Preliminary characterization of impulse radio intrabody communication

Intrabody communications (IBC) is a promising data communication technique for body area networks in biomedical applications. This short distance communication approach transmits signals through body tissue forming a wireless network among on-body sensors. It is defined as one of the physical layers for the new IEEE 802.15.6 or Wireless Body Area Network (WBAN) standard. It is meaningful to investigate the characterization of the IBC communication system for wearable and implantable biomedical applications. In this paper, an impulse radio (IR) type of transmitter was developed for galvanic coupling type IBC. A carrier-free transmission is implemented in a field programmable gate array (FPGA) board based on a pulse position modulation (PPM) scheme. PPM is a modulation technique which uses time based pulse characteristics to encode data and is based on impulse radio ideas. Results demonstrate that there is 40 dB attenuation after 20 cm data transmission through human arm. Additionally, the Signal-to-noise ratio (SNR) decreases about 8.0 dB for a range of arm distances (5-50 cm) between transmitter and receiver electrodes with the stable noise and various signal amplitude. The variations of the channel SNR is measured approximately 0.2 dB/cm for 5-50 cm on-body distances. The behavior of SNR shows how signals will propagate through the human body communication channel.