Body Area Networks: Radio Channel Modelling and Propagation Characteristics Aastha Gupta, Thushara D. Abhayapala Department of Information Engineering Research School of Information Sciences and Engineering Australian National University Canberra, ACT 0200 Australia aastha.gupta@rsise.anu.edu.au, thushara.abhayapala@anu.edu.au Abstract—Human body will act as a transmission channel in wearable wireless devices in the near future. Inclusion of the body as a transmission channel will see future wireless networks rely heavily on Body Area Networks (BAN) with applications in medical and personal area networks. In order to build BAN devices, it is imperative to model the channel accurately. Channel measurements are important, however, a closer look on the body channel can only be attained through Electromagnetic (EM) propagation modelling. This paper presents a preliminary analytical EM channel model for BAN. Specifically, the dyadic Green’s function for a simple cylindrical human body model is used to propose a channel model. Four possible cases are considered, where the transmitter and receiver are either inside or outside of the body. An exact analytical expression is derived for the case where both the transmitter and receiver are outside of the body. This case is then used to show how the received signal power varies around the body, with the receiver at a constant radial distance from the cylindrical axis of the body. I. I NTRODUCTION Medicine is an area of technology that has often been ignored by the Telecommunications community. As the aged population is increasing and healthcare professionals are de- creasing, hospitals throughout the world are facing a unique problem. There is an arising need to remotely monitor and treat patients. To realize this task, it is required to communicate between portable sensor devices worn on and implanted within the body of the user and an external interface. This will be achieved by Body Area Networks (BAN). BAN can be used not only on remote patients but also enables to make patients wireless within the hospital, es- pecially, in intensive care units and operating theatres. Not only this would enhance patient comfort but also it would make the work of doctors and nurses a lot more efficient and easy. On site accident communication can be performed via BAN, wherein a paramedic strap on the BAN sensors which can start providing vital information to the hospital directly, hence increasing efficiency, reducing reaction time, and saving crucial life critical minutes. There have been a few projects throughout the world which have started working in Healthcare BAN and related devices such as Human++ [1], Memswear [2], Motes [3], and Ambulant monitoring [4]. As BAN deals with connecting the body to wireless devices, it has applications in numerous other areas as well; such as, sports, entertainment, and defence forces. To build any wireless device, the first essential step is to study the transmission channel and model it accurately. In this attempt, a few research groups throughout the world have initiated channel modelling [5]. They have performed measurement campaigns and path loss studies for wireless nodes on the body [6], [7], [8], [9], [10], [11], [12]. Some have also considered implanted devices, an area of BAN called Intra-body Communication [13]. Due to the short-range low data-rate communication in BAN scenarios, measurement groups have considered UWB as the appropriate air-interface. Although there are quite a few measurement campaigns, each model developed by them is only a path loss model and does not provide any detail description of the propagation channel. In order to develop a general and accurate BAN channel model, it is important to study the propagation mechanism of wireless radio waves on and inside the body. Such a study will reveal the underlying propagation characteristics. This will assist in the development of enhanced BAN transceivers, which are more suited to the body environment. The human body is a very complex environment and has not been studied explicitly for wireless communication. Although, a while ago the human body was under focus for the measurement of electromagnetic absorption studies, such as specific absorption rate and dosimetry [14], [15], [16], [17]. For a BAN channel model, it is required to determine the electromagnetic field at each point on/inside the body for a given position of the transmitter on/inside the body. This is a huge problem numerically, which requires enormous amounts of computational power. Therefore, it is desirable to derive an analytical expression which performs this objec- tive. Analytically resolving this problem means solving the Maxwell’s equations for each point of the body. In effect this determines which propagation mechanism is taking place, i.e. diffraction, reflection, transmission, surface waves [18]. An elegant manner of doing this task is using the dyadic Green’s function. Dyadic Green’s functions have been used in Electromag- netic (EM) theory and have solutions for canonical problems,