Taking the low-power modular approach to LoRa in the IoT

November 04, 2016 // By EDN Europe
Adam Chidley, Senior Product Manager Passives - EMEA, Avnet Abacus
Adam Chidley of Avnet Abacus takes a  look at LoRaWAN and why choosing a dedicated module to run the communications can shorten time-to market.

LoRaWAN is an important Internet of Things (IoT) wireless communications technology that is happening right now. Designed to improve IoT efficiency, reducing both costs and energy use, LoRaWAN is a specification for the low-power wide-area networks (LPWANs) that are being deployed in ‘smart cities’ of the future. Targeting a range of applications in public infrastructure, smart metering, remote sensing and asset tracking, along with increased use in machine-to-machine (M2M) technology, the pace is picking up with major LoRaWAN network infrastructure being installed and rolled out, especially in major cities across Europe. In June 2016 the Netherlands became the first country to announce a nationwide LoRa network.

In terms of range, the specification broadly fits somewhere between LTE/cellular and the shorter-range technologies of, say, Wi-Fi and Bluetooth. A key advantage of LoRaWAN and other LPWANs is the use of ultra-narrow-band technology and inherent low-power demands from network edge devices. A classic example application that promotes the use of a LPWAN is a series of remotely located sensor-based devices making environmental measurements, such as monitoring flood levels in a smart city application. The application will most likely only require the endpoint device to send a very limited set of measurement data, and probably not continuously. LoRaWAN is designed to transport small packets of data – rates from 0.3 up to 50-kbps – and minimise the energy consumption of battery-powered devices.

Cellular is clearly an alternative for this type of use scenario, but is perhaps better targeted at premium applications. Today, at least, it is prohibitively expensive in terms of cost per byte and in terms of power consumption, making it highly unsuited to low-power devices running on small or coin-cell batteries. However, new LTE/cellular narrowband technologies are emerging, such as the new NB-IoT standard. But this is perhaps still some while away from serious market penetration, whereas LoRaWAN technology is mature and well established with a number of products and technologies already available. In all probability, the standards will co-exist at least in the short-to-medium term, but LoRaWAN is here today.

A major advantage is its openness: standardised by the LoRa Alliance, LoRaWAN is an open specification that allows anyone to build a module or gateway that conforms to the specification. The next question is what are the technologies available to take advantage of LoRaWAN? While there are other silicon licensees for LoRa, today most products are based on Semtech’s technology. For example, Murata’s new LoRaWAN module – measuring only 12.5 x 11.6 x 1.76mm – is a simple solution for developers to easily add LoRa-based wireless connectivity. The module is based on the Semtech RF front-end SX1276 transceiver and a low-power STM32L Cortex M0+ microcontroller from STMicroelectronics. The micro includes 192-kbytes of flash memory and 20-kbytes of RAM, which provides enough memory for customer applications, as well as the capability to host other modulation protocol stacks.

Murata understands both wireless communications and the production of modules, as one of the world’s largest suppliers of wireless modules to the smartphone market, including the market leaders. Which brings us to the key point that the module approach could be