## 6 Conclusions and Future Work
### Prevention of Accidents and the Spread of Epidemics  
If the tracking technology based on time and location can be developed into security-related applications, it is believed that governments and private enterprises will also be very interested. The faster and more real-time features of 5G will also bring more safety to the lives of citizens. The following explains how some 5G footprint tracking technologies are applied in security-related fields. For governments of all countries, maintaining urban traffic is a critical matter [21], and road repairs are also the most frequently complained item by citizens or questioned by parliamentarians. There are many roads in a city, and it is pretty expensive to do a road condition survey on each road. If governments wait for road conditions to cause problems before repairing, it will often cause citizens to complain and significantly impact citizens' traffic safety. However, if governments choose to repair regularly, it is not appropriate to formulate a fixed repair cycle due to the different usage conditions of each road. If the cycle is set too long, traffic safety issues will be generated. If the cycle is set too short, it may be questioned. If there is no more useful data to prove it, this will always be a puzzle. However, if it is through the vehicle trajectory data, we can clearly see each road's passing status. Not only does it not need to spend much budget to conduct a road condition survey, but it can also dynamically formulate the repair cycle of each road in real-time and accurately and reduce various possible disputes. For private enterprises, security issues are always the most business opportunities [22; 23]. If we take an apartment complex as an example, several common safety issues are related to real-time footprint tracking. Take an unruly visitor as an example. When he moves in the building, his real-time movement trajectory may differ from the typical movement trajectory. Through systematized automatic alarms, security personnel can reach the scene more quickly to support. Alternatively, take a resident who intends to commit suicide as an example. When a resident moves to the roof of the building abnormally, if the movement trajectory can be automatically linked with the access control system, there is a chance to lock the door at the last minute and avoid tragedy. In addition, with the advent of an aging society, the care of dementia in the elderly and location tracking may also become the new normal in a community. It seems that only the real-time footprint tracking technology of 5G can successfully complete these protective applications with urgent time requirements for the time being. The current COVID-19 epidemic has spread throughout the world and has caused countless deaths. If 5G footprint tracking technology can be used to alert more quickly and list those who need to be quarantined, this will be the best demonstration to use technology to protect the lives of whole peoples. At present, when a confirmed person is found, an epidemic investigation is often carried out. Once the number of confirmed cases is too large, the need for an epidemic investigation will paralyze all human resources. If the epidemic investigation is not carried out or the speed of the epidemic investigation is too slow, it will cause the epidemic to become more difficult to control. The slow speed referred to here means more than one day. Since the epidemic is growing exponentially, even if it is only a short day, the impact on the spread is still considerable. When faced with hundreds of confirmed cases a day, the limited staffing of a country cannot complete the epidemic investigation work in time. In addition, due to personal privacy, the results of the epidemic investigation may often be concealed, which will represent a significant epidemic prevention breach for the entire epidemic prevention operation.