4 factors to consider when choosing a wireless protocol for your sensor system
One of the first choices you’ll make when adopting a smart sensor system is whether to go for wired or wireless. And with wireless systems offering much greater flexibility, as well as ease of installation, more and more organisations are choosing to go down that route. Which brings us on to the next decision – which wireless standard do you use?
Wireless standards, also known as protocols, are technologies used to carry a signal wirelessly. Different protocols have different ranges, data requirements, security and power demands, and a number, including Bluetooth, EnOcean and ZigBee, are especially suited to IoT networks because they can support a lot of low-power devices spread around a home or building. (If you’re getting stuck with other terminology, take a quick look at our smart sensor technology definitions).
All have slightly different features and capabilities and you’ll need to consider your individual system requirements to find the best match. Here are the four main factors you’ll want to consider.
1. How much data to you need to transmit?
If you’re looking to transmit larger pieces of data, such as moving pictures, or you want to network computers, you’ll need a protocol that can carry large data quantities in a short time. WLAN and Bluetooth standards both offer this capability, but use a lot of energy in the process.
Most smart sensor systems only require short-term wireless transmission of small amounts of information. In that case, you could turn to a low-power solution like EnOcean or ZigBee. EnOcean is a low-power network that’s optimised for ultra-low-power wireless devices, while ZigBee 3.0 is a low-power, low data-rate wireless network used mostly in industrial settings.
2. How many devices will be transmitting data at the same time?
When too many devices in the same vicinity use the same frequency band, the radio signals can get pretty crowded. This leads to interference, which can cause delays in data transmission and even data losses.
Certain frequency bands are more widely used than others, which makes systems using certain protocols more prone to interference. The 2.4 GHz band is a good example – it’s used for the wireless networking of computers, printers and other IT equipment and is license-free all over the world, making it a popular choice. Bluetooth and WLAN both use this band, as do the majority of ZigBee devices.
You may have seen protocols that describe themselves as falling in the sub 1 GHz band. This means the protocol transmits data using radio waves with a frequency (RF) of less that 1 GigaHertz (GHz). This band is particularly useful for IoT devices as it’s less crowded, meaning you’re much less likely to experience interference.
The 868 MHz band, used by EnOcean and Z-Wave, falls into the sub 1 GHz category and generally provides more reliable signal transmission as a result. While it doesn’t allow continuous transmissions it’s perfectly adequate for very short transmissions. In addition, the laws of physics mean that 868 MHz radio waves will penetrate further and reflect less in a building than 2.4 GHz signals.
3. How will sensors be powered?
If sensors are battery powered, know how long you can expect the batteries to last before they need replacing. As well as monitoring sensors for battery condition you’ll also need to change them, dispose of them safely and make sure you’ve always got replacements ready to go.
One of the reasons we choose to use the EnOcean protocol is that it’s designed for use with extremely low-power, battery-free sensors. EnOcean is currently the sole provider of energy-harvesting sensors, which work by collecting tiny amounts of energy – such as light, temperature differences and kinetic motion – from their environment.
The EnOcean protocol only requires about 0.12 μWs to securely transmit one bit of information over a distance of 300 metres in free space. A batteryless wireless switch consumes about 50 μWs for a complete radio command – around 100 times less than the more usual, battery-powered wireless switch. So a conventional wireless radio, powered by an electrodynamic generator, would require 100 times the actuating force of an EnOcean switch, and a conventional wireless sensor in a living room would need a solar cell 100 times the size.
Those seeking a low-energy, low-maintenance solution should consider a batteryless, wireless solution. Currently EnOcean is the only standard enabling this, which is one of the reasons we’ve chosen the standard for our current range of sensors.
4. What technologies and platforms will you be using it with?
The key consideration here is compatibility. Since there are so many device manufacturers and building automation systems in use, you need to make sure the wireless protocol you select will work with the equipment you either already have or are intending to use.
Our smart gateway makes EnOcean sensor data securely available using industry-standard formats such as MQTT and JSON, meaning it can be integrated into any software or platform.
For more information about smart-building sensor technology, download our brochure.