Flexibility: the Key to M2M Connectivity

If you need global IoT connectivity for your devices and want to be able to change providers and services at will, you need to be flexible. Such flexibility is no longer a challenge with the Avnet Silica Arduino shield for low power wide area networks (LPWAN).

by Christopher Young

In addition to a state-of-the-art cloud solution and local intelligence for data preprocessing and decision-making, OEMs looking to provide new services and value through IoT connectivity of devices and sensors first and foremost need a connectivity solution that ensures secure, power-efficient and cost-effective end-to-end communication. With LTE Cat NB1 and LTE Cat M1 plus 2G EGPRS as fallback, the licensed radio bands available worldwide provide everything developers need for the next generation of cellular machine-to-machine (M2M) communications.

LTE Cat NB1 compliance
Many applications do not require high bandwidth or permanent connectivity, as is common with conventional 2G/3G/4G cellular technologies. Often, devices need to connect only from time to time to check in and send small data packets. This saves connection costs and valuable energy, enabling smart and affordable connectivity solutions with long battery life of up to 10 years. For this purpose, the wireless standard NB-IoT was created. It offers up to 250 kbps bandwidth and supports a particularly large number of connections per base station. NB-IoT further offers an additional 20 decibel link budget. Given the right infrastructure, this makes it possible to increase network coverage even in areas with previously poor coverage. It also boosts interference immunity and transmission quality – even for connections inside cellars. Compared to alternative LPWANs, NBIoT allows significantly more data to be transmitted in the licensed band and provides higher bandwidth. NB-IoT therefore addresses a much larger number of applications. In addition, the base station infrastructure for NB-IoT is usually already in place as it can rely on existing mobile networks. To use them, all that’s typically required is a software update of the base stations. Only a few locations need an additional hardware upgrade that’s relatively easy to implement. The use of NB-IoT by major mobile operators is therefore expected to accelerate exponentially in the near future. Areas of application can be found wherever limited data rates, such as Sigfox LPWAN, which can send 144 messages per day at 12 bytes in the direction of the cloud, are no longer sufficient. But even NB-IoT has its limits.

LTE Cat M1 add-on
A valuable addition to NB-IoT is Cat M1. Like NB-IoT, this is a 3GPP Release 13 standard. It offers an even higher peak data rate of up to 1Mb/s full duplex compared to NB-IoT and supports mobile solutions, something which NB-IoT cannot do because the network must establish a new connection after leaving a cell. Cat M1 further supports Voice over LTE (VoLTE), which may be of interest for IoT applications such as home care and elevator alarm systems; equipment access control and remote assistance solutions; as well as ticketing systems and vending machines. Measuring 10 to 15ms, latency is significantly lower here compared to NB-IoT, where values range from 1.6 to 10s. Combining these two technologies with 2G EGPRS fallback for regions where NB-IoT has not yet been rolled out, multi-mode connectivity cards can be used to generate extremely high network coverage for the large number of mass use cases that benefit from many years of battery operation and do not require a constant connection at high data rates.

Optional compatibility with eUICC
Mobile M2M applications, particularly those that are deployed globally, are flawed by the fact that the management of the SIM cards can be extremely complex, resulting in an immense administrative burden for large field deployments. However, a lot of the effort can be avoided by using eUICC compatible SIM technology. It makes SIM cards and components reprogrammable, allowing new Mobile Network Operator (MNO) profiles to be deployed ‘over the air’ at any time. A change of MNO and services is therefore always possible – regardless of whether this means a change in the manufacture of the device, commissioning, startup or even a transfer of ownership or relocation. For global solutions, this makes it possible to quickly secure the right tariffs from one or more of the world’s 20 largest network operators – which according to Vodafone already service 90 percent of the IoT coverage area1 – and install suitable MNO profiles depending on the location of the device. Corresponding updates of all base stations provided, of course. Another option are global Virtual Network Operators (VNOs) like Arkessa, especially if you want to use one provider for everything.

All the advantages offered by the new board
Avnet Silica has developed an application-ready Arduino compatible board for this new performance class. It supports LTE Cat NB1, LTE Cat M1 and 2G EGPRS plus optional eUICC compliant SIM cards. Based on the Arduino Uno R3 specification, it is ideal for small and medium sized industrial batch applications and as a starting point for high volume custom designs. Standardization of the Arduino connector format allows designers to access a variety of standard components.
For instance, there is a rich ecosystem of microcontroller or application processor boards as well as Arduino expansion shields. In a few simple steps, NB-IoT/Cat M1 connected IoT gateways, devices and smart sensors can be assembled on the basis of the open source Arduino standard. Advantages of this standardization include not only the use of commercial-off-the-shelf (COTS) hardware to avoid NRE costs; it is also the vendor independence from a specific solution that OEMs appreciate. There is usually a second provider of a comparable solution, which intensifies competition and lowers procurement costs. Ultimately, a large open source ecosystem also increases design security and enables long-term availability, which secures the investment in an OEM solution long into the future.

Features of the Sensor Shield
The new NB-IoT Sensor Shield from Avnet Silica with optional eUICC compatibility is based on the Quectel BG96 module and supports FTP/HTTP/MQTT and TLS as well as PPP/TCP/UDP protocols. Next to high flexibility, it also impresses with extremely low power consumption – around 10μA in power-saving mode – that results in exceptionally long battery life. In spite of its extremely energy-efficient design, the shield also offers the option to integrate geolocation for all common standards such as GPS, GLONASS, BeiDou/Compass, Galileo and QZSS. This makes it possible to optimize administration and maintenance tasks without having to buy additional Arduino shields for this feature – which is virtually already the standard for massively distributed IoT applications. The high flexibility of the shield is further enhanced by the Pmod connector, which can be used as an alternative to the Arduino shield interface to the processor board.

Flexible programming with ARM mbed
The Avnet Silica NB-IoT Sensor Shield supports all popular operating systems such as Android, Linux and Windows. The modem is controlled with the AT command set via UART or USB interfaces. The board also has its own network stack, including SSL/TLS encryption. In addition, further free network stacks for COAP and MQTT clients are available based on the ARM mbed eco-system.
This allows application libraries, component libraries, and toolchains to be used unchanged across multiple MCUs, allowing for the portability of own code and reducing NRE costs. At the heart of the mbed solution is the well established and widely used open-source CMSIS-RTOS RTX.

Starter kit for NB-IoT connectivity
Avnet Silica also provides OEMs with all the components they need to evaluate the new NB-IoT Sensor Shield, including X-Nucleo sensor boards and the STM32 Nucleo-64 board from STMicroelectronics.
Since this is also supported by the Arduino IDE, the vast majority of code libraries can work with these boards. But the STM32 Nucleo-64 board is just one example of potential customer configurations with this NB-IoT Arduino shield. A variety of development boards from suppliers such as ST, Renesas, Microchip, Nordic and NXP can also be provided.
Avnet Silica is already offering software demonstrations for all of these solutions based on the ARM mbed ecosystem, ST CubeMX, and the Renesas Synergy cellular framework, among others. Linux implementations for the application processor based platforms from Microchip (SAMA5D2) and NXP (i.MX6ULL) are also provided.

Shield-specific eUICC test pack
To enable customers to test eUICC, Avnet Silica can also provide a starter kit with appropriate SIMs that is tailored exactly to the function of the new shield. With this offering, Avnet can provide OEMs with all the required data services throughout the entire life of the product, even when product ownership is transferred.
Avnet’s LifeCycle services include, for example, downloading and exchanging profiles as needed and requirements-based G2 EGPRS fallback management. A generic kit offered by Avnet Silica and available today, consists of six eUICC compliant SIMs. Four of them in 2FF format (map) and two in MFF2 format (component) – each preloaded with a Vodafone and Arkessa test profile along with 2×50 MB of prepaid Vodafone and Arkessa data credit for Europe.
This data credit is valid for 3 months after activation. This gives customers time to trial the management of Vodafone and Arkessa connectivity without rush. In a next step, this test pack will be adapted and tested for interaction with the brand new NB-IoT Sensor Shield as part of Avnet Silica’s roadmap to offer comprehensive services around the new shield.

Cloud included for evaluation
Of course, this board also includes a cloud solution to evaluate connectivity. Customers can use the IBM Cloud™ IoT Platform to connect with the device and analyze its real-time data. For instance, they can create a rule to send an alert to the dashboard of a user’s device and an email to the administrator when the connection to the device is lost or when the temperature of the device reaches a set threshold. Of course, assisting customers with the development of their specific cloud solution is also part of the service offered by Avnet Silica’s consultants.

Chris Young is Embedded Systems and Software Specialist at Avnet Silica