RTK radio channel expansion system and communication method

Abstract

The invention relates to an RTK radio channel expansion system and a communication method. The system comprises an MPU, a plurality of LoRa signal channels and a LoRa antenna. The MPU receives and modulates the differential data sent by the base station, and transmits the modulated differential data to a plurality of mobile stations through a plurality of LoRa signal channels and LoRa antennas; wherein one LoRa signal channel corresponds to one mobile station, each LoRa signal channel uses a plurality of spreading factors, and LoRa signals of different spreading factors are mutually orthogonal. By adopting the system and the method, the original advantages of long distance and low power consumption of the LoRa can be maintained, and meanwhile, the throughput and the concurrent processing capability of the system are greatly improved.

Description

TECHNICAL FIELD

[0001] The application relates to the field of GNSS positioning technology, in particular to an RTK radio channel expansion system and a communication method. BACKGROUND

[0002] Real-time kinematic (RTK) is a high-precision positioning technology based on the global navigation satellite system. It realizes centimeter-level real-time positioning through carrier phase difference observation between the reference station and the mobile station. In order to solve the problem of signal transmission obstacles between the reference station and the mobile station, the prior art uses an RTK radio as a relay station. Specifically, the satellite receiving module of the reference station receives satellite observation data, calculates difference data based on the satellite observation data and its own real positioning, and sends the difference data to the RTK radio, which is forwarded to the mobile station by the RTK radio.

[0003] The existing RTK radio uses traditional LoRa technology. However, in real-time dynamic positioning and other scenarios that require high-frequency data transmission, the traditional LoRa technology faces serious challenges: when the number of terminal nodes increases, a single communication channel is prone to data congestion, resulting in critical data transmission delay or loss. Especially in industrial control scenarios that require millisecond-level response, this communication bottleneck can seriously affect system performance. Existing solutions usually use simple channel expansion or data compression techniques, but it is difficult to fundamentally solve the system capacity problem when multiple devices communicate concurrently.

[0004] Although the multi-channel LoRa technology improves system capacity through frequency division multiplexing, it still has obvious limitations in actual industrial application scenarios. When the number of terminal devices increases to a certain scale, even with multi-channel configuration, the overall communication performance of the system will still decrease significantly. This performance degradation is particularly pronounced in industrial Internet of Things scenarios that need to support a large number of terminal nodes communicating simultaneously. Traditional solutions often struggle to strike an ideal balance between communication distance and data rate, and in scenarios with a large number of mobile stations, packet loss and latency may occur. SUMMARY

[0005] Therefore, it is necessary to provide an RTK radio channel expansion system and a communication method that can significantly improve system throughput and concurrent processing capacity while maintaining the original long-range and low-power advantages of LoRa.

[0006] The technical solution of the application is as follows: An RTK radio channel expansion system, comprising: an MPU, a plurality of LoRa signal channels, and a LoRa antenna. The MPU receives and modulates the difference data sent by the reference station, and transmits the modulated difference data to a plurality of mobile stations through the plurality of LoRa signal channels and the LoRa antenna. Wherein, one LoRa signal channel corresponds to one mobile station, each LoRa signal channel uses several spreading factors, and the LoRa signals with different spreading factors are mutually orthogonal.

[0007] The application further provides a communication method based on the RTK radio channel expansion system, which comprises the following steps: S1: the MPU receives and modulates the differential data sent by the reference station; S2: selecting the LoRa signal channel and the spreading factor based on the modulated differential data; S3: transmitting the modulated differential data to the several mobile stations through the selected LoRa signal channel and the spreading factor.

[0008] Compared with the prior art, the beneficial effects of the technical scheme of the application are: The application utilizes the orthogonal characteristics of signals with different spreading factors in the time-frequency domain to realize parallel transmission of multiple data on each physical channel (LoRa signal channel); through intelligent dynamic allocation of the spreading factor and interference elimination algorithm, the system throughput and concurrent processing capacity are greatly improved while maintaining the original long-distance and low-power advantages of LoRa; this breakthrough design provides reliable communication guarantee for large-scale terminal access in the field of industrial Internet of Things, and is particularly suitable for key application scenarios such as intelligent manufacturing and remote monitoring which require high-density device access. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 The overall structure diagram of the RTK radio channel expansion system for the embodiment 1 is shown in the figure. Figure 2 The overall flow diagram of the communication method based on the RTK radio channel expansion system for the embodiment 2 is shown in the figure. Figure 3 The overall flow diagram of the differential data transmission method for the embodiment 3 is shown in the figure. DETAILED DESCRIPTION

[0010] In order to make the purpose, technical scheme and advantages of the application clearer, the application is further described in detail below in combination with the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the application and do not limit the application.

[0011] Embodiment 1 The embodiment provides an RTK radio channel expansion system, as shown in the figure, the system comprises: an MPU, several LoRa signal channels and a LoRa antenna. Figure 1 ​The MPU receives and modulates the differential data sent by the reference station, and transmits the modulated differential data to a plurality of mobile stations through a plurality of LoRa signal channels and LoRa antennas. Each LoRa signal channel corresponds to a mobile station, and each LoRa signal channel uses a plurality of spreading factors. The type and number of selected spreading factors are determined according to actual communication requirements.

[0012] In an optional embodiment, one LoRa signal channel corresponds to one frequency point, and each frequency point is within the communication frequency band of LoRa communication.

[0013] In an optional embodiment, the interval between every two frequency points is equal.

[0014] Embodiment 2 This embodiment is based on the RTK radio channel expansion system described in Embodiment 1, and proposes a communication method based on the RTK radio channel expansion system, as shown in Figure 2 The method comprises the following steps: S1: receiving and modulating the differential data sent by the reference station using the MPU; S2: selecting LoRa signal channels and spreading factors based on the modulated differential data and actual communication requirements; S3: transmitting the modulated differential data to a plurality of mobile stations through the selected LoRa signal channels and spreading factors.

[0015] In an optional embodiment, the S2 step comprises: Let the LoRa spreading factor be , ; The mobile stations within the circle with the farthest transmission distance of the LoRa signal of each spreading factor as the radius can normally communicate with the reference station. Let the selected spreading factors be , , , where the maximum transmission distance of the LoRa signal of the spreading factor is , the mobile stations within the range of use the LoRa signal with the spreading factor for communication; the users within the range of use the LoRa signal with the spreading factor for communication; and so on. The users within the range of use the LoRa signal with the spreading factor for communication, where d is the distance from the mobile station to the reference station.

[0016] In an optional embodiment, step S3 includes: S31: Activate the... Spreading factor in each LoRa signal channel It communicates using LoRa signals and sets the total number of LoRa signal channels. The initial value is 1, and the total number of spreading factors is 1. The initial value is 1; S32: Check for packet loss or delays; S33: If no packet loss or delay occurs, continue using step 3. Spreading factor in each LoRa signal channel Communicating via LoRa signals; S34: If packet loss or delay occurs, Increment the value by 1, and use the first to the last... Combination of spreading factors in each LoRa signal channel To communicate; S35: If If it is greater than 6, let , Then make a judgment Is the number of channels greater than the preset maximum? If yes, it means that all LoRa signal channels have been used up and a prompt indicating that the number of users is too large will be given. If no, proceed to step S36. S36: If If the value is less than or equal to 6, check for packet loss or delay. If packet loss or delay occurs, proceed to step S33; if no packet loss or delay occurs, continue using steps 1 through S34. Combination of spreading factors in each LoRa signal channel To conduct communication.

[0017] This invention also proposes a differential data demodulation method for an RTK radio channel extension system, comprising the following steps: The modulated differential data received by the mobile station is represented as:

[0018] in, This represents the modulated differential data received by the mobile station. It is the amplitude of the fading channel coefficient. With a mean of zero and a variance of , Additive white Gaussian noise; Indicates the first Discrete-time baseband signal expression for a LoRa signal. ; Represents noise power spectral density To recover the information bits, the received signal must first be multiplied by the complex conjugate of the initial LoRa signal corresponding to the spreading factor within all combinations of spreading factors. , * denotes the complex conjugate operation; Then, the dechirp signals are processed separately. The discrete Fourier transform of a point, where the discrete Fourier transform of the i-th point is:

[0019] Next, regarding this Take the maximum value of each sequence obtained by the discrete Fourier transform:

[0020] The peak values ​​of the discrete Fourier transform results of the signals corresponding to different spreading factors are obtained. , ; This is an estimate of the decimal information carried by the i-th LoRa signal; Finally, here Find the largest peak among the peaks:

[0021] Record the spreading factor of the LoRa signal corresponding to this peak value. and decimal information ; According to the spreading factor To obtain the number of bits in the modulated differential data; According to decimal information By converting decimal to binary, the bit information in the modulated differential data is obtained; Based on the number of bits and bit information, the estimated value of the modulated differential data is obtained, that is, the demodulation result is obtained.

[0022] In an alternative embodiment, The expressions include:

[0023] In the formula, Indicates the spreading factor as The corresponding discrete-time original rising chirp signal; This represents the energy carried by the i-th LoRa signal; ; This represents the decimal information carried by the LoRa signal, where n represents the time-domain index, and .

[0024] The embodiment also provides a computer device, including a memory, a processor and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the communication method based on the RTK radio channel extension system when executing the computer program.

[0025] The embodiment also provides a computer readable storage medium, which stores a computer program, and the computer program implements the steps of the communication method based on the RTK radio channel extension system when executed by a processor.

[0026] Embodiment 3 The embodiment based on the system of embodiment 1 and the method of embodiment 2 provides the following specific implementation examples.

[0027] The satellite receiving module of the reference station receives the observation data of the satellite, and then sends the observation data to the mobile station through the radio station. Since packet loss and delay may occur in the scenario of a large number of mobile stations, the present scheme is designed in view of this shortcoming.

[0028] Firstly, the present scheme uses different frequency points for multi-channel communication. That is, in the communication frequency band range of LoRa communication, the frequency band is divided into several frequency points according to the same frequency interval. For example, in the frequency band range of 470-480MHz, the frequency point interval is set to 1MHZ, so there are 470MHZ, 471MHZ, 472MHZ, 473MHZ, 474MHZ, 475MHZ, 476MHZ, 477MHZ, 478MHZ and 479MHZ, each of which is an independent channel for LoRa signals, and LoRa signals can be sent and received on different channels at the same time. Therefore, by using this characteristic, in the RTK technology, the reference station can simultaneously communicate with multiple mobile stations through different channels corresponding to different frequency points, which greatly improves the transmission rate.

[0029] In addition, since LoRa signals with different spreading factors are mutually orthogonal, different spreading factor LoRa signals can be transmitted at the same time in the same frequency band, because they will not interfere with each other. By using this characteristic, different spreading factor LoRa signals can be used in each channel to communicate with different users at the same time. This is equivalent to further expanding the number of channels. Since LoRa signals have six spreading factors, the transmission rate of the improved scheme can be increased by up to 6 times compared to multi-channel. Moreover, the combination of spreading factors can be adjusted according to actual needs (user quantity, communication distance, etc.), so as to achieve a transmission effect with lower power consumption.

[0030] Next, the specific method for selecting the combination of spreading factors is introduced. First, it is necessary to introduce each spread factor communication range as follows: with the farthest transmission distance of LoRa signal of each spread factor as the radius, a circle is made, and the users within the circle can communicate normally with the reference station. The range of spread factor of LoRa signal is , and 6 spread factors are selected for use according to the needs during communication, assuming that the selected v spread factors are , , and . Among them, the maximum transmission distance of LoRa signal with spread factor is . Therefore, the users within the range of (where r is the distance from the mobile station to the reference station) use LoRa signals with spread factor for communication; the users within the range of use LoRa signals with spread factor for communication; and so on, the users within the range of use LoRa signals with spread factor for communication.

[0031] As shown in Figure 3 , first, the SF=7 LoRa signal in channel 1 is turned on for communication, and b=1 and v=1 are set.

[0032] (1) Check whether there will be packet loss, delay, etc. If not, continue to use the SF=7 LoRa signal in channel 1 for communication. (2) If there is packet loss, increase v by 1. (3) Use the spread factor combination in channel 1 to channel b for communication.

[0033] (4) Determine whether v exceeds 6 (because there are a total of 6 spread factors). If it exceeds 6, set v=0 and b=b+1. Determine whether b is greater than the preset maximum number of channels. If it is greater, it means that the number of channels has been used up, indicating that the user volume is too large; if it is not greater, directly jump to step (6).

[0034] (5) If v does not exceed 6, determine whether there will be packet loss, delay, etc. If so, jump to (3).

[0035] (6) If there is no packet loss or delay, continue to use the spread factor combination in channel 1 to channel b for communication.

[0036] Next, the difference between the traditional LoRa demodulation and the proposed scheme demodulation in the physical layer will be introduced: (1) Traditional scheme The discrete-time baseband signal of LoRa modulation scheme can be written as

[0037] where represents the original up-chirp signal in discrete-time; represents the energy carried by each symbol; ; m represents the decimal information carried by LoRa signal, n represents the time domain index, and .

[0038] Then the transmitted signal passes through the wireless channel and reaches the target receiver. The received signal can be represented as

[0039] where h is the amplitude of the fading channel coefficient, is an additive white Gaussian noise with mean zero and variance To recover the information bits, first, the received signal needs to be multiplied by the complex conjugate of the initial LoRa signal, i.e. , (this step is called de-chirp). Where * represents the complex conjugate operation.

[0040] Then, the de-chirp signal is subjected to M-point Discrete Fourier Transform (DFT), which can obtain

[0041] where Finally, the DFT result is subjected to the modulo operation and selects the largest item, which can recover the transmitted information, i.e.

[0042] Finally, the decimal is converted to binary, which can recover the information bits.

[0043] (2) Proposed scheme In the proposed scheme, there are v LoRa signals in each symbol, and the spreading factor combination is: , The discrete-time baseband signal expression of the i-th LoRa signal (the corresponding spreading factor is ,, ) can be written as:

[0044] where denotes the spreading factor corresponding discrete-time original up-chirp signal; denotes the energy carried by the ith LoRa signal; denotes the decimal information carried by the LoRa signal, n denotes the time domain index, and

[0045] The transmitted signal then goes through the wireless channel and reaches the target receiver. The received signal can be represented as

[0046] where h is the amplitude of the fading channel coefficient, is an additive white Gaussian noise with mean zero and variance To recover the information bits, first, the received signal needs to be multiplied by the complex conjugate of the original LoRa signal corresponding to the spreading factor in all the spreading factor combinations, i.e. , (this step is called de-chirp). Here, * denotes the complex conjugate operation.

[0047] Then, the de-chirped signal is subjected to point Discrete Fourier Transform (DFT), where the Discrete Fourier Transform at the ith point is:

[0048] Next, the maximum value is taken from the sequences obtained from the v DFTs:

[0049] The peak values of the DFT results of the signals corresponding to different spreading factors are obtained , is the estimated value of the decimal information carried by the ith LoRa signal.

[0050] Finally, the largest peak value among the v peak values is found:

[0051] The spreading factor and the decimal information of the LoRa signal corresponding to this peak value are recorded. According to the obtained spreading factor , the number of bits in the transmitted LoRa signal can be known, and according to the obtained decimal information ​​​The bit information in the transmitted LoRa signal can be known (converted from decimal to binary), and the estimated value of the transmitted information is obtained.

[0052] The LoRa communication scheme based on orthogonal spread factor multiplexing provided by the application realizes a significant performance breakthrough in the field of industrial Internet of Things through innovative physical layer architecture design and intelligent resource scheduling mechanism. The scheme creatively utilizes the orthogonal characteristics of signals with different spread factors, so that a single physical channel can simultaneously carry multiple data streams, and the system capacity is improved to several times that of the traditional scheme without increasing the spectrum resource occupation. At the same time, through the adaptive spread factor dynamic allocation strategy, the system can intelligently match the communication demand of the terminal device and the channel condition, and control the end-to-end transmission delay within the range allowed by industrial applications while ensuring long-distance coverage. It is particularly worth noting that the scheme effectively reduces the implementation complexity of the receiver through an optimized signal processing process, so that the high-performance parallel demodulation function can stably run on a conventional hardware platform. In addition, the scheme is fully compatible with the existing LoRaWAN protocol standard, supports smooth upgrade of existing network equipment, greatly reduces the deployment cost and technical threshold, and provides a reliable and economically efficient communication solution for large-scale commercial application of industrial Internet of Things.

[0053] The application innovatively proposes an enhanced multi-channel LoRa communication architecture based on spread factor orthogonal multiplexing. The technology fully utilizes the orthogonal characteristics of signals with different spread factors in the time-frequency domain to realize parallel transmission of multiple data on each physical channel. Through intelligent spread factor dynamic allocation and interference cancellation algorithm, the system throughput and concurrent processing capacity are greatly improved while maintaining the original long-distance and low-power advantages of LoRa. This breakthrough design provides reliable communication guarantee for large-scale terminal access in the field of industrial Internet of Things, and is particularly suitable for key application scenarios such as intelligent manufacturing and remote monitoring that require high-density device access.

[0054] The application aims to solve the communication performance bottleneck problem of LoRa technology in the field of industrial Internet of Things in the large-scale terminal access scene, and break through the technical limitations of traditional LoRa radio in system capacity, real-time performance and reliability through innovative orthogonal spreading factor multiplexing technology. The core highlight of the application is: first, based on multi-channel LoRa, a multi-user parallel transmission mechanism based on orthogonal spreading factor multiplexing is proposed, the orthogonal characteristics of LoRa signal are deeply mined, and the parallel transmission of multiple data streams on a single channel is realized, so that the communication rate is several times more than that of multi-channel LoRa; secondly, an intelligent spreading factor dynamic allocation algorithm is developed, which can automatically select the optimal spreading factor for communication according to the channel conditions and business requirements of terminal devices. The application not only greatly improves the system capacity and communication efficiency of LoRa network, but also maintains its original long-distance and low-power advantages, providing a high-performance and high-reliability communication solution for large-scale terminal access of industrial Internet of Things.

Claims

1. An RTK radio channel extension system, characterized by, Comprise: MPU, a plurality of LoRa signal channels and LoRa antennas; The MPU receives and modulates the differential data sent by the reference station, and transmits the modulated differential data to a plurality of mobile stations through a plurality of LoRa signal channels and LoRa antennas; Wherein, one LoRa signal channel corresponds to one mobile station, each LoRa signal channel uses a plurality of spreading factors, and the LoRa signals with different spreading factors are mutually orthogonal.

2. The RTK radio path extension system of claim 1, wherein, One LoRa signal channel corresponds to one frequency point, and each frequency point is within the communication frequency band of LoRa communication.

3. The RTK radio path extension system according to claim 2, characterized in that, The interval between every two frequency points is equal.

4. A communication method based on an RTK radio channel extension system, characterized in that, Comprise the following steps: S1: the MPU receives and modulates the differential data sent by the reference station; S2: select LoRa signal channel and spreading factor based on the modulated differential data; S3: transmit the modulated differential data to a plurality of mobile stations through the selected LoRa signal channel and spreading factor.

5. The communication method based on the RTK station channel extension system according to claim 4, characterized in that, S2 step comprises: Let LoRa spreading factor be denoted as Then ; The mobile station in the circle with the farthest transmission distance of the LoRa signal of each spreading factor as the radius can communicate normally with the reference station; the selected The spreading factor of the LoRa signal is , , , wherein the maximum transmission distance of the LoRa signal of the spreading factor is , the mobile station in the range of communicates using the LoRa signal with the spreading factor ; the user in the range of communicates using the LoRa signal with the spreading factor ; and so on, the user in the range of communicates using the LoRa signal with the spreading factor , is the distance from the mobile station to the reference station.

6. The communication method based on the RTK station channel extension system according to claim 4 or 5, characterized in that, S3 step comprises: S31: turn on the spread spectrum factor of the LoRa signal channel , and set the initial value of the total number of LoRa signal channels to 1 , and set the initial value of the total number of spread spectrum factors to 1 ;​ S32: check if there is packet loss or delay phenomenon; S33: If there is no packet loss or delay phenomenon, continue to use the spread spectrum factor of the LoRa signal channel to communicate. ​​ S34: If packet loss or delay occurs, the value of n is increased by 1, and the first to the nth LoRa signal channel is used for communication with the combination of spreading factors. ​​​ S35: If greater than 6, let , , determine whether is greater than the preset maximum channel number. If yes, it indicates that all LoRa signal channels have been used up, and a prompt of excessive user quantity is given. If no, jump to step S36. S36: If less than or equal to 6, check whether there is packet loss or delay phenomenon, if there is packet loss or delay phenomenon, jump to step S33; if there is no packet loss or delay phenomenon, continue to use the spreading factor combination in the first to the LoRa signal channel communication.

7. A differential data demodulation method for an RTK radio channel extension system, characterized in that, Comprise the following steps: The modulated differential data received by the mobile station is expressed as: wherein, denotes the modulated differential data received by the mobile station, is the amplitude of the fading channel coefficient, is an additive white Gaussian noise with zero mean and variance ; denotes the discrete-time baseband signal expression of the th LoRa signal, ; denotes the noise power spectral density; To recover the information bits, first, the received signal needs to be multiplied by the complex conjugate of the original LoRa signal corresponding to the spreading factor within all the spreading factor combinations denotes the complex conjugate operation; Then, the de-chirped signals are respectively subjected to a discrete Fourier transform of the i-th point, where the discrete Fourier transform of the i-th point is Next, regarding this Take the maximum value of each sequence obtained by the discrete Fourier transform: The peak values ​​of the discrete Fourier transform results of the signals corresponding to different spreading factors are obtained. , ; This is an estimate of the decimal information carried by the i-th LoRa signal; Finally, find the largest one of these peaks: max = 0 for i in range (0, len (peaks)): if peaks[i] > max: max = peaks[i] and record the peak value corresponding to the spreading factor of the LoRa signal and decimal information ; According to the spreading factor , the number of bits in the modulated difference data is obtained; According to the decimal information , the bit information in the modulated differential data is obtained by converting the decimal information into binary information. Based on the number of bits and bit information, the estimated value of the modulated differential data is obtained, that is, the demodulation result is obtained.

8. The method of claim 7, wherein the method further comprises: The expression of includes: wherein denotes a spreading factor of corresponding discrete-time raw up-chirp signal; denotes the energy carried by the ith LoRa signal; ; denotes the decimal information carried by the LoRa signal, n denotes the time domain index, and .

9. A computer device comprising a memory, a processor, and a computer program stored on the memory and executable on the processor, characterized in that, The processor executes the computer program to realize the steps of the method in any one of claims 4 to 6.

10. A computer-readable storage medium having stored thereon a computer program, characterized in that, The computer program is executed by the processor to realize the steps of the method in any one of claims 4 to 6.

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