In this thesis, we introduce the fundamental operation of intra-body communications. The efficiency of the intra-body communications and the disturbance of intra-body communication are also studied. Intra-body communications propagate the signal by using the surface of human skin. Our study is mainly based on simulation. The accuracy of the simulation is verified by comparing with results in two papers. Then, five tissues are used to represent in the simulation. Firstly, we find design rules of transmitter and receiver for improving efficiency. The larger size of the circuit board is, the stronger signal receives. Length is more sensitivity than width but electrodes cannot be close. The signal does not vary widely with the location of the receiver. By setting proper parameters of skin, we can differentiate between wet skin and dry skin. Because the conductivity of wet skin is higher than dry one, the wet skin will give a stronger received signal. In the latter part of the thesis, we study the parameters cause the disturbance of intra-body communications. First, we study the effects of the person is close to the system. Second, we discuss the changes of the impedance of the system when another person touches the user. In the last, we discuss the variety of the receiving signal due to the bending of the arm, furthermore, we can distinguish the angles of the arm¡¦s bend from the coupling of electric field.

Capacitive communication using human body as a electrical channel has attracted much attention in the area of personal area networks (PANs) since its introduction by Zimmerman in 1995. The reason being that the personal information and communication appliances are becoming an integral part of our daily lives. The advancement in technology is also helping a great deal in making them interesting,useful and very much affordable. If we interconnect these body-based devices with capacitive communication approach in a manner appropriate to the power, size, cost and functionality, it lessens the burden of supporting a communication channel by existing wired and wireless technologies. More than that, using body as physical communication channel for a PAN device compared to traditional radio transmission seems to have a lot of inherent advantages in terms of power and security etc. But still a lot of feasibility and reliability issues have to be addressed before it is ready for prime time. This promising technology is recently sub-classified into body area networks (BAN) and is currently under discussion in the IEEE 802.15.6 Task Group for addressing the technical requirements to unleash its full potential for BANs. This could play a part in Ericsson's envision of  50 billion connections by 2020. This thesis work is part of the main project to investigate the models, interface and derive requirements on the analog-front-end (AFE) required for the system. Also to suggest a first order model of the AFE that suits this communication system.In this thesis work the human body is modeled along with interfaces and transceiver to reflect the true condition of the system functioning. Various requirements like sensitivity, dynamic range, noise figure and signal-to-noise ratio (SNR) requirements are derived based on the system model. An AFE model based on discrete components is simulated, which was later used for proof of concept. Also a first order AFE model is developed based on the requirements derived. The AFE model is simulated under the assumed interference and noise conditions. The first order requirements for the submodules of the AFE are also derived. Future work and challenges are discussed.

The aim of this thesis is to optimize the design of the Fat-IBC-based communication of a novel neuroprosthetic system in which a brain-machine interface is used to control a prosthetic arm. Fat-based intra-body communication (Fat-IBC) uses the fat tissue inside the body of the bearer as a transmission medium for low-power microwaves. Future projects will use the communication system and investigate ways to control the prosthetic arm directly from the brain. The finished system was able to individually control all movable joints of multiple prosthesis prototypes using information that was received wirelessly through Fat-IBC. Simultaneous transmission in the other direction was possible, with the control data then being replaced by sensor readings from the prosthesis. All data packets were encoded with the COBS/R algorithm and the wireless communication was handled by Digi Xbee 3 radio modules using the IEEE 802.15.4 protocol at a frequency of 2.45 GHz. The Fat-IBC communication was evaluated with the help of so-called "phantoms" which emulated the conditions of the human body fat channel. During said testing, packet loss measurements were performed for various combinations of packet sizes and time intervals between packets. The packet loss measurements showed that the typical amount of transmitted data could be handled well by the fat channel test setup. Although the transmission system was found to be well-functioning in its current state, increasing the packet size to achieve a higher granularity of the movement was perceived to be viable considering the findings from the packet loss measurements.