# Body Area Networks in Healthcare: A Brief State of the Art
## 3 Physical Layer Requirements
### Safety Issues in PHY Layer  
BAN safety is an important subject, especially in medical applications. The ISO 60601 standard [18] for medical devices defines what hazards a patient might experience when using these kinds of devices. The standard presents a list of aspects that could harm a patient: radiation, heat dissipation, biocompatibility, software errors, mechanical problems, and electric shocks. The principal objective is not harming the patient. Patient safety in medical BAN applications is a crucial point. Therefore, it has to be analyzed in the same way as the technical requirements. There are three perspectives to address when developing BAN systems:  
* All possible critical events that may occur must be handled with a methodological approach. If a characteristic of the solution can cause damage to the user, it has to be tested first without living test subjects like human skin alternatives and always monitor hazardous radiations. A correct mitigation of possible hazardous situations saves patients' lives.
* BAN solutions use networking to communicate all data collected from the peripheral nodes with the purpose of achieving the solution goal. In medical applications, a networking failure can produce a fatal error. The developers must analyze the impact of delays and package loss in critical operations. Through the results of the analysis, the developers must improve the design of the solution mitigating the possible problems in critical operations.
* Software is the core of medical applications. Any failure in software is going to cause a malfunction that can harm the patient. The software has to be reviewed eliminating coding errors and testing all possible events that it must confront. Given the continuous interaction, it is important for the software to offer a way to receive feedback from the human body in order to prevent harm to the patient.  
There are several options to ensure safety in all cases discussed before. For the purpose of assuring that BAN devices are safe to patients, experiments testing the effects of devices on human physiology are performed. These experiments are designed to mitigate the possible side effects to the subjects. Hardware models are also designed to emulate a part of the body in the case of medical applications. It is possible to test the device software and the control system through these models. Researchers must ensure that the software on BAN devices is working correctly by designing a large set of test cases.  
These tests cover a wide variety of plausible scenarios that the devices might encounter. The use of automaton devices helps to analyze the behavior of the BAN applications to provide safety guarantees.  
Model-based engineering (MBE) is used to evaluate the safety in BAN systems. A model of the real system is developed and analyzed for requirements verification. This model has two phases: (1) model development and (2) model analysis. In model development, the properties of the system are listed based on the system requirements. The resulting model is analyzed to verify the expected properties and requirements. Figure 1 shows an illustration of the methodology.  
Hazard analysis of medical devices starts with the creation of attackers models and possible security susceptibilities in the system. In order to reinforce the security, each component is analyzed and the design is improved for avoiding vulnerabilities.