LoRa technical points

LoRa mainly operates in free frequency bands worldwide (ie unlicensed frequency bands), including 433, 868, 915 MHz, etc. LoRa network is mainly composed of four parts: terminal (built-in LoRa module), gateway (or base station), server and cloud. LoRa application data can be transmitted in both directions.

　　LoRa technical points

　　 Generally speaking, the transmission rate, working frequency band and network topology are the three main parameters that affect the characteristics of the sensor network. The choice of transmission rate will affect the transmission distance and battery life of the system; the choice of working frequency band should compromise the frequency band and the design goal of the system; and in the FSK system, the choice of network topology is determined by the transmission distance requirements and the nodes required by the system. The number is determined. LoRa integrates digital spread spectrum, digital signal processing and forward error correction coding technology, with unprecedented performance. Previously, only those high-level industrial radio communications would integrate these technologies, and with the introduction of LoRa, the situation in the field of embedded wireless communications has undergone a complete change.

　　 Forward error correction coding technology is to add some redundant information to the data sequence to be transmitted, so that the error symbols injected during the data transmission process will be corrected in time at the receiving end. This technology reduces the need to create "self-healing" data packets to retransmit in the past, and performs well in solving sudden bit errors caused by multipath fading. Once the data packet grouping is established and the forward error correction code is injected to ensure reliability, these data packets will be sent to the digital spread spectrum modulator. This modulator feeds each bit in the packet data packet into a "spreader", which divides each bit time into many chips. 

　　 Even if the noise is large, LoRa can calmly deal with the LoRa modem. After configuration, the range that can be divided is 64-4096 chips/bit, and the highest spreading factor (12) in 4096 chips/bit can be used. Relatively speaking, ZigBee can only divide the range of 10-12 chips/bit.