Random distributed space-time frequency coding and decoding method in relay cooperative cross-border communication

Abstract

The invention provides a random distributed space-time frequency coding and decoding method in relay cooperative cross-border communication. The problem that a relay node loses efficacy in cross-border or underwater magnetic induction communication is solved, and a decoding algorithm is improved. According to the method, on the basis of distributed space-time block coding matrixes, the distributed space-time block coding matrixes are linearly combined through a random matrix, and a randomized distributed space-time block coding matrix is obtained; and the relay node selects the corresponding row in the matrix for transmission, so that the randomness of the relay node does not influence the orthogonality of the space-time coding matrix, and the influence of the failure of the relay node on the coding structure is avoided. And then, the random distributed space-time coding is subjected to direct sequence spread spectrum coding, the frequency spectrum of a transmitted signal is expanded, a receiving end utilizes related reception of a spread spectrum signal, the signal is enhanced, the noise is suppressed, the received signal-to-noise ratio is remarkably improved, and the decoding performance of the space-time coding signal under the condition that the signal-to-noise ratio is extremely low is ensured.

Description

Technical Field

[0001] This invention belongs to the field of communication technology and mainly relates to a random distributed space-time-frequency encoding and decoding method in relay cooperative cross-border communication. Background Technology

[0002] Magnetic induction communication has unique advantages in cross-air-sea interfaces (referred to as cross-border) and underwater communication, and its research has attracted increasing attention. However, since magnetic induction propagates in the near-field, the intensity of the magnetic induction signal decreases rapidly with increasing distance and frequency, which severely limits the communication distance and available bandwidth of magnetic induction communication. This makes it impossible to simultaneously meet the performance requirements of cross-border magnetic induction communication for large communication range and high data rate, thus limiting the widespread application of magnetic induction communication.

[0003] Currently, the hot technologies for improving the performance of magnetic induction communication are relay waveguide (passive relay) and relay transmission (active relay) technologies. Relay waveguide technology utilizes the coupling between multiple coils in series or parallel to improve communication distance or data rate performance; in comparison, relay transmission technology can more flexibly utilize the deployment of relay nodes to maximize communication coverage, improve connectivity and robustness, and thus can more effectively improve the performance of magnetic induction communication.

[0004] In magnetic induction communication based on relay transmission, the improvement of communication performance depends on effective relay coordination techniques and methods, including relay protocols and the deployment of relay nodes. Therefore, the optimal location or deployment of relay nodes and the decode-forward (DF) relay protocol are the focus of many studies.

[0005] Compared with relay protocols such as amplify-forward (AF) and decode-forward (DF), distributed space-time coding at relay nodes can achieve higher spectral efficiency. The simulation analysis of distributed space-time coding in the paper "Cross-border magnetic induction relay cooperative communication scheme based on distributed space-time coding," 2022 IEEE Conf.Signal Processing, Communications and Computing (ICSPCC), 25-27 October 2022, pp.1-4, verifies the role of distributed space-time coding in improving the performance of cross-border magnetic induction communication.

[0006] However, in practical applications of cross-boundary magnetic induction communication, relay nodes may move beyond their effective communication range due to the dynamic marine environment; or they may fail to participate in relay coordination due to node malfunction or failure. This results in the number of nodes actually participating in relay coordination being random or uncertain. In such cases, if the receiving end is unaware of the relays participating in coding, it will severely affect the decoding performance of STBC. Secondly, distributed space-time decoding has high requirements for the received signal-to-noise ratio (SNR). A low SNR will degrade the performance of space-time decoding, thus failing to effectively obtain diversity gain and coding gain.

[0007] However, in actual cross-border communication environments, there are two problems in obtaining diversity gain: (1) When affected by the dynamic marine environment, if a relay node moves beyond the range of direct communication, the received signal-to-noise ratio of the relay node will be very low, and it will not be able to correctly decode the source transmission information. Therefore, it will not be able to participate in the space-time coding of the coordination stage and will become a failed relay node. The existence of a failed relay node makes the number of relay nodes participating in distributed space-time coding random or uncertain, which will destroy the original structure of the distributed space-time coding and inevitably lead to a decrease in decoding performance, thereby reducing the obtainable diversity gain. (2) In order to make cross-border communication have a large underwater coverage range, there must be a large distance between the transmitter and the relay node, and between the relay node and the receiver. The magnetic induction signal attenuates rapidly with the increase of distance, resulting in a weak signal at the receiver and an extremely low signal-to-noise ratio. The extremely low signal-to-noise ratio will cause a large number of errors in space-time decoding, resulting in low decoding reliability, which also reduces or even makes it impossible to obtain diversity gain.

[0008] To address the two issues mentioned above, this invention proposes a randomized distributed space-time-frequency coding scheme. This scheme uses randomized distributed space-time coding to solve the problem of uncertain relay node numbers and employs spread spectrum coding and correlation reception to enhance the signal, improve signal quality, and solve the reliability problem of space-time decoding under low signal-to-noise ratio conditions.

[0009] In summary, existing technologies lack distributed space-time coding schemes that can overcome relay node failure problems and decoding algorithms that enhance signal detection capabilities in cross-boundary or underwater magnetic induction communication. Summary of the Invention

[0010] To overcome the shortcomings of existing technologies, solve the problem of relay node failure in cross-border or underwater magnetic induction communication, and improve the decoding algorithm, this invention provides a random distributed space-time-frequency encoding and decoding method for relay cooperative cross-border communication.

[0011] A random distributed space-time-frequency encoding and decoding method for relay-coordinated cross-border communication includes the following steps: Step 1: For those with N A communication system with one relay node and one receiver encodes the transmitted information to obtain an encoding matrix. G (s ), for the encoding matrix G ( s The randomization process is performed to obtain a randomized distributed R-DSTBC coding matrix; the elements of each row of the randomized distributed R-DSTBC coding matrix are spread-spectrum coded using pseudo-random noise PN codes to output the R-DSTFC signal; the R-DSTFC signal is then amplified and output by the first... i One effective relay node is transmitted; Step 2: Process the received R-DSTFC signal to obtain the despread output signal. For the despread output signal Sampling and decision-making are performed to output a digital sequence, which is the recovered R-DSTBC coded sequence; statistical decision-making for the transmitted signal is constructed to finally obtain the digital modulated signal sequence. Digital modulation signal sequence After digital demodulation, the original transmitted information is restored.

[0012] Furthermore, the acquisition of the encoding matrix G ( s The process is as follows: Assuming there are 2 in the signal constellation m For binary information, each point represents a single point. m =1; During a single encoding operation, a group km Each information bit is mapped into a signal constellation to select... k Each of the modulation signals is a modulated signal. m Selecting one point from each bit yields a digital modulation signal sequence. , ; The number of groups; sequentially grouping by length... L The data blocks are encoded to obtain the encoding matrix. G ( s ); according to G ( s The modulated signal is mapped to the space-time two-dimensional domain to generate... N A length of L Transmit codeword matrix X Transmit codeword matrix X It is a modulated signal and their conjugate signals The rows are composed of elements that are orthogonal to each other, satisfying the following equation: ; In the formula, c It is a constant. I N for N × NThe identity matrix, in Within each time slot, N Each relay antenna will respectively G (s) N One STBC codeword is transmitted; Transmit codeword matrix X The i The line indicates in L Within the transmission cycle from the first i The signal continuously transmitted by the relay antenna X The j Column representation j Through time N The signal transmitted by the root relay antenna; Furthermore, the step of obtaining the random distributed R-DSTBC encoding matrix is ​​as follows: Using randomized matrix R For the encoding matrix G ( s Perform a second mapping:

[0013] In the formula, the randomization matrix R for L × M The matrix is ​​represented as:

[0014] In the formula, M The number of valid relay nodes participating in the coding. M ≤ N Furthermore, each relay node is independent of the others; Therefore, in the time slot t output signal sequence X [ t ] is represented as: ; In the formula, , i = 1, 2, ..., M , i It is a randomized matrix R The i line, indicating the first i The random weighted vector corresponding to each relay antenna is also called the signature vector; G i, t ( s ) is the encoding matrix G ( s ) in the i Line number t The element of the column, the first t The column is also the firstt Time slot, t = 1, 2, ..., L ;but M One effective repeater antenna in L The random distributed R-DSTBC coding matrix for each time slot is:

[0015] In the formula, yes G ( s ) i Row vectors; The first random distributed R-DSTBC coding matrix i Okay, it is agreed that from the first i Encoded signals transmitted by each effective relay node; ; Furthermore, the randomization matrix R The construction methods include the uniform phase method, the Gaussian distribution method, and the uniform spherical method; The Gaussian distribution method is used to construct the randomization matrix. R The process is as follows: For each r i Independently generated L Each has zero mean and covariance. I Independent complex Gaussian components as vectors r i Element; The uniform phase method constructs a randomized matrix. R The process is as follows: Each element equals , In order to be in A random variable that is uniformly distributed in the middle.

[0016] The uniform spherical method is used to construct a randomized matrix. R The process is as follows: The random vectors generated by the Gaussian distribution method are normalized, so that... .

[0017] Furthermore, the step of outputting the R-DSTFC signal is as follows: In the i One valid relay node, i = 1, 2, ..., M Assume that the agreement is to send the first random distributed R-DSTBC encoding matrix. i OK x i , waveform signal g ( t The baseband signal formed mi ( t )for:

[0018] In the formula, g ( t () represents the baseband waveform signal. g ( t Select a rectangular pulse signal; T b The pulse width of the baseband signal; m i ( t ) bandwidth B m Baseband signal pulse width T b The reciprocal of, that is B m = 1 / T b ; PN baseband signal generated by PN code generator for:

[0019] In the formula, c n It is a binary PN code. T c The pulse width of the PN signal; T b >> T c ; m i ( t The signal is modulo-2 added to the PN baseband signal or multiplied by the waveform to generate a spreading sequence with the same rate as the PN code. d i ( t Simultaneously, a random distributed space-time-frequency coded R-DSTFC sequence is obtained. d i ( t )for:

[0020] In the formula,

[0021] d i ( t bandwidth B d Baseband signal pulse width T c The reciprocal of, that is Bd = 1 / T c ;because T b >> T c Therefore, B d >> B m In other words, the bandwidth of the R-DSTFC baseband signal has been greatly expanded; After carrier modulation, the output R-DSTFC signal is represented as:

[0022] After the R-DSTFC signal is amplified, it is then used by the... i One effective relay node is launched.

[0023] Furthermore, the process of obtaining the despread output signal The steps are as follows: At the receiving end, from M Received signals transmitted by each effective relay node Represented as:

[0024] In the formula, h i ( t ) is the first i The channel coefficients between each effective relay node and the receiver; w ( t () represents noise in the received signal; Demodulator output for:

[0025] In the formula, w c ( t () represents noise in the received signal w ( t The in-phase portion of ) The transmitted PN code copy is correlated and despread with the demodulator output. After correlation and integration, the despread output signal is output. for: ; In the formula, yes c PN ( t The average power of ) w d ( t )for wc ( t The output after correlation and integration is expressed as ; Despread output signal The calculation utilizes the following condition: within chip time T c internal signal m i ( t The channel coefficients are constant; assuming the channel coefficients are constant. h i ( t Channel probing is known.

[0026] Furthermore, the statistical decision-making process for constructing the transmitted signal ultimately yields a digital modulated signal sequence. The steps are as follows: Despread output signal The output sequence of numbers after sampling decision for:

[0027] in, h i ’ = h i P c The channel equivalence coefficient; x i yes m i Output value after sampling and decision; w These are sampled values ​​of the noise term; Assume the receiver probes a known channel through the channel. h i ’ Given the state information CSI, the maximum likelihood ML decoding should minimize the following metrics:

[0028] Construct transmission signal x i The statistical judgment is as follows: ; In the formula, sgn t ( i ) represents the encoding matrix G ( s ) t Column elements x i The symbol for ε; t ( i () is a symbol arrangement ε t The t In the list x i Location, ε t This represents the arrangement of symbols from column 1 to column t in the encoding matrix; Due to the encoding matrix G ( s The orthogonality of the signals is a property of the signals. x i The construction of decision statistics is independent of other transmitted signals. x i , j =1, 2, …, N , j ≠ i Therefore, each signal x i The decoding can be performed independently, ultimately yielding a digital modulated signal sequence. After digital demodulation, the original transmitted information is restored.

[0029] The beneficial effects of this invention are: the randomized distributed space-time-frequency coding (R-DSTFC) scheme proposed in this invention reduces the impact on diversity performance when the number of relay nodes is uncertain by randomizing the DSTBC coding matrix; this invention proposes to improve the received signal-to-noise ratio and ensure the performance of R-DSTFC signal decoding by spectral spreading and correlation despreading of the R-DSTFC coded signal. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of cross-border communication based on relay coordination. Figure 2 This is a channel model for cross-border communication based on relay coordination, where S represents the transmitter. D Indicates the receiving end. Indicates a relay node; Figure 3 A block diagram illustrating the principle of the Random Distributed Space-Time-Frequency (R-DSTFC) encoding and decoding scheme; Figure 4 This is a block diagram illustrating the principles of demodulation and despreading. Figure 5 Bit error rate curve of R-DSTBC coding scheme when the number of relay nodes is determined Figure 6 The bit error rate curve of the R-DSTBC scheme when the number of relay nodes varies randomly; Figure 7 The bit error rate curves are shown for using relay cooperative communication and without cooperative communication; Figure 8Bit error rate curves for R-DSTFC and R-DSTBC schemes Figure 9 A schematic diagram and a real-world scenario diagram of node deployment for the R-DSTBC scheme's field land test; where (a) is a schematic diagram of relay nodes and receivers; (b) is a deployment scenario of relay nodes; and (c) is a deployment scenario of receivers. Figure 10 The waveforms are the received signal and the noise-processed waveform when the receiving antenna is 15 meters away from the origin; where (a) is the received signal waveform and (b) is the noise-processed signal waveform. Figure 11 To demodulate the output waveform; Figure 12 The outputs are despreading and decoding results, where (a) is the related despreading output signal and (b) is the decoding output signal. Detailed Implementation

[0031] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0032] The overall scheme of this invention is as follows: A schematic diagram of cross-boundary magnetic induction communication based on relay coordination is shown below. Figure 1 As shown, the transmitter and receiver are located in the air and underwater, respectively, with relay nodes deployed underwater. When no relay node is available, direct cross-boundary communication (referred to as direct communication) occurs between the source transmitter and the destination receiver. Due to signal attenuation, the underwater communication range of direct communication is very limited. This invention uses a communication range threshold line to identify the communication range. Figure 1 The symbol indicates the communication range of cross-border communication from air to underwater (referred to as air-sea). When using relay coordination, relay nodes are placed within the direct communication range. Source information is first received by the relay node and then forwarded to the destination. This creates multiple independent transmission channels between the source and receiver. Distributed space-time coding is performed on the relay nodes to maximize spatial diversity gain and coding gain. With the help of diversity gain, the communication range and data rate performance of cross-border magnetic induction communication based on relay coordination (referred to as relay communication) will be significantly better than that of direct communication.

[0033] Channel model for cross-boundary magnetic induction communication based on relay coordination, such as... Figure 2 As shown. The relay cooperative communication process consists of two phases. The first phase is the broadcast phase, where the signal originates from the transmitting end. S The message was broadcast to all relay nodes. The first stage involves receiving signals; this stage does not involve space-time coding. The second stage is the coordination stage, involving each relay node. P i After demodulating and decoding the received signal, the original transmitted information is recovered; this information is then space-time encoded, and the encoded signal is modulated and forwarded. (Receiver end)D The space-time coded signal is received, demodulated, and then space-time decoded to recover the original information. This demonstrates the effectiveness of space-time coding in distributed relay nodes. P i The decoding process is completed at the receiving end, rather than being centralized on a single node; therefore, distributed space-time coding is employed. D Completed.

[0034] Clearly, the degree of performance improvement in cross-boundary communication after adopting relay-based cooperative communication depends on the magnitude of the diversity gain obtained. The diversity gain, in turn, depends on the design of the distributed space-time coding scheme; and the effective acquisition of the diversity gain depends on the reliable implementation of the decoding algorithm.

[0035] However, in actual cross-border communication environments, there are two problems in obtaining diversity gain: (1) When affected by the dynamic marine environment, if a relay node moves beyond the range of direct communication, the received signal-to-noise ratio of the relay node will be very low, and it will not be able to correctly decode the source transmission information. Therefore, it will not be able to participate in the space-time coding of the coordination stage and will become a failed relay node. The existence of a failed relay node makes the number of relay nodes participating in distributed space-time coding random or uncertain, which will destroy the original structure of the distributed space-time coding and inevitably lead to a decrease in decoding performance, thereby reducing the obtainable diversity gain. (2) In order to make cross-border communication have a large underwater coverage range, there must be a large distance between the transmitter and the relay node, and between the relay node and the receiver. The magnetic induction signal attenuates rapidly with the increase of distance, resulting in a weak signal at the receiver and an extremely low signal-to-noise ratio. The extremely low signal-to-noise ratio will cause a large number of errors in space-time decoding, resulting in low decoding reliability, which also reduces or even makes it impossible to obtain diversity gain.

[0036] To address the two issues mentioned above, this invention proposes a randomized distributed space-time-frequency coding scheme. This scheme uses randomized distributed space-time coding to solve the problem of uncertain relay node numbers and employs spread spectrum coding and correlation reception to enhance the signal, improve signal quality, and solve the reliability problem of space-time decoding under low signal-to-noise ratio conditions.

[0037] A random distributed space-time-frequency encoding and decoding method for relay-coordinated cross-border communication includes the following steps: Step 1: For those with N A communication system with one relay node and one receiver encodes the transmitted information to obtain an encoding matrix. G ( s ), for the encoding matrix G ( sThe randomization process is performed to obtain a randomized distributed R-DSTBC coding matrix; the elements of each row of the randomized distributed R-DSTBC coding matrix are spread-spectrum coded using pseudo-random noise PN codes to output the R-DSTFC signal; the R-DSTFC signal is then amplified and output by the first... i One effective relay node is transmitted; Step 1-1: Encode the transmitted information to obtain the encoding matrix. G ( s ); Distributed Space-Time Block Coding (DSTBC) employs an orthogonal design, enabling the receiver to perform maximum likelihood decoding by performing simple linear processing on the received signal, thus obtaining the signal obtained from the number of transmit antennas. N A defined complete diversity gain; For those N A communication system with one relay node and one receiver, assuming there are 2 relay nodes and 1 receiver in the signal constellation. m For binary information, each point represents a single point. m =1; During a single encoding operation, a group km Each information bit is mapped into a signal constellation to select... k Each of the modulation signals is a modulated signal. m Selecting one point from each bit yields a digital modulation signal sequence. , ; The number of groups; sequentially grouping by length... L The data blocks are encoded to obtain the encoding matrix. G ( s ); according to G ( s The modulated signal is mapped to the space-time two-dimensional domain to generate... N A length of L Transmit codeword matrix X Transmit codeword matrix X It is a modulated signal and their conjugate signals The rows are composed of elements that are orthogonal to each other, satisfying the following equation: ; In the formula, c It is a constant. I N for N × N The identity matrix, in Within each time slot, N Each relay antenna will respectively G (s) N One STBC codeword is transmitted; Transmit codeword matrixX The i The line indicates in L Within the transmission cycle from the first i The signal continuously transmitted by the relay antenna X The j Column representation j Through time N The signal transmitted by the root relay antenna; Orthogonality enables a specific number of relay antennas to achieve complete transmit diversity, allowing the receiver to separate the signals transmitted by different relay antennas, thus enabling maximum likelihood decoding through simple linear processing of the received signal; Number of relay nodes N When the values ​​are 2, 3, and 4, the encoding matrix G ( s The following are in order:

[0038]

[0039]

[0040] Step 1-2: For the encoding matrix G ( s The randomization process is performed to obtain a randomized distributed R-DSTBC encoding matrix; it is agreed that each relay node corresponds to a certain row of the randomized distributed R-DSTBC encoding matrix. Using randomized matrix R For the encoding matrix G ( s Perform a second mapping:

[0041] In the formula, the randomization matrix R for L × M The matrix is ​​represented as:

[0042] In the formula, M The number of valid relay nodes participating in the coding. M ≤ N Furthermore, each relay node is independent of the others; Therefore, in the time slot t output signal sequence X [ t ] is represented as:

[0043] In the formula, , i= 1, 2, ..., M , i It is a randomized matrix R The i line, indicating the first i The random weighted vector corresponding to each relay antenna is also called the signature vector; G i, t ( s ) is the encoding matrix G ( s ) in the i Line number t The element of the column, the first t The column is also the first t Time slot, t = 1, 2, ..., L ;but M One effective repeater antenna in L Random Distributed R-DSTBC Coding Matrix between Time Slots Represented as:

[0044] In the formula, yes G ( s ) i Row vectors; For random distributed R-DSTBC coding matrix The i Okay, it is agreed that from the first i Encoded signals transmitted by each effective relay node; ; By randomizing the matrix R The mapping will G ( s Decentralization processing ensures that the transmission sequence generated by each effective relay antenna is no longer a coding matrix. G ( s Instead of a single row of the encoding matrix, the relay node selects the corresponding row in the matrix for transmission. When a relay node becomes invalid, it is equivalent to deleting a combination of certain rows of the encoding matrix without affecting the structure and orthogonality of the encoding matrix. The corresponding low-dimensional code has the same diversity product as the original code, thus avoiding the impact of relay node failure on the encoding structure and decoding performance. The randomization matrix R The construction methods include the uniform phase method, the Gaussian distribution method, and the uniform spherical method; this invention adopts the Gaussian distribution method, that is, for each... r i Independently generated L Each has zero mean and covariance. I Independent complex Gaussian components as vectorsr i Element; The uniform phase method is as follows: Each element equals , In order to be in A uniformly distributed random variable; The Gaussian distribution method is as follows: It has zero mean and covariance. I Independent complex Gaussian vectors; The uniform spherical method involves normalizing the random vector generated by the Gaussian distribution method, so that... ; Steps 1-3: Encoding the random distributed R-DSTBC matrix Each row of elements is spread spectrum encoded using pseudo-random noise PN code, and the output is an R-DSTFC signal; The random distributed space-time frequency coding (R-DSTFC) proposed in this invention adds spreading coding to random distributed space-time block coding, thereby enabling the receiver to improve the signal-to-noise ratio and enhance the detection capability of weak signals by using correlation despreading of the spreading signal, thus ensuring the decoding performance of distributed space-time coding and obtaining effective diversity gain.

[0045] After completing the random distributed space-time block coding (R-DSTBC), it is then directly sequence spread spectrum (DSSS) encoded using pseudo-random PN codes to obtain the R-DSTFC encoded sequence or signal. The R-DSTFC encoded sequence or signal can be implemented by directly spreading the R-DSTBC code or by using baseband spread spectrum. Moreover, using baseband spread spectrum to represent the R-DSTFC code makes it easier to explain the process of improving the signal-to-noise ratio through spread spectrum and correlation despreading. The steps of the spreading coding are as follows: In the i One valid relay node, i = 1, 2, ..., M Assume that the agreement is to send the first random distributed R-DSTBC encoding matrix. i OK x i , waveform signal g ( t The baseband signal formed m i ( t )for:

[0046] In the formula, g ( t () represents the baseband waveform signal. g (t Select a rectangular pulse signal; T b The pulse width of the baseband signal; m i ( t bandwidth B m Baseband signal pulse width T b The reciprocal of, that is B m = 1 / T b ; PN baseband signal generated by PN code generator for:

[0047] In the formula, c n It is a binary PN code. T c The pulse width of the PN signal; T b >> T c ; m i ( t The signal is modulo-2 added to the PN baseband signal or multiplied by the waveform to generate a spreading sequence with the same rate as the PN code. d i ( t Simultaneously, a random distributed space-time-frequency coded R-DSTFC sequence is obtained. d i ( t )for:

[0048] In the formula,

[0049] d i ( t bandwidth B d Baseband signal pulse width T c The reciprocal of, that is B d = 1 / T c ;because T b >> T c Therefore, B d >>B m In other words, the bandwidth of the R-DSTFC baseband signal has been greatly expanded; After carrier modulation, the output R-DSTFC signal is represented as:

[0050] After the R-DSTFC signal is amplified, it is then used by the... i One effective relay node is transmitted; Step 2: Process the received R-DSTFC signal to obtain the despread output signal. For the despread output signal Sampling and decision-making are performed to output a digital sequence, which is the recovered R-DSTBC coded sequence; statistical decision-making for the transmitted signal is constructed to finally obtain the digital modulated signal sequence. Digital modulation signal sequence After digital demodulation, the original transmitted information is restored; Step 2-1: Process the R-DSTFC signal to obtain the despread output signal. For the despread output signal Perform sampling and decision-making, and output a digital sequence, which is the recovered R-DSTBC encoded sequence; The specific process of despreading is as follows: At the receiving end, from M Received signals transmitted by each effective relay node Represented as:

[0051] In the formula, h i ( t ) is the first i The channel coefficients between each effective relay node and the receiver; w ( t () represents noise in the received signal; The principle block diagram of demodulation and related despreading is as follows: Figure 4 As shown, the output of the demodulator for:

[0052] In the formula, w c ( t () represents noise in the received signal w ( t The in-phase portion of ) The transmitted PN code copy is correlated and despread with the demodulator output. After correlation and integration, the despread output signal is output. for:

[0053] In the formula, yes c PN ( t The average power of ) w d ( t )for w c ( t The output after correlation and integration is expressed as ; Despread output signal The calculation utilizes the following condition: within chip time T c internal signal m i ( t The channel coefficients are constant; assuming the channel coefficients are constant. h i ( t It is known through channel probing; Despread output signal Perform sampling and decision-making, and output a digital sequence, which is the recovery amount R-DSTBC encoded sequence; Despread output signal It is known that, in the despread output signal When making sampling decisions, although the signal amplitude is affected by the channel coefficient h i ( t The decay of ) is reduced, but the related despreading increases it again. P c The spread spectrum gain is increased by a factor of 1, which improves the signal amplitude and signal-to-noise ratio. Moreover, the longer the PN code sequence, the greater the spread spectrum gain and the higher the signal-to-noise ratio improvement. Step 2-2: Construct statistical decisions for the transmitted signal to finally obtain the digital modulated signal sequence. ; Despread output signal The output sequence of numbers after sampling decision for:

[0054] in, h i ’ = h i P c The channel equivalence coefficient; x i yes mi Output value after sampling and decision; w These are sampled values ​​of the noise term; Assume the receiver probes a known channel through the channel. h i ’ Given the state information CSI, the maximum likelihood ML decoding should minimize the following metrics:

[0055] Construct transmission signal x i The statistical judgment is as follows: ; In the formula, sgn t ( i ) represents the encoding matrix G ( s ) t Column elements x i The symbol for ε; t ( i () is a symbol arrangement ε t The t In the list x i Location, ε t This represents the arrangement of symbols from column 1 to column t in the encoding matrix; Due to the encoding matrix G ( s The orthogonality of the signals is a property of the signals. x i The construction of decision statistics is independent of other transmitted signals. x i , j =1, 2, …, N , j ≠ i Therefore, each signal x i The decoding can be performed independently, ultimately yielding a digital modulated signal sequence. After digital demodulation, the original transmitted information is restored; The following examples illustrate the process of the Random Distributed Space-Time Block Coding (R-DSTBC) scheme.

[0056] Distributed space-time block coding: Distributed Space-Time Block Coding (DSTBC) employs an orthogonal design, enabling the receiver to perform maximum likelihood decoding by performing simple linear processing on the received signal, thus obtaining the signal obtained from the number of transmit antennas. NDetermined complete diversity gain.

[0057] For those N A communication system with one relay node and one receiver, assuming there are 2 relay nodes and 1 receiver in the signal constellation. m For binary information, each point represents a single point. m =1. In a single encoding operation, a group... km Each information bit is mapped into a signal constellation to select... k Each of the modulation signals is a modulated signal. m Each bit selects a point to obtain digital modulated signal data packets. . Sequentially for lengths of L The data blocks are encoded to obtain the transmission matrix. G ( s The space-time block encoder is based on... G ( s The modulated signal is mapped to the space-time two-dimensional domain to generate... N A length of L Transmit codeword matrix X . X It is a modulated signal and their conjugate signals The rows are composed of elements that are orthogonal to each other, satisfying the following equation: (1) In the formula, c It is a constant. I N for N × N The identity matrix, in Within each time slot, N Each relay antenna will respectively G (s) N Each STBC codeword is transmitted.

[0058] X The i The line indicates in L Within the transmission cycle from the first i The signal continuously transmitted by the relay antenna X The j Column representation j Through time N The signal transmitted by the root repeater antenna. Orthogonality allows a specific number of repeater antennas to achieve complete transmit diversity, allowing the receiver to separate the signals transmitted by different repeater antennas, thus enabling maximum likelihood decoding through simple linear processing of the received signal.

[0059] Considering the number of relay nodes N For cases 2, 3, and 4, the encoding matrix is... G( s The following are in order: (2) (3) (4) Random distributed space-time block coding: After completing the DSTBC encoding, the randomization matrix is ​​used. R For the encoding matrix G ( s Perform a second mapping: (5) In the formula, R for L × M The matrix is ​​represented as: (6) In the formula, M The number of valid relay nodes participating in the coding. M ≤ N Furthermore, each relay node is independent of the others.

[0060] Therefore, in the time slot t output signal sequence X [ t This can be represented as: (7) In the formula, , i = 1, 2, ..., M , is a random matrix R The i line, indicating the first i The random weighted vector corresponding to each relay antenna is also called the signature vector; G i, t ( s ), t = 1, 2, ..., L , is the space-time encoding matrix G ( s ) in the i Okay, number t Column (i.e.) t The elements of a time slot. M One effective repeater antenna in L The output signal matrix between time slots can be represented as: (8) In the formula, yes G ( s )i Row vectors; R-DSTBC matrix X The i , can be agreed to start from the first i Encoded signals transmitted by each valid relay node.

[0061] As can be seen from equation (12), through the random matrix R The mapping will G ( s Decentralization processing ensures that the transmission sequence generated by each effective relay antenna is no longer a coding matrix. G ( s Instead of a single row in the encoding matrix, the relay node transmits a linear combination of rows. Relay nodes select the corresponding row from the matrix for transmission. When a relay node becomes invalid, it's equivalent to deleting certain combinations of rows from the encoding matrix without affecting its structure and orthogonality. The corresponding low-dimensional code has the same diversity product as the original code, thus avoiding the impact of relay node failure on the encoding structure and decoding performance.

[0062] The following three methods can be used to construct randomized matrices. R : 1) Uniform phase method: Each element equals , In order to be in A uniformly distributed random variable; 2) Gaussian distribution method: It has zero mean and covariance. I Independent complex Gaussian vectors; 3) Uniform spherical method: Normalize the random vector generated by the Gaussian distribution method to make it... .

[0063] This invention employs the Gaussian distribution method, that is, for each r i Independently generated L Each has zero mean and covariance. I Independent complex Gaussian components as vectors r i Element.

[0064] Random Distributed Space-Time-Frequency (R-DSTFC) Coding: The random distributed space-time frequency coding (R-DSTFC) proposed in this invention adds spreading coding to random distributed space-time block coding, thereby enabling the receiver to improve the signal-to-noise ratio and enhance the detection capability of weak signals by using correlation despreading of the spreading signal, thus ensuring the decoding performance of distributed space-time coding and obtaining effective diversity gain.

[0065] After completing Random Distributed Space-Time Block Coding (R-DSTBC), it is then directly sequence spread spectrum (DSSS) encoded using pseudo-random (PN) codes to obtain the R-DSTFC encoded sequence or signal. R-DSTFC encoding can be implemented by directly spreading R-DSTBC codes or by using baseband spread spectrum. Furthermore, using baseband spread spectrum to represent R-DSTFC encoding makes it easier to explain the process of improving the signal-to-noise ratio through spread spectrum and correlation despreading. The following section uses the spread spectrum encoding of a baseband signal as an example to illustrate the R-DSTFC encoding process.

[0066] In the i One valid relay node, i = 1, 2, ..., M Assuming that the agreement is to send the R-DSTBC number 1 i OK x i It uses waveform signals g ( t The baseband signal formed m i ( t )for: (9) In the formula, g ( t The signal is a baseband waveform signal, which can be selected as a rectangular pulse signal; T b This represents the pulse width of the baseband signal.

[0067] m i ( t ) bandwidth B m Its baseband signal pulse width T b The reciprocal of, that is B m = 1 / T b .

[0068] The PN baseband signal generated by the PN code generator is represented as: (10) In the formula, c n It is a binary PN code. T c The pulse width of the PN signal; typically there are T b >> T c .

[0069] m i ( t The spread spectrum sequence is generated by performing a modulo-2 addition or waveform multiplication with the PN sequence, resulting in a spread spectrum sequence with the same rate as the PN code. d i ( t This refers to the Random Distributed Space-Time Frequency Coded (R-DSTFC) sequence. d i ( t ), represented as: (11) In the formula,

[0070] d i ( t ) bandwidth B d Its baseband signal pulse width T c The reciprocal of, that is B d = 1 / T c .because T b >> T c Therefore, B d >> B m In other words, the bandwidth of the R-DSTFC baseband signal has been greatly expanded.

[0071] After carrier modulation, the output R-DSTFC signal is represented as: (12) After the signal is amplified, it is then transmitted by the first... i One effective relay node is launched.

[0072] Decoding R-DSTFC: Decoding R-DSTFC involves two steps: despreading and R-DSTBC decoding. The despreading process will be introduced first.

[0073] At the receiving end, from M The received signal transmitted by each effective relay node is represented as follows: (13) In the formula, h i ( t ) is the first i The channel coefficients between each effective relay node and the receiver; w (t () represents noise in the received signal.

[0074] The principle block diagram of demodulation and related despreading is as follows: Figure 4 As shown, the demodulator output is: (14) In the formula, w c ( t () represents the noise item w ( t The in-phase portion of ).

[0075] The output of the demodulator is correlated and despread using a copy of the transmitted PN code and the demodulator output. After correlation and integration, the output is: (15) In the formula, yes c PN ( t The average power of ) w d ( t )for w c ( t The output after correlation and integration is expressed as ; Equation (15) is calculated using the following condition: during chip time T c internal signal m i ( t The channel coefficients are constant; assuming the channel coefficients are constant. h i ( t Channel probing is known.

[0076] The despread output signal is sampled and decided to output a digital sequence, which is the recovery R-DSTBC encoded sequence.

[0077] From equation (15), it can be seen that, for the signal y ( t When making sampling decisions, although the signal amplitude is affected by the channel coefficient h i ( t The decay of ) is reduced, but the related despreading increases it. P c This results in a spread spectrum gain of 10 times, thus improving the signal amplitude and signal-to-noise ratio. Furthermore, the longer the PN code sequence, the greater the spread spectrum gain and the higher the signal-to-noise ratio improvement.

[0078] The following describes the decoding process of R-DSTBC.

[0079] The output after sampling and decision-making of equation (15) is expressed as: (16) in, h i ’ = h i P c The channel equivalence coefficient; x i yes m i Output value after sampling and decision; w It is a sampled value of the noise term.

[0080] Assume the receiver probes a known channel through the channel. h i ’ Given the Common State Information (CSI), maximum likelihood (ML) decoding aims to minimize the following metrics: (17) Therefore, DSTBC is decoded into the transmitted signal. x i The constructed statistical decision is as follows: (18) In the formula, sgn t ( i ) represents the encoding matrix G ( s ) t Column elements x i The symbol for ε; t ( i () is a symbol arrangement ε t The t In the list x i Location, ε t This represents the arrangement of symbols from column 1 to column t in the encoding matrix.

[0081] Due to the encoding matrix G ( s The orthogonality of the signals is a property of the signals. x i The construction of decision statistics is independent of other transmitted signals. x i , j =1, 2, …, N , j ≠ iTherefore, each signal x i The decoding can be performed independently, ultimately yielding a digital modulation sequence s, which, after digital demodulation, recovers the original transmitted information.

[0082] The effectiveness of this invention in achieving objective one is demonstrated by comparing the bit error rate under conditions where the number of relay nodes is fixed and under conditions where the number of relay nodes changes randomly.

[0083] (1) Bit error rate of the R-DSTBC scheme under the condition of a fixed number of relay nodes; The transmit signal data rate is set to 100 bps, using binary phase shift keying (BPSK) modulation. The total number of planned relay nodes is assumed to be... N = 4, number of effective relays M The value can be 1, 2, 3, or 4; encoding matrix for The DSTBC encoding matrix is ​​generated using the Gaussian distribution method. R The number of Monte Carlo attempts is 1000.

[0084] like Figure 5 The figure shows the number of different valid relay nodes. M , M The bit error rate curves of the R-DSTBC coding scheme are shown when the number of relay nodes is 1, 2, 3, or 4. It can be seen that as the signal-to-noise ratio (SNR) increases, the number of relay nodes... M The bit error rate (BER) gradually decreases under the same SNR conditions; with the number of effective relay nodes, the BER gradually decreases. M With the increase in SNR, the bit error rate performance was significantly improved. For example, when SNR = -4dB, M = N When the value is 4, error-free reception is already achievable. Compared to M = 1 in the extreme case. M When =3, the BER can be reduced by two orders of magnitude. , M A signal-to-noise ratio gain of 2.5dB to 7dB can be obtained when the value is >1.

[0085] Figure 5 The demonstration shows that the more effective relays participating in relay coordination, the better it is for improving the bit error rate performance of the communication system.

[0086] (2) Bit error rate of the R-DSTBC scheme under the condition of random variation in the number of relay nodes; The simulation conditions are similar to those above, except that the number of effective relay nodes is randomly changed during the simulation. M value. Figure 6The bit error rate curves of the R-DSTBC coding scheme under the condition of random variation in the number of effective relay nodes are given.

[0087] exist Figure 6 In the middle, curve M =1 and M = 4 indicates single and M = N = The BER curve for the case with 4 valid relay nodes serves as a control group for BER. The other three curves represent the BER when the number of relay nodes varies randomly: the curve for case 1 M The value is randomly changed between 1 and 2, case 2. M The value is randomly changed between 2 and 3, case 3. M Then it will randomly change between 3 and 4.

[0088] Depend on Figure 6 It is clear that when the number of effective relays M When the number of nodes is randomly changed, the bit error rate of the R-DSTBC scheme remains relatively stable. For example, curve 3 represents the bit error rate when the number of nodes is randomly changed between 3 and 4, and it is consistent with... M The bit error rate curve at 4 is quite close; it is even better than... Figure 5 middle M Bit error rate when = 3. Compare. Figure 6 Case 2, Case 1 and Figure 5 In M = 2 and M The curve marked with = 1 also shows similar results.

[0089] The above results demonstrate that the R-DSTBC scheme proposed in this invention enhances the robustness of the DSTC coding scheme. Under the condition of random relay node numbers, the R-DSTBC scheme can achieve a higher effective node count. M ≤ N Under the condition of obtaining full diversity gain, the performance of distributed space-time coding is guaranteed.

[0090] Figure 6 The results demonstrated show that when the number of effective relay nodes participating in coding is fixed, Random Distributed Space-Time Block Coding (R-DSTBC) and Distributed Space-Time Block Coding (DSTBC) schemes have the same bit error rate performance. When the number of effective relay nodes participating in coding is uncertain or changes randomly, R-DSTBC and DSTBC schemes with fixed relay nodes have similar bit error rate performance, without significantly degrading the performance of relay coordination, thus ensuring the stability of diversity gain. (3) Bit error rate of relay coordination and relay transmission; Figure 7Bit error rate (BER) curves are presented for relay cooperative communication using Distributed Space-Time Coding (DSTBC) and Random Distributed Space-Time Block Coding (R-DSTBC) schemes, and for relay transmission communication without coding (direct forwarding). Compared with uncoded relay transmission communication, the BER performance of relay cooperative communication using distributed space-time coding is significantly improved. For example, when... At this time, relay cooperative communication using DSTBC can achieve a signal-to-noise ratio gain of no less than 4dB. Furthermore, the bit error rate of the R-DSTBC scheme is very close to that of the DSTBC scheme, which again demonstrates that the R-DSTBC scheme can guarantee the stable performance of relay cooperative communication in dynamic relay environments.

[0091] Figure 7 The results demonstrated show that relay coordination using distributed space-time coding can significantly improve the performance of cross-domain magnetic induction communication based on relay transmission by acquiring diversity gain and coding gain.

[0092] Demonstration of the R-DSTFC solution's effectiveness; The effectiveness of this invention in achieving objective two is demonstrated by comparing the bit error rate simulation and experimental results of the R-DSTFC scheme with spread spectrum coding and the R-DSTBC scheme without spread spectrum coding.

[0093] Bit error rates of R-DSTFC and R-DSTBC schemes: Assume the transmitted signal has a data rate of 100 bps, uses BPSK modulation, and employs a 32-bit m-sequence as the PN code for spread spectrum encoding. The Monte Carlo simulation is 1000 times. Figure 8 The bit error rate curves of the R-DSTFC scheme with spreading coding and the R-DSTBC scheme without spreading coding are presented under different numbers of relay nodes.

[0094] Depend on Figure 8 It can be seen that, regardless of whether the number of relay nodes is 2 or 4, under the same number of relay nodes, the bit error rate performance of the R-DSTFC scheme with spread spectrum coding is better than that of the R-DSTBC scheme without spread spectrum coding. For example, when the BER is 10... -3 At that time, the R-DSTFC scheme can achieve a signal-to-noise ratio gain of about 4dB.

[0095] Figure 8 The demonstration shows that the random distributed space-time frequency coding scheme, which incorporates spread spectrum coding into random distributed space-time block coding, has better noise resistance.

[0096] Data processing for land-based trials of the R-DSTFC program; The following data processing results from field tests of the R-DSTFC scheme demonstrate the effectiveness of the R-DSTFC scheme in noise immunity and improving the received signal-to-noise ratio.

[0097] Since the R-DSTFC scheme is applied at relay nodes, and relay coordination occurs between the relay nodes and the receiver, the effectiveness of the R-DSTFC scheme can be demonstrated through communication experiments between the relay nodes and the receiver. Furthermore, considering that land-based experiments are easier to conduct and much cheaper than maritime cross-domain communication experiments, and do not affect the demonstration of the R-DSTFC scheme's effectiveness, the processing results of the experimental data obtained from the land-based experiments from the relay nodes to the receiver are used to demonstrate the effect of the Random Distributed Space-Time-Frequency Coding (R-DSTFC) scheme in improving the received signal-to-noise ratio.

[0098] The experiment used two relay nodes ( N = 2) A receiver-only mode where the transmitting antenna is positioned fixedly, and the communication distance is controlled by changing the position of the receiving antenna. A diagram and scenario illustration of the equipment deployment are shown below. Figure 9 As shown, where, Figure 9 (a) is a schematic diagram of the equipment deployment, where P1, P2, and P represent two relay nodes and the receiving end, respectively; (b) is a scene diagram of the relay node deployment, where the red arrows indicate the positions of the relay nodes; the red values ​​represent the distances between nodes; indicating that relay node P1 is the origin of the coordinate system, and relay node P2 is located at (6, 1, 7). Figure 9 (c) is a scene diagram of the receiver deployment. The receiver includes an omnidirectional receiving antenna and a data acquisition and storage board, which are placed in a sealed container to form a self-contained internal recorder. The transmission and reception distance is controlled by changing the position of the receiver, and the distance between the relay node and the receiver is measured with a ruler.

[0099] During the experiment, both relay nodes simultaneously transmitted their own R-DSTFC signals, with the synchronization signals of the two transmitted signals staggered in the data format design. To facilitate communication performance evaluation, the transmitted information was a 10-bit binary random sequence, with a total of 5 sets of data transmitted; the signal used BPSK modulation, and the data rate was 100 bps.

[0100] Figure 10 The waveform of the received signal is given when the distance between the receiver and node P1 is 15m. As can be seen from the figure, due to the large amount of interference in the test environment, even after noise suppression signal processing, there is still a lot of interference in the signal. This is reflected in the presence of large interference signals in places between data packets where there should be no signal. Figure 11 The demodulated output signal of one set of data is given. Due to the presence of interference signals, a large number of bit errors occurred when the demodulated signal was decoded and converted into a binary sequence. When space-time decoding was performed on this basis, the bit error rate reached 2%. Figure 12The output signals of correlation despreading and decoding are presented. As shown in the figure, after correlation despreading, decoding using the correlation peaks can error-freely convert the data into a binary sequence. Based on this, space-time decoding can error-free recover the original transmitted information.

[0101] Figure 10-12 The results demonstrated show that the random distributed space-time-frequency coding scheme has better noise immunity, can effectively improve the receiver signal-to-noise ratio, and ensure the performance of space-time decoding at the receiver.

[0102] Summary of the demonstration: Simulation and experimental results of the above-mentioned random distributed space-time-frequency coding and decoding scheme show that the proposed random distributed space-time-frequency coding (R-DSTFC) scheme has the same performance as the distributed space-time block coding (DSTBC) scheme when the number of relay nodes is determined; and similar performance to the DSTBC scheme when the number of relay nodes is uncertain, ensuring the robustness of the receiver in obtaining diversity gain. The R-DSTFC coding and decoding scheme can effectively improve the received signal-to-noise ratio, ensuring the performance of space-time decoding at the receiver in long-distance communication, thereby ensuring the role of relay cooperation in improving the performance of cross-domain magnetic induction communication.

Claims

1. A random distributed space-time-frequency encoding and decoding method for relay-coordinated cross-border communication, characterized in that, Includes the following steps: Step 1: For those with N A communication system with one relay node and one receiver encodes the transmitted information to obtain an encoding matrix. G ( s ), for the encoding matrix G ( s The randomization process is performed to obtain a randomized distributed R-DSTBC coding matrix; the elements of each row of the randomized distributed R-DSTBC coding matrix are spread-spectrum coded using pseudo-random noise PN codes to output the R-DSTFC signal; the R-DSTFC signal is then amplified and output by the first... i One effective relay node is transmitted; Step 2: Process the received R-DSTFC signal to obtain the despread output signal. For the despread output signal Sampling and decision-making are performed to output a digital sequence, which is the recovered R-DSTBC coded sequence; statistical decision-making for the transmitted signal is constructed to finally obtain the digital modulated signal sequence. Digital modulation signal sequence After digital demodulation, the original transmitted information is restored.

2. The random distributed space-time-frequency encoding and decoding method in relay cooperative cross-border communication according to claim 1, characterized in that, The obtained encoding matrix G ( s The process is as follows: Assuming there are 2 in the signal constellation m For binary information, each point represents a single point. m =1; During a single encoding operation, a group km Each information bit is mapped into a signal constellation to select... k Each of the modulation signals is a modulated signal. m Selecting one point from each bit yields a digital modulation signal sequence. , ; The number of groups; sequentially grouping by length... L The data blocks are encoded to obtain the encoding matrix. G ( s ); according to G ( s The modulated signal is mapped to the space-time two-dimensional domain to generate... N A length of L Transmit codeword matrix X Transmit codeword matrix X It is a modulated signal and their conjugate signals The rows are composed of elements that are orthogonal to each other, satisfying the following equation: ； In the formula, c It is a constant. I N for N × N The identity matrix, in Within each time slot, N Each relay antenna will respectively G (s) N One STBC codeword is transmitted; Transmit codeword matrix X The i The line indicates in L Within the transmission cycle from the first i The signal continuously transmitted by the relay antenna X The j Column representation j Through time N The signal transmitted by the root relay antenna.

3. The random distributed space-time-frequency encoding and decoding method in relay cooperative cross-border communication according to claim 1, characterized in that, The steps for obtaining the random distributed R-DSTBC encoding matrix are as follows: Using randomized matrix R For the encoding matrix G ( s Perform a second mapping: In the formula, the randomization matrix R for L × M The matrix is ​​represented as: In the formula, M The number of valid relay nodes participating in the coding. M ≤ N Furthermore, each relay node is independent of the others; Therefore, in the time slot t output signal sequence X [ t ] is represented as: ； In the formula, , i = 1, 2, ..., M , i It is a randomized matrix R The i line, indicating the first i The random weighted vector corresponding to each relay antenna is also called the signature vector; G i, t ( s ) is the encoding matrix G ( s ) in the i Line number t The element of the column, the first t The column is also the first t Time slot, t = 1, 2, ..., L ;but M One effective repeater antenna in L The random distributed R-DSTBC coding matrix for each time slot is: In the formula, yes G ( s ) i Row vectors; The first random distributed R-DSTBC coding matrix i Okay, it is agreed that from the first i Encoded signals transmitted by each effective relay node; .

4. The random distributed space-time-frequency encoding and decoding method in relay cooperative cross-border communication according to claim 1, characterized in that, The steps for outputting the R-DSTFC signal are as follows: In the i One valid relay node, i = 1, 2, ..., M Assume that the agreement is to send the first random distributed R-DSTBC encoding matrix. i OK x i , waveform signal g ( t The baseband signal formed m i ( t )for: ； In the formula, g ( t () represents the baseband waveform signal. g ( t Select a rectangular pulse signal; T b The pulse width of the baseband signal; m i ( t ) bandwidth B m Baseband signal pulse width T b The reciprocal of, that is B m = 1 / T b ; PN baseband signal generated by PN code generator for: ； In the formula, c n It is a binary PN code. T c The pulse width of the PN signal; T b >> T c ; m i ( t The signal is modulo-2 added to the PN baseband signal or multiplied by the waveform to generate a spreading sequence with the same rate as the PN code. d i ( t Simultaneously, a random distributed space-time-frequency coded R-DSTFC sequence is obtained. d i ( t )for: ； In the formula, ; d i ( t ) bandwidth B d Baseband signal pulse width T c The reciprocal of, that is B d = 1 / T c ;because T b >> T c Therefore, B d >> B m After carrier modulation, the output R-DSTFC signal is represented as: ； After the R-DSTFC signal is amplified, it is then used by the... i One effective relay node is launched.

5. The random distributed space-time-frequency encoding and decoding method in relay cooperative cross-border communication according to claim 1, characterized in that, The obtained despread output signal The steps are as follows: At the receiving end, from M Received signals transmitted by each effective relay node Represented as: In the formula, h i ( t ) is the first i The channel coefficients between each effective relay node and the receiver; w ( t () represents noise in the received signal; Demodulator output for: In the formula, w c ( t () represents noise in the received signal w ( t The in-phase portion of ) The transmitted PN code copy is correlated and despread with the demodulator output. After correlation and integration, the despread output signal is output. for: ； In the formula, yes c PN ( t The average power of ) w d ( t )for w c ( t The output after correlation and integration is expressed as ; Despread output signal The calculation utilizes the following conditions: within chip time T c internal signal m i ( t The channel coefficients are constant; assuming the channel coefficients are constant. h i ( t Channel probing is known.

6. The random distributed space-time-frequency encoding and decoding method in relay cooperative cross-border communication according to claim 1, characterized in that, The statistical decision-making process for constructing the transmitted signal ultimately yields a digital modulated signal sequence. The steps are as follows: Despread output signal The output sequence of numbers after sampling decision for: in, h i ’ = h i P c The channel equivalence coefficient; x i yes m i Output value after sampling and decision; w These are sampled values ​​of the noise term; Assume the receiver probes a known channel through the channel. h i ’ Given the state information CSI, the maximum likelihood ML decoding should minimize the following metrics: ； Construct transmission signal x i The statistical judgment is as follows: ； In the formula, sgn t ( i ) represents the encoding matrix G ( s ) t Column elements x i The symbol for ε; t ( i () is a symbol arrangement ε t The t In the list x i Location, ε t This represents the arrangement of symbols from column 1 to column t in the encoding matrix; Due to the encoding matrix G ( s The orthogonality of the signals is a property of the signals. x i The construction of decision statistics is independent of other transmitted signals. x i , j =1, 2, …, N , j ≠ i Therefore, each signal x i The decoding can be performed independently, ultimately yielding a digital modulated signal sequence. After digital demodulation, the original transmitted information is restored.

7. The random distributed space-time-frequency encoding and decoding method in relay cooperative cross-border communication according to claim 3, characterized in that, The randomization matrix R The construction methods include the uniform phase method, the Gaussian distribution method, and the uniform spherical method; The Gaussian distribution method is used to construct a randomized matrix. R The process is as follows: For each r i Independently generated L Each has zero mean and covariance. I Independent complex Gaussian components as vectors r i Element; The uniform phase method constructs a randomized matrix. R The process is as follows: Each element equals , In order to be in A uniformly distributed random variable; The uniform spherical method is used to construct a randomized matrix. R The process is as follows: The random vectors generated by the Gaussian distribution method are normalized, so that... .

8. A terminal device, comprising a processor, a memory, and a computer program stored in the memory; characterized in that, When the processor executes a computer program, it implements a random distributed space-time-frequency encoding and decoding method for relay cooperative cross-border communication as described in any one of claims 1-7.

Images