LoRa & LoRaWAN: A Simple Guide

Radio Interface LoRa / LoraWAN. Modulation

LoRa (Long Range) is a wireless communication technology designed for long-range, low-power, and reliable data transmission. It is highly resistant to interference, making it ideal for IoT applications, remote sensing, and low-power wide-area networks (LPWANs).

AM - Amplitude Modulation

FM- Frequency Modulation

Modulation: Modulation is the process of encoding information onto a carrier signal by varying its frequency, amplitude, or phase, allowing the transmission of useful signals over a distance.

Amplitude Modulation (AM) is a type of modulation where the amplitude of the carrier signal is varied in proportion to the information signal while the frequency and phase remain constant.

Frequency Modulation (FM) is a type of modulation where the frequency of the carrier signal is varied in proportion to the information signal while its amplitude remains constant.

LoRa uses a combined modulation technique based on linear frequency modulation (chirp spread spectrum, CSS). In this method, the signal's frequency continuously increases from low to high (or vice versa) within a defined range.

LoraWAN modulation refers to LFM (linear frequency modulation) or CSS (chirp spread spectrum). Type of carrier ( unmodulated) signal .

Radio Interface Lora / LoraWAN. Modulation

Chirp modulation in LoRa consists of irregular cycle breaks, meaning the cycle can stop at any point rather than at equal time intervals. This feature introduces a time shift, making LoRa signals more robust against interference and improving signal recognition even in noisy environments.

LoRaWAN modulation happens at "breaking" the cycle at one of the intermediate points and starting a new one, which can be interpreted as a time shift of the cycle.

Radio Interface . Spreading Factor

Spreading Factor (SF) - “ speed” of frequency change in the LFM signal. The higher the SF, the slower the frequency change.

Changing the SF by one unit means doubling the cycle (Chirp) time. For SF =7 and 125 kHz bandwidth, the chirp duration is 1.024 milliseconds

The length of the chirp affects signal noise, enhancing signal recognition at the output. It allows signals to be recognized even with lower energy and a reduced RSSI level.

Think of SF as a ‘zoom lens’—higher SF ‘zooms in’ for longer range but sends data slower.

Higher Spreading Factor = Longer Range but Slower Data.

Data encoding

Coding - adding redundant ( control) information to the transmitted user data to increase the probability of successful reception.

The level of redundancy is determined by the coderate (CR) ratio, such as 4/5, which means that for every 5 transmitted bits, 4 bits are useful data, and 1 bit is a control (redundant) bit.

CR value determines the rate of useful information transmission. LoraWAN uses Coderate from 4/5 to 4/8.

The data transmission rate in bits per second (bps) for a 125 kHz channel bandwidth depends on the Spreading Factor (SF) and CodeRate (CR).