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Using Low Power WAN Networks with Energy Harvesting Sensors in IoT

by Raghu B on January 8, 2016

Traditionally, when it comes to connecting to the Internet wirelessly, one has relied on a few major forms of connectivity:

  • Cellular e.g. 3G/4G/LTE etc
  • Satellite e.g. Dish, etc
  • Wifi – on a more localized level albeit and it then connects to some wired source

There have been other methods as well and many of them have fizzled out due to one or more reasons e.g. WiMax – got superceded by LTE.

With the advent of IoT, there will be more devices than ever and one needs to be able to communicate with them. Not every remote area e.g. agriculture or oil fields can be wired up easily to provide some localized Wifi given its limited range. Cellular requires erecting towers and relatively high power consumption e.g. think smartphone — think how often you have to charge it.

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Figure 1 Energy Harvesting Device Architecture

So, there is a need for low power wide area networks to communicate with remote devices. Keep in mind, these devices are usually sensors or beacons transmitting or receiving tiny amounts of data. Two such WANs that are beginning to make headlines are SigFox and LoRaWAN.

SigFox is a European company that has begun to wire-up several cities in Europe and now making headway in North America with its network. In a simple sense, they operate in the same way as cellular. One needs to have “towers” a certain distance apart for signals to hop from tower to tower eventually culminating at a wired conduit to the cloud.

LoRaWAN is a US based consortium backed by the likes of Cisco and IBM and has started to make headway. There are some exhibitors at this year’s CES who will be demonstrating some early releases of this technology.

Now, what would be the ideal device that would connect to a Low Power WAN such as SigFox or LoRaWAN? Well, it isn’t going to be your cellphone or laptop or connected TV. It is more for Machine to Machine, or M2M applications. Now, let’s imagine an agricultural situation where one needs to monitor the temperature, moisture levels and other such factors for optimal yield. In such a situation, one may employ a fleet of sensors in a large land mass.

Traditionally, such devices need batteries and one can still use battery powered solutions. However, it imposes some constraints: 1) One needs to monitor battery levels and replace them 2) cost. Since the amount of information being passed around is small, one option is to find alternatives to battery power. Herein, lies the attraction of energy harvesting devices.

There are several companies already coming up with energy harvesting chipsets (http://electronicdesign.com/power/energy-harvesting-and-wireless-sensor-networks-drive-industrial-applications). The link illustrates an architecture of a harvesting device with various methods for harvesting energy e.g. Photovoltaic cell, a way to store such energy and sensors to capture info e.g. Temperature sensor.

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Figure 2 Traditional Network Configurations for Wireless Sensor Networks

Now, how does the information gathered by this device get transmitted to the Cloud? Well, a few configurations are illustrated here. In addition to the four traditional ones, an additional configuration may bring the world of Energy Harvesting Sensors and Low Power WANs such as SigFox and LoRaWAN under a single umbrella in the future.

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Figure 3 Low Power WAN Networks with Energy Harvesting Sensors

We believe the ecosystem will evolve towards Figure 3. The benefit of this approach is that the power consumption is low network wide. It is lower cost in the long run.

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