Reference article:
LoRaWAN's terminal End Node classification:
There are three types of terminal devices, Class A/B/C, which are stipulated in the protocol. These three types of devices basically cover all application scenarios of the Internet of Things. Their energy consumption and wake-up delay are different. Among them, class A, as the foundation of the lorawan network, must be To be implemented, classes B and C are optional
Two-way transmission terminal (Class A): The terminal of Class A will follow two short downlink receiving windows after each uplink, so as to realize two-way transmission. The transmission time slot is arranged by the terminal when there is a need for transmission, and a certain random delay is added (ie, the ALOHA protocol). This Class A operation is the most power efficient and requires the application to perform downlink transmission from the server within a short time after the terminal uplink transmission. The downlink transmission performed by the server at any other time has to wait for the next uplink from the terminal.
Two-way transmission terminals (Class B) with allocated receive time slots: Class B terminals will have more receive time slots. In addition to the random receive windows of Class A, Class B devices also open other receive windows at specified times. In order for the terminal to open the receiving window at the specified time, the terminal needs to receive a time-synchronized beacon from the gateway. This allows the server to know that the terminal is listening.
Two-way transmission terminal (Class C) that maximizes the receiving time slot: The terminal of Class C basically keeps the receiving window open all the time, and only closes it briefly when sending. Class C terminals consume more power than Class A and Class B
terminals, but at the same time, the delay from the server to the terminal is the shortest.
| category | introduce | Downside timing | energy saving | Application scenarios |
| A | Class A terminals use the ALOHA protocol to report data on demand. Two short downlink receive windows are followed immediately after each uplink, so as to realize bidirectional transmission. This operation is the most power efficient. | You must wait for the terminal to report data before sending data to it. | optimal | Trash can monitoring, smoke alarms, gas monitoring, etc. |
| B | In addition to the random receiving window of Class A, the terminal of Class B will also open the receiving window at the specified time. In order for the terminal to open the receive window at the specified time, the terminal needs to receive a time-synchronized beacon from the gateway. | Data can be sent to the terminal when the receiving window is fixed, and the sending delay is improved. | better | Valve-controlled water, gas and electricity meters, etc. |
| C | Class C terminals basically keep the receiving window open all the time, and only close briefly when sending. Class C terminals consume more power than Class A and Class B terminals. | Since the terminal is in a continuous receiving state, data can be delivered to the terminal at any time. | poor | Street light control, etc. |
The uplink and downlink transmission sequence diagram of A\B\C terminal is as follows:
The sequence diagram of the uplink and downlink of Class A. The End Node uploads data packets according to its own needs, which can be received by one or more Gateways; after 1 second, the Gateway with the strongest signal sends data at the same frequency and rate of the uplink. Bag;
Currently, the receiving window RX1 generally starts 1 second after the uplink, and the receiving window RX2 starts 2 seconds after the uplink. If End Node receives successfully at Rx1, it no longer opens the Rx2 window
Class A has the best energy saving effect, because it is only sleeping outside of the transmit and 2 receive windows. Of course, the LoRaWAN Server can only communicate downstream when the End Node communicates upstream.
The End Node of Class B receives the Beacon broadcast by the Gateway every 128 seconds to calibrate its own clock. Between 2 Beacons, the End Node will open some receiving windows (ping slots), and if it receives the Gateway's data packet during the window period, it will receive the complete downlink data packet.
The End Node selects the number of ping slots according to its own power and application needs; in order to achieve a compromise between energy saving and afternoon communication.
Class C is designed for actuators with sufficient power, such as: smart sockets, remote electrical control switches, etc. The communication method is basically the same as that of A, except that during the sleep period of Class A, it opens the receiving window RX2. In addition to sending data packets and Rx slot 1, it is received during Rx slot 2, which can ensure that the Server communicates downstream at any time.
