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CN110275189B - Method and system for modulating chip time division navigation signal of mixed information rate - Google Patents

Method and system for modulating chip time division navigation signal of mixed information rate Download PDF

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CN110275189B
CN110275189B CN201910453240.XA CN201910453240A CN110275189B CN 110275189 B CN110275189 B CN 110275189B CN 201910453240 A CN201910453240 A CN 201910453240A CN 110275189 B CN110275189 B CN 110275189B
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speed
code
chip
code sequence
time division
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CN110275189A (en
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严涛
蒙艳松
周昀
王瑛
雷文英
王国永
边朗
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Xian Institute of Space Radio Technology
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/243—Demodulation of navigation message
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/29—Acquisition or tracking or demodulation of signals transmitted by the system carrier including Doppler, related
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • 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
    • G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/30—Acquisition or tracking or demodulation of signals transmitted by the system code related

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  • Radar, Positioning & Navigation (AREA)
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Abstract

A mixed information rate chip time division navigation signal modulation method and system, including (1) channel coding: respectively carrying out channel coding on a low-speed message and a high-speed message, (2) PRN code mapping: mapping the channel-coded low-speed message into a PRN code sequence, and mapping the channel-coded high-speed message into an N-1 PRN code sequence to obtain an N PRN code sequence; (3) chip time division: dividing N paths of PRN code sequences into one path of signals chip by chip; (4) and (3) modulation of a baseband waveform: and performing baseband waveform modulation on one path of signal obtained after time division of the chip to obtain a baseband signal.

Description

Method and system for modulating chip time division navigation signal of mixed information rate
Technical Field
The invention belongs to the field of satellite navigation, and mainly relates to a method and a system for modulating a chip time division navigation signal of a mixed information rate.
Background
At present, the structure of a Global Navigation Satellite System (GNSS) with four basic Global Navigation systems (GNSS) is already formed, and the GNSS can meet the most basic requirements of people on Navigation, positioning and time service. In order to further improve the service performance of the satellite navigation system, part of the system starts to provide enhanced services: japanese QZSS provides Centimeter Level enhancement Service (CLAS) at its L6, Galileo plans to provide precision positioning Service at its E6 frequency point.
Such navigation enhancement services provide precision Point location services (PPP) by rapidly broadcasting a precision text or precision correction. The precision correction number generally comprises parameters such as orbit, clock error, carrier phase deviation correction number, code deviation, URA and the like, and in order to realize high-precision positioning, the broadcasting interval of the precision correction number is short, taking QZSS as an example, the broadcasting interval of the clock error correction number is 5s, and the other is 30 s.
In the conventional GNSS signals, low-speed basic navigation messages are broadcast, and the information rate is usually only 50bps to 250 bps. In the enhanced service, the fast and precise correction digital message is broadcasted, and the information rate is obviously improved. QZSS provides the L6 signal for CLAS with information rates up to around 2 kbps. Therefore, GNSS is faced with a demand for simultaneously broadcasting a low-speed basic navigation message and a high-speed precision message.
GNSS signals are modulated using direct spread spectrum, and in order to increase the information rate, there are two conventional approaches. The first method is to keep the code rate constant and increase the information rate, which results in a reduction of the number of chips in a symbol, lowering the spreading gain and deteriorating the cross-correlation performance. The second is to keep the spreading gain unchanged and increase the information rate, which results in an increase in the code rate and a larger bandwidth occupied by the signal.
In order to increase the information rate without changing the Code rate and the spreading gain, QZSS applies a Code-Shift-Keying (CSK) modulation signal in its L6 signal. CSK is a M-system orthogonal modulation signal, and M kinds of spread spectrum modulation signal waveforms are shared, and each waveform can represent k ═ log2(M) bit information, the M kinds of spread spectrum modulation signal waveform are obtained by cyclic shift of the same basic code. For a spreading code with a code length L, each waveform is most representative
Figure BDA0002075792130000021
Bit information. However, the CSK modulated signal alone is not suitable for acquisition tracking measurements, but only for data transmission.
In order to broadcast low-speed text and high-speed text simultaneously, the patent "code shift keying modulation method with repeated phase shift for many times" and its demodulation method (patent number: CN 201811042847.0) proposes R-CSK signal, which is a special case of CSK signal, and modulates information by different cyclic shifts of the same code, but the maximum information rate is limited by the code length. The patent "a dual-rate composite telegraph text signal broadcasting control method" (patent number: CN 201810947305.1) and "an R-CSK dual-rate composite telegraph text signal broadcasting control method" (patent number: CN 201811078853.1) propose to use QPSK modulation with orthogonal phase, use traditional BPSK signal in the I branch, broadcast low-rate basic navigation telegraph text, use CSK signal or R-CSK signal in the Q branch, broadcast high-rate extended telegraph text. However, by means of phase separation, the I branch will consume a part of power, and when performing signal tracking or demodulation, it is unable to use all signal power, thereby reducing the accuracy and the demodulation threshold.
Disclosure of Invention
The invention aims to: the method and the system overcome the defects of the prior art and provide a chip time division navigation signal modulation method and a chip time division navigation signal modulation system with mixed information rate, and simultaneously realize high-precision measurement and low/high data rate telegraph text broadcasting on a spread spectrum navigation signal.
The technical solution of the invention is as follows:
a mixed information rate chip time division navigation signal modulation method includes the following steps:
(1) channel coding: respectively carrying out channel coding on the low-speed text and the high-speed text,
(2) PRN code mapping: mapping the channel-coded low-speed message into a PRN code sequence, and mapping the channel-coded high-speed message into an N-1 PRN code sequence to obtain an N PRN code sequence;
(3) chip time division: dividing N paths of PRN code sequences into one path of signals chip by chip;
(4) and (3) modulation of a baseband waveform: and performing baseband waveform modulation on one path of signal obtained after time division of the chip to obtain a baseband signal.
The original information rate of the low-speed text is Rb,LSymbol rate R after channel codings,LThe low speed text symbol has a width of Ts,L＝1/Rs,LCoding efficiency of Rb,L/Rs,LThe channel-coded information symbol stream is { d }L,m}，dL,m∈{0,1}；
The original information rate of the high-speed text is Rb,HSymbol rate R after channel codings,HHigh speed text symbol width of Ts,H＝1/Rs,HCoding efficiency of Rb,H/Rs,HThe channel-coded information symbol stream is { d }H,m}，dH,m∈{0,1}。
The mapping of the low-speed message PRN codes specifically comprises the following steps:
(2.11) generating a PRN code sequence for the low-speed text, the spreading code sequence being { c }L,i}，i＝0,1,2,…,Lc-1，cL,iE {0,1}, and a code rate Rc；
(2.12) determining a code period: a low-speed data symbol has
Figure BDA0002075792130000031
One code period, i.e. Ts,LIs Lc·TcInteger multiple of (L)cIs the code length, T, of the spreading codec＝1/RcAnd is the width of the chip,
(2.13) will slow down the message { dL,mC and spreading code sequence cL,iXOR is carried out to obtain a code sequence after mapping; i.e. when the data symbol dL,mWhen it is 0, the output code sequence is { cL,iWhen data symbol d is presentL,mWhen it is 1, the output code sequence is { cL,iGet the inverted sequence of }
Figure BDA0002075792130000032
The code sequence obtained by mapping is marked as { CL,i}。
The high-speed message PRN code mapping specifically comprises the following steps:
(2.21) generating a set of PRN code sequences of the high-speed message;
the number of the generated different orthogonal spread spectrum code sequences is NcEach is respectively
Figure BDA0002075792130000033
The code length of each spreading code is Lc(ii) a Each spread code is codedCyclic shift to obtain new orthogonal spread spectrum code sequence and obtain N at mostc·LcAn orthogonal spreading code sequence, each spreading code sequence representing
Figure BDA0002075792130000034
A bit;
(2.22) according to the rate of the high-speed text, each spreading code sequence represents a U bit,
Figure BDA0002075792130000035
total requirement M2UOrthogonal code sequence, denoted as
Figure BDA0002075792130000036
The orthogonal code sequences are derived from
Figure BDA0002075792130000037
And their cyclic shifts;
(2.23) high-speed text { dH,mAfter serial-to-parallel conversion, output (N-1). U circuit parallel text symbol stream, marked as d(N-1)·U,k＝[d1,k d2,k … d(N-1)·U,k]T，du,kA kth symbol value representing a u-th circuit textual symbol stream; symbol rate reduction after serial-to-parallel conversion to
Figure BDA0002075792130000038
(2.24) each column has (N-1) U bit telegraph text symbols, each U row telegraph text symbol is mapped into a code sequence, and N-1 code sequences are obtained; the code sequence of the (n-1) th U +1 to n.U circuit text symbol mapping is expressed as
Figure BDA0002075792130000041
The mapping relation between the U parallel text symbols and the spreading codes is as follows:
Figure BDA0002075792130000042
in the formula, xn,kIs a binary number [ d(n-1)U+1,k d(n-1)U+2,k … dn·U+1,k]TIn decimal number, i.e.
Figure BDA0002075792130000043
Chip time division is obtained by the following method:
(3.1) mapping a path of spread spectrum code { C) of the low-speed textL,iN-1 path spread spectrum code mapped by high speed text
Figure BDA0002075792130000044
N is more than or equal to 1 and less than or equal to N-1 as the N-path parallel code sequence;
(3.2) synthesizing N paths of parallel code sequences into a path of spreading code sequence in a chip-by-chip time division mode, wherein the spreading code sequence after chip time division multiplexing is recorded as: { CM,lWhen (i-1) N +1 is more than or equal to l is less than or equal to i.N,
Figure BDA0002075792130000045
Figure BDA0002075792130000046
(3.3) after passing chip time division, { CM,lThe code rate is increased by N times, which is recorded as N.Rc。
Baseband waveform modulation, obtained by the following method:
(4.1) designing a chip waveform p (t) according to the signal performance and compatibility requirements;
(4.2) code sequence { C) obtained by time-dividing chipsM,lModulating with a chip waveform p (t), wherein a signal modulated by a baseband waveform is represented as:
Figure BDA0002075792130000051
the chip waveform p (t) takes the form of a rectangular chip waveform or a binary offset carrier waveform.
For a rectangular chip waveform, there are:
Figure BDA0002075792130000052
for binary offset carrier waveforms, there are
Figure BDA0002075792130000053
In the formula (f)sSubcarrier frequency modulated for BOC, 2fs/(N·Rc) Are integers.
Further, the present invention also provides a navigation signal modulation system implemented by the chip time division navigation signal modulation method based on the mixed information rate, which comprises:
a channel coding module: and respectively carrying out channel coding on the low-speed text and the high-speed text, and interweaving after the channel coding so as to improve the anti-channel fading capability.
PRN code mapping module: mapping the channel-coded low-speed message into a PRN code sequence, and mapping the channel-coded high-speed message into an N-1 PRN code sequence to obtain an N PRN code sequence;
a chip time division module: dividing N paths of PRN code sequences into one path of signals chip by chip;
a baseband waveform modulation module: and performing baseband waveform modulation on one path of signal obtained after time division of the chip to obtain a baseband signal.
Compared with the prior art, the invention has the beneficial effects that:
(1) compared with a BPSK and R-CSK mixed structure modulated by QPSK, the method adopts a chip time division technology to broadcast one path of signal for modulating the low-speed message and multiple paths of signals for modulating the high-speed message after chip time division. When the signal is tracked and demodulated, all power can be used, and the tracking precision of the signal is improved.
(2) The existing chip time division is generally the chip time division of two paths of signals, and the chip time division of a plurality of paths of signals is adopted in the patent so as to improve the data rate.
(3) The traditional CSK modulation signal is only suitable for broadcasting data and is not suitable for tracking and code ranging.
(4) The prior CSK only uses the cyclic shift modulation data of one spread spectrum code, and the highest data rate is limited by the code length and the code rate of the spread spectrum code.
(5) In the existing CSK modulation mode, the chip waveforms are all rectangular chips, and the frequency spectrum and the ranging performance of signals are limited.
Drawings
FIG. 1 is a hybrid information rate chip time division navigation signal modulation scheme as disclosed in the present invention;
FIG. 2 is a diagram of PRN code mapping for a low speed message
FIG. 3 is a schematic diagram of high-speed text serial-to-parallel conversion into (N-1). U-path parallel
Fig. 4 is a schematic diagram of chip time division.
Detailed Description
The invention is described in detail below with reference to the figures and specific embodiments.
The invention broadcasts the code sequence which can modulate the low-speed message and has the distance measuring capability and the code sequence which modulates the high-speed message in time by a chip-by-chip time division technology. For convenience of description, in this patent, the logic level and the signal level are equivalent, and the convention in satellite navigation signals is adopted, wherein logic 0 is mapped to signal level 1.0, and logic 1 is mapped to signal level-1.0.
In order to achieve the purpose, the invention discloses a chip time division signal modulation method for mixing information rates.
1. The chip time division signal modulation method of mixed information rate includes the following steps, as shown in fig. 1:
(1) and (4) channel coding. Respectively carrying out channel coding on the low-speed text and the high-speed text, wherein the original information rate of the low-speed text is Rb,LSymbol rate R after channel codings,LThe low speed text symbol has a width of Ts,L＝1/Rs,LCoding efficiency of Rb,L/Rs,LThe channel-coded information symbol stream is { d }L,m}，dL,mE {0,1 }. The original information rate of the high-speed text is Rb,HSymbol rate R after channel codings,HHigh speed text symbol width of Ts,H＝1/Rs,HCoding efficiency of Rb,H/Rs,HThe channel-coded information symbol stream is { d }H,m}，dH,mE {0,1 }. After channel coding, interleaving technology can be adopted, and the channel fading resistance is improved.
(2) The PRN code maps. And mapping the low-speed message into a PRN code sequence, and mapping the high-speed message into an N-1 PRN code sequence to obtain an N PRN code sequence.
(3) Chip time division. And the N PRN code sequences are divided into one signal chip by chip.
(4) And modulating the baseband waveform. And performing baseband waveform modulation on one path of signal obtained after time division of the chip to obtain a baseband signal.
2. The low-speed message PRN code mapping in step 1 (2) is obtained by:
1) generating PRN code sequence of low speed text, spread spectrum code sequence being { cL,i}，i＝0,1,2,…,Lc-1，cL,iE {0,1}, and a code rate Rc。
2) A low-speed data symbol has
Figure BDA0002075792130000071
One code period, i.e. Ts,LIs Lc·TcInteger multiples of.
3) Will slow down the text { dL,mC and spreading code sequence cL,iAnd XOR is carried out to obtain a code sequence after mapping. I.e. when the data symbolNumber dL,mWhen it is 0, the output code sequence is { cL,iWhen data symbol d is presentL,mWhen it is 1, the output code sequence is { cL,iGet the inverted sequence of }
Figure BDA0002075792130000072
The code sequence obtained by mapping is marked as { CL,i}。
3. The high-speed message PRN code mapping in step 1 (2) is obtained by:
1) a set of PRN code sequences for the high-speed message is generated. The number of the generated different orthogonal spread spectrum code sequences is NcEach is respectively
Figure BDA0002075792130000073
The code length of each spreading code is Lc. Each spreading code is circularly shifted to obtain a new orthogonal spreading code sequence, and N can be obtained at most theoreticallyc·LcAn orthogonal spreading code sequence, each of which can represent
Figure BDA0002075792130000074
A bit.
2) From the rate of the high speed text, it is determined that each spreading code sequence is required to represent U bits,
Figure BDA0002075792130000075
total requirement M2UOrthogonal code sequence, denoted as
Figure BDA0002075792130000076
The orthogonal code sequences are derived from
Figure BDA0002075792130000077
And their cyclic shifts.
3) High speed text { dH,mAfter serial-to-parallel conversion, output (N-1). U circuit parallel text symbol stream, marked as d(N-1)·U,k＝[d1,k d2,k … d(N-1)·U,k]T，du,kRepresenting the kth symbol value of the u-th circuit text symbol stream.Symbol rate reduction after serial-to-parallel conversion to
Figure BDA0002075792130000081
4) Each column has (N-1). U bit telegraph symbols, each U row of telegraph symbols is mapped into a code sequence, and the code sequence of the (N-1) U +1 to n.U circuit telegraph symbol mapping is expressed as
Figure BDA0002075792130000082
The mapping relation between the U parallel text symbols and the spreading codes is as follows:
Figure BDA0002075792130000083
in the formula, xn,kIs a binary number [ d(n-1)U+1,k d(n-1)U+2,k … dn·U+1,k]TIn decimal number, i.e.
Figure BDA0002075792130000084
4. The chip time division in step 1 (3) is obtained by the following method:
1) one path of spread spectrum code { C) for mapping low speed textL,iAnd (N-1) path spread spectrum code mapped by high speed text
Figure BDA0002075792130000085
(1. ltoreq. n.ltoreq.N-1) as the N-way parallel code sequence.
2) Combining N paths of parallel code sequences into a path of spreading code sequence in a chip-by-chip time division mode, wherein the spreading code sequence after chip time division multiplexing is recorded as: { CM,lWhen (i-1) N +1 is more than or equal to l is less than or equal to i.N,
Figure BDA0002075792130000086
Figure BDA0002075792130000087
3) by chipAfter time division, { CM,lThe code rate is increased by N times, which is recorded as N.Rc。
5. The baseband waveform modulation in step 1 (4) is obtained by the following method:
1) the chip waveform, p (t), is designed according to signal performance and compatibility requirements. A rectangular chip waveform or a Binary Offset Carrier (BOC) waveform may be employed. For a rectangular chip waveform, there are:
Figure BDA0002075792130000091
for a sinusoidal BOC chip waveform, there are
Figure BDA0002075792130000092
In the formula (f)sSubcarrier frequency modulated for BOC, 2fs/(N·Rc) Are integers.
2) Code sequence C obtained by time-dividing chipsM,lModulating with a chip waveform p (t), wherein a signal modulated by a baseband waveform is represented as:
Figure BDA0002075792130000093
example (b): the invention discloses a method for modulating a chip time division navigation signal of a mixed information rate, which comprises the following operation steps:
(1) and (4) channel coding.
Respectively carrying out channel coding on the low-speed text and the high-speed text, wherein the original information rate of the low-speed text is Rb,L50bps, the symbol rate after channel coding is Rs,L100sps, 10ms for low-speed text symbol width, 1/2 for coding efficiency, and d for channel-coded information symbol streamL,m}，dL,mE {0,1 }. The original information rate of the high-speed text is Rb,H2.4kbps, symbol rate R after channel codings,H4.8ksps, coding efficiency 1/2The stream of encoded information symbols is dH,m}，dH,m∈{0,1}。
(2) The PRN code maps.
PRN code sequence of low speed text is { cL,i}，i＝0,1,2,…,1022，cL,iE {0,1}, and the code length is Lc1023, the code rate is Rc1.023 Mcps. One low-speed data symbol has 10 code periods. Will slow down the text { dL,mC and spreading code sequence cL,iXOR to obtain the code sequence after mapping { CL,iThe mapping process is shown in fig. 2.
A set of PRN code sequences for the high-speed message is generated. The number of the generated different orthogonal spread spectrum code sequences is NcThe code length of the spreading code is L as 1c1023. The spreading code is cyclically shifted to obtain M-32 orthogonal spreading code sequences, which are expressed as
Figure BDA0002075792130000101
Each spreading code sequence may represent U-6 bits. Will high speed text { dH,mAfter serial-parallel conversion, 4 × 6 ═ 24 parallel telegraph character streams are output, and recorded as d24,k＝[d1,k d2,k … d24,k]T，du,kThe kth symbol value, representing the u-th textual symbol stream, is reduced to 200sps after serial-to-parallel conversion. The parallel diagram of high-speed text serial-parallel conversion to (N-1). U path is shown in FIG. 3.
Each column has 4 × 6 ═ 24 bit telegraph symbols, each 6 groups are mapped into a code sequence, and the code sequences mapped by the 6(n-1) +1 to 6n telegraph symbols are expressed as
Figure BDA0002075792130000102
The mapping relationship between the 6 parallel text symbols and the spreading codes is as follows:
Figure BDA0002075792130000103
in the formula, xn,kIs a binary number [ d6(n-1)+1,k d6(n-1)+2,k … d6n+1,k]TIn decimal number, i.e.
Figure BDA0002075792130000104
(3) Chip time division.
One path of spread spectrum code { C) for mapping low speed textL,i4-way spread spectrum code mapped with high-speed text
Figure BDA0002075792130000105
As a 5-way parallel code sequence. Synthesizing 5 paths of parallel code sequences into a path of spreading code sequence in a chip-by-chip time division mode, wherein the spreading code sequence after chip time division multiplexing is recorded as: { CM,lWhen 5(i-1) +1 is less than or equal to l and less than or equal to 5i,
Figure BDA0002075792130000106
Figure BDA0002075792130000107
a chip time division diagram is shown in fig. 4. After time division by chips, { CM,lThe code rate is increased by 5 times, namely 5.115 Mcps.
(4) And modulating the baseband waveform.
The waveform modulation is carried out by adopting a chip waveform p (t), and the signal after the baseband waveform modulation is represented as:
Figure BDA0002075792130000111
for a rectangular chip waveform, there are:
Figure BDA0002075792130000112
in this example, a low-speed message with an information rate of 50bps is broadcast simultaneously with a high-speed message with an information rate of 2.4kbps, achieving high-information-rate broadcast. In this example, only 32 cyclic shifts of one spreading code sequence are used for high-speed text modulation, and by increasing the number of spreading code sequences, the information rate can be further improved. In addition, the spread code sequence for modulating the low-speed message and the spread code sequence for modulating the high-speed message are combined into one signal according to a time division pattern, signal tracking is carried out as a whole, and no other branch branches shunt signal power, so that all signal power can be used during signal tracking, and high-precision tracking can be realized.
Those skilled in the art will appreciate that those matters not described in detail in the present specification are well known in the art.

Claims (8)

1.一种混合信息速率的码片时分导航信号调制方法，其特征在于步骤如下：1. a chip time-division navigation signal modulation method of a mixed information rate, characterized in that the steps are as follows: (1)信道编码：将低速电文和高速电文分别进行信道编码；(1) Channel coding: channel coding the low-speed message and the high-speed message respectively; (2)PRN码映射：将经过信道编码的低速电文映射为一路PRN码序列，经过信道编码的高速电文映射为N-1路PRN码序列，共得到N路PRN码序列；(2) PRN code mapping: map the channel-coded low-speed telegrams to one PRN code sequence, and the channel-coded high-speed telegrams to N-1 PRN code sequences to obtain N PRN code sequences in total; 低速电文PRN码映射，具体为：Low-speed message PRN code mapping, specifically: (2.11)生成低速电文的PRN码序列，扩频码序列为{cL,i}，i＝0,1,2,…,Lc-1，cL,i∈{0,1}，码速率为Rc；(2.11) Generate the PRN code sequence of the low-speed message, the spreading code sequence is {c L, i }, i = 0, 1, 2,..., L c -1, c L, i ∈ {0, 1}, the code rate is R c ; (2.12)确定码周期：一个低速数据符号有
Figure FDA0003207287270000011
个码周期，即Ts,L是Lc·Tc的整数倍，Lc是扩频码的码长，Tc＝1/Rc，是码片宽度，(2.12) Determine the code period: a low-speed data symbol has
Figure FDA0003207287270000011
code period, that is, T s, L is an integer multiple of L c ·T c , L c is the code length of the spreading code, T c =1/R c , is the chip width, (2.13)将低速电文{dL,m}与扩频码序列{cL,i}异或，得到映射后码序列；即当数据符号dL,m是0时，输出码序列为{cL,i}，当数据符号dL,m是1时，输出码序列为{cL,i}的取反序列
Figure FDA0003207287270000012
映射得到的码序列记为{CL,i}；(2.13) XOR the low-speed message {d L, m } with the spreading code sequence {c L, i } to obtain the code sequence after mapping; that is, when the data symbol d L, m is 0, the output code sequence is {c L, i }, when the data symbol d L, m is 1, the output code sequence is the inverse sequence of {c L, i }
Figure FDA0003207287270000012
The code sequence obtained by mapping is denoted as {C L,i }; 高速电文PRN码映射，具体为：High-speed message PRN code mapping, specifically: (2.21)生成高速电文的PRN码序列集合；(2.21) Generate a set of PRN code sequences for high-speed telegrams; 生成的不同正交扩频码序列个数为Nc个，分别为
Figure FDA0003207287270000013
每个扩频码的码长都是Lc；将每个扩频码循环移位，得到新的正交扩频码序列，最多得到Nc·Lc个正交的扩频码序列，每一个扩频码序列表示
Figure FDA0003207287270000014
比特；The number of different orthogonal spreading code sequences generated is N c , which are
Figure FDA0003207287270000013
The code length of each spreading code is L c ; each spreading code is cyclically shifted to obtain a new orthogonal spreading code sequence, and at most N c ·L c orthogonal spreading code sequences are obtained. A spreading code sequence represents
Figure FDA0003207287270000014
bit; (2.22)根据高速电文的速率，每个扩频码序列表示U比特，
Figure FDA0003207287270000015
共需要M＝2U正交码序列，表示为
Figure FDA0003207287270000016
这些正交码序列来自于
Figure FDA0003207287270000017
以及它们的循环移位；(2.22) According to the rate of high-speed telegram, each spreading code sequence represents U bits,
Figure FDA0003207287270000015
A total of M = 2 U orthogonal code sequences are required, expressed as
Figure FDA0003207287270000016
These orthogonal code sequences come from
Figure FDA0003207287270000017
and their cyclic shifts; (2.23)高速电文{dH,m}经串并转换后，输出(N-1)·U路并行电文符号流，记为d(N-1)·U,k＝[d1,k d2,k … d(N-1)·U,k]T，du,k表示第u路电文符号流的第k个符号值；串并转换后符号速率降为
Figure FDA0003207287270000018
Rs,H为高速电文的通过信道编码后符号速率；(2.23) After the serial-to-parallel conversion of the high-speed telegram {d H,m }, the (N-1)·U parallel telegram symbol stream is output, denoted as d (N-1)·U,k =[d 1,k d 2,k … d (N-1) U,k ] T , d u,k represents the k-th symbol value of the u-th message symbol stream; after serial-parallel conversion, the symbol rate is reduced to
Figure FDA0003207287270000018
R s, H is the symbol rate of the high-speed message after channel coding; (2.24)每一列有(N-1)·U比特电文符号，每U行电文符号映射为一种码序列，共得到N-1种码序列；第(n-1)U+1到n·U路电文符号映射的码序列表示为
Figure FDA0003207287270000021
(2.24) Each column has (N-1) U-bit message symbols, and each U row of message symbols is mapped to a code sequence, and a total of N-1 code sequences are obtained; (n-1) U+1 to n. The code sequence of U-channel message symbol mapping is expressed as
Figure FDA0003207287270000021
 U个并行电文符号与扩频码映射关系如下表：The mapping relationship between U parallel message symbols and spreading codes is as follows:
Figure FDA0003207287270000022
Figure FDA0003207287270000022
 式中，xn,k为二进制数[d(n-1)U+1,k d(n-1)U+2,k … dn·U+1,k]T的十进制数表示，即In the formula, x n,k is the decimal number representation of the binary number [d (n-1)U+1,k d (n-1)U+2,k … d n U+1,k ] T , namely
Figure FDA0003207287270000023
Figure FDA0003207287270000023
 (3)码片时分：将N路PRN码序列逐码片时分为一路信号；(3) Chip time division: The N-way PRN code sequence is divided into one signal by chip time; (4)基带波形调制：将码片时分后得到的一路信号进行基带波形调制，得到基带信号。(4) Baseband waveform modulation: baseband waveform modulation is performed on a signal obtained after chip time division to obtain a baseband signal. 2.根据权利要求1所述的一种混合信息速率的码片时分导航信号调制方法，其特征在于：低速电文的原始信息速率为Rb,L，通过信道编码后符号速率为Rs,L，低速电文符号宽度为Ts,L＝1/Rs,L，编码效率为Rb,L/Rs,L，信道编码后的信息符号流为{dL,m}，dL,m∈{0,1}；2. the chip time-division navigation signal modulation method of a kind of mixed information rate according to claim 1, is characterized in that: the original information rate of low-speed message is R b,L , the symbol rate after channel coding is R s,L , the symbol width of the low-speed message is T s,L =1/R s,L , the coding efficiency is R b,L /R s,L , the information symbol stream after channel coding is {d L,m },d L,m ∈{0,1}; 高速电文的原始信息速率为Rb,H，高速电文符号宽度为Ts,H＝1/Rs,H，编码效率为Rb,H/Rs,H，信道编码后的信息符号流为{dH,m}，dH,m∈{0,1}。The original information rate of the high-speed message is R b,H , the symbol width of the high-speed message is T s,H =1/R s,H , the coding efficiency is R b,H /R s,H , and the information symbol stream after channel coding is {dH ,m }, dH , m∈{0,1}. 3.根据权利要求2所述的一种混合信息速率的码片时分导航信号调制方法，其特征在于：码片时分，通过以下方法得到：3. the chip time division navigation signal modulation method of a kind of mixed information rate according to claim 2 is characterized in that: the chip time division is obtained by the following method: (3.1)将低速电文映射的一路扩频码{CL,i}和高速电文映射的N-1路扩频码
Figure FDA0003207287270000031
作为N路并行码序列，1≤n≤N-1；(3.1) One channel of spreading code {C L, i } mapped to low-speed message and N-1 channel of spreading code mapped to high-speed message
Figure FDA0003207287270000031
As an N-way parallel code sequence, 1≤n≤N-1; (3.2)按照逐码片时分的方式，将N路并行码序列合成一路扩频码序列，码片时分复用后的扩频码序列记为：{CM,l}，当(i-1)N+1≤l≤i·N，
Figure FDA0003207287270000032
Figure FDA0003207287270000033
(3.2) According to the chip-by-chip time division method, the N parallel code sequences are synthesized into one spread spectrum code sequence, and the spread spectrum code sequence after chip time division multiplexing is recorded as: { CM,l }, when (i-1 )N+1≤l≤i·N,
Figure FDA0003207287270000032
Figure FDA0003207287270000033
 (3.3)通过码片时分后，{CM,l}的码速率增加为原来的N倍，记为N·Rc。(3.3) After passing the chip time division, the code rate of {C M,l } is increased to N times of the original, which is denoted as N·R c . 4.根据权利要求3所述的一种混合信息速率的码片时分导航信号调制方法，其特征在于：基带波形调制，通过以下方法得到：4. the chip time division navigation signal modulation method of a kind of mixed information rate according to claim 3, is characterized in that: baseband waveform modulation, obtains by the following method: (4.1)根据信号性能与兼容性需求，设计码片波形p(t)；(4.1) Design the chip waveform p(t) according to the signal performance and compatibility requirements; (4.2)将码片时分后的码序列{CM,l}与码片波形p(t)进行调制，基带波形调制后的信号表示为：(4.2) The code sequence {C M,l } after chip time division is modulated with the chip waveform p(t), and the modulated signal of the baseband waveform is expressed as:
Figure FDA0003207287270000034
Figure FDA0003207287270000034
 5.根据权利要求4所述的一种混合信息速率的码片时分导航信号调制方法，其特征在于：码片波形p(t)采用矩形码片波形或者二进制偏移载波波形。5 . The chip time-division navigation signal modulation method of a mixed information rate according to claim 4 , wherein the chip waveform p(t) adopts a rectangular chip waveform or a binary offset carrier waveform. 6 . 6.根据权利要求5所述的一种混合信息速率的码片时分导航信号调制方法，其特征在于：6. the chip time division navigation signal modulation method of a kind of mixed information rate according to claim 5 is characterized in that: 对于矩形码片波形，有：For rectangular chip waveforms, there are:
Figure FDA0003207287270000035
Figure FDA0003207287270000035
 对于二进制偏移载波波形，有For binary offset carrier waveforms, we have
Figure FDA0003207287270000036
Figure FDA0003207287270000036
 式中，fs为BOC调制的子载波频率，2fs/(N·Rc)为整数。In the formula, f s is the sub-carrier frequency of BOC modulation, and 2f s /(N·R c ) is an integer. 7.一种基于权利要求1所述的混合信息速率的码片时分导航信号调制方法实现的导航信号调制系统，其特征在于包括：7. A navigation signal modulation system realized based on the chip time-division navigation signal modulation method of the mixed information rate according to claim 1, is characterized in that comprising: 信道编码模块：将低速电文和高速电文分别进行信道编码，Channel coding module: channel coding the low-speed telegram and high-speed telegram respectively, PRN码映射模块：将经过信道编码的低速电文映射为一路PRN码序列，经过信道编码的高速电文映射为N-1路PRN码序列，共得到N路PRN码序列；PRN code mapping module: maps the channel-coded low-speed telegrams to one PRN code sequence, and the channel-encoded high-speed telegrams to N-1 PRN code sequences to obtain N PRN code sequences in total; 码片时分模块：将N路PRN码序列逐码片时分为一路信号；Chip time division module: divide the N-way PRN code sequence into one signal chip by chip time; 基带波形调制模块：将码片时分后得到的一路信号进行基带波形调制，得到基带信号。Baseband waveform modulation module: perform baseband waveform modulation on a signal obtained after chip time division to obtain a baseband signal. 8.根据权利要求7所述的导航信号调制系统，其特征在于：低速电文的原始信息速率为Rb,L，通过信道编码后符号速率为Rs,L，低速电文符号宽度为Ts,L＝1/Rs,L，编码效率为Rb,L/Rs,L，信道编码后的信息符号流为{dL,m}，dL,m∈{0,1}；8. The navigation signal modulation system according to claim 7 is characterized in that: the original information rate of the low-speed telegram is R b,L , the symbol rate after channel coding is R s,L , and the low-speed telegram symbol width is T s, L =1/R s,L , the coding efficiency is R b,L /R s,L , the information symbol stream after channel coding is {d L,m }, d L,m ∈{0,1}; 高速电文的原始信息速率为Rb,H，通过信道编码后符号速率为Rs,H，高速电文符号宽度为Ts,H＝1/Rs,H，编码效率为Rb,H/Rs,H，信道编码后的信息符号流为{dH,m}，dH,m∈{0,1}；信道编码后进行交织以提升抗信道衰落能力。The original information rate of the high-speed message is R b,H , the symbol rate after channel coding is R s,H , the symbol width of the high-speed message is T s,H =1/R s,H , and the coding efficiency is R b,H /R s,H , the information symbol stream after channel coding is {d H,m }, d H,m ∈ {0,1}; after channel coding, interleaving is performed to improve the ability to resist channel fading.
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