So you want to build a wireless device? With so many radio technologies available to choose from it can be hard to know which one is best for your project. Let's break this down into a few simple categories...
Sub GHz
Sub GHz options such as LoRa and SigFox, or even a propriatry protocol created by us or elsewhere, offer huge range (up to 15km) and low power with very affordable on board hardware. The longer wave length means it has better penetration (think buildings, trees, etc) because it uses less energy over a given distance. Seems great, right? Not always. Firstly, infrastructure... You're either going to need access to a gateway within range or invest in one.
There are also bandwidth limits which can become a barrier to certain projects. We have, however, made excellent use of Sub GHz radio on a number of projects where it has been utilised to great effect. The huge range and low power consumption have made it the obvious choice on some projects.
Pro's
- Long battery life
- Long range
- Low cost chipsets
Con's
- Limited data throughput
Bluetooth
Bluetooth has been around a long time and is used a lot in relation to our phones so everyone knows of Bluetooth. It works in the 2.4Ghz spectrum and therefore has a short range of about 100m maximum but is fast allowing much more data to be transmitted, maxing out at around 3Mbps.
Traditionally bluetooth has a high power usage but in 2011 Bluetooth 4.0 appeared (also known as Bluetooth Low Energy) which uses much less energy. It came about to answer the need of lower energy usage for devices which transmit occasional chunks of data rather than streaming. It has a similar range, around 100m, but tops out at around 1Mbps.
Pro's
- Fast data throughput
- Vast, well developed ecosystem
- low cost hardware
Con's
- Low range and high power usage (except Bluetooth LE - forfeiting data rate)
WiFi
Good old WiFi. We all know about this. It's fast, really fast, with speeds into the Gbps. At the moment it's the fastest option. This is another one in the 2.4GHz spectrum but more recently 5GHz radio is found alongside 2.4GHz offering greater speeds at lower range. Most WiFi routers now offer both ranges which work concurrently.
Great for relatively short range data communications because it's everywhere. If you offer a product which connects to WiFi it's likely no additional infrastructure will be needed by your customers. It does, however, have a limited range averaging at about 35-40 meters although that is improving and can be boosted with repeaters. Power usage is very high.
While there are public WiFi networks there's usually a cost or subscription involved and these certainly dont cover every corner of the country.
Pro's
- Extremely fast
- Well adopted and already in place in most buildings
Con's
- Very high power consumption means low battery life
- Doesn't offer true 'in the field' usage because of the private and individual nature of WiFi networks.
Mobile Data
Mobile data may be an option if you need to be able to transmit over some distance in a wide range of locations and the occasional loss of signal wont be a problem, such as when data is stored and uploaded in chunks after the event. Here's a run down on mobile data connections...
2G
Remember when this was a buzzword? You might be showing your age. 2G marked the turning point from mobile phones offering voice and SMS messaging to becomeing "smart". Ok, so looking back, those terrible cameras were, well, terrible and picture messaging was about all that came from it at first, but the protocol remains, as does the infrastracture, allowing for the use fo 2G data in IoT and other fields. Speed is good, not amazing, and not up to all jobs. A maximum, real world throughput of 40Kbps is the best you should expect.
Because of patchy coverage it's not recomended for devices needing to stream data constantly and reliably from a wide range of locations but if your project allows for data to be stored and transmitted in bursts 2G might be a fit.
Pro's
- Good coverage accross the country means you'll "usually" have a connection.
Con's
- High power consumption means lower battery life
- A subscription will be needed for each device
3G
It's OK, you can admit to remembering this one and still be fairly young! All much the same as 2G in real world terms but faster, at least 200Kbps and you can expect to pass up to 2Mbps.
Pro's
- Good coverage accross the country means you'll "usually" have a connection.
- Faster than 2G
Con's
- High power consumption means lower batter life
- A subscription will be needed for each device
4G
4G is an oddity in that it isn't fully defined. Your 4G phone is probably actually 4GLTE (or Long Term Evolution). In theory 4G could be faster than than domestic, fixed line broadband although, as you're probably aware, real world usage doesn't often pan out that way. Theoretical speeds up to a Gbps mean this technology can be used to transmit data in serious volumes.
Pro's
- Good coverage accross the country means you'll "usually" have a connection.
- Faster than 3G
Con's
- High power consumption means lower battery life
- A subscription will be needed for each device
USSD
You might not know about this one but you have probably encountered it. It's Unstructured Supplementary Service Data and if you've ever typed a code into your phone made up of *s, #s and numbers to change a setting on your mobile phone, or checked the balance on a prepaid phone, then USSD was probably used to communicate that to the network. A company called ThingStream now offer USSD connection for IoT and simillar uses. By way of a sim card, or a chip with all that embedded into it, the Thingstream network can be used to transmit text data or commands to another device or server. They offer a useful portal for creating "things" to listen to or send data to. It uses much lower power than the other technologies assosiated with "mobile networks". It initiates much faster and can send that all important alert very quickly.
Pro's
- Low energy usage compared to other "mobile" technologies.
- Very fast initialisation when transmission is needed.
Con's
- High power consumption (while lower than other mobile data) means lower batter life
- A subscription will be needed for each device