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The search for the right wireless technology

Posted: 28 Mar 2016 ?? ?Print Version ?Bookmark and Share

Keywords:cloud? Wi-Fi? Internet of Things? IoT? ZigBee?

We are inundated by great new ideas for cloud-connected devices. Choosing the right wireless solution to connect your device to the Internet can be challenging in a fragmented market of standards and technologies. The good news is that the number of good choices you can make for your application increases year over year. This article aims to point you in the right direction based on some fundamental properties of the technologies involved.

Infrastructure devices
Devices whose functions naturally belong to a house/building/location rather than to a person are infrastructure devices. We can loosely separate those again into house/building and outdoor infrastructure due to differences in range requirements between the two.

Can you count on Wi-Fi coverage and access to the Internet through that network? If that's the case, Wi-Fi is usually the simplest and cheapest way to connect your device to the Internet. You can now get Wi-Fi chipsets that in some applications can survive for a year on two AA batteries. An advantage of Wi-Fi over other protocols discussed here is that it can achieve very high throughput when needed and it supports all the commonly used Internet protocols and security out-of-the-box.

Consider a wireless video doorbell for example, where the device is generally sleeping, but a couple of times a day it needs to connect to the Internet and send video to your phone to show who is at the door. Anything above six months of battery life is probably acceptable and it is typically sold stand-alone without any requirement to interact directly with other devices in your home. Since the end user's Wi-Fi credentials are unknown at the production of your device, you will need to find a smart way for the end user to configure the Wi-Fi network settings. The most common method for Internet of Things (IoT) devices is to use Access Point mode, where the IoT node is first configured as an access point that you can use your phone to connect to and configure. Once configured with the local Wi-Fi network credentials, it will re-boot into station mode and connect to the local network. The process requires multiple steps, including disconnecting the user's phone from the local network. The other common option is to use Wi-Fi Protected Setup (WPS) with either a push-button or pin code pairing. This approach is easier for the user, but requires support of WPS in the Wi-Fi router and access to the router. There are also a wide range of proprietary or even out-of-band provisioning methods available.

If you cannot count on Wi-Fi coverage or your network includes devices that are too energy constrained for Wi-Fi, you should look at alternatives. Does your network include mains powered nodes that are spread throughout the house in addition to your energy constrained nodes? An example would be a lighting network. In that case, you should consider a 2.4GHz low-power mesh network such as ZigBee or 6LoWPAN. They have the advantage of being able to support very low power constrained nodes while covering a whole house or building in the worldwide 2.4GHz ISM band.

To 6LoWPAN or not to 6LoWPAN?
Whether or not to use IPv6 addressing all the way to low-power end nodes (6LoWPAN) depends on how much intelligence you want to put in your gateway and on the capabilities of the end devices.

Figure 1: Application intelligence in the cloud.

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