Selecting a safe power level for an indoor implanted UWB wireless biotelemetry link

Abstract

In this paper we analyze a wireless biotelemetry link for an implanted UWB antenna located in the upper arm of a human. We use finite element analysis to characterize the specific absorption rate (SAR) of the surrounding tissue to determine the limits on transmitter power level for safe operation within the FCC restrictions on implanted electronics. We show the tradeoffs of safe transmit power levels verses bit error rate (BER), distance and data rate (Rb) for line of sight (LOS) and non-line of sight (NLOS) indoor propagation channels. A link budget is created to determine the received power levels for our FCC SAR compliant system as a function of distance, data rate and system bandwidth. Results demonstrate that for a BER of 1e-6 and data rate of 100 Mbps, the biotelemetry system can communicate using FSK modulation for distances up to 3.5 m and 0.7 m assuming worst case LOS and NLOS path loss environments, respectively. The system is analyzed using the maximum bandwidth (7.5 GHz) of the UWB spectrum and various FCC limited transmit power levels.