Ultra-low power consumption space-based Internet of Things communication system design method

Abstract

The invention relates to the technical field of satellite design, and provides an ultra-low power consumption space-based internet-of-things communication system design method, which realizes direct communication with a satellite through ultra-low power consumption general terminal equipment through software upgrading of existing internet-of-things terminal electronic equipment and collaborative enhancement design of a spaceborne antenna and a communication machine. Comprising the following steps: S1, designing a satellite communication system: designing hardware and software structures of the satellite communication system, including satellite equipment, ground equipment, a communication protocol and the like, and cooperatively designing a multi-port communication machine and an antenna array: adopting a high-gain and orthogonal design for a multi-beam array antenna, reducing the transmitting power of ground terminal equipment, positioning the position of a terminal, and improving the communication efficiency; s2, communication protocol design: designing satellite-ground communication private protocols including a data transmission protocol, a connection management protocol and the like, and S3, communication data management: establishing a feed data transmission link with a satellite through a gateway station, and supervising communication permission and flow of ground terminal equipment.

Description

Technical Field

[0001] The present invention relates to the technical field of satellite design, and in particular to a design method for an ultra-low power consumption space-based Internet of Things communication system. Background Art

[0002] Traditional satellite communication systems usually use dedicated satellite communication equipment for communication, which requires unique communication terminal equipment, which is large in size, high in cost, and has limited application scenarios. In wireless communication systems, the quality of received signals is crucial to the quality of communication. Traditional reception methods usually rely on only a single antenna to receive signals, which has low spectrum utilization efficiency and weak received signal strength. Summary of the invention

[0003] The present invention proposes a method for designing an ultra-low power consumption space-based Internet of Things communication system. This system design method can realize the direct connection of ultra-low power consumption terminals to satellites, apply new narrowband Internet of Things communication technology to satellite communication systems, and rely on the existing consumer-grade communication chip application ecosystem. It only requires software upgrades for existing Internet of Things terminal electronic devices to directly connect to satellites. This method can reduce the cost of satellite communications and improve equipment portability and application flexibility.

[0004] The technical solution of the present invention is as follows: The present invention provides a system design method for directly connecting an ultra-low power consumption terminal to a satellite. The method realizes direct communication with a satellite through an ultra-low power consumption universal terminal device by upgrading the software of the existing IoT terminal electronic equipment and collaboratively enhancing the design of the satellite antenna and the communication machine.

[0005] The ultra-low power consumption space-based IoT system design method of the present invention comprises the following steps:

[0006] Satellite communication system design: Design the hardware and software structure of the satellite communication system, including satellite equipment, ground equipment and communication protocols.

[0007] Co-design of multi-port communicator and antenna array: The multi-beam array antenna adopts high-gain and orthogonal design to reduce the transmission power of ground terminal equipment, locate the terminal position, enhance the communication signal of the terminal, perform modulation and demodulation, error checking, etc., and realize the function of space-based IoT communication.

[0008] Communication protocol design: Design private protocols for satellite-to-ground communications, including data transmission protocols, connection management protocols, etc.

[0009] Communication data management: Establish a feed data transmission link with the satellite through the gateway station to supervise the communication permissions and traffic of ground terminal equipment.

[0010] Furthermore, the invention uses a collaborative design of antennas and communication machines, triggered by the characteristics of radio electromagnetic waves. Since the transmission power of ground terminal equipment is extremely low, the signal reaching the satellite is very weak. The present invention triggers the design of an orthogonally distributed multi-beam array antenna based on the phase fluctuation characteristics of electromagnetic waves in the process of space transmission, and each terminal signal is received by the multi-beam antenna in two orthogonal directions. This method can accurately locate the relative position relationship between the satellite and the terminal device, and can effectively overcome the Doppler effect caused by the high-speed movement of the satellite. The multi-port communication receiver combines and calculates the signals according to the fluctuation phase characteristics received by different beams, and amplifies the terminal's micro-signal by superimposing and combining N beam energies, thereby realizing the direct connection of the ground terminal micro-signal to the satellite.

[0011] Furthermore, the satellite is equipped with storage, feed data transmitter, feed antenna, and data transmission antenna, and the communication link established between the satellite and the gateway station is used to realize the permission and traffic management of the ground terminal equipment to connect to the satellite. The specific implementation process is as follows:

[0012] The ground terminal equipment sends signal data to the satellite;

[0013] The multi-beam array antenna receives the Bluetooth phase process signals;

[0014] The multi-port communication receiver modulates and demodulates the communication signal and forms a data stream to be sent to the storage;

[0015] The data is transferred to the data transmitter and then transmitted to the gateway via the data transmission antenna.

[0016] The information gateway interprets the data identification code and issues access permission after verification;

[0017] From the feed link through the feed antenna data transmitter, and then from the fixed storage to the multi-port communication machine;

[0018] The multi-port communicator sends a permission signal to the terminal from the multi-beam array antenna based on the previously interpreted terminal position, thereby enabling ultra-low power terminal direct communication with the satellite.

[0019] Furthermore, each antenna array spoke of the multi-beam array antenna receives radio energy from several concentrated areas, which may have different degrees of beam overlap. For an N-antenna linear array, approximately N / 2 of its radio receive beams have a smaller space on the circle within the elevation angle range of -45 degrees to 45 degrees. Although any number of M beams can be formed, there may be different degrees of spatial overlap between these M beams. Higher beam overlap can improve the positioning accuracy of terminal radio transmissions. In addition, since satellites travel at 7.8 kilometers per second in low-Earth orbit, if the terminal transmission is long enough to cross from one beam area to an adjacent beam area, beam overlap will also provide redundancy. Figure 2The calculations necessary to create M focused receive beams for a linear antenna array. The baseband signals received by each of the N antennas are denoted by x1 to xN. These signals are multiplied by the beamformer matrix, denoted by H. To create the beam, the beamformer matrix applies a constant phase shift to the signal received at antenna k relative to k-1, with the phase shift depending on the spacing between the antennas and the elevation angle of the beam to be formed. The phase shifted signals from each antenna are then accumulated together. The phase shift is chosen so that the radio energy at each antenna increases synchronously, thereby maximizing the signal strength for a particular beam direction. The phase shift is calculated by calculating the phase difference at each antenna of the radio arrival signal for a particular beam elevation angle along the direction of the antenna array. These phase shift values ​​are then used by the beamformer matrix in signal processing to align all received signal phases by multiplying the input baseband signal by the complex conjugate of the complex exponential representing the phase shift of the radio wave predicted to arrive at each beam elevation angle. When the antenna spoke is split into two spatially offset branches, the phase shift calculation is adjusted to account for the offset between the branches. Each input baseband signal may also be multiplied by a gain factor to trade off a wider main beam lobe width for a smaller beam lobe amplitude. To create M beams using an N-antenna linear array, a matrix H of size M×N is required that multiplies the input baseband signals by complex exponentials (and possibly tapering gains) to create the necessary phase shifts to align the received signals and create the beams. The phase shifts used to form a beam at a particular elevation angle in the receive direction may also be used in the transmit direction to form a transmit beam along the same elevation angle. In an alternative embodiment, the beamformer matrix H is selected so that the resulting beams sweep across the ground to offset the motion of the satellite and also adjust to offset any changes in the satellite's attitude. In this case, each beam will be focused on a specific area on the earth and the beam coverage area will not move with the motion of the satellite. In this case, the beamformer matrix H will be composed of time-varying complex exponentials.

[0020] Furthermore, the azimuth angle is defined as the propagation angle of the radio wave relative to the direction of the orbital plane. The elevation angle is defined as the propagation angle of the radio wave relative to the -Z axis of the orbital reference frame. When the beam is observed from the Earth, the beam profile of maximum beam energy is parabolic in shape, because the phase difference of the radio waves arriving at consecutive antennas is a function of the azimuth and elevation of the radio waves received in the spoke reference frame. Along the linear antenna array, the phase difference of the radio wave carrier of consecutive antennas spaced half a wavelength apart is calculated as:

[0021] Equation 1: Phase difference = πcos(azimuth_s)sin(elevation).

[0022] where azimuth_s is the azimuth angle in the spoke reference frame (azimuth_s=0° is the radio wave arriving along the length of the spoke). Figure 4Several beam profiles for 9 beams formed by each linear antenna spoke are shown for a two-spoke system with vertical spokes. These contours would be observed on a flat ground and the contours are created assuming a satellite altitude of 600 km. Ox and Oy represent the phase differences of the arriving radio waves between consecutive antennas of the x and y spokes, respectively. The horizontal contours in the figure are formed by the spokes pointing in the Y direction and the vertical contours are formed by the spokes pointing in the X direction. In the orbital reference frame, azimuth_x is defined as the azimuth of the x spoke and azimuth_y is defined as the azimuth of the y spoke. When the spokes are vertical, azimuth_x = azimuth_y + 90°. The phase difference between the consecutive antennas of the two spokes is pre-calculated for each received beam formed. For the two-spoke configuration, we obtain two equations and two unknowns when the beam receives the terminal symbol transmission from each spoke.

[0023] Equation 2: Phase difference (y spoke) = π cos (azimuth_sy) sin (elevation);

[0024] Equation 3: Phase difference (x spoke) = π cos (azimuth_sx) sin (elevation).

[0025] Where azimuth_sy is the azimuth of the radio wave in the y-radiation reference frame, and azimuth_sx is the azimuth of the radio wave in the x-radiation reference frame. Assuming that the satellite's pitch and roll angles are zero and converting them back to the orbital reference frame, we get:

[0026] Equation 4: azimuth_sy+satellite yaw angle=azimuth

[0027] Equation 5: azimuth_sx = azimuth_sy + φ

[0028] Where φ is the direction of the x-spoke relative to the y-spoke, which is 90 degrees when the spokes are vertical. The satellite yaw angle is defined as the azimuth of the Y-spoke relative to the orbital plane. The known variable is the phase difference that produces the beam from the two spokes. The unknowns are the azimuth and elevation of the radio wave, corresponding to the symbol mission transmitted from the corresponding terminal. From the above equations, the azimuth and elevation of the radio wave in the orbital reference frame can be calculated. These angles define the terminal position on the ground, because the position and attitude of the satellite relative to the earth are known by using the onboard GPS radio, magnetic sensors and solar sensors, and the attitude estimation method described later in this disclosure. Non-zero pitch angles and non-zero roll angles can be integrated into the above equations using appropriate rotation matrices. For each symbol received, the azimuth and elevation of the corresponding radio wave are calculated as described above, and the symbol is assigned a position coordinate.

[0029] Further, in radio communications, orthogonal modulation is used to increase the radio sensitivity for a target communication rate by spreading the available energy over as much bandwidth as possible. The disadvantage of orthogonal modulation is its low spectral efficiency. The combination of multi-antenna spoke beamforming and orthogonal modulation significantly improves the performance of a radio by increasing the spectral efficiency of the system compared to a single-antenna radio using orthogonal modulation. An example of orthogonal modulation is m-ary frequency shift keying (FSK) modulation. The FFT of a m-ary FSK symbol is shown in Figure 1. Figure 5 As shown in Figure 1, Log2(M) bits are mapped to one of M orthogonal frequency bins and one possible bin is sent over the communication channel to encode these bits. Figure 5 The case when M=256 is shown, where 8 bits are encoded into a specific meta-frequency. The bits '01001110'=78 are encoded by the meta-frequency in the example. At the receiving end, each received meta-frequency is demodulated and converted back into the correct bit. In a shared wireless network, if two orthogonal modulation symbols sent from two different terminals overlap in time, the receiver may be confused about which symbol corresponds to which transmitter. Figure 6 Depicted is a spectrum diagram of two symbols from two different terminals that overlap in time but not in frequency. A symbol that overlaps in time with one or more other orthogonal modulation symbols can only be correctly decoded if the symbol to be decoded does not overlap with other symbols within the orthogonal dimension (for M-ARY FSK, the orthogonal dimension is 2m frequency). The spectral efficiency of M-ary orthogonal modulation using a single antenna receiver is approximately Log2(M) / M bits / second / Hz. In multi-radial beamforming, in order to improve spectral efficiency, symbols that overlap in time from different terminals are assigned positions and distinguished based on each symbol position. As Figure 7 As shown, the symbol from Terminal 1 is picked up by Beam 4 and Beam 3, and the symbol from Terminal 2 is picked up by Beam 12 and Beam 3. If the two symbols overlap in time but not in frequency, then they can be distinguished and decoded separately because they are detected by a unique row and column beam pair. In order to successfully decode the two symbols with a single antenna receiver, the symbols need to be non-overlapping in time or non-overlapping in orthogonal frequency ranges.

[0030] Furthermore, the spectral efficiency of a two-spoke linear antenna receiver using M-ary FSK modulation and N non-overlapping beams per spoke is upper bounded by N*Log2(M) bits / sec / Hz, an N*M improvement over a single antenna receiver using M-ary FSK modulation. Another advantage of using orthogonal modulation is the improvement in energy efficiency. A 64-ARY FSK radio requires approximately 2 times (3dB in decibels) more energy than a 2-ARY FSK radio sending the same size packet over an additive white Gaussian noise (AWGN) channel (with a symbol error probability of 10%). In summary, multi-spoke beamforming receivers provide significant improvements in both network capacity and spectral efficiency compared to single-antenna receivers. The multi-spoke structure allows for a small antenna array that is easy to place in a small satellite and still provides good network capacity and spectral efficiency.

[0031] The working principle and beneficial effects of the present invention are:

[0032] The innovation of the present invention is to enhance the received signal through the coordinated design of the antenna array and the receiver. By utilizing the orthogonal design of the antenna array and the multi-beam receiver adjustment mechanism, the quality and reliability of the received signal are improved, providing good network capacity and spectrum efficiency. The new narrowband IoT communication technology is applied to the satellite communication system to achieve direct communication with the satellite through an ultra-low power consumption terminal.

[0033] Practical application: The ultra-low power consumption IoT communication system design method of the present invention can be widely used in the field of satellite communication, such as satellite phone, satellite positioning, satellite broadcasting, etc. By directly connecting the ground terminal to the satellite, convenient satellite communication can be achieved, which is suitable for various mobile communication scenarios.

[0034] The present invention has the following benefits and advantages:

[0035] Reduce costs: The function of direct connection to the satellite can be achieved through software upgrades of general terminal equipment, which can avoid the use of dedicated satellite communication equipment and reduce system costs.

[0036] Improve portability: Universal terminal equipment is usually small and portable, making satellite communications more convenient and flexible.

[0037] Flexibility: By directly connecting to the satellite through universal terminal devices, users can communicate with the satellite anytime and anywhere, with greater flexibility and freedom. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

[0039] Figure 1 Block diagram of the space-based IoT communication system;

[0040] Figure 2 A plurality of receiving radio beams generated by a linear antenna array of N antenna elements;

[0041] Figure 3 Orbital coordinate system;

[0042] Figure 4 Contour plot of radio beam energy for a dual-radial linear antenna array;

[0043] Figure 5 Fourier transform of M-ary FSK with M=256;

[0044] Figure 6 Spectrum plot of two M-ARY FSK symbols overlapping in time rather than frequency;

[0045] Figure 7 Symbols from two terminals are transmitted simultaneously and are received by the same column antenna beam but different row antenna beams. DETAILED DESCRIPTION

[0046] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0047] like Figure 1-2 As shown, this embodiment proposes a system design method for directly connecting an ultra-low power consumption terminal to a satellite. The method achieves direct communication with a satellite through an ultra-low power consumption universal terminal device by upgrading the existing IoT terminal electronic equipment software and coordinating and enhancing the design of the satellite antenna and the communication machine.

[0048] The ultra-low power consumption space-based IoT system design method of the present invention comprises the following steps:

[0049] Satellite communication system design: Design the hardware and software structure of the satellite communication system, including satellite equipment, ground equipment and communication protocols.

[0050] Co-design of multi-port communicator and antenna array: The multi-beam array antenna adopts high-gain and orthogonal design to reduce the transmission power of ground terminal equipment, locate the terminal position, enhance the communication signal of the terminal, perform modulation and demodulation, error checking, etc., and realize the function of space-based IoT communication.

[0051] Communication protocol design: Design private protocols for satellite-to-ground communications, including data transmission protocols, connection management protocols, etc.

[0052] Communication data management: Establish a feed data transmission link with the satellite through the gateway station to supervise the communication permissions and traffic of ground terminal equipment.

[0053] Furthermore, the invention uses a collaborative design of antennas and communication machines, triggered by the characteristics of radio electromagnetic waves. Since the transmission power of ground terminal equipment is extremely low, the signal reaching the satellite is very weak. The present invention triggers the design of an orthogonally distributed multi-beam array antenna based on the phase fluctuation characteristics of electromagnetic waves in the process of space transmission, and each terminal signal is received by the multi-beam antenna in two orthogonal directions. This method can accurately locate the relative position relationship between the satellite and the terminal device, and can effectively overcome the Doppler effect caused by the high-speed movement of the satellite. The multi-port communication receiver combines and calculates the signals according to the fluctuation phase characteristics received by different beams, and amplifies the terminal's micro-signal by superimposing and combining N beam energies, thereby realizing the direct connection of the ground terminal micro-signal to the satellite.

[0054] Furthermore, the satellite is equipped with storage, feed data transmitter, feed antenna, and data transmission antenna, and the communication link established between the satellite and the gateway station is used to realize the permission and traffic management of the ground terminal equipment to connect to the satellite. The specific implementation process is as follows:

[0055] The ground terminal equipment sends signal data to the satellite;

[0056] The multi-beam array antenna receives the Bluetooth phase process signals;

[0057] The multi-port communication receiver modulates and demodulates the communication signal and forms a data stream to be sent to the storage;

[0058] The data is transferred to the data transmitter and then transmitted to the gateway via the data transmission antenna.

[0059] The information gateway interprets the data identification code and issues access permission after verification;

[0060] From the feed link through the feed antenna data transmitter, and then from the fixed storage to the multi-port communication machine;

[0061] The multi-port communicator sends a permission signal to the terminal from the multi-beam array antenna based on the previously interpreted terminal position, thereby enabling ultra-low power terminal direct communication with the satellite.

[0062] Furthermore, each antenna array spoke of the multi-beam array antenna receives radio energy from several concentrated areas, which may have different degrees of beam overlap. For an N-antenna linear array, approximately N / 2 of its radio receive beams have a smaller space on the circle within the elevation angle range of -45 degrees to 45 degrees. Although any number of M beams can be formed, there may be different degrees of spatial overlap between these M beams. Higher beam overlap can improve the positioning accuracy of terminal radio transmissions. In addition, since satellites travel at 7.8 kilometers per second in low-Earth orbit, if the terminal transmission is long enough to cross from one beam area to an adjacent beam area, beam overlap will also provide redundancy. Figure 2 The calculations necessary to create M focused receive beams for a linear antenna array. The baseband signals received by each of the N antennas are denoted by x1 to xN. These signals are multiplied by the beamformer matrix, denoted by H. To create the beam, the beamformer matrix applies a constant phase shift to the signal received at antenna k relative to k-1, with the phase shift depending on the spacing between the antennas and the elevation angle of the beam to be formed. The phase shifted signals from each antenna are then accumulated together. The phase shift is chosen so that the radio energy at each antenna increases synchronously, thereby maximizing the signal strength for a particular beam direction. The phase shift is calculated by calculating the phase difference at each antenna of the radio arrival signal for a particular beam elevation angle along the direction of the antenna array. These phase shift values ​​are then used by the beamformer matrix in signal processing to align all received signal phases by multiplying the input baseband signal by the complex conjugate of the complex exponential representing the phase shift of the radio wave predicted to arrive at each beam elevation angle. When the antenna spoke is split into two spatially offset branches, the phase shift calculation is adjusted to account for the offset between the branches. Each input baseband signal may also be multiplied by a gain factor to trade off a wider main beam lobe width for a smaller beam lobe amplitude. To create M beams using an N-antenna linear array, a matrix H of size M×N is required that multiplies the input baseband signals by complex exponentials (and possibly tapering gains) to create the necessary phase shifts to align the received signals and create the beams. The phase shifts used to form a beam at a particular elevation angle in the receive direction may also be used in the transmit direction to form a transmit beam along the same elevation angle. In an alternative embodiment, the beamformer matrix H is selected so that the resulting beams sweep across the ground to offset the motion of the satellite and also adjust to offset any changes in the satellite's attitude. In this case, each beam will be focused on a specific area on the earth and the beam coverage area will not move with the motion of the satellite. In this case, the beamformer matrix H will be composed of time-varying complex exponentials.

[0063] Furthermore, the azimuth angle is defined as the propagation angle of the radio wave relative to the direction of the orbital plane. The elevation angle is defined as the propagation angle of the radio wave relative to the -Z axis of the orbital reference frame. When the beam is observed from the Earth, the beam profile of maximum beam energy is parabolic in shape, because the phase difference of the radio waves arriving at consecutive antennas is a function of the azimuth and elevation of the radio waves received in the spoke reference frame. Along the linear antenna array, the phase difference of the radio wave carrier of consecutive antennas spaced half a wavelength apart is calculated as:

[0064] Equation 1: Phase difference = πcos(azimuth_s)sin(elevation).

[0065] where azimuth_s is the azimuth angle in the spoke reference frame (azimuth_s=0° is the radio wave arriving along the length of the spoke). Figure 4 Several beam profiles for 9 beams formed by each linear antenna spoke are shown for a two-spoke system with vertical spokes. These contours would be observed on a flat ground and the contours are created assuming a satellite altitude of 600 km. Ox and Oy represent the phase differences of the arriving radio waves between consecutive antennas of the x and y spokes, respectively. The horizontal contours in the figure are formed by the spokes pointing in the Y direction and the vertical contours are formed by the spokes pointing in the X direction. In the orbital reference frame, azimuth_x is defined as the azimuth of the x spoke and azimuth_y is defined as the azimuth of the y spoke. When the spokes are vertical, azimuth_x = azimuth_y + 90°. The phase difference between the consecutive antennas of the two spokes is pre-calculated for each received beam formed. For the two-spoke configuration, we obtain two equations and two unknowns when the beam receives the terminal symbol transmission from each spoke.

[0066] Equation 2: Phase difference (y spoke) = π cos (azimuth_sy) sin (elevation);

[0067] Equation 3: Phase difference (x spoke) = π cos (azimuth_sx) sin (elevation).

[0068] Where azimuth_sy is the azimuth of the radio wave in the y-radiation reference frame, and azimuth_sx is the azimuth of the radio wave in the x-radiation reference frame. Assuming that the satellite's pitch and roll angles are zero and converting them back to the orbital reference frame, we get:

[0069] Equation 4: azimuth_sy+satellite yaw angle=azimuth

[0070] Equation 5: azimuth_sx = azimuth_sy + φ

[0071] Where φ is the direction of the x-spoke relative to the y-spoke, which is 90 degrees when the spokes are vertical. The satellite yaw angle is defined as the azimuth of the Y-spoke relative to the orbital plane. The known variable is the phase difference that produces the beam from the two spokes. The unknowns are the azimuth and elevation of the radio wave, corresponding to the symbol mission transmitted from the corresponding terminal. From the above equations, the azimuth and elevation of the radio wave in the orbital reference frame can be calculated. These angles define the terminal position on the ground, because the position and attitude of the satellite relative to the earth are known by using the onboard GPS radio, magnetic sensors and solar sensors, and the attitude estimation method described later in this disclosure. Non-zero pitch angles and non-zero roll angles can be integrated into the above equations using appropriate rotation matrices. For each symbol received, the azimuth and elevation of the corresponding radio wave are calculated as described above, and the symbol is assigned a position coordinate.

[0072] Further, in radio communications, orthogonal modulation is used to increase the radio sensitivity for a target communication rate by spreading the available energy over as much bandwidth as possible. The disadvantage of orthogonal modulation is its low spectral efficiency. The combination of multi-antenna spoke beamforming and orthogonal modulation significantly improves the performance of a radio by increasing the spectral efficiency of the system compared to a single-antenna radio using orthogonal modulation. An example of orthogonal modulation is m-ary frequency shift keying (FSK) modulation. The FFT of a m-ary FSK symbol is shown in Figure 1. Figure 5 As shown in Figure 1, Log2(M) bits are mapped to one of M orthogonal frequency bins and one possible bin is sent over the communication channel to encode these bits. Figure 5 The case when M=256 is shown, where 8 bits are encoded into a specific meta-frequency. The bits '01001110'=78 are encoded by the meta-frequency in the example. At the receiving end, each received meta-frequency is demodulated and converted back into the correct bit. In a shared wireless network, if two orthogonal modulation symbols sent from two different terminals overlap in time, the receiver may be confused about which symbol corresponds to which transmitter. Figure 6 Depicted is a spectrum diagram of two symbols from two different terminals that overlap in time but not in frequency. A symbol that overlaps in time with one or more other orthogonal modulation symbols can only be correctly decoded if the symbol to be decoded does not overlap with other symbols within the orthogonal dimension (for M-ARY FSK, the orthogonal dimension is 2m frequency). The spectral efficiency of M-ary orthogonal modulation using a single antenna receiver is approximately Log2(M) / M bits / second / Hz. In multi-radial beamforming, in order to improve spectral efficiency, symbols that overlap in time from different terminals are assigned positions and distinguished based on each symbol position. As Figure 7As shown, the symbol from Terminal 1 is picked up by Beam 4 and Beam 3, and the symbol from Terminal 2 is picked up by Beam 12 and Beam 3. If the two symbols overlap in time but not in frequency, then they can be distinguished and decoded separately because they are detected by a unique row and column beam pair. In order to successfully decode the two symbols with a single antenna receiver, the symbols need to be non-overlapping in time or non-overlapping in orthogonal frequency ranges.

[0073] Furthermore, the spectral efficiency of a two-spoke linear antenna receiver using M-ary FSK modulation and N non-overlapping beams per spoke is upper bounded at N*Log2(M) bits / sec / Hz, an improvement of N*M over a single antenna receiver using M-ary FSK modulation. Another advantage of using orthogonal modulation is the improvement in energy efficiency. A 64-ARY FSK radio requires approximately 2 times (3dB in decibels) more energy than a 2-ARY FSK radio sending the same size packet over an additive white Gaussian noise (AWGN) channel (with a symbol error probability of 10%). In summary, multi-spoke beamforming receivers provide significant improvements in both network capacity and spectral efficiency compared to single-antenna receivers. The multi-spoke structure allows for a small antenna array that is easy to place in a small satellite and still provides good network capacity and spectral efficiency.

[0074] In this embodiment, .

[0075] The above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A design method for an ultra-low power consumption space-based IoT communication system, characterized in that: This method achieves direct communication with satellites through ultra-low power universal terminal devices by upgrading the software of existing IoT terminal electronic equipment and coordinating and enhancing the design of satellite-borne antennas and communication devices. The ultra-low power consumption space-based IoT system design method of the present invention comprises the following steps: S1. Satellite communication system design: Design the hardware and software structure of the satellite communication system, including satellite equipment, ground equipment and communication protocols, etc. Co-design of multi-port communication machine and antenna array: The multi-beam array antenna adopts high gain and orthogonal design to reduce the transmission power of ground terminal equipment, locate the terminal position, enhance the communication signal of the terminal, perform modulation and demodulation, error checking, etc., and realize the function of space-based IoT communication. S2. Communication protocol design: Design private protocols for satellite-to-ground communication, including data transmission protocols, connection management protocols, etc. S3. Communication data management: Establish a feed data transmission link with the satellite through the gateway station to supervise the communication permissions and traffic of ground terminal equipment.

2. The ultra-low power consumption space-based IoT communication system design method according to claim 1, characterized in that: This invention adopts the collaborative design of antenna and communication machine, and is triggered by the characteristics of radio electromagnetic waves. Because the transmission power of ground terminal equipment is extremely low, the signal reaching the satellite is very weak. The present invention triggers the design of an orthogonally distributed multi-beam array antenna based on the phase fluctuation characteristics of electromagnetic waves in the process of space transmission. Each terminal signal is received by the multi-beam antenna in two orthogonal directions. This method can accurately locate the relative position relationship between the satellite and the terminal equipment, and can effectively overcome the Doppler effect caused by the high-speed movement of the satellite. The multi-port communication receiver combines and calculates the signals according to the fluctuation phase characteristics received by different beams, and amplifies the terminal's micro signal by superimposing and combining N beam energies, thereby realizing the direct connection of the ground terminal micro signal to the satellite.

3. The ultra-low power consumption space-based IoT communication system design method according to claim 1, characterized in that: The satellite is equipped with storage, feed data transmitter, feed antenna, and data transmission antenna. Through the communication link established between the satellite and the gateway, the ground terminal equipment is allowed to connect to the satellite and the traffic management is realized. The specific implementation process is as follows: The ground terminal equipment sends signal data to the satellite; The multi-beam array antenna receives the Bluetooth phase process signals; The multi-port communication receiver modulates and demodulates the communication signal and forms a data stream to be sent to the storage; The data is transferred to the data transmitter and then transmitted to the gateway via the data transmission antenna. The information gateway interprets the data identification code and issues access permission after verification; From the feed link through the feed antenna data transmitter, and then from the fixed storage to the multi-port communication machine; The multi-port communicator sends a permission signal to the terminal from the multi-beam array antenna based on the previously interpreted terminal position, thereby enabling ultra-low power terminal direct communication with the satellite.

4. The ultra-low power consumption space-based IoT communication system design method according to claim 1, characterized in that: Each spoke of a multi-beam array antenna receives radio energy from several concentrated areas, which can have varying degrees of beam overlap. For an N-antenna linear array, approximately N / 2 of its radio receive beams have a smaller space on the circle in the range of elevation angles from -45 degrees to 45 degrees. Although any number of M beams can be formed, these M beams may have varying degrees of spatial overlap. Higher beam overlap can improve the positioning accuracy of terminal radio transmissions. In addition, since satellites travel at 7.8 kilometers per second in low-Earth orbit, if the terminal transmission is long enough to cross from one beam area to an adjacent beam area, then beam overlap will also provide redundancy. Figure 2 shows the calculations necessary to create M focused receive beams for a linear antenna array. The baseband signal received by each of the N antennas is represented by x 1 to x N represents these signals multiplied by the beamformer matrix, denoted by H. To produce a beam, the beamformer matrix applies a constant phase shift to the signal received at antenna k relative to k-1. The phase shift depends on the spacing between the antennas and the elevation angle of the beam to be formed. The phase shifted signals from each antenna are then accumulated together. The phase shift is chosen so that the radio energy at each antenna increases synchronously, thereby maximizing the signal strength in a particular beam direction. The phase shift is calculated by calculating the phase difference of the radio arrival signal at each antenna for a particular beam elevation angle along the direction of the antenna array. These phase shift values ​​are then used by the beamformer matrix in signal processing to align the phases of all received signals by multiplying the input baseband signal by the complex conjugate of the complex exponential representing the phase shift of the radio wave predicted to arrive at each beam elevation angle. When the antenna spoke is split into two spatially offset branches, the phase shift calculation is adjusted to take into account the difference between the branches. offset between, each input baseband signal can also be multiplied by a gain factor to trade off a wider main beam lobe width for a smaller beam lobe amplitude. To create M beams using an N-antenna linear array, a matrix H of size M×N is required, which multiplies the input baseband signal by a complex exponential (and possibly a tapered gain) to create the necessary phase shifts to align the received signals and create the beams. The phase shift used to form a beam at a specific elevation angle in the receive direction can also be used in the transmit direction to form a transmit beam along the same elevation angle. In an alternative embodiment, the beamformer matrix H is selected so that the resulting beams sweep across the ground to offset the motion of the satellite and are also adjusted to offset any changes in the satellite's attitude. In this case, each beam will be focused on a specific area on the earth, and the beam coverage area will not move with the motion of the satellite. In this case, the beamformer matrix H will be composed of time-varying complex exponentials.

5. The ultra-low power consumption space-based IoT communication system design method according to claim 1, characterized in that: The azimuth angle is defined as the propagation angle of the radio wave relative to the direction of the orbital plane, and the elevation angle is defined as the propagation angle of the radio wave relative to the -Z axis of the orbital reference system. When the beam is observed from the earth, since the phase difference of the radio waves arriving at the continuous antennas is a function of the azimuth and elevation of the radio waves received in the spoke reference system, the beam profile of the maximum beam energy is parabolic in shape. Along the linear antenna array, the phase difference of the radio wave carrier of the continuous antennas spaced half a wavelength apart is calculated as: Equation 1: Phase difference = πcos(azimuth_s)sin(elevation), where azimuth_s is the azimuth angle in the spoke reference frame (azimuth_s = O° is the azimuth angle of the radio wave arriving along the length of the spoke). Figure 4 shows several beam profiles for the nine beams formed by each linear antenna spoke for a two-spoke system with perpendicular spokes. These contours would be observed on a flat ground. The contours were created assuming a satellite altitude of 600 km. Ox and Oy represent the phase differences of the arriving radio waves between consecutive antennas of the x and y spokes, respectively. The horizontal contours in the figure are formed by the spokes pointing in the Y direction, and the vertical contours are formed by the spokes pointing in the X direction. In the orbital reference frame, azimuth_x is defined as the azimuth angle of the x spoke and azimuth_y is defined as the azimuth angle of the y spoke. When the spokes are perpendicular, azimuth_x = azimuth_y + 90°. The phase difference between the consecutive antennas of the two spokes is pre-calculated for each received beam formed. For the two-spoke configuration, when the beam receives the terminal symbol transmission from each spoke, we obtain two equations and two unknowns. Equation 2: Phase difference (y spoke) = π cos (azimuth_sy) sin (elevation); Equation 3: Phase difference (x spoke) = πcos(azimuth_sx)sin(elevation), Where azimuth_sy is the azimuth of the radio wave in the y-radiation reference frame, and azimuth_sx is the azimuth of the radio wave in the x-radiation reference frame. Assuming that the satellite's pitch and roll angles are zero and converting them back to the orbital reference frame, we get: Equation 4: azimuth_sy+satellite yaw angle=azimuth Equation 5: azimuth_sx = azimuth_sy + φ Where φ is the direction of the x-spoke relative to the y-spoke, which is 90 degrees when the spoke is vertical. The satellite yaw angle is defined as the azimuth of the Y-spoke relative to the orbital plane. The known variable is the phase difference of the beam generated from the two spokes. The unknowns are the azimuth and elevation of the radio wave, which correspond to the symbol task transmitted from the corresponding terminal. From the above equations, the azimuth and elevation of the radio wave in the orbital reference system can be calculated; These angles define the terminal position on the ground. Since the satellite's position and attitude relative to the Earth are known using an onboard GPS radio, magnetic sensors, and sun sensors, and the attitude estimation method described later in this disclosure, non-zero pitch angles and non-zero roll angles can be integrated into the above equations using appropriate rotation matrices. For each symbol received, the azimuth and elevation of the corresponding radio wave are calculated as described above, and a position coordinate is assigned to that symbol.

6. The ultra-low power consumption space-based IoT communication system design method according to claim 1, characterized in that: In radio communications, orthogonal modulation is used to increase radio sensitivity for a target communication rate by spreading the available energy over as much bandwidth as possible. The disadvantage of orthogonal modulation is its low spectral efficiency. The combination of multi-antenna spoke beamforming and quadrature modulation provides significant performance improvements over single-antenna radios using quadrature modulation by increasing the system’s spectral efficiency. An example of orthogonal modulation is M-ARY frequency shift keying (FSK) modulation. The FFT of the M-ARY FSK symbol is shown in Figure 5. Log2(M) bits are mapped to one of the M orthogonal frequency bins, and one possible bin is sent over the communication channel to encode these bits. The case when M=256 is shown, where 8 bits are encoded to a specific bin frequency; The bits '01001110' = 78 are encoded by the meta frequency in the example. At the receiving end, each received meta is demodulated and converted back to the correct bit. In a shared wireless network, if two orthogonal modulation symbols sent from two different terminals overlap in time, the receiver may be confused about which symbol corresponds to which transmitter. The two terminals overlap in time but not in frequency. A symbol overlaps in time with one or more other orthogonal modulation symbols. Correct decoding can only be guaranteed if the symbol to be decoded does not overlap with other symbols within the orthogonal dimension range (for M-ARYFSK, the orthogonal dimension range is 2m frequency). The spectral efficiency of M-ary orthogonal modulation using a single antenna receiver is approximately Log2(M) / M bits / second / Hz. In multi-radial beamforming, in order to improve the spectral efficiency, the symbols overlapping in time from different terminals are assigned positions and distinguished according to each symbol position. The terminal 1 symbol picked up by beam 4 and beam 3, and the terminal 2 symbol picked up by beam 12 and beam 3, if the two symbols overlap in time but not in frequency, then they can be distinguished and decoded separately because they are detected by unique row and column beam pairs. In order to successfully decode these two symbols with a single antenna receiver, the symbols need to not overlap in time or in orthogonal frequency ranges.

7. The ultra-low power consumption space-based IoT communication system design method according to claim 1, characterized in that: The spectral efficiency of a two-spoke linear antenna receiver using M-ary FSK modulation and N non-overlapping beams per spoke is upper bounded at N*Log2(M) bits / second / Hz, an improvement of N*M over a single antenna receiver using M-ary FSK modulation. Another advantage of using orthogonal modulation is the improvement in energy efficiency. A 64-ARY FSK radio requires approximately 2 times (3dB in decibels) more energy than a 2-ARY FSK radio sending the same size packet over an additive white Gaussian noise (AWGN) channel (with a symbol error probability of 10%). In summary, multi-spoke beamforming receivers offer significant improvements in both network capacity and spectral efficiency over single-antenna receivers. The multi-spoke structure allows for a small antenna array that is easily placed in a small satellite and still provides good network capacity and spectral efficiency.

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