Cellular IoT (CIoT) – Mobile IoT using NB-IoT and LTE-M

Today, mobile networks are not limited to just mobile phones for consumers and businesses, but they also provide connectivity for machine-to-machine (M2M) and Internet of Things (IoT) devices. IoT, or the Internet of Things, has been around for a long time, and it is a system of devices connected to the internet to communicate with each other or with other systems.

Mobile IoT or Cellular IoT (CIoT) is a system that uses mobile cellular networks for IoT connectivity. It employs Low Power Wide Area (LPWA) technologies like NB-IoT, LTE-M and GSM-IoT to allow low-cost and low-powered IoT devices to securely connect using the licensed spectrum of a mobile operator.

Why use a mobile network instead of a Wi-Fi network for IoT?

IoT devices can connect over any network, and they do not necessarily require a mobile cellular connection such as GSM, UMTS, LTE or 5G NR. However, there are many key advantages of using a mobile network for IoT connectivity. The first and the most important benefit of mobile IoT (cellular IoT) is the reach of the network. As mobile IoT utilises the existing cellular networks, it is able to leverage the presence of existing infrastructure. In addition, mobile networks use a licensed frequency spectrum, which allows them to minimise interference and provide connectivity in a highly secure manner.

Cellular IoT can be currently enabled by variants of the GSM and LTE technologies, including EC-GSM-IoT, NB-IoT and LTE-M. GSM (Global System for Mobile Communications) belongs to the second-generation (2G) mobile networks and has been around since the early 1990s. Today, the latest cellular technology is New Radio (NR), which is used by the fifth generation of mobile networks or 5G; however, LTE (Long Term Evolution), which is a fourth-generation (4G) cellular technology, is the most widely available technology.

Why mobile IoT requires a low-powered network?

There are three key requirements for mobile IoT or cellular IoT connectivity: low power consumption so that the battery can last for up to 10 years, low cost so that mass deployment can take place, wide-area coverage so that the devices can connect to the network no matter where they are placed.

The standardisation of mobile IoT or cellular IoT is in line with 3GPP specifications. The mass deployment of billions of IoT devices requires some practical considerations. The first requirement is for the connectivity technology to support low power so that the devices using the technology do not run out of battery every now and then.

The second requirement is the cost of the device, which must be low in order to support mass deployment in an affordable way. The third requirement is for the coverage to be strong so that all devices can easily connect to the network no matter where they are situated. So, the key areas that outline the building blocks for cellular IoT (mobile IoT) are low device cost, extended network coverage and low power consumption.

Unlike our mobile phones which spend most of their time with us, IoT devices are often required to be placed in awkward locations. For instance, if we consider the smart meter use case, the gas and electric meters are usually found in indoor locations inside a cupboard which are not the most accessible places for a mobile signal to reach.

Therefore, a mobile signal needs to be extra strong in order to reach these problematic locations. As a result, the mobile IoT coverage requires the cellular signal to be 20 dB stronger than average. Furthermore, to keep the device costs low, the devices need to have a very low level of complexity. Finally, low power consumption requires the battery to last for several years (up to 10 years).

How important is the connectivity type for IoT devices?

IoT allows connected devices to provide information or trigger actions to facilitate many tasks that we encounter in our daily lives. While there are many ways to look at an IoT system, the three critical components of IoT are hardware, connectivity and software application.

A simple example can be a smart lighting system where a smart light bulb (hardware) can be connected to a local WiFi network (connectivity) and controlled by an app (software application). Even though the actual value of an IoT system comes from the hardware and the application, connectivity remains an essential part.

Cellular IoT is a type of IoT that uses a cellular network for connectivity. The key aspects of a good IoT connectivity technology include wide area coverage (long-range), low complexity and costs, and lower power consumption to save battery life.

LPWA technologies: EC-GSM-IoT, LTE-M and NB-IoT

EC-GSM-IoT, LTE-M (LTE for machines) and NB-IoT (Narrowband IoT) are low-powered wide-area (LPWA) technologies that utilise the existing cellular network infrastructure of mobile operators to provide connectivity to IoT devices using licensed frequency spectrum.

EC-GSM-IoT: Extended Coverage GSM Internet of Things

EC-GSM-IoT is based on 2G GSM networks. It is a long-range, low complexity, low-powered technology designed to be backwards compatible with existing GSM networks. EC-GSM-IoT uses the EGPRS (Enhanced GPRS) technology within GSM EDGE networks and can work with existing GSM base stations through a software upgrade without requiring additional hardware.

The application of EC-GSM-IoT is in IoT use cases where low data rates are needed for non-real-time scenarios, e.g. metre readings from a smart metre. It can facilitate data rates of 160 bits per second (bps) or more with a latency of around 10 seconds. Furthermore, the battery can last up to ten (10) years due to low power consumption.

LTE-M: Long Term Evolution for Machines

LTE-M is an IoT technology based on the 4G LTE networks. LTE-M is different from EC-GSM-IoT in that it is suitable for use cases where a higher data rate is required for real-time scenarios, e.g. patient monitoring.

LTE-M can enable up to 1 Mbps in both uplink and downlink with a bandwidth of around 1.080 MHz. The battery life for devices that support LTE-M is about ten years. It can support voice and data, and use cases include traffic lights, parking sensors and smart cities.

NB-IoT: Narrowband IoT

NB-IoT stands for NarrowBand Internet of Things or Narrowband IoT and is based on the 4G LTE technology. Like EC-GSM-IoT, it is designed for non-real-time use cases where a slight delay in the communication is acceptable, e.g. utility meters.

NB-IoT has multiple categories: Cat NB1 can offer peak downlink data rates of up to 226.7 kbps, whereas Cat NB2 can offer peak downlink data rates of up to 282 kbps. NarrowBand IoT, as the name suggests, employs low bandwidth of 180 kHz.

LTE-M vs NB-IoT: Which is better?

NB-IoT (Narrowband IoT) employs smaller bandwidths to enable data connections with lower bit rates and wider coverage. LTE-M (LTE for machines) is designed for real-time communication (e.g. emergency communication, including voice), and it can deliver higher data rates than NB-IoT.

The LTE-M technology can support most IoT use cases; however, the choice of the technology depends on the target use cases. LTE-M offers lower latencies and higher data rates, making it a perfect choice for use cases that require real-time communication (e.g. emergencies).

The Narrowband IoT (NB-IoT) technology uses smaller bandwidth (hence the word narrowband) and therefore offers lower data rates offering wider coverage but is not suitable for real-time communication. A typical use case device category for NB-IoT can be sensors.

Conclusion

Cellular IoT (CIoT) or Mobile IoT can be seen as umbrella terminologies encompassing various cellular technologies connecting IoT devices to the internet through mobile data. Mobile IoT employs various low-powered-wide-area (LPWA) technologies, including Extended Coverage GSM IoT (EC-GSM-IoT), NarrowBand IoT (NB-IoT) and Long Term Evolution for Machines (LTE-M) to connect IoT devices to the internet through GSM and LTE networks.

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