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Which are the best communications technologies for IoT and M2M?

Steve Rogerson
May 20, 2015
 
Drivers for the growth of the IoT and M2M are the increased use of data and the reduced costs of connectivity, Matt Cook, business development manager for UK-based Solid State Supplies, told the Device Developers’ Conference in Cambridge last week.

The origins of the IoT go back to 1998 when it was recognised that more and more things as opposed to people need to connect to the internet. Then it was realised there were just not enough IP addresses to deal with this and thus IPv6 was created.

“In the beginning, you would look at high-asset products,” he said, “but now we are connecting much smaller devices with less value. It now makes economic sense to connect them and do something useful with them.”

These devices either need to push out information when necessary – an event driven architecture – or be ready to receive a command. Also important are size and scalability.

“As we get more and more devices, we may need to scale up the infrastructure,” he said. “Now there are people providing infrastructure as a service, which is cheaper than creating your own network.”

The main connection means include Wifi, Bluetooth, Zigbee and proprietary RF in the short range and Wimax and cellular technologies for the longer distances. The benefits of Wifi, he said, included having a lot of devices already supporting it. It has a high throughput and existing infrastructure. There are also no roaming charges and it can use mimo technology.

“Latency can be an issue with Wifi,” he said, “when you come up from sleep mode. It doesn’t connect initially and that can eat up battery life.”

Bluetooth is lower power and lower cost, and there are no cellular charges. No infrastructure is needed and it has a reasonable throughput. The frequency hopping is good for finding a free channel.

“The downside is you can only have about eight devices connected,” he said. “If you want more, you have to set up multiple PANs.”

The Zigbee mesh network does not have this problem as a thousand devices can be on the network. It also needs no infrastructure, is low power and relatively simple. There is good latency when coming up from sleep. Network management can be a problem if too many devices are allowed to communicate at the same time.

“But it is nice and reliable,” said Cook. “And it is self healing. If a device goes out it will try to heal the network by finding another route.”

The cellular technologies of 3G and LTE have a good range and throughput, and an existing infrastructure. There are, however, places where they don’t work and roaming can be problematic, and expensive, though hardware and data costs are coming down. Like Wifi, it use mimo technology. Among the main disadvantages are that it is a power hungry technology and the approval process is complex.

Wimax is on its way out, said Cook. It was only ever popular in North America and users and providers are now moving to 4G cellular.

• Earlier in the conference, Chris Hills, chief technology officer at UK-based Phaedrus Systems, warned of the dangers of the IoT for safety critical systems.

“The IoT is not benign,” he said. “It is out to get you. Anything that is connected to the internet has to be made safe.”