CN114650612A

CN114650612A - LoRa networking method based on carrier sensing technology

Info

Publication number: CN114650612A
Application number: CN202210379883.6A
Authority: CN
Inventors: 濮斌; 苏静; 王鑫
Original assignee: Juyan Iotian Technology Jiangsu Co ltd
Current assignee: Juyan Iotian Technology Jiangsu Co ltd
Priority date: 2022-04-12
Filing date: 2022-04-12
Publication date: 2022-06-21

Abstract

The invention relates to a LoRa networking method based on a carrier sensing technology, which comprises the following steps: step S1: the LoRa terminal enters an initialization state; step S2: the LoRa terminal executes channel interception; step S3: the LoRa terminal executes a back-off mechanism; step S4: the LoRa terminal and the LoRa gateway execute a handshake mechanism; and step S5, the LoRa terminal performs data interaction with the LoRa gateway. According to the LoRa networking method based on the carrier sense technology, the channel sense and backoff mechanism is additionally arranged between the terminal and the gateway, whether the wireless channel has data transmission or not is judged through carrier sense, if the wireless channel is idle, communication is carried out immediately, waste of communication time caused by fixed allocation of time slots is avoided, and communication time delay is reduced.

Description

LoRa networking method based on carrier sensing technology

Technical Field

The invention belongs to the technical field of communication networking, and particularly relates to a LoRa networking method based on a carrier sensing technology.

Background

LoRa is a communication technology in a low-power wide area network, and is a wireless communication technology which is proprietary to Semtech company, is based on a spread spectrum technology and has an ultra-long transmission distance. The LoRa communication technology is also very wide in domestic application, and the main application fields comprise Internet of things agriculture, industrial Internet of things, intelligent wireless meter reading, robot control, security and protection systems, smart cities and the like.

At present, the LoRa communication protocol mainly adopts the LoRaWan protocol, and LoRaWan divides terminal devices into different classes, i.e., Class a, Class B, and Class C, according to different application requirements, and each terminal device can only be implemented by one Class, as shown in fig. 1, 2, and 3.

The Class A type is a bidirectional terminal device: after the uplink transmission of the terminal equipment is finished, two downlink receiving windows are opened, so that the A-type equipment can carry out two-way communication. The terminal device itself decides to transmit the time slot, the selection of which is related to the communication needs of the system network. Because the terminal equipment opens the receiving window for downlink communication for a short time only after the uplink transmission is completed, the power consumption of the terminal equipment of the type is the lowest, all downlinks of the gateway have to wait for the completion of the uplink communication, the gateway can not actively send data to the terminal, and the gateway can send data to the terminal only after the data is sent to the terminal, two short receiving windows Rx1 and Rx2 are opened after a certain delay after the uplink communication of the terminal, and the second receiving window Rx2 can not be opened if the first receiving window Rx1 receives the data;

class B bidirectional terminals with specific receive windows have more receive windows than Class a, Class B type devices, which are different from the random receive windows of Rx1, Rx2, and Class B devices start receiving for a certain time. To ensure that the node opens a window of reception for a fixed period of time, the terminal periodically opens a reception window between two beacons. The increased number of windows of Class B brings about the enhancement of power consumption, and because the downlink communication can be carried out in a fixed receiving window, the time delay and the complexity are obviously improved;

the receiving window of the Class C device is the largest, the Class C device can open the receiving window until transmitting data again after data transmission is finished, the power consumption of the Class C device is larger than that of the former two types, but the Class C device adopts the Class C device, the time delay of downlink communication between the gateway and the node is the smallest, the simple meaning is that the receiving is opened all the time, the receiving can not be carried out only when the data is transmitted, the receiving is carried out at other time, and for wired power supply and the mode that low power consumption is not considered can be adopted, the gateway can actively send the data.

In summary, in the conventional LoRaWan protocol method, no matter the communication protocol is the communication protocol of class a, class b or class c, the uplink and downlink time slots specified by the protocol are used for communication, and timely communication cannot be performed, so that communication delay is large, and the communication method cannot meet the requirements in some application fields requiring timely communication, such as industrial internet of things, smart cities and the like.

Disclosure of Invention

The invention aims to overcome the defects of the prior art and provide a LoRa networking method based on a carrier sensing technology.

In order to achieve the purpose, the invention adopts the technical scheme that: a LoRa networking method based on a carrier sensing technology comprises the following steps:

step S1: the LoRa terminal enters an initialization state;

step S2: the LoRa terminal executes channel interception;

step S3: the LoRa terminal executes a back-off mechanism;

step S4: the LoRa terminal and the LoRa gateway execute a handshake mechanism;

and step S5, the LoRa terminal performs data interaction with the LoRa gateway.

Preferably, in the step S2, the backoff mechanism is executed in the step S3 only when the channel is detected as idle and the time duration is DIFS duration.

Optimally, in step S3, a Backoff counter Backoff is randomly selected, whether a channel is occupied is detected again, and if the channel is occupied, the counter is suspended and the channel is waited for to be idle; if the channel is not occupied, step S4 is performed.

Optimally, in step S4, the LoRa terminal sends an RTS handshake mechanism and waits to receive a CTS feedback signal sent by the LoRa gateway, if the CTS feedback signal sent by the LoRa gateway is not received, the method returns to step S2, and if the CTS feedback signal sent by the LoRa gateway is successfully received, the method proceeds to step S5 to perform data interaction.

Preferably, in step S5, after the data transmission of the LoRa terminal is completed, the LoRa terminal continuously opens the Rx receive window to wait for the ACK acknowledgement of the LoRa gateway, and if no ACK response is received after timeout, the contention window CW is changed and the method returns to step S2 to perform channel detection again, and if an ACK response is received from the LoRa gateway, the data interaction is successful.

Optimally, the LoRa gateway is always in a receiving state, and enters a sending state only when replying CTS and ACK to the LoRa terminal node.

Optimally, the LoRa terminal consists of a LoRa module SX1278 and an MCU chip, and the LoRa module SX1278 serves as both a transmitting channel and a receiving channel.

Optimally, the loRa gateway consists of two loRa modules SX1278 and a master control MCU chip, wherein one loRa module SX1278 is used as a sending channel, and the other loRa module SX1278 is used as a receiving channel.

Due to the application of the technical scheme, compared with the prior art, the invention has the following advantages:

the LoRa networking method based on the carrier sense technology adds a channel sense and back-off mechanism between the terminal and the gateway, judges whether the wireless channel has data transmission or not through the carrier sense, and immediately communicates if the wireless channel is idle, thereby avoiding the waste of communication time and reducing the communication time delay through the fixed allocation of time slots.

Drawings

FIG. 1 is a timing diagram of ClassA in the LoRa communication protocol of the present invention;

FIG. 2 is a timing diagram of ClassB in the LoRa communication protocol according to the present invention;

FIG. 3 is a timing diagram of ClassC in the LoRa communication protocol according to the present invention.

FIG. 4 is a protocol flow diagram of the present invention;

FIG. 5 is a diagram of the LoRa terminal node architecture of the present invention;

fig. 6 is a diagram of the LoRa gateway architecture of the present invention;

fig. 7 is a state switching diagram of the LoRa terminal according to the present invention;

fig. 8 is a flow chart of the initialization of the LoRa terminal according to the present invention;

fig. 9 is a flow chart of sending by the LoRa terminal according to the present invention;

fig. 10 is a flowchart of the initialization of the LoRa gateway according to the present invention;

fig. 11 is a flow chart of the downstream communication of the LoRa gateway of the present invention;

fig. 12 is a flow chart of the LoRa gateway uplink communication according to the present invention.

Detailed Description

The invention will be further described with reference to examples of embodiments shown in the drawings to which the invention is attached.

As shown in fig. 1, a flowchart of the LoRa networking method based on the carrier sensing technology of the present invention includes the following steps:

step S1: the LoRa terminal enters an initialization state;

the LoRa terminal has the main function of data acquisition, transmits data to the Lora gateway through the Lora network, and responds to the control instruction of the Lora gateway. As shown in fig. 5, the architecture diagram of the LoRa terminal node is shown, the LoRa terminal is mainly composed of a LoRa module SX1278 and a low power consumption MCU chip, and is matched with other auxiliary modules, one side of the LoRa module SX1278 is connected with an antenna, and the other side of the LoRa module SX1278 is connected with an MCU chip, which is used as both a transmitting channel and a receiving channel, and different channels are used for transmitting and receiving (when used as the transmitting channel, the LoRa module SX1278 transmits data to the LoRa gateway through the antenna, and when used as the receiving channel, the LoRa module SX1278 receives feedback data transmitted by the LoRa gateway through the antenna). The MCU chip is also externally connected with a wiring terminal, an LED indicator light, a key and a power supply. The power is used for supplying power for the MCU chip, and the button is used for controlling the switch of MCU chip to show through the LED pilot lamp. The wiring terminal is a standby terminal and can be connected to the MCU chip through the wiring terminal when other terminals need the standby terminal.

Step S2: the LoRa terminal executes channel interception;

when an LoRa terminal needs to send data to an LoRa gateway, the LoRa terminal firstly enters a CAD channel detection state to detect whether a current channel is idle, and after the current channel detection is completed, the LoRa terminal needs to wait for an inter-detection interval, so that collision in a wireless transmission process is avoided, and information loss is prevented. The interframe spacing is three: SIFS (highest priority), PIFS (medium priority) and DIFS (lowest priority), the inter-frame space SIFS, PIFS or DIFS, depending on what message is intended to be sent. The highest priority is used for transmission of ACK (acknowledgement of transmission end) and CTS (control frame to avoid hidden node), and DIFS is used for transmission of general data. The inter-frame intervals are divided into 3 different priority intervals, which has the advantage of further avoiding channel usage collisions, avoiding simultaneous transmissions of different frames (data is the most common, and CTS and ACK are the more important information after a certain transmission, and they should be transmitted first, say, a host wants to transmit data information, while B host wants to transmit urgent CTS information to C host, then AB waits for an inter-frame interval when the channel is idle, but B waits for a short time and then starts a random backoff, which expects a shorter waiting time and is more likely to transmit earlier than a, and a starts to transmit a message again when a has not finished backoff (B transmits CTS message to C), and can only wait again. Therefore, the subsequent backoff mechanism is only entered when the channel is detected as idle and the duration of the inter-detection interval is long.

Step S3: the LoRa terminal executes a backoff mechanism;

when executing the Backoff mechanism, a Backoff counter Backoff is randomly selected, and then the current channel is detected again to detect whether the channel is occupied (if a sends information to B, C also sends information to B, and step 2 monitors that both AB and AC channels are idle, and after waiting for a corresponding detection interval, both the conditions for sending information to B are satisfied, but because the priorities between a and C are different, the other needs to be Backoff processed). If the channel is occupied, suspending the counter and waiting for the channel to be idle; if the channel is not occupied, step S4 is performed.

Step S4: the LoRa terminal and the LoRa gateway execute a handshake mechanism;

the LoRa terminal sends RTS to execute a handshake mechanism, waits for receiving a CTS feedback signal sent by the LoRa gateway, and if the CTS feedback signal sent by the LoRa gateway is not received, the step 2 is repeatedly executed within the maximum repeated transmission times until the CTS feedback signal sent by the LoRa gateway is received; if the repetition number exceeds the repetition transmission number, the transmission is abandoned, and the CW is updated, that is, the next LoRa terminal node is replaced, probably because the LoRa terminal ID is not recorded in the LoRa gateway, and therefore the CTS feedback signal issued by the LoRa gateway cannot be received after the LoRa terminal ID is repeated for many times, and the CW needs to be updated.

And step S5, the LoRa terminal performs data interaction with the LoRa gateway.

After executing a handshake mechanism, the LoRa terminal sends data to the LoRa gateway, after the data sending is finished, the LoRa terminal continuously opens an Rx receiving window to wait for ACK confirmation of the LoRa gateway, if no ACK response is received after timeout, the CW of the contention window is changed and the step S2 is returned to perform channel detection again, and if an ACK reply of the LoRa gateway is received, the data interaction is successful. For the LoRa gateway, the LoRa gateway is in the Rx reception mode most of the time, receives data from each LoRa terminal all the time, and enters the transmission state only when replying with CTS and ACK to the LoRa terminal node. The LoRa gateway has the main functions of being responsible for uplink and downlink forwarding of data of the user side and the terminal side and being responsible for management of terminal nodes. As shown in fig. 6, the architecture diagram of the LoRa gateway is that the LoRa gateway is composed of two LoRa modules SX1278 and a main control MCU chip, where one SX1278 is used as a transmission channel and the other SX1278 is used as a reception channel. Meanwhile, the LoRa gateway and the server communication module can be connected by a telecommunication module GPRS module or an Ethernet. The master control MCU chip is also connected with an LED lamp and a power supply, and the power supply is used for supplying power to the MCU chip and displaying the power through an LED indicating lamp.

As shown in fig. 7, the state switching diagram of the LoRa terminal is shown, the LoRa terminal is composed of an LoRa module SX1278+ MCU with low power consumption, the LoRa terminal receives the data on a channel F0 and transmits the data on a channel F1, and the terminal accesses the network by using CAD listening and random backoff. The LoRa terminal sends the join _ req network entry request only when the initialization is completed. Before a terminal accesses a network, an SX1278 is set to be in a CAD detection mode, frequency points are set to be F1, an F1 channel (a sending channel) is monitored, the monitoring time length of each time is SIFS, if F1 is not monitored within the time length range of the SIFS, the current channel is considered not to be occupied by other nodes, then the current channel is randomly retreated for a period of time T0, whether the channel is idle is monitored, if the channel is idle, an RTS/CTS handshake mechanism is entered, and after success, an access message (RTS means request sending, CTS means clear sending, RTS/CTS handshake mechanism is sent on the channel, which is equivalent to a handshake protocol and is mainly used for solving the problem of 'hidden terminal', the hidden terminal means that a base station A sends information to a base station B, a base station C does not detect that A also sends to B, therefore, A and C send signals to B at the same time, signal collision is caused, and finally, the signals sent to B are lost, firstly, A sends RTS signal to B, which indicates A wants to send some data to B, B sends CTS signal to all base stations after receiving RTS, which indicates ready, A can send, and the rest base stations which want to send data to B suspend sending; the two parties start real data transmission after successfully exchanging RTS/CTS signals (namely, completing handshake), so that when a plurality of invisible sending stations send signals to the same receiving station at the same time, only the station which receives the response of the receiving station to the CTS can actually send the signals, and collision is avoided.

After sending, the LoRa terminal switches to an Rx state (Rx is a receiving state, that is, after SX1278 sends RTS from F1 channel to the gateway, it changes to a receiving mode to wait for receiving a CTS signal sent by the gateway), and if Rx times out, it still does not receive a Join _ reply message replied by the gateway, repeats the above process and resends until network access succeeds, and the node does not process any message of the gateway before network access succeeds. CAD detection is performed on F1 channel (transmission channel) after the terminal is powered on, and if the LoRa signal can be detected within a specified time, the terminal is randomly backed off for a while before transmission (here, a back-off mechanism is operated, still to avoid collision). If the LoRa terminal has data to send to the gateway, the data is sent directly (here, the network access is successful, and CAD interception and random backoff are carried out on the channel, so that the data can be sent directly). After each data transmission, the gateway can update the state of the node to be the online state, and automatically ignores the node when polling the online state of the node next time. The terminal is in a dormant state under normal conditions and is awakened by an external sensor, if the terminal node has data or signaling to be sent, the node is awakened, initialized and enters a sending state, the terminal does not need to wait for the polling scheduling of the gateway, and the terminal sending process is responsible for selecting proper time to send.

When the LoRa gateway forwards the data messages in the uplink and the downlink, only a data bearing channel is needed, the downlink user messages are forwarded through the LoRa gateway and must be assigned with a terminal ID, and the uplink messages are only checked and forwarded through the LoRa gateway. Because a LoRa gateway can be connected with a plurality of LoRa terminals, the LoRa gateway is used for authentication, in short, each LoRa terminal sends information to the LoRa gateway, and the LoRa gateway authenticates the information, and only sends the information to the server if the information is sent by the LoRa terminal connected with the LoRa gateway, otherwise, the information is not sent to the server, so as to avoid hackers or viruses from maliciously attacking the server. Therefore, when the LoRa terminal sends information (i.e., an uplink packet) to the LoRa gateway, the LoRa gateway only checks the information, and forwards the information to the server if the information is qualified; when the server sends a feedback command (i.e., a downlink user packet) to the LoRa terminal, the feedback command also needs to be transmitted through the LoRa gateway, and at this time, the LoRa terminal needs to be specified (i.e., a specified terminal ID).

As shown in fig. 11, for the downstream communication flow diagram of the LoRa gateway, SX1278-1 on the LoRa gateway is initialized and then always stays in Rx state at F1, SX1278-2 initialization channel is configured to be F0 and stays in preparation state after initialization is completed, when there is data transmission, the SX1278-2 initialization channel is switched to Tx state to transmit data, and the LoRa terminal receives at F0 and transmits at F1. Considering that the frequency range supported by the terminal antenna is about 10MHz, and the frequency points between F0 and F1 are separated as much as possible to avoid interference between the frequency points, the frequency interval between F0 and F1 is set to 6 MHz. After the initialization of the LoRa gateway is completed, an instruction is sent, and the broadcast informs the node to send a network access request. The downlink data is not directly forwarded after the application layer or the IP layer receives the user message to be forwarded, and enters a sending queue. And after the enqueue is successful, informing the user program of completing the transmission, and after the transmission is finished, feeding back a message of success or failure of the user transmission, wherein the total number of the two messages is two. All frames needing to be sent are sent out from the queue by the LoRa gateway, two sending queues are provided, one signaling and one DATA are distinguished according to message types, and all downlink message types except DATA are input into the signaling queue. And the sending thread at the gateway side processes the signaling queue preferentially until the signaling queue is empty, and then processes the data queue. The sending of the LoRa gateway is not used for channel monitoring, and is sent from F0 directly after being pushed from the sending queue, if it is Confirmed DADA Down, a timer is started before sending, if the timer is overtime, the ACK of the terminal can be received, and seqNum is the same as DLSeqNum, it indicates that the sending is successful. If the ACK is not received at F1 after the timer expires, the node re-enters the data queue, and after the number of retransmissions exceeds the maximum number of retransmissions, the ACK replied by the terminal is still not received, the transmission fails, and the state of the node is updated to the offline state.

As shown in fig. 12, as a LoRa gateway uplink communication flow diagram, after receiving uplink data, the LoRa gateway queries the state of the LoRa terminal node according to the device ID in the terminal management list, and if the terminal state is offline, the state of the LoRa terminal node is modified to be online (a plurality of LoRa terminals are connected to the LoRa gateway, and there are IDs of all the LoRa terminals connected to the LoRa gateway in the LoRa gateway, and after one of the LoRa terminals sends data to the LoRa gateway, the LoRa terminal node displays an online state, which facilitates subsequent downlink data reception, and if the LoRa terminal node fails, even if the LoRa terminal sends data to the LoRa gateway, the LoRa terminal still displays an offline state, and therefore needs to be adjusted to be online, which belongs to a self-repairing process). If the situation of the LoRa terminal node exists, the LoRa gateway sends a broadcast message of connection confirmation after being powered on again, that is, the situation that the LoRa terminal node entry does not exist in the online terminal list of the LoRa gateway, the LoRa gateway needs to send a new terminal node online message first, then sends a piece of data message as a notification to be fed back to a user, and resends a connection confirmation request message to the terminal, if the LoRa gateway can receive a reply message of connection confirmation, the LoRa terminal is willing to join the LoRa gateway, performs data interaction with the LoRa gateway, and adds the ID of the LoRa terminal node into the online terminal list, and collocates the LoRa terminal node to be online; if the reply is not received, the LoRa terminal is not willing to join the LoRa gateway, the state of the LoRa terminal node is modified to be offline, and the user is informed of the offline message of the node (the LoRa terminal node connected with one LoRa gateway is not fixed, and can be expanded according to the actual situation, so that the LoRa gateway can be expanded through the method). If the data is the confirmation data, the ULSeqNum is updated, if the ULSeqNum is the same as the current data, only the ACK is replied, and the forwarding is not needed. The content of ACK is ULSeqNum. And if the data is uncertain data, directly forwarding the data.

The above embodiments are merely illustrative of the technical ideas and features of the present invention, and the purpose thereof is to enable those skilled in the art to understand the contents of the present invention and implement the present invention, and not to limit the protection scope of the present invention. All equivalent changes and modifications made according to the spirit of the present invention should be covered within the protection scope of the present invention.

Claims

1. A LoRa networking method based on carrier sense technology is characterized by comprising the following steps:

step S1: the LoRa terminal enters an initialization state;

step S2: the LoRa terminal executes channel interception;

step S3: the LoRa terminal executes a backoff mechanism;

step S4: the LoRa terminal and the LoRa gateway execute a handshake mechanism;

and step S5, the LoRa terminal performs data interaction with the LoRa gateway.

2. The LoRa networking method based on the carrier sensing technology according to claim 1, wherein: in step S2, the operation of the backoff mechanism in step S3 is only performed if the channel is detected as idle and the duration of the time is DIFS duration.

3. The LoRa networking method based on the carrier sensing technology according to claim 1, wherein: in step S3, a Backoff counter Backoff is randomly selected, whether the channel is occupied is detected again, and if the channel is occupied, the counter is suspended and the channel is waited to be idle; if the channel is not occupied, step S4 is performed.

4. The LoRa networking method based on the carrier sensing technology according to claim 1, wherein: in step S4, the LoRa terminal sends an RTS to execute a handshake mechanism, and waits to receive a CTS feedback signal sent by the LoRa gateway, if the CTS feedback signal sent by the LoRa gateway is not received, the process returns to step S2, and if the CTS feedback signal sent by the LoRa gateway is successfully received, the process proceeds to step S5 to perform data interaction.

5. The LoRa networking method based on the carrier sensing technology according to claim 1, wherein: in step S5, after the data transmission of the LoRa terminal is completed, the LoRa terminal continuously opens the Rx receive window to wait for ACK acknowledgement of the LoRa gateway, and if no ACK response is received after timeout, the contention window CW is changed and the method returns to step S2 to perform channel detection again, and if an ACK reply of the LoRa gateway is received, the data interaction is successful.

6. The LoRa networking method based on the carrier sensing technology according to claim 1, wherein: the LoRa gateway is always in a receiving state, and only when replying CTS and ACK to the LoRa terminal node, the LoRa gateway enters a sending state.

7. The LoRa networking method based on the carrier sensing technology according to claim 1, wherein: the LoRa terminal is composed of a LoRa module SX1278 and an MCU chip, and the LoRa module SX1278 is used as a sending channel and a receiving channel.

8. The LoRa networking method based on the carrier sensing technology according to claim 1, wherein: the LoRa gateway is composed of two LoRa modules SX1278 and a main control MCU chip, wherein one LoRa module SX1278 is used as a sending channel, and the other LoRa module SX1278 is used as a receiving channel.