### Security Imaging Using Ambient 5G Cellular Broadcasts Abubakar Abid

In light of recent tragic incidents of terrorism in Brussels, Istanbul, and Lahore among other places, as well as continuing gun violence in the United States, it seems that providing security for civilians is becoming harder and harder. Part of the issue is that the areas that these incidents are happening include schools, parks, and other "soft targets" where centralized security is difficult to provide.

As such, my proposal is to envision a system of distributed, underground "scanners" which use ambient RF generated by future 5G cellular broadcasts to scan passersby to determine the presence of guns, small explosives, or other potentially lethal weapons. Because 5G is expected to operate at the region of the electromagnetic spectrum that is on the order of a few mm or 1 cm, it can potentially resolve objects of interest. While passive millimeter-wave imaging technology exists [1], I believe that the addition of ambient sources will increase the ability to image

Specifically, my goals are to:

1. To determine whether 5G frequencies would be high enough to resolve relevant features.
2. To evaluate whether ambient power levels from 5G towers would significantly boost the distance at which millimeter-wave radiation would travel, and could be detected, and if so, how large those power levels would have to be.
3. To determine optimal receiving antenna placement to identify objects.
4. To describe the processing routine used by receiving antennas to identify metal object and shape
5. To determine whether towers operating at differing frequencies could be used to help distinguish objects

Solution:

1. A typical pocket knife is about 5 cm long, so we would need frequencies greater than $$\frac{c}{5 \text{ cm}} = 6 \text{ GHz}$$. Most guides to 5G predict that 5G frequencies will be above 6 GHz, and 30 or 90 GHz are likely, since these are frequencies that are not significantly attenuated in the atmosphere.

[1] http://ieeexplore.ieee.org/stamp/stamp.jsp?arnumber=4014829