August 30, 2018
If you listen to industry prognosticators, there will be about 31 billion Internet of Things (IoT) devices worldwide by 2020. From smart homes and factories to wearables and healthcare monitoring equipment, IoT applications are sprouting up everywhere. For mobile operators and contractors responsible for ensuring these connections – some of which are mission critical – the verification process is as diverse as the applications themselves.
One technology being implemented for this new era of wireless is Narrowband Internet of Things (NB-IoT) – sometimes referred to as LTE Cat-NB1. NB-IoT was included in 3GPP Release 13 to provide wide-area coverage for ultra-low-end IoT applications, such as smart meters, remote sensors and smart buildings. The technology is being selected in many IoT designs because it provides improved indoor coverage, support of massive number of low throughput devices, low delay sensitivity, ultra-low device cost, low device power consumption and optimized network architecture.
NB-IoT is being deployed in three different ways:
- Guard band – In this mode, NB-IoT is deployed within the guard bands of the 3G and LTE spectrum without reallocating resource blocks. Though these spectrums are designed to reduce interference, they are well suited for narrowband applications, as well.
- Standalone – NB-IoT can also be used as a standalone deployment within its own dedicated spectrum where deemed necessary. In standalone mode, NB-IoT can be deployed in re-farmed spectrum from GERAN systems utilizing standalone 200 kHz carriers. For these reasons, this mode may be the option taken by carriers for very dense IoT environments.
- In-band – Using available resource blocks within a normal LTE carrier, NB-IoT can be deployed within the existing LTE spectrum. The main advantage is that it can be enabled very quickly via firmware updates.
Let’s Talk NB-IoT Specifications
Because LTE Cat-NB1 (NB-IoT) is lower in cost and requires less power, it is being selected for low-end IoT user cases. NB-IoT user equipment also reduces complexity and extends coverage to 164 dB MCL. Cat-NB1 uses 180 kHz bandwidth and is currently specified for LTE FDD. Some 3GPP member companies, however, are considering specifying TDD operation in future releases. NB-IoT supports in-band deployment by utilizing a single RB within a normal LTE carrier. Another consideration when deploying Cat-NB1 is that it has a very small channel size of 200 kHz and 10s of kbps throughput.
Operational Challenges to Consider
Deploying and ensuring NB-IoT systems are working as intended poses a different set of challenges compared to conventional mobile device usage. Here are some ways NB-IoT verification is different than traditional cellular use.
- Penetrative signals – The environments in which NB-IoT is being used requires the signal to penetrate through several layers of brick, due to some applications that will be underground in tunnels and sewer networks, as well as in very rural settings. Therefore, the link budget of NB-IoT is enhanced 20 dB compared to traditional cellar networks.
- Low latency – As will be the case in 5G, packet loss is a common issue with IoT devices in challenging operating environments. For these devices to perform to specification, they need to transmit data within an acceptable latency period and avoid dreaded packet loss. For Cat NB1, latency can range from 1.4 seconds to as much as 10 seconds in some deployment scenarios.
Maintaining sub-10s latency means NB-IoT is well suited for underground application, so it is being used for live monitoring applications. It will also reduce packet loss, so devices provide more value to their end users.
Integrating NB-IoT Into Existing Networks
How NB-IoT devices and systems will work in the real world is only one part of the equation for mobile operators. Another big issue is to ensure that existing LTE networks and new NB-IoT services coexist. Operators must introduce these billions of IoT devices while maintaining the required quality of experience (QoS) consumers expect when they are texting, streaming, and surfing the Web.
Because of all these considerations, test solutions must be versatile and be able to conduct a series of measurements. Given the low-cost applications in which NB-IoT is being used and the LTE spectrum it is occupying, field test solutions must have multi-instrument capability. This will allow field technicians to use a single instrument to verify network operation for traditional cellular and IoT applications, which controls the cost of test.
Anritsu has NB-IoT support on its Spectrum Master™ handheld spectrum analyzers, and Cell Master™ and BTS Master base station analyzers. These solutions can conduct all the necessary RF measurements, such as carrier frequency, channel power, and occupied bandwidth, as shown in figure 2. The analyzers can also conduct channel spectrum and spectral emission mask measurements to ensure signal transmission.
Figure 2
To learn more about these handheld analyzers and how to conduct NB-IoT measurements, visit our Internet of Things technology (IoT) page.
