An FPGA-Based Transceiver for Human Body Channel Communication Using Walsh Codes

Abstract

In this paper, a body channel communication (BCC) transceiver with Walsh codes modulation is presented. In the transmitter part, data are encoded in Walsh code format, and the chosen Walsh codes restrict the maximum consecutive identical digit (CID) to increase the data transitions. In the receiver part, we use an analog front-end (AFE) circuit board to amplify the attenuated signal from the transmitter and restore the signal to the digital waveform. After the $\mathbf{8x}$ oversampling sampler and vote integrator recovery the clock and data, the Walsh code demodulator demodulates the original data. The proposed BCC transceiver has higher data reliability because of the orthogonal characteristic of Walsh codes. Moreover, the proposed Walsh code concatenated method strengthens the jitter tolerance and improve the code rate. The proposed BCC transceiver was verified on a field-programmable gate array (FPGA) board. The chip rate of the proposed transceiver ranges from 1.56 Mcps to 12.5 Mcps. Also, the bit error rate is $< \mathbf{10}^{-\mathbf{8}}$ and $< \mathbf{10}^{-\mathbf{5}}$ at 6.25 Mcps and 12.5 Mcps, respectively.