Low power cellular IoT

The nRF91 Series are Nordic’s first family of low power cellular devices for the Internet of Things. They have been engineered from inception to perform at the highest possible standards for energy-efficiency and security whilst simultaneously bringing advanced application performance and possibilities to cIoT. With an unprecedented level of integration bringing LTE-M, NB-IoT, GPS, all RF front end (RFFE) and power management into a very small package the nRF91 Series make single chip solutions a real possibility in many cases.

Nordic Semiconductor has been engaged in bringing the nRF91 Series cIoT products to market for the last three years. The development team in Finland are all cellular people with extensive track records in cellular design and test. With 1000’s of man-years of experience in the field and coming from such industry stalwarts as Nokia, Broadcom and Ericsson, Nordic Semiconductor is a genuine cellular player with an enviable reputation in cellular already.

This is a mantra many believe to be true, many industry greats have thought it essential to offering great products. Nordic believes in it too. Much of our significant success in the ultra low-power wireless area has been built on this synergy. When you make your own software for your own hardware the integration is always tighter, the performance better, the time taken to innovate is quicker. At Nordic, we make the software for our hardware. This mantra remains the same for the nRF91 Series and our cellular products.

When Nordic Semiconductor entered the world of Bluetooth Low Energy when it was launched we had some very clear goals. One was to become the market leader, another was to make Nordic Bluetooth Low Energy SoCs the most accessible, easy-to-use and well-supported devices in their category. Today’s start-up can be the next industry giant in The Internet of Things. We make our products available and affordable for everyone with almost all of our software and development tools being totally free of charge. Nordic is about exciting developers, all developers.

The introduction of LTE-M and NB-IoT to 4G cellular networks is setting the standard for broad range IoT that will deploy at a massive scale in coming years. Designed for reliable, secure, low power operation these standards together with the ubiquitous cellular coverage in most of the world offer an unparalleled choice for Low Power Wide Area Network (LPWAN) IoT connectivity.

LTE-M and NB-IoT are open standards developed and managed by the 3rd Generation Partnership Project (3GPP). This ensures interoperability and reliability of operation across the globe.

The nRF9160 is a compact System-in-Package device that supports LTE-M and NB-IoT together with a powerful Arm Cortex-M33 application processor and on-chip GPS.

LTE-M (also known as Cat-M1) is designed for low power applications requiring medium throughput. It has a narrower bandwidth of 1.4 MHz compared to 20 MHz for regular LTE, giving longer range, but less throughput. The throughput is 375 kbps downlink and 300 kbps uplink, providing approximately 100 kbps application throughput running IP. It is suitable for TCP/TLS end-to-end secure connections. Mobility is fully supported, using the same cell handover features as in regular LTE. It is currently possible to roam with LTE-M, meaning it is suitable for applications that will operate across multiple regions. The latency is in the millisecond range offering real time communication for time-critical applications.

LTE-M is perfect for medium throughput applications requiring low power, low latency and/or mobility, like asset tracking, wearables, medical, POS and home security applications.

NB-IoT (also known as Cat-NB1) is a narrowband technology standard that does not use a traditional LTE physical layer, but is designed to operate in or around LTE bands and coexist with other LTE devices. It has a bandwidth of 200 kHz, giving it longer range and lower throughput compared to LTE-M and regular LTE. The throughput is 60 kbps downlink and 30 kbps uplink. It is suitable for static, low power applications requiring low throughput.

NB-IoT is perfect for static, low throughput applications requiring low power and long range, like smart metering, smart agriculture and smart city applications. It also provides better penetration in, for example, cellars and parking garages compared to LTE-M.

Energy efficiency is a cornerstone of cellular IoT technology. Both LTE-M and NB-IoT are designed to make years of operation from a battery-driven power source a reality. This has been achieved by using a range of techniques. Data throughput is lower than standard LTE, and this brings the energy consumption down due to slightly simpler modulation schemes and less complex radios. However, as with all low power communication technology, the real key is managing sleep, wake-up and communication events effectively and efficiently.

Two energy efficiency innovations make a significant contribution to LTE-M and NB-IoT power-saving capabilities, eDRX (Extended Discontinuous Reception) and PSM (Power Saving mode). Both eDRX and PSM work in harmony to make battery operation for many months and years possible.

LTE uses a system of paging cycles which are 1.28 seconds in duration. A paging cycle is the window of time a device can be contacted by the network for an exchange of data. The resting period between the paging windows are known as hyper-frames. The benefit of eDRX is that it allows ‘N’ number (40+) of hyper-frames to occur at a period of 10.24 seconds each before a device wakes up again for activity in its next paging window. In this way devices can sleep and talk in a highly efficient and synchronized manner.

PSM mode simply enables the device to enter a deep sleep mode for whatever time is necessary, this could be perhaps an hour, a day, or weeks. For applications that have no real-time requirements and only communicate very periodically, for example an irrigation system in agriculture, this brings very high levels of energy conservation and can mean products can run on a few AA-sized lithium batteries for up to 10 years.

The nRF9160 is optimized to take full advantage of all the power saving efficiencies offered by LTE-M and NB-IoT including eDRX and PSM.

Cellular networks offer an unrivalled set of performance characteristics in the LPWAN sector. Cellular operates in licensed bands, the importance of this cannot be underestimated. Licensed bands come at great expense, typically billions of dollars, and for good reason. When you own the band, you can dictate and guarantee the performance and reliability of communication within those bands. You can also minimize wasted energy due to interference between devices.

Cellular is designed for very high Quality-of-Service (QoS). There are known number of connections and these can be accommodated and managed accordingly. Unlicensed bands have no such guarantees and anyone can operate there. For guaranteed performance and reliability licensed cellular is a clear winner for LPWAN.

Cellular 4G networks are already in place with dense cell tower coverage over most cities in the world and most countries having a high degree of country coverage. This puts cellular in a position to be ready to deploy at huge scale with minimal infrastructure building. 

Because LTE-M and NB-IoT are designed to be spectrally-efficient and because typical use-cases are low activity by nature it will be possible to connect several 10s of thousand devices to a single base station. Typically, cell-towers host several base stations, and this means deployment density can truly happen at a massive scale. 

LTE networks have unrivalled security measures as standard for the LPWAN sector. At device level is the SIM card or UICC, this is a secure element with a definitive identifier embedded in hardware for that particular device. It ensures authentication to the cellular service subscription and encrypts data over-the-air. Communication with LTE-M is typically TCP/IP, the language of the internet, and as such is equipped with the highest degree of security measures that are in current use. Transport Level Security (TLS) is the mechanism of secure data transactions, and is the state-of-the-art for internet security.

The nRF9160 implements significant extra security measures to further enhance device security including Arm TrustZone and Arm CryptoCell for secure and trusted execution and key generation and storage.

In the same way that updates are critical to any connected computers security, any connected device should be capable of downloading firmware updates over-the-air. This is to ensure that your device can be updated to fix security holes discovered after deployment either in standards or implementation. It also allows you to optimize your device’s performance over time and even deploy new features.

The nRF91 introduces the Arm Cortex-M33 as a dedicated application processor. It has 1MB of flash and 256kB of RAM with a broad array of peripherals. Beyond its LTE connectivity and positioning options, it is a very capable device that can support a broad selection of use-case demands and offers real edge compute possibilities for the world of cIoT.