Frequency offset pre-compensation method, device and system based on low-power wide area network

Abstract

The invention discloses a frequency offset pre-compensation method, device and system based on a low-power wide area network, and relates to the technical field of communication. The frequency offset pre-compensation method based on the low-power wide area network, the gateway node and the terminal node can perform signal transmission based on the low-power wide area network, the method is applied to the gateway node, and the method comprises the following steps: performing frequency offset estimation on a received signal according to signal characteristics of the received signal to obtain a frequency offset estimation result; and based on the frequency offset estimation result and the frame structure characteristic of the downlink signal, performing frequency offset pre-compensation on the downlink signal so as to send the downlink signal after frequency offset pre-compensation to the terminal node. According to the signal characteristics and the frame structure characteristics, carrier frequency offset pre-compensation is carried out through the gateway node, the terminal node does not need to carry out frequency offset pre-compensation calculation, and the requirements for the performance and the calculation capacity of the terminal node are reduced, so that the performance of the terminal node is optimized, and the power consumption of the terminal node is reduced.

Description

Technical Field

[0001] The present application relates to the field of communication technology, and in particular to a frequency offset pre-compensation method, device and system based on a low power wide area network. Background Art

[0002] LPWAN (Low Power Wide Area Network) is a wireless communication technology designed for IoT applications. It has the characteristics of wide coverage, low power consumption, low cost and long battery life. It is suitable for scenarios that require long-distance data transmission, such as smart cities, agriculture, industrial automation and smart homes.

[0003] Common standards for LPWAN technologies include LoRa, SigFox, and NB-IoT. Among them, LoRa technology has been rapidly promoted and applied due to its advantages such as no need for operator network coverage, flexible deployment in any region, easy networking, and low cost. LoRa uses chirp spread spectrum modulation technology, which has strong anti-frequency offset capabilities. In a system that uses Chirp modulation technology or LoRa modulation standards, it is necessary to correct or compensate for the carrier frequency offset (CFO) based on the received signal. By correcting the frequency offset of the received signal, the correct demodulation result can be obtained. Therefore, the effect of frequency offset estimation and correction also directly affects the demodulation performance.

[0004] LPWAN systems consider low power consumption and low cost, so the performance of LPWAN terminal nodes is usually low, and the algorithms used on the terminal nodes should be as simple as possible. The performance and computing power of the selected devices of LPWAN gateway nodes are stronger, and they can undertake more complex functions and algorithms. The effect of frequency offset estimation and frequency offset correction is related to the computing power that the node can provide. Processing more data or applying more complex algorithms on the terminal node will increase the power consumption of the terminal node and reduce the service life of the terminal node. Summary of the invention

[0005] The embodiments of the present application aim to solve at least one of the technical problems in the related art to a certain extent. To this end, the purpose of the embodiments of the present application is to propose a frequency offset pre-compensation method, device, gateway node, system, storage medium and program product based on low power wide area network.

[0006] The embodiment of the present application provides a frequency offset pre-compensation method based on a low-power wide area network. Gateway nodes and terminal nodes can perform signal transmission based on the low-power wide area network. The method is applied to the gateway node, and the method includes: estimating the frequency offset of the received signal according to the signal characteristics of the received signal to obtain a frequency offset estimation result; based on the frequency offset estimation result and the frame structure characteristics of the downlink signal, pre-compensating the frequency offset of the downlink signal so as to send the downlink signal after the frequency offset pre-compensation to the terminal node.

[0007] Exemplarily, the gateway node includes an uplink receiver and a downlink transmitter; before estimating the frequency offset of the received signal based on the signal characteristics of the received signal to obtain the frequency offset estimation result, the method also includes: in the case where there is a frequency offset between the uplink receiver and the downlink transmitter, correcting the carrier frequency offset of the received signal to obtain a corrected received signal.

[0008] Exemplarily, based on the signal characteristics of the received signal, the frequency offset of the received signal is estimated to obtain a frequency offset estimation result, including: calculating the received signal and the local signal to determine whether the signal characteristics of the received signal affect the signal peak; when it is determined that the signal characteristics of the received signal affect the signal peak, performing signal processing calculations on the received signal to obtain a frequency offset estimation result.

[0009] Exemplarily, when it is determined that the signal characteristics of the received signal affect the signal peak, signal processing calculations are performed on the received signal to obtain a frequency deviation estimation result, including: when it is determined that the signal characteristics of the received signal affect the signal peak, signal processing calculations are performed on the received signal to obtain a first carrier frequency deviation and a second carrier frequency deviation, wherein the first carrier frequency deviation affects the peak position of the signal, and the second carrier frequency deviation affects the peak drop and / or peak shift of the signal; the first carrier frequency deviation and the second carrier frequency deviation are determined as the frequency deviation estimation results.

[0010] Exemplarily, the frame structure of a downlink signal includes a preamble part, a control parameter part and a data payload part; based on the frequency offset estimation result and the frame structure characteristics of the downlink signal, the downlink signal is pre-compensated for frequency offset, including: based on the frame structure characteristics of the downlink signal, determining the preamble part, the control parameter part and the data payload part included in the frame structure of the downlink signal; based on the frequency offset estimation result, determining a first frequency offset compensation sequence for the preamble part, a second frequency offset compensation sequence for the control parameter part and a third frequency offset compensation sequence for the data payload part; based on the first frequency offset compensation sequence, the second frequency offset compensation sequence and the third frequency offset compensation sequence, frequency offset pre-compensating the preamble part, the control parameter part and the data payload part, respectively.

[0011] Exemplarily, based on the frequency offset estimation result, a first frequency offset compensation sequence for the preamble part, a second frequency offset compensation sequence for the control parameter part, and a third frequency offset compensation sequence for the data payload part are determined, including: determining a downlink offset value based on the frequency offset estimation result; determining a first frequency offset compensation sequence based on the frequency offset estimation result and the downlink offset value; determining a second frequency offset compensation sequence and a third frequency offset compensation sequence based on the downlink offset value.

[0012] Exemplarily, the gateway node includes an uplink receiver and a downlink transmitter; based on the frequency offset estimation result, a downlink offset value is determined, including: based on the frequency offset estimation result, the uplink carrier frequency of the uplink receiver, the downlink carrier frequency of the downlink transmitter, the uplink sampling frequency of the uplink receiver, and the downlink sampling frequency of the downlink transmitter, the downlink offset value is determined.

[0013] Exemplarily, the frame structure of a downlink signal includes multiple symbols, each symbol includes a preamble part, a control parameter part and a data payload part; based on a first frequency offset compensation sequence, a second frequency offset compensation sequence and a third frequency offset compensation sequence, frequency offset pre-compensation is performed on the preamble part, the control parameter part and the data payload part, respectively, including: for each symbol in the multiple symbols, frequency offset pre-compensation is performed on the preamble part in the symbol based on the first frequency offset compensation sequence; for the multiple symbols, frequency offset pre-compensation is performed on the control parameter part and the data payload part, respectively, based on the second frequency offset compensation sequence and the third frequency offset compensation sequence according to the symbol period.

[0014] Exemplarily, after the downlink signal after frequency offset pre-compensation is sent to the terminal node, the terminal node completes time synchronization before receiving the downlink signal.

[0015] Another embodiment of the present application provides a frequency offset pre-compensation device based on a low-power wide area network. Gateway nodes and terminal nodes can transmit signals based on the low-power wide area network. The device is applied to the gateway node, and the device includes: a frequency offset estimation module, which is used to estimate the frequency offset of the received signal according to the signal characteristics of the received signal to obtain a frequency offset estimation result; a frequency offset pre-compensation module, which is used to pre-compensate the downlink signal based on the frequency offset estimation result and the frame structure characteristics of the downlink signal, so as to send the downlink signal after the frequency offset pre-compensation to the terminal node.

[0016] Another embodiment of the present application provides a gateway node, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method of any of the above embodiments when executing the computer program.

[0017] Another embodiment of the present application provides a communication system based on a low-power wide area network, the communication system includes a gateway node and a terminal node, and the gateway node is used to sequentially implement the steps of the method of any of the above embodiments.

[0018] Another embodiment of the present application provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the method of any of the above embodiments are implemented.

[0019] Another embodiment of the present application provides a computer program product, which includes instructions. When the instructions are executed by a processor of a computer device, the computer device is enabled to perform the steps of the method of any of the above embodiments.

[0020] In the above implementation, the frequency offset of the received signal is estimated according to the signal characteristics of the received signal to obtain the frequency offset estimation result; based on the frequency offset estimation result and the frame structure characteristics of the downlink signal, the frequency offset of the downlink signal is pre-compensated so that the downlink signal after the frequency offset pre-compensation is sent to the terminal node. Based on the signal characteristics and frame structure characteristics, the present application performs carrier frequency offset pre-compensation through the gateway node to optimize the performance of the IoT terminal node and reduce the power consumption of the terminal node. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 A schematic diagram of a flow chart of a frequency offset pre-compensation method based on a low power wide area network provided in an embodiment of the present application;

[0022] Figure 2 A block diagram of a frequency offset pre-compensation method for a low power wide area network LPWAN digital transceiver system provided in an embodiment of the present application;

[0023] Figure 3 A schematic diagram of a frequency offset pre-compensation device based on a low power wide area network provided in an embodiment of the present application. DETAILED DESCRIPTION

[0024] The embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

[0025] LPWAN (Low Power Wide Area Network) is a wireless communication technology designed for IoT applications. It has the characteristics of wide coverage, low power consumption, low cost and long battery life. It is suitable for scenarios that require long-distance data transmission, such as smart cities, agriculture, industrial automation and smart homes.

[0026] Common standards for LPWAN technologies include LoRa, SigFox, and NB-IoT. Among them, LoRa technology has been rapidly promoted and applied due to its advantages such as no need for operator network coverage, flexible deployment in any region, easy networking, and low cost. LoRa uses chirp spread spectrum modulation technology, which has strong anti-frequency offset capabilities. In a system that uses Chirp modulation technology or LoRa modulation standards, it is necessary to correct or compensate for the carrier frequency offset (CFO: Carrier Frequency Offset) based on the received signal. By correcting the frequency offset of the received signal, the correct demodulation result can be obtained. Therefore, the effect of frequency offset estimation and correction also directly affects the demodulation performance.

[0027] LPWAN systems take low power consumption and low cost into consideration, so the device performance of LPWAN terminal nodes is usually low, and the algorithms used on the terminal nodes should be as simple as possible. The device performance and computing power selected for LPWAN gateway nodes are stronger, and can undertake more and more complex functions and algorithms. The effect of frequency offset estimation and frequency offset correction is related to the computing power that the node can provide. Processing more data or applying more complex algorithms on the terminal node will increase the power consumption of the terminal node and reduce the service life of the terminal node. If the frequency offset-related processing of the terminal node can be completed by the gateway (that is, the gateway node completes the downlink frequency offset pre-compensation function), the processing process of the terminal node can be reduced, and the performance requirements for the terminal node can be reduced.

[0028] Currently, the function of frequency offset pre-compensation is mainly used in cellular networks with accurate timing, and the use of this frequency offset pre-compensation solution has not been proposed in LPWAN systems.

[0029] In view of this, the present application proposes a frequency offset pre-compensation method based on a low-power wide area network, which performs carrier frequency offset pre-compensation through a gateway node based on signal characteristics and frame structure characteristics, so as to optimize the performance of the IoT terminal nodes and reduce the power consumption of the terminal nodes.

[0030] Figure 1 A schematic flow chart of a frequency offset pre-compensation method based on a low power wide area network provided in an embodiment of the present application.

[0031] like Figure 1 As shown, the frequency offset pre-compensation method 100 based on the low power wide area network provided in the embodiment of the present application includes steps S110-S120, wherein the gateway node and the terminal node can perform signal transmission based on the low power wide area network, and the method is applied to the gateway node.

[0032] Step S110: performing frequency offset estimation on the received signal according to the signal characteristics of the received signal to obtain a frequency offset estimation result.

[0033] Step S120: pre-compensate the downlink signal for frequency offset based on the frequency offset estimation result and the frame structure characteristics of the downlink signal, so as to send the downlink signal after frequency offset pre-compensation to the terminal node.

[0034] Exemplarily, the received signal is sent by the terminal node to the gateway node. After the gateway node receives the received signal, it can estimate the frequency offset of the received signal based on the signal characteristics of the received signal to obtain a frequency offset estimation result.

[0035] The downlink signal is, for example, a signal that the gateway node needs to send to the terminal node. The gateway node can perform frequency offset pre-compensation on the downlink signal based on the frequency offset estimation result and the frame structure characteristics of the downlink signal. After performing frequency offset pre-compensation on the downlink signal, the gateway node can send the downlink signal after frequency offset pre-compensation to the terminal node.

[0036] Based on the signal characteristics and frame structure characteristics, the present application performs carrier frequency offset pre-compensation through a gateway node, and the terminal node does not need to perform frequency offset pre-compensation calculations, thereby reducing the performance and computing power requirements of the terminal node, thereby optimizing the performance of the terminal node and reducing the power consumption of the terminal node.

[0037] Figure 2 A block diagram of a frequency offset pre-compensation method for a low power wide area network (LPWAN) digital transceiver system provided in an embodiment of the present application.

[0038] like Figure 2 As shown, the gateway node includes, for example, an uplink receiver and a downlink transmitter, and the terminal node includes a downlink receiver and an uplink transmitter. The uplink transmitter of the terminal node sends the received signal to the uplink receiver of the gateway node.

[0039] The uplink receiver of the gateway node estimates the frequency offset of the received signal according to the signal characteristics of the received signal, and then sends the frequency offset estimation result to the downlink transmitter of the gateway node. The downlink transmitter of the gateway node pre-compensates the frequency offset of the downlink signal based on the frequency offset estimation result and the frame structure characteristics of the downlink signal, and then sends the downlink signal after the frequency offset pre-compensation to the downlink receiver of the terminal node.

[0040] In addition to estimating the frequency offset of the received signal based on the signal characteristics of the received signal to obtain the frequency offset estimation result, the uplink receiver of the gateway node can also perform operations such as signal detection and time synchronization, frequency offset compensation, signal demodulation, and bit-level processing.

[0041] In addition to pre-compensating the frequency offset of the downlink signal based on the frequency offset estimation result and the frame structure characteristics of the downlink signal, the downlink transmitter of the gateway node can also perform bit-level processing, signal demodulation, frame the downlink signal after frequency offset pre-compensation and send it to the downlink receiver of the terminal node.

[0042] The downlink receiver of the terminal node can perform operations such as signal detection and time synchronization, signal demodulation, bit-level processing, etc. After the downlink transmitter of the gateway node sends the downlink signal after frequency offset pre-compensation to the downlink receiver of the terminal node, the downlink receiver of the terminal node needs to complete time synchronization before receiving the downlink signal.

[0043] The uplink transmitter of the terminal node can perform bit-level processing, signal modulation, framing and other operations on the signal, and then send the signal to the uplink receiver of the gateway node.

[0044] It can be seen that by performing the frequency offset pre-compensation function through the gateway node, the data processing logic executed by the downlink receiver of the terminal node is simpler. The downlink receiver of the terminal node only needs to complete time synchronization, and then the signal can be directly demodulated, thereby optimizing the performance of the terminal node and reducing the power consumption of the terminal node.

[0045] In one example, the received signal may be a chirp signal type, and the signal characteristics of the chirp signal are described below.

[0046] The mathematical expression of a typical chirp digital signal is as follows (1):

[0047]

[0048] Wherein, μ represents the rate of change of frequency: when the chirp signal is an uplink signal up-chirp, μ=1, and its instantaneous frequency increases continuously; when the chirp signal is a downlink signal down-chirp, μ=-1, and its instantaneous frequency decreases continuously; S∈[0,2 SF -1] represents the modulation information, SF represents the spreading factor; k represents the sampling frequency f s The multiple of the ratio of the signal bandwidth BW is an integer multiple.

[0049] The LoRa signal is a special case of the chirp signal. For the LoRa signal, the digital signal sampling rate f is based on the chirp signal. s =BW, signal period The expression of LoRa signal is formula (2):

[0050]

[0051] The following describes the influence and estimation of signal demodulation and carrier frequency deviation in the form of LoRa signals.

[0052] For the LoRa signal of formula (2), the demodulation of the signal can separate the received signal x[n] (such as the LoRa signal) from the local signal x Local [n] * (such as up-chirp signal or down-chirp signal, S=0) performs correlation operation as shown in formula (3), and the result obtained is a single-frequency sinusoidal signal, and the signal frequency point is the modulation signal information.

[0053]

[0054] As shown in formula (4), a Fast Fourier Transform (FFT) operation is performed on the result of formula (3), and the index of the maximum value in the obtained amplitude-frequency spectrum is the demodulation result.

[0055]

[0056] The above formulas (1)-(4) explain the signal characteristics of the received signal. When the gateway node includes an uplink receiver and a downlink transmitter, before the frequency offset of the received signal is estimated according to the signal characteristics of the received signal to obtain the frequency offset estimation result, if there is a frequency offset between the uplink receiver of the gateway node and the downlink transmitter of the gateway node, it is necessary to perform carrier frequency offset correction on the received signal to obtain a corrected received signal.

[0057] The received signal may be a LoRa signal or a Chirp modulated signal. For the LoRa signal or the Chirp modulated signal, if there is a carrier frequency offset at the transceiver (the uplink receiver of the gateway node and the downlink transmitter of the gateway node), the influence of the carrier frequency offset (CFO) may be added to the LoRa signal in formula (2). Assuming that the frequency offset between the transceiver and the transceiver is εppm, the received signal x affected by CFO is CFO [m] is in the form of formula (5):

[0058]

[0059] m=lN+n

[0060] Where l represents the symbol index in the entire frame. The symbol of the frame, for example, represents the time length of the frame, and l starts from 0; N represents the number of samples of 1 symbol; f c represents the carrier frequency, f s Represents the sampling rate.

[0061] After performing carrier frequency offset correction on the received signal to obtain a corrected received signal, frequency offset estimation is performed on the corrected received signal according to the signal characteristics of the corrected received signal to obtain a frequency offset estimation result.

[0062] Specifically, the corrected received signal and the local signal may be calculated to determine whether the signal characteristics of the corrected received signal affect the signal peak. If it is determined that the signal characteristics of the corrected received signal affect the signal peak, signal processing calculations are performed on the corrected received signal to obtain a frequency offset estimation result.

[0063] To determine whether the signal characteristics of the corrected received signal affect the signal peak, the relevant FFT calculation of formula (5) and the local signal can be performed, as shown in formula (6):

[0064]

[0065] As shown in formula (6), we can know that the integer carrier frequency offset (IFO) result Index IFO (i.e., the first carrier frequency offset) affects the position of the correlation peak, while the fractional carrier frequency offset (Fractional Carrier Frequency Offset, FFO) Index FFO (i.e., the second carrier frequency deviation) will cause the peak value to drop, and even cause the peak position to shift left or right, so an accurate estimation of the FFO is also required.

[0066] Second carrier frequency deviation Index FFO It can be obtained by performing correlation calculation on multiple Preamble symbols in the received signal, as shown in formula (7), by taking two adjacent symbols and performing conjugate multiplication:

[0067]

[0068] The superscript * in formula (7) indicates conjugation.

[0069] First carrier frequency deviation Index IFO The S obtained by demodulating the Preamble signal can be obtained using formula (4).

[0070] Then, the first carrier frequency offset Index IFO and the second carrier frequency offset Index FFO It is determined as the frequency offset estimation result. It can be seen that the uplink receiver of the gateway node performs frequency offset estimation based on the Preamble part of the received signal, and the estimated frequency offset value (the first carrier frequency offset Index IFOand the second carrier frequency offset Index FFO ) is used for frequency offset pre-compensation of the downlink transmitter of the gateway node. The frequency offset pre-compensation of the downlink transmitter needs to compensate all parts of the frame structure of the entire downlink signal.

[0071] The LPWAN system frame structure includes a preamble, a control parameter part PHDR for carrying the Payload part, and a data load part Payload.

[0072] It can be understood that the received signal can be detected, frequency offset estimated, demodulated and other related calculations can be performed according to formulas (1) to (7). The estimated carrier frequency offset value (CFO) result is divided into two parts: the first carrier frequency offset Index IFO and the second carrier frequency offset Index FFO Next, the frequency offset estimation result is used to perform downlink frequency offset pre-compensation.

[0073] Specifically, based on the frequency offset estimation result and the frame structure characteristics of the downlink signal, the downlink signal is pre-compensated for the frequency offset, including:

[0074] Firstly, based on the frame structure characteristics of the downlink signal, the preamble part Preamble, the control parameter part PHDR and the data load part Payload included in the frame structure of the downlink signal are determined.

[0075] Then, based on the frequency offset estimation result (the first carrier frequency offset Index IFO and the second carrier frequency offset Index FFO ), determine a first frequency offset compensation sequence for the preamble part, a second frequency offset compensation sequence for the control parameter part, and a third frequency offset compensation sequence for the data payload part.

[0076] Finally, based on the first frequency offset compensation sequence, the second frequency offset compensation sequence and the third frequency offset compensation sequence, frequency offset pre-compensation is performed on the preamble part Preamble, the control parameter part PHDR and the data payload part Payload respectively.

[0077] Specifically, based on the frequency offset estimation result, a first frequency offset compensation sequence for the preamble part, a second frequency offset compensation sequence for the control parameter part, and a third frequency offset compensation sequence for the data payload part are determined, including the following steps S0-S3.

[0078] Step S0, setting system parameters for LPWAN frequency offset pre-compensation.

[0079] Specifically, the system parameters include:

[0080] Signal bandwidth: BW;

[0081] Uplink carrier frequency:

[0082] Downlink carrier frequency: f c DL ;

[0083] Uplink receiving end sampling rate: Indicates the multiple relationship between the uplink receiving end sampling rate and BW;

[0084] Downlink transmitter sampling rate: Indicates the multiple relationship between the downlink transmitter sampling rate and BW;

[0085] Uplink spreading factor: SF UL ;

[0086] Downlink spreading factor: SF DL ;

[0087] Frequency deviation of the system: εppm;

[0088] Uplink estimated frequency deviation value:

[0089] Number of Preamble symbols in the downlink frame structure:

[0090] Number of PHDR symbols in the downlink frame structure:

[0091] Number of PHDR symbols in the downlink frame structure:

[0092] Step S1, based on the system parameters and the frequency offset estimation result (first carrier frequency offset Index IFO and the second carrier frequency offset Index FFO ) determines the downlink offset value, as shown in formula (8):

[0093]

[0094] The superscript UL represents uplink, and the superscript DL represents downlink.

[0095] Specifically, when calculating the downlink offset value, the downlink offset value is determined based on the frequency offset estimation result, the uplink carrier frequency of the uplink receiver, the downlink carrier frequency of the downlink transmitter, the uplink sampling frequency of the uplink receiver, and the downlink sampling frequency of the downlink transmitter. It can be seen that formula (8) takes into account the scenario where the uplink and downlink carrier frequencies of the LPWAN system are inconsistent, and the uplink and downlink sampling frequencies are inconsistent.

[0096] Step S2: Determine a first frequency offset compensation sequence based on the frequency offset estimation result and the downlink offset value. As shown in formula (9), generate a first pre-frequency offset compensation sequence for pre-compensating the preamble part:

[0097]

[0098] Among them, l represents the symbol index of the Preamble, ranging from 0 to Indicates the sample length of one downlink symbol; n indicates the sample within one symbol, and its value ranges from 0 to

[0099] Step S3, based on the downlink offset value, determine the second frequency offset compensation sequence and the third frequency offset compensation sequence. As shown in formula (10), generate the second frequency offset compensation sequence for the control parameter part PHDR and the third frequency offset compensation sequence for the data payload part Payload:

[0100]

[0101] Here, the sequence corresponding to l=0 in formula (9) can be used.

[0102] After the first pre-frequency offset compensation sequence for pre-compensating the preamble part is calculated by formula (9), and the second frequency offset compensation sequence for the control parameter part PHDR and the third frequency offset compensation sequence for the data payload part Payload are calculated by formula (10), the downlink signal can be pre-compensated. As shown in formula (11), assuming that the signal generated by the downlink is represented by z(l,n), l represents the symbol index, and n represents the time domain sample point index on 1 symbol, the downlink frequency offset compensation sequence (including the above-mentioned first pre-frequency offset compensation sequence, the second frequency offset compensation sequence, and the third frequency offset compensation sequence) is multiplied with the corresponding point of the corresponding data symbol to obtain the pre-compensated downlink symbol:

[0103]

[0104] Where symtype represents different types of symbols: Preamble, PHDR, Payload.

[0105] In an example, a frame structure of a downlink signal includes a plurality of symbols, each symbol includes a preamble part, a control parameter part, and a data payload part; based on a first frequency offset compensation sequence, a second frequency offset compensation sequence, and a third frequency offset compensation sequence, frequency offset pre-compensation is performed on the preamble part, the control parameter part, and the data payload part, respectively, including:

[0106] For each symbol among the multiple symbols, frequency offset pre-compensation is performed on a preamble part of the symbol based on a first frequency offset compensation sequence.

[0107] For multiple symbols, frequency offset pre-compensation is performed on the control parameter part and the data payload part respectively based on the second frequency offset compensation sequence and the third frequency offset compensation sequence according to a preset symbol period.

[0108] In the above step S1, it is necessary to fully consider that the uplink and downlink carrier frequencies may be different, and the sampling frequencies used by the uplink and downlink transmitters and receivers may be different, and calculate the frequency deviation result corresponding to the downlink to improve accuracy.

[0109] When calculating the Preamble symbol sent by the downlink frame in step S2, it is necessary to continuously perform carrier frequency offset compensation on all Preamble signals to adapt to the LPWAN system without precise timing.

[0110] In step S3, frequency offset compensation is performed on non-Preamble symbols only according to the symbol period.

[0111] After the downlink transmitter of the gateway node performs frequency offset compensation according to step S3, Figure 2 The downlink receiver of the terminal node needs to complete time synchronization before receiving.

[0112] In summary, the present application adopts a frequency offset pre-compensation scheme in the LPWAN system to reduce the complexity of the terminal nodes and reduce the power consumption of the terminal nodes. The design of the terminal nodes will become very simple, and the complexity of the system will be concentrated on the gateway nodes, which is beneficial to extending the service life of the terminal nodes. At the same time, if there is an optimized algorithm design in the future, it will also be easier to design and upgrade the gateway nodes, which has better network deployment flexibility.

[0113] Figure 3 A schematic diagram of a frequency offset pre-compensation device based on a low power wide area network provided in an embodiment of the present application.

[0114] like Figure 3 As shown, the gateway node and the terminal node can perform signal transmission based on the low power wide area network. The device is applied to the gateway node. The frequency offset pre-compensation device 300 based on the low power wide area network includes: a frequency offset estimation module 310 and a frequency offset pre-compensation module 320.

[0115] The frequency offset estimation module 310 is used to perform frequency offset estimation on the received signal according to the signal characteristics of the received signal to obtain a frequency offset estimation result.

[0116] The frequency offset pre-compensation module 320 is used to perform frequency offset pre-compensation on the downlink signal based on the frequency offset estimation result and the frame structure characteristics of the downlink signal, so as to send the downlink signal after frequency offset pre-compensation to the terminal node.

[0117] It can be understood that for the specific description of the frequency offset precompensation device 300 based on a low power wide area network, reference can be made to the description of the frequency offset precompensation method based on a low power wide area network above, which will not be repeated here.

[0118] Exemplarily, the gateway node includes an uplink receiver and a downlink transmitter; before estimating the frequency offset of the received signal based on the signal characteristics of the received signal to obtain the frequency offset estimation result, the device 300 also includes: a correction module, which is used to correct the carrier frequency offset of the received signal when there is a frequency offset between the uplink receiver and the downlink transmitter to obtain a corrected received signal.

[0119] Exemplarily, the frequency offset estimation module 310 is also used to: calculate the received signal and the local signal to determine whether the signal characteristics of the received signal affect the signal peak; when it is determined that the signal characteristics of the received signal affect the signal peak, perform signal processing calculations on the received signal to obtain a frequency offset estimation result.

[0120] Exemplarily, when it is determined that the signal characteristics of the received signal affect the signal peak, signal processing calculations are performed on the received signal to obtain a frequency deviation estimation result, including: when it is determined that the signal characteristics of the received signal affect the signal peak, signal processing calculations are performed on the received signal to obtain a first carrier frequency deviation and a second carrier frequency deviation, wherein the first carrier frequency deviation affects the peak position of the signal, and the second carrier frequency deviation affects the peak drop and / or peak shift of the signal; the first carrier frequency deviation and the second carrier frequency deviation are determined as the frequency deviation estimation results.

[0121] Exemplarily, the frame structure of the downlink signal includes a preamble part, a control parameter part and a data payload part; the frequency offset pre-compensation module 320 is also used to: determine the preamble part, the control parameter part and the data payload part included in the frame structure of the downlink signal based on the frame structure characteristics of the downlink signal; determine a first frequency offset compensation sequence for the preamble part, a second frequency offset compensation sequence for the control parameter part and a third frequency offset compensation sequence for the data payload part based on the frequency offset estimation result; and perform frequency offset pre-compensation on the preamble part, the control parameter part and the data payload part based on the first frequency offset compensation sequence, the second frequency offset compensation sequence and the third frequency offset compensation sequence, respectively.

[0122] Exemplarily, based on the frequency offset estimation result, a first frequency offset compensation sequence for the preamble part, a second frequency offset compensation sequence for the control parameter part, and a third frequency offset compensation sequence for the data payload part are determined, including: determining a downlink offset value based on the frequency offset estimation result; determining a first frequency offset compensation sequence based on the frequency offset estimation result and the downlink offset value; determining a second frequency offset compensation sequence and a third frequency offset compensation sequence based on the downlink offset value.

[0123] Exemplarily, the gateway node includes an uplink receiver and a downlink transmitter; based on the frequency offset estimation result, a downlink offset value is determined, including: based on the frequency offset estimation result, the uplink carrier frequency of the uplink receiver, the downlink carrier frequency of the downlink transmitter, the uplink sampling frequency of the uplink receiver, and the downlink sampling frequency of the downlink transmitter, the downlink offset value is determined.

[0124] Exemplarily, the frame structure of a downlink signal includes multiple symbols, each symbol includes a preamble part, a control parameter part and a data payload part; based on a first frequency offset compensation sequence, a second frequency offset compensation sequence and a third frequency offset compensation sequence, frequency offset pre-compensation is performed on the preamble part, the control parameter part and the data payload part, respectively, including: for each symbol in the multiple symbols, frequency offset pre-compensation is performed on the preamble part in the symbol based on the first frequency offset compensation sequence; for the multiple symbols, frequency offset pre-compensation is performed on the control parameter part and the data payload part, respectively, based on the second frequency offset compensation sequence and the third frequency offset compensation sequence according to the symbol period.

[0125] Exemplarily, after the downlink signal after frequency offset pre-compensation is sent to the terminal node, the terminal node completes time synchronization before receiving the downlink signal.

[0126] An embodiment of the present application provides a gateway node, including a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the steps of the method in any one of the above embodiments are implemented.

[0127] An embodiment of the present application provides a communication system of a low-power wide area network, the communication system includes a gateway node and a terminal node, and the gateway node is used to implement the steps of the method in any of the above embodiments.

[0128] An embodiment of the present application provides a computer-readable storage medium having a computer program stored thereon. When the computer program is executed by a processor, the steps of the method in any one of the above embodiments are implemented.

[0129] One embodiment of the present application provides a computer program product, which includes instructions. When the instructions are executed by a processor of a computer device, the computer device can perform the steps of the method of any of the above embodiments.

[0130] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in combination with these instruction execution systems, devices or apparatuses. For the purposes of this application, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in combination with these instruction execution systems, devices or apparatuses. More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection portion with one or more wirings (electronic device), a portable computer disk box (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium and then editing, interpreting or otherwise processing in a suitable manner if necessary, and then stored in a computer memory.

[0131] It should be understood that the various parts of the present application can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0132] In the description of the present application, the description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0133] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0134] In addition, the terms "first", "second", etc. used in the embodiments of the present application are only used for descriptive purposes and should not be understood as indicating or implying relative importance, or implicitly indicating the number of technical features indicated in the present embodiment. Therefore, the features defined by the terms "first", "second", etc. in the embodiments of the present application can explicitly or implicitly indicate that at least one of the features is included in the embodiment. In the description of the present application, the word "multiple" means at least two or two or more, such as two, three, four, etc., unless otherwise clearly and specifically defined in the embodiments.

[0135] In this application, unless otherwise clearly specified or limited in the embodiments, the terms "installed", "connected", "connected" and "fixed" etc. appearing in the embodiments should be understood in a broad sense. For example, the connection can be a fixed connection, a detachable connection, or an integrated connection. It can be understood that it can also be a mechanical connection, an electrical connection, etc.; of course, it can also be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal connection of two elements, or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to the specific implementation situation.

[0136] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0137] Although the embodiments of the present application have been shown and described above, it can be understood that the above embodiments are exemplary and cannot be understood as limitations on the present application. Ordinary technicians in this field can change, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A frequency offset pre-compensation method based on a low power wide area network, characterized in that: The gateway node and the terminal node can perform signal transmission based on the low power wide area network, and the method is applied to the gateway node, and the method includes: According to the signal characteristics of the received signal, frequency offset estimation is performed on the received signal to obtain a frequency offset estimation result; Based on the frequency offset estimation result and the frame structure characteristics of the downlink signal, the downlink signal is pre-compensated for frequency offset, so as to send the downlink signal after the frequency offset pre-compensation to the terminal node.

2. The method according to claim 1, characterized in that: The gateway node includes an uplink receiver and a downlink transmitter; Before performing frequency offset estimation on the received signal according to the signal characteristics of the received signal to obtain the frequency offset estimation result, the method further includes: In the case where there is a frequency offset between the uplink receiver and the downlink transmitter, the carrier frequency offset is corrected for the received signal to obtain a corrected received signal.

3. The method according to claim 1 or 2, characterized in that: The step of performing frequency offset estimation on the received signal according to the signal characteristics of the received signal to obtain a frequency offset estimation result includes: Calculating the received signal and the local signal to determine whether the signal characteristics of the received signal affect the signal peak; In the case where it is determined that the signal characteristic of the received signal affects the signal peak, signal processing calculation is performed on the received signal to obtain the frequency offset estimation result.

4. The method according to claim 3, characterized in that In the case where it is determined that the signal characteristic of the received signal affects the signal peak value, performing signal processing calculation on the received signal to obtain the frequency offset estimation result includes: In the case where it is determined that the signal characteristic of the received signal affects the signal peak, performing signal processing calculation on the received signal to obtain a first carrier frequency offset and a second carrier frequency offset, wherein the first carrier frequency offset affects the peak position of the signal, and the second carrier frequency offset affects the peak drop and / or peak shift of the signal; The first carrier frequency offset and the second carrier frequency offset are determined as the frequency offset estimation result.

5. The method according to claim 1, characterized in that The frame structure of the downlink signal includes a preamble part, a control parameter part and a data payload part; The pre-compensating the downlink signal for frequency offset based on the frequency offset estimation result and the frame structure characteristic of the downlink signal includes: Based on the frame structure characteristics of the downlink signal, determining a preamble part, a control parameter part and a data payload part included in the frame structure of the downlink signal; Based on the frequency offset estimation result, determining a first frequency offset compensation sequence for the preamble part, a second frequency offset compensation sequence for the control parameter part, and a third frequency offset compensation sequence for the data payload part; Based on the first frequency offset compensation sequence, the second frequency offset compensation sequence and the third frequency offset compensation sequence, frequency offset pre-compensation is performed on the preamble part, the control parameter part and the data payload part respectively.

6. The method according to claim 5, characterized in that The determining, based on the frequency offset estimation result, a first frequency offset compensation sequence for the preamble part, a second frequency offset compensation sequence for the control parameter part, and a third frequency offset compensation sequence for the data payload part, comprises: Determining a downlink offset value based on the frequency offset estimation result; Determining the first frequency offset compensation sequence based on the frequency offset estimation result and the downlink offset value; Based on the downlink offset value, the second frequency offset compensation sequence and the third frequency offset compensation sequence are determined.

7. The method according to claim 6, characterized in that The gateway node includes an uplink receiver and a downlink transmitter; and determining a downlink offset value based on the frequency offset estimation result includes: The downlink offset value is determined based on the frequency offset estimation result, the uplink carrier frequency of the uplink receiver, the downlink carrier frequency of the downlink transmitter, the uplink sampling frequency of the uplink receiver, and the downlink sampling frequency of the downlink transmitter.

8. The method according to claim 6, characterized in that The frame structure of the downlink signal includes a plurality of symbols, each symbol includes a preamble part, a control parameter part, and a data payload part; and performing frequency offset pre-compensation on the preamble part, the control parameter part, and the data payload part based on the first frequency offset compensation sequence, the second frequency offset compensation sequence, and the third frequency offset compensation sequence, respectively, including: For each symbol of the multiple symbols, perform frequency offset pre-compensation on the preamble part of the symbol based on the first frequency offset compensation sequence; For the multiple symbols, frequency offset pre-compensation is performed on the control parameter part and the data payload part respectively based on the second frequency offset compensation sequence and the third frequency offset compensation sequence according to the symbol period.

9. The method according to claim 1, characterized in that: After sending the downlink signal after frequency offset pre-compensation to the terminal node, the terminal node completes time synchronization before receiving the downlink signal.

10. A frequency offset pre-compensation device based on a low power wide area network, characterized in that: The gateway node and the terminal node can perform signal transmission based on the low power wide area network, and the device is applied to the gateway node, and the device includes: A frequency offset estimation module, used to perform frequency offset estimation on the received signal according to the signal characteristics of the received signal to obtain a frequency offset estimation result; The frequency offset pre-compensation module is used to perform frequency offset pre-compensation on the downlink signal based on the frequency offset estimation result and the frame structure characteristics of the downlink signal, so as to send the downlink signal after frequency offset pre-compensation to the terminal node.

11. A gateway node, comprising a memory and a processor, wherein the memory stores a computer program, characterized in that: When the processor executes the computer program, the steps of the method according to any one of claims 1 to 9 are implemented.

12. A communication system based on a low power wide area network, characterized in that: The communication system comprises a gateway node and a terminal node, and the gateway node is used to implement the steps of the method according to any one of claims 1 to 9.

13. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 9 are implemented.

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