A method and system for orthogonal correlation detection and reception of multi-sequence frequency hopping communication signals

Abstract

The present invention relates to an orthogonal correlation detection and reception method and system for a multi-sequence frequency hopping communication signal, and relates to the field of frequency hopping communication signal reception. The method comprises determining a communication signal received by each receiving channel at a current start-up and a frequency hopping sequence of each receiving channel at the current start-up; for any receiving channel, mixing the communication signal with a local oscillator signal corresponding to the frequency hopping sequence, then performing computational processing on a first signal and a second signal obtained through branching processing, and summing the obtained first computational results and the second computational results to finally obtain a test statistic; adopting a maximum variance decision method to perform decision calculation on the detection statistics of each receiving channel, and determining the best detection statistic among the detection statistics of all receiving channels; the communication signal in the receiving channel corresponding to the best detection statistic is the target information; and the present invention can improve detection and reception performance.

Description

Technical Field

[0001] The present invention relates to the field of frequency hopping communication signal reception, and in particular to an orthogonal correlation detection and reception method and system for multi-sequence frequency hopping communication signals. Background Art

[0002] Frequency-hopping communications, with its strong anti-interference, anti-interception, and confidentiality capabilities, offer unique advantages in modern electronic warfare, making it one of the most widely used and effective communication anti-interference technologies. However, with the continuous advancement of communication countermeasures and electronic technology, jammers are responding faster and using more intelligent jamming methods, enabling them to intercept certain parameters of frequency-hopping communications and implement targeted jamming strategies. Tracking jamming, the most effective jamming method against frequency-hopping communications, can cause a loss of frequency-hopping gain, making frequency-hopping communications as vulnerable as fixed-frequency communications.

[0003] In recent years, researchers at home and abroad have proposed a variety of novel frequency-hopping communication methods to combat tracking interference. Among them, novel frequency-hopping schemes that utilize channels to represent messages have garnered widespread attention due to their inherent resistance to tracking interference. Representative examples of these methods include message-driven frequency hopping (MDFH), differential frequency hopping (DFH), and multi-sequence combined frequency hopping (MSFH).

[0004] MDFH uses part of the transmission information to select the carrier frequency to achieve anti-interception and anti-interference purposes. Since the receiving end cannot know the carrier frequency in advance, MDFH needs to use broadband reception, causing the receiver to receive a large amount of noise energy, and at the same time making the system susceptible to fixed-frequency interference or high-power heterodyne interference. DFH establishes a correlation between each frequency hopping point based on the frequency transfer function and different transmission information, and uses the difference in correlation caused by the difference in the sequence to be sent to reversely infer the transmission information. It has an extremely high hopping speed, making it difficult for general tracking jammers to capture. It has the characteristics of fast data transmission rate and strong anti-interference ability. However, DFH uses broadband reception and is easily affected by fixed-frequency interference and heterodyne interference.

[0005] MSFH uses the difference between two (or more) frequency hopping sequences to convey messages. The data channel and compensation channel frequencies hop according to different frequency hopping sequences, making it difficult for the interfering party to accurately track the compensation channel, thus reducing the impact of tracking interference. The receiver's RF front end uses narrowband reception, which effectively suppresses interference in some frequency bands compared to wideband reception using differential frequency hopping. However, its information transmission rate is limited by the hopping rate, and higher-order modulation requires additional receive channels.

[0006] The MSFH method, which leverages narrowband reception characteristics, offers strong anti-interference capabilities and promising prospects. It relies on detecting the presence of signals in the channel at the receiving end to determine the transmitted symbols. However, existing methods often use square law or energy detection to detect signal presence, which limits the performance of MSFH when the signal-to-noise ratio is low.

[0007] This is because the energy detection method treats the received signal as a completely unknown signal and does not take advantage of the characteristic of MSFH that the received signal is a known single-frequency signal that reaches the receiver as a narrowband signal after passing through the wireless channel. Summary of the Invention

[0008] The purpose of the present invention is to provide an orthogonal correlation detection and reception method and system for a multi-sequence frequency hopping communication signal, so as to improve the detection and reception performance.

[0009] To achieve the above object, the present invention provides the following solutions:

[0010] A method for orthogonal correlation detection and reception of a multi-sequence frequency hopping communication signal, the method comprising:

[0011] Determining a communication signal received by each receiving channel at a current start and a frequency hopping sequence of each receiving channel at the current start; the communication signal is target information sent by a transmitting end;

[0012] For any receiving channel, mixing the communication signal with the local oscillator signal corresponding to the frequency hopping sequence to obtain an intermediate frequency signal, and performing branching processing on the intermediate frequency signal to obtain a first signal and a second signal of the receiving channel;

[0013] For any receiving channel, performing operation processing on the first signal and the second signal to obtain a first operation result and a second operation result, and performing a sum operation on the first operation result and the second operation result to obtain a test statistic of the receiving channel; the operation processing includes: an integration operation and a square operation;

[0014] The maximum variance decision method is adopted to perform decision calculation on the detection statistics of each receiving channel to determine the best detection statistic among the detection statistics of all receiving channels; the best detection statistic is the detection statistic corresponding to the minimum average error probability; the communication signal in the receiving channel corresponding to the best detection statistic is the target information.

[0015] Optionally, the adopting of the maximum variance decision method to perform decision calculation on the detection statistics of each of the receiving channels to determine the best detection statistic among the detection statistics of all the receiving channels specifically includes:

[0016] Determining a likelihood function of each of the receiving channels according to the communication signal and a local oscillator signal corresponding to the frequency hopping sequence;

[0017] Inputting each of the test statistics into a corresponding likelihood function, and determining an average likelihood ratio test discriminant based on all likelihood functions;

[0018] Based on the average likelihood ratio test discriminant, an optimal detection statistic among the detection statistics of all receiving channels is determined.

[0019] Optionally, the calculation formula of the test statistic is:

[0020]

[0021] in,

[0022]

[0023]

[0024] l1 is the test statistic; x 1I is the first signal; x 1Q is the second signal; T s is the period of each hop; x1(t) is the intermediate frequency signal; w1 is the frequency of the communication signal, and t is the time.

[0025] Optionally, the likelihood function is:

[0026]

[0027] Where P[x1(t)|a1,θ1;H0] is the likelihood function of the receiving channel; x1(t) is the intermediate frequency signal; H0 is the local oscillator signal corresponding to the frequency hopping sequence; a1 is the amplitude of the communication signal; F is a constant; T s is the period of each hop; N0 is the noise power; θ1 is the phase of the communication signal; ω1 is the frequency of the communication signal.

[0028] Optionally, determining the best detection statistic among the detection statistics of all receiving channels based on the average likelihood ratio test discriminant specifically includes:

[0029] Calculating the probability of wrong decision and the probability of correct decision corresponding to the detection statistic in the average likelihood ratio test discriminant using a probability density function;

[0030] Determining a probability judgment formula according to the probability of wrong judgment and the probability of correct judgment;

[0031] Based on the probability decision formula, the detection statistic corresponding to the minimum average error probability is determined as the best detection statistic among the detection statistics of all receiving channels.

[0032] Optionally, the probability density function is calculated as follows:

[0033]

[0034] p(l1|H0) is the probability density function between the detection statistic of the channel and the frequency hopping signal corresponding to the frequency hopping sequence; l1 is the test statistic; H0 is the local oscillator signal corresponding to the frequency hopping sequence; N0 is the noise power.

[0035] An orthogonal correlation detection and receiving system for a multi-sequence frequency hopping communication signal, the system comprising:

[0036] An acquisition unit, configured to determine a communication signal received by each receiving channel at a current start and a frequency hopping sequence of each receiving channel at a current start; the communication signal being target information sent by a transmitting end;

[0037] a signal processing unit configured to, for any receiving channel, mix the communication signal with a local oscillator signal corresponding to the frequency hopping sequence to obtain an intermediate frequency signal, and perform branching processing on the intermediate frequency signal to obtain a first signal and a second signal of the receiving channel;

[0038] a test statistic calculation unit, configured to, for any receiving channel, perform arithmetic processing on both the first signal and the second signal to obtain a first operation result and a second operation result, and perform a sum operation on the first operation result and the second operation result to obtain a test statistic of the receiving channel; the arithmetic processing includes: an integral operation and a square operation;

[0039] The optimal detection statistic determination unit is used to adopt the maximum variance decision method to perform decision calculation on the detection statistics of each of the receiving channels to determine the optimal detection statistic among the detection statistics of all the receiving channels; the optimal detection statistic is the detection statistic corresponding to the minimum average error probability; the communication signal in the receiving channel corresponding to the optimal detection statistic is the target information.

[0040] Optionally, the optimal detection statistic determining unit includes:

[0041] A likelihood function determination module, configured to determine a likelihood function of each of the receiving channels based on the communication signal and the local oscillator signal corresponding to the frequency hopping sequence;

[0042] An average likelihood ratio test discriminant determination module is used to input each of the test statistics into a corresponding likelihood function and determine an average likelihood ratio test discriminant based on all likelihood functions;

[0043] The optimal detection statistic determination module is configured to determine the optimal detection statistic among the detection statistics of all receiving channels based on the average likelihood ratio test discriminant.

[0044] According to the specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0045] The present invention provides an orthogonal correlation detection and reception method and system for a multi-sequence frequency hopping communication signal. The method, for any receiving channel, mixes a communication signal with a local oscillator signal corresponding to the frequency hopping sequence to obtain an intermediate frequency signal, and performs branching processing on the intermediate frequency signal to obtain a first signal and a second signal of the receiving channel; for any receiving channel, performs operation processing on the first signal and the second signal to obtain a first operation result and a second operation result, and performs a sum operation on the first operation result and the second operation result to obtain a test statistic of the receiving channel; adopts a maximum variance decision method to perform decision calculation on the detection statistics of each receiving channel, and determines the best detection statistic among the detection statistics of all the receiving channels; the best detection statistic is the detection statistic corresponding to the minimum average error probability. ; The communication signal in the receiving channel corresponding to the optimal detection statistic is the target information; since the communication signal received by the receiving channel can select the frequency hopping sequence controlled by the pseudo-random sequence as the carrier channel, the selected one is used as the communication channel, and the unselected one is used as the dual channel, it is necessary to detect the existence of the signal in the receiving channel and judge the transmitted communication signal sequence at the receiving end to determine the transmitted code element; the communication signals received by the multi-sequence frequency hopping system adopted by the present invention are all single-frequency signals, and the narrowband signal that reaches the receiving end after the single-frequency signal passes through the channel is consistent with the characteristics of the single-frequency signal. This property enables multiple receiving channels to adopt the same signal detection and reception method, fully utilize the prior knowledge of the frequency hopping communication signal, perform decision calculations, and improve the detection and reception performance of the signal. Therefore, the present invention can improve the detection and reception performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0046] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0047] Figure 1 A flowchart of a method for orthogonal correlation detection and reception of a multi-sequence frequency hopping communication signal provided by an embodiment of the present invention;

[0048] Figure 2 A structural diagram of an orthogonal correlation detection and receiving system for a multi-sequence frequency hopping communication signal provided by an embodiment of the present invention;

[0049] Figure 3 A schematic diagram of orthogonal correlation detection and reception of a multi-sequence frequency hopping communication signal provided by an embodiment of the present invention;

[0050] Figure 4 A theoretical curve diagram of the orthogonal correlation receiving bit error rate provided by an embodiment of the present invention;

[0051] Figure 5 Schematic diagram of the simulation results of DSFH orthogonal correlation receiving bit error rate performance under Rayleigh fading channel;

[0052] Figure 6 This is a comparison chart of the bit error rate performance of orthogonal correlation detection and energy detection.

[0053] Explanation of symbols:

[0054] Acquisition unit-1, signal processing unit-2, test statistic calculation unit-3, optimal detection statistic determination unit-4. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] The purpose of the present invention is to provide an orthogonal correlation detection and reception method and system for a multi-sequence frequency hopping communication signal, so as to improve the detection and reception performance.

[0057] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0058] Example 1

[0059] like Figure 1 As shown, an embodiment of the present invention provides an orthogonal correlation detection and reception method for a multi-sequence frequency hopping communication signal, the method comprising:

[0060] Step 100: Determine the communication signal received by each receiving channel at the current start time and the frequency hopping sequence of each receiving channel at the current start time; the communication signal is the target information sent by the transmitting end.

[0061] Step 200: For any receiving channel, mix the communication signal with the local oscillator signal corresponding to the frequency hopping sequence to obtain an intermediate frequency signal, and perform branching processing on the intermediate frequency signal to obtain a first signal and a second signal of the receiving channel.

[0062] Step 300: For any receiving channel, perform computation on both the first signal and the second signal to obtain a first computation result and a second computation result, and perform a summation operation on the first computation result and the second computation result to obtain a test statistic of the receiving channel; the computation processing includes: an integral operation and a square operation.

[0063] Step 400: Use the maximum variance decision method to perform decision calculations on the detection statistics of each receiving channel to determine the best detection statistic among the detection statistics of all receiving channels; the best detection statistic is the detection statistic corresponding to the minimum average error probability; the communication signal in the receiving channel corresponding to the best detection statistic is the target information.

[0064] In practical applications, the implementation steps of the orthogonal correlation detection and reception method for multi-sequence frequency hopping communication signals provided by the present invention may also be as follows:

[0065] Step 1: Assume that the transmitter and receiver have achieved frequency hopping synchronization in a multi-sequence frequency hopping communication system. For a frequency hopping communication system with M frequency hopping sequences operating in conjunction, the receiver has M receive channels. Each receive channel receives the received signal after amplification and filtering by the receive antenna and the RF front end, and the receive channels operate in parallel. This received signal is the communication signal.

[0066] Step 2: For the i-th receiving channel, i = 1, ..., M; use the frequency hopping sequence F corresponding to the receiving channel Si The generated local oscillator signal L Oi The received communication signal is mixed to obtain the intermediate frequency signal of the channel, and the intermediate frequency signal is bandpass filtered.

[0067] Step 3: For each receiving channel, the intermediate frequency signal after narrowband bandpass filtering is divided into two branches and multiplied by and Among them, T s is the jump period, f I is the intermediate frequency, and t refers to time; the I-channel signal and Q-channel signal of the receiving channel are obtained.

[0068] In each hop period T s In the receiving channel, the I and Q channels integrate the received signals respectively, square the integral results, and then sum the squared results of the two channels. The calculated result is used as the test statistic X of the k-th hop of the receiving channel. i (k), i=1,…,M; k is a positive integer greater than or equal to 1.

[0069] Step 4: The test statistics of the M receiving channels are sent to the comprehensive decision unit to decide the frequency hopping sequence used for information transmission. The decision is made once for each hop, and the decision time is when the hop ends. The decision method is the maximum variance decision method. Specifically, for each hop, the maximum variance value Y1(k) of each receiving channel is calculated:

[0070] Assume that the decision threshold is D, that is, when Y1(k)>D, the corresponding maximum variance value corresponding to the receiving channel test statistic is X a , where i=1,…,M

[0071]

[0072] The final decision is that the kth hop uses the ath frequency hopping sequence to send data.

[0073] Step 5: According to the correspondence between the frequency hopping sequence and the transmitted information codeword in the multi-sequence frequency hopping communication, the k-th hop outputs the information codeword corresponding to the a-th frequency hopping sequence. a The communication signal in the corresponding receiving channel is the target information.

[0074] Specifically, step 400 includes:

[0075] The likelihood function of each receiving channel is determined according to the communication signal and the local oscillator signal corresponding to the frequency hopping sequence.

[0076] Each test statistic is input into the corresponding likelihood function, and the average likelihood ratio test discriminant is determined based on all likelihood functions.

[0077] Based on the average likelihood ratio test discriminant, the best detection statistic among the detection statistics of all the receiving channels is determined.

[0078] Furthermore, the calculation formula of the test statistic is:

[0079]

[0080] in,

[0081]

[0082]

[0083] l is the test statistic; x 1I is the first signal; x 1Q is the second signal; T s is the period of each hop; x1(t) is the intermediate frequency signal; w is the frequency of the communication signal, and t is the time.

[0084] The likelihood function is:

[0085]

[0086] Where P[x1(t)|a,θ; H0] is the likelihood function of the receiving channel; x1(t) is the intermediate frequency signal; H0 is the local oscillator signal corresponding to the frequency hopping sequence; a is the amplitude of the communication signal; F is a constant; T s is the period of each hop; N0 is the noise power; θ is the phase of the communication signal; ω is the frequency of the communication signal.

[0087] During wireless communication, signals propagate in space in the form of electromagnetic waves. Due to the influence of random factors such as wireless channel fading, disturbance, and multipath effects, the amplitude of the received signal fluctuates randomly, and the phase is also random. Taking dual sequence frequency hopping (DSFH) as an example, the purpose of detecting the received signal at the DSFH receiving end is to determine the "dominant sequence" of the current frequency hopping communication by detecting the received signals of the two channels. Therefore, each channel of the DSFH communication system within a code element time can be equivalent to a simple binary random amplitude and random phase signal waveform detection problem, and then the test statistics of the two channels are combined for judgment. Figure 3 shown. Figure 3 The BPF in this article refers to a band-pass filter.

[0088] Assume that H1 represents the local oscillator signal received on the frequency hopping sequence FS0; H2 represents the local oscillator signal received on the frequency hopping sequence FS1; x0(t) represents the observation signal of the first receiving channel, that is, the intermediate frequency signal of the first receiving channel; x2(t) represents the observation signal of the second receiving channel, that is, the intermediate frequency signal of the second receiving channel.

[0089] H1:x0(t)=v1(t)+n1(t) x2(t)=n2(t) 0≤t≤T s

[0090] H2:x0(t)=n1(t) x2(t)=v2(t)+n2(t) 0≤t≤T s

[0091] v1(t)=a1cos(ω1t+θ1)

[0092] v2(t)=a2cos(ω2t+θ2)

[0093] Where v1(t) is the communication signal of the first receiving channel; a1 is the amplitude; θ1 is the phase; a1 and θ1 are random, and their prior probability density function is p(a1,θ1).

[0094] ω1 is a frequency, and satisfies ω1T=2mπ (m is a positive integer).

[0095] v2(t) is the communication signal of the second receiving channel. The amplitude a2 and phase θ2 are random. Its prior probability density function is p(a2,θ2). The frequency ω1 is known and satisfies ω2T=2mπ (m is a positive integer). n1(t) and n2(t) are Gaussian white noise with mean 0 and variance σ respectively. n 2 .

[0096] In the DSFH system, the intermediate frequency received signals of the two branches are v1(t)=v2(t)=a2cos(ω2t+θ2). Therefore, the above formula can be further simplified to:

[0097] H1:x0(t)=v1(t)+n1(t) x2(t)=n(t) 0≤t≤T s

[0098] H2:x0(t)=n(t) x2(t)=v1(t)+n(t) 0≤t≤T s

[0099] n(t) is Gaussian white noise.

[0100] First, we take x0(t) as an example for analysis. At this time, taking H1 as an example, we assume that the randomness of the received communication signal amplitude a1 and the randomness of the signal phase θ1 are independent of each other, that is, their prior probability density function p(a1,θ1) is:

[0101] P(a1,θ1)=P(a1)P(θ1)

[0102] And a1 follows Rayleigh distribution

[0103]

[0104] θ1 follows a uniform distribution

[0105]

[0106] Assuming H1 is true, the likelihood function of the observed signal x0(t) conditioned on the random amplitude a1 and random phase θ1 is:

[0107]

[0108] in, F is a constant, N0 is the noise power, and N is the number of observations.

[0109] Perform statistical averaging on θ1 and use the results of simple binary random phase signal waveform detection to obtain the likelihood function of x0(t) conditioned on amplitude a1

[0110]

[0111]

[0112]

[0113]

[0114] Then perform statistical averaging on a1 to further obtain the average likelihood function of x0(t)

[0115]

[0116] Using the integral formula

[0117]

[0118] Where u represents the statistic of the positive half axis of the random distribution signal.

[0119] Finally, assuming H0 is true, the average likelihood function of x0(t) is

[0120]

[0121] Assuming H1 is true, the likelihood function of x0(t) is

[0122]

[0123] If the likelihood ratio detection threshold is η, the average likelihood ratio test decision formula is:

[0124]

[0125] Take the natural logarithm of both sides of the above equation and simplify it to get l1 2 is the best decision formula for the test statistic

[0126]

[0127] γ is the decision threshold; its equivalent optimal decision formula is

[0128]

[0129] The test statistic l1 is given by

[0130]

[0131] The solution is obtained.

[0132] Since the receiving channels of the two branches are symmetrical, the optimal test statistics and equivalent decision formulas of x0(t) and x2(t) are the same.

[0133] The average likelihood ratio function of another receiving channel can also be obtained

[0134]

[0135]

[0136]

[0137]

[0138] Assuming the likelihood ratio detection threshold is η, the average likelihood ratio test decision formula is:

[0139]

[0140] The equivalent optimal decision formula is

[0141]

[0142] If the prior probability p(H j )(j=0,1) are equal, and the minimum average error probability detection criterion is adopted, then η=1, so we can get

[0143]

[0144] or

[0145]

[0146] Specifically, based on the average likelihood ratio test discriminant, determining the best detection statistic among the detection statistics of all receiving channels specifically includes:

[0147] The probability density function is used to calculate the probability of wrong judgment and the probability of correct judgment corresponding to the detection statistic in the average likelihood ratio test discriminant.

[0148] Determine the probability judgment formula based on the probability of wrong judgment and the probability of correct judgment.

[0149] Based on the probability decision formula, the detection statistic corresponding to the minimum average error probability is determined as the best detection statistic among the detection statistics of all receiving channels.

[0150] Furthermore, the probability density function is calculated as follows:

[0151]

[0152] p(l1|H0) is the probability density function between the detection statistic of the channel and the frequency hopping signal corresponding to the frequency hopping sequence; l1 is the test statistic; H0 is the local oscillator signal corresponding to the frequency hopping sequence; N0 is the noise power.

[0153] The detection performance of a single DSFH channel is analyzed based on a detection system structure with a simple binary Rayleigh distribution random amplitude and uniform distribution random phase signal waveform. Taking the detection statistic l of one of the channels as an example, when the hypothesis H0 is true, the probability density function of the test statistic l is:

[0154]

[0155] When assuming H1 is true, the probability density function of l conditioned on the random amplitude a is

[0156]

[0157] Taking the statistical average of p(l|a; H1) on a, we can get the probability density function of l when assuming H1 is true:

[0158]

[0159] Therefore, when assuming H0 is true, the probability of wrong judgment is:

[0160]

[0161] When assuming H1 is true, the probability of correct judgment is:

[0162]

[0163] Among them, the parameters twice That is the signal energy to noise ratio. is the expected value of the signal energy.

[0164] Note P FA =(H1|H0), P D =(H1|H1), then the correct decision probability P(H1|H1) can be expressed more intuitively as:

[0165]

[0166] The correct judgment probability P D =P(H1|H1) and the probability of wrong decision P FA =P(H1|H0) through the signal energy signal-to-noise ratio d 2 By connecting them together, the detection characteristics can be analyzed.

[0167] It can be concluded that improving the energy signal-to-noise ratio d 2 , the signal detection performance will be improved. The methods to improve the energy signal-to-noise ratio are: ① Increase the power of the signal ② Increase the observation time T (or increase the number of observations N); ③ Reduce the power of the noise The variance of Gaussian white noise represents its power.

[0168] Due to the application scenarios of the DSFH communication mode, there is generally no direct path between the sender and the receiver. The fading channel is generally a Rayleigh channel with multipath reflection and scattering. Therefore, the amplitude fading of the received signal follows the Rayleigh distribution, and the phase follows the uniform distribution.

[0169] Use Figure 3 The receiving structure shown in the figure has a bit error rate P of the upper branch. e for:

[0170]

[0171] Due to the symmetry of the upper and lower receiving branches of the DSFH system, the error probability of the two branches is equal, so the total bit error rate is:

[0172]

[0173] Where, is the average power signal-to-noise ratio, N0 is the noise power, and γ is the decision threshold.

[0174] If the receiving decision adopts the minimum bit error rate criterion, the decision threshold satisfies

[0175]

[0176] This gives the bit error rate performance under a fading channel.

[0177]

[0178] Taking DSFH (M=2) as an example, the theoretical curve of orthogonal correlation receiving bit error rate is as follows: Figure 4 As shown in the figure, increasing the number of signal observations can reduce the bit error rate, but it also increases the amount of computation required for receiver signal processing. As the number of signal observations increases, the detection performance gain decreases. In practice, the number of signal observations should be appropriately selected based on the receiver's computational processing capabilities.

[0179] Based on the orthogonal correlation signal detection method, a Simulink model of the DSFH receiving link can be built in practical applications to conduct simulation experiments. By comparing and analyzing the theoretical values and simulation values, the correctness of the theoretical derivation can be verified. Figure 3 The orthogonal correlation receiving structure shown in the figure designs a DSFH receiving link, which uses two sequences for joint frequency hopping, ie, M=2.

[0180] The simulation assumes strict synchronization between the receiver and transmitter. The simulation focuses on the received signal detection performance and does not consider gains from other methods such as channel coding. The simulation parameters are as follows: the frequency hopping band is 30 MHz to 88 MHz, the frequency hopping system channel spacing is 25 kHz, and the frequency hopping range contains 128 hopping frequencies.

[0181] The simulation analysis is carried out by taking a two-path Rayleigh fading channel as an example. The channel parameters are set as follows: the average path gain GAP is [0-3], in dB, and the sum of the received signals of all paths is set to 0 dB; the path delay vector is [02×10 -6 ], unit is s. Figure 5 The following are the simulation results of the DSFH orthogonal correlation receiving bit error rate performance under Rayleigh fading channel.

[0182] Figure 5 In the example, within the 1-hop dwell time, the number of sampling points N is 150, 375, 750, and 1500. It can be seen that as the number of sampling points increases, the bit error rate decreases significantly. When the number of sampling points is small, the gain brought by the increase in the number of sampling points is large, and the performance gain becomes smaller and smaller as the number of sampling points increases. When the number of sampling points is 750, the bit error rate increases from 10 -2 Down to 10 -3 , the signal-to-noise ratio increases by about 10dB, which is basically consistent with the theoretical curve.

[0183] The performance of the multi-sequence frequency hopping communication signal receiving method is compared by simulation, and the performance of the DSFH signal receiving method through energy detection and orthogonal correlation is analyzed by simulation. The results are as follows Figure 6 shown.

[0184] like Figure 6 The figure shows the performance of orthogonal correlation and energy detection bit error rate when the number of sampling points N = 375 and N = 750. It can be seen that when the bit error rate is 10 -3 When the orthogonal correlation method is used, the performance is 6-8dB higher than that of the energy detection method.

[0185] From the above analysis, we can see that under the same fading channel conditions, the energy detection method performs worse than the orthogonal correlation method. This is due to not fully utilizing the signal. For signals with unknown parameters, correlation or incoherent matched filtering can achieve performance between matched filtering and energy detection.

[0186] Example 2

[0187] like Figure 2 As shown, an embodiment of the present invention provides an orthogonal correlation detection and receiving system for a multi-sequence frequency hopping communication signal, the system comprising: an acquisition unit 1, a signal processing unit 2, a test statistic calculation unit 3 and an optimal detection statistic determination unit 4.

[0188] The acquisition unit 1 is used to determine the communication signal received by each receiving channel at the current start time and the frequency hopping sequence of each receiving channel at the current start time; the communication signal is the target information sent by the transmitting end.

[0189] The signal processing unit 2 is used to mix the communication signal with the local oscillator signal corresponding to the frequency hopping sequence for any receiving channel to obtain an intermediate frequency signal, and to perform branching processing on the intermediate frequency signal to obtain the first signal and the second signal of the receiving channel.

[0190] The test statistic calculation unit 3 is used to perform calculations on the first signal and the second signal for any receiving channel to obtain a first calculation result and a second calculation result, and to sum the first calculation result and the second calculation result to obtain a test statistic of the receiving channel; the calculation processing includes: integration operation and square operation.

[0191] The optimal detection statistic determination unit 4 is used to use the maximum variance decision method to perform decision calculations on the detection statistics of each receiving channel to determine the optimal detection statistic among the detection statistics of all receiving channels; the optimal detection statistic is the detection statistic corresponding to the minimum average error probability; the communication signal in the receiving channel corresponding to the optimal detection statistic is the target information.

[0192] Specifically, the optimal detection statistic determining unit 4 includes: a likelihood function determining module, an average likelihood ratio test discriminant determining module and an optimal detection statistic determining module.

[0193] The likelihood function determination module is used to determine the likelihood function of each receiving channel according to the communication signal and the local oscillator signal corresponding to the frequency hopping sequence.

[0194] The average likelihood ratio test discriminant determination module is used to input each test statistic into the corresponding likelihood function and determine the average likelihood ratio test discriminant according to all likelihood functions.

[0195] The best detection statistic determination module is used to determine the best detection statistic among the detection statistics of all receiving channels based on the average likelihood ratio test discriminant.

[0196] The beneficial effects of the present invention are:

[0197] The present invention addresses the problem of low bit error rate under low signal-to-noise ratio in the reception of multi-sequence frequency hopping communication signals in the prior art, and overcomes the problem that reception methods based on energy detection do not fully utilize the prior knowledge of multi-sequence frequency hopping communication signals. The communication signals received by the multi-sequence frequency hopping communication system at the receiving end are all narrowband signals that arrive at the receiver after passing through a wireless channel. The two have the same characteristics. Utilizing this characteristic, multiple receiving channels use the same signal detection method. The reception method proposed by the present invention fully utilizes the prior knowledge of multi-sequence frequency hopping communication signals, equating the received signal to a signal with known frequency, random amplitude, and random phase. It sets up received signal detection, derives the optimal decision formula for signal detection, and designs the detection system structure and reception method, thereby achieving better signal detection and reception performance. In particular, for the detection and reception of multi-sequence frequency hopping communication signals under low signal-to-noise ratio, better detection and reception performance is achieved.

[0198] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. Reference can be made to the common and similar parts between the various embodiments. For the systems disclosed in the embodiments, since they correspond to the methods disclosed in the embodiments, the description is relatively simple, and the relevant parts can be referred to the method description.

[0199] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only intended to help understand the method and core concept of the present invention. At the same time, those skilled in the art will find that the specific implementation methods and application scopes may vary based on the concept of the present invention. In summary, the contents of this specification should not be construed as limiting the present invention.

Claims

1. A method for orthogonal correlation detection and reception of a multi-sequence frequency hopping communication signal, characterized in that: The method comprises: Determining a communication signal received by each receiving channel at a current start and a frequency hopping sequence of each receiving channel at the current start; the communication signal is target information sent by a transmitting end; For any receiving channel, mixing the communication signal with the local oscillator signal corresponding to the frequency hopping sequence to obtain an intermediate frequency signal, and performing branching processing on the intermediate frequency signal to obtain a first signal and a second signal of the receiving channel; For any receiving channel, performing operation processing on the first signal and the second signal to obtain a first operation result and a second operation result, and performing a sum operation on the first operation result and the second operation result to obtain a test statistic of the receiving channel; the operation processing includes: an integration operation and a square operation; The maximum variance decision method is adopted to perform decision calculation on the detection statistics of each receiving channel to determine the best detection statistic among the detection statistics of all receiving channels; the best detection statistic is the detection statistic corresponding to the minimum average error probability; the communication signal in the receiving channel corresponding to the best detection statistic is the target information.

2. The orthogonal correlation detection and reception method for a multi-sequence frequency hopping communication signal according to claim 1, wherein: The maximum variance decision method is used to perform decision calculation on the detection statistics of each receiving channel to determine the best detection statistic among the detection statistics of all receiving channels, specifically including: Determining a likelihood function of each of the receiving channels according to the communication signal and a local oscillator signal corresponding to the frequency hopping sequence; Inputting each of the test statistics into a corresponding likelihood function, and determining an average likelihood ratio test discriminant based on all likelihood functions; Based on the average likelihood ratio test discriminant, an optimal detection statistic among the detection statistics of all receiving channels is determined.

3. The orthogonal correlation detection and reception method for a multi-sequence frequency hopping communication signal according to claim 1, wherein: The calculation formula of the test statistic is: in, l1 is the test statistic; x 1I is the first signal; x 1Q is the second signal; T s is the period of each hop; x1(t) is the intermediate frequency signal; w1 is the frequency of the communication signal, and t is the time.

4. The orthogonal correlation detection and reception method for multi-sequence frequency hopping communication signals according to claim 2, wherein: The likelihood function is: Where P[x1(t)|a1,θ1;H0] is the likelihood function of the receiving channel; x1(t) is the intermediate frequency signal; H0 is the local oscillator signal corresponding to the frequency hopping sequence; a1 is the amplitude of the communication signal; F is a constant; T s is the period of each hop; N0 is the noise power; θ1 is the phase of the communication signal; ω1 is the frequency of the communication signal.

5. The orthogonal correlation detection and reception method for multi-sequence frequency hopping communication signals according to claim 2, wherein: The determining, based on the average likelihood ratio test discriminant, the best detection statistic among the detection statistics of all receiving channels specifically includes: Calculating the probability of wrong decision and the probability of correct decision corresponding to the detection statistic in the average likelihood ratio test discriminant using a probability density function; Determining a probability judgment formula according to the probability of wrong judgment and the probability of correct judgment; Based on the probability decision formula, the detection statistic corresponding to the minimum average error probability is determined as the best detection statistic among the detection statistics of all receiving channels.

6. The orthogonal correlation detection and reception method for multi-sequence frequency hopping communication signals according to claim 5, characterized in that: The calculation formula of the probability density function is: p(l1|H0) is the probability density function between the detection statistic of the channel and the frequency hopping signal corresponding to the frequency hopping sequence; l1 is the test statistic; H0 is the local oscillator signal corresponding to the frequency hopping sequence; N0 is the noise power.

7. An orthogonal correlation detection and reception system for multi-sequence frequency hopping communication signals, characterized in that: The system comprises: An acquisition unit, configured to determine a communication signal received by each receiving channel at a current start and a frequency hopping sequence of each receiving channel at a current start; the communication signal being target information sent by a transmitting end; a signal processing unit configured to, for any receiving channel, mix the communication signal with a local oscillator signal corresponding to the frequency hopping sequence to obtain an intermediate frequency signal, and perform branching processing on the intermediate frequency signal to obtain a first signal and a second signal of the receiving channel; a test statistic calculation unit, configured to, for any receiving channel, perform arithmetic processing on both the first signal and the second signal to obtain a first operation result and a second operation result, and perform a sum operation on the first operation result and the second operation result to obtain a test statistic of the receiving channel; the arithmetic processing includes: an integral operation and a square operation; The optimal detection statistic determination unit is used to adopt the maximum variance decision method to perform decision calculation on the detection statistics of each of the receiving channels to determine the optimal detection statistic among the detection statistics of all the receiving channels; the optimal detection statistic is the detection statistic corresponding to the minimum average error probability; the communication signal in the receiving channel corresponding to the optimal detection statistic is the target information.

8. The orthogonal correlation detection and receiving system for multi-sequence frequency hopping communication signals according to claim 7, wherein: The optimal detection statistic determining unit includes: A likelihood function determination module, configured to determine a likelihood function of each of the receiving channels based on the communication signal and the local oscillator signal corresponding to the frequency hopping sequence; An average likelihood ratio test discriminant determination module is used to input each of the test statistics into a corresponding likelihood function and determine an average likelihood ratio test discriminant based on all likelihood functions; The best detection statistic determination module is configured to determine the best detection statistic among the detection statistics of all receiving channels based on the average likelihood ratio test discriminant.

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