An important step in the development of a swallowable body sensor network is the characterization of electromagnetic wave propagation between the devices inside the human body. This paper refers to the IEEE 802.15.6 channel model [32]. The path-loss between any two nodes is both distance and frequency dependent. Equation (1) gives the statistical model of path-loss, where d0 is equal to 50 mm as a reference distance, n is the path-loss exponent, S is the variation due to the phenomenon of shadowing and it follows normal distribution with mean of zero and standard deviation of σs. The 15.6 Task Group identified seven different propagation scenarios in which the sensor device may operate. For the swallowable BSN applications of this paper, only the scenarios of implant-to-implant and implant-to-body surface are involved. The corresponding parameters are expressed in Table 1. For each scenario, whether the propagation is in the deep tissue or near the body surface is classified. According to this model, the path-loss between any two sensor devices within the human body can be estimated: