Internet of Things

NB-IoT vs LTE-M for Low Power IoT Connectivity

February 24, 2024

NB-IoT vs LTE-M for Low Power IoT Connectivity

Introduction

As the Internet of Things (IoT) continues to expand, connecting more devices and sensors, cellular IoT technologies like NB-IoT and LTE-M have emerged to meet the need for low power wide area networks. Both NB-IoT and LTE-M provide low power connectivity for IoT devices, but they have some key differences that make each technology better suited for certain applications. In this article, I will do an in-depth comparison of NB-IoT and LTE-M across various factors to help you determine which technology is the right fit for your IoT use case.

Overview of NB-IoT and LTE-M

NB-IoT, which stands for Narrowband IoT, is a low power wide area (LPWA) technology that was standardized by 3GPP in Release 13. It operates in licensed cellular spectrum bands and enhances coverage for IoT devices compared to traditional cellular connectivity.

LTE-M, which stands for Long Term Evolution for Machines, is another LPWA technology standardized in Release 13 by 3GPP. It also operates in licensed cellular spectrum and is optimized for machine-type communications.

Both NB-IoT and LTE-M provide crucial advantages over unlicensed LPWA technologies like LoRa and Sigfox, such as better QoS, security, and seamless mobility. However, NB-IoT and LTE-M have some technical differences that make them suitable for different types of IoT applications.

Key Differences Between NB-IoT and LTE-M

Here is an overview of how NB-IoT and LTE-M differ across some key parameters:

As we can see, NB-IoT has a much narrower bandwidth compared to LTE-M, allowing it to operate with even weaker signals. This gives NB-IoT better indoor coverage and range. The trade-off is that data rates are lower on NB-IoT.

LTE-M has higher bandwidth and data rates, at the cost of reduced coverage and building penetration. LTE-M is better suited for applications that need lower latency or higher bandwidth. The battery life of both technologies can be up to 10 years with power saving mechanisms.

Now let’s take a deeper look at some of the key differences and how they impact real-world applications.

Bandwidth, Data Rates and Latency

The narrow 180 kHz bandwidth used by NB-IoT results in maximum data rates of around 250 kbps downlink and 20 kbps uplink. This is sufficient for sending small, intermittent packets of data from simple sensors and meters. However, NB-IoT cannot match the higher data rates of LTE-M.

LTE-M provides data rates comparable to 4G LTE, with peak rates of 1 Mbps downlink and 375 kbps uplink. This makes LTE-M suitable for applications with higher bandwidth requirements, like firmware updates, multimedia sensors, asset trackers, and remote monitoring using video.

Higher bandwidth also equates to lower latency on LTE-M. NB-IoT latency can range from 1.6 seconds to 10 seconds, while LTE-M latency is between 10-15 milliseconds. Time sensitive applications like voice over IP (VoIP), vehicle telematics, and critical connections should use LTE-M.

In summary, NB-IoT is ideal for low data rate, latency tolerant use cases while LTE-M suits high bandwidth applications requiring faster response times.

Mobility and Coverage

With a maximum coupling loss (MCL) of 164 dB, NB-IoT has better range and coverage than LTE-M (155.7 dB MCL). NB-IoT can reach challenging locations like underground parking structures and urban basements. It performs better in rural areas as well.

The narrowband transmissions of NB-IoT also make it more resilient to Doppler effects caused by mobility. NB-IoT supports speeds of up to 120 km/h, making it usable for tracking assets in transit. LTE-M has higher Doppler tolerance supporting up to 500 km/h, so it is preferred for real-time vehicle fleet management.

Therefore, NB-IoT is a better choice for largely stationary sensors and meters, while LTE-M is recommended if mobility is required.

Battery Life Considerations

Both NB-IoT and LTE-M are designed for long battery life of up to 10 years when using power saving mode (PSM) and extended discontinuous reception (eDRX). However, NB-IoT consumes slightly less power than LTE-M in most deployment scenarios.

The main reasons are:

Narrowband transmissions require less energy
Better indoor penetration results in fewer potential retransmissions
Lower data rates mean transmissions finish faster

For battery-powered devices that only need to send small amounts of data occasionally, like temperature sensors or utility meters, NB-IoT may provide marginally better battery life. For mobile applications or those needing high data rates, LTE-M is the superior choice.

Cost and Ecosystem Considerations

NB-IoT devices have a lower cost due to simpler radio designs. Chipsets and modules are now available for less than $10 in volume. The ecosystem for NB-IoT has also had a few more years to mature compared to LTE-M.

However, LTE-M rides on the strong ecosystem behind 4G LTE. There is broader vendor support and standardization for LTE-M since it utilizes the existing LTE network core. LTE-M module costs are coming down as adoption increases.

Over the long run, the cost difference between the two technologies is expected to narrow significantly. Both have a competitive cost structure ideal for large scale IoT deployments.

Coexistence With Existing Cellular Networks

An important consideration is that NB-IoT and LTE-M will commonly be deployed within existing cellular networks. Mobile operators have to minimize the impact on their customers using 4G/5G for smartphones and mobile broadband.

NB-IoT transmissions fit nicely within the unused resource blocks of an LTE carrier. The narrow bandwidth requirement does not subtract much capacity from the LTE network. LTE-M, on the other hand, requires a wider 1.4 MHz slice of bandwidth which directly reduces resources available for LTE.

Therefore, adding NB-IoT has less impact on the legacy network compared to adding LTE-M in the same spectrum band. This makes NB-IoT easier to deploy within existing 4G and future 5G networks.

Use Cases Suited to Each Technology

Based on the technical comparison, here are some guidelines on which technology is better suited for various categories of IoT applications:

NB-IoT is ideal for:
Smart metering (electricity, gas, water)
Smart city infrastructure (lighting, parking, waste management)
Environmental monitoring (air/water quality, noise monitoring)
Asset tracking and indoor positioning
Predictive maintenance and condition monitoring
Low power sensors (temperature, motion, soil moisture, etc.)
LTE-M is better for:
Digital signage and video surveillance
Voice-over-LTE (VoLTE) services
Telematics and fleet management
Point-of-sale and payment terminals
Wearables and health monitoring
Remote control of machinery and industrial robots
Mobile asset management

The use cases best served by NB-IoT need long battery life, small data packets, and extensive coverage. LTE-M suits applications requiring higher data rates, lower latency, and mobility support. However, there is significant overlap – either technology can work for many non-extreme IoT deployments.

Conclusion

In summary, NB-IoT has greater power efficiency, larger coverage footprint, and lower latency compared to LTE-M. This makes NB-IoT ideal for static, battery-powered devices that only send small amounts of non-urgent data.

LTE-M provides higher data rates, lower latency, and support for mobility at the cost of higher power consumption. It is better suited for IoT applications that need to send larger data packets in real-time.

When choosing between NB-IoT and LTE-M, carefully evaluate your requirements for battery life, data bandwidth, latency, mobility and consider coverage where the devices will be deployed. Both technologies will continue to evolve and be major driving forces behind cellular IoT adoption worldwide.