Non-coherent receiving method, receiver and system based on hadamard autocorrelation characteristics

Abstract

The application belongs to the technical field of wireless communication, and discloses a non-coherent receiving method based on Hadamard autocorrelation characteristics, a receiver and a system. The method comprises time index demodulation, code index demodulation and digital modulation demodulation. The time index demodulation performs correlation operation on a received ultrasonic signal and a delay copy of the ultrasonic signal, obtains a correlation decision variable of each time frame, and determines an active frame combination and a demodulation time index bit. The code index demodulation extracts a signal in each active frame according to the active frame combination, performs point product summation on each sub-section according to Hadamard code iteration segmentation, determines a code index bit and an active code word, and performs correlation operation on the active code word and each active frame respectively and accumulates the results to obtain a symbol decision variable and demodulate a digital modulation bit. The application can reduce the complexity and power consumption of baseband processing of the receiver without estimating a channel impulse response and a transmission reference signal, and can obtain time diversity gain by using multiple active frames, thereby improving the transmission efficiency and reliability of ultrasonic communication.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to an incoherent receiving method, receiver, and system based on the autocorrelation property of Hadamard. Background Technology

[0002] Currently, in vivo communication mainly employs two physical layer schemes: radio frequency (RF) and ultrasound. Compared to RF, ultrasound exhibits lower attenuation in biological tissues and offers better clinical safety, making in vivo ultrasound communication a hot research topic. In in vivo ultrasound communication research, techniques such as orthogonal amplitude modulation (OAM) and orthogonal frequency division multiplexing (OFDM) have been introduced; however, these techniques use continuous waveforms, which may produce thermal effects on tissues. Broadband ultrasound systems employ low duty cycle pulses to mitigate thermal effects and multipath interference, but pulse sparsity limits the data rate.

[0003] Existing coherent receivers require precise carrier synchronization, time synchronization, and channel estimation, resulting in high hardware complexity and power consumption, which is detrimental to integration into embedded devices. Incoherent receivers mainly include energy detection receivers and transmission reference receivers. Energy detection receivers utilize only signal energy but discard phase information, leading to significant performance degradation in bit error rate under fading channels. Transmission reference receivers require additional transmission of reference signals, reducing spectral efficiency.

[0004] Traditional techniques primarily involve correlation detection of the orthogonality of Hadamard codewords. This method requires correlation calculations proportional to the codebook size and is highly sensitive to synchronization errors.

[0005] The combination of these problems results in existing noncoherent receiving technologies being sensitive to synchronization errors, having low energy capture efficiency, and high power consumption in codeword correlation operations under ultrasonic channels. At the same time, the system is constrained by thermal effects and falls into bottlenecks in rate and bit error rate, thus failing to achieve stable and reliable medium- and high-speed data transmission. Summary of the Invention

[0006] The purpose of this invention is to provide an incoherent reception method, receiver, and system based on the autocorrelation characteristics of Hadamard, to solve the problems of insufficient performance and spectral efficiency of existing incoherent receivers, and to reduce the complexity and power consumption of the baseband processing of incoherent receivers and optimize their bit error rate performance without the need for channel estimation, precise synchronization, and channel reference.

[0007] To achieve the above objectives, the present invention provides a noncoherent reception method based on the Hadamard autocorrelation property, comprising the following steps: S1. Execution time index demodulation, specifically including: Receive ultrasonic signals, perform correlation operations on the received ultrasonic signals and their delayed copies, and obtain the relevant decision variables for each time frame; The relevant metrics of the activation frame combination are obtained based on the relevant decision variables, and the time index bits are demodulated based on the sequence number of the activation frame combination relevant metrics. S2, Execution code index demodulation, specifically includes: Based on the activation frame combination determined by S1, the signals within each activation frame in the activation frame combination are extracted from the ultrasonic signal, and the signals within each activation frame are divided into multiple sub-segments according to the iterative segmentation method of Hadamard codewords. Dot product operations are performed on the segments within each active frame according to a predetermined pairing method, and the dot product results are summed to obtain the decision variables corresponding to each code index bit; the corresponding code index bit and activation codeword are determined according to the sign of each decision variable. S3. Perform digital modulation and demodulation, specifically including: Based on the activation codeword determined in S2, correlation operations are performed between the activation codeword and each activation frame determined in S1, and the correlation operation results are summed to obtain the symbol decision variable corresponding to the digital modulation bit; the digital modulation bit is demodulated based on the symbol decision variable.

[0008] Preferably, in S1, the first The relevant decision variables for each time frame are calculated using the following formula: ; in, In order to receive signals, For time, superscript Representing relevant decision variables The decision variable corresponding to the time index bit. For the first The start time of each time frame The duration of a frame. To delay time, , Total number of frames; from Activation in each frame Each frame It is a positive integer, and There are a total of A combination of activation frames, in which The coefficients are binomial, and the number of bits for the time index is... , This is the floor function; using In the combination The first combination is used for time index modulation, the second ( ) types of activation frame combinations The relevant metric for active frame combination is: ; Therefore, the estimation result of the active frame combination is as follows: ; Time index bits are The binary representation is obtained.

[0009] Preferably, in S2, the Hadamard codewords have the following autocorrelation properties: Based on the number of bits in the code index The corresponding Hadamard matrix is Hadamard matrix There are a total of 10 Hadamard codes, each codeword is equal to 10 ... The elements are ±1; The code index bit sequence is Then the corresponding Hadamard matrix The line code character is ,in Hadamard matrix The The first element of the line codeword; code index AND code index bit sequence The relationship between them satisfies ,in, This is a binary-to-decimal conversion function; For the Code index bits , and its corresponding Code words are divided into There are 3 consecutive sub-segments, each with a length of 1. , No. Each sub-segment is represented as: ; in, , ; Calculate the dot product of each adjacent segment according to the predetermined pairing method, and sum the dot product results: ; The dot product represents the sum of corresponding element-wise multiplications. For the first Code index bits Corresponding Hadamard matrix The line code The Each segment; The relationship between code index bits and Hadamard codewords is described as follows: when hour, ;when hour, .

[0010] Preferably, in S2, the demodulation of the first... When indexing the individual code bits, the active frames of the received signal are divided equally. There are 3 consecutive sub-segments, each with a length of 1. , For the duration of the time slice, the first In each sub-segment Indicates the first [frame] within the active frame The hourly video to the first The received signal components of each time slice, To estimate the combination of activation frames The frame number in the data; No. Code index bits The corresponding decision variables are calculated using the following formula: ; Among them, superscript Indicator Decision Variables For the decision variables corresponding to the code index bits, To receive the signal in the active frame Each segment For time, The duration of a frame. The number of bits for the code index. The relationship between frame duration and slice duration satisfies ; No. Code index bits The criteria for judgment are: .

[0011] Preferably, in S3, correlation operations are performed on the activation codeword and each activation frame respectively, and the results of the correlation operations are summed to obtain the symbol decision variable: ; in, In order to receive signals, For time, superscript Indicator Symbol Decision Variables For the decision variables corresponding to the digital modulation bits, For the first The start time of each time frame Hadamard matrix The The first line of code words One element; The duration of a frame. The duration of the time slice; The decision criterion for digital modulation bits is as follows: when the symbol decision variable is greater than 0, the digital modulation bit is determined to be 1; when the symbol decision variable is not greater than 0, the digital modulation bit is determined to be 0.

[0012] This invention provides an incoherent receiver based on Hadamard autocorrelation characteristics for implementing the above method, comprising: The receiving front end is used to receive ultrasonic signals and convert them into electrical signals; The time index demodulation module is used to perform correlation operations on the electrical signal and its delayed replica, obtain the relevant decision variables of each time frame, obtain the activation frame combination correlation metric based on the relevant decision variables, determine the activation frame combination based on the activation frame combination correlation metric, and output the time index bits. The code index demodulation module is used to extract the signal within each active frame in the active frame combination from the electrical signal according to the active frame combination, divide the signal within each active frame into multiple sub-segments according to the iterative segmentation method of the Hadamard codeword, perform dot product operation on each sub-segment in each active frame according to a predetermined pairing method, and sum the dot product results to obtain the decision variable corresponding to each code index bit, and output the code index bit and the active codeword according to the sign of each decision variable. The digital modulation and demodulation module is used to perform correlation operations on each activation frame in the combination of the activation codeword and the activation frame, sum the correlation operation results to obtain the symbol decision variable corresponding to the digital modulation bit, and output the digital modulation bit according to the symbol decision variable.

[0013] Preferably, the time index demodulation module includes: Delay unit, used to delay an electrical signal by a predetermined time. ; A multiplier is used to multiply an electrical signal by a delayed electrical signal; An integrator is used to adjust the output of the multiplier over the duration of each frame. Integrate within the frame to obtain the relevant decision variables for each frame; The comparator is used to compare the relevant metrics of each active frame combination and determine the frame combination with the largest relevant metric as the active frame combination.

[0014] Preferably, the code index demodulation module includes: A frame signal extraction unit is used to extract signals from each active frame from an electrical signal according to the active frame combination. The segmentation unit is used to divide the signal within each active frame into multiple sub-segments according to the iterative segmentation method of Hadamard codewords; The dot product summation unit is used to perform dot product operations on the sub-segments in each active frame according to a predetermined pairing method, and sum the dot product results to obtain the decision variables corresponding to each code index bit. The symbol decision unit is used to determine the corresponding code index bit and activation codeword based on the symbol of each decision variable.

[0015] The present invention also provides an ultrasonic index modulation communication system, including a transmitter and a non-coherent receiver: The transmitter divides the bit stream to be transmitted into time index bits, code index bits, and digital modulation bits. It determines the active frame combination based on the time index bits, selects the corresponding codeword from the Hadamard matrix based on the code index bits, and uses the elements of the codeword as amplitude coefficients to transmit ultrasonic pulses at each time slot position of each active frame in the active frame combination. It also digitally modulates the ultrasonic pulses based on the digital modulation bits. The incoherent receiver uses a time index demodulation module to demodulate time index bits, a code index demodulation module to demodulate code index bits, and a digital modulation and demodulation module to demodulate digital modulation bits.

[0016] Preferably, the ultrasonic index modulation communication system is an ultrasonic code index modulation system or an ultrasonic time code index modulation system; when it is an ultrasonic code index modulation system, its total number of frames is... The time index demodulation module is not working or outputs a fixed frame sequence number.

[0017] Therefore, the present invention employs the above-mentioned incoherent receiving method, receiver, and system based on the Hadamard autocorrelation characteristic, and has the following beneficial effects: (1) The present invention adopts the above method, which does not rely on channel impulse response estimation and does not require precise synchronization at the time slice level, greatly reducing the complexity and power consumption of receiver baseband processing; all transmitted pulses carry information, improving spectral efficiency and energy efficiency.

[0018] (2) The present invention adopts the iterative segmentation structure of Hadamard code words. Each code index bit only needs to perform the corresponding dot product and accumulation operations, without traversing or storing the entire codebook, which can reduce the amount of computation and storage overhead of code index demodulation.

[0019] (3) By activating multiple frames, the present invention utilizes the sequence number of the activated frame combination to carry the time index bit, and utilizes the code index bit and digital modulation bit jointly carried by each activated frame to obtain time diversity gain. Even if individual activated frames are subject to deep fading, multipath distortion or noise interference, other activated frames can still provide effective information for code index decision, thereby improving communication reliability and data transmission efficiency.

[0020] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Attached Figure Description

[0021] Figure 1This is a schematic diagram of the transmitted waveform of an embodiment of the non-coherent receiving method based on the autocorrelation property of the present invention; Figure 2 This is a schematic diagram of the overall structure of an embodiment of the noncoherent receiving system based on the autocorrelation characteristics of the Hadamard autocorrelation of the present invention. Detailed Implementation

[0022] Unless otherwise defined, the technical or scientific terms used in this invention shall have the ordinary meaning as understood by one of ordinary skill in the art to which this invention pertains.

[0023] The terms "first," "second," and similar terms used in this invention do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed following the word and their equivalents, without excluding other elements or objects.

[0024] The present invention provides a non-coherent reception method based on the autocorrelation properties of Hadamard, comprising the following steps: S1. Perform time-index demodulation steps, specifically including: The system receives ultrasonic signals and performs correlation operations on the received ultrasonic signals and their delayed copies to obtain the relevant decision variables for each time frame.

[0025] No. The relevant decision variables for each time frame are calculated using the following formula: ; in, In order to receive signals, For time, superscript Representing relevant decision variables The decision variable corresponding to the time index bit. For the first The start time of each time frame The duration of a frame. To delay time, , This represents the total number of frames.

[0026] The relevant metrics for the activation frame combination are determined based on the relevant decision variables, and the time index bits are demodulated based on the sequence number of the relevant metrics for the activation frame combination.

[0027] from Activation in each frame Each frame It is a positive integer, and There are a total of A combination of activation frames, in which The coefficients are binomial. The number of bits for the time index is... , This is the floor function. (Using...) In the combination This combination is used for time-indexed modulation. ( ) types of activation frame combinations The relevant metric for active frame combination is: .

[0028] Therefore, the estimation result of the active frame combination is as follows: Time index bits are The binary representation is obtained.

[0029] S2, the execution code index demodulation step, specifically includes: Based on the active frame combination determined by S1, the signals within each active frame in the frame combination are extracted from the ultrasonic signal, and the signals within each active frame are divided into multiple sub-segments according to the iterative segmentation method of Hadamard codewords.

[0030] Among them, Hadamard code characters have the following autocorrelation properties: Based on the number of bits in the code index The corresponding Hadamard matrix is Hadamard matrix There are a total of 10 Hadamard codes, each codeword is equal to 10 ... The elements are ±1.

[0031] The code index bit sequence is Then the corresponding Hadamard matrix The line code character is ,in Hadamard matrix The The first element of the line codeword. Code index. AND code index bit sequence The relationship between them satisfies ,in This is a binary-to-decimal conversion function.

[0032] For the Code index bits , and its corresponding Code words are divided into There are 3 consecutive sub-segments, each with a length of 1. , No. The sub-segments are: ; in, , .

[0033] Then calculate the values ​​of adjacent segments (segment 1 and segment 2, segment 3 and segment 4, ..., segment 5). With the The sum of the dot products of the segments: ; The dot product represents the sum of corresponding element-wise multiplications. For the first Code index bits Corresponding Hadamard matrix The line code The Each segment.

[0034] The relationship between code index bits and Hadamard codewords is described as follows: when hour, ;when hour, .

[0035] Demodulation When indexing the individual code bits, the active frames of the received signal are divided equally. There are 3 consecutive sub-segments, each with a length of 1. , For the duration of the time slice, the first ( In each sub-segment Indicates the first [frame] within the active frame The hourly video to the first The received signal components of each time slice, This is the estimated sequence number of the activation frame.

[0036] No. Code index bits The corresponding decision variables are calculated using the following formula: ; Among them, superscript Indicator Decision Variables For the decision variables corresponding to the code index bits, To receive the signal in the active frame Each segment For time, The duration of a frame. The number of bits for the code index. The relationship between frame duration and slice duration satisfies .

[0037] No. Code index bits The criteria for judgment are: .

[0038] S3. Perform digital modulation and demodulation, specifically including: Based on the activation codeword determined by S2, perform correlation operations on the activation codeword and each activation frame determined by S1, and sum the results of the correlation operations to obtain the symbol decision variables corresponding to the digital modulation bits; demodulate the digital modulation bits based on the symbol decision variables.

[0039] Among them, the symbolic decision variables are: ; in, In order to receive signals, For time, superscript Indicator Symbol Decision Variables For the decision variables corresponding to the digital modulation bits, For the first The start time of each time frame Hadamard matrix The The first line of code words One element; code index AND code index bit sequence The relationship between them satisfies , The duration of a frame. The duration of the time slice.

[0040] The decision criterion for digital modulation bits is as follows: when the symbol decision variable is greater than 0, the digital modulation bit is determined to be 1; when the symbol decision variable is not greater than 0, the digital modulation bit is determined to be 0.

[0041] This invention provides an incoherent receiver based on the Hadamard autocorrelation characteristic, used to implement the above method, comprising: The receiving front end is used to receive ultrasonic signals and convert them into electrical signals.

[0042] The time index demodulation module is used to perform correlation operations on the electrical signal and its delayed replica to obtain the relevant decision variables for each time frame, obtain the activation frame combination correlation metric based on the relevant decision variables, determine the activation frame combination based on the activation frame combination correlation metric, and output the time index bits.

[0043] The code index demodulation module is used to extract the signal within each active frame of the active frame combination from the electrical signal according to the active frame combination, divide the signal within each active frame into multiple sub-segments according to the iterative segmentation method of the Hadamard codeword, perform dot product operation on the sub-segments within each active frame according to a predetermined pairing method, and sum the dot product results to obtain the decision variable corresponding to each code index bit, and output the code index bit and the active codeword according to the sign of each decision variable.

[0044] The digital modulation and demodulation module is used to perform correlation operations on each activation frame in the combination of activation codeword and activation frame, sum the correlation operation results to obtain the symbol decision variable corresponding to the digital modulation bit, and output the digital modulation bit according to the symbol decision variable.

[0045] The time index demodulation module includes: Delay unit, used to delay an electrical signal by a predetermined time. .

[0046] A multiplier is used to multiply an electrical signal by a delayed electrical signal.

[0047] An integrator is used to adjust the output of the multiplier over the duration of each frame. Integrating within the frame yields the relevant decision variables for each frame.

[0048] The comparator is used to compare the relevant metrics of each active frame combination and determine the frame combination with the largest relevant metric as the active frame combination.

[0049] The code index demodulation module includes: The frame signal extraction unit is used to extract the signal within each active frame from the electrical signal based on the combination of active frames.

[0050] The segmentation unit is used to divide the signal within each active frame into multiple sub-segments according to the iterative segmentation method of Hadamard codewords.

[0051] The dot product summation unit is used to perform dot product operations on the sub-segments in each active frame according to a predetermined pairing method, and sum the dot product results to obtain the decision variables corresponding to each code index bit.

[0052] The symbol decision unit is used to determine the corresponding code index bit and activation codeword based on the symbol of each decision variable.

[0053] This invention discloses an ultrasonic index modulation communication system, comprising a transmitter and the aforementioned incoherent receiver: The transmitter divides the bit stream to be transmitted into time index bits, code index bits, and digital modulation bits. It determines the active frame combination based on the time index bits, selects the corresponding codeword from the Hadamard matrix based on the code index bits, and uses the elements of the codeword as amplitude coefficients to transmit ultrasonic pulses at each time slot position of each active frame in the active frame combination. The transmitter then digitally modulates the ultrasonic pulses based on the digital modulation bits.

[0054] The incoherent receiver uses a time index demodulation module to demodulate time index bits, a code index demodulation module to demodulate code index bits, and a digital modulation and demodulation module to demodulate digital modulation bits.

[0055] The ultrasonic index modulation communication system of this invention is either an ultrasonic code index modulation system or an ultrasonic time code index modulation system; when it is an ultrasonic code index modulation system, its total number of frames... The time index demodulation module does not perform time index demodulation, that is, it does not work or outputs a fixed frame sequence number.

[0056] Example 1: This embodiment is based on an inherent structural property of Hadamard codewords that links the code index bits to the segmented autocorrelation results of the codewords.

[0057] make For one The Hadamard matrix has row vectors that are codewords with elements of ±1. Take any row... line code Let the corresponding code index bit sequence be... ,satisfy ,in, This is a binary-to-decimal conversion function.

[0058] For the Code index bits , will the corresponding Code words are divided into There are 3 consecutive sub-segments, each with a length of 1. , No. ( Each sub-segment is represented as: ; in, .

[0059] Then calculate the values ​​of adjacent segments (segment 1 and segment 2, segment 3 and segment 4, ..., segment 5). With the The sum of the dot products of the segments: ; The dot product represents the sum of corresponding element-wise multiplications. For the first Code index bits Corresponding Hadamard matrix The line code The Each segment.

[0060] By observing low-order Hadamard matrices, for example The 8×8 matrix has the following code index bit mapping rules: ; The following pattern can be observed: When hour, ;when hour, Utilizing this property, the receiver does not need to know the specific codeword; it only needs to combine the received time-slice signals in the same segmented manner and calculate the dot product to recover the code index bit by bit. This demodulation method is insensitive to amplitude scaling, and therefore suitable for incoherent detection.

[0061] The transmitter structure to which this invention applies is as follows: In ultrasonic time-code indexed modulation mode, each information block contains bits, of which the first Each is a time index bit. , Each is a code index bit. The last one is the digital modulation bit. .definition , The duration of a block is Divided into 1 frame, each frame lasts 1 frame Each frame is further divided into One hourly video, one hourly video continues .Every One frame is activated in each frame, and the position of each frame is the frame combination number.

[0062] Time index bits Determine the activation frame combination sequence number Code index bits Decision from Hadamard matrix Select the first line code ,in, Hadamard matrix The The first element of the line codeword. Digital modulation bit. The coefficients that determine digital modulation are .

[0063] The transmission signal of the first information block is represented as: ; in, For pulse energy, For continued The ultrasonic pulse waveform, and To avoid inter-symbol interference.

[0064] like Figure 1 The diagram shown is a schematic of the transmitted waveform of the ultrasonic time-code index modulation system in this embodiment, specifically including: at this time, Code index bits Select the first row of the second-order Hadamard matrix. Time index bits Select frame 1 as the active frame combination, digital modulation bits The digital modulation coefficient is set to 1.

[0065] In ultrasonic code-indexed modulation mode, there is no time index, i.e. Each block contains only With one index bit and one digital modulation bit, the transmitted signal is simplified to sending a selected Hadamard codeword within a single frame and performing digital modulation.

[0066] Ultrasonic waves propagating within the body typically exhibit frequency-selective fading and multipath effects. The received signal is the transmitted signal convolved through the multipath channel and superimposed with noise. ; in, For the number of multipaths, For the first The channel coefficient of the path, For time delay, It is additive white Gaussian noise, and its two-sided power spectral density is... .

[0067] In-body channel coefficient ,in Indicates the attenuation coefficient. For communication distance, and For the attenuation parameters of human tissue, The center frequency of the transmitted signal and the fading coefficient are given. Obey Nakagami- distributed.

[0068] like Figure 2 The diagram shown is a schematic representation of the overall structure of an embodiment of the noncoherent receiving system based on the autocorrelation properties of the Hadamard autocorrelation system of the present invention.

[0069] Specifically, for an ultrasonic time-indexed modulation system, the receiver first needs to determine the active frame combination. The time-indexed demodulation module then processes the input signal... Perform the following processing: For the start position of each frame In the time window Internal calculation: ; in, For a fixed delay, In order to receive signals, For time, superscript Indicator of relevant decision variables The decision variables corresponding to the time index bits are used to ensure the peak value of autocorrelation.

[0070] In the noncoherent receiver based on the Hadamard autocorrelation property of this invention, since the transmitted signal contains within each frame... These pulses are amplitude modulated according to Hadamard codewords, and their autocorrelation function has a sharp peak near zero delay, while the autocorrelation function of noise has... The average time is zero. Therefore, the comparator selects... Estimated sequence number of the largest combination of activation frames Then through The binary representation is used to recover the time index bit sequence. and activation code .

[0071] Obtain the estimated sequence number of the active frame combination. Then, the code index demodulation module extracts the complete waveform within the active frame of the frame combination from the received signal. In practice, the receiver needs to divide the intra-frame signal according to the time slot interval. Divide into, and obtain Each time-slice signal.

[0072] Then, for each code index bit Perform the following steps: (1) Each time-slice signal is divided into... Each sub-segment contains a continuous sequence of segments. This is a time slice. (Note: The last part is a fragment and doesn't translate directly.) ( The signal of each sub-segment is , indicating the first in the active frame The hourly video to the first The received signal components of each time slice, This is the estimated sequence number of the activation frame.

[0073] (2) Calculate the inner product of adjacent groups (1st and 2nd, 3rd and 4th, ...), and sum all the inner products: .

[0074] (3) Judgment: If ,but ;like ,but .

[0075] in, Indicates the first The decision variable corresponding to each code index bit, superscript Indicator Decision Variables For the decision variables corresponding to the code index bits, To receive the signal in the active frame Each segment For time.

[0076] Finally, correlation operations are performed on the activation codeword and each activation frame, and the results of the correlation operations are summed to obtain the symbol decision variable: ; in, In order to receive signals, For time, superscript Indicator Symbol Decision Variables For the decision variables corresponding to the digital modulation bits, For the first The start time of each time frame Hadamard matrix The The first line of code words One element; The duration of a frame. The duration of the time slice.

[0077] The decision criterion for digital modulation bits is as follows: when the symbol decision variable is greater than 0, the digital modulation bit is determined to be 1; when the symbol decision variable is not greater than 0, the digital modulation bit is determined to be 0.

[0078] The above process utilizes the segmented autocorrelation symbolic property of Hadamard codewords. For the first... Each bit is a block size such that time slices within the same block have the same symbol pattern, while the relative relationship between symbols in adjacent blocks is determined by... The decision is made. Therefore, the sign of the inner product sum directly reflects... .

[0079] Time index demodulation module output One time index bit, code index demodulation module output. Each codeword index bit is converted into a digital modulation bit by the digital modulation and demodulation module. These bits are then combined to form the recovered information block. It should be noted that this demodulation process does not require knowledge of the specific codeword index. Furthermore, there is no need to estimate the channel impulse response; only coarse frame synchronization (determining the frame start position) is required. The accuracy requirements for time-slice synchronization are also low because integration is performed over the entire time-slice interval, and the integration window only needs to cover the pulse main lobe.

[0080] Therefore, this embodiment can be used to achieve non-correlation demodulation based on Hadamard autocorrelation characteristics, correctly recover the received information bits, and realize reliable communication.

[0081] Those skilled in the art will understand that all or part of the steps in the methods of the above embodiments can be implemented by a program instructing related hardware, and the corresponding program can be stored in a computer-readable storage medium.

[0082] It should be noted that although the method operations of the above embodiments are described in a specific order in the accompanying drawings, this does not require or imply that these operations must be performed in that specific order, or that all the operations shown must be performed to achieve the desired result. On the contrary, the order of execution of the described steps may be changed. Additionally or alternatively, certain steps may be omitted, multiple steps may be combined into one step, and / or one step may be broken down into multiple steps.

[0083] In summary, this invention includes a receiving front-end, a time-index demodulation module, a code-index demodulation module, and a digital modulation and demodulation module. The time-index demodulation module includes a delay unit, a multiplier, an integrator, and a comparator. The delay unit delays the received signal by a preset time; the multiplier multiplies the received signal with the delayed received signal; the integrator integrates the multiplication result over the duration of each frame to obtain the relevant decision variables for each time frame; the comparator compares the relevant metric variables of each active frame combination used for comparing the relevant decision variables of each frame, and determines the frame combination with the largest relevant metric as the active frame combination.

[0084] The code index demodulation module includes a frame extraction unit, a segmentation unit, a dot product summation unit, and a symbol decision unit. The frame extraction unit extracts the received signal within each active frame from the received signal based on the active frame combination. The segmentation unit divides the received signal within each active frame into multiple sub-sequences according to the iterative segmentation structure of the Hadamard codeword. The dot product summation unit performs dot product operations on each sub-segment within each active frame according to a predetermined pairing method and sums the dot product results to obtain the decision variables corresponding to each code index bit. The symbol decision unit determines each code index bit and the active codeword based on the sign of each code-related decision variable.

[0085] The digital modulation and demodulation module includes a correlation operation unit and a symbol decision unit. The correlation operation unit performs correlation operations on the activation codeword and each activation frame, and sums the correlation operation results to obtain the symbol decision variables corresponding to the digital modulation bits; the symbol decision unit determines the digital modulation bits based on the symbol decision variables.

[0086] This invention utilizes the autocorrelation characteristics of Hadamard, the autocorrelation characteristics of ultrasonic pulse signals, and the time-sequential union of multiple active frames to effectively achieve low-complexity incoherent demodulation without channel estimation, enabling reliable intra-body ultrasonic communication in low signal-to-noise ratio communication scenarios.

[0087] Therefore, this invention employs the aforementioned noncoherent reception method, receiver, and system based on Hadamard autocorrelation characteristics. By utilizing the Hadamard autocorrelation characteristics and the autocorrelation characteristics of ultrasonic pulse signals, it effectively achieves low-complexity noncoherent demodulation without channel estimation, reducing the complexity and power consumption of receiver baseband processing. It eliminates the need to transmit a reference signal, resulting in higher spectral and energy efficiency of the transmitted pulses. It also reduces the complexity of code index demodulation and utilizes time diversity across multiple active frames. Even if individual active frames are affected by deep fading, multipath distortion, or noise interference, other active frames can still provide effective information for code index decision-making, thus achieving reliable intra-body ultrasonic communication.

[0088] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A noncoherent reception method based on Hadamard autocorrelation characteristics, characterized in that, Includes the following steps: S1. Execution time index demodulation, specifically including: Receive ultrasonic signals, perform correlation operations on the received ultrasonic signals and their delayed copies, and obtain the relevant decision variables for each time frame; The relevant metrics of the activation frame combination are obtained based on the relevant decision variables, and the time index bits are demodulated based on the sequence number of the activation frame combination relevant metrics. S2, Execution code index demodulation, specifically includes: Based on the activation frame combination determined by S1, the signals within each activation frame in the activation frame combination are extracted from the ultrasonic signal, and the signals within each activation frame are divided into multiple sub-segments according to the iterative segmentation method of Hadamard codewords. Dot product operations are performed on the segments within each active frame according to a predetermined pairing method, and the dot product results are summed to obtain the decision variables corresponding to each code index bit; the corresponding code index bit and activation codeword are determined according to the sign of each decision variable. S3. Perform digital modulation and demodulation, specifically including: Based on the activation codeword determined in S2, correlation operations are performed between the activation codeword and each activation frame determined in S1, and the correlation operation results are summed to obtain the symbol decision variable corresponding to the digital modulation bit; the digital modulation bit is demodulated based on the symbol decision variable.

2. The noncoherent reception method based on Hadamard autocorrelation characteristics according to claim 1, characterized in that, In S1, the first The relevant decision variables for each time frame are calculated using the following formula: ； in, In order to receive signals, For time, superscript Representing relevant decision variables The decision variable corresponding to the time index bit. For the first The start time of each time frame The duration of a frame. To delay time, , Total number of frames; from Activation in each frame Each frame It is a positive integer, and There are a total of A combination of activation frames, in which The coefficients are binomial, and the number of bits for the time index is... , This is the floor function; using In the combination The first combination is used for time index modulation, the second ( ) types of activation frame combinations The relevant metric for active frame combination is: ； Therefore, the estimation result of the active frame combination is as follows: ； Time index bits are The binary representation is obtained.

3. The noncoherent reception method based on Hadamard autocorrelation characteristics according to claim 1, characterized in that, In S2, Hadamard codewords have the following autocorrelation properties: Based on the number of bits in the code index The corresponding Hadamard matrix is Hadamard matrix There are a total of 10 Hadamard codes, each codeword is equal to 10 ... The elements are ±1; The code index bit sequence is Then the corresponding Hadamard matrix The line code character is ,in Hadamard matrix The The first element of the line codeword; code index AND code index bit sequence The relationship between them satisfies ,in, This is a binary-to-decimal conversion function; For the Code index bits , and its corresponding Code words are divided into There are 3 consecutive sub-segments, each with a length of 1. , No. Each sub-segment is represented as: ； in, , ; Calculate the dot product of each adjacent segment according to the predetermined pairing method, and sum the dot product results: ； The dot product represents the sum of corresponding element-wise multiplications. For the first Code index bits Corresponding Hadamard matrix The line code The Each segment; The relationship between code index bits and Hadamard codewords is described as follows: when hour, ;when hour, .

4. The incoherent reception method based on Hadamard autocorrelation characteristics according to claim 3, characterized in that, In S2, demodulation of the first When indexing the individual code bits, the active frames of the received signal are divided equally. There are 3 consecutive sub-segments, each with a length of 1. , For the duration of the time slice, the first In each sub-segment Indicates the first [frame] within the active frame The hourly video to the first The received signal components of each time slice, To estimate the combination of activation frames The frame number in the data; No. Code index bits The corresponding decision variables are calculated using the following formula: ； Among them, superscript Indicator Decision Variables For the decision variables corresponding to the code index bits, To receive the signal in the active frame Each segment For time, The duration of a frame. The number of bits for the code index. The relationship between frame duration and slice duration satisfies ; No. Code index bits The criteria for judgment are: 。 5. The noncoherent reception method based on Hadamard autocorrelation characteristics according to claim 1, characterized in that, In S3, correlation operations are performed on the activation codeword and each activation frame, and the results of the correlation operations are summed to obtain the symbol decision variable: ； in, In order to receive signals, For time, superscript Indicator Symbol Decision Variables For the decision variables corresponding to the digital modulation bits, For the first The start time of each time frame Hadamard matrix The The first line of code words One element; The duration of a frame. The duration of the time slice; The decision criterion for digital modulation bits is as follows: when the symbol decision variable is greater than 0, the digital modulation bit is determined to be 1; when the symbol decision variable is not greater than 0, the digital modulation bit is determined to be 0.

6. A noncoherent receiver based on the Hadamard autocorrelation property, used to implement the method of any one of claims 1 to 5, characterized in that, include: The receiving front end is used to receive ultrasonic signals and convert them into electrical signals; The time index demodulation module is used to perform correlation operations on the electrical signal and its delayed replica, obtain the relevant decision variables of each time frame, obtain the activation frame combination correlation metric based on the relevant decision variables, determine the activation frame combination based on the activation frame combination correlation metric, and output the time index bits. The code index demodulation module is used to extract the signal within each active frame in the active frame combination from the electrical signal according to the active frame combination, divide the signal within each active frame into multiple sub-segments according to the iterative segmentation method of the Hadamard codeword, perform dot product operation on each sub-segment in each active frame according to a predetermined pairing method, and sum the dot product results to obtain the decision variable corresponding to each code index bit, and output the code index bit and the active codeword according to the sign of each decision variable. The digital modulation and demodulation module is used to perform correlation operations on each activation frame in the combination of the activation codeword and the activation frame, sum the correlation operation results to obtain the symbol decision variable corresponding to the digital modulation bit, and output the digital modulation bit according to the symbol decision variable.

7. The incoherent receiver based on Hadamard autocorrelation characteristics according to claim 6, characterized in that, The time index demodulation module includes: Delay unit, used to delay an electrical signal by a predetermined time. ; A multiplier is used to multiply an electrical signal by a delayed electrical signal; An integrator is used to adjust the output of the multiplier over the duration of each frame. Integrate within the frame to obtain the relevant decision variables for each frame; The comparator is used to compare the relevant metrics of each active frame combination and determine the frame combination with the largest relevant metric as the active frame combination.

8. The incoherent receiver based on Hadamard autocorrelation characteristics according to claim 7, characterized in that, The code index demodulation module includes: A frame signal extraction unit is used to extract signals within each active frame from an electrical signal based on the active frame combination. The segmentation unit is used to divide the signal within each active frame into multiple sub-segments according to the iterative segmentation method of Hadamard codewords; The dot product summation unit is used to perform dot product operations on the sub-segments in each active frame according to a predetermined pairing method, and sum the dot product results to obtain the decision variables corresponding to each code index bit. The symbol decision unit is used to determine the corresponding code index bit and activation codeword based on the symbol of each decision variable.

9. An ultrasonic index modulation communication system, comprising a transmitter and an incoherent receiver according to any one of claims 6 to 8, characterized in that: The transmitter divides the bit stream to be transmitted into time index bits, code index bits, and digital modulation bits. It determines the active frame combination based on the time index bits, selects the corresponding codeword from the Hadamard matrix based on the code index bits, and uses the elements of the codeword as amplitude coefficients to transmit ultrasonic pulses at each time slot position of each active frame in the active frame combination. It also digitally modulates the ultrasonic pulses based on the digital modulation bits. The incoherent receiver uses a time index demodulation module to demodulate time index bits, a code index demodulation module to demodulate code index bits, and a digital modulation and demodulation module to demodulate digital modulation bits.

10. An ultrasonic index modulation communication system according to claim 9, characterized in that, The ultrasonic index modulation communication system can be either an ultrasonic code index modulation system or an ultrasonic time code index modulation system; when it is an ultrasonic code index modulation system, its total number of frames is... The time index demodulation module is not working or outputs a fixed frame sequence number.

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