Slice demodulation method and device for frequency shift keying communication

Abstract

The invention discloses a slice demodulation method and device for frequency shift keying communication, and belongs to the technical field of wireless communication. According to the method, frequency shift keying modulation is carried out at a sending end by using a large frequency interval, a received data stream is firstly sliced at equal intervals at a receiving end, then sliced data stream information extraction is carried out, sliced data stream information blind coherent combination is carried out, and sliced data stream demarcation point calibration is carried out; and finally, extracting a blind coherent combination result according to a slice data flow demarcation point calibration result. According to the invention, the problem of high instantaneous complexity of a timing synchronization algorithm in the traditional frequency shift keying incoherent demodulation process is solved, and incoherent frequency shift keying demodulation is completed with high performance under the condition of limited resources. The method also solves the problem of serious performance deterioration of frequency shift keying incoherent demodulation under the condition of large frequency deviation, and greatly reduces the performance loss of a demodulation algorithm under the condition of large frequency deviation between a receiving party and a transmitting party.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication technology, and in particular to a slicing demodulation method and device for frequency shift keying communication. Background Art

[0002] The frequency shift keying communication system is a common digital communication system with strong anti-noise capability and insensitivity to channel fading. Frequency shift keying communication transmits information through different frequencies, occupies a wide bandwidth, and is generally used in medium and low-speed data transmission scenarios. Frequency shift keying communication is divided into binary frequency shift keying (2FSK) communication and multi-level frequency shift keying (MFSK) communication according to the modulation order, and is divided into incoherent frequency shift keying communication and coherent frequency shift keying communication according to the demodulation method.

[0003] Compared with coherent frequency shift keying communication, incoherent frequency shift keying communication does not need to extract coherent carrier at the receiving end, which simplifies the implementation of the demodulator, but incoherent frequency shift keying communication still requires complex timing synchronization. Timing synchronization ensures that the receiving end samples and demodulates the signal at the correct time point, which is a very important part of frequency shift keying communication. Deviations in timing synchronization will lead to an increase in the bit error rate, affecting the communication quality, and severe timing deviations will even lead to communication interruption.

[0004] The timing synchronization algorithm needs to frequently perform complex correlation operations, and has very high requirements for the real-time performance of the calculation. When there is a large frequency deviation (frequency offset) between the sender and the receiver, the complexity of the timing synchronization algorithm will increase further, and the timing synchronization module needs to complete a large amount of instantaneous calculations. In addition, traditional incoherent frequency shift keying demodulation also has the problem of large performance loss when the frequency deviation is large. Summary of the invention

[0005] In order to reduce the problem of high instantaneous complexity of the timing synchronization algorithm of the frequency shift keying non-coherent demodulation in the above-mentioned background technology, and the problem of serious performance deterioration of the frequency shift keying non-coherent demodulation under the condition of large frequency deviation, the present invention proposes a slicing demodulation method and device for frequency shift keying communication. The present invention can greatly reduce the demand for real-time operation of the frequency shift keying communication demodulation algorithm, and has the characteristics of low demodulation resource occupancy, strong ability to resist frequency deviation, stable and reliable algorithm performance, and simple engineering implementation.

[0006] The technical solution adopted by the present invention is:

[0007] A slicing demodulation method for frequency shift keying communication is used to demodulate modulated data sent by a transmitting end, wherein the frequency interval used by the modulated data is P times the minimum frequency of the frequency shift keying system, and the method comprises the following steps:

[0008] The receiving end moves the sampled intermediate frequency signal to the baseband through an orthogonal down-converter and a low-pass filter, and then performs a decimation operation to obtain a complex baseband digital waveform;

[0009] Slice the complex baseband data stream equally, and slice a symbol into P slices with equal spacing;

[0010] Use fast Fourier transform to process each data stream segment after slicing, and store the information of all frequency points in the Fourier transform result;

[0011] For each frequency point, the P consecutive pieces of information extracted from the data stream fragments are again subjected to small-step parallel frequency deviation blind compensation and coherent merging using fast Fourier transform, and the blind coherent merging results and blind coherent merging result numbers of the sliced ​​data stream information of all frequency points are stored;

[0012] Match the received data according to the specific sequence of the sender, synchronize the blind coherent combination results one by one, and obtain the starting position of the data stream segment after successful synchronization;

[0013] Based on the starting position of the data stream segment, the slice data stream grouping and the extraction of the slice data stream information blind coherent merging result are completed according to the two symbol slice intervals.

[0014] A slice demodulation device for frequency shift keying communication, implemented based on FPGA, is used to demodulate the modulated data sent by the transmitter, wherein the frequency interval used by the modulated data is P times the minimum frequency of the frequency shift keying system; the device comprises a data stream equidistant slicer, a slice data stream information extractor, a slice information blind coherent combiner, a slice demarcation point calibrator and a blind coherent combining result extractor; wherein:

[0015] The data stream equally spaced slicer slices the complex baseband data stream equally spaced, and cuts a symbol into P slices with equal spacing;

[0016] The sliced ​​data stream information extractor uses fast Fourier transform to process each data stream segment after slicing, and stores the information of all frequency points in the Fourier transform result;

[0017] The blind coherent combiner of slice information extracts P consecutive pieces of information from the data stream fragments at each frequency point, and uses fast Fourier transform to perform small-step parallel frequency deviation blind compensation and coherent combination again, and stores the blind coherent combination results and blind coherent combination result numbers of the slice data stream information of all frequency points;

[0018] The slice demarcation point calibrator matches the received data according to the specific sequence of the sender, synchronizes the blind coherent combination results one by one, and obtains the starting position of the data stream segment after successful synchronization;

[0019] The blind coherent merging result extractor completes the slice data stream grouping and the slice data stream information blind coherent merging result extraction based on the starting position of the data stream segment and the interval between two symbol slices.

[0020] Compared with the traditional method, the present invention has the following beneficial effects:

[0021] 1. The present invention slices the received signal, which greatly increases the processing time interval of the timing synchronization algorithm, reduces the real-time requirements of signal processing, makes time division multiplexing of hardware resources possible, thereby reducing the resource overhead of timing synchronization operations, and enables non-coherent frequency shift keying communication to be deployed on a resource-constrained hardware platform.

[0022] 2. The present invention utilizes Fourier transform to complete the parallel blind frequency deviation compensation of the received signal in tiny steps, which reduces the influence of frequency deviation on the demodulation performance without the need for additional overhead. It has strong anti-frequency deviation capability and is suitable for communication scenarios with large frequency deviation.

[0023] In summary, the method of the present invention is simple, has stable and reliable performance, and solves the problem of excessive consumption of hardware resources in traditional methods at the expense of a small amount of demodulation performance, and can complete non-coherent frequency shift keying demodulation under resource-constrained conditions. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required for use in the embodiments or the description of the prior art are briefly introduced below.

[0025] Figure 1 This is an example diagram of four frequency shift keying modulation symbol waveforms when P=8 in the present invention.

[0026] Figure 2 It is a schematic diagram of receiving data flow in the present invention.

[0027] Figure 3 It is a schematic diagram of an ideal slice of the received data stream in the present invention.

[0028] Figure 4 It is a schematic diagram of non-ideal slicing of the received data stream in the present invention.

[0029] Figure 5 It is a flow chart of slice demodulation of frequency shift keying signal.

[0030] Figure 6 It is a structural diagram of a frequency shift keying slice demodulation device.

[0031] Figure 7 It is a structural diagram of the equally spaced slicers of the data flow.

[0032] Figure 8 It is the structural diagram of the slice data stream information extractor.

[0033] Fig. 9 It is a structural diagram of the slice information blind coherent combiner.

[0034] Fig.10 It is a structural diagram of the slice demarcation point calibrator.

[0035] Fig.11 It is the structural diagram of the blind coherent merging result extractor. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings.

[0037] The invention discloses a slicing demodulation method for frequency shift keying communication, which is applicable to binary frequency shift keying communication and multi-level frequency shift keying communication.

[0038] This method requires the use of a larger frequency interval for frequency shift keying modulation at the transmitting end. The specific parameters are as follows: in a frequency shift keying system with a modulation order of M, assuming that the receiving end cuts a symbol (symbol period is T) into P slices with equal intervals, then the minimum frequency interval required for frequency shift keying modulation is P / T, the number of effective frequency points of frequency shift keying is M, and the bandwidth occupied by frequency shift keying modulation is MP / T.

[0039] After the transmitting end meets the above minimum frequency interval, the receiving end specifically includes the following steps:

[0040] The sampled intermediate frequency signal is moved to the baseband through an orthogonal down-converter and a low-pass filter, and then decimated to obtain a complex baseband digital waveform;

[0041] Slice the complex baseband data stream equally, and slice a symbol into P slices with equal spacing;

[0042] Use fast Fourier transform to process each data stream segment after slicing, and store the information of all frequency points in the Fourier transform result;

[0043] For each frequency point, the P consecutive pieces of information extracted from the data stream fragments are again subjected to small-step parallel frequency deviation blind compensation and coherent merging using fast Fourier transform, and the blind coherent merging results and blind coherent merging result numbers of the sliced ​​data stream information of all frequency points are stored;

[0044] Match the received data according to the specific sequence of the sender, synchronize the blind coherent combination results one by one, and obtain the starting position of the data stream segment after successful synchronization;

[0045] Based on the starting position of the data stream segment, the slice data stream grouping and the extraction of the slice data stream information blind coherent merging result are completed according to the two symbol slice intervals.

[0046] In this method, most of the segments after slicing contain single-frequency signals with a complete period, avoiding the performance degradation caused by spectrum leakage during non-periodic slicing. The segment where the symbol switches contain partial signals of the two previous and next symbols, resulting in a small performance loss.

[0047] The information carried by the slice can be obtained by Fourier transforming the data stream fragment obtained after slicing. The slice demodulator needs to store the information of all M possible frequency points in the Fourier transform result, which is used for blind coherent merging of slice data stream information.

[0048] The blind coherent merging of sliced ​​data stream information is to coherently merge the information of any continuous P fragments at each possible frequency point in frequency shift keying communication. The implementation method is: for M frequency points, the information corresponding to the P data stream fragments stored at the frequency point is extracted in turn, the P data at the same frequency point is Fourier transformed, and the data with the largest energy in the Fourier transform result is defined as the result of blind coherent merging of sliced ​​data stream information. The equally spaced slices at the receiving end cut a symbol into P slices at equal intervals, but it cannot be determined which data stream fragments belong to the same symbol. Therefore, the slice demodulator needs to store the blind coherent merging results of the sliced ​​data stream information of all M frequency points.

[0049] According to the principle of blind coherent merging of sliced ​​data stream information, one of every P results must be the most likely result of merging with the same symbol. Therefore, the receiving end needs to use the sliced ​​data stream demarcation point calibration algorithm to determine a position that is most likely to be coherently merged by the same symbol fragment. The sliced ​​data stream demarcation point calibration is based on the timing synchronization algorithm of the special sequence. The transmitter sends several specific symbols in sequence according to the information content of a special sequence. The receiver extracts and accumulates the corresponding blind coherent merging results according to the information content and interval of the special sequence. When the blind coherent merging results are completely aligned with the sent special sequence, the receiving end will accumulate a large peak value. The location of this peak is the most likely position for the coherent merging of the same symbol fragment, which is also the starting position S of the data stream fragment.

[0050] After determining the starting position of the data stream segment, the data stream segment grouping and the blind coherent merging result of the data stream segment information can be extracted. For example, the segments numbered S+1 to S+P belong to the first symbol, and the result of their blind coherent merging is numbered S+P, the segments numbered S+P+1 to S+2P belong to the second symbol, and the result of their blind coherent merging is numbered S+2P, ..., the segments numbered S+(N-1)P+1 to S+NP belong to the Nth symbol, and the result of their blind coherent merging is numbered S+NP. The subsequent processing flow is the same as that of ordinary frequency shift keying communication.

[0051] Figure 1The following are examples of four frequency shift keying modulation symbol waveforms when P=8. The transmitter selects a symbol waveform for transmission according to the data to be transmitted.

[0052] Figure 2 Schematic diagram of received data flow. The first section is the first symbol waveform received, and the second section is the second symbol waveform received.

[0053] Figure 3 Yes Figure 2 The received data stream is sliced ​​according to the ideal position. Any symbol can be divided into 8 segments, and each segment contains at least one complete single-frequency signal. Because the transmission between the transmitter and the receiver cannot be determined in advance, the received signal cannot be ideally segmented. Figure 2 The effect of segmenting the received data stream according to non-ideal positions is as follows: Figure 4 As shown, each symbol, except the first segmentation interval, contains a complete single-frequency signal.

[0054] Figure 5 The flowchart of the slicing demodulation method of frequency shift keying communication is shown in Figure 1, where A is the receiver first performs digital orthogonal down-conversion, low-pass filtering and sampling rate conversion on the digital intermediate frequency signal to obtain Figure 2 The baseband data stream shown, B is the demodulated data obtained by the present invention, and the original data can be restored after frequency shift keying demapping. The slice demodulator first slices the received data stream at equal intervals, then extracts the slice data stream information, and then performs blind coherent merging of the slice data stream information, and then calibrates the demarcation point of the slice data stream, and finally extracts the blind coherent merging result according to the demarcation point calibration result of the slice data stream.

[0055] In this method, the data processing interval is increased after slicing, and the structure of multiple parallel Fourier transform modules inside the slice data stream information extractor and the slice information blind coherent combiner can be replaced by a Fourier transform module time-division multiplexing structure, reducing the consumption of demodulator resources.

[0056] A chip demodulation device for frequency shift keying communication, such as Figure 6 As shown, A / B and Figure 5 The device comprises a data stream equidistant slicer, a slice data stream information extractor, a slice information blind coherent merger, a slice demarcation point calibrator and a blind coherent merger result extractor.

[0057] The data stream equidistant slicer divides the received baseband data stream into the following Figure 4 The data stream equidistant slicer then outputs the baseband data stream of the current slice to the slice data stream information extractor.

[0058] The slice data stream information extractor sends the cut segments to the Fourier transform module, and extracts the information of all possible frequency points from the output of the Fourier transform module after the processing is completed. The slice data stream information extractor stores the information corresponding to all possible frequency points as the original demodulation information of the current slice data stream, and then outputs several original demodulation information that may be the same symbol to the slice information blind coherent combiner.

[0059] The blind coherent combiner of slice information sends the original demodulated information of the P-segment slice data stream output by the slice data stream information extractor to the Fourier transform module in sequence according to the frequency point, and the Fourier transform module completes the coherent combination of the slice data stream information by frequency point. Because the original demodulated information of the coherent combination does not necessarily belong to the same symbol, the coherent combination of the slice information here is a blind combination. The blind coherent combination uses the Fourier transform method to perform small-step parallel frequency deviation blind compensation on the received signal, reducing the impact of frequency deviation on the demodulation performance. The blind coherent combiner of slice information also needs to store and number each blind coherent combination result by frequency point.

[0060] The slice demarcation point calibrator reads and accumulates the blind coherent combination results of the corresponding frequency points at the current address O, the previous symbol address OP, ..., and the previous Q-1 symbol addresses O-(Q-1)P according to the special sequence (length Q) attached by the sender before the data. When the read blind coherent combination result sequence is exactly the same as the sent special sequence, the slice demarcation point calibrator will accumulate a large peak value. The position of this peak value is the most likely position where the same symbol fragment is coherently merged, and it is also the starting position S of the data stream fragment.

[0061] The blind coherent combination result extractor can extract the blind coherent combination result of the first symbol at the position numbered S+P according to the starting position S of the data stream segment, the blind coherent combination result of the second symbol at the position numbered S+2P, ..., the blind coherent combination result of the Nth symbol at the position numbered S+NP. The subsequent processing flow is the same as that of ordinary frequency shift keying communication.

[0062] Figure 7 It is the specific structure of the data stream equidistant slicer, where C is the enable signal output by the sampling rate converter, D is the data signal output by the digital low-pass filter and extraction, E is the slice enable output by the data stream equidistant slicer, and F is the slice data output by the data stream equidistant slicer. Under the action of the enable signal, the slice timing controller controls the storage of the received data. The slice timer takes itself as the reference, and when the slice time is reached, it controls the data storage to output the current slice data as a whole, and outputs the slice enable at the same time.

[0063] Figure 8 is the specific structure of the slice data stream information extractor, where E / F and Figure 7The definition is the same as in , G is the original demodulation information extraction enable output by the slice data stream information extractor, and H is the original demodulation information of the current slice output by the slice data stream information extractor. Under the control of the data stream information extraction controller, the slice data stream information extractor first sends the cut segments to the Fourier transform module for processing, and after the processing is completed, the information of all possible frequency points is extracted from the output of the Fourier transform module as the original demodulation information of the current slice data stream and stored in the original demodulation information memory, and finally the latest P original demodulation data are output to the slice information blind coherent combiner.

[0064] Fig. 9 is the specific structure of the blind coherent combiner of slice information, where G / H and Figure 8 The definitions in are the same, I is the blind coherent merging enable output by the blind coherent merging combiner of the slice information, J is the blind coherent merging data output by the blind coherent merging combiner of the slice information, and K is the blind coherent merging number output by the blind coherent merging combiner of the slice information. Under the control of the blind coherent merging controller, the blind coherent merging combiner of the slice information first sends the P original demodulated information of the M frequency points to the Fourier transform module for processing in sequence. The result of the Fourier transform is processed by the frequency energy calculation, filtering and maximum value extraction of the frequency energy maximum value extraction module to obtain the blind coherent merging result of the current P slice information of the frequency point, and the coherent merging information distributor distributes the blind coherent merging result to the coherent merging data storage device of the corresponding frequency point. After calculating the blind coherent merging results of the M frequency points, the blind coherent merging controller controls the coherent merging data storage device to read out the corresponding blind coherent merging results according to the specific sequence of the transmitting end, and outputs the blind coherent merging data enable and the current blind coherent merging number.

[0065] Fig.10 is the specific structure of the slice demarcation point calibrator, where I / J / K and Fig. 9 The definitions are the same as in , U is the synchronization success signal output by the slice demarcation point calibrator, and V is the starting position of the data stream segment output by the slice demarcation point calibrator. Under the control of the demarcation point calibration controller, the slice demarcation point calibrator accumulates Q blind coherent combined data to obtain the matching result of the blind coherent combined sequence at the current position and the specific sequence of the transmitter, and then sends the matching result to the synchronization decision device. When the blind coherent combined sequence is completely aligned with the special sequence sent, the energy accumulator will output a large peak value. After detecting the peak value matched when fully aligned, the demarcation point calibration controller calibrates the current position as the starting position of the data stream segment, and the synchronization decision device outputs the synchronization success signal and the starting position of the data stream segment.

[0066] Fig.11 is the specific structure of the blind coherent merging result extractor, where I / J / K and Fig. 9 Same definition, U / V and Fig.10The definitions are the same as in , X is the blind coherent merging result enable output by the blind coherent merging result extractor, and Y is the blind coherent merging result output by the blind coherent merging result extractor. The blind coherent merging result extractor locks the starting position of the data stream segment output by the slice demarcation point calibrator according to the synchronization success signal U output by the slice demarcation point calibrator. After the synchronization state is established, the blind coherent merging result extractor selects the real blind coherent merging result and its enable according to the locked starting position V of the data stream segment output by the slice demarcation point calibrator and the current blind coherent merging number K output by the slice information blind coherent combiner, and outputs it through the blind coherent merging result enable X and the blind coherent merging result Y.

[0067] Due to the slicing processing of the received signal, there is a large time interval between the data stream slices. Therefore, the structure of multiple Fourier transform modules in parallel inside the slice data stream information extractor and the slice information blind coherent combiner can be replaced by a time-division multiplexing structure of a Fourier transform module, reducing the consumption of demodulator resources.

[0068] The present invention slices the frequency shift keying demodulated data, increases the processing time interval of the timing synchronization algorithm, reduces the instantaneous complexity of the timing synchronization algorithm, makes time division multiplexing of hardware resources possible, and reduces the resource overhead of timing synchronization operations. The present invention also has a strong anti-frequency deviation capability and does not require additional overhead, and is suitable for communication scenarios with large frequency deviations.

[0069] The present invention solves the problem of high instantaneous complexity of the timing synchronization algorithm in the process of traditional frequency shift keying non-coherent demodulation, and completes the non-coherent frequency shift keying demodulation with high performance under the condition of limited resources. The present invention also solves the problem of serious performance deterioration of frequency shift keying non-coherent demodulation under the condition of large frequency deviation, and greatly reduces the performance loss of the demodulation algorithm under the condition of large frequency deviation between the transmitter and the receiver.

[0070] In summary, the method of the present invention is simple, has stable and reliable performance, and solves the problem of excessive consumption of hardware resources in traditional methods at the expense of a small amount of demodulation performance, and can complete non-coherent frequency shift keying demodulation under resource-constrained conditions.

Claims

1. A slicing demodulation method for frequency shift keying communication, characterized in that: Used to demodulate modulated data sent from a transmitting end, the frequency interval used by the modulated data is P times the minimum frequency of a frequency shift keying system, the method comprising the following steps: The receiving end moves the sampled intermediate frequency signal to the baseband through an orthogonal down-converter and a low-pass filter, and then performs a decimation operation to obtain a complex baseband digital waveform; Slice the complex baseband data stream equally, and slice a symbol into P slices with equal spacing; Use fast Fourier transform to process each data stream segment after slicing, and store the information of all frequency points in the Fourier transform result; For each frequency point, the P consecutive pieces of information extracted from the data stream fragments are again subjected to small-step parallel frequency deviation blind compensation and coherent merging using fast Fourier transform, and the blind coherent merging results and blind coherent merging result numbers of the sliced ​​data stream information of all frequency points are stored; Match the received data according to the specific sequence of the sender, synchronize the blind coherent combination results one by one, and obtain the starting position of the data stream segment after successful synchronization; Based on the starting position of the data stream segment, the slice data stream grouping and the extraction of the slice data stream information blind coherent merging result are completed according to the two symbol slice intervals.

2. A slice demodulation device for frequency shift keying communication, characterized in that: Based on FPGA implementation, it is used to demodulate the modulated data sent from the transmitter, and the frequency interval used by the modulated data is P times the minimum frequency of the frequency shift keying system; the device includes a data stream equidistant slicer, a slice data stream information extractor, a slice information blind coherent combiner, a slice demarcation point calibrator and a blind coherent combination result extractor; wherein: The data stream equally spaced slicer slices the complex baseband data stream equally spaced, and cuts a symbol into P slices with equal spacing; The sliced ​​data stream information extractor uses fast Fourier transform to process each data stream segment after slicing, and stores the information of all frequency points in the Fourier transform result; The blind coherent combiner of slice information extracts P consecutive pieces of information from the data stream fragments at each frequency point, and uses fast Fourier transform to perform small-step parallel frequency deviation blind compensation and coherent combination again, and stores the blind coherent combination results and blind coherent combination result numbers of the slice data stream information of all frequency points; The slice demarcation point calibrator matches the received data according to the specific sequence of the sender, synchronizes the blind coherent combination results one by one, and obtains the starting position of the data stream segment after successful synchronization; The blind coherent merging result extractor completes the slice data stream grouping and the slice data stream information blind coherent merging result extraction based on the starting position of the data stream segment and the interval between two symbol slices.

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