## Special Issue on Body Area Networks  
**[PERSON] 1,2,3,*(r), [PERSON] 1,3(r) and [PERSON] 4,5(r)**  
1 School of Technology and Management, Computer Science and Communication Research Centre, Polytechnic Institute of Leiria, Campus 2, Morro do Lena--Alto do Vieiro, Apartado 4163, 2411-901 Leiria, Portugal; [EMAIL_ADDRESS]
2 INOVENESC INOVACAO, Institute of New Technologies, Leiria Office, Campus 2, Morro do Lena--Alto do Vieiro, Apartado 4163, 2411-901 Leiria, Portugal
3 Computer Science Department, School of Technology and Management, Polytechnic of Leiria, Apartado 4163, 2411-901 Leiria, Portugal
4 Departamento de Sistemas Informaticos, Universidad de Castilla-La Mancha, 02071 Albacete, Spain; [EMAIL_ADDRESS]
5 Biomedical Research Networking Centre in Mental Health (CIBERSAM), 28029 Madrid, Spain
* Correspondence: [EMAIL_ADDRESS]  
Received: 12 April 2020; Accepted: 23 April 2020; Published: 20 May 2020  
Wireless body area networks (WBANs) are a fascinating research field offering wearable and implantable sensor technology [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13], communications and platforms [14, 15, 16, 17, 18, 19, 20, 21] that are revolutionizing healthcare, quality of life and interactions between physicians and patients. A WBAN is realized through the integration of different nodes (sensors and actuators) relying on different communication technologies (wired, wireless and human body communication [22, 23, 24, 25, 26, 27, 28, 29, 30]) to allow interconnection under skin, over skin, when embedded in clothes and in portable devices, to provide both managed and autonomous applications [31, 32, 33, 34, 35, 36]. Usually, WBANs are not confined to the human body. Gateways, networks and cloud technology [37] extend the number of applications a WBAN can offer and support. One example of such applications is (remote) healthcare [38, 39, 40, 41, 42, 43], where WBANs are considered a key technology to help facing the side effects of an aging population on healthcare systems and society in general. This special issue is devoted to collecting contributions from researchers on the realization of real-world and reliable wireless body area networks, platforms and applications, addressing the major associated challenges. Nine papers have been selected for this special issue, beginning with a paper [44] that gives the reader a general overview of the WBAN research field and highlights its main features and requirements, sensor types and contributions to healthcare, concluding with the main current challenges. The other eight research papers are segmented into three main application areas: energy harvesting, communications and applications in the research field of wireless body area networks. **Energy harvesting:** Under the assumption that a single energy harvester from a human body is not enough to reliably drive an electronic device, [PERSON] et al. [45] propose energy harvesting by combining multiple energy harvesters in wireless body area network applications. An efficient 0.13-\(\upmu\)m TSMC Complementary metal-oxide-semiconductor (CMOS) energy management and distributing circuit is defined that is able to combine up to three sources of harvested energy and is suitable for autonomous WBANs, with a special focus on implantable devices for which it is very difficult to maintain a battery. **Communications:** This special issue addresses the three physical layers defined by the Institute of Electrical and Electronics Engineers (IEEE) 802.15.6 standard. [PERSON] et al. [46] focused on the human body communication (HBC) physical layer to better understand its basic signal transmission paths when relying on one-electrode and two-electrode transmitters. In terms of off-body communications, [PERSON], [PERSON] and [PERSON] [47] present a study of system loss for both 868-MHz narrow band and 6489-MHz ultra-wide band radio channels in a very harsh environment is conducted, as opposed to the majority of currently designed WBANs which are focused in indoor environments. Additionally, [PERSON] et al.