## 2 Outdoor Positioning in the IoT Ecosystem
### Location-Enabled IoT Technologies
#### 2.3.5 5G  
The fifth-generation cellular network (5G) is a response to the IoT requirements caused by continuous expansions of these systems including massive connectivity, security, trustworthiness, coverage of wireless communication, ultra-low latency, throughput, and ultra-reliable. Several key techniques enable 5G to meet the IoT requirements. These key enabling techniques are Network Function Virtualisation (NFV), Heterogeneous Networks (HetNet), Software Defined Networking (SDN), Massive MIMO, and Beamforming techniques. To handle IoT systems that need long-range communication with low power consumption and low bandwidth, 5G will adopt LPWAN technologies. In [32], [PERSON] et al. introduce three main 5G application categories include Ultra-Reliable and Low Latency Communication (URLLC), Enhanced Mobile BroadBand (eMBB), and massive Machine-Type Communication (mMTC). They mentioned that LPWAN can provide an important application direction for 5G, especially mMTC, applications. On the other hand, they stated that 5G can help the development of LPWAN by building the fundamental infrastructure for communication services. In [33], the authors investigate the possibility to seamlessly integrate LPWANs with the upcoming 5G technology. They identified and discussed the four possibilities of integrating the LPWAN with a cellular network. The first two options are based on the use of either a 3 GPP access network or an untrusted non-3 GPP access network for the LPWAN gateway. The latter two options imply merging the LPWAN gateway with either the eNodeB or integrating it with the core network. The pros and cons of these solutions have been highlighted and discussed in the paper. Therefore, it is necessary to implement a transparent integration between LPWAN technologies with the upcoming 5G. Table 1 presents a summary of the most relevant LPWAN technologies. In addition, a graphical comparison of the main properties of LPWAN technologies is depicted in Figure 1. In this figure, the scalability stands for the number of supported devices (NB-IoT offers a very high scalability reaching 100 k end nodes per cell, while Sigfox and LoRaWAN can support up to 50 k end nodes per cell). Range determines the maximum distance that can be covered by an antenna cell (Sigfox covers a larger environment than LoRaWAN and NB-IoT). A mature technology will become established and commercially viable when adopted on a global scale, increasing the technology's trustability. The deployment factor identifies the time taken by a specific technology to become mature, meaning that the recent worldwide popularity of the LoRaWAN protocol results from its trustable and mature communication technology. Battery life specifies the average autonomy of the system (LoRaWAN is more energy efficient). Cost efficiency of a technology is determined based on various aspects including spectrum cost (license), network/deployment cost, and device cost (Sigfox and LoRaWAN are more cost-efficient when compared to NB-IoT). As NB-IoT works in a licensed spectrum, it can guarantee the QoS. Finally, NB-IoT and LoRaWAN (by providing class C) offer lower latency communication than Sigfox. As introduced earlier, long-range, low-power, and low-cost communication systems are crucial for the success of the IoT deployments. As depicted in Figure 1, LoRaWAN and Sigfox are more appropriate for IoT deployment due to their higher cost efficiency. Additionally, LoRaWAN technology has important strengths that may include: supporting private network deployment, no restriction on the number of messages per day, supporting delay-sensitive systems using different classes, providing more information about the channel because of the larger message payload size, and more efficient power consumption. As a result of these characteristics, LoRaWAN technology has become a widely used communication technology in several IoT application domains, and this article focuses the exploration of low-cost GNSS-free outdoor localization techniques with a focus on the LoRaWAN technology.