# Body Area Networks in Healthcare: A Brief State of the Art
## 2 Body Area Networks: Main Features and Requirements  
A BAN is an evolution of a wireless sensor network (WSN). WSNs were first used for personal devices like cellphones, laptops, and cameras. These devices form a personal area network (PAN). The same concept is applied to a BAN. A BAN is a network of nodes with sensors and actuators which communicate with each other.  
In addition to addressing aspects related to the lower layers of the OSI model, the design of BAN solutions should consider many general requirements such as safety, privacy and security and sustainability to ensure proper operation. However, in order to provide the best user experience, there are other aspects, e.g., quality of service and usability, which should be considered as well. A brief description of these issues is [15]:  
* Safety: These types of networks, which are in direct contact with the body, must be designed to ensure they are safe for the end user. Hence, this is a critical point in the development of BAN devices, especially when medical applications are being developed, as parameters are measured in sensitive parts.
* Privacy and security: BAN applications collect a great amount of sensitive information that must only be accessible to authorized people. Unauthorized use of private information may lead to abuse and discrimination. BAN solutions that have access or generate sensitive information need to implement authentication and encryption. However, security policies should not overhead the energy consumption of the BAN nodes.
* Sustainability: Finding a balance between energy consumption and energy source is mandatory in BAN products. Energy supply must be available when required to achieve a good performance of the BAN solution. Energy-supply models are divided into two groups: (1) the node is supplied directly by the harvesting energy source (SSCS), and (2) the harvesting source saves energy into a battery and the battery supplies energy to the node (SBCS). SSCS involves connecting the energy source (solar panel, wind turbine, etc.) to the computing unit without any energy storage in between. This configuration must be calibrated to match the power supply and the demand in order to be sustainable. The SBCS uses a battery to store energy for later use, which is useful in situations where the power supply is not available at any time, like solar power in the night. In SBCS, the energy generated must be in balance with the energy that the battery can store to reduce waste. Testing the energy consumption of nodes helps to choose the correct energy source needed for the deployment.
* Quality of service: Each type of BAN application has a different definition of quality of service (QoS) depending on the services offered. Some elements to measure QoS are latency, jitters, and bandwidth of the network, stats of data transmission, errors and useful information sent in a period of time. In any case, QoS includes adaptability, timeliness, reliability, robustness and credibility for most applications. QoS can be separated into two cases, namely application and network [16]. The application perspective refers to the quality of the user interface (UI). The UI must be understandable and meet all the user's requirements. The network case measures the quality of the application's information provider (latency, reliability, error management, etc.).
* Usability: This is another requirement that has to be considered when developing BAN applications. Usability refers to how easily a person without information and communication technology (ICT) knowledge sets up the solution.