LoRa wireless technology is a wireless communication technology dedicated to long-distance and low-power consumption. Its modulation method greatly increases the communication distance compared with other communication methods. It can be widely used in the field of long-distance and low-rate IoT wireless communication in various occasions. For example, automatic meter reading, building automation equipment, wireless security systems, industrial monitoring and control, etc. It has the characteristics of small size, low power consumption, long transmission distance, and strong anti-interference ability. The antenna gain can be adjusted according to actual application conditions.
2. LoRaWAN network architecture
The LoRaWAN network architecture is a typical star topology. In this network architecture, the LoRa DTU gateway is a transparent relay connecting terminal devices and servers. The gateway and the server are connected through standard IP, and the terminal device uses a single hop to communicate with one or more gateways. All nodes communicate in two directions.
LoRa DTU gateways and LoRa modules are networked in a star network, and LoRa modules can theoretically be networked in point-to-point polling, but the efficiency of point-to-point polling is much lower than that of a star network. The gateway can achieve multi-channel parallel reception and process multiple signals at the same time, which greatly increases network capacity. Ranging and positioning can also be achieved using LoRa. LPWAN has a long battery life and is truly low power consumption for sensors and applications that need to send small amounts of data.
Lora positioning and ranging
LoRa measurement distance is based on the air transmission time of the transmitted signal rather than the received signal strength RSSI value. Positioning can be based on the measurement of the air transmission time difference between multiple points (gateway) and one point (terminal). Its positioning accuracy can reach 5m.
LoRa frequency band selection
In theory, any frequency in the 150 MHz to 1 GHz band can be used. However, Semtech's LoRa chip cannot be used in all sub-GHz frequency bands. Some frequencies other than the commonly used frequency bands (such as 433MHz, 470MHz~510MHz, 780MHz and the commonly used 868MHz and 915MHz in Europe and the United States are common frequency bands) are not very good. support.
3. Three major advantages of LoRa wireless technology
The advantages of LoRa wireless technology are mainly reflected in the following aspects:
1. Greatly improved receiving sensitivity and reduced power consumption
The link budget of up to 157db enables the communication distance to be up to 15 kilometers (depending on the environment). Its receiving current is only 10mA and its sleep current is 200nA, which greatly delays the battery life.
2. The gateway/concentrator based on this technology supports parallel processing of multiple channels and multiple data rates, and has large system capacity.
The gateway is the bridge between the node and the IP network (via 2G/3G/4G or Ethernet). Each gateway can handle 5 million communications between nodes every day (assuming 10 Bytes are sent each time and the network occupancy is 10%). If the gateway is installed at the location of an existing mobile communication base station with a transmitting power of 20dBm (100mW), it can cover about 2 kilometers in a densely built urban environment, and in lower-density suburbs, the coverage can reach 10 kilometers.
3. Systems based on terminals and concentrators/gateways can support ranging and positioning.
LoRa's distance measurement is based on the air transmission time of the signal rather than the traditional RSSI (Received Signal Sterngth Ind-ication), while positioning is based on the measurement of the air transmission time difference between multiple points (gateways) and one point (node). Its positioning accuracy can reach 5m (assuming a range of 10km).
These key features make LoRa technology very suitable for IoT applications that require low power consumption, long distance, large number of connections, and location tracking, such as smart meter reading, smart parking, vehicle tracking, pet tracking, smart agriculture, smart industry, and smart cities. , smart communities and other applications and fields.
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