Arguably the leader in the war for low-powered, long-range, albeit low-bandwidth, wireless connectivity for the Internet of Things is the LoRaWAN standard. On a good day, with a reasonable antenna, you might well get 15 km (9 miles) of range from an off-the-shelf LoRaWAN station. But that doesn’t mean that this is the limit for the protocol, and there are a lot of people that are really keen to prove that long-range really does mean long-range when it comes to LoRaWAN.
Most of successful attempts at the LoRaWAN distance record rely on weather balloons, and earlier this month, a flock of seven balloons was launched from Alfamén in Spain into the stratosphere in another attempt at the record. Somewhat surprisingly, the attempt broke the record, not once, but twice.
Tracked by The Things Network, APRS, and by satellite, the 7 balloons headed skyward on Saturday 13th July. They carried 20 different experiments under the auspices of the Servet Project and, the previous world record of 702 km (436 miles) was broken with a new record distance of 741 km (460 miles).
The record was set by the PaPe I, experiment built by Jose Manuel Cuesta with that goal in mind.
The experiment used three 3D-printed directional Moxon Antennas, spaces 120º apart, and a reaction wheel for attitude control to prevent the payload from spinning underneath the balloon taking it aloft.
Each of these three antennas had an independent transmitter connected to a different micro-controller. The first was based around an Espressif ESP32 with an RFM95W LoRa module, the second around an Espressif ESP8266 also with an RFM95W, while the last antenna was connected to ASME Lion SOM based around the Microchip SAM D21.
However, and somewhat surprisingly perhaps, this new world record held for only 5 hours, until it was broken again. This time by one of the other balloons from the flock, Diana I, for a new record distance of 766 km (476 miles).
Launched at the same time as PaPe I, the Diana I experiment was built by Enrique Torres, and optimised to reach the highest possible altitude.
“…the balloon’s lift and capsule weight were optimised up to the grams. The climb was going to take extremely long (over 10 hours), and the route was likely to be very long, creating a high risk of losing the probe completely. The device was realised with a TTGO node with LoRa module because of its price, availability, weight and low power consumption.”
The payload weighed just 106 g (3.74 oz), and included a Bosch BME280 environmental sensor and a GPS, with a bazooka dipole antenna, consisting of two hand made 8.4 cm (3.3 inch) elements.
While flying at a height of 24,859 m (81,558 ft) above Ariza in Spain, the messages broadcast from the Diana I experiment were received by 24 gateways, the furthest located on a mountain in Chamrousse, a ski resort close to Grenoble in France, a record breaking 766 km (476 miles) away.
The new world record approaches the theoretical maximum a LoRaWAN packet can travel. Semtech’s LoRaWAN Academy argues that 800 km is the maximum distance in Europe, using 25mW transmission power in the 868Mhz ISM band. So while longer distances have been achieved in the past, their link budget had some solid help from the 5 m uplink antenna and 90W amplifier on the SES-2 satellite, and of course they were transmitting in the Ku-band rather than in the traditional LoRa bands. It therefore seems likely that this month’s new record distance will stand for some time to come.