The Machine Network: LTE NarrowBand IoT (NB-IoT)

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According to mobile communication providers, narrowband IoT (NB-IoT) will play a key role in the industrial and consumer-oriented Internet of Things. Does the LTE offshoot have what it takes?

With conventional mobile communications, nothing can be done in the Internet of Things ( (IoT). Energy consumption would be much too high and the networks would collapse under the load of thousands of IoT devices. With conventional mobile communications applications, the main focus is on high transmission rates, while the Internet of Things places other demands: high network coverage, robust transmission, low power consumption, minimum costs, and the highest possible security.

For a long time, networking industrial applications in the Internet of Things was not a focus of wireless carriers. However, in the meantime, telecommunication companies have jumped on the LPWAN bandwagon (low-power wide-area network):

The standardization committee 3rd Generation Partnership Project (3GPP), to which cellular network operators and manufacturers and government authorities worldwide belong, defined, among other things, in release 13 the LTE derivatives that are specialized for machine-to-machine communication (M2M): LTE Cat NB1 – also known as NarrowBand IoT (NB-IoT) – and LTE Cat M1. With these “slimmed down” LTE versions, cellular network operators are targeting M2M applications, such as battery-operated radio sensors.

Reliable transmission and worldwide roaming

NB-IoT is designed to transmit relatively low volumes of data reliably and relatively seldom – also in difficult surroundings and over large distances. Characteristics include high interference immunity and good penetration of solid objects:

LTE Cat NB1 penetrates thick concrete walls and, in some cases, also reaches basements. Since IoT devices, such as sensors, often transfer small data packets just once per hour or day, they last for up to 15 years with one set of batteries. NB-IoT also works with radio waves that allow wide-ranging coverage. Another bonus: NB-IoT allows worldwide roaming and, consequently, global scaling of IoT applications. Roaming is important, for example, for logistics tracking of containers across country borders.

Three types of operation are possible with LTE Cat NB1: within an LTE channel (in-band), in the gaps between LTE channels (guard band), and outside the LTE network (stand-alone), for example in a GSM channel. The LTE Cat-M1 variant with more bandwidth and handovers is aimed more at mobile use and also allows voice transmission. Both technologies work with the same modulation process as LTE.

Large range of applications

There are many potential applications. NB-IoT enables energy-efficient networking of sensor swarms in factories, smart buildings, logistics, agriculture, or waste management. Gas, electricity, and water meters installed in basements can be connected to the Internet and be read remotely (smart metering). Streetlights equipped with NB-IoT modules can be switched on and off and dimmed remotely. Intelligent parking guidance systems can direct drivers to the next empty parking lot via NB-IoT. The technology is also suitable in the areas of medicine and healthcare, for example, to monitor patients.

Competing radio technologies

Various technologies are competing for market shares in the wireless LPWA networking of IoT devices. The relatively mature technologies Sigfox, LoRa, and NB-IoT have proven successful.

NB-IoT has much lower power consumption than standard LTE connections. But the power consumption is higher and the range is lower than classic LPWANs, such as LoRa or Sigfox. But with up to 250 kbit/s, NB-IoT offers much more bandwidth in downlink and uplink. An LTE Cat-NB1 device works on a just 180 kHz wide channel. That corresponds to one single physical resource block (PRB) with LTE. As opposed to LoRa or Sigfox, NB-IoT uses worldwide licensed frequency ranges.

Software updates make radio systems fit for NB-IoT

From a hardware aspect, LTE base stations already support the narrowband network NB-IoT. In many cases, software updates are all that is required to make the radio systems LPWAN-ready. Consequently, a wide-ranging network expansion for NB-IoT is relatively easy and inexpensive. One cell can supply several thousand IoT devices.

Worldwide, more than 30 of the major cellular network operators that cover 90 percent of the worldwide IoT market are promoting NB-IoT. These include Deutsche Telekom, Vodafone, AT&T, Telefonica, China, Unicom, China Mobile, Verizon, and Telstra. NB-IoT also receives broad support from industry, such as from chip producers like Intel and Qualcomm, and cellular network suppliers, like Ericsson, Nokia, and Huawei.

Deutsche Telekom has introduced NB-IoT networks in Germany, in many European countries, such as Poland, Slovakia, the Czech Republic, Hungary, and Greece, and also in North America. Country-wide NB-IoT coverage was achieved in The Netherlands in 2017. According to Telekom, in Germany, the base stations in more than 600 locations are equipped with NB-IoT.

The rollout should be completed in most of Germany by the end of 2018. Many other European countries are also striving to achieve “country-wide coverage”. Telekom offers a flat rate for data in the European Union, Switzerland, and Norway: For €10, IoT devices can transmit small data volumes for ten years. The limit is 500 megabytes. NB-IoT should also be installed throughout the USA soon.

Cost efficiency through simple design

NB-IoT is designed to minimize costs for hardware and network operation – a benefit for industrial IoT applications, which aim to network many objects. Since NB-IoT does not use many LTE functions, simple, basic radio modules that can be manufactured cheaply are adequate. For example, NB-IoT hardware modules need only limited memory, in other words, less expensive PSRAM chips. There is just one antenna and no full-duplex operation, which saves the costs for an RF duplexer.

Compared to LTE, there are few restrictions with regard to time delays. Consequently, chip design and production are less complicated. NB-IoT devices have low clock speeds. This reduces the cost of the chips. The limited bandwidth reduces the size of the buffer and processing blocks. While an LTE device costs about $40, the production costs for an NB-IoT device are less than $10. The competition with technologies such as Sigfox and LoRa will likely lead to lower prices for components and systems.

IoT devices are in idle mode for most of the time. Power saving mode (PSM) allows LTE devices to be put to sleep – for a few minutes or for several days. But the device does not book out of the cellular network and can be reached constantly – although there may be a slight delay. In power saving mode, only a few microamperes of current are required.

LTE security gaps also threaten NB-IoT

NB-IoT is based on authentication and encryption from LTE. NB-IoT authenticates the network and the device mutually. It also encrypts data traffic between the device and the network. With the devices, secure and encrypted data transfer takes place by logging into the cellular network with a unique device ID.

To increase security, the device, communication, and application can be equipped with additional security layers. Firmware updates can be uploaded to the devices by radio to close security gaps and upgrade functions. However, according to a study from Purdue University and the University of Iowa, Cat-NB1 and Cat-M1 are potentially threatened by the same security gaps as LTE.

Licensed spectrums, industrial quality, and a relatively high security level could see NB-IoT rapidly becoming the wireless technology for M2M communication.

electronica 2018

Discover more about wireless technologies such as NB-IoT/M2M and LPWAN at the electronica Wireless Congress: Systems & Applications.

www.electronica.de

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