Long-range low-power wireless network have the potential to create the Internet of Agricultural Things

Mark Patrick
Long-range low-power wireless network have the potential to create the Internet of Agricultural Things
The application of technology has always driven an increase in productivity, the two are inextricably linked because it is often the demand for higher productivity that provides the motivation for achieving technological breakthroughs; necessity is the mother of invention, after all.

So it should come as no surprise that the benefits of adopting the IoT are derived from increased efficiency and productivity. If this were not the case, the evolution of the IoT would have stalled a long time ago. The opposite is, of course, the case, as the IoT mutates and reinvents itself to become the Internet of Industrial Things, the Internet of Medical Things and the Internet of Agricultural Things, to name but a few. 

In terms of wireless connectivity, the IoT owes much to cellular networks. Almost as soon as it was conceived and long before data overtook voice as the main form of cellular traffic, the cellular infrastructure supported non-human activity. Back then it was more commonly referred to as M2M, or Man/ Machine-to-Machine/Man. Early solutions involved machines sending simple SMS messages to ‘man’ and a common use-case often cited was a vending machine letting a service engineer know that its stock levels were low, that the refrigeration had stopped working or that the tamper alarm had been triggered. 

Fast-forward a couple of decades and SMS has been replaced by a format more easily understood by machines; raw data. Bits and bytes are the lifeblood of the IoT and sending them from one place to another defines it. The task of sending data through the ether now gets shared amongst a seemingly longer-by-the-day list of wireless solutions, such as Bluetooth, Zigbee, Thread, Wi-Fi and their many variants. 

Of course, none of these so-called Personal Area Network technologies can hope to match the range of cellular. However, while cellular networks still have a roll to play in this new world, there are newer and arguably more optimised long range wireless technologies coming online that will challenge its dominance. 

Star Wars? 

These new technologies are commonly referred to as Low Power Wide Area Networks, or LPWANs. They fall into two distinct camps; those that operate in the licensed part of the spectrum (and so controlled by cellular network operators) and those that operate in the license-free part of the spectrum (and are controlled by more overarching RF standards and some highly motivated associations). LTE now contains three technologies that target the IoT, which includes EC-GSM-IoT, LTE Cat M1, and NB-IOT. In the license-free arena the main technologies are LoRaWAN and Sigfox.  

All LPWANs balance range against bandwidth and power, with the aim of providing ‘just enough’ bandwidth to get the maximum range at the lowest possible power. This is what makes LPWANs so appealing in applications where proximity to a broadband connection of some kind is limited and the bandwidth requirements are low. This effectively describes a smart sensor in a remote location but it can include actuators, providing the network latency isn’t an issue. 

One of the main differences between a PAN and an LPWAN is the network topology; the former predominantly use a mesh network while LPWANs follow a star network topology (Figure 1). This essentially means that each endpoint in an LPWAN connects directly to one or more concentrators, or gateways, while mesh networks rely on many devices making many connections to maintain quality of service. 

Although the distant between endpoints in a mesh network is shorter than in an LPWAN, in situations where a number of endpoints are distributed around a property, such as a farm, a mesh topology is entirely viable. For others, their entire network could consist of a single sensor located in a remote area, and here it would make sense to use a star topology, as it is not dependent on neighbouring endpoints. With the right kind of gateway both types of network can coexist in an agricultural environment and the enabling technologies are already gaining acceptance in the sector. 

An example is the Hummbox soil and weather sensor from Green Citizen, which measures outside humidity levels, soil temperature and its moisture. It uses LPWAN (it is compatible with both LoRa and Sigfox) to send its data to the cloud, where a Platform-as-a-Service (PaaS) handles the analysis. 

No place to hide

As one of the LPWAN technologies operating in the license-free spectrum, LoRa offers a lot of flexibility. The Physical Layer (LoRa) is being used to create proprietary solutions that employ a protocol layer developed by a specific company, while the LoRa Association has also developed its own protocol, LoRaWAN, which offers a range of features appropriate to the IoT. 

Some of the main features of LoRaWAN include GPS-free geolocation for low-power tracking solutions, a range of as much as 30 miles in rural locations, and a battery life of up to 20 years. All of this can be achieved simply, using one of a growing number of pre-certified modules now available, such as the CMWX1ZZABZ from Murata. 

This LPWAN module integrates two enabling elements, the SX1276 ultra-long range spread spectrum transceiver from Semtech, and an STM32L0 Series ARM Cortex-M0+ based microcontroller from STMicroelectronics. Together, along with software from STMicro, they combine to make a module that offers all of the benefits of LoRaWAN with none of the development effort. 

LPWANs have the potential to connect more things over greater distances, in a way that other wireless technologies are not addressing. With the support of network providers and module manufacturers, using LPWAN in almost any application is a simple and safe approach to increasing efficiency and productivity, something that is becoming particularly pertinent in the agricultural sector. 

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