The influence of Lora parameters on communication performance

LoRa stands for the initials of "Long Range" and is a combination of communication technology and protocol developed by Semtech (Camarillo, CA, USA) that provides a longer range than other LPWAN technologies. Modulation using LoRa is based on spread spectrum techniques, and a variant of Chirped Spread Spectrum (CSS) modulation integrated with Forward Error Correction (FEC). Lora's CSS is a key factor for long-distance signal transmission with high-quality links, even when the signal power reaches 20dB lower than the noise floor. LoRa uses a unique frequency shift keying (FSK) to demodulate signals 19.5 dB below the noise floor. In contrast, other networking technologies can typically only demodulate signals with powers 8-10 dB above the noise floor. Модуль связи CAN2.0
The novelty of LoRa is to provide continuous phase between different chirp symbols in the preamble part of the physical layer packet, which enables simpler and more accurate timing and frequency synchronization without the need for An expensive component to generate a stable local clock. A single LoRa gateway can cover hundreds of square kilometers.
The LoRa MAC layer or LoRaWAN is the communication protocol and system architecture layer of the LoRa network. It has the greatest impact on network capacity, quality of service, battery life of individual nodes, and security. To isolate the tests of the LoRa physical layer and its ability to transmit images over a limited bandwidth.
LoRa can generally refer to two different layers: the physical layer and the link layer using CSS. The LoRa physical layer consists of many parameters that can be configured into 6720 different settings to provide a variety of options to ensure a high-quality link or consume less energy. The most important parameters of the LoRa physical layer are carrier frequency (CF), spreading factor (SF), bandwidth (BW), transmission power (TP) and coding rate (CR).
LoRa parameter setting and its impact on communication performance
Bandwidth: The value is 125,...,500. kHz Transmitting data at a high rate (1kHz = 1kcps) requires higher bandwidth. However, increasing this parameter reduces communication range and sensitivity. Модуль питания
Propagation factor: values 2 6, ..., 2 12. The higher spreading factor (SF) of the chip symbol increases the communication range, radio sensitivity and signal-to-noise ratio (SNR). However, energy consumption increases accordingly.
Encoding rate: Values are 4/5,...,4/8. Greater encoding rates increase protection against decoding errors and interference bursts at the cost of longer packets and higher power consumption.
Transmission Power: Values are -4,...,20 dBm. Signal-to-noise ratio is increased by increasing transmit power at the cost of energy consumption.
The following are the definitions of these parameters:
Carrier frequency: CF indicates the center transmission frequency used in the frequency band. This is programmable from 137 MHz to 1020 MHz in steps of 61 Hz.
Spreading factor: SF is the ratio between symbol rate and chip rate. It can be set between 6 and 12 in LoRa. For each SF, there are 2 SF chips per symbol. Compared with increasing transmission power, SF has a greater impact on energy consumption, which increases the communication range. Therefore, modifying SF is more effective in maintaining communication range while reducing energy consumption. Larger SF increases communication sensitivity and data bit rate, and reduces time-on-air (TOA).
Bandwidth: BW is the frequency range available for transmission. Larger BW allows transmission at higher data rates, but with shorter TOA and lower sensitivity. Conversely, a lower BW achieves higher sensitivity but at a lower data bit rate.
Coding rate: FEC provides anti-jamming protection and can be configured by setting CR to 4/5, 4/6, 4/7 or 4/8. In LoRa, stronger anti-jamming protection requires higher CR, which increases TOA.
Transmission Power: In LoRa, the power required to transmit a particular packet can be adjusted appropriately.
Among them, BW is the modulation bandwidth in Hz, and the spreading factor is proportional to the data rate.