A method for designing an integrated signal of medium wave communication and navigation

Abstract

The application discloses a kind of medium wave communication navigation integrated signal design method, comprising: generating frame synchronization code and navigation text;The binary code of navigation text is segmented according to fixed bit length, and segmented binary code is obtained;According to order, segmented binary code is two two as a group, and each group of segmented binary code is first converted into series / parallel, then BHC error correction coding is carried out respectively;For each group of BCH code, parallel / series conversion is carried out according to each bit order to output interleaved code, so as to complete the interleaving coding of navigation text;Interleaved coded navigation text and frame synchronization code are modulated using full hopping MPPSK modulation, framing is carried out, multiple frame signals are formed, the multiple frame signals are used to replace the sine carrier in broadcast signal, and composite modulation signal is generated by composite modulation with analog audio signal and transmitted through broadcast station.The application can realize the dual functions of broadcast and navigation without affecting the normal use of users.

Description

Technical Field

[0001] The present invention relates to the field of communication and navigation technology, and in particular to a medium wave communication and navigation integrated signal design method. Background Art

[0002] While widely used, the Global Navigation Satellite System (GNSS) is susceptible to interference and spoofing, making it unable to meet specific needs in complex electromagnetic environments. Existing ground-based navigation systems primarily rely on multiple fixed or mobile base stations on the ground for signal broadcasting, which is costly and susceptible to interference. Furthermore, positioning strategies based on two-way communication methods lack visibility. Current navigation and positioning systems lack the effective utilization of ubiquitous electromagnetic signals.

[0003] my country boasts a rich resource of medium-wave broadcast stations, and their broadcast signals are characterized by long transmission distances, high transmit power, and stable transmission characteristics. By embedding ranging information within medium-wave broadcast signals, a high-precision, highly reliable, flexible, and low-cost PNT solution can be provided. This ensures navigation and positioning capabilities for various terminals in satellite-denied environments, enabling reliable long-range positioning in these environments. Theoretical models for electromagnetic signal transmission across multiple media are still under development, and further research is needed on signal attenuation in complex electromagnetic environments and high-precision positioning methods. Therefore, new systems and theories for high-precision navigation and positioning using external electromagnetic signals are urgently needed.

[0004] my country's existing medium-wave (MW) communications utilize a double-sideband amplitude modulation (DSB-AM) signal system that retains the carrier, which suffers from drawbacks such as limited service. DSB-AM signals consist of a sinusoidal carrier wave that carries no information and two analog sidebands containing identical modulation information. To achieve the integration of MW broadcast and navigation signals, the DSB-AM signal's carrier wave must be digitally modulated. Previously, the mechanism for embedding navigation information within existing broadcast signals remained unclear. Summary of the Invention

[0005] The purpose of the present invention is to provide a medium wave communication and navigation integrated signal design method, which completely submerges useful information in the broadcast signal, thereby realizing the dual functions of broadcasting and navigation without affecting the normal use of users.

[0006] In order to achieve the above tasks, the present invention adopts the following technical solutions:

[0007] A medium wave communication and navigation integrated signal design method, applied to a transmitter, includes:

[0008] Generate frame synchronization code and navigation message;

[0009] Segmenting the binary code of the navigation message according to a fixed bit length to obtain a segmented binary code;

[0010] The segmented binary codes are grouped in pairs in sequence. Each group of segmented binary codes is first subjected to serial / parallel conversion, and then subjected to BCH error correction coding, so that each group of segmented binary codes finally corresponds to a group of BCH codes.

[0011] For each group of BCH codes, parallel / serial conversion is performed on each bit in sequence to output the interleaved code, thereby completing the interleaved coding of the navigation message;

[0012] The full-hop MPPSK modulation is used to interleave the coded navigation message and the frame synchronization code for modulation;

[0013] The frame synchronization code and the navigation message after full-hop MPPSK modulation are framed according to a preset format to obtain a frame signal; the framed signal is repeated multiple times to form a multi-frame signal, wherein the sending time of the navigation message part in each frame signal is different;

[0014] A multi-frame signal replaces the sinusoidal carrier in the broadcast signal, and is composite-modulated with an analog audio signal to generate a composite modulated signal, which is then sent. The composite modulated signal is sent through a broadcast station, and the receiving end performs coherent accumulation preprocessing on the composite modulated signal containing noise, and then demodulates and estimates the delay of the preprocessed signal to obtain navigation message information and distance information.

[0015] Furthermore, the frame synchronization code is a binary pseudo-random code;

[0016] The navigation message includes sending time, transmission delay, clock correction and communication information.

[0017] Furthermore, when the remaining binary code length is less than the fixed bit length, zeros are added to the high bits to form complete bit information.

[0018] Furthermore, the interleaving coding structure for any group of BCH codes is:

[0019]

[0020] Where: X i j is the jth information bit of the i-th BCH code in a group of BCH codes, i is 1 to 2, j is 1 to k; P i m is the mth check bit of the i-th segment of the BCH code, i is 1 to 2, and m is 1 to (nk); n is the total code length after BCH code encoding, and k is the code length of the information bit.

[0021] Furthermore, when performing full-hop MPPSK modulation, the position of the phase jump of the sinusoidal carrier in each symbol period is controlled by using the M-ary information symbol; the expression of full-hop MPPSK in one symbol period [0, NT] is as follows:

[0022]

[0023] Where y(t) is a full-hopping MPPSK signal of one symbol period, t is the time parameter; T is the carrier period; f c is the carrier frequency; K is the number of carrier flips in one hop; N is the ratio of the symbol period to the carrier period; the transmitted data is in M-base; the value range of k is 1≤k≤M-1; by adjusting the values ​​of M, N, and K, different signal bandwidths, transmission rates, and demodulation performances can be obtained.

[0024] Furthermore, the preset format is framed, wherein each frame signal includes a frame synchronization code portion, N f The navigation message part is repeated several times and the unmodulated sinusoidal carrier part; the navigation message contains the sending time, transmission delay, clock correction and communication information.

[0025] Furthermore, the waveform of the accumulated frame synchronization code or navigation message is:

[0026] (A0+m((K*T)+t))S((K*T)+t)+n((K*T)+t)

[0027] Where K is the number of accumulations, T is the period of the frame synchronization code or navigation message, S(t) is the frame synchronization code part or the navigation message part, and n(t) is the noise signal. For the frame synchronization code, it is necessary to use the frame synchronization code in multiple frame signals for coherent accumulation; for the navigation message, it is only necessary to use N frames in any frame signal for coherent accumulation. f The repeated navigation message parts are coherently accumulated.

[0028] Furthermore, the frame synchronization code portion after coherent accumulation is subjected to generalized cross-correlation processing with the frame synchronization code after full-hop MPPSK modulation to obtain a transmission delay, which is then used for ranging from the transmitter to the receiver.

[0029] A medium wave communication navigation system comprises a transmitting end and a receiving end; the transmitting end adopts the medium wave communication and navigation integrated signal design method to transmit navigation messages; the transmitting end comprises a medium wave broadcasting station.

[0030] A terminal device includes a processor, a memory, and a computer program stored in the memory; characterized in that when the processor executes the computer program, the medium wave communication and navigation integrated signal design method is implemented.

[0031] A computer-readable storage medium having a computer program stored therein; wherein when the computer program is executed by a processor, the medium-wave communication and navigation integrated signal design method is implemented.

[0032] Compared with the prior art, the present invention has the following technical features:

[0033] Compared to traditional AM broadcast transmitters, this invention replaces the original sinusoidal carrier with full-hop MPPSK modulation of the navigation message, enabling integrated transmission of the broadcast signal and navigation message without affecting the audio signal. In the time domain, the navigation message is modulated on the carrier phase, which does not interfere with the audio signal modulated on the envelope. In the frequency domain, the use of full-hop MPPSK modulation can further tighten the sidelobe power while increasing the symbol transmission rate, resulting in low sideband levels and ensuring that the digital carrier does not interfere with in-band analog audio or out-of-band signals. In terms of demodulation performance, the receiver can improve the signal-to-noise ratio by adopting a layered, multi-dimensional coherent accumulation method of the frame synchronization header and navigation message based on the design characteristics of this integrated communication and navigation signal. The medium-wave integrated communication and navigation signal designed by the present invention has strong anti-interference and long-distance diffraction capabilities. It is simple to modify existing equipment and can achieve long-distance precise positioning and navigation. It has special application value in long-distance navigation and timing in satellite navigation system-denied environments, and makes a powerful supplement to my country's comprehensive positioning, navigation, and timing (PNT) system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the block diagram of the communication and navigation integrated signal transmitter based on full-hop MPPSK modulation;

[0035] Figure 2 It is the integrated signal frame structure for medium wave communication and navigation;

[0036] Figure 3 Integrated signal frames for medium wave communication and navigation at different frequencies;

[0037] Figure 4 It is the power spectrum of the integrated communication and navigation signal based on full-hop MPPSK modulation;

[0038] Figure 5 (a), (b) and (c) are the waveforms of the signal after coherent accumulation under different signal-to-noise ratios. DETAILED DESCRIPTION

[0039] In response to the transmission bandwidth requirements of medium wave broadcasting stations, the present invention proposes an integrated communication and navigation signal system based on ultra-narrowband high-efficiency modulation. By embedding navigation message information in the broadcast signal, it can achieve integrated transmission without affecting the broadcast signal. In response to the problem that the integrated communication and navigation signal is difficult to accurately demodulate under low signal-to-noise ratio, the signal of the present invention can use the layered multi-dimensional coherent accumulation method of frame synchronization code and navigation message to improve the signal-to-noise ratio during reception and processing. The present invention adopts an integrated communication and navigation signal system based on full-hop MPPSK modulation, which realizes the simultaneous transmission of audio and navigation signals on the basis of compatibility with existing broadcasting systems, and has the advantages of simple modification of existing transmitter equipment, smooth transition from analog to digital, and no need for spectrum planning. In addition, the integrated communication and navigation signal has the advantages of high transmission power, long transmission distance, and stable transmission; at the same time, it has the characteristics of being difficult to be discovered and highly concealed, and the encrypted new signal system is not open to the public, so it is not easy to be cracked or deceived.

[0040] The present invention provides a method for designing a medium wave communication and navigation integrated signal, wherein steps 1-8 are applied to a transmitting end, and include the following steps:

[0041] Step 1: Generate a frame synchronization code. The frame synchronization code is an a-bit binary pseudo-random code used for estimating the transmission delay of the integrated communication and navigation signal and synchronizing the reception of the navigation message. The frame synchronization code value is fixed and known, so the receiver can use it to match the received signal, providing the necessary conditions for subsequent pseudorange measurement and correctly decoding the binary navigation message in the corresponding format.

[0042] Step 2: Generate a navigation message. A navigation message usually consists of the sending time, transmission delay, clock correction, and communication information. The navigation message to be transmitted is represented in the form of binary data. Assume that the navigation message has a total of b bits.

[0043] Sending time t0: The last observation time of the base station navigation message, which can be used to measure the time delay of signal propagation.

[0044] Transmission delay: The time delay between the generation of a signal and its departure from the base station's transmitting antenna. This value can be measured through inspection before the base station sends the signal and is used to correct the signal transmission time and improve positioning accuracy.

[0045] Clock correction: The navigation time system is based on UTC time. Due to the instability of the base station master clock, there is a deviation between it and UTC time. The receiver can use this parameter to correct the signal transmission time and improve positioning accuracy.

[0046] Communication information: data information sent by the base station to the receiver.

[0047] Step 3: The navigation message's binary code is segmented into k-bit segments to produce segmented binary codes. When the remaining binary code is less than k bits long, zeros are added to the upper bits to form a complete k-bit message. The receiver ignores these padded zeros during decoding and only recovers the original valid information bits. This allows the subsequent BCH encoding to adapt to information bits of varying lengths while maintaining its error correction capabilities.

[0048] Step 4: The segmented binary codes are grouped in pairs in order. Each group of segmented binary codes is first subjected to serial / parallel conversion, and then error correction coding is performed separately. The error correction coding adopts BCH (n, k, t) code, so that each group of segmented binary codes finally corresponds to a group of BCH codes; where n represents the total code length after encoding, t represents the maximum number of correctable error bits, and k represents the code length of the information bits.

[0049] Step 5: For each group of BCH codes, perform parallel / serial conversion on each bit in sequence and output an interleaved code with a length of 2n bits, thereby completing the interleaving coding of the navigation message. The interleaving coding structure for any group of BCH codes is:

[0050]

[0051] Where: X i j is the jth information bit of the i-th BCH code in a group of BCH codes, i is 1 to 2, j is 1 to k; P i m is the mth check bit of the i-th segment BCH code, i is 1 to 2, and m is 1 to (nk).

[0052] Step 6: Referencing the spectrum allocation scheme for in-band on-channel (IBOC) technology, if the power spectrum sidebands of the digital modulation information are at least 50dB below the carrier within the 9kHz frequency band of the analog main signal, the interference with the analog signal can be essentially ignored, thus achieving simulcast. In addition, the digital carrier carrying navigation information must also meet the following requirements:

[0053] The envelope is constant and will not interfere with the audio signal modulated on the envelope; the sideband power meets radio management specifications and cannot interfere with radio transmission in adjacent frequency bands; the symbol rate is high; and the demodulation performance is good.

[0054] According to the above requirements, full-hop MPPSK modulation is selected to modulate the interleaved coded navigation message obtained in step 5 and the frame synchronization code generated in step 1. Full-hop MPPSK modulation is a two-dimensional modulation that can be keyed in both position and phase shift. It mainly uses the data sequence to perform phase shift modulation on different positions of the sinusoidal carrier within one code element period. The M-ary information symbol is used to control the position of the phase jump of the sinusoidal carrier in each code element period, thereby improving the spectrum utilization and information rate under equal bandwidth.

[0055] The simplified expression of full-hop MPPSK in one symbol period [0, NT] is as follows:

[0056]

[0057] Where y(t) is the full-hopping MPPSK signal of one symbol period; T is the carrier period; f c is the carrier frequency; K is the number of carrier flips in one hop; N is the ratio of the symbol period to the carrier period; the transmitted data is in M-base; the value range of k is 1≤k≤M-1; by adjusting the values ​​of M, N, and K, different signal bandwidths, transmission rates, and demodulation performances can be obtained.

[0058] In the same symbol period, the information transmission rate is MPPSK uses the different relative positions of pulses to transmit different symbol information, which can compress the spectrum and carry information, while retaining the carrier and taking into account good demodulation performance.

[0059] Step 7: The frame synchronization code and navigation message after full-hop MPPSK modulation are framed according to a preset format to obtain a frame signal s(t); the framed signal s(t) is repeated multiple times to form a multi-frame signal s k (t), where the sending time of the navigation message part in each frame signal is different; the transmission time of each frame signal is 1s, and the sending time difference of the navigation messages in adjacent frames is 1s.

[0060] The preset format of the signal s(t) is:

[0061] Contains frame synchronization code part, N f The navigation message part is repeated times and the unmodulated sinusoidal carrier part; the navigation message contains the sending time t0, transmission delay, clock correction and communication information.

[0062] Step 8: multi-frame signal s k The (t) signal replaces the sinusoidal carrier in the broadcast signal and is composite-modulated with the analog audio signal to generate a composite modulated signal, which is then transmitted through the broadcast station. The composite modulated signal is expressed as follows:

[0063] Y(t)=(A0+m(t))s k (t)

[0064] Where t is the time parameter, Y(t) is the composite modulation signal; the analog audio signal m(t) is first added to the DC signal A0 and then added to s k (t) multiplied together, the DC and audio signals should satisfy A0 ≥ max(m(t)), ensuring that the signals are not overmodulated, so that the envelope detector at the receiving end cannot correctly demodulate the envelope of the AM signal. The broadcast station can be, for example, a medium wave broadcast station.

[0065] Step 9: The receiving end performs coherent accumulation on the received composite modulated signal Y(t) containing noise according to the signal design characteristics. Coherent accumulation is a process of periodically accumulating signals, which can effectively improve the signal-to-noise ratio of the received signal and enhance the sensitivity of the receiver.

[0066] From the received composite modulated signal, the frame synchronization code portion of each frame and the navigation message portion repeated multiple times within any frame are extracted according to the start time of the frame synchronization code, and coherent accumulation is performed on each of them. The waveform after the frame synchronization code or navigation message accumulation is:

[0067] (A0+m((K*T)+t))S((K*T)+t)+n((K*T)+t)

[0068] Where K is the number of accumulations, T is the period of the frame synchronization code or navigation message, S(t) is the frame synchronization code part or the navigation message part, and n(t) is the noise signal. For the frame synchronization code, it is necessary to use the frame synchronization code in multiple frame signals for coherent accumulation; for the navigation message, it is only necessary to use N frames in any frame signal for coherent accumulation. f The coherent accumulation of the repeated navigation message parts is sufficient. The longer the coherent accumulation time, the greater the improvement in signal-to-noise ratio.

[0069] The frame synchronization code portion after coherent accumulation is subjected to generalized cross-correlation processing with the frame synchronization code after full-hop MPPSK modulation to obtain the transmission delay, which is used for ranging and navigation from the transmitter to the receiver; the navigation message after coherent accumulation is demodulated to obtain the navigation message.

[0070] Example:

[0071] In one embodiment of the present invention, a 60-bit binary frame synchronization code and a 120-bit navigation message data code are generated respectively; the navigation message data code is BCH (31, 21) encoded and interleaved; the encoded navigation message data code and frame synchronization code are subjected to full-hop MPPSK modulation with N=900, M=32, K=25; the modulated frame synchronization header and navigation message part are transmitted as follows Figure 2The signal frame structure shown is framed, and the number of carriers occupied by the part without navigation information is less than that occupied by the part with navigation information. Taking the carrier center frequencies of 0.5MHz, 1MHz, and 1.5MHz as an example, the result after framing is as follows: Figure 3 The transmission time of each frame signal is 1s, and the coherent accumulation times of the navigation information part are 27, 41, and 55 times respectively.

[0072] like Figure 1 As shown in the figure, the "quasi-sine" signal obtained in the previous step replaces the sine carrier and performs composite ultra-narrowband modulation with the analog audio signal. The normalized power spectrum of the integrated communication and conduction signal based on full-hop MPPSK modulation is as follows: Figure 4 As shown, it can be seen that the composite modulated signal carrying audio still meets the -50dB bandwidth requirement.

[0073] Based on the signal design characteristics, the receiving end performs layered multi-dimensional coherent accumulation of the received signal frame synchronization header and navigation message, which can improve the signal-to-noise ratio of the received signal. Figure 5 As shown in the figure, the navigation message is coherently accumulated 40 times under the conditions of SNR of 10dB, 0dB, and -10dB. It can be seen that after multiple coherent accumulations, the SNR of the received signal is improved, the signal waveform is displayed, and the phase reversal part can be clearly found.

[0074] The above embodiments are only used to illustrate the technical solutions of the present application, rather than to limit them. Although the present application has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the scope of protection of the present application.

Claims

1. A method for designing integrated medium wave communication and navigation signals, characterized in that: The method is applied to a sending end and includes: Generate frame synchronization code and navigation message; Segmenting the binary code of the navigation message according to a fixed bit length to obtain a segmented binary code; The segmented binary codes are grouped in pairs in sequence. Each group of segmented binary codes is first subjected to serial / parallel conversion, and then subjected to BCH error correction coding, so that each group of segmented binary codes finally corresponds to a group of BCH codes. For each group of BCH codes, parallel / serial conversion is performed on each bit in sequence to output the interleaved code, thereby completing the interleaved coding of the navigation message; The full-hop MPPSK modulation is used to interleave the coded navigation message and the frame synchronization code for modulation; The frame synchronization code and the navigation message after full-hop MPPSK modulation are framed according to a preset format to obtain a frame signal; the framed signal is repeated multiple times to form a multi-frame signal, wherein the sending time of the navigation message part in each frame signal is different; A multi-frame signal replaces the sinusoidal carrier in the broadcast signal, and is composite-modulated with an analog audio signal to generate a composite modulated signal, which is then sent. The composite modulated signal is sent through a broadcast station, and the receiving end performs coherent accumulation preprocessing on the composite modulated signal containing noise, and then demodulates and estimates the delay of the preprocessed signal to obtain navigation message information and distance information.

2. The method for designing integrated medium wave communication and navigation signals according to claim 1, characterized in that: The frame synchronization code is a binary pseudo-random code; The navigation message includes sending time, transmission delay, clock correction and communication information.

3. The method for designing integrated medium wave communication and navigation signals according to claim 1, characterized in that: When the remaining binary code length is less than the fixed bit length, zeros are added to the high bits to form complete bit information.

4. The method for designing integrated medium wave communication and navigation signals according to claim 1, characterized in that: The interleaving coding structure for any group of BCH codes is: in: is the first The first segment of the BCH code information bits, for , for ; For the The first segment of the BCH code check digits, for , for ; n represents the total code length after BCH code encoding, k Indicates the code length of the information bits.

5. The method for designing integrated medium wave communication and navigation signals according to claim 1, characterized in that: When performing full-hop MPPSK modulation, use M The binary information symbol controls the position of the phase jump of the sinusoidal carrier in each symbol period; full-hop MPPSK is The expression is as follows: in, is a full-hopping MPPSK signal with a symbol period, t is the time parameter; is the carrier period; is the carrier frequency; The number of carrier flips in one hop; is the ratio of the symbol period to the carrier period; the transmitted data is Base; The value range is By adjusting M 、 N 、 K The value of can obtain different signal bandwidth, transmission rate and demodulation performance.

6. The method for designing integrated medium wave communication and navigation signals according to claim 1, characterized in that: The preset format is framed, wherein each frame signal includes a frame synchronization code portion, The navigation message part is repeated several times and the unmodulated sinusoidal carrier part; the navigation message contains the sending time, transmission delay, clock correction and communication information.

7. The method for designing integrated medium wave communication and navigation signals according to claim 1, characterized in that: The waveform after the frame synchronization code or navigation message is accumulated is: in, For analog audio signals, is a DC signal, is the cumulative number of times, is the period of the frame synchronization code or navigation message, It is the frame synchronization code part or the navigation message part. For the frame synchronization code, it is necessary to use the frame synchronization code in multiple frame signals for coherent accumulation; for the navigation message, it is only necessary to use the frame synchronization code in any frame signal for coherent accumulation. The repeated navigation message parts are coherently accumulated.

8. The method for designing integrated medium wave communication and navigation signals according to claim 1, characterized in that: The frame synchronization code after coherent accumulation is subjected to generalized cross-correlation processing with the frame synchronization code after full-hop MPPSK modulation to obtain the transmission delay, which is then used for ranging from the transmitter to the receiver.

9. A medium wave communication navigation system, comprising a transmitting end and a receiving end; characterized in that: The transmitting end transmits the navigation message by adopting the medium wave communication and navigation integrated signal design method according to any one of claims 1 to 8; the transmitting end includes a medium wave broadcasting station.

10. A computer-readable storage medium storing a computer program; wherein: When the computer program is executed by a processor, the method for designing a medium wave communication and navigation integrated signal according to any one of claims 1 to 8 is implemented.

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