This module focuses on how we can interconnect a large number of IoT devices, especially in a wide-area deployment environment that may span several kilometers. In general, one may utilize traditional WiFi or cellular based connectivity technologies, through which we already connect our regular devices such as notebooks or mobile phones. However, IoT devices and applications have special needs and requirements, giving rise to specific communication technologies designed for the lightweight and efficient connectivity of IoT entities.
As depicted in Figure 1.1, IoT deployments can be viewed as a layered architecture that interconnects the physical world (observed through IoT devices/sensors) with the digital world of IoT applications and services. The device connectivity layer, which is the focus of this module, plays a pivotal role by establishing the links for exchanging data and commands among the IoT entities.
¶ 1.1 IoT Application Types: “Massive IoT” vs. “Critical IoT”
When we think of IoT scenarios and application requirements, it is actually a very wide spectrum. 5G specifications by the standardization organization 3GPP introduces three different service types: Enhanced Mobile Broadband (eMBB), Massive Machine-Type Communications (mMTC) and Ultra-Reliable and Low-Latency Communications (URLLC). These are depicted as the corners of a triangle, where various services and applications are placed within the triangle. If we map this to the IoT domain, we can name two distinct types: “Massive IoT” (bottom-left) and “Critical IoT” (bottom-right).
On the bottom left side of the triangle, we have a very large number of low-cost, low-energy devices, each producing very small amounts of data. On the bottom right side, we have complex intelligent devices that require very reliable and near real-time communications for critical processes, such as connected and automated driving and e-health scenarios. Our focus in this module will be on the “Massive IoT” case, since it requires new types of communication technologies for IoT.
¶ 1.2 Key Challenges for Massive IoT
As mentioned above, “Massive IoT” applications involve a very large number of IoT devices, which may be dispersed in a large area, and have limited battery and computation resources. Accordingly, “Massive IoT” can be typically associated with the main challenges of
- Battery life / Energy Efficiency – Many IoT devices will be battery-powered, and often the cost of replacing batteries in the field is not viable.
- Coverage and Range – Regional (or even national or global) coverage is a prerequisite for many use cases. Deep indoor connectivity is also a requirement for many applications in the utility area.
- Quality of Service – Providing a certain low bitrate reliably is important for many applications, while latency is not that critical.
- Deployment and device cost – Clearly a key enabler for high-volume, mass-market applications, enabling many of the use cases. Moreover, in order to enable a Massive IoT market, networks need to scale efficiently.
¶ 1.3 Massive IoT Connectivity Characteristics
In general, when we deploy a base station for massive IoT, we would like to be able to cover all devices not within just a few meters but kilometers of range. When we have many thousands of battery-powered devices, we would like to avoid changing their batteries for a long time, so low-power operation is critical. The basic characteristics of massive IoT applications and associated connectivity requirements are provided in Table 1.1, with some indicative figures that are generally accepted in practice.
Table 1.1: Massive IoT application characteristics of and associated connectivity requirements
| Characteristic | Target for Massive IoT Technologies |
| Long range | 5–40 km in the open field |
| Ultra low power | Battery life time of ~10 years |
| Throughput |
Depends on the application, but typically a few hundred bit/s or less |
| Radio chipset costs | $2 or less |
| Radio subscription costs | $1 per device and year |
| Transmission latency | Massive IoT applications are typically insensitive to latency. |
| Geographic coverage and penetration | Excellent coverage also in remote and rural areas. Good in-building and in-ground penetration. |