Narrowband Internet of Things (NB-IoT)

Why NB-IoT?

  • The broad spectrum of capabilities is one of the main characteristics of Machine Type Communication (MTC). For instance, surveillance cameras deliver a massive amount of UL data while being almost stationary, while devices for fleet tracking have a fewer amount of data during performing a lot of handovers, devices for meter reading such as electricity, gas, or water consumption. They are often stationary, thus need not an optimized handover. Usually, only a small amount of data is transferred, which is not even delay sensitive.
  • However, the number of these MTC devices may become quite big, even up to several orders of magnitude compared to the traditional devices. Utilizing the already-existing LTE technology will lead to network overload because, in spite of their small amount of user data, the amount of signaling is still almost the same.

  • Therefore, there is a need for a new Radio technology, the first specification of NB-IoT focuses on this class of devices.

  • Usually, these devices are installed at places with no power supply. Consequently, they operate totally on battery and changing the battery might be expensive, because they need to be handled by trained staff. Therefore, the lifetime of the whole device can be determined by the battery lifetime in many cases.

  • Therefore, optimized power consumption is crucial for a good operation. Moreover, the coverage at these places is often very bad. The indoor coverage, therefore, has to be greatly improved, up to 23 dB are considered as a necessity, not an option.

What Is NB-IoT?

NB-IoT is a recent cellular radio access technology specified by 3GPP in Release 13 to match the fast-expanding market for low power wide area connectivity. In response to customer’s requirements and rising competition from non-3GPP proprietary technologies, it has been specified and standardized in a very short time.

NB-IoT is optimized for machine type traffic. It is kept as simple as possible in order to reduce device costs and to minimize battery consumption.

NB-IoT is tightly connected with LTE while being an independent radio interface. This shows up in its integration in the current LTE specifications.

Key Configurations NB-IoT Deployments:

  • Mobile operators should consider supporting IP (Internet Protocol) traffic over Control Plane as a minimum requirement to start supporting roaming. This choice is the best answer to support devices that need to consume as little power as possible. If Non-IP traffic is supported, the MNO should start by utilizing the SGi interface ( connects the PGW to an external network (PDN) ) and later on by SCEF (Service Capabilities Exposure Function), when the appropriate APIs (Application Programming Interface) is defined by 3GPP.
  • According to the latest survey, a minimum of six bands: 2, 3, 5, 8, 20, and 28 are needed for coverage in all the countries for which the NB-IoT members have given input.
  • SMS (Short Message Service) has not been added among the main minimum components in (2017/2018) edition, although considerations for both features have been suggested.

Minimum Baseline for NB-IoT Roaming and Interconnect:

  • MNOs must guarantee that devices and end-to-end services from different providers will connect to the NB-IoT systems that have been deployed. Also, it must ensure that the data transport capability and connection modes are well understood.
  • To ensure that their devices will connect to their systems, individual MNOs will have their own internal processes.
  • To expand and improve coverage and connectivity capability, MNOs and partners will also establish roaming agreements.
  • High-level coordination can help to ensure that MNOs’ forthcoming decisions regarding the deployment architectures are better informed. Also, make the enablement of device interconnect and roaming more straightforward.
  • Also, high-level coordination will help to ensure that NB-IoT RAN technology and devices fulfill the requirements that have created the technology’s development. This with the aim of the benefit of both application service providers and MNOs. For instance, many NB-IoT devices will need to be inexpensive to meet the requirements of MNOs’ customers. One solution to decrease costs is to limit the number of spectrum bands that will be supported by a particular device. So, customers have to know specifically which bands have been utilized to deploy NB-IoT by MNOs. 
  • An MNO may decide to align its deployment band with MNOs in adjacent or nearby territories in places where international roaming traffic is possibly significant.

Requirements for NB-IoT:

● Minimize the signaling overhead, especially over the radio interface.
● Appropriate security to the complete system, including the core network.
● Improve battery life.
● Support delivery of IP and non-IP data.
● Support of SMS as a deployment option.

In order to meet these needs, many advanced and basic features of LTE Release 8/9 are not supported.

The most striking example is the lack of handover for UEs in the connected state. Only cell reselection in the idle state is there, which is also restricted to exist within the NB-IoT technology.

The associated features are not supported as there is no interaction with other radio technologies. Examples
are the lack of LTE-WLAN inter-working, interference avoidance for in-device coexistence, and measurements to monitor the channel quality.

Most LTE-Advanced features are also not supported. This concerns e.g. Carrier Aggregation, Dual Connectivity, or device-to-device services. Moreover, because NB-IoT is not used for delay sensitive data packets, there is no QoS concept.

Hence, all services requiring an assured bit rate are not offered in NB-IoT, such as real-time IMS.

With these requirements, 3GPP uses a different approach than before. Instead of creating one air-interface for all types of applications, the air-interface for small non-delay sensitive data packets is split off and optimized separately. UEs which are supported to work on NB-IoT technology are tagged with the new UE category “cat-NB1”. 

 

References:
  • 3GPP TR 45.820 V13.1.0, November 2015; Cellular system support for ultra-low complexity and low throughput Internet of Things (CIoT).
  • 3GPP TS 23.272 V13.3.0, March 2016; Circuit Switched (CS) fallback in Evolved Packet System (EPS).
  • 3GPP TS 36.101 V13.4.0, June 2016; User Equipment (UE) radio transmission and reception.
  • 3GPP RP-161324 3GPP Work Item Description Enhancements of NB-IoT.
  • GSMA.