  Our long-term research goal is to model the in vivo wireless channel. As a
first step towards this goal, in this paper we performed in vivo path loss
measurements at 2.4GHz and make a comparison with free space path loss. We
calculate the path loss by using the electric field radiated by a
Hertzian-Dipole located inside the abdominal cavity. The simulations quantify
and confirm that the path loss falls more rapidly inside the body than outside
the body. We also observe fluctuations of the path loss caused by the
inhomogeneity of the human body. In comparison with the path loss measured with
monopole antennas, we conclude that the significant variations in Received
Signal Strength is caused by both the angular dependent path loss and the
significantly modified in vivo antenna effects.
