LoRa and LoRaWAN are quickly drawing global attention as a low-power wide area network (LPWAN) alternative to technologies like Sigfox, and gateways are springing up around the world. To the uninitiated, LoRa’s capabilities and potential are either a mystery, or completely unbelievable. It’s about time we dispel some of the misunderstandings or outright fallacies plaguing LoRa and LoRaWAN.
1. LoRa is LoRaWAN.
LoRaWAN is the communication protocol and system architecture for the network while LoRa is the physical radio layer enabling the long-range communication link. The LoRaWAN protocol and network architecture directly influence the battery lifetime of a node, network capacity, quality of service, security, and the variety of applications served by the network.
LoRa is the technology that modulates the data into electromagnetic waves. It uses a transmission method called “Chirp Spread Spectrum,” encoding data in frequency-modulated “chirps.” This transmission method has been used in military and space communication for decades.
2. LoRa signals can’t really transmit over 10 km. That’s nuts!
In a typical LoRaWAN network, range depends on numerous factors—indoor/outdoor gateways, payload of the message, antenna used, etc. On average, in an urban environment with an outdoor gateway, you can expect up to 2- to 3-km-wide coverage, while in the rural areas it can reach beyond 5 to 7 km. In some cases, extremely long range is also attainable—ref: 702 km!
LoRa’s range depends on “radio line-of-sight.” Radio waves in the 400- to 900-MHz range may pass through some obstructions, depending on their composition, but will be absorbed or reflected otherwise. This means that the signal can potentially reach as far as the horizon, as long as there are no physical barriers to block it. Elevating LoRa devices—placing them on rooftops or mountaintops, for example—will maximize their range. Other factors, such as antenna gain, will also have a large impact on range.
3. Okay, but there’s no way my device could last up to 10 years!
One of the unique features of LoRaWAN is long battery life. To achieve this, devices are generally programmed to go into deep sleep mode when not transmitting messages, maximizing battery life. The longevity of any node is still determined by the capacity of its battery, but going to sleep for extended periods will dramatically extend charge cycles.
Also, the LoRa signal itself doesn’t require a whole lot of power to generate and transmit. That means, even when the system is active and transmitting, power consumption is kept at a trickle. With a minimal amount of software tinkering, the Strata node from Gumstix idled at 20 mA in “idle” mode and topped out at less than 110 mA during transmission.