LTE
Long Term Evolution (LTE) technology enables devices to be connected to a base station without an intermediate device or gateway. LTE is the fourth-generation (4G) wireless broadband standard built on existing technologies, replacing 3G. LTE maximizes bandwidth utilization and supports data rates up to 300 Mbps. The following are main key features of the LTE protocol:
Purely packet-based.
Provides significantly high data rates.
Improves latency.
It uses the spectrum more efficiently.
It supports scalable carrier bandwidths.
It includes robust security features.
It is designed to be backward compatible.
LTE is managed by the 3rd Generation Partnership Project (3GPP). They develop and maintain the cellular standards, which are structured as releases.
Nordic Semiconductor offers a wide range of cellular products that support LTE connectivity, particularly focusing on the LTE-M and NB-IoT standards. For more information on the products, see Cellular IoT SiPs.
LTE-M and NB-IoT
LTE-M is a low-power wide-area network (LPWAN) communication standard, introduced in 3GPP release 13. It offers higher bandwidth and lower latency compared to other similar technologies. This makes it suited for applications such as asset tracking, health monitors, alarm panels, environmental monitoring, and smart parking.
NB-IoT, or Narrowband IoT, is another LPWAN communication standard that was introduced in 3GPP release 13. It is designed for indoor coverage, low cost, and long battery life. NB-IoT operates in a small radio frequency band of 200 kHz. It is ideal for applications like smart metering, environmental monitoring, and smart lighting.
nRF91 Series devices such as nRF9151 DK, nRF9161 DK, nRF9160 DK, and Thingy:91 support both LTE-M and NB-IoT technologies.
Comparison between LTE-M and NB-IoT
The following table shows a comparison between LTE-M and NB-IoT in terms of advantages in using any of these standards:
LTE-M |
NB-IoT |
|
|---|---|---|
Strengths |
Higher throughput |
Longer range |
Lower latency |
Better penetration |
|
Better roaming agreements |
Power efficient at lower data rate |
|
Power efficient at medium data rate |
||
Suitable for TCP/TLS secure connection |
You can find the key feature comparison between LTE-M and NB-IoT in the nWP044 - Best practices for cellular IoT development documentation.
Factors to be considered for LTE
Following are some key aspects to ensure LTE support for your SiP using Nordic Semiconductor’s devices, such as the nRF91 Series.
LTE bands
There are 56 LTE bands from 400 MHz to 6 GHz. Some bands use Frequency Division Duplex (FDD) and some use Time Division Duplex (TDD). The different bands are licensed by different Mobile Network Operators (MNO) around the world. Half-duplex operation opens for much simpler multiband support and enables User equipment (UE) to operate in a larger region. For LTE-M and NB-IoT, the only known deployment is FDD.
nRF91 Series SiPs support up to 18 LTE bands for global operation. For details of LTE band support in an nRF91 Series SiP for LTE-M and NB-IoT, see nRF9151 Product Specification, nRF9161 Product Specification, or nRF9160 Product Specification, depending on the SiP you are using.
Physical layer parameters
The following table provides physical layer parameters for LTE-M and NB-IoT:
LTE-M |
NB-IoT |
|
|---|---|---|
Bandwidth |
1.4 MHz |
200 kHz |
Antenna Techniques |
Single antenna |
Single antenna |
OFDM subcarriers |
72 subcarriers |
12 subcarriers |
Duplexing |
Full-duplex or half-duplex, but networks use only half-duplex FDD |
Half-duplex |
Modulation in Uplink (UL) and Downlink (DL) |
QPSK or 16QAM in both UL and DL depending on signal quality |
BPSK or QPSK in UL depending on signal quality, only QPSK in DL |
Network support
A factor governing the selection of the access technology is the MNO support in the areas where you wish to deploy your product. Most cellular operators support both LTE-M and NB-IoT, but there are geographic locations where only one of these is supported. See Mobile IoT deployment map for more information.
Certifications
Some MNOs, such as Verizon and Vodafone, have their own certification requirements. In such cases, it is advised to engage with the MNO certification programs and contact them at the earliest. This is to receive certification-related requirements and better understand the potential certification costs, processes, and timelines. But many operators only require GCF (Global Certification Forum) or PTCRB certifications that devices work as per standard, and regulatory certifications.
For more information about certification related to the nRF91 Series SiP, refer to the following pages:
SIM card support
SIMs that are used with the nRF91 Series devices must support LTE-M, NB-IoT, or both. The iBasis SIM is bundled with the nRF9160 DK and Thingy:91, the Onomondo SIM with an nRF91x1 DK, and the Wireless Logic SIM card with the nRF9151 DK. Check the iBasis IoT network coverage, Onomondo LTE-M coverage, Onomondo NB-IoT coverage, or Wireless Logic LTE-M/NB-IoT network coverage pages to see the network coverage for different countries, depending on the SIM card you are using.
Software SIM
The nRF91 Series supports software SIM, which allows the usage of software SIM-based solutions to reduce energy consumption associated with physical SIMs. The following are some of the key advantages of using software SIM:
Cost savings and simplified design by excluding the SIM hardware layer.
Power savings, especially in idle mode using Extended Discontinuous Reception (eDRX).
The traditional carriers (not MVNOs like iBasis or Onomondo) do not allow their profiles to be provisioned or uploaded into SoftSIMs. These carriers need to use profiles from SoftSIM providers like Onomondo. See the software SIM support section of the Cellular IoT unique features documentation for information on software SIM.
The software SIM support is available in the nRF Connect SDK from the v2.5.0 release. The Onomondo SoftSIM integration with the nRF91 Series guide describes the integration of software SIM into nRF Connect SDK, and the SoftSIM guide demonstrates the transfer of SIM data between the modem and the application.
Power consumption
Both LTE-M and NB-IoT support Power Saving Mode (PSM), eDRX, and Release Assistance Indication (RAI) to minimize power consumption. For more information on power-saving techniques, refer to the DevAcademy’s Power saving techniques documentation.
Security
The nRF91 Series devices include a range of security features, such as Arm TrustZone and Arm CryptoCell for secure application and data handling. For more information, refer to the Processing environments documentation.
Security best practices are also implemented to protect data transmitted over the LTE network. This includes using Transport Layer Security (TLS) for Transmission Control Protocol (TCP) and Datagram Transport Layer Security (DTLS) for User Datagram Protocol (UDP). For more information, refer to the Security protocol for cellular IoT documentation.
Getting started with cellular products
For getting started with the cellular products, you can refer to the Developing with nRF91 Series documentation, which guides through the features, getting started steps, and advanced usage of the boards. For a self-paced, hands-on course, enroll in DevAcademy’s Cellular IoT Fundamentals course, which describes the LTE and NB-IoT technologies and the software architecture of a cellular IoT application based on Nordic Semiconductor nRF91 Series devices.
The System mode section provides information about switching between LTE-M and NB-IoT.
Cellular IoT in nRF Connect SDK
The following sections explain the different applications, libraries, and samples that use the cellular IoT products.
Modem library
The nRF Connect SDK applications for the nRF91 Series devices that communicate with the nRF91 Series modem firmware must include the Modem library.
The Modem library is released as an OS-independent binary library in the nrfxlib repository and it is integrated into nRF Connect SDK through an integration layer, nrf_modem_lib.
The Modem library integration layer fulfills the integration requirements of the Modem library in nRF Connect SDK. For more information on the integration, see Modem library integration layer.
Library support
The following nRF Connect SDK libraries are used for cellular IoT:
LwM2M carrier library
Memfault library
Applications and samples
The following applications use the cellular IoT in nRF Connect SDK:
The following samples are used for the cellular IoT development in nRF Connect SDK:
Memfault sample.
Networking samples - These samples use an nRF91 Series device over LTE or an nRF70 Series device over Wi-Fi® for communication and connection.
Integrations
The following integrations are available for cellular IoT in nRF Connect SDK:
nRF Cloud - nRF Cloud is Nordic Semiconductor’s IoT cloud platform that allows you to remotely manage and update your IoT devices using Firmware Over-the-Air (FOTA).
Memfault - A cloud-based web application with nRF Connect SDK compatibility that monitors devices and allows you to debug issues remotely through an LTE or Wi-Fi network.
AVSystem - Software solution provider that provides a device management platform.
Power optimization
For optimizing the power consumption of your cellular application, you can use the Online Power Profiler (OPP) tool. See Power optimization for nRF91 Series for more information.
References
nWP044 - Best practices for cellular IoT development whitepaper - Describes the guidelines that you need to consider when you start the development for a low power cellular IoT product.