CN113055862B - Self-adaptive time slot scheduling method applied to LoRaWAN - Google Patents
Self-adaptive time slot scheduling method applied to LoRaWAN Download PDFInfo
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Abstract
The invention discloses a self-adaptive time slot scheduling method applied to LoRaWAN (Long area network), belonging to the technical field of wireless communication. The method provided by the invention overcomes the defects of insufficient real-time performance and reliability on the premise of ensuring the advantages of low power consumption, long-distance communication and the like of LoRaWAN, so as to adapt to wider application scenes. The real-time performance of the concerned priority node is improved in a self-adaptive and dynamic mode through the node data information, and the total data transmission amount of the system is controlled within a reasonable range while the real-time performance is improved; and by adopting a self-adaptive time slot scheduling algorithm, data collision is avoided, and the data transmission reliability of the concerned priority node is ensured.
Description
Technical Field
The invention belongs to the technical field of wireless communication, and particularly relates to a self-adaptive time slot scheduling method applied to LoRaWAN.
Background
LoRa is one of low-power consumption wide area network communication technologies, and according to introduction of LoRa alliance official white paper "what is LoRaWAN", LoRaWAN is a set of communication protocol and system architecture designed for LoRa long-distance communication network. LoRaWAN has the characteristics of low power consumption, long distance and ad hoc network communication, so that LoRaWAN can be used in long-period structure monitoring and fire-fighting monitoring of large buildings. However, for the purpose of low power consumption, in general, LoRaWAN communication has the following two problems:
1) problem of data real-time
As described in chinese patent application No. 201811033515.6, the LoRaWAN technology implements long distance and low power consumption at the cost of low data rate and higher delay, and in order to access enough devices, some limiting measures need to be taken, such as reducing the communication rate of the devices or using an unacknowledged message communication mechanism, so that the time interval period for reporting data at a network node is long, and it is difficult to ensure real-time data. In the existing methods for improving the time slots, for example, chinese patent applications with application numbers 201811033515.6 and 201910187121.4 all allocate fixed time slots by a server, the priority of an abnormal node is not calibrated according to a specific scene, and the problem of insufficient real-time performance of data still exists.
2) Data reliability problem
The improvement of the real-time performance is usually to increase the Data transmission Rate indiscriminately for all nodes in the network, as described in the overview "a Survey on Adaptive Data Rate Optimization in lorans: Recent Solutions and Major changes", lorans face the main challenge that the loras specification does not describe how the network server adapts the Rate to the end node. Therefore, many schemes for adaptively improving the rate have been proposed for various applications, quality of service requirements, different indexes and radio frequency conditions of the internet of things technology, but this brings about the problems of channel collision and data collision, and greatly affects the data reliability.
Disclosure of Invention
Because the LoRaWAN has the advantages of low power consumption, long distance, ad hoc network and the like, and the defect of insufficient real-time performance of LoRaWAN data transmission is brought, the problems of data collision and channel conflict still exist in the existing method for improving the real-time performance. Aiming at the problems, the invention provides a self-adaptive time slot scheduling method applied to LoRaWAN, which ensures the advantages of LoRaWAN and enables each node in the network to adaptively and dynamically change the data uplink time slot so as to improve the data transmission real-time performance of the priority node, avoid channel conflict and ensure the improvement of the data transmission reliability of the priority node.
The technical problem proposed by the invention is solved as follows:
a LoRaWAN Internet of things accessed through ALOHA and TDMA comprises a terminal, a gateway, a network server and an application server, wherein the terminal is in wireless communication connection with the gateway through LoRa, the gateway is in wired connection with the network server through Ethernet, and the network server is connected with the application server through local network service;
the terminal comprises a sensor, a first main control chip and a LoRa radio frequency chip and is used for regularly acquiring and uploading data;
the gateway comprises a second main control chip and a multi-channel LoRa radio frequency chip and is used for forwarding data of the terminal and the network server;
the network server comprises a network resource server and a forwarding server; the network resource server carries out time slice resource management and channel resource management, is used for carrying out initial quality evaluation on signals of the terminal, allocating a spreading factor, a communication rate and a TDMA time slot of the terminal, and executing a time slot allocation instruction of the application server to dynamically allocate the time slot for the terminal; the forwarding server realizes the scheduling of downlink data and the forwarding of uplink data of the gateway;
the application server comprises a registration authentication server, a terminal user server and a database; the registration authentication server provides registration and network access authentication services of the terminal and distributes a terminal number and a secret key for the terminal; the terminal user server analyzes data, dynamically allocates the TDMA time slot of the terminal and provides an interface for interaction for the user; the database is used for storing data evaluation criteria and registration information and caching uplink data of the terminal.
A self-adaptive time slot scheduling method applied to LoRaWAN comprises a daily monitoring condition and an emergency monitoring condition;
based on the functional modules, the time slice division and the specific steps of initialization and daily monitoring are as follows:
the time slice resources of the terminal are divided into: a Beacon time slice, a synchronous acquisition time slice, an ALOHA time slice and a TDMA time slice; the Beacon time slice is used for synchronizing terminal network time and receiving broadcast messages, the synchronous acquisition time slice is used for acquiring sensor data by a terminal, the ALOHA time slice is used for uploading network access application to the terminal, the terminal is only waken up in a time slot of the TDMA time slice, the sensor data is uploaded and unicast downlink messages are received, and the rest time is low in power consumption;
step 1-1, a gateway sends Beacon signals in a Beacon time slice, a terminal waits for the first Beacon signal after being electrified, sampling is carried out in a synchronous acquisition time slice after the Beacon time slice locks the Beacon signals sent by the gateway, a network is requested to be accessed in an ALOHA time slice, the gateway receives and forwards the request to a network server, and the network server forwards the request to an application server;
step 1-2, the application server receives the terminal request, compares the registration information, receives the network access after the comparison is successful, distributes a secret key and sends the terminal network access permission to the network server;
step 1-3, after receiving the network access permission sent by the application server, the network server plans an initial spreading factor, a communication rate and a terminal self TDMA time slot for the terminal according to the communication quality at the moment when the ALOHA time slice requests to access the network, packages the planning result and the network access permission into a data packet, and sends the data packet to the terminal through a gateway;
step 1-4, after receiving a data packet sent by a gateway, a terminal sets local parameters according to a planning result in the data packet, enters a low power consumption state after initialization is completed and waits for a next Beacon signal;
step 1-5, the terminal enters a daily monitoring mode after receiving the second Beacon signal: network time is synchronized in the Beacon time slice, the time slice is synchronously acquired to acquire sensor data, the TDMA time slot of the Beacon time slice uploads the data, and the rest of the time is in a low power consumption state and waits for the next period.
The time slice division and the specific steps during the mode conversion are as follows:
the time slice resources of the terminal are divided into: a Beacon time slice, a synchronous acquisition time slice, an ALOHA time slice and a TDMA time slice; the Beacon time slice is used for terminal network time synchronization and broadcast message receiving, the synchronous acquisition time slice is used for acquiring sensor data by a terminal, the ALOHA time slice is used for uploading burst messages by the terminal, in the TDMA time slice, the terminal is only waken up in own time slot to upload the sensor data and receive unicast downlink messages, and the rest time is low in power consumption.
Step 2-1, in a daily monitoring mode, the application server compares sensor data uploaded by all terminals in a TDMA time slice with a data interval preset and stored in the terminal server by a user in real time; if the uploaded sensor data are within a preset data interval, judging that the terminal corresponding to the sensor data is a normal terminal, and not allocating a self TDMA time slot to the normal terminal; otherwise, judging as an abnormal terminal, switching the system state into an emergency monitoring mode by the application server in the next period, allocating self TDMA time slots for the abnormal terminal in a Beacon time slice and a synchronous acquisition time slice, shortening the period in the emergency mode, and then issuing a time slot adjustment queue to the network server, wherein the time slot adjustment queue comprises a terminal number, a terminal normal or abnormal identifier and the allocated self TDMA time slots;
step 2-2, the network server receives the time slot adjustment queue and the period information of the application server, transmits the allocated self TDMA time slot information to the terminal in the TDMA time slice, and transmits the period information to the gateway;
step 2-3, the gateway changes the self period;
and 2-4, the terminal performs self-configuration after receiving the distributed self TDMA time slot information in the TDMA time slice, simultaneously uploads the acquired sensor data to the gateway, the gateway forwards the sensor data to the network server, the network server forwards the sensor data to the application server, the application server waits for a Beacon signal of the next period, and the system state is converted into an emergency monitoring mode.
The time slice division and the specific steps of the emergency monitoring are as follows:
the time slice resources of the terminal are divided into: a Beacon time slice, a synchronous acquisition time slice, an ALOHA time slice, a TDMA time slice and a downlink time slice; the Beacon time slice is used for synchronizing terminal network time and receiving broadcast messages, the synchronous acquisition time slice is used for acquiring sensor data by a terminal, the ALOHA time slice is used for uploading burst messages and receiving downlink messages by the terminal, in the TDMA time slice, the terminal is only awakened in own time slot to upload the sensor data and receive unicast downlink messages, and in other time, the power consumption is low, and the downlink time slice is used for unicasting or broadcasting messages by a network server.
Step 3-1, the terminal receives a Beacon signal of the next period, enters a Beacon time slice to realize time synchronization, and acquires a sensor signal in the synchronous acquisition time slice;
step 3-2, the normal terminal uploads the sensor data in an ALOHA time slice in a competitive uplink mode and receives a response signal of an application server, and the abnormal terminal uploads the sensor data in a TDMA time slot of the abnormal terminal and receives new TDMA time slot information of the network server;
3-3, the application server receives the sensor data of each terminal in the ALOHA time slice and the TDMA time slice and then compares the sensor data, if the uploaded sensor data are in a preset data interval, the terminal corresponding to the sensor data is judged to be a normal terminal, and the normal terminal does not allocate the TDMA time slot of the normal terminal; otherwise, judging as an abnormal terminal, allocating self TDMA time slots for the abnormal terminal in the Beacon time slice and the synchronous acquisition time slice, shortening the period in the emergency mode, and then issuing a time slot adjustment queue to the network server; the network server receives the time slot adjustment queue and the period information of the application server, transmits the allocated self TDMA time slot information to the terminal in the TDMA time slice, and transmits the period information to the gateway;
step 3-4, the gateway changes the self period; the abnormal terminal receives the self TDMA time slot information in the self TDMA time slot, and the normal terminal receives the self TDMA time slot information in the downlink time slice; and the terminal completes the self TDMA time slot configuration and waits for the next Beacon signal, and the step 3-1 to the step 3-4 are repeated.
The invention has the beneficial effects that:
the method provided by the invention overcomes the defects of insufficient real-time performance and reliability on the premise of ensuring the advantages of low power consumption, long-distance communication and the like of LoRaWAN, so as to adapt to wider application scenes. The real-time performance of the concerned priority node is improved in a self-adaptive and dynamic mode through the node data information, and the total data transmission amount of the system is controlled within a reasonable range while the real-time performance is improved; and by adopting a self-adaptive time slot scheduling algorithm, data collision is avoided, and the data transmission reliability of the concerned priority node is ensured.
Drawings
FIG. 1 is a schematic diagram of the LoRaWAN Internet of things system;
FIG. 2 is a schematic diagram of channel resource division of the adaptive timeslot scheduling method according to the present invention;
FIG. 3 is a schematic diagram of time slice division in a daily monitoring mode of the adaptive time slot scheduling method according to the present invention;
FIG. 4 is a schematic diagram of time slice division in an emergency monitoring mode of the adaptive time slot scheduling method according to the present invention;
FIG. 5 is a schematic diagram of a system initialization process of the adaptive timeslot scheduling method according to the present invention;
FIG. 6 is a schematic diagram of a system daily monitoring process of the adaptive time slot scheduling method according to the present invention;
FIG. 7 is a schematic diagram illustrating a transition of a monitoring mode of the adaptive timeslot scheduling method according to the present invention;
fig. 8 is a schematic diagram of a system emergency monitoring process of the adaptive time slot scheduling method according to the present invention.
Detailed Description
The invention is further described below with reference to the figures and examples.
The embodiment provides a LoRaWAN Internet of things accessed through ALOHA and TDMA, the system composition schematic diagram of the LoRaWAN Internet of things is shown in figure 1, and the LoRaWAN Internet of things comprises a terminal, a gateway, a network server and an application server, wherein the terminal and the gateway are connected through LoRa wireless communication, the gateway and the network server are connected through an Ethernet cable, and the network server and the application server are connected through a local network service;
the terminal comprises a sensor, a first main control chip and a LoRa radio frequency chip and is used for periodically acquiring and uploading data;
the gateway comprises a second main control chip and a multi-channel LoRa radio frequency chip and is used for forwarding data of the terminal and the network server;
the network server comprises a network resource server and a forwarding server; the network resource server carries out time slice resource management and channel resource management, is used for carrying out initial quality evaluation on signals of the terminal, allocating a spreading factor, a communication rate and a TDMA time slot of the terminal, and executing a time slot allocation instruction of the application server to dynamically allocate the time slot for the terminal; the forwarding server realizes the scheduling of downlink data and the forwarding of uplink data of the gateway;
the application server comprises a registration authentication server, a terminal user server and a database; the registration authentication server provides registration and network access authentication services of the terminal and distributes a terminal number and a secret key for the terminal; the terminal user server analyzes data, dynamically allocates the TDMA time slot of the terminal and provides an interface for interaction for the user; the database is used for storing data evaluation criteria and registration information and caching uplink data of the terminal.
Based on the system, the embodiment provides a self-adaptive time slot scheduling method applied to LoRaWAN, which is divided into daily monitoring conditions and emergency monitoring conditions;
based on the functional modules, the flow diagrams of initialization and daily monitoring are respectively shown in fig. 5 and 6, and the specific steps are as follows:
a schematic diagram of time slice division in the daily monitoring mode is shown in fig. 3, and time slice resources of the terminal are divided into: a Beacon time slice, a synchronous acquisition time slice, an ALOHA time slice and a TDMA time slice; the Beacon time slice is used for synchronizing terminal network time and receiving broadcast messages, the synchronous acquisition time slice is used for acquiring sensor data by a terminal, the ALOHA time slice is used for uploading network access application to the terminal, the terminal is only waken up in a time slot of the TDMA time slice, the sensor data is uploaded and unicast downlink messages are received, and the rest time is low in power consumption;
step 1-1, a gateway sends Beacon signals in a Beacon time slice, a terminal waits for the first Beacon signal after being electrified, sampling is carried out in a synchronous acquisition time slice after the Beacon time slice locks the Beacon signals sent by the gateway, access to a network is requested in an ALOHA time slice, and at the moment, the terminal and the gateway form LoRa networking; because the terminal and the gateway are in LoRa wireless connection, long-distance and large-range networking of a plurality of terminals is realized; the gateway receives the request and forwards the request to a network server, and the network server forwards the request to an application server;
step 1-2, the application server receives the terminal request, compares the registration information, receives the network access after the comparison is successful, distributes a secret key and sends the terminal network access permission to the network server;
step 1-3, after receiving the network access permission sent by the application server, the network server plans an initial spreading factor, a communication rate and a terminal self TDMA time slot for the terminal according to a Signal-to-Noise Ratio (SNR) at the moment when the ALOHA time slice requests to access the network, encapsulates the planning result and the network access permission into a data packet, and sends the data packet to the terminal through a gateway; different spreading factors divide different virtual channels, and data transmission on the virtual channels is not interfered mutually.
Step 1-3-1, if the SNR is-20 dB, setting the spreading factor of the terminal to be 12 according to the SNR, and further determining the communication rate of the terminal; the principle is that the worse the communication quality, the slower the communication rate; the communication rate includes a data rate and a symbol rate;
data rate:
DR＝SF*(BW/2^SF)*CR
wherein DR (data rate) represents data rate, SF (spreading factor) represents spreading factor, BW (band width) represents bandwidth, CR (coding rate) represents coding rate, and the value range is 1-4;
symbol rate:
RS＝BW/2^SF
wherein, rs (rate of symbol) represents the number of symbol transmissions that can be achieved per unit time;
step 1-3-2, calculating data transmission time, and the specific process is as follows:
calculating the symbol time:
TS＝1/RS
wherein, ts (time of symbol) represents the time required for reliable transmission of a single symbol.
Calculating the preamble duration:
preamble duration ═ (preamble length +4.5) × TS
And (3) calculating the number of load symbols:
wherein, the PLAYLOAdSymNb represents the number of load symbols, max represents the maximum value, ceil represents rounding up, and PL represents the number of bytes of the effective load;
when the header is used, H is 0, otherwise it is 1. LowDateOptimize is for lora packets with data transmission time greater than 16ms, and LoRaWAN packets must be turned on, and when set to 1 (default to 1), DE is 1, otherwise 0.
Calculating the load duration:
duration of load (playoadsymnb TS)
Calculating data transmission time:
data transmission time-preamble duration + payload duration
And 1-3-3, the terminals with the same signal-to-noise ratio have the same spreading factor at the same time, and the terminals belong to the same virtual channel. The data transmission time determines the minimum time slot required by the terminal for transmitting data, after the communication rate and the data transmission time are calculated according to the spreading factor, when the TDMA time slot is divided for each terminal, the time slot which is more than or equal to the data transmission time is distributed, and the terminals in the same virtual channel are divided into a complete TDMA time slice. A schematic diagram of channel resource partitioning is shown in fig. 2.
Step 1-4, after receiving a data packet sent by a gateway, a terminal sets local parameters according to a planning result in the data packet, enters a low power consumption state after initialization is completed and waits for a next Beacon signal;
step 1-5, the terminal enters a daily monitoring mode after receiving the second Beacon signal: synchronizing network time in a Beacon time slice, acquiring sensor data in the synchronous acquisition time slice, uploading the sensor data and a terminal number in a TDMA time slot of the Beacon time slice, and waiting for the next period when the rest of time is in a low power consumption state;
and 1-6, in the TDMA time slice, the gateway receives the terminal number and the sensor data sent by the terminal and forwards the terminal number and the sensor data to the network server, and the network server forwards the terminal number and the sensor data to the application server after receiving the terminal number and the sensor data.
The schematic diagram of mode conversion is shown in fig. 7, and the specific steps are as follows:
the time slice resources of the terminal are divided into: a Beacon time slice, a synchronous acquisition time slice, an ALOHA time slice and a TDMA time slice; the Beacon time slice is used for terminal network time synchronization and broadcast message receiving, the synchronous acquisition time slice is used for acquiring sensor data by a terminal, the ALOHA time slice is used for uploading burst messages by the terminal, in the TDMA time slice, the terminal is only waken up in own time slot to upload the sensor data and receive unicast downlink messages, and the rest time is low in power consumption.
Step 2-1, in a daily monitoring mode, in each TDMA time slice in each daily monitoring period, the application server compares sensor data uploaded by all terminals in the TDMA time slice with a data interval preset and stored in the terminal server by a user in real time; if the uploaded sensor data are within a preset data interval, judging that the terminal corresponding to the sensor data is a normal terminal, and not allocating a self TDMA time slot to the normal terminal; otherwise, judging as an abnormal terminal, switching the system state into an emergency monitoring mode by the application server in the next period, allocating self TDMA time slots for the abnormal terminal in a Beacon time slice and a synchronous acquisition time slice, shortening the period in the emergency mode, and then issuing a time slot adjustment queue to the network server, wherein the time slot adjustment queue comprises a terminal number, a terminal normal or abnormal identifier and the allocated self TDMA time slots;
the allocation principle of the TDMA time slot of the abnormal terminal is as follows:
calibrating the priority according to the deviation value of the sensor data of the abnormal terminal and a preset data interval, wherein the larger the deviation value is, the higher the priority is; and dividing the priority into three levels, allocating 50% of TDMA time slices in a physical channel for the first-level abnormal terminal, allocating 30% of TDMA time slices in the physical channel for the second-level abnormal terminal, and allocating 20% of TDMA time slices in the physical channel for the third-level abnormal terminal.
The period in the emergency mode is shortened to half of that in the daily monitoring mode.
Step 2-2, the network server receives the time slot adjustment queue and the period information of the application server, transmits the allocated self TDMA time slot information to the terminal in the TDMA time slice, and transmits the period information to the gateway;
step 2-3, the gateway changes the self period;
and 2-4, the terminal performs self configuration after receiving the allocated self TDMA time slot information in the TDMA time slice, simultaneously uploads the acquired sensor data to the gateway, the gateway forwards the sensor data to the network server, the network server forwards the sensor data to the application server, and waits for a Beacon signal of the next period, at the moment, the system state is converted into an emergency monitoring mode.
Fig. 8 shows a schematic flow chart of emergency monitoring, which includes the following steps:
fig. 4 shows a schematic diagram of a time slice division process of an emergency monitoring mode, where time slice resources of a terminal are divided into: a Beacon time slice, a synchronous acquisition time slice, an ALOHA time slice, a TDMA time slice and a downlink time slice; the Beacon time slice is used for synchronizing terminal network time and receiving broadcast messages, the synchronous acquisition time slice is used for acquiring sensor data by a terminal, the ALOHA time slice is used for uploading burst messages and receiving downlink messages by the terminal, in the TDMA time slice, the terminal is only awakened in own time slot to upload the sensor data and receive unicast downlink messages, and in other time, the power consumption is low, and the downlink time slice is used for unicasting or broadcasting messages by a network server.
Step 3-1, the terminal receives a Beacon signal of the next period, enters a Beacon time slice to realize time synchronization, and acquires a sensor signal in the synchronous acquisition time slice;
step 3-2, the normal terminal uploads the sensor data in an ALOHA time slice in a competitive uplink mode and receives a response signal of an application server, and the abnormal terminal uploads the sensor data in a TDMA time slot of the abnormal terminal and receives new TDMA time slot information of the network server;
3-3, the application server receives the sensor data of each terminal in the ALOHA time slice and the TDMA time slice and then compares the sensor data, if the uploaded sensor data are in a preset data interval, the terminal corresponding to the sensor data is judged to be a normal terminal, and the normal terminal does not allocate the TDMA time slot of the normal terminal; otherwise, judging as an abnormal terminal, allocating self TDMA time slots for the abnormal terminal in the Beacon time slice and the synchronous acquisition time slice, shortening the period in the emergency mode, and then issuing a time slot adjustment queue to the network server; the network server receives the time slot adjustment queue and the period information of the application server, transmits the allocated self TDMA time slot information to the terminal in the TDMA time slice, and transmits the period information to the gateway;
step 3-4, the gateway changes the self period; the abnormal terminal receives the self TDMA time slot information in the self TDMA time slot, and the normal terminal receives the self TDMA time slot information in the downlink time slice; and the terminal completes the self TDMA time slot configuration and waits for the next Beacon signal, and the step 3-1 to the step 3-4 are repeated.
Claims (3)
1. A self-adaptive time slot scheduling method applied to LoRaWAN is characterized by comprising a daily monitoring condition and an emergency monitoring condition;
the LoRaWAN Internet of things based on ALOHA and TDMA access comprises a terminal, a gateway, a network server and an application server, wherein the terminal is in wireless communication connection with the gateway through LoRa, the gateway is in wired connection with the network server through Ethernet, and the network server is connected with the application server through local network service;
the terminal comprises a sensor, a first main control chip and a LoRa radio frequency chip and is used for regularly acquiring and uploading data;
the gateway comprises a second main control chip and a multi-channel LoRa radio frequency chip and is used for forwarding data of the terminal and the network server;
the network server comprises a network resource server and a forwarding server; the network resource server carries out time slice resource management and channel resource management, is used for carrying out initial quality evaluation on signals of the terminal, allocating a spreading factor, a communication rate and a TDMA time slot of the terminal, and executing a time slot allocation instruction of the application server to dynamically allocate the time slot for the terminal; the forwarding server realizes the scheduling of downlink data and the forwarding of uplink data of the gateway;
the application server comprises a registration authentication server, a terminal user server and a database; the registration authentication server provides registration and network access authentication services of the terminal and distributes a terminal number and a secret key for the terminal; the terminal user server analyzes data, dynamically allocates the TDMA time slot of the terminal and provides an interface for interaction for the user; the database is used for storing data evaluation criteria and registration information and caching uplink data of the terminal;
the time slice division of initialization and daily monitoring comprises the following specific steps:
the time slice resources of the terminal are divided into: a Beacon time slice, a synchronous acquisition time slice, an ALOHA time slice and a TDMA time slice; the Beacon time slice is used for synchronizing terminal network time and receiving broadcast messages, the synchronous acquisition time slice is used for acquiring sensor data by a terminal, the ALOHA time slice is used for uploading network access application to the terminal, the terminal is only waken up in a time slot of the TDMA time slice, the sensor data is uploaded and unicast downlink messages are received, and the rest time is low in power consumption;
step 1-1, a gateway sends Beacon signals in a Beacon time slice, a terminal waits for the first Beacon signal after being electrified, sampling is carried out in a synchronous acquisition time slice after the Beacon time slice locks the Beacon signals sent by the gateway, a network is requested to be accessed in an ALOHA time slice, the gateway receives and forwards the request to a network server, and the network server forwards the request to an application server;
step 1-2, the application server receives the terminal request, compares the registration information, receives the network access after the comparison is successful, distributes a secret key and sends the terminal network access permission to the network server;
step 1-3, after receiving the network access permission sent by the application server, the network server plans an initial spreading factor, a communication rate and a terminal self TDMA time slot for the terminal according to the communication quality at the moment when the ALOHA time slice requests to access the network, packages the planning result and the network access permission into a data packet, and sends the data packet to the terminal through a gateway;
the specific process of the step 1-3 is as follows:
step 1-3-1, representing the communication quality by using a signal-to-noise ratio (SNR), wherein the SNR is-20 dB, and setting a spreading factor of a terminal to be 12 according to the SNR; the communication rate includes a data rate and a symbol rate;
data rate:
DR＝SF*(BW/2^SF)*CR
wherein DR represents a data rate, SF represents a spreading factor, BW represents a bandwidth, CR represents a coding rate, and the value range is 1-4;
symbol rate:
RS＝BW/2^SF
wherein RS represents the number of symbol transmissions achievable per unit time;
step 1-3-2, calculating data transmission time, and the specific process is as follows:
calculating the symbol time:
TS＝1/RS
wherein TS represents the time required for reliable transmission of a single symbol;
calculating the preamble duration:
preamble duration ═ (preamble length +4.5) × TS
And (3) calculating the number of load symbols:
wherein, the PLAYLOAdSymNb represents the number of load symbols, max represents the maximum value, ceil represents rounding up, and PL represents the number of bytes of the effective load;
when the header is used, H is 0, otherwise, H is 1; the lowdateoptimization is for lora data packets with data transmission time greater than 16ms, when the data transmission time is set to 1, DE is 1, otherwise, 0;
calculating the load duration:
duration of load (playoadsymnb TS)
Calculating data transmission time:
data transmission time-preamble duration + payload duration
Step 1-3-3, the terminals with the same signal-to-noise ratio can be obtained from 1-3-1 and 1-3-2, and the terminals also have the same spreading factor, and belong to a virtual channel; the data transmission time determines the minimum time slot required by the terminal for transmitting data, after the communication rate and the data transmission time are calculated according to the spreading factor, when the TDMA time slot is divided for each terminal, the time slot which is more than or equal to the data transmission time is distributed, and the terminals in the same virtual channel are divided into a complete TDMA time slice;
step 1-4, after receiving a data packet sent by a gateway, a terminal sets local parameters according to a planning result in the data packet, enters a low power consumption state after initialization is completed and waits for a next Beacon signal;
step 1-5, the terminal enters a daily monitoring mode after receiving the second Beacon signal: synchronizing network time in a Beacon time slice, synchronously acquiring sensor data of the time slice, uploading data in a self TDMA time slot, and waiting for the next period when the rest of time is in a low power consumption state;
the time slice division and the specific steps during the mode conversion are as follows:
the time slice resources of the terminal are divided into: a Beacon time slice, a synchronous acquisition time slice, an ALOHA time slice and a TDMA time slice; the Beacon time slice is used for synchronizing terminal network time and receiving broadcast messages, the synchronous acquisition time slice is used for acquiring sensor data by a terminal, the ALOHA time slice is used for uploading burst messages by the terminal, the terminal is only waken up in a time slot of the TDMA time slice to upload the sensor data and receive unicast downlink messages, and the rest time is low in power consumption;
step 2-1, in a daily monitoring mode, the application server compares sensor data uploaded by all terminals in a TDMA time slice with a data interval preset and stored in the terminal server by a user in real time; if the uploaded sensor data are in a preset data interval, judging that a terminal corresponding to the sensor data is a normal terminal, and not allocating a self TDMA time slot to the normal terminal; otherwise, judging as an abnormal terminal, switching the system mode into an emergency monitoring mode by the application server in the next period, allocating self TDMA time slots for the abnormal terminal in the Beacon time slice and the synchronous acquisition time slice, shortening the period in the emergency mode, and then issuing a time slot adjustment queue to the network server, wherein the time slot adjustment queue comprises a terminal number, a terminal normal or abnormal identifier and the allocated self TDMA time slots;
step 2-2, the network server receives the time slot adjustment queue and the period information of the application server, transmits the allocated self TDMA time slot information to the terminal in the TDMA time slice, and transmits the period information to the gateway;
step 2-3, the gateway changes the self period;
2-4, the terminal performs self configuration after receiving the allocated self TDMA time slot information in the TDMA time slice, and simultaneously uploads the acquired sensor data to the gateway, the gateway forwards the sensor data to the network server, the network server forwards the sensor data to the application server, waits for a Beacon signal of the next period, and the system state is converted into an emergency monitoring mode;
the emergency monitoring comprises the following specific steps:
the time slice resources of the terminal are divided into: a Beacon time slice, a synchronous acquisition time slice, an ALOHA time slice, a TDMA time slice and a downlink time slice; the Beacon time slice is used for synchronizing terminal network time and receiving broadcast messages, the synchronous acquisition time slice is used for acquiring sensor data by a terminal, the ALOHA time slice is used for uploading burst messages and receiving downlink messages by the terminal, the terminal is only awakened in the time slot of the terminal in the TDMA time slice, the sensor data is uploaded and the unicast downlink messages are received, the rest time is low in power consumption, and the downlink time slice is used for unicasting or broadcasting messages by a network server;
step 3-1, the terminal receives a Beacon signal of the next period, enters a Beacon time slice to realize time synchronization, and acquires a sensor signal in the synchronous acquisition time slice;
step 3-2, the normal terminal uploads the sensor data in an ALOHA time slice in a competitive uplink mode and receives a response signal of an application server, and the abnormal terminal uploads the sensor data in a TDMA time slot of the abnormal terminal and receives new TDMA time slot information of the network server;
3-3, the application server receives the sensor data of each terminal in the ALOHA time slice and the TDMA time slice and then compares the sensor data, if the uploaded sensor data are in a preset data interval, the terminal corresponding to the sensor data is judged to be a normal terminal, and the normal terminal does not allocate the TDMA time slot of the normal terminal; otherwise, judging as an abnormal terminal, allocating self TDMA time slots for the abnormal terminal in the Beacon time slice and the synchronous acquisition time slice, shortening the period in the emergency mode, and then issuing a time slot adjustment queue to the network server; the network server receives the time slot adjustment queue and the period information of the application server, transmits the allocated self TDMA time slot information to the terminal in the TDMA time slice, and transmits the period information to the gateway;
step 3-4, the gateway changes the self period; the abnormal terminal receives the self TDMA time slot information in the self TDMA time slot, and the normal terminal receives the self TDMA time slot information in the downlink time slice; and the terminal completes the self TDMA time slot configuration and waits for the next Beacon signal, and the step 3-1 to the step 3-4 are repeated.
2. The adaptive timeslot scheduling method applied to LoRaWAN according to claim 1, wherein in step 2-1, the allocation rule of the TDMA timeslots of the abnormal terminal itself is:
calibrating the priority according to the deviation value of the sensor data of the abnormal terminal and a preset data interval, wherein the larger the deviation value is, the higher the priority is; and dividing the priority into three levels, allocating 50% of TDMA time slices in a physical channel for the first-level abnormal terminal, allocating 30% of TDMA time slices in the physical channel for the second-level abnormal terminal, and allocating 20% of TDMA time slices in the physical channel for the third-level abnormal terminal.
3. The adaptive timeslot scheduling method for LoRaWAN according to claim 1, wherein in step 2-1, the period in the emergency mode is shortened to half of the period in the daily monitoring mode.
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