New M2M radio specs could challenge mobile networks


Wide area of possibilities.

Two new low power standards for wireless machine-to-machine (M2M) communications have been released in the past couple of weeks. The Zigbee Alliance and the Weightless special interest group have published specifications for wide area networking standards that address the low power, low bit rate needs of many M2M applications. Both are initially targeting the smart grid sector, which is growing rapidly as electricity providers deploy tools to intelligently manage power distribution systems in real time.

The new Zigbee IP specification is the more interesting of the two. As the name implies, traffic is transmitted over a Zigbee mesh using the IPv6 standard, which means it can flow directly onto the Internet or into a plain vanilla local area network, at speeds up to 250 Kbps. That’s plenty fast enough to handle the short bursts of data that are typical of M2M applications.

The range of a single radio varies, with 30 meters being a common limit for indoor applications and 100 meters or more outdoors. The maximum, albeit difficult to achieve, range is somewhere around 1,000 meters. But the mesh architecture means that data can be relayed from device to device, extending the practical range of a network within a building or over a large outdoor area. Those additional hops can slow the throughput rate way down, but we’re talking about numeric sensor readings, not streaming video.

The Weightless protocol has a longer theoretical range – 10 kilometers – and a wider selection of data rates – 1 Kbps to 10 Mbps – in its trade space. It relies on a hub architecture, with low power field devices communicating back to base stations, which then convert the traffic to IP and send it upstream. It uses TV whitespace spectrum, which partly accounts for the longer range, while Zigbee relies on common unlicensed spectrum, for example in the 900 MHz and 2.4 GHz bands.

The differences between the two standards should allow for reasonably peaceful coexistence, since each should eventually settle into separate market segments. Deployment on smart grids will be an early test of whether either are practical for wide area, outdoor applications. If so, M2M devices designed around relatively expensive commercial mobile data networks and technology will see serious competition.

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