Characteristics of baseband digital signal transmission for intrabody communications

Intrabody communications (IBC) is a new physical layer outlined in the recently ratified IEEE 802.15.6 Wireless Body Area Network (WBAN) standard. This data communication method uses the human body itself as the signal propagation medium. It is significant to investigate the signal characteristics for baseband digital data transceiver design in IBC. In this paper, we present preliminary channel attenuation characteristics of a time division multiple access (TDMA) scheme implemented based on baseband digital signal transmission. A digital block implemented on a field-programmable gate array (FPGA) board as well as a digital Pulse Generator are employed as the IBC transmitters. The timeslot occupancy is simulated by adjusting the duty cycle of a square wave of varying frequencies. The measurements using FPGA indicate the signal attenuation of 32.76 and 27.82 dB at frequency of 10 and 25 MHz, respectively, for digital signals with 50% duty cycle. In addition, the attenuation of signal with 20% and 50% duty cycle at 50 MHz are 32.76 and 30.63 dB when Pulse Generator is used as the IBC transmitter. The variation of duty cycle in pulses was then used to simulate a time division multiplexed transmission scheme. It was observed that the attenuation decreases around 4.0 dB when data pulses are increasingly present from 1 to 5 timeslots. Therefore, digital baseband signals deployed in a time division multiplexed mode with higher timeslot occupancy leads to lower attenuation for IBC transmissions.