Sensor network based on LoRa long-distance wireless communication technology

1. Background overview:

In August 2013, Semtech released a new type of chip based on ultra-long-distance low-power data transmission technology (LoRa) below 1GHz to the industry. Its receiving sensitivity has reached an astonishing -148dbm. Compared with other advanced sub-GHz chips in the industry, the highest receiving sensitivity has been improved by more than 20db, and its power consumption is extremely low.

LoRa, as a long-distance communication technology of low-power wide area network (LPWAN), has received more and more attention in recent years. With the development of the Internet of Things from short-distance to long-distance, some new industry applications and business models are bound to emerge. Cisco, IBM, Semtech, Microchip, etc. are actively promoting LoRa technology.

2. Technical features:

The advantage of LoRa lies in its long-distance technology. LoRa technology has outstanding features in terms of high performance, long distance, low power consumption, support for large-scale networking, ranging and positioning, which makes this solution (terminal + gateway) an ideal for large-scale promotion and application of the Internet of Things Technology choices.

LoRa is a kind of low-power wide area network communication technology. It is a physical layer or wireless modulation used to establish a long-distance communication link. Many traditional wireless systems use Frequency Shift Keying (FSK) modulation as the physical layer because it is a very effective modulation for low power consumption. LoRa is based on chirp spread spectrum modulation, which maintains the same low power consumption characteristics as FSK modulation, but significantly increases the communication distance.

LoRa technology itself has super high receiving sensitivity (RSSI) and super signal-to-noise ratio (SNR). In addition, frequency hopping technology is used to perform frequency shift keying through a pseudo-random code sequence to make the carrier frequency continuously hop and spread the spectrum to prevent fixed frequency interference.

Three, LoRa network architecture

In a mesh network, individual terminal nodes forward the information of other nodes to increase the communication distance of the network and the size of the network area. Although this increases the range, it also increases complexity, reduces network capacity, and reduces battery life, because nodes accept and forward information from other nodes that may not be relevant to it. When realizing long-distance connection, the long-distance star architecture is most meaningful to protect the battery life.

If the gateway is installed in the location of the existing mobile communication base station, the transmission power is 20dBm, (100mW), then it can cover about 2 kilometers in the densely-built urban environment, and the coverage area can reach 10 kilometers in the low-density suburbs. The gateway/concentrator also contains the MAC layer protocol, which is transparent to the higher layers.

4. Solution platform architecture:

The solution system architecture is: network/application server, LoRa gateway, LoRa node;

Five, application cases

1. Picture of smart oil field

2. Smart Water

3. Smart heating

4. Smart gas