Wireless: Transmitting in the Internet of Things

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In the future, all objects and devices on the Internet of Things will communicate with the user and, above all, with one another. Around the world, established wireless standards such as WiFi and Bluetooth, but also newer technologies such as ZigBee, Z-Wave, EnOcean and Sigfox, are competing for market shares.

Whether it comes to building automation, connected cars or wearables: On the Internet of Things (IoT), the computer chips and sensors that are embedded in devices are becoming increasingly smaller and efficient. For them to communicate, transmission techniques are required that have low power consumption, achieve high data rates, have lower latencies and transmit information securely and reliably in critical infrastructures.

WiFi, Low-Power WiFi and Passive WiFi

WiFi or WLAN (wireless local area network) is one of the most widely used wireless standards for local networks. Its advantages include high transmission rates up to 600 MBit/s (nominal) with 802.11n and high security. The wireless standard is recommended for broadband applications that require high-speed data transmission. However, WLAN is very energy intensive, so it is less suitable for battery-operated devices. The energy-saving variant Low-Power WiFi (IEEE 802.11ah) was developed for embedded applications. Researchers at the University of Washington recently found out how sensors, actuators and small devices can transmit via WLAN without their own power supply. The technique known as Passive WiFi takes advantage of the fact that antennas can convert radio waves into energy and reflect a portion of those waves (backscatter communication). Components with Passive WiFi can transmit data on the reflected waves. In tests, data was sent over a distance of 30 meters at up to 11 MBit/s. The energy needed to do so was approximately 60 microwatts—one one-thousandth of what ZigBee or Bluetooth LE would need and 10,000 times less than using conventional active WiFi. When Passive WiFi will be ready for market remains unclear.

Ad hoc WLANs for Car2Car and Car2X

Vehicles can use the WLAN standard IEEE 802.11p (ETSI ITS-G5 or IEEE 1609 WAVE) to communicate with one another (Car2Car) and with the traffic infrastructure (Car2X). As soon as a car comes into the WLAN radio range of another vehicle, it automatically sets up a local radio network with it and alerts other vehicles using the road in the event of an accident, black ice or a traffic jam. Dynamic ad-hoc networks are formed in which vehicles function as transmitters, receivers and WLAN routers. The more cars join the ad-hoc WLAN, the larger the range and the IP data throughput. Thanks to “multi-hopping,” data transmission rates up to 6 MBit/s are possible, even at high speeds. According to experts, only ten percent of vehicles would need to communicate by WLAN to realize full-coverage traffic information. Alternatively, data could be transmitted by mobile radio—today via LTE and in the future at a rate of 10 GBit/s using 5G.

ZigBee 3.0, ZigBee Green Power and ZigBee RF4CE

EnOcean uses its own wireless technique with extremely low energy consumption for energy-harvesting applications in buildings.
EnOcean uses its own wireless technique with extremely low energy consumption for energy-harvesting applications in buildings.

Wireless standards such as ZigBee, Z-Wave and EnOcean are competing with one another in the building-automation sector. ZigBee was developed for small embedded devices that transmit small amounts of data over short distances. Due to its extremely low power requirements, it is easier on rechargeable batteries, and batteries don’t need to be replaced as often. ZigBee is primarily used in radio-sensor controller networks such as lighting, heating and security technology. Mesh networking makes it possible to extend the range because every node in the network can function as a repeater and refresh the signal—ZigBee’s strict security protocols are also advantageous. Another advantage: short latency times. The low-power variant ZigBee Green Power was designed for devices that harvest the energy that they need to operate from the environment (energy harvesting). Green Power is suitable for devices that are only connected to the network occasionally such as light switches, and it makes it possible to switch devices on and off reliably. ZigBee spin-off RF4CE consumes less electricity and has a low latency of 30 milliseconds.

Industry-capable transmission with Jupiter Mesh

The ZigBee Alliance developed a standard for the Industrial Internet of Things (IIoT) that transmits at 868 MHz (Europe), 915 MHz (America) and 2.4 GHz—Jupiter Mesh, also known as the neighborhood area network (NAN). The energy-efficient transmission technology supposedly allows batteries to operate for several years. It has higher data rates, lower latency and satisfies the stringent security and reliability requirements needed in industry infrastructures. Jupiter Mesh addresses energy providers (smart grid) and smart cities.

Z-Wave and EnOcean

Like ZigBee, Z-Wave targets networking in the home automation sector. The wireless standard is stabile and has a high security level. Meshed networks maintain communication between devices and the central control even if a terminal device fails. In Europe, Z-Wave transmits at 868 MHz on the ISM band. Munich-based manufacturer EnOcean uses its own EnCana radio standard for energy harvesting applications in building and industrial automation. Battery less switches and sensors use it to transmit at 868 MHz in Europe, 902 MHz in North America and 928 MHz in Japan. The standard is characterized by extremely low energy consumption. A radio light switch with a piezo harvester draws enough energy from the motion of a finger pressing the switch to transmit an “On” or “Off” signal to the lamp. IBM and EnOcean have an IoT kit for intelligent buildings available that uses EnOcean technology and an IBM Watson IoT platform.

Short-range communication via Bluetooth

Like WLAN, Bluetooth is an extremely common radio standard. Almost every reasonably modern mobile device has a Bluetooth interface. There will supposedly be more than 6.3 million of them in use in the coming year. Bluetooth established itself as a point-to-point connection to replace wires and cables. The radio technology is designed to transmit data between devices at short range and has established itself as the standard for personal area networks related to the smartphone. Bluetooth is suitable for small-volume applications with low bandwidth requirements such as phone calls or to transmit sound files and wearable data. Bluetooth’s major weaknesses: extremely short range and low data rates. The software-based solution Thread ensures the interoperability of various radio standards on the basis of IPv6. It makes it possible to use Bluetooth, WLAN or WPAN and 6LoWPAN simultaneously in the same control system.

Bluetooth Low Energy

The low-power variant Bluetooth Low Energy (BLE)—also known as Bluetooth Smart—should make Bluetooth fit for the Internet of Things. Due to its extremely low energy consumption and shorter latency times, BLE is suitable for industrial applications. In the smart-home sector, BLE has become popular due to iBeacons for indoor navigation. However, with data throughput of 100 KBit/s, it is considerably slower than conventional Bluetooth with 2.1 MBit/s. But because sensors only produce small quantities of data anyway, the speed is sufficient. Another advantage is high data security using AES-128 encryption. In addition, speed has supposedly doubled and range quadrupled—without increasing energy consumption. Bluetooth mesh networking supposedly allows Bluetooth devices to connect with networks that cover entire buildings.

LoRa and Sigfox for low-power WANs

According to market researchers at Beecham, low-power wide-area networks (LPWANs) will cover more than one-fourth of the entire IoT connectivity market by the year 2020. LPWANs make is possible to transmit small volumes of data over large distances. An expensive, energy-intensive broadband connection is not necessary. What is needed instead are radio technologies with long range and low energy consumption. The best-known LPWAN technologies include LoRa and SigFox. LoRa from Semtech is based on the chirp-spread-spectrum technique, and Sigfox is a narrowband technique with BPSK modulation. Both have low power consumption, bridge large distances, allow high penetration in buildings, support bi-directional communication and are economical. Sigfox licenses its technology to large network operators. In addition, chipsets and communication modules will supposedly be sold by electronics markets such as Conrad. Semtech licenses LoRa to chip manufacturers such as Microchip. Semiconductor distributor Avnet Silica offers modules for Sigfox and LoRa for its own IoT solutions.

NB-LTE for narrowband IoT

The international cellular telecommunications standardization organization 3rd Generation Partnership Project (3GPP) coined the term narrowband IoT (NB-IoT) for narrowband LPWAN radio technologies that are designed for long range, high building penetration, low data rates and low energy consumption such as those required for smart metering or tracking goods. Narrowband LTE (NB-LTE), an optimized variant of the 4G mobile communications technology LTE, established itself as a standard for machine-to-machine communication over the LTE network. The standard can be integrated into existing LTE networks and works with current LTE bands. The companies driving the new technology include industry giants such as Deutsche Telekom, whose network infrastructure gives it the main prerequisites for putting NB-IoT into operation, and chip manufacturer Intel, which is developing radio chips for NB-LTE. Nokia and Ericsson have network upgrades available for upgrading existing LTE networks to NB-LTE.

What comes after WLAN, Bluetooth and Co.?

Existing radio technologies are reaching their limits on the Industrial Internet of Things. Whether it comes to WiFi, Bluetooth or ZigBee: None of the existing solutions achieve the transmission rates and response times that are required in industrial plants and meet the high security requirements at the same time. Furthermore, the large number of radio systems are actually obstructing one another. “In the worst case, that leads to expensive production losses,” says Uwe Meier, High Frequency Technology Expert at the Institute for Industrial Information Technology (inIT) in Lemgo. What is needed is “a radio system in which the communication layers are designed to complement one another.” Which is why inIT has set out to develop a completely new industrial wireless standard to replace existing wireless technologies. The HiFlecs project stands for “high-performance, secure wireless technologies and their system integration in future industrial closed-loop automation techniques.” Cognitive radio systems recognize the presence of other systems and regulate themselves. “In a group with several conversation partners, it is best to use a moderator who regulates the conversation, i.e. stipulates the sequence of the statements and intervenes if someone becomes overly demanding. That is basically what we are doing with our radio systems,” explains Meier.

IoT wireless standard in comparison

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1) The letter indicates the speed and the frequency of the network.

2) 2.5-GHz Wi-Fi has a greater range than 5-GHz WiFi. The range can also be increased using antennas?

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