CN115941021A - LDPC-BICM-ID system based on power modulation under hypersonic aircraft telemetering SIMO channel - Google Patents
LDPC-BICM-ID system based on power modulation under hypersonic aircraft telemetering SIMO channel Download PDFInfo
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Abstract
The invention discloses an LDPC-BICM-ID system based on power modulation under a hypersonic aerocraft telemetering SIMO channel, which comprises a modeling module, a system model construction module, a sending module and a receiving module, wherein the modeling module is used for establishing a system model; the modeling module is used for modeling a plasma sheath channel of the hypersonic aircraft; the system model construction module is used for constructing a large-scale SIMO (simple inertial modeling and optimization) telemetry channel model of the hypersonic aircraft; the sending module comprises LDPC coding, interleaving and adaptive optimized power modulation; the receiving module comprises incoherent detection, probability density function estimation based on an RRJ-MCMC algorithm, soft information calculation and iterative decoding. The invention realizes high-reliability and high-efficiency information transmission under the telemetering SIMO channel of the hypersonic aircraft.
Description
Technical Field
The invention belongs to the technical field of aerospace measurement and control communication, and particularly relates to a power modulation-based LDPC-BICM-ID system under a hypersonic aerocraft telemetering SIMO channel.
Background
When an aircraft flies at a hypersonic speed or reenters the earth atmosphere, a plasma layer (plasma sheath) coated on the surface of the aircraft absorbs, reflects and scatters Electromagnetic (EM) waves, which causes the electromagnetic wave signals to be remarkably attenuated, and even the aircraft measurement and control communication is interrupted (black barrier). Furthermore, for the plasma sheath, an unstable flow field around the hypersonic vehicle may cause the plasma sheath to introduce highly dynamic plasma turbulence, and such highly dynamic channel variations may also cause communication degradation. It has been demonstrated that the plasmonic sheath channel exhibits non-stationary, deep fading, fast time varying characteristics, and is accompanied by a parasitic modulation effect that is dual in amplitude and phase. Therefore, a communication black-barrier mitigation method that accommodates the channel variation of the plasma sheath has attracted a wide attention. The communication method for alleviating the black barrier mainly includes increasing the transmission power, increasing the communication frequency or adapting the communication strategy/method. The state self-adaptive adjustment communication strategy of the plasma sheath channel is a self-adaptive communication method, and for example, a code rate, a coding parameter and the like are self-adaptively adjusted by utilizing channel estimation and prediction conditions, and the methods can relieve black faults. Modulation and demodulation methods that accommodate the channel variations of the plasma sheath are also of interest, as are power modulation methods proposed in the literature. However, there is a lack of breakthrough in designing joint demodulation and decoding techniques based on new modulation methods suitable for the plasmonic sheath, and the joint gain brought by the joint demodulation and decoding techniques has not been exploited. The plasmonic sheath channel is unknown because it has high dynamic, non-stationary characteristics and is accompanied by parasitic modulation effects, making it difficult to obtain real-time state of the channel at the receiving end, and causes constellation rotation of the PSK signal, resulting in loss of demodulation. Aiming at the problems of unknown channel information and constellation rotation, a multi-antenna SIMO technology and a power modulation method can be introduced, and in order to improve the telemetry performance, a joint demodulation decoding framework can be built: LDPC-BICM-ID system.
As a typical joint demodulation and decoding framework, the LDPC-BICM-ID system generally adopts a 4-QAM or QPSK modulation method, while the 4-QAM or QPSK modulation scheme is generally used in the fields of mobile communication, satellite communication, remote telemetry, deep space exploration, and the like, but due to the influence of a sheath parasitic modulation effect, these modulation methods are not suitable for a high-speed sound velocity scenario. In other words, the traditional method for calculating soft information is difficult to be applied to the LDPC-BICM-ID system design based on power modulation in a super scene. Therefore, the effective combination of the power modulation under the multi-antenna SIMO technology and the LDPC-BICM-ID system is a great difficulty, and the joint gain caused by the effective combination is not excavated yet. Meanwhile, the prior art does not fully utilize airspace resources.
Disclosure of Invention
In order to overcome the defects in the prior art, the invention aims to provide the LDPC-BICM-ID system based on power modulation under the hypersonic aerocraft telemetering SIMO channel, so that high-reliability and high-efficiency information transmission under the hypersonic aerocraft telemetering SIMO channel is realized.
In order to achieve the purpose, the invention adopts the technical scheme that:
an LDPC-BICM-ID system based on power modulation under a hypersonic aerocraft telemetering SIMO channel comprises a modeling module, a system model construction module, a sending module and a receiving module;
the modeling module is used for modeling a plasma sheath channel of the hypersonic aircraft;
the system model building module is used for building a large-scale SIMO (simple inertial modeling unit) telemetry channel model of the hypersonic aerocraft, wherein the telemetry channel comprises a plasma sheath channel and a Rice fading channel;
the sending module comprises LDPC coding, interleaving and adaptive optimized power modulation;
the receiving module comprises incoherent detection, probability density function estimation based on RRJ-MCMC algorithm, soft information calculation and iterative decoding;
the relationship of the four modules: a modeling module of a hypersonic aircraft plasma sheath channel is a part of a system module (a telemetry channel comprises a plasma sheath channel and a rice fading channel), a communication system is researched on the basis that the system module constructs a complete SIMO telemetry channel, and a transmitting module and a receiving module form a complete transceiving communication module.
Modeling a plasma sheath channel of the hypersonic aircraft, and establishing a layered electron density model of a time-varying plasma sheath; and calculating a plasma sheath transmission coefficient;
the method for constructing the large-scale downlink SIMO telemetry channel model of the hypersonic aircraft comprises a single antenna at the end of the hypersonic aircraft and a multi-antenna receiving station.
The modeling method of the plasma sheath channel specifically comprises the following steps:
(1) Establishing a layered electron density model of a time-varying plasma sheath: non-uniform plasma sheath thickness z near the input hypersonic aircraft antenna window max The total number of plasma sheath layers N and the thickness of each plasma sheath layer d m M is plasma sheath layering serial number m =1,2, …, N, plasma sheath time-varying time T, and according to the electron density of the plasma sheath, the plasma sheath obeys double-Gaussian distribution along the direction vertical to the antenna window of the aircraft, and a first Gaussian function influence parameter c 1 And a second Gaussian function influence parameter c 2 Peak electron density Ne peak The peak electron density is z in z-axis peak ，Ne peak Determining the electron density distribution function of the sheath of the time-varying plasma along the time direction according to the distribution rule of the sinusoidal distributionTo establish a time-varying plasma sheath electron density model Ne dyn (z,t)；
(2) Calculating a plasma sheath channel T dyn (t,f 0 ): carrier frequency f of input communication signal 0 Time parameter t, electron mass m e The electron impact frequency v of the time-varying plasma sheath, the eigenwave impedance z of the layers of the plasma sheath m (m =1,2, …, N), intrinsic wave impedance z of vacuum 0 Vacuum dielectric constant ε 0 Angular frequency ω =2 π f 0 Using a time-varying plasma sheath electron density model Ne dyn (z, T) calculating the time-varying transmission coefficient T of the plasma sheath by an equivalent transmission line method dyn (t,f 0 )；
Calculating plasma sheath frequency ω p (z,t)：
Calculating the complex dielectric constant epsilon of the plasma sheath r (z,t)：
Calculating the propagation coefficient k (z, t):
The amplitude H (t) and phase phi (t) of the plasmonic sheath channel are respectively:
H(t)＝exp(-∫α(z,t)dz),
obtaining a plasma sheath channel:
the method for constructing the large-scale SIMO telemetry channel model of the hypersonic aircraft comprises the following steps:
the system consists of a hypersonic aircraft terminal single antenna and a multi-antenna receiving station, wherein the receiving station is provided with n (n → ∞) antennas, and the system receives signals in one time slot;
y＝hx+v；
where y is a received signal vector of dimension n x 1, x is a transmitted signal (the transmitted signal x is obtained after LDPC encoding, interleaving and optimized power modulation of information bits), h is a channel matrix of dimension n x 1,
by matrix elements h i Is formed wherein>
Each element of (a) is subjected to a Lais fading distribution, alpha is a plasma sheath channel, v is n × 1 receiving end complex Gaussian white noise, each element of v is subjected to a circularly symmetric complex Gaussian CSCG distribution, the mean value is zero, and the variance is sigma 2 I.e. v i ～CN(0，σ 2 )，i＝1，2，…，n。
The adaptive optimized power modulation: transmitting symbols
Wherein p is k ∈P＝{p 1 ，p 2 ，···，p L Is the power of the kth symbol, P is the codebook (i.e., the transmit constellation), L is the base of P, P is the base of P k (k =1,2, ·, L) with equal probability of being transmitted and satisfying an average power constraint ·>
According to plasmaAverage power attenuation q of sub-sheath channel 2 And the progressive nature of the downlink telemetry channel.
The adaptive design method for transmitting the constellation P (i.e., codebook) specifically includes:
(1) For p k ，
Let p be k Demodulation interval (d)>
Wherein d is l，k >0，d r，k >0，a k Indicates the demodulation boundary r (p) k )+d r，k Let us order
Independent random variable U from 0 mean k Implementation, U k Has a moment mother function of
Make/combine>
For optimizing constellation P opt Is provided with
Order to
(2) Searching for the highest t satisfying the power constraint using Algorithm 1 and Algorithm 2 opt And corresponding optimal constellation P opt The algorithm 1 is used for initializing and updating a t value, and the t value obtained by the algorithm 1 is substituted into the algorithm 2; searching a sending constellation under the current t value by using an algorithm 2; algorithm 1Updating the value t according to whether the constellation obtained by the algorithm 2 meets the power constraint condition; algorithms 1 and 2 are cycled until the value of t meets the set precision 10 -3 To obtain the highest t of which the output meets the power constraint opt And corresponding optimal constellation P opt 。
The algorithms 1 and 2 are specifically as follows:
algorithm 1: initialization t l ＝0，t u ＝∞，
Substituting t into algorithm 2; if the algorithm 2 constellation satisfies the power constraint condition, let t l = t; if the algorithm 2 constellation does not satisfy the power constraint condition, let t u = t; continuously substituting the obtained t value into the algorithm 2 to obtain the t value again, and circulating the algorithm 1 until the t value meets the set precision 10 -3 ；
And 2, algorithm: let p be 1 ＝0，
Selection of p 2 So that J (p) is 2 ) Is t, and
this process is performed in order until p is found L (ii) a Checking whether a power constraint condition is satisfied; if yes, the constellation is retained, t is incremented by algorithm 1 and the process is repeated; if not, the constellation should be discarded, t is reduced using Algorithm 1 and the process repeated.
The non-coherent demodulation, soft information Probability Density Function (PDF) estimation and soft information calculation:
a. calculate the average power of the received vector y:
b. soft information Probability Density Function (PDF) estimation:
because of the high dynamic and deep fading characteristics of the plasma sheath channel, | | y | | non-conducting phosphor 2 The conditional probability density function of/n is unknown, and the receiving station end adopts variableEstimation of the inverse-jump Monte Carlo (RJ-MCMC) algorithm
The Conditional Probability Density Function (CPDF);
in order to demodulate the transmitted symbols correctly, the receiving station needs to know the probability density function f (c) of the reception statistic c. However, the receiving statistic c is randomly disturbed along with the change of the non-stationary plasma channel, the receiving station has difficulty in obtaining the prior information of the telemetering SIMO channel link, and the receiving statistic c can be regarded as a multi-state quasi-stationary random variable and can be described by a mixed Gaussian process
Adopting RJ-MCMC algorithm to pair f (c) and f (c) k |x k ) The estimation is performed as follows:
wherein L is the number of states, ω k ,μ k And σ k (k =1, …, L) are the steady state probability, mean and standard deviation, respectively, of the kth gaussian distribution;
the soft output of the map detector can be expressed as:
wherein the content of the first and second substances,
is u i A subset of transmitted signals of = k, f (c | x) is a conditional probability density function, L a,i (i)＝In(P(u i ＝0)/P(u i ＝1)),n＝0,…,N-1；
Iterative decoding between the MAP detector and the BP decoder is performed until a maximum number of iterations is performed.
The LDPC-BICM-ID system based on power modulation under the hypersonic aerocraft telemetering SIMO channel is used for a high-speed aerocraft.
The invention has the beneficial effects that:
the invention provides an LDPC-BICM-ID system based on orthogonal binary space-frequency modulation aiming at an MIMO telemetry channel (hypersonic aerocraft MIMO channel for short) combining a plasma sheath channel and a Rayleigh channel or a Rice channel, and high-reliability and high-efficiency communication is realized under the telemetry channel. The scheme can improve the communication quality and effectively relieve the black barrier.
Aiming at the problem that a receiving end of an MIMO channel of a hypersonic aerocraft is unknown to channel information and a PSK signal constellation rotates, the multi-antenna MIMO technology is adopted to effectively improve the channel capacity and the communication performance, and novel efficient orthogonal binary space-frequency modulation is designed by utilizing the progressive orthogonality of a Rayleigh channel under multiple antennas or the progressive correlation of a Rice channel to solve the problem. Meanwhile, in order to further improve the remote measuring performance, an LDPC-BICM-ID system based on orthogonal binary system space frequency modulation is built, demodulation and decoding can be carried out in a combined mode, high-reliability and high-efficiency signal transmission of an MIMO channel of the hypersonic aerocraft is achieved, the communication quality can be improved, and black obstacles can be effectively relieved.
Drawings
FIG. 1 is a flow chart of the present invention.
Fig. 2 is a system block diagram of the present invention.
FIG. 3 is a diagram of a hypersonic aircraft large scale SIMO system scenario.
Fig. 4 is a time-varying graph of plasma sheath electron density.
Fig. 5 is a graph of amplitude versus time for a plasma sheath channel.
FIG. 6 is a schematic diagram of the change of the bit error rate of the LDPC-BICM-ID system based on power modulation along with the signal-to-noise ratio under the hypersonic aerocraft telemetry SIMO channel when the receiving antenna n = 10.
FIG. 7 shows the bit error rate with gamma of the LDPC-BICM-ID system based on power modulation under the hypersonic aerocraft telemetry SIMO channel with different electron density peaks b Simulation analysis of the change in (c).
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
Aiming at the problems in the prior art, the invention provides an LDPC-BICM-ID system based on power modulation under a hypersonic aerocraft telemetering SIMO channel, and the invention is described in detail by combining the attached drawings
As shown in fig. 1, the LDPC-BICM-ID system based on power modulation under the hypersonic aerocraft telemetry SIMO channel provided by the embodiment of the present invention includes the following steps:
1 modeling a hypersonic aerocraft plasma sheath channel;
2. constructing a large-scale SIMO system model of the hypersonic aircraft;
3. the system sending module comprises LDPC coding, interleaving and adaptive optimized power modulation;
4. and the system receiving module comprises incoherent detection, probability density function estimation based on an RRJ-MCMC algorithm, soft information calculation and iterative decoding.
The technical scheme of the invention is further described in the following with reference to the attached drawings.
The scheme can realize high-reliability and high-efficiency information transmission under the telemetering channel of the hypersonic aircraft, and is an effective means for relieving black obstacles.
As shown in fig. 1 and fig. 2, the method includes the following steps:
step 1: modeling of hypersonic aircraft plasma sheath channel:
1) Establishing a layered electron density model of a time-varying plasma sheath: non-uniform plasma sheath thickness Z near the antenna window of the input hypersonic aerocraft, total number of plasma sheath layers N and each plasma sheath layer thickness d m M is plasma sheath layering serial number m =1,2, …, N, plasma sheath time-varying time T, and according to the electron density of the plasma sheath, the plasma sheath obeys double-Gaussian distribution along the direction vertical to the antenna window of the aircraft (set as the z axis), and a first Gaussian function influence parameter c 1 And a second Gaussian functionParameter c 2 Peak electron density Ne peak The peak electron density is z in z-axis peak 。Ne peak Determining the electron density distribution function of the time-varying plasma sheath according to the distribution rule of sinusoidal distribution along the time direction, and establishing a time-varying plasma sheath electron density model Ne dyn (z,t)；
2) Calculating the transmission coefficient T of the plasma sheath dyn (t,f 0 ): carrier frequency f of input communication signal 0 Electron mass m e Frequency of electron impact v of time-varying plasma sheath en Intrinsic wave impedance z of the layers of the plasma sheath m (m =1,2, …, N), intrinsic wave impedance z of vacuum 0 Using a time-varying plasma sheath electron density model Ne dyn (z, T) calculating the time-varying transmission coefficient T of the plasma sheath by an equivalent transmission line method dyn (t,f 0 ) (ii) a The magnitude of the transmission coefficient will be calculated and the result assigned to the plasma sheath channel B = diag { α } 1 ,α 2 }。
Step 2: constructing a large-scale SIMO system model of the hypersonic aircraft:
as shown in FIG. 3, the system is composed of a hypersonic aircraft terminal single antenna and a multi-antenna receiving station, wherein the receiving station is provided with n (n → ∞) antennas, and the system receives signals in a time slot at the receiving station terminal baseband signal
y＝hx+v；
Where y is an M × 1-dimensional received signal vector, x is a transmission signal (obtained after LDPC coding, interleaving, and optimal power modulation of information bits), h is an n × 1-dimensional channel matrix,
by matrix elements h i Is formed wherein>
Subject to a leis fading profile, a is the plasma sheath channel obtained from step 1. v is complex Gaussian white noise of n x 1 receiving end, and each element of v obeys to followThe distribution of the CSCG is circularly symmetric and complex Gaussian, the mean value is zero, and the variance is sigma 2 I.e. v i ～CN(0，σ 2 )，i＝1，2，…，n；
And step 3: the system sending module comprises LDPC coding, interleaving and adaptive optimized power modulation;
optimized power modulation: transmitting symbols
Wherein p is k ∈P＝{p 1 ，p 2 ，···，p L Is the power of the kth symbol, P is the codebook, L is the base of P, P k (k =1,2, ·, L) with equal probability of being transmitted and satisfying an average power constraint ·>
Mean power attenuation q in terms of plasma sheath channel 2 And designing optimized P according to the progressive characteristics of the downlink telemetry channel.
The adaptive design method for sending the constellation P specifically comprises the following steps:
(1) For p k ，
Let p be k Demodulation interval (d)>
Wherein d is l，k >0，d r，k >0，a k Indicates the demodulation boundary r (p) k )+d r，k Let us order
Independent random variable U from 0 mean k Implementation, U k Has a function of->
Make->
For optimizing constellation P opt Is provided with
Order to
(2) Searching for the highest t satisfying the power constraint using Algorithm 1 and Algorithm 2 opt And corresponding optimal constellation P opt The algorithm 1 is used for initializing and updating a t value, and the t value obtained by the algorithm 1 is substituted into the algorithm 2; searching a sending constellation under the current t value by using an algorithm 2; the algorithm 1 updates the value t according to whether the constellation obtained by the algorithm 2 meets the power constraint condition; algorithms 1 and 2 are cycled until the value of t meets the set precision 10 -3 To obtain the highest t of which the output meets the power constraint opt And corresponding optimal constellation P opt (ii) a Algorithms 1 and 2 are specifically as follows:
algorithm 1: initialization t l ＝0，t u ＝∞，
Substituting t into algorithm 2; if the algorithm 2 constellation meets the power constraint condition, let t l = t; if the algorithm 2 constellation does not satisfy the power constraint condition, let t u = t; continuously substituting the obtained t value into the algorithm 2 to obtain the t value again, and circulating the algorithm 1 until the t value meets the set precision 10 -3 ；
And 2, algorithm: let p be 1 ＝0，
Selection of p 2 So that J (p) is 2 ) Is t, and
this process is performed in order until p is found L (ii) a Checking whether a power constraint condition is met; if yes, the constellation is retained, t is increased by using an algorithm 1, and the process is repeated; if not, the constellation should be discarded, t is reduced using Algorithm 1 and the process repeated.
And 4, a receiving module comprises incoherent detection, probability density function estimation based on the RRJ-MCMC algorithm, soft information calculation and iterative decoding.
a. Non-coherent demodulation: calculate the average power of the received vector y:
b. soft information Probability Density Function (PDF) estimation:
in order to correctly demodulate the transmitted symbols, the receiving station needs to know the probability density function f (c) of the reception statistic c. However, the receive statistic c perturbs randomly with changes in the non-stationary plasma channel, and it is difficult for the receiving station to obtain a priori information about the telemetry SIMO channel link. The received statistic c can be regarded as a multi-state quasi-stationary random variable which can be described by a mixed Gaussian process
The RJ-MCMC algorithm is adopted to pair f (c) and f (c) in the text k |x k ) The estimation is performed as follows:
wherein L is the number of states, ω k ,μ k And σ k (k =1, …, L) are the steady state probability, mean and standard deviation, respectively, of the kth gaussian distribution.
Soft output of the map detector may be expressed as
Wherein the content of the first and second substances,
is u i A subset of transmitted signals of = k, f (c | x) is a conditional probability density function, L a,i (i)＝In(P(u i ＝0)/P(u i ＝1)),n＝0,…,N-1。
Iterative decoding between the MAP detector and the BP decoder is performed until a maximum number of iterations is performed.
The technical effects of the present invention will be explained below by simulation.
Simulation conditions are as follows:
layered electron density model of time-varying plasma sheath: the thickness Z =0.06m of the non-uniform plasma sheath near the antenna window of the hypersonic aerocraft, the total number N =100 of plasma sheath layering, and the thickness d of each layering of the plasma sheath m =0.06cm, m is a plasma sheath layer number m =1,2, …, N, and a plasma sheath time-varying time T =0.1s, and a first gaussian function influencing parameter c follows a double-gaussian distribution in a direction perpendicular to an aircraft antenna window (set as z-axis) according to an electron density of the plasma sheath 1 ＝2.56×10 3 And a second Gaussian function influence parameter c 2 ＝3.55×10 3 Peak electron density Ne peak ＝1×10 19 m -3 The peak electron density is z in z-axis peak =0.036m. Determining the electron density distribution function of the time-varying plasma sheath, and establishing a time-varying plasma sheath electron density model Ne dyn (z,t)；
Calculating the transmission coefficient T of the plasma sheath dyn (t,f 0 ): carrier frequency f of input communication signal 0 =32GHz, carrier angular frequency ω =2 pi f 0 Mass m of electrons e ＝9.10953 -31 kg, electron impact frequency v of time varying plasma sheath en =1GHz, calculating plasmaDaughter frequency
And a complex dielectric constant->
Giving the intrinsic wave impedance of each layer of the plasma sheath +>
The intrinsic wave impedance of the vacuum->
Electron density model Ne using time-varying plasma sheath dyn (z, T) calculating the time-varying transmission coefficient T of the plasma sheath by an equivalent transmission line method dyn (t,f 0 )；
Simulation results and analysis:
referring to fig. 4, in fig. 4, a time-varying plot of plasma sheath electron density is depicted. It is seen that small scale jitter occurs in the plasma sheath electron density affected by the flow perturbation.
Referring to fig. 5, in fig. 5, the amplitude result of the transmission coefficient of the electric wave through the plasma at the carrier wave 32GHz is depicted, and the high dynamic disturbance occurs in the amplitude of the transmission coefficient of the electric wave through the plasma affected by the disturbance of the electron density or the like.
When 2,n =10 is simulated, the error rate of the LDPC-BICM-ID system based on power modulation under the hypersonic aerocraft telemetering SIMO channel changes along with the signal-to-noise ratio
Simulation conditions are as follows:
the plasma sheath parameters used in simulation 1 were carrier 28GHz, power modulation order L =8, and electron density peak Ne peak ＝6×10 18 m -3 The rice factor K =10, the number of receiving antennas n =40, the ldpc code rate R c =1/2 and code length L c =528. This patent uses simulation 3The efficient prototype graph LDPC code recommended in the GPP TS 38.212 protocol. Firstly, the LDPC-BICM-ID system based on power modulation is compared with a corresponding uncoded power modulation system, and three constellation schemes are considered: minimum distance constellation P min ASK constellation P ASK And optimizing the constellation P opt . The rice channel parameters are shown in table 1:
table 1: rice channel parameter
| Major diameter maximum doppler | Maximum doppler of other paths | Sampling frequency | Leise factor |
| 600kHz | 500kHz | ||
| 10 7 |
10 |
Simulation results and analysis:
referring to fig. 6, the use of a minimum distance constellation P is depicted in fig. 6 min ASK constellation P ASK And optimizing the constellation P opt In time, the change situation of the bit error rate of the LDPC-BICM-ID system based on power modulation along with the signal-to-noise ratio can be seen to optimize the constellation P opt Superior to ASK constellation P ASK Better than minimum distance constellation P min And the LDPC-BICM-ID system based on power modulation obtains huge joint demodulation decoding gain compared with the system based on pure power modulation.
Simulation conditions are as follows:
the plasma sheath parameter was the parameter in simulation 1, carrier 28GHz, power modulation order L =2,n =10,r c =1/2 and L c =528. The rice channel parameters are shown in table 1:
table 1: rice channel parameter
| Major diameter maximum doppler | Maximum doppler of other paths | Sampling frequency | Leise |
| 600kHz | 500kHz | ||
| 10 7 Hz | K |
Simulation results and analysis:
referring to FIG. 7, ne is depicted in FIG. 7 as varying peak Decoding performance of LDPC-BICM-ID system based on power modulation under numerical channel along with signal-to-noise ratio gamma b A change in (c). As shown, ne peak From 2X 10 18 m -3 Increase to 1 × 10 19 m -3 Error rate is lower than 10 -6 Desired gamma b An increase of about 12db. This is because of Ne peak The larger the channel is, the stronger the channel non-stationarity is, and the worse the system performance is; and following Ne peak The relative strength of the received signal decreases, resulting in a rapid increase in the system error rate.
FIGS. 6 and 7 demonstrate the efficient performance of the LDPC-BICM-ID system based on power modulation under the SIMO channel.
Simulation shows that the LDPC-BICM-ID system based on power modulation under the hypersonic aircraft telemetry SIMO channel can obviously improve the error rate performance of communication under the aircraft telemetry channel and improve the communication quality.
The invention discloses an LDPC-BICM-ID system based on power modulation under a hypersonic aerocraft telemetering SIMO channel. Firstly, establishing a hypersonic aircraft plasma sheath channel model and establishing a hypersonic aircraft large-scale SIMO telemetry system model. The system sending end carries out LDPC coding, interleaving and power modulation methods; the receiving end of the system carries out incoherent demodulation, soft information probability density function estimation, the MAP detector carries out soft information calculation, and the soft information is substituted into a BICM-ID iterative decoding frame. Simulation shows that the method can improve the communication quality by increasing the number of the base station antennas and improving the signal-to-noise ratio. The LDPC-BICM-ID system based on power modulation under the hypersonic aircraft telemetering SIMO channel can obviously improve the error rate performance of hypersonic flight telemetering, improve the communication quality and relieve the communication black barrier.
Aiming at a hypersonic aerocraft SIMO (SIMO) remote measuring channel (referred to as a hypersonic aerocraft SIMO remote measuring channel for short) combining a plasma sheath channel and a Leise channel, the invention designs an LDPC-BICM-ID system based on a novel optimized power modulation scheme by utilizing the gradual correlation of the SIMO channel.
Aiming at the problem of communication 'black barrier', the invention adopts an optimized power modulation method to resist the parasitic modulation effect of a plasma sheath channel, a suitable LDPC-BICM-ID system is built, a receiving end carries out joint demodulation and decoding processing to obtain high-quality joint gain, so that high-reliability and high-efficiency wireless communication is realized under the plasma sheath channel, and the black barrier is effectively relieved.
Claims (9)
1. An LDPC-BICM-ID system based on power modulation under a hypersonic aerocraft telemetering SIMO channel is characterized by comprising a modeling module, a system model construction module, a sending module and a receiving module;
the modeling module is used for modeling a hypersonic aircraft plasma sheath channel;
the system model building module is used for building a large-scale SIMO (simple inertial modeling unit) telemetry channel model of the hypersonic aerocraft, wherein the telemetry channel comprises a plasma sheath channel and a Rice fading channel;
the sending module comprises LDPC coding, interleaving and adaptive optimized power modulation;
the receiving module comprises incoherent detection, probability density function estimation based on an RRJ-MCMC algorithm, soft information calculation and iterative decoding.
The relationship of the four modules: a modeling module of a hypersonic aircraft plasma sheath channel is a part of a system module (a telemetry channel comprises a plasma sheath channel and a Rice fading channel), a communication system is researched on the basis that the system module constructs a complete SIMO telemetry channel, and a transmitting module and a receiving module form a complete transceiving communication module.
2. The power modulation-based LDPC-BICM-ID system under the hypersonic aerocraft telemetry SIMO channel according to claim 1, wherein modeling of the hypersonic aerocraft plasma sheath channel is establishing a layered electron density model of a time-varying plasma sheath; calculating the transmission coefficient of the plasma sheath;
the method for constructing the large-scale downlink SIMO telemetry channel model of the hypersonic aircraft comprises a single antenna at the end of the hypersonic aircraft and a multi-antenna receiving station.
3. The system of claim 1, wherein the modeling method for the plasma sheath channel specifically comprises:
(1) Establishing a time-varying plasma sheathLayered electron density model of the sleeve: non-uniform plasma sheath thickness z near the antenna window of the input hypersonic aircraft max A total number of plasma sheath layers N and a thickness of each plasma sheath layer d m M is plasma sheath layering serial number m =1,2, …, N, plasma sheath time-varying time T, and according to the electron density of the plasma sheath, the plasma sheath obeys double-Gaussian distribution along the direction vertical to the antenna window of the aircraft, and a first Gaussian function influence parameter c 1 And a second Gaussian function influence parameter c 2 Peak electron density Ne peak The peak electron density is z in z-axis peak ，Ne peak Determining an electron density distribution function of the time-varying plasma sheath along the time direction according to the distribution rule of sinusoidal distribution, and establishing a time-varying plasma sheath electron density model Ne (z, t);
(2) Calculating the plasma sheath channel T (T, f) 0 ): carrier frequency f of input communication signal 0 Time parameter t, electron mass m e The electron impact frequency v of the time-varying plasma sheath, the eigenwave impedance z of the layers of the plasma sheath m (m =1,2, …, N), intrinsic wave impedance of vacuum z 0 Vacuum dielectric constant ε 0 Angular frequency ω =2 π f 0 Using the time-varying plasma sheath electron density model Ne (z, T), the plasma sheath channel T is calculated by the following procedure dyn (t,f 0 ) (ii) a Calculating plasma sheath frequency omega p (z,t)：
Calculating the complex dielectric constant epsilon of the plasma sheath r (z,t)：
Calculating the propagation coefficient k (z, t):
The amplitude H (t) and phase phi (t) of the plasmonic sheath channel are respectively:
H(t)＝exp(-∫α(z,t)dz),
obtaining a plasma sheath channel:
4. the LDPC-BICM-ID system based on power modulation under the telemetering SIMO channel of the hypersonic aerocraft according to claim 1, wherein the building of the large-scale SIMO telemetering channel model of the hypersonic aerocraft specifically comprises the following steps:
the system consists of a hypersonic aircraft terminal single antenna and a multi-antenna receiving station, wherein the receiving station is provided with n, n → ∞ antennas, and the system receives signals in one time slot:
y＝hx+v；
wherein y is a n × 1-dimensional received signal vector, x is a transmission signal, information bits are subjected to LDPC coding, interleaving and optimized power modulation to obtain the transmission signal x, h is an n × 1-dimensional channel matrix,
by matrix elements h i Is formed wherein>
Each of (1)Each element obeys Lace fading distribution, alpha is a plasma sheath channel, v is n multiplied by 1 receiving end complex Gaussian white noise, each element of v obeys circularly symmetric complex Gaussian CSCG distribution, the mean value is zero, and the variance is sigma 2 I.e. v i ～CN(0，σ 2 )，i＝1，2，…，n。
5. The system of claim 1, wherein the adaptive optimized power modulation is based on LDPC-BICM-ID modulation under hypersonic aircraft telemetry SIMO channel: transmitting symbols
Wherein p is k ∈P＝{p 1 ，p 2 ，···，p L Is the power of the kth symbol, P is the codebook, L is the base of P, P k (k =1,2, ·, L) with equal probability of being sent and satisfying the average power constraint ·>
Mean power attenuation q in terms of plasma sheath channel 2 And the progressive nature of the downlink telemetry channel.
6. The LDPC-BICM-ID system based on power modulation under the SIMO channel according to claim 5, wherein the adaptive design method for sending constellation P specifically comprises:
(1) For p k ，
Let p be k Is demodulated and/or demodulated>
Wherein d is l，k >0，d r，k >0，a k Indicates the demodulation boundary r (p) k )+d r，k Let us order
Independent random variable U from 0 mean k Implementation, U k Has a moment mother function of
Make->
For optimizing constellation P opt Is provided with
Make->
(2) Searching for the highest t satisfying the power constraint using Algorithm 1 and Algorithm 2 opt And corresponding optimal constellation P opt The algorithm 1 is used for initializing and updating a t value, and the t value obtained by the algorithm 1 is substituted into the algorithm 2; searching a sending constellation under the current t value by using an algorithm 2; the algorithm 1 updates the value t according to whether the constellation obtained by the algorithm 2 meets the power constraint condition; algorithms 1 and 2 are cycled until the value of t meets the set precision 10 -3 To obtain the highest t of which the output meets the power constraint opt And corresponding optimal constellation P opt 。
7. The system of claim 6, wherein the algorithms 1 and 2 are specifically as follows:
algorithm 1: initialization t l ＝0，t u ＝∞，
Substituting t into algorithm 2; if the algorithm 2 constellation meets the power constraint condition, let t l = t; if the algorithm 2 constellation does not satisfy the power constraint condition, let t u = t; continuously substituting the obtained t value into the algorithm 2 to obtain the t value again, and circulating the algorithm 1 until the t value meets the set precision 10 -3 ；
And 2, algorithm: let p be 1 ＝0，
Selection of p 2 So that J (p) is 2 ) Is t, and
this process is performed in sequence until p is found L (ii) a Checking whether a power constraint condition is met; if yes, the constellation is retained, t is incremented by algorithm 1 and the process is repeated; if not, the constellation should be discarded, t is reduced using Algorithm 1 and the process repeated.
8. The system of claim 1, wherein the non-coherent demodulation, soft information Probability Density Function (PDF) estimation, and soft information calculation are performed by a power modulation based LDPC-BICM-ID system under hypersonic aircraft telemetry SIMO channel:
a. calculate the average power of the received vector y:
b. soft information Probability Density Function (PDF) estimation:
because of the high dynamic and deep fading characteristics of the plasma sheath channel, | | y | | non-conducting phosphor 2 The conditional probability density function of/n is unknown, and the receiving station end adopts a variable reverse-jump Monte Carlo (RJ-MCMC) algorithm to estimate
The Conditional Probability Density Function (CPDF);
in order to correctly demodulate the transmitted symbols, the receiving station needs to know the probability density function f (c) of the reception statistic c, however, the reception statistic c is randomly disturbed along with the change of the non-stationary plasma channel, the receiving station has difficulty in obtaining the prior information of the telemetering SIMO channel link, and the reception statistic c can be regarded as a multi-state quasi-stationary random variable which can be described by a mixed Gaussian process
Adopting RJ-MCMC algorithm to pair f (c) and f (c) k |x k ) The estimation is performed as follows:
wherein L is the number of states, ω k ,μ k And σ k (k =1, …, L) are the steady state probability, mean and standard deviation, respectively, of the kth gaussian distribution;
the soft output of the map detector can be expressed as:
wherein the content of the first and second substances,
is u i = k subset of the transmitted signal, f (c | x) is the conditional probability density function, L a,i (i)＝In(P(u i ＝0)/P(u i ＝1)),n＝0,…,N-1；
Iterative decoding between the MAP detector and the BP decoder is performed until a maximum number of iterations is performed.
9. The system of any of claims 1-8, wherein the system of LDPC-BICM-ID based on power modulation in the telemetric SIMO channel of hypersonic aircraft is used for high-speed aircraft.
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