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9 By Barry Manz The electronics industry has a long history of developing standards to serve the same goal: Betamax versus VHS, Windows versus Mac OS, USB versus Thunderbolt, and in the cellular world CDMA versus GSM (TDMA); however, competition between more than two or three standards has been rare. IoT changes this paradigm, as at least seven different solutions are available for connecting IoT devices over short distances— nearly all of which are incompatible. Each one has unique advantages and disadvantages, and all are continuously evolving. The result: A fragmented IoT industry leading to frustration, confusion, and skepticism about IoT, ranging from designers to potential customers—the opposite of what's necessary for IoT to achieve its projected massive growth. To grasp what all this means for IoT requires digging down into the details of the competing connectivity technologies and their applications. First, it's important to differentiate between IoT connectivity solutions, which can be grouped into two broad categories: Short-range and long-range. The former, covered in this article, is the domain of technologies such as Wi-Fi, Bluetooth, ZigBee, Z-Wave, Thread, 6LoWPAN, and ANT+. This article explores key capabilities of short-range solutions, compares the seven primary solutions available today, identifies two leading solutions, discusses challenges that design engineers face in implementing short-range solutions, and looks ahead to continued improvements in these solutions. Short-Range Communication Functionality Short-range solutions comprise multiple requirements and capabilities: • Support a large number of IoT devices to communicate with each other over a network, preferably a mesh • Enable IoT devices to operate for many years on a coin cell battery • Provide robust security • Achieve the lowest possible complexity and hardware costs • Accommodate Internet Protocol Version 6 (IPv6) Network Connectivity In nearly all IoT applications, IoT devices must be able to connect to each other so the information they gather can be aggregated and sent on for processing and analysis, performed both locally and over long distances to reach data center resources (i.e., the cloud). In the comparatively simple example of home automation, the amount of gathered information is much less than in a massive network of electric meters; however, rather than simply gathering one type of measurement (e.g., voltage and current), measurements can be numerous, including temperature and humidity, power usage, video, equipment status, and many others. Nevertheless, both applications require information to be gathered by wireless-enabled sensors. All short-range IoT connectivity solutions incorporate networking capability except for Wi-Fi, which was never designed for IoT-type applications, and can accommodate from several hundred to tens of thousands of devices. Not all network types have the same capabilities, though. The one best suited for IoT is the mesh network (Figure 1), in which all devices can communicate with each other without needing to first pass information through a hub such as a router or a gateway. Mesh networking is crucial for the largest applications where IoT devices may span vast areas, such as on a farm, large production facility, and hundreds of other environments. Figure 1: In a mesh network, all devices can connect directly to each other. Low Power Consumption In home automation systems, most devices can be powered by 120V AC , but others such as "smart" door locks and alarm system sensors are powered by coin cells or other small batteries. In most other applica- tions, such as in a production facility or a farm, nearly all the devices are powered by batteries or possibly by solar cells. As envisioned, the majority of IoT devices would be powered by batteries, so connectivity solutions have been designed to accommodate this requirement. To achieve this, the devices themselves must consume very little power, and the network must use communication techniques that feature very low data rates and minimal sensor RF transmit power. IoT devices rarely, if ever, need to communicate continuously, but they still need to be able to receive a command from an external source such as a long-range communication system and from the components that they serve. IoT devices meet this need by enabling the devices to "sleep," keeping only those functions awake that are required to detect activity from the component the sensor serves or from the network. Except for Wi-Fi, every IoT connectivity solution has been designed with this in mind. Sorting Out IoT's Proliferating Short- Range Connectivity Solutions 6LoWPAN

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