Personal Area Networks: Near- field intrabody communication By T.G Zimmerman

Introduction Use the human body as the communication medium Many I/O devices are duplicated –Watch,PDA,Cell-phone, all have displays Network devices that are close to the body using capacity coupling though the body Such communication can be achieved in a power efficient manner

Advantages Makes use of near field effects –Low frequencies, below 1MHz, typically MHz, Low power (few mW) –Very short range Higher density More difficult to intercept Less Interference Well below FCC limits so no strict licensing limits Avoids duplication of personal devices

Challenges Privacy/Security –Beacon signals can be used to keep track of people –Personal information such as credit card numbers, telephone numbers and computer passwords can be stolen Communication becomes difficult or stops when touching good conductors

A Closer Look Information transmitted on a modulating picoamp displacement current Electrical Model

Electrical Model of PAN System

The PAN Prototype Using the Hartley Shannon Law –Capacity = B log (1+S/N) –B -bandwidth, S -signal, N Noise -3dB BW is around 400KHz –max channel capacity 417kbps assuming SNR =10 Actual transceiver prototype 2400bps Dimensions 8 x 5 x 1 cm

PAN Prototype (cont.) Modulation schemes –on-off keying ( on = 1, off = 0 ) –DSSS

Electronic Handshakes Transmitter placed inside shoe insets –can be charged during walking When 2 people are in close proximity they can exchange business card information. –Business card information is continuously transmitted as a set of ASCII characters. –When people shake hands the information can be downloaded to each others PDAs.

Conclusions Design based on 7 layer ISO model –Only physical and data link layers developed here, rest of the layers need to be developed. Many traditional digital communication principles can apply to this domain –Higher data rates seem feasible Concept of power sneakers seems promising