High range with LoRa® on worldwide 2.4 GHz band

The ability to achieve high communication ranges both for outdoor and indoor applications is often of essential interest. In Europe, such applications are often realized in the license-free sub-gigahertz frequency bands at 433 MHz or 868 MHz. The reason for this is that applications that are operating on low frequencies are subject to less propagation losses compared to applications that are operating on higher frequencies. That means that working on lower frequencies enables to achieve higher communication ranges when the transmit power is kept the same.

However, the advantage of higher range is faced by two disadvantages of those sub-gigahertz frequency bands. First, a duty cycle that has to be fulfilled and second the fact that the sub-gigahertz frequency bands are not harmonized worldwide. Especially the latter can lead to enormous costs for the necessary radio approval outside of Europe.

Especially applications in the field of home automation, such as light control, heating, air conditioning, and automatic meter reading (AMR) are currently often developed in the sub-gigahertz frequency range due to the high range requirement. The limitation by a duty cycle is normally accepted as the application by itself rarely transmits data. But sometimes a higher transmission rate is desirable, especially when thinking about some sensor applications. From a worldwide regulatory point of view the sub-gigahertz frequency range looks like a rag rug, while the 2.4 GHz band is globally harmonized and therefore offers a better alternative. In addition, an application within the 2.4 GHz frequency band is not subject to any duty cycle restrictions.

Well known wireless technologies that work within the 2.4 GHz frequency band are WLAN, Bluetooth® or Zigbee. But without any additional power amplifiers those technologies can only achieve communication ranges of a few tens meters. Higher range requirements result directly in complex and expensive radio systems with power amplifiers and higher power consumption. Those radio systems are probable not suitable for battery-driven devices.

This balancing act between long range, battery-driven operation and the use of a worldwide harmonized frequency band is only achieved by the iM282A. It is able to achieve communication ranges of more than 10 km (LoS) within the 2.4 GHz frequency band. The iM282A provides a powerful Cortex M3 controller and the new SX1280 radio module from Semtech®. In addition to the well-known LoRa® modulation, the SX1280 offers also a conventional (G) FSK / MSK modem as well as a FLRC (Fast Long Range Communication) modem. Thus, different raw data rates from 476 bps up to 2.0 Mbps can be realized depending on the range to be achieved, see [1]. With a sensitivity of down to -130 dBm and an integrated 12 dBm power amplifier, an extraordinary link budget of up to 142 dB can be achieved. Furthermore, the 20 x 25 mm sized module consumes less than 40 mA in transmit mode, less than 10 mA in receive mode and below 1µA in sleep mode and is therefore ideal for battery-driven applications.

With the iM282A, the successful LoRa® technology from Semtech is now also available for the 2.4 GHz frequency band. The LoRa® modulation is already known since 2013 from the Semtech chip family SX127x for the sub-gigahertz frequency bands. At that time, IMST GmbH presented the world’s first LoRa® radio module iM880A at the “Innosecure” trade fair. Based on this technology, the LoRaWAN® standard has evolved over time. The LoRaWAN® standard is specified for the sub-gigahertz frequency bands and is constantly being developed by the LoRa Alliance®, which consists of several hundred well-known companies worldwide.