CN107004418B - Digital communication method and device based on audio channel - Google Patents
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Abstract
The embodiment of the application relates to the technical field of digital communication, in particular to a digital communication method and device based on an audio channel. The digital communication method based on the audio channel comprises the following steps: step a: a sending end packages original data to be sent, carries out Manchester coding on the packaged data packets, and sends the coded data packets through an audio channel; step b: and the receiving end samples the data packet sent by the sending end, and performs synchronous frame header detection and Manchester decoding on the sampled data to obtain original data. According to the embodiment of the application, the Manchester coding is adopted at the sending end, and the Manchester decoding is carried out on the received data at the receiving end by adopting a correlation method, so that the data transmission rate can be higher under the requirement of higher data packet demodulation success rate, the data transmission rate far exceeds the data transmission rate of a conventional audio communication mode, and the data transmission method is applicable to the two-way communication between an upper computer and a lower computer.
Description
Technical Field
The embodiment of the application relates to the technical field of digital communication, in particular to a digital communication method and device based on an audio channel.
Background
At present, the communication modes of the mobile terminal and other devices are divided into two types: wired transmission and wireless transmission. The wired transmission comprises data line transmission and audio channel transmission; wireless transmissions include Bluetooth, 802.11(Wi-Fi), ZigBee, Ultra Wideband (UWB), infrared, and the like. Different communication modes show specific advantages according to different application scenes.
The audio channel transmission mode fully utilizes the existing resources of the mobile terminal, and when the transmission frequency is higher than the audible frequency band (frequency range of sound waves audible by human ears), the normal playing of sound is not influenced. With the development of technology, audio channel-based terminal devices such as ear thermometers, heart rate headsets, and the like are widely used. However, the conventional communication method based on the audio channel usually adopts Dual Tone Multi Frequency (DTMF) technology, which can achieve a low data transmission rate, and when the data transmission rate is increased, because different types of terminal devices have distortions of different degrees in the waveform obtained by sampling under the condition of high-rate data transmission, when the distortion degree is large, the conventional decoding algorithm is difficult to perform accurate analysis, which may cause the demodulation success rate of the receiving end to decrease sharply. Therefore, for application scenarios of large amount of data interaction, a high-rate and high-reliability communication method based on an audio channel needs to be considered. In the prior art, the decoding success rate is low under the conditions of high data rate and high signal waveform distortion degree.
The prior art does not solve the decoding problem when the signal waveform is seriously distorted, and the data transmission rate of the prior art cannot meet the higher rate requirement.
Disclosure of Invention
The embodiment of the application provides a digital communication method and a digital communication device based on an audio channel, and aims to solve the technical problems that the existing digital communication method based on an audio signal cannot solve the decoding problem when the signal waveform is seriously distorted, and the data transmission rate is not high enough.
In order to solve the above-mentioned problem, the technical solution adopted in the embodiment of the present application includes:
a method of digital communication based on an audio channel, comprising:
step a: a sending end packages original data to be sent, carries out Manchester coding on the packaged data packets, and sends the coded data packets through an audio channel;
step b: and the receiving end samples the data packet sent by the sending end, and performs synchronous frame header detection and Manchester decoding on the sampled data to obtain original data.
The technical scheme adopted by the embodiment of the application further comprises the following steps: in the step a, the step of packing, by the sending end, original data to be sent specifically includes: and forming a data packet by the synchronous frame header, the data field and the CRC check code.
The technical scheme adopted by the embodiment of the application further comprises the following steps: in step b, the sampling, by the receiving end, the data packet sent by the sending end further includes: and (4) forming the sampling data into an array.
The technical scheme adopted by the embodiment of the application further comprises the following steps: and (4) forming the sampling data into an array.
The technical scheme adopted by the embodiment of the application further comprises the following steps: in the step b, the performing synchronous frame header detection on the sampled data specifically includes: and carrying out synchronous frame header detection on the current array by adopting a correlation method.
The technical scheme adopted by the embodiment of the application further comprises the following steps: in the step b, the detecting the synchronization frame header of the current array by using the correlation method specifically includes:
step b 10: sequentially calculating the correlation coefficient of the data in the current array and a specific array; the specific array is a correlation window, and the size of the correlation window is the number of sampling points in one symbol period;
step b 11: judging whether the calculated correlation coefficient is larger than a first threshold value, if so, indicating that a synchronous frame header is detected, wherein a section of data behind the synchronous frame header is valid data; if the correlation coefficient is not greater than the first threshold value, performing step b 12;
step b 12: judging whether the current data position of the calculated correlation coefficient reaches the tail of the current array or not, and finishing the processing of the current array if the current data position of the calculated correlation coefficient reaches the tail of the current array; if the end of the current array has not been reached, the correlation window is slid one step back and step b10 is re-executed.
The technical scheme adopted by the embodiment of the application further comprises the following steps: in the step b, the performing Manchester decoding on the sampled data specifically includes: and carrying out Manchester decoding on the effective data behind the synchronous frame header by adopting a correlation method.
The technical scheme adopted by the embodiment of the application further comprises the following steps: the Manchester decoding specifically comprises:
step b 20: sequentially detecting peaks or valleys in the valid data, and executing step b21 when the peaks or valleys are detected;
step b 21: judging whether the wave crest or the wave trough is larger than a second threshold value; if the peak or the trough is larger than a second threshold value, executing step b 22; if the peak or the trough is not larger than the second threshold value, the correlation window is slid backward by one step, and step b20 is executed again;
step b 22: bit parsing: resolving to be '1' if the detected wave peak is the wave trough, resolving to be '0' if the detected wave trough is the wave trough, and sliding the relevant window backwards by M steps; and M is the number of sampling points in one symbol period.
The technical scheme adopted by the embodiment of the application further comprises the following steps: the sliding the relevant window backwards by M steps further comprises:
step b 23: judging whether the correlation window reaches the tail of the current array, and if the correlation window reaches the tail of the current array, outputting the result of bit analysis; if the correlation window does not reach the end of the current array, step b20 is re-executed.
The technical scheme adopted by the embodiment of the application further comprises the following steps: in the step b, the Manchester decoding the sample data further includes: and displaying the analysis result after performing CRC on the analysis result.
Another technical scheme adopted by the embodiment of the application is as follows: a digital communication device based on audio frequency channel includes a sending end and a receiving end;
the sending terminal comprises a first control module and a first audio communication module, wherein the first control module is used for packaging original data to be sent and carrying out Manchester coding on the packaged data packet, and the first audio communication module is used for sending the coded data packet through an audio channel;
the receiving end comprises a second audio communication module and a second control module, the second audio communication module is used for sampling the data packet sent by the sending end, and the second control module is used for carrying out synchronous frame header detection and Manchester decoding processing on the sampled data to obtain original data.
The technical scheme adopted by the embodiment of the application further comprises the following steps: the first control module comprises a packaging unit, and the packaging unit is used for forming a data packet by the synchronous frame header, the data field and the CRC check code.
The technical scheme adopted by the embodiment of the application further comprises the following steps: the sampling, by the second audio communication module, the data packet sent by the sending end further includes: and (4) forming the sampling data into an array.
The technical scheme adopted by the embodiment of the application further comprises the following steps: the second control module also comprises a frame header detection unit, and the frame header detection unit is used for carrying out synchronous frame header detection on the current array by adopting a correlation method.
The technical scheme adopted by the embodiment of the application further comprises the following steps: the frame header detection unit specifically performs synchronous frame header detection on the current array by adopting a correlation method, and comprises the following steps: sequentially calculating the correlation coefficient of the data in the current array and a specific array; the specific array is a correlation window, and the size of the correlation window is the number of sampling points in one symbol period; judging whether the calculated correlation coefficient is larger than a first threshold value, if so, indicating that a synchronous frame header is detected, wherein a section of data behind the synchronous frame header is valid data; if the correlation coefficient is not larger than the first threshold value, judging whether the current data position of the calculated correlation coefficient reaches the tail of the current array or not, and if the current data position of the calculated correlation coefficient reaches the tail of the current array, finishing the processing of the current array; and if the tail of the current array is not reached, sliding the correlation window backward by one step, and recalculating the correlation coefficient of the data in the current array and the specific array.
The technical scheme adopted by the embodiment of the application further comprises the following steps: the second control module further comprises a decoding unit, and the decoding unit is used for carrying out Manchester decoding on the effective data after the synchronous frame header by adopting a correlation method.
The technical scheme adopted by the embodiment of the application further comprises the following steps: the decoding unit adopts a correlation method to carry out Manchester decoding on the effective data after the synchronous frame header, and specifically comprises the following steps:
sequentially detecting wave crests or wave troughs in the effective data, and judging whether the wave crests or the wave troughs are larger than a second threshold value or not when the wave crests or the wave troughs are detected; if the wave peak or the wave trough is not larger than the second threshold value, the relevant window slides backwards by one step, and the wave peak or the wave trough in the effective data is detected again; if the wave crest or the wave trough is larger than a second threshold value, performing bit analysis: resolving to be '1' if the detected wave peak is the wave trough, resolving to be '0' if the detected wave trough is the wave trough, and sliding the relevant window backwards by M steps; and M is the number of sampling points in one symbol period.
The technical scheme adopted by the embodiment of the application further comprises the following steps: the sliding the relevant window backwards by M steps further comprises: judging whether the correlation window reaches the tail of the current array or not, and outputting an analysis result if the correlation window reaches the tail of the current array; and if the correlation window does not reach the tail of the current array, re-detecting the wave crest or the wave trough in the valid data.
The technical scheme adopted by the embodiment of the application further comprises the following steps: the second control module further comprises a checking unit, and the checking unit is used for performing CRC checking on the analysis result and displaying the analysis result.
Compared with the prior art, the beneficial effects of the embodiment of the application lie in that: the digital communication method and device based on the audio channel in the embodiment of the application adopt Manchester coding at the sending end, and the receiving end adopts a correlation method to carry out Manchester decoding on the received data.
Drawings
Fig. 1 is a flowchart of a method for transmitting data by a transmitting end according to an embodiment of the present application;
FIG. 2 is a schematic diagram of Manchester encoding according to an embodiment of the present application;
fig. 3 is a flowchart of a receiving-end data processing method according to an embodiment of the present application;
FIG. 4 is a bit stream of a synchronization frame header encoded by Manchester;
FIG. 5 is a flow chart of frame header detection according to an embodiment of the present application;
FIG. 6 is a flow chart of data decoding according to an embodiment of the present application;
fig. 7 is a schematic structural diagram of an audio channel-based digital communication apparatus according to an embodiment of the present application.
Detailed Description
To facilitate an understanding of the present application, the present application will now be described more fully with reference to the accompanying drawings. Preferred embodiments of the present application are shown in the drawings. This application may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.
Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the description of the present application is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.
The digital communication method and device based on the audio channel of the embodiment of the application package, encode and modulate original data to be transmitted by adopting Manchester encoding at a transmitting end (a lower computer) through improving an encoding and decoding algorithm, convert a digital signal into an analog signal, and transmit the analog signal through the audio channel. Sampling the received analog signal at a receiving end (an upper computer) by adopting a correlation method, and filtering, synchronizing frame header detection and Manchester decoding the sampled data to obtain original data; the embodiment of the application achieves higher data transmission rate by improving the coding and decoding algorithm, improves the decoding success rate and accuracy, and is suitable for the lower computer to transmit data to the upper computer and also suitable for the upper computer to transmit control information to the lower computer.
Specifically, please refer to fig. 1, which is a flowchart of a method for transmitting data by a transmitting end according to an embodiment of the present application. The method for sending the data by the sending end in the embodiment of the application comprises the following steps:
step 100: packaging original data to be sent;
in step 100, the packing of the original data to be sent specifically includes: and forming a data packet by the synchronous frame header, the data field and a Cyclic Redundancy Check (CRC) Check code, wherein the length of the data packet is determined by the length of the synchronous frame header, the length of the data field and the length of a CRC Check value. In the embodiment of the application, the adopted synchronization frame header is 0xFF, 0x5A, the data field includes data type 8bit, data length 8bit, packet sequence number 8bit and original data 56bit, and the data field is different according to different application environments. The CRC check code, i.e., a cyclic redundancy check code, is a check value of a data field, and is calculated from the data field, and the CRC polynomial is: 1+ X2+X8. The data packet structure of the embodiment of the present application is shown in table 1 below:
table 1 packet structure
| Name of field | SynchronizationFrame header | Data field | CRC |
| Length (bit) | 16 | 80 | 8 |
Step 110: encoding the packed data packet;
in step 110, encoding the data packet specifically includes: the data packet is encoded by adopting a Manchester (Manchester) encoding technology, and a clock signal is contained in the data stream by the Manchester encoding, so that the Manchester encoding has self-synchronizing capability and good anti-interference performance. The specific coding mode is as follows: the original data "0" in the packet is mapped to "10", and the original data "1" is mapped to "01". Specifically, as shown in fig. 2, it is a schematic diagram of Manchester encoding according to an embodiment of the present application. Let the transmission time occupied by each original bit (bit) be T, then the transmission time of each bit after Manchester encoding be T/2.
Step 120: modulating the coded data packet into an analog signal on a channel, and transmitting the analog signal through an audio channel;
in step 120, modulating the encoded data packet into an analog signal on a channel specifically includes: mapping the encoded digital signal onto an audio channel; the mapping mode is as follows: the digital signal "0" corresponds to the low level-V of the analog signal, and the digital signal "1" corresponds to the high level + V of the analog signal. The hold times of the digital signals "0" and "1" are both T/2. Under the condition of certain channel noise, the signal-to-noise ratio of a signal at a receiving end is determined by the size of the level V, the larger the value of the level V is, the higher the signal-to-noise ratio is, and otherwise, the lower the signal-to-noise ratio is; in the embodiment of the present application, the value of the level V is set to 500 mV. Under the condition of certain channel conditions, the size of T determines the identifiability of a signal at a receiving end, the larger the T is, the smaller the influence of signal distortion on the whole waveform is, the higher the identifiability of the signal is, and otherwise, the lower the identifiability of the signal is.
According to the digital communication method based on the audio channel, the original data to be transmitted are packaged, coded and modulated by adopting Manchester coding at the transmitting end, the analog signal is transmitted through the audio channel after the digital signal is converted into the analog signal, the higher data transmission rate is achieved, and the high-speed data transmission requirement of digital communication is met.
Please refer to fig. 3, which is a flowchart illustrating a receiving-end data processing method according to an embodiment of the present application. The receiving end data processing method of the embodiment of the application comprises the following steps:
step 200: sampling the analog signals, and forming an array by data obtained by sampling according to a set length;
in step 200, sampling the analog signal specifically includes: sampling the analog signal at a sampling frequency fs to obtain a digital signal, wherein the higher the sampling frequency is, the more accurate the description of the analog signal by the obtained digital signal is; when the sampling frequency is low, the resulting digital signal will have difficulty in recovering the corresponding analog signal. In the embodiment of the present application, the length of the set array is 5000, and the sampling parameters may be specifically set according to actual requirements.
Step 210: performing band-pass filtering on data in the current array to eliminate noise interference outside a data frequency band;
in step 210, the filter used in the embodiment of the present application is an FIR filter ((Finite Impulse Response, Finite single-bit Impulse Response filter)), the passband frequency is 8KHz to 12KHz, a Hanning window (Hanning window) is used as the window, the order of the filter is 25 orders, and the above filter parameters can be specifically set according to actual requirements.
Step 220: performing synchronous frame header detection on the current array, judging whether a synchronous frame header is detected in the current array, and executing step 230 if the synchronous frame header is detected in the current array;
in step 220, the embodiment of the present application performs synchronous frame header detection on the groups by using a correlation method. Specifically, as shown in fig. 4 and fig. 5, fig. 4 is a bitstream obtained by Manchester encoding of a synchronization frame header, and fig. 5 is a flow chart of frame header detection according to an embodiment of the present application. The frame header detection method of the embodiment of the application comprises the following steps:
step 221: sequentially calculating the correlation coefficient of the data in the current array and the specific array;
in step 221, the specific array is a correlation window with a specific length, the size of the correlation window is the number of sampling points in one symbol period, and the elements in the specific array are expected values corresponding to specific original data bits. In the embodiment of the present application, the adopted specific original data bit is "1", the corresponding Manchester code is "01", and the corresponding correlation window is [ -1, -1,1,1 ]. The correlation coefficient is calculated as follows:
in the formula (1), x1kRepresenting data in array 1, x2kThe data in array 2 is represented by,
representing the mean of the data in array 1,
the data mean value in the array 2 is shown, k is an array subscript, k is 1,2, …, n is n, and n is the number of data in the array.
Step 222: judging whether the calculated correlation coefficient is larger than a set first threshold value, if so, indicating that a synchronous frame header is detected and finishing the detection of the synchronous frame header; if the correlation coefficient is not greater than the set first threshold, go to step 223;
in step 222, if a synchronization frame header is detected in the array, it indicates that the current array is an effective array, and a section of data after the synchronization frame header is effective data; and if the synchronous frame head is not detected in the current array, indicating that the processing of the current array is finished. In the embodiment of the present application, it is determined that the first threshold of the correlation coefficient is 0.6, and the first threshold may be specifically set according to practical applications.
Step 223: judging whether the current data position of the calculated correlation coefficient reaches the tail of the current array, if the current data position reaches the tail of the current array, indicating that the detection of the current array is finished, and if no synchronous frame header is detected, finishing the processing of the current array; if the tail of the current array is not reached, the relevant window is slid backwards by one step, and step 221 is executed again;
in step 223, assuming that the length of the current array is 6 and the adopted specific array is [ -1, -1,1,1], first calculating the correlation coefficient between the 1 st to 4 th data of the current array and the specific array, and if the calculated correlation coefficient is greater than a set first threshold value, indicating that a synchronization frame header is detected, then performing the subsequent steps; if the calculated correlation coefficient is not greater than the set first threshold, indicating that no synchronization frame header has been detected, the correlation window is slid backward by one step (i.e., shifted backward by one data), the correlation coefficient … between the data of the 2 nd bit of the current array and the data of the 5 th bit of the current array and the specific array is calculated, and so on until the correlation window is slid to the last data of the current array.
Step 230: carrying out Manchester decoding on the effective data after the synchronous frame header to obtain corresponding original data;
in step 230, the embodiment of the present application performs Manchester decoding on the valid data by using a correlation method. Specifically, please refer to fig. 6, which is a flowchart illustrating data decoding according to an embodiment of the present application. The data decoding method of the embodiment of the application comprises the following steps:
step 231: sequentially detecting peaks or valleys in the valid data, and executing step 232 when the peaks or valleys are detected;
in step 231, the peak refers to the maximum value of the wave amplitude in a range of wavelengths, and the relative minimum value is called the trough; taking transverse wave as an example, the highest point of the protrusion is the peak, and the lowest point of the depression is the trough.
Step 232: judging whether the wave crest or the wave trough is larger than a set second threshold value; if the peak or trough is greater than the set second threshold, go to step 233; if the peak or trough is not greater than the set second threshold, the correlation window is slid backward by one step, and step 231 is executed again;
in step 232, the second threshold of the peak or the trough is determined to be 0.8 in this embodiment, which may be specifically set according to practical applications, and the sliding manner of the relevant window is the same as that in step 223, which will not be described herein again.
Step 233: bit parsing: resolving to "1" if a peak is detected, resolving to "0" if a trough is detected, and sliding the relevant window backwards by M steps (i.e., backwards by M data);
in step 233, M is the number of sampling points in one symbol period, and M in this embodiment is 4.
Step 234: judging whether the correlation window reaches the tail of the current array, if so, outputting an analysis result, and ending bit analysis of the current array; if the correlation window does not reach the end of the current array, step 231 is re-executed.
Step 240: and carrying out CRC (cyclic redundancy check) on the analyzed original data, and displaying an analysis result.
According to the digital communication method based on the audio channel, the received analog signals are sampled at the receiving end by adopting a correlation method, and the sampled data are filtered, subjected to synchronous frame header detection and Manchester decoding to obtain the original data, so that the decoding success rate and accuracy are improved, and the demodulation problem when the signal waveform is seriously distorted is solved.
Please refer to fig. 7, which is a schematic structural diagram of a digital communication apparatus based on an audio channel according to an embodiment of the present application. The digital communication device based on the audio channel in the embodiment of the application comprises a sending end and a receiving end, wherein the sending end and the receiving end are respectively provided with an audio interface (not shown), and the sending end and the receiving end are connected with each other through the audio interfaces.
Specifically, the sending end comprises a first control module and a first audio communication module; the first control module is used for packaging and coding original data to be sent by adopting Manchester coding and then transmitting the data packets to the first audio communication module; the first audio communication module is used for converting the digital signals in the data packets into analog signals and then sending the analog signals through an audio channel.
The first control module comprises a group packaging unit and an encoding unit;
the packaging unit is used for packaging original data to be sent; the packing of the original data to be sent specifically includes: and forming a data packet by the synchronous frame header, the data field and the CRC check code, wherein the length of the data packet is determined by the length of the synchronous frame header, the length of the data field and the length of the CRC check value. In the embodiment of the application, the adopted synchronization frame header is 0xFF, 0x5A, the data field includes data type 8bit, data length 8bit, packet sequence number 8bit and original data 56bit, and the data field is different according to different application environments. The CRC check code, i.e., a cyclic redundancy check code, is a check value of a data field, and is calculated from the data field, and the CRC polynomial is: 1+ X2+X8. The data packet structure of the embodiment of the present application is shown in table 1 below:
table 1 packet structure
| Name of field | Synchronous frame header | Data field | CRC |
| Length (bit) | 16 | 80 | 8 |
The encoding unit is used for encoding the packed data packet; the encoding of the data packet specifically includes: the data packet is encoded by adopting a Manchester encoding technology, and a clock signal is contained in a data stream by the Manchester encoding technology, so that the Manchester encoding has self-synchronizing capability and good anti-interference performance. The specific coding mode is as follows: the original data "0" in the packet is mapped to "10", and the original data "1" is mapped to "01". Let the transmission time occupied by each original bit (bit) be T, then the transmission time of each bit after Manchester encoding be T/2. In the embodiment of the present application, T is 0.1ms, and the data transmission rate is 10 Kbps.
The first audio communication module modulates the coded data packet into an analog signal on a channel and then sends the analog signal through an audio channel; the modulating the encoded data packet into an analog signal on a channel specifically includes: mapping the encoded digital signal onto an audio channel; the mapping mode is as follows: the digital signal "0" corresponds to the low level-V of the analog signal, and the digital signal "1" corresponds to the high level + V of the analog signal. The hold times of the digital signals "0" and "1" are both T/2. Under the condition of certain channel noise, the signal-to-noise ratio of a signal at a receiving end is determined by the size of the level V, the larger the value of the level V is, the higher the signal-to-noise ratio is, and otherwise, the lower the signal-to-noise ratio is; in the embodiment of the present application, the value of the level V is set to 500 mV. Under the condition of certain channel conditions, the size of T determines the identifiability of a signal at a receiving end, the larger the T is, the smaller the influence of signal distortion on the whole waveform is, the higher the identifiability of the signal is, and otherwise, the lower the identifiability of the signal is.
The receiving end comprises a second audio communication module and a second control module, wherein the second audio communication module is used for sampling the received analog signals by adopting a correlation method and transmitting the sampling data to the second control module; and the second control module is used for filtering the sampled data, detecting a synchronous frame header and decoding the sampled data by the Manchester to obtain original data.
The sampling of the analog signal by the second audio communication module specifically comprises: sampling the analog signals at a sampling frequency fs to obtain digital signals, and forming an array by using the sampled data according to a set length; the higher the sampling frequency is, the more accurate the description of the obtained digital signal on the analog signal is; when the sampling frequency is low, the resulting digital signal will have difficulty in recovering the corresponding analog signal.
The second control module comprises a filtering unit, a frame header detection unit, a decoding unit and a checking unit;
the filtering unit is used for carrying out band-pass filtering on the data in the current array and eliminating noise interference outside a data frequency band; the filter that this application embodiment adopted is FIR filter, and the passband frequency is 8KHz-12KHz, and the window adopts Hanning window, and above-mentioned filtering parameter specifically can set for according to actual demand.
The frame header detection unit is used for carrying out synchronous frame header detection on the current array, judging whether a synchronous frame header is detected in the current array or not, and if the synchronous frame header is detected in the current array, decoding the synchronous frame header through the decoding unit; in the embodiment of the application, a correlation method is adopted to perform synchronous frame header detection on the groups. The frame header detection method comprises the following steps:
a 1: sequentially calculating the correlation coefficient of the data in the current array and the specific array; the specific array is a correlation window with a specific length, the size of the correlation window is the number of sampling points in one symbol period, and the elements in the specific array are expected values corresponding to specific original data bits. In the embodiment of the present application, the adopted specific original data bit is "1", the corresponding Manchester code is "01", and the corresponding correlation window is [ -1, -1,1,1 ]. The correlation coefficient is calculated as follows:
in the formula (1), x1kRepresenting data in array 1, x2kThe data in array 2 is represented by,
representing the mean of the data in array 1,
denotes the data mean in array 2, k denotes the array index, k is 1,2, …, n, n tableThe number of data in the array is shown.
a 2: judging whether the calculated correlation coefficient is larger than a set first threshold value, if so, indicating that a synchronous frame header is detected and finishing the detection of the synchronous frame header; if the correlation coefficient is not larger than the set first threshold value, executing a 3; if the synchronous frame header is detected in the array, the current array is an effective array, and a section of data behind the synchronous frame header is effective data; and if the synchronous frame head is not detected in the current array, indicating that the processing of the current array is finished. In the embodiment of the present application, it is determined that the first threshold of the correlation coefficient is 0.6, and the first threshold may be specifically set according to practical applications.
a 3: judging whether the current data position of the calculated correlation coefficient reaches the tail of the current array, if the current data position reaches the tail of the current array, indicating that the detection of the current array is finished, and if no synchronous frame header is detected, finishing the processing of the current array; if the tail of the current array is not reached, sliding the correlation window one step backwards and re-executing a 1; assuming that the length of the current array is 6, the adopted specific array is [ -1, -1,1,1], firstly calculating correlation coefficients of the 1 st to 4 th data of the current array and the specific array, and if the calculated correlation coefficients are greater than a set first threshold value, indicating that a synchronous frame header is detected, executing subsequent steps; if the calculated correlation coefficient is not greater than the set first threshold, indicating that no synchronization frame header has been detected, the correlation window is slid backward by one step (i.e., shifted backward by one data), the correlation coefficient … between the data of the 2 nd bit of the current array and the data of the 5 th bit of the current array and the specific array is calculated, and so on until the correlation window is slid to the last data of the current array.
The encoding unit is used for carrying out Manchester decoding on the effective data after the frame header is synchronized to obtain corresponding original data; the embodiment of the application adopts a correlation method to carry out Manchester decoding on the effective data. The data decoding method comprises the following steps:
b 1: sequentially detecting peaks or valleys in the valid data, and when the peaks or valleys are detected, performing b 2;
b 2: judging whether the wave crest or the wave trough is larger than a set second threshold value; if the wave crest or the wave trough is larger than a set second threshold value, b3 is executed; if the wave crest or the wave trough is not larger than the set second threshold value, the relevant window slides backwards by one step, and b1 is executed again; in the embodiment of the present application, the second threshold for determining the peak or the trough is 0.8, which may be specifically set according to practical applications.
b 3: bit parsing: resolving to be '1' if the detected wave peak is the wave trough, resolving to be '0' if the detected wave trough is the wave trough, and sliding the relevant window backwards by M steps; wherein, M is the number of sampling points in one symbol period, and the value of M in the embodiment of the application is 4;
b 4: judging whether the correlation window reaches the tail of the current array, if so, outputting an analysis result, and ending bit analysis of the current array; if the correlation window does not reach the end of the current array, b1 is re-executed.
And the checking unit is used for displaying the analysis result after CRC checking is carried out on the analyzed original data.
In the above embodiment, the sending end and the receiving end include terminal devices having audio interfaces, the sending end is, for example, an ear thermometer, a heart rate earphone, and the receiving end is, for example, a smart phone, a computer, and the sending end is the heart rate earphone, and the receiving end is the smart phone, and the digital communication method based on the audio channel includes: collecting heart rate data through a heart rate earphone, packaging, coding and modulating the collected heart rate data by adopting Manchester coding, and transmitting the heart rate data to the smart phone through an audio channel; the smart phone samples the received heart rate data by adopting a correlation method, performs filtering, synchronous frame header detection and Manchester decoding post-processing on the sampled data, and displays the heart rate data through the smart phone or an application program installed on the smart phone.
The above embodiments are preferred embodiments of the present application, but the present application is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present application should be construed as equivalents and are included in the scope of the present application.
Claims (13)
1. A method for digital communication over an audio channel, comprising:
step a: a sending end packages original data to be sent and carries out Manchester coding on the packaged data package; mapping the digital signals in the coded data packets to an audio channel to be modulated into analog signals on the channel, and sending the coded data packets converted into the analog signals through the audio channel;
the original data comprises a synchronous frame header, a data field and a CRC (cyclic redundancy check) code, wherein the length of the data packet is determined by the length of the synchronous frame header, the length of the data field and the length of the CRC code; the data stream in Manchester coding contains a clock signal; the mapping of the digital signal in the encoded data packet to the audio channel specifically includes:
the digital signal '0' corresponds to the low level-V of the analog signal, and the digital signal '1' corresponds to the high level + V of the analog signal;
step b: the receiving end samples the data packets in the analog signal form sent by the sending end, the data packets obtained by sampling form an array according to a set length, then the data in the current array sampled is subjected to synchronous frame header detection by adopting a correlation method, and effective data after the synchronous frame header is subjected to Manchester decoding by adopting the correlation method, so that the original data in the digital signal form is obtained.
2. The audio channel-based digital communication method according to claim 1, wherein in the step b, the performing frame header synchronization detection on the current array by using the correlation method specifically comprises:
step b 10: sequentially calculating the correlation coefficient of the data in the current array and a specific array; the specific array is a correlation window, and the size of the correlation window is the number of sampling points in one symbol period;
step b 11: judging whether the calculated correlation coefficient is larger than a first threshold value, if so, indicating that a synchronous frame header is detected, wherein a section of data behind the synchronous frame header is valid data; if the correlation coefficient is not greater than the first threshold value, performing step b 12;
step b 12: judging whether the current data position of the calculated correlation coefficient reaches the tail of the current array or not, and finishing the processing of the current array if the current data position of the calculated correlation coefficient reaches the tail of the current array; if the end of the current array has not been reached, the correlation window is slid one step back and step b10 is re-executed.
3. The digital communication method based on audio channel according to claim 2, wherein said Manchester decoding specifically comprises:
step b 20: sequentially detecting peaks or valleys in the valid data, and executing step b21 when the peaks or valleys are detected;
step b 21: judging whether the wave crest or the wave trough is larger than a second threshold value; if the peak or the trough is larger than a second threshold value, executing step b 22; if the peak or the trough is not larger than the second threshold value, the correlation window is slid backward by one step, and step b20 is executed again;
step b 22: bit parsing: resolving to be '1' if the detected wave peak is the wave trough, resolving to be '0' if the detected wave trough is the wave trough, and sliding the relevant window backwards by M steps; and M is the number of sampling points in one symbol period.
4. The audio channel-based digital communication method according to claim 3, wherein said sliding the correlation window backward by M steps further comprises:
step b 23: judging whether the correlation window reaches the tail of the current array, and if the correlation window reaches the tail of the current array, outputting the result of bit analysis; if the correlation window does not reach the end of the current array, step b20 is re-executed.
5. The digital communication method based on audio channel according to claim 4, wherein in the step b, the performing Manchester decoding process on the valid data after the synchronization frame header further comprises: and displaying the analysis result after performing CRC on the analysis result.
6. A digital communication device based on audio frequency channel is characterized in that the device comprises a sending end and a receiving end;
the transmitting end comprises a first control module and a first audio communication module, wherein the first control module is used for packaging original data to be transmitted and carrying out Manchester coding on the packaged data packets; the first audio communication module is used for mapping the digital signals in the encoded data packets to an audio channel to modulate the digital signals into analog signals on the channel, and transmitting the encoded data packets converted into the analog signals through the audio channel;
the original data comprises a synchronous frame header, a data field and a CRC (cyclic redundancy check) code, wherein the length of the data packet is determined by the length of the synchronous frame header, the length of the data field and the length of the CRC code; the data stream in Manchester coding contains a clock signal; the mapping of the digital signal in the encoded data packet to the audio channel specifically includes:
the digital signal '0' corresponds to the low level-V of the analog signal, and the digital signal '1' corresponds to the high level + V of the analog signal;
the receiving end comprises a second audio communication module and a second control module, wherein the second audio communication module is used for sampling the data packets in the analog form sent by the sending end and forming an array of the data packets obtained by sampling according to a set length; the second control module is used for carrying out synchronous frame head detection on data in the sampled current array by adopting a correlation method and carrying out Manchester decoding processing on effective data behind the synchronous frame head by adopting the correlation method to obtain original data in a digital signal form.
7. The digital communication device based on audio channel according to claim 6, wherein the first control module comprises a packet packing unit for packing the synchronization frame header, the data field and the CRC check code into a data packet.
8. The audio channel-based digital communication device according to claim 6 or 7, wherein the second control module further comprises a frame header detection unit, and the frame header detection unit is configured to perform synchronous frame header detection on the current array by using a correlation method.
9. The digital communication device based on audio channel of claim 8, wherein the frame header detecting unit performs frame header detection for synchronization of the current array by using correlation method specifically comprises: sequentially calculating the correlation coefficient of the data in the current array and a specific array; the specific array is a correlation window, and the size of the correlation window is the number of sampling points in one symbol period; judging whether the calculated correlation coefficient is larger than a first threshold value, if so, indicating that a synchronous frame header is detected, wherein a section of data behind the synchronous frame header is valid data; if the correlation coefficient is not larger than the first threshold value, judging whether the current data position of the calculated correlation coefficient reaches the tail of the current array or not, and if the current data position of the calculated correlation coefficient reaches the tail of the current array, finishing the processing of the current array; and if the tail of the current array is not reached, sliding the correlation window backward by one step, and recalculating the correlation coefficient of the data in the current array and the specific array.
10. The digital communication device based on audio channel according to claim 9, wherein the second control module further comprises a decoding unit, and the decoding unit is configured to perform Manchester decoding on the valid data after the synchronization frame header by using a correlation method.
11. The digital communication device based on audio channel of claim 10, wherein the decoding unit performing Manchester decoding on the valid data after the synchronization frame header by using the correlation method specifically comprises:
sequentially detecting wave crests or wave troughs in the effective data, and judging whether the wave crests or the wave troughs are larger than a second threshold value or not when the wave crests or the wave troughs are detected; if the wave peak or the wave trough is not larger than the second threshold value, the relevant window slides backwards by one step, and the wave peak or the wave trough in the effective data is detected again; if the wave crest or the wave trough is larger than a second threshold value, performing bit analysis: resolving to be '1' if the detected wave peak is the wave trough, resolving to be '0' if the detected wave trough is the wave trough, and sliding the relevant window backwards by M steps; and M is the number of sampling points in one symbol period.
12. The audio channel-based digital communication device of claim 11, wherein the sliding the correlation window back M steps further comprises: judging whether the correlation window reaches the tail of the current array or not, and outputting an analysis result if the correlation window reaches the tail of the current array; and if the correlation window does not reach the tail of the current array, re-detecting the wave crest or the wave trough in the valid data.
13. The digital communication device based on audio channel as claimed in claim 12, wherein the second control module further comprises a checking unit for performing CRC check on the parsing result and displaying the parsing result.
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