Authorization-free scale random access method and system

Abstract

The invention provides an authorization-free scale random access method and system, and belongs to the technical field of narrowband Internet of Things communication. Comprising the following steps: randomly selecting a preamble sequence by a sensor end, adding a guard interval cyclic prefix, a time timing amount and a time slot pointer into the preamble sequence to form a preamble, and combining with an access request data packet to form a data frame; the sensor end copies a data frame for N1 copies and randomly selects a plurality of time slots to send the data frame to the gateway end in an orthogonal frequency division multiplexing form; the gateway end receives and stores the data frame received by each time slot; traversing all the time slots, and if the time slots do not collide, extracting corresponding sending data frames in the data receiving window for decoding; for the successfully decoded data frame, the gateway end eliminates other time slot data interference according to the time timing amount of the time slot pointer; the gateway end sends an information packet on a corresponding physical downlink shared channel resource for the sensor end which is successfully accessed; and the sensor end receives the information packet returned by the gateway end, and performs subsequent data transmission by using the timing advance information.

Description

Technical Field

[0001] The present invention relates to the field of narrowband Internet of Things communication technology, and in particular to a method and system for authorization-free large-scale random access. Background Art

[0002] In terms of network coverage, narrowband IoT communication technology has new requirements for network coverage range and network coverage depth, and also independently deploys frequency band resources to resist interference from various factors. In terms of deployment methods, narrowband IoT communication technology transforms low-speed and low-frequency data transmission, thereby improving the stability of the entire system.

[0003] Random access (RA) is an important process for the sensor end and the gateway device to complete the uplink and downlink time and frequency synchronization and establish an effective communication link. The process occurs when the user turns on the device or reconnects after the connection is disconnected. Traditional sensor applications using 4G public networks, such as 4G or 5G, adopt a four-step random access strategy. Random access adopts an "instant send" strategy, that is, within the sensor range covered by the gateway, once the sensor terminal has a communication demand, it will immediately initiate access to the gateway without establishing a link or allocating time and frequency resources in advance. If the gateway end cannot demodulate due to data collision, the system will retransmit it using a specific mechanism. The terminal usually uses a four-step random access process to access the gateway. The specific process is: the terminal sends a random access preamble in the uplink, the gateway feeds back a random access response in the downlink, the terminal sends a random access request in the uplink, and the gateway resolves the downlink contention. When the four-step random access fails, the terminal will re-initiate a four-step random access attempt until the maximum number of random access attempts is reached or the random access succeeds, which has low flexibility. The four-step access process can meet the needs of small-density devices to access the public network and use the public network for transmission. However, for local areas such as power stations where there are a large number of densely distributed sensors and sensor information needs to be uploaded quickly at irregular or regular intervals, the four-step random access strategy will bring large signaling overhead and access delay, affecting the access speed of the sensors and, in turn, the upload speed of abnormal data information of the power station. Summary of the invention

[0004] In view of this, the present invention provides an authorization-free large-scale random access method and system, which adopts a two-step multi-time slot high-speed random access process, and simultaneously realizes effective data transmission in the two-step access process, which can improve the efficiency of random access of large-scale sensor devices in the regional range to the gateway end and the data transmission efficiency, and has the characteristics of high flexibility and low error rate.

[0005] The technical solution adopted by the embodiment of the present invention to solve the technical problem is: A method for random access without authorization, comprising: Step S1, the sensor end randomly selects a preamble sequence, adds a sensor ID, a guard interval cyclic prefix, a time timing quantity, a data transmission interval, and a time slot pointer of a time slot selected by the sensor end to the preamble sequence to form a preamble code, and combines the access request data packet to form a data frame, wherein the preamble code of the data frame and the data packet do not interfere with each other in the time domain and the frequency domain; Step S2, the sensor end copies N1 copies of the data frame and randomly selects N2 time slots to send to the gateway end 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 code of the data frame received in each time slot, and then traverses all time slots. If no collision occurs in the time slot, the corresponding transmission data frame is extracted from the data receiving window for decoding; if the gateway detects that a collision occurs in the time slot, the time slot where the collision occurs is skipped; Step S4, for the successfully decoded data frame, the gateway end performs interference elimination on the data frame and preamble sent by the sensor end in other time slots according to the time slot pointer time timing quantity selected by the sensor end, and determines that the sensor end is successfully connected; Step S5, the gateway sends an information packet to the successfully accessed sensor on the corresponding physical downlink shared channel resources, wherein the information packet includes the sensor ID, the information of the successful access preamble, the data transmission interval specified by the gateway, and the corresponding timing advance information; Step S6, the sensor receives the information returned by the gateway, detects whether the access is successful, and if the access is unsuccessful, re-initiates random access; if the access is successful, the timing advance information and the data transmission interval specified by the gateway are used for subsequent data transmission.

[0006] Preferably, in step S3, the gateway receives and stores the data frames received in each time slot, and detecting the preamble code of the data frame received in each time slot includes: Decode the sensor ID to obtain the sensor end number. The gateway identifies the identity of the sensor. If the number is within the gateway processing range, continue to decode the subsequent leading sequence, otherwise directly deny access; decode the cyclic prefix of the data frame to ensure that the sensor information transmission carriers are orthogonal to each other; For the time timing quantity, decoding the timing advance quantity set according to the different physical distances between the sensor and the gateway, and compensating for the propagation delay corresponding to the timing advance quantity; Decoding the data transmission interval to obtain the time interval between the sensor end repeatedly sending the access request and sending subsequent data to the gateway end; The time slot pointer is decoded to obtain the time slot for the sensor end to transmit data, and the gateway end stores the time slot and the device number of the sensor end.

[0007] Preferably, the step S6 of performing subsequent data transmission using the timing advance information and the data transmission interval specified by the gateway includes: Step S61, the sensor end performs identity authentication based on its own encryption chip, and then encrypts the data to be transmitted, and transmits the encrypted data uplink to the gateway end 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 end use the same encryption and decryption mechanism; the data to be transmitted includes the sensor data obtained by the sensor end 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.

[0008] A non-licensed large-scale random access system includes a sensor end and a gateway end: The sensor end initializes module-related peripherals, data interface peripherals, and security encryption interfaces; uses AT commands to send commands and check return values, sets basic parameters to prepare for network access; randomly selects a preamble sequence, adds a sensor ID, a protection interval cyclic prefix, a time timing quantity, a data transmission interval, and a time slot pointer of a time slot selected by the sensor end to the preamble sequence to form a preamble code, and combines an access request data packet to form a data frame, wherein the preamble code of the data frame and the data packet do not interfere with each other in the time domain and the frequency domain; The gateway receives and stores the data frames received in each time slot, detects the preamble code of the data frame received in each time slot, and then traverses all time slots. If no time slot collision occurs, the corresponding sent data frame is extracted in the data receiving window for decoding; if the gateway detects that a time slot collision occurs, the time slot where the collision occurs is skipped; for the successfully decoded data frame, the gateway eliminates interference with the data frame and preamble code sent by the sensor end in other time slots according to the time slot pointer time timing amount selected by the sensor end, and determines that the sensor end is successfully connected; for the successfully connected sensor end, an information packet is sent on the corresponding physical downlink shared channel resource, and the information packet includes the sensor ID, the information of the successful access preamble code, the data sending interval specified by the gateway, and the corresponding timing advance information; The sensor end receives the information returned by the gateway end, detects whether the access is successful, and if the access is unsuccessful, re-initiates random access; if the access is successful, the timing advance information and the data sending interval specified by the gateway are used for subsequent data transmission.

[0009] Preferably, the gateway receives and stores the data frames received in each time slot, and detects the preamble code of the data frame received in each time slot as follows: Decode the sensor ID to obtain the sensor end number, and the gateway end identifies the identity of the sensor. If the number is within the gateway processing range, continue to decode the subsequent leading sequence, otherwise directly deny access; Decoding a cyclic prefix of the data frame to ensure that sensor information transmission carriers are orthogonal to each other; For the time timing quantity, decoding the timing advance quantity set according to the different physical distances between the sensor and the gateway, and compensating for the propagation delay corresponding to the timing advance quantity; Decoding the data transmission interval to obtain the time interval between the sensor end repeatedly sending the access request and sending subsequent data to the gateway end; The time slot pointer is decoded to obtain the time slot for the sensor end to transmit data, and the gateway end stores the time slot and the device number of the sensor end.

[0010] Preferably, the sensor end performs identity authentication based on its own encryption chip, and then encrypts the data to be transmitted, and transmits the encrypted data uplink to the gateway end 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 end use the same encryption and decryption mechanism; the data to be transmitted includes the sensor data obtained by the sensor end 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 end receives the confirmation message returned by the gateway end.

[0011] Preferably, the structure of the sensor end is composed of a main control module, a radio frequency module, a communication processing module, a security encryption module, and a power 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 end, including data acquisition, processing, storage and transmission, and reading data collected by external sensors; The RF module is used to control the reception of RF signals at the gateway end and to preprocess RF signals, wherein the preprocessing includes filtering, signal enhancement and signal amplification, and the preprocessed RF signals are sent to the main control module; The communication processing module is used to establish a communication connection with the downlink sensor; securely access the gateway end; and perform data transmission with the gateway end; The security encryption module is used to implement data encryption and decryption, identity authentication, and access control; The power supply module is used to supply power to each device in the sensor end; The crystal oscillator is used to provide a clock beat for the sensor end.

[0012] Preferably, the system also includes a cloud, and the cloud, the gateway, and the sensor are in a downlink communication connection relationship in sequence. The sensor accesses 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.

[0013] Preferably, the system uses narrowband wireless Internet of Things and LPWAN low-power wide area network transmission technology.

[0014] It can be seen from the above technical solution that an unlicensed large-scale random access method and system provided by an embodiment of the present invention is an improved two-step random access mechanism, and the process is as follows: the sensor end randomly selects a preamble sequence, adds a sensor ID, a protection interval cyclic prefix, a time timing quantity, a data transmission interval, and a time slot pointer of the time slot selected by the sensor end to the preamble sequence to form a preamble code, and combines an access request data packet to form a data frame, and the preamble code of the data frame and the data packet do not interfere with each other in the time domain and the frequency domain; the sensor end copies the data frame N1 copies and randomly selects N2 time slots to send to the gateway end in the form of orthogonal frequency division multiplexing; the gateway end receives and stores the data frames received in each time slot, detects the preamble code of the data frame received in each time slot, and then traverses all time slots. If no collision occurs in the time slot, the corresponding data frame is extracted in the data receiving window. The data frame should be sent for decoding; if the gateway detects that a time slot collision occurs, the time slot where the collision occurs is skipped; for the successfully decoded data frame, the gateway eliminates interference with the data frame and preamble sent by the sensor end in other time slots according to the time slot pointer time timing amount selected by the sensor end, and determines that the sensor end has successfully accessed; for the successfully accessed sensor end, the gateway sends an information packet on the corresponding physical downlink shared channel resource, and the information packet includes the sensor ID, the information of the successful access preamble, the data transmission interval specified by the gateway, and the corresponding timing advance information; the sensor end receives the information returned by the gateway end, detects whether the access is successful, and if the access fails, re-initiates random access; if the access is successful, the timing advance information and the data transmission interval specified by the gateway are used for subsequent data transmission. The present invention adopts a two-step multi-time slot high-speed random access process, and realizes effective data transmission simultaneously in the two-step access process, which can improve the efficiency of random access of large-scale sensor equipment to the gateway end within the regional range and the data transmission efficiency, and has the characteristics of high flexibility and low error rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 The present invention is a flowchart of a method for random access without authorization.

[0016] Figure 2 This is the hardware framework diagram of the sensor side. DETAILED DESCRIPTION

[0017] The technical scheme and technical effects of the present invention are further elaborated in detail below in conjunction with the accompanying drawings of the present invention.

[0018] refer to Figure 1 As shown, the present invention provides a method for random access without authorization, including: Step S1, the sensor end randomly selects a preamble sequence, adds the sensor ID, the guard interval cyclic prefix, the time timing, the 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 combines 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 end copies N1 (N1≥2) copies of the data frame and randomly selects N2 (N1≥2) time slots to send to the gateway end 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 code of the data frame received in each time slot, and then traverses all time slots. If no collision occurs in the time slot, the corresponding transmission data frame is extracted from the data receiving window for decoding; if the gateway detects that a collision occurs in the time slot, the time slot where the collision occurs is skipped; Step S4, for the successfully decoded data frame, the gateway eliminates interference with the data frame and preamble sent by the sensor in other time slots according to the time slot pointer time timing quantity selected by the sensor, and determines that the sensor is successfully connected; Step S5, the gateway sends an information packet to the successfully accessed sensor on the corresponding physical downlink shared channel resources, where the information packet includes the sensor ID, the information of the successful access preamble, the data transmission interval specified by the gateway, and the corresponding timing advance information; Step S6, the sensor receives the information returned by the gateway and detects whether the access is successful. If the access is unsuccessful, random access is re-initiated; if the access is successful, subsequent data transmission is performed using the timing advance information and the data transmission interval specified by the gateway.

[0019] Wherein, in step S3, the gateway receives and stores the data frames received in each time slot, and detecting the preamble code of the data frame received in each time slot includes: Step S31, decoding the sensor ID to obtain the sensor end number, the gateway end identifies the identity of the sensor, if the number is within the gateway processing range, then continue to decode the subsequent leading sequence, otherwise directly deny access; Step S32, decoding the cyclic prefix of the data frame to ensure that the sensor information transmission carriers are orthogonal to each other; Step S33, for the time timing quantity, decoding the timing advance quantity set according to the different physical distances between the sensor and the gateway, and compensating for the propagation delay corresponding to the timing advance quantity; Step S34, decoding the data transmission interval to obtain the time interval for the sensor end to repeatedly send the access request and send subsequent data to the gateway end; Step S35, decoding the time slot pointer to obtain the time slot for the sensor end to transmit data, and the gateway end stores the time slot and the device number of the sensor end.

[0020] The specific implementation of step S6 using the timing advance information and the data transmission interval specified by the gateway to perform subsequent data transmission includes: Step S61, the sensor end performs identity authentication based on its own encryption chip, and then encrypts the data to be transmitted, and sends the encrypted data uplink to the gateway end 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 end use the same encryption and decryption mechanism; the data to be transmitted includes the sensor data obtained by the sensor end 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 a confirmation message returned by the gateway.

[0021] Furthermore, the present invention provides a non-licensed large-scale random access system, which adopts narrowband wireless Internet of Things and LPWAN low-power wide area network transmission technology to execute Figure 1 The method comprises a sensor end and a gateway end, wherein: On the sensor side, initialize module-related peripherals, data interface peripherals, and security encryption interfaces; use AT commands to send commands and check return values, set basic parameters to prepare for network access; randomly select a preamble sequence, add the sensor ID, protection interval cyclic prefix, time timing, data transmission interval, and the time slot pointer of the time slot selected by the sensor side to the preamble sequence to form a preamble code, and combine 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 frame received in each time slot, and then traverses all time slots. If there is no collision in the time slot, the corresponding sent data frame is extracted in the data receiving window for decoding; if the gateway detects that a collision occurs in the time slot, the time slot where the collision occurs is skipped; for the successfully decoded data frame, the gateway eliminates the interference of the data frame and preamble sent by the sensor in other time slots according to the time slot pointer time timing selected by the sensor, and determines that the sensor is successfully connected; for the successfully connected sensor, an information packet is sent on the corresponding physical downlink shared channel resource, and the information packet includes the sensor ID, the information of the successful access preamble, the data sending interval specified by the gateway, and the corresponding timing advance information; The sensor receives the information returned by the gateway and detects whether the access is successful. If the access fails, random access is re-initiated. If the access is successful, subsequent data transmission is performed using the timing advance information and the data sending interval specified by the gateway.

[0022] The gateway receives and stores the data frames received in each time slot, and detects the preamble code of the data frame received in each time slot: Decode the sensor ID and get the sensor number. The gateway identifies the sensor. If the number is within the gateway processing range, it will continue to decode the subsequent leading sequence. Otherwise, it will directly deny access. Decode the cyclic prefix of the data frame to ensure that the carriers transmitting sensor information are orthogonal to each other; For time timing, decode the timing advance set according to the different physical distances between the sensor and the gateway, and compensate for the propagation delay corresponding to the timing advance; Decode the data sending interval to obtain the time interval between the sensor end repeatedly sending access requests and sending subsequent data to the gateway end; The time slot pointer is decoded to obtain the time slot for data transmission on the sensor side, and the gateway side stores the time slot and the device number of the sensor side.

[0023] The sensor performs identity authentication based on its own encryption chip, and then encrypts the data to be transmitted. Based on the timing advance 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 on the gateway use the same encryption and decryption mechanism. The data to be transmitted includes the sensor data obtained 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 side receives the confirmation message returned by the gateway side.

[0024] Please refer to Figure 2 As shown, the structure of the sensor end is composed of a main control module, a radio frequency module, a communication processing module, a security encryption module, and a power 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 end, including data collection, processing, storage and transmission, as well as reading data collected by external sensors; The RF module is used to control the reception of RF signals at the gateway end and to pre-process RF signals, including filtering, signal enhancement and signal amplification. The pre-processed RF signals are sent to the main control module. The communication processing module is used to establish a communication connection with the downstream sensor; securely access the gateway; and transmit data with the gateway to achieve safe and reliable data transmission; Security encryption module, 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 prevent data leakage and attacks; A power module is used to supply power to various devices in the sensor end; Crystal oscillator, used to provide clock beats for the sensor end.

[0025] Furthermore, the system may also include a cloud, wherein the cloud, gateway, and sensor are sequentially connected in downlink communication relationship, the sensor accesses the gateway through unauthorized random access, 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.

[0026] The authorization-free random access method of the present invention provides a faster and more efficient access scheme for a terminal to join a gateway. The traditional two-step or four-step random access scheme is to first use a preamble to initiate an access request to the gateway. After successful access, the gateway determines the data transmission interval for subsequent transmission by the sensor end, and the sensor end then performs data transmission. This can effectively relieve the transmission pressure of the gateway end when the gateway end is busy with data transmission, or improve the transmission efficiency of the gateway end when the gateway end is idle for data transmission. The method of the present invention combines the preamble with the data packet itself and sends it to the gateway through multiple time slots. The two functions of data transmission and access request are performed simultaneously. The gateway end accepts the access and indicates that the data packet is successfully received. This authorization-free random access scheme greatly improves the access efficiency and transmission efficiency.

[0027] What is disclosed above is only a preferred embodiment of the present invention, which certainly cannot be used to limit the scope of rights of the present invention. A person skilled in the art can understand that all or part of the processes of the above embodiments and equivalent changes made according to the claims of the present invention still fall within the scope of the invention.

Claims

1. A method for grant-free large-scale random access, characterized in that: include: Step S1, the sensor end randomly selects a preamble sequence, adds a sensor ID, a guard interval cyclic prefix, a time timing quantity, a data transmission interval, and a time slot pointer of a time slot selected by the sensor end to the preamble sequence to form a preamble code, and combines the access request data packet to form a data frame, wherein the preamble code of the data frame and the data packet do not interfere with each other in the time domain and the frequency domain; Step S2, the sensor end copies N1 copies of the data frame and randomly selects N2 time slots to send to the gateway end 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 code of the data frame received in each time slot, and then traverses all time slots. If no collision occurs in the time slot, the corresponding transmission data frame is extracted in the data receiving window for decoding; If the gateway detects that a time slot collision occurs, the time slot where the collision occurs is skipped; Step S4, for the successfully decoded data frame, the gateway end performs interference elimination on the data frame and preamble sent by the sensor end in other time slots according to the time slot pointer time timing quantity selected by the sensor end, and determines that the sensor end is successfully connected; Step S5, the gateway sends an information packet to the successfully accessed sensor on the corresponding physical downlink shared channel resources, wherein the information packet includes the sensor ID, the information of the successful access preamble, the data transmission interval specified by the gateway, and the corresponding timing advance information; Step S6, the sensor receives the information returned by the gateway, detects whether the access is successful, and if the access is unsuccessful, re-initiates random access; if the access is successful, the timing advance information and the data transmission interval specified by the gateway are used for subsequent data transmission.

2. The method for grant-free large-scale random access according to claim 1, characterized in that: In step S3, the gateway receives and stores the data frames received in each time slot, and detecting the preamble code of the data frame received in each time slot includes: Step S31, decoding the sensor ID to obtain the sensor terminal number, the gateway terminal identifies the identity of the sensor, and if the number is within the gateway processing range, continues to decode the subsequent leading sequence, otherwise directly refuses access; Step S32, decoding the cyclic prefix of the data frame to ensure that the sensor information transmission carriers are orthogonal to each other; Step S33, for the time timing amount, decoding the timing advance amount set according to the different physical distances between the sensor and the gateway, and compensating for the propagation delay corresponding to the timing advance amount; Step S34, decoding the data transmission interval to obtain the time interval for the sensor end to repeatedly send the access request and send subsequent data to the gateway end; Step S35, decoding the time slot pointer to obtain the time slot for the sensor end to transmit data, and the gateway end stores the time slot and the device number of the sensor end.

3. The method for grant-free large-scale random access according to claim 1, characterized in that: The step S6 uses the timing advance information and the data transmission interval specified by the gateway to perform subsequent data transmission, including: Step S61, the sensor end performs identity authentication based on its own encryption chip, and then encrypts the data to be transmitted, and transmits the encrypted data uplink to the gateway end 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 end use the same encryption and decryption mechanism; the data to be transmitted includes the sensor data obtained by the sensor end 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. A system for random access without authorization, characterized in that: Including sensor side and gateway side: The sensor end initializes module-related peripherals, data interface peripherals, and security encryption interfaces; Use AT commands to send commands and check return values, set basic parameters to prepare for network access; randomly select a preamble sequence, add sensor ID, protection interval cyclic prefix, time timing, data transmission interval, and time slot pointer of the time slot selected by the sensor end to the preamble sequence to form a preamble code, and combine the access request data packet to form a data frame. The preamble code of the data frame does not interfere with the data packet in the time domain and frequency domain; The gateway receives and stores the data frames received in each time slot, detects the preamble code of the data frame received in each time slot, and then traverses all time slots. If no collision occurs in the time slot, the corresponding transmission data frame is extracted in the data receiving window for decoding; If the gateway detects that a time slot collision occurs, the time slot where the collision occurs is skipped; for successfully decoded data frames, the gateway eliminates interference with data frames and preambles sent by the sensor in other time slots according to the time slot pointer time timing amount selected by the sensor, and determines that the sensor is successfully connected; for the successfully connected sensor, an information packet is sent on the corresponding physical downlink shared channel resource, and the information packet includes the sensor ID, the information of the successful access preamble, the data transmission interval specified by the gateway, and the corresponding timing advance information; The sensor end receives the information returned by the gateway end, detects whether the access is successful, and if the access is unsuccessful, re-initiates random access; if the access is successful, the timing advance information and the data sending interval specified by the gateway are used for subsequent data transmission.

5. The authorization-free large-scale random access system according to claim 4, characterized in that: The gateway receives and stores the data frames received in each time slot, and detects the preamble code of the data frame received in each time slot as follows: Decode the sensor ID to obtain the sensor end number, and the gateway end identifies the identity of the sensor. If the number is within the gateway processing range, continue to decode the subsequent leading sequence, otherwise directly deny access; Decoding a cyclic prefix of the data frame to ensure that sensor information transmission carriers are orthogonal to each other; For the time timing quantity, decoding the timing advance quantity set according to the different physical distances between the sensor and the gateway, and compensating for the propagation delay corresponding to the timing advance quantity; Decoding the data transmission interval to obtain the time interval between the sensor end repeatedly sending the access request and sending subsequent data to the gateway end; The time slot pointer is decoded to obtain the time slot for the sensor end to transmit data, and the gateway end stores the time slot and the device number of the sensor end.

6. The authorization-free large-scale random access system according to claim 4, characterized in that: The sensor end 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 end 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 end use the same encryption and decryption mechanism; the data to be transmitted includes the sensor data obtained by the sensor end 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 end receives the confirmation message returned by the gateway end.

7. The authorization-free large-scale random access system according to claim 4, characterized in that: The structure of the sensor end is composed of a main control module, a radio frequency module, a communication processing module, a security encryption module, and a power 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 end, including data acquisition, processing, storage and transmission, and reading data collected by external sensors; The RF module is used to control the reception of RF signals at the gateway end and to preprocess RF signals, wherein the preprocessing includes filtering, signal enhancement and signal amplification, and the preprocessed RF signals are 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 end; Performing data transmission with the gateway end; The security encryption module is used to implement data encryption and decryption, identity authentication, and access control; The power supply module is used to supply power to each device in the sensor end; The crystal oscillator is used to provide a clock beat for the sensor end.

8. The authorization-free large-scale random access system according to claim 4, characterized in that: The system also includes a cloud, and the cloud, the gateway, and the sensor are in a downlink communication connection relationship in sequence. The sensor accesses 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.

9. The authorization-free large-scale random access system according to claim 4, characterized in that: The system adopts narrowband wireless Internet of Things and LPWAN low-power wide area network transmission technology.

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