Emergency broadcast communication method in complex electromagnetic environment

Abstract

The invention discloses an emergency broadcast communication method in a complex electromagnetic environment, and the method comprises the following steps: S1, a transmitter generates a broadcast signal, carries out the digital-to-analog conversion and radio frequency operation of the broadcast signal, and then transmits the broadcast signal; s2, assisting a receiver to carry out real-time broadband detection, receiving a self-interference signal and an environment signal at the same time, and carrying out broadband folding processing on the received signal; s3, the assistance receiver performs the same broadband folding operation on the transmitted baseband signal to generate a reference signal, and then performs interference reconstruction and interference cancellation; and S4, after the interference is cancelled, the auxiliary receiver senses the residual signal, and then decides the working frequency of the whole emergency broadcast platform according to an interference sensing result. According to the invention, the working frequency of the emergency broadcast platform is decided through real-time reconnaissance of the broadband signal, and the anti-interference capability of the emergency broadcast platform is improved.

Description

Technical Field

[0001] The invention relates to an emergency communication system, and in particular to an emergency broadcast communication method in a complex electromagnetic environment. Background Art

[0002] In emergency broadcasting scenarios, such as counter-terrorism operations, the dense deployment of electromagnetic spectrum equipment (including radios, navigation systems, and jammers) can cause serious electromagnetic interference. To ensure reliable communication in complex electromagnetic environments, the emergency communication platform introduces an assisting receiver to conduct reconnaissance of environmental signals and assist in deciding the optimal frequency for emergency broadcasting. The assisting receiver uses broadband folded sampling technology to sense environmental signals within a wide frequency band. However, during real-time reconnaissance, broadcast signals and environmental signals exist simultaneously, and the receiver must face the self-interference problem caused by high-power signals from the transmitter. Summary of the invention

[0003] The purpose of the present invention is to overcome the shortcomings of the prior art and provide an emergency broadcast communication method in a complex electromagnetic environment. By real-time detection of broadband signals, the operating frequency of the emergency broadcast platform is determined, thereby improving the anti-interference ability of emergency broadcast communication.

[0004] The object of the present invention is achieved through the following technical solution: an emergency communication method in a complex electromagnetic environment, comprising the following steps:

[0005] S1. The transmitter generates a broadcast signal, performs digital-to-analog conversion and RF operation on it before transmitting;

[0006] S2. Assist the receiver to perform real-time broadband detection, receive self-interference signals and environmental signals at the same time, and perform broadband folding processing on the received signals;

[0007] S3. Assist the receiver to generate a reference signal by performing the same broadband folding operation on the transmitted baseband signal, and then perform interference reconstruction and interference cancellation;

[0008] S4. Assist the receiver to sense the residual signal after the interference is cancelled, and then make a decision on the working frequency of the entire emergency broadcasting platform based on the interference sensing result.

[0009] Wherein, the step S1 includes the following sub-steps:

[0010] S101. The transmitter generates a broadcast signal s(n), performs digital-to-analog conversion and RF operation on it, and obtains a transmission signal:

[0011]

[0012] The broadcast signal is expressed as s(t) after digital-to-analog conversion, f s With θs are the carrier frequency and initial phase of the transmitted signal, respectively.

[0013] S102. The transmitter broadcasts the obtained transmitted signal.

[0014] Among them, the step S2 includes the following sub-steps:

[0015] S201. Assist the receiver to perform real-time broadband detection. After down-conversion, the received signal can be expressed as:

[0016]

[0017] where represents the received self-interference signal, and r e (t) represents the environmental signal, and n(t) is Gaussian white noise, f r and θ r are the carrier frequency and initial phase of the receiver respectively, τ represents the propagation delay, and h x is the channel complex gain.

[0018] After the analog-to-digital conversion operation of the received signal r(t), it can be respectively expressed as:

[0019] r(n) = h x s(n - D)e -j[2πΔfn+Δθ] + r e (n) + ω(n)

[0020] where D = τ / T s represents the normalized propagation delay, T s represents the sampling period, Δf = (f s - f n )T s represents the normalized frequency offset, Δθ = (θ s - θ n )T s represents the normalized phase error. Without loss of generality, it is assumed that Δf > 0.

[0021] S202. Represent the received signal as a vector:

[0022] r = r x + r e + ω

[0023] = [r(n + 1), r(n + 2),..., r(n + N)] T

[0024] where n represents the time, r x 、r e\(\mathbf{r}\), \(\mathbf{w}\), and \(\mathbf{\omega}\) are the vector representations of the self-interference signal, the environmental signal, and the Gaussian white noise, respectively. The self-interference signal is expressed as:

[0025] r x = e -j[2πΔfn+Δθ] h_s

[0026] = [r x (n + 1), r x (n + 2),..., r x (n + N)] T

[0027] That is:

[0028]

[0029] where \(h = [h x1 h x2 … h xN T is the vector representation of the complex channel gain, and \(s\) is the vector representation of the broadcast signal;

[0030] S203. Perform broadband folding on the received signal. After broadband folding, the received signal \(r Φ is represented as a vector of length \(K\):

[0031]

[0032] where and \(\omega Φ respectively represent the self-interference signal, the environmental signal, and the noise after broadband folding. \(r(n+\alpha_1), r(n+\alpha_2),..., r(n+\alpha M ) respectively represent the \(\alpha_1, \alpha_2,..., \alpha M -th elements of the folded vector \(r\), and \(\Phi\) is the observation matrix:

[0033]

[0034] \(\alpha = [\alpha_1, \alpha_2,..., \alpha M is the index vector of \(\Phi\). In the observation matrix, is 1 for \(m = 1, 2,..., M\), \(1\leq\alpha m \leq N\), and the remaining elements are 0;

[0035] The folded self-interference signal is expressed as:

[0036]

[0037] where the step S3 includes the following sub-steps:

[0038] ​S301. Assist the receiver to perform interference reconstruction on the transmitted baseband signal after broadband folding operation to obtain the reconstructed self-interference signal, expressed as:

[0039]

[0040] S302. After the receiver performs interference cancellation operation, the residual self-interference signal is expressed as:

[0041]

[0042] The residual signal is expressed as:

[0043]

[0044] At this time, when the residual self-interference signal and the noise ω Φ can be ignored, the residual signal Δr Φ is equivalent to the environmental signal after broadband folding.

[0045] Among them, the step S4 includes the following sub-steps:

[0046] S401. Assist the receiver to perform frequency point detection on the residual signal to obtain the frequency point range of the environmental signal, that is, the interference perception result;

[0047] S402. According to the frequency point range of the environmental signal obtained in S401, the emergency broadcast platform switches the working frequency of the emergency broadcast transmitter to avoid the frequency point range of the environmental signal.

[0048] The beneficial effects of the present invention are: The present invention uses an assist receiver to perform real-time broadband reconnaissance on the environmental signal, analyzes the influence of frequency offset on the self-interference suppression of the assist receiver, makes a decision on the working frequency of the emergency broadcast platform based on the reconnaissance result, and improves the anti-interference ability of the emergency broadcast platform. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] Figure 1 is the method flow chart of the present invention;

[0050] Figure 2 is the schematic diagram of the principle of the emergency broadcast system model in the embodiment;

[0051] Figure 3 is the performance diagram of the environmental signal frequency detection of the assist receiver in the embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0052] The technical solution of the present invention will be further described in detail below with reference to the drawings, but the protection scope of the present invention is not limited to the following.

[0053] As Figure 1As shown, an emergency communication method in a complex electromagnetic environment is implemented based on an emergency broadcast communication platform, such as Figure 2 As shown, the emergency broadcast communication platform includes a transmitter and an assisting receiver. The assisting receiver decides the broadcast signal frequency point through real-time reconnaissance of the environmental signals to avoid interference to the broadcast signal. However, the high-power broadcast signal causes serious self-interference to the assisting receiver. To eliminate the influence of the broadcast signal, the baseband signal of the transmitter is coupled as a reference. Subsequently, the assisting receiver performs broadband folding processing on the received signal and uses the reference signal to reconstruct and cancel the folded self-interference signal. The method includes the following steps:

[0054] S1. The transmitter generates a broadcast signal, performs digital-to-analog conversion and radio frequency operations on it, and then transmits it;

[0055] S2. The assisting receiver performs real-time broadband interception, simultaneously receives the self-interference signal and the environmental signal, and performs broadband folding processing on the received signal;

[0056] S3. The assisting receiver generates a reference signal by performing the same broadband folding operation on the transmitted baseband signal, and then performs interference reconstruction and interference cancellation;

[0057] S4. After interference cancellation, the assisting receiver senses the residual signal, and then decides the operating frequency of the entire emergency broadcast platform according to the interference sensing result.

[0058] Among them, the step S1 includes the following sub-steps:

[0059] S101. The transmitter generates a broadcast signal s(n), and after performing digital-to-analog conversion and radio frequency operations on it, obtains a transmitted signal:

[0060]

[0061] The broadcast signal is expressed as s(t) after digital-to-analog conversion, and f s and θ s are respectively the carrier frequency and the initial phase of the transmitted signal.

[0062] S102. The transmitter broadcasts the obtained transmitted signal.

[0063] Among them, the step S2 includes the following sub-steps:

[0064] S201. The assisting receiver performs real-time broadband interception, and the received signal can be expressed as:

[0065]

[0066] where represents the received self-interference signal, With r e (t) represents the environmental signal, and n(t) is Gaussian white noise, f r and θ r are the carrier frequency and initial phase of the receiver respectively, τ represents the propagation delay, h x is the channel complex gain.

[0067] After the analog-to-digital conversion operation of the received signal r(t), it can be respectively expressed as:

[0068] r(n) = h x s(n - D)e -j[2πΔfn+Δθ] + r e (n) + ω(n)

[0069] where D = τ / T s represents the normalized propagation delay, T s represents the sampling period, Δf = (f s - f n )T s represents the normalized frequency offset, Δθ = (θ s - θ n )T s represents the normalized phase error. Without loss of generality, assume Δf > 0.

[0070] S202. Represent the received signal as a vector:

[0071] r = r x + r e + ω

[0072] = [r(n + 1), r(n + 2),..., r(n + N)] T

[0073] where n represents the time, r x 、r e and ω are the vector representations of the self-interference signal, environmental signal and Gaussian white noise respectively. The self-interference signal is expressed as:

[0074] r x = e -j[2πΔfn+Δθ] hs

[0075] = [r x (n + 1), r x (n + 2),..., r x (n + N)] T

[0076] That is:

[0077]

[0078] where, h = [hx1 h x2 … h xN T is the vector representation of the complex channel gain, and s is the vector representation of the broadcast signal;

[0079] S203. Perform broadband folding on the received signal. After broadband folding, the received signal r Φ is represented as a vector of length K:

[0080]

[0081] where and ω Φ respectively represent the self-interference signal, the environmental signal, and the noise after broadband folding. r(n+α1), r(n+α2), …, r(n+α M ) respectively represent the α1, α2,, α M -th elements after the vector r is folded, and Φ is the observation matrix:

[0082]

[0083] α = [α1, α2,..., α M is the index vector of Φ. In the observation matrix, is 1, m = 1, 2,, M, 1 ≤ α m ≤ N, and the remaining elements are 0;

[0084] The self-interference signal after folding is represented as:

[0085]

[0086] Among them, the step S3 includes the following sub-steps:

[0087] S301. Assist the receiver to perform interference reconstruction on the transmitted baseband signal after broadband folding operation to obtain the reconstructed self-interference signal, which is represented as:

[0088]

[0089] S302. After the receiver performs interference cancellation operation, the residual self-interference signal is represented as:

[0090]

[0091] The residual signal is represented as:

[0092]

[0093] At this time, when the residual self-interference signal and the noise ω Φ ​When it can be ignored, the residual signal Δr Φ is equivalent to the environmental signal after broadband folding.

[0094] Among them, the step S4 includes the following sub-steps:

[0095] S401. Assist the receiver to perform frequency point detection on the residual signal to obtain the frequency point range of the environmental signal, that is, the interference perception result;

[0096] S402. According to the frequency point range of the environmental signal obtained in S401, the emergency broadcast platform switches the operating frequency of the emergency broadcast transmitter to avoid the frequency point range of the environmental signal.

[0097] In the embodiments of the present application, according to the method of the present invention, an emergency broadcast model is constructed, and the principle is as Figure 2 shown. The transmitter transmits broadcast signals, and at the same time assists the receiver to receive broadcast signals and environmental signals in real time. The propagation environment is an AWGN channel. Simulation verification was carried out on the MATLAB tool, and the simulation parameters are shown in the following table:

[0098]

[0099] Figure 3 shows the relationship between the correct rate of frequency estimation of the assisting receiver and the power ratio of the broadcast signal to the environmental signal under different frequency offset conditions. It can be observed that compared with the assisting receiver without interference suppression, the correct rate of environmental signal frequency reconnaissance of the assisting receiver after interference cancellation has been significantly improved. When the power ratio of the broadcast signal to the environmental signal is in the range of -30 to 0 dB, the correct rate of environmental signal frequency reconnaissance remains stable at about 89%. When the power ratio of the broadcast signal to the environmental signal increases above 0 dB, the correct rate of environmental signal frequency reconnaissance gradually decreases as the frequency offset increases. Specifically, when the power ratio of the broadcast signal to the environmental signal reaches 30 dB and the frequency offset is 10 -2 , the correct rate of environmental signal frequency reconnaissance drops to about 14.7%. These results indicate that as the power ratio of the broadcast signal to the environmental signal increases, the adverse effect of frequency offset on the interference suppression performance becomes more obvious, resulting in a decrease in the correct rate of environmental signal frequency reconnaissance.

[0100] The present invention has been described and proven in detail here, so that those skilled in the art can understand and apply the present invention. For those of ordinary skill in the art, other different forms of changes or modifications can be made on the basis of the above description. And the changes and modifications made by those skilled in the art that do not depart from the spirit and scope of the present invention shall fall within the protection scope of the appended claims of the present invention.

Claims

1. An emergency broadcast communication method in a complex electromagnetic environment, characterized by: The following steps are involved: S1. The transmitter generates a broadcast signal, performs digital-to-analog conversion and RF operation on it before transmitting; S2. Assist the receiver to perform real-time broadband detection, receive self-interference signals and environmental signals at the same time, and perform broadband folding processing on the received signals; S3. Assist the receiver to generate a reference signal by performing the same broadband folding operation on the transmitted baseband signal, and then perform interference reconstruction and interference cancellation; S4. Assist the receiver to sense the residual signal after the interference is cancelled, and then make a decision on the working frequency of the entire emergency broadcasting platform based on the interference sensing result.

2. The method for emergency broadcast communication in a complex electromagnetic environment according to claim 1, characterized in that: The step S1 comprises the following sub-steps: S101. The transmitter generates a broadcast signal s(n), performs digital-to-analog conversion and RF operation on it, and obtains a transmission signal: The broadcast signal is represented as s(t) after digital-to-analog conversion, f s With θ s are respectively the carrier frequency and initial phase of the transmitted signal; S102. The transmitter broadcasts the obtained transmission signal.

3. The method for emergency broadcast communication in a complex electromagnetic environment according to claim 1, characterized in that: The step S2 comprises the following sub-steps: S201. Assist the receiver to perform real-time broadband detection. The received signal is expressed as follows after down-conversion: in, represents the received self-interference signal, With r e (t) represents the environmental signal, and n(t) is Gaussian white noise, f r With θ r are the carrier frequency and initial phase of the receiver, τ represents the propagation delay, h x is the channel complex gain; After the analog-to-digital conversion operation of the received signal r(t), it is expressed as: r(n)=h x s(nD)e -j [ 2 p Δfn+Δ θ]+r e (n)+ω(n) Where D = τ / T s represents the normalized propagation delay, T s represents the sampling period, Δf=(f s -f n )T s represents the normalized frequency deviation, Δθ=(θ s -θ n )T s represents the normalized phase error, Δf>0; S202. Represent the received signal with a vector: r=r x +r e +ω =[r(n+1),r(n+2),...,r(n+N)] T Where n represents the time, r x 、r e and ω are the vector representations of the self-interference signal, the environmental signal and Gaussian white noise respectively. The self-interference signal is expressed as: r x =e -j[2πΔfn+Δθ] hs =[r x (n+1),r x (n+2),...,r x (n+N)] T Right now: Where h = [h x1 h x2 h xN ] T is the vector representation of the complex channel gain, s is the vector representation of the broadcast signal; S203. Perform broadband folding on the received signal. After broadband folding, the received signal r Φ Represented as a vector of length M: in With ω Φ They represent the self-interference signal, environmental signal and noise after broadband folding, r(n+α1), r(n+α2),..., r(n+α M ) represent the α1, α2, ..., α M elements, Φ is the observation matrix: α=[α1,α2,...,α M ] is the index vector of Φ, in the observation matrix, is 1, m=1,2,...,M,1≤α m ≤N, the rest of the elements are 0; Get the folded self-interference signal:

4. The emergency broadcast communication method in a complex electromagnetic environment according to claim 1, characterized in that: The step S3 comprises the following sub-steps: S301. The assisting receiver performs interference reconstruction on the transmitted baseband signal after broadband folding operation to obtain a reconstructed self-interference signal, which is expressed as: S302. After the assisting receiver performs interference cancellation operation, the residual self-interference signal is expressed as: The residual signal is expressed as: At this time, the residual self-interference signal and noise ω Φ Ignoring, the residual signal Δr Φ It is equivalent to the ambient signal after broadband folding.

5. The method for emergency broadcast communication in a complex electromagnetic environment according to claim 1, characterized in that: The step S4 comprises the following sub-steps: S401. Assist the receiver to detect the frequency of the residual signal to obtain the frequency range of the ambient signal, that is, the interference perception result; S402. The emergency broadcast platform switches the operating frequency of the emergency broadcast transmitter according to the frequency range of the environmental signal obtained in S401 to avoid the frequency range of the environmental signal.

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