LPWANs - Making data affordable for internet of things devices
By Jon Eggins, Director and Chief Operations Officer at Genesys Electronics Design. Jon has 20+ years’ experience advising, designing and developing electronics solutions.
What is an LPWAN?
LPWAN stands for Low-Power Wide Area Network. It is a technology that has come into play to support and enable the Internet of Things, or IoT.
The Internet of Things connects billions of smart devices – or things – to monitor, track and control everything from the air conditioning in your house to remote mining operations and critical hospital equipment.
Existing networks such as WiFi, 3G and 4G are not suitable or practical for connecting these low powered and prolific smart devices. They are great for high-speed data, but this new generation of connected smart devices requires a low-cost network that offers ubiquitous connectivity and power conservation.
Who owns and operates an LPWAN?
There are options that allow stand-alone “off-grid” networks to be used, where the network is owned by an individual entity. In these scenarios, the up-front costs are offset by the fact that there are no middleman providing (and charging for) network connectivity and data service.
At the other extreme, you can piggyback on a telco or other service provider, and leverage their network. There is also some grey, and more democratised middle ground.
One of the anxieties that surround LWPAN rollouts is how the big telcos plan to “play their hands”. They have indicated support for NB-IoT, and this is beginning to become a reality, but it has been slow going. In the meantime, an opening for SigFox and LoRa et al has emerged.
Theoretically at least, LPWANs such as LoRa tend to give you more flexibility on how you commit to application-specific infrastructure rollout and ongoing service costs.
What are the key technical characteristics?
LPWAN supports installations where hundreds, thousands or tens of thousands of devices are used, but the data throughput per device is very small. The cost of the device, installation and servicing is generally low.
Key characteristics of LPWAN are that it’s low standby power, short connection times, low data throughput and long-range. This means battery-powered devices such as sensors and actuators that do not require much data transfer can work for long periods of time on a single charge.
Traditional cellular data transport such as 3G often has significant time overheads where a “sleepy” device needs to re-establish a connection after it has been in a low-power or sleep mode. This connection establishment time can be prohibitively costly in terms of power consumption, and can dominate the energy usage of the device, which is obviously very undesirable!
What is the process for setting up an LPWAN?
The good news is that LPWAN networks already exist in many places, and their presence is growing. Service providers such as SigFox provide an easy way to connect devices without needing to invest in a dedicated network.
In the case of SigFox, there are some terrific chipsets on the market from Wisol that are excellent value for money at a few dollars, give or take.
To connect a device onto the SigFox network you simply purchase a token from the SigFox service provider and register your device’s SigFox module on the network. Your device is then available as an Internet-connected ‘thing’ via the service provider’s API.
Top tips for using an LPWAN with your IoT Solution
Determine how much data you need, when, and in what direction, as well as whether or not you need actuation.
If you’re not familiar with actuation, it is where one ‘thing’ makes another ‘thing’ perform some action. Actuation is the other half of IoT and, sadly, is rarely discussed because it is harder to do and most of the IoT hype focuses on sensors and ‘wearables’.
The key thing with actuation is that it requires a timely reverse data channel to your ‘thing’. Depending on how often you want to change the state of your thing’s actuator, you may need to send it 1 or 1,000 commands per day. If this is you, then a SigFox LPAN is currently not your best choice. However, if you are sending small amounts of data a few times a day, then SigFox may be perfect.
Choose your battery wisely.
There is no more important choice in a wireless IoT device than battery selection. Capacity, maximum discharge current (which is different to capacity), whether or not you will make your ‘thing’ rechargeable and how it will be recharged, are some of the key considerations. It also helps to optimise the power consumption of the electronics so that the demands on your battery are minimised.
Are you going to bury it?
Many IoT things get buried underground, installed up poles or hidden inside boxes in obscure locations. This presents a logistic challenge, which I won’t discuss here. It also presents a technical challenge related to the antenna type, location, nearby objects, geographical topology of the installation site, and proximity of the nearest base stations. Apart from mitigating your logistical risks, you need to do the maths on your radio link.
If you’d like to find out more about LPWANs we recommend looking at the wiki of Engineers Australia's applied IoT Engineering Community.