CN111868545B - Satellite communication navigation signal generation method and device and satellite communication navigation signal receiving method and device - Google Patents
Satellite communication navigation signal generation method and device and satellite communication navigation signal receiving method and device Download PDFInfo
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- CN111868545B CN111868545B CN201980007696.1A CN201980007696A CN111868545B CN 111868545 B CN111868545 B CN 111868545B CN 201980007696 A CN201980007696 A CN 201980007696A CN 111868545 B CN111868545 B CN 111868545B
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- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
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Abstract
A satellite communication navigation signal generation method based on spread spectrum code time shift position modulation comprises the following steps: generating pilot signalsA signal component spreading code and a data signal component spreading code (110); modulating and generating a pilot component spread spectrum modulation signal S according to the pilot signal component spread spectrum codepilot(t) (120); according to the data signal component spread spectrum code, adopting the mode of modulating the spread spectrum code until time shifting to modulate binary text or data information to generate data component spread spectrum modulation signal Sdata(t) (130); using a centre frequency of fcCarrier waves with different phases, spread spectrum modulating signal S with pilot frequency componentpilot(t) and data component spread spectrum modulated signal Sdata(t) modulating to radio frequency to obtain two radio frequency component signals, and superposing the two radio frequency component signals to obtain a radio frequency modulation signal SRF(t) (140). The invention also relates to a satellite communication navigation signal receiving method, a generating device and a receiving device.
Description
Technical Field
The invention relates to the technical field of satellite navigation parts, in particular to a satellite communication navigation signal generating method and device and a satellite communication navigation signal receiving method and device.
Background
The international research process of the satellite navigation signal spread spectrum modulation mode can be roughly divided into three stages: the first stage is BPSK (before 2000), from the beginning of GPS establishment in the 70 th 20 th century to about 2000 years, the navigation signals all adopt BPSK-R direct sequence spread spectrum modulation technology; the second stage is BOC period (2000-2004), Betz provides the BOC modulation concept, and pulls open the sequence curtain of the new generation satellite navigation signal design, compared with BPSK-R, the pseudo-range measurement precision is improved from the signal body system, and the multi-path suppression and anti-interference capability are better; the third stage is the MBOC period (to date in 2005), Betz and his team proposed the concept of BCS modulation in 2005, and derived spreading modulation techniques such as Crazy BPSK, Composite BCS (CBCS), Alternate BCS (ABCS), Composite BOC (CBOC), time division multiplexing BOC (tmboc), quadrature multiplexing BOC (qmboc), etc., which further improve the flexibility of satellite navigation spreading modulation.
At present, on the basis of the third-stage evolution, in order to take into account the capture, the tracking precision and the transmission of text data, in the satellite navigation systems such as GPS, galileo, big dipper, the transmission mode of separating the pilot channel from the text data channel is generally adopted, wherein the pilot channel does not transmit data information, and is only used for transmitting ranging positioning signals, and the data channel is then used for transmitting data information such as text, short messages, and the like, so that the integration time of the ranging signals can be far longer than the duration of spread spectrum modulation code elements, and the capture, tracking and ranging precision of the receiver is improved.
In the prior art, increasing the power ratio of the pilot signal to the text data signal can further improve the performance of the receiver, but means reducing the transmission rate or reliability of the text data.
The method is characterized in that a new system satellite communication navigation signal design is explored, limited satellite transmitting power is fully utilized, the power ratio of a pilot signal to a data signal is further increased on the premise that the transmission rate and reliability of a text data signal are not reduced, and technical performance indexes such as the acquisition tracking performance and the positioning accuracy of a receiver are further improved.
Disclosure of Invention
The invention aims to solve the technical problem of the prior art and provides a satellite communication navigation signal generation method and device and a satellite communication navigation signal receiving method and device.
The technical scheme for solving the technical problems is as follows: a satellite communication navigation signal generation method, comprising:
generating a pilot signal component spreading code and a data signal component spreading code;
modulating and generating a pilot component spread spectrum modulation signal S according to the pilot signal component spread spectrum codepilot(t)；
According to the data signal component spread spectrum code, adopting spread spectrum code time-shifting position modulation mode to modulate binary telegraph text or data information to generate data component spread spectrum modulation signal Sdata(t), the spreading code time shift position modulation means: according to the difference of the pre-modulated binary text or data information, the data component spread spectrum code sequence is in the position code element time interval TsThe minimum time interval of the shift is 1 spreading code chip period Tc，TsSpreading code period T with pilot signal componentpilotThe corresponding relation is as follows: t iss＝k×Tpilot，k>0；
Using a centre frequency of fcDifferent phase carrier, spread spectrum modulating signal S with pilot frequency componentpilot(t) and data component spread spectrum modulated signal Sdata(t) modulating to radio frequency to obtain two radio frequency component signals, and superposing the two radio frequency component signals to obtain a radio frequency modulation signal SRF(t)。
On the basis of the above technical solution, the spreading code time shift position modulation may be further embodied.
Firstly, the method comprises the following steps:
for spreading code sequences of length N in the data signal component, Ts＝N×TcThe method for modulating the time shift position of the spread spectrum code adopted by the data signal component comprises the following steps: cyclic code shift keying modulation method.
Further, for a spreading code sequence with length N in the data signal component, cyclic shift may generate N different spreading code time shift sequence sets, and the spreading code time shift position modulation method adopted by the data signal component is: selecting K spread spectrum code time shift sequence sets to modulate log in N spread spectrum code time shift sequence sets2K bits of text or data information, K is less than or equal to N.
Secondly, the method comprises the following steps:
the method for modulating the time shift position of the spread spectrum code adopted by the data signal component comprises the following steps: spread spectrum code time shift position modulation;
the spreading code time shift position modulation means: for length of NxTcThe code sequence of (1), the position symbol time interval Ts > (N +1) × TcSpreading code sequences in time intervals T, depending on the text or data information of the premodulated binarysInternal direct shift, containing a total of M ═ Ts/TcN +1 different positions, modulation log2M bits of text or data information.
The first and second modulation methods are only two specific examples of the spreading code time shift position modulation method, and the method of the present invention is not limited thereto, and the spreading code time shift position modulation according to the present invention can be extended to other modifications and variations, and such modifications and variations are within the spirit and scope of the present invention.
Another technical solution of the present invention for solving the above technical problems is as follows: a satellite communication navigation signal receiving method, comprising:
generating a spreading code local reproduction code of the pilot signal component and the data signal component;
receiving a radio frequency modulated signal S via an antennaRF(t) using a center frequency of fcTwo carriers with 90-degree phase difference, and modulating the radio frequency modulation signal SRF(t) down-converting to a baseband to obtain a received baseband signal;
capturing and tracking the received baseband signal by using a spreading code local reproduction code of a pilot signal component, extracting clock information of the pilot signal according to a capturing and tracking result, and obtaining the clock information of the pilot signal according to a relation Ts＝k×TpilotDetermining a time shift modulation interval for each symbol data signal component;
performing correlation operation on the receiving baseband signal by using a spreading code local recurrence code of a data signal component to obtain a correlated signal sequence to be detected;
and comparing the sequence value of the signal to be detected, taking the moment corresponding to the maximum value as the position detection moment, and judging the position detection moment to obtain binary telegraph text or data information according to the mapping relation between the binary data and the displacement of the spread spectrum code sequence in the modulation process.
Another technical solution of the present invention for solving the above technical problems is as follows: a satellite communication navigation signal generating apparatus, comprising:
a spread spectrum code generating module for generating a pilot signal component spread spectrum code and a data signal component spread spectrum code;
a pilot signal component modulation module for generating a pilot component spread spectrum modulation signal S according to the pilot signal component spread spectrum codepilot(t)；
A spread spectrum code time shift position modulation module for modulating binary text or data information by adopting a spread spectrum code time shift position modulation mode according to a data signal component spread spectrum code to generate a data component spread spectrum modulation signal Sdata(t), the spreading code time shift position modulation means: according to the difference of the pre-modulated binary text or data information, the data component spread spectrum code sequence is in the position code element time interval TsThe minimum time interval of the shift is 1 spreading code chip period Tc，TsSpreading code period T with pilot signal componentpilotThe corresponding relation is as follows: t iss＝k×Tpilot，k>0；
An up-conversion module for generating a center frequency of fcDifferent phase carrier wave, and spread spectrum modulating signal S with pilot frequency componentpilot(t) and data component spread spectrum modulated signal Sdata(t) modulating to radio frequency to obtain two radio frequency component signals, and superposing the two radio frequency component signals to obtain a radio frequency modulation signal SRF(t)。
On the basis of the above technical solution, the spreading code time shift position modulation module may be further embodied.
Firstly, the method comprises the following steps:
the spread spectrum code time shift position modulation module is a spread spectrum code cyclic shift keying modulation module, and for a spread spectrum code sequence with the length of N in a data signal component, Ts＝N×TcThe spread spectrum code cyclic shift keying modulation module adopts circulationThe code shift keying modulation method modulates binary text or data information.
Further, for a spreading code sequence with a length of N in the data signal component, cyclic shift may generate N different spreading code time-shifted sequence sets, and the spreading code cyclic shift keying modulation module is specifically configured to select K spreading code time-shifted sequence sets from the N spreading code time-shifted sequence sets to modulate log2K bits of text or data information, K is less than or equal to N.
Secondly, the method comprises the following steps:
the spread spectrum code time shift position modulation module is a spread spectrum code time shift position modulation module and has a length of NxTcSpreading code sequence of (2), position symbol time interval Ts＞(N+1)×TcAccording to the difference of the pre-modulation binary text or data information, the spread spectrum code sequence is directly shifted in the time interval Ts, and the spread spectrum code sequence totally contains M ═ Ts/TcN +1 different positions, modulation log2M bits of text or data information.
The first and second modulation modules are only two specific examples of the spreading code time shift position modulation module, and do not limit the technical solution, and the spreading code time shift position modulation module according to the present invention may be extended to other modifications and variations, and such modifications and variations are within the spirit and scope of the present invention.
Another technical solution of the present invention for solving the above technical problems is as follows: a satellite communication navigation signal receiving apparatus, comprising:
a spread spectrum code local reproduction code generation module for generating a spread spectrum code local reproduction code of the pilot signal component and the data signal component;
a down-conversion module for generating a local carrier signal and modulating the received RF signal S via an antennaRF(t) down-converting to baseband to obtain a received baseband signal, the local carrier signal comprising a center frequency fcTwo carriers with 90-degree phase difference;
a pilot signal acquisition tracking module for acquiring and tracking the received baseband signal by using a spreading code local reproduction code of a pilot signal componentTracking, extracting the clock information of the pilot signal according to the result of the acquisition tracking, and obtaining the clock information of the pilot signal according to the relation Ts＝k×TpilotDetermining a time shift modulation interval for each symbol data signal component;
and the spread spectrum code time-shifting position demodulation module is used for carrying out correlation operation on the received baseband signal by using a local reproduction code of a spread spectrum code of a data signal component to obtain a correlated signal sequence to be detected, comparing the sequence value of the signal to be detected in a time-shifting modulation interval, taking the moment corresponding to the maximum value as a position detection moment, and judging the position detection moment to obtain binary text or data information according to the mapping relation of the displacement of binary data and a spread spectrum code sequence in the modulation process.
Additional aspects of the invention and its advantages will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments of the present invention or in the description of the prior art will be briefly described below, and it is obvious that the drawings described below are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a method for generating a satellite communication navigation signal according to an embodiment of the present invention;
FIG. 2 is a signal flow diagram of a method for generating a satellite communication navigation signal according to an embodiment of the present invention;
FIG. 3 provides a schematic flow chart of a method of receiving a signal generated by the generation method shown in FIG. 1 in accordance with an embodiment of the present invention;
FIG. 4 is a signal flow diagram of a method for receiving a signal generated by the generation method shown in FIG. 1 according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of a signal generated by the generation method shown in FIG. 1 and subjected to correlation processing according to an embodiment of the present invention
Fig. 6 is a schematic structural diagram of a satellite communication navigation signal generating device according to an embodiment of the present invention;
FIG. 7 is a schematic block diagram of an apparatus for receiving signals generated by the generating apparatus shown in FIG. 6 according to an embodiment of the present invention;
FIG. 8 is a graph showing a graph at E in the prior artb/N0Obtaining error rate curve diagrams of traditional BPSK modulation and MPPM modulation of the invention under the standard;
fig. 9 is a graph of a bit error rate curve under the received signal-to-noise ratio SNR standard obtained by the signal receiving method according to the embodiment of the present invention;
fig. 10 is a schematic diagram of a modulation waveform of a spreading code time shift position in a signal generating method according to an embodiment of the present invention;
fig. 11 is a bit error rate curve diagram under the received signal-to-noise ratio SNR standard obtained by the signal receiving method according to the embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, not all, embodiments of the present invention. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, shall fall within the scope of protection of the present invention.
Pulse position modulation is a way to load information using different positions where pulses occur, and has wide application in the field of laser communication. From the viewpoint of power efficiency, the pulse position modulation signal has a lower average signal power, and the power efficiency of pulse position modulation is higher than that of a modulation method such as BPSK. The code element grouping time shifting position spread spectrum modulation method utilizes the relative position of the spread spectrum code element to load information, solves the problems of large duty ratio and low transmission spectrum efficiency of the traditional multi-system position modulation, and is an efficient modulation method in the spread spectrum field.
The satellite communication navigation system requires precise synchronization, and the time positioning precision of the receiver to the pilot channel signal reaches more than 1% of the time duration of a chip. The accurate clock synchronization provides a natural 'scale' for position modulation, and the position modulation and demodulation of spread spectrum codes can be realized by utilizing the accurate time scale, so that the power distribution ratio of pilot frequency communication and a data channel can be further increased, and a solution is provided for improving the precision of a satellite navigation system and expanding the user capacity.
The inventor of the invention finds that the comprehensive performance index of a satellite navigation system can be greatly improved by applying the technical approach to satellite navigation signal design. Specifically, a method and an apparatus for generating a satellite communication navigation signal, a method and an apparatus for receiving a satellite communication navigation signal according to an embodiment of the present invention are described in detail below with reference to fig. 1 to 11.
Example 1
A satellite communication navigation signal generation method 100 as shown in fig. 1, comprising:
110. a pilot signal component spreading code and a data signal component spreading code are generated.
120. Modulating and generating a pilot component spread spectrum modulation signal S according to the pilot signal component spread spectrum codepilot(t)。
130. According to the data signal component spread spectrum code, adopting spread spectrum code time-shifting position modulation mode to modulate binary telegraph text or data information to generate data component spread spectrum modulation signal Sdata(t)。
Wherein, the modulation of the time shift position of the spread spectrum code means: according to the difference of the pre-modulated binary text or data information, the data component spread spectrum code sequence is in the position code element time interval TsThe minimum time interval of the shift is 1 spreading code chip period Tc，TsSpreading code period T with pilot signal componentpilotThe corresponding relation is as follows: t iss＝k×Tpilot，k>0。
140. Using a centre frequency of fcCarrier waves with different phases, spread spectrum modulating signal S with pilot frequency componentpilot(t) and data component spread spectrum modulated signal Sdata(t) modulating to radio frequency to obtain two radio frequency component signals, and combining the two radio frequency component signalsSuperposing the RF signal components to obtain RF modulated signal SRF(t)。
In particular, in this embodiment, reference may also be made to the signal flow diagram shown in fig. 2. In fig. 2, the time shift interval of the spread spectrum modulation is the time interval of the position modulation, and the minimum time shift gap of the time shift position modulation is a single chip duration. Multiplying the modulated time shift position by a data channel spread spectrum code to obtain a spread spectrum code time shift position modulation signal; then, the pilot frequency channel spread spectrum modulation signal and the carrier wave complete up-conversion modulation to obtain a modulation signal SRF(t)。
It should be noted that: pilot signal S in fig. 2pilot(t) from cos (f)ct) modulation of the carrier is merely an example, and in practice, the pilot signal Spilot(t) may further be comprised of two or more spreading code modulated signal components, and two or more signal components may be comprised of cos (f)ct) and cos (f)ct + θ) two carriers.
The navigation signal generated in the embodiment of the present invention includes: the pilot signal component and the data signal component, the data signal component adopts the way of spread spectrum code time shift position modulation to modulate binary telegraph text or data information, replaces the traditional BPSK or QPSK modulation way, and greatly improves the power efficiency of the data signal component.
Optionally, in step 130, for a spreading code sequence of length N in the data signal component, Ts＝N×TcThe method for modulating the time shift position of the spreading code adopted by the data signal component may be: cyclic code shift keying modulation method.
Further, for a spreading code sequence with length N in the data signal component, cyclic shift may generate N different spreading code time shift sequence sets, and the spreading code time shift position modulation method adopted by the data signal component is: selecting K spread spectrum code time shift sequence sets to modulate log in N spread spectrum code time shift sequence sets2K bits of text or data information, K is less than or equal to N.
Optionally, in step 130, the spreading code time shift position modulation method adopted by the data signal component may also be: spreading code time shift position modulation.
Spreading code time shift position modulation refers to: for length of NxTcSpreading code sequence of (2), position symbol time interval Ts＞(N+1)×TcSpreading code sequences in time intervals T, depending on the text or data information of the premodulated binarysInternal direct shift, containing a total of M ═ Ts/TcN +1 different positions, modulation log2M bits of text or data information.
Example 2
A satellite communication navigation signal receiving method 200 shown in fig. 3 receives the signal generated by the generating method 100 of embodiment 1, and the method 200 includes:
210. a spreading code local recurrence code of the pilot signal component and the data signal component is generated.
220. Receiving a radio frequency modulated signal S via an antennaRF(t) using a center frequency of fcTwo carriers with 90-degree phase difference, modulating the radio frequency signal SRF(t) down-converting to baseband to obtain a received baseband signal.
230. Capturing and tracking the received baseband signal by using the local reproduction code of the spread spectrum code of the pilot signal component, extracting the clock information of the pilot signal according to the capturing and tracking result, and obtaining the clock information of the pilot signal according to the relation Ts＝k×TpilotA time-shifted modulation interval for each symbol data signal component is determined.
240. And performing correlation operation on the received baseband signal by using the local reproduction code of the spread spectrum code of the data signal component to obtain a correlated signal sequence to be detected.
250. And comparing the sequence value of the signal to be detected, taking the moment corresponding to the maximum value as the position detection moment, and judging the position detection moment to obtain binary telegraph text or data information according to the mapping relation between the binary data and the displacement of the spread spectrum code sequence in the modulation process.
Specifically, in this embodiment, reference may also be made to the signal flow chart shown in fig. 4 and the signal schematic diagram after the correlation operation processing shown in fig. 5.
In fig. 4, the received signal is first multiplied by the carrier and then low-pass filtered to be converted into a baseband signal; then, making sliding correlation between the spread spectrum code and the received baseband signal to obtain a series of sliding correlation values, then making decision on the amplitude and position of the correlation values so as to implement demodulation of data, and finally, recombining the demodulated data into original data stream form and outputting it.
To further explain the modulation scheme and its difference from the original spread spectrum modulation system, 2 spread spectrum code periods are taken as time shift intervals, and 1 chip period is taken as a time shift slot. Fig. 5 shows a received signal related to a conventional spread spectrum modulation scheme and a received signal related to a spread spectrum code time shift position modulation in the data signal component. In fig. 5, the time of occurrence of the original spread spectrum received signal is fixed, a correlation peak occurs in the signal after correlation operation at a fixed time, and the decision is made to recover the modulation data according to the positive or negative of the correlation peak; and the correlation peak of the time-shift position modulation signal appears at a certain moment in the time-shift interval according to the difference of modulation data, and the modulation data information is judged and recovered according to the appearing position moment.
In the satellite communication navigation signal receiving method provided in the above embodiment, the signal generated by the generation method in embodiment 1 is received, and after the correlation operation processing, the demodulation detection of the received signal is converted into the demodulation detection of the conventional pulse position modulation signal.
It should be well known to those skilled in the art that the correlation operation or sliding correlation can be implemented by a fast fourier algorithm to effectively reduce the complexity of the calculation, and therefore, a processing method based on the fast fourier algorithm is also within the scope of the present invention.
Example 3
A satellite communication navigation signal generating apparatus 300 as shown in fig. 6 includes: a spreading code generation module 310, a pilot signal component modulation module 320, a spreading code time shift position modulation module 330, and an up-conversion module 340. Wherein the content of the first and second substances,
the spreading code generation module 310 is used to generate a pilot signal component spreading code and a data signal component spreading code. The pilot signal component modulation module 320 is used for generating a pilot component according to the pilot signal component spreading codeMagnitude spread spectrum modulated signal Spilot(t)。
The spread spectrum code time shift position modulation module 330 is configured to modulate a binary text or data information in a spread spectrum code time shift position modulation manner according to a data signal component spread spectrum code to generate a data component spread spectrum modulation signal Sdata(t) of (d). Wherein, the modulation of the time shift position of the spread spectrum code means: according to the difference of the pre-modulated binary text or data information, the data component spread spectrum code sequence is in the position code element time interval TsThe minimum time interval of the shift is 1 spreading code chip period Tc，TsSpreading code period T with pilot signal componentpilotThe corresponding relation is as follows: t iss＝k×Tpilot，k>0。
The up-conversion module 340 is used for generating a center frequency fcCarrier waves with different phases and spread spectrum modulating signal S by pilot frequency componentpilot(t) and data component spread spectrum modulated signal Sdata(t) modulating to radio frequency to obtain two radio frequency component signals, and superposing the two radio frequency component signals to obtain a radio frequency modulation signal SRF(t)。
It should be understood that, in the embodiment of the present invention, the generating apparatus 300 according to the embodiment of the present invention may correspond to an execution body of the generating method 100 according to the embodiment of the present invention, and the above and other operations and/or functions of the generating apparatus 300 are respectively for implementing corresponding flows of the methods in fig. 1 and fig. 2, and are not described herein again for brevity.
Optionally, the spreading code time shift position modulation module 330 is a spreading code cyclic shift keying modulation module, and for a spreading code sequence with length N in the data signal component, T iss＝N×TcThe spread spectrum code cyclic shift keying modulation module modulates binary telegraph text or data information by adopting a cyclic code shift keying modulation method.
Further, for a spreading code sequence of length N in the data signal component, the cyclic shift may generate N different sets of spreading code time-shifted sequences, the spreading code cyclic shift keying modulation module is specifically configured to generate, among the N sets of spreading code time-shifted sequences,time-shift sequence set modulation log for selecting K spread spectrum codes2K bits of text or data information, K is less than or equal to N.
Optionally, the spreading code time shift position modulation module is a spreading code time shift position modulation module, and for a length of nxtcSpreading code sequence of (2), position symbol time interval Ts＞(N+1)×TcAccording to the difference of the pre-modulation binary text or data information, the spread spectrum code sequence is directly shifted in the time interval Ts, and the spread spectrum code sequence totally contains M ═ Ts/TcN +1 different positions, modulation log2M bits of text or data information.
Example 4
Fig. 7 shows a satellite communication navigation signal receiving apparatus 400, which receives the signal generated by the generating apparatus 300 according to embodiment 3. The receiving apparatus 400 includes: a spreading code local reproduction code generation module 410, a down conversion module 420, a pilot signal acquisition tracking module 430, and a spreading code time shift position demodulation module 440. Wherein the content of the first and second substances,
the spreading code local reproduction code generation module 410 is used to generate spreading code local reproduction codes for the pilot signal component and the data signal component. The down-conversion module 420 generates a local carrier signal, which is a radio frequency modulated signal S received via an antennaRF(t) down-converting to baseband to obtain a received baseband signal, the local carrier signal comprising a center frequency fcTwo carriers 90 out of phase.
The pilot signal capturing and tracking module 430 is configured to capture and track the received baseband signal by using the local reproduction code of the spreading code of the pilot signal component, extract the clock information of the pilot signal according to the result of capturing and tracking, and extract the clock information of the pilot signal according to the relation Ts＝k×TpilotA time-shifted modulation interval for each symbol data signal component is determined.
The spreading code time-shift position demodulation module 440 is configured to perform correlation operation on the received baseband signal by using a local reproduction code of a spreading code of a data signal component to obtain a signal sequence to be detected after correlation, compare the signal sequence value to be detected in a time-shift modulation interval, take a time corresponding to a maximum value as a position detection time, and determine a binary text or data information according to a mapping relationship between binary data and a shift of a spreading code sequence in a modulation process by using the position detection time.
It should be understood that, in the embodiment of the present invention, the receiving apparatus 400 according to the embodiment of the present invention may correspond to an execution main body of the receiving method 200 according to the embodiment of the present invention, and the above and other operations and/or functions of the receiving apparatus 400 are respectively for implementing corresponding flows of the methods in fig. 3 and fig. 4, and are not described herein again for brevity.
In order to further illustrate the advantages of the technical solution of the present invention, some technical performance index results of the method provided in the embodiments of the present invention will be given below.
First, data signal component demodulation error rate
Since the spreading code has a good autocorrelation characteristic, the received data signal component is subjected to correlation operation with the locally generated spreading code, the correlation integral value is 1 (normalized) when the data signal component is synchronized with the locally generated spreading code, and the correlation integral value approaches zero when the received data signal component is not synchronized with the locally generated spreading code (the synchronization error is greater than one chip interval).
After the correlation operation, the signal demodulation detection process is changed into the demodulation detection of a multi-system pulse position modulation (MPPM) signal, and the binary demodulation data can be obtained only by comparing a plurality of correlation operation values to obtain the position corresponding to the maximum value and mapping from the 'spread spectrum code time shift position' to the 'binary data' according to the mapping rule from the 'binary data' to the 'spread spectrum code time shift position' during the modulation.
As can be seen from the signal receiving and processing process, the error rate of the data signal component demodulation detection is the same as that of the MPPM modulation signal.
In order to more intuitively show the error performance advantages of the present invention, the following description will be combined with the accompanying drawings to respectively use the bit signal-to-noise ratio (E) under the condition of Gaussian white noise channelb/N0) And the signal-to-noise ratio (SNR) of the received signal is taken as a standard, and the performances of the method provided by the invention and the existing BPSK modulation mode are compared.
1、Eb/N0Standard of merit
Fig. 8 shows the error rate curve of the conventional BPSK modulation and MPPM modulation. As can be seen from fig. 8, the error code performance of 2PPM modulation is 3dB worse than BPSK, and when the signal-to-noise ratio is higher, the error code performance of high-level PPM modulation is better than that of BPSK modulation, and the higher the level number is, the better the error code performance is. At a bit error rate of 10-6And meanwhile, the signal-to-noise ratio required by 1024PPM modulation is about 5.2dB lower than that of BPSK modulation, and the technical system advantage of PPM modulation is shown.
However, in a satellite navigation system, we usually consider the relationship between the signal-to-noise ratio and the bit error rate of the overall received signal (superposition of pilot signal and data signal). The error performance of the data signal component will be further explained below with reference to the SNR of the received signal.
2. Received signal-to-noise ratio (SNR) criterion
Assuming that the power ratio of the pilot communication channel to the message data channel is 3:1, the energy of the PPM spread spectrum modulation symbol can be ensured to be 4 times of the symbol energy of the single BPSK data channel symbol by reasonable design, so that the error rate curve under the SNR standard of the received signal to noise ratio can be obtained as shown in fig. 9.
As can be seen from fig. 9, under the SNR standard, the higher the order of PPM modulation is, the worse the error rate is, but the error rate does not increase sharply with the increase of the order; compared with BPSK modulation, the error code performance of multilevel PPM modulation is poorer under the condition of low signal-to-noise ratio, the error code performance of multilevel PPM modulation is better than that of BPSK modulation under the condition of high signal-to-noise ratio, and when the error code rate is 10-6The required signal-to-noise ratio for 1024PPM modulation is about 1.1dB lower than for BPSK modulation.
In practical transmission, the requirement of the error rate of data is usually 10-6And the amplitude is lower than the amplitude, under the condition, both BPSK modulation and PPM modulation are in a state of higher signal-to-noise ratio, and the error rate performance of the PPM modulation is superior to that of the BPSK modulation.
Second, comparative experiment
A baseband pilot and data channel spread spectrum signal in spread spectrum code time shift position modulation is schematically shown in fig. 10.
In fig. 10, the time shift interval of the position modulation of the data signal component spreading code is 2 spreading modulation symbol times, and the sum of the square of the amplitude of the I channel pilot signal and the amplitude of the Q channel signal is constant 1 in the time interval in which the Q channel spreading code appears (in the time interval in which the Q channel is zero, the amplitude of the I channel is 1), so that the constant envelope value of the modulation signal is constant 1, and the pilot-to-data channel power ratio can be adjusted by adjusting the amplitude in the non-zero interval of the Q channel.
It should be noted that the 2 spreading symbol periods in fig. 10 are only schematic, and the actual time shift interval may be increased or decreased as needed.
According to the design scheme of the modulation system, the Beidou B2a is referred to for modulating signals (the signal power ratio of a pilot channel to a data channel is 1:1, and the length N of a spread spectrum code is 10230), and PPM time shift position modulation is designed. Taking the time shift interval of two spreading code periods as an example, when the length of the Q channel time shift spreading code sequence is one spreading code sequence period, the number of movable positions is N +1, that is 10231; the maximum bit information that can be loaded is log2(10231) 13.3 bits. In the B2a signal modulation scheme, the data channel spread spectrum modulation symbols all adopt a BPSK modulation method, and 2bit information is loaded in 2 spread spectrum code modulation periods, so that the data transmission rate is increased by 6.65 times as much as the original rate by the method provided by the embodiment of the present invention.
Because the modulation order and the bit error rate have a direct relation, the increase of the modulation order and the increase of the information rate have a logarithmic relation, the increase of the demodulation detection complexity can be brought, only 1024 positions are not adopted, and 10-bit information is loaded. The main technical parameter pairs for the two modes are shown in table 1.
TABLE 1 comparison of signal system parameters
| Modulation system | 1024PPM | QPSK |
| Pilot data channel power ratio | 1:1 | 1:1 |
| Bit rate (5 bits before coding) | 5kb/s | 1kb/s |
| Information rate (after 5-bit coding) | 1000bit/s | 200bit/s |
| Signal to noise ratio (error rate of 10)-6) | 15.4dB | 13.5dB |
As can be seen from the above table, comparing the two modulation schemes, under the condition that the power ratios of the spreading code, the pilot and the data channel are the same, the spreading code time shift position modulation scheme can increase the spreading transmission rate before coding from 1kb/s to 5kb/s (the corresponding information rates after coding are 1000b/s and 200b/s respectively), and the error rate is 10-6In time, the signal-to-noise ratio required by the modulation scheme of the time-shifting position of the spreading code is only 15.4dB, compared with the original modulation scheme, the error code performance is 1.9dB worse, and the error code rate curve is shown in fig. 11. However, the transmission rate is increased by 5 times at the cost of the signal-to-noise ratio loss of 1.9dB, and the method has great theoretical significance and application value.
It can be seen from the comparison that the PPM modulation scheme can greatly improve the transmission rate of the message data, and in practical application, the data volume of the message of the satellite navigation system is small, the requirement on the updating time is not high, and the requirements on the tracking acquisition and positioning accuracy are higher, that is, the higher power ratio of the pilot frequency to the data channel is required.
One of ordinary skill in the art can recognize that various technical indexes in the satellite communication navigation signal are interchangeable, and the transmission rate of the data signal component is reduced to obtain a lower data signal component transmission power, so that the transmission power of the pilot signal component is increased on the premise that the total power is not changed, and the acquisition tracking performance and the positioning accuracy of the satellite navigation receiver are further improved.
In summary, compared with the prior art, the technical scheme of the invention has the following beneficial effects:
1. spread spectrum code time shift position modulation is introduced into the data signal component, and compared with the traditional BPSK modulation mode, the modulation mode has higher power efficiency and can more efficiently use the limited transmitting power to complete the transmission of text or data. The direct effects brought by this include:
under the premise of not changing the power ratio of the pilot signal component to the data signal component, the information transmission rate of the data component signal can be greatly improved. On one hand, the transmission of the message information can be completed more quickly; on the other hand, on the basis of transmitting the message information, information such as short messages, disaster broadcasting, early warning and the like can be additionally transmitted, and the application field of the satellite navigation system is widened.
Under the premise of not increasing the information transmission rate of the data component signal, the power ratio of the pilot signal component to the data signal component can be further increased, and the acquisition tracking performance and the positioning accuracy of the receiving end of the satellite navigation system are further improved. According to the technical scheme provided by the invention, the power ratio of the pilot signal component to the data signal component can be improved by 10:1, and the acquisition and tracking performance of the receiver is respectively improved by 2.60 dB and 0.84dB compared with the currently used signals with the power ratios of 1:1 and 3: 1.
And thirdly, the transmission rate of the data signal component and the power ratio of the pilot signal component to the data signal component can be simultaneously improved.
2. Compatibility transition with the original system can be realized. The design of the satellite navigation signal provided by the invention does not change the pilot signal component, the receiving processing process of the pilot signal component is the same as the receiving processing process of the prior art, and the traditional receiver can still capture and track the pilot signal provided by the invention.
Those of ordinary skill in the art will appreciate that the elements and algorithm steps of the examples described in connection with the embodiments disclosed herein may be embodied in electronic hardware, computer software, or combinations of both, and that the components and steps of the examples have been described in a functional general in the foregoing description for the purpose of illustrating clearly the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the implementation. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus and method may be implemented in other ways. For example, the above-described apparatus embodiments are merely illustrative, and for example, a division of a unit is merely a logical division, and an actual implementation may have another division, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may also be an electric, mechanical or other form of connection.
Units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment of the present invention.
In addition, functional units in the embodiments of the present invention may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit. The integrated unit can be realized in a form of hardware, and can also be realized in a form of a software functional unit.
The integrated unit, if implemented in the form of a software functional unit and sold or used as a stand-alone product, may be stored in a computer readable storage medium. Based on such understanding, the technical solution of the present invention essentially or partially contributes to the prior art, or all or part of the technical solution can be embodied in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
While the invention has been described with reference to specific embodiments, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A satellite communication navigation signal generation method, comprising:
generating a pilot signal component spreading code and a data signal component spreading code;
modulating and generating a pilot component spread spectrum modulation signal S according to the pilot signal component spread spectrum codepilot(t)；
According to the data signal component spread spectrum code, adopting spread spectrum code time-shifting position modulation mode to modulate binary telegraph text or data information to generate data component spread spectrum modulation signal Sdata(t) inThe spreading code time shift position modulation is as follows: according to the difference of the pre-modulated binary text or data information, the data component spread spectrum code sequence is in the position code element time interval TsThe minimum time interval of the shift is 1 spreading code chip period Tc，TsSpreading code period T with pilot signal componentpilotThe corresponding relation is as follows: t iss＝k×Tpilot，k>0；
Using a centre frequency of fcCarrier waves with different phases, spread spectrum modulating signal S by the pilot frequency componentpilot(t) and data component spread spectrum modulated signal Sdata(t) modulating to radio frequency to obtain two radio frequency component signals, and superposing the two radio frequency component signals to obtain a radio frequency modulation signal SRF(t)。
2. The method of generating a satellite communication navigation signal of claim 1, wherein T is the length N of the spreading code sequence in the data signal components＝N×TcThe method for modulating the time shift position of the spread spectrum code adopted by the data signal component comprises the following steps: cyclic code shift keying modulation method.
3. The method of claim 2, wherein the cyclic shift generates N different sets of spreading code time shift sequences for the spreading code sequence of length N in the data signal component, and the spreading code time shift position modulation method used for the data signal component is: selecting K spread spectrum code time shift sequence sets to modulate log in N spread spectrum code time shift sequence sets2K bits of text or data information, K is less than or equal to N.
4. The method of generating a satellite communication navigation signal according to claim 1, wherein the data signal component is modulated by a spreading code time-shift position by: spread spectrum code time shift position modulation;
the spreading code time shift position modulation means: for length of NxTcSpreading code sequence of (2), position symbol time interval Ts＞(N+1)×TcSpreading code sequences in time intervals T, depending on the text or data information of the premodulated binarysInternal direct shift, containing a total of M ═ Ts/TcN +1 different positions, modulation log2M bits of text or data information.
5. A satellite communication navigation signal receiving method that receives a signal generated by the generation method according to any one of claims 1 to 4, comprising:
generating a spreading code local reproduction code of the pilot signal component and the data signal component;
receiving a radio frequency modulated signal S via an antennaRF(t) using a center frequency of fcTwo carriers with 90-degree phase difference, and modulating the radio frequency modulation signal SRF(t) down-converting to a baseband to obtain a received baseband signal;
capturing and tracking the received baseband signal by using a spreading code local reproduction code of a pilot signal component, extracting clock information of the pilot signal according to a capturing and tracking result, and obtaining the clock information of the pilot signal according to a relation Ts＝k×TpilotDetermining a time shift modulation interval for each symbol data signal component;
performing correlation operation on the receiving baseband signal by using a spreading code local recurrence code of a data signal component to obtain a correlated signal sequence to be detected;
and comparing the sequence value of the signal to be detected, taking the moment corresponding to the maximum value as the position detection moment, and judging the position detection moment to obtain binary telegraph text or data information according to the mapping relation between the binary data and the displacement of the spread spectrum code sequence in the modulation process.
6. A satellite communication navigation signal generating apparatus, comprising:
a spread spectrum code generating module for generating a pilot signal component spread spectrum code and a data signal component spread spectrum code;
a pilot signal component modulation module for generating a pilot component spread spectrum modulation signal S according to the pilot signal component spread spectrum codepilot(t)；
A spread spectrum code time shift position modulation module for modulating binary text or data information by adopting a spread spectrum code time shift position modulation mode according to a data signal component spread spectrum code to generate a data component spread spectrum modulation signal Sdata(t), the spreading code time shift position modulation means: according to the difference of the pre-modulated binary text or data information, the data component spread spectrum code sequence is in the position code element time interval TsThe minimum time interval of the shift is 1 spreading code chip period Tc，TsSpreading code period T with pilot signal componentpilotThe corresponding relation is as follows: t iss＝k×Tpilot，k>0；
An up-conversion module for generating a center frequency of fcDifferent phase carrier wave, and spread spectrum modulating signal S with pilot frequency componentpilot(t) and data component spread spectrum modulated signal Sdata(t) modulating to radio frequency to obtain two radio frequency component signals, and superposing the two radio frequency component signals to obtain a radio frequency modulation signal SRF(t)。
7. The satellite communication navigation signal generation apparatus of claim 6, wherein the spreading code time shift position modulation module is a spreading code cyclic shift keying modulation module, and for a spreading code sequence of length N in the data signal component, Ts＝N×TcThe spread spectrum code cyclic shift keying modulation module modulates binary telegraph text or data information by adopting a cyclic code shift keying modulation method.
8. The satellite communications navigation signal generation apparatus of claim 7, wherein for a spreading code sequence of length N in the data signal component, the cyclic shift produces N different sets of spreading code time-shifted sequences, and wherein the spreading code cyclic shift keying modulation module is specifically configured to select K sets of spreading code time-shifted sequences to modulate log in the N sets of spreading code time-shifted sequences2K bits of text or data information, K is less than or equal to N.
9. The satellite communication navigation signal generation apparatus of claim 6, wherein the spreading code time shift position modulation module is a spreading code time shift position modulation module for a length of nxtcSpreading code sequence of (2), position symbol time interval Ts＞(N+1)×TcAccording to the difference of the pre-modulation binary text or data information, the spread spectrum code sequence is directly shifted in the time interval Ts, and the spread spectrum code sequence totally contains M ═ Ts/TcN +1 different positions, modulation log2M bits of text or data information.
10. A satellite communication navigation signal receiving apparatus that receives a signal generated by the generating apparatus according to any one of claims 6 to 9, comprising:
a spread spectrum code local reproduction code generation module for generating a spread spectrum code local reproduction code of the pilot signal component and the data signal component;
a down-conversion module for generating a local carrier signal and modulating the received RF signal S via an antennaRF(t) down-converting to baseband to obtain a received baseband signal, the local carrier signal comprising a center frequency fcTwo carriers with 90-degree phase difference;
a pilot signal capturing and tracking module for capturing and tracking the receiving baseband signal by using the spread spectrum code local recurrence code of the pilot signal component, extracting the clock information of the pilot signal according to the capturing and tracking result, and according to the relation Ts＝k×TpilotDetermining a time shift modulation interval for each symbol data signal component;
and the spread spectrum code time-shifting position demodulation module is used for carrying out correlation operation on the received baseband signal by using a local reproduction code of a spread spectrum code of a data signal component to obtain a correlated signal sequence to be detected, comparing the sequence value of the signal to be detected in a time-shifting modulation interval, taking the moment corresponding to the maximum value as a position detection moment, and judging the position detection moment to obtain binary text or data information according to the mapping relation of the displacement of binary data and a spread spectrum code sequence in the modulation process.
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| CN103269236A (en) * | 2013-05-24 | 2013-08-28 | 王红星 | Method for spread spectrum modulation and demodulation of code element grouping time-shifting position |
| CN103560872A (en) * | 2013-11-13 | 2014-02-05 | 中国人民解放军国防科学技术大学 | Accurate time measurement method based on OFCDM |
| CN109039975A (en) * | 2018-09-07 | 2018-12-18 | 航天恒星科技有限公司 | A kind of code shifting key modulation method and its demodulation method that phase shift is repeated several times |
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| CN101278207A (en) * | 2005-07-01 | 2008-10-01 | 欧洲太空署 | Spread-spectrum code for satellite navigation system |
| CN103269236A (en) * | 2013-05-24 | 2013-08-28 | 王红星 | Method for spread spectrum modulation and demodulation of code element grouping time-shifting position |
| CN103560872A (en) * | 2013-11-13 | 2014-02-05 | 中国人民解放军国防科学技术大学 | Accurate time measurement method based on OFCDM |
| CN109039975A (en) * | 2018-09-07 | 2018-12-18 | 航天恒星科技有限公司 | A kind of code shifting key modulation method and its demodulation method that phase shift is repeated several times |
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