Will the next wireless infrastructure be humans wearing radios?

A team of Irish researchers are studying how humans can become the next wireless infrastructure, by wearing sensors, radios and gateways linked together in "body-to-body" networks.

With redesigned antennas, low-power radios, and new network protocols, potentially huge, constantly shifting body networks could create an "ultra-high-bandwidth mobile infrastructure." Such networks could offload even large file transfers from cellular networks, by making use of parallel transmission and routing through a mesh of body nodes. The body node can link to fixed access points, gateways, or cellular networks when needed. (The body network connections are shown in this drawing.

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The work on "body-centric" communications has been a focus of the Institute of Electronics, Communications and Information Technology at Queen's University, Belfast, Northern Ireland. The researchers recently were awarded a  grant of about $800,000 from the Royal Academy of Engineering and the Engineering and Physical Research Council.

This new work is a five-year exploration of the challenges of body-to-body wireless communications, including how human bodies and movement affect radio signal propagation, according to Dr. Simon Cotton, a research fellow with the Institute.

The concept of body networks is an extension of the work that's being done with wireless medical sensors that are placed on, or implanted in, a patient's body and with battlefield sensors worn or carried by soldiers. The sensors can monitor a wide range of very specific activities and thresholds, collect data, and then transmit the information to a fixed system.

The Institute's work looks at creating an on-body network of wireless sensors that can also communicate externally, through some kind of cooperative mesh network infrastructure, according to Cotton.

"The basic idea is that, instead of communicating with a cellular base station 1 to 2 km away, in densely populated areas the information would be transmitted to the nearest available person -- using cooperative communications, where all users make a small amount of their bandwidth available for other network users -- and so on, until reaching the intended recipient or being relayed on to the cellular network," Cotton writes in an e-mail response to questions.

Similar to networks based on the IEEE 802.15.4 standard for wireless sensor networks, body networks could run with "much lower power levels…as the signal will be transmitted over distances of 10-100's of meters," Cotton says.

Carnegie Mellon University is researching the challenges of getting thousands of wireless sensors to cooperate with each other intelligently. (See "Turning the world into a sensor network".)

Another benefit is that frequency allocations for such a network can be re-used over much shorter distances, "meaning that the precious radio spectrum is utilized much more fully," Cotton says.

A fully functional, reliable body-to-body network could even make at least some cellular base stations in heavily populated areas redundant, Cotton predicts. He envisions such networks being used to transmit even high-definition video content. "The software on the user's device intelligently splits the file into smaller streams and transmits the content to multiple nearby persons, who then forward data to other humans acting as network nodes and so on," he explains. "The file is reassembled when reaching the intended user."

To do this will require a network software stack that can deal with a dynamically changing network configuration. "Disruption tolerant networks" are emerging as a major research focus of their own. (See "Disruption-tolerant nets set for large-scale test".)

Antenna design is key

A key element in "wireless body-area networking" is the antenna design. According to the Institute's Web site, "an ideal antenna for WBAN use will be low profile or conformal, efficient with minimal power losses in body tissues and won't be adversely affected by the user's movements."

The institute has been developing antenna designs, for the 400MHz to 2.4GHz frequencies, to link sensors over the human body, and to also propagate in an omni-directional coverage pattern for external connectivity.

The signal can be affected by the body itself, as anyone can demonstrate just by touching an AM/FM antenna, by the body's motion, including breathing, and the reflection of radio signals (a phenomenon called multipath) in a constantly changing network as the living "nodes" move around and through buildings and streets.

The new grant will enable the Queens University team to evaluate a range of technologies, from microwave frequencies used in popular ISM bands, such as 2.4GHz, to high bandwidth communications at millimeter-wave frequencies, such as 60GHz, according to Cotton. One antenna technology to be examined will be multiple input, multiple output (MIMO), used in the IEEE 802.11n wireless LAN standard.

John Cox covers wireless networking and mobile computing for Network World.

Twitter: http://twitter.com/johnwcoxnww

Email: john_cox@nww.com

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