# Long-Range Wireless Radio Technologies: A Survey
## 3 Discussion
### On Which Technology to Use  
Considering all the above, mobile IoT technologies have numerous advantages to be used as a one-hop technology to access the Internet. First, considering coverage, mobile technology is more likely to be available worldwide than ISM-based LPWAN. Using ISM-based LPWAN, there is a need to deploy base stations in isolated areas which is costly. Furthermore, deploying a network connected to the Internet may not be part of a company's purpose. In reverse, using mobile would also mean that there is no way to extend the base mobile network in an isolated area if needed, as the spectrum is under licensed use. As for the spectrum, many long-range technologies make use of the sub-GHz ISM unlicensed bands. This means that everyone can use it, and it is likely that a high level of interference will become common as the number of connected devices using those technologies increases, especially considering technologies such as LoRa that spread the signal across a wide bandwidth. Mobile may bypass noise produced in the sub-GHz, but on the other side, mobile IoT technologies are partly based on the existing and already widely used LTE bands, which are also used for cellphone communications (i.e., more interference). Regarding the financial cost of using mobile networks, several things need to be taken into account. A summary of the module and connectivity costs depending on the technology is shown in Table 1. The prices are given on an indicative basis, as they depend on the countries, the operators and different other factors. Alternative solutions exist, e.g., Hologram [46], which proposes worldwide mobile connectivity and provides a universal SIM card for 1$ per month plus 40 cents (prices vary depending on the number of devices). As it gives an access to every mobile network available on our planet, hologram benefits from an excellent coverage, as depicted in Figure 6.  
If we consider using mobile IoT, we need to choose which technology. EC-GSM-IoT and 5G can be put aside right away. The former is not going to be deployed anymore and the network may even be decommissioned soon [14], while the latter is not deployed at all by the time of writing and will not be usable before several years. eMTC and NB-IoT both propose interesting features and are likely to be deployed and used increasingly in the upcoming years, while being already available in several countries. Choosing between one or the other is difficult: eMTC supports FotA updates, while NB-IoT does not. On the other side, eMTC have a high energy cost, while NB-IoT consumes less power. Considering world coverage, restricting to only one of the two would also restrict the possible deployments to the countries where that technology is available (cf. Figure 3). Regarding these issues, the best answer may be to keep both technologies. Several radio chips supporting both eMTC and NB-IoT are already available (e.g., [44]). A simple idea could be to use NB-IoT for regular monitoring communications, and eMTC for FotA updates. However, this can create new issues too, as areas where coverage for both technologies may be scarce. So, we would need to provide viable solutions also for scenarios where only one of these two technologies are available. This is where LPWAN technologies presented in Section 2.2 may be useful. Devices could form a network in a multi-hop fashion where only one node would need to relay the communications to the Internet, whereas the other nodes would use an ISM-based LPWAN technology to share their data. This would extend the range for nodes out of direct mobile coverage. As mobile technologies cannot