LoRa is a linear frequency modulation spread spectrum IoT modulation technology, also known as broadband phenomenon FM (Chirp Modulation) technology. Compared with the traditional FSK technology, LoRa has a longer transmission distance under the same power consumption, and has strong anti-interference ability.

low power consumption

LoRa applications are generally IoT devices, usually powered by batteries, and used for more than a few years, which requires LoRa to have extremely low power consumption. The realization of LoRa's low power consumption is mainly determined by two aspects: on the one hand, the chip needs to have low power consumption; on the other hand, the software communication protocol also needs to have low power consumption.

First of all, the power consumption of LoRa in hardware is very low. For example, the current of SX126X series hot start sleep mode is only 1.2uA, the receiving current at 125kHz is 4.6mA, and the sending current at 17dBm power is only 58mA.

Secondly, in terms of software communication protocols, LoRa does not have complex communication protocols like other wireless technologies. The data packets are very simple, and there is no need to send a large amount of handshake data. In order to achieve the purpose of saving power, the industry widely uses the Wake on Radio (WOR) method, as shown in the figure:

The chip enters the receiving (RX) mode periodically to listen for the wake-up preamble, and is in the sleep (Sleep) mode at other times. The receiving current of WOR is shown in the figure below. Most of the time it is in sleep mode, and only a small part of the time is woken up in receiving mode, so its overall power consumption is very low. For example, Ebyte's E22 and E32 modules all have WOR function, which can meet the low power consumption requirements very well.

long distance

In wireless communication, the standard to measure the communication distance is the link budget, which is equal to the transmit power minus the sensitivity. Sensitivity is a negative number, and the higher the sensitivity, the more negative, so the way to improve the link budget is to increase the transmit power and improve the sensitivity. However, the transmission power has strict requirements in various countries and regions, so the only way to increase the communication distance is to increase the sensitivity. The LoRa sensitivity has reached -123dBm when BW=125kHz, SF=7; when BW=7.81kHz, SF=12, the sensitivity has reached -149.1dBm. The sensitivity of Bluetooth is around -90dbm, and ZigBee is around -85dBm, so the transmission distance of LoRa is much longer than that of other wireless communication technologies. However, LoRa uses bandwidth in exchange for sensitivity, which will result in a very slow transmission rate, so LoRa is suitable for long-distance, low-speed, and small-volume applications.

Anti-jamming

LoRa can achieve long-distance transmission. In addition to the advantage of sensitivity, another very important factor is its super anti-interference ability. LoRa can still communicate when the noise is lower than 20dB, which is not available in existing traditional communication technologies. As shown below:

LoRa can normally demodulate the signal 20dB below the noise, while FSK theoretically needs to be 8dB above the noise to ensure demodulation. When the communication process encounters external electromagnetic signal interference, LoRa can continue to communicate stably, while traditional wireless technologies cannot communicate. Therefore, in some areas with serious channel interference, customers will choose LoRa technology as the core technology for stable communication.

The reason why LoRa modulation has such a strong anti-interference ability is mainly because Chirp debugging can gather useful LoRa signals under the noise during coherent demodulation, and the noise is still noise after coherent demodulation.