TCP/IP Body Area Network in intra-body transmission using OFDM-based wideband modulation

Intra-body transmission, which uses human body as part of the transmission medium is one of the promising data transmission methods for constructing Personal Area Network (PAN) or Body Area Network (BAN). Since signal propagates mainly through the human body, power consumption is smaller and transmission is less susceptive to eavesdropping. One of the difficulties in intra-body transmission is that the transmission characteristics vary among individuals and change by surrounding environment. Even the posture of the user may affect the transmission characteristics. These variations make it difficult to construct IP networks using protocols such as TCP/IP. We have investigated transmission characteristics of intrabody transmission system in frequency range from 300 kHz to 1 GHz. The transmission efficiency through the human body showed a peak at around frequency of 1 MHz, and was better than that through the air at all frequency less than 80 MHz. The difference was 20 dB or more at frequency less than 55 MHz. To achieve IP network using TCP/IP protocol, we focused on Orthogonal Frequency-Division Multiplexing (OFDM) method, which is tolerant to the frequency transmission characteristic variations. We used frequency range from 2 to 28 MHz and investigated the feasibility of TCP/IP communication in intrabody transmission. We evaluated characteristics of TCP/IP-based intra-body transmission using OFDM communication system on an experimental basis. Throughput of 53.5 Mbps on UDP and 15.2 Mbps on TCP were achieved between the transmitting and receiving electrodes gripped by right and left palms, and throughput of 68.1 Mbps on UDP and 16.8 Mbps on TCP were achieved between an electrode gripped by one hand and an electrode put on the wrist. We confirmed that the TCP/IP-based high-speed communication in intra-body transmission was achievable using OFDM modulation with 2 -- 28 MHz.