Connectivity and networking describe the (often) wireless technology used to transfer information from the sensors/ end nodes to the cloud. To connect and talk to each other, all IoT devices need connectivity. There is a wide range of wireless technologies that enable this connectivity, each with their own strengths and weaknesses. Choosing the right technology will ensure the IoT application runs smoothly, at the lowest cost, and with the best power efficiency.
Some wireless technologies existed pre-IoT, whereas some have been designed specifically for it, but all have their own advantages and disadvantages.
Generally, the communications module will have the highest power consumption out of all the system components in an IoT device when sending/receiving data, so developers should consider keeping the amount of data transmitted and received by the sensor to a minimum.
‘Peak power’ can be used to understand power consumption; however, this doesn’t include factors such as time for network connection, data transfer rate and power consumption in sleep. In general, the higher the data rate and range, the higher the power consumption.
This list is by no means comprehensive but details some of the most popular wireless standards for IoT.
Near Field Communication (NFC): NFC is an ultra-low range, low-power, and low-bandwidth technology. Its function is to exchange very small amounts of data between two devices in extremely close proximity to one another. It is most commonly used in mobile phone contactless payment systems. It can be a very useful means of introducing the ability to quickly configure the parameters of a device while it is deployed in the field, without having to physically connect to it, or reprogram it. No power source is needed for the secondary device (tag). The magnetic field of the primary device powers the secondary device.
Radio Frequency Identification (RFID): RFID is used for uniquely identifying items using radio waves. It is most commonly used in card contactless payment systems but is also used in asset tracking. RFID tags can operate with or without a power source with range and cost increasing with powered versions.
Bluetooth: Bluetooth is a global 2.4GHz personal area network designed for short-range wireless communication. Device-to-device file transfers, wireless speakers, and wireless accessories are some common examples of where this technology is most often used.
Bluetooth Low Energy (BLE): BLE is a version of Bluetooth designed for lower-powered devices that uses less data. An ideal application for BLE is wearable fitness trackers and health monitors. The Bluetooth standard is continuously developing further functionality, and is gaining traction in smart building applications. It is one of the cheapest modules out of the wireless standards and is a popular choice in devices requiring short range, power and efficient communications.
ZigBee: ZigBee is a 2.4GHz mesh Local Area Network (LAN) protocol with a primary use case of building automation and control applications with low data rates. For example, wireless thermostats, lighting systems, appliance control.
Z-Wave: Z-wave is a sub-GHz mesh network protocol which is used in similar applications to ZigBee. It is the dominant standard for smart home applications.
Wi-Fi: Wi-Fi offers a high data rate (>100Mbit/s) but to achieve this, it has a higher power consumption than other short-range standards. It is therefore suitable for high data rate applications, e.g., video streaming and unsuitable for remote locations or battery-operated devices.
Low-Power-Wide-Area Networks (LPWANs): The rise of IoT has driven the development of new wireless technologies that are designed specifically to meet the needs of IoT applications. These wireless technologies are known as LPWANs. Commonly used LPWAN standards using unlicensed bands are LoRaWAN and Sigfox, with the emerging cellular standards NB-IoT and CAT-M1 operating in the licensed bands.
Low power: The communication protocol is optimised for power consumption, meaning LPWAN transceivers have the potential to run on batteries for 5+ years.
The only real constraint for developers with LPWANs is the low bandwidth, although this trade-off allows battery operated devices a long-life, while maintaining long range communication. These two features are essential to realise most IoT applications. For the majority of IoT applications, large amounts of bandwidth are unnecessary as only small amounts of data are generated by the sensors.
LoRaWAN: LoRaWAN is designed with the aim of achieving long battery life whilst being capable of communicating over long distances. The LoRaWAN gateway is responsible for passing messages from connected devices to the internet. It is an open licence-free technology which means anyone can buy a gateway and setup a network to talk to devices. There are also network operators deploying LoRaWAN networks where the deployment is managed by the operator and users are charged on a monthly basis for connection.
Sigfox: This was the first LPWAN network to achieve significant network coverage across large amounts of the UK and Europe. All of the infrastructure is owned and managed by Sigfox.
Cellular LPWAN: NB-IoT and CAT-M1 are the standards that cellular operators are using to target the IoT markets and will form the key part of the 5G IoT offering from cellular providers. They differ from cellular in that they have better power efficiency and a lighter protocol suitable for IoT applications. These are still relatively new networks currently rolling out worldwide. They will play a big part in IoT but full coverage is not available in the UK, so ensure you check availability.
NB-IoT: NB-IoT is the lower bandwidth cellular LPWAN IoT standard. It is designed for fixed device location use for low power battery device operation. It has higher bandwidth that LoRaWAN and Sigfox however this comes with higher power consumption for transmitting and receiving.
Cat-M1: Cat-M1 has higher data bandwidth than the other LPWAN standards. The increased bandwidth also comes with the trade-off of the highest power consumption of the LPWAN technologies. The higher bandwidth means that Cat-M1 can carry a voice connection (VoLTE) which opens up multiple different use cases that are not currently achievable with other LPWAN standards. It is expected that this technology will be integrated into wearables and health and telecare applications. The Cat-M1 standard also supports roaming between cells by using the same protocol as the current cellular networks. Cat-M1 is gathering momentum in the North American market with the network going live.
Cellular: Cellular is the wireless protocol most familiarly used in mobile devices to access the internet and send SMS messages. It is a technology which is ubiquitous around the world, with existing infrastructure already in place. This can make it suitable for those applications which require connectivity in multiple countries or in more remote areas (provided of course there is a signal). It favours bandwidth and range at the expense of power consumption. Summary: Best option if high data rates, mobility and global coverage are priorities. Can send large amounts of data over a long distance but will quickly drain the battery.