This article looks at the harmonization of European wireless standards for IoT devices (EN 300 328 V1.9.1) in the 2.4 GHz band, given the context of 2.4 GHz against other cellular bands such as LTE-M and narrowband LTE. The new standard comes into force in November 2016 and the article looks at how this impacts of developers of IoT devices
Standardization can be a challenge for innovation around the world. Waiting for frequency bands to be allocated in different geographies, for technologies to be approved for use and for licenses to be allocated can slow down the roll out of new applications. This has certainly been the case with the use of mobile phone technologies for the Internet of Things (IoT). While there is a central standards body, the 3GPP, the development of the latest narrow-band LTE (LTE-NB) technology for IoT has been slow. The prospects of 5G are even more challenging as 4G is combined with Wi-Fi in high speed channels.
In contrast, the unregulated ISM (Industrial, Scientific and Medical) bands provide an easy way for wireless technologies to be used for the IoT. The 2.4 GHz band is particularly popular for wireless links with a wide range of technologies available without the need for global approvals. Wi-Fi, Bluetooth and ZigBee all operate in this band, and that has been causing some challenges. While each has its own standards body – IEEE802.11 for Wi-Fi, IEEE802.15.4 for ZigBee and L4PAN and the Bluetooth Special Interest Group for Bluetooth, there is limited collaboration between the groups.
Market researchers Machina Research predict the total number of IoT connections will grow from 6 billion in 2015 to 27 billion in 2025, a growth of 16% a year. The vast majority of these connections (71%) are the short range, 2.4 GHz links such as Wi-Fi and ZigBee, highlighting how the frequency band is set to become even more crowded.
The increasing use of cellular technology has not been missed by one of the leading Bluetooth chip designers. Nordic Semiconductor is looking to support the coming 3GPP Release 13 LTE-M and NB-IoT cellular technologies. The nRF91 Series (scheduled for release in 2018) is designed specifically to address the needs of emerging low power cellular IoT applications, including long battery life, low cost deployment and maintenance, scalability for potentially billions of devices, a miniaturized form-factor that can fit almost anywhere, and ubiquitous network coverage.
LTE-M and NB-IoT are aiming to provide low power, secure, reliable, future-proofed, open standard and interoperable cellular connectivity for cost, size, and power-constrained IoT applications. The two technologies are set to drive breadth and growth for the emerging cellular IoT market projected to surpass 1.5 billion connections by 2021. Nordic expects broad coverage for the technologies in the 2018-2019 timeframe, with initial coverage starting in 2017.
“The combination of our ultra-low-power wireless DNA and unique cellular expertise in Finland puts Nordic in a strong position to drive and fuel the market for low power cellular IoT,” said Svenn-Tore Larsen, CEO of Nordic Semiconductor. “For us this roadmap is about taking Nordic Semiconductor as a company to the next level by providing scale for our technology, and on-going organizational and R&D investments.”
Figure 1: Laird Technologies uses silicon from Nordic Semiconductor for its Bluetooth module.
“We believe that the cellular IoT market is still in its infancy and that the new low-power LTE technology variants will drive a massive growth curve in many ways similar to what Bluetooth low energy is doing for short-range wireless,” said Thomas Embla Bonnerud, Director of Product Management at Nordic Semiconductor. “Some years down the road this market is going to look very, very different compared to how it looks today. That is what the Nordic Semiconductor nRF91 Series is all about: a new and different solution for a new and different market.”
With more cellular devices being used and an explosion in the use of IoT nodes in the ISM band, the European Telecommunications Standards Institute (ETSI) has updated its standards on the use of two GHz band standards. These are mandatory for any manufacturer shipping equipment in Europe and will come into force in November 2016.
The aim is to harmonize the activity of devices within the band, which is even more important with new technologies on the horizon and an explosion in the number of wireless IoT nodes operating in the band.
The two new standards are ETSI EN 300 328 v1.9.1 covering the 2.4 GHz band and ETSI EN 300 893 v1.8.1 for the 5 GHz ISM band that is also used by 802.11a. These cover the channel-based frequency-hopping spread spectrum (FHSS) technology that are used by Wi-Fi, ZigBee and Bluetooth to ensure that the radio links can operate collaboratively in such a crowded radio environment. It doesn’t cover the ultra-wideband technologies (UWB) that spread the data across many bands.
The European directive that covers the CE mark approval includes the EN 50371 standard of compliance to human exposure to electromagnetic fields, EN 301 489 for electromagnetic compatibility and EN 300 328. Version 1.8.1 did not classify Bluetooth Low energy (BLE) as FHSS, instead listing it as “other type of wideband modulation” under Sec 4.2.1, with the test requirements defined in Sec. 4.3.2. The move to 1.9.1 brings this in line with the other 2.4 GHz technologies.
Figure 2: Texas Instruments Bluetooth approval process.
The new revisions of the standards also cover use of satellite positioning technologies from GPS to GLONASS and Galileo as more IoT tags are moving around on trucks, pallets or high value products and include geo-positioning information. While these operate at 1.6 GHz, there can be interference effects, and demonstrating the coexistence of all these technologies for the European approvals is a key part of shipping a design.
German test house TÜV SÜD has been evaluating the differences between v1.8.1 and v1.9.1 of the standard and how this fits in with the current approvals for equipment, such as whether re-testing is required.
If a product is compliant with version 1.8.1, then no re-testing is required in moving to 1.9.1. Companies can simply update their Technical Construction File (TCF) detailing that the changes in version 1.9.1 do not affect the compliance of their products, and therefore conformity against version 1.9.1 can be assumed. The Declaration of Conformity (DoC), can then be updated to V1.9.1.
However, a new declaration is required by manufacturers if the geo-location capability is supported, although no additional testing is required. If using V1.8.1 test results for V1.9.1, this will need to be factored into the TCF.
Demonstrating the compliance of frequency-hopping standards such as Bluetooth can be difficult as the signal hops between channels. The new standard allows manufacturers to provide a statistical analysis of the ‘Accumulated Transmit Time and Frequency Occupation’ (Clause 5.3.4), which will help to reduce testing time and cost to the manufacturer.
The new version of the standard comes as the next generation of Bluetooth, version 5.0, is planned for the same timescale. This aims to make the Bluetooth technology more applicable to IoT applications. Increased range will provide more robust, reliable IoT connections, while higher speeds will make systems more responsive. Increased broadcast capacity will drive the next generation of “connectionless” services like beacons and location-relevant information and navigation.
“Bluetooth 5 will transform the way people experience the IoT by making it something that happens simply and seamlessly around them,” said Mark Powell, executive director of the Bluetooth SIG. “Increasing operation range will enable connections to IoT devices that extend far beyond the walls of a typical home, while increasing speed supports faster data transfers and software updates for devices. And now with the ability to broadcast a much richer set of information, Bluetooth 5 will make beacons, location awareness, and other connectionless services an even more relevant part of an effortless and seamless IoT experience.”
Silicon devices that support Bluetooth 5.0 will come to the market at the end of 2016 and into 2017 so that module makers can provide a certified way of adding the technology to designs. These will have to go through the EN 300 328 V1.9.1 process.
A key change to that process is that EN 300 328 V1.9.1 no longer refers to the values of ‘R’ and ‘Q’, so the module and system makers don’t need to contact chipset vendors for this information. At the same time, the minimum Clear Channel Assessment (CCA) value a manufacturer can declare has been reduced from 20 µs to 18 µs which will allow more channels to be used. This will reduce congestion in the band and allow more devices to work effectively and with lower power. The receiver blocking requirement is also reduced from -30 dBm to -35 dBm (Clause 5.3.7) to help with the spectral efficiency.
The standard has also been tweaked to remove some elements that have proved to be irrelevant. For example, testing at extreme temperatures in the out of band frequencies is no longer a requirement, reducing test time and cost.
Other changes to the standard include clarifications and additional wording to assist manufacturers and test labs during the test process for module makers, although chip makers such as Texas Instruments are also offering a faster certification process for customers using their silicon, firmware and high level software that is designed directly into a product. This can also be used by the module makers to speed up pre-certifying modules that customers can drop into a design.
Figure 3: Speeding up the approval process with firmware and high level software from a TI reference design.
Getting a wireless product on the market requires a range of qualifications and approvals that involve both testing and paperwork, which can be relatively complex and costly for those unfamiliar with the process. Approvals under wireless and regulatory standards cannot be obtained on the chips, so this falls to the module maker such as Laird Technologies and Taiyo Yuden who have the responsibility of ensuring the modules meet the EN standards. But the module makers rely on the core performance of devices from companies such as Texas Instruments, NXP and Nordic Semiconductor.
Figure 4: Taiyo Yuden develops wireless modules for both the Wi-Fi and Bluetooth standards.
For example, Laird is using the nRF52832 System-on-Chip from Nordic for its BL652 module. This module is pre-approved to all necessary wireless certifications and qualifications including Bluetooth 4.2, features an integrated or optional external antenna, and is qualified over the full industrial -40º to +85ºC operating temperature range.
The nRF52832 is the first such device to use a 64 MHz ARM® Cortex®-M4F processor core combined with 512 kB Flash and 64kB RAM, a proprietary 2.4 GHz radio with -96 dB RX sensitivity, 5.5 mA peak RX/TX currents, and an on-chip RF Balun as well as near field communication (NFC). Laird has implemented robust security and encryption (secure 128-bit AES with Diffe Hellman-enabled pairing) so that it can be easily used in IoT applications in both industrial and enterprise designs.
“Modules are a valuable option for companies and developers that are new to RF technology or wish to fast-track a product to market,” said Geir Langeland, Nordic Semiconductor's Director of Sales & Marketing. “The IoT will grow to include many companies that may not have any background in RF design or Bluetooth low energy wireless technology. By using a module such as the Laird BL652 they will be able to access the latest market-leading wireless technology without having to go up a steep learning curve with all the design risk and time that will necessarily involve.”
Conclusion
The explosion in the Internet of Things, in both industrial and enterprise applications, is driving more focus on the approvals and certification processes. As technologies in the 2.4 GHz and 5 GHz ISM bands dominate the growth in the IoT, the need to ensure that they operate effectively without compromising other systems is essential to compete with the emerging IoT cellular standards. The changes in the ETSI EN standards that come into force in November aim to improve that certification process further, making it less onerous and costly for module and system manufacturers while improving the performance of all the devices in the IoT.
