Sonde energy saving method based on superposition coding technology

Abstract

The invention discloses a sonde energy-saving method based on a superposition coding technology, and belongs to the field of wireless communication. In order to solve the problem that energy consumption is too high due to the fact that a wireless communication module is frequently started by a traditional sonde, superposition coding transmission of meteorological data is achieved through a Hadamard orthogonal matrix. The method specifically comprises the steps that after meteorological data packets collected at multiple adjacent moments are subjected to constellation modulation, Hadamard matrix row vectors are distributed for signal expansion; superposing the extended signals into a single transmitting signal, and completing multi-packet data transmission through single communication; and the ground station demodulates and recovers each data packet by using the orthogonality of the row vector of the Hadamard matrix. A dynamic adjustment strategy is innovatively introduced, the number of superposed packets is optimized in real time according to the bit error rate feedback of a ground station, and energy is saved to the maximum on the premise that the communication quality is guaranteed. According to the method, the communication energy consumption is reduced, the endurance of the lithium battery is effectively prolonged, the method is suitable for an aerial sonde system released by an unmanned aerial vehicle, and the meteorological data acquisition efficiency is remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of wireless communication, and particularly to a sounding device energy-saving method based on superposition coding technology. Background Art

[0002] Meteorological conditions are important factors affecting flight safety. Especially in the era of low-altitude economy, they are important bases for the development and utilization of airspace and time-domain resources in the aviation field. Therefore, meteorological detection plays a key role in understanding meteorological conditions and predicting weather. Traditional meteorological detection methods mainly rely on ground station observations, releasing radiosondes, and the use of meteorological radars. With the further development of unmanned aerial vehicle (UAV) technology, modern high-altitude meteorological detection can be achieved through meteorological detection UAVs. Meteorological detection UAVs usually carry multiple radiosondes with meteorological detection functions. When flying to a predetermined airspace (a typical altitude of 10,000 meters), the meteorological detection UAV throws out the carried radiosondes one by one. After being dropped by the UAV, the radiosonde will select the parachute-opening time according to the upper computer instruction to implement a slow descent, and rely on various sensors to collect meteorological data during this descent process. When all the configured sensors (such as temperature sensors, humidity sensors, pressure sensors, etc.) have completed the collection of meteorological information, the sounding sensor will use its own wireless communication module to send the collected data to the ground station.

[0003] Since the radiosonde is mainly powered by a lithium battery carried by itself, in order to ensure the smooth progress of meteorological data collection work, how to achieve energy saving of the radiosonde is particularly important. The energy consumption of the radiosonde is mainly concentrated in the sensor perception module, the signal processing module, and the wireless communication module, among which the energy consumption of the wireless communication module accounts for the vast majority of the energy consumption of a single radiosonde. In the traditional radiosonde data transmission process, every time the sensor collects data, the radiosonde will send the collected data to the ground station through the wireless communication module. Obviously, the frequent activation of the wireless communication module for data transmission increases the energy consumption of the radiosonde and reduces the battery life of the lithium battery.

[0004] For this reason, the present invention improves the data transmission mechanism of the existing radiosonde wireless communication module. By introducing a data transmission strategy based on superposition coding technology (SC), the meteorological data collected at adjacent multiple moments can be superposed and coded, and then sent within one transmission time slot, so that the meteorological data that originally needed to activate the wireless communication module multiple times for transmission can be completed under the premise of only activating the communication module once, thereby greatly reducing the communication energy consumption of the radiosonde and achieving the purpose of energy saving of the radiosonde. Summary of the Invention

[0005] In view of the above deficiencies in the prior art, the present invention provides a sounding device energy-saving method based on superposition coding technology.

[0006] In order to achieve the above-mentioned object of the invention, the technical solution adopted by the present invention is: A radiosonde energy-saving method based on superposition coding technology comprises the following steps: S1. The radiosonde collects meteorological data during its descent, generates a meteorological data bit stream at time t, and performs constellation modulation on the obtained meteorological data bit stream to obtain a modulation symbol sequence; S2. Superimposing the modulation symbol sequences of meteorological data collected at multiple adjacent moments, and transmitting the superimposed data in one transmission time slot; S3, distinguishing the multiple different meteorological data packets sent in S2, assigning different row vectors or column vectors to the multiple data packets for signal superposition, and demodulating them at the receiving end using the orthogonality of the row vectors or column vectors to recover the bit information corresponding to each data packet; S4. After the sonde is powered on, the ground station notifies the sonde of the maximum number of superimposed data through uplink remote control commands. After the ground station completes the reception of meteorological data, it will dynamically adjust the maximum number of superimposed data based on the data reception quality.

[0007] Furthermore, the S1 specifically includes the following steps: S11. When the weather drone reaches the predetermined altitude and enters the target detection airspace, the drone will Fly at a constant speed in the target airspace and at time intervals Drop the carried radiosondes one by one; S12. After being dropped, the sonde will deploy its parachute and descend slowly according to the drone's instructions. During this descent, it will sense and detect meteorological information such as atmospheric temperature, relative humidity, pressure, wind speed, and wind direction within the target airspace. S13, will The meteorological data at each moment is uniformly quantized and converted into a bit stream , through Perform constellation modulation to obtain the modulation symbol sequence .

[0008] Furthermore, the size of the S2 is The Hadamard orthogonal matrix The obtained modulation symbol sequence is superimposed and coded, and the length Greater than the total amount of meteorological data collected.

[0009] Furthermore, the S3 specifically includes the following steps: S31, modulate the symbol sequence By length Divide into blocks and remember A symbol block is ; S32. Assign the th row of the Hadamard orthogonal matrix to , the th symbol block in the sequence . After expansion, the expanded data can be obtained; S33. The transmitter performs superposition coding on the th symbol block in the meteorological data and sends it. After being affected by the wireless channel and noise, it is received by the ground station; S34. After receiving the transmission signal of the radiosonde, the ground station performs received signal equalization based on the estimated channel state information by the zero-forcing equalization method. The ground station distinguishes the symbol sequences at different times before superposition according to the orthogonal sequence.

[0010] Furthermore, the signal after superposition coding at the transmitter in S33 is expressed as:

[0011] The signal received by the ground station is expressed as:

[0012] where , are the transmission signal and the received signal respectively, represents the convolution operation, is the channel coefficient, is the additive white Gaussian noise.

[0013] Furthermore, the signal after signal equalization by the zero-forcing equalization method in S34 is expressed as:

[0014] Distinguish the symbol sequences at different times before superposition according to the orthogonal sequence is expressed as:

[0015] In the formula, is the signal after signal equalization by the zero-forcing equalization method, is the received signal, is the th row of the Hadamard orthogonal matrix.

[0016] Furthermore, S4 specifically includes the following steps: S41. After the radiosonde is powered on, the ground station will notify the radiosonde of the maximum number of stackable data set by the uplink remote control command. ; S42. Let the radiosonde receive the quantity . If the received quality meets the bit error rate requirement of the system, the radiosonde will be notified by the remote control command to maintain the current value. Otherwise, the radiosonde needs to reduce the value, that is, let .

[0017] The present invention has the following beneficial effects: Compared with the prior art, the major breakthrough of the present invention is that by introducing the superposition coding technology in the radiosonde, the meteorological data collected at adjacent multiple sampling moments are superposed and coded, so that the radiosonde can send multiple meteorological data packets through only one transmission time slot. Since most of the energy consumption of the radiosonde occurs in the wireless communication process, based on the present invention, the energy consumption of the radiosonde can be significantly reduced for more meteorological data collection work. In addition, by dynamically adjusting the superposition coding parameters according to the ground station data reception quality, the maximum energy saving of the radiosonde can be achieved while ensuring the meteorological data reception quality. Brief Description of the Drawings

[0018] Figure 1 It is a schematic flow chart of the energy-saving method for the radiosonde based on the superposition coding technology of the present invention.

[0019] Figure 2 It is a schematic diagram for comparing the transmission modes of the meteorological data sending end in the embodiment of the present invention.

[0020] Figure 3 It is a schematic diagram for comparing the processing modes of the meteorological data receiving end in the embodiment of the present invention.

[0021] Figure 4 For different values in the embodiment of the present invention, it is a schematic diagram for comparing the bit error performance.

[0022] Figure 5 It is a schematic diagram for comparing the bit error performance corresponding to different sequence lengths in the embodiment of the present invention.

[0023] Figure 6 It is a comparison of the energy consumption of the communication module corresponding to different data acquisition frequencies in the embodiment of the present invention. Detailed Embodiment

[0024] The specific embodiments of the present invention will be described below to facilitate those skilled in the art to understand the present invention. However, it should be clear that the present invention is not limited to the scope of the specific embodiments. For those of ordinary skill in the art, as long as various changes are within the spirit and scope of the present invention defined and determined by the appended claims, these changes are obvious, and all inventions made using the concept of the present invention are within the scope of protection.

[0025] A sounding balloon energy-saving method based on superposition coding technology includes the following steps: S1. During the descent of the sounding balloon, meteorological data is collected to generate a meteorological data bitstream at time t, and the obtained meteorological data bitstream is subjected to constellation modulation to obtain a modulated symbol sequence; In this embodiment, when the meteorological unmanned aerial vehicle (UAV) flies to a predetermined altitude and enters the target detection airspace, the UAV will fly horizontally at a constant speed in the target airspace and release the carried sounding balloons one by one at time intervals . After being released, the sounding balloon will open the parachute and descend slowly according to the instructions of the UAV, and during this descent process, it will sense and detect meteorological information such as atmospheric temperature, relative humidity, pressure, wind speed, and wind direction in the target airspace. Denote the meteorological data vector as the meteorological data sensed by the sounding balloon at time , where , , , , and represent the six parameters of atmospheric temperature, relative humidity, atmospheric pressure, altitude, wind speed, and wind direction at time . The meteorological data at time is uniformly quantized and converted into a bitstream . Denote that the meteorological data bitstream contains a total of binary bits. The meteorological data (in units of bits) is subjected to constellation modulation to obtain a modulated symbol sequence .

[0026] S2. The modulated symbol sequences of the meteorological data collected in multiple adjacent time intervals are subjected to data superposition, and the superimposed data is sent within one transmission time slot; To achieve energy-saving transmission of the sounding sensor, the present invention introduces superposition coding technology (SC) to perform data superposition on the meteorological data collected in multiple adjacent time intervals and complete the transmission of the superimposed data within one transmission time slot. If the collected meteorological data ( ) For superimposed coding, it is first necessary to generate a Hadamard orthogonal matrix of size , and it is stipulated that is greater than the total number of collected meteorological data.

[0027] The Hadamard matrix is a square matrix, whose elements are +1 or -1, and it satisfies that the product of the matrix and its transpose matrix is equal to the identity matrix of the matrix order, that is , is the identity matrix. The main properties of the Hadamard matrix are as follows: (1) Orthogonality, the row vectors and column vectors of are all orthogonal, and the dot product of any two different row vectors or column vectors is 0; (2) Normalization, the length (square root of the sum of the squares of the elements) of each row vector and column vector of is equal to ; (3) Order,

[0028] S3. Distinguish multiple different meteorological data packets sent in S2, assign different row vectors or column vectors to multiple data packets for signal superposition, and use row vectors or column vectors for demodulation at the receiving end to recover the bit information corresponding to each data packet; Based on the main properties of the above Hadamard matrix , the present invention uses its orthogonality to distinguish multiple different meteorological data packets. By assigning different row vectors or column vectors to multiple data packets for signal superposition and using row vectors or column vectors for demodulation at the receiving end, the bit information corresponding to each data packet can be correctly recovered. Specifically: S31. Divide the modulation symbol sequence into blocks according to the length , denoted as , where is the number of blocks, , is represented by the formula, where is the number of blocks, is the bit length.

[0029] S32. Assign the -th row of the Hadamard orthogonal matrix to , in the -th symbol block The extended data can be obtained after the sequence ; S33. The transmitter superimposes and encodes the th symbol block of the meteorological data and transmits it. After being affected by the channel and noise, it is received at the ground station; Assume that the ground meteorological station is in an open area and is not blocked by hills, trees, etc. Then the wireless channel between the radiosonde and the ground station during the entire descent process is a typical air-to-ground (A2G) channel. If only considering the propagation loss in free space, the wireless channel can be modeled as a linear time-invariant constant parameter channel. In the present invention, it is assumed that the A2G is a Rayleigh fading channel, and the channel coefficient is .

[0030] The transmitted signal of the transmitter After being affected by the channel and noise, the received signal at the ground meteorological station can be expressed as

[0031] where represents the convolution operation, is the additive white Gaussian noise.

[0032] S34. After receiving the transmitted signal of the radiosonde, the ground station will perform receive signal equalization based on the estimated channel information. Based on the equalized signal, the ground station can distinguish the symbol sequences at different times before superposition according to the orthogonal sequence.

[0033] Assume that the ground station can perform perfect channel estimation through the training sequence. After receiving the transmitted signal of the radiosonde, the ground station will perform receive signal equalization based on the estimated channel information. If zero-forcing equalization is adopted, the signal after zero-forcing equalization can be expressed as: .

[0034] Based on the signal after zero-forcing equalization, the ground station can distinguish the symbol sequences at different times before superposition according to the orthogonal sequence, that is . Based on , the ground station further performs QPSK demodulation on it and calculates the final bit error rate.

[0035] S4. After the radiosonde is powered on, the ground station notifies the radiosonde of the maximum number of superimposable data set through the uplink remote control command, and after the ground station completes the reception of the meteorological data, it will dynamically adjust the maximum number of superimposable data according to the data reception quality.

[0036] It can be known from the energy-saving principle of the radiosonde described in the present invention that in addition to the system complexity introduced by the superimposed coding technology, the method of the present invention can reduce the by up to The energy consumption of the secondary communication module. However, limited by the system's performance requirements for the bit error rate (BER), the complexity of system implementation, and the hardware capabilities of the radiosonde, the value cannot be infinitely large.

[0037] The present invention selects an adaptive adjustment strategy for energy-saving efficiency at the ground station. After the radiosonde is powered on, the ground station will notify the radiosonde of the maximum number of stackable data set through an uplink remote control command . Subsequently, the radiosonde sets the received quantity .

[0038] After the ground station completes the reception of meteorological data, it will dynamically adjust according to the data reception quality. If the reception quality meets the system's error rate requirements, the radiosonde will be notified through a remote control command to maintain the current value; otherwise, the radiosonde needs to reduce the value, that is, make . Through the above method, the energy consumption of the radiosonde can be minimized while ensuring that the reception quality of meteorological data meets the system requirements.

[0039] The data communication and data demodulation processes between the radiosonde and the ground meteorological station are referred to Figure 2 and Figure 3 . <( Figure 2 Shown in Figure 3 is a comparison between the meteorological data transmission method designed by the present invention and the traditional radiosonde data transmission method. In the traditional radiosonde data transmission method, every time meteorological data is collected, the wireless communication module needs to be called once to transmit the meteorological data to the ground station. In the data transmission method designed by the present invention, the radiosonde can first store multiple adjacent meteorological data packets, and then use superposition coding technology to superimpose the multiple data packets. Subsequently, only one activation of the wireless communication module is required to send multiple data packets to the ground station. As shown in Figure 2 , corresponding to the

[0040] The embodiments described below will describe a complete radiosonde sounding operation process. When the meteorological unmanned aerial vehicle (UAV) flies to a predetermined altitude of 10,000 meters in a predetermined airspace, a radiosonde is thrown out. The radiosonde then powers on and deploys a parachute for a slow descent. Assuming good weather conditions on that day and no obvious severe convective weather, the radiosonde will descend at a constant speed of 10 m / s. During the descent, the sensors carried by the radiosonde will collect meteorological data at a sensing frequency of 2 Hz. During this process, the signal processing unit of the radiosonde will, according to the preset value, store the data packets before a certain time. After completing the meteorological data collection at

[0041] a certain time, the signal processing unit will superpose and encode the previous

[0042] data packets and the data packet at the current time together. The signal processing unit will first generate a Hadamard matrix and assign a unique row vector to each data packet. By taking the dot product of the data information with the row vector, multiple extended data streams are obtained. Subsequently, the multiple data streams are added together and then sent to the ground meteorological station through a wireless communication module. After receiving the superposed signal, the meteorological station will first estimate the channel coefficient according to the training sequence in the data frame and determine whether the current data packet meets the error code performance requirements. When the error code performance does not meet the system requirements, the ground station will notify the radiosonde in the uplink remote control command to adjust the number of superposed data packets; if the requirements are met, the ground station will not make any notification. After estimating the channel coefficient, the ground station will first perform ZF equalization on the received signal. Subsequently, by multiplying the equalized signal by the row vectors of the Hadamard matrix used for each data packet respectively, the received data corresponding to each data packet is obtained. Based on the despread data, the ground station further demodulates the constellation to obtain the final information bit stream. The same operation is performed on meteorological data packets until all superposed data packets are demodulated. To simplify the simulation process, the present invention first uses the zero-forcing (ZF) channel equalization method for the received signal at the ground station receiver and assumes that the A2G channel information from the radiosonde to the ground station can be perfectly estimated at the ground station through the training sequence. The dimension of the Hadamard matrix used in the simulation is

[0043] Figure 4 The error code rate performance corresponding to different values after using superposition coding is shown in Figure 4 . As can be seen from When the value is larger, each superimposed data packet will be composed of more data packets superimposed, which can significantly reduce the energy consumption of the radiosonde on the wireless communication module, but when the value is larger, the bit error performance of the communication system is worse, and more powerful storage capabilities are required to store the meteorological data collected at previous times. Therefore, in actual communication the value will be dynamically selected according to the system's requirement for the bit error rate. The ground station can obtain an estimated value of the bit error performance based on the training sequence known to both the transmitter and receiver during communication, and then notify the radiosonde through an uplink telecommand what kind of value should be adopted in the next transmission time slot to minimize its energy consumption while meeting the bit error performance.

[0044] Furthermore, Figure 5 shown is the bit error performance corresponding to Hadamard matrices of different sizes. As can be seen from the figure, when using four data packets for superimposed coding (i.e., ), when the dimension of the Hadamard matrix is larger, the sequence length corresponding to its row vectors or column vectors is larger, which in turn leads to better orthogonality between different row vectors or different column vectors and better bit error performance.

[0045] Figure 6 shown is the comparison of the energy consumption of the communication module at different data acquisition frequencies. When the sensing frequency of the sensor is 2 Hz, the sensing time interval of the sensor is 0.5 s at this time. Figure 6 The simulation results shown assume that the radiosonde is thrown out by a meteorological unmanned aerial vehicle at an altitude of 10,000 meters, then opens the parachute and descends at a constant speed of 10 m / s. Since the entire descent process will last for 1000 s and the sensing time interval of the sensor is 0.5 s, the radiosonde can collect 2000 packets of meteorological data in total. In the traditional meteorological data transmission method, 2000 packets of meteorological data need to be wirelessly communicated 2000 times to be sent to the ground station. In the present invention, by introducing the superimposed coding transmission technology, multiple data packets can be transmitted together in one time slot, significantly reducing the number of wireless communications and achieving the purpose of energy saving. When two data packets are superimposed, the wireless communication module needs to be activated at most 1000 times; when three data packets are superimposed, at most 667 times are required, and when four data packets are superimposed, at most 500 times are required. Similarly, when the sensor sensing frequency is 1 Hz, the maximum required transmission times corresponding to two superimpositions, three superimpositions, and four superimpositions are 500 times, 334 times, and 250 times respectively.

[0046] In the present invention, specific embodiments are used to elaborate on the principles and implementation manners of the present invention. The description of the above embodiments is only used to help understand the method of the present invention and its core idea; at the same time, for those of ordinary skill in the art, according to the idea of the present invention, there will be changes in the specific implementation manners and application scopes. In summary, the content of this specification should not be construed as a limitation on the present invention.

[0047] Those of ordinary skill in the art will realize that the embodiments described herein are for helping the reader understand the principles of the present invention, and it should be understood that the protection scope of the present invention is not limited to such specific statements and embodiments. Those of ordinary skill in the art can make various other specific deformations and combinations that do not depart from the essence of the present invention based on the technical revelations disclosed in the present invention, and these deformations and combinations are still within the protection scope of the present invention.

Claims

1. A sounding balloon energy-saving method based on superposition coding technology, characterized in that It includes the following steps: S1. The radiosonde collects meteorological data during the descent process, generates a meteorological data bitstream at time t, and performs constellation modulation on the obtained meteorological data bitstream to obtain a modulated symbol sequence; S2. Data superposition is performed on the modulated symbol sequences of meteorological data collected within multiple adjacent time instants, and the superimposed data is sent within one transmission time slot; S3. Distinguish multiple different meteorological data packets sent in S2, allocate different row vectors or column vectors to the multiple data packets for signal superposition, and perform demodulation at the receiving end using the orthogonality of the row vectors or column vectors to recover the bit information corresponding to each data packet; S4. After the radiosonde is powered on, the ground station notifies the radiosonde of the set maximum number of superimposable data through an uplink remote control command, and after the ground station completes the reception of the meteorological data, the maximum number of superimposable data will be dynamically adjusted according to the data reception quality.

2. The sounding balloon energy-saving method based on superposition coding technology according to claim 1, characterized in that The specific steps of S1 include the following: S11. When the meteorological unmanned aerial vehicle (UAV) flies to the predetermined altitude and enters the target detection airspace, the UAV will fly horizontally at a constant speed in the target airspace, and release the carried radiosonde one by one at time intervals ; S12. After the radiosonde is dropped, it will deploy the parachute and descend slowly according to the instructions of the unmanned aerial vehicle, and during this descent process, it will sense and detect the meteorological information of atmospheric temperature, relative humidity, pressure, wind speed, and wind direction in the target airspace where it is located; S13. Quantize the meteorological data at the moment evenly and convert it into a bit stream , and obtain a modulated symbol sequence through constellation modulation of .

3. The sounding balloon energy-saving method based on superposition coding technology according to claim 1, characterized in that In S2, the obtained modulation symbol sequence is superimposed and encoded by using a Hadamard orthogonal matrix of size , and the length is greater than the total number of collected meteorological data.

4. A radiosonde energy-saving method based on superposition coding technology according to claim 1, characterized in that, The specific steps of S3 include the following: S31. Divide the modulation symbol sequence into blocks according to the length of . Denote the th symbol block as ; S32. Assign the row of the Hadamard orthogonal matrix to the , th symbol block in . After being extended by the sequence , the extended data can be obtained; S33. The sender pairs the th symbol block in the meteorological data for superposition coding and transmission, and is received by the ground station after being affected by the wireless channel and noise; S34. After receiving the transmission signal of the radiosonde, the ground station will perform receiving signal equalization based on the estimated channel state information by the zero-forcing equalization method, and the ground station distinguishes the symbol sequences at different times before superposition according to the orthogonal sequence.

5. A radiosonde energy-saving method based on superposition coding technology according to claim 4, characterized in that, The signal after superposition coding at the transmitting end in S33 is expressed as: The signal received by the ground station is expressed as: Among them, and are the transmitted signal and the received signal respectively, represents the convolution operation, is the channel coefficient, is the additive white Gaussian noise.

6. A radiosonde energy-saving method based on superposition coding technology according to claim 4, characterized in that The signal after signal equalization by the zero-forcing equalization method in S34 is expressed as: Distinguish symbol sequences at different times before superposition according to orthogonal sequences Expressed as: In the formula, is the signal after signal equalization by the zero-breaking equalization method, is the received signal, is the th row of the Hadamard orthogonal matrix.

7. A radiosonde energy-saving method based on superposition coding technology according to claim 1, characterized in that The specific steps of S4 include the following: S41. After the radiosonde is powered on, the ground station will notify the radiosonde of the maximum number of stackable data set by the uplink remote control command ; S42. Number of radiosondes received , if the received quality meets the system's bit error rate requirement, the radiosonde is notified via a remote control command to maintain the current value. Otherwise, the radiosonde needs to reduce the value, i.e., set .

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