LoRa uses a spread spectrum modulation technique to transmit data. While LoRa has some advantages, such as its ability to transmit data over long distances and its low power consumption, it is not considered to be a spectrum-efficient technology.
There are several reasons why LoRa is not considered to be spectrum-efficient:
- Modulation technique: LoRa uses a modulation technique, which spreads the data signal across a wide frequency band. This can lead to a lower spectral efficiency, as the signal is spread across a wider frequency band than is necessary.
- Low data rate: LoRa is designed for low-data-rate applications, such as sensor networks and IoT devices. While this can be beneficial for certain applications, it also means that LoRa is not well-suited for higher-data-rate applications, which can be more spectrum-efficient.
- Listen-before-talk (LBT): LoRa is not able to use LBT due to it’s modulation technique. LBT increases the spectrum efficiency reducing the number of collisions and retransmissions.
- In-Building environments: LoRa (Long Range) has been developed for use in long range applications (kilometers) but is being used in building environments in which the long range is not needed. Higher data-rate modulation techniques, such as FSK or BPSK, allows for a shorter on-air transmission time therefore being more spectrum efficient.
LoRa is not as spectrum efficient as other modulation schemes such as BPSK or TurboFSK, which can be implemented in an commercial of-the-shelf radio transceiver. Going forward, The number of IoT devices per square meter will only increase and since the amount of frequency spectrum available is is a natural and finite resource, we should strive to use it as efficiently as possible.

Fun fact: The first wireless transmissions was done by Marconi using spark-gap transmitters, back in 1896. They basically emitted white noise, which could then be detected at long distances. Whenever a spark-gap transmission was in progress, it was using the entire frequency spectrum and hence only room for one transmission at a time! As time went on, the ability to modulate signals caused the frequency spectrum to be used much more efficiently.