Ordinary WiFi can easily detect weapons, bombs, and explosive chemicals in bags at museums, stadiums, theme parks, schools, and other public venues using a low-cost suspicious object detection system that is easy to set up, reduces security screening costs, and avoids invading privacy such as when screeners open and inspect bags, backpacks, and luggage.
WiFi, or wireless, signals in most public places can penetrate bags to get the dimensions of dangerous metal objects and identify them, including weapons, aluminum cans, laptops, and batteries for bombs. WiFi can also be used to estimate the volume of liquids such as water, acid, alcohol, and other chemicals for explosives. The new system requires a WiFi device with two to three antennae and can be integrated into existing WiFi networks. The system analyzes what happens when wireless signals penetrate and bounce off objects and materials.
Experiments with 15 types of objects and six types of bags demonstrated detection accuracy rates of 99 percent for dangerous objects, 98 percent for metal, and 95 percent for liquid. For typical backpacks, the accuracy rate exceeds 95 percent and drops to about 90 percent when objects inside bags are wrapped.
Traditional screening typically requires high staffing levels and costly specialized equipment. In large public areas, it is difficult to set up an expensive screening infrastructure such as that found in airports. Next steps include trying to boost accuracy in identifying objects by imaging their shapes and estimating liquid volumes.