Xandem's technology is capable of detecting, locating, and counting humans. Unlike global positioning systems (GPS),
and radio-frequency identification (RFID), Xandem's technology does not require that the individuals being tracked carry any electronic tag or device, nor does it require those individuals to cooperate with the system. In other words, Xandem's technology is used in device-free location (DFL), and it is extremely valuable in applications where carrying a location tag is not possible.

Xandem's technology has the very powerful ability of "seeing" through opaque obstructions like walls. Radio waves are a form of electromagnetic energy that can penetrate solid materials, which is why a cell phone can successfully make a call from inside a building. Since Xandem's sensors rely on radio frequency measurements, the sensing is successful even when the device is placed around the external perimeter of an enclosed area.

Our DFL technology is based on the fact that the human body causes disturbances to radio waves. As a radio wave travels through space, some of the wireless energy is reflected and absorbed if a person is standing along the path from transmitter to receiver. This causes a disturbance in the wave that can be detected at the receiver. By surrounding an area with a network of transmitters and receivers, the disturbance in the radio field that blankets the area can be used to detect and infer the position of individuals moving throughout.

Intellectual Property

All of Xandem's products are backed by strong patents, trademarks, copyrights, and other intellectual property. In certain cases, it is possible for Xandem to license these rights to other organizations.

A New Network Paradigm

When computer networks were developed decades ago, organizational rules and protocols were designed for wired connections. Networks were organized into 5 (sometimes 7) "layers" of functionality. They are:

• Application: This is the stuff the end-user sees. For example, when you open up your email program, you're using the application layer.
• Transport: This layer provides a mechanism for transferring data to/from end-users.
• Network: This is where packets of information are routed through many devices.
• Link: This is the lowest level of "1s" and "0s."
• Physical: This is the part where electromagnetic signals travel through space or material from transmitter to receiver.

In general, a layer does not "know" anything about the internal workings of another layer. The application layer, for example, does not know how information is actually sent, it simply knows that it can communicate with others by passing data to the transport layer. It's kind of like sending a letter to someone. You don't actually know how the letter gets there, you just know that if you put an address on it and place it in your mailbox, it gets there. You don't need to worry how the post office actually routes it.

Under this paradigm, it's easy to see how the application layer would have no business getting involved in the physical layer. That's like a mail sender telling the postal service what truck to put their letter in. In wireless networks, however, strict layering breaks down. Since nodes are mobile and transmit through space instead of a wire, layers must pass information to each other in a "cross-layer" architecture.

While wireless networks and cross-layer architecture present many challenges, Xandem views the wireless channel as a fertile ground for innovation. Specifically, there are many opportunities that arise when the application and physical layer are connected. By measuring how strong the physical layer signals are, for example, technologies like radio tomographic imaging and device-free localization are possible (see figure below).

A photo of a simple radio tomographic imaging network with its corresponding result.