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Skip to 0 minutes and 8 secondsIt turns out that despite the much higher power consumption, Wi-Fi is actually a great candidate to ensure connectivity indeed. In contrast to ZigBee and variants, Wi-Fi has enjoyed tremendous growth over the past years. Today, most places where there is something to send or some data to be transmitted, there's Wi-Fi coverage. Access to the network is not always easy, but network coverage is virtually ubiquitous. From a solution provider point of view, this is really an attractive value proposition since one does not need to worry about getting sensors connected and thus does not need extra stuff to handle these issues. However, Wi-Fi has been out of reach for sensor communications due to the fairly large energy consumption.

Skip to 0 minutes and 59 secondsThis has changed as of late. That is when the Wi-Fi community started to apply duty cycling, that is, putting chips to sleep for most of the time when no sensing or transmission is happening, with the result of an extremely energy efficient system. Early optimisation efforts show that Wi-Fi could be 10 times more energy efficient than ZigBee. In addition, given the wide spectrum of data rates required for I.T. applications, Wi-Fi is better coping with this requirement since it can provide rates from a few kilobits per second to megabits per second. Understanding these potentials, the IEEE has started working on the low power Wi-Fi version, which is standardised in IEEE 802.11ah.

Skip to 1 minute and 51 secondsThe aim was to design an energy efficient protocol allowing thousands of devices to be connected. I summarise here some core features of these emerging standards. In terms of use cases, given the excellent home and corporate coverage of Wi-Fi, obvious applications include smart metering, industrial process management, and health and social care applications among many others. In terms of typical network configurations, a preferred embodiment is the use of up to 6,000 sensors attached to a single access point, communicating at about 100 kilobits per second. In terms of frequency bands and power and range, the system communicates in the sub gigahertz ISM bands at the default Wi-Fi transmission power of 200 miliwatts.

Skip to 2 minutes and 39 secondsThe low centre frequencies narrow bandwidth and fairly high power, as compared to ZigBee, gives a system an attractive range of about a kilometre to connect all your sensors-- I repeat, one kilometre. Compare that to ZigBee's tens of metres. Many of more features have been and are being added to make the IEEE 802.11ah the reference standard for embedded connectivity at home in corporate environments and industrial plans. The increasing dialogue between 3GPP and Wi-Fi communities also seems to underpin that, shortly, we will be able to offer unified connectivity platform, making equal use of Wi-Fi or 3GPP technologies.

Low power Wi-Fi

In this video, Mischa introduces the first of the emerging IoT connectivity technologies, low power Wi-Fi.

When you are thinking about connectivity for your product, note that if the legacy Wi-Fi system is used to connect sensors, then no upgrade to the Wi-Fi access point is needed; whereas, if the new IEEE 802.11ah low power Wi-Fi is used, then an upgrade is needed.

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This video is from the free online course:

The Internet of Things

King's College London

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