boxes.

[0060] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the above embodiments, ordinary technicians in the relevant field should understand that the specific implementation methods of the present invention can still be modified or replaced by equivalents. Any modification or equivalent replacement that does not depart from the spirit and scope of the present invention should be covered within the scope of protection of the claims of the present invention.

Claims

1. A method for constructing an integrated communication and guidance signal based on OFDM, characterized in that: The following steps are involved: S1. Construct a reference signal of a mixed linear offset carrier and a binary offset carrier, called an MLBOC signal; S2. Embed the MLBOC signal into the OFDM communication signal to generate the communication and navigation integrated signal OFDM-M.

2. The method for constructing an OFDM-based integrated communication and guidance signal according to claim 1, characterized in that: Assume that the number of subcarriers of OFDM communication signal is , the subcarrier numbering starts from arrive , the subcarrier frequency spacing is ; In S1, MLBOC signal The expression is: in, is the OFDM symbol time; n Indicates the OFDM symbol number; k Indicates the subcarrier number; t To indicate a moment; Indicates that the reference signal is n symbol time k The modulated data on the subcarriers is a predefined pseudo-random sequence; Indicates reference data The location set of The support time is The rectangular function of It is k The expression of the subcarrier waveform.

3. The method for constructing an OFDM-based integrated communication and guidance signal according to claim 2, characterized in that: Abbreviated as , is a rectangular function, defined as: 。 4. The method for constructing an OFDM-based integrated communication and guidance signal according to claim 2, characterized in that: Abbreviated as , It has two forms of expression. k The waveform of the subcarrier with a smaller absolute number adopts LOC, and the waveform of the subcarrier with a larger absolute number adopts BOC. The specific expression is: in, is the threshold index, represents the imaginary unit, is a sign function, Indicates the subcarrier frequency spacing.

5. The method for constructing an OFDM-based integrated communication and guidance signal according to claim 4, characterized in that: The value is ,in Represents the ceiling function.

6. The OFDM-based integrated communication and guidance signal construction method according to claim 1, characterized in that: S2 is specifically: by replacing the traditional OFDM reference signal with the MLBOC signal, a new multi-carrier modulation scheme is established to obtain OFDM with MLBOC signal, called OFDM-M, which is expressed as: in, Represents communication signals, represents the reference signal after replacement.

7. The method for constructing an OFDM-based integrated communication and guidance signal according to claim 2, characterized in that: The power spectral density of the MLBOC signal is denoted as , is the sum of all subcarrier power spectral densities, expressed as: in, f is the frequency independent variable, It is k The power spectral density of the subcarriers; MLBOC signals have two types of subcarrier waveforms, LOC and BOC. The power spectrum density of the subcarriers is divided into two categories: in, f represents the frequency independent variable, It is k The power spectral density of the LOC subcarriers, It is k The power spectral density of BOC subcarriers; It is k The spectrum of the subcarriers of LOC type, It is k The spectrum of the subcarriers of BOC type; is the chip duration of the pseudo-random sequence, which is equal to ; is the threshold index, k Indicates the subcarrier number.

8. A communication and guidance integrated signal construction system based on OFDM, characterized in that: include: A reference signal building module is used to construct a reference signal of a hybrid linear offset carrier and a binary offset carrier, called an MLBOC signal; The signal embedding module is used to embed the MLBOC signal into the OFDM communication signal to generate the communication and navigation integrated signal OFDM-M.

9. A computer device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that: When the processor executes the computer program, the steps of the OFDM-based communication and guidance integrated signal construction method as described in any one of claims 1 to 7 are implemented.

10. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed by a processor, the steps of the OFDM-based communication and guidance integrated signal construction method as described in any one of claims 1 to 7 are implemented.

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