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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?

Bluetooth SIG has announced that it will add functionality in its 2016 version of the standard that makes Bluetooth Smart more suitable for infrastructure applications such as long range and mesh. This will likely make it a future contender in homes and buildings.

Outdoor installations
Considerations for outdoor installations are much like the ones for indoor infrastructures. Can I get the range I need on the power budget I have? Can I take advantage of existing infrastructures?

If you can rely on cellular coverage, are willing to bear the cost of the connection and meet the power requirements, the simplest way to connect a node to the Internet is through a cellular modem. If your network includes nodes that for cost, form factor, or power budget reasons should not be directly connected to a cellular tower, a good option is to look into a hybrid solution. For street/city lighting, environmental monitoring or similar, a common solution is to build a network with one or more concentrator/gateway nodes that include a low-power, long-range RF interface as well as a cellular modem for Internet connection. The rest of the devices in the network are then connected to the concentrator using a Sub-1GHz radio network with or without mesh routing capability. In the case of a street lighting network, the concentrator can locally control lights based on input from sensors while its rule set and schedule can be updated from a cloud server through the cellular network. A standards based solution would be based on IEEE 802.15.4g star network or the same PHY with a mesh stack on top. An open source implementation can be found in Contiki OS and 6LoWPAN stack for example.

An alternative to the cellular infrastructures are the new low-power, long-range infrastructure subscription networks like SIGFOX. The end nodes can be implemented with low-power, low-complexity narrowband radios and coverage grows at a fast pace. The data throughput is limited, but you will get an easy way to transfer small amounts of data to and from your node for status and configuration.

Personal devices
If your device is personal, portable, or wearable, it is natural to consider a phone to be the ideal gateway to the Internet. Phones generally support Bluetooth BR/EDR and Bluetooth Smart in addition to its upstream facing Wi-Fi and phone modem. If your application includes audio streaming, Bluetooth BR/EDR is ideal with its high throughput and ready to use A2DP solutions. If you do not have high throughput requirements (less than ~150 kbps), Bluetooth Smart is the right way to go. It offers application layer interoperability for a few standardised applications like 'heart rate monitor,' but more importantly it offers full freedom and flexibility to define your own profile with services and characteristics that suit your application. All you then have to do is write a phone application that offers some local functionality and communicates with the cloud service in the background (much like the non-6LoWPAN routers for infrastructure applications). A good example application of sensors connected to the cloud through a phone is the SimpleLink SensorTag ecosystem.

Implementation considerations
Regardless of the wireless technology you end up choosing, if you are not making a large number of units right away and do not have special form factor requirements, it is always a good idea to consider buying a pre-certified module. You will get decent RF performance and the higher per-unit price is offset by not having to do RF tuning, regional regulatory compliance testing (ETSI, FCC) etc. With Wi-Fi and other standards, you even save money not having to do the full standards certification.

About the author
Peder Rand holds a Masters Degree in Computer Science from the Norwegian University of Science and Technology. He has worked for Chipcon/Texas Instruments since 2005 holding positions as digital designer, systems architect, strategic marketer and applications manager. He is currently responsible for EVM and software development tools in the Texas Instruments Wireless Connectivity group.

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