A method and system for unlicensed large-scale random access

Abstract

This invention provides an unlicensed, large-scale random access method and system, belonging to the field of narrowband Internet of Things (IoT) communication technology. It includes: a sensor randomly selecting a preamble sequence, adding a guard interval cyclic prefix, a timing parameter, and a time slot pointer to the preamble sequence to form a preamble code, and combining this with an access request data packet to form a data frame; the sensor copying the data frame N1 times and randomly selecting several time slots to send it to the gateway in orthogonal frequency division multiplexing (OFDM); the gateway receiving and storing the data frames received in each time slot; traversing all time slots, if no collision occurs, extracting the corresponding transmitted data frame from the data receiving window for decoding; for successfully decoded data frames, the gateway eliminating interference from other time slots based on the time slot pointer timing parameter; for successfully accessed sensor terminals, the gateway sending an information packet on the corresponding physical downlink shared channel resource; the sensor receiving the information packet returned by the gateway and using the timing advance information for subsequent data transmission.

Description

Technical Field

[0001] This invention relates to the field of narrowband Internet of Things (IoT) communication technology, and in particular to an unlicensed, large-scale random access method and system. Background Technology

[0002] In terms of network coverage, narrowband IoT communication technology places new demands on both the coverage range and depth of the network. It also requires independent deployment of frequency band resources to resist interference from various factors. Regarding deployment methods, narrowband IoT communication technology modifies low-speed, low-frequency data transmission, thereby improving the stability of the entire system.

[0003] Random Access (RA) is a crucial process for sensor terminals and gateway devices to synchronize uplink and downlink time and frequency, establishing a valid communication link. This process occurs when the user powers on or reconnects after a disconnection. Traditionally, sensor terminals using 4G public networks employ a four-step random access strategy, employing an "instantaneous transmission" strategy. This means that within the sensor's coverage area, if a sensor terminal has a communication need, it immediately initiates access to the gateway without prior link establishment or time-frequency resource allocation. If the gateway cannot demodulate due to data collision, the system will retransmit using a specific mechanism. Terminals typically use a four-step random access process to connect to the gateway: the terminal sends a random access preamble uplink, the gateway responds with a random access response downlink, the terminal requests a random access uplink, and the gateway resolves downlink contention. If the four-step random access fails, the terminal will re-initiate the attempt until the maximum number of attempts is reached or a successful connection is established, resulting in low flexibility. The four-step access process can accommodate low-density devices accessing the public network and utilizing it for data transmission. For situations where there are a large number of densely distributed sensors in a localized area, such as power plants, and where sensor information needs to be uploaded quickly at irregular or regular intervals, the four-step random access strategy will result in significant signaling overhead and access latency, affecting the sensor access speed and consequently the speed at which abnormal data information from the power plant is uploaded. Summary of the Invention

[0004] In view of this, the present invention provides an unlicensed large-scale random access method and system, which adopts a two-step multi-timeslot high-speed random access process, and achieves effective data transmission simultaneously during the two-step access process. This can improve the efficiency of random access of large-scale sensor devices to the gateway and the data transmission efficiency within a region, and has the characteristics of high flexibility and low error rate.

[0005] The technical solution adopted by the embodiments of the present invention to solve its technical problem is as follows:

[0006] An unlicensed, large-scale random access method includes:

[0007] Step S1: The sensor randomly selects a preamble sequence and adds the sensor ID, guard interval cyclic prefix, time timing value, data transmission interval, and time slot pointer of the time slot selected by the sensor to the preamble sequence to form a preamble code. This code is combined with the access request data packet to form a data frame. The preamble code of the data frame and the data packet do not interfere with each other in the time domain and frequency domain.

[0008] Step S2: The sensor copies the data frame N1 times and randomly selects N2 time slots to send it to the gateway in the form of orthogonal frequency division multiplexing.

[0009] Step S3: The gateway receives and stores the data frames received in each time slot, detects the preamble of the data frames received in each time slot, and then traverses all time slots. If no collision occurs in a time slot, the corresponding transmitted data frame is extracted from the data receiving window for decoding. If the gateway detects a collision in a time slot, the time slot in which the collision occurs is skipped.

[0010] Step S4: For a successfully decoded data frame, the gateway performs interference cancellation on the data frames and preambles sent by the sensor in other time slots according to the time slot pointer time selected by the sensor, and determines that the sensor has successfully accessed the network.

[0011] Step S5: For a successfully connected sensor, the gateway sends an information packet on the corresponding physical downlink shared channel resource. The information packet includes the sensor ID, the successful access preamble, the data transmission interval specified by the gateway, and the corresponding timing advance information.

[0012] In step S6, the sensor receives the information returned by the gateway and checks whether the connection is successful. If the connection fails, it re-initiates a random connection. If the connection is successful, it uses the timing advance information and the data transmission interval specified by the gateway for subsequent data transmission.

[0013] Preferably, in step S3, the gateway receives and stores the data frames received in each time slot, and the detection of the preamble of the data frame received in each time slot includes:

[0014] The sensor ID is decoded to obtain the sensor terminal number. The gateway identifies the sensor. If the number is within the range processed by the gateway, the subsequent preamble sequence decoding is continued; otherwise, access is directly rejected. The cyclic prefix of the data frame is decoded to ensure that the sensor information transmission carriers are mutually orthogonal.

[0015] For the aforementioned timing amount, the decoding process determines the timing advance amount set based on the different physical distances between the sensor and the gateway, and compensates for the propagation delay corresponding to the timing advance amount.

[0016] Decode the data transmission interval to obtain the time interval between the sensor repeatedly sending access requests and sending subsequent data to the gateway.

[0017] The time slot pointer is decoded to obtain the time slot for data transmission from the sensor. The gateway stores the time slot and the device number of the sensor.

[0018] Preferably, step S6, which utilizes the timing advance information and the data transmission interval specified by the gateway for subsequent data transmission, includes:

[0019] Step S61: The sensor performs identity authentication based on its own encryption chip, then encrypts the data to be transmitted, and transmits the encrypted data uplink to the gateway based on the timing advance information and the data transmission interval specified by the gateway; the encryption chip and the decryption chip of the gateway use the same encryption and decryption mechanism; the data to be transmitted includes the sensing data acquired by the sensor itself and the data uploaded by the downlink sensor;

[0020] Step S62: After receiving the encrypted data, the gateway uses the decryption chip to decrypt the encrypted data, uploads the decrypted data to the cloud, and returns a confirmation message to the sensor.

[0021] Step S63: The sensor receives the confirmation message returned by the gateway.

[0022] An unlicensed, large-scale random access system includes a sensor terminal and a gateway terminal:

[0023] The sensor terminal initializes the module's peripherals, data interface peripherals, and security encryption interface; it sends commands using AT commands and checks the return value, sets basic parameters, and prepares for network access; it randomly selects a preamble sequence, adds the sensor ID, guard interval cyclic prefix, time timing value, data transmission interval, and time slot pointer of the time slot selected by the sensor terminal to the preamble sequence to form a preamble code, and combines it with the access request data packet to form a data frame. The preamble code of the data frame and the data packet do not interfere with each other in the time domain and frequency domain.

[0024] The gateway receives and stores data frames received in each time slot, detects the preamble of each data frame received in each time slot, and then iterates through all time slots. If no collision occurs in a time slot, the gateway extracts the corresponding transmitted data frame from the data receiving window for decoding. If the gateway detects a time slot collision, it skips the time slot where the collision occurred. For successfully decoded data frames, the gateway performs interference cancellation on data frames and preambles transmitted by the sensor in other time slots according to the time slot pointer time selected by the sensor, and determines that the sensor has successfully accessed the network. For successfully accessed sensor terminals, the gateway transmits an information packet on the corresponding physical downlink shared channel resource. The information packet includes the sensor ID, information about the successful access preamble, the data transmission interval specified by the gateway, and the corresponding timing advance information.

[0025] The sensor receives information returned by the gateway and checks whether the connection was successful. If the connection fails, it re-initiates a random connection. If the connection is successful, it uses the timing advance information and the data transmission interval specified by the gateway to perform subsequent data transmission.

[0026] Preferably, the gateway receives and stores the data frames received in each time slot, and the detection of the preamble of the data frame received in each time slot specifically involves:

[0027] The sensor ID is decoded to obtain the sensor terminal number. The gateway identifies the sensor. If the number is within the range processed by the gateway, the subsequent preamble sequence decoding is continued; otherwise, access is directly rejected.

[0028] Decode the cyclic prefix of the data frame to ensure that the sensor information transmission carriers are mutually orthogonal;

[0029] For the aforementioned timing amount, the decoding process determines the timing advance amount set based on the different physical distances between the sensor and the gateway, and compensates for the propagation delay corresponding to the timing advance amount.

[0030] Decode the data transmission interval to obtain the time interval between the sensor repeatedly sending access requests and sending subsequent data to the gateway.

[0031] The time slot pointer is decoded to obtain the time slot for data transmission from the sensor. The gateway stores the time slot and the device number of the sensor.

[0032] Preferably, the sensor performs identity authentication based on its own encryption chip, then encrypts the data to be transmitted, and transmits the encrypted data uplink to the gateway based on the timing advance information and the data transmission interval specified by the gateway; the encryption chip and the decryption chip of the gateway use the same encryption and decryption mechanism; the data to be transmitted includes the sensing data acquired by the sensor itself and the data uploaded by the downlink sensor;

[0033] After receiving the encrypted data, the gateway uses the decryption chip to decrypt the encrypted data, uploads the decrypted data to the cloud, and returns a confirmation message to the sensor.

[0034] The sensor receives the confirmation message returned by the gateway.

[0035] Preferably, the structure of the sensor terminal consists of a main control module, a radio frequency module, a communication processing module, a security encryption module, and a power supply module and a crystal oscillator module to support the operation of the module.

[0036] The main control module is used for the operation and data processing of the sensor, including data acquisition, processing, storage and transmission, as well as reading data acquired by external sensors;

[0037] The radio frequency module is used to control the reception of radio frequency signals at the gateway and to preprocess the radio frequency signals. The preprocessing includes filtering, signal enhancement, and signal amplification. The preprocessed radio frequency signal is then sent to the main control module.

[0038] The communication processing module is used to establish a communication connection with the downlink sensor; securely access the gateway; and perform data transmission with the gateway.

[0039] The security encryption module is used to implement data encryption and decryption, identity authentication, and access control;

[0040] The power module is used to supply power to the various devices in the sensor terminal;

[0041] The crystal oscillator is used to provide a clock cycle for the sensor.

[0042] Preferably, the system also includes a cloud, and the cloud, the gateway, and the sensor are connected in a downlink communication relationship. The sensor connects to the gateway via an unauthorized random access method, and the gateway uploads the data transmitted by the sensor to the cloud. The cloud is used to receive the data uploaded by the gateway.

[0043] Preferably, the system adopts narrowband wireless IoT and LPWAN low-power wide area network transmission technology.

[0044] As can be seen from the above technical solution, the unlicensed large-scale random access method and system provided by the embodiments of the present invention is an improved two-step random access mechanism. The process is as follows: The sensor randomly selects a preamble sequence, and adds the sensor ID, guard interval cyclic prefix, time timing quantity, data transmission interval, and time slot pointer of the time slot selected by the sensor to the preamble sequence to form a preamble code. This preamble code is combined with the access request data packet to form a data frame. The preamble code of the data frame and the data packet do not interfere with each other in the time domain and frequency domain. The sensor copies the data frame N1 times and randomly selects N2 time slots to send it to the gateway in the form of orthogonal frequency division multiplexing. The gateway receives and stores the data frames received in each time slot, detects the preamble code of the data frames received in each time slot, and then traverses all time slots. If no collision occurs in the time slots, the preamble code is extracted from the data receiving window. Data frames should be sent for decoding. If the gateway detects a collision in a time slot, it skips the colliding time slot. For successfully decoded data frames, the gateway performs interference cancellation on data frames and preambles sent by the sensor in other time slots based on the time slot pointer time selected by the sensor, and determines that the sensor has successfully accessed the network. For successfully accessed sensors, the gateway sends an information packet on the corresponding physical downlink shared channel resource. The information packet includes the sensor ID, the successful access preamble information, the data transmission interval specified by the gateway, and the corresponding timing advance information. The sensor receives the information returned by the gateway and checks whether the access was successful. If the access is unsuccessful, it re-initiates random access. If the access is successful, it uses the timing advance information and the data transmission interval specified by the gateway for subsequent data transmission. This invention adopts a two-step multi-time slot high-speed random access process, achieving effective data transmission simultaneously during the two-step access process. This can improve the efficiency of random access of large-scale sensor devices to the gateway and the data transmission efficiency within a region, and has the characteristics of high flexibility and low error rate. Attached Figure Description

[0045] Figure 1 This is a flowchart of an unlicensed large-scale random access method according to the present invention.

[0046] Figure 2 This is a hardware framework diagram for the sensor. Detailed Implementation

[0047] The technical solution and effects of the present invention will be further described in detail below with reference to the accompanying drawings.

[0048] refer to Figure 1 As shown, the present invention provides an unlicensed large-scale random access method, comprising:

[0049] Step S1: The sensor randomly selects a preamble sequence and adds the sensor ID, guard interval cyclic prefix, time timing value, data transmission interval, and time slot pointer of the time slot selected by the sensor to the preamble sequence to form a preamble code. This code is combined with the access request data packet to form a data frame. The preamble code of the data frame and the data packet do not interfere with each other in the time domain and frequency domain.

[0050] In step S2, the sensor copies the data frame N1 (N1≥2) times and randomly selects N2 (N1≥2) time slots to send it to the gateway in the form of orthogonal frequency division multiplexing.

[0051] Step S3: The gateway receives and stores the data frames received in each time slot, detects the preamble of the data frames received in each time slot, and then traverses all time slots. If no collision occurs in a time slot, the corresponding transmitted data frame is extracted from the data receiving window for decoding. If the gateway detects a collision in a time slot, the time slot in which the collision occurs is skipped.

[0052] Step S4: For successfully decoded data frames, the gateway performs interference cancellation on data frames and preambles sent by the sensor in other time slots according to the time slot pointer time selected by the sensor, and determines that the sensor has successfully accessed the network.

[0053] Step S5: For a successfully connected sensor, the gateway sends an information packet on the corresponding physical downlink shared channel resource. The information packet includes the sensor ID, the successful access preamble, the data transmission interval specified by the gateway, and the corresponding timing advance information.

[0054] In step S6, the sensor receives the information returned by the gateway and checks whether the connection was successful. If the connection fails, it re-initiates a random connection. If the connection is successful, it uses the timing advance information and the data transmission interval specified by the gateway to perform subsequent data transmission.

[0055] In step S3, the gateway receives and stores the data frames received in each time slot, and the detection of the preamble of the data frame received in each time slot includes:

[0056] Step S31: Decode the sensor ID to obtain the sensor terminal number. The gateway identifies the sensor. If the number is within the range processed by the gateway, it continues to decode the subsequent preamble sequence; otherwise, it directly rejects access.

[0057] Step S32: Decode the cyclic prefix of the data frame to ensure that the carrier waves transmitting sensor information are mutually orthogonal;

[0058] Step S33: For the timing quantity, decode the timing advance amount set according to the different physical distances between the sensor and the gateway, and compensate for the propagation delay corresponding to the timing advance amount;

[0059] Step S34: Decode the data transmission interval to obtain the time interval between the sensor repeatedly sending access requests and sending subsequent data to the gateway.

[0060] Step S35: Decode the time slot pointer to obtain the time slot for data transmission from the sensor end. The gateway end stores the time slot and the device number of the sensor end.

[0061] Step S6, which utilizes the advance timing information and the data transmission interval specified by the gateway for subsequent data transmission, includes the following specific implementation:

[0062] In step S61, the sensor performs identity authentication based on its own encryption chip, then encrypts the data to be transmitted, and sends the encrypted data uplink to the gateway based on the advance timing information and the data transmission interval specified by the gateway; the encryption chip and the decryption chip of the gateway use the same encryption and decryption mechanism; the data to be transmitted includes the sensing data acquired by the sensor itself and the data uploaded by the downlink sensor;

[0063] Step S62: After receiving the encrypted data, the gateway uses the decryption chip to decrypt the encrypted data, uploads the decrypted data to the cloud, and returns a confirmation message to the sensor.

[0064] Step S63: The sensor receives the confirmation message returned by the gateway.

[0065] Furthermore, this invention provides an unlicensed, large-scale random access system that employs narrowband wireless IoT and LPWAN (Low Power Wide Area Network) transmission technologies for execution. Figure 1 The method involves a system comprising a sensor terminal and a gateway terminal, wherein:

[0066] At the sensor end, initialize the module's peripherals, data interface peripherals, and security encryption interface; send commands using AT commands and check the return values, set basic parameters to prepare for network access; randomly select a preamble sequence, add the sensor ID, guard interval cyclic prefix, time timing quantity, data transmission interval, and the time slot pointer of the time slot selected by the sensor end to the preamble sequence to form a preamble code, and combine it with the access request data packet to form a data frame. The preamble code of the data frame and the data packet do not interfere with each other in the time domain and frequency domain.

[0067] At the gateway, the data frames received in each time slot are received and stored. The gateway detects the preamble of each data frame received in each time slot and then iterates through all time slots. If no collision occurs in a time slot, the gateway extracts the corresponding transmitted data frame from the data receiving window for decoding. If the gateway detects a collision, it skips the time slot where the collision occurred. For successfully decoded data frames, the gateway performs interference cancellation on the data frames and preambles transmitted by the sensor in other time slots according to the time slot pointer time selected by the sensor, and determines that the sensor has successfully accessed the network. For successfully accessed sensors, the gateway transmits an information packet on the corresponding physical downlink shared channel resource. The information packet includes the sensor ID, the successful access preamble information, the data transmission interval specified by the gateway, and the corresponding timing advance information.

[0068] At the sensor end, the information returned by the gateway end is received to check whether the connection is successful. If the connection fails, a random connection is re-initiated. If the connection is successful, subsequent data transmission is carried out using the timing advance information and the data transmission interval specified by the gateway.

[0069] The gateway receives and stores the data frames received in each time slot, and detects the preamble of the data frames received in each time slot as follows:

[0070] Decode the sensor ID to obtain the sensor number. The gateway identifies the sensor. If the number is within the range that the gateway can process, it continues to decode the subsequent preamble sequence; otherwise, it directly rejects access.

[0071] Decode the cyclic prefix of the data frame to ensure that the carrier waves transmitting sensor information are orthogonal;

[0072] For timing parameters, the decoder sets a timing advance based on the different physical distances between the sensor and the gateway, and compensates for the propagation delay corresponding to the timing advance.

[0073] Decode the data transmission interval to obtain the time interval between the sensor repeatedly sending access requests and sending subsequent data to the gateway;

[0074] The time slot pointer is decoded to obtain the time slot for data transmission from the sensor. The gateway stores the time slot and the device number of the sensor.

[0075] At the sensor end, authentication is performed based on its own encryption chip, and then the data to be transmitted is encrypted. Based on the advance timing information and the data transmission interval specified by the gateway, the encrypted data is sent uplink to the gateway. The encryption chip and the decryption chip at the gateway end use the same encryption and decryption mechanism. The data to be transmitted includes the sensing data acquired by the sensor end itself and the data uploaded by the downlink sensor.

[0076] At the gateway end, after receiving encrypted data, the gateway uses a decryption chip to decrypt the encrypted data, uploads the decrypted data to the cloud, and returns a confirmation message to the sensor end.

[0077] The sensor receives an acknowledgment message from the gateway.

[0078] Please refer to the above as well. Figure 2 As shown, the sensor end structure consists of a main control module, an radio frequency module, a communication processing module, a security encryption module, and a power supply module and a crystal oscillator module to support the operation of the module.

[0079] The main control module is used for the operation and data processing of the sensor, including data acquisition, processing, storage and transmission, as well as reading data acquired by external sensors;

[0080] The radio frequency (RF) module is used to control the reception of RF signals at the gateway and to preprocess the RF signals. The preprocessing includes filtering, signal enhancement, and signal amplification. The preprocessed RF signals are then sent to the main control module.

[0081] The communication processing module is used to establish communication connections with downlink sensors; securely access the gateway; and perform data transmission with the gateway, thereby achieving secure and reliable data transmission.

[0082] The security encryption module is used to implement security functions such as data encryption and decryption, identity authentication, and access control, to ensure the confidentiality, integrity, and availability of data, and to prevent data leakage and attacks.

[0083] The power module is used to supply power to the various components in the sensor.

[0084] A crystal oscillator is used to provide a clock cycle for the sensor.

[0085] Furthermore, the system may also include a cloud, in which the cloud, gateway, and sensor are connected in a downlink communication relationship. The sensor connects to the gateway through an unauthorized random access method, and the gateway sends the data transmitted by the sensor to the cloud. The cloud is used to receive the data sent by the gateway, forming a complete data acquisition system of node module + gateway + cloud.

[0086] The unlicensed random access method of this invention provides a faster and more efficient access solution for terminals joining gateways. Traditional two-step or four-step random access schemes first initiate an access request to the gateway using a preamble. After successful access, the gateway determines the data transmission interval for subsequent data transmission from the sensor, and the sensor then transmits data. This can effectively alleviate the transmission pressure on the gateway when data transmission is busy, or improve the gateway's transmission efficiency when data transmission is idle. The method of this invention combines the preamble with the data packet itself, sending it to the gateway through multiple time slots. This allows data transmission and access request functions to occur simultaneously. The gateway accepts access and simultaneously indicates successful data packet reception. This unlicensed random access scheme greatly improves access efficiency and transmission efficiency.

[0087] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for unlicensed, large-scale random access, characterized in that, include: Step S1: The sensor randomly selects a preamble sequence and adds the sensor ID, guard interval cyclic prefix, time timing value, data transmission interval, and time slot pointer of the time slot selected by the sensor to the preamble sequence to form a preamble code. This code is combined with the access request data packet to form a data frame. The preamble code of the data frame and the data packet do not interfere with each other in the time domain and frequency domain. Step S2: The sensor copies the data frame N1 times and randomly selects N2 time slots to send it to the gateway in the form of orthogonal frequency division multiplexing. Step S3: The gateway receives and stores the data frames received in each time slot, detects the preamble of the data frames received in each time slot, and then traverses all time slots. If no collision occurs in the time slots, the corresponding transmitted data frame is extracted from the data receiving window for decoding. If the gateway detects a collision in the discovery time slot, it skips the time slot where the collision occurred. Step S4: For a successfully decoded data frame, the gateway performs interference cancellation on the data frames and preambles sent by the sensor in other time slots according to the time slot pointer time selected by the sensor, and determines that the sensor has successfully accessed the network. Step S5: For a successfully connected sensor, the gateway sends an information packet on the corresponding physical downlink shared channel resource. The information packet includes the sensor ID, the successful access preamble, the data transmission interval specified by the gateway, and the corresponding timing advance information. In step S6, the sensor receives the information returned by the gateway and checks whether the connection is successful. If the connection fails, it re-initiates a random connection. If the connection is successful, it uses the timing advance information and the data transmission interval specified by the gateway for subsequent data transmission.

2. The unlicensed large-scale random access method as described in claim 1, characterized in that, In step S3, the gateway receives and stores the data frames received in each time slot, and the detection of the preamble of the data frame received in each time slot includes: Step S31: Decode the sensor ID to obtain the sensor terminal number. The gateway identifies the sensor. If the number is within the range processed by the gateway, continue decoding the subsequent preamble sequence; otherwise, directly reject the access. Step S32: Decode the cyclic prefix of the data frame to ensure that the sensor information transmission carriers are mutually orthogonal; Step S33: For the time timing amount, decode the timing advance amount set according to the different physical distances between the sensor and the gateway, and compensate for the propagation delay corresponding to the time advance amount; Step S34: Decode the data transmission interval to obtain the time interval between the sensor end repeatedly sending access requests and sending subsequent data to the gateway end; Step S35: Decode the time slot pointer to obtain the time slot for data transmission from the sensor end. The gateway end stores the time slot and the device number of the sensor end.

3. The unlicensed large-scale random access method as described in claim 1, characterized in that, Step S6, which utilizes the timing advance information and the data transmission interval specified by the gateway for subsequent data transmission, includes: Step S61: The sensor performs identity authentication based on its own encryption chip, then encrypts the data to be transmitted, and transmits the encrypted data uplink to the gateway based on the timing advance information and the data transmission interval specified by the gateway; the encryption chip and the decryption chip of the gateway use the same encryption and decryption mechanism; the data to be transmitted includes the sensing data acquired by the sensor itself and the data uploaded by the downlink sensor; Step S62: After receiving the encrypted data, the gateway uses the decryption chip to decrypt the encrypted data, uploads the decrypted data to the cloud, and returns a confirmation message to the sensor. Step S63: The sensor receives the confirmation message returned by the gateway.

4. An unlicensed, large-scale random access system, characterized in that, Including the sensor end and the gateway end: The sensor terminal initializes the module's related peripherals, data interface peripherals, and security encryption interface; Send commands using AT commands and check the return value, set basic parameters to prepare for network access; randomly select a preamble sequence, add sensor ID, guard interval cyclic prefix, time timing quantity, data transmission interval, and time slot pointer of the time slot selected by the sensor to the preamble sequence to form a preamble code, and combine it with the access request data packet to form a data frame. The preamble code of the data frame and the data packet do not interfere with each other in the time domain and frequency domain. The gateway receives and stores the data frames received in each time slot, detects the preamble of the data frames received in each time slot, and then traverses all time slots. If no collision occurs in the time slots, the corresponding transmitted data frame is extracted from the data receiving window and decoded. If the gateway detects a collision in a time slot, it skips the time slot where the collision occurred. For successfully decoded data frames, the gateway performs interference cancellation on data frames and preambles sent by the sensor in other time slots according to the time slot pointer timing selected by the sensor, and determines that the sensor has successfully accessed the network. For successfully accessed sensor terminals, an information packet is sent on the corresponding physical downlink shared channel resource. The information packet includes the sensor ID, information about the successful access preamble, the data transmission interval specified by the gateway, and the corresponding timing advance information. The sensor receives information returned by the gateway and checks whether the connection was successful. If the connection fails, it re-initiates a random connection. If the connection is successful, it uses the timing advance information and the data transmission interval specified by the gateway to perform subsequent data transmission.

5. The unlicensed large-scale random access system as described in claim 4, characterized in that: The gateway receives and stores the data frames received in each time slot, and the detection of the preamble of the data frame received in each time slot is specifically as follows: The sensor ID is decoded to obtain the sensor terminal number. The gateway identifies the sensor. If the number is within the range processed by the gateway, the subsequent preamble sequence decoding is continued; otherwise, access is directly rejected. Decode the cyclic prefix of the data frame to ensure that the sensor information transmission carriers are mutually orthogonal; For the aforementioned timing amount, the decoding process determines the timing advance amount set based on the different physical distances between the sensor and the gateway, and compensates for the propagation delay corresponding to the timing advance amount. Decode the data transmission interval to obtain the time interval between the sensor repeatedly sending access requests and sending subsequent data to the gateway. The time slot pointer is decoded to obtain the time slot for data transmission from the sensor. The gateway stores the time slot and the device number of the sensor.

6. The unlicensed large-scale random access system as described in claim 4, characterized in that: The sensor performs identity authentication based on its own encryption chip, then encrypts the data to be transmitted, and transmits the encrypted data uplink to the gateway based on the timing advance information and the data transmission interval specified by the gateway; the encryption chip and the decryption chip of the gateway use the same encryption and decryption mechanism; the data to be transmitted includes the sensing data acquired by the sensor itself and the data uploaded by the downlink sensor; After receiving the encrypted data, the gateway uses the decryption chip to decrypt the encrypted data, uploads the decrypted data to the cloud, and returns a confirmation message to the sensor. The sensor receives the confirmation message returned by the gateway.

7. The unlicensed large-scale random access system as described in claim 4, characterized in that, The sensor terminal consists of a main control module, an radio frequency module, a communication processing module, a security encryption module, a power supply module and a crystal oscillator module that support the operation of the module. The main control module is used for the operation and data processing of the sensor, including data acquisition, processing, storage and transmission, as well as reading data acquired by external sensors; The radio frequency module is used to control the reception of radio frequency signals at the gateway and to preprocess the radio frequency signals. The preprocessing includes filtering, signal enhancement, and signal amplification. The preprocessed radio frequency signal is then sent to the main control module. The communication processing module is used to establish a communication connection with the downlink sensor and securely access the gateway. Data transmission is performed between the gateway and the gateway. The security encryption module is used to implement data encryption and decryption, identity authentication, and access control; The power module is used to supply power to the various devices in the sensor terminal; The crystal oscillator is used to provide a clock cycle for the sensor.

8. The unlicensed large-scale random access system as described in claim 4, characterized in that, The system also includes a cloud platform. The cloud platform, the gateway, and the sensor are connected in a downlink communication relationship. The sensor connects to the gateway via an unauthorized random access method. The gateway uploads the data transmitted by the sensor to the cloud platform. The cloud platform is used to receive the data uploaded by the gateway.

9. The unlicensed large-scale random access system as described in claim 4, characterized in that, The system adopts narrowband wireless IoT and LPWAN low-power wide area network transmission technology.

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