Medium wave communication and navigation integrated signal design method

Abstract

The invention discloses a medium wave communication and navigation integrated signal design method. The method comprises the following steps: generating a frame synchronization code and a navigation message; segmenting a binary code of the navigation message according to a fixed bit length to obtain segmented binary codes; taking every two segmented binary codes as a group in sequence, performing serial / parallel conversion on each group of segmented binary codes, and then performing BCH error correction coding respectively; for each group of BCH codes, parallel / serial conversion is carried out according to each bit sequence to output interleaving codes, so that interleaving coding of the navigation messages is completed; and modulating and framing the navigation message and the frame synchronization code after full-hop MPPSK modulation interleaving coding to form a multi-frame signal, replacing a sine carrier in a broadcast signal with the multi-frame signal, performing composite modulation on the multi-frame signal and an analog audio signal to generate a composite modulation signal, and sending the composite modulation signal through a broadcast station. According to the invention, dual functions of broadcasting and navigation can be realized under the condition that normal use of a user is not influenced.

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] Although the Global Navigation Satellite System (GNSS) is widely used, it is susceptible to interference, deception, etc., and cannot meet specific needs in complex electromagnetic environments. The existing land-based navigation system mainly relies on the establishment of multiple fixed or mobile base stations on the ground for signal broadcasting, which is costly and susceptible to interference, and the positioning strategy based on the two-way response method has poor concealment. The current navigation and positioning system lacks effective use of ubiquitous signals in electromagnetic space.

[0003] my country has abundant resources of medium wave broadcasting stations, and the broadcasting signals have the characteristics of long transmission distance, high transmission power, and stable transmission characteristics. By embedding ranging information in medium wave broadcasting signals, a high-precision, high-reliability, flexible and low-cost PNT solution can be provided to ensure the navigation and positioning functions of various terminals in satellite-guided denial environments, and realize long-range reliable positioning under satellite-guided denial. The relevant theories of electromagnetic signal transmission models across multiple types of media are still in the exploratory stage, and the weakening rules of signals in complex electromagnetic environments and high-precision positioning methods need to be further explored. Therefore, it is urgent to explore new systems and new theories for high-precision navigation and positioning using electromagnetic signals from other sources.

[0004] my country's existing medium wave communication uses a double sideband amplitude modulation (DSB-AM) signal system that retains the carrier, which has disadvantages such as single service. The DSB-AM signal consists of a sinusoidal carrier that does not carry any information and two upper and lower analog sidebands that contain the same modulation information. In order to achieve the integrated design of medium wave broadcast signals and navigation signals, it is necessary to use the carrier of the DSB-AM signal for digital modulation. Previously, the mechanism of embedding navigation information based on existing broadcast signals was not clear. 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 transmitting end, comprises:

[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 segmented binary code;

[0010] The segmented binary codes are grouped in pairs in order, and each group of segmented binary codes is firstly subjected to serial / parallel conversion, and then subjected to BCH error correction coding respectively, 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 in each bit 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 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 and send it; wherein the composite modulated signal is sent through a broadcast station, and after receiving the composite modulated signal containing noise, the receiving end performs coherent accumulation preprocessing, and then demodulates and estimates the delay of the preprocessed signal to obtain navigation message information and distance information.

[0015] Further, 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, m is 1 to (nk); n represents the total code length after BCH code encoding, and k represents 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 part, N f The navigation message part is repeated 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] (A 0 +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 in any frame signal. f The repeated navigation message parts are coherently accumulated.

[0028] Furthermore, the frame synchronization code part 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 navigation integrated signal design method to transmit navigation messages; the transmitting end comprises a medium wave broadcasting station.

[0030] A terminal device comprises a processor, a memory and a computer program stored in the memory; the characteristic is 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 with the traditional AM broadcast transmitter, the present invention replaces the original sinusoidal carrier with full-hop MPPSK modulation of the navigation message, which can realize the integrated transmission of the broadcast signal and the navigation message without affecting the audio signal. In the time domain, the navigation message is modulated on the carrier phase and will not interfere with the audio signal modulated on the envelope; in the frequency domain, the full-hop MPPSK modulation can further tighten the sidelobe power while increasing the symbol transmission rate, and the sideband is low-level, ensuring that the digital carrier does not interfere with the in-band analog audio and out-of-band signals; in terms of demodulation performance, the receiving end can improve the signal-to-noise ratio by adopting the layered multi-dimensional coherent accumulation method of the frame synchronization header and the navigation message according to the design characteristics of the integrated communication and navigation signal. The medium wave communication and navigation integrated signal designed by the present invention has strong anti-interference ability and long-distance diffraction ability. It is simple to modify the existing equipment and can realize long-distance precise positioning and navigation. It has special application value in long-distance navigation and timing in the satellite navigation system denial environment, and makes a powerful supplement to my country's comprehensive positioning, navigation, and timing (Positioning, Navigation, Timing, PNT) system. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 This is the block diagram of the integrated communication and navigation 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 frame 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 view of 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, integrated transmission can be achieved without affecting the broadcast signal; in view of 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 in the receiving process to improve the signal-to-noise ratio. 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 transformation 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 large 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 and deceived.

[0040] The present invention provides a medium wave communication and navigation integrated signal design method, wherein steps 1-8 are applied to the 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, which is used for the transmission delay estimation of the integrated communication and navigation signal and the reception synchronization of the navigation message; the frame synchronization code value is fixed and known, so the receiving end can use it to match the received signal, providing the necessary conditions for subsequent pseudo-range measurement and correct decoding of the binary navigation message in the corresponding format.

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

[0043] Sending time t 0 : 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 the leaving of the transmitting antenna of a base station. Its value can be measured through inspection before the base station sends the signal. It 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: Segment the binary code of the navigation message according to the length of each k bits to obtain segmented binary code; when the remaining binary code length is less than k bits, fill the high bits with zeros to form a complete k-bit information. The receiving end will ignore these filled zeros during decoding and only restore the original valid information bits. This allows the subsequent BCH encoding to adapt to information bits of various lengths and maintain its error correction capability.

[0048] Step 4, group the segmented binary codes in pairs in order, perform serial / parallel conversion on each group of segmented binary codes first, and then perform error correction coding respectively. 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; wherein 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 bit.

[0049] Step 5: For each group of BCH codes, perform parallel / serial conversion in the order of each bit, and output an interleaved code with a length of 2n bits, thereby completing the interleaving coding of the navigation message; wherein 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: Refer to the spectrum allocation scheme of the In Band On Channel (IBOC) technology. If the power spectrum sideband of the digital modulation information is at least 50dB lower than the carrier in the 9kHz frequency band of the analog main signal, its interference to the analog signal can be basically 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; M-ary information symbols are used to control the position of the phase jump of the sinusoidal carrier in each code element period, thereby improving 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 not only compress the spectrum but also carry information, and it also takes into account good demodulation performance while retaining the carrier.

[0059] Step 7, 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 s(t); the framed signal s(t) is repeated multiple times to form a multi-frame signal s k (t), where the sending time contained in the navigation message part of each frame signal is different; the transmission time of each frame signal is 1s, and the sending time difference contained in the navigation messages of 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 repeated times and the unmodulated sinusoidal carrier part; the navigation message contains the sending time t 0 , transmission delay, clock correction and communication information.

[0062] Step 8: convert the 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 sent through the broadcast station; the expression of the composite modulated signal is:

[0063] Y(t)=(A 0 +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 firstly 0 After adding, add k (t) multiplied, DC and audio signals should satisfy A 0 ≥max(m(t)), ensuring that the signal will not be overmodulated, so that the envelope detector at the receiving end cannot correctly demodulate the envelope of the AM signal. The broadcast station may be a medium wave broadcast station, for example.

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

[0066] According to the start time of the frame synchronization code, the frame synchronization code part of each frame and the navigation message part repeated multiple times in any frame are extracted from the received composite modulated signal, and coherent accumulation is performed respectively. The waveform after the frame synchronization code or navigation message accumulation is:

[0067] (A 0 +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 in any frame signal. f The coherent accumulation of the repeated navigation message parts is sufficient. The longer the coherent accumulation time is, the more the signal-to-noise ratio is improved.

[0069] The frame synchronization code part 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 encoded by BCH (31, 21) and interleaved; the encoded navigation message data code and frame synchronization code are modulated by full-hop MPPSK with N=900, M=32, K=25; the modulated frame synchronization header and navigation message part are modulated as follows Figure 2 The signal frame structure shown in the figure 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 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] The receiving end can improve the signal-to-noise ratio of the received signal by performing layered multi-dimensional coherent accumulation of the received signal frame synchronization header and navigation message according to the signal design characteristics. Figure 5 As shown, the navigation message is coherently accumulated 40 times under the conditions of SNR of 10dB, 0dB and -10dB respectively. It can be seen that after multiple coherent accumulations, the SNR of the received signal is improved, the signal waveform has been 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 embodiments of the present application, and should all be included in the protection scope of the present application.

Claims

1. A method for designing a medium wave communication and navigation integrated signal, characterized in that: The method is applied to a sending end, comprising: Generate frame synchronization code and navigation message; Segmenting the binary code of the navigation message according to a fixed bit length to obtain segmented binary code; The segmented binary codes are grouped in pairs in order, and each group of segmented binary codes is firstly subjected to serial / parallel conversion, and then subjected to BCH error correction coding respectively, 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 in each bit 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 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 and send it; wherein the composite modulated signal is sent through a broadcast station, and after receiving the composite modulated signal containing noise, the receiving end performs coherent accumulation preprocessing, and then demodulates and estimates the delay of the preprocessed signal to obtain navigation message information and distance information.

2. The method for designing a medium wave communication and navigation integrated signal 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 a medium wave communication and navigation integrated signal 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 a medium wave communication and navigation integrated signal according to claim 1, characterized in that: The interleaving coding structure for any group of BCH codes is: 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, m is 1 to (nk); n represents the total code length after BCH code encoding, and k represents the code length of the information bit.

5. The method for designing medium wave communication and navigation integrated signals according to claim 1, characterized in that: When performing full-hop MPPSK modulation, the M-ary information symbol is used to control the position of the phase jump of the sinusoidal carrier in each symbol period; the expression of full-hop MPPSK in a symbol period [0, NT] is as follows: 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.

6. The method for designing medium wave communication and navigation integrated signals according to claim 1, characterized in that: The preset format is framed, wherein each frame signal includes a 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, 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: (A0+m((K*T)+t))S((K*T)+t)+n((K*T)+t) 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 in any frame signal. f The repeated navigation message parts are coherently accumulated.

8. The method for designing medium wave communication and navigation integrated signals according to claim 1, characterized in that: The frame synchronization code part 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 using 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, wherein a computer program is stored in the medium; characterized in that: When the computer program is executed by the 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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