Difference Between NB-IoT and LTE-M

The Internet of Things (IoT) is one of the key components of digital and digital transformation along with big data and analytics. However, the maturity of IoT applications and networking technologies has caused an explosion in the number of connected devices. The number of connected IoT devices is expected to reach 50 billion by 2022. The current IoT evolution is very different from the regular mobile evolution. While the latter is focusing on connectivity only, the IoT evolution should be addressed from end to end. However, the existing cellular technologies are not particularly well adapted to devices and objects specifically developed for the Internet of Things. Mobile broadband networks have to evolve to become compatible with IoT.

Industries are now considering smart approaches to cater for low power, low throughput, a very high number of connections, and a very low cost for the end unit or modem. This leads to a need for new, low-power wide area networks (LPWANs) to meet the changing requirements of WSNs. This started with the definition of new LTE device categories. The aim was to align with specific IoT requirements, such as low mobility, low power consumption, long range, and low cost. Both LTE-M and NB-IoT play an important role in connecting a range of IoT devices. But the question arises: which one’s the best choice to address the requirements of a massive number of IoT devices?

LTE-M

LTE-M, short for LTE Cat M1, is a low-power wide area network (LPWAN) technology standardized by 3GPP in 2016 in Release 13 to address the requirements of the Internet of Things (IoT). The 3GPP (Third Generation Partnership Project) is the standardization body that specifies LTE/LTE-Advanced as well as 3G ULTRA and 2G GSM mobile communication systems. The initial version of the LTE MTC standards was realized with 3GPP Release 8 based on Category 1. In order to enhance the LTE capability for the evolving IoT market, the key focus of the Release 13 is to define a new low complexity UE category type that supports reduced bandwidth, reduced transmit power, long battery life and extended coverage operation. This is Cat-M1, previously known as Cat-M, which brings coverage enhancements to achieve further power consumption improvements.

NB-IoT

The new LTE-M device category, however, was not sufficiently close to support LPWAN IoT requirements. So, in 2015, 3GPP approved a proposal to standardize a new narrowband radio access technology called Narrowband IoT, or simply NB-IoT. The new standard specifically addresses the requirements of a massive number of low-throughput devices, low device power consumption, improved indoor coverage, and optimized network architecture. Unlike eMTC that can only be deployed in-band, utilizing resource blocks within a normal LTE carrier, NB-IoT can also be deployed in the unused resource blocks within a LTE carriers’ guard-band, or standalone for deployments in dedicated spectrum. The requirements of NB-IoT are the same for MTC, but with the focus on low-end massive MTC scenarios.

Difference between NB-IoT and LTE-M

Basics

LTE Cat-M1, also known as enhanced Machine Type Communication (and sometimes just called Cat-M), or simply called LTE-M, is a low-power wide area network (LPWAN) technology standardized by 3GPP in 2016 in Release 13 to address the requirements of the Internet of Things (IoT). It was designed to target IoT and M2M use cases with low cost, low power and range enhancements. However, the new LTE-M device category was not sufficiently close to LPWA capabilities. In 2015, 3GPP approved a proposal to standardize a new narrowband radio access technology called Narrowband IoT, or simply NB-IoT. The NB-IoT is yet another LPWAN protocol governed by the 3GPP in Release 13 and further extended in Release 14 and Release 15.

Architecture

LTE-M follows other late 3GPP protocols that are IP-based. While not a MIMO architecture, throughput is capable of 375 Kbps or 1 Mbps on the uplink as well as downlink. Multiple devices are allowed on a Cat-M1 network using the traditional SC-FDMA algorithm. It also makes use of more complex features such as frequency hopping and turbo-coding. NB-IoT also operates in the licensed spectrum, just like LTE-M and is based on OFDMA (downlink) and SC-FDMA (uplink) multiplexing and uses the same subcarrier spacing and symbol duration.

Deployment

Unlike eMTC that can only be deployed in-band, utilizing resource blocks within a normal LTE carrier, NB-IoT can also be deployed in the unused resource blocks within a LTE carriers’ guard-band, or standalone for deployments in dedicated spectrum. The requirements of NB-IoT are the same for MTC, but with the focus on low-end massive MTC scenarios. Part of an LTE carrier frequency is allocated for use as an NB-IoT frequency. This allocation is typically done by service provider and IoT devices are configured accordingly. This allows for flexibility in LTE, WCDMA, and GSM deployments. This in turn allows for deployments of up to 200,000 devices in theory per cell.

NB-IoT vs. LTE-M: Comparison Chart

Summary

In a nutshell, both LTE-M and NB-IoT play an important role in connecting a range of IoT devices. LTE-M reduced the channel width to 1.4 MHz, NB-IoT reduces it further to 180 KHz for the same reasons, reducing cost and power substantially. Regardless of the differences, NB-IoT is based on OFDMA (downlink) and SC-FDMA (uplink) multiplexing and uses the same subcarrier spacing and symbol duration. This allows mobile service providers to optimize their spectrum with a number of deployment options for GSM, WCDMA, and LTE spectrum.

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