WO2020134855A1 - Satellite communication system - Google Patents

Abstract

A narrow band multi-channel satellite communication system, wherein a signal is transmitted to at least one narrow band satellite by means of a ground station, the ground station at least comprising an encoding module and a first modulation module, and the ground station being configured as follows: the encoding module being configured to encode a signal so as to acquire an encoded signal; and the first modulation module being configured to execute serial-to-parallel conversion on the encoded signal so as to generate a first branch bit stream and a second branch bit stream, wherein delay processing is executed in the first branch bit stream such that, in the situation in which a code element period is set between the first branch bit stream and the second branch bit stream at intervals, the first branch bit stream sequentially executes first level filter processing and first level modulation processing to acquire a first modulated signal, and the second branch bit stream executes first level filter processing and second level modulation processing to acquire a second modulated signal; and the first modulated signal and the second modulated signal jointly undergo second level modulation processing so as to obtain a third modulated signal, the third modulated signal undergoing second level filter processing to finish modulation processing.

Description

A satellite communication system Technical field

The invention belongs to the technical field of wireless communication, and particularly relates to a satellite channel system.

Background technique

Space spectrum resources are limited, and the increase in the data transmission rate of satellite communications comes at the expense of the bandwidth of information, so that it continues to have a huge impact on spectrum resources. In order to avoid multiple transmitters transmitting signals in the same frequency band and causing the same frequency signals to interfere with each other, the receiver cannot adjust the correct information. In order to solve the existing problems, a fixed spectrum allocation mode is often adopted, that is, the right to use fixed frequency bands is assigned to specific users and other users or services are prohibited from accessing the allocated spectrum. The fixed frequency band allocation mode effectively solves the interference caused by the use of radio. However, with the rapid development of wireless technology, more and more services need to access the spectrum. The original static allocation management mode of the spectrum makes the spectrum resources unable to be fully utilized, thereby making the spectrum resources increasingly scarce. Therefore, the research of narrow-band communication technology with high spectrum utilization rate, fast transmission rate and long transmission distance has become inevitable.

OFDM (Orthogonal Frequency Division Multiplexing) is a modulation technique that uses a multi-carrier transmission method to transmit a data string through sub-carriers with a low transmission rate. OFDM technology uses a discontinuous multi-tone modulation technology to combine a large number of signals in carriers of different frequencies into a single signal to complete signal transmission. The development of OFDM technology is to improve the spectrum utilization rate of the carrier. Its characteristic is that each subcarrier is orthogonal to each other, so the spectrum after spread spectrum modulation can overlap each other, thus reducing the mutual interference between the subcarriers. WiMAX communication system is a communication system based on OFDM modulation technology. One of the important keys to using OFDM is to increase the ability to resist frequency selective fading, while also increasing the ability to resist narrowband interference. However, the condition that the OFDM system can resist narrow-band interference is assuming that the power of the OFDM signal is much larger than that of the narrow-band interference; however, in practical applications, the transmission power of the OFDM signal is limited, so that when the external narrow-band interference signal is strong enough Normal demodulation performance will be deteriorated. Therefore, how to suppress narrow-band interference in limited spectrum resources is a problem that cannot be ignored.

Narrow-band strong interference is a common interference in practical applications, and its suppression can be done in the time domain or the frequency domain. The time-domain method uses the correlation of narrow-band interference to perform adaptive filtering using the least mean square algorithm or the recursive least square algorithm. The frequency domain method uses fast Fourier transform or inverse fast Fourier transform to zero the frequency of interference to eliminate interference. Specifically, the common frequency domain filtering mainly has the following two methods: The first method is a simple interference suppression technology based on FFT/IFFT, which outputs the data through windowing, FFT calculation, NBI filter processing and IFFT calculation, In the second way, in order to reduce the signal-to-noise ratio loss caused by windowing, an interference suppression technique based on superimposed fast Fourier transform is proposed. The basic idea is to copy and shift the input data into windowing, get two windowed data together with the original windowed data, perform FFT transformation, and perform filtering in the frequency domain. After filtering, perform IFFT to obtain interference-free time-domain data. Align and merge the two data to get the final output.

The patent document with publication number CN105549035B discloses a device and method for detecting and eliminating narrowband interference in the frequency domain of a baseband signal. The method includes: dividing an intermediate frequency signal into two channels, which are respectively output to a narrowband interference detector and a narrowband interference canceller. The narrow-band interference detector performs interference detection on a received intermediate frequency signal to obtain interference detection information, and sends it to the narrow-band interference canceller, and the narrow-band interference canceller performs an operation on another received intermediate frequency according to the interference detection information. The signal is processed for narrow-band interference cancellation. The invention multiplies the time domain of the signal by a window function to perform windowing before performing the fast Fourier transform. The multiplication in the time domain is equivalent to the convolution in the frequency domain, so the effect of windowing is only to reduce interference Sidelobes produced by the source. The performance that windowing can improve depends on the frequency of the interference source. When the interference source is not located on a certain subcarrier frequency, spectrum leakage will occur, and narrowband interference will affect all adjacent subcarriers. And it does not consider the elimination of inter-carrier interference.

Summary of the invention

The term "module" as used herein describes any type of hardware, software, or combination of hardware and software that is capable of performing the function associated with the "module."

In view of the shortcomings of the prior art, the present invention provides a satellite communication system, especially a narrow-band multi-channel satellite communication system. The signal can be transmitted to at least one narrow-band satellite via a ground station, and several ground stations can be based on each other Narrowband satellite relays are communicatively coupled. The ground station includes at least an encoding module and a first modulation module. The ground station is configured to modulate the signal as follows: The encoding module is configured to The signal performs an encoding process to obtain an encoded signal; the first modulation module is configured to perform a serial-to-parallel conversion process on the encoded signal to generate a first branch code stream and a second branch code stream, where: in the first When the branch code stream performs delay processing so that the first branch code stream and the second branch code stream are spaced apart from each other by a set symbol period, the first branch code stream sequentially performs the first The first-stage filtering process and the first-stage modulation process obtain the first modulation signal, and the second branch code stream performs the first-stage filtering process and the second-stage modulation process in sequence to obtain the second modulation signal; the first modulation The signal and the second modulation signal are jointly subjected to the second-stage modulation process to obtain a third modulation signal, wherein the third modulation signal is subjected to the second-stage filter process to complete the modulation process. The first-stage filtering process is performed by a raised cosine roll-off filter, and the second-stage filtering process is performed by a band-pass filter. After the signal is filtered in the first stage, due to the subsequent modulation re-sampling process, the signal spectrum will have a periodic extension phenomenon, which eventually generates inter-symbol interference, and there will be side-lobe interference within the frequency range of the modulated signal, which reduces the modulated signal. The quality of the code increases the bit error rate. The second-stage filtering process can reduce the size of side lobes in the frequency range to the specified decibel range, and can eliminate inter-symbol interference. The third modulation signal generated by modulation has a lower average power ratio peak value than the prior art. And through the first-stage filtering process, any phase discontinuities of the first branch code stream and the second branch code stream can be effectively removed smoothly.

Advantageously, the encoding module is configured to perform encoding processing on the signal in the following manner: the BCH code generated by the signal through the BCH encoding process and the transmitted information frame together constitute several information subframes with set bits, the The information subframes are subjected to synchronous scrambling to sequentially perform RS encoding and convolutional encoding. The convolutionally encoded data and the carrier synchronization bits, pilot sequence, unique code, and frame tail together form a complete modulated data frame, in which: When the bit length of the information subframe is less than the set bit length, it is complemented in a manner of supplementing zero codes.

Advantageously, the ground station further includes a filtering module, a second modulation module and a frequency conversion module, and the ground station further processes the signal in the following manner: the encoded signal is transmitted to the first modulation module at a set code rate After the modulation process is performed in, the first carrier frequency is transmitted to the filter module; the filter module is configured to perform a filter process on the signal it receives and transmit it to the second modulation module; the second modulation module uses the second The carrier frequency transmits the signal it receives to the frequency conversion module, wherein the frequency conversion module is configured to frequency convert the signal it receives to a set radio frequency output frequency.

Advantageously, the narrowband satellite includes at least a signal conditioning module and an interference cancellation module, and in the case where the signal is transmitted to the narrowband satellite via the ground station, the narrowband satellite is configured to perform on the signal as follows Processing: The signal conditioning module is configured to: determine the frequency component of the signal and acquire several decomposed signals in different time-frequency spaces to separate the frequency content of the interference signal. The interference cancellation module is configured to: align the frequency of the interference signal with the center of the subcarrier frequency of the communication channel and establish a first complex sinusoid, and obtain based on the multiplication processing of the first complex sinusoid and the signal to obtain Offset signals and introduce inter-carrier interference therefrom; sequentially performing windowing processing and fast Fourier transform processing on the offset signals to generate a frequency domain signal, which can eliminate the frequency by setting the subcarrier frequency to zero Interference signal to obtain an interference cancellation signal; in the case where the interference cancellation signal is processed by inverse fast Fourier transform to generate time-domain sampling samples, a second complex sine curve is established and according to the second complex sine curve and the time domain The sampling samples perform multiplication processing to eliminate the inter-carrier interference.

Advantageously, the signal conditioning module obtains the decomposed signal as follows: configure a filter bank with several different filtering levels, and each filtering level includes at least a low communication channel and a high communication channel, the low communication channel and Each of the high communication channels is configured with at least one set of discrete wavelet transformers, wherein: based on several filter levels of the filter bank, several subbands of different frequency bands will be acquired; The discrete wavelet transform process decomposes into several different time-frequency spaces.

Advantageously, the first complex sine curve is given by the formula

Limited, the second complex sine curve is given by the formula

Limited; the generator polynomial for BCH coding is g(x) = x ¹⁰ + x ⁹ + x ⁸ + x ⁶ + x ⁵ + x ³ +1; the generator polynomial for RS coding is g(x) = x ⁸ + x ⁴ + x ³ +x ² +1; the generator polynomials of the two output ports of convolutional coding are g1(x)=x ⁶ +x ⁵ +x ⁴ +x ³ +1 and g2(x)=x ⁶ +x ⁴ +x ³ +x ¹ +1; the scrambling code period and polynomial of the synchronous scrambling process are 2 ¹⁵ -1 and 1+X ¹⁴ +X ^{15 respectively} ; where F _s represents the sampling frequency and N is the number of fast Fourier transform sampling points .

Advantageously, the first-stage filtering process is performed by a first filter, and the second-stage filtering process is performed by a second filter, wherein: the first filter is a raised cosine roll-off filter, and the first The second filter is a band-pass filter; the first-stage modulation process is a quadrature modulation process, and the second-stage modulation process is an in-phase modulation process.

Advantageously, the narrowband satellite further includes an interference detection module and a demodulation module, the interference detection module is configured to calculate an average power of the signal to determine whether there is an interference signal in the subband, and the demodulation module is configured to interfere with the interference The output signal of the elimination module is demodulated.

Advantageously, the interference cancellation module is further configured to obtain the frequency Δf of the fast Fourier transform filter bank closest to the frequency of the interference signal, wherein: the frequency of the first complex sinusoid is Δf, and the second complex The frequency of the sine curve is -Δf.

Advantageously, for the subcarrier frequency involved in the calculation of the frequency Δf of the fast Fourier transform filter bank, the interference cancellation module can set the frequency of the fast Fourier transform filter bank corresponding to the subcarrier frequency to zero to set the frequency The interference signal is eliminated.

The present invention also provides a satellite communication system, especially a narrow-band satellite communication system, at least including a narrow-band satellite and a ground station, the narrow-band satellite is configured to at least suppress interference of the signal during signal relay Processing to realize the transmission of the signal between several ground stations, which converts the signal it receives to several different RF output frequencies to establish multi-channel transmission with the narrow-band satellites , Wherein the narrow-band satellite is configured to: respectively establish a first complex sinusoid and a second complex sinusoid, and determine the frequency component of the signal to separate the frequency content of the interference signal; based on the first complex sinusoid and The first-stage multiplication processing of the signal acquires the first processed signal and introduces inter-carrier interference; eliminates the interference signal in a manner that the subcarrier frequency is set to zero to obtain the second processed signal; after the second processed signal is subjected to Fast Fourier In the case of inverse transform processing, the second-stage multiplication processing based on the second complex sinusoid and the second processed signal eliminates the inter-carrier interference.

Advantageously, the narrow-band satellite is further configured to: align the frequency of the interference signal with the frequency of the sub-carrier frequency of the communication channel; obtain the frequency Δf of the fast Fourier transform filter bank closest to the frequency of the interference signal; The interference signal is eliminated by setting the frequency Δf of the fast Fourier transform filter bank corresponding to the subcarrier frequency to zero.

Advantageously, the narrowband satellite is further configured to configure a filter bank with several different filtering levels, and each filtering level includes at least a low communication channel and a high communication channel, the low communication channel and the high communication channel Each is configured with at least one set of discrete wavelet transformers, wherein: several subbands of different frequency bands are obtained based on several filter levels of the filter bank; the signals contained in the subbands can be decomposed into several by discrete wavelet transform processing, respectively Different time-frequency space to separate the frequency content of the interference signal.

Advantageously, the ground station includes at least an encoding module, a first modulation module and a filtering module, the ground station is configured to process the signal it receives in the following manner: the encoding module performs at least BCH encoding processing, RS The encoding process and the convolutional encoding process perform a common processing on the signal to encode the signal to obtain an encoded signal; the first modulation module performs modulation processing on the encoded signal and transmits it to the filter module at a first carrier frequency, wherein : When acquiring the first tributary code stream and the second tributary code stream with a symbol period set apart from each other based on the encoded signal, at least based on the first tributary code stream and the second tributary code stream The tributary code stream obtains the first modulation signal and the second modulation signal respectively; the first modulation signal and the second modulation signal acquire the third satisfying the first carrier frequency in a manner of sequentially performing modulation processing and filtering processing Modulated signal.

Advantageously, the encoded signal acquires the first branch code stream and the second branch code stream in a manner of performing serial-parallel conversion processing, the first branch code stream or the second branch code The streams can be set at intervals from each other in a manner to perform delay processing, wherein: in the case where the first branch code stream performs the delay processing, the first branch code stream performs the first The first modulation signal is acquired in the manner of first-level filtering and second-stage modulation, and the second branch code stream is acquired in the manner of sequentially performing the first-stage filtering and second-stage modulation A modulation signal; the first modulation signal and the second modulation signal acquire the third modulation signal in a manner of sequentially performing a second-stage modulation process and a second-stage filter process. The first-stage filtering process is performed by a raised cosine roll-off filter, and the second-stage filtering process is performed by a band-pass filter. After the signal is filtered in the first stage, due to the subsequent modulation re-sampling process, the signal spectrum will have a periodic extension phenomenon, which will eventually produce inter-symbol interference, and there will be side-lobe interference within the frequency range of the modulated signal, which reduces the modulated signal. The quality of the code increases the bit error rate. The second-stage filtering process can reduce the size of side lobes in the frequency range to the specified decibel range, and can eliminate inter-symbol interference. The third modulation signal generated by modulation has a lower average power ratio peak value than the prior art. And through the first-stage filtering process, any phase discontinuities of the first branch code stream and the second branch code stream can be effectively removed smoothly.

Advantageously, the encoding process includes at least the following steps: the signal is subjected to the BCH encoding process to generate a BCH code, and the BCH code and the transmitted information frame together constitute a number of information subframes with set bits in the manner of supplementary zero codes; In the case where the information subframe is sequentially subjected to synchronous scrambling processing, RS coding processing and convolutional coding processing to obtain processed data, the processed data is at least complete with the carrier synchronization bit, pilot sequence, unique code and frame tail Modulation data frame.

Advantageously, the ground station further includes a second modulation module and a frequency conversion module, and the filter module includes at least a first filter and a second filter, wherein: the filter module controls the first One branch code stream and the second branch code stream perform the first-stage filtering process and the second filter performs the second-stage filtering process on the third modulated signal in a manner The signal is filtered; in the case where the third modulated signal is transmitted to the second modulation module through the filter module, the second modulation module transmits the signal it receives to the frequency conversion at the second carrier frequency Module; the frequency conversion module converts the signal it receives to a set radio frequency output frequency.

In view of the shortcomings of the prior art, the present invention provides a satellite communication system based on suppression of narrow-band interference. The narrow-band satellite and the ground station communicate with each other in a multi-channel manner to relay transmission of a combined signal having several constituent signals. Characteristically, the narrowband satellite is configured to:

Establish a first complex sinusoidal curve and a second complex sinusoidal curve, respectively, and determine the frequency components of the signal to separate the frequency content of the interference signal; based on the first multiplication process of the first complex sinusoidal curve and the signal to obtain the first 1. Process the signal and introduce inter-carrier interference; eliminate the interference signal in a manner that the subcarrier frequency is set to zero to obtain the second processed signal;

In the case where the second processed signal is processed by inverse fast Fourier transform, the second-stage multiplication processing based on the second complex sinusoid and the second processed signal eliminates the inter-carrier interference;

Wherein, the narrow-band satellite includes at least an interference detection module, a windowing module, a separation module and a regeneration module. When the component signals have frequency overlap with each other, the narrow-band satellite is configured to Combined signal processing: the windowing module is configured to generate a window processing signal after limiting the frequency of the combined signal based on windowing processing; the interference detection module is configured to perform n-th power processing based on the window processing signal to Determining the modulation characteristic of at least one component signal and the symbol rate of its corresponding carrier; the separation module is configured to be based on the symbol rate when the window processed signal generates at least one continuous wave based on the nth power processing Resample the window processing signal by m times to generate a resampled signal, and use this to determine at least one symbol trajectory and at least one modulation type; the regeneration module is configured to pair based on the symbol trajectory and the modulation type The component signals are synthesized and reproduced to generate a synthesized signal.

Advantageously, the narrow-band satellite further includes a cancellation module and an inversion module, and in the case where the synthesized signal is determined to be an interference signal, the narrow-band satellite is configured to process the synthesized signal as follows: The conversion module is configured to invert the synthesized signal to generate an inverted copy; the cancellation module is configured to receive a copy of the combined signal and superimpose the inverted copy and the combined signal to Generate the first-level interference suppression signal.

Advantageously, the narrowband satellite further includes a signal preprocessing module and an interference cancellation module, the narrowband satellite is configured to process the first-level interference suppression signal in the following manner: the signal preprocessing module is configured to establish a A complex sinusoidal curve and a second complex sinusoidal curve, and determining the frequency component of the first-stage interference suppression signal to separate the frequency content of the interference signal. The interference cancellation module is configured to: introduce inter-carrier interference in a manner of performing multiplication processing of the first interference suppression signal and the first complex sinusoidal curve to generate an offset signal; and obtain interference in a manner of setting a subcarrier frequency to zero Eliminating the signal and acquiring its time-domain sampling samples; eliminating the inter-carrier interference in a manner that the time-domain sampling samples and the second complex sinusoidal curve perform multiplication processing.

Advantageously, the interference cancellation module acquires the interference cancellation signal as follows: aligns the frequency of the interference signal with the frequency of the subcarrier frequency of the communication channel and acquires the fast Fourier transform filter closest to the frequency of the interference signal The frequency Δf of the group; performing the windowing process and the fast Fourier transform process on the offset signal in sequence to generate a frequency domain signal; and setting the frequency Δf of the fast Fourier transform filter bank corresponding to the subcarrier frequency to zero.

Advantageously, the signal preprocessing module is configured to configure a filter bank with several different filtering levels, and each filtering level includes at least a low communication channel and a high communication channel, the low communication channel and the high communication channel Each channel is configured with at least one set of discrete wavelet transformers, wherein: based on several filter levels of the filter bank, several subbands of different frequency bands are obtained; signals contained in the subbands can be decomposed into discrete wavelet transforms to Several different time-frequency spaces.

Advantageously, the ground station includes at least an encoding module and a first modulation module, the ground station is configured to modulate the signal as follows: the encoding module is configured to perform encoding processing on the signal to obtain Coded signal; the first modulation module is configured to perform a serial-to-parallel conversion process on the coded signal to generate a first branch code stream and a second branch code stream, wherein: performing delay on the first branch code stream Processing such that when the first branch code stream and the second branch code stream are separated from each other by a set symbol period, the first branch code stream sequentially performs the first-stage filtering process and the first The first-level modulation process obtains a first modulation signal, and the second branch code stream sequentially performs the first-level filter process and the second-stage modulation process to obtain a second modulation signal; the first modulation signal and the second The modulated signals are collectively subjected to the second-stage modulation process to obtain a third modulated signal, wherein the third-modulated signal is subjected to the second-stage filter process to complete the modulation process. The first-stage filtering process is performed by a raised cosine roll-off filter, and the second-stage filtering process is performed by a band-pass filter. After the signal is filtered in the first stage, due to the subsequent modulation re-sampling process, the signal spectrum will have a periodic extension phenomenon, which will eventually produce inter-symbol interference, and there will be side-lobe interference within the frequency range of the modulated signal, which reduces the modulated signal. The quality of the code increases the bit error rate. The second-stage filtering process can reduce the size of side lobes in the frequency range to the specified decibel range, and can eliminate inter-symbol interference. The third modulation signal generated by modulation has a lower average power ratio peak value than the prior art. And through the first-stage filtering process, any phase discontinuities of the first branch code stream and the second branch code stream can be effectively removed smoothly.

Advantageously, the encoding process includes at least the following steps: the signal undergoes BCH encoding processing to generate a BCH code, and the BCH code and the transmitted information frame together constitute a number of information subframes with set bits in a manner of supplementing zero codes; In the case where the information subframe is processed by synchronous scrambling, RS encoding, and convolutional encoding in order to obtain processed data, the processed data at least together with the carrier synchronization bit, pilot sequence, unique code, and frame tail form a complete modulation Data Frame.

Advantageously, the ground station further includes a filtering module, a second modulation module and a frequency conversion module, and the ground station further processes the signal in the following manner: the encoded signal is transmitted to the first modulation module at a set code rate After the modulation process is performed in, the first carrier frequency is transmitted to the filter module; the filter module is configured to perform a filter process on the signal it receives and transmit it to the second modulation module; the second modulation module uses the second The carrier frequency transmits the signal it receives to the frequency conversion module, wherein the frequency conversion module is configured to frequency convert the signal it receives to a set radio frequency output frequency.

Advantageously, the narrowband satellite further includes a demodulation module, the interference detection module is configured to calculate the average power of the signal to determine whether there is an interference signal in the subband, and the demodulation module is configured to output the interference cancellation module The signal is demodulated, where the frequency of the first complex sinusoid is Δf and the frequency of the second complex sinusoid is -Δf.

Advantageously, the filtering module performs the first-stage filtering process on the first branch code stream and the second branch code stream according to a first filter and a second filter on the third modulated signal Performing the second-stage filtering process by filtering the received signal; in the case where the third modulated signal is transmitted to the second modulation module through the filtering module, the second modulation module The second carrier frequency transmits the signal it receives to the frequency conversion module; the first filter is a raised cosine roll-off filter, the second filter is a band-pass filter; and the first-stage modulation processing is In quadrature modulation processing, the second-stage modulation processing is in-phase modulation processing.

The beneficial technical effects of the satellite communication system of the present invention are:

(1) In the iterative process of the present invention, when each narrow-band interference signal is aligned with the center of the sub-carrier frequency of the communication channel, it will cause inter-carrier interference. The signal will no longer carry the narrow-band interference after the sub-carrier frequency aligned with the narrow-band interference is removed, and then the inter-carrier interference is removed from the signal. Therefore, before decoding, the signal removes all narrow-band interference and any potential side lobes, thereby eliminating spectral leakage.

(2) The digital shaping filter of the present invention can eliminate inter-symbol interference, and thus can meet the Nyquist characteristic without inter-symbol interference, and can also smooth the waveform, and thus can accelerate the out-of-band attenuation speed of the modulated signal and improve the spectrum utilization rate. . The processing of the band-pass filter can make the modulation envelope smoother.

(3) The present invention can receive signals with overlapping frequencies, detect and filter the interference signals contained therein, and can effectively improve the utilization rate of spectrum resources.

BRIEF DESCRIPTION

1 is a schematic diagram of the modular connection relationship of the preferred narrowband multi-channel satellite communication system of the present invention;

2 is a schematic diagram of the modular structure of the preferred ground station of the present invention;

3 is a schematic diagram of the modulation processing flow of the first modulation module preferred in the present invention;

4 is a schematic diagram of the modular structure of the preferred narrowband satellite of the present invention;

5 is a schematic diagram of the processing flow of the preferred interference cancellation module of the present invention;

6 is a block diagram of a preferred RS code encoding of the present invention;

7 is a coding block diagram of a preferred convolutional code of the present invention;

8 is a schematic diagram of the processing flow of the preferred encoding module of the present invention;

9 is a schematic diagram of a modular structure of another narrow-band satellite preferred by the present invention; and

FIG. 10 is a schematic diagram of the processing flow of the combined signal of the narrowband satellite of the present invention. .

List of Reference Marks

1: Narrow-band satellites 2: Ground station

101: interference detection module 102: interference cancellation module 103: demodulation module

104: signal conditioning module 105: analog-to-digital conversion module 106: windowing module

107: Separation module 108: Regeneration module 109: Delay module

110: Elimination module 111: Reverse module

201: coding module 202: first modulation module 203: filter module

204: second modulation module 205: frequency conversion module

102a: offset logic circuit 102b: first multiplier 102c: window function circuit

102d: First fast Fourier transform circuit 102e: Interference cancellation circuit

102f: inverse fast Fourier transform circuit 102g: correction circuit 102h: second multiplier

102i: Second fast Fourier transform circuit

2a: First ground station 2b: Second ground station

203a: first filter 203b: second filter

202a: first modulator 202b: second modulator 202c: third modulator

detailed description

The following is a detailed description with reference to the drawings.

Each "module" in the present invention may be one or more of a dedicated integrated chip, a server, and a server group. The module of the present invention describes any kind of hardware, software, or combination of hardware and software that can perform the function associated with the “module”.

According to a feasible manner, the present invention provides a multi-channel satellite communication system, which includes at least one narrow-band satellite 1 and several ground stations 2 that communicate with each other. For example, as shown in FIG. 1, the multi-channel satellite communication system includes a narrow-band satellite 1, a first ground station 2a, and a second ground station 2b. The first ground station 2a may send the data signal it receives to the narrowband satellite 1, and then relay it to the second ground station 2b through the narrowband satellite 1. Similarly, the second ground station 2b may also relay the data signal it receives to the first ground station 2a through the narrowband satellite 1. The first ground station 2a and the second ground station 2b may individually have their respective gateways, and all the gateways may be communicatively coupled to each other through a common network.

Preferably, as shown in FIG. 2, the ground station 2 includes at least an encoding module 201, a first modulation module 202, a filtering module 203, a second modulation module 204, and a frequency conversion module 205. The encoding module 201 is used to encode the original data information received by the ground station 2 and transmit the encoded digital signal to the first modulation module 202 according to the set code rate. The first modulation module 202 is used to modulate the digital signal to be converted to the set first carrier frequency. The digital signal modulated by the first modulation module 202 is transmitted to the filtering module 203 for filtering. The digital signal filtered by the encoding module 201 of the filtering module 203 is transmitted to the second modulation module 204 for re-modulation to switch to the set second carrier frequency. The digital signal with the second carrier frequency is transmitted to the frequency conversion module 205. The frequency conversion module 205 is used to convert the digital signal processed by the second modulation module 204 to a set transmission frequency point so as to upload it to the narrowband satellite 1.

Preferably, the encoding module 201 may be configured to encode the original data information based on cyclic encoding or convolutional encoding. The first modulation module 202 and the second modulation module 204 may be based on one of digital phase modulation, multi-ary digital phase modulation, phase shift keying modulation, quadrature phase keying modulation, offset quadrature phase shift keying modulation Or a combination of multiple types to modulate the digital signal. The filtering module 203 can be a digital shaping filter. The digital shaping filter can eliminate inter-symbol interference, which can meet the Nyquist characteristic without inter-symbol interference, and can also smooth the waveform, which can accelerate the out-of-band attenuation speed of the modulated signal. To improve spectrum utilization.

Preferably, the frequency conversion module 205 may be a programmable phase-locked loop chip. By configuring the parameters of the frequency-division register of the phase-locked loop chip, the modulation signal can be converted to a set RF output frequency range, and then the frequency division interval can be set by setting Divide the available spectrum at equal frequency intervals into several carrier channels. Dividing the spectrum into multiple channels can improve the spectrum utilization. For example, if the available frequency band is 100.0000MHz to 100.0100MHz, and if the frequency division interval is 100Hz, the frequency band can be divided into 100 channels. The narrowband signal can be obtained through the frequency conversion module. Furthermore, narrow-band multi-channel communication between the ground station 2 and the narrow-band satellite 1 is realized.

Preferably, the ground station 2 may send the original data to the first modulation module 202 at a code rate of 600 bps after being encoded by the encoding module for modulation processing. The first modulation module 202 transmits to the filter module 203 with a carrier frequency of 15 KHz to perform filter processing. The second modulation module 204 remodulates the 15 KHz modulation signal so that it is transmitted to the frequency conversion module 205 at a carrier frequency of 10.685 MHz.

Preferably, as shown in FIG. 3, the first modulation module 202 is further configured to modulate the encoded signal processed by the encoding module 201 according to the following working mode:

S1: The coded signal undergoes serial-parallel conversion processing to generate a first branch code stream and a second branch code stream, where the first branch code stream and the second branch code stream are spaced apart from each other by setting codes Metacycle.

Specifically, after the coded signal undergoes serial-to-parallel conversion processing to generate the first tributary code stream and the second tributary code stream, the respective code rates of the first tributary code stream and the second tributary code stream are two One in one. The first tributary code stream can be transmitted in a serial transmission manner, and the second tributary code stream can be transmitted in a parallel transmission manner. The set symbol period may be a half symbol period. Either the first branch code stream or the second branch code stream can be shifted by half a symbol period after being delayed by half a symbol period. cycle.

S2: When the first branch code stream is delayed by half a symbol period, the first branch code stream and the second branch code stream are respectively transmitted to the filtering module 203 in a one-to-one correspondence Perform filtering processing, where the filtering module 203 includes at least a first filter 203a and a second filter 203b, and the first branch code stream and the second branch code stream are transmitted to the first filter 203a in a one-to-one correspondence Perform filter processing. The first-stage filtering process can be performed by the first filter 203a.

Specifically, the first filter 203a is a digital shaping filter. The digital shaping filter may be a raised cosine roll-off filter. By controlling the roll-off coefficient, the shaped waveform of the encoded signal can be changed, thereby reducing the influence of sampling timing errors. The frequency response H(f) of the raised cosine roll-off filter can be expressed by the following formula:

Among them, the corresponding time-domain waveform function is:

Among them, the symbol period T _s =1/2f _N , where f _N is the Quinnest frequency. α is the roll-off factor, which determines the shape of H(f), and α takes a value between [0, 1]. When α is large, the time-domain waveform attenuation block and the oscillation fluctuation are small, which is beneficial to reduce the impact of inter-symbol interference and timing error, but the occupied frequency band becomes wider, the frequency band utilization rate is reduced, and the effect of in-band noise on the signal Will increase accordingly. When α is small, the utilization rate of the frequency band increases, and the influence of in-band noise is weakened, but the fluctuation of the waveform increases, and the influence on the inter-symbol interference and timing error increases, which ultimately leads to an increase in the bit error rate. Preferably, the roll-off factor α can be selected as 0.5, and the order of the digital shaping filter is set to 32.

S3: The first branch code stream and the second branch code stream after being filtered by the first filter 203a are respectively transmitted to the first modulation module 202 for modulation processing.

Specifically, the first modulation module 202 includes at least a first modulator 202a, a second modulator 202b, and a third modulator 202c. The first modulator 202a is a quadrature modulator, and the second modulator 202b and the third modulator 202c are both in-phase modulators. The first branch code stream is transmitted to the first modulator 202a for orthogonal modulation processing to obtain a first modulated signal, and the second branch code stream is transmitted to a second modulator for in-phase modulation processing to obtain a second modulated signal. Both the first modulation signal and the second modulation signal are uniformly transmitted to the third modulator 202c for in-phase modulation processing to obtain a third modulation signal. The first-stage modulation process can be performed by the first modulator 202a. By the second modulation its 202b and the third modulator 202c can perform a second-stage modulation process.

S4: The third modulated signal is transmitted to the second filter 203b for filtering processing to complete the modulation processing of the encoded signal.

Specifically, the second filter 203b is a band-pass filter that allows signals within a specific frequency range to pass, and can attenuate signals outside the specific frequency range to a very low level. The coded signal is based on the modulation re-sampling process of the modulation module, which causes periodic extension of the signal spectrum and generates inter-symbol interference, which in turn leads to an increase in the error probability of the modulation module. Preferably, the order of the band-pass filter can be set to 64. The processing of the band-pass filter can make the modulation envelope smoother. The second-stage filtering process can be performed by the second filter 203b.

According to a feasible manner, referring again to FIG. 1, the first ground station 2a may send the first signal to the narrowband satellite 1, and then relay the first signal to the second ground station 2b through the narrowband satellite 1. When the second ground station 2b transmits the second signal to the narrow-band satellite, the second ground station 2b can simultaneously receive the echo of the second signal and the first signal as a combined signal. Similarly, the first ground station 2a can simultaneously receive the echo of the first signal and the second signal as a combined signal. The first ground station 2a and the second ground station 2b can use the echo cancellation method to eliminate the interference caused by the echo. By canceling the echo, the demodulation of the first signal and the second signal can be facilitated. The first signal and the second signal are subject to different environments and different degrees of interference during transmission, resulting in the combined signal received by the ground station requiring at least the transmitted signal, the echo of the transmitted signal, and the noise floor. The transmission signal that needs to be transmitted refers to the first signal or the second signal that needs to be transmitted between the first ground station and the second ground station. The noise floor refers to the sum of all noise sources and unwanted signals in the communication system, that is, any other signal except the transmitted signal.

Preferably, as shown in FIG. 4, the narrow-band satellite 1 includes at least a signal conditioning module 104. The signal conditioning module 104 includes several filters to resolve, analyze, or suppress interfering signals on the combined signal. The signal conditioning module 104 is configured to process the combined signal as follows:

S1: Fast Fourier transform processing is performed on the combined signal to determine the frequency component of the combined signal. For example, the signal conditioning module 104 may include a fast Fourier transformer, and transmitting the combined signal to the fast Fourier transformer can implement the fast Fourier transform of the combined signal. The fast Fourier transformer can add the product of the combined signal samples and the complex sinusoid of the frequency to obtain the frequency domain representation of the combined signal, where the processing process of the fast Fourier transformer can be expressed as:

x _n is the digital sample of the combined signal. N is the total number of samples being processed.

S2: The output signal processed by the fast Fourier transform is decomposed to obtain multiple decomposed signals in different time-frequency spaces. Specifically, the output signal may be transmitted into the filter bank, and the filter bank may include several different filtering levels. Each filtering level may include a low communication channel and a high communication channel, and the low communication channel and the high communication channel are each configured with a set of discrete wavelet transformers. Through different filtering levels, the output signal can be divided into subbands of different frequency bands. The signals contained in different subbands can be decomposed into multiple different time-frequency spaces by the discrete wavelet transform processing of the discrete wavelet transformer. The time-frequency content of the transmitted signal is separated from the frequency content of the interference signal.

Preferably, referring again to FIG. 4, the narrow-band satellite 1 includes at least an interference detection module 101, an interference cancellation module 102, and a demodulation module 103. The narrowband satellite 1 may have a signal receiving module such as an antenna, and thus can receive signals transmitted by the ground station 2 or other signal terminals. The interference detection module 101 is used to perform interference detection on signals in several different sub-bands output by the signal conditioning module 104, and thus can determine frequencies corresponding to all interference sources present in the combined signal. The interference cancellation module 102 is configured to perform, for example, filtering processing on the interference source detected and determined by the interference detection module, so as to achieve interference cancellation. The demodulation module 103 is used to demodulate the signal to facilitate further transmission of the signal. Preferably, the interference detection module 101 can calculate the average power of the combined signal and set a standard threshold. When the interference detection module analyzes and determines that the actual power of the combined signal is higher than the set standard threshold, it can be determined that there is interference. The set value of the standard threshold can be determined in advance through the simulation of the interference signal in advance.

Preferably, as shown in FIG. 5, the interference cancellation module 102 may include an offset logic circuit 102a, a first multiplier 102b, a window function circuit 102c, a first fast Fourier transform circuit 102d, an interference cancellation circuit 102e, an inverse fast Fourier transform circuit 102f and signal correction circuit 102g. The offset logic circuit 102a is used to align the frequency of the interference signal with the frequency center of the subcarrier of the communication channel. The offset logic circuit can determine the frequency between the interference signal and the center frequency of the fast Fourier transform filter bank frequency Δf The difference and the offset logic circuit can determine one or more of the frequency of the fast Fourier transform filter bank that is closest to the frequency of the interference signal. Preferably, the offset logic circuit can also create a first complex sinusoidal curve with respect to the received signal for performing multiplication of the analog signals with each other in the first multiplier 102b. The frequency of the first complex sinusoid can be expressed by -Δf, and the first complex sinusoid can be expressed by the following formula

(n=0, 1, ..., N-1). F _s represents the sampling frequency. N is the number of fast Fourier transform sampling points. The first multiplier 102b may receive the first complex sinusoid and the combined signal from the offset logic circuit, where the combined signal contains sampled samples of the interference signal. The first multiplier 102b multiplies the first complex sinusoid by the sampled sample to obtain the offset signal. At the same time, inter-carrier interference can also be introduced into the first multiplier 102b by multiplying the first complex sinusoid by the sampled samples.

Preferably, the window function circuit 102c is used to receive the output of the first multiplier 102b and perform windowing processing on it. The window function circuit may use, for example, a Hanning window function, a rectangular window function, or a Bartley window function to window the signal. Through the windowing process, the output of the first multiplier 102b can be limited to the main lobe. The first fast Fourier transform circuit 102d can receive the output of the window function circuit 102c and perform fast Fourier transform processing on it to generate a frequency domain signal. The interference cancellation circuit 102e can receive the demodulated fast Fourier transform signal processed by the first fast Fourier transform circuit 102d, and the interference cancellation circuit 102e can use the offset logic circuit 102a in the fast Fourier transform signal during the calculation of Δf The determined subcarrier frequency is removed to obtain an interference cancellation signal. Specifically, for the subcarrier frequency involved in the Δf calculation process, the interference cancellation circuit 102e can set the frequency of the fast Fourier transform filter bank corresponding to the subcarrier frequency to zero. Since the frequency of the interference signal has been processed by the offset logic circuit 102a to be aligned with the frequency center of the subcarrier, and the frequency of the current subcarrier is set to zero by the interference cancellation circuit 102e, the interference signal is eliminated. Preferably, the interference cancellation signal can be transmitted to the inverse fast Fourier transform circuit 102f and is subjected to inverse fast Fourier transform processing to generate time-domain sampling samples. Preferably, the correction circuit 102g is configured to generate a ramp signal with a frequency equal to Δf, the ramp signal may pass through the second complex sinusoid

(n=0, 1, ..., N-1). Therefore, the correction circuit 102g can eliminate inter-carrier interference. Specifically, the second complex sine curve generated by the correction circuit 102g and the output signal generated by the inverse fast Fourier transform circuit 102f are simultaneously transmitted to the second multiplier 102h for multiplication processing to eliminate inter-carrier interference. Preferably, the output signal of the second multiplier 102h can be transmitted to the second fast Fourier transform circuit 102i to perform fast Fourier transform processing again to demodulate the signal. The output signal of the second fast Fourier transform circuit 102i is finally transmitted to the demodulation module 103 for decoding processing. Preferably, the first fast Fourier transform circuit 102d and the second fast Fourier transform circuit 102i jointly define a fast Fourier transform filter bank.

Preferably, during the iterative process, when each narrow-band interference signal is aligned with the frequency center of the sub-carrier of the communication channel, it will cause inter-carrier interference. The signal will no longer carry the narrow-band interference after the sub-carrier frequency aligned with the narrow-band interference is removed, and then the inter-carrier interference is removed from the signal. Therefore, before decoding, the signal removes all narrow-band interference and any potential side lobes, thereby eliminating spectral leakage.

According to a feasible manner, preferably, as shown in FIG. 8, the encoding module 201 is further configured to encode the signal as follows:

S1: The BCH code generated by the signal after the BCH encoding process and the transmitted information frame form a set bit information subframe, where the bit length of the information subframe does not meet the set bit length, according to the supplementary 0 code Way to fill it.

Specifically, the b-bit BCH code output can be obtained by encoding the a-bit signal through BCH(b, a), and the b-bit BCH code and the transmitted information frame form a c-bit information subframe. For example, b can be set to 31 and c can be set to 223.

Preferably, the generator polynomial of the BCH code can be expressed by the formula g(x)=x ¹⁰ +x ⁹ +x ⁸ +x ⁶ +x ⁵ +x ³ +1.

S2: The information subframe is synchronously scrambled. In digital communication, when a continuous long 0 code or a continuous 1 code is sent, it will be interfered by the electromagnetic field existing in the spatial transmission channel, thereby generating bit errors. The scrambling code is an n-pseudo-random sequence. Adding the linear feedback of the n-sequence to the data can balance the number of occurrences of the 0 code and the 1 code. It can convert the data into approximately white noise and reduce the spatial signal fading and bit error rate. . Specifically, the scrambling code period of the synchronous scrambling process can be set to 2 ¹⁵ -1, the polynomial is 1+X ¹⁴ +X ¹⁵ , the n sequence of the starting register value is 1001_0101_0000_000, and all the data after the frame is scrambled .

S3: The subframes subjected to the scrambling process are sequentially subjected to RS encoding and convolutional encoding. For example, the specific parameters of RS coding can be configured as follows: code length n=255, supervisory terminal k=223, and generator polynomial g(x)=x ⁸ +x ⁴ +x ³ +x ² +1. Convolutional coding has 1 input port and 2 output ports. The generator polynomials corresponding to the two output ports are g1(x)=x ⁶ +x ⁵ +x ⁴ +x ³ +1 and g2(x)=x ⁶ +x ⁴ +x ³ +x ¹ +1.

Preferably, FIG. 6 shows the coding block diagram of the RS code. The input information polynomial h(x) is divided by g(x) to obtain the remainder r(x), and r(x) is spliced to the tail of h(x) to obtain the output. Codeword. Specifically, h(x) is directly output through the gate A, and h(x) enters the RS verification circuit. At this time, the output of the verification circuit is disconnected. When all 223 elements enter the verification circuit, several registers are stored The data is the RS check digit. At this time, the output of the check circuit is open, and the check bit is output to complete r(x) splicing to the tail of h(x), thereby forming 255-bit RS coded data.

Preferably, FIG. 7 shows a coding block diagram of a convolutional code. The code rate is 3/4 bits/symbol, the constraint length is 7 bits, the connection vector G1=1111001, and G2=1011011. The output is determined by the puncturing scheme, where C1: 101, C2: 110, 1 represents the transmitted symbol, and 0 represents the symbol that is not transmitted. The shift register is used to store bit information. The output code stream sequence enters the shift register and divides the code stream sequence into two branches, and performs two XOR operations respectively. The operation polynomial of the first branch is g1(x), and the operation polynomial of the second branch is g2(x). The first branch and the second branch can send the operation results to the puncturing unit, where the operation results of the two branches enter the puncturing unit alternately, and the puncturing unit divides the continuous 6-bit data shift into a group, The order of entry for each group is C ₁ (1)C ₂ (1)C ₁ (2)C ₂ (2)C ₁ (3)C ₂ (3)... Finally, the puncturing unit performs convolution coding 3/4 puncturing and outputting on a set of data according to the puncturing scheme, and the output sequence is C ₁ (1)C ₂ (1)C ₂ (2)C ₁ (3)...

S4: The data generated after the convolutional coding, together with the carrier synchronization bit, pilot sequence, unique code, and frame end, form a complete modulated data frame. For example, the data generated after convolutional encoding can be combined with a 320-bit carrier synchronization bit, a 160-bit pilot sequence, a 64-bit unique code, and a 64-bit frame tail to form a complete modulated data frame. By organically combining the coding methods, the resulting combined coding method has low bit error rate, high confidentiality, and high spectrum utilization.

According to a feasible way, the present invention may also be a satellite communication system based on suppressing narrow-band interference.

Preferably, when the narrow-band satellite 1 and the ground station 2 communicate with each other, the narrow-band satellite 1 may also receive a combined signal composed of multiple component signals. The combined signal may include a demand signal and an interference signal. The demand signal refers to a signal that needs to be relayed and transmitted through the narrow-band satellite 1. The narrowband satellite 1 further includes an analog-to-digital conversion module 105, a windowing module 106, a separation module 107, a regeneration module 108, a delay module 109, a cancellation module 110, and an inversion module 111. Multi-channel transmission is established between the narrow-band satellite 1 and the ground station 2. The signals transmitted by the multi-channel can have frequency overlap with each other, which can improve the utilization rate of spectrum resources.

Preferably, the narrow-band satellite 1 is configured to perform separation processing on the combined signal with frequency overlap as follows:

S1: Perform windowing processing based on the windowing module 106 to obtain a window processing signal, and perform nth power processing on the window processing signal based on the interference detection module 101 to determine the modulation characteristic of the component signal and the symbol rate of the carrier corresponding to the component signal.

Specifically, the analog-to-digital conversion module 105 is used to perform analog-to-digital conversion on the combined signal received by the narrowband satellite to convert the analog signal into a digital signal. The combined signal received by the narrowband satellite 1 is first transmitted to the analog-to-digital conversion module 105 for analog-to-digital conversion processing to generate a digital signal. The windowing module 106 can receive the digital signal generated by the analog-to-digital conversion module 105. The windowing module 106 can limit the bandwidth of the digital signal or pay attention to a part of the digital signal to ensure that it can effectively process the spectrum part of the demand signal, and then can Generate window processing signals. The interference detection module 101 can receive the window processing signal and identify and determine its signal components. For example, the interference detection module 101 may be configured to perform n-th power processing on the window processing signal until it is converted into a continuous wave. When the window processing signal contains a variety of different signals, for example, it may contain two demand signals and three interference signals. Different signals have different modulation characteristics, and thus can form multiple different n-th power processing, that is, the window The processed signal may obtain a continuous wave when performing the fourth power processing, and another continuous wave when performing the eighth power. The window processing signal with 5 kinds of signals can generate 5 continuous waves independent of each other in 5 different nth powers. The n-th power processing is executed in multiples of 2, that is, the power-of-two processing, power-of-four processing, power-of- six processing, etc. can be executed. Preferably, when the n-th power processing is performed, it is performed in a manner that each stage is incremented by 2 stages. For example, when continuous waves are not generated when the second power processing is performed, the fourth power processing, the sixth power processing, the eighth power processing, and the like are sequentially executed. Preferably, the modulation characteristic of the component signal can be determined at least by one or more of phase offset, frequency offset, bandwidth and time delay of the component signal. The waveform of the continuous wave formed after the nth power processing can determine the phase offset, frequency offset, bandwidth and time delay.

Preferably, the symbol rate of the window processing signal may be determined based on the nth power processing process of the window processing signal. For example, when the signal is performing n-th power processing, the phases of the symbols will be correlated or the correlation between them will be eliminated, and then a continuous wave represented by a single frequency in the frequency domain can be formed. This process can produce a distribution. For the small side lobes around the frequency of the continuous wave, the interval between the small side lobes is related to the symbol rate of the carrier of the corresponding component signal, and the symbol rate of the carrier can be determined based on the interval between the small side lobes.

S2: When the window processing signal generates at least one continuous wave based on n-th power processing, the separation module 107 resamples the window processing signal in a manner based on m times of the symbol rate to generate a resampled signal, and determines at least One symbol track and at least one modulation type.

Preferably, when the interference detection module 101 determines that there are multiple constituent signals in the combined signal, the window processing signal may be transmitted to the separation module 107, and the separation module may process the signal in a manner of m times the symbol rate based on the determined modulation characteristics Resample. That is, the separation module 107 samples its received signal at a higher rate, and can then derive the symbol trajectory, shaping factor, and modulation type. The shaping factor can be used to evaluate the degree of concentration or dispersion of signal energy. For example, the shaping factor may be the root-raised cosine spectrum of the window processed signal. Preferably, signals with different components can generate multiple continuous waves in different n-th power processing. For example, when using binary phase keying to modulate a signal, a continuous wave can be generated when the power is processed twice. When using quadrature phase shift keying to modulate the signal, continuous waves can be generated during the fourth power processing. Therefore, the modulation type of the signal can be determined according to the number of times of self-multiplication processed by the nth power. The value of m may be an integer greater than 2.

Preferably, the regeneration module 108 synthesizes each component signal based on at least one symbol trajectory and at least one modulation type to generate a composite signal. In the case where it is determined that the composite signal is an interference signal, the inversion module 111 performs inversion processing on the composite signal To generate an inverted copy, the delay module 109 delays the transmission of the copy of the digital signal to the cancellation module 110, and the cancellation module 110 superimposes the inverted copy with the copy of the digital signal to eliminate the interference signal, thereby obtaining the first-level interference Suppress the signal.

Preferably, as shown in FIG. 9, the first-level interference suppression signal can be transmitted to the signal preprocessing module 101 for processing to separate the time-frequency content of the transmitted signal from the frequency content of the interference signal. The first-level interference suppression signal processed by the signal preprocessing module 101 can be transmitted to the interference cancellation module 102 to further eliminate the interference signal.

Although the present invention has been described in detail, modifications within the spirit and scope of the present invention will be apparent to those skilled in the art. Such modifications are also considered to be part of this disclosure. In view of the foregoing discussion, relevant knowledge in the art, and the references or information discussed above in conjunction with the background (both are incorporated herein by reference), further description is considered unnecessary. In addition, it should be understood that various aspects of the present invention and various parts of various embodiments may be combined or interchanged in whole or in part. Moreover, those of ordinary skill in the art will understand that the foregoing description is merely an example, and is not intended to limit the present invention.

Claims (15)

1. A narrow-band multi-channel satellite communication system, signals can be transmitted to at least one narrow-band satellite (1) via a ground station (2), and several ground stations (2) can communicate with each other based on the narrow-band satellite (1) relay Communication connection, characterized in that the narrow-band satellite (1) is configured as:

   Establish a first complex sinusoidal curve and a second complex sinusoidal curve respectively, and determine the frequency component of the signal to separate the frequency content of the interference signal;

   Acquiring the first processed signal based on the first complex multiplication process of the first complex sinusoid and the signal and introducing inter-carrier interference;

   Eliminate the interference signal in a manner that the subcarrier frequency is set to zero to obtain the second processed signal;

   In the case where the second processed signal is subjected to inverse fast Fourier transform processing, the second-stage multiplication process based on the second complex sinusoid and the second processed signal eliminates the inter-carrier interference.
2. The narrow-band multi-channel satellite communication system according to claim 1, wherein the narrow-band satellite (1) is further configured to:

   Align the frequency of the interference signal with the center of the subcarrier frequency of the communication channel;

   Acquiring the frequency Δf of the fast Fourier transform filter bank closest to the frequency of the interference signal;

   The interference signal is eliminated in such a manner that the frequency Δf of the fast Fourier transform filter bank corresponding to the subcarrier frequency is set to zero.
3. The narrow-band multi-channel satellite communication system according to claim 1 or 2, characterized in that the ground station (2) includes at least an encoding module (201) and a first modulation module (202), and the ground station (2) Is configured to modulate the signal as follows:

   The encoding module (201) is configured to perform encoding processing on the signal to obtain an encoded signal;

   The first modulation module (202) is configured to perform serial-to-parallel conversion processing on the encoded signal to generate a first branch code stream and a second branch code stream, where:

   In the case where the first branch code stream performs delay processing so that the first branch code stream and the second branch code stream are spaced from each other by a set symbol period, the first branch The code stream performs a first-stage filtering process and a first-stage modulation process in sequence to obtain a first modulation signal, and the second branch code stream sequentially performs the first-stage filtering process and a second-stage modulation process to obtain a second modulation signal;

   The first modulation signal and the second modulation signal are jointly subjected to the second-stage modulation processing to obtain a third modulation signal, wherein the third modulation signal is subjected to the second-stage filter processing to complete the modulation deal with.
4. The narrowband multi-channel satellite communication system according to claim 3, wherein the encoding module (201) is configured to perform encoding processing on the signal as follows:

   The BCH code generated by the BCH encoding process of the signal and the transmitted information frame together constitute several information subframes with set bits, and the information subframes are subjected to synchronous scrambling processing to sequentially perform RS encoding processing and convolutional encoding processing. The product coded data together with the carrier synchronization bits, pilot sequence, unique code, and frame tail form a complete modulated data frame, in which:

   In the case where the bit length of the information subframe is less than the set bit length, it is complemented in a manner of supplementing zero codes.
5. The narrow-band multi-channel satellite communication system according to any one of the preceding claims, wherein the ground station (2) further includes a filter module (203), a second modulation module (204), and a frequency conversion module (205), so The ground station (2) also processes the signal as follows:

   The coded signal is transmitted to the first modulation module (202) at a set code rate, and after performing the modulation process, it is transmitted to the filter module (203) at the first carrier frequency;

   The filtering module (203) is configured to perform filtering processing on the received signal and transmit it to the second modulation module (204);

   The second modulation module (204) transmits the signal it receives to the frequency conversion module (205) at a second carrier frequency, wherein the frequency conversion module (205) is configured to frequency convert the signal it receives to a set RF output frequency.
6. The narrow-band multi-channel satellite communication system according to any one of the preceding claims, characterized in that the narrow-band satellite (1) at least includes a signal conditioning module (104) and an interference cancellation module (102). In the case where the ground station (2) transmits to the narrow-band satellite (1), the narrow-band satellite (1) is configured to perform processing on the signal as follows:

   Configuring the signal conditioning module (104) to: determine the frequency component of the signal and obtain several decomposed signals in different time-frequency spaces to separate the frequency content of the interference signal;

   The interference cancellation module (102) is configured as:

   Align the frequency of the interference signal with the center of the subcarrier frequency of the communication channel and establish a first complex sinusoid, and obtain an offset signal based on the multiplication process of the first complex sinusoid and the signal to introduce the inter-carrier interference;

   Performing windowing processing and fast Fourier transform processing on the offset signal in sequence to generate a frequency domain signal, where the frequency domain signal can cancel the interference signal in a manner that the subcarrier frequency is zeroed to obtain an interference cancellation signal;

   In the case where the interference cancellation signal is processed by inverse fast Fourier transform to generate time-domain sampled samples, a second complex sine curve is established and eliminated in such a manner that the second complex sine curve and the time-domain sampled samples perform multiplication processing The inter-carrier interference.
7. The narrow-band multi-channel satellite communication system according to claim 6, wherein the signal conditioning module (104) acquires the decomposed signal as follows:

   A filter bank with several different filter levels is configured, and each filter level includes at least a low communication channel and a high communication channel, and the low communication channel and the high communication channel are each configured with at least one set of discrete wavelet transformers, where:

   Acquiring several sub-bands of different frequency bands based on several filtering levels of the filter bank;

   The signals contained in the sub-bands can be decomposed into several different time-frequency spaces by discrete wavelet transform processing, respectively.
8. The narrow-band multi-channel satellite communication system according to any one of the preceding claims, wherein the first complex sinusoid is calculated by the formula

   

   Limited, the second complex sine curve is given by the formula

   

   limited;

   The generator polynomial of the BCH code is g(x) = x ¹⁰ + x ⁹ + x ⁸ + x ⁶ + x ⁵ + x ³ +1;

   The generator polynomial of RS coding is g(x)=x ⁸ +x ⁴ +x ³ +x ² +1;

   The generator polynomials of the two output ports of convolutional coding are g1(x)=x ⁶ +x ⁵ +x ⁴ +x ³ +1 and g2(x)=x ⁶ +x ⁴ +x ³ +x ¹ +1 ;

   The scrambling code period and polynomial of the synchronous scrambling process are 2 ¹⁵ -1 and 1+X ¹⁴ +X ^{15 respectively} ;

   Among them, F _s represents the sampling frequency, N is the number of sampling points of the fast Fourier transform.
9. The narrow-band multi-channel satellite communication system according to any one of the preceding claims, wherein the first-stage filtering process is performed by a first filter (203a), and the second-stage filtering process is performed by a second filter (203a) 203b) Implementation, where:

   The first filter (203a) is a raised cosine roll-off filter, and the second filter (203b) is a band-pass filter; the first-stage modulation processing is quadrature modulation processing, and the second-stage modulation processing The modulation processing is in-phase modulation processing.
10. The narrow-band multi-channel satellite communication system according to one of the preceding claims, characterized in that the narrow-band satellite (1) further includes an interference detection module (101) and a demodulation module (103), and the interference detection module (101 ) Is configured to calculate the average power of the signal to determine whether there is an interference signal in the subband, and the demodulation module (103) is configured to demodulate the output signal of the interference cancellation module (102).
11. The narrow-band multi-channel satellite communication system according to claim 10, wherein the interference cancellation module (102) is further configured to obtain the frequency Δf of the fast Fourier transform filter bank closest to the frequency of the interference signal, wherein :

    The frequency of the first complex sinusoid is Δf, and the frequency of the second complex sinusoid is -Δf.
12. The narrowband multi-channel satellite communication system according to claim 11, characterized in that, for the subcarrier frequency involved in the calculation of the frequency Δf of the fast Fourier transform filter bank, the interference cancellation module (102) can The frequency of the fast Fourier transform filter bank corresponding to the carrier frequency is set to zero to eliminate the interference signal.
13. A satellite communication system based on suppressing narrow-band interference. The narrow-band satellite (1) and the ground station (2) communicate with each other in a multi-channel manner to relay transmission of a combined signal having several constituent signals.

    The narrow-band satellite (1) is configured as:

    Establish a first complex sinusoidal curve and a second complex sinusoidal curve respectively, and determine the frequency component of the signal to separate the frequency content of the interference signal;

    Acquiring the first processed signal based on the first complex multiplication process of the first complex sinusoid and the signal and introducing inter-carrier interference;

    Eliminate the interference signal in a manner that the subcarrier frequency is set to zero to obtain the second processed signal;

    In the case where the second processed signal is processed by inverse fast Fourier transform, the second-stage multiplication processing based on the second complex sinusoid and the second processed signal eliminates the inter-carrier interference;

    among them,

    The narrow-band satellite (1) includes at least an interference detection module (101), a windowing module (106), a separation module (107), and a regeneration module (108). In the case where the component signals have frequency overlap with each other, The narrowband satellite (1) is configured to process the combined signal as follows:

    The windowing module (106) is configured to generate a window processing signal after limiting the frequency of the combined signal based on windowing processing;

    The interference detection module (101) is configured to determine the modulation characteristic of at least one component signal and the symbol rate of its corresponding carrier based on the nth power processing of the window processed signal;

    The separation module (107) is configured to resample the window processing signal based on m times the symbol rate when the window processing signal generates at least one continuous wave based on the nth power processing Generating a resampled signal, and using this to determine at least one symbol trajectory and at least one modulation type;

    The regeneration module (108) is configured to synthesize and regenerate the component signals based on the symbol trajectory and the modulation type to generate a composite signal.
14. The narrow-band multi-channel satellite communication system according to claim 13, characterized in that the narrow-band satellite (1) further includes a cancellation module (110) and an inversion module (111), which determines that the synthesized signal is an interference signal In this case, the narrowband satellite (1) is configured to process the synthesized signal as follows:

    The inversion module (111) is configured to invert the synthesized signal to generate an inverted copy;

    The cancellation module (110) is configured to receive a copy of the combined signal and superimpose the inverted copy and the combined signal to generate a first-stage interference suppression signal.
15. The satellite communication system according to claim 13 or 14, wherein the narrowband satellite (1) further includes a signal preprocessing module (104) and an interference cancellation module (102), the narrowband satellite (1) is configured In order to process the first-level interference suppression signal as follows:

    The signal pre-processing module (104) is configured to establish a first complex sinusoidal curve and a second complex sinusoidal curve, and determine the frequency components of the first-stage interference suppression signal to separate the frequency content of the interference signal;

    The interference cancellation module (102) is configured as:

    Introducing inter-carrier interference in a manner of performing multiplication processing of the first interference suppression signal and the first complex sinusoid to generate an offset signal;

    Obtain the interference cancellation signal according to the way of subcarrier frequency zero setting and obtain its time domain sampling samples;

    The inter-carrier interference is eliminated in a manner that the time-domain sampling samples and the second complex sinusoidal curve perform multiplication processing.

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