Energy-efficient body-channel communication/MICS dual-band transceiver for unified body sensor network

Abstract

This dissertation presents an energy-efficient dual-band transceiver for a unified body sensor network (BSN) controller. The transceiver communicates with implanted medical devices using 402 - 405MHz MICS band. For on-body communication, the body channel communication (BCC) using the human body itself as a transmission medium is adopted for low power. To optimize operation of the dual-band transceiver in body area, the characteristics of the in and on-body channels are studied. The path loss of the human body channel is measured at frequencies from 100kHz to 150MHz and distances up to 1.2m. A distributed RC model is developed to analyze large variation of the channel properties according to the frequency and channel length. The radiation and interference issues related with body antenna effect are also examined. From the body channel analysis, 30 - 70MHz guarantees BER less than $10^{-8}$ in BCC. The attenuation of an electromagnetic wave is studied when it passes through the conductive human tissue, and the results are used to set the sensitivity of implanted radios. The in-band interferences in the BCC and MICS are avoided by an adaptive frequency hopping (AFH) and a listen-before-talk (LBT) protocol, respectively. The 40MHz BCC band is divided into sub-channels for AFH. The bandwidth, and hence the number of the sub-channels is scalable according to interference condition. The 3MHz MICS band is divided into 10 channels by following the FCC regulation. In contrast to typical dual-band transceivers, the proposed one receives BCC and MICS band signals concurrently. Low energy of the transceiver is achieved by sharing the front end circuits of the BCC and MICS RXs during the concurrent operation. As a result, 30% of the overall energy is saved. The dual-band front-end circuits consist of a cascaded LC tank LNA and a current-recycling concurrent-down conversion mixer. The proposed LNA provides constant 23dB gains both in the BCC and MICS bands and suppresse...