How NB-IoT facilitates energy-efficient and latency-tolerant IoT solutions

The global IoT connectivity market is growing at a rapid pace, with the narrowband-IoT (NB-IoT) segment expected to increase from 14% this year (with 301 million connections) to 34% in 2025 (with over 1.214 million connections).

NB-IoT modules now account for the overwhelming market share – about 75% – compared to LTE-M, which is more applicable to socially and industrially significant applications.

IoT connections and devices, especially the NB-IoT specification, are extremely complex, vast and fragmented. 

This article will explore how NB-IoT facilitates energy-efficient and latency-tolerant IoT solutions to cover hard-to-reach locations.

But before we dive deep into the ins and outs of the NB-IoT, let's take a look at the Low-Power Wide-Area (LPWA) ecosystem first.

LPWA market overview 

In the first half of 2020, IoT devices using unlicensed LPWA (for example, Long Range (LoRa and Sigfox) accounted for 53% of the market share. At the same time, licensed LPWA (NB-IoT and LTE-type machines communications (LTE-M)) accounted for 47% of global LPWA connections. 

In 2021, LPWA licensed devices are ahead of the curve with a 54% share, while unlicensed LPWA accounts for 46%. In fact, the NB-IoT connections were up 75% YoY in 1H 2021. NB-IoT as a separate technology now dominates the LPWA connection market with a 44% market share, while LoRa has dropped to second place with a 37% of the global market share.

Several standardized IoT device systems have a short-range, up to about 100 m. The best-known among them are Bluetooth and Wi-Fi, although there are others such as ZigBee. Bluetooth is suitable for low speeds, up to 1MB per second, and Wi-Fi – from 1MB to 1GB per second.

However, the most widely accepted and used IoT systems are those with low power consumption and broad coverage, known collectively as LPWA (Low-Power Wide-Area). 

LTE-M and NB-IoT are two of the new low-power protocols for the cellular network specially designed to address the IoT issues of connected objects. They are both 5G ready.

LTE-M is more applicable to mobility environments, while NB-IoT provides extreme optimization for extremely low-bandwidth networks and latency-tolerant data distribution. NB-IoT devices are cheaper than LTE-M devices, which encourages their broader mass adoption.

There are other LPWA technologies on the market, such as Sigfox or LoRa. They aim for greater visibility and implementation, especially in the United States. Still, it seems that the balance is steadily shifting in favor of NB-IoT, and for some specific applications, from LTE-M.

Licensed vs unlicensed frequency spectrums

In many IoT applications, four properties are particularly important:

• Low deployment and maintenance costs.
• Low power consumption.
• Reliable network coverage.
• The ability to interconnect a large number of devices.

LPWAN fulfil these criteria very well. There's now a whole host of different LPWAN standards, some of which differ greatly from one another. The four most important are NB-IoT, LTE-M, Sigfox and LoRa. These technologies can be roughly divided into two groups: the licensed spectrum (LTE-M and NB-IoT) the unlicensed spectrum (LoRa and Sigfox).

Advantages of licensed mobile communication frequencies

• Both NB-IoT and LTE-M can be built on top of the existing infrastructure and use the existing resources of the mobile network operators.
• Both mobile technologies are based on standards from 3GPP. 3GPP has introduced the standards for existing mobile communications technologies such as GSM, UMTS and LTE, and the new 5G. These standards, which are constantly being developed further, ensure that mobile communications technologies meet customer needs for international operation, stability, reliability, security, cost efficiency and high scalability.
• For NB-IoT and LTE-M, 3GPP standardization means that they will be available in the long term and that investments in these technologies are thus secured and not lost. NB-IoT and LTE-M are therefore fit for 5G.
• Another advantage of mobile networks is their interoperability: NB-IoT and LTE-M multimode radio modules can be switched to other carriers, including 2G and 3G. This means that these components also work in countries where mobile IoT networks are not yet available.
• NB-IoT and LTE-M benefit from the extensive support of mobile operators and a large ecosystem of chipset and device manufacturers. This ultimately reduces the risk of vendor lock-in.

Advantages of unlicensed frequency spectrums

The main advantage of Sigfox and LoRa is that they use free frequency bands for which no license fees are charged. SIM cards and contracts with mobile network providers are also not required, and roaming charges do not apply. The costs for operation are therefore lower overall. However, Sigfox and LoRa have other significant differences to NB-IoT and LTE-M, which may be beneficial or detrimental depending on your use case.

Sigfox, in particular, but also LoRa, are designed for connecting basic and very simple devices. Therefore, they are often referred to as 0G networks. Sigfox and LoRa require very little energy. However: for some IoT use cases, the data volumes may be too small, the transmission speed too slow, and the latency too high.

Both SigFox and LoRa have already been on the market for several years and are therefore field-proven. Nevertheless, the infrastructure at SigFox still has shortcomings. With LoRa, users must take care of the network themselves. However, companies in some countries are offering nationwide coverage with LoRaWAN networks. Setting up your own network can have its advantages. You can use it to cover an area that mobile network providers do not cover. And: Within your own delimited network, the data remains in your own hands.

Unlicensed, proprietary spectrums require a large commitment.

SigFox is a proprietary technology developed by a French company of the same name and launched in 2009. A non-profit organization called the LoRa Alliance is behind LoRa. But being patented and proprietary means the technology only works with particular chips (from the Chinese manufacturer Semtech). The users are, therefore, dependent on the two companies as suppliers. If they want to switch to a different transmission technology, they also have to change their hardware.

Key Features of NB-IoT

• Narrowband-IoT requires much less energy than conventional mobile devices such as smartphones. Battery runtime can last up to 10 years.
• The overall costs are much lower than those of GSM, UMTS or LTE. An NB-IoT module currently costs less than $5.
• The data rate is limited, with a maximum of 250 kb per second (download and upload). NB-IoT is designed for the transmission of data and not for voice or SMS.
• About 100 times more devices can be networked per radio cell compared to GSM.
• The latency of NB-IoT is low: mobile technology is less suitable for transmitting real-time data or time-critical alarm messages.
• Compared to GSM, UMTS or even LTE, NB-IoT has much better building penetration and is still available in basements.

NB-IoT vs LTE-M

Now let's see how NB-IoT compares to LTE-M in terms of power consumption, penetration and range, latency, mobility, and bandwidth.

Power consumption

When NB-IoT-enabled devices do not change location and thus do not have to switch between cells, they tend to be way more efficient than devices communicating via LTE-M. This is a decisive factor for many IoT applications, as maintenance costs of manually switching batteries can be extensive, especially for large-scale operations that may have tens of thousands of devices deployed. In theory, NB-IoT devices may have a battery life of up to ten years. However, there are many factors influencing battery life.

Penetration and range

By utilizing a single narrowband of 180 KHz or 200 KHz, NB-IoT achieves a great transmission power density, which significantly improves its range. Thus, NB-IoT is more suitable for IoT devices deployed in buildings, tunnels, basements, or similar locations than LTE-M. 

Latency

LTE-M may be the better option for IoT networks, where latency is crucial (for example, when companies need to rapidly analyze sensor data in real-time). LTE-M has a latency of around 50ms to 150ms. In comparison, NB-IoT has a latency of 1600 to 10000ms (10 seconds).

Mobility

NB-IoT does not yet support full mobility. NB-IoT devices need to alternate between different cells as they change location and travel around; this can decrement the battery life of the devices. LTE-M devices do not have to reselect cells when they change location.

For example, Shared scooter applications or fleet tracking operations may decide to opt for LTE-M. While NB-IoT connections may be theoretically possible, the devices will likely suffer from faster battery depletion, increased latency and a less reliable connection. Intrinsically, by design, NB-IoT was designed to be used for stationary devices.

Bandwidth

Bandwidth is rarely an issue, as most sensor data is fairly compact, and IoT projects rarely revolve around data-intensive IoT applications. Datasets tend to be binary and in the kilobyte range. Some IoT devices, such as CCTV cameras, may need to transmit high data volumes in real time. In this case, LTE-M may be the battery choice. While it isn’t on par with standard LTE networks in terms of connection speed, it is way faster than NB-IoT. LTE-M’s data rate is around 300 Kbps to 1 Mbps, while NB-IoT can only achieve around 100 Kbps.

Deployment of NB-IoT

The specifications of NB-IoT improve the ranges and signal levels of the mobile radio network. At the same time, the complexity of the radio module is reduced, and the maximum transmission rates in the transmit and receive directions are limited. Thus, NB-IoT achieves an additional 20dB in its power transmission balance and network coverage.

Due to the limited data rates, only narrowband applications are possible. The maximum download and upload data rates are 250 kilobits per second. The channels are each only 180 kilohertz wide. Thanks to these narrow channel widths, NarrowBand IoT can be operated both inband on regular LTE carriers and outband, for example, in the guard band (a gap between the radio bands).

Suppose LTE bands such as the 900 MHz and 800 MHz range are used. In that case, this results in even better building penetration, as the longer-wave radio signals of lower frequency penetrate objects and obstacles better than, for example, LTE signals in the 1,800 MHz or 2,600 MHz frequency bands. The range increase of NarrowBand IoT is achieved, among other things, by a more robust modulation technology.

NB-IoT limitations for IoT project development

NB-IoT may not be the optimal LPWAN connectivity protocol to use for your project, if:

• Your project spans across multiple countries, thus requiring roaming.
• Latency is a factor crucial to the viability of your project. (e.g. If your project involves emergency response based on real-time data.)
• Your end devices will transmit high volumes of data. While there is no defined limit, most NB-IoT projects would need to transmit less than 1 MB per end device to be economically feasible.
• Your project requires fast data transmission. NB-IoT has a datarate of around 250Kbps download and 20Kbps upload). Thus the transmission of optical sensor data (i.e. CCTV footage) is thus out of the question.
• Your end devices must communicate directly as an M2M (machine to machine) system or mesh network.
• The connection between server and end devices needs to be initiated on the server-side.
• Your end devices are mobile and frequently change location.

NB-IoT power-saving capabilities

eDRX (Extended Discontinuous Reception): eDRX extends the battery life of regular DRX, which already exists in LTE networks today. It is very useful when regular paging “listening” is required. The user equipment (UE) can save power by turning off the module’s receive function for a few seconds or longer. Although it does not offer the same power reduction as PSM, eDRX can be a viable trade-off between device accessibility and power consumption.

PSM (Power Saving Mode): This mode puts the end device into a sleep/hibernation mode to save energy. During power saving mode, downlink transmission (from server to end device) is not possible. Therefore, it can only be woken up via a timer (i.e. preset intervals defined by the network operator) or through its own sensors when they are being triggered. No additional energy is required to re-register the network device when waking up, since the session (PDP Context) remains active, even during sleep mode.

Most promising areas of NB-IoT application

Smart Cities

Connected smart cities technologies make everyday life in urban areas more efficient. Numerous major cities have already embarked on the path to becoming smart, connected cities. They face complex challenges, not least of which is the threat of traffic and environmental collapse. Since most end devices used in smart city IoT projects are stationary sensors, NB-IoT is an attractive LPWAN. Its low operating and deployment costs further lower the economic barrier of entry, enabling cities to test new projects without taking big financial risks.

One prime example of smart cities IoT projects using NB-IoT is “Park and Joy” in Hamburg (Germany). One of the numerous parking solutions can check whether parking spaces are occupied and direct drivers to the nearest available space. Due to the high number of networked, stationary sensors, low cost, and long battery runtimes, the technology is perfectly suitable.

Logistics & transportation

One way to enable real-time inventory and consignment tracking is to deploy NB-IoT. Let's assume you're looking to build a smart consignment inventory management for hospital logictics. The solution should allow for tracking down consignment items, informing customers of product usage and returning items to customers without hospital integration. Here's how the project can look like from an NB-IoT perspective.

It'd be best if you built a smart tracker and applied it to consignment items before shipping. The tracking device can be based on an STM32 microcontroller. The radio network connectivity is covered using S2-LP transceiver for the SigFOx version and a Quectel NB-IoT transceiver for the NB-IoT version. 

The inventory tracker is registered to a management platform and periodically sends information about the tracked package's state.

When a consignment item is used in the hospital (e.g. for surgery), the device will send a message triggering a decrease in the stock level. The customer will get a daily report which includes consumed product data. This automatically triggers the invoicing and stock replenishment processes on the hospital side.

Utility

In combination with digital services, modern metering devices and smart metering systems provide numerous benefits that can increase energy providers' productivity and transparency for consumers. In this way, energy suppliers ensure the efficient operation of their infrastructure and lay the foundation for new, data-based business models. Smart meters can provide the utility company with detailed information about the condition of the grid. They also increase competitiveness provide customers with more transparencies, which can greatly increase their loyalty towards their energy provider. The metering can be more accurate, and data-driven billing can be further improved. Since most meters managed by utility companies are stationary devices that only need to transmit small amounts of data in relatively large intervals, NB-IoT is likely the most attractive connectivity solution for such projects.

Waste Management

Smart waste collection can ensure that trash cans are emptied on demand (only when they reach their maximum capacity) rather than a fixed schedule. Manual labour time and fuel costs can be greatly reduced by optimizing the routes of nearby garbage trucks. Waste garbage cans equipped with NB-IoT modules can measure the volume or weight of their content and notify the waste collection company once they are full.

Final Thoughts

NB-IoT provides a significant opportunity for mobile operators to create new revenue streams beyond the highly competitive consumer segment. By moving further in the value chain beyond connectivity, in areas such as IoT software / platforms and analytics, operators will be able to capture a larger share of the IoT market and diversify into more industries.