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The billions of electronic devices that will comprise the Internet of Things (IoT) universe may one day tell us at a glance all we need to know. Such devices will feed data from equipment in homes, offices, warehouses, and vehicles to the internet for fast and easy access from a mobile device. While some communications systems operate with physical cables, such as landline telephone networks, cable-television (CATV) systems, and power utilities, most IoT devices and IoT networks will rely on wireless technology. The choice of wireless technology will have a great deal to do with the success of these IoT networks.
IoT technology is projected to be the basis for such phenomena as “smart cities,” “smart factories,” and “smart homes,” where lights and appliances can be remotely programmed and controlled via their connections to the internet (see figure). In these IoT networks, multiple sensors provide data on temperature, humidity, open doors, unlocked cars, and even when lights are on or off. Adding intelligence in the form of a microprocessor to each IoT sensor will allow for interaction with data from other sensors and a certain amount of decision-making.
The wireless-connectivity options for IoT are typically short-distance, low-power wireless technologies such as Bluetooth Low Energy (BLE), IEEE 802.15.4 (the ZigBee wireless standard), and the IEEE 802.11 wireless-local-area-network (WLAN) standards. Some of the concerns in applying any type of wireless technology for an IoT network include:
• Low-power consumption in support of long battery life for portable devices or devices not connected to the power grid.
• Flexibility to modify these networks with future advances.
• Data security from would-be hackers.
The modern automobile can be thought of as a moving sensor network. It depends heavily on multiple sensors for proper operation and, if equipped with wireless sensors as in an IoT network, lays the groundwork for a highway system that can monitor traffic conditions and fuel consumption while even improving on overall road safety.
In support of future IoT network growth, the costs of components like electronic sensors and microcontrollers are dropping. Thus, devices and components for wireless connectivity are still vital parts of expanding IoT capabilities.
When trying to pinpoint the optimal wireless technology for an IoT application, one must consider key concerns such as data security, wireless connectivity distance (the coverage area), interference to or from other wireless devices in the area, and power consumption for battery-powered IoT devices. That said, a number of different wireless technologies are currently in use for IoT, each with its own characteristics.
What Are the Wireless Options?
Perhaps the best-known wireless standards in use for IoT at present are IEEE 802.11 Wi-Fi and variations of Bluetooth, including low-power BLE. Wi-Fi wireless connections, also known as WLANs, operate at industrial-scientific-medical (ISM) band frequencies of 2.4 and 5 GHz. Wi-Fi systems are widely used in homes, factories, offices, and many public places as internet access points known as “hot spots,” and represent starting points for the many internet gateways that will be needed for full IoT coverage.
For short-distance wireless connectivity, Bluetooth and BLE (IEEE 802.15.1), which operate in the same frequency range from 2.400 to 2.4835 GHz, are used in some wireless medical devices as well as in a variety of wrist- and body-worn health and fitness equipment with wireless IoT access, including “smart” watches. BLE (also known as “Bluetooth Smart”) is an attractive wireless option for many of these applications due to its low energy consumption versus standard Bluetooth, although it lacks backwards compatibility with standard Bluetooth. BLE uses 40 2-MHz channels, while Bluetooth works with 79 1-MHz channels.
Another wireless candidate for IoT sensor networks is ZigBee (IEEE 802.15.4), a low-power standard developed for use in machine-to-machine (M2M) wireless networks. Along with ZigBee PRO, a version optimized for lower power consumption targeting thousands of IoT devices, these wireless standards are designed for energy consumption through low latency and low-duty-cycle operation. In fact, ZigBee PRO includes a feature known as “Green Power” that supports the use of energy harvesting in self-powered IoT devices capable of operating without batteries or power lines.
ZigBee provides global operation in the 2.4-GHz band as well as regional operation at 915 MHz in the U.S., 868 MHz in Europe, and 920 MHz in Japan. It uses industry-standard AES-128-CCM encryption for data security.
WiMAX (IEEE 802.16), short for Worldwide Interoperability for Microwave Access, is a much-longer-distance wireless transmission method than the earlier standards, providing wireless access across a radius of approximately 50 km compared to meters for the other standards. It can also transfer data at rates to 50 Mb/s and higher. WiMAX operates in licensed and unlicensed frequency bands from 2 to 11 GHz and from 10 to 66 GHz. The tradeoff for increased wireless coverage is WiMAX’s higher power consumption compared to the other wireless standards. Thus, it would serve as a practical IoT wireless technology candidate more for large-area coverage than in short-distance applications.
In addition to these short-range wireless standards, some of the hopes for the coming Fifth Generation (5G) of cellular wireless communications will rest on the network’s capacity to handle the enormous amounts of data generated by an untold number of IoT devices. In preparation, proposed 5G systems are being designed with many performance-enhancing, capacity-boosting features to ensure robustness in an operating environment where IoT devices will not only transmit data, but in a large number of cases, expect signals back from a user.
Use of IoT devices in industrial environments is spreading rapidly, as part of a phenomenon known as the Industrial Internet of Things (IIoT). Sensors actually have been an integral part of manufacturing environments for years, helping to control vibration, temperature, even the duration of a specific manufacturing process. Rather than just operate under the local control of a facility’s computer system, IIoT devices enable remote monitoring and control of manufacturing processes wherever there is Internet access.
The wireless technologies noted so far are well-recognized standards with strong industry backing, but they are not the only options for IoT. For example, LoRa is a low-power wireless technology supported by a growing number of companies (over 400) in the LoRa Alliance as a potential solution for the wireless interconnection of myriad IoT and M2M devices.
Designed to serve wide area networks (WANs), the LoRaWAN specification is meant to provide simple, secure wireless interconnections of IoT devices for homes, businesses, and industry with bidirectional communications capability. The infrastructure includes gateways serving as transparent wireless bridges between network servers and IoT devices.
LoRaWAN systems employ frequency shift keying (FSK) in the form of frequency hopping for reliable reception amidst radio-congested environments, with encryption for security. The IoT network operates on lower frequencies than the more-established wireless standards for enhanced range, about 15 to 20 km. The systems use unlicensed frequencies at 902 to 928 MHz in North America, 867 to 869 MHz in Europe, and 433 MHz in Asia for wide coverage areas and employ high-efficiency amplification formats for long battery life. LoRaWAN technology operates with an adaptive-data-rate (ADR) scheme (data rates of 0.3 to 50 kb/s) to conserve network data capacity.
Other IoT Wireless Influences
Admittedly, not all IoT growth is about wireless technologies. For instance, specifications established by the Infrared Data Association (IrDA) establish a set of protocols for wireless infrared communications over short distances, including for IoT devices. Data rates exceeding 1 Gb/s are possible, depending on the modulation and coding scheme, with coverage distances of about 0.2 m for communications between two low-power IrDA devices and about 1.0 m between two standard-power IrDA devices.
In addition, the computing/processing side of future IoT networks will determine just how much human involvement will be needed in operating these networks. For example, computer giant IBM recently announced that it will invest more than $200 million on the new Watson Internet of Things Center in Munich. The center will be devoted to using artificial intelligence (AI) for coordinating events on various IoT networks, and designing distributed databases to work with virtual currencies for different IoT scenarios. IBM expects to invest more than $3 billion on bringing cognitive computing to IoT networks.