5G networks have become the most significant direction in current wireless communication development. The world's first non-cellular 5G technology, DECT NR+, obtained standardization by the ETSI organization in 2020 and was subsequently adopted as a 5G standard in 2022, drawing recent attention from the industry. The DECT NR+ standard holds the potential to be a crucial factor in the large-scale Internet of Things (IoT) deployment. This article will introduce the development and features of the DECT NR+ standard, along with the related solutions offered by Nordic Semiconductor.
The 5G standard based on non-cellular technology
In the past, DECT technology stood for Digital Enhanced Cordless Telecommunications, primarily used for wireless telephone systems. DECT NR+ (or technically known as DECT-2020 NR) is the first non-cellular technology that has been incorporated into the ITU-R defined 5G standard. The DECT-2020 NR standard was developed by ETSI to meet the requirements of ITU-R for 5G technology, officially referred to as IMT-2020 requirements.
DECT NR+ supports point-to-point, star, and mesh topologies. It's important to note that the mesh topology referred to here is a type of partial mesh, known as the cluster-tree topology. This means that devices are grouped into several independent trees, known as clusters. The cluster-tree topology is a form of star topology with branches. All clusters are interconnected to form a mesh network, which is a partial mesh since not all nodes are interconnected like in a complete mesh topology.
In DECT NR+ networks, nodes can take on roles as aggregator nodes, relay nodes, or leaf nodes. Aggregator nodes act as gateways accessing the internet, selecting operating frequencies, and initiating beacon frame transmissions indicating their routing to the outside world. The network can have multiple aggregator nodes with external connectivity. Relay nodes extend the network by routing information to other clusters and leaf devices within their cluster. Leaf nodes are the outermost nodes in the network and can only send data.
In point-to-point and star topologies, nodes with internet backhaul are defined as aggregator nodes, and all other nodes are defined as leaf nodes connected to the aggregator nodes. In the case of mesh topology, the mechanism allows devices to autonomously assign device roles based on network needs, supporting "self-organization" and "self-repair" of network topology and resolving congestion issues under high traffic. Each device individually determines the next hop based on available routes to the aggregator nodes, which means the cluster-tree is formed autonomously.
As a DECT technology, DECT NR+ can utilize the unlicensed 1.9 GHz DECT frequency band, which is globally dedicated, except for a few regions (China, India, Japan) where the DECT Forum is working to expand its usage.
DECT NR+ can coexist with classic DECT on the DECT frequency band. Since DECT NR+ was designed for coexistence, it can also use the ISM frequency band. In fact, the standard supports multiple licensed and unlicensed frequency bands ranging from 450MHz to 6GHz.
A solution suitable for large-scale IoT deployment in smart cities
The 5G standard defines three independent use cases for 5G technology, including Enhanced Mobile Broadband (eMBB), which focuses on providing faster data rates and larger network capacity compared to previous generations of mobile networks. Additionally, there is Massive Machine-Type Communications (mMTC), which aims to connect a large number of low-power devices and sensors, emphasizing low power consumption, high density, and scalability. Lastly, there is Ultra-Reliable Low Latency Communications (URLLC), which aims to provide extremely low latency and ultra-high reliability for critical communications and applications that require real-time responsiveness.
mMTC addresses the need to connect a large number of low-power devices and sensors, which is relevant to various fields such as smart cities, agriculture, manufacturing, and healthcare. Technologies that meet the ITU-R defined use case requirements for mMTC must support several features, including high device density (1 million devices per square kilometer), long battery life, and asynchronous access.
On the other hand, URLLC emphasizes ultra-low latency and ultra-high reliability, catering to critical mission-critical communications and applications that require instantaneous data transmission with no room for failure. The URLLC use case enables low-latency systems to consider wireless operations for the first time, providing low latency and reliability previously achievable only with wired connections. Applications for URLLC include autonomous robots, power distribution, motion control, and more.
Currently, there is almost no convergence of existing IoT technologies because "there is no perfect standard for every application". For instance, LTE-M and NB-IoT cellular IoT aim to provide long-range LPWAN with reduced latency demands but use licensed spectrum, resulting in data costs. LoRaWAN, on the other hand, requires the construction of expensive infrastructure. The lack of tailored wireless solutions has made the design of applications like smart streetlights more complex, cumbersome, and costly, making cash-strapped city authorities look for low-cost, wireless M2M technologies such as intelligent trash bins, micro-mobility solutions, public transportation systems, and delivery tracking, among others, which need to be deployed on a large scale for millions to billions of terminal devices. These technologies have proven difficult to meet the requirements perfectly.
A solution suitable for smart cities has emerged, and DECT NR+ is well suited for large-scale IoT applications in smart cities. It is a single, secure, and reliable radio standard that supports a multi-vendor ecosystem, is future-oriented, and scalable. Additionally, as DECT NR+ uses license-free radio spectrum allocation, it incurs no data costs, making its operational cost cheaper compared to licensed counterparts. DECT NR+ is poised to democratize wireless 5G, allowing for large-scale device deployment, and offers all the advantages of cellular but at a much lower cost for large-scale IoT deployments.
Highly integrated solutions supporting DECT NR+
Recently, Nordic has expanded its wireless product portfolio by introducing a brand-new SiP (System in Package) solution for cellular IoT and DECT NR+ facilities. This new end-to-end cellular IoT solution, the nRF91 series SiP, includes three devices with two new devices -- nRF9161™and nRF9131™, along with evaluation and development tools, development software, nRFCloud services, and technical support. Nordic is committed to providing comprehensive design and deployment solutions for IoT enterprises. Their offerings encompass design support, chipsets, modules, software, and services, bringing usability, stability, and cost-efficiency, marking the first time such a comprehensive cellular IoT solution has been offered by a single enterprise.
The nRF91 series features the Arm Cortex-M33 as a dedicated application processor, enabling users to achieve full programmability. It boasts 1MB of flash memory, 256kB of RAM, and multiple peripherals. Apart from LTE connectivity and positioning capabilities, the series also supports a wide range of applications and opens up possibilities for true edge computing in the cellular IoT and DECT NR+ (limited to nRF9161 and nRF9131) domains. Nordic further provides an open-source nRF Connect SDK (Software Development Kit), allowing users to develop their customized applications on the dedicated application processor. It's worth noting that the nRF9131 mini SiP doesn't integrate PMIC (Power Management Integrated Circuit), passive devices, and crystals.
The nRF91 series is a fully integrated cellular IoT solution supporting LTE-M and NB-IoT applications, and its energy-efficient innovations significantly contribute to power savings for LTE-M and NB-IoT, namely eDRX (extended discontinuous reception) and PSM (power saving mode). eDRX and PSM work in harmony to enable battery life of months and years. The nRF91 series also supports Quality of Service (QoS) which governs and guarantees the performance and reliability of communications within these frequency bands, while minimizing power wastage due to interference between devices.
With high deployment density and extensive coverage, the nRF91 series enables truly large-scale and high-density deployments. The nRF9160 includes critical additional security measures, enhancing device security with features like Arm TrustZone and Arm CryptoCell for secure, trusted execution and key generation and storage, providing optimal security.
A highly integrated DECT NR+ solution in SiP package
Nordic's nRF9161 SiP is specifically designed for cellular IoT and DECT NR+ applications, setting a new standard for highly integrated SiP solutions. Leveraging low-power LTE technology, advanced processing capabilities, and robust security features, the nRF9161 delivers outstanding high performance and versatility. Compared to its predecessor (nRF9160), it incorporates several enhancements, including support for DECT NR+ and 3GPP Release 14 LTE-M/NB-IoT.
The nRF9161 boasts a range of added features, including support for DECT NR+ and 3GPP Release 14 LTE-M/NB-IoT LTE protocol stacks, enabling global connectivity and high efficiency. Its integrated modem achieves worldwide connectivity without geographical limitations and incorporates unique modem features, further improving energy efficiency and ease of use. To fully harness the potential of DECT NR+, the nRF9161's DECT NR+ protocol stack enables secure, long-range, and scalable large-scale mesh applications.
Nordic also offers the nRF9131 Mini SiP, a powerful solution perfectly tailored for DECT NR+ applications. Moreover, it shares the same LTE stack support for cellular communication operation as the nRF9161 SiP. The nRF9131 simplifies chip-based traditional designs, making it an ideal choice for large-scale cellular IoT applications. Compared to the nRF9161 SiP, the nRF9131 has lower integration, resulting in a reduced Bill of Materials (BOM) cost. However, it is essential to note that non-recurring expenses (NRE) for cellular end product certification will increase based on the desired geographical coverage. Therefore, the nRF9131 Mini SiP is well-suited for global NR+ applications and large-scale cellular products targeting specific regions.
The nRF9131 is perfectly suited for DECT NR+ applications, demonstrating excellent performance and functionality in this context. It offers a smaller form factor and flexible procurement options, making it more compact than the nRF9161 and compatible with PMICs featuring other characteristics. Furthermore, the firmware functionality of the nRF9131 is fully compatible with the nRF9161, enabling seamless switching between the two SiPs. Nordic also provides reference designs, and the nRF9131 can be combined with Nordic's nPM6000 PMIC to achieve power consumption similar to that of the nRF9161.
Conclusion
DECT NR+ is expected to provide massive IoT access for large-scale M2M applications in markets such as industry, agriculture, asset tracking, smart cities and smart energy, at a low cost per node and based on a powerful and efficient self-organizing network, the market development potential is extremely considerable. Nordic has a history of early adoption of key wireless technologies for rapid commercialization and was one of the first companies to bring a DECT NR+ commercial solution to market. Nordic's nRF91 series can help customers support the rapid development of DECT NR+ applications, and it is worth your further understanding.